For what reasons might a taxiway be mistaken for a runway? In this article, an airliner landed on a taxiway instead of a runway. What might be the reasons that a pilot can mistake a taxiway for a runway?

(I mostly know the answer for this question, but I want to see what you guys can find out too as well as making a reference point for others.)

Essentially, some taxiways look very like runways and they might even be more visible to pilots in certain conditions. That leads the pilots to focus on the taxiway rather than the runway.

In 2007 the FAA commissioned a study into ways to avoid pilots landing on taxiways, with special emphasis on KSEA (Seattle-Tacoma). One of their goals was to address exactly the scenario in the article you linked to:

  Find a solution for the Seattle-Tacoma International Airport (SEA-TAC)
  problem by  identifying possible visual aid enhancements to prevent
  pilots from mistakenly  identifying taxiway Tango as the adjacent
  runway 16R as a landing surface.

The study mentions several reasons why pilots mistake taxiways for runways:

A pilot will generally associate an air traffic control (ATC) instruction such as “cleared to land runway 16R,” with their visual presentation of the runway configuration. In other words, pilots see a taxiway where they expect to see a runway: this was a particular problem at KSEA because until the third runway was built, it had 16L and 16R, with taxiway T located to the right of 16R. Therefore a pilot landing on 16R would see three 'strips' with taxiway T as the rightmost one and might assume it was 16R. KSEA now has 3 runways with taxiway T between 16R and 16C.
Some taxiways look physically very like runways, i.e width, surface material, square edges etc.
Some taxiways stand out more clearly in low light conditions because their surface is lighter than the runways
Sun glare can hide runway and taxiway markings so that pilots can't tell the difference visually

There's also an FAA engineering brief that explains how to identify potential problem taxiways, it gives essentially the same information as the study.

Both documents say that the most important point is to alert pilots in advance about the potential problem by giving warnings via ATIS, charts and so on. That's especially true for pilots who aren't familiar with the airport, and GA pilots make more mistakes than airline pilots so presumably training and general currency/professionalism as well as having at least 2 pilots in the cockpit makes a difference too.


What is the input range of common fly-by-wire controls? What's the range that typical fly-by-wire controls (let's take A320 and B777 as examples) allow inputs in?

The A320 controls in the y-axis of the side stick (forward/backward axis) the g load - what's the minimal g load you can input when pushing the stick fully forward / the maximum when pulling it fully backwards? Is this a fixed value or does it depend on factors like speed (IAS / TAS / ...), attitude, altitude / air density or anything / ...? Or is it just the maximum value that the flight controls could give you at any moment?

Same for roll rate, what's the maximum you can command there? And for the B777, it's basically the same question except for the yoke instead of the sidestick.

Also, is the relation between control input (side stick movement / yoke movement) and controlled variable (g-force, roll rate, ...) a linear curve? I.e., if the side stick gives you at the neutral position 1g and e.g. 1cm backwards it gives you 1.1g, does 2cm backwards give you 1.2g?

A320
Max/min stick g:

+2.5 g to -1 g for clean configuration.
+2 g to 0 for other configurations.

Roll:

The roll rate requested by the pilot during flight is proportional to the sidestick deflection, with a maximum rate of 15 °/s when the sidestick is at the stop.

And as it says, is proportional to deflection. (Source: A320 FCOM)
777
I checked the 777's FCOM but did not find similar stated values/explanation.
Since there are trim switches on the 777's yoke, unlike the lack thereof on the A320's stick, the trim switches change the reference speed, and the thrust levers command pitch change. It's designed to mimic, say a Cessna: adding power pitches up; trimming down increases speed.

The trim reference speed is the speed at which the airplane would eventually stabilize if there were no control column inputs. Once the control column forces are trimmed to zero, the airplane maintains a constant speed with no column inputs. Thrust changes result in a relatively constant indicated airspeed climb or descent, with no trim inputs needed unless airspeed changes.


What are the differences between these IFR Low Altitude Chart Navaid Symbols? Below are three NAVAID chart symbols. There is almost no explanation on the aeronautical chart user's guide. It even says that a navaid with an FSS will be shaded but the third box has an FSS and it isn't shaded!

I would like to understand what everything on each of these boxes stands for.

The shadow in the NAVAID box indicates that the NAVAID and FSS have the same name, as in your top image. If they are different, the FSS name is given in brackets below the NAVAID box, as in your bottom image. If the FSS is not available, a thin line box is used for NAVAID (without brackets at the bottom), as in the middle figure.

FAA Aeronautical Chart User's guide should help you understand it better.

Image from FAA Aeronautical Chart User's guide


Is the Soloy Dual Pac recognised as two engines or one engine? The Soloy Dual Pac apparently allows two engines to rotate one propeller -- here's a picture of it on an Otter:

Is this recognised as a centreline thrust twin engine aircraft, a "standard" twin engine aircraft or just an aircraft with a single engine for FAA certification? What about for pilot licensing?

According to the certificate is a

  Twin Power Section Turboprop

and, later, note 7: (emphasis mine)

  This engine is certificated as a unit comprising two separate power sections with the capability of single engine operation with either power section alone in multi-engine airplanes. The unit is also approved as a single engine with either or both engines operating continuously.

No explicit remark is given about pilot licensing, but given the note reported, I would say that a licence for a single engine is sufficient.


When is the logo light on the tail turned on? I noticed sometimes aircraft taxi with the logo light illuminating their tail, while others have it off. So is turning on the tail light at the discretion of the pilot?

There can be several lights on the empennage (tail section) of an airplane. There are two as shown here:

Image Source

The red light is called aircraft beacon. The white light is called strobe.

When to turn them on is explained here:

  All aircraft built after 11 March 1996 must have an anti-collision
  light system (strobe lights or rotating beacon) turned on for all
  flight activities in poor visibility. The anti-collision system is
  recommended in good visibility, where only strobes and beacon are
  required.

Another one is logo light:

This light illuminates the livery design on the vertical stabilizer.

For more details, please see this question:
When to use Beacon, Anti Collision, Strobe, Logo and Navigation lights?


Are you allowed to do your entire PPL on a medium-sized jet aircraft from day one? I'm wondering if say, hypothetically, I had a friend who had a large aircraft (e.g. Learjet), could I do my PPL hours on it from day one, or is there anything stopping this?

It will not work in EASA for a variety of reasons. Of the top of my head:

Like Lnafziger mentioned, you will need to do at least 10 hours solo. Most jet engines (but the smallest such as the D-Jet) have a minimum required crew of two. Also, you are not allowed to switch airplanes in the PPL course (ie. fly solo with one airplane and dual with another see FCL.235) so you are stuck.
Most jet aircraft (and as far as I know all commercial ones) are multi-engine. You will need 70 hours PIC before you can receive instruction on multi-engine, and you cannot fly PIC before you have your PPL.
Multi-engine jet aircraft require a type rating, which has a lot of license pre-requisites before you are even allowed to enter the cabin: MCC, IR, MEP(land)

There are a few prerequisites specified in  Part-FCL about getting your first class or type rating, and to accomplish most of them you will need to have at least a PPL (eg IR(A), ATPL theory tests, hours PIC ,etc)

FCL.235 Skill test
(b) An applicant for the skill test shall have received flight instruction on the same
class or type of aircraft, or a group of balloons to be used for the skill test.
FCL.720.A Experience requirements and prerequisites for the issue of
class or type ratings — aeroplanes
Unless otherwise determined in the
operational suitability data established in accordance with Part-21,
an applicant for a  class or type rating shall comply with the
following experience requirements and prerequisites for the issue of
the relevant  rating:
(a) Single-pilot multi-engine aeroplanes. An
applicant for a first class or type rating on a single-pilot
multi-engine  aeroplane shall have completed at least 70 hours as PIC
on aeroplanes.
(b) Single-pilot high performance non-complex aeroplanes. Before starting flight training, > an applicant for a first class or
type rating for a single-pilot aeroplane classified as a high performance aeroplane shall:
(1) have at least 200 hours of total flying experience, of which 70 hours as PIC on aeroplanes; and
[...]
(c) Single-pilot high performance complex aeroplanes.
Applicants for the issue of a first type rating for a complex single-
pilot aeroplane classified as a high performance aeroplane shall, in
addition to meeting the requirements of (b), have  fulfilled the
requirements for a multi-engine IR(A), as established in Subpart G.
[...]
(d) Multi-pilot aeroplanes [...] or comply with the following
requirements:
(1) have at least 70 hours of flight experience as PIC
on aeroplanes;
(2) hold a multi-engine IR(A);
(3) have passed the
ATPL(A) theoretical knowledge examinations in accordance with this
Part; and  [...]


What are the missions of high-endurance aircraft? What have been the missions of some notable high-endurance aircraft -- ones that can stay airborne for several days. Obviously, high-endurance missions have refueling, food, and human factors concerns that have to be addressed; what have been the missions that necessitated high-endurance aircraft?

Historically long duration flights were simply a way to fly further. Before the jet age crossing oceans was a time consuming affair and required what some may consider a "high endurance" aircraft/flight. Keep in mind it took Charles Linbergh in the Spirit of St. Louis 33.5 hours to cross the Atlantic and this was done with no refueling.

On the scientific/record setting front

A variety of airframes have been used for setting world records arguably a stunt in some cases and others with the pursuit of scientific progress. The current flight endurance record is held by  Robert Timm and John Cook at a whopping 64:22:19:05 (thats 64 days, 22 hours, 19 minutes and 5 seconds) in a Cessna 172 of all airplanes quite an endorsement for the endurance of the airframe/engine combo.

Solar Impulse a modern experimental solar aircraft that recently flew around the world regularly flew 15-22 hour legs due to its slow airspeed. In this case the mission effectively required long legs due to the aircrafts performance. This was a purpose built plane.

The Rutan Voyager was another purpose built aircraft that became the first airplane to circumnavigate the globe, non stop and with out refueling remaining aloft for 216 hours 03 minutes and 44 seconds.

On the operational front:

The Air Force operated Boeing VC-25 (often called "Air Force Once") is capable of aerial refueling and could remain aloft for quite some time and is built to be a mobile command center should the need arise for it.

The Boeing E-3 Sentry commonly known as AWACS provides aerial radar support and is capable of air to air refueling allowing it to stay aloft for well above its standard 8 hour endurance. I dont know a whole lot about its standard mission so Im not sure it ever flys multi-day missions.

There is a nice list of long range airliners here all of which have considerable endurance (but dont meet your multi-day requirement) and are all built (more or less) for servicing non stop routes from far locations.

Its worth noting that the general civilian use case of and airplane does not really lend to high endurance planes (multi day kinda stuff) in practice. Planes are generally for moving people and cargo in a timely manner and not really for taking off and just loitering for a while. The various militaries of the world simply move their aircraft around on aircraft carriers and launch them closer to where they are needed or fly high speed aircraft from farther away when needed. Airplanes also have the luxury (if permitted by laws and airspace regs) to move directly from point to point greatly reducing the distance traveled to get between locations over other methods of transit, again cutting down on travel time.

Some consider the space shuttle an aircraft and it was capable of multi day missions for the purpose of space exploration, satellite service and delivery and ISS transportation.


Are bigger and / or heavier aircraft more resistant to crosswind compared to smaller / lighter aircraft? When watching heavy crosswind video compilations, I noticed heavy aircraft like the A380 an B747 have a more stable approach compared to the B737 or A320 where the plane banks left and right on approach more frequently.

A constant crosswind affects all aircraft equally. A crosswind gust will however affect a lighter aircraft more than a heavy one due to lower inertia. The acceleration $a$ felt from the gust is

$$ F = m \times a \;\; \Leftrightarrow \;\; a = \frac{F}{m} $$

where $F$ is the force from the gust and $m$ is the total mass of the aircraft. The force is roughly proportional to the area that the wind sees, which scales with the scale factor squared: $ F \sim s^2 $. The mass however is proportional to the volume, which scales with the scale factor cubed: $ m \sim s^3 $. This results in less sideways acceleration from a wind gust for larger aircraft: $ a \sim s^2 / s^3 = 1 / s $. Therefore, there is less need to correct by sharply banking left or right.

Additionally, larger aircraft react to control inputs from the pilots more slowly (for the same reasons), which also makes them look more stable even when the pilots make sudden control inputs.


Do planes have keys? One thing I've always wondered is: do airplanes have keys that you put in the ignition to start?

And on the outside doors? Otherwise how are they secured and started?

I'm interested to know about a broad range of aircraft; from GA, all the way to airliners.

Small planes tend to have keys, but not all.  The bigger the plane the less likely a key is needed and once you get into jets, I can't think of any that need keys for engine starts.  The starting and securing of engines with no keys comes down to switches and knobs.

Likewise with exterior doors, on smaller planes including private end executive jets, you can find keyed exterior doors and luggage compartments.  With transport jets at airlines you won't find keys. To secure those doors the jet bridge is pulled away from the airplane so there is no physical access to the boarding door.


What measures can the aerospace industry take to deal with changes in the electronic industry that are incompatible with its own conservatism? The development of computer flight systems is characterised by lengthy certification processes, exceptionally rigorous testing regimes and a default position of extreme caution.

A change in any component at any layer in the hardware/software stack could introduce new incorrect behaviour. For example, microprocessors are so complex that different manufacturing revisions of the same model can introduce bugs.

As a result, these systems are very tightly specified at all levels and very slow to change, so that many systems still in production use what in most other contexts would be considered obsolete technology.

CPUs such as the 68040 and 80486 (both introduced around 1990) were designed into systems a quarter of a century ago that are still being produced today.

Summary of the problem

The pace of development of the electronics industry has accelerated hugely since the first generation of computerised flight control systems were introduced in the early 1970s, and is becoming increasingly incompatible with the needs of the aviation industry. It means that for example:

Devices now have manufacturing lifetimes of just a few years (compared with several times that a few decades ago).
Devices are now intended to have much shorter service lives than they used to (by orders of magnitude).
Increasingly tiny widths in microprocessors mean they succumb increasingly early to problems such as oxide breakdown.

Aerospace represents a very small portion of the manufacturers' business: their main customers make consumer devices, and have utterly different demands on the electronics industry from those of customers in aviation.

Research into the issue

These and other issues are outlined in some detail in Microelectronics Reliability: Physics-of-Failure Based Modeling and Lifetime Evaluation (and no doubt elsewhere - this was just one I found while trying to answer my own question).

The Aerospace Vehicle Systems Institute (AVSI) Consortium Project #17 Methods to Account for Accelerated Semiconductor Device Wear Out has attempted to quantify these risks.

The question

What can the aerospace industry do - or what is it already doing - to mitigate the problems and risks this poses?

The aviation industry is strongly cognisant of these risks.

At least one research programme has attempted to analyse them in depth, the Aerospace Vehicle Systems Institute (AVSI) Consortium Project #17 Methods to Account for Accelerated Semiconductor Device Wear Out.

The project ran for six years until 2007 with a budget of ~US$1.2 million.

However, the project's scope was analysis, development of guidelines, testing methods and so on, and did not include ways of addressing the fundamental problem.

A paper from the project Microelectronics Reliability: Physics-of-Failure Based Modeling and Lifetime Evaluation discusses some of the issues in depth.


Why does the faster-moving air over the static port not result in a lower static pressure? I understand the concept that the static port is measuring "static" pressure, meaning the pressure the air is exerting on its surroundings.  However, there is also Bernoulli's principle, which, put simply, states that as the velocity of air increases, the pressure it exerts on its surroundings decreases.  We see this in effect in venturis, of course, but it seems to me that Bernoulli's principle would also imply that the pressure observed from the static port would similarly decrease as the aircraft accelerates.  Obviously this doesn't happen however, since the altimeter is unaffected by acceleration.

Thus my question: why does the faster-moving air over the static port not lower the pressure it exerts?

Here is a video explanation of Bernoulli's principle being used in pitot-static systems, which seems to suggest the static port would indeed observe a pressure decrease (I've labeled the part I think the narrator is using as the static port):

Bernoulli's principle would also imply that the pressure observed from the static port would similarly decrease as the aircraft accelerates.

It's not that simple. Aircraft are complicated shapes. The fuselage is composed of all sorts of angles of attack, things sticking out into the airflow, and the pressure distribution of air across it is very uneven, just like that of a wing is. Take a look at this diagram from an FAA mechanics publication.

There are zones (like points 2,3, and 5 in the diagram) where the static pressure deviation is zero. This is where the engineers put the static ports.

Another way to think about this is that you're right that the airflow over the static ports should make the pressure lower--- but the question is: lower than what? The answer is: lower than the airflow's stagnation pressure, when the outside airflow is at rest (relative to the aircraft). Which happens at the nosecone, or the leading edge of the wing... or at the pitot tube. It's lower than that by the same amount that the pitot pressure is higher than ambient, making the pressure at the static port exactly ambient outside pressure. Which should make sense, because in the reference frame of the air, that static air isn't doing anything but sitting around waiting for an airplane to come by.

The Bernoulli effect does, however, have an overall average result: the cabin pressure in the airplane is lower than static, because the angle of attack of the various surfaces of the fuselage generates suction, pulling a small amount of air out of the cabin, just as it does for the wing if there are little holes in the wing. Which is why you get the little blip when you pull the Alternate Static open.


How do airplane "life jackets" compare to marine life jackets? I have recently taken up boating in addition to being a pilot, and that experience has given me a better understanding of marine life jackets, also called "personal floatation devices (PFDs)". For boats there are four different types of life jackets, Type I, II, III, and IV, with Type I being the best.

On my boat I typically wear an offshore inflatable life jacket which qualifies as a Type II and as backup I usually have a Type I sitting or hanging in the cabin where it can be easily reached. These are big, strong, bulky things. By comparison the "life jackets" I see stewardesses wear when they do the monotonous lecture at the beginning of the flight seem to be extremely small and flimsy. How do these things compare to marine life jackets?

Marine inflatable on the left, airline inflatable on the right.

Source - Been a pilot for years. Sailboat liveaboard for 1 year.

Aviation life jackets are reliable, but the overall intent is for a rescue operation to occur within hours.  One piece of advice is to stay away from debris.

Marine life jackets are designed to provide flotation for a longer amount of time.  They are also more durable due to the material in which they are constructed from.  Marine life jackets are also designed for multiple uses.


Who flies planes on ferry flights? Two questions regarding ferry flights:

When an aircraft has to be delivered, who flies it to the destination airport? Does the manufacturer have a dedicated crew for this or is it up to the airline to send someone over?
When an aircraft is sent to Victorville (Southern California Logistics Airport), who flies the plane? Is it a dedicated airline crew or is it a contracted-out service?

Thanks!

Ferry flights encompass much more than delivery and retirement flights.  Any time an airplane has a problem that can't be fixed on-site they can generally obtain a ferry permit to get it to an airport that the maintenance can be completed at.

At the airline I worked for, all flights, including initial delivery, were conducted by pilots on our seniority list and other airlines I'm familiar with have the same requirements in their contract language.  Our airplanes were manufactured in Brazil and a crew would be take an airline flight down to the Embraer factory, accept the airplane and fly it to a US customs station and then on to our main maintenance airport.  These flights were fairly uncommon and often went to very senior and management pilots.

Normal ferry flights for aircraft repositioning or maintenance needs were generally done by low-seniority reserve crews because those tended to be non-scheduled activity and show up with short notice.

In all cases though, at my airline, ferry flights were conducted by company pilots.  This can vary by airline and there probably isn't a universal definitive procedure common to every airline.


Is there any electrical component on an aircraft which can never be turned off by a pilot? Am I correct to assume that every electrical system on an aircraft can be manually switched OFF/ON by the Pilot OR is there indeed any system, on which the Pilot does not have the ability to switch OFF/ON ?

One example of a system that cannot be switched off by the pilot that is probably more common to all other airframes than just the one airframe I'm indicating.

Whenever electrical power is applied to a Gulfstream G550, whether it is powered by battery, generators, an apu, or some external power source, each engine's FADEC Electronic Engine Control (EEC) computer will be powered and the pilot can not switch them off.

The pilot could only indirectly turns them off by switching off all power sources.

However, when the engines are running, he can't even do that since there is an engine-driven generator dedicated to powering the EECs in the event of a total power loss.

In fact, while the engine is running or even windmilling above 35% rpm, the EEC's dedicated generator is supplying all power to the EEC and there is no switch or circuit protection that can be manipulated by the pilot to interrupt it.


Why is the V1-speed callout automated in modern commercial aircraft while VR is not? In some modern aircraft such as the Airbus A380 or Boeing B787, the callout of the V1 speed is automated through a synthetic voice, based on the V-speeds entered into the flight management system. However, the rotate speed VR is still announced by the Pilot Monitoring. Why is the VR callout not automated?

from my experience (A310, A320 family, A340), V1 and VR speeds are often very close together, sometimes they even are the same.

The automatic callout system can only output one signal at a time; during landings, one can often hear the decreasing radar altitude callouts being overlapped. Therefore, the VR callout would often supersede the - more safety relevant - V1 callout.


Long pole on the tail of a Cessna, what could it be? I live just near the finals for our local airport. Today while in the backyard I saw a Cessna fly overhead for landing, it was a tricycle gear and looked like a 150/152, but may have been a 172.
There was a long pole that appeared to be coming out of the tail, although there is a small chance it could have been from the wing on the other side of the aircraft from me. It wasn't very wide in diameter (I couldn't tell even an estimate), was maybe around two-thirds of the length of the aircraft, was painted the same white as the aircraft and capped at the end by a black piece that appeared to be hemispherical.

Does anybody know what this pole could be?

What you describe does not match any banner tow rig I am familiar with, and I have towed banners.

What it sounds like is a magnetometer, which might be on a survey aircraft. They can be on a boom (stinger) or sometimes towed.  I have seen them on Cessna 182, 210 and 208 aircraft, as tail mounted booms.

Magnetometers are typically used for geophysical survey work.  Towed magnetometers may be more sensitive and might be useful for detecting submarines, mines, etc. The P-3 typically has a rear boom with a magnetometer or magnetic anomaly detector (MAD).


What is the angle of Incidence of wing of Airbus A320? What is the Angle of Incidence/ Mounting Angle of the wing of AIRBUS A320?

The A320 wing is a complex design with no clear mention of chord or angle of incidence, as it is not topical to the operation of the aircraft. The wing is swept back, has variable symmetry from root to tip , as some say twisted. This info is not shared by Airbus.


Are there any autopilots that are capable of landing a damaged aircraft better than any human? How close are we to commercial aircraft with autopilots that can, as safely as theoretically possible, land an aircraft with damaged, missing, or otherwise inoperative control surfaces; or altered aerodynamics (e.g. ice on the wings), missing or misleading avionics (e.g., frozen pitot tubes), etc.?

Remember the Gimli Glider? An autopilot that could do that would be a good start.

And the computer in Space Shuttle Columbia made a valiant effort to keep the nose pointed in the right direction even as the aircraft was disintegrating.

Reconfigurable flight control systems have been a topic of research in military aircraft for decades. The science is existing and mature, but not an easy one: damage cannot be predefined, and therefore cannot be explicitly programmed in.

Classical re-configurable flight control systems attempt to re-program on the fly: the transfer function between input and expected aircraft response is constantly monitored, and if actual response differs from expected response, the gains in the loop are reset on the fly in order to get closer to a stable, matching response with neutral trim.

From this paper, which is almost 20 years old:

  The goal of control reconfiguration is to maintain handling qualities in the presence of a large universe of damage and failure modes. In contrast to robust control design methods of the past, the emphasis in control reconfiguration involves a combination of on-line parameter identification control redesign and/or adaptation for a degraded mode of flight.

Neural networks are now being implemented in reconfigurable flight control systems. These work as the synapses in our brain: there are a lot of possible connections, which are defined in our childhood as a result of positive and negative experiences. The system is self learning, from a multitude of outcomes that are labeled either "desirable" or "not desirable". Neural networking is what makes Google Translate possible; translating a language by programming is just not possible because of all of the different inflictions and double meanings in a language.

So in military aircraft an auto-damage-pilot is very well possible. Civil airliners are a different matter, not because of technology but because of certification. Safety is of the highest importance, and how can we prove that our re-configuration is actually helpful?


Can/do commercial flights change their flight path during flight? Looking at the paths of the same flight on two different days, I noticed they flew very different paths.

Short Path:1

YAY N184B TOPPS ENE PARCH1

Long Path:1

NIBAX G462 TUMAK UL602 ORSOL UL602 DAVUS UL602 TASMI UL602 ITBIT UM860 KABAN UT334
INB UL852 UDROS L621 REVDA UP193 CND UP193 KARIL UL624 LABUK UY444 ELMEK UL726 OKG
UL984 NOSPA TOLVU UN857 GIMER UT300 EVX UT176 LGL UN491 KOKOS UN585 REGHI UN480
ETIKI NATD DOVEY LACKS BERGH L454 OWENZ CAMRN CAMRN4

I asked a similar question in the past. This is what I want to know:

What are the reasons which can cause a commercial flight to change its path mid-route?
How it is planed and executed?
I am sure the captain is the final authority on this, but who else is informed?

1Route Source: FlightAware.

P.S.: I could not understand the routes at all.

A flight plan is just that, a plan.  A flight can deviate from its cleared route for many reasons, the most common of which are:

Weather
Traffic
Shortcuts

Weather reroutes are often initiated by the crew.

  Center, N12345 request 15 right for weather
  N12345 15 right approved for 100 nm, report direct XYZ.

Or they can be initiated by ATC

  N12345, Atlanta, your arrival into EWR is in perpetual holding, I can re-route you over PA or NY or do you need to divert? state intentions.

Large scale re-routing for weather will occur when an organized line of convection impacts a major route.  Even a short deviation for weather may result in an amended route if the controller has an alternate clearance he can put you on that works for you (being on a clearance and on-route is slightly less work for a controller than being on a carte-blanche deviation).

Traffic conflicts are usually short term vectors, but if you have an aircraft slowly overtaking you, you may be moved to a parallel route or have you altitude changed.  These, like the weather example above, would result in amended clearances.

Shortcuts are often requested to cut corners or try to make up some time lost in a long taxi on the ground.  These are usually crew initiated, but sometimes ATC will solicit them.  Regardless of what route is submitted in a flight plan, ATC will generally clear you via a preferred routing.  These routes aren't always the shortest distance between a departure and arrival and this is where shortcuts can be requested.  Usually this just means skipping a fix or getting direct routing to a later fix in your clearance.  The availability of shortcuts is a function of traffic, time of day, agreements between ATC sectors, what region you are in and what altitude you are at.

When you are on international flights, another issue you may run into is political and could result in some or all aircraft being routed to avoid certain airspace.

Lastly, your dispatcher may re-route you and ATC will clear you along a new route.

In all cases, whether deviation is pilot or controller initiated, both parties are in sync with what the airplane is doing, which will either be a vector or a new clearance.  Your dispatcher will be notified of this change automatically via their dispatch software (which is likely fed data from both ACARS and the FAA).


Is MIL-STD-1553 still used in modern aircraft? I am working on an assignment for my "Avionics Systems Design" class and I want to use MIL-STD-1553 for my aircraft system. But according to some shady blogs this STD has been deprecated or superseded by MIL-STD-1773.
If I don't want to use an optical solution, what is the best bus for my system?

MIL STD 1553 is alive and still in use.  Backwards compatibility will keep it around for some time.  Not only is it used in aircraft but also on spacecraft.

It tends to be used for control applications and lower data rates.  High volume data, for example from sensors, will employ different bus structures.  Many control, communications and guidance applications can readily be accomplished with 1553.

Having said that, I cannot say whether it is right for you application, as I know little about your application.  Noise, data rates, latency and other factors may cause you to look at different interconnection architectures. There are many competing bus/LAN structures.


What is airport tax used for? Since a very large sum of your ticket goes to airport tax, I was wondering how do they justify it and what is it used for?

Take your tax paid on your ticket and multiply it with the number of seats on that airplane and you realise that, per flight, the airports are receiving a substantial amount.

Is it all going to the government?

This question is very 'general' and just to get a loose idea of what the tax goes for. To get detailed information of every country is unnecessarily complex.

As jwenting pointed out, there isn't one "airport tax" - there's a whole bunch of them, and they're not all taxes (some are "fees").

airlines.org has a list of the common ones you'll pay in the USA, and approximately what they cost you.

Broadly the taxes you're paying on airline tickets break down into two categories:

Taxes that fund the Airport and Airway Trust Fund
These taxes pay for Air Traffic services (a little under half the operating butdget for ATC), maintenance of the airway infrastructure (radio navigational aids, RADAR sites, etc.), research and development to improve the airway infrastructure (e.g. NextGen), and to fund the Airport Improvement Program (which provides grants to airports, mainly to implement safety improvements).

The actual tax categories themselves break down further (again, airlines.org's breakdown is excellent).

Fees that fund DHS programs
These are often called "security taxes", and include things like the "September 11th fee", APHIS fees (for inspecting plants and livestock), and customs/immigration charges.
Note that all of these are technically fees, not taxes -- these are only levied when a flight is using the services the fee is funding (or at least that's what's supposed to happen. In practice the airline is responsible for paying the appropriate fee as a cost of doing business. They can recoup that cost any way they'd like (typically they lump it in with "taxes" or itemize it out on the ticket rather than including it in the base fare, so they can advertise lower base fares).

What about the little planes?
General aviation doesn't pay "ticket taxes", but that doesn't mean they get to escape paying for the infrastructure the flights are using. The government recognizes that the air traffic system costs money, and they like to ensure that the money is available.
Accordingly there is a tax levied on all aviation fuel purchased in the US:

Airlines currently pay about $0.04/gallon in taxes for the jet fuel they burn
Non-Airline flights burning jet fuel pay about $0.22/gallon in taxes
(the higher rate making up for the other taxes they're not paying)
Piston-powered planes burning aviation gasoline pay $0.19/gallon in taxes
(higher than what the airlines pay for jet fuel, but lower than the standard jet fuel tax because piston planes don't travel as far, and are thus less of a burden on the air transport system)


What aerodynamic implications would a fictional two-pronged fuselage have? Often I see some fictional futuristic aircraft with a two-pronged fuselage, as if they were absurdly oversized canards.

Is there any remote possibility for an aircraft to benefit from such a design?

What would the implications of it be in an actual aircraft?

picture merely demonstrative

Image source: Vic Viper, You are Cleared for Take-Off—kotaku.com

  EDIT: Just to clarify things up a little, since I kind of came out of nowhere asking this weirdness.
  These forked-wing designs is notoriously an aesthetic artifact, my intention is to design a handful of fictional aircraft for a hard-sci-fi novel. I find this design very beautiful but it just screams out impracticity, since I don't like the idea of designing something that wouldn't even take off, i'm after thoughts from specialists and enthusiasts about such design, to seek for any feasible excuses to use it, if it does not gives any positive point except for looking nice, i may just scrap it and get going with more rational designs.

I don't see any benefit (besides optics, but this is debatable). Compared to a single fuselage, these disadvantages exist:

More wetted surface for the same volume, so more friction drag.
Twin fuselages will obstruct the pilot's view more than one.
The two-pronged fuselage has a higher roll inertia, so it reduces agility.
Any instrumentation will be blocked at the side of the other fuselage, so you need more complex sensors and a sensor fusion algorithm.
The wake from the fuselage will affect the wing more than that of a single fuselage. One consequence will be lower maximum lift of the wing. This is compensated by forebody lift, but this lift is created in a very inefficient way.

Also, the fin in the picture is too small to provide sufficient directional stability without artificial enhancement.


How are pilots trained to prepare for crashes? I once read somewhere that pilots can go to some facilities so get trained for crashes.

  I actually went to a facility in New London, CT where they actually
  dunk you in water strapped in the seat of an airplane upside down and
  with your eyes closed in a big pool.

Is there any formal training for the commercial pilots to be prepared for crashes? If yes, how far do they go in training pilots and for what kind of crashes?

From my research to date it seems that most general aviation and commercial fixed wing pilots are instead trained rigorously in crash avoidance rather than crash escape. Flight attendants and other cabin staff drill regularly in crash preparation and cabin evacuation in several situations (gear-down landing, belly landing, water landing, fires blocking escape doors X, Y and Z, etc) but in an emergency, the job of the people behind the yokes is to first make sure the plane gets back on the ground in as close to one piece as possible; nobody's walking away from a nose-down dive into a mountain.


How could "aggressor" pilots fly foreign aircraft without speaking the language? Context

I watched a couple documentaries recently and found one where they were mentioning the training of American forces against Mi-24 that were captured and brought back to the US to test fly them. Shortly afterward General Chuck Yeager tweeted a quote from General Boyd saying

  Because of Yeager, we now know more about the MiG-15 than the Russians do.

after he flew one in 1953 that was captured during the Korean War.

Research

This piqued my curiosity because as far as I know Russian aircraft have:

Different units for instruments (metric system with km/h, meters etc.)
Different approach to instruments (as explained in this question)
Obviously, everything written in Cyrillic with alerts in Russian

I checked the page on Constant Peg program in the US to train aggressors and them flying foreign aircraft (like MiG 17, 21 and 23) as well as other aircraft. While I understand that this specific program is still classified, there are other occurrences of aircraft flown by "non-Russian speakers" or at least non-Natives.

While it is totally possible that General Chuck Yeager is fluent in Russian, I have some doubts about flying an aircraft where everything is written in another language from the fuel dump to the auto-pilot settings, and be able to operate it easily (on top of that without a manual).

Question

Now this led me to this question, how do you fly an aircraft without speaking the language and how do you read the instruments and their functions ?

I very much doubt that they just put sticky notes over all instrument panels with the label of instruments (but I could be wrong, who knows).

A couple of things come to mind that enable this:

you don't become a fighter pilot if you are not intelligent and highly motivated
you are not learning a new skill, just doing what you are already trained to do in an environment that just looks different (this would somewhat exclude Russian helicopters)
the list of things to learn is really not that long, I'm taking the liberty to throw in a guess of 100 items
you have a huge organization backing you up (translations as mentioned in comments, intelligence data etc.)

So: You are a person that is able to fly fighter jets, most probably you are damn good at it if you are given the opportunity to fly a fighter caught from the enemy.

You learn new stuff easily, and you are thrilled to do this, which of course helps in the learning process. Your organization provides you with pretty much every bit of information about the task you are about to undertake, translated manuals etc.

Regarding the cockpit language barrier, it's not that hard to learn the labels on switches and gauges. For example the picture in the question: I took a not-so-wild guess that it's an altimeter, checked with translator and yes: высота is altitude in English (pronounced something like vysota but that really doesn't matter). From now on, when I see text that says высота, I know it means altitude. On Russian planes the pilot just has to remember the altitude is in meters, but since the label looks "weird" I don't think there's much chance of a mix-up.

Anyways, when operating a fighter jet, you learn the location and operation of the critical switches and systems by heart, you do not browse around the cockpit searching for switches when you need to do something.

Once you've become familiar with the user interface, the basic flying will be pretty much the same as in any western fighter.

P.S. There's one thing that really helps: Cyrillic numbers are not used anymore :)

P.P.S. this short film on Air&Space Magazine website tells very nicely and in a compact package of the findings made by Chuck Yager (Major at the time) and General Albert Boyd during test flights of the MiG-15. Thorough testing gave USAF critical information of the capabilities and weaknesses of the enemy fighter, giving them strategic and operational advantage.


What is area in equation of lift?Does it remain constant during flight? I am beginner & learning aerodynamics concept. What is area in equation of lift(L) =Coffecient of lift x area x density x square of velocity/2. Does increase in angle of attack increases the area & thus increasing lift?

The área $A$ in lift equation $L=\frac{1}{2} \rho AV^{2}C_{L}$ is a reference area, so you can choose the one you prefer, but some election can be more apropiate than others depending on what you want to compute. For example if you are going to relate lift coefficient with drag one, the reference area should be the same, in this case a good selection will be the projected area in lift direction (aka planform area). It has the drawback that it depends on angle of attack/incidence since the true area is the same but lift vector changes. Another well selected area could be the true area (aka wetted) when working with drag, specially when friction drag is dominant considering that viscous stresses are proporcional to this area.

I give you some references when this is better explained:

  There are several different areas from which to choose when developing the reference area used in the drag equation. If we think of drag as being caused by friction between the air and the body, a logical choice would be the total surface area (As) of the body. If we think of drag as being a resistance to the flow, a more logical choice would be the frontal area (Af) of the body which is perpendicular to the flow direction. This is the area shown in blue on the figure. Finally, if we want to compare with the lift coefficient, we should use the same area used to derive the lift coefficient, the wing area, (Aw). Each of the various areas are proportional to the other areas, as designated by the "~" sign on the figure. Since the drag coefficient is determined experimentally, by measuring the drag and measuring the area and performing the necessary math to produce the coefficient, we are free to use any area which can be easily measured. If we choose the wing area, the computed coefficient has a different value than if we choose the cross-sectional area, but the drag is the same, and the coefficients are related by the ratio of the areas. In practice, drag coefficients are reported based on a wide variety of object areas.

Size effects on drag - NASA

  A comment is in order regarding the reference area Sin Eqs. (2.3) to (2.5). This
  is nothing other than just a reference area, suitably chosen for the definition of the
  force and moment coefficients. Beginning students in aerodynamics frequently want
  to think that S should be the total wetted area of the airplane. (Wetted area is the
  actual surface area of the material making up the skin of the airplane-it is the total
  surface area that is in actual contact with, i.e., wetted by, the fluid in which the body
  is immersed.) Indeed, the wetted surface area is the surface on which the pressure
  and shear stress distributions are acting; hence it is a meaningful geometric quantity
  when one is discussing aerodynamic force. However, the wetted surface area is not
  easily calculated, especially for complex body shapes. In contrast, it is much easier
  to calculate the planform area of a wing, that is, the projected area that we see when
  we look down on the wing.

Aircraft performance and design - John D. Anderson


How robust are modern parachutes to folding errors, wear, or other problems? My 8 year old recently got a guided tour of the parachute-packing station at the local sport airport. Afterwards she asked me what happens if the parachute is improperly packed. Since it seemed to me that each parachute is packed by one person, there is no checking of human error.

How resilient are modern sport parachutes to packing errors? I would include in that any improper packing method or the packer overlooking some detail such as wear or tears. I'm not a parachutist so I don't know the intricacies to ask a more nuanced question.

Proud father update: A bit belated, but she's no longer eight years old and she enjoys, in her words, floating on imagination.

Qualification: I am a master parachute rigger, taught the sport for 10 years and have packed a couple of thousand emergency parachutes.

I can put an apartment-size piece of nylon into a purse in under 5 minutes, and guarantee that it will open. How nicely it opens is a different question. It usually takes about 45 minutes to service an emergency parachute - 20 minutes to inspect it, 10  to fold it up nicely, another 10 to stuff it into the pack, then the paperwork. Double that time if it's a large 2-passenger parachute.

The "fold it up nicely" part is to make it go into the pack without any unsightly bulges, and the emergency packs are never a nice open bag like the main - the canopy has to be shaped around the closing apparatus and the spring-loaded extraction chute has to fit in the middle. Very little of this process has anything to do with ensuring it opens when needed.

A packer would have to be spectacularly incompetent to fold a canopy in a way that would cause it to malfunction. If you feel the fabric used to make main parachutes you will find that it is extremely slippery - good luck keeping that stuff in the proper place when it goes into the bag, but you don't need to. These things sort themselves out quite nicely most of the time.

There are two important tools used in packing emergency packs - one is appropriately called the Death Strap. It is wrapped around the middle of the canopy as you are folding it into the bag, and if you forget to remove it the canopy will not open. The other is a locking pin used to close each part of the pack in stages. Your mistake will probably make the front page of the local newspaper and involve a lot of time with your lawyer, so packers typically only own one of each and all tools are counted after each job.

Going back to the incompetent packer for a moment - the main parachute is usually packed by the owner, and very occasionally you need to open and re-close the pack. If you are lazy or rushed it is very easy to close the main pack in a way that prevents it from opening. Owners (almost) never open their emergency packs, and riggers follow a standard process to prevent these errors from happening.


Does a military equivalent to civil ATC exist? There are specific military ATC facilities, e.g. at military airfields, or temporary airstrips:

Mobile ATC towers used by US Air National Guard’s for access to hurricane-devastated areas. Source: AAR

But is there usually an overall specific military ATC system for training and/or war operations so that:

Military aircraft / formations are kept separated.
Drones and aircraft don't collide.
Military traffic is well-ordered over large areas.

The scope for answers could be NATO or other large military organization worldwide.

Yes, for their airspace.

Generally speaking, US Military has its own ATC for domestic military installations and other venues such as US Navy aircraft carriers. Most of these military-staffed airports are rarely transited by civilian aircraft, and are instead designed to let the military run their own show with their own aircraft.

At some airports around the country which provide provide joint military-civilian use, such as Charleston Air Force Base in South Carolina, Scott Air Force Base in Illinois, and Marine Corps Air Station Yuma in Arizona. These airports have significant military traffic and also allow civilian aviation operations. At such airports, typically FAA controllers are in place and military aircraft work with them.

Most of the airspace in the US is owned by Air Route Traffic Control Centers, which are staffed exclusively by FAA-employed civilian controllers. These controllers handle all air traffic between airports, including military aircraft transiting the national airspace system, which means that civilian and military facilities all around the country must interact with each other on a daily basis. As a result, both civilian and military air traffic controllers use a commonly shared phraseology.

For exclusive military use, there is special use airspace which includes:

  ... restricted airspace, prohibited airspace, military operations
  areas (MOA), warning areas, alert areas, temporary flight restriction
  (TFR), national security areas, and controlled firing areas, typically
  up to FL180 or 18,000 ft above sea level.

Source

As discussed in this question, supersonic operations in the US are also performed in airspace which belongs exclusively to military.


What makes a visual approach quicker than an ILS approach? In the question What's the preferred approach for a passenger jet? it is mentioned that pilots prefer Visual Approaches over ILS Approaches, as they are a lot quicker.

Why would a visual approach be quicker than an ILS approach?

Visual approaches can be conducted from any point around the airport where the runway is in sight, e.g. if you are approaching from the north of the airport, you can be vectored to a position which is closer to the airport and be cleared for a visual approach from a position where you can turn visually and reach the runway threshold.
ILS approaches begin at the approach gate before the final approach fix (FAF) for the localizer and glidepath indications to be correctly used and the aircraft configured for the approach. The FAF is at many airport around 10 NM from the runway threshold at 3.000ft AGL, thus placing the approach gate at around 12-14 NM.
A pilot on a forum has summed it up like this:

Visual approaches are usually shorter than instrument approaches. By that, I mean that the turn to final is accomplished closer to the runway when on a visual approach.
When traffic is heavier, or weather is around, or it's hazy, smoggy, etc, ATC will usually route everyone out for an ILS.
Many times, a pilot will call runway in sight, yet be sequenced behind someone who is on the ILS. So, he'll get routed out for an ILS approach, even though he'll go visual within the cockpit.
Airport size doesn't have a whole lot to do with it. Also, even though an aircraft may be on a visual approach, that does not absolve ATC of separation resposibility.

(Source: www.airliners.net - Author: Tom in NO)
Effectively, this means that visual approaches tend to be shorter and quicker than ILS approaches with vectors to the FAF/approach gate.


How can an aircraft turn if the horizontal force component is zero? Here is the simplest coordinated turn diagram

Picture from https://physics.stackexchange.com/questions/100169/pendulum-in-a-turning-airplane

Being:

$L$ = aerodynamic lift

$\tau$ = angle between vertical component and lift

$Fc$ = centrifugal "force"

In many books you can read that:

$L\cdot sin(\tau) = Fc = m \cdot (V^2)/R$
 where $R$ is the curvature radius.

Then, how can an aircraft turn if there is no net force? I mean, from Newton's second law we have that $F = m \cdot a$ and in this case centrifugal force compensates for lift component in the horizontal plane.

It is easier if we look only at the forces experienced by the aircraft, and in an inertial frame of reference

In this revised diagram, the vertical component of the lift balances the weight, which is vertical. There is a remaining horizontal component of the lift, and this causes the turning.

"Centrifugal force" does not exist (and is not needed) in an inertial frame of reference

The problem with the original diagram in the question is it superimposes an imaginary force, the centrifugal force, upon the real list of forces on the aircraft.

It is hard for the general public to understand Newton's first law of motion, that any object tends to travel in a straight line when no force is acting it. It is hard for them to understand that motion in a circle is dramatically different from straight-line, constant-speed motion, since both seem (in a sense) steady or continuous.

"Centrifugal force" is a term produced by humans to describe what they think must be happening

In the case of a passenger going round a corner in the car, this inward force is applied by the outer door of the car, against which the passenger ends up leaning during the turn. It is an inward (centripetal) force, but for the general public who is not aware of the special status of inertial frames of reference will likely use the car (which seems large and solid and therefore plausible) as a frame of reference and say "something must be pushing me against the door" rather than "the door is pushing me towards the centre of the circle".

Because of this use of a non-inertial frame of reference, the general public explanation needs to an extra force to explain why objects seem to accelerate towards the outer door of the car and the passenger feels pressed against it. In an inertial frame of reference it is the outer door of the car pressing in on the passenger, and accelerating towards any objects moving freely inside the car.

In everyday life we sometimes use special frames of reference for convenience

We say the sun "comes up" in the morning, rather than the earth "rotates bringing the sun into view". This is because it is convenient for humans to use a non-inertial, but readily identifiable, frame of reference. It does not mean that people really think that the sun orbits around a stationary earth.

It is perfectly reasonable to imagine the sun travelling around the earth, for convenience, but if we want to make calculations about space travel with multiple objects (stars, planets etc) affecting a body's motion, it will get very complicated indeed to add in all the numerous centrifugal forces etc we would have to add in. It would be simpler to use an inertial frame of reference, and all objects moving relatively simply in relation to that.

Likewise we can learn to be sophisticated about circular motion. Let the general public speak of "centrifugal force" as this simplifies conversation, but when trying to calculate things, use an inertial frame of reference to avoid agony.

Even apparently inertial frames of reference may have unconsidered rotation  in relation to a larger-scale environment

Jan Hudec in the comments below brilliantly deflates the above criticism of rotating frames of reference by pointing out that even my notionally inertial frame of reference (the earth) is in fact rotating, so that the gravitational force measured is lower than it would be for a plane moving similarly above a non-rotating earth, i.e. is attenuated by a centrifugal component. Ouch!

And of course the earth is rotating around the sun, and the sun around the galaxy, etc:

Big fleas have little fleas,
Upon their backs to bite 'em,
And little fleas have lesser fleas,
and so, ad infinitum.

So it is just a question of how much rotation one wants to accept as part of one's frame of reference. My suggestion is that when a questioner is feeling puzzled as the original poster was, a good way to break the problem down is to keep the frame of reference outside the rotation being studied, so that the studied rotation appears as a rotation: in this case the only acceleration (and therefore force on the orbiting object) will be centripetal.


How does retracting flaps help extend the glide of an aircraft? As per the video from Smithsonian channel

BA flight 38's captain retracted the flaps of the Boeing 777 by 5 degrees to extend glide, to travel further.  Why?

Some answers presume that raising flaps reduces lift.

That is wrong.*

All it does is to increase angle of attack, until the change in flap setting is so severe that the airplane stalls. Only then will the airplane lose lift. With a smaller flap setting, the pitch trim changes and the airplane pitches up a little to keep lift constant. If the (auto)pilot does not correct the pitch trim for the new flap setting, the airplane will settle at a new, higher speed. Here, however, we can be sure that the autopilot kept speed constant (it only disengaged at 150 ft, and then the copilot took over. He certainly did not dive to pick up speed at this altitude!).

Raising the flaps does, however, reduce drag. See below for the A320; with a B777 the result will not be all too different.

A320 polar with 3 different flap settings (picture source)

Assume the airplane flies at a lift coefficient of 1.2 with flaps at 35°. Raising them to the next setting of 22.5° will move the operating point horizontally forward to the 22.5°-polar curve. Here the airplane flies at the same lift, but a smaller drag coefficient.

Retracting the flaps completely will not allow it to stay at this lift coefficient because the baseline polar stops below a lift coefficient of 0.9. The airplane will stall and needs to accelerate to keep flying. Only then will the airplane have to pick up speed.

I remember two occasions where that happened to me and raising the flaps saved my butt:

Landing in a field that turned out to be an asparagus field on short final. Ugh! Poor preparation - from higher up the field looked fine, even and smooth without vegetation. Coming closer I saw the rows of earth under which the asparagus grows (see here for a picture how this looks). Flying an ASW-20C and with flaps on "L", I changed them back to "4" and made a 90° turn to a different, adjacent field. I had played with the flaps at altitude before, so I knew that switching between "L" and "4" does not affect altitude.
Landing the SB-8 on an unfamiliar airfield that sits on a hill. Landing against the wind means I fly trough the leeward side of the hill during approach, but I did not keep some margin for the downdraft but started final at an altitude appropriate for a normal airfield without downdraft. I quickly noticed what was going on and switched the flaps from +8° back to 0° without changing speed and also retracted the wheel again. I just made it. When I climbed out of the airplane, someone came closer with a big grin and revealed to me that just a week before another pilot (who was as unfamiliar with the airfield as I was) had landed his glider into the bushes which mark the airfield perimeter. Of course, I also had tried out the effect of different flap settings at altitude when getting familiar with the SB-8.

* Since this statement raises blood pressure in others, let me explain. I only posted here after one answer after the next repeated this meme. Now some authors have edited and improved their answer. Would that had happened without clear words? Judge for yourself.

Now to the issue of lift loss: When the flaps move up (slowly), the lift force decreases just a tiny bit. The aircraft starts to sink, which immediately raises the angle of attack and puts an end to any further lift loss. Liftforce is immediately restored to its old value. That is why I simplified this process and said there is no lift loss, because there effectively isn't.

Next, the change in pitching moments from flap movement lets the aircraft pitch down unless pilot or autopilot retrim for the new flap setting. This is a much slower process because it involves a rotation of the airplane and its lengthwise acceleration.


Does diving after a take-off help gaining altitude? I have often read fictions about aircraft, where a pilot does an action that I cannot explain:

During a takeoff with an heavy aircraft (four motors for example), the pilot rolls to the end of the airstrip, and starts to climb.
Then he says: I am too heavy to climb enough in order to avoid the mountain/trees/whatever obstacle in front of us.
So the pilot starts to dive to the ground in order to gain more speed, and then he climbs again and is able to have enough altitude.

How do you explain this action?

Considering the drag, why does the dive gain enough energy to go to an altitude above the one reach by the take off?

I might not be clear, please don't hesitate to ask details.
Here is a schema:

    Not enough         /Climb enough
        /  \          /
strip  /    \        /
              -------

When an aircraft can barely climb after take-off, it may be flying on what is called 'the backside' of the power curve.

Flying at very low speed:

costs a lot of power because of high induced drag
means that the engines are inefficient because they are optimised for higher speeds.

As a result, the excess power available, that is the difference between the required power and the maximum available power, is very low when the aircraft flies close to the minimum flight speed. And the excess power is what is needed to climb the aircraft.

When the aircraft is flying below the speed at which the best angle of climb is achieved (Vx), it will be able to improve its climb angle by accelerating. To do so, the aircraft needs to use available power to accelerate, instead of using the power to climb.

Stopping the climb or even descending a bit will convert the available excess power and optionally height (potential energy) into speed. While this initially does not give extra clearance above the obstacle, the available excess power increases drastically. This in turn gives the ability to climb at a much steeper angle, allowing the aircraft to clear the obstacle.


How do pilots avoid clouds under night VFR? When flying under visual flight rules (VFR), pilots have to be able to see far enough away to be able to avoid running into other aircraft or the ground.  Therefore, VFR flight requires good visibility with a high (or no) cloud ceiling; this is known as visual meteorological conditions (VMC).  It also requires that pilots avoid clouds like the plague, since clouds (on Earth, at least) tend to be on the opaque side, and a cloud that you can't see through could potentially be hiding something that it would be very bad to run into (such as someone else's aircraft).

Avoiding clouds is easy enough during the daytime, if the weather is good (the big white things tend to be fairly visible as long as you aren't actually inside one), but, in many countries (including such biggies as the US, France, and Australia), VFR flight is also permitted at night.  As clouds are not usually polite enough to illuminate themselves for the benefit of nearby pilots, they tend to blend in rather well with the dark sky (except sometimes when bright moonlight is present), the only hint of their presence being that they occlude background stars (which provides absolutely no information about whether those stars are being hidden by a small cloud close by, or by a big cloud further away, and depends on the stars being easily visible to begin with [which is not always the case, even at night]).

So how do pilots avoid clouds when flying VFR at night?

I will caveat my answer by saying that most of my night flying has been under IFR, but because of that I have lots of experience going in and out of clouds at night.

It starts with a good weather brief, and don’t forget to ask for PIREPS that might cover areas further away from the field.  True enough the bases can be ragged, and little puffies can lurk in unexpected places, but if you know where the layers are called you are well on your way to avoiding being at the same altitude.

To add to one of the comments, moonlight is helpful, but so is ground lighting.  At night distant clouds can be difficult to see, but you can use ground lighting to gauge where the coverage is.  For example, if your eyes can trace a lighted road off in the distance, but at approximately 20 degrees below the horizon the car lights become blurry, then disappear, it is probably because of a cloud between you!  Angle away, or descend below the deck until the horizontal visibility range increases.

If you start skimming clouds you will know it immediately because your anti-collision light will blossom and reflect red all over the inside of the cockpit.  If you still have ground lights in sight and you know the clouds are stratified, I would start a gentle descent.  If there are a lot of vertical buildups and you pop into one and lose sight of the ground, make a level 180 and get out of there.  Most non-instrument rated pilots are taught to deal with inadvertent IMC in this way.

As I mentioned in my answer to your other question, make sound risk decisions.  If you are uncomfortable with the weather conditions or your ability to remain clear of clouds, then choose to not fly VFR at night.  But once you get a few night flights under your belt I think you will find that they can be very enjoyable when conditions are good.  It opens up a whole new perspective on things!


Definition of "Rotation Speed" vs "Lift Off Speed" vs "Fly Off Speed" Is rotation speed and lift-off speed ever used interchangeably? (AMENDED Question) Is lift off speed and fly off speed the same? (See supplemental info below)

I thought I clearly understood the difference between these two terms:

Rotation is the point at which the longitudinal axis of the aircraft is "rotated" about its lateral axis from a horizontal orientation in order to increase the angle of attack of the wing.
Lift-off is the moment when the aircraft is no longer in contact with the surface (i.e. ground or water).

However, I was reading something the other day where the two terms appeared to be used interchangeably, which I accepted at first, but now its bothering me. It was a POH and it said that for normal take-off rotate at 70-75 KIAS. However, the POH also says that the "Normal takeoff distance in Section 5 is based on lift off at 65 KIAS."

Found it, here is the text:

So to get the Normal takeoff performance, you can't use normal takeoff procedure?

By the way, after further reading of the POH, I don't think the "lift off at 65 KIAS" is a typo. See the maximum performance takeoff which says to rotate ASAP and "fly off" at 61 KIAS the single engine stall speed of the aircraft. (See Copy Below).

I think they were just hard-core back then. So this raises another terminology question "fly off" speed. So we have rotation speed, lift off speed, and fly off speed. My interpretation is that for max performance takeoff rotate ASAP, if airplane flies below 61 KIAS, then keep it in ground effect until 61 KIAS, then fly off.

Your original understanding is correct.  Rotation speed and liftoff speed are two different things, the former being the speed you are to make an input, and the latter the speed at which you get a result (weight off wheels).

That's almost certainly a typo and is supposed to say 75kts (my guess), which would be the demonstrated maximum distance to weight-off-wheels with rotation initiated late in the 70-75 kt range. Manuals published as integrated handbooks like that tend to never get revised unless a new edition is published, and the Cougar was only in production for a couple of years making a little over 100 aircraft, so I'd be surprised if there is a newer edition than the 1978 one, especially if it involved publishing a new handbook over a minor typo on an out of production airplane.

On a light aircraft the input and result are just about instantaneous and a rotation initiated at 75kt will result in a liftoff pretty much at 75kt or maybe a knot or two higher.  On high performance aircraft rotation speed and actual liftoff may be 1 or 2 seconds apart and it's more obvious that they are different things.


When may commercial pilots release their shoulder harness? In one answer to a similar question I found a hint to 14 CFR 91.105:

  (b) Each required flight crewmember of a U.S.-registered civil
  aircraft shall, during takeoff and landing, keep his or her shoulder
  harness fastened while at his or her assigned duty station.

Now, I assume this also applies to Part 121 operations?

What exactly does that mean with regards to when are the shoulder harnesses released in practice? Is there an altitude (i.e. 10000ft) at which pilots usually release the shoulder straps - is that maybe company-specific?

You essentially have two questions, which I will answer in turn:

When may commerical pilots release their shoulder harnesses when operating under commercial operations rules such as §121
When do such pilots actually release their harnesses in practice

Regarding your first question:

14 CFR 91.105 does generally apply to commercial operators and air carriers. However, §121, §135, and §137 each provide equivalent regulations which duplicate or exceed the language found in §91.105.

14 CFR 91.105 states, in pertinent part:

  (b) Each required flight crewmember of a U.S.-registered civil
  aircraft shall, during takeoff and landing, keep his or her shoulder
  harness fastened while at his or her assigned duty station. This
  paragraph does not apply if—

  (1) The seat at the crewmember's station is not equipped with a
  shoulder harness; or

  (2) The crewmember would be unable to perform required duties with the
  shoulder harness fastened.

14 CFR 121.311 states, in pertinent part:

  (h) Each occupant of a seat equipped with a shoulder harness or with a combined safety belt and shoulder harness must have the shoulder harness or combined safety belt and shoulder harness properly secured about that occupant during takeoff and landing, except that a shoulder harness that is not combined with a safety belt may be unfastened if the occupant cannot perform the required duties with the shoulder harness fastened.

14 CFR 135.171 states, in pertinent part:

  (b) Each flight crewmember occupying a station equipped with a shoulder harness must fasten the shoulder harness during takeoff and landing, except that the shoulder harness may be unfastened if the crewmember cannot perform the required duties with the shoulder harness fastened.

14 CFR 137.42 states, in pertinent part:

  No person may operate an aircraft in operations required to be conducted under part 137 without a safety belt and shoulder harness properly secured about that person except that the shoulder harness need not be fastened if that person would be unable to perform required duties with the shoulder harness fastened.

Under each regulation, the flight crewmember may generally unfasten his or her shoulder harness at any times other than during takeoff and landing, or if the shoulder harness would interfere with performing required duties. The one exception to these allowances is found under §121 in instances where the shoulder harness and safety belt are combined1.

These allowances notwithstanding, a certificate holder may include in its General Operating Manual provisions that flight crewmembers must adhere to requirements that exceed those given by regulation.

Regarding your second question:

In practice I never release my shoulder harnesses from the time I seat myself and fasten my safety belt and shoulder harness until the aircraft has come to a stop and I am ready to leave my seat at the end of the flight. I have also never seen a fellow pilot at my air carrier release his or her shoulder harnesses while in flight. Others will doubtless have different experiences.

Prior to my time with my present employer I have witnessed pilots who make a practice of not wearing the installed shoulder harness at all (given the circumstances I don't think they would have had a very good argument that it would otherwise interfere with performing their duties). I have also witnessed pilots who unfasten both the shoulder harness and safety belt after landing while still taxing at the end of a flight. This later practice is not against regulation2 but may be of questionable judgment in some cases.

1 §121 requirements for combined safety belt and shoulder harness:

14 CFR 121.311 also gives the following, in regards to the requirements for aircraft to be equipped with combined safety belts and shoulder harnesses:

  (f) No person may operate a transport category airplane that was type certificated after January 1, 1958, or a nontransport category airplane manufactured after March 20, 1997, unless it is equipped at each flight deck station with a combined safety belt and shoulder harness that meets the applicable requirements specified in §25.785 of this chapter, effective March 6, 1980, except that—

  (1) Shoulder harnesses and combined safety belt and shoulder harnesses that were approved and installed before March 6, 1980, may continue to be used; and

  (2) Safety belt and shoulder harness restraint systems may be designed to the inertia load factors established under the certification basis of the airplane.

I read this to mean that, for aircraft specified under §121.311(f) above, unless a shoulder harness was approved and installed before 6 March 1980, then the aircraft must be equipped at each flight deck station with a combined safety belt and shoulder harness. Furthermore, under the requirements of §121.311(h), when the flight deck stations is so equipped with the combined safety belt and shoulder harness, no provision of §121 allows for that shoulder harness to be unfastened during takeoff and landing, even if the shoulder harness would interfere with performing required duties. Presumably the approval process for those harness systems would ensure that no interference would be possible.

2 14 CFR 91.107 does generally require that each person on board a U.S.-registered civil aircraft must have a safety belt and any installed shoulder harness properly secured about him or her during movement on the surface. However, this requirement does not apply to required flight crewmembers or to any operations conducted under §121, §125, or §135. See §91.107(b).


How do navigation displays depict turn anticipation? I'm working on a navigation display for a simulation and I want to know if someone can explain me how the navigation display displays the "curved lines" for fly-by waypoints.I know how to calculate the distance needed for turn anticipation and the turn radius but how would a real ND draw this ? I attached a screenshot for the ADMAG2X departure for gatwick from a simulator navigation display but why does the turn start after "KKW02" and "KKW02" is no overfly waypoint ? :)

First, the ND doesn't calculate anything. It just renders the navigation data sent to it from the FMS. Yes, it can pan and rotate and scale the nav data. It also displays the compass rose with heading or track from the IRS/AHRS and various data fields around the edge.

The green line on your ND is the lateral path computed by the FMS. The source data for the path is the flight plan which is a list of waypoints and associated leg types. The FMS builds the path by connecting the waypoints as defined by the leg types (ref ARINC 424).

As you noted, it also builds transitions between each of the legs. They can be fly-over or fly-by transitions. The 'normal' transition is a fly-by. Within procedures defined in the nav database, some waypoints will be coded as fly-over. Others will be fly-over due to the specific leg type. Some legs end at fixes, others end at a 'floating' waypoint such as an altitude.

For altitude terminated legs the FMS can predict roughly where it will be, but ultimately the end of the leg is only known with certainty when the altitude is reached at which time you just did a fly-over of the 'fix'.

In your example, KKW02 is a fly-over because it is altitude terminated. Takeoff legs are typically coded in the database as a VA (Heading to Altitude) or CA (Course to Altitude) leg, commonly terminating at 400 feet above the runway altitude.

The FMS builds the transitions based on the actual geometry of the inbound and outbound legs, bank angle limits from the aircraft manufacturer, aircraft speed, altitude, and what it knows of the wind. The resulting transition will be an arc that is tangent to both the inbound and outbound legs. For large course changes like the one shown in your example, it may require two arcs.

Thus the path is made up of a series of straights and arcs. The straights are defined by their start and end positions (latitude/longitude). Arcs have the start and end positions (lat/lon) as well as the radius of the curve (NM) and the center of the arc (lat/lon).

The display gets the aircraft position and track from the FMS/GPS/IRS and heading
from the IRS. Based on the pilot's selected display range the display plots out the path on the display.

RTCA DO-283 Minimum Operational Performance Standards for Required Navigation Performance for Area Navigation covers the generation of the path. RTCA DO-257, Minimum Operational Performance Standards for the Depiction of Navigation Information on Electronic Maps is the standard for NDs. How the manufacturers actually accomplish it is up to them and they don't share that information.


Are runways "one-way"? Do runways always handle traffic in the same direction? Another question asked how runways were labelled left and right (8L and 8R, for example). But of course "left" and "right" depend on your perspective. If you were approaching from the opposite direction, then left would be right and vice versa.

Does this mean that runways only handle traffic coming from the same direction all of the time? Are there no ambidextrous runways that flip depending on the prevailing winds or whims of ATC?

As noted in the linked question to the question you linked to (this one), runways are almost always bidirectional. In your example, the other runway would be simply numbered 18 higher or lower, for 180 degrees off. Thus, the runways would be 26R and 26L - the "L" and "R" would swap, because you are pointed at them the opposite way. You can see this in the diagram of LAX below (src):

Yes, generally they flip based on prevailing winds, though I can't imagine they flip based on the "whims" of ATC often. Most airports will have a "calm wind runway", which is the preferred runway for operations in calm or near-calm winds.

Due to terrain or similar factors, some runways may be only usable one direction, but both directions will still be numbered, as you will takeoff and land pointing different directions (for example, Lukla airport in Nepal). Alternatively, as Jan Hudec noted, some will operate one-way, such as TNCM, though again, both runways are numbered. Occasionally, the opposite direction is not numbered, though this is rare.


Does angle of attack change in a sustained climb? I saw this question on a closed Facebook group, generating wildly differing answers. So I thought I would ask it here.

You're in a C172 flying straight and level at 5000 feet and 100 knots IAS. You apply full power and go into a sustained climb maintaining this airspeed.

Has the angle of attack increased, decreased, or remained the same?

We have seen that

  A climbing aircraft needs less aerodynamic lift than in horizontal flight, not more.

this means that if we keep constant airspeed and if we do not alter the configuration, the angle of attack will be (slightly) smaller, at least until the air density does not change.

As your assumption is that

  You apply full power

to enter the sustained climb, you will have even more thrust during the climb, and this will reduce even more the needed lift. This, together with the fact that you are slightly accelerating, reduces even more the angle of attack.


Does ground effect scale 1:1 with wingpsan? The rule I have been taught is that ground effect begins within 1 wingspan of the ground.

What is the derivation of this measurement?  Is it actually true, or just an urban-legend/rule-of-thumb style teaching aid?

If it is a valid way to assess where ground effect begins for any given airplane, what limitations does it have?  Do particularly heavy or airplanes with exceptionally long wingspans not fit this rule the same as a smaller more common build of aircraft?

It's most definitely not urban legend. However, it also does not scale 1-1 with wingspan. Rather, it scales nonlinearly with above ground height to span ratio ($h/b$). The simplest analytical prediction for ground effect can be derived from potential theory and the circulation theory of lift.

We know that the wing can be modeled as lifting line consisting of a line of vortex bound to the wing and trailing vortices that look like horseshoes. The trailing vortices induce downwash on the wing and everywhere else. But what about at the ground directly underneath the wing? Due to the tangency boundary condition of non-viscous flow, induced downwash must necessarily be zero everywhere on the ground.

Within the context of circulation theory of lift, the only way we can achieve this is if we have a mirror wing underneath the ground with the ground plane being the plane of symmetry, like this:

Since the image wing is exactly inverted, it produces upwash that reduces the overall downwash on the real wing. In the super simplified case of a single horseshoe vortex (which is incorrect), after some maths, the induced downwash at the wing root is now:

$$w_i=-\frac{\Gamma}{\pi b}\frac{16(\frac{h}{b})^2}{1+16(\frac{h}{b})^2}=w_{i_\infty}\frac{16(\frac{h}{b})^2}{1+16(\frac{h}{b})^2}$$

where $w_{i_\infty}$ is the downwash induced without the ground image (i.e. free-air). Turns out the latter factor is an ok approximation of total reduction of induced drag in ground effect as well. As you can see, at half wing span away from the ground, we have 80% of the free-air induced drag; at one full wing span away, we are at 94%. The effect falls away quickly.

You can read this MIT lecture on ground effect (from which I've taken the above diagram) for the derivation of the simplified ground effect prediction. More precise ground effect accounting can be found in references such as Raymer and ESDU Item 72023.


What about an airfoil's shape makes air flow faster around it? An airfoil's shape causes air above the wing to move faster than below the wing to allow for the difference in air pressure as dictated by Bernoulli's principle. This is what many sources say, but I have yet to see any explain what about the airfoil's shape or why exactly air speeds up above but doesn't below the airfoil. If I were to assume, maybe it would have something to do with the law of conservation of momentum or energy?
If you could send any sources, that would be much appreciated too!

The flow of a viscous fluid can be described using the Navier-Stokes equations. This includes describing flow of air around an airfoil. Your assumption about conservation of momentum or energy is correct, both of these enter in the derivation of Navier-Stokes, together with conservation of mass:

[The Navier-Stokes Equations] describe how the velocity, pressure, temperature, and density of a moving fluid are related. [...]
The Navier-Stokes equations consists of a time-dependent continuity equation for conservation of mass, three time-dependent conservation of momentum equations and a time-dependent conservation of energy equation.

(NASA, emphasis mine)
Since there is no generic way to analytically solve Navier-Stokes, numerical approximations are typically used to derive a solution (see Computational Fluid Dynamics). When solving for the flow around a wing, the solutions show faster flow at lower pressure above the wing and slower flow at higher pressure below the wing. This might not be the simple answer you are looking for, but any answer that does not involve complex maths usually oversimplifies something.
While you are right that Bernoulli's principle relates the speed of the flow and its pressure, you have to be careful about implying causality from this:

Bernoulli-only explanations imply that a speed difference arises from causes other than a pressure difference, and that the speed difference then leads to a pressure difference by Bernoulli's principle. This implied one-way causation is a misconception. The real cause-and-effect relationship between pressure and velocity is reciprocal.

(Wikipedia)
To understand why airfoils are shaped the way they are, I recommend you have a look at the NASA page on Aerodynamic Forces. They have a good description of how the total force is generated from the pressure difference:


What are some disadvantages that come with a design like a B-2 spirit bomber? Here is a B-2 Spirit:

source

Source

Many different things can get in the way with a design like a B-2. Although it has really good stealth and looks, does it have any disadvantages that come with the good stealth and looks?

What kind of disadvantages would this aircraft have of an
airliners design or another bombers design like the B-52 or B-1?
What system does this aircraft use to overcome not having
stabilizers?
Why have only 22 ever been built?

The main problem with the B-2 Spirit (or any flying wing aircraft, for that matter) is that they are statically unstable.

Source

If the lift vector of the wing acts before the center of gravity (as is the usual case when only wings are considered), any perturbation which results in an increase in angle of attack results in a positive moment about the center of gravity, which further increases the angle of attack an so on.

The only way to control such an aircraft is through computers, which continuously detect any changes in the aircraft attitude and apply corrections as required, as it is near impossible (or incredibly taxing) for human pilots to fly the aircraft.

This is the method used in order to 'fly' the B-2 Spirit in the absence of a horizontal stabilizer. If there is any problem with the flight computer (which is remote) or with the sensors supplying data to it, the aircraft will become unflyable and crash.

Another control issue with the B-2 is that the aircraft has little directional stability with no vertical tail. The swept wing offers some stability, though not in the same level as a vertical tail.

Source

Actually, only 21 of these were built, for the following reasons:

The B-2 is costly; by costly I mean probably the most expensive aircraft ever built. With a total program cost of over 45b USD, each aircraft costs a whopping 2.1b USD (which was caused due to reduction in numbers from the initial 132). Also, the (hourly) operating costs of B-2 are twice that of other bombers in the USAF fleet.
With the dissolution of the Soviet Union, the B-2 had effectively become an aircraft without a mission, as it was primarily designed to penetrate Soviet air defence systems.


A380 reverse thrust on only half the engines I noticed on this video of an A380 landing in rain that reverse thrust was applied to only the inboard engines. Do the outboard engines not have reverse thrusters? If they don't, then why not? If they do, then why not use them on a slippery landing?

Yes, the outboard engines do not have reverse thrust to avoid them kicking up dirt. On a regular runway they will be outside of the concrete surface, so using reverse thrust there will incur the risk of foreign object damage.

This was already covered in this answer.


To what extent is LLF forecast of icing conditions a concern in VMC? First off, I know that flying into actual icing conditions in an aircraft not equipped to handle icing is a Very Bad Idea ™ for any number of reasons. That's not what I am asking about here.

Rather, the situation I am asking about is where (for example) the low-level forecast indicates a possibility of or the existence of (particularly, light or moderate) icing conditions, while visual meteorological conditions prevail throughout the area of one's flight, and there are few or no clouds (scattered or clear) nearby.

In such conditions, is icing an actual concern?

Well if you have a forecast of icing, and you go outside and the sky is clear, the forecast is wrong no?

In any case, when you are flying around VFR and there is the possibility of icing on your route, your main concern is the freezing level, and whether you can stay well below it in the event you encounter rain or drizzle or whatever (aside from visibility requirements of course).  If you will find yourself close to or above the freezing level where you plan to cruise, you have to avoid visible moisture, period.

You're VFR so you will be avoiding cloud anyway, but if there is anything coming down out of the clouds you will pass through, you need to be a couple thousand feet below the freezing level to be safe.

So, if you're going from a to b, at 5000 ft, and the freezing level is 8000 ft, and there is light rain forecast with icing expected, say between 8000 and 15000ft, you're fine at 5000 ft IF, the freezing level is going to stay well above you on your route, but you need to be confident that temperatures aren't going to drop and force you lower part way there.

If the sky is clear or scattered, nice VFR in other words, you are unlikely to see icing in a forecast anyway.


Do all Class B and Class C towers operate 24/7? For Class B airports, I think the answer is realistically yes, due to traffic flows. How about Class C airports? Are there any legal requirements that it has to operate in 24/7, or is a convention?

The short answer is no. It's easy to find examples of class C towers that aren't 24/7, by checking in the Chart Supplement. Two examples are KXNA (as mentioned in the comments) which operates 1130-0500Z and KHSV, which operates 1200-0600Z. Note that the airspace changes when the tower is closed: KXNA becomes class G, and KHSV becomes class E.

As for class B, I would also assume that they're 24/7. I checked a few (KATL, KBOS, KSEA) in the Chart Supplement and they are indeed 24/7 but I don't feel like checking them all :-)


What type of aircraft did these drop tanks come from? I am trying to identify what type of plane my two recently acquired drop tanks came from. They measure 23" in diameter and about 12' long. Made of aluminum and "ALCOA" appears in raised letters on the rear end. Come apart into three pieces sealed by large o-ring style gaskets and have a metal rod that goes directly through the center of the three sections that screws together to hold the 3 sections together.

I looked all over the web as best I could and can't find anything that matches. Have two metal attachment points. No fins. Front more blunted. Rear more angular with small (5") removable tail cone that allows access to the main nut that allows the three sections to be separated (or mated and held snug). Fuel filler in front of attachment points. Very simple internal plumbing consisting of a fuel filter and a two short pieces of stainless tubing.

I believe they are at least 30 years old based on the story of the man I got them from.

I have embedded one picture of the tank, but there are more pictures available on the Ebay listing.

It looks like they were used some on the F-80 like you said, but also on RF-80s, T-33s, F-94s, and Navy TO-1s, TV-1s.  They look similar to the Misawa tanks, but are different.

http://tailhooktopics.blogspot.com/2017/06/lockheed-pf-80-shooting-star-tip-tanks.html

https://commons.wikimedia.org/wiki/File:TV-1_Shooting_Star_at_NAS_Oakland_in_1954.jpg


How does one reset an attitude indicator that doesn't have a cage? I was up flying today – VFR – and the attitude indicator tumbled. It's a 6-year-old RC Allen 22-7, without the ability to cage, so I just wound up letting it be all off-kilter until things stabilized... which took almost an hour. The vacuum was in the green the entire flight, and at no point was I doing any wild maneuvering.

Is there anything I could have done to accelerate the process? Could I have caused damage by not landing and shutting down?

Only a mechanical inspection is likely to give you a definitive answer for why the AI tumbled, but typically it'll happen for one of two reasons: either the vacuum pump has decided to take a break, in which case the AI gyros slow down and will eventually no longer hold the instrument up, or you've exceeded the instrument's pitch and/or bank limits and caused it to tumble.

In the case of the former, there's not much you can do in a stock -172 about that. Section 3 in the PIM just tells to verify that the vacuum pump is operating with normal parameters (green arc is 4.5-5.5 in.hg). I've seen PA-28Rs with electric vacuum pumps that served as standbys to the engine-driven ones, but never seen one in a -172, not even as an STC mod. You could always try increasing the throttle; pumps in older aircraft will sometimes fail to perform as expected at lower throttle settings, but there's no guarantee there.

The latter case can happen during maneuvering flight if you exceed +/-30 degrees of pitch and 60 degrees of bank on a non-acrobatic AI. This can inadvertently happen when certain training maneuvers such as power-on or cross-controlled stalls are performed... enthusiastically. I've also seen tumbling occur during spin training. And then there was the Husky we used for banner-towing and which was pitched to 45 degrees on a regular basis during banner picks (waivers are wonderful things). The AI tumbled so regularly, the owner gave up on having mechanics reset it.

But yea, should this happen to you again, run any checklists that might exist on the topic (either directly concerned with the AI or with the vacuum pump system), and switch to partial panel ops if necessary.


What's the difference between FAA Part 61 and Part 141 training? I've got schools with both part approvals in my area. I'm just interested in recreational flying, I'm not sure which part is more suited to my needs.

What are the differences I should consider before choosing one or the other?

There's no singular right answer, it's up to the individual and how he or she learns best. The biggest difference between the two you'll find is that part 141 schools are always very structured in their training regiment. That is not to say part 61 isn't (nor does it imply that it's better for everyone), it's just that part 61 does things according to what they wish with less FAA oversight.

You might know that under part 141, the earliest you can get your ticket is 35 hours, while part 61 requires a minimum of 40 hours. Don't let that red herring influence you; almost everyone takes more than 40 hours regardless of the school type.


Can an increased current rating of a Ground Power Unit damage an aircraft? Assuming you are working on an Aircraft, where the Ground Power Unit (GPU) is rated at 28V DC with max. 1000 amperes. What is the danger involved if your are to increase the current rating of the GPU to 1200 amps?

I find the easiest way to think about Volts and Amps is that the voltage is "pushed" and the amps are "pulled".

This is the same with pretty much any kind of power supply, whether we're talking mobile phones or planes.

To that end, the voltage requirement always needs to match. If your device is expecting 28Volts in DC then your power supply MUST provide 28Volts in DC - anything else is likely to damage it, could cause a danger and almost certainly won't work.

But current (Amps) is different - your power supply needs to meet or exceed the current demands. So if your device can pull up to 1000 Amps, the power supply MUST be able to provide 1000 Amps or more.

So, to answer your two possible questions. You can increase the Power Supply (GPU) to a 1200 Amp model (or beyond) with no ill effects, but your device (The aircraft) must have a current demand that meets or is less than that.