Which aircraft have made notable use of lateral asymmetry? I'm asking about functional asymmetry - doors on one side but not the other wouldn't count.

Examples

I can think of three examples:

experiments with oblique wing designs, such as NASA's utterly hideous AD-1, designed apparently by Burt Rutan
displaced fuselage designs, such as the Blohm & Voss BV 141 or (another Burt Rutan aircraft), the Boomerang
all single-propeller aircraft, in which the torque of the engine exerts asymmetrical forces on the aircraft

Symmetrical asymmetry doesn't count

(Then there are some that I don't think really count - for example, the Wright brothers' Flyer 1 placed the engine and the pilot side-by-side, but since they were intended to balance each other out and the twin propellors were symmetrically placed, that counts as an attempt at symmetry as far as I am concerned!)

Other examples, and the reason for their asymmetrical design

Are there any other good examples? The more ugly and wrong-looking, the better.

I'm interested in the problems that the asymmetry aimed to solve - for example, oblique wing designs aimed to procure aerodynamic advantages (which turned out to be at the expense of handling issues), or Rutan's Boomerang which "was intended to be a multi-engine aircraft that in the event of failure of a single engine would not become dangerously difficult to control due to asymmetric thrust" (Wikipedia)

Visual reference

Just for reference, here's the AD-1 (NASA, via Wikipedia):

... and the BV 141 (Deutsche Bundesarchiv, via Wikipedia):

There are quite a few asymmetric aircraft, most of which are,

experimental
engine test beds

A good example of experimental aircraft is the NASA F-16XL

F-16XL with supersonic laminar flow control experiment (black area on left wing, front) or "glove." Image from nasa.gov

Aircraft used as engine test beds are usually asymmetric. The following image shows a B-47 Stratojet used as engine test bed for the the Orenda engine earmarked for Avro Arrow program.

Image from silverhawkauthor.com

A closeup of the rear:

Image from google

English Electric Canberra PR9s had offset canopies.

By MilborneOne - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13266605

So did the de Havilland Sea Vixens.

By Yeovilton_Vixen_2009-001.tif: Nigel Ishderivative work: Cobatfor - This file was derived from  Yeovilton Vixen 2009-001.tif: , CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19477903

Of course, all 'conventional' helicopters (with tail rotors on one side) are asymmetric, but I don't think that's what you're after here.

Also, see this page and the Wikipedia page on asymmetric aircraft. As a disclaimer, I wouldn't call any of these aircraft 'ugly'.


Why ground a plane while fueling? Why does a plane need to be grounded while fueling, but we never ground our cars? Does the potential for a spark magically exist for an airborne vehicle but not for an earth bound one?

On cars I think it's because static charges don't build up as much but theoretically it's still possible for a spark to occur when the nozzle touches the tank inlet and provides a ground path.

On airplanes there are two issues:

Static charges built up in the airframe in flight.  For this it is essential to ground the aircraft before the fuel nozzle is brought to the tank inlet.  The risk is of a spark just before the nozzle touches the filler neck, the nozzle itself being grounded, which is right at the location where the air fuel ratio is favourable to ignition. It's also a good idea to touch the nozzle to the fuel cap before you remove it in case the tank isn't adequately bonded to the rest of the airframe, but I don't think anybody does this.

The other one is static charges built up within the fuel tank by the shearing action of the incoming fuel column when adding fuel.  In a large refueling operation, the column of fuel builds huge static charges within the mass of fuel itself, which result in static discharges within the fuel (there are films that show this; a freakin' light show).

Most dangerous is fueling from a plastic can.  When I used to fuel my airplane from cans I made a grounding wire arrangement that bonded the fuel in the can, the fuel tank flange and the ground (using a nail on the end of the wire pushed into the dirt) together.


Does an F/A-18 require a lot of rudder in turns? I am an aspiring Navy fighter pilot and I use an X-Plane add on for FA-18 Hornet as a fighter. It's made by a creator named Colimata. I think the turns are unrealistic. When I begin a bank a lot of rudder is required to keep coordinated. Does anyone know if this is realistic?

I used to be an avionics instructor teaching maintenance type courses for the F/A-18. I have plenty of hours flying in the simulator where I would get the students to conduct navigation flights to familiarise themselves with the operation of the instruments as well as flight controls. I can confirm 100% that the rudder is barely touched once airborne. There is no need to co-ordinate turns as the flight control system does it for you. These things are incredibly easy to fly. It is the controlling of your radios, weapons, FLIR, navigating and keeping an eye on the RADAR all at the same time that is the hard part.


What is the average cost/timeframe of obtaining a pilot job at a major passenger airline in the US? Please note that I'm not asking about getting a certificate good enough for flying a wide-body passenger jet (see related question). Rather, I'm asking about getting from zero flying experience to an actual pilot/co-pilot job at a major US airline (AA/Delta/UA/Southwest).

Perhaps some regulatory organization maintains such a statistics? Or even the airlines themselves?

I'm well aware that people can have various career paths (from ex-military pilots to guys who paid for 10000 flights hours out of their pockets), but with 40,000+ pilots employed by major airlines there must be a statistically-significant median experience.

The distribution of how pilots get to the majors is bimodal.

If you can get a military pilot slot and give 4-10 years to the USAF, you can then get an FAA ATP and start interviewing at whatever majors are hiring and have your ex-mil buddies on the hiring board. Great way to get in at FedEx or UPS. This costs a few grand for your ATP but that's about it.

If you can't get a military slot, getting up to the point you can instruct from nothing can vary wildly in cost. The accelerated flight training programs will do this for around $70,000. Next you instruct until you hit 135 mins and do either that or instructing. At this point you shouldn't be paying for time anymore. When you get on at a regional you'll sit right seat for a few to many years then you'll upgrade. After about 1.5-2 years in the left seat you'll have the bare minimums to apply at a major.


Why are the affected engine's bleed and pack switched off when there is an engine bleed under MEL? My question mainly pertains to A320neo's equipped with PW engines. The MEL procedure states that the crew has to switch off the affected side's engine bleed, and its associated pack pushbutton to off.

One of the reasons given by my company is that with the engine operating at idle it may cause a reduction in the air supply and then lead to the automatic closure of the remaining bleed system due to a low pressure related failure.

However, this doesn't convince me, and I also tried raising it but I haven't gotten a response. The reason why it doesn't convince me is that one engine bleed can supply both packs, and the idle N1 automatically increases once the crossbleed is placed to open.

It's not unique to the neo and the PW engine option.
Yes a single engine can supply both packs, but it's a big load on the remaining bleed system that can lead to its loss when used for a long duration.
An example from 2013 is Swiss A320 near Marseille on Sep 12th 2013, loss of cabin pressure (avherald.com). The plane was dispatched with 1 pneumatic system, the operator did not have the revised MEL procedure, and the working pneumatic system failed.
An explanation given in an Operations Engineering Bulletin for the AIR ENG 1(2) BLEED FAULT is:

(...) due to undetected failure, the remaining bleed may not succeed in sustaining this increase in air demand. In that case, it can result in an overheat of the remaining engine bleed and subsequent loss of the entire engine bleed system, leading to possible emergency descents. (...)

There is also the Airbus publication, Avoiding Dual Bleed Loss (airbus.com; PDF), from which:

Over the past years, the A320 family fleet experienced a significant number of dual air engine bleed losses. The consequences of these losses ranged from in-flight turn backs shortly after take-off, to full blown cabin depressurization events and flight diversions. (...)
The dual bleed loss events usually happen when one bleed fails, resulting in the remaining bleed on the other engine to compensate for it. (...)
In case of one engine bleed loss, the remaining bleed fails when the Fan Air Valve (FAV) does not let enough cold air reach the Precooler (PCE).

What's unique to the PW engine from my discussion with you, is that the one engine taxi procedure calls for crossbleed to AUTO, because the higher-idle of ON (used with CFM/IAE) would negate the fuel savings. For the ceo engines, one engine taxi is not a long duration, and the denser air on ground helps the precooler.
The MEL item being asked about is still as outlined by Airbus above.


Why are the cockpit controls of airplanes so complicated? For a layman like myself, the cockpit of every single modern airplane that I've laid my eyes on seems like a complex, intimidating mess with knobs, buttons, screens and levers literally covering every single square centimeter. Every time when seeing this, from my point of view, chaos of control surfaces and indicators, I'm always thinking to myself "This HAS to be possible to make easier!"

Maybe my intuition is correct. Maybe it isn't. Anyhow, I can see a lot of possible reasons why one actually would want cockpits to be designed in this way. Maybe it makes it harder for an amateur to just wing it (no pun intended) and make it looks like (s)he knows what (s)he's doing. Maybe it forces the pilot to really understand every single nuance of the plane and its operation before even being able to taxiing. Maybe it fosters speed and security in an emergency situation by having everything accessible right away, accessible through muscle memory on the part of the pilot.

Or maybe most cockpit designers like to make the operation of aircraft a pain in the behind for everybody else. I don't know.

What's the design philosophy behind the design of the cockpit controls?

I would argue that the controls of an aircraft are not complicated, but rather that they are simply foreign to you.

In the vast majority of cases, the various controls in the aircraft do one thing:  Turn something on, or turn it off.  They are quite simple actually, but what makes it appear complicated to you is that there are so many of them.  As you learn about the airplane (especially modern ones) you will see that these individual controls are grouped together by system, in a way that actually makes pretty good sense.

To put it in perspective, let's say that you had never seen a laptop computer before:

This...  thing (remember, you've never seen one before!) has 94 buttons on the top alone!  It has all kinds of little jacks and plugs on the outside.  It has things that pop open from the side.  It's just...  complicated.

Then someone points out that most of the buttons on the top are buttons that you can press to make a letter show up on the screen.  This takes much of the mystery out of the complicated mess on the top, but then as you start to learn more you figure out that some of the less commonly keys are grouped together by function.  You have the arrow keys, the function keys, the key modifiers, the CD controls...  Suddenly it doesn't seem quite so complicated anymore.

You complain to your friend that the monitor (hey, we've learned a fancy new word!) is a little too small, and they suggest that you hook up an external monitor.  We can do that??  Of course, that's what this port is for.  Cool, now that's one less mystery.  This goes on, and before long you can even pick up a different brand of laptop, with different buttons and pretty much figure it out on your own.  Before long...  the mystery is gone and it's just a laptop computer.

And so it goes with airplanes.  Newer airplanes are being designed with fewer switches and gauges.  Take a look at the progression in the Falcon 900 series aircraft:

Falcon 900B

Falcon 900EX

Falcon 900EX-EASy

Each iteration has fewer and fewer controls and instruments.  You may even say that they look less complicated.  However, I can assure you that each newer model has far more capabilities and a lot more to learn in order to understand and safely fly the airplane.  They each have the full capability of the model before it, along with additional features and more to learn.  Certain systems no longer have switches or dials and you have to look through different menus in order to access them.

Appearances... can be deceiving.


How does an airliner adjust and move exactly over the coloured lines before stopping in front of the jetways? How does an airliner adjust and move exactly over the coloured lines before stopping in front of the jetways?

There are a few different ways. Probably the most low-tech and widespread is by marshaller guidance, which is a person outside the aircraft guiding the pilots by means of visual signals:

The exact hand signals to use are defined by the ICAO, meaning that they are identical no matter where in the world you are flying.
Most larger airport have some sort of "docking system" at some or all of their stands. There are different types, but they are all external systems that provide visual guidance for the pilots, just like a marshaller. The simplets form is a big mirror next to the parking position:

More common are electronic docking systems, which use various sensors to detect the exact position of the aircraft and calculate any corrections needed by the pilots. They are placed directly in front of the position where the aircraft must stop, typically mounted on the terminal building or a high mast:


How do aircraft windshields not crack when flying at supersonic speeds through precipitation? Randall Munroe (author of XKCD and What If), once wrote a What If about how fast one would have to drive a car in order to have rain water shatter the windshield.

In the post he mentions that water hitting a windshield at supersonic speeds has the potential to shatter the glass.**

The article, unfortunately, is only talking about automobile glass.  And while I'm sure it's true that automobile glass would shatter if rain hit it at super sonic speeds, it's pretty clear to me that the glass on supersonic aircraft is not shattering when it flies through precipitation.

So, what is done to a super sonic aircraft's windshield to keep it from shattering when flying through precipitation?

** Here's a block quote of all the pertinent text in the post from Munroe.  I figured I'd post it for those who are Too Lazy™ to go read the article.  (Though, honestly, you ought to.  It's informative and entertaining.)

  Here's what happens when a raindrop hits a glass surface at high speed:
  When the droplet makes contact with the surface, a shockwave travels back up through the droplet...

  ...Normally, this shockwave would move at the speed of sound within the liquid—about 1300 m/s, four times faster than in air. However, at high impact speeds, this shockwave actually moves substantially faster than the speed of sound in water.

  The water is squeezed between the incoming drop and the glass surface, which makes it squirt sideways in all directions. These jets of water can move even faster than the original (already supersonic) droplet, and even faster than the shockwaves we mentioned...

  ...The sharp pulse from the shockwave can crack glass...

  ...In addition to the direct downward pressure, the water jetting sideways can cause damage, too. If the material has any microscopic holes, cracks, or bumps, those jets can strike them and create new cracks or widen existing ones.

  source: What If #93, Randall Munroe

The Concorde had 2 discrete windshields for different stages of flight. During subsonic flight (mainly take off and landing) the nose was drooped and the inner windshield was exposed. For supersonic flight the Concorde would raise its drop nose which also contained an outer windshield that would cover the inner windows. This outer windshield was made of special heat resistant glass that was also tinted. It can be assumed that this outer windshield could also withstand any pressure exerted during supersonic flight. The bigger problem in the Concorde was heat: the nose had to have fuel pumped through it just to keep it cool enough. For what it's worth the Concorde flew at about 50,000ft when it was supersonic; this is well above most weather systems.

Drooped

(source)

In Place

(source)

If you are interested, there is an old paper you can find here that covers windshield failures and lists the Concorde as the #2 aircraft for it (747 comes in at #1) over the years the paper covers. Interestingly enough here is a table of causes:

Heat fatigue and manufacturing defects (what I assume they mean by saying the windshield itself is the issue) are the primary cause of the issue according to this data. Here is one of the patents filed for what appears to be the Concorde windshield; it's an interesting read!

Going further, if we look at the most extreme case of supersonic planes, the SR-71 Blackbird, the inside of the windshield was in excess of 120°C and the exterior of the nose area would be closer to 260°C during supersonic flight. This would turn any water into vapor if it came into contact with the surface. While I don't know the specifics of that, the Blackbird flew at close to 80,000ft, so it too was above most (if not all) weather. I can't yet find an official quote of what that windshield was made of, but heat was still a larger issue than hitting rain.

(source)

Here is an interesting paper on what happens to water droplets when they suddenly encounter a high-speed airstream. It might suggest that such an impact with an aircraft would also cause vaporization, aside from the heat of the surface causing it.

Even subsonic aircraft windshields are extremely strong; they can take continuous hits from solid hail chunks and not shatter.

(source)


What is the meaning of "altimeter three-zero-one-one"? I've been listening to a lot of liveatc.net recently (mostly at CYVR).

What does it mean when the ATC give an "altimeter" reading (usually around the 3000 area).

  Altimeter three-zero-one-one.

I'm assuming it's like a QNH setting? But not in kPa?

Addon Question:

Is inches of mercury specific to the Americas? North America or other places as well? I've only flown in South Africa where we use kPA (SI). We'd get information from tower along the lines of QNH 1013.

That is a QNH altimeter setting in inches of mercury, with the decimal omitted.  So in the case given, that is a QNH of 30.11 inHg or about 1020 hPa.


Wing dihedral in a biplane Would a biplane be able to fly if the upper and lower wings were in opposite dihedral? Imagine a wing configuration similar to the fictional "X-wing" design from StarWars. What would be the theoretical pros and cons of using such an approach? Ignore the engines, fuselage, tail, etc

What happens if you take it to its logical extreme and make all wings at 45 degree angles?

There's a line of airplanes that have already done it, at least a bit.
The Rutan tandem wing Quickie designs are exactly that configuration, except that the wings are radically staggered because the forward one is the trimming/pitch control surface, and the dihedral/anhedral angles are shallower.  But looked at from straight ahead, there it is.

The anhedral of the front wing is mostly there because that's where the wheels go. Versions of the 2 seat Q2 that have a conventional tricycle gear, have a nearly straight lower wing because the most of the anhedral is "in the way" (tips near the ground become a problem now without wheels there).
The problem with the configuration is other than being able to put the gear at the wing tips in Rutan's application, there's no point to it.  That anhedral wings cancel out the dihedral wings, form a roll stability perspective, making the result more or less the same as making all the wings straight.  If you do want to put the wheels there, you have to make the spars do double duty as really long leaf springs (bending loads from landing are much harder on the spars than flight loads), and there are ground handling issues with the wheels so far apart.
So might as well avoid the hassles of fabricating bent spar beams and make them straight across in the first place, or at least with more normal dihedral angles. It's more or less just something that looked cool from a science fiction perspective.


ground staff radio controll Hoping someone can help me in understand who is who when using a aviation radio. eg: "Delta Delta, Tac"
I understand some of them but am still quite unsure as to who is a sierra, whiskey, alpha etc. hoping someone can help a newbie out

Delta, ta[ngo], sierra, whiskey, alpha, etc... are all letters in the ICAO phonetic alphabet, which is a system used to speak letters in a way they can be clearly understood over the radio. Just as letters like "D" and "T" have no particular meaning on their own, these letters can be used to mean many different things depending on the context.

The letters could be part of a callsign (to identify an aircraft, e.g. "november four four charlie kilo" is a particular Cessna Citation), taxiways at an airport ("turn right on taxiway hotel" means turn right onto the taxiway marked "h"), to spell out the name of a location when needed to avoid ambiguity, really anything where spelling out one or more letters is required on the radio.

You might want to read up on the basics of how aviation radio communications are conducted to help understand the format of typical communications.


What are some symptoms of a clogged fuel filter? I can certainly imagine one of the symptoms could potentially be engine fuel starvation. If the fuel flow to the engine isn't totally blocked, how can one recognize a clogged fuel filter?

The effect would almost certainly be similar to running lean - ie, if not enough fuel is making it to combustion your fuel to air ratio will be that of a lean mixture
Effects of lean mixture include

Overheating
Knocking sound when running, perhaps even popping/backfiring from exhaust
The RPM will "hunt", meaning it will increase/decrease attempting to find a stable RPM
Slow to pickup, ie when increasing throttle it will not change quickly RPM as it should


Why does the Boeing 737 have 5 x the passenger fatalities of the Airbus 320? I thought I'd compare the accident rates of these two similar, competing, very successful aircraft.

                    737     A320

Introduced          1968    1988
Number Built        8104    6171
Accidents/Incidents  329      60
Hull Loss Accidents  154      23
Fatalities          4287     782

These figures are from the respective Wikipedia pages. I assume they have not been the subject of edit-war falsification by fanboys of planemakers.

I wondered what might be the reason for the 737 seeming a much less safe plane.

The 737 design is 20 years older?

But it's still in production, so 1988...current 737s can be built with many of the same safety features found in an A320 produced the same year. Were 3,500 of those fatalities in the first 20 years?

There are lots more older less-safe 737s being flown by corner-cutting budget airlines in third-world kleptocracies?

Are there that many 40-year old 737s in the hands of incompetent airlines?

The 8,104 737s have, on average, flown many times more cycles than the 6,171 A320s?

But they address the same market, why would their usage differ so markedly?

The 737s have, together, flown many times more passenger-miles than the A320s?

See above. Plus I imagine older 737s have mostly been retired.

My speculation doesn't seem very convincing to me. Is there a better explanation supported by reputable studies?

For one, the early 737s had a design flaw which allowed the rudder to reach a hard-over position, and get stuck there. Boeing initially dragged their feet in rectifying this, so it took a number of accidents before this design flaw was corrected. This is a major contributor to the high number of fatalities in the early operational years.

To have a more meaningful comparison, I would suggest to compare the fatalities per year, so the status in operational procedures can be excluded as a factor. As others have pointed out, this should give a more equal basis for a comparison.

If you look at fatalities per year, beginning in 2000, these numbers emerge:

Now you need to factor in the number of flight hours per type per year, which I do not have available. But I would expect that the low fatality rate in the early 2000s is more due to the small number of A320s around. But if we just compare the 737 NG with the A320, this advantage is reversed, and still the A320 comes out slightly ahead.

But thankfully, there are very few accidents for each type per year, so the statistical base is too low for a meaningful comparison. If we want to draw any conclusions, it could be that the A320 is indeed a safer aircraft, but the certainty of this conclusion is very low, being based on a very small number of accidents.


Did the SR-71 have any windshields? In this video of a more complex cockpit, belonging to the SR-71, why don't we see any windshields? Were they not required for the SR-71, or are they not captured in this video? If windshields were actually not there, then please elaborate why!

Video

It did!
You can see a bit of it here

or in the reflection here

And here it is from the exterior


Is "hacking small planes" a separate or larger problem from/than general small-aircraft security? Apparently the DHS has issued a "hacking alert" for small aircraft:

  The alert warns if a hacker gained physical access to certain small planes, they could attach a common device to its wiring. This could provide false flight data including altitude and airspeed, as well as possible access to the autopilot system, potentially leaving a pilot unable to tell whether the reading was accurate and potentially lose control of the aircraft.

This involves physical access to the aircraft, which the FAA said "is unlikely."

Is this particularly different from other attacks not involving "computer hacking" that could be mounted given physical access to an aircraft? For example, is this in some way much less likely to be caught via a pre-flight inspection than any other attack on avionics or other equipment, or much harder to mitigate in flight?

Or is this just more Security Theatre from Homeland Security, raising what's essentially already a known mode of failure (potentially from reasons other than a "hacking attack") for which the aviation community already has procedures in place to mitigate it and continues to monitor and improve these procedures as technology changes over time?

It sounds like just another theoretical scenario.
If that "hacker" wanted to do harm, he could also loosen a few bolts, disrupt the engine timing, plant a bomb, you name it.

Sure, in today's world of aircraft loaded with electronic systems the operators have little knowledge of and trust implicitly, it's quite possible that something that deliberately feeds wrong data to those systems goes unnoticed than disrupting the cylinder timing or mixture control cables would have in the past, but it's still a highly remote possibility.

What it sounds to like me is someone taking the scare of "hackers" breaking into your car and taking over the engine electronics to the next level.


What are the rules for PIC change during flight? Per the FAA FARs - Are there any rules governing a "change of who is the PIC during flight, and thus who can log hours? Say a friend and I go flying together - can we switch as PIC half way through and each log half the time? Also, would the time not spent as PIC (if it is possible to switch) be logged as total flight time in addition to the time spent as PIC?

@ymb1 is correct in that it does not matter who the legal pilot in command is per §1.1.  What does matter is following the rules in §61.51(e).

  (e) Logging pilot-in-command flight time. (1) A sport, recreational, private, commercial, or airline transport pilot may log pilot in command flight time for flights-

    (i) When the pilot is the sole manipulator of the controls of an aircraft for which the pilot is rated, or has sport pilot privileges for that category and class of aircraft, if the aircraft class rating is appropriate;

    (ii) When the pilot is the sole occupant in the aircraft;

    (iii) When the pilot, except for a holder of a sport or recreational pilot certificate, acts as pilot in command of an aircraft for which more than one pilot is required under the type certification of the aircraft or the regulations under which the flight is conducted; or

    (iv) When the pilot performs the duties of pilot in command while under the supervision of a qualified pilot in command provided—

If in your example both pilots are rated to fly that airplane on your license whether or not you have the required endorsements or ratings to act as the legal pilot in command you can log PIC time.  It does not matter who the legal pilot in command is at that time.  Both pilots will log the flight time as PIC and total time for the time you are the sole manipulator of the controls.

Other ways both pilots can log PIC time is where one pilot who is the safety pilot is the legal pilot in command while the other pilot who is flying the airplane and sole manipulator of controls is under simulated instrument flight.

Let me be very clear here.  If both pilots were to log PIC time under this condition, and many pilots do, they are making the statement in their logbook that could get them in trouble later on.  Let me explain, pilot A and B go out and fly together; Pilot A is under the hood and the other is the legal pilot in command.  On another day, Pilot B is under the hood and the other is the legal pilot in command.  Both pilots log exactly the same amount of flight time for both PIC and total time on these flights.  At this point, a precedence is set.

What is that statement you are making in your logbook?
Who the legal pilot in command is for each flight.  Read the regulation again.  If the safety pilot logs PIC time they are accepting legal pilot in command responsibilities and all that goes with it.  If the pilot under the hood has an incident or accident or airspace infraction the FAA will want to know who the legal pilot in command was during that flight.  The logbooks tell the story regardless what the pilots say at that moment.


Is there any current and/or upcoming technology that alerts Air Traffic Controllers in case of loss of aircraft separation? Currently doing an assignment and it to analyse an accident where older atc systems could have been at fault. In 1995 there was an incident where two aircraft came closer than the then current separation standard due to an air traffic controllers miscalculation. With new tech such as ADS-B, are there ways the controller can be alerted of possible loss of separations with the aircraft they are handling?

Most air traffic control systems nowaday have various safety net functions built into them. Short Term Conflict Alerting is one of these functions.

Short Term Conflict Alerting (STCA) works on the basis of extrapolating the current position using velocity and turn rate to predict imminent separation violations. If such a imminent separation violation is detected, the system will alert the air traffic controller.

The next level of conflict alering is Medium Term Conflict Detection (MTCD); this is not considered a safety net, but a tool that assists the Controller in detecting conflicts early on (up to 20 minutes in advance). Instead of relying on simple position extrapolation, MTCD uses more advance trajectory predictions that combine knowledge of the current aircraft position and velocity with information from aircraft performance models, flight plan, weather and given ATC instructions.
MTCD development started 20 years ago, and the tool is now being implemented in various ATC systems.


Who logs Pilot-in-Command time with all automation, autopilot, auto throttle, FMS, Autoland doing the flying? Who gets to log PIC, if the First Officer programs the FMS and turns on the autopilot at 1000FT AGL while the Captain calls the checklist?

In the US, there are two types of "PIC" that can be logged & may be interesting to report -- such as for an interview, perhaps.

Most common when starting out is "sole manipulator of the controls" -- and FAR Part 61 (61.51.e.1.i) defines this.  This includes essentially "sole manipulator of the autopilot," so the pilot who is designated as the PF -- pilot flying -- can log his time as PF as PIC, even though the autopilot is engaged & is driving the controls.  Early on, the time that you've spent "flying the plane" is of interest -- are you proficient and experienced taking off, landing, using the automation, and so forth.  (The standards for logging don't really give a way to distinguish between 10 minutes of hand-flying and an hour on autopilot, vs the whole time being hand-flown. It's not a perfect system.)

Of more interest when interviewing for jobs requiring significantly more experience is PIC as defined in FAR part 1 (1.1, definition of "Pilot in Command"), which amounts to essentially "who signed for the aircraft & is reponsible for the overall flight?"  Airlines who are considering hiring you are interested in this sort of PIC time, because they want to know that somebody has entrusted you with their expensive aircraft for enough hours (typically 1000+) that you've proven to be a good pilot IN COMMAND of not just the controls but the overall flight.

One person I talked to who did airline interviews (as an interviewer), said that when he looked at a logbook and saw every other leg logged as PIC, he knew that this pilot was essentially the copilot, the second-in-command of the flight, flying every other leg, but still responsible to the other pilot, who'd signed for the aircraft & was going to answer for it if things went wrong.  Then at the point when the logbook started showing every leg as PIC, that's when this pilot became the designated PIC, per the FAR Part 1 definition, and every leg was his responsibility, regardless of who was PF and who was PM.  That's the point at which the hours were "interesting" for hiring purposes.

At some point in one's career, the ability to manipulate the controls starts to become a given, and what distinguishes the pilots you want to hire from those you don't becomes factors like judgement or decision making.  Regardless of who is flying the leg, somebody has to be the final authority on decisions like, do we need to upload more gas?  Is this airport acceptable (not just legal, but wise) as an alternate? How long are we willing to hold before we punt on Plan A and divert to the alternate?  All sorts of stuff like that.  And the captain is the final authority on all of that just as much on the First Officer's legs flying as he is on his own legs flying.  (Which isn't to say he doesn't solicit input -- he certainly should -- but the final decision is his.)  Those are the decisions that occur during FAR Part 1 PIC, that may or may not be yours to make during Part 61 PIC.  Thus the different ways to count and report one's flight time.

Related discussion of Part 1 and Part 61 PIC time and logging thereof.


What is the typical angle of attack aircraft fly at and at what angle of attack do they stall? At what angles of attack do aircraft typically fly at? How much of a margin is there before aircraft stall due to an increase of an angle attack due to factors such as gusts or rotation of the wing section due to deformation?

It depends basically on the wing section. Some of them stall at a higher angle of attack than others...

To quote typical values (for wing + body, since not only the wing gives lift...) a given plane may achieve the flattest glide (best range, L/D = 12, at 155 knots) with an angle of attack of 4º. If you wish to fly slower, you can do it at 115 knots, with L/D = 8, and a steeper AoA (13º) or you can choose to fly faster, at 210 knots, always with L/D = 8, but with an AoA of 1.5º.

Thus, and except for the best L/D, there are always two angles of attack for the same L/D, one of them steep (slower flight) or flat (fast flight)...

The stall, for the example I'm quoting (book 'Mechanics of Flight, by A.C. Kermode)' takes place at 15º...


Is there a common route that Seattle GA pilots use to circle Mt Rainier while avoiding class B airspace? I'd like to fly around Mount Rainier in a C172 out of Renton (KRNT). What route do people usually take? I wonder if I can climb quickly enough once out of Seattle class B airspace for terrain around Mt Rainier. What do people usually do?

I fly out of BFI and RNT.  The short answer is go East to clear the B, then South to parallel terrain as you climb.  You will have more time to do this if there is a North flow.
There’s no specific route per se, just climb as best you can while keeping between the two.
The Lake Youngs departure gets you going in the right direction, and once just past Enumclaw you can make a circling climb to get comfortably above the ridges.


If you file a flightplan with "NO SID", can you still get assigned a graphical ODP in your clearance? Recently, the FAA has been moving to migrate Obstacle Departure Procedures from the textual form they are in in the A/FD Departure Procedures section to use the same graphical/charted format that SIDs use -- in addition, this means that charted SIDs are just a kind of charted Departure Procedure, just like charted Obstacle Departure Procedures.

However, when SIDs were originally implemented, there was a safety valve put in for pilots who weren't up for handling a complex departure procedure on their own -- you could file "NO SID" in your flight plan and ATC wouldn't assign you a SID as part of the clearance.  However, if the airport has a charted (graphical) Obstacle Departure Procedure and you're filing IFR, will you still get assigned the ODP as part of your clearance even if you are filing "NO SID" in your flight plan?  Or will ATC do something else instead?

ATC can indeed include an ODP in a clearance; this is from the ATC orders section 4-3-2:

  Where an obstacle departure procedure (ODP) has been published for a
  location and pilot compliance is necessary to ensure separation,
  include the procedure as part of the ATC clearance.

  EXAMPLE−
  “Depart via the (airport name)(runway number) departure procedure.”
   Or
  “Depart via the (graphic ODP name) obstacle departure
  procedure.”

The "NO SID" note is exactly what it says, i.e. it applies to SIDs only. This is from the orders 4-3-3:

  If a pilot does not wish to accept an ATC clearance to fly a SID,
  he/she is expected to advise ATC or state “NO SID” in his/her flight
  plan remarks.

Note that SIDs and ODPs exist for slightly different reasons: SIDs are primarily to simplify communication and automation; ODPs are specifically designed to help ensure obstacle clearance and you can fly one without an ATC clearance (unless ATC assigned some other departure procedure). That means it's usually in your interest to fly an ODP if possible.

Having said all that, a pilot can always decline some or all of a clearance that he isn't capable of flying or is just uncomfortable with. But if you reject both SIDs and ODPs, then ATC has to vector you and that could easily cause delays, especially at a busy airport.


Is engine damage due to a fan blade failure irreparable? I have a question related to this question and this video. The question says that sometimes a fan blade failure can occur.

My question now is, if a fan blade separates or a malfunction occurs, is the engine still repairable?
I think the damage to the engine's structure would be quite high?
According to the video a fan blade malfunction occurred on start-up, how could a malfunction appear on start-up?

This depends on the failure: A fan blade can be damaged by birds, debris, or aircraft parts (pitot probe for example).  In this case the blades are dented, in which case it is possible to replace the damaged parts, inspect the engine and re-use it.

For this kind of damage it has to be disassembled and inspected by the engine manufacturer.

Inspection of blades is done with a microscope: For example, I have seen an HPT blade declared unserviceable because of a small scratch.

Obviously if the repair costs more than a new engine you don't repair the old one.

Many more things can happen in startup:

The engine is run on full power
There is a lot of possible interactions (like birds for example) that you don't have in a steady cruise at 40,000 feet.

Aside from debris, you can also have a compressor stall like this.


How do you know the maximum load a control surface can withstand? source

This is a separate strength testing (load testing) of the elevator of an airplane, how was the load determined? How did the engineers determine the maximum elevator load?

Elevator loads are the function of the design and flight envelope. Looks like a small plane, so look up for example CS-VA 391 (or the correct national code for your category) how to calculate the loads. Base air force distribution on the horizontal tail can usually be assumed to be triangular, and increment from control surface deflection need to be added, also usually approximated as a triangular distribution acting from the hinge line.


On the ICAO Flight Plan Form, does /S replace O, V, and L? I know the S stands for standard equipment (VOR, ILS, VHF radio).

Is the format like G/S (GPS with standard equipment), or does the /S not imply coverage of the other line items, i.e., VLGO/S?

I wanted to address your formatting first since equipment type identifiers come before the transponder identifier (i.e. before the slant). The format for the new ICAO Domestic flight plan form for item 10 (equipment) is as follows:

(equipment type letters) / (transponder type)

So as an example, if your aircraft has standard equipment, VOR, GPS (GNSS), DME and you were Mode C Transponder equipped, your entry for item 10 would look like this:

SGD / C

*notice that your equipment type doesn't include "O" for VOR since S also includes VOR.

To answer your concrete question, S does indicate the presence of O, V, and L.

I've attached the following tables from 5-1-21 and 5-1-22 in the AIM for your reference. Table 5-1-4 covers equipment letter identifiers and table 5-1-5 covers transponder letter identifiers.


How do helicopters turn using rotor? I know that airplanes use rudder to turn, and use elevator for nose up and down.

How do helicopters change their altitude and how do they make turns?

Airplanes do not use their rudder to turn; they do it by banking into the direction of the desired turn, then the wings "lift" the plane in that direction.  The rudder is only used to maintain lateral trim, so that the airflow doesn't impinge on the side of the fuselage and drag is minimized.  To initiate a turn, the pilot uses the stick or yoke to actuate the ailerons on the wingtips, causing the wing on the inside radius of the turn to go down and the wing on the outside radius of the turn to go up.  A slight back-pressure of the stick or yoke raises the nose, causing a "climb" to be initiated, but since the plane is banked toward the center of a circle, the "climb" doesn't cause a change in altitude, instead it causes the plane to fly a circular path.  Small, simultaneous changes in engine power and rudder deflection are needed in order to maintain proper trim and constant altitude in what is called a "coordinated turn".

Helicopters turn in a manner analogous to that of an airplane.  In forward flight, the cyclic stick (between the pilot's legs) is pushed slightly in the direction of the desired turn, causing the rotor disc to tilt, just as the wings of an airplane are tilted in a banked turn.  The collective lever and throttle (at the pilot's left side) are adjusted as needed to maintain altitude and the rudder pedals are adjusted to maintain a coordinated turn.  Since the fuselage of a helicopter is suspended from the rotor hub like a pendulum, as the helicopter enters the turn, the fuselage tends to be flung outward, so it banks, just like the fuselage of the airplane that is rigidly connected to its wings.  (In a hover, with no forward airspeed, a helicopter can turn in any direction with the rudder pedals alone, something an airplane cannot do.  In this special case the fuselage remains level.)

To change altitude, it is necessary to add power to climb or reduce power to descend.  This is true of any heavier-than-air aircraft, as, for a constant velocity, increasing altitude implies increasing potential energy and decreasing altitude implies reducing potential energy.  In helicopters in forward flight, a climb is accomplished by first pulling back slightly on the cyclic stick to raise the nose and establish a climb attitude, then raising the collective lever and twisting the throttle grip on the collective lever to maintain constant rotor speed.  As the collective is raised, the pitch of the main rotor blades increases, giving them more "bite" on the air and, therefore, more lift.  A skilled helicopter pilot will perform these actions in a coordinated manner, such that everything appears to happen simultaneously.  In the special case of a hover, a helicopter can climb and descend with the rotor disk in a constant horizontal attitude.  As described above, the collective lever is raised and power is increased with the throttle to put more energy into the system, raising the aircraft; to descend the collective lever is lowered and power is decreased with the throttle.  Directional control in a hover is maintained entirely with the pedals; if the helicopter is the most common type with an anti-torque tail rotor, moving the rudder pedals requires the throttle to be increased or decreased slightly to compensate for the varying power consumed by the tail rotor and to maintain constant altitude.

(If this sounds complicated to you, you're right.  Rotary wing flight is considerably more difficult than fixed wing flight, and it took decades longer to perfect helicopters after fixed wing aircraft had taken to the skies.)


Why some WWII fighters still have fabric/wood control surfaces? I've heard people say that the reason US in WWII preferred designs with fabric control surfaces with either a metal or plywood frame is they can sustain some small arms fire without disintegrating. Is this really the reason? Or is it simply weight saving?

A metal control surface can also sustain some small arms fire without disintegrating -- aircraft with metal rudders and elevators used to routinely come home with bullet holes in those surfaces.

The real reasons wood and fabric surfaces might have been preferred (though they weren't always; several designs had all-metal control surfaces) are the classic reasons for everything in aviation: cost and weight.  In the late 1930s, when many of the aircraft used in WWII were designed, it was still possible to make a wood and fabric structure, especially a control surface (as opposed to a wing), that would give the needed performance and strength and come in lighter than an all metal one, and frequently at lower cost in volume manufacturing.

As performance specifications continually crept up (higher speed, higher loading, more vibration from a larger engine, etc.), metal surfaces gained the advantage.  They could ultimately be stronger than wood and fabric, hold their surface shape over a broader speed and pressure envelope, and as noted, wouldn't disintegrate if they took a few bullets -- in fact, they were usually more durable than wood and fabric, because metal is less prone to tears and splintering.


What is the "compression ratio" of air hitting the nose? Sorry but I don't know how to accurately phrase this question. I want to know how much compression results from air hitting the nose of an aircraft.

I'm interested in the traditional airliners (Mach 0.85, blunt nose, like B747 or A320), as well as the supersonic stuff like Concorde and even Mig-31.

Is there an equation for this? Presumably with cross section area and some kind of coefficient of form drag. I'm looking for a density and/or pressure change.

I want to know if this is significant, like if the aircraft actually has to do a lot of extra work to overcome the greater density in the nose air. But there are actually several reasons. I want to calculate how much heat arises from the adiabatic compression, which will let me know if some kind of active cooling is required for a given material. I want to know if the increased density of the nose air actually changes the general drag equation, like if you have to put in a higher density value when just calculating the fuselage drag. I want to know what possible boost you can get from the "ram effect" such as from a ramjet.

In this question, all I'm really asking for is the compression ratio...or change in density, or change in pressure...sorry I don't know which one is more accurate. If I just have that, then I think I can answer the rest using other equations I know of.

I wanted to explain myself in case this appears too broad or too xyz thing, sorry can't remember that term either. Hopefully someone will know an equation that can answer this. Equations give hard numbers, so they're always better than relative adjectives like "larger", "negligable", etc.

Also, if someone can suggest tags, please do so. Couldn't think of anything better than "drag".

I think what you seek is called the stagnation pressure, which is the pressure rise experienced in a given parcel of air if all the kinetic energy associated with that parcel's velocity were to be converted without losses into potential energy (stored work) of compression according to the ideal gas law. The equation for stagnation pressure is

$$ \frac{P_\text{stagnation}}{P_\text{static}} = \left( 1 + \frac{\gamma - 1}{2} \times M^2 \right) ^ \left( \frac{\gamma}{\gamma - 1} \right) $$

where $\gamma$ is the ratio of specific heats for air and $M$ is the Mach number.


Is a propeller with two long blades more efficient than one with three shorter blades? Is a longer, two-bladed propeller more efficient than a three-bladed propeller with a smaller diameter?

As Troy E and Dave said, most of this question is already answered here.

In addition to this previous answer, just remember that a propeller is a technological solution to a simple question: how do we make the aircraft fly ? Therefore, there is no single solution, but multiple compromises that can be found depending on various parameters, mostly based on the type of operations the aircraft should take part in :

Speed
Altitude
Mass of the aircraft
FOD / injestion risks and tolerance
...

Since your question only states the efficiency of the propeller, you actually miss at least part of the real problem.
Let's say you manage to make a propeller with an efficiency of 1, but that it weighs 1 ton or is impossible to manufacture, you won't get far.

In that sense, only considering the efficiency to say what is the best solution is not good enough. The best solution is the best compromise between all of your requirements, that's why it is so difficult to find ;) !


Why aren't there more stringent checks for switching off electronic devices during takeoff-landing? I understand from discussions such as these, that it is crucial that to avoid electronic interference with flight instruments, all electronic devices should be shut off during takeoff and landing. And yet, in my experience, there are always rebels getting away with brazenly keeping their instruments on.

My question is, given the critical nature of possible interference (tiny probability but catastrophic consequences), why aren't airlines looking at more stringent measures than a routine announcement/request by the pilot? For example manual checks, frisking?

There are some problems with this as electronic equipment are not banned in aircraft per se, but only during some (critical) phases of flight.

First, how to determine if someone is operating electronic instruments. It'll be difficult, considering that everyone is seated. The only way is to put a lot of cameras (who's going to monitor them?) or by asking everyone to check their fellow passengers, hardly a good option.
Even if someone operating an electronic equipment is detected, what to do? During takeoff and landing, seat belts are mandatory and the only option (except announcing the seat number over PA) is to ask the person in nearby seat to snatch the offending equipment; again not a good solution.

As most of the electronic equipment (like camera or music players) emit little radiation and no air crash has been attributed to use of electronic devices, I doubt airlines will do something to physically to prevent passengers from using electronics.


What is the purpose of this loop in a taxiway? This image is of Mariscal Sucre International Airport near Quito, Ecuador.  (Official site / in English)

What is the purpose of the loop in the taxiway plainly visible in this image?

From Google Earth (with the contrast punched up a bit)

Addendum

To respond to the comments to jwzumwalt's answer, I really don't think the hills and mountains to the north of this airport are an operational concern.  See below image:

Source plus my copy-and-paste extras

The airport's elevation is 7900 feet (verified by Skyvector), the first ridge in jwzumwalt's 2nd image is 6.4 miles distant from the north end of the runway and lower in elevation, and the second ridge is 8 miles distant but only 500 feet higher.  Distances verified by Google Maps.

If an aircraft can't comfortably clear a ridge 500 ft above the airfield in eight miles, well then that's a whole other issue. :-)

But, I do like jwzumwalt's answer.  Thanks!

In the US, this is called a "run up area". It is used by small piston powered airplanes to test their engine prior to takeoff.

The circular design allows several aircraft to full throttle their engines without the prop blast hitting the aircraft behind it. It also allows other aircraft like a business jet, to pass the testing aircraft and takeoff immediately.

Larger aircraft or turbine powered aircraft don't usually test their engines near taxi-ways and other aircraft (or aren't allowed). If they need to test their engines, a special blast "pen" or blast "barrier" is used.

Youtube video of a FedEx engine test.

This Youtube video of a airplane landing shows a ground view of the significance of the hills and mountains off the departure end of 36.

Why the run-up is at this end - Google Earth 3D


Under what conditions are passengers required to take precautionary measures during refueling? I was on a recent flight with a fuel emergency, during which the passengers were required to take precautionary measures. Under what circumstances are the precautionary measures mentioned below required?

The plane was diverted to a small regional airport apparently unequipped to service the Airbus we were flying in. Though the fuel truck had arrived at the plane and cones had been placed around the aircraft, we waited quite some time for the fire brigade to arrive before the fuel could be pumped. During this time and during the refueling operation, all the doors were opened (in the rain) and the passengers were required to be in our seats with no electronic equipment. Additionally, seatbelts were required to be unbelted.

The fuel emergency occurred while we were circled the Atlantic for 45 minutes waiting for the weather to clear up at Miami International Airport. When the alternate airport shut down as well (Fort Lauderdale International Airport) we were diverted to a small airport in West Palm Beach. From what I was told by a crew member after we had landed, we did not have enough fuel reserve to safely make it to Orlando.

Myself and other pasengers were under the impression that the in-the-seats-with-no-belts restriction is standard for refueling with passengers on board, but in the comments of another question I discovered that this is not the case. What are some likely reasons that these precautions were taken?

The incident occurred on 2014-05-15 on Iberia 6123 leaving Madrid at 11:50 with a scheduled arrival at Miami at 15:20. I'm pretty sure the plane was an A330 but it might have been an A320.

Doc 965, CAT.OP.MPA.195(b), regarding Refuelling/defuelling with passengers embarking, on board or disembarking, says:

  For all other types of fuel, necessary precautions shall be taken and the aircraft shall be properly manned by qualified personnel ready to initiate and direct an evacuation of the aircraft by the most practical and expeditious means
  available.

So no-belts restriction is one of the elements that ensures "expeditious evacuation". The same goes for keeping the doors open and keeping the passengers in their seats.

Although the legal requirement is not that specific, probably the detailed procedure (with all the elements you described and others that were not visible for the passengers) can be found in the company Operations' Manual.


Why does the Cessna 172S Skyhawk use only two blade fixed pitched prop? Surely it would get more thrust from a three blade variable pitch propeller. From what I've read it's all about the area swept and also should be far enough apart to not cause too much interference. Besides having a constant speed prop would allow for a wider range of optimum operation.

You're not wrong, but a fixed pitch two-blade prop has a pretty big advantage: it's cheap. Cheap to buy, cheap to install, cheap to maintain, cheap to repair. 172s are predominantly trainers in FBO fleets, and cheap is the winner. The efficiencies of a better prop are lost when you're just doing pattern work and short cross countries.

Also, when you're not climbing, a two-bladed prop is actually going to be more efficient, not less as it's creating less drag. According to the linked Hartzell FAQ:

  Depending on the combination of [engine power, operating RPM for the propeller, diameter limitations, design requirements, etc] a 2-blade propeller may be most efficient, but as power increases additional blades are generally required to efficiently utilize the increased power.

This means that on a 160 horsepower engine like the 172 is rocking, you aren't going to see particularly tangible benefits from increasing the number of blades. Going to a constant speed prop would, on the other hand, give you greater utilization of power across the entire flight envelope.

For example...

An overhauled McCauley fixed pitch 2-blade propeller that fits a Cessna 172 is $2,100 on ebay. It has no moving parts (I mean, aside from itself) and is relatively easy to balance.

A (non-overhauled?) Hartzell 3-blade constant speed prop off a Piper PA-46-350 Malibu Mirage is $15,000 on ebay with no logs, which is usually a bad sign. It's not a direct comparison to, say, the prop on a C182, but it's probably in the ballpark. It's harder to balance, and requires more maintenance to make sure the constant speed mechanism is up to snuff.

I was only able to find prices on ebay, which isn't the most scientific comparison ever, but it's a start.


Why didn't Cirrus make the SR-22's parachute steerable? After the parachute is deployed there is no control where the plane is going, so why didn't Cirrus make the SR-22's parachute steerable?

Remember what the purpose of the CAPS/BRS airframe parachute is: It's a last-resort emergency measure to put the aircraft on the ground in a condition that is likely to be survivable for those onboard.

Steerable parachutes add considerable complexity: Control lines would need to be routed into the cabin, and connected in such a way as to not interfere with the chute deployment under any circumstances.
Assuming a suitable design could be devised to accomplish that a steerable parachute (even for a single person) requires quite a bit of training and skill to use. This is not something that can be adequately trained for in the case of the Cirrus airframe chute (because pulling the chute on perfectly good aircraft to teach steering would be cost-prohibitive).

Faced with the risks and complexity of a steerable chute or the relative simplicity and safety of a simple drag chute to decelerate the airframe prior to impact (hoping you land in a suitable 40-by-40 foot square) Cirrus and BRS opted for the latter. The result is a dead-simple "Pull the handle!" system that's proven very successful thus far.


What is the typical reaction time for most pilots? I'm doing a manned aircraft design and make it easy to fly by making it hard to enter a pilot induced oscillation (PIO). I got a range of natural oscillation frequencies for my design in pitch, roll, and yaw, and now I'm trying to see if the period of these frequencies fall close or far away from most people's reaction time. I searched on Google, but only got data on twitch time, which doesn't seem applicable for an aircraft where some muscle power will be needed, hence my asking this question.

My reasoning is that if it falls an order of magnitude below or above the reaction time of most pilots, the aircraft will be easy to fly (as long as it doesn't go through extreme high G maneuvers). An additional question I have related to this is, how can one design an aircraft to make it difficult for pilots to enter PIO's?

Its a bit dated but here is a paper published by the Navy on visual reaction time you can find. Keep in mind these are navy pilots, often considered the best of the best and in peek physical condition. Based on the publish year I would suspect all subjects were male as well.

Here is another study by NATO on reaction times for pilots on low sleep.

This is a nice study comparing the reaction times of pilots to non pilots, might be of some help.

  An additional question I have related to this is, how can one design
  an aircraft to make it difficult for pilots to enter PIO's?

This is an interesting question and in some regards could be its own question here. One of the big debates (mainly between Boeing and Airbus) is if systems like this should exist and who has the final say in terms of control deflection. Airbus takes the approach that the computers should prevent the pilot of say pulling back on the stick and stalling the plane. While Boeing generally allows pilots to be the final say and while their systems will warn of a stall you can ultimately pill back the column until the plane stalls.

In terms of how you would design something like this you would have to limit control input after an approach to oscillation was detected.


Why is the S-duct intake on the Tu-154 uniquely oblong? Is there an advantage to the oval/elliptical shape of the Tu-154's S-duct intake? It appears to be taller and an overall different shape than the side-mounted cowlings.

This doesn't appear to be a feature common to trijets or even on those with S-ducts.

EDIT: Upon further research, it appears the 727-100 had an oblong intake (Thanks Terry!), and the Hawker Siddeley Trident had an entirely unique shape. So my original premise of the Tu-154 being "unique" no longer holds. I am still curious about the implications of the different designs.

This doesn't fully answer the question, but the B727-100 also had an oval engine intake.

AIRLINERS magazine Sept/Oct 99 edition:

"The oval shape inlet on the 727-100 series was changed to a circular design on the stretched 727-200. This was a direct result of the new aircraft's longer fuselage. In flight, the increased lengths from the nose to the center engine inlet increased the thickness of the "boundry layer" of air on the fuselage forward of the inlet. This would have caused aerodynamic "blanking," or disruption of airflow into the center engine, without changes to the design. The circular inlet allowed a smooth flow of air into the engine, as it elevated the bottom of the inlet away from the fuselage boundry layer and into the air stream."


Do thermals stop rising when clouds are formed? Glider pilots know that one indication of thermal lift is the formation of cumulus-type clouds.

My question is: Does the rising air (that lifted the moisture to form the the cloud) stop rising after the water vapor condenses?  Is there rising air above a cumulus cloud, or does the condensation somehow stop the upward movement of the air?

No, the opposite is in fact true. When the water condenses, it releases latent thermal energy, causing the air to rise even faster. That is why some glider pilots (who are appropriately licensed) fly, not just under, but into cumulus clouds to gain height.

When water vaporizes, it absorbs thermal energy. That is why, for example, humans sweat to cool down. As the sweat vaporizes, it removes thermal energy (heat) from the body. This thermal energy is stored in the water vapor, and will be released when it condenses.

The air in a thermal will only stop rising once it reaches the temperature of  the surrounding air, which can happen at different altitudes, depending on the state of the atmosphere. The main reason rising air cools down is because there is a relation between temperature and pressure. As the air rises higher, the pressure drops, and the temperature does the same. This can be depicted on a diagram of the temperature gradient, like this:

The thick red line is the ambient temperature of air at different levels. The oblique lines indicate the rate at which a column of rising air will cool down as it rises. As long as the thick red line is more inclined than the oblique lines, it is an indication that air will continue to rise, since it will not cool down fast enough to reach the temperature of the surrounding air.


Why didn't Air India always fly DEL-SFO over the Pacific? I read a 2016 article that said Air India broke a record for the longest flight (distance) by flying from New Delhi to San Francisco over the Pacific rather than a polar/Atlantic route. The total flight time was shorter because of the jet stream.

Why didn't they always do this?

(gcmap.com) Great circle route.

The polar route is mostly over land and is in close proximity to airports and navigational aids. Flying over long stretches over water requires (among other things) enhanced navigation, using specific communication protocols, and adhering to criteria set by the countries overseeing the region. Picking the new Pacific route is not easy (authorization, training, and the associated costs).

The Pacific communication, navigation, and surveillance requirements also allow the utilization of flex routes to adapt to the changing jet stream, as the linked document below explains. (The flight's history also shows the different routes.)

The relevant operational circular—Operational Authorization Process for Pacific Operations—can be found on the DGCA website (.pdf). The document covers all the requirements, of which, the carrier seeking the authorization may need to demonstrate to the authorities a flight or more:

  (...) the final step of the approval process may require a validation flight through Pacific airspace by a DGCA Flight Operations Inspector to verify that all relevant procedures are applied effectively.

In short, when an airline selects a new challenging route, it must prove it is prepared for it, and to set up new training procedures. It's like a pilot who has never flown over the Atlantic, when that time comes, they undergo special training for it. In this case, flying over the Pacific was new grounds for Air India.

The requirements (published August 2016) were put in place after Air India sought this route. Air India has been undergoing major changes recently due to large amounts of debt, so they've been streamlining their operations.

Related (question about same flight): Could winds of up to 150 km/h impact the structural loads on a Boeing 777?


Carrier VTOL takeoff or not? In this picture, shown in a recent news article, a "shooter" seems to be giving a "go forward" command to what I believe is a Lockheed-Martin F-35 aircraft already prepped in a VTOL configuration. But since VTOL's take off and land vertically, under what circumstances would a shooter give the pilot this "go forward" command?

The rolling takeoff is a STOVL or Short Takeoff and Vertical Landing operation.  The F-35B is too heavy to hover with full fuel and a warload, but can use its vertical lift system to augment lift generated by the wings allowing an F-35B to lift off in less than 500ft ground roll with a Vr of around 70 knots or so.  The procedure is also used by Harriers flying off assault ships as well.  Some carriers likes the Royal Navy’s HMS Queen Elizabeth make use of a ‘ski jump’ to augment the takeoff roll and launch the aircraft upwards, allowing for a greater launch load and/or shorter takeoff roll.

Once the warload and at least 60% of the total fuel capacity has been depleted, the F-35B can enter into a full hover and land vertically.  This allows the F-35B to recover on an assault ship without the use of arresting gear.

An additional variant of the F-35, the F-35C, has a larger wing and tailplane, different landing gear and an arrestor hook in the tail.  This allows it to launch and recover aboard larger CATOBAR aircraft carriers, but cannot do so aboard assault ships like the F-35B can.

The pointing signal by the launch officer is the takeoff signal.  It can be used as instructions to fire the catapult/EMALS or for the pilot to release brakes and make a short takeoff, as in this case.


Are there ILS approaches where descending by the glide slope outside final might be dangerous? Are there ILS approaches out there where descending by the glide slope on a segment of the approach that's outside the final approach segment would cause the aircraft to descend below the no lower than altitude for the segment?

Here's why I'm asking. It's not uncommon for pilots to intercept the glide slope before the published glide slope intercept point and then to track it all the way down. If doing this could be dangerous or might not provide the protections ILS approach are designed to provide, it might be a better procedure to descend using step downs to the no lower than altitude for each segment only intercepting the glide slope at the published point for all approaches.

Are there ILS approaches out there where descending by the glide slope on a segment of the approach that's outside the final approach segment would cause the aircraft to descend below the no lower than altitude for the segment?

Yes.  See InFO 11009.

In part the InFO reads:

  On ILS approaches, stepdown fixes are established for obstacle or traffic separation.  For all practical purposes, the glide slope remains stationary regardless of atmospheric temperature and pressure.  Conversely, stepdown fixes are published for a pilot to fly using indicated altitude, which varies with temperature and pressure changes.  Therefore, the proximity of stepdown fixes in reference to the glide slope, changes with the weather.

We know the old adage:

  From high (hot) to low (cold) look out below.

What isn't obvious about that adage is the perspective of that statement.  It is from the perspective of the pilot to the ground.  A glide slope's perspective, if you will, is from the ground to the pilot.  Thus what you will experience is this.  In warm weather, the stepdown altitudes will be higher than the glideslope and you will need to level off to remain above the MEA until crossing the next stepdown fix.

You must remain above the MEA at all times till crossing the precision final approach fix.


Can Flight Simulators (FSX P3D) give you the expecience you need to fly a RW plane? So I am flying on the sim for about 7 years now, which 3 years on the (PMDG) 777 and 737NG. Flying on the sims is almost like the real world right now, you can download multiple addons (PMDG, Aerosoft for planes ORBX for scenery, REX and ACSC for weather, etc, etc), download checklists, join online networks (IVAO, VATSIM) and so on. But can step into a 737NG right now and fly it with my sim experience?

What are the real differences between the sim and real world if it's about flying. And if I would step into a 737 now, what challenges can I expect during flight, which I probably didn't encounter during my flights in the simulator.

Consider this:

I fly 7 years on the sim
3 years on the PMDG 737 and PMDG 777
Flown with multiple failures (Engine Fire, ADIRU failing, etc, etc)

Thanks in advance!

GdD brings up some good points but that really depends on what you mean by "home simulator" and it depends on the airplane. There are some people that have taken it to the extreme and built simulators that are fairly close to real and provide a solid learning platform not only for the flying but the actual physical operation of the controls. You can fairly easily build a home sim for a small plane that has all the controls and instruments you would see in a real plane and even in emergency situations you will see real warning lights in your sim and be able to mitigate it as you would in a real plane (nothing is stopping you from wiring in a smoke machine either).

As for the flight dynamics they get more real as time goes on and computers get better and better. I use X-Plane and simulate the Piper Archer I fly in real life which I find to be pretty close to the real thing from a flight dynamics/response stand point. My simulator did a great deal for my cross wind proficiency when I was training. I cant say I learned to fly in the sim but I did a great deal of honing of my skills in my home sim.

  The sim is a tool not a replacement

If you understand this you will better be able to realize that the sim can provide you a great deal of proficiency and can suffice for training in some (not all) cases. Even the big guys use simulation to train for the real thing (this article provides some nice pros and cons). The FAA even considers approved simulator time to count towards certain things.

Unless you have a full motion sim at home, the sim wont provide you with the feeling of flying which is very hard to replicate. It wont disorient you in IMC by having G-Forces cause your vestibular sense to distrust the instruments. It wont physically throw you around on a bad cross wind landing with wind sheer causing your knee to bump the yoke. It wont shake you to the point you drop your iPad while briefing an approach plate. It wont spin you until your lunch decides it wants to be elsewhere. These are the kinds of experiences you may only find in a real plane...

One last thing to consider as well is some what of the reverse case. Aircraft cockpits are actually getting closer to computer based units as time moves on. Its common to see keyboards in airbus cockpits and many of the former steam gauges have been all but replaced with screens. As we move into a more automated era some switches have even been lost to digital control units. Even the flight controls them selves have moved into the modern age with fly-by-wire systems removing physical linkage from the side stick to the control surfaces.


What does "1%" mean in ICAO Annex 14 § 3.9.9 (longitudinal slope changes)? — 1 per cent per 30 m (minimum radius of curvature of 3 000 m) where the code letter is C, D, E or F; and
  — 1 per cent per 25 m (minimum radius of curvature of 2 500 m) where the code letter is A or B.

Can someone explain what "1% per 30 m" means?

Does it mean 0.3 m of elevation difference for every 30 meters? Or 1/100 per 30 m?

You are referring to ICAO  Annex 14 Volume I, Aerodrome Design and Operations. Section 3.9.9 says:

  Recommendation.— Where slope changes on a taxiway cannot be avoided, the transition from one slope to another
  slope should be accomplished by a curved surface with a rate of change not exceeding:

  1 per cent per 30 m (minimum radius of curvature of 3 000 m) where the code letter is C, D, E or F; and
  1 per cent per 25 m (minimum radius of curvature of 2 500 m) where the code letter is A or B.

To better understand this, lets see what the previous section says:

  3.9.8 Longitudinal slopes

  Recommendation.— The longitudinal slope of a taxiway should not exceed:

  1.5 per cent where the code letter is C, D, E or F; and
  3 per cent where the code letter is A or B.

So: for a taxiway with a code letter D for example, a maximum slope of 1,5% is recommended. That would be 1,5 meters up or down within a distance of 100 meters.

If a part of the taxiway in question is 1,5% uphill, and another part is 1,5% downhill, the transition from the uphill portion to the downhill part should not happen at a rate faster than 1% within a distance of 30 meters.

In addition to this, the radius of the curvature should not be less than 3000 meters. This means transitions must be smooth within that 30 meters distance.


What is the dark spot visible below the cockpit on A-10s? On most A-10s I have seen, the area under the cockpit is darker than the rest of the plane. Is there a reason for this?

It's a false cockpit, a type of camouflage patented in 1980 by Keith Ferris, a US artist and camouflage designer. From some angles, it makes it difficult to determine the orientation of the aircraft. The Canadians were the first to apply it; pictured is a CF-18 Hornet with one:

Notice how at a glance, it takes a second to realize the Hornet is inverted and pulling towards the ground. During dogfights this can be enough to make opposing pilots think the aircraft is going a different direction. It might not seem like much in a photo, or if you're watching an aircraft fly past at an air show or airport. In the stress of combat while pulling extra Gs it's more than enough to confuse or delay a reaction.

For the air to ground mission, this is particularly important. If an A-10 encountered antiaircraft fire or an enemy aircraft it would have to rely on its own agility to escape or gain the upper hand. Other nations have adopted this technique — I've seen French and Russian types, and possibly Gripens of some air force. As far as I know, the A-10 is the only US aircraft regularly camouflaged in this way.


What aircraft is this flying near Greenford? I live in the suburbs of London in Greenford (near RAF Northolt Base) and today I heard a droning sounds which, albeit from my limited experience, sounded like a propeller plane. I checked my generic flight radar application on my smart phone, no result. I then checked the ADS-B tracking website which identifies most military aircraft that aren't flying covertly but, again, no result.

I did manage to take a picture of the aircraft and it looks like a small passenger turboprop plane - so any ideas about what aircraft this is and why it wouldn't be showing up on any radars? It does not seem like a stealthy fighter jet by any means.

Spy planes!!! Looks like I found an answer after two years when I came across a blog called 'secret bases'.

"Keen MI5 spy plane spotters should continue to lurk around RAF Northolt. A company formed by former elite RAF pilots, 2 Excel Aviation, actually based at Sywell Aerodrome, Northamptonshire, is now performing those spooky Northolt tasks, as part of its Scimitar special projects team.

They are using Piper PA31 Navajo aircraft "G-SCIR" (ModeS 40729C), "G-SCTR" (ModeS 40029D) and "G-SCMR" (ModeS 40729E) — all registered to 2 Excel in February / March 2017. They joined regular "sneaky-beaky" craft "G-UMMI" (ModeS 400C86) which is regularly spotted with special communications equipment attachments.

All three RAF Northolt Piper Navajo PA31 craft had been purchased by 2 Excel from Mike Jones Aircraft Sales Inc in Murfreesboro, Tennessee, America, who specialise in Colemill Panther conversions for performance and safety boosts. G-SCTR previously carried registration mark N331DB. G-SCIR had been supplied with tail number N522AW and G-SCMR had previously carried N27773.

Military aviation enthusiast Alan Warnes blogged on the subject in August 2017 on his Warnesy's World website, but strangely he only noted two out of the three Piper Navajos and missed G-SCIR. Curious, as the three registrations all took place at the same time – February / March 2017.

The London Evening Standard's Business Pages reported on my findings in an article headlined "Lift Off: Home Office privatises MI5 spy plane operations"."


Is there a Non Directional Beacon(NDB) morse code sound database? I need to know what is the morse code sound of:

CALL: OZ
Khz: 212
QTH: RUCKR
lat: 31.2292
long:-85.7917

I found this website, but I could not find the sound of different NDBs:
http://classaxe.com/dx/ndb/rna

Here’s a website that has some NDB sounds that can give you examples of what an NDB sounds like.

Basically each NDB transmits a one, two, or three letter identification.

On the chart, you can tell what to listen to by looking at the dots and dashes next to the identifier. In the example below, Chualar is UAD

..-
.-
-..


Should I land a Cessna 172 with or without a little power? Cessna 172 landings with full flaps. I have been taught to land with and without power. Give me feedback please. Which way should I continue my training?

This is really a question for your instructor: if you've been taught both methods then he should be able to explain when to use a little power and when not to.

Having said that, it all depends: there are good reasons to land with and without power, depending on the situation.

A normal landing with full flaps in a 172 is typically done without power. The Cessna 172S POH I have doesn't even mention power in the normal landing procedures; it gives a target airspeed instead.

A short-field landing is also usually without power, to minimize the runway distance needed. The same POH says:

  Power -- REDUCE to idle after clearing obstacle

For a soft-field landing on the other hand, it's normal to carry a little power in order to touch down as gently as possible and avoid sinking into the runway surface. The FAA's Airplane Flying Handbook says in Chapter 8:

  Power is used throughout the [soft-field] level-off and touchdown to ensure
  touchdown at the slowest possible airspeed,

Finally, you might also use a little power if you bounce on landing, to stabilize the aircraft and re-flare (runway length permitting). But that's a bit more challenging and most low-time pilots should just apply full power and go around instead.


Has anyone been able to verify ADS-B works without radar? I know that one of the biggest advantages of ADS-B is "supposed" to be that it will directly communicate between equipped aircraft without ground support. Has anyone actually seen that in action? That is, seeing another aircraft on an ADS-B display where radar coverage is impossible, say, a remote valley surrounded by mountains with no radar station near.

Obviously both aircraft would need to be ADS-B equipped for this to work.

I can confirm that ADS-B works without radar. I have been involved in several ADS-B trials in areas where there was no or only partial radar coverage. It works. No surprise, it has been designed that way.


Why don't airliners have rudders on the winglets? There are a couple airplanes out there that use the winglet as the rudder, but why doesn't the winglet have a rudder on it to increase the turn of the aircraft?

The purpose of the rudder is to control the heading of the aircraft. It turns the aircraft by creating an aerodynamic moment about the vertical axis of the aircraft. The moment is product of the aerodynamic force and the arm.

image: NASA

The aerodynamic force is the the side force on the rudder, the arm is the distance between the rudder and the centre of gravity of the aircraft.

If the rudder would be on the winglets, the side force of the rudder would act at a short distance behind the centre of gravity, reducing the effectiveness very much.

It would be possible the have airbrakes on the winglets / wingtips and use differential braking to create the rotating moment. This is done for example on the B2 which doesn't have a vertical stabilizer. The added complexity and weight increase makes it an unattractive option for conventional aircraft.


Are large passenger aircraft steered during taxi by changing the angle of the front landing gear? When moving to and from the runway, does a large passenger aircraft turn by changing the thrust difference on its side engines, or by turning the front landing gear to a different angle? If it is by turning the front landing gear, through what device does the pilot control the angle?

During taxiing aircraft turn using their nose wheel.

The nose wheel is usually hydraulically controlled. The pilot operates it through a tiller. The nose gear can rotate usually quite far, sometimes to almost 90 degrees.

At high speeds, directional control is achieved using the rudder pedals. The nose gear is often linked to the rudder pedals, however the maximum rotation is limited. The nose gear steering does not exactly match to the the rudder steering at all speeds. At low speeds the rudder is ineffective so the nose wheel steering is dominant. For sharp turns the tiller is always used because of the limited rotation by the pedals.

A320 Nose wheel tiller

B747-400 Nose wheel tiller


Was any MiG-29 modernized to incorporate digital systems? Did any air force using the MiG-29 ever modernize their aircraft so that they can fly on fully digital equipment such as the following?

Digital HUD
Digital fly-by-wire
Digital navigation system
Digital ...

IOW, from this

Cold-war era Mig-29

to this

Mig-35

Yes, India has designed and installed their own home-grown digital cockpit upgrades for their MIG-29's.


What would be the potential effects of not having an accumulator in the hydraulic system? In an aircraft, what would be the potential effect of not having an accumulator in the hydraulic system?

Accumulators act as storage for flow. At times of peak flow demand, the accumulator delivers a large flow supply at nominal pressure until its oil has been used up, after which the maximum flow is the pump flow. The same functionality that a capacitor or a battery has in an electric system.

If there are no accumulators installed:

Peak hydraulic power is greatly reduced: peak flow supply equals the pump flow, and pressure drops when the pump supplies high flow.
Pressure surges are high when the pump is running and demand suddenly stops, the accumulator evens out the pressure peak, again like how a capacitor functions. (From @Gerry comment).


How are aircraft size classes defined? How come I see some large planes, such as the 747, classified as either Category 5 or 6 Gate Sizes, depending on the publication. Why do some sites count the plane as one size, while others state otherwise? Is there a definitive guide, or is it relative to the country/airport?

I would believe that you are talking about Aircraft Design Group classification which is based off of aircraft wingspan and tail height. These classifications can also dictate what taxiways a certain model of airplane can use.

Group I: Wingspan - Less than 49' (15m)
Group II: Wingspan - Between 49' (15m) and 79' (24m)
Group III: Wingspan - Between 79' (24m)  and 118' (36m)
Group IV: Wingspan - Between 118' (36m) and 171' (52m)
Group V: Wingspan - Between 171' (52m)  and 214' (65m)
Group VI: Wingspan - Between 214' (65m)  and 262' (80m)

PDF for list of Boeing Airplane Group classifications


Why does the A-320 allow 1.3 degrees more left rudder trim than right? On the a320, can someone explain why this is:

  AMM 27-22-00 PB 001
  NOTE:The maximum admissible rudder trim limits
  indicated on the control panel when the aircraft is stabilized in
  heading with the AP engaged are RH 1 DEG and LH 2.3 DEG.

Why is there a 1.3 difference in deg between LH & RH?

Both engines turn the same way, and the bypass fans exert torque in order to accelerate the air passing through them. The torque needs to be trimmed out using aileron & rudder trim.


What happens when a takeoff clearance is cancelled by the ATC? Let's say an commercial passenger jet is accelerating down the runway, taking off. The ATC receives some signal that he/she should cancel all takeoff clearances.

Exactly what happens in the control room?
What does the ATC do and how does he/she make sure pilots understand the cancellation?
How do the pilots in the aircraft taking off respond? Are they trained for this scenario?
Is a takeoff cancelled even after V1?

What happens in the control room?

Aborting a take-off at high speed is dangerous, even if the aircraft is travelling below V1. If the aircraft is already rolling, the controller will make a quick decision whether the situation justifies an aborted take-off. For example, if there is traffic infringing the runway and a crash is imminent the controller would attempt to stop the aircraft. If an aircraft is attempting to take-off from a taxiway in snowy conditions it might be safer to just let him take-off unless there is other traffic on the taxiway.

If the aircraft hasn't started rolling the decision is of course easily made.

  What does the ATC do and how does he/she make sure pilots understand
  the cancellation?

Using standard phraseology is the best way of making sure the message comes across, especially in international aviation.

If the aircraft is not yet rolling, the proper ICAO phraseology is:

  Tower: Big Jet 345 hold position, Cancel take
  - off, I say again cancel take
  - off (due to vehicle on the runway)

  Big Jet: Holding, Big Jet 345

If the aircraft already started rolling the controller would say:

  Tower: Big Jet 345 stop immediately, (Big Jet 345 stop immediately )!

  Big Jet: Stopping, Big Jet 345

No immediate verbal reply is to be expected as the flight crew have other things to care about at that moment. The effect of their actions should be clearly visible from the tower.

  How do the pilots in the aircraft taking off respond? Are they trained for this scenario?

The crew will assess whether they can stop safely. Below V1, they will probably abort the take-off, above probably not. The final judgement is made by the captain. He might reason that it is safer to get airborne and pass the infringing traffic overhead than running into it at full brakes. They are trained for aborted take-offs, but since there are so many non-standard situations the final decision is made on the basis of a mix of training and expert judgement.

  Is a takeoff cancelled even after V1?

Since ATC does not know when the aircraft passes V1, a controller might attempt to cancel the takeoff after V1. The flight crew will only attempt to cancel the take-off after V1 if it is clear that there is no way the aircraft can become - and stay - airborne safely. In such a case it becomes damage control rather than damage prevention.


Can you escape an aircraft through the lavatory? In his book "Catch me if you Can", Frank Abagnale claims he evaded arrest by removing a panel in the lavatory of a VC10, climbing through it and hence escaping out of the (taxiing) aircraft through a hatch.

Could this actually have been done?

Plagiarism disclaimer: I found this question on another forum but didn't see a suitable answer there.

Depends if there is any pressurized space behind the lav, and if there are any hatches in the pressure hull within that space.  On most airliners I would say it's not plausible, but looking at a VC10 cutaway it looks like the pressure hull extends all the way back to the tail cone, to a small bulkhead under the rudder, and there is a hatch forward of that.  IF the mechanism can be worked from the inside, the hatch could be opened when taxiing because the hull is vented to atmosphere at that point.  It's possible that a panel in the aft most lav would expose a service hatch in the non-pressurized bulkhead where the engine support beam goes across, which would lead to the tail cone hatch.

Lot of ifs there, but from what I can see I wouldn't rule it out.

https://www.flickr.com/photos/27417638@N07/7408063162


What would be the hazard of raising flaps on the ground? I was reading ASRS report when I found something I don’t understand. What would be the hazard of raising flaps on the ground? What bad thing can happen?

However, with all the activity around the aircraft, including refueling, it was not safe to raise the flaps. I elected…not to raise the flaps until the area cleared.

https://asrs.arc.nasa.gov/publications/callback/cb_482.html

Without knowing what type of aircraft was involved in this incident, it is hard to tell. But, in general, a moving flap would provide a pinch point for any personnel in the area. Considering the article mentions that the hydraulics were in the on position, there would be a possibility of crushing a body part of maintenance personnel.


Are frisbees and boomerangs technically gliders? Frisbees and Boomerangs are heavier-than-air, unpowered, and fly through the air. So are they technically gliders?

They also rotate, so I wonder if these are actually some kind of rotorcraft-type gliders. I looked up all types of rotorcraft on wikipedia, which listed 4 things: helicopters, auto-gyros, gyrodynes, and cyclocopters. All of them were powered, so none of them were rotor-gliders. But then, auto-rotation in a helicopter might be considered gliding (with a pretty bad glide ratio).

One reason I ask is because I want to try to figure out the glide ratio or lift-to-drag ratio of these weird things. Not so easy to do empirically for a boomerang since it takes a weird ascending and descending path. How would you calculate that for a rotating assymetric airfoil?

No, they are airfoils. Airfoils are the contoured shape of the wings that give a boomerang the proper amount of lift as it's launched and spinning through the air. They operate on the same principle as the wings and propellers of airplanes and helicopters. You might even say that a boomerang is a combination of a wing and propeller. Frisbees operate under two main physical concepts, aerodynamic lift and gyroscopic stability. When flying through the air, a Frisbee can be viewed as a wing, with Bernoulli’s Principle governing the magnitude of the lift force which keeps it aloft.


As at 2020, why don't fighter jets have ≥ 200 rounds for their cannons? I already read Why do fighter jets still have guns/cannons?, but it doesn't expound why 100-200 rounds suffice or how "6 seconds is actually a lot of 'gun time' for modern air-to-air systems considering speeds, targeting systems and lethality of the projectiles involved."

I acknowledge that "It's not like WWII anymore where you'd slowly pull up behind a bomber and then have to spend several seconds pumping a bunch of crappy .50-cal lead in, hoping to poke enough holes in an oil cooler to make a difference."
Revolver cannons
"The Mauser BK27 is a 27mm calibre [revolver] cannon manufactured by Mauser (now part of Rheinmetall) of Germany. It was developed in the late 1960’s for the Multi Role Combat Aircraft programme that ultimately became the Panavia Tornado, it is used on a variety of aircraft including Typhoon, which carries 150 rounds."
"For that role the [SAAB JAS-39 Gripen] aircraft is armed with a 27 mm Mauser BK-27 revolver cannon with 120 rounds and with up to six short-range AIM-9 Sidewinder air-to-air missiles."
Rotary cannons
"The F-35A is armed with a 25 mm GAU-22/A rotary cannon mounted internally near the left wing root with 182 rounds carried". The Dassault Rafale fighter
"is equipped with the GIAT 30-millimeter cannon with 125 rounds of ammunition."
MiG-35 "is also armed with the 30 mm Gryazev-Shipunov GSh-30-1 autocannon with 150 rounds.". "The Su-35's armament includes a GSh-30-1 30mm autocannon with 150 rounds".

They don't need more rounds.

Modern fighters contain a targeting system that can calculate where the bullets will go, allowing the pilot to fire only when he's sure to hit the target. In some aircraft, the gun is slaved to the targeting system so it can be set to fire automatically when the target crosses the firing line.

In WW2, aiming was more primitive and usually involved firing a long salvo, using the tracer rounds to see where the bullets go and adjusting your aim to hit the target. This required far more rounds for a kill.

The gun is a weapon of last resort, to be used when all primary weapons have been expended. It doesn't make sense to add a large gun magazine when that would reduce the primary payload.

Gun strafing has been superseded by cluster bombs. Since the 2008 treaty forbade their use, small smart munitions have been used instead.