What were the common crew ranks on WWII US Navy flying boats and bombers? I have been trying to figure this out for some time, but have not had much luck elsewhere. I have found info on USAAF bombers, and what ranks the crewmembers often had, but nothing for larger navy aircraft.
I know Pan-Am's Boeing 314 Clipper flying boat was operated by the US Navy for some time during WWII, but I don't know if the USN operated any heavy bombers or other large aircraft. If they did, what would the ranks of the crew (pilot/plane commander, co-pilot, flight engineer, bombardier, radioman, navigator, gunners, etc.) be?
Thanks in advance for any help.

The Navy did operate some large aircraft, notably the PB4Y-1 Liberator and PB4Y-2 Privateer, variants of the B-24 Liberator. This was a late-war addition, the first being delivered in 1944 with the majority being delivered after the war. It was difficult to find crew compositions - the best bet I had was searching for reports of crashes based off of this list, but the newspaper clippings I found did not mention any crews.
There was a post-WWII (1950) shoot-down of a Navy PB4Y-2 by the Soviets and the article does have the list of the crew members that went down, but without the crew positions (notes added based off of information here. This was an electronic intelligence flight, but the crew ranks would have been similar for the flight crew at least. Note: Navy enlisted have ranks and rates, rates being associated with their profession and as such will often be more difficult to determine where there is little information.

LT Howard W. Seeschaf

LT John H. Fette

LTJG Robert D. Reynolds

ENS Tommy L. Burgess (Ensign/O-1)

AT1 Frank L. Beckman (Avionics Electronic Technician)

AL3 Joseph J. Bourassa (Aviation Electronics Man)

AD 1 Joseph H. Danens (Aviation Machinist's Mate)

CT3 Edward J. Purcell (Communications Technician)

AN Joseph N. Rinnier (Airman)

AD 1 Jack W. Thomas (Aviation Machinist's Mate)


Is a CFII required in order for a flight Instructor to provide training for added class ratings? Must a flight instructor have a CFII to provide multi-engine add-on training to a customer meeting the following criteria:

Holds a commercial pilot certificate with a single engine land class rating.
Holds an instrument airplane rating.
Holds a valid medical certificate.

So, put plainly, our hypothetical customer holds a commercial pilot certificate with a single engine land class rating and an instrument rating.  He/she has a "single engine commercial-instrument ticket" to use industry lingo.
Does the customer's MEI have to have a CFII to give the add-on training?

An instructor need not be a CFII to provide training for an additional class rating to an existing instrument pilot with a category rating under which the additional class falls.
If a customer already holds a commercial airplane certificate with a single engine class rating and instrument airplane rating, an instructor does not need to hold a CFII to provide training that customer’s multi-engine class training.  My regulation walk is laid out below.  Please read it before voting or commenting.
Important note: if the customer is NOT instrument rated and is seeking the instrument rating for the category -and/or- the customer is seeking to upgrade from a PPL to a CPL or CPL to ATP, the instructor must hold a CFII/MEI.
Regulation Walk
First, when is an instructor required to hold a CFII?
61.195(c) outlines instructor limitation and qualification related to the instrument training.  This reg specifies that an instructor must be a CFII to provide instrument training for the issuance of an instrument rating, a type rating not limited to VFR, the commercial certificate, and the ATP certificate.
If we stop there it sounds like an instructor needs to be a CFII to provide training to a customer seeking a simple ME class add-on to an existing airplane SE comm-inst.  But wait…
Are we really conducting “instrument training” while preparing for an additional class rating to an existing SE comm-inst ticket?  No, we’re not.  “Instrument training” has a definition in 61.1:

Instrument training means that time in which instrument training is
received from an authorized instructor under actual or simulated
instrument conditions.

61.1 also defines “flight training” which is different from “instrument training":

Flight training means that training, other than ground training,
received from an authorized instructor in flight in an aircraft.

The training for an additional class rating to an existing airplane SE comm-inst is not “instrument training,” it is flight solely by reference to instruments and that’s an important distinction.  It sounds pedantic, but the FAA intentionally uses these two terms very carefully:
61.109(b)(3) – PPL airplane multi-engine aeronautical experience requirement

3 hours of flight training in a multiengine airplane on the control
and maneuvering of an airplane solely by reference to instruments,
including straight and level flight, constant airspeed climbs and
descents, turns to a heading, recovery from unusual flight attitudes,
radio communications, and the use of navigation systems/facilities and
radar services appropriate to instrument flight.

61.129(b)(3)(i) – CPL airplane multi-engine aeronautical experience requirement

Ten hours of instrument training using a view-limiting device
including attitude instrument flying, partial panel skills, recovery
from unusual flight attitudes, and intercepting and tracking
navigational systems. Five hours of the 10 hours required on
instrument training must be in a multiengine airplane.

Do you see the difference?  It’s carefully written to allow a non-CFII to conduct PPL ME training but requires a CFII to perform CPL ME training (which is also true for CPL SE).  But wait, there’s more…
61.109 and 61.129 are aeronautical experience requirements for the PPL and CPL certificates.  Note that our customer already holds a CPL certificate for airplane SE and an instrument airplane rating.  The instructor does not need to meet the hour requirements in 61.129 because 61.63(c)(3) [Additional Class Ratings] gives us:

A person who applies for an additional class rating on a pilot certificate…need not meet the specified training time requirements
prescribed by this part that apply to the pilot certificate for the
aircraft class rating sought; unless, the person only holds a
lighter-than-air category rating with a balloon class rating and is
seeking an airship class rating, then that person must receive the
specified training time requirements and possess the appropriate
aeronautical experience.

This means that no “instrument training” is required and that any training that takes place is “flight training solely by reference to instruments” and can be performed by a MEI without a CFII.
So, to conclude…
…a customer seeking to add a ME class rating who already holds a commercial pilot certificate for single engine land airplane with and instrument airplane rating is not receiving commercial certificate training because he/she already holds a commercial certificate.  They're merely adding another class to their commercial certificate.
…a customer seeking a ME class rating who already holds a commercial pilot certificate for single engine land airplane with and instrument rating is not receiving instrument training because he/she already holds an instrument airplane rating.  Again, just a class add-on, not a new rating.  There are no ME or SE instrument ratings, it's a category rating.
…the training received is purely multi-engine operation training and covers how to exercise the privileges of their existing commercial pilot certificate and instrument airplane rating while flying a multi-engine airplane.  It is not training for an instrument airplane rating (they already have it) and it’s not commercial certificate training (because they already have it).  It’s an additional class rating per 61.63.
…our CFI/MEI (no CFII) can give the training and endorse the customer for a practical exam.
Important notes:
A customer seeking to upgrade a cert from PPL to CPL -or- CPL to ATP must receive training from a CFII/MEI.
A customer going for an initial instrument rating must receive training from a CFII/MEI.


Why select the transponder to TA only in the case of engine failure? Part of the 777 engine failure checklist is to set the transponder to TA only.

What is the purpose of this step?

The TA mode is selected when there is an issue, basically telling the 'other' aircraft that you cannot maneuver if a RA situation occurs. The other aircraft has to do all the maneuvering (as they can still generate RAs).
From Eurocontrol ACAS II bulletin from Dec 2012:

In the TA-only mode,the equipment still performs the surveillance function (i.e.  it  scans  for  proximate traffic) but it will only generate TAs. Other TCAS II aircraft can still generate uncoordinated  RAs  against  the  aircraft which has its TCAS II in TA-only mode.
The TA-only mode may be explicitly specified in operating procedures as a response to in-flight malfunctions such as an engine failure with consequent aircraft performance implications or a pressurisation system failure followed by an emergency descent.


What are the properties of the wing (airfoil symmetry, angle of incidence) of an aerobatic aircraft? On an aerobatic aircraft, such as an Sbach342, what type of airfoil does it have and what angle of incidence does it have in relation to the fuselage?

There are a few things to consider for a good aerobatic airfoil. The transition between attached and separated airflow has a big influence for spins or snap rolls, and a good aerobatic airfoil needs only a small change in AoA (angle of attack) to fully transition between the two. To achieve this, it helps to shape the forward part similar to an ellipse (a lemniscatic function, to be precise), and to use a nearly straight line for the last 70% of chord. The goal is to have a Stratford pressure rise on those 70% which gives the maximum possible pressure gradient without separation. Increase AoA just a little, and you have fully separated flow over those 70%.

When all works as planned, you can get the plane out of a spin by applying rudder at, say, 45° before the fuselage points in the desired direction and get out of the spin within 10° of that direction. Same goes for snap rolls, they get really snappy. It is a real pleasure to fly such planes, but you need some discipline. There are no aerodynamic warnings before you stall, and stalling comes immediately. On the other side, with the limited lift loss of such an airfoil and the powerful engines of aerobatic airplanes, stalling is no big issue.

A major reason for mounting the wing at 0° incidence is that you need little elevator correction in a roll. Rolling happens about the longitudinal axis of inertia, and if the wing is aligned with this axis, it has 0° AoA at 90° and 270° of the roll and at 180° the inverse of the AoA it had in level flight. With a symmetrical airfoil, lift is always correct, and if the aircraft flies at zero stability, you need not to move the elevator.

Mistimed elevator movement in rolls leads to immediate changes in flight path direction (happens really easily, and is easy to observe from the ground), and it is very hard to pitch the whole airplane just at the right time so it has no lift (read: side force) in knife edge flight, but the right lift in inverted flight. Just for flying inverted, many regular airfoils are just fine, but it is in the transitions where the symmetric airfoil has a clear advantage. A fast roll with a cambered airfoil will result in a corkscrew-shaped flight path because you cannot pitch quickly, let alone precisely, enough.


Why are there full-fledged entertainment systems on aircraft when today everyone has a smart phone? Today, many large commercial aircraft have full-fledged entertainment systems, sometimes going as far as putting a personal LED screen in every seat.

Let's just consider the costs of this for a moment:

• weight of the devices and their wiring

• power and waste heat

• cost of designing and approving the system with the FAA

There may be more I missed.

So now let's consider that today, most people (and certainly most people who can afford to fly) have a smart phone of some kind. They will most definitely bring it with them on the flight. And most people will also bring the charger and headphones (or earbuds) with them.

So you can see where this is going. If the airliner wants to provide movies or music, why not just have a jack (USB?) at every seat to plug in your smart phone and get it that way? Or possibly even provide streaming Wifi once in the air (not a true connection to the internet at large, but just as a way to distribute the movies/music). There might still be bandwidth challenges, but surely, surely this is better than a traditional IFE system as it exists today.

Am I missing something?

Here are some points to consider:

The screen size is a huge part of the experience. People with smartphones mostly still view content on a large regular screen when they are home or at a hotel etc. Hence, given a choice a passenger is always going to prefer the larger screen you can pack into the seat back than the relatively smaller smartphone display.
If you can be sure every seat has an IFE screen you can use it for other purposes like mandatory safety announcements & videos. Unless  you can be sure there's no seat without a smartphone owner depending on them for such messages is hard
If you have an existing aircraft the cost & effort to modify it & recertify the changed config. isn't worth it
Smartphones have only become ubiquitous in the last 5 years.
Average fleet age is much more than that. A typical aircraft you fly on might have been built 10, 15 or even 20 years before today.
Manufacturing date is not as important as the design date: If you are flying even in a 5 year old aircraft but the design was made 20 years ago there's no chance the designer could even forsee the smartphone revolution so he put in the IFE.
New designs you can expect modifications e.g. Many recent aircraft have a local USB port you mention & allow the passenger to plug in his device & view his own movies or listen to his own music on the IFE screen. http://www.turkishairlines.com/en-int/travel-information/frequently-asked-questions/on-board/in-flight-entertainment

  Connections enabling passengers to listen to, or watch on their
  individual screens, content on their personal iPods or USB devices are
  available on B777 and some of our A330 aircraft.

The power and waste heat tradeoff of smartphones vs dedicated IFE isn't clear: If you encourage IFE via smartphones you would need to provide charging capacity for simultaneous plug in of hundreds of phones. The electrical resources for that aren't  insignificant.
The devil you know is better than the one you don't: Dedicated IFE is tested & certified with well known characteristics. Having hundreds of unknown chargers plugged in & batteries charging adds other variables to the game. You'd also have to support multiple OSs, screen sizes etc. on the software side.


What happens at a ramp check when I forgot my license and medical? I wonder what happens if I would get ramp checked and don’t have my license and medical with me. Especially in EASA territory. Anyone ever had this case?

If you get ramp checked in a country under EASA jurisdiction, they will follow the EASA ramp check SAFA procedures, which include 53 points of inspection, not all of which may be performed during a check. Licenses are part of the inspection. Medical certificates are not mentioned, but I assume they are as well. Discrepancies found can be minor, significant or major. As a former auditor myself, I am going to make an educated guess that not having your license in your possession is the same as not having a license at all and would be a major discrepancy, and might result in the inspector directing the facility not to allow you to depart in your aircraft until you go get your license. It is almost 100% certain that the discrepancy would also be reported to the FAA.
At what stage of the flight the ramp check is performed will also make a difference, of course. Getting ramp checked before you leave and not having your license may result in nothing more than a stern warning and being told to go get it. You will likely not get off as easily if you are ramp checked as you are arriving in your aircraft.
Solution: Follow your checklist and verify your documentation prior to even starting the engine.


Why does the NASA X-57 need a "gust control system"? Why are NASA's engineers concerned about gusts affecting the X-57?
I understand that NASA is recommending automatic torque based prop speed control to be used in flight but also in gusty conditions.
Source: https://en.wikipedia.org/wiki/NASA_X-57_Maxwell

The speed of each propeller can be controlled independently, offering
the ability to change the over-wing airflow pattern to cope with
flying conditions, such as wind gusts.

I understand:

The original airplane being used had a wing loading of about 17lbs/sq ft.

The X-57 has a wing loading of 45 lbs/sq ft with its new smaller wings.

The higher the wing loading, the less an airplane is affected by wind gusts as it needs much more wind velocity to generate lift. E.g. frontal wind gust hitting one wing, then the other on a lower wing loading would create much more roll.

Source: https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-109.html

High-Aspect Ratio Experimental Wing
Perhaps the most noticeable difference from the X-57’s Modification II
configuration is the development and integration of an experimental,
high-aspect ratio wing. Designed by Xperimental of San Luis Obispo,
California, the wing features a large reduction in area, with wing
loading increasing from 17 pounds per square foot to 45 pounds per
square foot.
The reduction in wing area also contributes to more efficient cruise
flight through decreasing friction drag. The final Modification IV
effort will demonstrate that the high aspect ratio wing with the
integrated high lift motor system will allow the X-57 to take off and
land at the same speed as the baseline P2006T. The aircraft will also
be less sensitive to gusts and turbulence, leading to a smoother
flight.

If the X-57 is less sensitive to gusts, why does it need a "gust control system"?
One possible answer is that the X57 needs that flow over the wings to generate lift.
I understand that the X57:

has 14 x 24" 5 bladed props
props spin at about 4,500 rpm
motors generate about 14,000W of power
stalls at about 60mph.

Entering that into java foil, the programs generates a prop exit speed multiplier of 1.6 or roughly 100mph.
See pics below
<img src="https://i.stack.imgur.com/VgvjO.png" alt="X57 prop specs
" />

Example:
10 mph headwind, gusting to 20 mph, increase is 10mph, which is only a 10% of 100mph airflow over the wings at a stall speed of 60mph, with wings that should be 300% less affected by wind due to 300% higher wing loading.
So why does it need a "gust control system"?

It would depend on the direction of gust. High-aspect-ratio wings have a lower rate of roll. Thus, an upward crosswind gust that introduces a rapid uncommanded rolling action may not be sufficiently correctable by aileron deflection alone, and may require the asymmetrical application of thrust to increase the control surface authority and lift of the lower wing.


Wind correction on downwind during circling A timing must be started when flying abeam the threshold on a circling approach. The FCTM of the B777/787 mentions 35 seconds and the SOPs of the Embraer 190 30 seconds. Do they need to be corrected for head/tailwind? If yes, how are they corrected?

Yes, they need to be corrected, mainly for two reasons:

1) Legally, the horizontal criteria for circling is the distance from the threshold of each usable runway (search for TERPS circling criteria if you are interested in US rules, or PANS-OPS circling criteria for the rest of the world). In other words: you need to stay within a given distance of the runway. If you have a very strong tailwind, without correcting for it, you might leave the circling domain.

2) In order to facilitate the base/final. If you have a very strong headwind (which is indeed not very likely, as it means you will land in a very strong tailwind), you will drift towards the runway during your entire base/final-turn. This means you will roll out on the final course a lot closer to the runway than you would in zero wind. This could be a problem, since your stable approach criteria usually requires you to be "wings level" at some altitude (typically 300 ft for circling).

Now, for the how, this will depend on aircraft and operator. One example is however to add/subtract half the wind component in knots from your timing in seconds. Example: Zero-wind outbound: 30 s, Tailwind component: 20 kt. Wind-corrected outbound: 30 - 0.5*20 = 20 s.

(In addition, outbound timing is usually also determined by circling height, since the higher you are, the longer you will need for your descent. A typical SOP here is to take the circling height in hundreds of feet, and multiply it by 3, to get your zero wind outbound timing. Example: Circling height: 1000 ft. 1000/100 * 3 = 30 s.)


What do these weather depiction chart symbols mean? I have several present weather symbols from the weather depiction chart that I'm not clear on and AC-0045 doesn't have in it's legend.

I know the mist and fog symbols, and these look very similar, but I'm not sure what the broken lines imply.  I've added three variations on the symbol below.

Since the other user posted a link that contained the answer that could in the future go 404, I'll provide the answer I found there.

The first symbol means "Fog in patches"

The second symbol is not present but by extrapolations likely means either "Mist in patches" or "Mist with sky visible".  The former seems more likely to me.

The third symbol means "Fog, sky visible."


Help identify an unknown airborne object In the wee hours of the morning of last Saturday (July 30, 2016), while out stargazing, I saw something odd which I am unable to explain.

The object was traveling with a bearing of about 5-20° east of straight south.
The object flew nearly straight overhead, somewhat near the star Vega, sometime between 1:10-1:30AM local time (6:10-6:30AM GMT).  I was stargazing at the latitude and longitude 44.795614 N, 94.377516 W (https://goo.gl/maps/FB4yDsR8GYv).
The object was moving at a speed similar to an airplane.
The object's light blinked 3-4 times, but at a seemingly lower frequency than a typical airplane.  Also, while planes typically have a very short duration flash, this object had much longer flashes (1-2 seconds, probably), with the light being lit for about the same proportion of time as it was unlit.
I did not hear any propeller sounds, indicating that either that the object was relatively far away or that this was not a plane/helicopter.
The light also seemed brighter than a typical airplane's light, although I can't be entirely sure.  It was certainly brighter than every star in the sky.
After the 3-4 blinks, there were no more blinks (and this is on a wonderfully clear night; it's not possible that it was obscured by clouds, as I could still see the stars along the path it was flying)

From all this information, I am able to deduce that it was not a satellite, as satellites don't blink like this.  It is presumably not a typical commercial or private flight, even though there is a small airport roughly 4.5 miles north of where I was, because the lights stopped blinking, and that is presumably prohibited in nighttime flights.  I have not heard of any plane crashes nearby, which I expect I would have, had this been a plane that went down in flight.

Any ideas what I might have seen?

My best guess is you saw a high altitude aircraft flashing its landing lights.

Landing lights serve a number of purposes. Besides illuminating the landing surface, they can also be used to signal other planes as they are so bright. To experience how bright they are, stand near the approach or departure path of a busy airport at night.

The reason for the pilots flashing the landing lights in your scenario is unknown. It could be signaling another plane on a potential collision course, or just a way of saying hello to other traffic (hey, cruising a commercial airliner is kinda bored, huh?).

Without any visual reference, judging distances on a nighty sky can be tricky. Flashing a light is a convenient way of saying "hey I'm here!" to other planes. It is likely that your judgment of the flying object's distance was also impaired by the night environment. The only reliable observation I would pick is that you did not hear any sound, which suggests the object was very far away.


How Cabin Pressures Are Selected? The pilot puts the cruise altitude to the FMC and the plane auto adjusts the cabin pressure. I know that but I once heard the cabin pressure is set to three thousand feet.

Is it true? Why is the cabin pressure set to 3000 feet? How does plane designers of Boeing/Airbus/Bombardier etc. choose which altitude the cabin pressure will be set to?

As a generic answer, the only setting the crew inputs in most pressurization systems is the destination field elevation. This determines the pressure schedule on descent, and the system will use a cabin altitude descent rate that will put the pressure differential to near zero, usually slightly positive (that is, a hundred feet or so below field elevation) upon landing before the outflow valves are opened fully to vent the cabin to atmosphere.

So if the crew sets the field elevation at 3000 ft, the system will use a pressure differential reduction schedule on descent that gets the pressure hull close to zero differential when at 3000 ft, so there is minimum effect on people when the system goes into dump mode to vent the cabin.


When is jet engine thrust maximum? Assuming we have a convergent nozzle I've read that the maximum thrust is achieved just in the moment the nozzle exit -minimum area- is chocked, i.e., the nozzle is adapted in the sense the pressure in the exit area equals the ambient pressure. How can I demostrate this with formulas?

Let's look at two cases, choked exhaust and complete expansion:

1. Choked exhaust

With a convergent exhaust pipe, the jet engine thrust reaches a maximum at the speed of sound of the exhaust gas stream.

The velocity of the gas flow increases if it was subsonic at the entrance of the pipe. In a convergent nozzle the maximum gas exhaust velocity is M = 1, the speed of sound at the temperature of the hot exhaust gas. With a choked exhaust, at M = 1 in the exhaust outlet, the static pressure is higher than ambient pressure.

The exhaust area needs to be reduced until the gas exit velocity is M = 1, which at for instance 800 ºC is 657 m/s. The pressure $p_e$ at the exhaust outlet will then be:

$$ p_e =\frac {\dot{m}\cdot R \cdot T_e}{V_e \cdot A_e }$$

which is greater than the ambient pressure $p_0$.

The net thrust $F$ of a pure jet engine is
$$ F = \dot{m} * (V_e - V_0) + A_e * (p_e - p_0)  $$

$R$ is the gas constant. Parameters you need to know:

outlet mass flow from the turbine $\dot{m}$ in kg/s
gas outlet temperature $T_e$ in ºK
speed of sound at $T_e$ in m/s, which for a choked exhaust is equal to $V_e$
outlet area $A_e$ in $m^2$
airspeed $V_0$ in $m/s$ and ambient pressure $p_0$ in $N/m^2$

If we use the following example of an aircraft flying M 0.85 at 30,000 ft, choked converging exhaust, exit area 0.1 $m^2$, mass flow 70 kg/s, exhaust temperature 1073 K, we get:

F = 70 * (657 - 258) + 0.1 * (328,106 - 30,100)

= 27,962 N from kinetic energy + 29,801 N from pressure difference, about the same amount.

2. Complete expansion

$p_e$ is now equal to $p_0$. This condition occurs if total pressure at the turbine exit $p_{Tt} \leq \epsilon_{kr} * p_0$, with $\epsilon_{kr}$ for a hot exhaust gas being around 1.95.

Analogous to the choked exhaust case:
$$ A_e =\frac {\dot{m}\cdot R \cdot T_e}{V_e \cdot p_e }$$

For the same conditions at 30,000 ft follows: $A_e$ = 1.09 $m^2$

and F = 70 * (657 - 258) = 27,962 N

The net thrust in this case is a lot lower because the turbine exit pressure is lower than in the choked case, and therefore the propulsive power of the jet engine is lower. Usually, in the case of a turbojet the turbine exhaust pressure $p_{Tt}$ is a lot higher than $\epsilon_{kr} * p_0$, which will lead to the choked exhaust case above.

Turbofans with a high bypass ratio have a low enough $p_{Tt}$ to allow complete expansion, most of the gas generator power being used for the bypass air compression.


Does a decreasing shape factor correspond to greater or reduced probability of separation? The shape factor ($H=\frac{\delta^*}{\theta}$) is the ratio of displacement thickness, a measure of the thickness of the boundary layer, to the momentum thickness, a measure of the shear stress. I think that a larger shape factor indicates that the boundary layer is larger and there is less shear stress, so it seems like a larger shape factor should be associated with a greater likelihood of separation. Is that right? If not, why?

Yes you're reasoning is spot on. As the momentum thickness decreases, that indicates the velocity gradient at the wall is less, indicating a greater likelihood of separation occurring.


Should I keep specific distance from Class B? I was wondering if I fly my c172 in class E airspace, and Class B base was 5000 MSL. should I keep specific distance from Class B? or is it okay to go up to 4900 MSL but not reaching 5000 MSL?

You should remain at least 500 feet vertical separation from the Class B airspace, considering your direction of flight in accordance with FAR 91.159 (proper VFR cruising altitude) if you are more than 3000 feet AGL.  Or 2-3 miles lateral separation from Class B airspace (no regulation, just common sense).

If the Class B floor base altitude of 5000 feet msl is at or less than 3000 feet AGL, you could legally fly up to just below the base of the Class B and therefore come dangerously close to other aircraft operating at 5000 feet msl within the Class B.  This is too close for safety (considering allowable altimeter error, you could actually be at the same true altitude as an aircraft flying in the Class B).

Bottom line, in my opinion, you should always be at least 500 feet vertically or 2-3 miles laterally from Class B airspace.

This is what the Aeronautical Information Manual states regarding Class B:

(see the AIM):AIM 3-2-2


Do you need an instrument rating to fly in IMC in Class G airspace? I’ve been watching IFR checkride prep videos and several of them mention that among the things you can do with your IFR ticket is to:

Fly in Instrument Meteorological Conditions (IMC) in controlled airspace.

If you have your IFR ticket, you can depart Class G in IMC if you have filed a flight plan. So I’m a bit confused about why they put that restriction on the privilege.

But it also got me thinking. You need an IFR ticket to fly in IMC in controlled airspace, but is there a regulation that says you need one to fly in IMC in uncontrolled airspace? Or does NTSB 3935 mean that flying in IMC without your IFR ticket automatically imply careless and reckless flying?

In the US, an appropriate instrument rating is needed to fly when WX conditions are below VFR minimums, and at night for SVFR.  14 CFR 61.3(e)

Additionally, one needs an appropriate instrument rating to fly under an IFR clearance when in controlled airspace, regardless of the WX.

Notes: ATP and things like a category and class in an airship are exceptions. Also an airplane instrument rating works in gliders. Etc.

Addendum: Specific to the OP's citing a NTSB report, the following comment is added: To rely on the mentioned NTSB report, it is important to read the findings, and understand that, a.) the pilot intended to hit VFR conditions before 700AGL and upon entering controlled airspace, b.) the pilot told people he was taking off despite qualified observers noting 200 ft clouds, c.) the airport where approach was based said they were below IFR, which would leave the pilot few options if he needed to land nearby. Given that, it is easy to agree with the NTSB. Just because something is legal, doesn't mean it is best practice, and in this case it is likely the pilot did not do as stated.

One final point, IFR without a clearance in Class G is a decision which should not be taken lightly. Years ago, I routinely did it, and the airspace was uncontrolled at safe IFR enroute altitudes.  Departing a Class G airport, with less than VFR conditions, and expecting VFR before hitting controlled airspace at 700AGL is dubious. The vest majority of my IFR flights in uncontrolled airspace, that were without benefit of clearances, were where there are large areas of uncontrolled airspace, and safe IFR altitudes could be flown enroute. Furthermore, while ATC did not issue clearances for flight in uncontrolled airspace, coordination with ATC where possible, and also with local FSS were done. That is different from popping off an airport that is likely IMC, and stating that one intends to climb into VFR weather before hitting 700AGL and controlled airspace. The frosting on the cake is having the field in the area be below IFR limits for approaches.  Good judgment is hard to legislate.


During "partial panel" flying, in what ways is a turn rate indicator more useful than a turn coordinator? This question deals with flying by reference to old-fashioned "steam gauges", not a modern "glass cockpit".

I recall hearing some pilots very experienced (ATP) pilots advocate for the older-style "turn rate indicator" (senses rotation about the aircraft's up/down axis) over the newer-style "turn coordinator" (senses rotation around an axis canted about 35 degrees from vertical, to sense roll as well as yaw.)  Specific reasons were given, but I don't recall them. In what ways is a turn rate indicator more useful than a turn coordinator, during "partial panel" flying (no working attitude indicator or heading indicator) in clouds?

The purpose of canting the gyro's axis of rotation to sense roll as well as yaw is to give an earlier warning to the first stages of a developing bank and turn, and in my experience this is indeed helpful, but apparently there are some drawbacks as well.

A turn coordinator's axis of rotation is tilted around 30 degrees and rotates in the opposite direction. Because of this, looping errror is reversed and it under-reads at more than 1g. This makes it essentially useless when recovering from an unusual attitude on instruments, which is one situation in which you can easily find yourself when flying partial-panel.

With a turn rate indicator the instrument will over-read when the pilot is pulling excess G's in a turn; all the pilot has to do is relax the backpressure on the stick or yoke to correct.


When do I need to worry about a course deviation indicator reverse sensing? I understand that if I am tracking a radial inbound I will set that radial as the reciprocal so I don't have to worry about reverse sensing. On an approach however, do I need to set the CDI to the reciprocal? If I go missed and track the same course outbound do I then leave the CDI on the same heading?

On this approach plate, which was talked about here, why is the back course on two different sides (one is shaded on the left, one is shaded on the right)?

How does a front course and a back course affect your CDI settings?

Are there any difference between these two CDIs?

(And also, why is it labeled a VOR receiver? I thought both of these instruments were called Course Deviation Indicators.

On this approach plate, which was talked about here, why is the back course on two different sides (one is shaded on the left, one is shaded on the right)?

The 108.5 IPKN localizer is there only to mark safe path out for missed approach procedure and is intended to be flown outbound, so it has the signal swapped so it indicates normally when flown outbound.

  How does a front course and a back course affect your CDI settings?

It does not affect settings of CDI at all, because ILS does not take the OBS course into account. It indicates left when it senses more of the left signal and right if it senses more of the right signal, independent of anything else.

What it affects is:

The left signal is on the left when flying the normal direction and this applies both before and after the transmitter. So when you fly in opposite direction, the left signal is on the right from your point of view, causing the reverse sensing.
With HSI you can compensate for it by selecting the normal course in the OBS. The instrument then still senses the same, but the instrument is now upside down, negating the reverse sensing.

  Are there any difference between these two CDIs?

No, since these are both CDIs.

There is a difference if you have HSI:

The difference between CDI and HSI is that on CDI the needle always moves left-right, indicating whether your position is left or right of the selected radial (via OBS for VOR, but fixed for ILS) independent on direction you are flying. So if you are actually flying the opposite direction, you must steer the other way.

In contrast the inner part of HSI rotates with compass, always pointing the arrow in the selected direction. This has two advantages:

you see how your direction of flight relates to the selected heading and
when you are flying in the opposite direction (backcourse), the needle is upside-down, negating the reverse sensing.

  And also, why is it labeled a VOR receiver?

Because it is (also) used to display VOR signal. Both CDI (where the needle always moves left-right) and HSI (where the inner part with the needle rotates with compass) are VOR indicators.

Note that almost always the same tuner is used to receive VOR and ILS signals and the same instrument is used to display them though the processing logic is different (VOR detects phase while ILS detects differences in the depth of modulation from the two signals).


What are the technical details of how airline seats are installed on an airliner? What are the technical details of how airline seats are installed on an airliner? The step by step.  Not made how they are installed.

Economy seats are removed (and installed) row by row. The row of seats (typically 2 - 5 individual seats) are bolted to a track on the airframe floor. You can see them being removed in this video (~18:30) during a D-Check. The rows are usually held in place with bolts, often in the corners and where seats meet. You can see an example bolt pattern here.

Modern First class seats (the more sophisticated individual ones) will be removed one at a time often with the whole entertainment center around them. The above linked video also shows this.

And, of course, installation is the reverse of removal.


Why are updraft carburetors standard in aviation? My only detailed experience with carburetors is in aircraft. I'm pretty familiar with the principles behind float-type carbs, but I recently saw a schematic for a "downdraft carburetor" with a choke valve. This got me curious, so I did a little research and found that what I'm used to is an "updraft carburetor", and that (according to wikipedia) they fell out of fashion in the automotive industry in the 1930s.

Why is the updraft carburetor design so prevalent in aviation? Does an updraft carb actually have a choke valve?

Images below to provide a little context for those of us who are not engine experts!

Typical aviation carb:

Typical downdraft automotive carb:

I can think of three reasons to use an updraft carburetor in a single-engine GA airplane:

Anti-flooding:

The float-bowl regulator in your carburetor is cheap and simple, but it is far from perfect under all conditions.  Short periods of zero-G or negative-G operation, caused by a quick dive, turbulence, or even bumping over uneven ground, can jiggle the float and spill liquid fuel into the venturi.

In a downdraft or sidedraft carburetor, this liquid falls into the intake manifold and wets the interior walls and may get into the cylinders, causing an over-rich mixture condition.  The engine is said to be "flooded" and will not run until the liquid is cleared out.

With an updraft carburetor, the spilled fuel tends to fall out before it can foul anything.

Gravity feed:

If your aircraft has fuel tanks higher than the carburetor when in cruise attitude, you may be able to remain under power if your fuel pump fails.  An updraft carburetor can be mounted lower in the engine compartment than sidedraft or downdraft types; in fact, it is usually under the engine.

Early automobiles did this to avoid the need for a fuel pump; fuel was fed by gravity from a fuel tank higher than the carburetor, e.g. just below the windshield.  The lower the position of the carburetor, the deeper the fuel tank could be.

Convenience:

If you look inside the cowling of most GA planes, you will see much more space under the engine block than above it.  That seems to be the best place for lots of auxiliary equipment and attachments, including the carburetor and air filter.


What will happen if we start the A320 engines but we don't wait for the amber crosses on the E/WD to disappear? My logic is that we should wait for the sensors to register the present indications so we have a proper idea of what state the engine is in particularly the EGT if we have to consider a manual start.

Amber X's mean the FADEC is not yet energized. Once the X's disappear it means the FADEC is ready and can provide monitoring (even passive monitoring in a manual start).

Without FADEC there is no means to start the engine, as the valves are also FADEC controlled.

(A320 FADEC schematic.)

FADEC is needed even for manual start.


What winglet airfoils are used on the Boeing B737? I would like to know what airfoils are used for the Boeing 737 winglets.

Aviation Partners Boeing, a joint venture between the two companies, developed the winglets for 737NG, 757 and 767 aircraft.  They are offered in two varieties, a "blended" version, which is where the wingtip is upturned to near vertical and a newer, "split scimitar" version which adds a downward pointing tip as well.  They are made of a composite material with aluminium leading and trailing edges.

Their purpose is not to generate lift, but rather, prevent wingtip vortices (which generate a significant amount of induced drag) from spilling onto the top of the wing.

The design characteristics of the blended winglet are described in US Patent 5,348,253.


What are the consequences of an airline pilot deviating from a flight plan to perform a random maneuver? What are the consequences of a pilot flying a scheduled airline flight with passengers deviating from a flight plan to perform a random maneuver?

Say during a normal landing procedure, he spots something interesting not in his normal flight plan nor in the normal landing procedure, and decides to do a fly over, then returns to land the plane normally.

I imagine he would be fired from his company, but would there be legal action against him? If so, what would be the severity of the crime? (We can assume the US or Europe).

As long as the pilots clear it with ATC and it doesn't violate the general rule against careless or reckless actions, there is nothing illegal about it. Pilots frequently request minor route changes, and ATC generally grants them if conditions permit. For instance, aircraft departing SFO often request a scenic pass by the Golden Gate Bridge as a treat for themselves and/or their passengers.

As long as no laws are broken (see above), their employer won't know whether the deviation was initiated by ATC or by the pilot, nor would they probably care even if they did know.

OTOH, if a pilot deviates from ATC instructions, it could potentially get them killed, so few pilots would knowingly do that. Deviations are almost always unintentional, and unless the pilot has a history of such problems that calls his qualifications into question, he/she will most likely get a "counseling" session and perhaps some refresher training.


Do swept back wings affect the moment of inertia of an aircraft enough to be relevant for the roll response? I have studied that swept back wings help in delaying the shock waves formed on the wing, but also to my understanding I feel swept back wings reduce the moment of inertia (like for example a ballerina dancer where she spins so easily when she keeps her hands close to her body).

This in turn helps in improving the roll response which is an advantage to a fighter jet. So is my understanding correct?

A wing has three basic design parameters—span, chord and sweep—which are all independent of each other.

Span is always measured along the perpendicular axis of the whole aircraft and chord is always measured along the longitudinal axis. So pivoting the wing around its root will change all three parameters and affect the properties that depend on them.

When designing the aircraft, you choose area (span times chord) to give you the needed amount of lift, then span to give you the desired minimum lift-to-drag speed and sweep for transsonic capability and/or stability. So you should be comparing swept and unswept wing of the same span and area, and those somewhat obviously have the same moment of inertia in roll.


Can a US pilot residing in the EU fly N-reg under IFR on a US PPL? I am a US citizen living in the Netherlands, and I have an FAA PPL(A) with current IR as well as an EASA PPL(A) without IR.  I am currently trying to figure out my easiest path to IR conversion, as I do not have the required 50 hrs PIC time to do a direct conversion.  I know I can do the CBIR, but I'm wondering if I'm permitted to fly N-reg aircraft under IFR in order to build the required hours.  I've heard that as an EU resident I'm required to fly using both an EASA PPL and FAA PPL in an N-reg, and therefore I assume the answer is technically no.  Am I correct in this assessment?

Long story short, European residents apparently require an EASA license to operate a foreign aircraft, even if they also hold a foreign license from the country the aircraft is registered in.

European regulations are really difficult to pin down because implementation is delegated to member states, however it looks like as a resident in an EASA country you do need an EASA license to operate an N-registered aircraft based there. There are many online sources that say that, although they typically don't link to actual regulations. Several of them mention that you get a 12-month period to acquire the EASA license, during which you can still fly with your foreign license.
For example:
AOPA blog article:

The European Aviation Safety Agency, a pan-European regulator, had
passed a regulation some years earlier requiring that European
residents acquire a European equivalent license to fly an N-registered
aircraft in Europe. This requirement didn’t apply to nonresident
foreigners.

A UK Flight Examiner's website:

If your N-reg aircraft would be classified as an EASA aircraft if you
registered it under the G registration, AND it is based in the UK now,
you do need either an EASA licence to fly it or an EASA validation. If
you wanted to fly it outside the UK, you would need your FAA licences
too.

The underlying EASA regulation appears to be REGULATION (EC) No 216/2008, which says that it applies to foreign aircraft if the operator is based in Europe (Article 4, paragraph 1(c), emphasis mine):

registered in a third country and used by an operator for which any
Member State ensures oversight of operations or used into, within or
out of the Community by an operator established or residing in the
Community

Paragraph 2 says that the regulations apply to personnel too, it's not just about the aircraft itself:

[...] Personnel involved in the operations of aircraft referred to in
paragraph 1(b), (c) or (d) shall comply with this Regulation

The tricky part is that EASA leaves it to each member state to actually implement the regulations and sometimes they implement at different times (see comments in the AOPA article above). I couldn't find the Dutch regulations, but the UK regulations do confirm that only non-residents are exempt from European licensing requirements. Air Navigation Order, Article 149, emphasis mine:

This paragraph applies if the operator of the aircraft is neither
resident nor established in the European Union, and the person
acting as a member of the flight crew is the holder of an appropriate
licence granted or rendered valid under the law of the country in
which the aircraft is registered or the State of the operator.

(As an aside, the ANO article is written in a very confusing, double-negative construction, but it does line up with other sources.)
Because EASA delegates to each member state, the best way to get a definitive answer that applies to your situation is to contact the Dutch civil aviation authorities. When and if you do find out what the requirements are, it would be great if you would come back here and add your own answer to this question. There's surprisingly little definitive, sourced information available about this and a first-hand answer would be really helpful.


In what order were the runways built at Paris Charles de Gaulle? At its commission time (in 1974), Roissy-CDG airport did not have all its runways in service. As an example, I found an article (fr) saying the fourth (and last) runway was built in 2000. But this article does not precise which runway it was.

I'm curious about how the extension of this airport was handled. Wikipedia gives an overview of terminal  extension history but not of runway.

I imagine the first runway to be commissioned is the 09L/27L as it is the nearest to the first terminal, but then, what happened? Was the 09R/27R commissioned before the southernmost runways? Did they built a runway on the south before building the smaller outer runways? In short, in what order did they build the runways?

Bonus question: Did they already have changed the runway names?

Overview

(background image: Wikimedia)

Details

The first runway was finished in 1971 as 09/27 and it corresponds to todays 09R/27L:

  Work on the satellites started in late 1970. Also built were Air France and UTA hangars and a pooled cargo terminal.
  Construction on the first 11.800-foot (3,600-meter) runway, 09/28, and its associated taxiways started on August 1st, 1969.

  The runway was inaugurated by the Ministry of Transport on September 9th, 1971. The earthworks of Runway 2 were started in 1972.

(airporthistory.org)

The second runway was finished in 1976 as 10/28 and corresponds to todays 08L/26R:

  In 1976, Charles de Gaulle handled 7.5 million passengers and opened a second runway. Initially, the second runway was built at a reduced length of
  9.400 feet (2,900 meter) and without a parallel taxiway. It was only used as a backup when the main runway was inoperative or at the instruction of air
  traffic control. The runway could be built out to its full length of 11,800 feet (3,600 meters) and taxiways added when traffic demand required.

(airporthistory.org)

The following ground chart shows the layout in 1977:

(image source: flickr.com by jwhshd)

By 1994, the terminals had been greatly expanded to the south and the new runway was at its full length (I don't know when exactly the expansion happened):

(image source: flickr.com by jwhshd)

The third runway was finished in 1999:

  Expansion of Paris Charles de Gaulle (CDG) Airport has also helped Air France. A third runway at CDG opened in 1999, with a fourth to open in 2002.

(Strategic Management in Aviation: Critical Essays)

Unfortunately, the source does not detail which runway this was. By searching through pictures of CDG from 1999 on airliners.net, I was able to find the following quotes:

  Landing on runway 26L

(airliners.net, May 1999)

  Taxiing out runway 27

(airliners.net, May 1999)

This would suggest that the runway numbering had already changed and the second runway to the south (08R/26L) was built first (in 1999). This would leave runway 09L/27R to be the fourth runway added in the early 2000s.


What is the difference between an aviation training device (ATD) and a flight training device (FTD)? According to FAR 61.57, the regulation requires different experience requirements when a pilot uses FTD or ATD for their experience minimums. So I have tried to look up the difference between those two but I don't really understand.

According to Advisory Circular 61-136A, the definition of ATD is a training device, other than a FFS or FTD, that includes

  a replica of aircraft instruments, equipment, panels, and controls in an open flight deck area or an enclosed aircraft cockpit.

The definition of FTD, according to FAR Part 1, is also

  a replica of aircraft instruments, equipment, panels, and controls in an open flight deck area or an enclosed aircraft cockpit

They look pretty much same to me.

Could you give me the examples of those two?

14 CFR Part 141, Chapter 41 Flight simulators, flight training devices, and training aids. Requirements for a FTD:

  (1) Be a full-size replica of instruments, equipment panels, and
  controls of an aircraft, or set of aircraft, in an open flight deck
  area or in an enclosed cockpit, including the hardware and software
  for the systems installed that is necessary to simulate the aircraft
  in ground and flight operations;

The important mention is it must be a full-size replica of controls and panels. This doesn't apply for an ATD (see definition in AC 61-136A, appendix 2).

See also:

Sorting the simulators.
FAA withdraws ATD rule.


Can I get an FAA restricted ATP certificate with 1000 hours total time? I have an FAA Commercial Single-Engine certificate with 260 hours total time and a Bachelor's degree in Electrical Engineering issued in Indonesia. I have an Indonesian Passport and I'm working as a copilot flying DHC-6 Twin Otters in Indonesia. I'm planning to get a restricted ATP certificate in the USA but there's a question.

Is it possible to go and get a restricted ATP in the USA after flying 1000 hours TT on DHC 6 Twin Otter in Indonesia?

Unless you were trained through a military flight school, the answer is no.  Part 61 states that you need a minimum 1500 hors TT to apply for an ATPL unless you either attended a military flight training program or an aviation degree from an accredited institution.


How do humanitarian flights arrange special permissions to fly when ATC isn't available? In natural disasters, transportation infrastructure is often among the first and most critical of public services to be disrupted. Not coincidentally, it's also a time that tends to see small airports become vital intake for international support.

If aircraft acting on humanitarian concerns, say a commercial airliner loaded with doctors and medicine, wants to land in a major city affected by a natural disaster where radar is destroyed, ATC is non-functional, and runways are... surprisingly clear, what is the procedure for arranging landing?

In practice, do humanitarian support just approach, land, and deal with the consequences later?

In the U.S. at least, HADR doesn't launch aircraft until a crisis aka disaster has been identified, even if at launch they don't yet know if the problem is lack of potable water or civil unrest over rigged elections.

An already flying commercial airliner won't have a glut of doctors and medicine unless it's been chartered for an already identified crisis, so it's unlikely to divert to this one.

If, after an identified disaster, an aircraft flies there to assist:

A helicopter doesn't need ATC support to land in an off-airport parking lot, of which a major city would have many.
A fixed-wing aircraft, needing an approach path, lacking ATC response, would revert to non-ATC protocols, just like at a small Midwestern grass strip or an Alaskan inlet.  VFR.

Non-aero analogy:  fire trucks and ambulances don't fret over parking tickets.


Circular arc airfoil wing: why does the wing nose down twist due to camber? I am reading this paper:
"Computational Investigation of Microscale Shrouded Rotor
Aerodynamics in Hover" Vinod K. Lakshminarayan, James D. Baeder ; JOURNAL OF THE AMERICAN HELICOPTER SOCIETY56, 042002 (2011).

In part "Rotor and Shroud Configuration" (page 2), the paper said:

  " The blades used have a 2:1 taper starting at the 60% span location with the leading edge remaining straight and the trailing edge tapering toward the leading edge; this results in about 11 degrees nose down twist in this region due to the camber. The radius and the chord of the blade are 121 mm and 25 mm, respectively, making the aspect ratio equal to 4.84. A circular arc airfoil with 10% camber, 2% thickness, and leading edge sharpened from the 8% chord location is used."

I thought taper has nothing to do with angle of attack of airfoil section and the chord lines of every section lie in the same plane. How could the wing nose down due to camber?

I think it may be related to the geometric construction of the blade :

Usually taper is made by scaling down airfoil at wingtip, which doesn't alter angle of attack at all.

In this case the airfoil itself is cut along a line going from root trailing edge to tip mid-chord, which alters angle of attack with desired negative twist.


How does latitude affect the air temperature at 8 km altitude where planes fly? Is the air temperature (at 8km) above the North or South poles colder than the same altitude above the equator?  Why?

Ground level air temperature difference between coldest and warmest places on Earth can be >70C. As you get higher, the temperature drops, of course. Does it mean that near Arctic circle air temperature at let's say, 8km altitude still maintains approximately the same difference with the 8km altitude above equator as at the ground level? Or does it even out? Is it perhaps even possible to have air at some altitude significantly warmer than at ground level?

In the troposphere, air at altitude is colder than air at ground level. But surprisingly, air at altitude at the poles can be warmer than air at altitude at the equator. From the wiki article on troposphere (I added the bullet points):

  The troposphere is heated from below by latent heat, longwave radiation, and sensible heat. Surplus heating and vertical expansion of the troposphere occurs in the tropics.

  At middle latitudes, tropospheric temperatures decrease from an average of 15 °C (59-degree Fahrenheit) at sea level to about −55 °C (-67-degree Fahrenheit) at the tropopause.
  At the poles, tropospheric temperature only decreases from an average of 0 °C (32-degree Fahrenheit) at sea level to about −45 °C (-49-degree Fahrenheit) at the tropopause.
  At the equator, tropospheric temperatures decrease from an average of 20 °C (68-degree Fahrenheit) at sea level to about −70 to −75 °C (-94 to -103-degree Fahrenheit) at the tropopause.

  The troposphere is thinner at the poles and thicker at the equator. The average thickness of the tropical troposphere is roughly 7 kilometers greater than the average tropospheric thickness at the poles.

There is quite a bit of variation in the troposphere as a function of place on earth, and much effort has been put into creating a standardised atmosphere that can be used for practical purposes around the world. The ICAO standard atmosphere serves that purpose. It cannot account for local wind conditions and humidity.

I found a graph in an old paper format uni book on the atmosphere, depicting average conditions in two separate places on earth, Berlin and 40° latitude in North America. The graph shows that although the temperature lapse rate is very similar in both cases, there is a difference in temperature at a given height. The arrow gives the temperature difference at 8 km height, also transported to 0 m (less average difference) and to 10 km (more average difference).

Above is for average temperature at two different places on earth, at similar latitudes. I could not find any direct comparison between average temperature at altitude of the poles and the equator - the wiki article seems to indicate that average temperature at the poles is higher at high altitude, a surprising indicat


Do any aircraft possess washed-in wing characteristics? I have been teaching ground school at my local Canadian Air Cadets. When I was teaching about the wing twist of an aircraft, I was asked if any aircraft possess washin characteristics (vs washout). The book teaches that wing twist is either washin or washout. Washout is supposed to decrease the wingtip's angle of attack in order to promote better stall characteristics, while washin does the opposite (worse stall characteristics). Not sure why one would want washed-in wingtips, but was wondering if anyone knew of such aircraft.

According to Wikipedia, the Grumman X-29 had washed-in wings, as its considerable forward wing sweep gave it a strong tendency to stall at the roots.  As the wing roots on a forward-swept-winged aircraft are located aft of the wingtips, a root stall on such an aircraft would cause a strong pitch-up tendency, so the X-29's wings were washed in to mitigate the root-stall tendency.


Bed sheet as wing skin? https://en.m.wikipedia.org/wiki/Aircraft_fabric_covering
This article states several early aircrafts that successfully used cotton as wing skin including Wright flyer.  "Colditz Cock" glider had its wingskin made from bedsheets plus this guys

             used bedsheets to make their wingskin and the plane kinda took for like 2 seconds.
Can a  good,strong bedsheet successfully replace tedlar in an airplane without any problem?

Absolutely you can use a fabric for covering and airframe.  I used to build large scale R/C aircraft much like they used to build real world aircraft. I used fine silk to cover the wings, elevator, tail, and fuselage. I used epoxy to adhere it to the wooden airframe and then later apply some kind of lacquer, which serves to shrink and pull tight the silk and also makes it airtight. This can then be painted or not.  Silk is a very strong lightweight material. The performance is actually probably better than many modern materials, but probably would not hold up to the elements as well over time.


What are the CONT and FLT modes of the 737 start switches? I pilot the PMDG 737 in my simulator and I know that before takeoff and before landing, the start switches must be set to CONT mode and at high altitudes in FLT mode. But what exactly are CONT and FLT mode? What they do ?

The 737 has two separate engine-igniter systems (each of which has igniters on both engines).  Each engine has four possible igniter modes (except for earlier-model Originals, which have five) - in clockwise order 'round the knob, they're GND, OFF, CONT (or, for early Originals, L IGN and R IGN), and FLT.

CONT mode turns one of the igniter systems on (which igniter system is used depends on the position of a separate switch), and is used for takeoff and landing.

GND mode on an Original or Classic, or on an NG that's on the ground, also uses a single igniter system, and is used for ground-starting the engines.

FLT mode turns both igniter systems on, the better to help keep the engines operating under adverse conditions, or maximise the chance of a successful midair relight.  In the real world, FLT mode is used only in conditions posing a significant risk of engine flameout (for instance, extreme turbulence or very heavy rain), or if a flameout has already occurred and one or both engines need to be restarted in flight - not for high-altitude cruise flight in general.

On an NG, GND mode is another option for inflight restarts, in which case it uses both igniters (unlike how it operates for ground starts).

Your simulator might be confusing FLT mode with OFF mode (neither igniter system operating), which is the setting normally used in flight (as combustion in a gas-turbine engine is generally self-sustaining unless the engine, or its fuel or air supply, is severely abused).

Additionally, on an NG, the EECs can automatically switch both igniter systems on (if an engine flames out) or off (if bad things happen during ground-starting), no matter what the position of the ignition knobs.


Is there a difference between a chart and map? Does the use or meaning of "chart" or "map" vary worldwide?

Is there a difference between a chart and map?

Colloquially, I would say not really, by definition yes.
I think the simplest way to put is is:

All charts are maps but not all maps are charts.

Websters defines a chart as

: map: such as
a : an outline map exhibiting something (such as
climatic or magnetic variations) in its geographical aspects
b : a map for the use of navigators

while they define a map as

a : a representation usually on a flat surface of the whole or a part
of an area
b : a representation of the celestial sphere or a part of it
c : a diagram or other visual representation that shows the
relative position of the parts of something

In other words, maps are outlines of part or all of something while charts contain potentially more information like that needed to navigate or identify airspace. Interestingly according to the definition, if used for navigation its a chart.


Do landing strips suffer from potholes or rutting? In companion to the other question asking about wheel tire tracks.

Planes come down and stop with a significant amount of force which I would expect to cause either rutting or potholes.

Are runways susceptible to ruts and potholes?

And do these cause significant issues for landing planes?

Yes, they do, and it can indeed pose significant problems for aircraft.

Asphalt runways are susceptible to ruts (because asphalt isn't really solid - it's solid aggregate suspended in an extremely viscous liquid). The friction (heat) from landings partially melts the asphalt, and the weight of the aircraft slowly pushes it outward away from the landing gear, creating ruts. (There are also other ways you can cause ruts on asphalt runways, such as landing overweight aircraft on them on extremely hot days).
Concrete runways are theoretically less susceptible to rutting, but have their own maintenance challenges.

Runways can also develop potholes, cracks, and spalling - just like a road surface.
Because a pothole can cause loss of control on landing (if the landing gear falls into it and blows a tire or yanks the plane to one side), or serious damage to aircraft engines (if some of the material ejected from the pothole gets pulled into a jet engine's intake or kicked up by a propeller) airports take a lot of effort to prevent (and where necessary, repair) this kind of damage, and routinely inspect their runways.

Airports also do a lot of preventative maintenance on their runways, sealing open cracks and joints in the pavement material to prevent water from infiltrating under the runway and causing potholes (see the image below - click to enlarge).

The FAA has a lot of information on runway pavement design, which I will affectionately call "More than anyone ever wanted to know about runway design, and never asked!"


Laminating required documents? Airworthiness Certificates, Registration Certificates, Radio Licenses, Medical Certificates, Temporary Airman Certificates and other important documents are commonly printed on paper, which can be easily damaged or destroyed. Replacement can take weeks or months, grounding the plane or pilot unnecessarily.

Is there any regulation (or other general legal principle regarding official documents) that prohibits lamination to protect them?  If so, is there another widely accepted solution?

For protecting non-wallet documents, consider using a vacuum seal bag for food. To prevent warping the simplest thing is to squeeze the air out and only use the seal function, without vacuum.

This way way if somebody has an issue or you need to modify the documents, you can cut open the pouch and retrieve them in original state.


What is the correct range of the 787-10? There are two conflicting values for the 787-10's range; they are:

6,345 NM (11,750 km) -- boeing.com

7,000 NM (12,975 km) -- on the same website few years ago, as well as flightglobal.com

Note: In its early development the value was 6,345 NM (11,750 km), same as #1.
Which is correct and why do the values keep changing?

The range of an aircraft depends on the payload. The value you typically find is the range at typical payload.
You can find the payload/range diagram in the Boeing 787 Airplane Characteristics for Airport Planning document:

As you can see, at maximum zero fuel weight, the 787-10 range is only ~4200 NM. According to Wikipedia, the typical passenger configuration for the 787-10 is 330 seats in a 2-class layout. Assuming 195 lbs per passenger (FAA average adult passenger weight in winter) plus 50 lbs baggage per passenger, gives a typical payload of 80,850 lbs. This would result in a range of ~6000 NM. If not everyone onboard is an adult and not everyone takes the full 50 lbs for baggage, the range can be higher of course. Completely empty, the 787-10 can easily fly over 8500 NM.


How do I differentiate between different types of installed wire lock/safety wire on planes? Common wire-locking/wire safe-tying materials used in aviation include copper, stainless steel, Monel and Inconel.

Is there any way one can differentiate an installed stainless steel one from an installed Monel or Inconel one? Copper can be differentiated from the rest by its colour.

Monel is more expensive than stainless steel so it's use is limited to where it is an advantage, mainly in high temperature applications such as securing engine accessories, piping etc.  If the locking application is not in a high temperature, high humidity, high oxidisation area, then it's probably stainless steel.

There are chemical tests you can do on small samples using acids and reagents but you asked about an installed lock. The only way I know for testing an installed lock is to  polish it. Monel is duller than stainless steel and does not polish to a shine so  the quick way to tell is to try to polish a piece of it with a cloth.  If it shines up, it's stainless steel.  If it doesn't, it's monel.


Can a commercial aircraft be detected by ATC's / Radar systems if all its engines fail? In an event of failure of all engines of a commercial aircraft in mid air and no secondary backup or generators powering the plane (plane is virtually powerless and no comp systems work on board), would the ATC still be able to detect the aircraft with accuracy and if yes how is it done ? Are there any conditions that it has to be flying in an area which is monitored or any basic stuff which HAS to be working for ATC to detect ?

In an event of failure of all engines of a commercial aircraft in mid air ...

That would be a very rare event. In the modern cases where this has happened within an ATC area, it has not prevented location of the aircraft so far as I know.

  ... and no secondary backup or generators powering the plane

Even a two-engined airliner has an Auxiliary Power Unit (APU) and a Ram-Air Turbine(RAT). I believe they also typically have 10-15 minutes battery power for critical systems. I don't know if any airliner has ever lost all generators other than in cases where the aircraft was destroyed in flight (e.g. PanAm 103).

  would the ATC still be able to detect the aircraft with accuracy

If an aircraft's transponder and secondary-radar are not operating, ATC would rely on primary radar, which is less accurate, particularly for altitude. They would also ask the pilots for their position over VHF radio and ask other aircraft in the area to locate the aircraft.

Example: British Airways Flight 9

All four engines flamed out due to ingestion of volcanic ash.

  Despite the crew "squawking" the emergency transponder setting of 7700, the aeroplane could not be located by Air Traffic Control on their radar screens.

The pilot communicated with ATC over VHF radio and later restarted the engines.

  The engines had enough electrical power to restart because one generator and the onboard batteries were still operating

Example Air Canada Flight 143 (the "Gimli Glider")

This 767 ran out of fuel mid-air and all engines stopped.

  The 767 was one of the first airliners to include an Electronic Flight Instrument System (EFIS), which operated on the electricity generated by the aircraft's jet engines. With both engines stopped, the system went dead, leaving only a few basic battery-powered emergency flight instruments.

The pilot communicated with ATC Winnipeg and

  First Officer Maurice Quintal began to calculate whether they could reach Winnipeg. He used the altitude from one of the mechanical backup instruments, while the distance traveled was supplied by the air traffic controllers in Winnipeg, measuring the distance the aircraft's echo moved on their radar screens.

So yes, If the aircraft with all engines out is in radar range and ATC are attentive, they can track the aircraft's location.


Are Aircraft yokes self centering in non-auto pilot mode? In a typical car steering wheel if you release it while the car is in motion, it will return to its center, neutral position.

What's the corresponding situation in an airplane? Is a yoke self centering? Or does it stay put until corrected by the pilot inputs? Let's stick to non autopilot modes to simplify the basic behavior.

The forces on the control surfaces ought to be high when deflected from their default position, right? So I'm assuming that offers a restoring torque? E.g. with the rudder if you take your feet off the pedals then it centers, I think.

Some additional points:

As a simplified case what happens on the ground when the aircraft is stationary. If I deflect the control surfaces to their extreme position & release the yoke would they all return to the neutral position? Is the restoring force gravity or spring loading?
The answers on the other question seem to focus on ailerons but what about elevators?
Does the rudder typically self center with more alacrity than the other surfaces? Why?

With respect to "centering", a yoke only "centers" itself in the equilibrium point where forces on both ailerons and on both top and bottom of the elevator/stabilator are equal. That said, I wouldn't want to let the yoke "center and fly itself" as the forces on the control surfaces can be equal even when the aircraft is not straight and level. If not enough power is applied the plane will pitch down and "center" as you say, and if too much power is applied the plane will pitch up and then "center". As for roll, I find that in light aircraft (Cirrus excluded as the side stick has a spring mechanism) you don't usually want to leave the yoke out of hand as slight wind and light wind shear will cause the airplane to roll somewhat. So - short answer is - yes, it will "center" eventually but you might not like the attitude the plane is in when it's done, much of this depending on power setting and gusts/shear aloft/turbulence. As for autopilot, a roll and pitch (2-axis) autopilot actually continually applies force to the controls to keep the airplane level or turning as commanded, and at a constant altitude or climb/descent/airspeed as commanded, so I wouldn't say the controls really "center" when on autopilot either. Cheers!

As a bit more of an explanation, a "nice" airplane (one with positive aerodynamic stability) with the appropriate power setting should re-enter and maintain straight and level flight if the controls are disturbed and the yoke is released (but I've always had to input a little roll to keep the wings level). Check out the following picture from the FAA Pilot's Handbook of Aeronautical Knowledge Page 4-14:

Notice that the orange line eventually gets more and more flat. You can expect that in a Cessna 172 or something of the like... not in a more aggressive plan like aerobatic planes and fighter jets - you'll see something a little more like the green or red line. You can read more in Chapter 4 of the FAA PHAK (link here).


Can I safely plug something that draws 6 amps into the cigar lighter (power port) in my Piper Archer lll? Can I safely plug something that draws 6 amps into the cigar lighter (power port) in my Piper Archer lll ?

Yes, you can safely plug in a 6A load. Possibly a circuit breaker will pop out after some time. That depends on the rating of the circuit breaker serving the outlet and if there are any other loads on that circuit breaker. But it is completely safe to try it.


Do check rides completed by part 141 schools with self-examining authority count like normal check rides for CFI renewal and gold seal? Some schools have self-examining authority issued by the FAA.

Do check rides completed in this manner count the same way as a standard check ride for the purpose of CFI renewal and gold seal applications?

No, check rides completed by a part 141 flight school with self-examining authority are not considered to be FAA checkrides for any purposes.

They do not count toward CFI renewal credit for maintaining an 80% 1st-time pass rate, and they do not count toward the requirement to obtain a gold seal CFI certificate.

My source is a direct answer from the chief instructor of a large part 141 flight school who received this information from the local FSDO.


Which jet engines have the highest thermal efficiency? Some automakers (Mercedes-Benz, Toyota) have recently been making news about the improved thermal efficiency of their engines, stating that they reached the 50% mark. I was wondering if it was the same for airplanes.

I think I'm pretty sure the aviation industry is well beyond the 50% mark due to the high compression ratio, but what is the most efficient jet engine in existence (currently in use or tested prototype) per category (fan, turbojet, bypass, turboprop, ...)?

Thermal efficiencies are very rarely quoted for aviation gas turbines. The metrics of interest are specific fuel consumption, and power to weight ratio. While a higher thermal efficiency will increase these, SFC and thrust/weight are performance terms that are easier to comprehend, and describe the performance in terms that can directly be used in performance calculations of the aircraft. However, this article from Pratt & Whitney indicates the best aviation gas turbines had just reached about 55% in 2010. But there is no indication of which engine has the highest figure.

Land based gas turbines are more efficient than avaition gas turbines, for a number of reasons. According to this article, the most efficient land based gas turbines, where just under 60%, in 2010. The most efficient installation was a Japanese company, with 59.1% verified on an M701G2 gas turbine at the 1500 MW Tokyo Electric Kawasaki power station in Japan.

Since then GE claimed on the 28th of April 2016, a world record for thermal efficiency, with 62.22%, for a combined cycle plant, in France. GE state that it normally takes about a decade to gain 1% in efficiency. The high thermal efficiency is significantly due to operating at a very high temperature. GE state this plant runs at 2,800 deg. F, but the real number is probably proprietary. They say it's like running the engine at takeoff conditions for its entire flight. As you could imagine, this makes cooling very important. It also takes about 30 minutes to get the turbine from idle to maximum speed. Clearly, that won't work in an aircraft.

This is the GE 9HA gas turbine. You can see the fuel nozzles (one circled) - and that weight does not matter. So, an aviation turbine will never match this level of performance.

In comparison, the first simple cycle model, developed in 1939 is said to have had a thermal efficiency of just 18%.

But maximum efficiency is not always the ultimate goal. A product director from Rolls Royce says:

  Everyone would love 60% but the cost is often prohibitive. Not everyone needs a heavy-duty combined-cycle plant. Machines that can achieve baseload within ten minutes such as the Trent 60 are important for the peaking market and a lot cheaper.

Land based combined cycle gas turbines are more efficient than aviation turbines, because;

their design can be optimised with out having to worry about weight. Fuel nozzles in particular are optimised in land based gas turbines.
they can use steam or water inlet fogging (see above!)
they operate at a single rotational speed, so can be optimised for that.


What are the different structural weight limitations that have to be considered when loading large aircraft? What are the different structural weight limitations that have to be considered when loading large aircraft? Is there a difference in complexity as to whether it's a passenger aircraft or a freighter being loaded?

I think I know the answers, but it's precisely because I have to say "I think" rather than just "I know" that I'm asking the question. I'm hoping those here more technically oriented than I will be able to add to what I know.

Is there a difference in complexity as to whether it's a passenger aircraft or a freighter being loaded?

Yes, very much so. The resulting load of a passenger in every seat is nowhere near close to the structural limits (note that I said structural limits, not performance limits). Generally speaking, having to check for the load being within structural limits is a concern for freighters, not passenger aircraft.

There are a lot of structural considerations for the semi-monocoque design used for all modern large aircraft. Using one variant of a 747-400F as an example, its Weight and Balance Control and Loading Manual runs to 584 pages. Items that need to be checked for each load include:

Linear and Floor Loading

The manual snippet above covers the main deck; there are like tables for each cargo area. The linear loading is the lb/in measured along the longitudinal axis of the airplane. I don't really understand why it's necessary to check both the linear loading and the floor loading, given above as lb/sq ft.

Not only does the linear loading for each cargo compartment need to be checked, but the combined linear loading of all decks together along the longitudinal axis has separate linear limits as tabled below:

Cumulative Loading

There are cumulative load limits for both the forward body and the aft body. Using the forward body for example, you add up individual items (more often than not ULDs) starting at the front and proceeding to a point over the wing box. I'm not sure exactly how that point is chosen insofar as structural and aerodynamic considerations are concerned. The aft body cumulative load starts from the tail and proceeds to the same point.

Below is a forward body cumulative limits graph. Note that there are two lines: one for use when the ZFW is 610,000 lbs or below, one from that weight up to 635,000 lbs. For this particular airplane, the aft body also has two lines, but the differentiation is based on the takeoff c.g.. Some 747s have only one line for each, some one line for one but two lines for the other. Obviously things can get tediously complex, and loadmasters and the software they're using has to accommodate all the possibilities.

Unsymmetrical Main Deck Limits

Widebody aircraft that can accommodate two rows of ULDs on the main deck have the option of carrying more weight in one container if the container laterally next it is given a lower limit. I know of one operator that didn't want to contend with the limit of, say, the position on the left being higher than the position on the right, and chose to forego the flexibility of unsymmetrical limits. An unsymmetrical limit graphs is below:

So, does anyone want to do a weight and balance for a large cargo aircraft? Fortunately we have software to do that for the great majority of loads that are containerized. However, loadmasters might still have to contend with unusual loads manually.


What aerodynamic phenomenae can decrease the pressure gradient in Boundary Layer Ingestion? I'm exploring a question concerning whether or not boundary layer airflow presents physical limitations that are too great for current technologies to overcome (I'm holding the position that it is in fact doable) but I've seem to only be able to find one main method of active flow control in the inlet of an embedded engine.

Specifically, pulsating air jets for active manipulation of the air ingested into the engine. As to create uniformity along any modeling 3D or otherwise for future flow sims I am using the basic frame of the Boeing BWB 450-1U concept with the proposed GE58 F2/B1 UEET turbofans.

I would like to know if there are any aerodynamic phenomena that would decrease or eliminate a pressure gradient that would naturally build up on the face of a Boundary Layer Ingestion.

As previously noted, I am aware of active control measures, but I would prefer a passive solution like vortex generators (as they present a minimal detriment in aerodynamic quality yet a significant advantage in efficient solution to the given lift problem)

P.S. I have checked all related posts/answers and none are either recent enough nor complete enough for my question in particular, so please don't disregard it as such.

First, let me explain the context of your question: It is about a concept for a future airliner:

Boeing Blended-Wing-Body Model 450-1U, taken from NASA/CR-2006-214534.

In the artist impression above the engines are podded and sit on struts in order to achieve a uniform flow field at the intake face. However, the strut and nacelle surface area will contribute drag that could be avoided if the engines would be mounted closer to the rear fuselage. The picture below, taken from the same source, shows a CAD rendering of a possible geometry with semi-buried engines:

The disadvantage of this concept is the ingestion of boundary layer flow such that the speed profile over the intake face shows a speed gradient (BMI = boundary layer ingestion). This will result in distorted flow at the compressor and cyclic pressure variations for the compressor blades, which in turn will require a more robust and less optimized compressor geometry or run the risk of compressor stalls and early blade failure. Also, the energy loss within the boundary layer results in lower pressure recovery ahead of and inside the intake, which will increase specific fuel consumption.

Or to quote the NASA page on inlets:

  As the air is brought from free stream to the compressor face, the flow may be distorted by the inlet. At the compressor face, one portion of the flow may have a higher velocity or higher pressure than another portion. The flow may be swirling, or some section of the boundary layer may be thicker than another section because of the inlet shape. The rotor blades of the compressor move in circles around the central shaft. As the blades encounter distorted inlet flow, the flow conditions around the blade change very quickly. The changing flow conditions can cause flow separation in the compressor, a compressor stall, and can cause structural problems for the compressor blades. A good inlet must produce high pressure recovery, low spillage drag, and low distortion.

The question now is: What can be done to keep the semi-buried engine concept but to avoid the intake flow distortion from boundary layer ingestion?

Solution 1:

As it turns out, the same NASA paper proposes a simple diverter ahead of the engines which is supposed to push the slow boundary layer to the side:

Solution 2:

An even better solution is to use a splitter plate; after all, the semi-buried engine has an intake very similar to the side-mounted intakes of trainer and combat aircraft. Below is an example from another subsonic aircraft, the Czech L-39 Albatros jet trainer:

Subsonic splitter plate intake on the L 39 (picture source)

Solution 3:

Less commonly used, boundary layer suction can be employed to remove the slow-moving air close to the surface and to re-establish a more uniform speed profile. Here my example is the Eurofighter EF-2000 intake, where boundary layer suction is used to remove the boundary layer that has accumulated on the splitter plate itself:

EF-2000 intake, here abused as a baggage compartment. The grid of holes is used to suck away the boundary layer.

A similar arrangement was used on the intake cone of the SR-71, but I did not find a good picture. Boundary layer suction, however, is not the kind of passive solution you desire. But it has the advantage of being adaptable to the specific flight situation.

Solution 4:

Also not passive, and not being used in existing airplanes, would be a moving surface ahead of the inlet. This has been tried with rotating cylinders at flap breaks, and there is some literature covering the topic. The moving surface will reverse the effect of the wing ahead of the intake and re-energize the boundary layer right ahead of or inside the intake.

In all cases, you need to check whether the newly incurred losses of the boundary layer manipulation will be lower than the gains in engine efficiency. I did not go into vortex generators: They might help to equalise the speed loss or at least to reduce the speed gradient towards the surface, but they incur new and intense losses all by themselves and would most likely reduce efficiency a lot. If well placed, they will reduce intake distortion, but at the price of a much reduced pressure recovery.


Has it happened before the EASA and the FAA disagreed on the airworthiness of a plane? With the Continued Airworthiness Notification and with the updated statement https://pbs.twimg.com/media/D1fZ4GTW0Ac4Qsr.jpg in contrast with EASA   2019-0051-E it is crystal clear the EASA and the FAA disagrees on the airworthiness of the 737 MAX at this time. Had this happened before?

It seems FAA and EASA did disagree since 2016 about 737max certification, and not just after the crashes. EASA certification was conditioned by training and more information to the pilots, which hasn’t been done.

Please refer to the following website:

https://www.cnbc.com/2019/03/29/reuters-america-insight-regulators-knew-before-crashes-that-737-max-trim-control-was-confusing-in-some-conditions--document.html

You read the following:

  The European Aviation and Space Agency (EASA) certified the plane as safe in part because it said additional procedures and training would “clearly explain” to pilots the “unusual” situations in which they would need to manipulate a rarely used manual wheel to control, or “trim,” the plane’s angle.

You may also read about EASA:

  The undated EASA certification document, available online, was issued in February 2016, an agency spokesman said:

  It specifically noted that at speeds greater than 230 knots (265mph, 425kph) with flaps retracted, pilots might have to use the wheel in the cockpit’s centre console rather than an electric thumb switch on the control yoke.

So when agencies give their approval it doesn’t mean the approval conditions are the same, it was not the case since the origine  for the 737max, and not just after the crashes.


What is the width of seat tracks on airliners? I've been scouring the internet for the track width of seats in airlines, and can't find anything on it. Does anyone know around what that dimension might be?

I'm not looking for the dimensions of the seats themselves, but the width of the tracks that the seats attach to.

The attachment rail/track width (gauge) is not fixed. It differs from plane to plane, and the chosen seat manufacturer obliges.

21" or 55 cm seems the average though.

Source: stanford.edu

Above image shows B717 cross section, you can notice the 3-abreast and 2-abreast both are on two rails. No high-res available.

Different plane models:

Some are wall mounted.


Can St. Elmo's Fire cause instruments to fail? Can St. Elmo's Fire on an aircraft cause instruments to fail or give erratic readings, primarily with glass cockpits? Are there backup instruments that would not be affected? Does it affect radio transmissions?

Yes, the strong magnetic fields which are created can cause all of those problems if it gets bad enough.

To quote the AIM where they talk about Precipitation Static (which is one method of creating St. Elmo's Fire):

AIM 7-5-11. Precipitation Static

  b. A review of pilot reports often shows different symptoms with each
  problem that is encountered. The following list of problems is a
  summary of many pilot reports from many different aircraft. Each
  problem was caused by P-static:

  1. Complete loss of VHF communications.

  2. Erroneous magnetic compass readings (30 percent in error).

  3. High pitched squeal on audio.

  4. Motor boat sound on audio.

  5. Loss of all avionics in clouds.

  6. VLF navigation system inoperative most of the time.

  7. Erratic instrument readouts.

  8. Weak transmissions and poor receptivity of radios.

  9. "St. Elmo's Fire" on windshield.

  c. Each of these symptoms is caused by one general problem on the
  airframe. This problem is the inability of the accumulated charge to
  flow easily to the wing tips and tail of the airframe, and properly
  discharge to the airstream.


How do airlines replace a pilot at the last minute if they're unable to fly? I would like to know what decision do the commercial airline carriers take when there is emergency case of a pilot who cannot fly the plane because of personal emergency conditions?
Emergency conditions could be the pilot falling sick with a medical emergency, family member, close relative death etc.
The event has happened just a few hours before the final plane departure.
Does the co-pilot fly the plane in that case? Do the specific airline carriers always have pilots in reserve?

The airplanes can't depart without the minimum crew, which means 2 pilots, or 3 if there is a Flight Engineer.
The airlines have "Reserve" and "Ready Reserve" types of duty to cater to this, and pilots will be scheduled for one or the other at different times (depending on seniority and what they bid for).
Reserve is on-call at home, with the ability to show up at the airport within, say, 1 or 2 hours of being called.  This is for pilots who call in sick etc, a number of hours before departure.
Ready Reserve is you show up in uniform and with your gear at the operations dept of the airline and hang around in the crew lounge in case they need a crew right now. If they don't, you go home at the end of your shift without flying.
A pilot who is incapacitated just before a flight will be replaced with someone who is on Ready Reserve, and if none are available, then the flight takes a delay until a Reserve pilot can show up.


Is a stall warning horn required to fly? I need an answer in reference to 14 CFR 23.207. I looked there and couldn't say 100% if it was a yes or a no.

No, many aircraft don't have them, like the Cherokee since it uses a gear warning horn. The horn signifies that the gear isn't down and you don't want to confuse that with the stall warning, so they don't have one.

23.207 says that an audible or visual indication is not required as long as the aircraft exhibits a "warning" 5 knots before the stall, in the case of the Piper Comanche the warning that satisfies the requirement is the stall buffet.

The relevant section of 23.207 is part (b):

  (b) The stall warning may be furnished either through the inherent aerodynamic qualities of the airplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual stall warning device that requires the attention of the crew within the cockpit is not acceptable by itself.

So the stall buffet, as long as it is pronounced, is adequate indication of a stall to satisfy 23.207.


What is the relation between IAS and TAS at a constant altitude? I have noticed that when calculating True Air Speed for any given altitude, the faster the Indicated Air Speed, there seems to be a larger increase in TAS?
My thinking was that at a constant altitude the relationship between IAS/TAS would be linear, e.g you double IAS, and TAS would double.. But it seems to increase more? Not sure if I'm missing something here?

For example:
5000ft at 100knts IAS = 114knts TAS
, 5000ft at 110knts IAS = 126knts TAS

Only a couple Knots difference, and it seems to make sense but I can't find any answers on it to confirm it? Would appreciate anybody to shed light on it, thanks!

If you divide 114/100 and 126/110 you'll find the common factor is ~1.14.

Which means for that altitude TAS ≈ 1.14 * IAS.

1.14 is the square root of the ratio of standard sea level ISA air density ($\rho_0$) to the air density at that altitude ($\rho$). This is assuming IAS = CAS = EAS (i.e., ignoring positioning, calibration, and compressibility effects).

The formula at low-speed flight is:

$$
\text{TAS}
=
\text{EAS}
\sqrt{
\frac{\rho_0}{\rho}
}
$$

It looks like you got the numbers from this online converter. Note its preset is not a standard ISA, as the altimeter setting reads 28.16 inHg. Instead I recommend this one, which is for standard ISA. For 5,000 ft the values are:

CAS    TAS
100    107.7
110    118.4
120    129.2

With the multiplier at 5,000 feet ISA being ~1.077, and the relation looks like this: