Could vortex generators be used to preserve aileron authority during a stall? I know that using aileron input in the approach to a stall is generally inadvisable; what if vortex generators are placed at the wingtip (where the ailerons sit), meaning that the ailerons will still have roll control authority available even when the rest of the wing is stalled? In this case, would aileron input be permissible?

Vortex generators re-energize the boundary layer and can slightly postpone flow separation at high angles of attack. Therefore, adding them in front of a control surface is a realistic way of retaining authority. In fact there are real life examples:

[picture by Peter Kämpf]

That being said, these devices are a crutch that is best avoided on clean-sheet designs. They add drag in every flight condition in exchange for some more margin at high alpha, this margin could be achieved by designing the aircraft better in the first place. That is why you will mostly see vortex generators applied as fixes late in the design process or as outright aftermarket modification kits. This constant penalty is compounded by the extra maintenance needed to keep the VGs clean and in good condition.

Ultimately, re-energizing the boundary layer can only do so much to prevent separation. A hard down aileron input at high angle of attack can stall the wing even with VGs, they are not a silver bullet.


Which standard is applicable to the electric power system in civilian US aircraft? I am trying to close a gap in my answer to this question:
Are there general accuracy requirements for aircraft power supplies?

There is MIL-STD-704(F) Aircraft Electrical Power Characteristics for military aircraft.

Which standard is applicable to the electrical power system for civilian aircraft under the authority of the FAA?

The answer is not straightforward.  Power supplies used in commercial aircraft LRUs are required to meet RTCA DO-160G, sections: 16 Power Input, 17 Voltage Spike, and 18 Audio Frequency Conducted Susceptibility - Power Inputs.

The issue is this is what the consumers of aircraft power have to deal with.  It doesn't actually specify what the aircraft power distribution system has to provide. Though by inference, the power generation system must deliver power within the bounds of what the consumers can accept.

In my experience, aircraft OEMs design their power distribution system and then levy specific requirements on the power supply design of all consumers on the aircraft. While DO-160 covers the majority of the need, the OEM requirements will include additional requirements deemed necessary by their design and analysis. As a Boeing engineer explained to me, "The requirements are not to protect your power supply.  They're there to protect my power bus."

The reality is aircraft power is a small dynamic system and it is impacted by everything on the bus.  It has to be designed as a system unique to each aircraft. Since it's part of the aircraft, the aircraft rules come into play.  For air transport aircraft, that means 14 CFR Part 25. The applicable portions include 14 CFR 25.1310 and the Electrical Systems and Equipment subject section.

Additional guidance is available in Advisory Circular AC 25.1353-1a ELECTRICAL EQUIPMENT
AND INSTALLATIONS.


Can a helicopter like the R44 be lifted up by his rotor head? I am curious if a rotorcraft could be suspended from rotorhead for an extended period of time.

I am curious about R22 and R44.  I believe I have seen them in the shop lifted up from the 2 holes in the rotor head.

I am also curious if all helicopters have mount/lift points in the rotor head like an MD500C. Would you be able to do the same?

Or are you better lifting from the skids for a longer term lifting?

Yes, but you better know what the heck you are doing. :) Whether an individual helicopter can be lifted this way is a different question. You'd have to look at the maintenance manual for the individual aircraft for the answer.


What kind of supervision do new captains get on their first flight? Is there any special consideration for the first flight as a captain? I mean, the first officer gets promoted to captain, does his/her first flight gets supervised by any special way?

PS: I'm tagging this question as faa-regulation, not so sure if it is correct.. please correct me if I'm wrong

After a new captain is done with schoolhouse training (classroom and simulator) they will fly on-line as a captain and will have a training captain in the right seat.  After some number of flights (for me it was a 4-day pairing) you will be joined by a check airman in the jumpseat and have a line check.

Once you pass the line check if you are a first time captain you are a high minimums captain for your first 100 hours and then a normal captain. During high mins time you are subject to a few restrictions in approaches you can fly. All the flying after the line check is with normal (low time) first officers.


What was the earliest plane in push-pull configuration that flew or at least took off? I am looking for the earliest plane in push-pull configuration that flew or at least took off.

I have found such planes ("Short Triple Twin" and "Short Tandem Twin") flown in 1911. So, I would be especially interested in push-pull flying machines that took off before 1911.

I have found a plane, that had both a pusher and a tractor propeller, which flew for the first time over Cotroceni airfield, Bucharest, Romania, on June 17, 1910. Likely there are other planes like this that flew before.

Vlaicu I plane during construction

Newspaper article about Aurel Vlaicu's first flight June 17, 1910

Source: A Vlaicu I - Wikipedia


Closest RL Match for Fictional Helicopter Design? Erm, not sure if this is the best place to post this but it seems like the best place to get a pretty straight answer thus far in my search.

So yeah, this helicopter is obviously from a cartoon – but I'm writing a story and I wanted to refer to it more specifically if possible, and also I'm just plain curious about what real rotorcraft(s) it was most likely based off of. And so far the entire rest of Google has not been much help. Plus, I've tried comparing some of the era models (i.e. 1960s, 1966-1968) I've found pics of on my own – but yeah, I am pretty clueless here. =(

Can anyone help? Thank you so very much for your time!

EDIT: I mentioned the year and I put the source in the pic description, but I'll reiterate both here. It's Michi/Trixie's helicopter from the Japanese anime Mach GoGoGo/Speed Racer 1966-1968.

Possibly the Bell 47J:

Source: Wikipedia

The Bell 47 was configurable with floats more in-line with the image originally posted, but I can't find a lot of images with the full skin frame and floats, but here is one:

Source: Goodall Aircraft History


Where can I find FAA procedure amendments? I'm looking at the IFR Takeoff Minimums and (Obstacle) Departure Procedures for Goodyear, AZ (KGYR). It says:

  Takeoff Minimums and (Obstacle) Departure Procedures AMDT 1 14317
  (FAA) Departure Procedure: Use POTER RNAV Departure

I would like to read this amendment but my Google-Fu is failing me. Help?

As far as I know, you're looking at them: that number is telling you that the current procedure is AMDT 1 14317. Have a look at the other procedures throughout the same document and you'll see they're all numbered in a similar way.

In your example, AMDT 1 14317 is Amendment 1, made on November 13, 2014. The date format is a Julian date or, if you prefer, YYDDD: it's the 317th day of 2014, i.e. November 13, 2014. The format is explained in the FAA's FAQ on obstacle data (and it's mentioned in other documents).

If the procedure has never been amended it's marked ORIG, e.g. at Beaver Muni (U52):

  BEAVER, UT
  BEAVER MUNI (U52)
  TAKEOFF MINIMUMS AND (OBSTACLE) DEPARTURE PROCEDURES
  ORIG 07242 (FAA)
  TAKEOFF MINIMUMS: [...]


Which frequencies does VDL Mode 2 use when used via the ATN (rather than ACARS)? If I understand the slide below correctly (source), CPDLC can be used either via ACARS or via ATN.

I know that, in the case of VDL Mode 2, there are specific ACARS frequencies. Which frequencies are used when CPDLC runs over ATN?

Some additional information (and corrections)...

The slide is not totally correct (sorry for Airbus) as the same VDL-2 ground stations are used to transport both FANS-1/A CPDLC (A623) and ATN CPDLC over the AVLC protocol (VDL-M2). The two networks are interconnected... But depending on the media access scheme (Plain Old ACARS (POA - refered as VDL-A on the slide) or AOA (VDL2)) the modulation and the frequencies used differs.
In Europe, VDL-M2 is used between 136.7 and 137 (ICAO).

As by 2020 ATN-B1 CPDLC above FL285 will be mandatory, datalink will only be performed on this band using VDL-M2 and no POA.

However, it is true to say that there are two CPDLC. The  ICAO-standaridzed  one (or compliant to the ICAO-ATN  -- as used in Europe) and the non-ICAO compliant initially developed by Boing (as used in the US and oceanic -- also known as FANS-1/A). The two CPDLCs have very similar features and capabilities contrary to what have been told previously. The difference between the two is the end-to-end performance requirements and insurance of delivery (PM-CPDLC - PM=Protected Mode) available on ANT CPDLC and not for FANS-1/A CPDLC (there is no way to ensure a message have been successfully transmitted with FANS-1/A).

FANS-1/A CPDLC is transmitted via the ACARS network using Plain Old ACARS (POA - refered as VDL-A on the slide) or AOA (VDL2), while ATN CPDLC is only transmitted via VDL2 (SATCOM is being validated at the time of writing).

Link2000+ is the name of the development project of VDL2 (US and Europe).

ATN-B1 refers to the implementation of specific CPDLC services and/or messages standardized by ICAO. At the time of writing ATN-B1 is implemented in Europe and tests are being conducted for ATN-B2. ATN-B2 adds some new CPDLC messages but also the ADS-C which is the precursor for I-4D trajectory management.
ATN-Bx refers to the ground implementation, and FANS-xx refers to the airborne implementation (FANS-2/B refers to the ATN-B1 airborne implementation, FANS-3/C to the ATN-B2 -- Don't try to find logic here ;-) )

Have a look in the book "Aeronautical Air-Ground Data Link Communications" for further information between the two (with some historical background).


Will the new airmen certification standards make it more difficult to add ratings? As of June 15, 2016, the FAA has changed from PTS/Knowledge tests to the Airmen Certification Standards which is a relatively significant paradigm shift in how airmen are certified.

The underlying reason to move to the ACS was to evolve the outdated PTS (practical test standards) and to align airmen certification towards risk management and the existing national airspace system.

The question I have though is for people who have earned their certificates under the old PTS system and would like to add a rating like an Instrument rating, or another certification like commercial.

Will the new ACS make it more difficult for existing pilots to add ratings? I'd like to know from the standpoint of part 141 and part 91 training centers.

One of the reasons I ask is I went up with my CFI last week and went into some slow flight. I set up to bring the aircraft into the stall buffet and fly it a few knots above stall speed but he said that the new ACS said that the stall horn cannot sound during slow flight, which seems counter intuitive to me. The point of slow flight is to know how to handle the aircraft at or near stall. There is a lot of handling difference between VS0 and VS0+20kts.

So that got me thinking, what would I have to relearn in pursuit of an instrument rating that would make it harder that I probably wouldn't have to under the old PTS?

Not significantly. The fundamentals of evaluation have not changed, and certainly the fundamentals of your next rating haven't changed. A few of the specific tasks have changed between PTS and ACS, like the point you raise. And, yes, you will need to review the ACS or PTS (whichever is in effect for your next rating -- not all have transitioned) in detail, so that you're aware of what's expected of you.

The major parts of any checkride will be your basic knowledge of the subject, your ability to move the aircraft through the air to standard, your ability to demonstrate sound judgment including a thorough evaluation of pre-flight risks and your overall attitude toward flying. That really hasn't changed with the ACS. The regulations have not changed either. The ACS is meant to give instructors and examiners a more holistic approach to evaluate the above factors.


What's a similar looking aircraft to this illustration? There is this crazy picture of a plane or a boat or both...?

This is just a drawing, I know, but if this aircraft does not exist, is there perhaps a similar looking one in reality?

is there perhaps a similar looking one in reality?

Not really, however the fictional five-deck flying boat depicted is clearly an extrapolation of flying boats of the first half of the 20th century.

Visually, the Short Empire class is the most similar:

domed cockpit at front of hull
hull chines
four radial engines mounted in-wing with three-blade propellers
conventional empennage

Photo of a Short Empire, Public Domain

Photo of a Short Sunderland, CCASA3.0 Nick.D

The largest all-metal flying boat developed for civilian passenger service was the Saunders-Roe Princess which only had two passenger-decks.

Photo of a Saunders-Roe Princess, Public Domain

The largest flying boat was probably the Hughes H-4 Hercules, popularly known as the Spruce Goose. It was designed for military transport (hence no windows). I believe it would have accomodated both troops and military vehicles but probably no more than two decks.

Photo of Hughes H-4 Hercules, Public Domain


Are there any safety hazards when testing the F-16's fire control radar on the ground? What are the procedures for ground testing an aircraft's fire control radar - for the F-16 or any other aircraft - and are there safety hazards associated with exposures to humans?  Most importantly, for a pregnant woman?

Yes, and aircraft equipped with emitters have their arcs clearly indicated in their manuals, for example, take this diagram for the A-7E (in pink, the wider cone coming off the radome, the other areas are engine intake or turbine blade-off hazards):

There are two main ways in which a radar installation can be harmful.

Radar waves

These are the desired emission of a radar and are emitted from the antenna in a well known arc.

Based on this page by the WHO (emphasis mine):

  Military radars are numerous and vary from very large installations, which have large peak (1 MW or greater) and average powers (kW), to small military fire control radars, typically found on aircraft. Large size radars often evoke concern in communities living around them. However, because its power is radiated over a large surface area, the power densities associated with these systems vary between 10 and 100 W/m2 within the site boundary. Outside the site boundary RF field levels are usually unmeasurable without using sophisticated equipment. However, small military fire control radars on aircraft can be hazardous to ground personnel. These units have relatively high average powers (kW) and small area antennas, making it possible to have power densities up to 10 kW/m2. Members of the general public would not be exposed to these emissions because during ground testing of radars access to these areas by all personnel is prohibited. The military also use most other types of radars described below.

The specific risks are listed as:

  Possible health effects
  Most studies conducted to date examined health effects other than cancer. They probed into physiological and thermoregulatory responses, behavioural changes and effects such as the induction of lens opacities (cataracts) and adverse reproductive outcome following acute exposure to relatively high levels of RF fields. There are also a number of studies that report non-thermal effects, where no appreciable rise in temperature can be measured.

  Cancer-related studies: Many epidemiological studies have addressed possible links between exposure to RF and excess risk of cancer. However, because of differences in the design and execution of these studies, their results are difficult to interpret. A number of national and international peer review groups have concluded that there is no clear evidence of links between RF exposure and excess risk of cancer. WHO has also concluded that there is no convincing scientific evidence that exposure to RF shortens the life span of humans, or that RF is an inducer or promoter of cancer. However, further studies are necessary.

  Thermal effects: RF fields have been studied in animals, including primates. The earliest signs of an adverse health consequence, found in animals as the level of RF fields increased, include reduced endurance, aversion of the field and decreased ability to perform mental tasks. These studies also suggest adverse effects may occur in humans subjected to whole body or localized exposure to RF fields sufficient to increase tissue temperatures by greater than 1°C. Possible effects include the induction of eye cataracts, and various physiological and thermoregulatory responses as body temperature increases. These effects are well established and form the scientific basis for restricting occupational and public exposure to RF fields.

  Non-thermal effects: Exposure to RF levels too low to involve heating, (i.e., very low SARs), has been reported by several groups to alter calcium ion mobility, which is responsible for transmitting information in tissue cells. However, these effects are not sufficiently established to provide a basis for restricting human exposure.

Incidental radiation

@Dohn Joe pointed out that a secondary danger of radars, which is actually common to most high frequency energy sources: incidental radiation in the form of high energy photons (X-rays) generated in parallel to the desired radiation. Basically, the process used to generate high frequency electromagnetic waves is not 100% efficient, meaning some energy goes into generating other stuff, like heat, or X-rays. Note that at these energy levels it is often more common to use particle theories instead of waves, since they are the same.

This phenomenon led to a number of health cases in Germany in the 2000s (link in German), when crews who had worked on radar systems in the '60s and '70s without adequate protection developed health complications. Some also passed them on to their children due to genetic damage.

A report dealing with the dosage rates for technicians can be found here. One conclusion that stands out is that the effects and dosage rates were heavily dependent on the position of the operator, since x-rays attenuate when travelling through any media, and while air is not the best shielding material, it does help.

To obtain a rough estimate of how far would this incidental radiation propagate, we can run some numbers. The F-16 has had a number of radars along its service life, but we will use the AN/APG-68 radar introduced in the F-16C/D Block 25 as it is the one with the most readily available information.

X-ray attenuation follows this exponential formula:

$$
I/I_0 = e^{-\mu \rho x}
$$

Where $I/I_0$ is the ratio of energy after attenuation to the original energy, $\mu$ is the linear attenuation coefficient, $\rho$ is the density of the medium and $x$ is the distance traveled. It is important to know the energy of the emitted particles as $\mu$ is different at different energies. Wikipedia gives the peak operating voltage in the Traveling Wave Tube of the AN/APG-68 as 24kV, which should limit the theoretical energy of any emitted photons to 24keV.

Taking $I/I_0 = 1/e$ we can obtain the distance after which the intensity will have been reduced to about 36.7% of the original. Taking $\mu= 0.56585\,cm^2/g$ (from here, interpolating for 25keV) and $\rho = 0.0012\, g/cm^3$, we obtain $x=1472.7\,cm$.

This means that after about 15 meters the intensity will have dropped by almost two thirds, and it will continue doing so for every 15 meters afterwards. This is a conservative value, the real distance should be less due to moisture in the air and a lower median energy in the emitted beam, meaning that even if the equipment was improperly shielded, the risks should be limited to people working directly on the radar.


Why does a rectangular wing stall first at the root? Why does a rectangular wing stall first at the root? as opposed to tapering of the wing which causes the stall at the tip and moving inboard?

The tip vortex (caused by higher pressure air from below the tip moving into the low pressure region on top by rolling around the tip) reduces the effective angle of attack at the tip and keeps the boundary layer attached longer as the stall progresses.  The tip vortex has this effect with any wing shape, but shapes that reduce drag by shrinking the tip vortex will gain less from it, while a wing with less chord will tend to stall at lower AoA -- causing highly tapered wings to stall at the tip first.

I say "gain" because a tip stall is usually considered bad -- it can cause a spin entry, where a root stall with the tips still flying leads to a straight-ahead stall, other factors equal.


What is the meaning of Spirit ###? This Popular Mechanics article writes (about the B-2 Spirit).

  Only 543 people have ever flown in the cockpit of a B-2. Upon landing I'll become number 544, with the new Air Force handle "Spirit 544."

Do people who have flown in B-2 Spirits have the Air Force handle "Spirit ###?"
If so, which regulation/directive/etc. specifies that the handle of people who have ever flown in the cockpit of a B-2 Spirit be "Spirit ###?"

Taking your questions in order:

  Do people who have flown in B-2 Spirits have the Air Force handle "Spirit ###?"

It's plausible. The author of the article says so and there doesn't seem to be any reason to lie about such a trivial detail. That said, he also refers to the pilot as "Scar" rather than as "Spirit [whatever]" so even if Spirit-number is a callsign that a pilot has earned, it doesn't mean it's necessarily the one that they'll always fly with.

  If so, which regulation/directive/etc. specifies that the handle of people who have ever flown in the cockpit of a B-2 Spirit be "Spirit ###?"

There seem to be no such regulations, or if any do exist, they are applied individually. Pilot callsigns are generally given informally, according to this article, which is not an official military publication. Although the content of this article is unfortunate, it substantiates the first one. Finally, the Air Force publishes official voice call sign guidelines, which do not list regulations for pilot callsigns.


What can a pilot do if an air traffic controller is incapacitated? I watched this video:

where a Las Vegas controller is on duty alone and suffers a stroke.

The pilots become quite uncomfortable with the situation and basically everything is stopped.
Someone finally calls the company and gets them to check up on the controller.
Fortunately it was not that busy, and no other emergency emerged.

What else could the pilots have done to remedy the situation?

In theory, if the lone tower controller is incapacitated, the airport is no longer controlled and pilots should use the standard procedures for uncontrolled airports, i.e. making traffic calls on CTAF.

In the KLAS case, the pilots had every reason to expect the tower to be open, and rather than getting no response, they were getting unintelligible gibberish. As a result, their reactions varied.

If the situation had persisted, one of them would have notified Las Vegas Approach, who in turn would have started advising pilots of the uncontrolled field ("change to advisory" rather than "contact tower"), and everything would have proceeded fairly normally. Since it happened at night, traffic volumes were low enough that CTAF would have worked okay, which is probably why only one controller was on duty in the first place.

However, a supervisor was in the tower on break at the time, just not in the cab, so he was able to take over relatively quickly and resume normal operations before that actually happened.


What are the abilities and limits of a hexapod-based flight simulator? So, that's a professional hexapod- a. k. a. Stewart platform-based flight simulator (image source: Wikipedia - "Stewart platform").  By moving the simulated cockpit, it simulates the movements of a plane during its maneuvers.

But the range of maneuvers it can realistically simulate is certainly limited - it can certainly simulate a straight flight, but I doubt it can give its occupants the realistic impression of a full barrel roll.

Given an existing, recent (i. e., modern and advanced) siulator for commercial aviation:

What are the actual limits on maneuvers and their parameters (i. e. turn and turn radius, banking and bank angle)?

Bonus question: How does this compare to the flight situations encountered in a typical flight?

What they can do.
Motion systems can produce accelerations that stimulate the acceleration sensors in our inner ear. Higher frequency acceleration can be sensed instantaneously in surge, sway and heave. From this answer:

  Motion systems can do a pretty good job at reproducing direct accelerations, until the actuator stroke runs out of course. So for short term accelerations.

This direct acceleration sensing is essential for pilot-in-the-loop motion control, that is why we have the sensors in the first place. The velocity information we get from our peripheral vision is an integrated signal and has 90° phase shift, causing a delay in sensing of motion.
What they cannot do.
Produce sustained accelerations. Six Degree of Freedom motion systems get by by tilting the sim, so that a component of gravity can be used for the feeling of sustained motion. But with some restraints on tilt velocity and angle, the tilt must happen imperceptibly and is of course also limited by the actuator stroke:

Imperceptively, by rotating at a rate below what the inner ear sensors can detect, and by not changing the visual image horizon.
Limited by stroke: in a 6-DoF system, using full tilt means that some of the other DoFs cannot be used. Full aft tilt has the front actuators fully extended, so linear surge cannot be actuated anymore.

Motion software contains a lot of fine balancing and frequency filtering code, to make optimal use of the available stroke and of the peculiarities of the inner ear acceleration sensors. Large stroke systems are essential for pilot-in-the-loop tasks in airliner and helicopter pilot training, and make the difference between being in an immersive simulated atmosphere, or being aware of the fact that you're inside some device firmly on the ground.


Dual Ignition Systems Is it possible to back up a single magneto ignition system using an electronic system on the same spark plugs rather than having to change to two plg heads?

For a homebuilt or ultralight, yes.  There are high voltage diodes that take a high tension lead from 2 separate sources with a single output, made for racing, that allow you to run a single plug from either of two sources, whatever they are.  They are popular on Corvair aircraft engine conversions.   You can run a mag and battery system together, or two battery systems, or whatever, with a one-or-the-other ignition switch.


What are the pros and cons of a pulsejet? I've heard pulsejet powered aircraft can fly at very fast speeds but are there any drawbacks to this type of engine? And are the disadvantages greater than the advantages or vice versa?

The pulse jet engine works because it uses the dynamic pressure of air for compression. Consequently, it needs speed to work well. If the pulse jet is on the ground, it is not easy to start - it needs to be fed with compressed air, and once it runs (it can run even when not moving because the oscillating pressure wave inside the tube will compress the inflowing air), it develops litte thrust.

Thrust will go up with airspeed, so you need additional thrust sources for initial acceleration and take-off. In case of the V-1, this was done by a steam catapult or by air-launching the device. Note that the V-1 was accelerated to 370 km/h on a 45 m long catapult which means more than 100 m/s² (10g) average acceleration. Most of the development work went into making the airframe withstand this acceleration. A modern design would need additional engines as well, and once those are included, the rationale for pulse jets becomes very weak. They make sense if you have an air-launched, disposable application, such as long-range air-to-air missiles. This is a niche in which their higher-speed cousins, the ramjets, will still be used.

Pros:

Very easy to build, very light.
Runs and produces some thrust when at rest (as opposed to ramjets).

Cons:

Thrust grows with flight speed. This can be seen as a pro, but normally requires additional means of acceleration. Therefore listed as contra here.
Low fuel efficiency. The fuel energy is converted to other forms of energy: Just listen to the videos of Colin Furze to get an idea.
High levels of vibration due to the intermittent operation. When the Heinkel 280 was tried out with Argus pulsejets, the aircraft experienced unacceptable vibration.
Need heat-resistant materials. The central part will get very hot in operation, so at least nickel-chrome stainless steel is needed if air cooling is insufficient.
Cannot go supersonic. For this, there are ramjets.

EDIT:

NACA tested the As 014 pulse jet and wrote a report, from which the performance data depicted below is taken:

It seems that Bruce Simpson over in New Zealand has improved the pulse jet design a lot: He needs no compressed air for starting and makes clever use of surrounding cold air to increase mass flow and keep material temperatures down.


Why is there a pressure drop in the combustion section of a jet engine? This image, referenced in this question, shows in green the pressure value in a jet engine:

The combustion section between compressor and turbine is where fuel is injected, mixed with air, and burnt. Why is there a pressure drop while combustion occurs and temperature suddenly increases by 1,500°C (to be compared with pressure increase after ignition in a reciprocating engine).

The air moves¹ in direction of decreasing pressure except where forced by the compressor. So the pressure must be decreasing to maintain desired flow. If the pressure was increasing, the flow would stop and reverse and the engine would stop operating.

In fact, that's exactly what happens if fuel is added too fast: the energy quickly raises, but the still slow-spinning turbine provides too much resistance, so pressure will increase above what the compressor can provide and the compressor will stall, the engine will emit loud bang and some flames from both ends and likely flame out as it runs out of oxygen for a moment.

As already explained, in the normal flow the released energy increases the velocity of the flow instead of pressure.

¹ More precisely accelerates. If the pressure was constant, it would keep moving. But it must not raise. It decreases slightly due to friction.


Are fighter jet cabins pressurized? I heard once that fighter jet cabins are NOT pressurized, but the pilot's suit is, which prevents problems with decompression if the cabin gets shot.

But a military fighter pilot much later told me that the cabin is, in fact, pressurized and that getting shot (the cabin) and the resulting decompression are not that much of a bother, at all.

Cabins of fighter jets are in fact pressurized, but not same as the passenger airplanes. Cabin pressure in a passenger airplane will increase (almost in a linear fashion) as the airplane climbs. However, fighters keep ambient air pressure to a certain altitude. It maintains this pressure until a certain pressure differential is met, and then cabin altitude increases to maintain this differential.

Therefore at higher altitudes, cabin pressure in a fighter jet is low enough that supplemental oxygen is required for the pilot(s). This is supplied via On-Board Oxygen Generation Systems.

By not pressurizing the cabin completely reduces stress on air frame and is beneficial during an unplanned decompression.

By the way, your friend (military fighter pilot) is correct.


What programming languages are used for equipment onboard aircraft? Generally speaking, What programming language is used in aviation for (ATC Radio, Radar, ILS, Auto-pilot and on-board avionics)?

Is there a standard enforced by ICAO?
Does every plane manufacturer use the programming language they like as long as it's reliable and it goes through testing?

I remember watching a documentary on YouTube last year about aviation and it said something about the EU, after WWII, started making standards for aviation systems inside Europe.
I will link the video if I can find it

There are no language recommendations or requirements, other than what is sensible given the verification requirements in the various standards (e.g., DO-178B/C). For the highest design assurance levels, the generated code must be inspected down at the op-code level to ensure no known processor gotchas are invoked. You also end up having to test every part of every conditional, both the true and the false sides, and ensure that no jump instructions will take you someplace where you didn't expect it to go.

For these reasons, the big three languages in use in embedded avionics today are:

C++ (as a better C. The OO nature is often used only sparingly. Things like polymorphism are just too expensive to verify)
Ada (You may not like it, but a TON of current avionics are written in Ada, and are currently being maintained and updated with new features)
C - As close to the hardware as you want to get and still be highly productive (not intending to offend anyone who is productive in something else)

Assembler is frequently used for specific needs, but it would not be used to a greater degree than one of the above-mentioned languages.

What makes these languages ideal for avionics is that they are relatively close to the hardware and memory structure, not too abstract. Their tools are mature and well-known. People have years of experience certifying software written in them. And there are lots of programmers who can get up to speed in them quickly (Yes, even Ada).

Non-safety critical software, both on and off the aircraft, will be written in any of the big languages of the day: Java, C#, VB, C, C++, Python, Perl, Ruby, etc.

iPads are becoming useful inside the cockpit and are approved in limited situations. iOS apps are written in Objective-C, C, C++, and increasingly, Swift (Apple's new language).


What should I expect for an unannounced GA visit for touch-n-gos at San Jose? I understand that KSJC is a busy airport. I have done touch'n'gos at Oakland (also a busy Class C airport), but they have three dedicated runways for GA aircraft.

There is nothing about which runway is preferred for GA operations at SJC in the Airport Facility Directory notes.

What should I expect if planning an unannounced trip to SJC (arriving from the north/north-east)? Are touch-n-goes tolerated (i.e. staying in the pattern)? Which runway should I expect to be directed to? Is there anything else I should know?

I'm looking for local knowledge from someone with experience flying in the area, for example "GA operations are usually conducted on 30L, as the air carrier terminal is on the the other runway, and transient parking is adjacent to this runway" [I'm not sure this is the case, this is just an example of the type of information I'm looking for].

I have flown several times to SJC for touch and goes. I have always been on the weekends, and probably in the afternoons. It is a lot of fun, especially because the runways are so long for a small plane. I think I’ve been three times, and each time they have accommodated me on 30L. The wind is almost always favoring the 30 runways, and I don’t remember ever being cleared for 30R.

They will occasionally make you circle briefly before entering the C. They will also sometimes make you extend for a pretty long pattern to the SE if they have a big fella cleared for 30R. All the big commercial jets seem to be sent to 30R, and it is small GA jets that use 30L.

I have only done touch and goes, as I wanted to get out of the way quickly. But I get the impression that the tower is happy to accommodate as long as they’re not too busy. My instructor told me that they sometimes will say ‘no’ if they are busy, especially during the morning push, but I have no experience of that.

Have fun! There’s a beautiful 787 that is often at the terminal, keep an eye out for it!


How is altitude reached by aircraft flying above the stratosphere measured? Aircraft flying above the stratosphere (above 30km) are rare, but there is still the X-15 and the spaceship two. For those aircraft, maximal altitude is measured to within 500 ft.
As described in this question, barometric altimeters are not accurate nor practical that high. Yet, those aircraft are aircraft and as such I expect them to be fitted with barometric altimeters.
How is altitude measured with such precision (X-15: 354,200 ft in 1963, 15 years before GPS)?

They used inertial altitude on the X-15 for high altitude measurements. This works just like an IRS (Inertial Reference System), which was used on airliners of that era: you can get the position (latitude and longitude) based on a manually entered (or GPS derived) start position by integrating rotations and accelerations over time. The principle also works in 3D, if you also enter the start altitude. Note however that inertial altitude (true altitude above mean sea level) is not equal to barometric altitude, which can deviate based on local environmental conditions.

On the instrument panel was an attitude indicator whose source was inertially derived. Also provided were inertial velocity, altitude, and rate-of-climb. Barometric instruments included an altimeter and a combined Mach-airspeed indicator; these instruments were usable only below about 75,000 feet and were used mainly in the traffic pattern. An angle of attack and a sideslip indicator were provided; the source of these two instruments was selectable, inertial for high altitude flight and barometric for the end of the mission.

(NASA - Dryden History - X-15 Lessons Learned, emphasis mine)
You can see both instruments in the following image:

(modified from source)


Who controls airspace and time in my area on helicopters? I live in Newport Beach which is located in Orange County, California. I recently moved to an area where helicopters fly once in a while at 2-3 am above my house. Since I live on a hill, the sound is pretty loud and it wakes me up at night.

I was wondering where can I find more information about who controls the airspace in my area in regards to helicopters and how I look up the rules. I've googled a few things but can't find any answers. I'm not sure if it is the FAA or the county or the city or the state. Any pointers in the right direction would be appreciated.

Like others said, if it's military you're probably out of luck. If it's police, they don't fall under federal jurisdiction, so it'd be up to whatever department is operating the helicopter, city, county, etc. At 2am it's unlikely to be civil aircraft, but if it is and they are operating out of John Wayne Airport, their noise abatement rules are published here.


What is the indicated device under the tail of this B-29? Was lucky enough to have the B-29 "Doc" flying over the house this weekend.
What's the mechanism under the tail indicated by the red arrow? Tail-strike preventer?
I did some searching and found it in other pictures, but never a labeled diagram.

(Personal photograph)

Its a "tail bumper":

Source: Fiddlersgreen.net
Because the B-29 is so long, it helps prevent tail scrapes when taking off/landing.
Here is a close-up picture of the one on "FiFi":

Source: Airport-data.com


Can you fly a glider in a cloud on primary instruments? Assume you enter a cloud with no visibility of the horizon. Your glider is not equipped with an artificial horizon, turn speed indicator or the like.

You must fly within safe limits, using air speed, ball, yarn, compass, variometer, altimeter and what basic instruments are available.

Is this possible, and how difficult is it? Can most "normally skilled" pilots do that without extensive previous training?

For example, if you just correct the yarn with the ailerons, the speed with the elevator and keep rudder neutral or fly a fixed compass heading, is that likely to keep you flying safely until you're out of the cloud?

Edit:
I now remember an old "story". I am not sure I remember it correctly though. What is certain is that in the "old days" some instruments were sometimes sealed before a competition, in order to (try to) make it impossible to go into clouds. I think it was the turn speed indicator and also the compass? But some pilots were caught cheating by bringing a small compass in their pocket.
OK, I am not sure I am telling this story correctly. (Nowadays they check GPS logs and compare to cloud base altitude.) If I remember correctly, these pilots were willing to fly in clouds and also curve using only primary instruments.

With basic instruments (altimeter, speed and climb indicator and compass): Forget it!

A glider can enter a cloud when thermalling into it from below. Below the cloud the rising air was governed by dry adiabatic laws. Once it crosses into the cloud, the air is fully saturated and humidity starts to condense - after all, this is how clouds form. Now the rising air gets additional energy from condensation (its lapse rate goes down from the usual degree per 100 m of the dry adiabatic lapse rate to half a degree per 100 m) and the thermals inside the cloud become stronger. This is to say that turbulence will be more violent and the airplane will be tossed around. It will bank and pitch, and there is little chance that it will stay level for long. Since the spiral dive motion has very little damping, the glider will soon enter a spiral dive and overspeed.

The advice I got for the case that you are "sucked" into the cloud always was: Let go of the stick and open the speed brakes. Then wait until it gets light again.

In the 1930's some competition pilots tried to gain additional altitude by entering clouds. The results were catastrophic. In some cases the cover of the wings was torn to shreds by hail, and even bailing out would not be safe: One pilot froze to death when strong thermals inside the cloud lifted him to more than 8000m while he hung on his parachute.

I have done it once on a calm day when returning from the Alps. In the mountains the cloud base is higher, so it is entirely possible to arrive at the clouds over the alpine upland above their base height. I had a GPS on board that told me that I would reach the glider port safely when flying a straight line. It was late in the day, the thermals had died down and the clouds were fuzzy already, so little turbulence could be expected. One was in my way, and I went into it and flew out less than a minute later. The whole thing was completely uneventful, but I would not had done it with active thermals.


What is the speed limit in European airspace? In Did this aircraft illegally exceed 250kts below 10,000ft? it was mentioned that unlike here in the US, EASA does not have a 250 kt. speed limit below 10,000 ft.

So does this mean that are we allowed to go as fast as we want?

Mach 8? ;-)

What is the maximum indicated airspeed specified by EASA when operating in the European Union?

Airspace regulations do not fall under the authority of EASA. Each country has their own set of rules published under supervision of their own National Aviation Authority in the AIP.

The origin of the 250 knots IAS limitation below 10000ft can be found in the ICAO airspace classes definitions. The ICAO airspace definitions include a 250 knots IAS limitation below 10000ft / FL100 in:

Class C: VFR
Class D, E, F and G: both VFR and IFR

That means that in class A and B there is no speed limitation below 10000ft / FL100. In class C, IFR has no speed limitation, but VFR has. In Europe you will find a lot of class A, B and C airspace below 10000ft. In the US, there is no class A airspace below 18000' feet. There is class B and C airspace below 10000ft, but the FAA basically put a blanket speed limitation of 250knots below 10000ft, even inside class B and C airspace.

Also note that ICAO airspace classes are recommendations, countries have the authority to deviate from the ICAO recommendations as long as they publish these deviations.

Section ENR (En-route) 1.4 of the AIP contains the ATS Airspace Classifications and states includes the deviations from the ICAO airspace definition.


Can propeller driven aircraft sustain speeds at or above Mach 1? Has any propeller driven aircraft ever achieved and sustained supersonic speed? If not, why can't propeller airplanes achieve that speed?

Supersonic level flight?  No.

The fastest propeller-driven aircraft is either the turboprop-powered TU-114 with a measured top speed of Mach 0.73 or the turboprop-powered XF-84H "Thunderscreech" with a design top speed of Mach 0.9 and an actual top speed of either Mach 0.83 or Mach 0.7 (sources disagree).  The latter is an indication of why supersonic propeller-driven aircraft are unlikely: the continuous sonic boom coming off the propeller tips made the Thunderscreech the loudest airplane in the world.

The record for piston-engine aircraft is slightly lower, at Mach 0.71.


What happens when more than one agency investigates a plane crash? Does one accident report overrule the other or would there be two possible outcomes for the disaster?

Some examples

EgyptAir Flight 990 had the NTSB and the ECAA investigate and produced two different reports.

SilkAir Flight 185 had the NTSB and the NTSC investigate and also produced two different reports.

Two reports are published and everybody is free to believe whichever they choose.

According to ICAO rules the (investigation board1 of) country of occurrence (or country of operator if it happens over international waters) leads the investigation and (investigation boards of) country of operator, country of aircraft registration and country of aircraft manufacture are asked to take part in the investigation2. So it is expected that the investigators from country where the accident happened will publish the official report.

But some investigators may choose to publish their own report if agreement about the probable cause is not reached. Since even the official report does not have any legal effect (the investigation boards don't have any legal power), so it does not really matter much.

An accident report identifies factors that contributed to the accident and suggests improvements to safety practices to reduce risk of the accident reoccurring. But whether the recommendations are implemented depends on aviation authorities3, which are separate governmental bodies with legislative power. And they decide which recommendations they will incorporate into the legal rules.

Of course each such authority only has power over that country. So while the accident is investigated just once (even when multiple reports are published, the investigation is joint effort, just the investigators don't agree on the conclusion), the rules may be implemented differently in different countries. ICAO tries to coordinate, but it does not have any legal powers itself either. So it is up to the aviation authorities to choose which report they believe more.

Assigning blame is explicitly not purpose of the investigation according to ICAO rules. A criminal trial or civil litigation may be started about the accident by complaint from police, state attorney or damaged person, in which case the investigation report will likely appear as expertise in the court, but if there is not agreement between the investigators, it is again up to the court to decide which explanation it believes most.

Finally, the investigators not agreeing is rare in practice. Usually the investigation continues until they get something they can agree on; for several years if needed. Suspected intentional crashes by pilot (which is both cases you mention) seem to be the main exception as there may be political reasons why the leading investigators (from the same country the pilots were) don't want to accept that resolution.

1Investigation board in USA is NTSB, in Canada TSB (the most rigorous investigation board in the world (or at least they very carefully collect and report even the smallest incidents, see here)), in UK AAIB, in France BEA etc.

2It is not strictly necessary, but it is the usual setup. The country of occurrence handles most investigation on site, country of registration takes care of interviewing operator and maintenance personnel and country of manufacture cooperates with manufacturer on identifying mechanical damage and usually reads the FDR and CVR data as there are only a few labs in the world that do that. Plus some of the large investigation boards may be asked for additional help. And in politically sensitive cases like MH17 additional countries may be involved to reduce risk of manipulation with the results.

3Aviation authority in USA is FAA. In Europe there is EASA, which coordinates the regulations, and separate authorities in each country that carry out the actual oversight.


Can I use my aviation handheld transceiver on MURS? Is there a regulation or rule about using handheld aviation transceivers e.g. Icom A-24 for ground to ground communication on MURS frequencies?

Can I just use Icom A-24 for ground to ground? or do I need FCC licence?

Update:

Can I use my handheld aviation transceivers (Icom A-24) for ground to ground communication? or do I need a FCC license?

You asked for legal opinion, so the main "legal" reason would be that a radio must be type-accepted for the service for which you want to use it. So unless Icom A-24 is MURS type accepted, and it is not, then it's illegal to use it.

You don't need a special FCC license. FCC says this about licensing:

  MURS is licensed by rule. This means an individual license is not
  required for an entity to operate a MURS transmitter if it is not a
  representative of a foreign government and if it uses the transmitter
  only in accordance with Section 95.1309. There is no age restriction
  regarding who may operate an MURS transmitter.

But the transmitter itself must be marked as MURS transmitter. FCC has this to say about that:

  A MURS transmitter must be certified by the FCC. A certified MURS
  transmitter has an identifying label placed on it by the manufacturer.

There is technical reason as well which makes it impossible to use it on higher VHF frequencies: Above 137 MHz, the traditional modulation type is FM. Aviation VHF is AM. So even if you wanted to talk to MURS users, you wouldn't be able to do so normally due to different modulation types used. Another technical issue is frequency coverage. A-24 can transmit 118.000 MHz to 136.975 MHz. I don't know if it's possible to unlock it for extra coverage (but I'd be surprised is that was possible, due to use case), but with default frequency coverage you can't go high enough to reach MURS frequencies.

UPDATE:  I just checked and it seems that AM is actually allowed on MURS. So it is, and you can somehow unlock the A-24 to operate on those frequencies, you could technically speak to other AM MURS users, but again it wouldn't be legal due to licensing system used for MURS.


What safety issues led the FAA to ban Constellation flights into/out of the U.S.? Although the Lockheed Constellation (like the other late, large piston airliners) was superseded in the 1960s and 1970s by newer jets (plus turboprops for shorter/lighter routes), it hung on into the 1990s with various Latin American airlines, who used them for international flights to and from the U.S.; this only ended in 1993, when the FAA abruptly banned the last of these airlines (all of them from the Dominican Republic, weirdly enough) from flying their Constellations in U.S. airspace.  According to Wikipedia, this ban was due to some sort of safety concerns:

  Most Super Constellations were retired by their original operators after the advent of the Boeing 707 and Douglas DC-8 jet airliners. The last commercial flight of the L-1049 Super Constellation was in 1993, when the Federal Aviation Administration banned all airlines from the Dominican Republic that flew Constellations to the United States (due to safety concerns). The Dominican airlines were the last operators of any version of the Constellation.

I’m at a loss as to what those safety issues could be:

Was it due to concern about poor safety practices at those airlines, rather than concern about poor safety of the Constellation per se (but, then, why weren’t there at least one or two Constellation-flying carriers that did meet the FAA’s safety standards)?
The Constellation being an old, pressurised aircraft, were they worried about metal fatigue (but, then, why did the FAA impose a total flight ban on the Constellation, when fatigue-life concerns haven’t caused them to impose such a penalty on any other aircraft - especially since fatigue would be less of a concern with piston airliners like the Constellation than with jetliners, due to their lower cruising altitudes and resultant lower cabin pressure differentials)?
Were the old, large, temperamental multi-bank radials used by large piston airliners such as the Constellation simply incapable of meeting increasingly-strict engine-reliability requirements?
Was the FAA casting a jaundiced eye on the safety hazards of U.S. airports having to store vast quantities of the extremely-high-lead grades of avgas needed by the aforementioned engines?
Something else?

Individual airlines, or even all of the airlines from entire countries, are sometimes banned for safety reasons. It was the Dominican airlines, not the aircraft, that were banned by the FAA.

It is just coincidence that many of these un-safe airlines flew Lockheed Constellations. They were banned from flying ANY aircraft into the USA.

The Wikipedia article talks about the end of Constellations used in commercial airline service, but it was the grounding of the airlines that caused the end, not the grounding of any particular aircraft.

Here is a link to a NY Times article describing a ban of all airlines from nine different countries.

Sept 3rd 1994 NY Times article

  The Federal Aviation Administration has barred airlines from nine nations from flying to the United States because of poor safety procedures.

  The unusual action, announced today, is a response to safety questions
  from consumer groups. Officials say they hope the economic fallout of
  the ban will encourage the airlines to follow safety guidelines.

  The aviation agency surveyed safety procedures in 30 of the 93
  countries that have commercial flights to the United States. The
  agency sought to determine if the aviation authorities in each country
  were meeting the safety requirements of the International Civil
  Aviation Organization, a United Nations agency. Its rules are less
  strict than those of the Federal Aviation Administration.

  The aviation agency did not reveal details about the safety
  deficiencies that had prompted it to ban the nine airlines.

  The banned airlines are from Belize, the Dominican Republic, Gambia,
  Ghana, Honduras, Nicaragua, Paraguay, Uruguay and Zaire. Four other
  countries were allowed to continue flying into the United States, but
  under increased supervison by the aviation agency. They are Bolivia,
  El Salvador, Guatemala and the Netherlands Antilles.


What aircraft could make non-stop transatlantic flights in 1958? According to Wikipedia:

  TWA flew to Europe nonstop from O'Hare starting in 1958

The Great Circle Route distance from ORD/KORD to LHR/EGLL is 3953 miles. Other major European airports would have been farther away.

What aircraft were capable of making that non-stop flight in 1958 (also, how long would it have taken)?

The first scheduled trans-atlantic air service was made possible with Zeppelins. The LZ-127 started flying the route in 1931, mostly to Lakehurst, NJ, or Pernambuco in Brazil, but was disassembled in 1940.

The first airliner which was able to cover the distance (back then it was Berlin - New York) was the Focke-Wulf 200, which in 1938 needed almost 25 hours East-West and 20 hours on the return leg. With its slow cruise speed, wind made a lot of difference. Sadly, the US did not allow Lufthansa to start the scheduled service it had planned to open in 1939. Lufthansa had opened regular air mail services in 1934 between Europe and South America using flying boats and a relay ship in the middle of the Atlantic. Air France added its transatlantic mail service flying from Africa to South America and back.

The first heavier-than-air transatlantic passenger service opened between New York and Marseille in 1939 on Boeing 314 Clippers operated by Pan Am. It crossed the Atlantic between Foynes, Ireland and Botwood, Newfoundland. A British service, also using flying boats, was in preparation but stopped by the beginning of WW II.

In the 1950s, there were already several options for transatlantic air travel, but none of them non-stop from Chicago: Pan Am, TWA, Trans Canada Airlines (TCA), BOAC (successor of Imperial Airways), and Air France all operated large propeller aircraft which covered the distance with refueling steps, typically in Gander (Newfoundland) and Shannon (Ireland). Typical aircraft were the Douglas DC-4 and DC-6, and the Lockheed 149 Constellation, but also the French Latecoere 631 flying boat was used until 1955. Of these airlines, only Pan Am and BOAC serviced O'Hare in 1957, before the first international terminal opened there in the following year.

Still, the prevailing eastward wind made the East-West crossing hard and required airlines to reduce payload, and only the advent of faster  airliners like the Douglas DC-7 (from 1956) and the Lockheed 1649 Starliner (from 1957) made the transatlantic services more reliable and economical. Beginning with the DC-7C, their range was sufficient to support transatlantic service directly from Chicago O'Hare.

In October 1958 the first transatlantic jet airliner service was opened by BOAC using the de Havilland Comet 4, followed shortly after by Pan Am, operating the Boeing 707 and connecting London with New York (with an occasional refueling stop at Gander on westbound flights). O'Hare could only participate in this progress after its main runway was extended to accommodate large jets in June 1960.

Therefore, the most likely airplanes to fly transatlantic directly from O'Hare would have been the DC-7C (but operated by Pan Am, not TWA), the Lockheed L-1049G and the L-1649, which both were operated by TWA. For the flying time, the 3628 miles from JFK/Idlewild to Paris Orly took 14¼ hours with the DC-7C and 14.83 hours with the Lockheed 1649. So it is fair to assume a flying time of 15½ to 16 hours for the slightly longer distance between Heathrow and O'Hare.

Quote from Wikipedia:

  In January 1958 Pan American scheduled the DC-7C from Orly to Idlewild
  in 14 hr 15 min; TWA scheduled the 1649 in 14 hr 50 min.


Where to find the LSA exporting requirements from the USA? I'm planning to visit the US to buy an LSA (light sport aircraft) then export it to Saudi Arabia, I'm not a US citizen, where to find the requirements?

Go to Appendix 2 of AC 21-2, and select Saudi Arabia from the drop down menu.

For example:

  It will be the responsibility of the Saudi Arabian importer to ensure that the nationality and registration marks are properly displayed on the aircraft prior to departure from the exporter's base and to ensure that the necessary flight documents are installed and carried in the aircraft during the delivery flight.

The full document lists all the requirements, too many to copy and paste here. For the regulations, that would be Title 14, Code of Federal Regulations (14 CFR) part 21, subpart L (.pdf).


Is the 737-800 a different plane from the 737 MAX 8? I am flying on March 16 from Barbados to Toronto on a Westjet Boeing 737-800 also referred to as an aircraft type 73H on my ticket. Is this a different plane from the Boeing 737 MAX 8, grounded by several countries?

They are different, yes. The 73H is not the Max 8. The 73H is an -800 with winglets. The -800 has been in service since 1998, with 4,991 deliveries as of February 28, 2019.

See here: What is the difference between Boeing 73G, 73H and 737?

  73H - Boeing 737-800 with winglets (8th letter of the alphabet)

The Max 8's IATA code you'd find on a ticket is 7M8.

For visual identification, see: Is this a 737-800 or 737 MAX 8?


What are these wavy lines on fighters' canopy? As shown in the images below, what are these wavy lines on the canopy of the aircraft? Do these lines have any utility?

These are mostly captured in videos of cockpit views of carrier-based aircraft.

It is an explosive cord which helps to crack the canopy (pdf!) before the ejection seat has to do this all by itself. When ejection is commanded, the harness is tightened and the canopy is shattered, and only then the real ejection starts. Earlier designs would blow the full canopy off, but this takes longer than shattering it, especially when the canopy is large.

Some seats have their own canopy breakers, but thick, tough canopies which are needed for flying at high dynamic pressure and for surviving bird strikes would slow the seat down too much. The F-16 canopy is 12mm thick in the area above the pilot.

They are used widely for both land- and carrier-based aircraft, and modern designs try to make them less obvious. The F-35 canopy uses just one line down the middle.


Help reading a FAA departure procedure chart I was hoping to get a few answers regarding how to read a FAA departure procedure chart.  Let's take the JUDTH SEVEN DEPARTURE chart shown below:

From what I can tell, it seems that the diagram in the upper left indicates that those taking off from either runway 3 or runway 21 should make an appropriate turn to heading 335 degrees.  Is this correct?

Following the "thence...," it says to expect RADAR vectors to GBN VORTAC.  So does this mean ATC will guide the aircraft to the GBN VORTAC fix?

Can someone explain what MOHAK TRANSITION (JUDTH7.MOHAK) means?  Is this saying that the MOHAK fix represents a transition to en route airspace from terminal airspace?

How would one identify the departure fix in this chart and in general?  Is the departure fix MOHAK? JUDTH? GILA?  Additionally, what would be the departure procedure transition fix?

Thanks!

You have a good grasp on departures so far.
This particular SID advises the pilot departing Runway 3/21 to turn heading 335° and expect Radar Vectors to the GBN VORTAC. This is normal procedure considering the fact that so many airports in the same area share SIDs. Not all airports will have a co-located Navaid from which to start a SID. In this case, ATC would vector the aircraft back around the Phoenix airspace to GBN (Southwest) since the original 335° heading would be taking the aircraft away from GBN (due True North). Depending on traffic and ATC availability, ATC might vector you to the 249 Radial between GBN and JUDTH.
On other SIDs, there will be multiple fixes from which to leave the SID and transition to the en route portion of your flight. You, and/or ATC would file/assign for the fix most directly on your route of flight. In this case, there is only one, MOHAK.


Is it possible to land a 737 on an aircraft carrier? I have seen a flight simulator (X-Plane 11) video of landing a 737 on an aircraft carrier (and stopped). Is it possible to land a 737 in real life? What is the biggest aircraft that it is possible to land on an aircraft carrier?

An unloaded 737, flown by a top-tier pilot can stop incredibly fast, generally in a shorter distance than a Cessna-172 flown by a student (typically around 900 ft:  I've seen planes at Boeing Field, land 32L and stop well before A9).

Because the brakes are meant to stop a fully loaded plane on a wet runway, they are extremely powerful when the plane is empty and the braking action is good.

Although it has never been attempted (to the best of my knowledge), I think a 737, near empty weight, in optimal conditions, could likely land on a carrier with a 1,000 ft deck steaming into the wind (lets estimate headwind + carrier speed for a combined effective wind of 50kts).

Another consideration, however, would be if there's enough space for the 737's massive wing span.


Could New York build a new mega airport? Both New York and London have insufficient air traffic capacity. One option for London is to build a new mega airport to replace LHR. However, this option is not discussed much in NY. Would it be feasible to build a new mega airport to serve New York?

I think I'd challenge your assumption of insufficient air traffic capacity.  You could equally well look at it as too many planes wanting to land, or (for NYC at least) insufficient passenger rail service.

Beyond that, have you looked at land prices in the vicinity of NYC or London?  Perhaps in some countries you can just seize land to build airports, over the objections of the people living there.  In the US (and presumably the UK, though I'm not certain), it's much more difficult to obtain, and should properly involve paying a fair market price - after long and expensive legal battles.

Then you have to consider trip duration.  It's not just time spent flying, but time getting to and from the airport.  In NYC, it's IIRC about a 15 minute bus ride from LaGuardia to Manhattan, and I think not much more from JFK.  Put the airport way out in the country, and people would spend an hour or two just getting there, negating the speed advantage of air travel for short & medium length flights.


Are there any aircraft with powered landing gear? My student asked me a question this morning.  It was:

  A car drives by turning its wheels against the Earth. An airplane taxis by rolling on its wheels while the engines push against the air.  Are there any airplanes that taxi by turning their wheels, like a car?

I assume the answer is no for reasons of weight, complexity, and so on, but it's dangerous to say never.  Are there in fact any airplanes that fit her description?

Edits in response to comments:

She was thinking of "normal" airplanes, not airplane/car hybrids.
Peter Kämpf's link is the kind of thing she was thinking of.

WheelTug makes an addon motor for a nose wheel. This is a demo of the unit being developed for a B737. They intend to lease it to airlines. It works well under most circumstances, but has difficulty on icy aprons and the aircraft would need a pushback so it could taxi using its engines. The terms of the lease would financially compensate. They have "reservations" for 1100 units from two dozen airlines.

youtube

There are a number of financial considerations, such as cost to carry the weight of the unit. Here is a presentation of their business case. They claim direct cost savings similar in value to installation of winglets, and time savings value twice as great as replacing a current generation 737/320 with a Max/Neo.

youtube

Safran also had a joint venture to develop a similar unit for aircraft maingear, but that is no longer being pursued. I don't know of any OEM that offers this kind of capability on commercial aircraft.


Why are almost half of the world's helicopters in North America? I was reading this report and came across the following quote:

  North American purchase plans [for civilian-use helicopters] are a significant component of the overall 2017 survey demand, as the region represents more than 40 percent of the current world fleet.

I don't know a ton about the helicopter industry, so this quote surprised me.  What are most of these civilian helicopters in North America being used for?  More specifically, in North America what are the uses for helicopters that aren't common in other parts of the world?  Does this unique demand come mostly from offshore drilling, police, or medical usage? Why don't they use helicopters for those purposes in other countries?

What are most of these civilian helicopters in North America being
  used for?

As listed below, Medical and Police use are quite common in the US. The Coast guard runs a fleet of rescue choppers and divers along with their boats. Many news stations also run helicopters for traffic and other areal coverage. There is a fairly sizable market for Powerline, Pipe-Line and Survey related work from rotocraft. There is even a case for moving precarious items.

There is of course a large market here in the US for private, owner flown/operated helicopters in the US. This is at least in part due to the lower costs of private flying in the states. The US airspace system is largely funded by taxes on avgas as well as other federal funding and does not have the same user fee structure that Europe has implemented. In other words here in the states you need to pay to rent or own the plane and gas it up but the use of the air is free. In Europe you will have the same costs with an added cost to use the airspace. In Europe you can also expect AvGas prices to be a bit higher across the board. Although many helicopters are turbine based and run on Jet-A.

  More specifically, in North America what are the uses for helicopters
  that aren't common in other parts of the world?

Moving people relatively trivial distances... In many places, general sightseeing. If your bold enough, aerobatics. Although many of these uses are also common elsewhere in the world. However due to the nature of aviation laws here in the US, its a bit easier (and somewhat cheaper) to fly small aircraft.

  Does this unique demand come mostly from offshore drilling, police, or
  medical usage?

Police and Medical is fairly common around the world. Oil rig transport occurs only in places where off-shore rigs are used/drill (many reside close to the US or Asian shores).

  Why don't they use helicopters for those purposes in other countries?

They do, for example the UK has a pretty large helicopter medical effort and there is the WestPac life saver helicopter service in Australia. There are efforts in Greece and many other places in the world for that matter.


How does angle of incidence affect an aircraft's stability? How does angle of incidence affect an aircraft's stability?

I've tried searching the web for the simplest answer that makes sense but so far I've come up with nothing as yet.
I know it sounds simple, but I'm still new to this so its pretty hard to grasp my mind around the concept yet.

The angle of incidence is the angle between the wing chord and longitudinal axis of the aircraft as depicted here. From years of building model aircraft and flying aircraft I can explain one way that it affects the aircraft, and that is by reducing drag caused by the fuselage. A given wing requires a certain angle of attack (pitch up attitude) in order to fly at a given weight and speed. If the angle of incidence is 0 degrees, then that would require a nose high attitude and expose more of the underside of the fuselage to the relative wind. However, having an appropriate angle of incidence allows the fuselage to have a more horizontal orientation (and better visibility for the pilot from the cockpit) than if the wing was mounted exactly parallel to the longitudinal axis of the fuselage.

So how does it affect an aircraft's stability? It affects an aircraft's stability by reducing its drag at certain airspeeds.


What's this biplane built by a 16-year old? I was told that this plane was built by a 16-year old in the 90s. Ever since, I've been bent on finding the specifications, name, etc., of this airplane with no success.

I don't know about this being from the 90s, but it sure looks like the Laird Baby Biplane in the Florida Air Museum to me:

On display at Florida Air Museum, Lakeland Linder Regional Airport, Florida (wikimedia.org)

The identifying features that I observe to be common between this picture and other pictures of the aircraft are the shape of the nose, the details along the fuselage, the shape and placement of the struts, the tanks beneath the top wing and the shape of the engine protrusion. I would also note that the Wikipedia page indicates that the specimen in the museum is a replica that was built in the 90s (whereas the original is from 1912).


What is a simple way to explain why best range airspeed is below normal cruise airspeed? Without using complex mathematics, please explain why best range airspeed is less than normal cruise airspeed.

Normal cruise is a compromise between being fuel efficient while getting to your destination at a reasonable speed.  It all comes down to drag; the faster you go the more parasitic drag you pick up and economy suffers.

Just like in your car - if you wanted to squeeze max efficiency (range) out of a trip you could drive at 55mph on the freeway.  In fact you could even make it law!  But, people are generally willing to burn a little more fuel to get there faster.


Why are there many different approach lighting systems? Why not just have only 2 or 3? What's the point of having such a number of different configurations? What's the practical application of each lighting scheme? I mean, do they really help pilots in a different kind of way?

(source)

The different systems generally have to do with ILS landings and the ability to have the runway in sight. As approach systems have gotten better and our understanding of flight mechanics and general operations has increased the need for different systems has evolved. As new requirements come out and new (generally lower) minimums are allowed different lighting requirements may accompany that but not all airports can always afford to install new lighting (and other related things) as such most regulations allow older systems to stay in place so long as the minimums remain.

In some cases airports simply don't have the physical land at the runway threshold to install larger/longer light systems. In some cases they need to do things like extend out into the ocean to install the lights.


Does the avoidance of thrust reverser save fuel? On 2017-06-17 I took an AirAsia Airbus A320-200neo from Hong Kong (VHHH) to Kuala Lumpur (WMKK).

The flight crew did not use reverse thrust for slowing down the plane.

Trying to find an explanation to this, I would like to know so much as possible about the use of thrust reversal by commercial flights, including low-cost airlines, which would probably like to use any feasible technique for saving fuel.

Without further knowledge of the procedures/state of the (a) airport, (b) airline and (c) aircraft , I don't think any conclusive answer could be made. To throw some thoughts in:

All of Kuala Lumpurs's runways are over 4000 meters long, and braking an A320 (at landing weight) can easily be done without thrust reversers over that distance.
Depending where the gate was, they may simply have wanted use more of the runway to speed up the taxi, in which case excessive braking would have been undesirable. Most standard procedures call for a minimum of idle reverse thrust however.
The thrust reversers may have been inoperable, i.e. broken. You are allowed to fly an A320 in that state.

Update: Since you said you didn't sense any thrust reversers (vibration/sound, i.e. no visual confirmation), here's a video to show that they can be pretty quiet even if the doors are opened. If you follow the spiral painted on the spinner note the speed doesn't appear to change a lot even after the plane leaves the runway and the reverser doors are closed.

(Touchdown at 6:50)


Why do we never see high-bypass turbofan engines sharing the same nacelle on large airliners and similar aircraft? I'm talking about this sort of thing (this is the fictional airplane from Casino Royale), rather than two (or more) engines per wing in individual nacelles:

If we ignore the weird 'drop tanks' on the outer pylons, what makes this design inferior to one with individual nacelles? I can think of some highly speculative pros and cons for both layouts:

Pros for shared nacelles:

Shared nacelle and pylon potentially means less frontal and wetted area per engine, which could maybe reduce overall drag.
Overall, this scheme seems to allow the 'center of thrust' for all the engines on one wing to come closer to the centerline of the aircraft. In some designs like the A380, where a massive vertical fin is needed to maintain yaw authority in an engine(s)-out situation, it seems like this could save quite a bit of weight and drag by reducing the size of the vertical fin.

Cons for shared nacelles:

Obviously there is an increased risk that an uncontained engine failure like the one on an A380 a few years ago could cause cascading failures in its 'neighbor'. I'm not sure how to quantify this risk, but it seems significant.
Additionally, a structural failure in a pylon/nacelle (extremely rare but it does happen IIRC) will affect two engines instead of one.
Maintenance will be probably be more difficult, since you'll have to mess with two engines just to get at one.
I'd expect that due to the structural requirements of supporting two engines on one pylon, you probably wouldn't save much weight and you might actually end up with a heavier aircraft, all other things being equal.
Maybe you'd lose some efficiency in the interaction between the exhausts of both engines in a nacelle?
It might turn out that you can't fit two large high-bypass turbofans into one nacelle without choosing between flow separation issues and greatly increased frontal area.

This is all layman speculation, though. In reality, from an engineer's point of view, is the choice of one layout over the other obvious? Why or why not?

Short answer

It's the vastly different flow conditions from static to cruise which demand a separate placing of high-bypass-ratio jet engines. They would produce less thrust and more drag when paired.

Why were there paired engines at all?

The early jets had their engines mounted directly beneath or in the wing, and comparisons between separately mounted and twinned engines showed a slight advantage for the latter due to lower wetted surface area and less impact on the wing.

Arado built two four-engined prototypes of their Ar-234 jet, one with separate engines (V6, see directly below) and one with paired engines (V8, further down). The V8 became the prototype of the C version of the Ar-234.

However, with the increasing airflow of high-bypass-ratio engines the interference between both will turn pairing into a disadvantage. In cruise, only the central stream tube flowing towards the engine will be ingested, and the rest will spill over the intake lip. Placing a second engine directly next to the first will block the flow of spilled air on that side and will increase spill flow on the opposite side. This will most likely cause massive separation there if the intake is not heavily modified, leading to a noticeable drag increase. Also, the now asymmetric flow in the intake would reduce the efficiency of the fan - it needs very homogenous flow over the full cross section in today's engines.

Conversely, at low speed the engine sucks in air from all around and will face competition from a second engine, such that both will not be able to ingest as much air as when mounted separately. The consequence of pairing would be reduced thrust during take-off.

The initial disadvantage of separate engines, their collective impact on wing aerodynamics, is now greatly reduced by mounting them on pylons, so they are ahead and below the wing.


Why would the outer tanks fuel on the A320 be colder than the inner tanks? I have noticed in a number of instances during long flights typically over 5 hours the fuel in the outer tanks on the A320 are colder than the fuel in the inner tanks. This goes against the system logic as warm fuel gets first recirculated to the outer tanks then the inner tanks.

However in the FCOM it's mentioned in a note if the outer tanks are full, fuel spills over into the inner tank, does this mean that the warm fuel is now going directly into the inner tanks? Also can any other variables play a factor like fuel temperature on ground?

Short answer:

This is very normal because the outer wing is thinner.
The warm fuel (which is warmed by the IDG) is not always returned to outer/inner tanks.

Some explanation is needed wrt the circulation function on the A320. Excerpts below will be denoted (M) and (F), for maintenance and flight manuals, respectively.

  The FADEC controls the fuel return valve.
  If the outer tank is already full, the fuel overflows to the inner tank through a spill pipe. On ground, the fuel recirculation is not inhibited if there is an overflow in the surge tanks. (F)

The main takeaway from this is the first line. The fuel isn't always returned. The return is managed by the engine's FADEC, not the fuel system. The second thing is that the circulation also works on ground.

  The fuel system:

  Stores fuel in the tanks.
  Supplies fuel, in the correct quantities, to the fuel tanks during refueling.
  Supplies fuel to the engines and the Auxiliary Power Unit (APU).
  Circulates fuel to cool the Integrated Drive Generator (IDG).
  Keeps fuel in the outer tanks for wing bending and flutter relief. (F)

The function of the circulation is cooling the IDG, not warming the fuel. But the fuel is indeed warmed due to the process, but the engine fuel system mixes that warm fuel (inside the fuel IDG cooling system) with fresh supply of cold fuel, to be used again by the engine (combustion) and for the IDG cooling.

In other words, the engine burns the same fuel that was used for cooling the IDG (not necessary to return it to the tank).

The FADEC only returns the fuel to the outer tank in 1 condition, and it does that by opening the FRV (fuel return valve). That condition:

  The return valve opens at low engine fuel flow if the engine oil temperature is above 93°C (199°F). (M)

Low engine FF (e.g., idle) will not be encountered in cruise. Because of the low FF, there is no high demand for the warm fuel (inside the fuel IDG cooling system), i.e., the engine is not using it quickly for combustion. And it will only keep getting warmer. So the FADEC mixes it with fresh fuel, and reintroduces it to the outer tank (schematic below). The mixing ensures it will be reintroduced at less than 100°C.

In other words, when the engine is not burning enough fuel, the fuel inside the IDG cooling system is returned to the tank, because it will keep getting hotter since it is not being consumed at a fast enough rate.

  The return valve mixes the hot fuel with cold fuel from the LP pump to maintain the temperature of the returned fuel below 100°C (212°F). (M)

This means, for example, if the plane is sitting on the ground with the engines running for too long, the outer tanks will become warmer than the inner tanks.

In cruise, because the outer wing is thinner, the surface area to volume ratio is higher than the inner wing, and thus the fuel will lose temperature faster than the inner tanks. This is highlighted in Airbus' FAST magazine issue 36:

As you can see, the outer tanks cool down at a faster rate. Note: the magazine discusses the long-range operation of the A340, which unlike the A320, does have a fuel transfer procedure when a LO TEMP message is shown.

And below is the A320 IDG cooling schematic. Close the FRV, and you'll see how the fuel is mixed and reused by the engine:

The above explains why when the crew gets a confirmed FUEL L (R) OUTER (INNER) TK HI TEMP warning, the actions could be:

Turning off the galley (reduces load on IDG).
Delaying takeoff and shuting down affected engine (side).
Disabling auto thrust and increasing FF of affected engine (side).
Using APU IDG instead of engine IDG (taking it offline).

(Source: A320 QRH)

All this would reduce the hot fuel being fed back into the affected tank.

A slightly more detailed operation of the FRV is found in the engine technical training manual (CFM56):

  The purpose of the Fuel Return Valve (FRV) is to bypass warm fuel from the Hydromechanical Unit (HMU) to maintain the efficiency of the Integrated Drive Generator (IDG) Oil Cooler and engine oil/fuel heat exchanger.

  Consequently this prevents engine and IDG oil over temperature.

  FRV logic: the FRV is fuel pressure operated, and electrically controlled by the Electronic Control Unit (ECU).

  The ECU control logic of the FRV is mainly based on the engine oil temperature.

  Above a certain engine oil temperature, the ECU orders a low fuel flow return to the A/C fuel tanks.

  When the engine oil temperature increases, the ECU orders a high fuel flow return to the A/C fuel tanks.

  The two return fuel flow levels are 500 kg/h and 1000 kg/h, or 1100 lb/h and 2200 lb/h. The hot fuel is mixed with the cold fuel to limit its temperature, before it is returned to the A/C fuel tanks.


To what extent have political (race, gender, social class) attitudes been implicated as human factors in the cockpit? This question is related to:

How does cultural difference impinge upon human factors in aviation industry safety?
How have deep-seated cultural human factors (particularly in east Asia) in the cockpit been successfully managed in the past 20 years?

Standard industry practices of cockpit management can invert or disrupt very deep cultural and political expectations of command and authority.

The question

What evidence is there, in research, incident reports or other documented sources, that has identified political attitudes around race, gender or social class as human factors in the cockpit?

For example:

With more women in airline cockpits, have new human factors emerged (for example, a male pilot displeased to be questioned by a woman)?

In regions with troubled racial histories (southern Africa, the USA) have race relations and attitudes in the cockpit been responsible for incidents?

In cultures where social class or even caste is very significant, have these been implicated as human factors in the cockpit?

There are numerous accident reports that state cultural issues as contributing factors, especially respect for elders / superiours / social class in Asian countries leading to poor "Crew Resource Management" - typically the co-pilot failing to challenge the captain.

The first examples that come to mind are:

https://en.wikipedia.org/wiki/Korean_Air_Cargo_Flight_8509 - According to the Mayday episode, the captain was of a higher social class than the co-pilot.
https://en.wikipedia.org/wiki/Korean_Air_Flight_801
https://en.wikipedia.org/wiki/Air_China_Flight_129


Practice Pans - are there any genuine reasons not to use them? I'm a low time PPL.  In my personal opinion, practice pans, perhaps one or two a year, are a good thing.  Practice in a procedure that builds confidence removes one more item from the pucker factor list if it does all go wrong and lets your brain focus on the situation.

The D&D cell are always happy to assist and I know that they welcome it as it gives them practice as much as it does me. They are always excellent and it's comforting to know that they are there if I ever need them for real.

However, I know that many pro pilots do not approve of this.  I am aware that they are often required to monitor guard and that practice pans can be a source of noise but is it really that disturbing?  I've even had that terse "transmitting on guard" broadcast which to me is a) entirely rhetorical and b) great irony.

If something genuine crops up on guard, then of course I'd shut up and continue on my way but are there any genuine reasons for amateurs to not practice?  Surely it's better for all users of the sky to be as good as they can?

I presume you are from UK since it is the only country I know of that uses practice pans.

Basically, ICAO (ICAO Annex 10, Volume V, § 4.1.3.1.1) states that the emergency frequency 121.5 MHz (sometimes called "guard") shall be used only for genuine emergencies. So typically any other use is considered misuse.

However, countries can file deviations from this rule and publish these deviations in their AIP. One such example is the UK, where 121.5 can be used for practice PAN calls to ensure pilot familiarity with the process.

Pilots not familiar with the situation in the UK sometimes frown upon this use, and as you mention, jump in with the dreaded "transmitting on guard" sentence. But those doing that seem to have the same reaction when a real emergency is going on.

If you are flying in the UK and want to practice an emergency situation you are encouraged to do so by the D&D cells. But remember to ask permission first:

  A/C > London Centre, callsign, request Practice Pan

If they have the time to accommodate you, the reply will be something like

  London > callsign, Practice Pan acknowledged, continue when ready

And remember, it is not only a practice for you, but also for controllers. There is a benefit for everyone flying around.


Is the takeoff power always maximum? I used to think that for commercial aircraft from Airbus, Boeing, Embraer, etc., the take off power was always maximum and selected by the TOGA selection on the thrust levers. But I have been told that some companies would lower the takeoff power to save money (at the expense of a longer take-off length).

So the question is: for regional, continental, and long-haul aircraft, is the takeoff power always maximum or can it be adjusted depending on the configuration? And can lowering takeoff power allow savings?

Takeoff power is almost never maximum engine power.

Maximum power affects engine life as it brings significant wear to the engine. IIRC, if max power is used on takeoff, the crew must log an entry in the logbook to notify maintenance.
Turbo-fans produce a lot of power. If you require max power to takeoff, you better double-check your numbers, or you're operating with a pretty narrow margin.

The reality is the reverse: airlines love to do low power takeoffs, and they avoid a high power takeoff as much as practical. Occasionally, a condition such as high ambient temperature (resulting in high pressure altitude), heavy load, obstacle on departure path may demand a max power takeoff. Possible wind shear may also prompt the crew to select a higher takeoff power.


What is the optimum design: elliptical lift distribution or elliptical span loading parameter distribution? I am getting very confused with these terms. I'm trying to analyse a span loading  distribution given as cl(y)c(y)/ccL. This distribution is almost elliptical but when I plot just cl(y) it changes and I have more cl near the tips due to the reduction in chord.

This made sense from my point how view since the AR is low, the sweep is high and the taper ratio is small. It is like the figures I remember for these cases. However, when I have searched in google I have seen this image:

This wing is pretty similar to mine, and the distribution is similar to my cl(y) distribution. However, the parameter here is cl(y)c(y)/ccL!!

I don't understand completely the difference. When we talk about elliptical distribution for minimum induced drag it is about cl(y) or cl(y)c(y)/ccL? Why is this parameter used and plot and not cl(y)?

Minimum induced drag is reached when the circulation distribution over span is elliptical. Circulation is indeed proportional to the product of the local lift coefficient and the local chord (c$_l \cdot$c). The diagram in your question normalizes this with the overall lift coefficient c$_L$ and the mean chord $\overline{\text{c}}$.

But this is only true if you disregard the structural weight of the wing. Using less load near the tips will reduce the wing root bending moment and, consequently, wing mass, so less lift and wing area are needed in order to carry the same non-lifting load. Even though your drag coeffcient might be higher, your overall drag will be lower.

The optimum will also depend on the size of the wing. Small wings should indeed use an elliptical circulation distribution because their structural weight is low, but in large airplanes a more triangular distribution will be better.

One last word: Please try to avoid the high loads near the wingtips if you want a nice, docile stall behavior.


What can I do if my carb-heat cable breaks in-flight? If I'm flying in conditions that are conducive to carburetor icing, and my carb-heat cable becomes in-operable, is there anything I can do to prevent engine failure if my carburetor starts icing up? Assuming there are no immediate landing-areas to stop and fix the problem.

Well, this depends a little on your situation.

In all cases your goal is get on the ground in a controlled manner that leaves the pilot, passengers, and airframe intact - so obviously you'll be heading for the nearest airport (and if you can get in contact with ATC and explain your situation doing so would be a really good idea).

No signs of carb ice (yet).

If you're flying in conditions conducive to carburetor icing but don't yet have signs of icing there are a few things you can do to help prevent it from forming:

Seek a warmer/drier altitude
There's a wonderful diagram I'm sure everyone has seen that gives an idea of the probability of carb ice. If you can find an altitude where the temperature/dew point spread is less conducive to carb ice formation fly there until you can land.
Lean the mixture (as practical) to limit evaporative cooling from the fuel vaporizing.
This can limit the temperature drop in the carburetor, and if it's only a few degrees of difference between ice and no ice it might help.
Avoid low-power operation (<60% power).
A partially closed throttle plate is more likely to pick up ice (there is a greater pressure drop across the throttle plate which means a greater temperature drop).
"Clear" the engine periodically by opening & closing the throttle.
This helps ensure the throttle plate does not freeze in place, and can dislodge any small ice patches before they become a more serious problem.

  I think this would qualify as an "urgency" situation (pan-pan), per this answer.
  If you can get in contact with ATC don't hesitate to let them know that.

Signs of carb ice are apparent.

If you do have signs of carb icing you can do all of the things above too, but how effective they are may vary.

As xpda noted adjusting the mixture can help (typically carb ice makes the engine run over-rich).
In extreme cases wide-open throttle and an aggressively leaned mixture may keep the engine producing power (and will reduce the pressure drop across the throttle plate, possibly bringing the carb temperature up enough that the ice will melt off).

In many light singles your alternate air is the carb heat box, but if you have an alternate air source for the engine besides carb heat that may be worth trying as well (especially if it's in the engine compartment or heated cabin).

  Carburetor icing with carb heat inoperative is a bona-fide emergency.
  I can't imagine not making a mayday call in this case. Best-case scenario you wind up making an uneventful landing with fire trucks waiting to greet you ; Worst-case scenario you wind up landing somewhere that's not an airport, but at least someone knows where you are.


When are aircraft required to dump fuel for emergency landings? I've heard that in a lot of instances a jet that is making an emergency landing is required to dump excess fuel.  In a lot of instances this would make a lot of sense.  For example, if the gear cannot be lowered and the plane must land on its belly.   The last thing you want is a hundred tons of jet fuel involved.

But, I have to assume there are also emergencies where a plane isn't required to dump its fuel.  I just am not sure what they would be?

So, my question is: When are aircraft required to dump fuel before landing (or, at very least, when is it advisable to dump fuel before landing).

Bonus points:

How much fuel does an aircraft retain after an emergency dump? I'm
assuming they don't dump it all or they would have no fuel to
maneuver with.
Examples would be great.

For many medium and large sized jets the maximum gross takeoff weight is higher than the maximum landing weight.  If the airplane has an emergency that requires an air return or other landing in the early part of flight, it is very likely overweight for landing.  The plane has 3 options at this point:

Land overweight
Dump fuel (if able)
Fly around at low altitude and high power to burn fuel

For some airplanes, option 2 is not available.  This includes airplanes that are not equipped to dump fuel (not all airplanes have this capability or have the capability under MEL) or are not approved to dump fuel at their current location and altitude.  For these airplanes, only option 1 and 3 are available.

The choice between option 1 and 2/3 comes down to what kind of emergency it is.  If you have to be on the ground now, you won't care about being overweight, and will just put it down.  If you have time and landing now isn't a priority, then you would choose to dump or burn fuel.

If an airplane chooses to dump, they will generally choose one of two values of remaining fuel:

fuel such that they land at the maximum landing weight
absolute minimum safe fuel to land

This choice comes down to how likely the landing will end in an accident.  If you are sure the landing will be a non-event (e.g. air return for anti-ice failure) then you'll likely just dump until landing wont be overweight.  Conversely, if you have a control issue or something that may end badly, you want minimum fuel to lessen the potential for fire.  In these cases the ARFF crew will spray the runway with foam to assist in reducing the fire potential.