What dictates the aspect ratio of an aircraft's wing? When designing an aircraft, there has to be a decision as to the aspect ratio of a wing. It's been said that having a higher aspect wing will reduce drag for the same wing area, however most of the time wings are shorter than they can be. So my question is, what exactly dictates the aspect ratio of a wing, and why don't they make them as long as possible?

Now I am going to commit a heresy, but keep reading to get an explanation:

Increasing the aspect ratio of a wing will not change its induced drag. Increasing the span will.

The induced drag coefficient of a wing is $c_{Di} = \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$, and this seems to indicate that a bigger aspect ratio AR would lower the induced drag coefficient $c_{Di}$. But only at the same lift coefficient $c_L$!

Now let's look at the real numbers and compare two wings of the same span, but different aspect ratios. For simplicity, wing 1 has an AR of 5 and wing 2 has an AR of 10. Let's further assume that both wings have the same mass. Since both wings have the same span, wing 1 has twice the wing area of wing 2. To create the same lift, wing 1 needs only half the lift per area than wing 2! This means its $c_L$ is only half as big as that of wing 2, and now lets look at the induced drag again: $D_i = q_\infty\cdot S\cdot c_{Di}$

Wing 1: $D_{i_1} = q_\infty\cdot S_1\cdot\frac{c_{L_1}^2}{\pi\cdot AR_1\cdot\epsilon}$

Wing 2: $D_{i_2} = q_\infty\cdot S_2\cdot\frac{c_{L_2}^2}{\pi\cdot AR_2\cdot\epsilon} = q_\infty\cdot 0.5\cdot S_1\cdot\frac{4\cdot c_{L_1}^2}{\pi\cdot 2\cdot AR_1\cdot\epsilon} = D_{i_1}$

If both have the same span efficiency $\epsilon$, both have the same induced drag at the same lift. To reduce induced drag requires a span increase, regardless of aspect ratio.

However, a higher aspect ratio wing does have advantages:

Lower surface area means less friction drag
Lower surface area also means less mass, at least at moderate aspect ratios.
Smaller pitching moments, requiring a smaller tailplane

but also disadvantages:

Less internal volume for fuel or the landing gear
Needs more complex high lift devices for the same landing speed

In the end, the wing chord is chosen to minimize wing mass and to yield the minimum required fuel volume, and the aspect ratio is just a consequence of the selected wing span. Driving wing mass down is also reducing induced drag, and the $\epsilon$ of modern airliner wings is only 0.75 to 0.8, which shows how little importance the induced drag coefficient has for finding an overall optimum.


Are there limits to speeds at certain altitudes? Are there speeds that cannot be exceeded at certain altitudes?

The following maximum speeds apply in the US (A few aren't based on altitude, but I've included them to be more complete):

91.817: Mach 1 over land (with a few exceptions that are noted in Appendix B to 91.817)
91.117(a): 250 KIAS below 10,000 ft. MSL
91.117(b): 200 KIAS below 2,500 ft. within 4NM of the primary airport for Class C and D airspace (unless within Class B airspace)
91.117(c): 200 KIAS under the shelf of Class B airspace
91.117(c): 200 KIAS in a VFR corridor through Class B airspace
AIM 5-3-8(2): Maximum holding speeds:

At or below 6,000 ft. 200 KIAS
6,001 to 14,000 ft. 230 KIAS
Above 14,000 ft 265 KIAS

Some NOTAMs specify a maximum speed when operating within their limits.
AIM 5-7-2: Maximum speed as assigned by ATC

91.117(d): Any of these speeds may be exceeded if the minimum safe airspeed for the aircraft is higher and you notify ATC.

91.101 and AIM 5-7-2 NOTE 2 state that none of these apply when more than 12 NM from the coast of the united states.  Because of this, you will often see pilots fly at greater than 250 KIAS when below 10,000 feet and more than 12 NM off-shore.

Aircraft specific limitations must also be complied with.


MH370 blackbox - is it still possible to retrieve data from it? If the blackbox of MH370 were to be found today, would it actually still provide any information, assuming that it was in 5km deep water or so for some 5 years now?
If not, why would you still be looking for the missing aircraft and especially the blackbox, if there was nothing to find out about the reason that caused the 777 to disappear?

There are precedents: the flight recorders of AF447 spent two years at the bottom of the ocean, and revealed all that had happened after being retrieved. So they had survived being immersed in salty water at high pressure, making it very likely that MH370s boxes have survived as well.

Time of immersion is less relevant: oxidation (rust forming) is much slower at greater depth, due to much less dissolved oxygen and lower temperatures. The corrosion that does take place is mainly anaerobic, through bacterial sulfide formation. As posted in for instance this link.


How to find the distance if the points are above Earth's surface? There is a lot of information online about how to find the distance between two points if both the points are on the surface of the earth. But no article mentions about how to find the distance if both the points are above earth surface. Haversine formula works only for the points that are on the earth surface. But what about points that are above earth surface?

Note: I think we should consider the curvature of the earth as well while computing the distance.

With the Earth's mean radius being 6,371 km, adding 10 km to that adds about 0.15% to the geometric distance at 10 km altitude. But since you have tagged it flight-planning, the difference is very small that you can neglect.

Since the atmosphere moves with the Earth, TAS ≈ GS in no wind is good enough for the altitudes where planes operate.

However, for a very accurate air distance, use a radius based on the altitude in the haversine formula. But if such high accuracy is needed, you also need to consider the exact Earth's radius at the point of measurement as it varies from 6,353 to 6,384 km. You also need to consider the true altitude as a height above the geodesic, and not just a pressure altitude.


What are the best places to gain the most altitude in a glider? I'm a beginner pilot and I started with gliding. How to spot the best thermals and what is the most efficient way to climb?

First, you need practice. Take every opportunity to expand your experience. Theory helps but will never compensate for missing practical experience.
But then you also need to know how thermals form. Let's start low, close to the ground. Two things are important: A chance for the sun to heat the ground (and, consequently, the air above), and an opportunity for that heated air to ascend. Dry ground will heat up better than moist ground, and dark earth better than light sand. If the ground is completely featureless, the air will stay on the ground. So you need to find the trigger which determines where air starts to rise up. Once it does this, more air will be sucked in from the side, and will follow up. That is how a thermal starts.
And that summer gust, which is the horizontal motion of more warm air flowing towards the point where a thermal starts, should indicate to you that now you have a chance to stay up, so now you need to get into your glider. Early in the day the thermals will not go high, so don't be impatient. On the positive side, there are many thermals and a good chance of finding the next one quickly.
Once in the air, look for triggers. One of the easiest is a windward edge of a forest. Warm air is driven towards the forest by the prevailing wind, and the trees will push the air up, kickstarting its ascent. Fly along and a bit leeward of the ridge and you can't miss the thermals there. But even a closed forest is a good source of thermals: The dark trees heat up well and the air between the trees heats up quickly. A small elevation is normally enough to start a thermal. In the mountains, a windward ridge is also an obvious trigger, and it is advisable not to drop below the height of the lowest ridge, as you suddenly might find yourself unable to find any more thermals.
Once higher up the ground features become more and more unimportant. For one, wind is shifting everything sideways, but also now the large-scale vorticity which forms the clouds dominates where the thermals form. Think of cumulus clouds as giant thermal vacuum cleaners which collect the rising air from all around. But not any cumulus cloud: Most promising are the ones which grow, have sharply defined edges and a dark bottom which is bulged upwards towards the center. Flee from the fuzzy ones with a round bottom: They have lost their pulling power and are about to disappear.
Why the bulged-in bottom? THAT is where the heated air goes up and pushes the bottom of the cloud up. But what goes up must come down: In the vicinity of the best clouds you will also find the worst downdrafts. Fly through those quickly and pull up as soon as the downdraft stops.
If you fly cross-country, the most important knowledge is in which direction the wind is blowing. If the wind is strong enough (more than a soft breeze), thermals will line up in wind direction, so you can just leave one straight into the wind (or with the wind) and be sure to hit the next one shortly. This works particularly well if there are no clouds to follow (blue thermals). Just remember where exactly that one-before-last thermal was and fly off in exactly the opposite direction. When that brings you too far off the planned course, cross the valley of downdrafts orthogonal to the wind direction until you arrive in the next lineup of thermals.
Now to how to circle properly. A glider will fly at its minimum sink speed when induced drag is three quarters of total drag - given the high aspect ratio of gliders this means at a really high lift coefficient. Close to stall. Therefore, it is most important to learn how the glider warns you that you are about to stall. Also, some gliders will happily let you fly in a stalled condition (the Discus is a prime example) with really poor sink speed but without loss of control. Go up to maybe 1000 m and then stall the glider slowly. Learn how that feels. Then continue with circles. Stall the glider again. At some point you will feel how the stick forces lighten (that is when flow separation starts on the ailerons!) and you will learn to fly just a bit faster than that. Similarly, the stalled Discus has really soft and mushy controls - fly faster until the controls feel stiff again!
Since circling with more than 45° of bank is rather stressful, fly between 30° and 45° of bank angle. You need to catch the core of the thermal, where the climb speed is highest, and banking more is worth the tradeoff in many cases. Tighten the circle when the climb speed decreases and widen it when speed increases - that helps you to center your circling with the center of the thermal. Learn the hysteresis of your instruments - maybe you need to phase-shift your reaction so you really land in the center of the thermal. For me, I found it easier to remember where the climb speed was best and to shift my next circle in that direction when flying two-seaters - they are too sluggish to do that on-the-fly optimization you can do with the more nimble single seaters.


Is any single-axis autopilot for a light piston single certified for unusual-attitude recovery? Recovery from unusual attitudes is required during primary training and must be demonstrated during the checkride. In the case of an incapacitated or disoriented pilot, will activating a single-axis autopilot in ROL mode while in an unusual attitude safely recover straight-and-level flight?

You would need a three-axis autopilot. The nature of an unusual attitude is that it needs corrections around all three axes.


Which approach category minimums should I use when conducting an instrument approach? FAR 91.3 says:

  Aircraft approach category means a grouping of aircraft based on a
  speed of VREF, if specified, or if VREF is not specified, 1.3 Vso at
  the maximum certificated landing weight. VREF, Vso, and the maximum
  certificated landing weight are those values as established for the
  aircraft by the certification authority of the country of registry.
  The categories are as follows—

  (1) Category A: Speed less than 91 knots.

  (2) Category B: Speed 91 knots or more but less than 121 knots.

  (3) Category C: Speed 121 knots or more but less than 141 knots.

  (4) Category D: Speed 141 knots or more but less than 166 knots.

  (5) Category E: Speed 166 knots or more.

So an aircraft category never changes because it is always Vref at max landing weight.

What if I fly an approach at a speed that falls into a different category?  For instance, a jet may land at significantly less than this speed if very light, or more than this speed if landing with less than full flaps due to a failure (or any other operational reason).  Which minimums do you use then?

According to the FAA Safety Alert for Operators issued on 09/20/2012 (SAFO 12005):

A pilot may never use the approach minimums specified for an approach category lower than their certified approach category, even if the actual approach is flown at a speed that would be in the lower approach category.
A pilot must always use the approach minimums specified for an approach category higher than their certified approach category if the actual approach will be flown at a speed that would be in the higher approach category.

Note that this is different in other areas of the world (Canada for example uses the actual approach speed of the aircraft to determine the approach category).


What happens if an aircraft tries to land at MTOW (if greater than MLW)? Here's a scenario:

Just after Take-Off, there's an emergency on-board and pilot wants to land immediately. But, the weight of the plane wouldn't have decreased by large margins (usually 0.02*MTOW). Is the aircraft allowed to land with a weight more than Maximum Landing Weight?

What will happen if the plane tries to lands with a weight more than Maximum Landing Weight?

Most (all?) modern airliners are, in fact, certified to land at any weight up to MTOW if necessary, but if they do land at more than MLW then a special "Overweight/Heavy Landing Inspection" must be performed before the aircraft can be used again.

As this Boeing document states:

  Overweight landings are safe because of the conservatism required in the design of transport category airplanes by FAR Part 25.

  FAR criteria require that landing gear design be based on:

  A sink rate of 10 feet per second at the maximum design landing weight; and
     A sink rate of 6 feet per second at the maximum design takeoff weight.

  Typical sink rates at touchdown are on the order of 2 to 3 feet per second, and even a “hard” landing rarely exceeds 6 feet per second. Additionally, the landing loads are based on the worst possible landing attitudes resulting in high loading on individual gear. The 747-400 provides an excellent example. The 747-400 body gear, which are the most aft main gear, are designed to a 12-degree nose-up body attitude condition. In essence, the body gear can absorb the entire landing load. The wing gear criteria are similarly stringent: 8 degrees roll at 0 degrees pitch. Other models are also capable of landing at maximum design takeoff weight, even in unfavorable attitudes at sink rates up to 6 feet per second. This is amply demonstrated during certification testing, when many landings are performed within 1 percent of maximum design takeoff weight.


Is there a name for change in attitude with respect to time? I'm in the process of writing a flight-dynamics software program, but I'm not sure what to call the derivatives of the aircraft attitude. If it was in one dimension, they would be the "angular velocity" and "angular acceleration" respectively.

In aviation, is there a special name for these vectors?

The components of attitude vector are called:

yaw (or heading) is the angle of longitudinal (x) axis in horizontal plane,
pitch is angle of longitudinal (x) axis from the horizontal and
roll is angle of lateral (y) axis from the intersection of the yz (orthogonal to longitudinal axis) plane with horizontal.

And their derivatives are usually yaw-rate, pitch-rate and roll-rate. Second derivative names probably vary.

Regarding coordinate system, the first axis, called x, is always longitudinal and positive direction is forward. The second axis, called y, is usually lateral one, but positive direction is right in some systems and left in others. And z completes a right-handed coordinate system (so your vector products work the usual way), so z down if y points right.

Edit: I thought u,v,w is sometimes used as alias for the axis, but actually they are usually rather used for the velocity vector components.


For airplane spotting, what minimum specs should a telescope have? We are thinking about buying a telescope for viewing planets, stars, the moon, and aircraft! What is the absolute minimum zoom and/or size to achieve getting a good glimpse of an aircraft at its cruising altitude?

Does anyone have experience doing this that they could share to help us out?

I would not recommend a telescope for viewing aircraft.
As others have pointed out, a telescope that is suitable for astronomy would be incredibly overpowered for viewing aircraft - the aircraft would move out of the viewing frame very quickly, and you would have a difficult time tracking them.

I would suggest picking up a spotting scope (the kind of thing bird watchers and hunters use - good ones can be had in the 50 to 100 dollar price range, and excellent ones abound from about $100 up), or a pair of good binoculars for your plane watching. The zoom factor is far better suited to plane spotting, and either option would be substantially more portable than a full telescope rig.

As for advice on a telescope, there is an Astronomy stack exchange site, and while the entire network generally doesn't do "product recommendations" the Astronomy site's chat might be a good place to ask for advice on picking a telescope. (I'm not sure how active their chat room is, but it's worth a shot!)


How do missiles steer (mainly air to surface)? How do missiles steer in the air? What techniques do they use?

Take a look at the following image. What do you see?

The Fins, Wings, and Canards, as seen in the diagram, work in a similar fashion to rudders/elevators/ailerons to develop drag to yaw/pitch/roll respectively.
Fins: Most missiles use tail fins which give extreme maneuverability and high angles of attack. Often they are fitted with wings to give extra lift and improved range. Maverick, Harpoon, AIM-9X Sidewinder are good examples of tail fin controlled missiles.

Seen above: Grid fins
Wings: Generally, wings play the same role as for an aeroplane by providing lift, and are the oldest type of control surface. Moreover, wings cannot work independently and in most cases are used as vortex generators to improve the efficiency of the fins. In addition, they are mostly used in subsonic cruise missiles like Tomahawk and Sparrow AIM-7. The problem is that the wings must be long enough to produce necessary lift.

Canards: They work more effectively with great maneuverability on low angle of attack, and work the same way as fins. However, located near to the nose of a missile, canards can cause a missile to stall at high angles of attack, which limits them to short range. Almost all smart bombs and laser-guided missiles use canards.
Furthermore, the split canard is a modern development (found in missiles like Python-4 and AA-11) which uses two canards, one of which is fixed, and the second is located just behind the first set and is movable. The role of the fixed canard is to develop high power vortices for the movable canards, for better performance at high angle of attack.
Source


What's a quick way to determine which runway to use? Let's say I call up Wx and have the wind direction and I know the runway headings from my charts and the pattern is empty. I can do the math, but it's tedious and slow and even worse when there are multiple runways. This is what I usually do:

Runways are 13 and 31
Wind is 253° which rounds to 25
$25-13=12$
$31-25=6$
I'm going to use Runway 31

Is there a trick to determine best runway quickly without doing the math?

This might take a few seconds longer, but it's math-free: On your kneeboard, draw a quadrant (like this: +). Draw a line through it for your runway(s). Draw an arrow to represent the wind. The answer will be apparent. Do it enough times, and you'll be able to visualize the drawing without actually doing it.

It's also a great technique for calculating holds.


Can Somebody use Takekoputa to fly? Takekoputa(タケコプター) is one of the most famous and common gadget in the Japanese manga series Doraemon.

Regardless the power issue, Can it be used to fly in real world, as like as in the animation?

In a manner of speaking yes (although its highly unlikely). If the propellor on his head can generate enough lift to get his mass off the ground there is nothing to say he cant fly. That does not mean that the flight will be very stable or controllable but it may lift off. Since the animal does not have the equivalent of a tail rotor the torque effect generated from the propellor may spin him around. It does appear there may be flyable toy versions

Although for what its worth there is no identifiable power plant that is spinning this head propellor...


What kind of valves are used to prevent flashback in turbine engines? In a college experiment with Small Turbine Engine, we were told about the use of Valves for preventing flashbacks in engines. What are the available valves used for preventing flashbacks and what are the pros and cons of using different kind of flashbacks?

VERICOR POWER SYSTEMS has a patent for these valves, number US 6357216 B1 and title Flashback control for a gas turbine engine combustor having an air bypass system
The patent includes the following image:

SUMMARY OF THE INVENTION
An object of the present invention is to provide for a control and method for arresting flashback in a gas turbine engine combustion system having a venturi for delivering a mixture of air and fuel to a combustion chamber and a valve for controlling the amount of air flowing to the venturi.
The present invention achieves this object by providing a flashback control system and method having a flashback detection routine, a valve position trim routine, and a reference flame temperature adjustment routine. The flashback detection routine detects a flashback in the venturi by comparing the temperature at the venturi to the temperature of the air entering the valve. The valve position trim routine receives this flashback signal and in response causes the valve to open until the flashback is arrested. Finally, to prevent the flashback from recurring, the reference flame temperature adjustment routine adjusts a reference flame temperature in the control system so as to prevent the valve from returning to the position at which the flashback occurred.
These and other objects, features and advantages of the present invention, are specifically set forth in, or will become apparent from, the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.

The patent can be viewed here on Google patents list, however, it has expired.


Why are so few heliports depicted on sectionals? Pretty much every aerodrome, from an international airport to a private grass strip is depicted on a sectional chart. But there are few or no heliports shown. Why is this? Do helicopters have a separate sectional chart? It seems that even for a fixed wing pilot they would be useful as easily recognizable landmarks.

Just as a caveat, I don't have any actual paper sectionals. I am referring to what is shown at vfrmap.com. I have always presumed that their site is a good representation of the official charts, but it's possible there are things not shown online that are on the actual sectionals.

I would disagree with the statement that pretty much every grass strip is charted.  This is common in CONUS, Alaska and Canada. There are at least 30 within a 10nm radius of mine which are not. The reasons for charting grass strips are usually:
1. You are inviting people.
2. You want to notice people that the strip is restricted.
3. You are in an area, where charting your strip for emergency use is a public service you choose to offer.
4. You have tenants on your strip, and you want to ease their navigation and those who may visit.

As for heliports being charted: If they are intended for public use, they frequently are.  They are also charted if they have allot of traffic (eg Hospital / EMS / police barracks). Many private helipads do not wish to invite the public, and there is no purpose in charting them.


What does the ATR72-600 MFD System display look like? I'm curious how MFD System display looks in real life in ATR72-600, especially electrical mode. I've found three different images showing it, but they seems to be ambiguous. Last one attached comes from FCOM, two others from other docs. Which one is closest to real life? Buses symbols should be as rounded corner rectangles or simple one? States (like "OFF", "SHED") should be out or inside rectangles? Maybe it depends on software version or some specal mode? Maybe someone has real life photos showing it? Any info is highly appreciated.

For me, it looks like the first picture is something like a screenshot. It looks real. (A bit blurred and pixelated)

The second one looks like a graphic made in a graphics program. There can be small deviations from the original screen design, because it's only for informational purposes.

The third one is a black/white graphic that is made for printing (in the FCOM). I think it should be showing the real MFD quite close to reality because pilots must see it as in real life. But this saves printer color and has more contrast.

I am pretty sure, the first one is a real screenshot. It shows commonalities with the drawing in the FCOM and it looks real.


Is there any cockpit procedure used to avoid shutting the good engine, instead of the bad one (on fire, for example)? Reading some reports, about the failure of crew members to fully understand the fault on engines, rarely, but it happens, the crew can misjudge the engine on fire, shutting down the good one. On airlines where you fly, is there any standard procedure to avoid this event, I mean, shutting the good engine, instead of the bad one?

Procedures exist

If you read about the Kegworth crash you will see that the pilot started to follow a procedure he has been trained on but was interrupted by an ATC call and failed to complete the procedure. The procedure involves checking the engine vibration meters and reviewing decisions.

So, yes, procedures exist.

Procedures vary

Procedures vary depending on exact aircraft model and on the airline operating the aircraft. Some airlines use more memory checklists than other airlines. So it isn't possible to list a specific procedure that is used by all pilots of multi-engined aircraft.

Identifying problems

Pilots don't start from the point "we need to shut down engine No 2" they start from some observable event like "smoke in the cockpit" (as in the example incident above)

There are instruments on the instrument panel that show engine temperatures, vibration and other parameters that should usually make it evident which engine is not performing normally.

Here's an example procedure - note that this isn't the one for the airline and plane model in the incident above but it is probably similar

Note the points

Eliminates No 2 engine as source ...
...
Eliminates No 1 engine as source ...


When rearranging the lift force equation to solve for lift coefficient instead of lift force, why is the numerator often given as F not 2F? the standard description of the Lift force affecting the lift surface is:

$$
F={\dfrac{1}{2}}\rho v^{2} SC_{L}
$$
the basic rearrangement gives the following definition of the lift coefficient:
$$
C_{L}={\dfrac{2F}{\rho v^{2}S}}
$$

why is the above expression met so rarely? with the standard skipping the 2 multiplier?
$$
C_{L}={\dfrac{F}{\rho v^{2}S}}
$$

I've checked 30 scientific papers, those measuring the lift\drag coefficients.

28 papers have had F
2 papers have had 2F

The definition of the coefficients differs between countries/regions. The factor ½ is used in most of Europe and in Russia, because it is part of the dynamic pressure equation. In the USA the 2 is incorporated in the coefficient.


How is the area rule applied on airliners like the A380? Wikipedia says that because of the area rule's impact on wave drag:

  aircraft have to be carefully arranged so that at the location of the wing, the fuselage is narrowed or "waisted", so that the total area doesn't change much.

This much makes sense to me. Though it's a bit difficult to tell, I understand that in the picture supplied there, the green circle toward the front of the aircraft is intended to have roughly the same area as the blue circle and lines through the wing cross-section:

All images from Wikipedia unless otherwise noted

This is more clear in the picture of the F-106 Delta Dart where one can easily see the Coke bottle waist where the wings near their widest:

That's an awesome picture! You could stare at it all day, couldn't you?

Peter Kämpf even provides a nice explanation of the area rule in his answer here including a drawing from the Junkers patent on the subject:

Image posted by Peter in his answer, referenced above

In this image, I can see how the areas through several lines across the fuselage, wings & engines are all intended to be (roughly) equal.

What I don't understand is how this is applied to airliners like the Airbus A380 which they say is:

  showing obvious area rule shaping at the wing root

in reference to this image:

To me, it appears that the cross-section at the wing root consists of the same area at the front of the plane (roughly behind the cockpit appears to be where maximum diameter is achieved), plus the area of the wing root, plus the area through the wing, plus the area through a pair of engines (depending on exactly where you make the cross section). As I see it, there's no slimming of the body to make the area through the wing cross section equal to the area of the cross section just behind the cockpit.

This shot from above of another A380 shows that there is no Coke bottle waist near the wings:

Am I not seeing this correctly, or do I not understand the area rule correctly?

First of all, not the area should be equal, but the area gradient along the direction of flow should be shallow. The minimum drag with a given volume can be achieved when the area distribution is that of a Sears-Haack body. Ideally this rule applies only at Mach 1, and once you go faster, the cross sections which matter are those along a Mach cone, not those of the aircraft's cross section.

For subsonic flight, the penalty for neglecting the area rule is small; it only matters when local flow is supersonic ahead of a contraction of the contour of the aircraft. Subsonic flow would decelerate, whereas supersonic flow will accelerate further and result in a drag-intensive shock downstream. Adding something to fill up the contraction will reduce the pressure gradients and ideally avoid the shock. By this, area ruling will help to shift the onset of the Mach-related drag rise and enables airliners to cruise a little faster. Honestly, I cannot see the "obvious" area rule shaping on the A380 - to me this is classic subsonic aerodynamics which tries to avoid sharp pressure gradients in the area of the wing airfoil's rear loading. Especially the outer engine pylons could be done better, but I digress.

For airliners, it is much more important to have a constant fuselage cross section, which makes stretching the fuselage simpler and is much easier to build. Area-ruling the fuselage simply is not worth it (yet) when your maximum cruise speed is just Mach 0.85. It is enough to add some Küchemann bodies to smooth out pressure gradients.

Below is a comparison of a swept wing at Mach 0.9, on the left clean and on the right with Küchemann bodies. Note the massive flow separation on the left wing, whereas the flow pattern on the right wing shows attached flow.

Mach 0.9 wing comparison (picture source)


Why is "clearway minus stopway" used in V1 adjustments? Illustrations and/or satellite imagery to explain the difference between clearway and stopway and explaining how they are used by turbine aircraft would be great.

From B787 FCOM.

What is the difference between clearway and stopway?

The definitions linked in the question for a clearway and stopway are fairly adequate.

AC 150/5300-13A Airport Design

Clearway - is an area extending beyond the runway end available for completion of the takeoff operation of turbine-powered aircraft. A clearway increases the allowable aircraft operating takeoff weight without increasing runway length.  No object or terrain may protrude through the clearway plane except for threshold lights no higher than 26 inches (66 cm) and located off the runway sides. The area over which the clearway lies need not be suitable for stopping aircraft in the event of an aborted takeoff.  A clearway must be under the airport owner’s control, although not necessarily by direct ownership. The purpose of such control is to ensure that no fixed or movable object penetrates the clearway plane during a takeoff operation.
Stopway - is an area beyond the takeoff runway centered on the extended runway centerline and designated by the airport owner for use in decelerating an aircraft during an aborted takeoff.  It must be at least as wide as the runway and able to support an aircraft during an aborted takeoff without causing structural damage to the aircraft.

Opa-Locka Executive Airport (KOPF) has both a clearway and a stopway at the end of runway 12:

The 1,000 ft of clearway extends to the end of the area.  The stopway is shown with yellow chevrons.

Why is clearway minus stopway used in V1 adjustments?

To answer this question some background information must be given.  A clearway is used for turbojets where the airplane manufacturer provides accelerate-go distance calculations.  A stopway is used for turbojets where the airplane manufacturer provides accelerate-stop distance calculations.  Neither clearway nor stopway distances can be used for turbojet aircraft that use a balanced field length concept.

Aircraft with unbalanced field length calculations can use the clearway for accelerate-go calculations and the stopway for accelerate-stop distances.  The idea is to allow the aircraft to increase their maximum takeoff weight by utilizing those airport features.

A change in V1 speed has the effect of increasing one of the takeoff distances while simultaneously decreasing the other takeoff distance.  For example, if V1 is decreased, accelerate-go distance is increased while accelerate-stop distance is decreased.  There isn't an easy way to calculate a max allowable takeoff weight (MTOW) by adjusting both V1 and aircraft weight.

To make the calculation easier some practical things are implemented.  A stopway will always be equal to or shorter than a clearway.  This effectively increases the length of the runway to the end of the stopway for performance calculation reasons.  At this point, we can go into the performance charts for both accelerate-go and accelerate-stop and come up with a MTOW.  Since both calculations are using the same distance we need to adjust the accelerate-go distance by the difference between the clearway and stopway.  We can then adjust V1 by the appropriate chart in the aircraft AFM by that difference.

We can perform an accelerate-go and accelerate-stop distance calculation again to come up with a corrected MTOW.


What preflight passenger briefing items are required under Part 91? I have been taught to use the SAFETY acronym, mostly for checkride purposes. Which of those items are explicitly required (give references please) to include on a PAX brief for non-compensatory pt 91 flight?

My most recent DPE told me that only the seatbelts and the emergency exits are actually required. I found in 91.107(a)(1) the seatbelt requirement but cannot find the emergency exit req. He is right? Are there others?

Note: this scenario is assumed excempt from 91.519.

As far as I can find, the only briefing requirements in part 91 are for large or turbine powered aircraft at 91.519 (which you assume exempted from), the one you found along with the seatbelt requirement at 91.107(a)(1), and 91.1035 which deals with fractional ownership aircraft.

An AOPA article on briefings also states that:

  Operation of seat belts is the only FAA-required briefing item.

The only references to emergency exits under part 91 is 91.607 which pertains to passengers for hire. It only mentions the requirements for the number of exits and does not mention passenger briefing.


Why don't aeroplanes automatically put out engine fires? When an engine fire is detected the fire handle lights up and the pilot pulls it to extinguish the fire.

Why doesn't it do that automatically?
Why does the pilot have to pull the handle?

Shutting off the computer is difficult from a technical implementation standpoint. You're handing over a lot of power to the computers and sensors letting it shut down an engine, where these usually do not have access and control. This is certainly not always a good idea.

Pulling the fire handle is a pretty aggressive move: It will typically disable hydraulics, electrical power, and bleed air coming from that engine. If you're not prepared for it, it can end badly.

The engine will often be partially functional, depending on the type of failure. If you get dual engine fire indications, you'd probably wait with shutting them down, if doing that at all. This sort of behaviour would have to be coded into the flight computers.

I don't think there are any catastrophic consequences of not switching the engine within 8 seconds rather than maybe 2 seconds. It does not make a great difference. To set off the detectors, it must already have spread a little. I don't think you could do it much faster with the pilot staying updated on what's going on.

Needless to say, computers sometimes get things wrong. There is a human level to check what's going on before proceeding.

There are times when you don't want the computer doing it's own thing. Airbus states that:

If an engine fire occurs during takeoff or go-around, the Pilot Flying shall first establish and stabilise the aircraft on a safe climb path and then proceed with the ENG FIRE procedure.

Footnote:
It could certainly be done, but with the pilot-computer relationship on current flightdecks it's not a good idea.


What is the difference between OAT, RAT, TAT, and SAT? When I first started flying jet aircraft, I found different instruments that measure temperature in different ways and it was quite confusing.

What is the difference between Outside Air Temperature, Ram Air Temperature (RAT), Total Air Temperature (TAT), Static Air Temperature (SAT), and any that I might have missed?

As you measure temperature moving at high velocities, your outside thermometer will measure a higher temp than what is actually outside (what a non-moving thermometer would get). That's because as the air rams into your thermometer it gets a little bit compressed, and that makes it heat up a little bit.

Amazingly, some smart people have even calculated how much that "ram rise" is, and you can actually compensate (well, in theory) from the indicated temperature to calculate what the actual outside air temp is:

$$Ram~Rise=SAT\times0.2\times{M}^2$$

Where $SAT$ is Static Air Temperature in Kelvin, $M$ is Mach number

Problem is, not all instruments will compress that air in the same way, and not all of them will pick up this Ram Rise entirely. So they will publish a $K$, a ram-rise-coefficient (also called recovery factor) meaning how much of from the theoretical Ram Rise they actually pick up.

(OAT/SAT) Static Air Temperature = noted as $T_S$, actual temperature of the air outside, the same your thermometer will pick up if you were not moving
(say, in a balloon?)

(RAT) Ram Air Temperature = noted as $T_M$, actual measured temperature by your instrument.

$$RAT=SAT+k\times{Ram~Rise}$$

(TAT) Total Air Temperature = noted as $T_T$, total temperature as measured by an instrument with $K$-coefficient of $1$.

$$TAT=SAT+Ram~Rise$$


Do pilots of commercial aircraft have ready access to a map or data showing nearest airports in case of a need to make an emergency landing? As a passenger I often wonder that if a pilot had to make an emergency landing, do they have access to live information to direct them to the nearest airport or is this something that they have to rely on from air-traffic controllers?  I'm thinking that seconds could mean the difference between life and death and having information as such on-board could be a life saver, rather than rely on others to figure out where to go during a crisis.

Since you asked about commercial aircraft, I will answer for a modern airliner: The Boeing 777. The details will differ between aircraft models, but the general functionality should be available in every modern airliner.
With a modern airliner equipped with an EFIS (Electronic Flight Instrument System), there is no need to carry paper maps with possible diversion airports any more. Selecting a suitable alternate and navigating there can be done with the FMC (Flight Management Computer).
On the 777, the FMC has a page with alternate airports that are selected automatically from the navigation database, but can also be overridden by an uplink (where the airline dispatch sends suitable alternate airports to the aircraft) or manually (e.g. required for ETOPS flights with selected ETOPS alternates). This page looks something like this:

(Boeing 777 FCOMv2 11.43.21 - Flight Management, Navigation - FMC Descent and Approach)
The list of four airports is shown in 1 and the estimated time of arrival (ETA) as well as the fuel at the diversion airport is shown in 4 and 5 respectively. 2 allows a request of alternate airports from the airlines dispatch via ACARS. In order to divert to one of these airports, you select the respective line from 1 and the press DIVERT NOW (9). This will set up the flight plan with a direct line towards the selected airport.

Alternate Airport Diversions
ALTN page 1/2 data aids the flight crew in finding a suitable alternate airport.
The page displays up to four airports in ETA sequence. Each airport on the list has an XXXX ALTN page with more data. [...]
Three alternate airport uplinks can be received. ALTN LIST page 1/2 can get an uplink for the entire page or just the ALTN INHIB line. ALTN LIST page 2/2 can receive an uplink of alternate airport names.

(Boeing 777 FCOMv2 11.43.20 - Flight Management, Navigation - FMC Descent and Approach)
These four diversion airports can also be displayed on the Navigation Display (ND):

(Boeing 777 FCOMv2 10.10.35 - Flight Instruments, Displays - Controls and Indicators)
This is particularly helpful if adverse weather is in the area (e.g. thunderstorms) because the weather radar would depict areas with large amounts of precipitation on the ND as well. Should an alternate diversion airport be out of display range, it will be shown like this:

Displays the FMC or pilot selected primary alternate airport. Displays up to four alternate airports when the EFIS control panel ARPT map switch is selected on.
Offscale airports (those beyond 640NM with 640 scale selected), directional arrow relative to the airplane position or PLAN center point and distance (distance remove in PLAN).

(Boeing 777 FCOMv2 10.40.20 - Flight Instruments, Displays - Navigation Displays)
All of this allows a fast decision for an alternate diversion airport. Nonetheless, communication with ATC (Air Traffic Control) is of course essential in an emergency and ATC will assist in finding a suitable diversion airport if necessary. I don't quite agree with

I'm thinking that seconds could mean the difference between life and death [...].

If you only have seconds to make such a decision, it means you are at very low altitude, meaning either just after takeoff from your departure airport or already very close to your destination airport. In this case, the usual choice in case of an emergency is to return to the departure airport or continue to the destination. There are exceptions of course, like e.g. a takeoff alternate:

A take-off alternate aerodrome should be specified in the operational flight plan if either the meteorological conditions at the departure aerodrome are below the applicable landing minima or in case it should not be possible to return to the departure aerodrome for some other reason.

(SKYbrary - Alternate Aerodrome)
In this case the takeoff alternate would however be chosen before even departing, so no quick decision is necessary.


What are the STOL features on the Pilatus PC-6 Porter? What's so special about the Pilatus PC-6 Porter that makes it a world-leading STOL aircraft? How do its features work?

Quite simple.  Big wings with decent flaps, lots of power.

11.2 lb/hp at gross.  Wing loading of 19 lb/sf.

Comes down to how slow can you fly, and how fast you can get to that speed.  Without exotic high lift devices, it's mostly about wing loading and power loading.  The Pilatus only has to accelerate to a little over 60 mph and there is power to get it there in around 600 feet.  So there you go.

It's STOL, but not what I would call "super STOL".  For that you'd need full span flaps and slats and or bigger wings and a higher power to weight.  Like a Helio Stallion.

The Porter isn't a unique super-plane and it doesn't have any fancy high lift secrets.  It still needs about an 800 ft runway.  It just has a good all around configuration for its job, easy to load, and is simple and rugged.  It's the simple and rugged + good-enough-for-most-short-strips short field performance that's made it successful.


Why don't commercial aircraft have drag chutes for aborted takeoffs? We were watching the program  Air Crash Investigation and there was an episode where it was too late to abort the take-off and the pilots had to attempt to climb still but since an abort was not possible at that speed.

My 5 year old son asked and I quote: "If the brakes don't have enough power to stop at that speed, why don't they use the parachute brakes?"

So why don't big jets have drag chutes to help with emergency braking if there is some margin still, but not enough for the tyre brakes to stop safely in time?

The answer to this is much the same as they answer to any "Why don't airliners have [XYZ safety equipment]?"; the answer is generally along the lines of questioning whether the occurrence of such incidents (and the danger presented by them), outweigh the extra weight/certification/maintenance/cost of the equipment.

I'd argue that the danger presented by, and the relatively infrequent nature of, late aborts does not require braking parachutes to be added.

See also

Do any commercial airline models have a parachute at rear to help in landings?
Could ejector seats save lives in commercial aircraft?
Airframe parachute on commercial airlines and Why don't commercial jet aircraft have a break-apart, parachute escape system?


What is the weight at which an aircraft no longer requires a licensed pilot on board in Europe? According to this (somewhat dubious looking article):

  Since it is so light, the FlyNano falls under the weight of what is considered to be a plane, so in most countries you won't need a flying license to take this baby to the skies.

The aircraft weight needs to be 70 kg or less. FlyNano mentioned this on their FAQs page (my paraphrasing):

  Do I need a pilot's license to operate FlyNano?

  According to the European Aviation Safety Association regulation
  ... FlyNano is below the necessary weight of 70kg ... In Finland for
  example no classification, no aviation license or medical
  certification are needed. But skill is needed. Nevertheless a good
  understanding of water plane operation, rules and aviation safety is
  requested. ...

I found that any aircraft less than 70kg is not affected by EASA regulations. But regardless, and emphasized by FlyNano also, pilot skills are required.


Is a fixed wing more efficient in reaching a certain altitude than rotary wing? Given the limited amount of energy (battery or fuel) let's reach the maximum possible altitude!

Rotary wing aircraft pushes the air directly downwards and propels itself straight up.

Fixed wing, however, must gain forward speed to produce lift, so it wastes some energy for unnecessary circling and associated drag. Anyway, eventually, its wings must somehow push the air downwards to gain altitude (that's what Newton says), energy-wise is it really different from rotary wing? (especially when circling really tightly?)

Moreover, imagine our fixed might wants to pitch up really hard and has powerful engine - at some point this makes it similar to rotary wing, in that the thrust direction becomes more and more vertical. Oh, so the distinction might be not that obvious!

Anyway, the question is, for this specific requirement of going just up, is the fixed wing still more energy efficient to reach a certain altitude than a rotary wing and why?

A helicopter in forward flight is more efficient than a helicopter in vertical hover, due to less induced drag (and more form drag which becomes a problem at high fwd speed).

Fixed wing aircraft are more efficient than forward flying helicopters because:

The rotor flow in forward flight causes fearsomely complex aerodynamic interactions in flow with the fuselage and other components, which causes a particular type of drag that a fixed wing simply does not have.
When the helicopter is in forward flight, the rotor disk has the same characteristics as a fixed wing: less induced drag, higher form drag. But it will be a circular wing, which is always less efficient than a beautiful slender fixed wing. The slenderer (is that a word?) the better.


How can we calculate the fuel that we need? Let's assume that we are crossing the Atlantic (about 3,878 miles) with a 737-8 MAX. How can we calculate the fuel that we will use during our flight?

You need to know the fuel burn per distance covered which depends, among other things, on aircraft weight, speed, altitude and wind (all of which probably change over time), and then you add it up over the trip distance for the planned route (which is likely to differ from shortest possible great circle route for various reasons like airspace organisation and weather). As mentioned by OverD, regulations require some extra bits on top to cover for unforeseen circumstances. As also observed by OverD,  this is also dependent on the individual aircraft - e.g. old engines might need more fuel than new ones, a dent in the fuselage might create additional drag, an inoperative component might require extra fuel or off-optimum altitude etc. etc.

The manufacturer, in your example Boeing, provides the aircraft‘s performance data (e.g. fuel mileage etc.) to the operators.


Why do I get a severe headache just before landing? I had severe painful headaches two times in my entire lifetime and both times I was in flight. I see some common factors in this two occurrences which I thought could be some known pattern so I would like to know if we can take precautions to avoid a headache.

The first time it happened to me in June 2007 while I was traveling from San Francisco to Newark. I clearly remember that I was in deep sleep and the crew member woke me up and asked me to open the blind as we were going to land soon. After opening the blind I was exposed to the sunlight and immediately I got a severe headache. It got settled just before the flight landed. I initially thought it could be due to tiredness, insufficient sleep and sudden exposure to sunlight from dark until a similar thing happened to me after 11 years.

The second time it happened to me was during my return flight last week (Jun 2018) from US to India; it was a connecting flight from Phoenix to London. Just a few (10-15) minutes before landing, the pilot started his announcement about the landing; I got this headache for a few minutes and it settled after a few minutes.

Trust me, when it happened the first time it was such a pain I never felt before in my lifetime and I got so scared that something bad is going to happen to me. The second time it was only a little better but very similar. Though I had traveled more than a couple of dozen times in between these two events, I experienced this only twice and I remember common factors in this two events

Traveling from East-West.
Moving to different timezone and at the destination it was dawning.
Pilot announcement.
Window seat.

Are there any patterns to it and can we take precautions?

Your sinus passages were obstructed and it was atmospheric pressure squeezing your skull as the increasing pressure on the descent tried to equalize the pressure.

The air in your sinuses escapes much easier than it goes back in so the problem is always after a descent.

Feels like someone trying to drive a nail into your skull between your eyes.   Plug your nose with your fingers with your mouth closed and blow GENTLY and you will feel the air enter your sinuses and relieve the pressure.

Good idea to take a sinus medication like Otrivin with your travel kit if you are having that problem regularly.


why are turboprop/turboshaft engines rated only in horsepower and never in ft-lbs of torque like diesel engines or electric motors? I realize torque and horsepower are essentially the same measurement since horsepower is simply torque over time. But I'm curious as to why diesel engines or electric motors always provide torque ratings whereas turboprop engines are only rated in horsepower. Is there any reason for this?

The reason a Diesel engine has a torque figure and a horsepower power figure is because max torque and max horsepower occur at different engine RPMs. Have a look at any performance curves of a piston engine and this will be evident. Hence, to define in a few numbers the maximum performance of the engine, you need to give both figures.

However, turboprop engines for propeller aircraft, and turboshaft for helicopters, operate differently. Maximum efficiency for a rotor or propeller occurs at a certain RPM. Operating at different RPMs is inefficient. Hence, propellers and helicopter rotors are designed to operate at a fixed RPM. As load changes, the blade pitch angle is changed so it “bites” into more or less air. Hence, RPM can be kept constant, despite the load (and hence torque demand) changing. Now, since the power turbine is running at a constant fixed RPM, only 1 performance figure is needed (SHP or TQ) because the other can simply be derived from it.

Torque is just as important in a turboshaft or turboprop as a piston engine. These engines all have a torque sensor that usually works by measuring the twist in the power turbine shaft. Most helicopters do an engine performance check daily that involves reading TQ of the gauge prior to flight to ensure adequate performance.


Why are rotary wing aircraft less efficient than fixed wing aircraft? This question showed that rotary wing is less efficient than fixed wing, but the answers don't really address why.

Why are rotary wing aircraft less efficient than their fixed-wing counterparts?

It seems to me that the most important thing for efficiency is lift-to-drag ratio, so what makes this ratio much worse in rotary wing? Presumably it can use the same airfoil shape as fixed wing aircraft, so I could imagine a similar lift to drag ratio.

Quick answer:

The rotary wing is moving at different speeds over the radius, and on the left and right side in forward flight, and since there can be only one optimum speed, most of the rotor is working at less than optimum speeds, lowering the lift-to-drag ratio overall.
The slim rotor blade needs a reflex airfoil, an airfoil with low pitching moment, which is less efficient at creating high lift coefficients. If it would use a regular wing airfoil, it would twist horribly.


Can a single seater airplane fly with 50 lbs of thrust An airplane with 10 sq meters of wing five meters fuselage and including one person. can it fly with 50 lbs of thrust? And the max weight  is 400 lbs

A key thing you need to provide is the ratio of L/D, which is also equivalent to the ratio of Cl/Cd, where Cl and Cd are the lift and drag coefficients.
Thrust required for level flight = D/L ratio * Weight.
Without knowing more information, including L/D ratio and Weight, the answer to your question can only be "maybe".
If the L/D ratio is 10:1 or better and the total weight is 500 pounds, then the answer is "yes".  Increase the weight or decrease the L/D ratio, without changing the other variables to compensate, and the answer becomes "no".
Also, naturally, we have to know the thrust available at the airspeed that we are actually going to fly at, which may, or may not, have been what you were referencing-- (I assumed it was, in the preceding paragraph.)
Edit: since you've now provided the total max weight at 400 pounds, the answer is "yes, as long as the L/D ratio is at least 8:1, and the full 50 pounds of thrust is actually available at the airspeed at which you are flying."  An 8:1 L/D ratio is certainly doable.  Of course there would be no excess margin to allow for climbing, if the thrust were exactly equal to drag (50 pounds in the case of an 8:1 L/D ratio) and no more.  If you can get the L/D up to, say, 15:1, the performance will be a lot better.  (I'll leave the actual calculation for achievable climb angle in that case up to you, but all the required information is present here.)


What is the technical name of the electric window dimming system? I have recently flown from Mexico City (MMMX) to Tokyo, Japan (RJAA) in a Boeing 787 of All Nipon Airways (ANA).

The plane had an electric system for dimming the windows.

Does the window-dimming system have a technical name?

From a Boeing article:

  Electro-chromatic dimmable windows

It's generically described in the article as being an electronically controlled and can dim or lighten the cabin at the push of a button. They claim 70k cycles or 20 years of service

Gizmodo provides a succinct description of it's operation

  The dimming effect is the result of an electrified gel sandwiched between two thin pieces of glass. As the electric current increases, the gel darkens and as it drops, the gel lightens.

The maker appears to be Gentex and they have a variety of electric dimming window patents but it's not clear which one is used in the 787


Does a pilot of Air Force One receive any special privileges? I know that flying Air Force One is a position of high responsibility. I am curious to know what extra privileges, if any, come along with being the pilot of Air Force One. What extra he can do which a usual commercial/US Air Force pilot is not allowed to do (in air or on ground both)?

First off the pilot of Air Force One may or may not not be a commercial pilot (in the FAA sense) on account of the plane is operated by the military. For example the previous pilot of AFO Colonel Mark W. Tillman has no listing in the FAA database for pilot certificates so he does not cary any civilian privileges of flight although some might.

Being in the service the pilot would carry all the privileges associated with his given rank at the time.

As for other privileges there would be nothing stopping him from receiving a free meal at a local airport diner or the such but as far as I can find they have no special privileges anywhere.

If you are asking what privileges they may have in the air that is a completely different question. They still must follow ATC procedures as any other plane in civilian airspace but the flight will undoubtably be treated in a certain way.


Other than the 747, are there any other current, recent or planned airliners with a nose door option? Boeing has recently announced that the 747 program is coming to an end. One of the key features of the freight 747s was the nose door, which facilitated faster loading of freight and allowed the loading of freight that could not otherwise be carried.
Other than the 747 are there any current, recent or planned airliners that have the option for a nose door? will this be a facility that the cargo carriers lose as their current 747s gradually reach end of life? (which granted will be decades after production stops)
I am aware of several other planes with nose-doors but they are either old military-derived types (e.g. the AN-124 and AN-225) or are specialist planes designed for carrying awkward cargo (e.g. the Airbus Beluga and Beluga XL).

Excluding those aircraft in your question the answer is no. The 747 started really as a cargo aircraft, but given that more and more aircraft are available, the cost of development of another cargo only aircraft doesn’t make sense. Cargo operators can just buy old passenger aircraft, and they will continue to as the cost of development of aircraft is enormous, and most airlines at the moment (and most likely for the foreseeable future) are favoring smaller, thinner routes.
Sadly, the 747 and its nose door will be only a sight for cargo airlines soon.


How much time does it take to calculate the leveling and weighing of big and small aircraft? What methods are used to achieve that?

According to my search :

For old planes they use a plumb bob and measuring tools.
On new and big planes, the process is computerized. Built-In Electronic Weighing like the Boeing 777

Having recently weighed my plane I can tell you what's involved for determining the Basic Empty Weight for a small aircraft:

The aircraft equipment list is checked and updated.
This is kind of important as the equipment list includes the weight and arm of everything installed on the airframe. If this list is not accurate future weight and balance updates based on adding/removing equipment using the weights and arms on that list will be incorrect, and your computed weight and balance will start to diverge from the actual weight and balance until the plane is weighed again.
The aircraft interior is cleaned to "factory empty" status.
Pens, pencils, 3-year-old charts, note pads, and other things not on the equipment list are all removed, and things like tow bars are placed in their appropriate location/holder.
The aircraft is serviced with "fluids" per the manufacturer's procedures for weighing.
For most small planes this means de-fueled, full engine oil, & full hydraulic/brake fluid.
The shop sets up and zeros their scales.
You tow/push the aircraft onto the scales.
(Or lift it on jack stands with integrated scales designed for this purpose.)
The aircraft is leveled on the scales.
The plane must be leveled laterally (left-to-right) and longitudinally (nose-to-tail), otherwise the computations made later will be inaccurate.
The numbers on the scales are recorded.
The Weight and Balance is determined:

Add the numbers from all scales used. This is your Empty Weight.
You do some math on the scale numbers to determine the Center of Gravity.
(Since you know the station/arm of each scale you can figure out the CG based on the weights)

As Terry mentioned, setting up took more time than the actual weighing and calculations. In my case I spent about a day straightening out the equipment list, and the shop that did the weighing spent about 20 minutes verifying that I hadn't missed anything. Defueling the aircraft adds a significant amount of time to the process as well. Moving the plane onto the scales and leveling it took approximately 15 minutes, and doing the math took maybe another 5 minutes.

On larger aircraft the same general process can be used with larger scales (or jacks) - load cells integrated into a taxiway or ramp area are another option for doing this.

I'm not sure if aircraft that can determine their operating weight (by load cells installed in the gear assembly) can also determine their own empty weight - I know the weighing report I received includes calibration information for the scales used, so presumably weighing a large aircraft using its built-in load cells would require those cells to be properly (traceably) calibrated prior to using them for this purpose.


Is this planned building in a runway approach legal? A 50 story building is planned in Santa Clara, CA three miles from the SJC 12R runway end. Such a building is at least 500ft tall and many such buildings are 700ft or more, is this legal? Nothing around it is more than 100ft tall. Taller than 200ft qualifies it at least as an obstruction.

If it falls within the limits set out by FAA FAR Part 77 then its legal. You can find a nice breakdown of Part 77 here but you would need measurements more precise than what google maps is going to give you to be sure. Depending on the height the FAA may also require them to light the top of it. This is actually an interesting break down as the FAA is a federal organization and building approval generally comes down at the city/town/municipality level. If a building is approved for construction by a city one can assume it is legal to be built and that the city accounted for the FAA regulations. According to AC 150/5190-4A which quotes the Airport an Airway Improvement Act of 1982 it looks like its on the city to ensure that nothing gets in the approach path:

  ...Sec. 511 (a) SPONSORSHIP. As a condition precedent to approval of an
  airport development project contained in a project grant application
  submittted under this title, the Secretary shall receive assurances in
  writing, satisfactory to the Secretary that ... (4) the aerial
  approaches to the airport will be adequately cleared and protected by
  removing, lowering, relocating, marking, or lighting or mitigating
  existing airport hazards and by preventing the establishment or
  creation of future airport hazards; (5) appropriate action, including
  the adoption of zoning laws has been or will be taken, to the extent
  reasonable, to restrict the use of land adjacent to or in the
  immediate vicinity of the airport to activities and purposes
  compatible with normal airport operations, including landing and
  takeoff aircraft; ...."

In other words, the city needs to have zoning laws that keep the approach path clear. This is largely covered under the above linked Part 77 but generally speaking if the building has been approved its more than likely legal as per approved zoning laws.

A bit of a related story: you should not put it past people to build out of spite. A farmer once built a silo right off the end of Chatham Airport's runway to try and stifle traffic that he claimed was buzzing him while he was working. The silo is now gone and I cant find any info on what happened to it but this was also some time ago and I dont know what the regulations were when it happened.

And in some rare cases, if there is something in your way, an approach can be devised around it.


Why are 4 engine civilian turboprops not produced anymore As per subject why are 4 engine turboprops not produced anymore for civilian flights if turboprops are so efficient?

How comes the military still use them (see Airbus A400 and C130)

It would be amazing to fly on a 150 seater powered by 4 propellers.

What favours jet engines?

Well, military turbo-props are supposed to carry a large load at lower speeds, they wouldn't work well in passenger airplanes now because a jet plane can carry the same amount of passengers for a longer distance and faster than a turbo-prop can. However, they still use double-engined ones because they fly short, low-density routes to save money over using larger jet planes.


Is it possible to fly using a small engine? I'm currently a high school student trying to build an ultralight aircraft from scratch (I'm self taught and still learning from educational videos), but I don't have much savings (about RM 2.5k, which converts to roughly 587 USD), so I could only afford a small engine.

Is it possible to achieve a certain propeller's efficient rpm by using gears while still using a small engine? Like those gearboxes found in cars to increase rpm.

The short answer is yes you can use some cheaply available engines to achieve flight however you are presumably asking about things like small car engines or motorcycle engines etc. The issue you have here is that these engines are inherently different from a use case standpoint than your typical aircraft engine. Generally speaking, most car/motorcycle engines rev too high to be used in an aircraft, you actually want to lower the RPM, not raise it. You can read up on it here and here and here. You can pull it off with a stepper gear box (like a turbo prop uses) and it was even been done on a piston plane back in the 80's by Mooney. The other problem you will have with car engines is cooling them, generally cars are watercooled, something that adds a lot of weight and is not ideal for flight. A two stroke or other similar air cooled motorcycle/scooter engine may be a better thing to use.

Many small engines will produce more than enough horsepower to achieve flight. Keep in mind the early piper cubs only had 40HP which can be easily found in many 2 stroke engines.

Your best bet may be to look for a used VW bug engine as they are very similar to aircraft engines and even were used in some air frames at one point in history. Due to the cars high production numbers the engines are fairly easy to come by.

You did not list a jurisdiction in your question but the regulations and legislation on this change from place to place, so you may need to see what exactly you are allowed to do in your jurisdiction in relation to home built and experimental aircraft.


How do endplates reduce induced drag? I have heard the explanation which states that the endplates reduce the tip vortex formation thereby reducing induced drag. From what I understand induced drag is the backwards component of the total force acting on the wing and a consequence of lift creation over a finite span. Thus it depends on the downwash angle. Vortex is an after effect of this lift. I dont understand how induced drag is reduced by suppressing this vortex.

I would appreciate some clarity on this topic or an explanation which doesn't include vortices.

The vortex itself isn't the issue, it's the "leakage" that is resulting in the vortex.  The leakage is from the air near the tip being free to flow around it and results in wasted energy.

The wing is moving along driving air down, but near the tip some of the air, instead of being made to accelerate down, is taking the path of least resistance around the tip (being sucked toward the low pressure side you might say) instead and doesn't contribute to the lift force.  It was displaced, and energy was consumed, but the displacement was out and around the tip instead of down.

The tip plate is just supposed to inhibit some part of the lateral flow around the tip by blocking it, reducing the leakage and resulting in more of the air package being forced downward than without the tip plate.  What is referred to as a reduction in induced drag is just an improvement of the ratio of lift to drag due to less leakage losses, so for a given amount of total lift force, the induced drag is less than for the same lift force without the tip plates.

To do any good, tip plates have to be quite large (because the circulation field extends quite a distance from the wing), which being draggy themselves, cancels out most of the benefit, which is why you don't really see them used very much, except where the end plate effect can be created by default, such as with a T tail where the horizontal stab makes a nice end plate for the top end of the rudder.


Is there currently a measurable shortage of pilots? Is there a clearly identifiable and measurable pilot shortage right now? If so, is it a shortage of pilots or of captains, i.e. more experienced pilots? Are airlines changing any personnel rules - like time to go from first officer to captain - that would imply there is a pilot shortage?

If any shortage is for captains couldn't airlines 'upgrade' first officers to fill the places? But presumably that would create a shortage of FOs in turn.

Here in the US (because this varies around the world) some sources do say there is a pilot shortage. There are many reasons that have been cited for the decrease in pilots here in the states. But the main points seem to be,

Rising Costs of training
FAA upping the required hours (250 -1500) for a full ATP ticket
Lower conversion from military pilots (there was a time when many of the commercial pilots out there were former service pilots)
Lower Salary Prospects: its no mystery that pilots don't make what they once did nor get the perks they once did.

Another factor that effects this once you are in the industry is the fact that "seniority" does not transfer over from airline to airline. Generally this is not an issue if you work for someone like American or Delta who have plenty of jobs and steady routes. But if you are captain at NotSoWellEstablishedAir and they go belly up you will most likely join one of the others lower in the ranks if not at the bottom.

Another thing that is worth mentioning is that it may be more advantageous for a pilot to remain a very senior first officer instead of becoming a very junior captain. You may have more power over your route choice, time off, and general schedule as a senior first officer than as a newly minted captain. For some pilots, like those who may be trying to start a family this may be seen as an advantage.

As for the shortage over seas (outside the US) that stems from different issues. First and foremost many countries have seen great and more importantly fast economic prosperity which has allowed them to get into the aviation game. A game traditionally filled with high costs and heavy regulations. As such many newly wealthy nations have been able to enter the aviation world much faster than their regulations and training programs can keep up with. The FAA is almost 60 years old with aviation regulations dating back to the 30's with the CAA. There are even some american issued pilots licensed signed by the Wrights them selves from the very early days. Other countries simply don't have the history of growing with aviation like the US and similar countries have had. Thus they have all these new planes but no one to fly them and no well established programs and regulations to create the pilots. In turn they are forced to import trained, certified pilots from elsewhere.


What is the maximum body weight allowed for a pilot? What is the maximum allowed body weight for a new commercial pilot student?

Would someone weighing 130kg be rejected on the basis of health? If so, what should that person weigh to avoid the rejection?

I have read about regulations mentioning 75 kg + 10 kg for flight crews, but I doubt if all pilots fall under that category because I have seen many pilots who look heavier than that. But I need some professional advice on this regarding current commercial aviation.

I'm interested in rules in India, Canada and the USA.

In the US there's no specific weight limit in the regulations. Instead, they just say that you must be capable of performing the duties of a pilot, e.g. 14 CFR 61.113:

  The general medical standards for a first-class airman medical
  certificate are:

  [...]

  (b) No other organic, functional, or structural disease, defect, or
  limitation that the Federal Air Surgeon, based on the case history and
  appropriate, qualified medical judgment relating to the condition
  involved, finds—

  (1) Makes the person unable to safely perform the duties or exercise
  the privileges of the airman certificate applied for or held; or

  (2) May reasonably be expected, for the maximum duration of the airman
  medical certificate applied for or held, to make the person unable to
  perform those duties or exercise those privileges.

But the FAA is concerned about some conditions that are strongly linked with obesity, like heart disease, diabetes or sleep apnea. Those could be an issue for getting a medical certificate.

Apart from the regulations, there may be some practical weight limits for other reasons:

Military pilots have much stricter medical requirements (I know you're asking about commercial pilots), partly because they have some special considerations
A very large pilot may be physically unable to fit into some cockpits and/or move the controls to their limits
A very heavy pilot may be too heavy to fly in some smaller aircraft (including training aircraft) because of weight and balance limitations


Is it possible to go-around at Lukla Airport? On this airport, it seems the runway end with a wall followed by a mountains. Thus the pilots physically can't overrun the runway and if they decide to interrupt the landing, the go-around maneuver seems to include a very tight turn to avoid the mountain unless performed very soon during the approach. Is it possible to perform a go-around, and a which point it becomes impossible for this particular airport?

No, it is almost impossible.

The only runway (06/24) Lukla Airport is just 1500 feet long. This article lists some interesting facts:

  The topography of the place makes any go-around impossible. At the
  south, the runway is the end of an angled drop of about 2000 feet.
  This cliff is fenced off as a precautionary measure. At the northern
  end of the runway there is a huge mountain terrain. It leaves no room
  for error.

A pilot mentions the same here:

  "Because there is no way to go around again, we have to calculate many
  things like air speed, tail wind, fog. If you don't do the proper
  calculation or proper exercise, then it (an accident) happens."

Planes land on runway 06 (Heading 060 or ENE) and takeoff from runway 24 (Heading 240 or WSW). This picture shows the cliff on North:

There have been several accidents at this airport.


On an energy-maneuverability (E-M) diagram how does the shape of a specific excess power (Ps) curve change as thrust is increased or decreased? Most E-M diagrams for high-performance aircraft show a "dog house" plot with turn rate on the Y axis and velocity on the x axis.  They may also have additional lines for constant turn radius and load factor.  There are also Ps curves that show specific excess power at an given point in the performance envelope.  The Ps curves tend to be shaped like a "rainbow" when superimposed on this chart.  Most curves that I've found only demonstrate performance at maximum thrust (normally maximum afterburner).  However, I'm curious what the Ps curves would look like at 100%, 75%, 50% power, etc.  I theorize that the Ps curves would tend to become flatter and would shift to the left of the chart.  Ideally, I'd like to see a comparison of two charts at different (known) throttle settings (with all other parameters being equal).

The shape does not change much, but they shift up and down. Below you see a diagram I once made for a HALE unmanned airplane with a turbofan engine. Instead of varying thrust I calculated the instationary turn rate at different sink speeds. Sinking frees up energy similar to a thrust increase, so these curves should look the same for different thrust levels. After all, the unit for SEP is a speed, too.

Turn rate diagram for different sink speeds and flap settings. Blue lines are for cruise and red curves for the landing setting of a simple camber flap. The aerodynamic model did not include wave drag, so the results above Mach 0.7 are not correct.
As you rightly assumed, the curves shift to lower speeds for lower thrust, but only the red ones become flatter for lower sink speeds / thrust levels.


How does a normal aircraft exhaust nozzle (the base model) generates a lot noise? How does a normal aircraft exhaust nozzle (base model) generates noise and, whats the difference between the operation of the normal base model of aircraft exhaust nozzle and the new design of aircraft nozzle with an add of chevrons ?
Is the chevrons effects the aircraft or engine performance in any way ?

Those "chevrons" are vanes that modify the air and exhaust flow (those are turbo-fan- engines in those two images) and create air vortexes that quiet the noise but also create some drag. They are engineered to maximize noise reduction with a minimum of drag.

(popularmechanics.com) Quiet engine air brake.

There is a company called ATA Engineering that is now developing a product called a "quiet engine air brake" that create more drag but is stowable during cruise flight. The R&D work was commissioned by NASA.  They use the same vortex flow concept. Because most of the noise from airliners during approach comes from things that stick out in the airflow, like flaps and spoilers, landing gear doors, etc., this allows the aircraft designer to generate drag to slow down the aircraft while at the same time reducing noise.

Its a pretty nifty concept, if you ask me. Over time I think we will see the design of exhaust systems on jet engines become stranger and stranger! 8)


Was the Space Shuttle landing sequence executed manually or automatically? I was motivated by another SE Aviation Question where the complex set of manouveres needed to land the space shuttle is described to ask the following question:

Is the landing handled manually or is there an auto landing system? I suppose there is a high fidelity simulator to train all this on?

I wonder if that simulation engine has gotten into any of the enthusiast flight simulator software?

How does the space shuttle slow down on the re-entry, descent, and landing?

Since that's really three questions, I'll address them separately.
1. Did the shuttle have or use autoland?
The space shuttle did have autoland capability, in theory. When the shuttle was being developed, it was imagined that flights could last so long that human pilots might get rusty, or have their ability to function under gravity impaired due to muscle atrophy from extended time in micro gravity.
Unfortunately, testing autoland on the space shuttle was a bit risky. If anything went wrong, the shuttle has no ability to disengage and go-around, and it might be too late for a human pilot to intervene and still make a safe landing.
They did try evaluating an incomplete implementation of the autoland on STS-3, where the lineup, final approach (outer glide slope), and preflare maneuvers would be performed by the autopilot, at which time the commander would take control and complete the landing.
The result was one of the worst landings in the history of the program. The autopilot was unable to maintain a stabilized airspeed, at first closing the speedbrake completely, then opening it again until airspeed was low, then closing again at 4000 feet which caused the orbiter to be too fast by the time commander Jack Lousma took over. He didn't really have enough time to get a feel for the aircraft or make corrections, so it hit hard and fast.
Afterwards, it was decided to discontinue testing of the autoland system, although the implementation was eventually completed.

Development of an automatic approach and landing system was terminated indefinitely due to the inability to implement an FAA [Federal Aviation Administration]-like powered aircraft certification program for an unpowered glider like the Space Shuttle. That is, an automatic system cannot be reasonably certified for an aircraft without a go-around capability in the event of an autoland system failure, because the only recourse in the Shuttle is to land rather than to execute a wave-off maneuver as in a powered aircraft. The practice of having to salvage a good landing out of a poor approach is not professionally accepted airmanship.
Further, the STS-3 experience was classified as a “late-takeover” action in which a failure of the autoland system in even closer proximity to touchdown could result in an upset too late in the landing phase to be reasonably recoverable. "Monitoring" the approach versus actually "controlling" it induces a time lapse in the mental-to-physical control conversion process which increases in criticality for manual takeover as the aircraft approaches touchdown. An automatic failure on the IGS, with no recourse for a wave-off, would be unsafe compared to a totally manual- controlled approach.

The quote is from NASA Johnson Space Center Oral History Project where Jack Lousma gives a great description of the flight and landing a little less than half way down the page.
The Columbia Accident Investigation Board Report did recommend testing the autoland system, but to my knowledge, it never was.
Just to clarify, the autopilot was used for most of reentry on every flight, but I believe your question was specifically about the final stages of flight and landing.
2. What sort of simulator was used for training?
So the shuttle was hand-flown for landing (a fly-by-wire system, so it's arguable that there's no true manual mode), and that means pilots have to be trained.
They were actually trained in several different simulators. There was SAIL (Shuttle Avionics Integration Lab) where they did serious integrated systems and software testing.
There were also fixed and motion-based simulators in Houston. These were collectively referred to as the SMS (Shuttle Mission Simulator). These were used for training for all phases of shuttle flights, not just landing. They were particularly useful for simulating contingencies, like an RTLS abort (return to launch site). It's similar to how simulators are used in the aviation industry to train for scenarios which would be too dangerous to train for in a real aircraft.

The motion-base SMS. Image Source
For nominal conditions, the best simulator for landing the space shuttle was actually another aircraft referred to as the STA (shuttle training aircraft). This was a modified Gulfstream II which would fly with its main landing gear lowered and thrust-reversers engaged to simulate the high drag profile of the orbiter. The left side of the STA cockpit was built to mimic the layout of the shuttle, including the heads up display.

Images from the STA's Wikipedia page
The STA was used for both training shuttle pilots and for evaluating weather conditions at landing sites on launch and landing days.
Lastly, there was also an on-orbit simulator that the pilots would use for practicing in the day or two before landing. It was basically a laptop with special flight-simulator software.
3. Is the simulator available in any flight simulators?
The answer depends on exactly what it is that you're asking. The actual software used on shuttle computers (written in HAL/S) is ITAR restricted, so it is not available to the public. Sadly, even the on-orbit simulator has never been released, to my knowledge.
However, there are several simulators which let you fly some or all of reentry and landing to varying degrees of realism.

SSMS 2007 is a pretty high-fidelity simulator, but has a horrible, not even remotely accurate, reentry and landing.
On phones and tablets, I love fsim Space Shuttle. It's decently realistic, but only lets you fly the subsonic portion of flight.
Orbiter, which isn't a shuttle-specific simulator, but there are shuttle plugins. I've flown several manual reentries in Orbiter, but you really have to know what you're doing or you won't make the runway. That's probably the best option if you're really interested in orbital mechanics, and a terrible option if you're not.
X-Plane has a Space Shuttle scenario, but it's not particularly realistic.
I know some people fly Shuttle missions on Kerbal Space Program, but I've never played with it at all so I can speak to it one way or the other.

Interestingly, the motion-based simulator from the SMS was donated to the Aerospace engineering department of Texas A&M, and it was discussed making the simulator at least partially available to the public. Unfortunately, I think they ran out of money to actually put the thing together and run it, so it's effectively just sitting in boxes in a room somewhere. They have a facebook page, but it's been a long time since I've seen any progress.


Why is flutter a function of true, not indicated, airspeed? I am learning about gliders in preparation for an exam. It says in the textbook I am reading that for a glider, you use indicated airspeed for most relevant speeds (stall speed $V_s$, best glide speed $V_{BG}$ etc). However, $V_{NE}$ should never be exceeded in true airspeed. As far as I can tell, this is because flutter depends on true airspeed rather than indicated airspeed. (Let me know if this assumption is wrong, because that would make the title wrong.)

Why is this the case? Is flutter somehow related to the speed of the air molecules, rather than to the energy provided by them?

Flutter happens when structural and aerodynamic eigenfrequencies converge. Aerodynamic eigenfrequencies depend on the time the air molecules take to transverse an aerodynamic surface.


How is "information relating to the safety of flight" defined by the FAA? 14 CFR 91.183 states:

  Unless otherwise authorized by ATC, the pilot in command of each aircraft operated under IFR must report the following as soon as possible: Any unforecast weather conditions encountered; and any other information relating to the safety of flight.

This language is very vague and probably causes a lot of confusion for pilots who are studying it. Does the FAA elaborate on this concept or provide an examples or a more specific definition somewhere else? If not, what are some examples of reports ATC would expect based on this reg?

The language is intentionally vague.
Much like Justice Stewart said about pornography, when it comes to "information relating to the safety of flight" you'll know it when you see it.

Birds flying around in the approach path? Yup.
Wind shear on short final? Yup.
(Even if it's forecast/reported telling them how much airspeed you gained or lost helps.)
"Drone" buzzing around in the traffic pattern? Yup.
Deer grazing in the middle of a grass runway? Yup.
Bird strike? Absolutely.
(There are regs/procedures specifically for this.)
The guy in row 3J is threatening the flight attendants? Yup.
The guy in row 3J spilled his soda on his lap? …Not so much.


How are flight hours counted? I was watching a presentation from a software developers' conference in which the presenter went through the steps leading to the crash of United Airlines Flight 232 to make a point about Crew Resource Management and how it relates to software development.
This prompted me to read the above linked Wikipedia article and see mentions of the flight hours the captain and first officer had accumulated. Now the Wikipedia article on flight hours doesn't explain it, so I was wondering: how are these flight hours logged (and I don't mean on which medium)?

Are fractions of an hour taken into account or only ever full hours? I.e. if some pilot flew 1:27 h on one flight and 1:33 h on another how does that count towards the logged flight hours?
Given many regulations surrounding aviation seem to be global, is the way flight hours are logged uniform around the world?
Any differences between commercial, private and military aviation?

NB: I'm a layperson.

Originally my question also asked for this detail:

Is the time from the gate to the runway counted?

In regard to US regulations it's been answered here

I can answer part of this by experience, as a non-professional hobbyist pilot, and partly by information which is fairly easy to come by. So here goes:

Are fractions of an hour taken into account or only ever full hours? I.e. if some pilot flew 1:27 h on one flight and 1:33 h on another how does that count towards the logged flight hours?

Fractions of hours are absolutely taken into account. Typically accuracy is not to the minute, as this would be fairly pointless but typical schemes are to round to the nearest 1/10th of an hour (6 minutes) or 5 minutes. Personally, a long time ago I chose to go for 5 minute rounding and have regretted it ever since - 6 minutes is much easier to add up when dealing with hours & minutes!

Given many regulations surrounding aviation seem to be global, is the way flight hours are logged uniform around the world?

Nothing in aviation is global, or very little. Although there are bodies such as ICAO (International Civil Aviation Organisation) which most member states tend to derive most of their rules from. For the purpose of logging flight time, I expect most civil pilots log on the basis of "Chock to chock" time. Which is to say when the aircraft moves under it's own power until it stops.

Any differences between commercial, private and military aviation?

From what I can tell, the only difference is military which seem to log in-air time. This, I'm told, is why military airmen who intend to pursue a commercial pilot career after they're discharged maintain a separate record of their flight time.


When was the pitot-based ASI first used on aircraft? The pitot was first invented well before aircraft, yet early aircraft lacked an airspeed indicator (ASI). What aircraft first had a pitot-based ASI, and when?

From the book History of Technology, Volume 18, page 99:

  The first reliable air speed indicator was a U-tube manometer called the velometer, designed and patented by Frank Short at the Royal Aircraft Factory at Farnborough in 1912. Connection to a pitot-static head on a wing strut allowed the measuring element to be well away from the slipstream, while the indicator could be placed in front of the pilot. The velometer was manufactured by Casella and Elliott Brothers and was often supplied to military aircraft on a standard instrument panel.

It reminds me of the question: What was the first aircraft fitted with both an FDR & CVR?

Since the technology is not aircraft specific, say unlike the first flaps/air-brakes, the supplier can fit different aircraft at the same time. Which makes it near impossible to find the exact airplane as the above text suggests by mentioning a standard panel.

Interesting find: in 1910 there was a £5 prize (~£550 in 2017) for a speed-alarm design.


How do GA glass cockpit attitude indicators handle aerobatics? For example, consider you are flying the 8KCAB Super Decathlon (a fairly common acrobatic plane) that had G1000 (using the flagship Garmin glass cockpit as an example, answers for other types of GA glass are welcome) avionics fitted to it, and you were about to go off and practice your favorite aerobatic routine in the local aerobatics box.  Would you have to do anything equivalent to "caging" in order to keep the attitude indication functions of the G1000 from misbehaving during aerobatic maneuvers, or is that not an issue with the types of "glass cockpit" instrumentation used in the GA world?

Caging was required when Gyros were mechanical masses actually spinning at many rpms in their cases. That mass resisted rotational motion and produced a resistance force that was measured and translated into useful info like pitch and roll. That spinning mass carried much momentum in the form of its mass times its rotational velocity. And too much sudden motion and the resistive force/momentum could  cause mechanical stress to the unit and/or cause the instrument to tumble. So it became helpful to cage a gyro before acrobatics to keep the thing from busting or wearing out prematurely.

In modern glass cockpits like the G1000, there are no mechanical gyros with high mass parts (excepting a standby instrument independent of the glass system, which may need caging if it's a mech type). The gyros that are used for a G1000 system are called MEMS (micro electro mechanical system) gyros which do not have a spinning mass. They have tiny metal discs that merely vibrate. When they are rotated (by pitching or rolling), the vibration dynamics change a little bit and a capacitive reactance apparatus measures this change which is directly proportional to the rate of rotation.

The MEMS gyros can take aerobatics without enduring any mechanical stress what so ever so there is no need to cage them.

The system does however, loose accuracy. The rotation rates offered by the MEMS gyros are prone to micro errors and these errors add up over time. The more rotations, the sooner the sum of all errors becomes significant. There is a software algorithm that re-aligns the system periodically and basically erases the errors (it kind of reminds the system which way is up). The algorithm uses accelerometers (like the one in your phone) to sense stable, un-accelerated motion, and at that time, the accelerators can sense gravity which points straight down. When this occurs, pitch and roll angles are keyed off the accelerometers and the rotation rates are reset to zero and the system is ready to start keying off the gyros again and adding up errors. In normal flight like touch and goes or cross country flight, there are lots of opportunity to reset the errors. In aerobatic flight there are fewer opportunities but once the aircraft eventually returns to level flight for some period of time, it will reset itself. Whether or not the error can be significant enough to be noticed by the pilot, I don't know... probably depend on many factors, but I'd probably be intimate with a sic sack by then.