What exactly do "captain", "pilot", "co-pilot" and "first officer" mean? I know the co-pilot sits beside the pilot. But it's not clear for me, who is the captain and who is the first officer?

And where they are sitting during the flight? Who is in right seat and who is in left seat, and probably who will seat behind the front seats for an aircraft with more than two flight crew?

Capt left, 1st officer or copilot right. On older airlines with a flight engineer, he is behind and is called 2nd officer.

It's the same as a ship.  Capt is boss, 1st officer is second in command, 2nd officer if on board is 3rd in command.

Capt always starts the engines and taxis the airplane since most airliners only have a steering tiller on the left, and FO usually handles radios and checklists, FMS programming etc when on the ground.  FO, if it's his/her turn to fly, only controls the airplane from the start of the takeoff roll until completion of the landing roll.

On a pairing (sequence of trips over 2 or 3 or 4 days), capt and FO normally alternate on each leg of the trip as pilot flying with the other as pilot monitoring.  But as I said, if FO is PF for a particular leg, he/she will still do the radios until the start of the takeoff roll, then takes control of thrust and stick once the capt has lined up, upon which capt looks after comms/FMS/button pushing, until completion of the landing roll, when the FO hands control of the airplane back to the capt and the FO (who only has rudder pedal steering and can't make sharp turns) takes over the radios again.

On an older airliner with a Flight Engineer/Second Officer, that person is type rated on the aircraft as a pilot but never actually flies the plane until he/she moves up to right seat as FO.  So in the old 3 crew days a new pilot would be hired as a Flight Engineer in an airline with only 3 crew aircraft and might go several years in the 3rd seat before actually flying the plane, or if upgrading from 2 crew to 3 crew in the same airline.

Up until the 60s you also sometimes had a 4th crew, a Navigator.  Don't think there were any Navigators left by 1970.

Job... Pilot flies the airplane, co-pilot helps by doing radios and knobs and switches. Can sit in either seat.
Rank... Captain is usually the senior person of the two, and is basically the decision-maker. Is seen as a more prestigious and higher-paid job then First Officer. Conventionally sits on the left (but there is no legal requirement for this). Thye Captain is also the 'commander' of the airplane, which is a legal position for "if it goes wrong, the buck stops here".


What configuration of autothrottle is required when pilots are landing an Airbus? Do Airbus pilots normally disengage the Auto Throttle on a manual landing?

Do pilots (Airbus or Boeing) normally prefer a manual landing to a A/P landing?

Do Airbus pilots normally disengage the Auto Throttle on a manual landing ?

Depends on what you mean.

During the initial part of the approach, no, they do not deactivate the autothrust (not autothrottle, in this case):

But the autothrust is not designed for landing and just before touchdown there is an automatic callout in the cockpit: Retard. Retard. (it can be heard in this video 4 times).

The callout is needed because of the A/THR inner working: while in SPEED mode it can apply any throttle between 0 and the current throttle lever position; i.e., if for example the throttle is at the 80% setting, the autothrust can apply any throttle between 0% and 80% (based on the required airspeed). At the Retard callout the pilots will move the levers to the IDLE position, effectively deactivating the autothrust:

Most (but absolutely not all) pilots let the aircraft land itself most of the time.  I asked a number of different pilots this question (30+ year captain at USAirways, a 3 year FO at Spirit, a 20+ year captain at Delta) and their estimate was that 75% or more of landings were done via auto-pilot.  One of these pilots was almost exclusively Boeing, one was almost exclusively Airbus, and the other estimated that his experience was roughly 60% Boeing.


How does jet engine water injection work? How did the "wet takeoff" of old days work? Was the water used ordinary distilled water, or did it have additives? Where is it carried in the aircraft?

On many early jet airliners water was sprayed it into the engine air intake or compressor where evaporation cooled the air and allowed cooler, denser air to be ingested by the engine. The result was increased thrust, especially needed for operation from hot and high airfields, or a cooler temperature in the hot section of the engine at the same thrust. From SAE Paper Number 2004-01-3108:

  Water injection was first used over 45 years ago on commercial
  transport aircraft to increase thrust. Boeing 707-120 aircraft with
  Pratt & Whitney JT3C-6 engines and later, the Boeing 747-100 & 200
  aircraft with Pratt & Whitney JT9D-3AW and -7AW engines, all used
  water injection for thrust augmentation.

This report discusses various techniques for water injection:

ahead of the low pressure compressor. This is the common method for thrust increase in hot and high conditions.
ahead of the high pressure turbine. This is used in cold weather, when injection ahead of the low pressure compressor would run the risk of ice accretion.
together with fuel into the combustor. This technique is commonly used with stationary gas turbines in order to reduce nitrogen oxide emissions.

And NASA-TM-2010-213179 is more specific on the system:

  Four water-injected Pratt & Whitney JT3C–6 engines were used on early
  Boeing 707–120 Stratoliner aircraft to augment takeoff thrust on days
  above 20 °F. This system used a belly tank to store demineralized
  water and an electrically driven boost pump to deliver water to the
  four engines. At that point, an engine-driven mechanical pump
  increased the pressure to about 400 psi for injection before the
  low-pressure compressor (LPC) on days as cold as or colder than 40 °F
  and for injection into the high-pressure compressor (HPC) only on days
  between 40 and 20 °F.

What would happen if kerosene instead of water was filled into the water tanks was tried out by a BAC-111 on September 6, 1971:

  The aircraft collided with a bridge, shearing off both wings, after a
  double engine failure occurred during takeoff. The water-injection
  system to cool the engines during takeoff was inadvertently filled
  with kerosene instead of water.

More recent work on water injection focused on the reduction of nitrogen oxides which form in lean combustion and high temperature. By lowering the temperature level of the combustion process, the nitrogen oxide pollution can be greatly reduced.

water molecules do contribute in the combustion process, since in the turbine the temperatures and pressures reach the thermolytic ratio for water ignition.
At 1  bar that temperature is 5600C. At elevated pressures, the temperature is reduced subsequently, since volume remains the same, by n is increased relatively.
At BAC-111 the crash incident was due to luck of thrust since no water spray was made available.


Why do the F/A-18 and the F-22 Raptor have horizontal stabilizer as well as canted rudders for pitch control? F/A-18, F-22 Raptor have a horizontal tailplane as well as canted rudders? Why can't the horizontal tailplane done away with (as in the F-117) and have only the ruddervators for pitch control?

The rudders on modern fighters are canted mostly to reduce their radar cross section. A straight vertical tail would produce a corner reflector in combination with the fuselage or the wing and would send radar waves straight back to their source. To reduce the detection radius, such a behavior must be avoided. The first aircraft to use this trick was the SR-71.

On the F-18 an additional reason was to move the tips of the vertical tails into the lateral position of the chine vortex: The wing's big leading edge extension produces a strong vortex at high angle of attack which improves the effectiveness of the tails and gives better yaw control. However, the bursting of the vortex would cause heavy buffeting, and an additional fix was needed to improve the fatigue life of the tails.

The horizontal tail is a necessity for pitch control and to trim the flap moments in the landing configuration. Just look at Boeing's entry to the JSF competition: The X-32 was initially planned as a delta with only vertical tails, but when the Navy refined their carrier operation requirements, Boeing had to add a conventional horizontal tail to achieve the required angle of attack and minimum speed.

Boeing X-32 (left, source) and the planned production version (right, source) with the added horizontal tail. The F-117 was an Air Force plane with very limited agility, so it could get away with a tailless design. Real fighters and carrier airplanes cannot.

Giving the horizontal tail dihedral reduces its effectiveness in two ways:

Angle of attack changes from pitch variations are reduced by the cosine of the dihedral angle, and
the vertical component of the aerodynamic force is also reduced by the cosine of the dihedral angle.

Note that the drag of a V-tail depends on the total lift created, regardless of its direction. Only the horizontal component is effective for pitch control, so a steeply angled V-tail is very ineffective for pitch control. In air combat the high drag will reduce performance when it is needed most.

On the F-18, the elevators do not generate enough downward force for takeoff. The rudders provide the additional force required. Visible in this video:

Notice that both rudders are inward on takeoff. Clearly if the elevators do not provide enough pitch control, the rudders along are not going to do it either.


Is there a difference between MEA and MOCA within 22 nm of a VOR? As we all know from our instrument training, the MOCA is:

  MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)- The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.

Whereas the MEA is:

  MINIMUM EN ROUTE IFR ALTITUDE (MEA)- The lowest published altitude between radio fixes which assures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes. The MEA prescribed for a Federal airway or segment thereof, area navigation low or high route, or other direct route applies to the entire width of the airway, segment, or route between the radio fixes defining the airway, segment, or route.

(Both quotes taken straight from the Pilot/Controller Glossary)

The only difference in language is the bit about 22 miles from a VOR.

Therefore, when you're within those 22 miles, there's no practical difference between a MEA and a MOCA, right?

If that's true, why is there an 1800 foot difference between the MEA and the MOCA within 22 miles of the PMM VOR on V84?

You are right. Within 22 nautical miles of the VOR, there is no practical difference between an MEA and a MOCA.

However, it should be noted that the 22 nmi is only a limitation if navigating via VOR's.

14 CFR - CHAPTER I § 91.177  Minimum altitudes for IFR operations

  (a) Operation of aircraft at minimum altitudes.
  Except when necessary for
  takeoff or landing, or unless otherwise
  authorized by the FAA, no person may
  operate an aircraft under IFR below—

  (1) The applicable minimum altitudes
  prescribed in parts 95 and 97 of this
  chapter. However, if both a MEA and a
  MOCA are prescribed for a particular
  route or route segment, a person may
  operate an aircraft below the MEA
  down to, but not below, the MOCA, provided
  the applicable navigation signals
  are available. For aircraft using VOR
  for navigation, this applies only when
  the aircraft is within 22 nautical miles
  of that VOR (based on the reasonable
  estimate by the pilot operating the aircraft
  of that distance)

The MOCA provides "obstacle clearance requirements for the entire route segment," so if the applicable navigation signal is GPS, and you're receiving it, then you've met the requirements. This is why sometimes you see a MOCA on segments which aren't within 22 nmi of any VOR.

One other practical difference to keep in mind is that, especially in mountainous areas, you're much more likely to get radar coverage, and have better communcations clarity, at the MEA than the MOCA (I saw this a lot in Idaho). In those cases, ATC is probably going to prefer the MEA.

You need to be at or above 4000 to ID CLAUD if using the cross radial (197) from the vor that is out of view , that is why a MOCA is there.


How does the aneroid wafer expands? (ASI) So, how does it expand? (aneroid wafer - intend to the airspeed indicator) I have two “theories” (from what I’ve learned) which are :

The ram air entering through the pitot tube physically hitting, pushing the aneroid wafer forcing it to expand - giving us the actual indication in the cockpit. faster airspeed—> more air hitting, pushing  the aneroid wafer at higher velocity —> greater  expansion?
The ram air rapidly filling the aneroid wafer making the air more dense —> more pressure, therefore forcing it to expand due the pressure differential between the aneroid wafer and the sealed case, which contain the outside atmosphere pressure. Faster airspeed —> more air —> increasing pressure inside the aneroid wafer —> larger pressure differential—> greater expansion?

Which one is true ? or both maybe ?

The aneroid wafer is just a metal balloon.  Add air into its interior, above ambient pressure, and it expands.

The outside of the wafer is exposed to ambient static pressure.  The inside of the wafer is plumbed to the pitot inlet.  Ram air into the pitot raises the pressure within the pitot plumbing to above ambient, which being connected to the interior of the wafer, inflates it.  The movement of the inflating wafer is geared to the airspeed indicator and voila, ya got yer speed indication.

The irony here is that aeronautical engineers build models of air flow based on a misapplication of data from pressure taps fed into the Bernoulli Equation to calculate airspeed at the surface of the wing at various points, claiming without any proof whatsoever that the results are accurate, while pilots use a device that does not use the Bernoulli Effect at all to accurately measure airspeed, which is critical to their survival.

Air has mass. Mass implies momentum. Changes in momentum constitute acceleration. When a closed tube (a pitot tube) is thrust into an airstream, the air that goes into that tube is quickly accelerated into the direction of the pitot tube. That acceleration creates weight, measured by the aneroid wafer. The greater the differential between the speed of the ambient air and the pitot tube, the more acceleration, and the more weight.

That weight compresses the air, so yes, it is denser in the tube than it is in the ambient air. That air would decompress out through the mouth of the tube to match the pressure of the ambient air, except that this is disallowed by the acceleration of more air striking the mouth of the tube.

The constant stream of oncoming air maintains the pressure in the tube, so as the relative speed of the air and tube change, so does the pressure, and so does the pressure reading, which is translated into airspeed.

The Bernoulli Equation was invented to measure blood flow in a blood vessel in the 1700s. It assumed an incompressible fluid flowing through a vessel with parallel walls, neither converging nor diverging.

Einstein ignorantly developed the "Longer Path" theory of lift generation of wings based on a misapplication of the Bernoulli Effect. Orville Wright argued that he was wrong, and Einstein accepted that he was ignorant and should not have posited the theory, but because of hero worship for Einstein's intellectual prowess, engineers really, REALLY want to use the Bernoulli Equation to measure airspeed.

Pressure taps measure pressure. They do not measure airspeed. Models of airspeed at the surface of wings based on data from pressure taps are deeply flawed, and yet they dominate aeronautics.

If the Bernoulli Equation could give you an accurate airspeed, then airplanes would use a device different from a pitot tube with an aneroid wafer to accurately measure airspeed. Engineers proclaim that air is "incompressible" at subsonic speeds, and yet here, inside the pitot tube is compressed air. If it wasn't compressed, the instrument would not measure airspeed.

And yet, it does.


Did Boeing really use ferrets to run wires through aircraft during construction? I've seen many articles on the internet (here, here & here) claiming that Boeing used a team of ferrets to run cables through hard to reach areas when building aeroplanes, but I've never seen any official sources to back these claims.

Is there any truth to this, or are they just baseless internet rumours?

No, Boeing didn't do that.
I asked their assembly plant tour
to confirm or deny this, when I found
a report that around 2010 some visitors heard this from a tour guide.  On 2020 Nov 3 they replied:

Hello,
Thank you for contacting us with your inquiry. This is a popular urban myth, there are no records or any other evidence that this was done at Boeing.
Thank you again for your interest.

That's a clever idea...
No, they won't do that
Too many accidents, defect in an airplane is from tiny things like a wrong gasket, wrong pipe fitting, small crack that you'd have to take out a microscope to see. There are better tools and ways for doing that.

However, I can not say this isn't an idea somebody has tried, there are some reasonable truth to it... but definitely they won't use this method on the critical part of the airplane


What do the callouts "approaching minimums" and "minimums " mean? When landing, what exactly do the phrases "approaching minimums" and "minimums" mean in a commercial jet aircraft,  when heard from the onboard cockpit voice.

The "Approaching Minimums" callout is made by the Pilot Monitoring (or, in some cases equipment, the GPWS -- Ground Proximity Warning System) as the aircraft is descending on an instrument approach and has reached an altitude 100 feet above the minimums for that approach -- the Decision Altitude (DA -- typically used for a Cat I ILS, and set as XXX' MSL) or Decision Height (DH -- typically used for a Cat II or Cat III ILS and set as XXX' or XX' on the Radio Altimeter) or Minimum Descent Altitude (MDA -- typically used for a nonprecision approach and set as XXX' MSL).  The response by the Pilot Flying is usually standardized and indicates he is looking outside in order to acquire the visual references he'll need to land.

The "Minimums" callout is made at the minimum altitude, and this is the point that the Pilot Flying has to make a decision -- continue or go around.  His response at this point is again standardized so that the other pilot is entirely clear on the course of action.  His response is usually something like "Landing" or "Continue", or else "Go Around."  Often, the autopilot comes off at this point as well & you hear the horn indicating such on the CVR as well.

Approaching minimums is the decision making altitude or minimum altitude ( Generally 100  feet above the minimum altitude ). Captain callout ‘approaching minimums’ in order to decide that they will land on the runway or they will go around, that depends on the Captain. In their final approach if they are going for landing then the other pilot callout “ continue” or else the other pilot callout “Goaround” and then the landing was aborted....the Pilot pushes the thrust levers to its maximum position  in order to get the maximum thrust generated by the engines and then the landing gear was retracted in order to goaround....


How much of an airplane's forward energy is lost to lift? An airplane needs to move forward to generate lift, and because energy isn't created from nothing, all the kinetic energy of lift comes in the form of drag, where air (air resistance) turns forward motion into upward motion.

Some of the drag on an airplane is therefore "productive" in that it produces lift, and some is "unproductive" in that it takes forward motion from the plane without providing lift.

What percentage of an airplane's forward kinetic energy loss due to drag is productive as opposed to unproductive?

In the most simple model for subsonic aerodynamics, drag is split into two components:

Zero-lift drag, that is all the drag created when the airplane produces no net lift. This kind of drag has again two components: Friction and pressure drag, that is the aerodynamic drag parallel and perpendicular to the local surface. This drag would dominate in a vertical dive or a zero-g parabola.
Drag created due to lift. Since that was explained mathematically first by using the Biot-Savart law for electromagnetic induction, this is called induced drag. The simplest explanation is: Lift is created by bending the oncoming air slightly downwards, and the reaction force is perpendicular to the mean angle of that airstream. Induced drag is the force component parallel to the initial direction of motion of the air relative to the airplane, and lift is the perpendicular component of that force. Thus, induced drag is lift times half the tangent of the bending angle.

While zero-lift drag increases with dynamic pressure, i.e. with the square of airspeed times density, induced drag decreases with dynamic pressure. Like this:

Drag components over speed for a typical glider (own work). The nonlinearity at the lowest speed is due to flow separation when the lift-creating limits of the aircraft are approached. The physics for large aircraft are the same, only the numbers will be larger.

Due to the dependency on the square of airspeed, the sum of both components has a minimum when they are of equal magnitude. However, given enough thrust, a motorized aircraft can sustain level flight at the far right end of that diagram when lift-dependent drag almost vanishes.

About 6%

You're looking for the "Lift to Drag" ratio - see here for some examples of different things: https://en.wikipedia.org/wiki/Lift-to-drag_ratio

A paraglider is a 10:1 glide ratio.

A 747 at cruise is 17:1  - thus - 6% of the power keeps it up, and the rest, 94%, offsets the drag of flying at mach 0.85.


What are the advantages/disadvantages of diesel/Jet A-1 piston engine? Some GA aircraft, notably the DA40/DA42, are equipped with piston engines that use Jet A-1 and/or automotive-grade diesel instead of aviation gas (avgas). An example of such engine is the Austro Engine AE300:

What are the advantages/disadvantages of these engines and why are they not more common?

Advantages

Compression-ignition engines have higher compression ratio which leads to being more efficient. So the aircraft range improves and on longer flights payload capacity may improve as well. Fuel consumption is usually about 30% lower.
The higher efficiency combined with the fact that Jet A-1 fuel is cheaper mean they have lower operating cost. Especially since in Europe the leaded avgas is heavily taxed to discourage it's use for environmental concerns.
They should be a bit more reliable. A diesel engine needs high pressure fuel pump, but apparently there are less problems with those than there are with spark-plugs.
They are somewhat easier to operate, since they don't have separate throttle and mixture controls.
They don't suffer the problems associated with incorrect settings of those controls, namely knocking/detonation and pre-ignition.
Turbo-charging them does not carry the risk of pre-ignition and most of them are turbo-charged, so the performance does not decline as fast with density altitude.
There is lower risk of fire since jet/diesel fuel is less flammable (has higher ignition temperature).
Jet A-1 has much wider availability, especially in the third world, so it's easier to plan for fuel stops on a flight through say, Latin America or Africa

Disadvantages

They are heavier for the same power, because they need to be made from stronger material due to the higher compression ratio and because they need to have larger cylinder volume because of lower maximal rpm. On longer flights the reduction in fuel weight often makes up for the heavier engine.
Turbo-charging comes with specific operating procedures unfamiliar to those used to normally aspirated engines and a slight lag in thrust lever (it's not a throttle) response.
As others mentioned, small airports may not have jet fuel yet. This is probably better in Europe where the pressure to phase out 100LL avgas is stronger. Some engines also use automobile diesel fuel or even either jet or diesel fuel as diesel engines are less picky about what they burn.

Diesel engines in GA uses radiator cooling and thus heats the cabin with a water heat exchanger, inherently safer than taking heat directly off the exhaust manifold/pipe.


What is the Difference between mogas and avgas? Could anybody tell me the primary differences between mogas and avgas?

Chemically speaking, The difference in the fuels is the inclusion of lead-based additives that increase the Octane rating of the fuel, which are otherwise banned for use in other settings due to the negative effect on air quality. The other common use of leaded fuels I can think of is in auto racing, which also doesn't particularly prioritise air quality. Unleaded high-octane fuels do exist for aircraft engines, but those engines have to be certified to use those fuels, a long and expensive process. This is why they are less common.

Octane rating itself measures how resistant the fuel is to detonation.

Engines run at a specific level of compression. Simplistically, More compression produces more power, which is important in smaller piston engines. But having too high a compression ratio causes the mixture in the cylinder to detonate on it's own before the proper point in the timing cycle where it should be ignited by the spark plug. This is called 'knocking'.

In the best case, the result is increased fuel consumption as the ECU (ironically) throws more fuel into the mixture to reduce the possibility of detonation (at least in fuel-injected car engines this the case). In the worst case, the result is damage to the engine as uncontrolled detonation can put large unwanted loads on the crankshaft and the con-rods. Power output will be reduced in any case, which can be a massive issue for heavily laden aircraft attempting to climb in high or hot conditions.

100LL is essentially 94 octane premium ‘mogas’ mixed with tetra ethyl lead to boost its octane rating.


Why is the static margin expressed as percentage of the MAC? Most textbooks use the static margin (the distance between the aircraft's centre of mass and its aerodynamic centre) to assess the longitudinal static stability.

Instead of using an absolute value for the allowable range of the static margin, it is expressed as a percentage of the Mean Aerodynamic Chord (MAC) - for example between 5 and 30%. Why is this so?

For a given aircraft, the higher its aspect ratio for a given wing area the shorter will the chord become. Hence the MAC will also be smaller. This will in turn reduce the absolute value of the allowable range for the static margin.

Is this simply a convention or is there an aerodynamic or flight mechanics reason why the allowable range for the centre of mass is smaller for smaller MACs or shorter wing chords?

The static margin is the distance between the center of gravity and the neutral point. By itself, this is a dimensional value. This makes it hard to compare between aircraft, so it makes sense to divide it by some other length. That the mean aerodynamic chord has been chosen has several reasons:

The MAC is the reference length for all parameters of longitudinal motion.
The wing's pitching moment scales with the MAC.
The wing's pitch damping changes with the square of the MAC. The biggest contribution to pitch damping, however, is the lever arm of the horizontal tail.

Normally, the tail lever arm is also chosen as a multiple of MAC. A higher wing chord means more tail force is needed in order to set the correct angle of attack. If you compare different airplanes, you will notice that the relative size of the horizontal tail goes down with a higher wing aspect ratio. While GA airplanes have horizontal tails sized to between 20% and 25% of their wing surface, gliders have horizontal tails of around 10% to 15%. It must be said, however, that gliders need less flexibility in their cg location, which is another reason for reducing horizontal tail size.

If all linear dimensions are referenced to MAC and all areas referenced to the wing area, calculations become easier and similarities between different aircraft become obvious.

For lateral motion parameters the usual reference length is the semispan or the span of the wing.

I'd like to offer a different viewpoint.  The wing's pitch damping contributes little to aircraft pitch damping, so that is not a reason to base the static margin on MAC.  Believe it or not tail size is almost entirely based on trim requirements, not stability, so again basing tail size on wing area or MAC is not important to stability.  Two aircraft can have widely different MAC's, yet have the same actual stability, so comparisons between aircraft using MAC is not really useful nor accurate.  The ONLY reason MAC is referenced for static margin is for convenience for one particular plane only.  If you look at various aircraft (military, commercial, private) you'll find static margins that range from 35% (literally in front of the leading edge - some lear jets) to near 0% for essentially the same flying qualities.  In my (and others) opinion, there is no true relationship between MAC and stability, but I will soon publish a new theory on stability that mostly solves the "how much stability is needed and how do you measure it" problem.  It is interesting that every article/paper I've ever seen (lots of them) shows elaborate stability calculations that conclude nothing more than the CG should be in front of the neutral point - with nothing about how much in front (except the traditional 5-15% MAC).

Hope this peaks your curiosity.


Why are FDR's called "black boxes" when they are actually orange? Why do they call flight data recorders a "black box" if it's orange in color?

Just curious about this since I've seen several images of black boxes but they all come in orange colors, and not black.  I can understand orange being used to help brightly identify the box , but then why call it a "black" box?

The Wikipedia article on Flight recorder offers a possible explanation for the origin of the term:

  ... they were essentially photograph-based flight recorders since the record was made on a scrolling photographic film. The latent image was made by a thin ray of light deviated by a mirror tilted according to the magnitude of the data to record (altitude, speed, etc.). Since the inside of the recorder was pitch black, this may be the origin of the "black box" name, often used as a synonym for a flight recorder.

Interestingly, the Wikipedia article on Black box claims that the term entered the English language around 1945, which is a few years after the first flight data recorder was built.

The black box was invented by Professor Gordon Black at Farnborough in 1948 - hence the name 'black' box. See Who really invented the black box?


What is a demonstrated crosswind component? What is a demonstrated crosswind component? Is it possible to land in a crosswind greater than the demonstrated crosswind component? Is it safe to?

A demonstrated crosswind component is highest crosswind (corrected to make it 90°) which has been shown to be possible to safely land by a test pilot. It shall not require exceptional skill by an ordinary pilot, however it does not mean every pilot will be able to do so. It is also NOT a limit (contrary to what some say) - if the pilot does decide to land higher crosswinds, they can do so (but please take caution).

This number may not necessarily be the highest crosswind component that it's possible to land in -- it just has to be above the minimum capabilities required in the regulations. For example, say an aircraft, flown perfectly (yes, we're dreaming), was capable of handling a 30 knot crosswind component (no gust, ISA conditions), the manufacturer only needs to demonstrate safe landing with a crosswind component of one-fifth of the reference stall speed in the landing configuration. This would be:

10 knots @ 50KIAS VS0
12 knots @ 60KIAS VS0
14 knots @ 70KIAS VS0
15 knots @ 75KIAS VS0

Reference:

  (a) A 90 degree cross-component of wind velocity, demonstrated to be safe for taxiing, takeoff, and landing must be established and must be not less than 0.2 VS0.

I teach a way simpler definition:
The maximum crrosswind component that a plane can hold the fuselage aligned to the centerline up until full deflection of the controls.
Any additional wind requires adding in crab and would result in a side-loaded touchdown which is therefore out if control.


Why has the 777x been designed with folding wingtips? I recently visited the Boeing factory outside Seattle, WA and noted in the distance a new 777x being built with, what looked like very large winglets.

However, on closer inspection they're not - the ends of the wings are designed to fold up.

Source: aviation today

I didn't get a chance to ask our tour guide, so I was wondering if anyone here can explain why this aircraft has been designed with folding wingtips. I'm presuming this is only for ground operations, and my guess is something to do with size - but are they really so big that they need to fold up? I would have imagined that other large wide body jetliners would have similar dimensions.

Please note that I'm not asking about whether this should have winglets, or if winglets provide any benefits, I'm asking specifically why the ends of these wings fold up rather than just fixed as per previous 777 models.

The Boeing 777X website states that this is to enable a more efficient wing (read: wider span) while maintaining the airport gate and taxi footprint of the classic 777 (which ensures airlines can use the 777X on roughly the same airports and intermix operations with the classic fleet).

Folding them up reduces wing tip vortex. So, take of and landing planes can be stacked closer together without encountering wake turbulence.
Then fold them out in the cruise to benefit from the bigger wing area.


Are there design differences between propellers powered by air (wind-power) and propellers for aviation? What is the difference of design between a propeller designed to be powered by the wind (i.e. those huge wind power turbine blades) and those designed to be used to propel a plane that are powered by an engine (i.e. a Cessna 172's props)?

(To be clear, I'm talking about one that is powered by the air vs one that powers through the air.)

Blades of wind turbines, airplanes and helicopters are essentially the same. They are all wings, roughly to do the same job. However, each one is designed or enhanced to do their special job. The differences can be:

Number of revolutions
Wing span
Rate of flow
Tip speed
Density of medium
Material
Load

Turbine blades are designed to move in large volumes of rather slow moving air (usually 10-30 mph, 16-50 km/h) and not create turbulence that fouls the next blade. Aircraft propellers are designed to move high velocity air and avoid the turbulence by moving out of the way.

Wind turbines use blade pitch to adjust the rotation speed and the generated power. Wind turbine's control system adjusts the blade pitch to keep the rotor speed within operating limits as the wind speed changes. In aircraft, blade pitch is usually described as "coarse" for a coarser angle, and "fine" for a finer.

There is a BIG difference.  The curve of the blades is reversed.  On a propellor, the leading edge is close to the propellor disk, with the flatter surface towards the rear.  In a turbine, the leading edge points forward (into the wind), with the flatter surface also forward.


Could one see stars from the Concorde in daytime? The Concorde flew to an altitude of 60,000 ft (18.3 km) where stars should be visible at noon, aren't they? This question asks on how high stars become visible, and it is said Blackbird pilots could see them at 80,000 ft. The Concorde flew at the Armstrong line when highest, above more than 90% of the atmosphere's mass. Are there reports of passengers and pilots on the Concorde seeing stars (other than the Sun) when at peak altitude? Also, did the Sun appear whiter due to the thinner atmosphere?

Yes, in at least one exceptional circumstance.
The book Racing the Moon’s Shadow with Concorde 001 describes a 1973 scientific flight that remained in the moon's umbra for more than an hour, in daytime.  As stars are quite visible from the ground during a solar eclipse's totality, they would have been even more visible from a 17 km altitude.

This page has some images of the view from the Concorde. On one image two stars can be seen. So obviously one could see some.


Would this hovercraft be stable? Would this two-rotor hovercraft design work? The bold black line is weighted metal on the lower to stable it. If it helps, this is a human sized hovercraft.

Would it work if:

prop1 lift > prop2 lift
prop1 lift = prop2 lift
prop1 lift < prop2 lift

The difference between prop1 and prop2 lift should be in a range of 0-30%

NOT TO SCALE, assume that lower weighted bars are equidistant from middle of hovercraft.

Yes - it can work. Colin Furze (UK inventor & TV personality) built an essentially similar device. Skip to about 1:40 to see some of the problems he had.

If the weight is located low enough, it should have "pendulum stability", just like this toy --

If the props are running at different speeds and generating different amounts of lift, then (assuming that is a top view not a side a view), the pilot's weight will need to be off-center to compensate.


For training with a grace month, is it legal to fly in the month after training expires before going to school? Most 135 training/testing says something like this:

  §135.343   Crewmember initial and recurrent training requirements. No
  certificate holder may use a person, nor may any person serve, as a
  crewmember in operations under this part unless that crewmember has
  completed the appropriate initial or recurrent training phase of the
  training program appropriate to the type of operation in which the
  crewmember is to serve since the beginning of the 12th calendar month
  before that service. This section does not apply to a certificate
  holder that uses only one pilot in the certificate holder's
  operations.

Before that though, 14 CFR 135.323 states:

  §135.323 - Training program: General.

  ...

  (b) Whenever a crewmember who is required to take recurrent training
  under this subpart completes the training in the calendar month
  before, or the calendar month after, the month in which that training
  is required, the crewmember is considered to have completed it in the
  calendar month in which it was required.

  ...

So let's say that I completed initial training in March.  This says that if I complete recurrent training in February or April that they consider the training to have been completed in March.

So what happens if a year passes and recurrent training is due.  I don't make it in February or March, but the company schedules me for recurrent training towards the end of April.  Is it legal for me to fly in April before I go to recurrent training?

At this point, I don't meet 135.343 (because I am no longer within the required 12 calendar months) but I haven't been to training yet, so 135.323 doesn't really apply.

From my interpretation of the regulations I would say no, however every 135 company that I have ever flown for continues using pilots until they go to school, or stop flying at the end of the late grace month if they still haven't gone.  The POI's have never complained about it.  I feel like I must be missing something.

Is it legal for me to fly 135 trips during the late-grace month??  Note that the same the same scenario applies to 61.58 PIC checks as well, which also have a provision to train during the eligibility period (the month before or the month after it is due).

Yes, the FAA issued a Letter of Interpretation from their Chief Counsel in May 2015 which covers Section 61.58 proficiency checks and specifically addresses this issue.

It says that a pilot may continue to act as PIC during the grace month under Parts 91, 121, and 135.  It says (in part, and emphasis added by me):

  Section 61.58(i) states that, if a pilot completes the proficiency
  check in the calendar month before or the calendar month after the
  month it is due, "the pilot is considered to have taken it in the
  month in which it was due for the purpose of computing when the next
  pilot-incommand proficiency check is due."

  You have asked whether the language in paragraph (i) creates a "grace
  month" during which a pilot whose currency has lapsed under paragraph
  (a) may continue to act as pilot in command. The FAA has previously
  stated in a legal interpretation that § 61.58 includes a "grace month"
  for purposes of complying with the 12- and 24-month proficiency check
  requirements. We did not explicitly state, however, that a pilot may
  continue to act as PIC during this grace month. Legal Interpretation
  to Sean Conlin (Feb. 24, 2000). We have indicated, however, that
  similar provisions in parts 121 and 135 create a "grace month" during
  which a pilot may to continue to act as PIC during the month after the
  pilot's currency has lapsed? Legal Interpretation to Gregory S. Winton
  (2006), Legal Interpretation to J. Dennis Vanatta (June 25, 1996).

  The FAA intended the grace month to limit disruptions in operations
  conducted under parts 121 and 135 by accommodating pilots who are
  unable to complete recurrent training requirements in the month they
  are due. At the same time, the FAA did not want operators to use the
  grace month as a means of regularly extending a 12-month proficiency
  check to a 13-month proficiency check. For that reason, a proficiency
  check under part 121 or part 135 that is completed in the grace month
  is considered to be completed in the month it is due. The FAA believes
  that the same approach is appropriate for§ 61.58 proficiency checks.
  As such, a pilot may continue to act as pilot in command during the
  month after a§ 61.58 proficiency check is due. However, when a pilot
  completes a §61.58 proficiency check during this grace month, it is
  considered to have been completed during the month it was due for the
  purpose of calculating the next proficiency check.

You mention that it includes FAR Part 91.  No where in the text does the part 91 appear.

So lets say the pilot gets their last recurrent Jan 10 of the previous year.  Of course this is just an example.  Their recurrent would be due in January of the following year.  Now this pilot just happens to have two months of vacation available.  They schedule that vacation in January through February of the next year.  Training would put them into class for recurrent in March.

So now their completion date shows March of that year.  When is the period of grace begin (clearly month before and month after) however this training event does on occur anytime within those guidelines.

Is there now a new training month that will be referenced?  Remember this is FAR part 91 and not 135 or 121.

61.58 does not address specifically part 91 events, only the regulated carriers of 135 and 121.

The only sentence that might even be construed to be part 91 would be aircraft that require a PC.


Why don't multiengine aircraft have to demonstrate spin recoverability? (Building off this earlier question about spin-testing airliners.)

For normal-category aircraft1 in the U.S. (at least), only single-engine (or, in the case of some gliders, no-engine) airplanes need to demonstrate the ability to recover from a one-turn (or, if the aircraft is intended to be certified for intentional spinning, six-turn) spin.  This means that, for instance, the single-engine Cessna 208 (MTOW 3630 kg) has to be successfully recovered from a one-turn spin, whereas the much-smaller Piper PA-34 (MTOW 2155 kg) is exempt from this requirement solely by virtue of having a second engine.

There is nothing about multiengine aircraft that makes them inherently resistant to spinning compared to single-engine aircraft; indeed, if anything, it would be expected to make spins somewhat more likely (think "aftermath of botched or absent pilot response to an asymmetrical engine failure"2).  If, instead, the number of engines is being used as a proxy for the size and intended audience of the aircraft (as suggested in this comment on the aforelinked question), then I don't see any reason not to simply use a dividing line based directly on weight (especially since, as noted above, there are many large single-engine airplanes and small multiengine airplanes).3

Given all this, why aren't multiengine airplanes (especially small multiengine airplanes, such as the aforementioned PA-34) required to demonstrate spin recovery like their single-engined compatriots are?

1: Utility and aerobatic airplanes do have to demonstrate spin recoverability even if they have more than one engine.

2: Especially for multiengine tractor-propeller aircraft with wing-mounted engines, where, when flying at very low airspeeds, simply shutting down one engine or losing it to a mechanical failure can be enough to immediately stall its respective wing (due to said wing losing the air previously being blown over it at high speed by said engine's propeller).

3: Granted, even large multiengine airliners can find themselves spinning on occasion, something that (inadvertently) happened to (for instance) the first 307 and the first 737;4 however, I accept that an airplane requiring an ATPL and a specific type rating, not to mention a second pilot, is (by virtue of hopefully-good piloting) rather less likely (barring a major structural failure) to be placed in a spin than one requiring merely a PPL, and also that very large aircraft such as these are likely to become debris clouds if spun.

4: For the record, both the Stratoliner and the 737 were successfully recovered from their spins, although the former then almost immediately disintegrated in flight due to an overly-aggressive pullout from the subsequent dive.5

5: Hey, I can nest footnotes!

Because it would impose severe constraints on their design.

Factors such as mass distribution make many twin-engine and multi-engine aircraft inherently resistant to spin recovery, despite the large rudder or large rudder moment-arm that is often present on these aircraft.  In many cases these aircraft are prone to flat spins.  Also, during the recovery from a nose-down spin, a large aircraft may exceed Vne before pulling out of the resulting dive, or may be overstressed during the pull-out.  In the real world, a pilot should avoid spinning a typical twin-engine or multi-engine aircraft, because recovery might not be possible.

"No multiengine airplane is approved for spins, and their spin recovery characteristics are generally very poor."
-- from https://www.flightliteracy.com/stalls-in-multiengine-aircraft/

Related questions on ASE:

Is spin recovery possible in an airliner?

Why aren't airliners spin-tested?

Other related links:

https://www.flightliteracy.com/stalls-in-multiengine-aircraft/

https://www.pprune.org/flight-testing/226351-spinning-airliner.html

https://www.airlinepilotforums.com/hangar-talk/6370-spinning-airliner.html

google "spin recovery twin" or ("multi") for much more

I can only speculate on why the FAA does not require it since I don't know their reasoning. Here is why I don't think it is necessary:

The primary tool to stop an aircraft from spinning is the rudder:

  Power to idle
  Ailerons neutral
  Rudder opposite the spin until rotation stops
  Elevator forward to break the stall

(What is the Beggs/Mueller emergency spin recovery technique?)

In a single engine aircraft, the spin recovery needs to be demonstrated because the rudder might otherwise not be sized to be able to stop the spin. It would only be large enough to provide lateral control during takeoff and landing as well as coordinate turns in flight. Full rudder will never be used except for spin recovery, so this becomes the dominating factor.

On multi-engine aircraft, the rudder must be sized to compensate asymmetrical thrust in case of an engine failure. This limits the takeoff performance via $V_\text{mcg}$ (Are there any aircraft where minimum-V1 is limited by Vmcg?). The rudder will therefore already be sized large enough and spin recovery is no longer the dominating factor determining the required size of the rudder. I assume that is why it does not need to be demonstrated.


Do box-wings suffer from induced drag the same way as normal wings? Most wings suffer from induced drag due to a pressure difference above and below the wing causing air to sneak around the tip, forming a vortex. There are various methods to minimize these effects, such as winglets.

However, looking at the Synergy aircraft as an example, box wings have no wing tips. Disregarding any other parts of the aircraft, are the wings actually free from induced drag? Or are they still causing induced drag, just in a way I'm not able to think of with my limited fluid dynamics experience?

Synergy aircraft with box wings (picture source)

I've read somewhere that a traditional bi-plane design is less efficient due to the wings interfering with each other (apparently something addressed by the synergy aircraft by placing the upper wing further back or something), and the upper wing is actually more of a tail-plane, pushing down, thus further increasing the airspeed in between the airfoils if I understand correctly and eliminating the pressure differential from the top of the upper wing to the bottom of the lower wing, and both wings would of course generate normal drag by cutting through the air, but I'm only interested in the induced drag at this point.

The box wing is only better when you compare wings with identical span. The two wings of a box wing work in different Treffz planes, so the downwash is spread out vertically. The difference in induced drag to a single wing is not big, just a few percent. The friction drag is higher (see below), as is the structural mass, so the box wing needs to create more lift. This makes the induced drag of a box wing effectively higher than that of a single wing.

What is induced drag, anyway? It is the consequence of creating lift over a limited span. The wing creates lift by deflecting air downwards. This happens gradually over the wing's chord, and creates a reaction force orthogonally to the local speed of air. This means the reaction force is pointing up- and slightly backwards. This backwards component is induced drag! Wingtips are not involved and are not causing induced drag. Lift creation is.

If you fly fast, there is a lot of air mass streaming past the wing per unit of time, so you need to deflect the air only slightly. Your induced drag is small. Sames goes for a large span: There is more air which can be deflected, so the induced drag is small.

A box wing needs two slim wings per side, which will have a smaller chord than a single wing of the same surface area. So their Reynolds number is smaller, and their friction drag is higher. Also, the wing spar is less thick and will need to be heavier to carry the same lift!

If you drop the restriction of keeping span identical, the optimum single wing can afford to have more span (due to its better structural efficiency), and away goes the advantage of the box wing. And once you look at the full picture and add structural mass, the box wing never had this advantage in the first place.

Yes, but what about the Synergy?

The Synergy is a clever design with some advantages, but it cannot cheat physics. These are the advantanges:

The pusher prop keeps the airframe free of wake turbulence, so more area can be kept in laminar flow.
The pusher prop sucks the air from the rear fuselage, effectively avoiding separation.
The two stubby tailbooms and fins give great protection for the propeller area on the ground.
The compact layout keeps the stabilizing effect of the propeller small, so maneuverability does not suffer much.
The use of composites and glider airframe technologies reduce friction drag.
The diesel engine consumes cheaper jet fuel and is more fuel-efficient than a gasoline engine.

Note that I did not mention the box wing design?

Here are the disadvantages:

Wing sweep in a propeller aircraft looks cool, but increases drag, because the wing must be bigger to create the same lift.
In total, this configuration has four vertical tails, each of them with its own interference drag and a short chord which, again, increases drag over a comparable single vertical tail.
The stretched-out horizontal tail is also less effective than a smaller single surface with more chord and more distance from the center of gravity.
The compact layout provides little pitch or yaw damping. I wonder what the ride qualities in gusty weather are.

I would expect that a more conventional layout along the lines of the fs-28 would be even more efficient.

Akaflieg Stuttgart fs-28 in flight (picture source)

Closed systems (Box Wing is only a particular type of closed wing), C-wings and biwings are actually related as far as the minimization of induced drag is concerned.

If you are interested in technical answers regarding the induced drag minimization/performance of Box Wings, closed systems, bi-wing systems, and multiwings, you can find all the details in the following publications (I can also send to you the papers if you email me at the address luciano.demasiATgmail.com):

=====Article 1 =====

Demasi Luciano, Monegato  Giovanni, Dipace  Antonio and Cavallaro  Rauno "Minimum Induced Drag Theorems for Joined Wings, Closed Systems, and Generic Biwings: Theory", Journal of Optimization Theory and Applications, 2015, pages 1-36, DOI: 10.1007/s10957-015-0849-y, ISSN:0022-3239

=====Article 2 =====

Demasi  Luciano, Monegato  Giovanni, Rizzo  Emanuele, Cavallaro  Rauno and Dipace  Antonio "Minimum Induced Drag Theorems for Joined Wings, Closed Systems, and Generic Biwings: Applications" Journal of Optimization Theory and Applications, 2015, Pages 1-25,Doi: 10.1007/s10957-015-0849-y, ISSN:0022-3239

=====Article 3 =====

Demasi  Luciano, Monegato  Giovanni, Cavallaro  Rauno "Minimum Induced Drag Theorems for Multi-Wing Systems" ,2016,4-8 January,SciTech2016, San Diego, California, AIAA 2016-0236

=====Article 4 =====

Demasi  Luciano, Dipace  Antonio, Monegato  Giovanni, Cavallaro  Rauno
"Invariant Formulation for the Minimum Induced Drag Conditions of Nonplanar Wing Systems", AIAA Journal, 2014,October,10,2223-2240,52, Doi:10.2514/1.J052837
  Url: http://arc.aiaa.org/doi/abs/10.2514/1.J052837

Sincerely,

Luciano Demasi


When are winds given with respect to true vs. magnetic north? Wind information can be reported by various sources (ATIS, METAR, TAF, spoken on the radio, etc). I was taught that officially some of these sources are relative to magnetic north and others to true north (although practically this isn't always followed). Which sources are supposed to use which reference system?

The general rule is:

If you read it, it's true. If you hear it, it's magnetic.

All charts and textual sources (METAR, TAF, winds aloft, surface analysis charts, etc) use true north as the reference.

ATIS/AWOS/ASOS broadcasts, or any information a controller gives you over the radio, is magnetic.

  Wind direction broadcast over FAA radios is in reference to magnetic north.

AIM Section 7-1-11 (page 7-1-26 in the 5/26/16 edition)

One exception to the "if you hear it" rule is that a FSS briefer will read you the winds referenced to true north, since they're just reading you the charts/textual information.

(This is at least true in the United States... other countries may vary in some instances)

Another good general rule

Everything the weather man tells you it's true ... the rest is magnetic


Can some IAFs be skipped if more than one IAF exists? Take, for example, this FAA official IAP plate (ILS RWY 13L CAT II JFK). Its Initial Segment consists of more than one Initial Approach Fix (IAF): COVIR, KMCHI, and BUZON. As far as I can interpret this, when an aircraft enters from the en route structure, it is obliged to follow the route COVIR → KMCHI → BUZON → TELEX etc.

My question is, is the aircraft supposed to follow this particular route or, depending from where it comes, it can "skip" e.g. the first Initial Approach Fix, and follow the route KMCHI → BUZON → TELEX (instead of COVIR → KMCHI → BUZON → TELEX)?

Also, if the answer is yes, does that mean that it can even ignore all the IAFs and enter Intermediate Segment directly, provided that this serves its purpose better?

Any initial approach fix (IAF) is a valid point at which an aircraft can start the procedure. Many procedures also have IAFs on multiple paths to choose from to get to the final approach. Standard Terminal Arrivals (STARs) sometimes include a certain IAF so that pilots can go straight from the arrival to the approach. Aircraft not on one of these STARs could use any other IAF.

Aircraft can also start even later in the procedure at an intermediate fix (IF), such as TELEX in the above example, provided it is coordinated with ATC and certain conditions are met.

After entering a procedure, aircraft are expected to fly the procedure as published. While it's not as common as with a SID or a STAR, ATC could certainly give an aircraft instructions for a shortcut on an approach, for traffic or other reasons. ATC would need to authorize this to ensure clearance from traffic and obstacles and compliance with restrictions such as noise abatement.

Clearance will be as directed by ATC at time of departure, or as modified by ATC while enroute.


Why are there no Mach 4+ fighter planes? Why are there no Mach 4+ fighter aircraft?  It seems that such aircraft would have massive advantages when it comes to being able to fire longer range missiles and evade return fire.

Today's fighter are designed with a max speed around mach 2 (max speed is generally calculated with no emport and 50% fuel, the operational top speed is way lower). They keep this ability to pass Mach 1 only to be able to respond fast enough to intercept / air policing missions.

Countries do not design very fast fighters (and planes in general) because :

It's extremely hard to achieve.
It does not give any advantage.
It has no use anymore.

Back in the cold war period, radars and SAMs where not very sophisticated yet, they did not see very far and Ground to Air missiles were not able to get very high. So to protect their airspace from potential intruders / enemy bombers, countries were relying on interceptor aircraft, a fast jet able to catch up the target before it gets to its objective.
At this time, going very fast, very high was an advantage : SAMs where not threatening. The US made a very successful reconnaissance plane exploiting that: the SR-71 Blackbird (max speed : mach 3.3). Many missiles were fired towards the SR-71, none reached its target.

Speed was used for intercept and reconnaissance / intel.

But radars and SAMs improved, getting more range, becoming able to threaten very fast planes. Also satellite images got better and better. The need for very fast interceptors decreased as radar range increased, and the need for very fast recon aircraft decreased as satellite images got better.

Now why does going very very fast not give any advantage to a fighter? Because you cannot turn.
The thing to keep in mind is G force: force the same turn rate, the faster you go, the more g you have to take. And a human can sustain a very limited amount of g. This means a plane going at Mach 4 will barely be able to turn without blacking out its pilot. And if you can't turn, you won't evade enemy missiles, making useless the bit more range gained on the missiles.

And then there is the technical challenge, dealing with a little drag as possible (that means no missile / bomb / fuel under the wings), heat, airframe deformation and wear ... for an advantage which isn't there anymore.

Despite all that, the US are suspected to work on a Mach 6+ aircraft, probably unpiloted.

(Please keep in mind that I simplified a lot of things to not make this post too complex)

Fuel consumption and combat range. Going to mach 4 it would be a problem for the fuel consumption.

Some legends, they say something there is but we do not know it :-)


Why does the IL-76 have a lump at the bottom of its nose? Why does the IL-76 have this lump at the bottom of its nose?
Why can't it be gotten rid of?

The 'lump' holds a ground surveillance (mapping) radar.
IL-76 has two radars: the usual meteo radar in the nose and the ground surveillance radar (primarily for navigation). In addition to that, like all contemporary Soviet long(er)-range transports (esp. military ones), it has a dedicated navigator position with the glassed 'verandah' for better view of the ground.
Most commonly, this navigator position took up the nose cone space that is (nowadays) usually reserved for the radar. If you look at most modifications of Tu-134 or Tu-114, you'll see they have a similar (but smaller) 'hump' underneath to house the meteo radar. But the widebody IL-76 could afford both the nose radar and the navigator station under it, plus a dedicated mapping radar.
The navigator's seat and equpment don't extend much below the lowest window, so most of the space is used for the radar rather than the navigator.

The lump acts primarily as an extension to the cockpit, as it is known that soviet military planes require more pilots to operate them. The lump is used as a bay to get the navigator a view of the ground.
See (related): Quora: Why-does-the-Ilyshin-Il-76-have-glass-under-the-nose

Despite being equipped with all possible navigational equipment,  there was always the possibility that it all fails (or plane will have to flight in BAD CONDITIONS), in godforsaken places where there is no navigational aids. So there must always be a glass cupola for ground observation, so that navigator could just take a map and give position by visual signs.


Would a takeoff be aborted if 'rotate' is not called out? As captain of a Boeing 747 on a take-off roll I am expecting my co-pilot to call out V1, Rotate, but he does not call out rotate. Do I abort the take-off?

That could end up being a really bad idea if you've accelerated past your V1 speed -- your abort would then put you off the end of the runway, and the consequences from that range from bad to catastrophic.

A much better idea would be to look at the markers on your airspeed indicator, and if you're at/above rotation speed, go ahead and rotate.  Then sort out what's up with your copilot.

The worst case is, he's incapacitated, unconscious, experiencing a stroke or heart attack or something similar, and you'll probably end up returning to land as quickly as possible.  While the idea of staying on the ground to get him EMS help sooner might seem to be appealing, he'll probably NOT get better attention if your aircraft just ran off the runway, through the airport fence, and into whatever terrain/water/civilization lies beyond, because you didn't start your abort until several seconds after you should have been flying.  Better to come back and land with ONE sick person on the airplane, rather than crash, making your copilot now one of potentially MANY injured/scared/incapacitated people on a damaged jet -- and he with the very least ability of any of them to evacuate himself!

Or, maybe he got distracted and he's fine, and after he overcomes his embarrassment for missing the important callouts, the rest of the flight will go fine.

So, no, if the copilot doesn't call "V1, Rotate" I would NOT recommend aborting the takeoff.  If you see him slumped over when he should be making an "80 knots" or "airspeed alive" call, that might be a different decision; at that sort of speed you're in no danger of running off the runway & you could probably taxi back to the gate promptly.  But if he's missed his calls at significantly higher speeds, aborting is a bad plan.

Very well stated answer and valid common sense reasons not to abort above V1 and on a missed V speed call.

80 kts and 100 kts also serve as incapacitation calls and 100kts  caution yu are entering a high energy state in case pf any abort and something to be extra mindful in case of wet/slippery runways.

Here is a good case why not to abort at V1 and above gor a heavy jet

https://aviation-safety.net/database/record.php?id=19720418-1

https://aviation-safety.net/database/record.php?id=19960613-0

There is a case, exceptionally. When a take off must be aborted after V1 ...when you have no other choice but to.One case might be encounterng flight control failure such as horizontal stabilizer.Another case might be dual/all engines failure case
 You are not going anywhere with these two scenarios and better salvage a crash close to the runway,stopway and clearway then at height.
Another case where it might be tempting to abort a feq seconds after V1 and if particularly second segment limited is encountering a Microburst(ofcourse ypu should not takeoff within sight or radar coverage of any thunderstorm cell..but if a severe speed lag or speed burst occurs close to or at V1 im the given scenario with second segment climb limited case..it might be better to abort if on a dry runway Do expect an overrun and so exert maximum brake energy..and expect a fire in the wheel well or even overrun and crash at the end of an overrun.You have the choice to push throttles to max thrust(Firewall) and totate at a slightly higher speed to countermand the debilitating effects of the microburst during the first and second segment..not forgetting NOT to raise the gear or change any configuration except after flying through the shear..typically past 1500 feet.


What is the maximum altitude allowed to fly a model plane/copter in Germany? What is the maximum altitude I'm allowed to fly a model plane or 'copter in Germany?

The maximum altitude you can operate your RC plane or copter vertically without any clearance from ATC or another government body is the upper limit of class G airspace in Germany, which is the first available airspace from GND to the lower vertical limit of controlled airspace C/D/E, which can be 2.500ft AGL1, 1.700ft AGL or 1.000ft AGL, depending on surrounding airspace and airports in the vicinity. You can register at the website of the DFS AIS to obtain the ICAO charts for your area and take a look at the airspace structure near you.

The actual ceiling of airspace G can be significantly lower in the vicinity of larger airports, where the controlled airspace C/D/E has been lowered. The below picture shows how the dark green section around Frankfurt Airport has an airspace C with the vertical limits 1.500ft (MSL)/FL100. The airspace E in that area (not visible in this picture) has a vertical limit of 1.000ft AGL/C. Some areas within that section already have an elevation of 700-1100ft MSL, which leaves less than 100-400ft of airspace G before the overlying airspace C begins.

If you want to get your RC plane or copter into class C/D/E airspace, which is controlled airspace, you will need to obtain a clearance through the ATC unit in control of the sector or the FIS sector responsible, as postulated in LuftVO §16a

  § 16a LuftVO
  Besondere Benutzung des kontrollierten Luftraums
  (1) Bei Inanspruchnahme des kontrollierten Luftraums ist von der zuständigen Flugverkehrskontrollstelle eine Flugverkehrskontrollfreigabe einzuholen für
  1. Fallschirmsprünge und den Abwurf von Gegenständen an Fallschirmen;
  2. Aufstiege von Flugmodellen und anderen fern- oder ungesteuerten Flugkörpern mit Eigenantrieb;
  3. Aufstiege von unbemannten Freiballonen mit einer Gesamtmasse von Ballonhülle und Ballast von mehr als 0,5 kg sowie Aufstiege von gebündelten unbemannten Freiballonen und Massenaufstiege von unbemannten Freiballonen.

Please also mind LuftVO §15a, which dictactes that any RC plane or UAV needs to remain within the visbility range of the controller, so the maximum altitude can vary depending on the size of your RC plane or copter, the weather minima at your location and your own eyesight:

  (3) Der Betrieb von unbemannten Luftfahrtsystemen ist verboten, wenn

  1. er außerhalb der Sichtweite des Steuerers erfolgt oder
  2. die Gesamtmasse des Geräts mehr als 25 Kilogramm beträgt.

1: AGL = Above Ground Level
2: MSL = Mean Sea Level

Try this link: http://www.rc-network.de/magazin/artikel_02/art_02-0001/art_02-0001-00.html#3.  If you want an even broader view, go to this link here: http://www.rc-network.de/magazin/artikel_02/art_02-0001/art_02-0001-00.html.  Hope this helps!

This is a quote from the first link:

  Basically, it can be stated that the model airplane at the latest at
  FL 100 (FL = flight level, flight level), which is about 3 km above
  sea level, comes to an end.

The page is in German, and of course, Chrome didn't provide a perfect translation.  So model airplanes aren't allowed to fly higher than 3 km.  Higher airspace is reserved for commercial flights, military, etc.


Can a non-instrument rated safety pilot log PIC during an IFR flight? The Scenario:
An instrument-rated private pilot files and flies IFR while accompanied by a non-instrument-rated private pilot who is otherwise fully certified and endorsed to act as PIC in that aircraft under VFR flight rules. While in VMC, the instrument rated pilot uses a view limiting device in order to practice IFR scan and procedures towards maintaining currency, while the other pilot acts as safety pilot. Both pilots meet all medical and currency requirements for the flight.
The Question:
Can the safety pilot in the previous scenario log as PIC that time during which he/she acted as safety pilot?
Note: This question differs from the question, How should time as safety pilot be logged?. This question is not answered there; this question concerns whether or not a non-instrument-rated pilot is qualified as required crew during simulated instrument flight in VMC while operating on an IFR flight plan, and whether that pilot is qualified to act as PIC in the given scenario.

No

The way that both pilots can log PIC is that the pilot using a view limiting device is logging PIC as sole manipulator and the safety pilot is logging PIC because he is acting PIC and a required crew member.

If the flight is operating under an instrument clearance then the acting PIC must be instrument rated. If only the pilot with the view limiting device is rated then he is acting PIC and is the only one eligible to log PIC. The safety pilot is also not allowed to log SIC as a required crewmember without an instrument rating while operating under IFR.

If you are in actual IMC then you shouldn't be logging anything and they other guy shouldn't be wearing a view limiting device.

If you want the PIC time ask your friend to fly VFR or get yourself an instrument rating.

The issue for me is 91.109(c)

  No person may operate a civil aircraft in simulated instrument flight unless—

The word simulated seems to me that while on an IFR flight plan the flight isn't simulated hence there is no need for a safety pilot.  As a result, the other pilot irregardless of whether or not they are capable of acting as the legal pilot in command cannot log PIC time.

They are not a required crew member so they cannot log SIC time either.

While in VMC conditions on an IFR flight plan it is prudent for all pilots to see and avoid other aircraft.  If one is wearing a view limiting device, the other pilot is still not required due to being on an IFR flight plan.


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

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

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

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

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

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

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

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

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

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

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

Falcon 900B

Falcon 900EX

Falcon 900EX-EASy

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

Appearances... can be deceiving.

There is progress please take a look at the ICON A5 and the Cirrus Vision SF50 cockpit controls.
And I agree a lot of Pre-Flight checks and controls could be simplified or computer checked.
The big difference between a car (simple interface) and a plane is if there is an issue with your car you pull it aside and with a plane you drop from the skies :(  although autogyro's like the Cavalon dont have that issue :)


Which photo more accurately represents Flaps 1 in a 737-800? or  A recent update in a sim craft changed the visuals from what I'm used to, but from my research it looks to be more realistic. This post clearly reflects the more extended option being more realistic - but can anyone confirm that that is how it looks on a flaps 1 setting irl?

Thanks in advance!

On the 737, flaps 1 actually means leading edge slats only and no trailing edge flaps.

Therefore the first photo is definitely wrong, while the second one is probably correct (since the slats cannot be seen).


What happens if Solar Impulse II encounters un-expected head wind and runs out of battery power? I noticed that battery charge level dropped to fair levels in some occasions in this article. It dropped to around 20% at the end of day 5 before morning of day 6.

To what extent will a flight be affected by unexpected strong head wind that results in lower Eastward ground speed and delaying time to next sun shine and battery runs out?

I tend to think weather prediction is quite good nowadays, what is the plan if this happens on long ocean flight? Does the ocean have thermals where a glider can stay up 'forever' while waiting for morning sunshine?

On Solar Impulse, or similar 'experimental' (at the edge of limits) flights, like the solo circumnavigation balloon flight, do they usually have a 'chaser/spotter' plane flying along?

Solar Impulse has two means to store energy: Batteries and altitude. Weather permitting, both will be fully charged at sunset, and mostly depleted over the night. The rate of depletion at sunrise depends only on the time between sunset and sunrise, not on the direction and strength of the wind.

Headwind only means that less ground is covered. Solar Impulse is optimized to fly at a certain speed and will not fly much faster or slower, regardless of wind. If the wind is strong enough, it will simply not cover any ground but be blown back. But the wind will not cause the batteries to be depleted earlier, and the next day they will be recharged if the sky is clear.

Wind speed and direction vary with altitude, so the aircraft might well overcome a wind that had prevented it to make any progress the night before by flying at a different altitude the next day. After all, flight duration is limited by the pilot, not the power source.

If the battery level goes to low, due to poor planning or an bad weather forecast (winds end up less favorable than forecast) then solar impulse doesn't make it to its destination.  If they are over water they crash into the water.

Look, solar impulse is a totally impractical aircraft, built to give the two pilots some records.  Everything about the aircraft is impractical and dangerous.  There isn't enough power for a decent climb rate or cruise speed. Even a quite common low altitude headwind would be enough to have the aircraft flying backwards. There isn't enough energy storage for sufficient range to safely go any reasonable distance.  The structure had to be built extremely light weight so the aircraft is fragile (can't take much turbulence).  And there is no way to overcome these limitations with further development.

The maximum solar power reaching earth is about 1kw/sqM, and this is only achieved in clear sky's, when the solar cells are directly facing the sun.  Since there is no way to have the solar cells face the sun on an aircraft (the cells have to be flush with the airframe) this means that most of the day you will get even less than 1 kw/sqM (half of the day you will get zero).

To put this in perspective this would mean a light aircraft, like a Cessna 172, would receive a maximum power of 10-15kw of solar energy over the entire airframe.  In reality, using very expensive cells with the best efficiency available, the actual energy collected would be more like 3-5kw.  A Cessna 172 is a very low powered, low performance aircraft but even still, it gets about 120kw of power from its little 4 cylinder Lycoming engine.  The 3-5 kW of electricity that a solar Cessna 172 could collect in the most favorable conditions wouldn't be nearly enough to keep the airplane in the sky.  And again, this comparison is not about trying to make a solar powered commuter airliner or something of similar performance, there isn't enough sun for even the lowest performing human carrying aircraft.


Why don't transponders have active and stand-by value like radios? This answer explains how pilots when switching code on transponder should either carefully avoid temporarily squawking one of the emergency codes, or should temporarily put the transponder in stand-by.

Radios (both comm and nav) usually have an active frequency and a stand-by frequency and the pilot selects the stand-by frequency and then activates it with a button, which avoids temporarily selecting different frequency and limits the time when the radio is not receiving.

Why don't transponders have similar mechanism? It seems it would be much more useful for them than it is for the radio.

For navigation and communication radios the feature of having a second readout that can be pre-set to the next frequency is useful since the next frequency is usually known in advance. Your next transponder code is a somewhat random number and the moment that you will get it is not as predictable as a frequency change. Therefore there is no need for a pre-set / standby squawk code in a transponder.

Also, in a communication radio, when you pre-set the wrong frequency and cannot establish communication after the switch over, a single button press will bring you back to the original frequency. This prevents prolonged communication loss. This is similar in navigation radios.
For a transponder such a feature has no value, you won't switch back to the previous squawk code.

The problem of inadvertently selecting a special code can be addressed by other means. For example a digital interface that requires confirmation of the selected code before it is activated.

Transponders are more technologically conservative than radios and the old models have a lot of analog electronics in them. You could certainly add the electronics and additional buttons to have them do a switchover the way radios do, and I think newer models can, but the older models are more primitive, which is why you see those instructions to use standby.


Are 'human factor' specialists consulted during the UX design of cockpit controls and avionics? I have always been struck by the complexity of cockpit controls. Aviation specialists are always on the hunt for ways to reduce cognitive overload on pilots to reduce human error.

That being said, air crash investigations have proven in a number of incidents that labelling, controls interactivity, affordances and other interface design issues impact on how pilots operate.

So, I have few questions:

How do human factor specialists and user experience designers differ (or not) when it comes to designing for avionics?
If user experience design skills are so different from human factor skills, wouldn't they be required when designing avionics?
If they are not so different has anyone came across a situation where user experience skills were utilised within the aviation industry?

My thesis, which I wrote so long ago that I no longer recall the title, was a complete redesign of the Boeing 747 cockpit from a human factors and usability point of view.

My designs, which were submitted to Boeing at the time, likely helped create the foundation for the modern glass fly-by-wire cockpit.

At the time, glass cockpits did not exist (the term refers to the glass in the CRT monitors that were eventually used within the cockpit, later replaced by LCD displays).  Fly-by-wire, which is the concept of replacing conventional flight controls with an electronic interface, was in its infancy.

I remember working tirelessly to create a comprehensive new human interface for pilots that would minimize errors and improve safety.

My research was based in the cognitive sciences, which consisted of university coursework in human physiology, neuroanatomy (rudimentary at the time), psychology, statistics, engineering, computer science, mathematics, linguistics, neural networks (the very first ones), and artificial intelligence.  It was a rigorous and diverse education.

I spent hours and hours watching films of pilots performing a vast array of different procedures.  Sometimes they were successful, and sometimes they were not.  When they were not, it often resulted in serious consequences.  I spent long nights listening to hour after hour of dialog between air traffic controllers and pilots.  I studied detailed accident and near-accident reports.  I also interviewed pilots and spent a fair amount of time inside commercial cockpits, between flights, gathering essential data.

One of the challenges that I vividly recall was reducing complexity for pilots, while keeping the tasks difficult enough so they would stay engaged to their tasks and not fall asleep or become distracted.

The most rewarding part of developing my thesis was converting the cockpit from what I called a control-based center to a task-based center.  Up until that time, most controls available to pilots were designed to directly impact a flight control surface such as the rudder.  There were some rudimentary "intelligent" controls to perform basic horizontal and vertical navigation (but nothing that integrated the two!).

I designed a new system that was based on high level tasks that the pilot would need to perform.  No longer were ailerons, elevators, flaps, and thrust the focus.  Instead, I changed the focus of the cockpit to center on essential tasks such as taking off, landing, route planning, communications, and traffic and weather avoidance.

During this work, I learned that I had to seamlessly integrate my human factors engineering and user experience design skills.  In my opinion, and from my personal experience, they always need to be.

Whenever I fly, I ask to take a look at the cockpit after we land.  It's a joy to see the evolution of my designs.  Whether I was the originator of these designs or one of many human factors engineers who came up with them at the same time, I will never know.  But similarities of the current designs to what I proposed in my thesis many years ago gives me a little insight into a possible answer to that question.

I suspect cockpits for complex aircraft like airliners are improving with regards to human factors due to glass cockpits which help to group information most important to the pilot in one place.

Just compare pictures of the 707 and 787 cockpits. Glass avionics make a huge difference.

With regards to specific avionics companies, I imagine they do have consultants when designing the interface. When it comes to avionics, I'm quie a fan of Garmin. All their devices from avionics to bike GPSs are well designed and intuitive to use. And given how Garmin releases products besides avionics to the general public, I'm sure they know thing of two about good interface design.


Why are propeller airplanes still made? Airplanes with propellers were invented a long time ago. After that, jet engines came into existence. My question is: why do we still have propeller engines?

The reasons I can think of are:

They are cheaper;
They cannot achieve very high speed;
They are not very noisy (though not always).

Besides these, are there any other reasons general aviation airplanes built nowadays don't have jet engines?

Jet engines are only efficient at high altitudes and high speed (25,000+ feet or so and 300+ knots or so true airspeed).  The cost of making and operating an airplane capable of flying there is very high, and most general aviation flights have no need of such performance (or expense) hence, propeller airplanes.

Reciprocating engine propeller airplanes are relatively efficient at low altitudes and airspeeds, they are more economical for the average types of general aviation flights.  They are also much cheaper to build and operate than a turbine powered airplane.

Turboprops fill the efficiency gap between reciprocating and pure jet engines, being most efficient at mid altitudes and airspeeds.  Still more expense and performance than most general aviation flights need though.

It's very simple: Prop planes are manufactured because most airports around the world have runways too short for jets.


Why do we still use pilots to fly airplanes? With the recent advances in drone and remote control technology, why are there still commercial and military pilots?

I understand that there can be some serious tactical advantages to human pilots in military operations, but for patrol and commercial flights what are the advantages of a human pilot in the aircraft as opposed to a drone or a remotely controlled airplane?

That's a good question, and brings up a joke that many pilots know well:

  "What's going to be in the cockpit of the future?"

  "A dog and a pilot."

  "A dog?  Why a dog?"

  "Well, the dog is there to keep the pilot from touching anything."

  "Ummm, why have the pilot then?"

  "Well, someone has to feed the dog! "

Technology has improved to the point where airplanes can pretty much fly and even land themselves.  They are even getting pretty good at handling "normal" emergencies like engine failures and depressurizations.

Where pilots really shine though are the type of abnormal and emergency situations that aren't "in the book".

When an engine flies apart and shreds the hydraulic lines on all three redundant hydraulic systems, a computer will be out of options because it was never programmed to handle that (because it was considered "virtually impossible" when it was designed).  A pilot on the other hand can analyze and experiment until he finds enough of a solution to keep the airplane in the air as he works through other issues.

During a total electrical failure, the computers won't be much good.  Sure, you can design redundant systems and make it so that it "can never happen", but what about when it does?

There are also all of the little things that a pilot is constantly making decisions on how to handle.  Some examples could include:

Can the airplane fly with a particular feature inoperative?
What about multiple features inoperative?
How do they interact with each other?
What do you do when the passengers take too long to board and you are going to miss your departure slot?
What do you do when the ground crew forgets to close a door?
What about when the tug driver doesn't push you back quite far enough?
Or ATC wants to change you to a different runway?
Or you ask ATC to change you to a different runway because it might save a few minutes and that will keep you from having to deice again?
Or another airplane unexpectedly pulls out in front of you while taxiing?
A pilot can see "ugly" clouds off the end of the runway and decide that it would be better to wait a bit before taking off.
What happens when a flock of birds suddenly appears during the takeoff roll?
What happens when a passenger gets sick or unruly?
When do you need to divert and when can you continue?

On a typical flight, a pilot will make hundreds of small decisions that can make a big difference in the flight.  Any one of these (or one of the tens or hundreds of thousands of other things that could happen) could trip up a computer.

The pilot is also there as the "final authority".  If a hacker were to somehow hack into the automated systems, a pilot can always disconnect them and fly the airplane manually.  He can turn off systems, he can be...  Well, the pilot can be creative and a computer can only do what it was programmed to do.

Right now when a drone crashes it isn't such a big deal because nobody was on board.  If an airliner with a load full of paying passengers crashes it is a big deal.  Even just one.

Many of these problems can be overcome.  Some of them already have been.  Some of them may never be fully handled in an automatic way but maybe we could still do automated flights with an acceptable level of safety.  Some automation is actually better than some pilots in certain areas.

However, the biggest reason that we don't have fully automated passenger airplanes is because the general public feels comforted by a person being up front who can take over and carry them to safety if needed.  Even if the technology were 100% ready for automated passenger flights, I think that the number of people willing to purchase a ticket would be so low that it would be financially unfeasible for an airline to deploy it.

Even for military applications, having fully automated aircraft isn't the best of options (except when it comes to cost, pilots cost more than computers).
Quite apart from the risk of accidentally losing control over the drone (a solar flare at just the wrong moment, oops), there's the risk of the control link being jammed or even the control systems being hacked and taken over by an opponent.
While that's not that great a risk sending a Predator drone over Afghanistan of Somalia, sending the equivalent of a B-2 piloted by computers on a strike to say China does invoke that risk.
And I'm not talking about Terminator style robots taking over the world and hunting humans to extinction (which is a big reason why the public has trouble with armed drones) but human interference causing the drone to either crash, divert to an enemy base and be captured, or be reprogrammed to strike back at its owner by the enemy.

And in part that plays in commercial aircraft as well. A well equipped criminal gang could break into the control systems and take them over, sending an airliner with several hundred passengers out of control (or into a holding pattern, demanding ransom). No more trying to sneak people with funny accents onto airliners with plastic explosives in their shoes or underwear, which (romantic though it may be to some, and providing martyrdom to the 'volunteer') isn't very likely to succeed.
And that was already a real worry when Boeing and Airbus introduced their Electronic Flight Bag equipment, the idea that someone could break in in an airliner's systems and reprogram those to provide false data to the pilots who'd then use that to fly to the wrong place caused serious headaches (and those things can be reprogrammed only on the ground using a cable from a laptop...).


When is this Class D airspace not Class D airspace? The Terminal Area Chart (TAC) shows the Class D airspace for Los Angeles International Airport (KLAX) view the full TAC. I have highlighted in green the north and south portions of the Class D airspace. The surface area directly over KLAX airport is Class B airspace.  The note - "See NOTAMs/Supplement for Class D eff hrs" is highlighted in green on the left side with arrows pointing to the two Class D areas (2700 and 2500).

This note suggests that at certain times, these two KLAX Class D areas may not be effective.

The excerpt just below the TAC is from FAA Order 7400.11 - Airspace Designations and Reporting Points and describes the official dimensions of the KLAX Class D airspace and also indicates it (Class D) may not be continuously effective.

The next to last section below is an excerpt from the Chart Supplement Southwest U.S.  (just the pertinent part). The Airspace description shows it is Class B airspace and Class D airspace with "...other times CLASS G"

The final section below is a 2012 FAA Notice (NOTC 3900) announcing the activation of LAX Class D airspace, validating that LAX has Class D airspace north and south of its runways.

My question is: When are these two (2700 msl and 2500 msl) Class D airspace sections (bordered in green) other than Class D?

FAA NOTICE NOTC 3900 - LAX CLASS D Airspace Activation

Great question. The short answer to your question is "Full Time." Ultimately that Class D airspace will be incorporated into the LAX Class B, but there is a lot of red tape involved so step one was to add the Class D extensions, then it will be incorpoated into LAX Class B at a later date. Its a big deal, Title 14 CFR Part 71 had to be amended, here is the Federal Register page that explains the rule change. By the way, you're not alone in being confused about the effective hours, apparently that language was erroneously included in the charts and had to be removed.

According to Foreflight:

  Activation Continuously (excl holidays)

This is specifically for the areas you indicated.  Otherwise, generally, class D is not class D when the tower that controls the class D is closed.  Usually this is every night.


How do fire crews handle hot brakes? Let suppose an emergency aircraft has made an overweight landing. The brakes are white hot, and the fire crews are requested to be on scene.

What can be done about the hot brakes? Can they just shoot water at the gear assembly? If flames are visible, would they shoot foam instead?

This related question asks how do fire crew inspect the brakes, but not what they do when the brakes are known to be very hot.

(Airbus) A320 landing gear approach paths.
It's important to approach the landing gear from the right angle, because an explosion could throw deadly debris at the firefighters.
Cooling
According to Airbus, water-mist is to be used to cool the brakes.
Water, CO2, or foam, are not to be used. All those cause sudden cooling that can lead to wheel cracks or rim burst.
Fire
If there is fire, then large amounts of water or water-mist is to be used. Foam is to be used if fuel tanks are at risk.
(YouTube) Fire crew attending to 1400°C brakes.

Not an emergency, but interesting:
(airliners.net)

Upon deplaning back in Pyongyang, we noticed the brakes of the main gear were being cooled down with water. Naturally, this led to a mass gathering downstairs, as everyone wanted to take a photo of this event. We learned that this is actually standard procedure, which seemed legit as I remembered seeing water on the apron after our [Ilyushin Il-62] flight as well.

Related: When the brakes are checked, what do the firemen actually do?

I'm working on B747 cl. Here they used to use water when the temperature is close to 700°F, almost every time there is a wheel change the maintenance crew found the rotor brakes shattered like a crystal, but they continue doing it as a mean to not generate any cargo delay due to deflated wheel. Unsafe condition?
 Yes very much unsafe, a risk of a stuck wheel on takeoff or landing can occur.