What is the relative safety record of the Sukhoi Superjet 100? After the last crash, numerous articles state that the Superjet has a poor safety record. Two fatal crashes in 8 years is not a lot, but then again, only around 150 planes have been delivered. Does anybody have numbers of fatal crashes pr. million flights, or similar?

Accidents pr. million flights for other major airplane models: http://www.airsafe.com/events/models/rate_mod.htm

The plane was flown into the ground with a clearly visible and well-known landing error, pitching down after a bounce. That said, to blame it squarely on the pilots is premature, especially as the crew will soon be able to shed light on what happened. I've done some of the same in simulators with heavy instrument failures, although their poor/lacking damage models let you get away with it.

On the actual question, the Superjet does not yet have a meaningful safety record of any kind, good or bad. It's seen far too little use, and it only had two accidents, one of which was confirmed as a pure human error CFIT. Driving a perfectly intact plane into a mountainside is akin to driving a car off a bridge.

This leaves one accident where the plane had any faults at all, and such a small sample size is not enough to build any sort of statistics out of.

It's also difficult to distinguish cause and effect in the plane's simultaneous loss of popularity and reduction in support service levels amidst a political rift between its manufacturer's home country and most of the world, or infer anything technical from that.


What coming changes might render current IFR equipment worthless in the foreseeable future? I'm shopping for my first aircraft.  I have found a very well cared for 172 that is VFR.  I also found an IFR-certified 172 that is higher time and cosmetically is showing its age.  I inquired about the expense of updating the VFR plane to IFR and the seller mentioned that due to some upcoming changes in IFR requirements even a plane that is IFR rated today may require a substantial investment to keep it IFR.

I've done a lot of searching and can't find anything to substantiate that statement.  The closest thing I found was an article from the AOPA way back in 1997 where the FAA had proposed rule changes that would have made a lot of (then) IFR compliant GPS units non-compliant.

What, if any, regulatory changes are on the horizon that might render the IFR certified equipment I buy today worthless tomorrow in the context of IFR?

At the moment the answer is "None" - with two exceptions:

LORAN receivers
These are already worthless because the US has shut down our LORAN chains.
They are jokingly referred to as "IFR-Certified Lead Bricks".
ADFs
The FAA is killing off NDBs one by one - an ADF is basically an expensive, drag-producing AM Radio in many parts of the country, and its utility is in steady decline.

Other than that the core IFR technologies are pretty much sticking around:

VOR/LOC/ILS isn't going anywhere.
Some VORs are getting decommissioned, but even the bleakest plans call for the FAA to maintain a "minimal operational network" of VORs as a backup in the event of trouble with the GPS satellites..
DME is sticking around.
Lots of planes flying around use DME still, and there are lots of DME approaches which serve as good backups for GPS approaches.
(WAAS) GPS is the current "best technology" & isn't going away soon.
The FAA LOVES WAAS GPS. It lets them get ILS-type approaches to pretty much any runway without expensive ground equipment to install/maintain/test. If you have an IFR-Certified WAAS GPS in your aircraft you're on the cutting edge of IFR navigation equipment, even if the GPS itself is older-generation technology (such as the popular Garmin 430W).
If your GPS is not WAAS capable it's still going to be usable, but it's much more limited. It may also pose some problems for you down the road (see below).

Some equipment regulations are changing (as part of the ADS-B Out mandate coming in 2020), but that's not an IFR-specific thing.

The crux of the ADS-B Out mandate is if you want to fly in airspace where a Mode C transponder is currently required you will need two things in your aircraft (if they're not already installed):

An ADS-B Out transmitter to broadcast your position.
This can be achieved in two ways:
A Mode S transponder with Extended Squitter (1090ES); or
A 987MHz Universal Access Transceiver (UAT)
A suitably accurate position source to talk to the transmitter.
Currently that means a WAAS GPS - either a panel-mounted device or a separate "blind" box.

The cost of complying with this mandate falls somewhere within a wide range: If you want a modern WAAS GPS with a touchscreen interface that will let you fly GPS approaches and a new transponder to do the broadcasting part you're going to spend a lot more money than if you install a Universal Access Transceiver and blind GPS source that do the absolute minimum required to comply.


Can anyone identify this object? In La Réunion, people are currently searching for plane debris that could be from the MH370 crash and this morning this object was found.

Can anyone identify it?

We really shouldn't speculate, but it does not look like a panel piece for a door or window. Aside from two small warning lights on some models there shouldn't be very much.

This is very much speculation: Aside from the deep inset, which looks like it could have housed a CRT monitor, there are two holes for square aviation-style switches, and two holes, perhaps for backlighting, above it. The left hole looks very similar to an SD card slot.

Then again, it could have come from a boat or anything.


Does a pilot have to request altitude changes when receiving flight following? Let's say that during a VFR flight the pilot requests flight following from ATC, giving information about the aircraft type, type of equipment, destination and cruise altitude. ATC responds by giving a squawk and saying "maintain VFR".

In that scenario:

Does the pilot have to request an altitude change from ATC during flight following, even though the flight is under VFR?
Or, does he need to just advise ATC and start descending/climbing to another VFR altitude?
Or, is it not necessary to say anything to ATC about VFR altitude changes during flight following?

Finally, where can I find information about the regulations for flight following? I could not find anything in the FAR/AIM.

No, you wouldn't need to advise of changes if all that they instruct is "maintain VFR."

  91.123(b): "... no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised."

It would depend on the instruction received.  Let's say, after departing from class 'C' airspace, they told the pilot, "maintain VFR and resume own navigation," they are giving him freedom to choose his own headings and altitudes.

On the other hand, if the controller said, "maintain 5,500 and turn heading 030," then the pilot would need to cancel flight following or make a request to change instructions.

Bottom line: don't not do something they do tell you to do.


As a general rule, must the cg of a tandem ultralight be greater than 25% mean aerodynamic chord? As a general rule, must the cg of a tandem ultralight ( Re 500k-1,000k) be greater than 25% mean aerodynamic chord?

I understand the centre of pressure of a classic wing is at it's quarter point. It also produces a nose down moment, so that the cg and/or and horizontal tail moment need to offset this, or the plane will dive.
To provide a nose up moment, the horizontal tail must produce a tail down force.

If you want a tandem airplane, you want the exact opposite.

So the to provide a nose up moment, I would imagine you want the cg always behind the Cp ( 25% MAC) of the wing, but in front of the plane neutral point, as you want to the tail to provide an offsetting tail up force,(nose down moment)

Is this correct?

you want the cg always behind the Cp (25% MAC) of the wing, but in front of the plane's neutral point, as you want the tail to provide an offsetting tail up force

Yes, that is correct. The cg should be between the forward wing's quarter point and the common neutral point (NP) of both wings. However, if you want some agility when maneuvering the plane, it should be much closer to the neutral point. If both wings are of equal size, you definitely want the rear wing to contribute some lift. Since it flies in the downwash of the forward wing, it will see a smaller change in effective angle of attack and have a smaller lift curve slope, which already supplies some stall margin by helping to let the forward wing stall first. By shifting the cg a bit forward of the NP (10% to 25% of MAC should be sufficient), you will reduce lift on the rear wing further and increase stability.

  I understand the centre of pressure of a classic wing is at it's quarter point.

Only if the wing has a symmetric or reflex airfoil. With regular cambered airfoils the cp is further aft and moves forward to the quarter point with increasing angle of attack.


What's the name of this part of combustion chamber and what is it for? There are two "excrescences" Near the end of diffuser of some combustion chambers. e.g. CFM56 and F101
What's the name of this part of combustion chamber and what is it for?

On depictions of the CFM56 combustion chamber, that's part of the cross-section depiction of the diffuser.


Is Jetman flying above other aircraft allowed? How it is possible? According to the Times of India:

  Yves Rossy and Vincent Reffet - have achieved the rare feat of flying with the innovative Jetman wings, on either side of an Emirates A380 aircraft, the world's largest passenger aircraft, 4000 feet above sea level.

My Questions are:

Is flying near other aircraft is legal?
How they avoid getting into jet turbulence and other forces?
Is there Jetman suit available to catch up to the jet engined planes?

Yes.  This is part of a series of promotional stunts, "adverts", Emirates are undertaking.  Aircraft can fly in formation, all other rules taken into account, if the captains agree.
By flying above the aircraft.  As the article states, it was meticulously planned for safety (after all, an accident would be disatrous PR), and the Jetman flyers would know exactly where not to go.
Yes.  The video shows that!  The aircraft will likely be flying at slow speed.  As you can see, the flaps are extended.  I'm guessing about 160 kts.  I would also imagine the flyers will have dived down from above to pick up speed.


I have an idea about how to resolve a conflict between the pilots and an automated flight control system. Does it make sense? I am thinking about the 737-MAX crashes.  There is a similar question at Is it common for automated control systems to use non-redundant sensors?  There was an article in yesterday's Seattle Times In key step for potential late-November ungrounding of Boeing’s 737 MAX, FAA details minimum pilot training which references Why Boeing’s emergency directions may have failed to save 737 MAX.
My thinking is that if the pilots are applying a force to a control which is near the limit of the strength of a human being, then the control system ought to recognize that the pilot is fighting with it.  If the control system recognizes that the pilot is fighting with it, then it ought to assume that the pilot knows what he or she is doing, and let the pilot do what he or she wants to do.  There might be an indication along the lines of "Are you sure you know what you are doing?".
I order to recognize that the pilot with fighting with the system, I propose adding a strain gauge to the controls.  Normally, one should be able to fly the airplane with one hand.  If a pilot is using two hands to fly and is using large forces to do so, the strain gauge will detect that (technically, the pilot is stressing the control by applying a force, and the strain gauge is measuring the deformation of the parts the pilot is forcing), and that will tell the automatic system to "let go" and do what the pilot wants to do.
Does this sound like a good idea?  I am neither a pilot nor an aeronautical engineer.  However, I once worked as a computer programmer in a test lab and I wrote software to test strain guages.
Thank you

You actually bring up an interesting point.
The force gradients in the elevator system in a non FBW airplane are set by  some form of bungee system, like springs, that you are pulling against.  The hydraulics drive the control surfaces and there is no actual tactile feel, beyond what the feel force system imposes (think of fully hydraulic power steering in a big earth mover where there is no mechanical feedback to the steering wheel other than some form of spring centering unit).
The feel force is typically set to increase to about 50lbs at full travel, less at lower speeds and with flaps out, maybe 30lbs.  So the "two hand pull" required to get full elevator is there by design.  The force gradient is necessary to give the pilot a sense of how hard to pull and tries to approximate the forces on an airplane with mechanical controls.
You could easily design the feel force unit in the airplane to reduce the spring load to make the stick lighter for whatever purpose you want, and modern airplanes with the newer flight data recorders already have force sensors in the control linkage to provide data to the Flight Data Recorder, so the hardware is already there.
Problem is, the force gradient is needed to keep from overcontrolling, and either overstressing the airframe when above "maneuvering speed" or going into an accelerated stall when below it, from making large control inputs.
Where that kind of feature could be useful however, is during stab trim runaways, especially runaways to full nose down, and what happened in the MAX events, which was more or less similar to a ND stab runaway (the MAX's inadequate MCAS architecture got away with it by taking credit for the existing stab runaway procedure as a mitigation).
I've done those sorts of runaway scenarios in the simulator during recurrent training for the CRJs and the full nose down runaway leaves you wishing the feel force could be reduced as you have to continuously hold 20 or 30 or 40 pounds to keep the nose up.  It's very unpleasant (in the RJ, the fix was to get the flaps out one way or another, which drastically reduced the required feel force thanks to the pitching moment of the flaps reducing trim speed,  plus the feel force reduction that results from flap extension).
To implement what you suggest, you would have to have the feel force system set up to respond to an uncontrolled stab trim runaway by reducing the feel forces.  I'm not aware of anyone who has done this, and certification would probably be quite difficult (there will be many many unintended consequences that have to be ironed out, such as how to get the system to decide what a legitimate runaway is in a reliable way, and then how to get around the basic feel force requirements in a temporary way).  The certification hurdles are the likely reason this concept has never been done.


How does the location of a propeller affect an aircraft's stability? Some aircraft possess propellers on front of the fuselage, like the Cessna 172, and some aircraft have propellers located at the rear of the fuselage, like the Velocity 173RG-E.

How does the propeller's location affect the aircraft? Why don't we see back-propeller planes more often than front-propeller planes?

There is a misconception that putting the prop at the back is destabilizing in yaw/pitch, like you were pushing a car as opposed to pulling it.  That only applies if the thrust element has a flexible connection to the body it's pushing/pulling.
When rigidly connected, the thrust axis is the same at any location along the plane's length and has no effect on stability.  All that matters is how far the thrust axis is from the center of mass where it passes by.  If the thrust axis is above the center of mass, power will make it pitch down whether the prop is forward or aft, and vice versa for a low thrust line.
Beyond that, the location of the engine/prop can have inertial effects related to the mass of the engine relative to center of mass, and gyroscopic propeller effects that vary because of the different location of the precession source, and the tail pusher can actually have enhanced stability due to various aerodynamic factors like an effective fin area increase due to the extra surface area of the engine/prop aft, but the actual placement of the thrust element on the longitudinal axis is not part of it.
Engine/propellers are usually on the front because it resolves so many design compromises much more readily.  Pushers are tail heavy when unloaded, which is a big problem (tail pusher jets have to have their main gears farther aft than optimal for takeoff and landing so they don't tip back when unloaded, which requires a larger horizontal tail to provide downforce for rotation).  The prop is subjected a lot more to junk thrown up by the wheels.  Aluminum propeller blades can suffer from corrosion from carbon in the exhaust. All sorts of little problems present themselves, that go away if the engine is at the front.


In an airplane wing, which control surfaces are primary, and which ones are secondary? I got this device detail of a wing. Those parts are:

1: wingtip fence, one of the wingtip device beside winglet.
2 & 3: aileron.
4: flap track.
5 & 6: slat.
7 & 8: flap.
9 & 10: spoilers.

2 & 3, 5 & 6, 7 & 8, 9 & 10, are part of controls.

In controlling an airplane (if it really has that pairing devices), if we have to use them one after another, which one is said main (primary) and which is secondary?

Generally speaking, if a wingtip fence or a winglet is there, it's fixed and can't be moved, so there is no question of it being used before or after the others, although since it's always there I supposed you could say it's used before any of the others. I say generally because I seem to recall hearing recently of an aircraft that has a movable winglet in some manner, but that may just be my imagination.

Insofar as labeling is concerned, control surfaces that are split—an inboard and an outboard section—are usually called just that, as in the inboard ailerons and the outboard ailerons.

Different makes of aircraft may have different orders of usage in some manner, but since your image pretty much matches that of a Boeing 747-100/200 (except they have no wingtip fence or winglet), let's use them for explanation.

The inboard ailerons, are always in use. The outboard ailerons come into use when the aircraft is in slow flight (relatively speaking), in other words, when slats/flaps are deployed. It's automatic, the pilots don't have to select using the outboard ailerons specifically.

The flap tracks (what you see on the image are the "canoes" covering the actual flaps tracks) move when the flaps are deployed. The flaps will usually operate fine even if a canoe leaves the airplane in flight (happened to me once), and as I remember you're allowed to defer replacing at least one of them, but with a performance penalty.

The movement of the slats is connected to the deployment of the flaps. Any flap selection results in the inboard slats being extended. On the 747, the inboard slats extend when the flap selection handle is moved to flaps 1°. When flaps 2° is selected, the outboard slats extend.

The flaps are deployed as called for by the pilots moving the flap handle to select whatever degree of flaps they want. On the 747 there are detents at flaps up, 1°, 2°, 5°, 10°, 20°, 25°, and 30°.

The spoilers/speed brakes (whatever you want to call them—the argument still rages—are deployed by the pilots using a handle, pulling it aft deploys them, and the inboard spoilers always deploy. Whether the outboard spoilers deploy depends on aircraft speed as determined by the flap setting: no flap deployment, no outboard spoiler deployment.


Where can I find references that directly relate drag coefficient increases to passenger capacity reductions? In these notes, the authors state that:

  On the Concorde, a one count drag increase (∆CD = .0001) requires two
  passengers, out of the 90 ∼ 100 passenger capacity, be taken off the
  North Atlantic run.

and refer to this article (paywalled). I've seen other statements that an increase of one drag count is equivalent to 5-10 passengers, but do not recall the source.

Do you know of any other references that list the equivalence between drag count increases with reduced numbers of passengers?

The book "Airplane Design Part I: Preliminary Sizing of Airplanes" by Jan Roskam covers this extensively.

Nothing tabulated, mind you but the text goes into extensive detail of the equations involved for the sizing of a prospective aircraft and the relationships between the aircraft range, drag polars under various flight conditions and payload weights.

It also gives the equations for calculating the sensitivity of the change of aircraft range with drag polar and payload weight, which is essentially what your passenger is.

EDIT

Relevant section is in chapter 2 from page 74 onwards.Problem 1 on page 85 is practically custom tailored for your needs here.

Bear in mind there is no one size fits all application of a rule of thumb for this question as every aircraft will differ on account of any number of factors.


Is it a rules violation for a pilot to intentionally frighten a passenger to the point of hysterics? I saw a "viral video" inside what looks like an inline two-seater being flown from the front seat (shot from the back seat). In the video the pilot slumps over sideways against the window and throttles down, increasingly letting the nose dip, while his passenger freaks out behind him thinking he's passed out and they're going to crash. Eventually the pilot throttles back up and levels off, then turns and smiles at his passenger, having played a trick on him.

The video is almost certainly staged (given how steadily the supposedly-hysterical passenger holds the phone taking the video), but it made me think: Given the unpredictability of people when faced with a life-threatening situation, if it were real, would the pilot in question be breaking a rule and/or law by inciting hysteria in that way? (As opposed to just acting like a massive [expletive deleted].)

Dave, whose eyes are clearly better than mine, says the plane is at about 2,900ft when the pilot starts his little trick and 2,400ft by the end of it, briefly exceeding 1000fpm descent. In addition to my main question, I'm curious whether that's a factor in whether it was a violation; goofing around at low(ish) altitude seems like a Bad Idea™. But the altitude is a side thing (particularly as they were clearly much higher than I originally thought), I'm primarily interested in intentionally inducing hysteria in a passenger.

I suppose we have to choose a locale, so let's say in the U.S.

There's no regulation that I can see that says "don't frighten your passengers". And there probably shouldn't be: almost anything could frighten a nervous person who isn't familiar with aircraft, even if the maneuver (or whatever) is completely normal.

Having said that, if the FAA thinks you've done something stupid then they do have a 'catch-all' regulation that they could argue you violated.

14 CFR 91.13

  No person may operate an aircraft in a careless or reckless manner so
  as to endanger the life or property of another

I haven't watched the video but I think it's at least plausible that the FAA could say that there was a real risk that the panicked passenger would take the controls and try to fly the aircraft themselves. In a dive, pulling up suddenly could easily stall the aircraft and stall recovery is not intuitive or obvious to a non-pilot. In the worst case, pulling up suddenly from a dive can actually tear the wings off. So it would be very easy for the passenger to damage or destroy the aircraft and potentially fly into people or property on the ground.

Finally, apart from the aviation regulations, it might be possible for the passenger to sue the pilot for causing stress and emotional damage. You could always ask on law.SE about that.


What are the consequences of turboclair system on restriction due to turbulences? A turboclair system basically consisted of jet engines used to warm the air around the runway and dissipate the fog. I understand that better visibility due to less fog allows less-well-equipped aircraft to land safely, but such an artificial temperature elevation may create strong turbulence (due to convection) and, thus, restrict the types of aircraft than can land safely (e.g., only heavier aircraft, which could be less affected by localised turbulence).

(I imagine that, nowadays, ILS is more effective than a fog removal system in bringing an aircraft safely to the runway.)

My question is: Because of probable turbulence due to this system, do operations into runways using a turboclair system come with additional restrictions compared to the same runway without fog?

I found a Turboclair addon checklist for the SE.2 Caravelle landing procedure and it says nothing about turbulence.  This procedure is intended for ferry flights without passengers and specifies the use of a braking parachute, so it is not for normal flights. It is possible that this was the checklist used during 1968-69 testing of the system before general approval and that a turbulence warning or restriction was added later, but it seems likely that any severe turbulence problem would have been recognized very early.

There are standard weather checks at the destination. There is evidently a Turboclair specific approach that must be requested and the pilot must announce arrival at outer marker, at 400ft, that he has landed and again when he has cleared the runway. He is to continue the use of instruments when on the ground due to poor visibility.

Initial testing in 1961 was conducted using modified De Haviland SE 252 jet aircraft as heaters, which could be re-positioned to find most effective locations.

Under construction from 1970 to 1974, the system's jet engines were permanently installed in underground pits. The reference shows the installation on Orly runway 07, remnants of which can still be seen in Google maps which now shows the runway as 06.

The system was also installed at Charles DeGaulle airport. It was used for fewer than 1000 landings between the two airports before being decommissioned in 1982.


Can a turbofan have a fan driven electrically so as to run at optimal speed? I just watched this pretty dumbed-down video about the idea of putting a gearbox in a turbofan so the fan can run at its optimum slower speed while the core runs at its optimum high speed.

And I immediately remembered this answer from Peter Kampf that said basically, a normal gearbox would have huge waste heat.

Then I suddenly remembered an old question of mine about driving a helicopter engine with a diesel-electric system.

So now the obvious 2-and-2 together: Can the fan of a turbofan be driven with an electric motor (powered by the already-existing generator of the engine)? Or the more detailed questions: Can an electric motor be small enough to fit around the fan's axle and still power the fan? How much it would weigh? I'm interested in large turbofans on the orders of 100 to 500 kN, but I think that would make the task easier since there's more room plus weight increases have diminishing returns against a huge airliner.

This would have obvious advantages. The fan:core ratio can be variable without any gearing. Presumably much less maintenance, or at least no more maintenance than the generator requires.

There are plans to run a turbofan-like engine with an electric motor rather than the gas generator used today. But the weight of electric engines does not promise an immediate advantage - only when the electricity is generated in a much more efficient way that what today's gas generators offer will the overall propulsion mass be lower. An example is a hydrogen-powered fuel cell somewhere in the fuselage.

We had a similar discussion here and here.


How big is the influence of color on the stability of the boundary layer? I'm not sure if this is the best place, or physics.SE would a better place. I guess the aerospace engineers might be on both.

In class we were talking about stability of the boundary layer, and the influence of the temperature on the boundary layer.

The governing equation is given by Wiki boundary layer:

$$ u{\partial u \over \partial x}+\upsilon{\partial u \over \partial y}=-{1\over \rho} {\partial p \over \partial x}+{\nu}{\partial^2 u\over \partial y^2} $$

If we evaluate this $y=0$, where both $u$ and $v$ are zero:

$${1\over \rho} {\partial p \over \partial x}={\nu}{\partial^2 u\over \partial y^2} $$

We then deduced that, since $\nu=f(T)$, the instabilitiy of a boundary layer is thus a function of the temperature.

One of us mentioned that this was the reason that the Pepsi-livery Concorde had a lower maximum operating speed, since it is not white, but blue:
This would increase the temperature at the wing, making the boundary layer less stable.

I did so a search, which brought me to this Concorde SST website, which says that the wings were kept white, to reduce the temperature of the wing, but because of the fuel temperature. As the wings are white, the effects we were talking about are not relevant anymore, but still it made me wonder.

Could the color of a surface have so much influence on the stability of the boundary layer?

Technically, yes. Practically, no.

Boundary layer stability

You are right that boundary layer stability depends on viscosity, but it depends much more on the pressure gradient. Accelerating flow exhibits extreme stability: Even if there is movement orthogonal to the flow direction (due to Tollmien-Schlichting waves), their speed becomes an ever smaller fraction of flow speed in accelerating flow. This kind of flow is always found right after the stagnation point, when the suction area over the mid section of the wing accelerates flow into it.

Conversely, decelerating flow has lower stability: Now any crossflow becomes relatively stronger simply because flow speed is decreasing. This kind of flow is found aft of the suction peak, when the flow has to manage the long and arduous pressure rise to the trailing edge. It does not take long, and transition into turbulent flow happens.

On the Concorde at high angle of attack, lift was created by a strong vortex. The boundary layer became turbulent right after the leading edge.

In cruise, the flow would hit the leading edge at a small angle, so the speed distribution over the wing was less peaky. The long chord length and high flow speed would still cause an early transition, however, so most of the wing had turbulent flow. Indeed, cooling the wing would lengthen the laminar portion, and heating would shorten it, but the difference in friction drag would be small when looking at the full picture.

Air temperature over the wing

In supersonic flow you always have both a temperature boundary layer and a viscous boundary layer. Air is heated when compressed and cools when it expands, and in supersonic flow these effects become too large to be ignored. Also, friction in the boundary layer heats up the air near the wing's surface.

The stagnation temperature increase at Mach 2 is 173°C. The leading edge temperature can be expected to be around 120°C (standard atmosphere air temperature being at -56°C in FL 600). Past the stagnation point, the flow accelerates into a suction field in which air temperature drops below its ambient value. At the bottom of the boundary layer, however, the temperature stays almost as high as at the stagnation point due to frictional heating. In a turbulent boundary layer on a flat plate the frictional effect would increase temperature by 152°C. Without the pressure distribution over the wing I cannot give a value for the absolute temperature, though.

Due to heat transfer with the wing, the air is cooled over much of the wing in the vicinity of the wing's surface. A dark coating will add a few degrees and result in a higher equilibrium temperature over much of the wing. A hotter boundary layer is thicker due to the expansion of air with temperature and will have higher viscosity. The most simple explanation why viscosity increases with temperature is that the mean molecular velocities, which are directly related to temperature, facilitate more transfer of shear forces between molecules. However, when it comes to wall friction, the effect of lower density with temperature outweighs the increase in viscosity, and wall friction is lower in a hotter boundary layer.

Thus, a heated boundary layer shows earlier transition and lower friction drag. The dark paint should actually help to lower the friction losses, and since the influence of temperature on the transition point is small, the change in friction due to lower density at the wall should dominate.

Maximum wing temperature

The maximum speed of the Concorde was limited by the stagnation temperature of air. If we assume that a switch from white to dark blue paint increases the equilibrium temperature of the wing leading edge by 10°C (which is not unreasonable), this increase could be compensated by a reduction of the maximum flight Mach number from 2.0 to 1.94. A restriction of the Pepsi Concorde to Mach 1.7 seems to me to be the result of extreme (and unreasonable) caution.

My verdict

I did not run the numbers, but I would expect that a different paint job would not change wing temperature much. At the leading edge and over much of the wing it adds a little to aerodynamic heating. A warmer wing would translate into less friction, but the difference is extremely small.

On the ground, in the absence of the strong convective heat transfer during supersonic flight, the temperature difference between white and dark wings is much more pronounced (in the order of 30°C to 50°C), and in this case a white wing is very effective in keeping the fuel temperature down and avoiding gas bubbles in the fuel line.


Is there any evidence that the downwash vortices impact the performance of a wing? Or is it merely flow separation on the upper surface towards the end of the wing? The assumption seems to be that the air "leaks" from under the wing to low pressure above with sufficient rapidity to overcome or offset the forward flight speed.

You've correctly called them downwash vortices. They are caused by the air behind the wing—over all of its span—moving downward, while the air outside the span does not, which creates a pair of vortices that move downward at half the speed of the downwash (and somewhat slower later as there is more air below them in their way).

The air moves down behind the wing because the lift is an upward force acting on the wing, so the corresponding reaction force is downward and acts on the air, which, being free to move, accelerates downward.

This acceleration of air, however, requires energy (because its kinetic energy increases), and because energy is conserved, work has to be done to provide it. This work is done by induced drag.

There are several other ways to show, from basic laws of physics, that induced drag is a necessary consequence of producing aerodynamic lift that is proportional to the amount of lift and inversely proportional to wing span and dynamic pressure  (that is density and square of speed). If the span-wise distribution of lift is suboptimal, it will increase the induced drag, but there is a known minimum for optimal, elliptic, distribution, and it is well known it can't be reduced below that.


How short does a trip need to be before flying is less safe than other forms of transportation? It's often mentioned that flying is the safest form of transportation, and no doubt this is true when considering only a long-haul trip. There's no doubt, for example, that driving (or taking a train or bus) 3,000km would be more dangerous than flying the same distance.

However, most flight crashes occur at take-off or landing and so I suspect there must be a break-even point after which flying becomes more dangerous than alternatives. For instance, if a flight is only 300km, would it be safer to drive?

For the purposes of this question, it can be assumed that I'm talking about OECD countries, which by and large have very high standards for both flight safety and the safety of other forms of transportation.

Note: This does not take travel to/from the airport into account.

The Wikipedia page on aviation safety has a nice table with deaths per journey, time and distance (based on data from the UK between 1990 and 2000):

Car: 40 deaths per billion journeys, 3.1 deaths per billion km
Aircraft: 117 deaths per billion journeys, 0.05 deaths per billion km

Assuming that car accidents are equally distributed along a journey, we only need to consider the 3.1 deaths per billion km. Further assuming that all aircraft accidents are related to takeoff and landing (i.e. once per journey), we only consider the 117 deaths per billion journeys. While the first assumption is probably reasonable (there are differences between types of road though), the second one is not quite true since aircraft can also develop problems during cruise.

With these basic assumptions, we can calculate when the expected number of deaths are equal:

$$ N_\text{death} = 117 \cdot 10^{-9} = 3.1 \times \frac{d}{10^9 \, \text{km}} \; \Leftrightarrow \; d = \frac{117}{3.1} \, \text{km} \approx 38 \, \text{km} $$

So any flight longer than 38km is safer than driving the same distance.

Let us now try to take the cruise part for aircraft into account. According to this page 20% of all fatalities are due to accidents during cruise. We can subtract 20% from the 117 deaths per billion journeys (so this only takes the parts of the flight into account that happen once per journey). Modifying the 0.05 deaths per billion km is not so straight forward. Since most of the distance is traveled in cruise, I am going to be conservative and just leave this number unchanged, therefore providing an upper limit on the deaths per km.

Now, we can make a more accurate comparison:

$$ N_\text{death} = 0.8 \times 117 \cdot 10^{-9} + 0.05 \times \frac{d}{10^9 \, \text{km}} = 3.1 \times \frac{d}{10^9 \, \text{km}} $$
$$ \Leftrightarrow \; d = \frac{0.8 \times 117}{3.1 - 0.05} \, \text{km} \approx 31 \, \text{km} $$

This is actually lower now, because the deaths during cruise are irrelevant for such a short flight. And this gives the final answer: Flights longer than 31km are safer by airplane than driving the same distance by car.


Why were the ailerons of the Fokker Dr. I (Red Baron) located on the top wing? Photos' source are here: Fokker Dr. I (Red Baron), and here: a Sopwith triplane. They are probably not the actual airplane but only (claimed) authentic models.

It makes sense to me that the Sopwith had ailerons on all three wings. But the Dr. I only had them on the top wing.

My question is, what is the aerodynamic explanation of this design? Why not have ailerons on the middle and on the bottom wing? Which design is better?

The top wing is always the most efficient, as the lower ones suffer reduced lift due to interference from the air flowing beneath the one above. Ailerons will therefore be most effective on the top wing. If they do the job OK then there is no need for any more.
Reasons for adding more below include:

The upper set are likely to be (or found to be) inadequate.
Making both wings identical to simplify production.

The outermost part of the wing is also the most effective position. So if a short aileron is inadequate then the designer faces a choice of two less efficient additions, to widen it inboard or to place another one underneath. Another issue is which brings more drag or weight penalties, a small aileron which must be sharply deflected or a larger aileron which needs more subtle movement.

Such decisions were often based on the designer's personal experience and preference rather than firm knowledge. They would stick with what they knew rather than take arbitrary risks. Historically the Sopwith came first, following their earlier successful biplanes such as the 1 1/2 Strutter and Pup in having identical upper and lower wings with short ailerons. Fokker responded in his own equally successful house style, with a single aileron on the top wing only, having a long span and outboard balance tab.

Which design is better depends on how you define "better" - less weight, less drag during turns, less cost, optimal distribution of aerodynamic forces through the structure? The basic technical tradeoff is between a single large and strong upper aileron vs. several smaller and lightly-built lower ones. I doubt if anybody has ever crunched realistic numbers.


Why is it called "STBY RUD" on a Boeing 737? (Source: b737.org.uk)

Anyone knows why "STBY RUD" is named "STBY RUD" when the selection of the switch position activates the standby hydraulic system as well as the standby rudder system (by opening  rudder shutoff valve)? Is it because the standby rudder is more important than the standby hydraulic system as a standby system?

According to the Boeing 737 Flight Crew Operation Manual, the "Standby Hydraulic System" only powers the following:

thrust reversers
rudder
leading edge flaps and slats (extend only)
standby yaw damper

It does not power, for example, brakes, ailerons, spoilers and the landing gear.

I speculate that the word is chosen to remind pilots that the system powers the rudder but not other primary flight controls.


How to estimate the altitude of an aircraft at a given distance from a runway? What altitude should a heavy class commercial freighter be at on a descent path 17 nautical miles from a runway? (Say SDF airport)

Straight in, on glidepath, about 6000' above the runway. Straight-in & fast, below glidepath at 3000 to 4000 feet above the runway.

That's based on about 3 miles per thousand feet is a standard glidepath, and it takes in the ballpark of 5 miles at idle power & level flight to slow from 250 knots to a configuration for starting down the glideslope.

Those are ballpark numbers; a heavy aircraft slows less rapidly than a lightweight one does, headwinds can shorten those distances, while a tailwind at altitude can extend them. And there are techniques to slow a little faster than that, and you can leave the power in & slow down over a (much) longer distance if desired.

But for ballpark values, those are good approximations.


"Airplane mode" does not disable GPS... is it safe to use GPS in flight? I noticed that even when my phone is in "airplane mode", I can still use the GPS.

Theoretically a GPS receiver just receives data, so I guess it would not jam anything.

On the contrary, on the iPhone airplane mode disables GPS, so it means that at least a few engineers at Apple are worried about people using GPS in flight.

Is it really OK to use my phone's GPS in plane, as a passenger of a typical commercial flight?
(when use of electronic device in airplane mode is allowed, obviously)

theoretically? GPS IS receive only. There's no way to talk to the GPS satellite network except using the big antennas of the network owners (the US DoD) and the communications are no doubt heavily encrypted.

Now, does that mean it's "safe" for aircraft electronics. Any receiving antenna does have an EM field around it, so if you believe the myth that those electronics are so sensitive and easy to jam that any EM field at all causes them to malfunction the answer is an obvious NO.
But that myth is just that, a myth. If they were so sensitive, that old walkman you were using in the 1980s during flights would have brought down that aircraft. Because not only do antennas have EM fields around them, any electrical device that's turned on has one (in fact any electrical cable with a current flowing through it has one, including the headphone cord for the in flight entertainment system).
And that GPS system in your cellphone uses a lot less power than that walkman, has a far weaker field surrounding it.

Of course it's theoretically possible that a strong enough EM field might interfere with the electronics in an aircraft, but then to you'd need just the right signal. Which would indicate you need intent (or incredible bad luck)!

Effectively the GPS in your cellphone is a lower powered version of the GPS receiver in the belly of the aircraft, which has its own antenna (which no doubt has a similar field around it, but of higher strength).


Is it bad form to call "ready to depart" when you know you won't be cleared yet? My local aerodrome is towered and has parallel hard and grass runways. Simultaneous parallel departures or landings are not normally allowed. On one occasion we had been instructed to "line up and wait" on the grass runway. While I was performing the pre-take-off checks, an arriving aircraft was cleared for touch-and-go on the main runway. I observed it on short final as I completed my checks, and called "ready to depart", even though I knew that we would not be granted take-off clearance until it was well into its climb-out.

My instructor later told me that asking for clearance when you know you can't have it yet is bad form, and that he would have told me not to, if he had seen the traffic (which had been in his blind spot). I can see how it could seem like impatience or poor situational awareness, but it seemed to me like it helps the controller by letting them know they can get me off the runway as soon as they're able. Additionally, I've been taught that in other situations it's good to get a call in as soon as I can and there is clear air (such as downwind and final calls).

I'd like to get some clarification on this. Is it bad form? Why: for one of the reasons I suggested, or because of some other reason? What other situations does this generalise to?

Informing the controller that you are ready to depart and requesting a takeoff clearance aren't the same thing.

It isn't bad form to inform the controller when you're ready for the next phase; if the controller isn't ready yet, you won't receive a takeoff clearance, but the good news is that now the controller is ready to get you going as soon as possible since your intentions have been declared, and she also has some time to think about what will happen next.

It opens up time for the controller to plan and coordinate.

Situation A:  You wait until the landing traffic is clear of the runway before you state that you're ready for departure, and then the tower clears you; you takeoff.

In this situation, the tower had a short time to react to your request and possibly plan other traffic around you.

Situation B:  You state that you're ready for departure, the tower acknowledges and requests for you to hold short for landing traffic. The traffic lands, and then, the tower clears you; you takeoff.

In this situation, the tower could have altered other inbound traffic to provider a bigger safety buffer for you due to the increased time given to asses the current traffic conditions at the airport.


Are there any photos or videos of the drones at Gatwick? The Gatwick Airport drone incident from 19-21 December 2018 involved "67 reports of drone sightings close to the runway" (Wikipedia).

However, police stated there were no photos or videos of the drone (The Guardian, 23 Dec.).  Later, police said that statement had been the result of "poor communication" (The Guardian, 24 Dec.).

Regardless, I haven't found any photos or videos of the drones.  Are there any?  If not, why not?  Were they too small (or far away) to be seen by a cellphone camera?  But then how could humans see them?  How can 67 people see a drone in this day and age and none of them record it?  Is it plausible that there actually were no drones?

It is very likely that there were no drones, and this was a case of mass hysteria.

One actual crashed drone was discovered during the search, but that could very likely have been a hobbyist drone that got away, days, perhaps weeks earlier.  Lost toy drones happen all the time (even though it shouldn't happen near a major airport, it does...)

https://www.secretflying.com/posts/police-admit-it-is-a-possibility-there-was-never-a-drone-at-gatwick-airport/


How is risk managed in single engined piston aircraft flights? I have already read this post:  How dangerous is flying in a single-engine plane?

Recently as reported in the NTSB accident database, a pilot of a light aircraft encountered engine failure after take off. The pilot found no suitable area for performing and emergecny landing and deployed the aircraft parachute, escaping with some injuries.

It appears that some phases of flight of a piston single, there are sections of the flight for which safe recovery from an engine failure is not possible due to the lack of reachable emergency landing areas.

For example, after take off, the aircraft may be in a position that a safe landing and stop cannot be made with remaining runway. After take off, the pilot may encounter a heavily wooded or built up area, but a few minutes later may cross a highway or an empty field. In any case, his chances for safe landing keep changing throughout the flight, going from high to low to medium and so on.

Is it correct to say that this risk has to be taken, cannot be avoided?
Is it possible to reduce this risk with either better pre-flight checks and through purely technological means? Suppose I am taking flight instruction can I do anything to reduce the risk of engine failure?

"A ship in harbor is safe, but that is not what ships are built for."

You said in your question:

  It appears that some phases of flight of a piston single, there are sections of the flight for which safe recovery from an engine failure is not possible due to the lack of reachable emergency landing areas.

This is true not only of piston singles, but also of anything that flies out of gliding distance of good landing sites - think about Amelia Earhart's Lockheed Electra.

You'll usually hear this called "inherent risk", but the correct term for the concept that you're describing is systemic risk. As you suggested in your question, this risk has to be taken, it cannot be eliminated.  The only way to eliminate it is to not fly; and sometimes, when the risk of the flight becomes too great, that's exactly the decision that a pilot has to make.

  Is it possible to reduce this risk with either better pre-flight
  checks and through purely technological means?

Yes, as long as you're willing to pay for it. Everything in aviation is a tradeoff, and it's usually a trade either between safety and cost or safety and weight. As an exaggerated example, you could build a piston single with 30mm armor plating to mitigate the risk of incoming artillery fire, but it wouldn't fly very well and not many piston singles routinely take artillery fire anyway.

Those safety improvements which are simple and economical to make, we've already made mandatory (for example, all IFR aircraft certified in the USA need to have an alternate source of power for their artificial horizon if the primary source of power is electric).  Safety improvements which aren't simple or economical are left to the discretion of the owner of the aircraft.

  Suppose I am taking flight instruction can I do anything to reduce the risk of engine failure?

Sure is.

Pay attention to your instructor and do what she tells you.  You can't prevent an engine failing because an oil pump blows out.  You can prevent the engine failing because you ran the fuel tanks dry.
Fly well-maintained aircraft. Talk to the mechanics who work on your airplane. Do what they say.  Avoid operators who let maintenance slide.  If you're the owner, don't let maintenance slide.
Fly aircraft that fly a lot. The worst thing for an aircraft engine is to sit in the hangar for three months, fly for an hour, and then go back into the hangar for three more months.  The more that engine gets used, the happier it is.
Have a contingency plan. For example, examine the area at the departure end of the runway and make a plan of where you would land in the event of an engine failure at any point before a turnback would be feasible. - Thanks Jonathan Walters!
If you do go down in a field, have a 24-hour survival/medical kit on board, and wear clothes suitable for the climate. Rescue doesn't get there instantly. Speaking of rescue, you did file a flight plan, didn't you?


Which engine(s) do airliners taxi with? I  have read that pilots only taxi on 1 engine to save fuel.  Which engine does a twin engine jet such as a 737, 777, a320 or similar use to taxi? Left or right, or does it vary by pilot or some other factor?

On 4 engine jets such as a 747 or a380 pilots use 2 engines. I assume its a matching pair, inner or outer.  But again, which pair?

In my experience it is not "common" for air carrier aircraft to taxi with an engine shut down.  It does happen of course, but there is generally a specific reason behind that procedure if used.

Reasons may be:

Fuel load is close to the minimum required for the flight at the start of taxi (a variety of reasons for this).
Long line up on the taxiway awaiting takeoff clearance.
Captain discretion to save fuel.

For most Air Carriers, the engines are started using air pressure from an APU (auxiliary power unit) affixed to the fuselage (at the tail of the aircraft). The start procedures are initiated while the aircraft is being pushed back from the gate by a tug.  Shortly after the aircraft is pushed back and generally aligned for taxi both engines (twin engine aircraft in this example) have been started and an "after start" (or similar) checklist has been completed. Besides the engine noise, which is sometimes quite low and hard to hear, the end of the start procedure can be noticed when the lights blink in the cabin as the electrical power generated by the APU is being replaced by the engine driven generators.  Also, there is generally an increased airflow into the cabin as air from the engines is vented to the cabin by the air conditioning system.  Very little air is available during engine start from the APU because the air is being used to start the engines.

Anyway, this is probably a more expansive explanation than necessary for your question (I just wanted to give some context to the process of engine start for air carrier jet aircraft).

If the aircraft is taxied out using a single engine, the crew can either start the remaining engine at some point prior to takeoff using the APU (if left operating) or by cross-bleeding the engine air from the running engine to the engine now being started.

If the aircraft is taxied with one of its engines not started at the gate, the crew has to run an additional checklist during the taxi as and after the engine is started.  Not a big deal, but a bit more workload.

Lastly, there have been occasions where problems have resulted from taxiing with one of the engines not started.  For example, many years ago a B727 (3 engine aircraft) started its takeoff roll with only two engines running because the crew failed to start the third engine.  It crashed on takeoff.  Also, there have been occasions where the aircraft was not configured properly for take off (e.g., engine bleed switches in the wrong position) due to a failure to properly follow/run the appropriate checklist for starting an engine during taxi or configuring the bleed/pressurization system properly for take off.

Again, taxiing with an engine not yet started does happen. But considering how many flights occur every day in the world it would be difficult to say this procedure would be anything close to common.

Just my two-cents


How does a long inlet affect a jet engine's performance? How, for example, would the long inlet of the tail-engine on an MD-11 or an L-1011 affect its thrust production/performance, if at all?

(Source)

I am not well versed in fluid dynamics, so any insight on this would be helpful. I wouldn't be surprised if the effect of the aforementioned distance is negligible, as the airflow would not seem to be disrupted. Nonetheless, this piques my curiosity.

Long, winding intake ducts can increase the drag on the airflow moving through them, reducing the amount of air which the engine can ingest as opposed to a traditional diffuser design on a nacelle.  Aircraft like the Harrier as well as the F-22, F-35 and F-117 have solved this problem with the use of large, suck in doors along the length of the intake duct in order to provide additional air mass flow during low speed or ground operations, where ram pressure cannot provide the additional airflow through the fan or engine core.


Is ADS-B intended to replace other traffic management systems? What is the main purpose of ADS-B? How do aircrafts interact with each other using them?

Is it intended to replace the Traffic Collision Avoidance System (TCAS) or ground based Air Traffic Control (ATC)?

Also, why they need the Global Navigation Satellite System (GNSS)? Are there other systems that has a dependency relationship with ADS-B?

For a short introduction on what ADS-B is and why it is called dependent see this answer.

ADS-B is a surveillance technology whereby the aircraft broadcasts information about its identity, position, altitude and velocity of the aircraft to any interesting party. The position and velocity information is derived from GNSS (GPS).

TCAS

ADS-B is not intended to replace TCAS, although in the future it will augment TCAS. The TCAS algorithm currently only uses distance and altitude to calculate whether there is a conflict and to determine the best conflict resolution strategy. With the more accurate ADS-B position available to the system as well, the number of TCAS interrogation can be reduced (the surveillance radio frequencies are getting congested in some areas) and the performance of TCAS can be improved. A new standard for this hybrid approach was published in 2013.

It may also be possible to have a passive TCAS-like system that does not require active interrogation but is purely depending on ADS-B. Currently a technical standard for a new Airborne Collision Avoidance System (ACAS, the generic name for TCAS) is being developed in a joint RTCA / EUROCAE committee (RTCA SC-147 / EUROCAE WG-75), which will take advantage of more data offered by ADS-B. This new standard will eventually replace TCAS II.

A 'TCAS light' for small aviation has also been developed based on ADS-B. It is called  Traffic Situation Awareness with Alerts (TSAA), a standard that was published last year. Within the next couple of years we will see manufacturers start offering products based on this standard.

ATC

The purpose of ADS-B is neither to replace ground based ATC. But it will change the way ATC is done. ADS-B IN will improve the situation awareness of pilots; they will have a display of accurate positions of other aircraft. New procedures will allow pilots to maintain visual separation to other aircraft in marginal Visual Meteorological Conditions (VMC), where they currently would often lose sight of other traffic. A more advanced usage of ADS-B will be flight deck based interval management (FIM) where ATC will be able to instruct aircraft to 'follow that plane XX seconds behind for landing on runway YY'. A first technical standard for FIM is being worked on, it is intended to be published before the end of this year.

ADS-B is neither a replacement for all radars, although it will allow the number of radars to be reduced. For remote areas that currently do not have radar coverage because of the associated high costs, ADS-B will be a cost effective alternative. Over the oceans, satellite ADS-B receivers will be able to provide surveillance, changing the way ATC is performed over the high seas.

GNSS

Given the examples above, it is easy to understand the requirements on the reliability of ADS-B are substantial. Not only must the system be able to deliver accurate position data, it must be able to deliver that data with high integrity. That means, the probability that the system transmits inaccurate position data, even when there is a failure in the system, must be extremely small. To achieve this, a positioning systems must be able to do internal cross checks to detect failures and not depend on possible erroneous inputs from humans. GPS can meet the position source requirements using Receiver Autonomous Integrity Monitoring (RAIM).

The ADS-B technical specifications have all been written in such a way that they do not explicitly require GNSS to be the position source, but at the moment it is the only system that meets the requirement effectively. Most certification documents are written with the assumption that a GNSS will be used to provide position data. Theoretically one could put another system forward, but the costs of certifying that would be very high.


How to convert a PPL (Gyrocopter) to a PPL (Helicopter)? If I have a Private Pilot License (PPL) for gyrocopters, and I want to convert it to PPL for helicopters, are my flight hours in the gyrocopter considered for me as flight hours in helicopters?

In the US, Gyroplane and Helicopter are class ratings within the Rotorcraft category. FAR 61.63(c) specifies that the addition of a class rating does not require any specific amount of flight training time, and no more total experience than would be required for the gyroplane rating you already have, so the question is moot. All you need is an instructor willing to sign you off and to pass the abbreviated practical test.


What security clearances does a foreign citizen doing a flying course in the United States have to pass? I remember reading that the security for foreigners doing a flying license in the United States were rigorous (as would be expected). As a European Union citizen, what would I expect to need to do from a paperwork/legal standpoint (FAA, CBP etc.) to be allowed to pursue a private licence in the USA, assuming I have no previous flying experience?

You need 2 things before you can start flight training in the U.S.:

An appropriate visa. A tourist visa (B2), business visa (B1) or VWP (Visa Waiver Program) is not accepted
TSA clearance through the Alien Flight Student Program (AFSP)

The complete process is documented at the AOPA website.

In a nutshell, this is what you need to do:

Make sure you have a proper visa or permanent resident card (green card). A visa that allows you to live in the U.S. is fine (you don't need a specific visa for flight training). Examples of appropriate visas: H1B, H4, L1, L2 but there are many others
If you don't have one of the visas mentioned above, you need to apply for a student visa (M-1). You need to contact a flight school that will assist you with the visa application.
Contact a flight school if you haven't already done so in the previous step. They will register your "case" and provide you with information you need when applying for TSA clearance.
Apply for the AFSP program on the TSA website
Wait for approval by the TSA (is a multistep process that could take a while. It includes having your fingerprints scanned, among other things)
Start your training


How does one learn to sky write? It seems like skywriting would be pretty difficult to learn, since there doesn't seem to be any way to step back and see if you made a mistake. And yet people have been doing it since the early days of flying.

So here is my question: how does one go about learning to sky write, and are there any tools to make it easier (a ground mounted webcam with a panel mounted display was an idea that came to mind, have no idea how feasible that is)?

Try reading this article from businessweek.  It's going to give you an answer, but you're probably not going to like it.  Here a quote:

  “It requires an incredible level of precision flying,” Oliver says. “There are so many factors. Where’s the sun, which way is the wind blowing, where’s your crowd? You only learn that over time, after doing it enough. And you can’t go practice when skywriting fluid is 10 [dollars] a gallon and gasoline is 7 [dollars] a gallon.”
  It’s also difficult to learn the craft of skywriting when nobody is willing to teach it. Oliver and Asbury-Oliver won’t share any of their secrets. In fact, while Asbury-Oliver was employed by Pepsi, she was contractually forbidden from discussing her skywriting techniques with anybody, including friends, colleagues, and journalists. “In the ’30s and ’40s, there were a lot of skywriters trying to make a living,” she says. “So they shared nothing. They wouldn’t tell each other what kind of fluid they used to make the letters, what kind of exhaust pump they used. Everything was top secret.” While an air of secrecy might’ve made sense a century ago, why do they continue to be clandestine, despite their competition being essentially nonexistent? “We’re old enough and we’ve been around long enough that we’re both traditionalists,” says Oliver.


How are maps loaded in UAVs? My question intends to find out how maps are downloaded/buffered at Ground Control Station's for UAV operations. I understand GPS transmitters relay the exact location of an aircraft on a map. However, the map needs to be loaded/buffered in real time as the UAV covers ground.

For a UAV as large as the RQ-4 Global Hawk, with a range of 14000 kms, how is the map loaded in real time?

On the other hand, for amateur or small scale UAVs/MAVs, is the map updated in real time as the aircraft/rotorcraft covers more ground? Or is that the map is downloaded pre-flight, based on the range of the aircraft? This would be preferable in terrains with poor or no signal connectivity.

You seem to assume the maps are being transmitted from the UAV.
They are almost certainly not (and if they are that's a poorly engineered system and I would be embarrassed that my government wasted my tax dollars on such a lousy design).

Maps are relatively static data, so it would be logical to store them on the computers at the ground control station (where you could have the entire world's terrain and likely aeronautical charts/airspace boundaries on your hard drive, along with current weather data and other useful information).

Moving the map to keep up with the position being relayed from the UAV is computationally trivial: iPads do it for real aircraft (ForeFlight & similar products) and your car's GPS system does it when you drive - neither system is as powerful as the typical desktop computer.

All the UAV would relay to the ground station is its position (and any other pertinent data dictated by its mission, such as photos/video). This arrangement minimizes the bandwidth required to control the vehicle, as well as its RF signature (less stuff to transmit back to base).

For autonomous UAVs, particularly ones which have to avoid airspace incursions, some subset of airspace data appropriate to the route of flight may be loaded on the vehicle, but I wouldn't call these "maps" - it's a much more compact representation of coordinates marking boundaries in 3D space (similar to the Jeppesen NavData products - possibly even using those products) . Such vehicles may also have terrain data loaded before flight if they lack other means to avoid collisions with terrain while operating autonomously.

  Disclaimer: I have no experience with the RQ4 or any other military UAVs - this is just a common-sense engineering assessment.


Can large aircraft go VFR? Is it legal for large, multi-crew, aircraft (such as the A380 or B747) to go VFR? I would guess it's legal just as any other aircraft. Is this ever done, like during training or test-flights? If it isn't legal, what's the limiting factor?

I'm talking real VFR from take-off to landing, not an VFR-on-top IFR clearance.

As I don't have a spare 747 sitting around waiting for me to take it out for an afternoon spin, I'm interested more in the general sense, is it legal anywhere, and are airlines taking advantage of it?

The FAA treats large airplanes the same as any other airplane when it comes to VFR flight.  They are required to maintain the same distance from clouds, only fly with the same minimum visibility, see and avoid other aircraft, etc.

However, since only IFR flights are allowed above FL180 (without a special exemption), and large turbine airplanes are terribly inefficient at low altitudes, so it doesn't happen very often.

In the US, Part 121 flights have the most restrictions of any of the operating rules, and they have multiple regulations relating to VFR flight, including this one1:

  14 CFR 121.611 Dispatch or flight release under VFR.

  No person may dispatch or release an aircraft for VFR operation unless the ceiling and visibility en route, as indicated by available
  weather reports or forecasts, or any combination thereof, are and will
  remain at or above applicable VFR minimums until the aircraft arrives
  at the airport or airports specified in the dispatch or flight
  release.

So yes, even if it is operated by a 121 carrier, they are allowed to fly VFR by the regulations.  However, they must also comply with their Operations Specifications and Flight Operations Manuals which will have detailed procedures covering the conditions where it is allowed.

Outside of 121 there are even fewer restrictions on VFR flight.

1 There is also:

§121.347 - Communication and navigation equipment for operations under VFR over routes navigated by pilotage.
§121.349 - Communication and navigation equipment for operations under VFR over routes not navigated by pilotage or for operations under IFR or over the top.
§121.649 - Takeoff and landing weather minimums: VFR: Domestic operations.
§121.667 - Flight plan: VFR and IFR: Supplemental operations.


What is the takeoff decision speed (V1) for a Gulfstream G500? Can someone tell me what is the decision speed (V1) of the Gulfstream G500? Is it 200kt as shown in this picture?

Your decision speed also called V1 is the speed at which ou have to commit to taking off whatever happens because you won't be able to stop before the end of the runway after that. This speed is related to the airfield runway length, aicraft TOW, temperature and altitude and will change for each take-off. Therefore there is not a fixed value for a given aicraft.
For the G500 I did find this review

Today our take-off weight with three persons on board and 11500 pounds  of jet fuel (one-third of the max fuel) is 60 000 pounds and our computed speeds are V1: 118 kt for a rotation speed (Vr: 123) and a take off safety speed V2: 129 kt.

And this other one

The G500 was relatively light, loaded with 12,000 pounds of fuel for our flight, which was scheduled for 1.5 hours. Takeoff weight was 59,863 pounds, well below the 79,600 mtow. The avionics calculated V1 at 116, Vr 118, V2 132, and Vref in case of immediate return at 136 knots.

As you can see the value changes slightly but V1 seems to stay around 120kts. Your 200kt speed limit and the altitude and range limit related seems more likely to be linked to the 91.117(b) FAA regulation

Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph.). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.


What is this US Navy airplane seen at Westover AFB? This Navy aircraft was at Westover AFB in either 1987 or 1990. Type unknown.


What restrictions are there for flying near urban areas in the United States? Say you've got your own plane and take off and land from the same airport.
Weather is good, fuel is good, etc...
What would be the restrictions for flying near urban places like a city in the United States?

I live near a bunch of sea-planes that take off and land from lakes encircled by high-rises. Never thought about it till now, but how is that and other private flying entities like news choppers and ad-banner planes governed?

This varies from country to country but here in the US the Federal Aviation Regulations define the minimum safe altitudes:

  Sec. 91.119 Minimum safe altitudes: General.

  Except when necessary for takeoff or landing, no person may operate an
  aircraft below the following altitudes:

  (a) Anywhere. An altitude
  allowing, if a power unit fails, an emergency landing without undue
  hazard to persons or property on the surface.

  (b) Over congested
  areas. Over any congested area of a city, town, or settlement, or over
  any open air assembly of persons, an altitude of 1,000 feet above the
  highest obstacle within a horizontal radius of 2,000 feet of the
  aircraft.

  (c) Over other than congested areas. An altitude of 500 feet
  above the surface, except over open water or sparsely populated areas.
  In those cases, the aircraft may not be operated closer than 500 feet
  to any person, vessel, vehicle, or structure.

  (d) Helicopters,
  powered parachutes, and weight-shift-control aircraft. If the
  operation is conducted without hazard to persons or property on the
  surface--

      (1) A helicopter may be operated at less than the minimums
  prescribed in paragraph (b) or (c) of this section, provided each
  person operating the helicopter complies with any routes or altitudes
  specifically prescribed for helicopters by the FAA; and

      (2) A powered parachute or weight-shift-control aircraft may be operated at less than the minimums prescribed in paragraph (c) of this section.

In your case, the sea-planes can fly closer than regulated since it falls under the "Except when necessary for takeoff and landing" clause.

These minimums apply in all air spaces however different airspaces surrounding cities (typically Class B and Class C) may prevent you from ever getting within 1000ft (or even a few miles) of the city due to clearance. For example you can't get near a city under a bravo space without ATC clearance and even then you can't fly where you want like in other airspaces.

  but how is that and other private flying entities like news choppers

News choppers and the like still must fly by these rules. They often compensate with bigger camera lenses. The somewhat exception to this rule is generally police, fire, and rescue/medical operation choppers/aircraft. This of course is taken on a case by case basis but ATC usually gives them precedent and clears them for whatever they ask within reason. I actually met a guy that was on the council that designed the Philadelphia Bravo Airspace. The airspace is specially designed so that the medical helicopters can take off and fly under the bravo shelf from any hospital in the city. They can do this and still be a safe distance from buildings as well.

  and ad-banner planes governed?

Banner towing planes, like helicopters must also fly by these rules. Although they are not seen in cities all too often I generally see them at the beach. Although beaches are generally not defined as a congested area and generally the planes are flying over "open water" thus they must be only 500ft from the people on the beach (depending on how you interpret the law).


Is there ATC audio from the Sled Driver Speed Check story? I love this story, like a lot of people, but is it possible to find the actual ATC recording from that story?
Excerpt:

Then, I heard it. The click of the mic button from the back seat. That was the very moment that I knew Walter and I had become a crew. Very professionally, and with no emotion, Walter spoke: "Los Angeles Center, Aspen 20, can you give us a ground speed check?" There was no hesitation, and the replay came as if was an everyday request. "Aspen 20, I show you at one thousand eight hundred and forty-two knots, across the ground."
I think it was the forty-two knots that I liked the best, so accurate and proud was Center to deliver that information without hesitation, and you just knew he was smiling. But the precise point at which I knew that Walt and I were going to be really good friends for a long time was when he keyed the mic once again to say, in his most fighter-pilot-like voice: "Ah, Center, much thanks, we're showing closer to nineteen hundred on the money."

Sadly, there likely are no official recordings of this story.

Unfortunately, there was no LiveATC.net archive at the time, and unless there is an accident or incident, audio is not routinely archived by the FAA or NTSB.

Even when you want to request recent data, the FAA warns, "Because air traffic data is routinely destroyed or disposed of in the normal course of business, time is of the essence." (I've seen elsewhere but couldn't find an official source that it can be anywhere from 5-45 days), so even if you could find a date of this event, you wouldn't be able to file a FOI request.


What are the safety demonstration time-constraints? On airliners, the safety demonstration includes many items (seat belt, life vest, evacuation, etc.) and each of those items may raise questions from the passengers (when to inflating the life vest, how to unlocking the seat belt, ...) and thus need more time to explain why those items are detailed.

Given the following elements:

the safety demonstration should begin while leaving the gate.
an average passenger may not pay attention for more than few minutes
the briefing should be finished before take-off (I hardly see flight attendants moving and manipulating life vest, seat belts and other objects in the middle of the aisle while taking off)
many items may need a better (and longer) explanation

I have several questions:

Are there any regulations about the timing of the safety demonstrations?
Is it up to the airline (automated videos are quite easy to time)?
What if the safety demonstration are not finished when the aircraft is ready to take off (on the runway with all clearances)?

I haven't heard of any regulations about the length of the safety demo, just the content, which is pretty much as you described. However it's in the airline's interest to keep it as short as possible. The aircraft cannot take-off before the chief of cabin notifies the cockpit that the cabin is ready for take-off. The cabin is ready after all passengers are on their seats, safety demo completed, galleys secured and hand luggage stowed away.


On modern fighter aircraft, why do most carry a rotary cannon when they tend to have little use against aircraft? I understand that in multirole or strike aircraft the cannon has a CAS use, but on a purely fighter aircraft, does the benefit of a fallback weapon outweigh the handicap of added weight?

I think this question is highly opinion-based and should be closed.

But here are my $0.02

Historically there were attempts to remove cannons but turns out too early: Missiles are not that good. The benefit of fallback weapon indeed outweight the weight.

  MIG21 VS RF-4C

  One instance of combat during Project Dark Gene was an engagement on
  November 28, 1973 between an RF-4C aircraft piloted by IIAF Major
  Shokouhnia and backseater USAF Colonel John Saunders and a Soviet
  MiG-21 flown by Captain Gennadii N. Eliseev. The Soviet pilot fired
  two Vympel K-13 missiles at the Iranian aircraft, failing to destroy
  it. He was ordered from ground control to press his attack at any
  cost, and with his cannon jammed after the first shot,[8] he continued
  by ramming into the Iranian aircraft and losing his life in the
  process. He struck the RF-4C's tail assembly with his wing and then
  flew into high ground. It was the first deliberate jet-to-jet ramming
  by a Soviet aircraft during an interception, a practice common in the
  propeller age of World War II. Eliseev was posthumously awarded as a
  Hero of the Soviet Union.[3][9] The crew of the RF-4C aircraft were
  captured by Soviet ground forces and released after 16 days.2[10]

US military reached the same conclusion around the same time as well, to add cannons to F-4 Phantom II.

Maybe now is the time to rethink this question again after 40+ years advancement of AA missiles. But if you ask the pilot, for the same weight, do they want fuel, gun+ammo, or nothing? A significant portion, if not the majority, would pick the gun I guess.

A lot of fighter pilots, or even astronauts, carry pistols. How useful is that?


How can I use a Bluetooth headset in an ATR 72 cockpit? Is there any device available to connect a pair of Bluetooth earphones to the audio system of an ATR 72 aircraft, to receive and transmit on the radio?

The stock headsets are horrible. I own a David Clarke headset too but the cables are a little annoying. If there's a solution to use a Bluetooth headset with a mike to replace the headset in the aircraft it would be lovely.

Flying Magazine reviewed headsets for pilots back in 2013 and four years ago there were already bluetooth-capable headsets in the market from Bose, David Clark, Sennheiser and Lightspeed. You might want to start there...


Why is port-starboard terminology used in aviation? I am not a pilot - just a student & play Ace Combat sometimes

Intrigued by the words Starboard & Port-side I researched why these words are used instead of the simple ones, I found that:

  Port is derived from the practice of sailors mooring ships on the left side at ports in order to prevent the steering oar from being crushed. src

Also, quite notably:

  Since port and starboard never change, they are unambiguous references that are independent of a mariner’s orientation, and, thus, mariners use these nautical terms instead of left and right to avoid confusion. When looking forward, toward the bow of a ship, port and starboard refer to the left and right sides, respectively.src

I see both the reasons are derived upon the concerns of the marine world - so why do we use them in aviation world?

This is specially interesting if we consider the fact that flying machines can manevur in all 3D, newbies (me) tend loose track of my VS. plane's left & right when not in level flight. Then why the added confusion?

It isn't (much).

Ships are the most similar thing to aircraft that existed before them, so it made sense that aviation took over many terms and conventions from seafaring (the pilot in command is called captain, the cockpit is the flight deck, distances and speeds are given in nautical miles and knots etc.)

However since there is no physical port in an aircraft to serve as reference (most aircraft have doors on both sides), everybody has to learn to give the sides relative to the direction of flight and then it does not make sense to teach them new words when they already know “left” and “right”. So “port” and “starboard” are only used where there is a naval tradition.

I know British military aviation (RAF) used it (in wartime stories and documents it is common, but according to Simon's comment it is not common any more) and the US Navy uses it with ships, but I don't know to what extent they apply it to aircraft.

However, it remains popular in simulator games, presumably because it is catchy and unusual and using jargon makes people feel special.


What happens if a crew complies but does not read back ATC instructions? For example, a commercial airliner is inbound and is in the traffic pattern; ATC instructs the aircraft to reduce speed to 160 knots, which the airliner does. ATC notice the aircraft has complied but never read back the instruction. Would the air traffic controller file some type of complaint against the crew?

No, ATC would not file a complaint for a single missed read back. In order to file a complaint they'd need to have very good reason to believe that the pilots were willingly breaking communication regulations, and there are so many other valid reasons for why this scenario could happen:

The pilots may have responded but it may not have been received. If two stations talk at the same time the stronger one wins, so they may have read it back but it was lost
The pilots may be dealing with a problem, or have a high workload. Communication is the lowest priority, flying the airplane safely is first, then navigation
The pilots may have a technical problem with the radio
The frequency could be too busy to get a read back in, sometimes the frequency can be so dense with communications you can't get a word in edgewise, so the pilots may comply and eventually just give up

These are just a few reasons from my own personal experience when I haven't read back an instruction or my read back wasn't received. If ATC is worried about it they can always call me back.

EDIT: The readback is a requirement for some instructions and I am in no way saying it's okay not to. My answer is for the specific scenario given, I think that the FAA would and should bust people who fail to readback in certain circumstances.


How to relay an emergency to ATC while on the ground? So we have somebody that contacted ATC via a Facebook post. Suppose I saw that Facebook post and believed it to be a genuine emergency. How can I contact ATC?

Call the police if in doubt who to call they have contact with Air Traffic Control.

Also calling the wrong facility can mean that it can take quite a while for the information to make it to correct facility.

Finding direct line phone numbers to ATC facilities can be intentionally hard. Prank call anyone! They are usually somewhere in the local Aeronautical Publication Books but where you can get a copy of them and then finding the number inside the book is difficult. Just call the police!


Are Ground Crew Airline or Airport Personnel? Are ground crews (baggage, tug operators, fuel, aircraft parking guides, etc.) hired by the airline or by the airport authority? I’ve always been curious.

What are the norms worldwide vs US? Small town Regional vs International Hub?

Ground crew are typically employed by a handling agency, which is a company dedicated to performing ground handling of aircraft (exactly the things you describe).

Some airports have several different handling agencies. Have you ever noticed, when waiting for your luggage to arrive at an airport, that there are several different help desks to choose from, depending on your airline? Those are the different handling agencies at that airport.

At a given airport, a certain airline will typically have a contract with just one handling agency. Sometimes, airlines have their own handling agencies. The exact structure can vary.

Smaller airports often do not have third party handling agencies, but instead offer handling services directly to the airlines. In such cases, the ground crew is employed directly by the airport, and could also have other tasks, for example as airport fire fighters.


Do airlines have to get permission from the FAA if they want to change their livery? Do airlines have to get permission from the FAA to change their livery? It would be great if someone can throw in some examples where this has happened.

Not the FAA, but the manufacturer.

If the parts are composite, only a small range of colors may be approved, depending on the glass transition temperature of the resin matrix. For gliders, only white is allowed for most of the surface area, and similarly composite parts of airliners must be painted in a light color so they don't heat up too much in sunlight. Curiously, the lower surface has the most restrictions, because here the reflected light from a concrete surface and the restricted ventilation create the highest surface temperatures.

Next, the UV absorption capability, moisture protection characteristics and the chemical stability of the paint when in contact with aviation fuel, hydraulic fluids, de-icing fluids and other solvents is important. Composite gliders must use a special topcoat which is more brittle than the composite structure, so cracks will show up. Airliners may use more flexible paints, but must then undergo regular inspections of their composite parts.

Metal surfaces are less demanding and can be painted in any color. Only the area in front of the windshield should be dark enough to reduce glare and irritating reflections.


For how long can a single-engine turboprop safely run the engine at idle? Can a single engine turboprop (such as a Piper Meridian or TBM) allow idling long enough to drop off a passenger or package without shutting down the engine? If so, would the prop be feathered but still spinning? Would idling with the prop not spinning (if possible) hurt the engine?

It's not stressful at all for a turbine engine to run at idle, you could run it until the fuel runs out. The prop is not feathered (in line with the air stream, pitch 90°) but will be at ground fine, in line with the direction of blade turn, pitch angle 0°.

There is usually no way to disconnect a propeller from a single spool turbine engine: if the engine runs, the propeller turns.


Do transatlantic flight plans have alternates routes? Does every international flight have more than one flight route in the flight plan?

For example, after the incident with MH-17, most of the flights were diverted from that route. Were the alternate routes already planned or were they chosen at that moment? If they were chosen at that moment, who planned the new routes?

Each airborne flight has only one flightplan, which was submitted for that particular flight.
The routing is embedded into that flightplan and only that one routing is valid for that flight.

In case the routing is no longer available for the next flight due to airspace closure via NOTAM or airways being restricted by time of flight / day of flight, another routing will be used for that flight and submitted in the flightplan.

In case the routing needs to be changed for an already airborne flight, a new IFR clearance is read to the crew en-route, which alters the existing flightplan.

Alternate routings are usually managed by the airline's dispatch / planning centre and the best routing for a specific flight is created by the dispatchers, taking into account weather, NOTAMS, restrictions and many other factors.

En-route changes to a flightplan are made by ATC units and their data processing centres, if an impromptu change needs to be made due to airspace closures or other restrictions coming into effect which were unforseen.


Has there ever been a diesel-electric helicopter? Occasionally I come across the diesel-electric (DE) design for submarines and freight trains. They say something like "a diesel engine powering an electric drive lets the two operate at their most efficient RPMs, and the electric drive has very little losses in efficiency."

So the question hit me: Has there even been a DE helicopter? Is there something about the DE system that makes it bad for the aviation industry? Weight maybe? But note we do not need a bunch of batteries like on a submarine. We don't need to store the power, we just convert it to electricity which goes immediately into the electric drive for the rotors.

Helicopters currently use lightweight but fairly inefficient gas turbines. Diesel-electric engines have great energy efficiency, in terms of mechanical energy delivered per kilo of fuel. However, they're quite heavy. This means that you need more lift, which in turn means more power is needed. This negates the initial advantage.

With the advent of lightweight materials, the latter effect decreases so this situation might change.

Diesel engines can throttle up and down quite a bit, unlike gas turbines,  but this capacity is irrelevant to helicopters. Note that helicopters need a pretty constant amount of lift.


What is the difference between COM and Auxilary COM signals? when the aircraft navigation system is tuned to VHF COM frequency (118-137.990MHz) then COM receiver will able to receive two types of signals one is COM signal and the other is AUX COM signal what is the difference between them ?

That frequency range is not for navigation equipment at all, so I would speculate that it isn't related to the navigation system.

They don't receive two types of signals; they do the exact same thing, but the reason someone may want two radios is to make things easier during flight.

What I think you are seeing is your primary communications radio system, and then a switch for an additional, optional "Com 2" unit that may or may not be installed in the aircraft.

Let's say you are talking to air traffic control, and you want to listen to an automated weather station without having to leave the ATC frequency; most systems provide you with an option to listen to both Com 1 and Com 2 at the same time, while allowing you to transmit on only one of them.  That way, you could monitor and talk on ATC's frequency on Com 1 while getting a weather update on Com 2.

Another advantage is that you can transition between frequencies faster by simply changing from Com 1 to Com 2 (ie. "AUX COM") after having already set the frequency you want to switch to in the other Com.

Yet another advantage is that one com will act as a backup to the other if either one stops working for some reason.


Is this the shortest route served by an Airbus A320? Is this the shortest route served by an Airbus A320? Port Louis to Saint-Denis, 231 km (144 mi). Air Mauritius flight MK248.

This site seems to indicate that they had the shortest route using the A-320 family of aircraft at just over 70km. The page also shows a list of flights, and it looks like one of them is listed at 58km. Based on that list, it looks like your 231km flight wouldn't even break the top 10.

Its difficult to search based on the length of the route and the aircraft type. As far as I can find though, 58km ACE->FUE shortest scheduled route for the A-320.


Are commercial pilots incentivized to reduce fuel consumption? Commercial airlines spend a lot of their operating income on fuel, so in order to maximize shareholder value presumably like to use as little fuel as is safely possible.

Are commercial pilots ever given incentives (e.g. financial, performance review) for reducing fuel usage, or given dis-incentives for excessive fuel usage?

There have been, at various times, and with various carriers, incentive programs set up to encourage pilots to save fuel, improve on-time performance, or some combination of the two.

An example of a fuel-saving incentives program existed at the former Continental Airlines in the early 90s, where pilots would be paid a bonus for using less fuel than planned. The problem was that it wreaked havoc with the schedule itself, as pilots would simply dial back to economy cruise thrust settings, saving fuel but taking noticeably longer to reach their destinations.

An example of an actual-vs-scheduled block incentive program intended to help with on-time performance existed at Silver Airways in their Beech 1900D fleet, whereby pilots would be paid a bonus for each minute they were able to shave off a baseline target time. Ironically enough, it was called the "Green Incentive Program" (don't ask). And it was a can of worms.

I vaguely remember other airlines experimenting with incentives programs relating to fuel consumption and on-time performance, but it's been several years since I left the industry and can't recall any other examples.

In short, yes they do get implemented fairly regularly, but they can be very problematic due to the difficulty in properly designing and managing them (incentivization is a complex problem).

Lastly, since another poster has brought this up, dispatchers do indeed perform most, if not all the flight planning, but the PIC (i.e. Captain of the flight) has the option of overriding most everything the dispatcher plans and arranges for (subject to the carrier's Operational Specifications), including amount of fuel to be carried. Basically, if the Captain decides that the plane is to be filled with as much fuel as it can carry up to MTOW, that's what's going to happen. Might not be the most business-savvy (or even prudent) decision, but it's part of their prerogative as PIC (i.e. the person ultimately responsible for the craft, crew, passengers, and goods onboard).


Why does my Cherokee PA28-180 Lycoming motor run hot? Regarding my Cherokee PA28-180. Could you please explain me why my new Lycoming engine with 800 hrs runs hot?

My mechanic says that the EGT #2 should be around 1350 degrees. The minute you lean the fuel at cruise alt, you have to richen it back up to stay < 1350 degrees.
During 1800 rpm run-up & during cruise speed of 135 mph, the oil pressure is just barely under the red line & it stays there for the duration of the flight. My mechanic says that's ok for this motor.
My mechanic says that we are to stay away from the 2100 rpm to 2400 rpm range. That's red line for our motor. Why?

You say it runs hot.  Why do you say that?  Is the oil temp pushing redline?  Do you have a CHT gauge?

EGT alone means nothing. Don't use it to set cruise settings.  What if the probes aren't all set 5" (or whatever) from the exhaust valve? What if they're only 3"?  Or 7"?  Or staggered between 3" and 7"?  Point is, the EGT number is just a repeatable value.  Don't think of it as a temperature.  Your Archer with probes 5" from the exhaust valve may read 1350° at full rich takeoff from sea level.  Your hangar mate with an identical plane (except for having probes only 3" from the valves) might see 1420° at the exact same setting.  Once you understand that EGTs aren't really temperatures and are merely reference numbers (or some type of "heat unit that isn't 'temperature'") the whole thing makes more sense.
Also, if you just have a single point EGT then just pretend it's not there and simply use the POH.  Single point EGTs tend to do more harm than good, especially if they're reading the confluence of two cylinder exhausts.  What possible useful information can you glean from an averaged temperature from half the cylinders on your engine, especially if it's carbureted?!?!

Does your mechanic know (and can he explain) why his tips make sense?  I'd love to hear his reasoning because I don't think it'll make sense.

You either have a bad oil pressure gauge or your pressure it too low.  Fix that.  A good gauge running below red line is very bad.  A bad gauge is better, but still bad.  The limits are not arbitrary.

Engine RPM limits are important.  Does Lyc publish a limitation between those RPMs for your specific engine suffix and serial number range?  If the limitation is an AD, has it been complied with and the limitation removed?
Running your engine at redline will not hurt anything provided the engine does not have a limitation (in the limitation section of the POH) on max RPM.  I know it feels right to "baby" the engine but there is no practical effect unless a limitation exists.  Note that "recommended procedures" are not "limitations."

I'd seriously consider talking with another mechanic if that's at all practical.  Your mechanic may be an airframe god but his advice regarding engines would have me shopping for a new IA.