Why is lift larger than thrust? It's been a while since I tried to read a little about flight mechanics and aerodynamics, but I remember one question I had back then:

Is the thrust of a common passenger aircraft (A320, B737) greater than its lift-off weight and thus could it take off vertically?

A320:

Max take-off weight   73.5 (78) tonnes
Thrust range  98 (120) kN

73,5 tonnes = 73500 kg * 9.81 m/s^2 = 721035 N = 721 kN

If my calculations are correct, it could clearly not (a result like what one would expect intuitively)!

But how can the dynamic lift be larger than the weight using comparatively little thrust?
Rephrased: How can the dynamic lift be larger than the thrust?

Is there an invisible equivalent to gears at work here?

Thrust is needed to overcome drag, and a good airplane design can create a lot of lift for little drag. In the case of an A-320, the lift-to-drag ratio is 18 in cruise (a little less during take-off), so to lift those 78 tons needs only 4.33 tons of thrust. All it needs is the right amount of forward speed, and the engines only need to maintain this speed.

Gliders are even more efficient, their L/D can approach 60. A glider of maybe 450 kg mass (= 4412 N weight) will create a drag force of only 74 N, admittedly at a much slower speed than an A-320.

To be more precise, in a climb the thrust will actually compensate a little of the weight, in addition to the drag, depending on the climb angle. The thrust needs to grow by weight $\cdot$ sin($\gamma$), where $\gamma$ is the flight path angle. If the A-320 had enough thrust to lift all its weight, it could take off vertically, flying in a nose-up, vertical attitude. Modern fighter aircraft do really have that much thrust installed.

This drawing shows a climbing aircraft. There are four forces at work:

Lift L (blue arrow)
Drag D (red arrow)
Thrust T (green arrow), and
Weight m$\cdot$g (black arrow)

For a trimmed state, the concatenated arrows should form a closed trapezoid (lightly shaded arrows). Note that both thrust and drag are drawn longer here in relation to weight and lift than they are in reality.

To answer the why part needs a few more lines. Lift is created by deflecting the airstream over the wings downwards. This change in momentum is lift, and creating it would be free of drag if the wing's span would be infinite and the air inviscid. In reality, flying causes these drag components:

Lift creation incurs a small backwards-pointing component which is biggest at slow speed and decreases with speed. To be precise: This drag component is proportional to the aircraft's span loading (weight divided by wingspan) and the inverse square of airspeed. It is called induced drag because it could be successfully calculated first with the same equations that describe electric induction.
Flying through air causes friction. This friction drag grows almost with the square of airspeed and is proportional to air density and surface area.
In inviscid flow, the sum of pressures around a body would just cancel out. In reality, the pressure on the forward-facing sections is normally higher than that on the aft-facing sections. This drag component is called pressure drag and is also proportional to the square of airspeed at the same angle of attack.

At the speed of best L/D the sum of 2 and 3 is equal to 1, and 2 and 3 are of the same magnitude for a well-designed airplane. High subsonic and supersonic flight adds a fourth component, called wave drag, and it's onset is the reason why the A-320 prefers to fly not much faster than Mach 0.78.


What are the helicopter frequencies on the LA heli charts used for? The LA heli charts list frequencies for the different heli routes in LA:

Are the frequencies used as a "CTAF" for helicopters, or is there an air traffic controller on that frequency telling helicopters what to do? I'm also wondering if the helicopter freq 119.80 at LAX issues class bravo transitions?

This is the frequency for the tower controller who is due to control inbound helicopters. You can see LAX 119.8, HHR 121.1 and LGB 120.5 frequencies noted. These are all frequencies used by the tower controller at these aerodromes.

At LAX, the class bravo transition will be issued by the tower controller on 119.8.


For slow-flying ultralights, how would a delta wing compare to a biplane layout of equal wing area? Context: By "slow-flying" I refer to ultralights that can be classed as  "motorfloaters" - similar wing loading to a hang-glider, stall speed below 40km/h, cruise speed not much above.

I'm interested in designing something of similar capabilities to M. Sandlin's Bloop ( http://m-sandlin.info/bloop/bloop.htm ) where the plan is to get into the air as cheaply as possible and then "fly too slowly/lightly to really be able to hurt yourself". (See also Ron Wheeler's Skyscout, more traditional ultralight design but manages an empty weight of 55kg, MTOW 135kg and a stalling speed of 32km/h, and and first flew in 1974 - http://all-aero.com/index.php/54-planes-p-q-e-r-s/9873-skycraft-scout- .)

The Bloop's designer chose a biplane layout as an easy way to achieve high wing area and structural strength for a given span, with cheap/light materials. The wings are approx 9m^2 each, with a span of 7.6m. (Due to diminishing aerodynamic returns on additional wings, I'm not sure whether to treat this as a total wing area of 18m^2m, or less - I have seen some sites suggest *1.5 instead of *2 as a good estimator.)

Given deltas also offer a large wing area and good structural strength, I am curious: Assuming similar wing construction - rigid metal frame, foam LE supports, stiff fabric covering - what differences in flight performance could be expected if an otherwise-similar craft flew with a single delta wing, of equal total area but lesser span? For example's sake, let's say a span of 5m.

Off the bat, I would expect induced drag to be much higher due to vastly lower aspect ratio, but I'm unsure to what degree that may be balanced by the removal of an extra wing's worth of profile drag, interference between the two wings, and parasite drag from struts and bracing wires etc. Plus, possible improvements in lift coefficient for same AoA range as I would think the wing would operate at much higher Reynolds numbers due to greater average chord length.

One major issue with a delta wing was discovered in the early days of supersonic fighters: delta wings don't handle well at low speeds.  At high angle of attack, they (like any highly swept planform) exhibit strong "Dutch roll" in which roll and yaw are coupled in an oscillation, and because they stall at very high angles of attack the Dutch roll comes on when control authority is at its lowest.

Your plan, to fly just above the stall at very light wing loading, will require control surfaces that make up a very large percentage of the total wing area, effectively compromising lifting area.  You'll also need a very large vertical fin to maintain stability, and much/most of that will need to be movable for yaw control.

Generally, the main reason Rogallo-derived designs have maintained dominance in hang gliders is because they overcome most of these failings of rigid deltas, and can be made lighter, store more compactly, and cost less to construct as well.


What is the maximal acceptable delay between pilot's input and flight control surface actuation? While I was watching a cockpit video of an A330 landing in which the pilot was frenetically moving its sidestick,  I wander what was the reaction time of this flight by wire system. Indeed, the time for transmiting the signal from the sidestick to flight computer, the time for computer  to  interpret all its inputs (pilot's  input, probes,...) and to decide to act on flight control surfaces, the aircraft's reaction is not instantaneous.

Then, I realize that whatever the transmission system, there are delay between pilot's input and air control surfaces movement (material's elasticity, time for hydraulic fluid to transmit pressure, other mechanism I can't imagine).

Thus my question is: is there a maximal delay between pilot's input and flight control surface deflection to certify an aircraft?

If needed, for the FBW system, a direct law can be considered (no complex computation as flight control surface movement is proportional to input)

If needed, the question can be restricted to airliners flying under FAA and EASA jurisdictions.

EDIT: given the first feedback (comments, edits, answer), I want to highlight this question is not restricted to fly-by-wire (transmitting pilot's input through mechanical links may also induce delay)

EDIT: I think I didn't emphasize enough that this question is only about delay between pilot's input and control surface reaction. I understand that this delay is negligible compared to all other delay, but this is the one the question focus on.

Excessive phase lag is a direct contributor to Type I Pilot-Induced Oscillation (PIO). Phase lag comes from:

Rigid body dynamics of the aircraft (e.g. delay between elevator surface and pitch rate response)
Actuators (finite acceleration time between input and desired surface angle)
Structural compliance (e.g. cable friction)
Transport delay in signals
Finite computational bandwidth (e.g. loop closure bandwidth)

From NASA Report 4683, PIO susceptibility can be expressed assuming the pilot is compensatory; that is, the pilot input and the aircraft response would be exactly in phase, except for a constant time delay (across frequencies). This model is expressed as:

$$G(s)=\frac{K}{s}e^{-\tau_e s}$$

where $\tau_e$ is the effective time delay, or equivalently, phase rate as a function of frequency

From its research, it found that an effective time delay larger than 0.3 sec leads to PIO issues. Given a typical pilot time delay of 0.2 sec, this would imply an upper bound aircraft effective time delay of 0.1 sec at higher frequency (around 5 rad/s), end to end.


Where is the official definition of pressure altitude? I know that pressure altitude for a certain pressure is defined to be the altitude in the standard atmosphere which has that pressure.

But I can't find whatever standard, regulation, or glossary officially defines it to be so. I tried to look in the AIM, the P/CG, a search of the FARs for "pressure altitude" wading through a ton of results, and what searchable partial copies of the US Standard Atmosphere of 1976 I could find. I don't have access to a copy of the ISO standard that defines the International Standard Atmosphere.

Does anyone know of an FAA, ICAO, or ISO document providing this definition?

Pressure Altitude

As defined by FAA in the Pilot's Handbook of Aeronautical Knowledge:

  Pressure altitude is the height above a standard datum plane (SDP),
  which is a theoretical level where the weight of the atmosphere is
  29.92 "Hg (1,013.2 mb) as measured by a  barometer. An altimeter is essentially a sensitive barometer calibrated to indicate altitude in
  the standard atmosphere. If the altimeter is set for 29.92 "Hg SDP,
  the altitude indicated is the pressure altitude. As atmospheric
  pressure changes, the  SDP may be below, at, or above sea level.
  Pressure altitude is important as a basis for determining airplane
  performance, as well as for assigning flight levels to airplanes
  operating at or above 18,000 feet.

  The pressure altitude can be determined by either of two  methods:
  1. Setting the barometric scale of the altimeter to 29.92 and reading the indicated altitude.
  2. Applying a correction factor to the indicated altitude according to the reported altimeter setting.

More info from the FAA here.

From Docket No. 18334, 54 FR 34304, Aug. 18, 1989, as amended by Amdt. 91-314, 75 FR 30193, May 28, 2010

  §91.217 Data correspondence between automatically reported pressure altitude data and the pilot's altitude reference.

  (a) No person may operate any automatic pressure altitude reporting equipment associated with a radar beacon transponder—

  (1) When deactivation of that equipment is directed by ATC;

  (2) Unless, as installed, that equipment was tested and calibrated to transmit altitude data corresponding within 125 feet (on a 95 percent probability basis) of the indicated or calibrated datum of the altimeter normally used to maintain flight altitude, with that altimeter referenced to 29.92 inches of mercury for altitudes from sea level to the maximum operating altitude of the aircraft; or

  (3) Unless the altimeters and digitizers in that equipment meet the standards of TSO-C10b and TSO-C88, respectively.

  (b) No person may operate any automatic pressure altitude reporting equipment associated with a radar beacon transponder or with ADS-B Out equipment unless the pressure altitude reported for ADS-B Out and Mode C/S is derived from the same source for aircraft equipped with both a transponder and ADS-B Out.

ICAO has described how they calculate Pressure Altitude

Source

In relation to QNE:

  When the ISA mean sea level standard pressure of 1013.2 hPa is set on
  an aircraft altimeter subscale, the height so indicated upon landing
  at an airfield is known as the QNE reading. More widely, this is also
  the PRESSURE ALTITUDE, which is alternatively defined as the height of
  any level in the international standard atmosphere (ISA-see above),
  above the level corresponding to a pressure of 1013.2 hPa.

Here is a free tool to calculate standard atmospheric conditions (ISA) at a given geometric or pressure altitude and ambient temperature.


Is there any regulation on how often a private aircraft should be washed? Is there any regulation on how often a private aircraft, such as a Cessna, should be washed?

Yes
...sort of.
There is a general requirement to clean privately operated aircraft as part of the annual inspection. There is no requirement to actually accomplish an annual inspection for a non-flying aircraft stored in a hanger. However, for an aircraft to be airworthy, the mechanic performing the annual inspection shall accomplish the required cleaning as part of the inspection. See 14 CFR 43, Appendix D:

(a) Each person performing an annual or 100-hour inspection shall, before that inspection, remove or open all necessary inspection plates, access doors, fairing, and cowling. He shall thoroughly clean the aircraft and aircraft engine.

Note that the annual inspection is generally the only inspection required of many privately operated aircraft. For aircraft operated commercially for flight instruction or carrying passengers for hire, the 100 hr inspection is also required, which might increase the required cleaning interval.
This regulation applies to all aircraft subject to FAA regulation. There are otherwise no special FAA regulations regarding aircraft washing or cleaning that are applicable to the Great Lakes area.

There may also be manufacturer recommended wash intervals. However, these are not regulations.
Operating certain types of aircraft under an approved maintenance program, the manufacturer could conceivably mandate a wash schedule which would then become mandatory in order to maintain continued airworthiness under that approved maintenance program. Such a mandate could conceivably apply to a specific geographic area based on climate issues. However, in the context of private aircraft, the requirement for such maintenance programs would only apply to certain large, turbojet, or multi-engine turbine aircraft. For this reason, neither of the types originally tagged in your question (Cessna 172 and 208) would be subject to a requirement for an approved maintenance program, though the Citation series originally mentioned in your title would be.
Moreover, if a manufacturer instituted such a change to their maintenance programs, such a change would generally only affect newly approved maintenance programs. Existing maintenance program approvals are "frozen" meaning new manufacturer maintenance program recommendations are recommendations only.

There may be local ordinances that limit water usage or otherwise regulate activities involved in aircraft washing.
Questions regarding EPA regulation are beyond the scope of this site.


How do the uninterrupted and interrupted flaps compare? (wikimedia.org) Airbus A350.

There aren't many wide-bodies out there. Whether it's Douglas, Boeing, or Ilyushin, they all have the high-speed aileron interrupting the flaps. Whereas Airbus uses uninterrupted flaps in all their fly-by-wire aircraft with the two ailerons outboard.

After Boeing has adopted fly-by-wire, it is still sticking with its flaps design in the 777 and 787. I'm aware Boeing now uses flaperons, but as the image below shows, its deflection is not all the way to avoid the jet blast, but how does Airbus get away with it?

For the uninterrupted, here are some reasons I can think of but can't link:

Smaller deflection for takeoff and landing is better for noise and fuel, but may incur a weight penalty because the flaps are in the jet blast and need to be built stronger.
A smaller overall wing is better for weight reduction, but worse for wing loading.

(wikimedia.org) Boeing 777.

Why did Airbus choose this design (apart from its A300/A310)? They must have a good reason. Equally for Boeing for not using them with its FBW aircraft. Unless it doesn't matter, or a patent is involved.

Related:

Why do similar Airbus and Boeing aircraft use different flap and slat mechanisms? Asks about the number of slots, slat types, etc.
When Boeing designed the 737NG, what factors influenced the change in the flap system? Asks about the 737 Original, here the engine was the split:

(Source)

The two designs are indeed based on compromises.

Earlier Boeings were designed for high-Mach cruise, which means high sweep and the need for elaborate flaps when flying at approach speeds. The 'thrust gate' reduces the thrust/flap interference and drag, especially in a go-around. It is also a good choice when more powerful engines will be offered as the MTOW increases.

Since the A320, Airbus have used high-lift planform layouts, which allow the continuous single-slotted flaps to work. An A380's approach speed is slower than a 747 or a 737, despite having single-slotted flaps. Owing to its high-lift wing.

When Airbus designed the A330/A340, it helped that they launched the bigger variants first. A targeted (tailored) design is not good when the aircraft would later be stretched, which would require a re-design of the flaps, i.e., if the shorter variant comes first, then 'over-designing' the flaps and having a thrust gate is a good choice.

Interestingly for the A350-1000 (a stretch of the -900), Airbus had to increase the wing area by 4% by modifying the wing trailing edge to maintain the same approach speed (flightglobal.com).

Losing the gap does save weight, complexity, and by extension, maintenance. But the limitations are:

Slower cruise speeds (not a problem since it's by design, flaps follow wing).
Thinner spoilers due to thicker flaps, they have to be made stronger.
Must demonstrate controllability during a go-around.
When stretching a variant, a flap redesign will be needed (ala A350).
Limits the flap span to allow for the innermost aileron to be inboard enough to not cause aileron reversal (lots of wind-tunnel and CFD models help fine tune this).

Own work based on scaled drawings from boeing.com and airbus.com.

Comparing the wings of the A330-200 and 777-200(ER):

The maximum operating Mach numbers (MMO) are 0.86 (A330) and 0.89 (777). Note the higher sweep on the 777.
The MTOW and MLW of the 777-200ER are 55 and 31 tonnes heavier, further evidence to the higher wing loading of the 777, which would indeed need more elaborate flaps.
Keeping in mind in the development cycle, the 777 was stretched, while the A330 was shrunk.

In short:

Boeing tends to prefer higher MMO, higher MTOW, and to offer the base-variant then scale it up. All of which would benefit from the 'thrust gate' and the more elaborate flaps. The overall trend however shows Boeing going for simpler designs:

This answer is based on a publication by an Airbus engineer:

Reckzeh, Daniel. (2017). Aerodynamic Design of Airbus High-Lift Wings in a Multidisciplinary Environment.


How does a Delta-3 hinge on a helicopter tail rotor work? I am trying to understand how adding offset hinges would provide a self-feathering force.  Does anyone have more information on Delta hinges on helicopters? I am a bit confused with the information I have available. A video would be nice, but I couldn't fidn much on YouTube.

Here are two references illustrating the concept, and a picture from the first link (b).
Delta-3 Hinge
Delta-3 Hinge - AOPA Explanation

The AOPA explanation does not have the offset/angled blade:

It's because the blade's span-wise axis is "swept" relative to its flapping hinge line, so when it flaps, the sweep angle results in the blade's effective AOA changing somewhat (for the advancing blade, reducing; that's what the feathering part means).

To picture it, imaging you are standing directly in front of the tail rotor disc watching the advancing blade of the plain rotor come over the top or bottom straight toward you.  All you see is its thin leading edge.  If the plain blade flaps left or right, still all you see is the thin leading edge because the blade's axis is perpendicular to the feathering hinge axis.

Now imagine the Delta three rotor blade from the same vantage point, and the hinge flaps left or right. Because the blade's span-wise axis is offset, or  "trailing" the flapping hinge axis, you will be able to see some of the upper or lower surface of the blade from your vantage point when it flaps. To the airstream, this is effectively a slight reduction in AOA ("feathering") compared to the AOA of the unflapped blade as set by the pitch change linkage (or an increase when flapping while retreating).


How does flying at ECON computed speeds optimise fuel burn.? I read in the FCTM GREEN OPERATING PROCUDURES that it’s recommended to fly at ECON computed speeds throughout the flight profile to optimise speed in accordance with the CI.

The key is the word 'Econ', which has nothing to do with 'Fuel Burn'. The 'Econ' setting is a MIN COST method of operating, taking into account not just the cost of the fuel, but also the other operating costs of the airplane.
If your hourly costs (maintenance, crew) are high, then you'd burn fuel to get there fast with reduced hours. If your hourly costs are low, then it's worth flying slow, and thus conserving fuel.


What exactly are "clipped" wings? What exactly does "clipped wing" mean? Been having a rather heated debate. My understanding is that clipped means the tips were removed after manufacture. The other party claims that if it was designed squared off and built that way, it is called clipped.

As far as I can find you may both be correct. The term originally was used to describe a stock aircraft having it's wings shortened after-market.
Here is a reproduction of the December, 1970 issue of SPORT AVIATION Magazine article comparing stock vs clipped
http://home.xcountry.tv/~dann/id72.htm

This modification has become well known and the clipped wing design sought after that there are planes (at least kits) being manufactured with "clipped" wings.
http://www.monocoupe.com/

It appears that whether is was done 'aftermarket' or manufactured that way, clipped wings are those that have been shortened from original design to improve aerobatic capabilities.

Hopefully that will give you some more points to debate over!

~Hoff


Why do airlines not use direct routes? Why do airlines use SIDs and STARs when flying IFR. Wouldn’t it be easier and make more sense for them to use direct routes (for example KDFW.KLAX instead of KDFW.L4D.ZIBIT.J5N.BUBIN.P3K.KLAX (not a real route, just an example)?

You assume that airlines always fly the published SID or STAR. That's not true though. SIDs and STARS are used in procedural control to separate arriving and departing flights. When you have radar, then you don't necessarily need the procedures to do that.

When a flight is cleared for takeoff they are assigned a SID that is relevant to its destination. After takeoff and when the flight is handed off to approach (1) controller, the controller will give a vector (heading) to the flight or direct to a point on the TMA boundary. If for any reason (see below) they intend to keep the flight on the SID the controller says proceed as cleared(2) on first contact.

For approach, the flight is assigned a STAR and when it reaches the TMA boundary, the approach controller will give them a vector and the flight will deviate from the assigned STAR. See this video from NATS  and watch the arrivals to Gatwick. Compare the trajectories to what you see in the instrument procedure maps from their website. They don't seem to follow a route looking like that

source: UK AIP chart AD 2-EGKK-7-5

They seem to go direct to the holding stacks. And after exiting holding they don't seem to follow any of these routes

source: UK AIP chart AD 2-EGKK-7-12

Now when will a flight actually do the SID or STAR you will ask. There are several cases like for example TMAs without radar service. Normally the control is procedural in that case and that includes flying the assigned SID or STAR. Another case is during unusual circumstances like for example equipment failure (radar, communications etc) that will make radar vectoring harder or even impossible.

It's worth noting that it's common for pilots to ask for shortcuts if that can be done legally. For example if the weather conditions are VMC an arriving flight might request a visual approach. In that case IFR is canceled and the pilot will deviate from the STAR or IAP.

During takeoff, a pilot might request direct to an en-route point and thus exit the SID. If the current controller cannot grant it (let's say no radar contact), they will ask the next controller (en-route controller) if they can grant it. If yes (the en-route radar has the flight) then the flight is handed over to en-route and they are granted the direct, exiting the SID. That might not always be the case. If for example en-route control has radar contact, but because of heavy military activity the direct cannot be given safely, then the flight stays on the SID until the end.

Notes

Links to pdfs unfortunately don't work; you need to open them manually from NATS AIS page, linked in main answer.

(1) Or departure, sometimes it's the same controller.

(2) This phraseology is used in Greece (and I hope I remember it correctly). Other jurisdictions might use something slightly different.


What is Class E3 airspace? I am not aware of Class e3 airspace that is now associated in an area I used to be able to fly my ultralight, model airplane, or drone.  It is now apparently requiring FAA authorization.

It looks like its an extension of Class C Airspace from a class E3 announcement,

  ...Class E3 airspace areas are designated as arrival extensions to a
  Class C surface area. Class E arrival extensions are primarily
  designated to provide additional controlled airspace ancillary to a
  surface area to protect instrument operations for the primary airport,
  without imposing additional communications burdens on airspace users.


Is there a convention for type of switch used and where? In most cockpits, you'll find the full gamut of switch types in use. Toggle, rocker, push-button and more. Each has their own "feel" and might be used for different situations.

Is there any convention for what type of switch is used in a cockpit, and where/for what?

Such as, is the Generator usually/always a toggle switch, and would it be "weird" or unexpected for it be a rocker switch instead? Everything could be a toggle switch, so why do manufacturers choose to use different types of switches for different things?

The 737's overhead panel uses toggle, rocker, push-button, and rotary dial all together:

These images are from a simulator, but the aircraft is modeled after the TBM 850. In it, you'll notice toggle, rocker and push-button switches:

Same thing up top in the same aircraft:

Here's a real image showing the same thing:

I can't give you a 100% correct answer, but I'll try as best as I can, having some experience with much smaller aircraft (even than the TBM850):

As far as I know, there are no strict conventions for this and this is why you see most aircraft types equipped with their own panels and cockpit design.

You always have to keep in mind that aircraft manufacturers put most of their engineering efforts into designing aircraft concepts for a specific market and then casting their ideas into an actual airframe that fits all the systems that are needed to operate the aircraft.

Allmost everything else (engines, landing gear, avionics, A/C, lights, APU, steering, braking and anti-skid systems etc.) is developed and manufactured by external suppliers with the aircraft manufacturer responsible for adapting and orchestrating all the systems.

This might lead to the aircraft manufacturer simply using already available switch assemblies or only slightly modifying the suppliers' reference designs for panels in the actual aircraft.

IMHO, this is easily recognizable when looking at the cockpits of (especially older) aircraft where there was no concept of the cockpit as a whole. Whatever switch assembly was needed was just somehow installed into the panels.

As Boeing's 707 was a great success, its cockpit design (at least partly) found its way into the 707s successors/derivates/siblings 727 and 737. This lead to the 707 setting the cockpit design paradigms for following (Boeing) aircraft.

Also, from a pilot's point of view, there are some semantic aspects about choosing a switch that 'feels right'. For example:

push-buttons to start an automated process
korry-type switches for switching automatic systems on or off or for on-off switches that might be controlled automatically (And therefor show their status; Airbus uses these a lot due to their cockpit philosophy)
toggle switches for everything that needs an on-off type switch on low-level without other systems needing access to it (for critical switches with safety cap as seen in the 737 overhead panel)
rotary switches for mode selectors
potentiometers for everything that is finely controlled by the pilot
rockers maybe for mode selection between two modes where neither of both is just "off"

are very intuitive to me. This might be training or just experiences from everyday life, but I understand what they are doing even before having read the manuals thoroughly, which makes it easier to remember which switch does what.


How is a stator like a diverging passage? I've read in a lot of places that stators in an axial compressor are responsible for diffusing air and removing the radial velocity to make the flow parallel to the shaft. What I don't understand is how this is accomplished. One way I've heard it explained is this:

  With these fundamental points in mind, let us consider the energy transfer between the moving blades and the fluid. For this discussion, consider an axial-flow compressor with such a large ratio of hub diameter to tip diameter that the blades may be approximated by a linear cascade, that is, an infinite row of blades moving in a straight line, as at the top of figure 5.1. If we were to follow an element of fluid as it passed through the moving rotor, we would note changes in both its velocity and its pressure. The character of the changes is more easily seen by transforming to a coordinate system stationary in the rotor, where the flow seems steady, but from an angle as shown by the dashed vectors. If the blades are shaped to turn the flow toward the axis in this coordinate system (in the direction of blade motion), they form diverging passages which (for subsonic flow) result in rising pressure as the fluid passes through the cascade. When this pressure increase is carried back to the stationary coordinate system, as we see from equation 5.5, energy is added to the flow.

Source: Aircraft Engines and Gas Turbines (2nd Edition) by Jack L. Kerrebrock)

Can someone explain in more detail how a stator is like a diverging passage (diffuser?) as Kerrebrock proposes?

An explanation I would propose (but would appreciate confirmation for) is that there is a pressure gradient along the axial flow due to the rotor/stator's generating lift giving them a suction side upstream and a pressure side downstream. This pressure gradient would cause the flow to slow down (and hence increase pressure). Right?

If you take a look at the geometry of the path between two stator blades and compare the cross section of the path(relative to the direction of the traveling gas), you can see, that they form a divergent path.


Is it possible to get permission to fly in the DCA “no drone” area? The entire immediate Washington D.C. area is in a “no drone zone”, in a 15 mile radius from DCA.
Are there ways to get an exemption for activities such as film making, property inspections, etc?

Yes. This page comes up on a quick Google search.

Flying an unmanned aircraft within the 15-mile radius inner ring is prohibited without specific FAA authorization.

Experienced Part 107 and public aircraft operators with justification can file your request through the on-line Access Program (AAP) https://waivers.faa.gov


What is wing inductance? I am currently trying to understand the ground roll and climbing stage of normal aircraft.
I came across this formula which is an expression of the airplanes drag:

$X_a = c_{{x}_a} S \frac{\rho V^2}{2}$

where: $ c_{{x}_a} = c_{x0} + A c^2_{x_{a}}$

S: wing area
$\rho$: air density
V: velocity
$c_{x0}$: drag coefficient when the lifting force = 0
$c_{x}$: drag coefficient

A is said to be the wing inductance. Could somebody explain what is meant by wing inductance?

$$A = \frac{1}{\pi \cdot e \cdot AR}$$
where
$\pi = 3.14159....$, $e$ is the Oswald efficiency factor, and $AR$ is aspect ratio of the wing.


Does flow separation starts earlier at higher airflow speeds? For same AoA,will flow separation starts earlier (point of separation more upstream) at higher airflow speeds (=higher air inertia) compare to lower airflow speeds?
High speed airflow has more air inertia so it seems inuitevly that air will harderd follow curved surface and leave surface earlier?
Question referes to subsonics speeds,but you can expand your answer at supersonic speeds as well.
Same topic at physics site,but we heve problem here because members have opposite oppinions:
https://physics.stackexchange.com/questions/602876/does-flow-separation-starts-earlier-at-higher-airflow-speeds/602888?noredirect=1#comment1356599_602888
??

It is generally assumed in incompressible aerodynamics that the Reynolds number over a wing is so high that the effect of the Reynolds number (same air viscosity, same wing chord, only variable in Re is speed) on the lift coefficient is negligibly small. I can think of two areas where this assumption breaks down:

Very small (for example RC model scale) wings, where the Reynolds number is appreciably reduced. As the air in this case is less turbulent, flow separation occurs earlier.
Compressibility effects such as shockwaves occuring on top of the wing at transonic speeds, where we have to include not Reynolds but Mach number in our lift coefficient estimation. The effect of Mach number on max. lift coefficient depends on the wing design, some fighters are optimized for it, while most aircraft have their max lift coefficient and max angle of attack reduced at transonic speeds.


How do wing tip vortices interact with the airflow on an wing with winglets? If winglets are added to an aircraft, do the vortices still interact with the airflow and create up wash and down wash. If the vortices do interact with the rest of the flow I am wondering how they do it.

So basically I am asking if wingtip vortices can affect airflow when there are winglets on an aircraft.

Winglets do not change the laws of physics. In particular, they do not change the flow around a wing such that there is no up- or downwash. All they do is to involve a little more air into the creation of lift such that the vortex strength is slightly reduced.

With winglets, wingtip vortices now form at the tip of the winglet instead of at the wingtip. The wake behind the wing still rolls up and creates the usual wake vortices into which the wingtip vortices are absorbed. In order to create the same lift with a slightly less powerful vortex, the distance between both vortices is increased slightly. Actually, in order to support the winglet's weight, the aircraft needs to create slightly more lift with winglets than without, which reduces their benefit.


How can a headset cause continuous transmission (PTT blocked)? I own three aviation headsets:
- BOSE A20
- David Clark H10-13.4
- Compilot Lite (a cheap headset bought recently, for occasional use by passengers)

I tested the Compilot Lite last week (co-pilot side), but I ended up blocking the frequency at a local airport. Unfortunately, it took me some time, and somebody waving furiously at me, before I found out.

I was wondering how this issue could occur and what could be wrong with the headset. I found an explanation on this forum, which states that the tip of the connector functions as a PTT button when grounded. However, the connector does not seem to differ a lot from the other headsets.
Left = Compilot, middle = DC, right = Bose.

Could it be caused by something else? The type of microphone?

Any tips or suggestions are welcome.

Thanks!
David

PS the aircraft was a C172N, a rental which I often use, but never had this issue before with the other headsets

Apparently the tip connection is being grounded activating the PTT. From the photo the only thing that could possibly be a problem is the Compilot plug being a tiny bit longer than the DC. But the detent in the tip is what should decide where the plug sits in the jack and that looks fine. It almost has to be a wiring problem in the Compilot. If you have a multimeter check for continuity between the barrel and the tip. There should be no continuity unless a PTT button is being pressed.


Given an exact date, time, and coordinate, can I locate a plane that flew overhead? I need to identify an aircraft seen at 36.841900,-87.673600 Kentucky on July 4, 2020, at 12:29am.
Is there a way to do this feasibly?

Figured out what it is:

I recommend using flightradar24. In addition to its many other features, it has a playback mode. I'm not sure if there is a simple way to view a specific coordinate; however it should be easy enough to navigate to your desired location using the map view. If looking at coordinates is a must, I have found that you can put them after the url like so:
https://www.flightradar24.com/-36.38,128.09
Edit
According to Jan Hudec, you need a flightradar24 subscription to access dates this old.


How fast can an airliner (like a Boeing 747) taxi backwards? Forgive my lack of understanding, I thought I'd just buy a simulator and mess with it.  I really don't know much of anything in terms of MSFS2020 or simming really at all.
I realize that airliners can taxi backwards.  So, I'm wondering.  At its top speed, how fast can a 747 taxi backwards, if it tried to do so?

From a pure theoretical standpoint, the speed limit would be whatever rolling speed can be achieved with max reverse thrust. If you deployed max reverse on a landing, and left the max reverse on until you stopped, then released the brakes and left it on as you started to roll backward, you would accelerate backwards, and if you were able to maintain steering control (unlikely) and the engines were able to operate with the turbulent reverse inlet conditions without stall/surge, you'd accelerate until there was no longer any surplus reverse thrust.
You'd eventually be careening along backwards along the runway at, maybe 30kt, 50kt, 80kt... who knows? You could probably estimate some number based on available thrust and rolling friction/air resistance, but safe to say it's never been tried, or even thought of.  Don't even think of touching the brakes once rolling backward with any velocity.
From a practical standpoint, some operators may allow backing up under reverse thrust in specific circumstances, keeping in mind that you can't see where you're going so people need to be outside to clear the area behind, debris is being stirred up and ingested into the engines (ramp areas are a rich source of luggage zipper tags), and there's the problem of stopping without tipping over onto the tail when braking (the airplane's loaded C of G is not that far ahead of main gear, so it won't take much braking force for inertia to lever it over; safer to use forward thrust to stop than brakes).
So you may see power-back operations in the right circumstances, but the maximum speed in such cases won't generally be faster than a walking, (or maybe jogging) pace.


Why do 20-series Learjets have such an extreme susceptibility to mach tuck? Mach tuck is a change (usually nosedown) in an aircraft’s pitching tendency during transonic flight relative to its pitching tendency in below-transonic flight, caused by the appearance of areas of supersonic airflow (with attendant formation of shockwaves, sometimes accompanied by regions of flow separation) around the aircraft when it exceeds its lower critical mach number.  It first showed up immediately prior to and during World War II, as a completely unexpected, and quite deadly, type of loss of control at high speeds (especially on aircraft using the very thick airfoils then in fashion); however, by the mid-1950s, advances in wing and airframe design had reduced mach tuck to little more than a nuisance, allowing even first-generation jetliners to safely fly at transonic speeds without risking a loss of control.1

In contrast, 20-series Learjets, although dating from the 1960s (by which point we already knew very well how to make aircraft highly mach-indifferent), tuck like an aircraft from the 1940s, pitching down suddenly and violently at approximately mach 0.81.  This extreme susceptibility to mach-induced loss of control at high speeds caused a rash of crashes in the 1970s and 1980s, and is one of the many factors that make first-generation Learjets some of the most unforgiving aircraft ever sold to the public (at least, if the NTSB’s AAR archive is anything to go by).2

It is quite hard to see what about these aircraft would cause them to have such evil overmach characteristics; admittedly, they do have straight, rather than swept, wings, but this should impact more where the lower boundary of the transonic flight regime is - not so much how the aircraft behaves once it’s already in transonic flight - and, besides, the thinness of the wings should compensate for their lack of sweep.3

What is the cause of the extreme susceptibility of first-generation Learjets to mach tuck?

1: First-generation jetliners are, nevertheless, generally kept below their lower critical mach numbers in normal line operations, due to the greatly-increased drag associated with transonic flight; however, further design advances, first seen on the Convair 990, greatly mitigated even the transonic drag penalty, with the result that second-generation and later jetliners routinely cruise at transonic speeds.

2: Other factors included a balky autopilot, spoilers that make the aircraft go faster when extended (by causing a large pitch-down tendency of their own), and the fact that their original certificated service ceilings were well into the coffin corner.

3: The reason swept wings help with transonic flight is that they make the wing appear, to the air flowing over it, to be thinner than it actually is, thereby helping to delay and mitigate shockwave formation and flow separation.  These same benefits can also be gained by actually making the wing thinner.

The early series 20 Lears have always had boundary layer separation issues, so much so that any time the wings are removed and reinstalled the aircraft must be test flown. Mach tuck is an issue with all aircraft capable of trans-sonic flight, but on the early Lears this is apparently exacerbated by the susceptibility to boundary layer separation from the laminar flow airfoil.

To address this and other shortcomings in the 20-series wings, a number of modifications have been developed. Vortex generators were installed in front of the ailerons, and then a boundary layer energizer "fence" was developed. Dee Howard and Gates Learjet jointly developed a "cuff" for the Lear 25 wing that resulted in the 25G variant, with better performance at cruise and an increase in range of some 360 nautical miles.

There has been some talk that the problems of the Lear wings come from the FFA P16 design. Bill Lear's son has clarified that his father did not use the P16 as the basis of the Lear 23. The two aircraft use different, though similar airfoils.


Does a skinless fuselage add to the likeliness of an unrecoverable spin? While at Air Venture this week, I happened to hear a pilot of a small experimental airplane say that he liked the skinless (Naked) look his airframe had at one point during the build, but that he believed flying it that way made it more susceptible to an unrecoverable (I assume flat) spin.

Thinking about it later, I realized that I wasn't sure I understood how this could be.  My understanding of airplane behaviour is that a flat spin is mostly a result of CG being to far aft.  Anyway, I was wondering if anyone knew this?

Well, I would solve with transparent Monokote if it was a model.  No accounting for people's taste.

Although some very early aircraft featured that look, designers soon realized that covered "slab" sides not only reduced drag, but also improved directional stability.  Note that covered area aft of CG acts as an extension of the empennage, allowing for a smaller Vertical stabilizer.  Many 100 years ago were comparitively tiny.

As far as behavior in a spin, what he has on the tail may be sufficient for safety, as well as good CG management.   But I would certainly not recommend denuding your fuselage for a certain "look" without some expert advice and testing.

Designers do compare side area ahead of CG to aft of CG to estimate yawing tendency in a slip.  So he may be OK.


How many fastener can an aircraft lose? I see this GIF animation a few times then I wonder how many fastener can an aircraft lose before it becomes dangerous. I’m sure losing one wouldn’t be an issue due to safety margin built into every component of aircraft. But how many fastener?

Original link https://www.gifng.com/wtf/65633/

There is no straight answer as it depends on the individual fastener and specific aircraft in question. Pressurized aircraft create a whole new set of issues.

In some cases you can lose a whole bunch of them and even lose a full panel without issue as was the case on Delta  2412. While in other cases single bolts or fasteners are far more critical. Fasteners on stationary parts wont create the same imbalance issues as say, losing a fastener from a prop spinner or the such. Fasteners coming loose and being ingested into engines or other critical components can be an issue which is similar to the issue with the Concorde incident.


When is the descent clearance requested from ATC? Is there a rule / Standard Operating Procedure as to when request the descent clearance during cruise flight? Something like one minute before reaching the Top of Descent point?

Whether there are any formal policies for when to request descent will depend on the airline. However, I doubt formal procedures are established, since it should be pretty obvious to pilots when to request descent.

From a controller point of view, I will expect you to request descent when you are ready for it - so a minute or so before reaching your top of descent point. Controllers are able to estimate when you are going to request descent, based on experience, known level restrictions and typical aircraft performance. Controllers who have been working the same sector for a few years will be able to tell pretty much exactly when a certain flight is going to request descend, based on the current wind, runway in use, airline and aircraft type. What this means to you, as a pilot, is that you can expect the controller to be ready for your request; You can normally expect to receive a clearance for descent immediately after requesting it - so there is no reason to request it several minutes in advance.

Very few pilots will request descent several minutes before ToD. If they do, I can - if traffic flow permits - use the phrase "When ready descent to FL160". You are then free to start your descent when passing the ToD. Honestly though, if you call me up and say "Request descent in 5 minutes", I will most likely just reply with "Roger, call me back when ready for descent". The traffic situation can change significantly in 5 minutes, so I don't want to issue a clearance that may not fit into the future traffic picture. In the end, the early request just costs time on the frequency, which can be a scarce resource in a busy sector.

Moral of the story: as a controller, I know my airspace very well, and I have a pretty good idea of when you are going to be ready for descent. Because of this, there is no reason to request descent before you are ready for it. If you do, it will not matter at best, and be slightly annoying at worst.

ATC can of course also descend you before your ToD for various reasons, but that is another discussion.


Where is the fire suppression material injected into a jet engine? This question is regarding the P&W 4000 engine that was involved in the recent incident on UAL 328, but it doesn’t have to be specific to that engine.
From what I gather in this incident the fire continued after both fire suppression bottles had been deployed. I’m wondering where exactly does the suppression material go into the engine? Does it all flow into the core or is it distributed to different places. Does the loss of the cowl render it ineffective? I expect that halon would only work in an enclosed space. It appears that the fire in this incident was outside the core and without the cowl there wouldn’t be much that could be done in flight to put it out.

I’m wondering where exactly does the suppression material go into the engine? Does it all flow into the core or is it distributed to different places.

It is distributed with some nozzles. But the exact position of them depends on the specific engine. In this slides you can get an idea of the positions for a turboprop engine. They usually cover at least the core, and some other zones that should be separated by firewalls. This image (from Boeing) gives you an idea of the different zones, which I expect they are covered by different nozzles:

and this image (from the same link) contains the position of the fire detectors, which I expect to be covered by at least one nozzle:

Does the loss of the cowl render it ineffective? I expect that halon would only work in an enclosed space. It

Probably yes. Engines are not designed to have catastrophic failures like the Flight UA-328 (they are supposed to contain any failure). So, probably not even the fire protection system is designed to handle such case. A large destruction like that may have potentially cut some of the fire protection tubes and damaged the firewall protections.


Why is AVGAS so much more expensive than car gas? Why is 100LL so much more expensive than gasoline for cars?

I get the fact that it's 100LL, instead of 87, 91, etc.

For example (as of now, 13 Oct 14), the 91 unleaded gas at my local gas station is 3.41USD, and the 100LL at my local airport is 5.49USD (for the self serve).

What's the reason for the huge increase in price between car and aviation gas?

The LL of 100LL stands for Low Lead as it has tetra-ethyl lead added as a detonation inhibitor for high-performance engines. Despite the "low" moniker there actually is a lot of it in there, and it's toxic. This fuel is expensive for a number of reasons:

The lead itself is expensive
The lead additive means that a refinery must shut down and clean the lead before producing other fuels, this means more refinery time and therefore more costs
Lead in fuel cannot be allowed to contaminate other fuels so you cannot pipeline leaded fuel. It has to be transported in containers, adding to shipping costs
There are extra controls around the lead in many parts of the world, namely storage requirements and paperwork, all which costs
100LL fuel has many more "aromatic" hydrocarbons than mogas (auto fuel) in order to increase the octane levels and prevent fuel from vaporizing in your lines at high altitude. It's much higher grade, so it costs more
It's a specialist fuel made in much less quantities than other fuels, so a premium is added to ensure a profit

Keep in mind that the Avgas is taxed less than Mogas in most places. It would cost even more if it were taxed the same!

Efforts are underway to come up with a 100LL replacement that will work the same in all engines and situations, which is a hard problem to solve. Whatever fuel they come up with, while having no lead, will still likely be more expensive than mogas just because of the more expensive hydrocarbon mix and the specialist nature of the fuel.


How does a true airspeed indicator work? How does a True Airspeed Indicator work?
I am aware of how the air speed indicator works, but how is the density input being provided to this instrument?

For a basic True Airspeed Indicator (TAS Meter) like the one shown below, you simply dial your pressure altitude into the top window using the knob (aligning it with the appropriate temperature mark at the bottom of that window), and then read your true airspeed in the other window at the bottom.

Your pressure altitude can be obtained by setting your altimeter to 29.92 and reading the indication, the air temperature can be obtained from an outside air temperature (OAT) gauge (or you can use one from the Winds Aloft forecast if your aircraft does not have an OAT gauge), and the combination of the two gives you your density altitude.
The meter itself is simply a mechanical slide rule, performing the same functions as you could do manually on an E6B flight computer.

The indicator above is showing a true airspeed of about 202 MPH, at a pressure altitude of 10,000 feet and a temperature of -15 degrees.

For a nice video tutorial check out this one from the University of Oklahoma.


Why do airliners have to park so accurately? I was watching some airport documentary and I noticed that the planes always had to park precisely. I honestly didn't think so much of it before, but in the documentary, an aircraft parked badly because the VDGS couldn't detect it correctly due to fog, so it had to be pushed back to park again with the help of a marshaller.

The only two reasons for this I could come up with are the following:

Jetways: I figured it's because of the jetways, but they can move about so as to adapt to where the plane is. Plus, when parking on stands, the accuracy is the same and there is no jetway.
Aesthetics:  I also thought it could be about aesthetics, but the systems used to help the pilot park (a marshaller or VDGS) can be expensive so business-wise, it wouldn't make sense to be so strict on parking if it's just for the looks.

This is to ensure that there is space for all equipment around the aircraft. It's not critical to the centimeter, but if it's off by a meter or more there may be problems. For example, the tail may stick out into the taxiway behind or the nose may stick into the service road in front of the aircraft. While most aircraft stop with the nose wheel on or very near the stop-mark, the main wheels can be off by a few feet, depending on how early/late the pilot turns into the stand.

Modern aerobridges have a wide range of movement to cater to various aircraft types, but nowadays there is a lot of equipment buried in the ground. You might see ground power and air conditioning hoses which plug into the ground next to the aircraft nosewheel area. If the aircraft is off by a few feet the hose/wires may cause obstruction to the ground crew. The hydrants for fuel also need to be near the fuelling ports - too far and the hoses might not reach.


Can an airliner provide ground level cabin pressure, temperature, humidity etc? Apart from the cost angle, which seems to be the biggest factor in airlines, is it technically possible to bring cabin atmosphere (includes pressure, temperature, humidity) etc. at par with ground level, at the cruising altitude of most airliners (say 35000 ft).

I just want to understand what stops airliners from providing this kind of comfort to the passengers. I am assuming there might be issues of hull integrity in order to maintain higher cabin pressure etc.

I'll touch on the humidity a bit.

This is actually a big issue for planes; they tried to make it a bit better on the Dreamliner and were able to bump it up a bit

  Humidity is improved, yet still dry as the desert. Humidity levels on the Dreamliner are 10%-15% — better than 7% on other planes on long trips

source

but it's still a big issue. There are two main reasons they can't really increase it that much.

First off, water is very heavy. Since planes pump in dry exterior air they would have to humidify it which means they need to carry enough water to do so. This weight would greatly affect the useful load of the plane. Now you could try to recycle some of the ambient moisture, but on a large scale that takes power, which takes fuel, which comes back to the weight issue.

The other issue (although not as often thought about) is the longevity of the airframe. The extremely dry conditions that airliners see for most of their time actually helps to prevent corrosion on the airframe as well as rust on any rustable parts. By pumping moisture into the airframe you will run the risk of it causing real damage to the metal components.

The temperature is a simple energy problem. To keep a plane hot you need to heat it faster than the exterior temp is cooling it (or evenly to keep it a constant temp). Insulation can help with this but you are still going to see some cooling. On a rudimentary level you can apply Newton's law of cooling here and keep in mind the exterior temperature is in the -40 (and below) area (according to today's charts).

On to the pressure,

This, of course, is a big one, but, in reality, it's not a big deal. While it may seem a bit irritating, 8000ft atmosphere equivalent is still more than breathable. The FAA does not require continuous O2 until 14,000 ft for unpressurized planes, so an 8000 ft equivalent cabin is more than fine. Now from a comfort standpoint, your ears may pop and you may feel some discomfort, but it's more than safe.

From a purely technological standpoint we can do this, but from an engineering use case standpoint it's better to sacrifice some of the pressure to build a lighter, thinner plane. This saves on fuel and material costs down the line. There is great hope that carbon fiber may bring a change to all this and 8000 ft equivalency will be a thing of the past. Boeing has been pushing this with the 787 having only a 6000ft pressure level which they claim alleviates problems. I have not yet flown one so I don't know first hand how much better it really is. Then again I fly unpressurized stuff often and have become somewhat acclimated to it.


On acquiring an aircraft for my own PPL training and later use I know that this matter has already been discussed in several other questions but the aircraft under consideration were almost exclusively Piper Warriors or a Cessna 172s which are 40 year old designs and heavy on fuel consumption.

Instead, I am considering light sport aircraft such as a Blackshape Prime or a Sling 2, for instance. I'd prefer a Blackshape Prime fitted with a CSU.

As I am still half-way towards obtaining my PPL, my question would be the following one: would it financially and technically (from a skill-set building perspective) make sense to acquire such an aircraft and lease it back to a school to do my training?

One of the school at my airport has two Sling 2 aircraft and they're quite popular with students. Most Warriors and 172s are now in their 3rd or 4th decade and seem to have run their course. Financially, in Australia, the dual hourly rate on a Piper or 172 is in the AUD 360 - 400 range, which includes AUD 100 for the instructor whereas dual rate on a Sling 2 is just about AUD 280, which makes it much more attractive to students and at no extra expense to the school.

Would it therefore be a good idea to buy a sport light aircraft such as those mentioned and lease it back to the school? Am I missing anything that is specific to them that still makes learning in Warriors and 172s relevant? Thanks for your inputs.

Is it possible? Sure. But there are pitfalls you need to be aware of...

First, you may find it difficult to find financing for a new(er) aircraft especially if you are still a student, and especially if you are intending to offer it as a lease-back.

Then there is insurance, which for a student purchaser is going to be expensive, and even more so if you are leasing back with the idea of it being used in a flight school as a primary trainer.

The AOPA has a good article on leasebacks:

Lenders Leery of Leasebacks
AIrcraft Owners Guide to Aircraft Leasing
Turning the tables on leasebacks

Along with any number of other articles.

Another thing you need to keep in mind is that when you put an aircraft on leaseback, you, even as the owner, are subject to the same scheduling issues as renters.

The biggest thing to remember is that buying an aircraft for use in training is not a way to save money, you would be surprised at what it costs to own an aircraft, even on leaseback. You have annuals, maintenance, insurance, etc.


What does the "BA/" stands for in this ATIS? LTBA ARR
  ATIS V
  0920Z EXP ILS DME APPCH 05 BA/ FOR RWY 05 TRL 110 AFTER VACATING RWY CONTACT 121.8 WIND RWY 05 340 DEG 07KT VRB BTN 310 AND 020 DEG VIS 9999 FEW/02000 FT BKN/03000 FT T 21 OP 15 QNH 1017 NOSIG
  END OF ATIS V

I think the BA/ references "Braking Action" in the ICAO D-ATIS sequence. Since the example report from LBTA (Istanbul Ataturk International Airport) does not suggest that a Braking Action value would be assigned (no rain, etc), it appears to be a placeholder for that information if it was provided.

Below is an excerpt from Annex 11, to the publication - Convention on International Civil Aviation (Air Traffic Services), showing the sequencing (where it would normally appear in the D-ATIS report) of a Braking Action report (if provided/available).


See-through/transparent aircraft I am a pilot who loves the aviation experience. Can we build a full see through plane using material as strong as the current materials used to build the body of an aircraft. Is there research or work being done on this?
I think that aviation should see through the glasses of adventure travel. And, we should be able to see it all as we fly. Is this possible??
Thank you for your time and excitement,
jason

It is possible, but not using typical modern construction techniques.
You have to build a structural frame and then clad it with a non-structural skinning. This technique was widely used in the early days, although the skinning was doped fabric and not transparent.
The frame technique is still used for many ultralights and hang gliders, and some transparent films are strong enough to be used for the skinning. But these types seldom have a significant fuselage. One exception I can think of is Paul MacCready's man-powered Gossamer Condor and Gossamer Albatross prize-winning man-powered aircraft, which had a fuselage nacelle slung under the wing, containing pilot Bryan Allen and the drive train.
Some helicopters such as the Bell Sioux have such large "fishbowl" cockpit glazing that it exposes all the cockpit innards. The Edgley Optica was a prototype observation aircraft along similar lines.
Talking of cockpit glazing, some flying wings had a prone pilot with the glazing forming part of the wing leading edge. These included some of the Northrop and Horten designs.
The Junkers G.38 airliner accommodated some passengers in wing cabins and the glazing to these formed the wing leading edge.
So yes it can be done in principle. But materials such as plexiglass or mylar film are not really suited to such things as enclosing engines or resisting birdstrike, while strengthened glass or polycarbonate get heavy and expensive so that on most planes, only small windows are practicable.
Advanced materials such as structural glass are being increasingly used in architecture, and I have no doubt that the manufacturers and researchers will keep pushing the envelope to develop new materials and new applications. But I don't know of any research focused on airframes.


What would happen if an airliner had too much fuel for its next flight? There's an old saying that there's never too much fuel left in your tanks or too much altitude below you.

However, in terms of airline fuel planning, could there be a situation where an airliner would land with more fuel than is needed for its next flight, to the point that this extra fuel would be problematic?

Would this, or other circumstances, necessitate that fuel be removed from an airliner before a flight, for example due to a higher payload on the upcoming flight?

This would be an uncommon situation and the decision on what to do will typically be handled by your dispatcher.

Take the extra gas and restrict passenger/cargo weight as necessary.

This is the easy option but it could mean leaving people behind.
Defuel to the normal amount of fuel needed (e.g. release + taxi + contingency fuel)

This normally means the fuel is considered contaminated and will be disposed of.  There are ways of de-fuelling and re-using that fuel for another plane, but it requires specific operations and equipment that only likely to be available in the hub or perhaps a maintenance station.  De-fuelling can be slow and will delay the flight.

In the end this comes down to either weight restricting the plane or taking a delay and wasting some fuel.  The timing and economics of the decision will depend on many factors and each case would be judged individually.


Which pilot (pilot flying, pilot monitoring) handles CPDLC (operates CPDLC interface)? This question relates to commercial flights, typical two-pilot crew: In some airspaces, e.g. North Atlantic, pilots and Air Traffic Control use Controller Pilot Data Link Communication (CPDLC, datalink) to communicate instead of VHF or HF.
Voice communication is ususally handled by the Pilot Monitoring (PM, or pilot non-flying PNF) - meaning the PM does the communication, and the PF executes instructions from ATC. With regards to CPDLC, which pilot handles datalink communication, is this also the PM as per standard operations? Are there standard operations for this?

With most airlines, the PM(pilot monitoring) handles datalink communication, with confirmation from the PF(pilot flying) before executing any  instructions, clearances, or changes.

As with everything, there might be some exceptions at some airlines.


How can I estimate the required T/O power for propeller aircraft? How can I estimate the maximum required take-off power for a propeller aircraft with the following available data?

Wing surface S
Max. lift coefficient in T/O configuration cL
Take-off distance available d (regardless of obstacle clearance etc.)
MTOW
Airfield altitude (let us assume MSL)

Is the data available even enough?

You need takeoff speed (from the lift coefficient, wing surface and altitude) and the time in which you need to achieve it (before you run off the runway). That'll give you the needed acceleration ($a = \frac{\Delta v}{s}$)

From that you can know how much force the prop must generate ($F = ma$).

Add some margin to account for friction losses.


What are the main differences piloting Boeing vs. Airbus aircraft? What are the main differences in flying a Boeing vs an Airbus aircraft?

Ignoring cosmetics, e.g. nose/window shape (see How can I tell apart an Airbus from a Boeing?)

On a pilot-vs-FBW system perspective, as mentioned in the comments to the question, the most notable difference is the authority priority:

Boeing trusts more the pilots: they can supersede the Fly-by-wire automatic commands by exerting enough force on the controls
Airbus trusts more the FBW system: if the system is fully functional ("Normal law") it will always have priority over the pilots to protect the aircraft and keep it in the envelope, but they still have room for "non-standard" maneuvers, e.g. commanding bank angles between 33° and 60°. The autopilot can be activated and de-activated at will by the pilots, and it sits on top of the FBW envelope protection.

One of the most famous examples where this comparison emerges (and the subsequent debate about which approach is better) is the China Airlines 006 accident.
I won't go into detail, there is the accident report that will provide much more information that I can remember, but suffice to say that this 747 was recovered from a quite unusual attitude

As mentioned in the wiki article, the report states that the passengers were subject up to 5 gs during the maneuver and the stress on the horizontal tail surface has been so great that as a result it was damaged:

The usual argumentation goes along the lines that, would this had been an Airbus, the pilots would not have been able to save the aircraft.
See for example this PhD thesis at page 184 of the pdf, section 6.2.3 "Pilot Authority at the Boundary":

  It is likely that if the aircraft had prevented the crew from initiating control commands that would lead to aircraft damage, the aircraft (and passengers) would have been lost.

The problem with such a comparison? It focuses on the recovery after the unusual attitude was achieved and totally forgets about the sequence of events that lead to it or, to the very least, assumes that an Airbus would have responded in the same way to the preceding events (then why make a comparison at all?)

An honest comparison would take into account this and acknowledge that an Airbus in Normal Law would not enter a spiral dive in the first place, even with an engine out, as bank protection/attitude-hold would prevent it.


Can pilots turn off warning alarms? Re: Aeroperu Flight 603 I just watched the Mayday S1E4 episode concerning Aeroperu Flight 603.  Gut wretching to see the pilots in that situation.  On listening to the recording tape, alarms were blaring constantly, some for maybe as long as 15 minutes straight.  I can only imagine that that constant blaring adds stress and confusion to the cockpit.  So I wanted to ask if pilots have the ability to silence alarms after a certain period of time?

Sometimes they can sometimes they cant, how to do it varies by aircraft but generally alarms can often be silenced by acknowledging they are going off and pressing some kind of button. On my little Piper Archer the alternator under volt it just a light and can't be shut off but if my G430 throws an alarm or warning it can usually be silenced.

On the 737 some alarms cant be silenced and some can

  Cockpit aural warnings include the fire bell, take-off configuration
  warning, cabin altitude, landing gear configuration warning,
  mach/airspeed overspeed, stall warning, GPWS and TCAS. External aural
  warnings are: The fire bell in the wheel well and the ground call horn
  in the nose wheel-well for an E & E bay overheat or IRS’s on DC. Only
  certain warnings can be silenced whilst the condition exists.

A lot of aircraft display failures on some kind of annunciator panel or glass cockpit equivalent. These lights typically can not be turned off until the error is addressed (fire suppressed, breaker pulled etc.). Master Caution lights (and audio warnings) can typically be shut off through the use of a Master Caution Reset switch.

  Once notified, the pilot may cancel the master caution, but a
  dedicated system or component annunciator light stays illuminated
  until the situation that caused the warning is rectified. Cancelling
  resets the master caution lights to warn of a subsequent fault event
  even before the initial fault is corrected.

The FAA's full advice on warning and caution light design can be found here.

They shed more light on the topic in this AC

  Clearing and Recalling Visual Alert Messages. Clearing visual alert messages from the current warning, caution, and advisory display
  allows the flightcrew to remove a potential source of distraction and
  makes it easier for the flightcrew to detect subsequent alerts. a. The
  following guidance should be applied for clearing and recalling or
  storing the visual alert messages:

  (1) If a message can be cleared and
  the condition still exists, the system should provide the ability to
  recall any cleared visual alert message that has been acknowledged. 11
  12/13/2010 AC 25.1322-1

  (2) Either through a positive indication on the display or through
  normal flightcrew procedures, a means should be provided to identify
  if alert messages are stored (or otherwise not in view). b. The visual
  alert message must be removed from the display when the condition no
  longer exists (§25.1322(a)(3)).

In short, if a message can be cleared you should be able to pull it back up easily and if the problem goes away the alert should clear as well.


Why didn’t the space shuttle have flight control manual-reversion capability? The Wikipedia article on STS-1 (the first orbital space shuttle mission), in a discussion of all the problems and malfunctions occurring during the mission, mentions that, due to an unexpected shockwave during booster ignition, Columbia’s rear bodyflap (part of its pitch control system) was (unbeknownst at the time to either Mission Control or the crew) bent upwards beyond the point where damage to the shuttle’s hydraulic systems would have been expected.

According to the article, had Columbia’s hydraulic lines actually been breached, resulting in a total loss of hydraulic fluid, this would have rendered the shuttle uncontrollable as soon as the aerodynamic forces on the orbiter during reentry exceeded the control authority of its reaction-control system.

Small- to medium-sized aircraft with hydraulically-actuated flight controls essentially always have some form of manual reversion capability in case a no-hydraulics situation occurs, where the primary flight control surfaces (always the elevator and ailerons, and sometimes the rudder as well) are operated manually by the pilots, usually by control cables attached to the pilots’ yokes and pulling (depending on the aircraft) either on the control surfaces directly or on servo tabs which then generate aerodynamic forces which move the control surfaces.  (Large aircraft generally don’t, even though even partial control authority would still be better than nothing, but that’s another question.)

To the best of my knowledge, the largest Western aircraft to have flight controls with manual-reversion capability is the Boeing 737 MAX,1 which has provisions for full manual control of the ailerons and elevator, plus a small amount of undocumented manual rudder control (as the rudder is rarely or never used during normal flight, manual rudder control is far less critical to have than manual elevator and aileron control, and using a manual aileron-and-elevator system rather than a manual three-axis system allows for a simpler system; however, due to the design of the 737’s rudder system, the rudder can nevertheless be manually moved slightly by a sufficiently large amount of force on the rudder pedals).  The 737 MAX is considerably larger than a shuttle orbiter, with a maximum weight of 88,300 kg, as compared to the shuttle’s empty weight (as its flight control capability, or lack thereof, would only be relevant during descent, when it would generally be empty, and, therefore, at its lightest) of 68,600 kg; even with the shuttle orbiter at its maximum allowable weight (to allow for the possibility of a hydraulic failure during an abort scenario while carrying the absolute heaviest possible payload) of 109,000 kg, it would be less than a quarter again the size of a 737 MAX 9, which would seem to indicate that including manual-reversion capability for the shuttle’s flight controls would have been doable.

Why, therefore, wasn’t it included?

1 The Ilyushin Il-62 is almost twice as heavy as the 737 MAX 8, with an MTOW of 165,000 kg, and has a fully mechanical flight control system (no hydraulics even in normal operation); however, it was a Soviet aircraft, making it somewhat unlikely that the space shuttle design teams could have gotten access to its technical data (especially given the heavy involvement of the U.S. Air Force in the design and development of the shuttle - for instance, the shuttle would have had much smaller wings were it not for the design requirement to launch into a polar orbit to either deploy a U.S. spy satellite or kidnap a Soviet one, and then reenter and land after just one orbit, with the consequent large crossrange requirements).

The biggest reason (as is typically the case with space craft) was likely weight. It costs quite a bit of money to get even small amounts of mass into space, when talking about a vehicle keeping it light while maintaining a basic level of safety is key.

Unlike the 737 the shuttle lacked the yoke style controls that would be required for this kind of a system. The shuttle stick not only operated the flight control surfaces while on approach but also drove the reaction control system while in space. So there would be no way to operate a manual backup system even if there was one (without changing all the control surfaces).

The orbiter also had a triple redundant hydraulic system which was considered fail safe enough, and due to the highly automated flying of the orbiter hydraulic systems proved to be what was needed to make the system a reality. Cable controls for manual reversion in a flight regime barely flyable by humans would have largely been dead weight.


What is the stall speed of the KC130? Saw the video of the helicopter chopping off its own refueling probe. That made me wonder what the stall speed of the tanker is, and how difficult it is to fly slow enough for the helis to keep up.

The stall speed is around 95-100 knots for the older F variant, and something like 90-95 knots for the newer J variants.

A KC-130 can refuel between around 100 and 270 knots. The lower end of this is well within the maximum speed of many military helicopters, eg the Pave Hawk, Black Hawk, Chinoook or Sea Stallion.

That leaves an "overlap" of around 20-40 knots, without having to approach too close to either the stall speed of the KC-130 (around 90-95 knots) or the VNE of the helicopter (usually between 140 and 170 knots for a military helicopter). This is enough for aerial refuelling, which usually states a fairly tight bracket for the refuelling speed.

As mentioned here:

  The United States Marine Corps has chosen the KC-130J tanker to replace its aging KC-130F tanker fleet. The new KC-130J offers increased utility and much needed improvement in mission performance. As a force multiplier, the J tanker is capable of refueling both fixed wing and rotary wing aircraft as well as conducting rapid ground refueling. The refueling speed envelope has been widened from 100 to 270 knots indicated airspeed, offering more capability and flexibility.


Why do aircraft need Mach number? Why don't aircraft operates with IAS only?

Is there any other usage of Mach number except monitoring of shock waves formation?

How Mach number is calculated?

Mind you, not all aircraft need one, especially slower piston ones.

As you get closer to higher speeds, where compressiblity becomes significant, and you are approaching the speed of sound, the air starts to behave differently aerodynamicaly.

Also: remember how the air is a little bit accelerated over the wing because of the shape of the wing? Well, if you fly close to mach 1 and accelerate the air even further, a little bit of that air is now moving supersonically over the wing. And you now have a shockwave on your wing.

The plane might start pitching down (wing momentum changes), wing stalls (yeap, from too much speed), aerodynamic center moves etc, flight controls might stop working. Google ‘Mcrit’ and ‘mach tuck’ for more, but there are a lot of bad things generally happening in that region.

What it all boils down to is that the wing now has a built-in limitation by the engineers:do not fly faster than (say) mach 0.9 or you will be in trouble.

Now that we have a speed limit that depends on the speed of sound, we really need an instrument to show the pilots when that limit is approaching.


Are there any missile systems as of 2019 capable of shooting down aircraft in excess of mach 6? Are there any missile systems, ground based, or air to air, as of 2019 that are capable of shooting down aircraft in excess of mach 6, such as the X-15?

For simplicity I'm ignoring the fact that the X-15 may be considered a spacecraft or "space plane".

The Russian S-400 SAM System is claimed to be capable of speeds in excess of Mach 12 and ranges of 400 km (250 miles).  It can, in theory successfully engage and defeat hypersonic targets, albeit with a much smaller lethal envelope than against conventional aircraft or missiles


Is this really a British Airways 727? I came upon this clip on YouTube this week:

It appears to depict a Boeing 727 in British Airways livery. My first thought was that it's a Trident, but it is definitely a B727. I was a regular visitor to Heathrow and Gatwick in the 70s and 80s in my plane spotting days and I don't remember BA ever operating 727s.

So, how did this 727 come to be painted in BA colours?

Bonus question: which airport was this filmed at, since it's not either of the two main London airports?

Interesting question!

In the background, a Lufthansa Boeing 747-400 can be seen. Therefore, I assume the airport is a Lufthansa destination. Since the 727 is not exactly a long range aircraft, but the 747 is, my first thought would be that the airport is in Germany.

I couldn't really see what livery the 737-200 in front of the LH 747 was, but soon in the take-off roll (0:10 seconds) a propeller aircraft (Dash 8?) with a South African Airlines tail appears. Then during the rest of the video many SAA tails are visible and also a number orange tails. I needed to get my first aircraft book (printed 1989) to discover that the old livery of SAA featured an orange tail.

It is thus pretty safe to assume that the airport is in South Africa.

That makes it quite rare for a British Airways 727 to appear there. The range of the aircraft is approximately 2000 nautical miles which is a bit short of the almost 5000 nautical miles that London - Johannesburg measures.

I then remembered a recent accident in South Africa involving a Comair Boeing 737-400 in British Airways livery. This led me to believe that this particular Boeing 727 in the video may be a Comair 727 in BA livery too.

A little search turned up this picture on airliners.net, confirming that Comair indeed operated the 727 in BA livery.

The airport is O.R. Tambo in Johannesburg:

A still from the youtube video showing some buildings in the background

The same buildings in Google Maps


Does a flight instructor rating supercede a ground instructor rating? In the FAA jurisdiction, if an instructor candidate were to become a ground instructor (advanced and instrument) and receive that certificate, then later become a flight instructor (and CFII), would there be any value in retaining the ground instructor certificate? The flight instructor certificates held at that point provide all the same privileges. Is the ground instructor certificate superceded?

The flight instructor certificates held at that point provide all the same privileges.

This is not true.  A ground instructor certificate is valid to give ground training for all aircraft... airplane, helicopter, glider, balloon, etc.  A flight instructor must have those ratings on their certificate.

Record keeping requirements also differ between the two certificates.

§61.189(b)(2) requires the flight instructor to keep a record of all knowledge test endorsements to include the student name, date, kind of test and result.

The ground instructor has no such requirement.

The flight instructor must also have an advanced or instrument ground instructor certificate to qualify for a gold seal.


What happens if I cross the ADIZ line without a flight plan and no clearance or contact with ATC? I'm on a flight to/from the Caribbean on a single engine Cessna and I crossed the ADIZ (Air Defense Identification Zone) line.  I haven't filed a flight plan, I don't have clearance from ATC, and I'm not in contact with ATC.  I do have mode c transponder active on ALT and code is 1200 (VFR) and my altitude 6500 ft MSL.

The ATC would see the aircraft, its altitude, and its velocity.  Based on this flight data, ATC would most likely conclude this was an ignorant or lost pilot or lost drone, and no threat posed.  Have there been any instances where military or coast guard air craft were actually sent for  interception of such small and slow aircraft?  What are the statistics on this?  What would the fines and penalties be?  I'm assuming this would apply more when entering the US ADIZ than exiting.

In the late 60's, in a C152. I flew a guy, at a low altitude out of Key West to the Marquessa Islands area to look for sunken Spanish galleons.  On the return trip I was nervous flying at 200 feet above the ocean and climbed up to 3,000 feet.  After a few minutes al said altitude my windscreen flashed black. A F-4 had come from behind and below - zoomed up a few yards in front of me! Looking behind me I saw his wingman, gear and flaps down, S_turning on my six.

A quick call to FSS clarified the situation.

That is what happened to me upon inadvertent entry into the ADIZ. I don't expect it has changed.  There were no followup actions other than the echos of the F-4's pilots laughter.


Static port and Bernoulli Static ports open directly to the outside of fuselage. When aircraft is flying, there will be air flowing outside of static port. How does this not cause a vacuum effect inside the static port. Due to the Bernoulli Effect, as the speed of air flowing outside of fuselage increases, the pressure inside static port should decrease. This means, on same altitude, depending on my aircrafts speed, I will read different values on my altimeter. What prevents this ?

When aircraft is flying, there will be air flowing outside of static port.

No, that is not true if the aircraft flies without sideslip and at constant altitude (which it should do most of the time). Instead, there will be a pressure equilibrium between the air in the lines leading to the static port and the static pressure outside. The position of static ports is carefully chosen so the airflow around them is neither accelerated (which would lower local static pressure) nor retarded (which would increase local static pressure). Also, static ports are on both sides of the fuselage so the ram effect of the windward static port in a sideslip is equalised by the suction on the leeward static port. Note that in this case there is indeed some air flowing from the windward to the leeward side through the static line connecting both.

Now to the Bernoulli effect. It says in essence that the sum of static and dynamic pressure is constant (if we disregard the height term, which is not needed in this context). Since you want to measure the same pressure that a stationary observer would measure, you need to pick a place along the airframe where the dynamic part of the pressure is zero because all flow is tangential to the port opening. Small errors can be corrected by calibrating measurements in flight test.


How do rocket engines produce more thrust than aircraft jet engines? I can't find the reason why rockets are able to produce so much thrust when compared to turbojets.

I do know that the rockets carry their own own supply of oxygen since there is no oxygen in space or the upper region of our atmosphere. And that the upper stages use hydrogen for longer range.

But given that RP-1 is kerosene basically. A highly refined form of kerosene that is used in jets but kerosene nevertheless. Is there something else that gives the first stage of the rocket it's unbelievable thrust or is it just all down to the RP-1 fuel?

For one, don't only look at the engine, but at the whole propulsion system. This includes tanks, piping, controls, pumps and the actual engine. Now the rocket looks much less favorable, especially if you size the tanks for equal running times.

The rocket does not need any of the parts which are ahead of the combustion chamber of a jet and also does not need the turbine. Also, being designed for full thrust only, it does not need an adjustable nozzle. Please look below at the engine installation of a typical airliner (I tried but could not find a fitting cross section of a turbojet plus intake):

Jet engine and nacelle cutaway drawing (picture source). As @Talisker correctly observed in the comments, the labels "high speed jet" and "low speed jet" have to be swapped in order to be correct.

Only the part labeled "combustor" and the section aft of the turbine are actually comparable to a rocket engine - all else is needed to condition and compress air or drive the turbo machinery in front. A rocket enjoys the luxury of being fed propellant and oxidizer at just the right ratio, condition and at high pressure, and since the oxidizer is mostly pure liquid oxygen, the turbo pumps for compressing it can be much smaller than the turbo machinery of a jet which works with an 80% nitrogen - 20% oxygen mixture of gasses.


What do these two METAR codes mean? METAR YPJT 070300Z AUTO 10010KT 9999 // NCD 27/10 Q1018 RMK
RF00.0/000.0

In the above METAR report, I have two questions:

What does the fraction "27/10" mean?
What does "RF00.0/000.0" also mean?

The term 27/10 is the temperature (27°C) and dew point (10°C).
The RF term in the remark section is used to indicate the accumulated rainfall (in this case 0, so no rain):

What is the meaning of the RF group in METAR/SPECI and TTF?
This group reports rainfall in the last ten minutes and accumulated rainfall since 0900 local. For example, RF02.2/024.4 reports that 2.2mm of rainfall has fallen in the 10 minutes prior to the report time; and 24.4mm has fallen since 0900 local.

(Australian Government - Bureau of Meteorology)


Do most airport use one and only one runway for landing? Do most airports (especially busy ones) use only one runway at a time for landing? For example, I know Heathrow uses only one of its runways at a time (although they might switch to another half way through the day).

In general, any runway can be used for both takeoffs and landings. However, switching back and forth requires substantial safety margins. If you can use one runway for just takeoffs and another for just landings, efficiency goes up. If those runways are parallel, efficiency goes up again. This is why major airline hubs tend to have pairs of parallel runways.

Averaged over a day, the number of takeoffs and landings should be about the same, so the normal mode would be to split the runways as evenly as you can. If the number of runways isn't even, the last runway will often alternate throughout the day to mitigate short surges in one or the other.

As to which runways are used for what, the ones used for landing should be as far from each other as possible to maximize lateral separation of arriving traffic on instrument approaches. (Departing traffic mostly separates itself.) So, if you had four runways organized as two pairs, you'd expect the "inner" one of each pair to be used for takeoffs and the "outer" one of each pair for landings.

In the case of Heathrow specifically, runway usage is largely dictated by noise abatement agreements with nearby towns, rather than what makes the most sense operationally.


Do airlines have contingency plans to keep passengers warm in the event of an Arctic emergency landing (or otherwise a diversion)? Imagine you're flying to Los Angeles in February, but find yourself landing in Iqaluit instead, with a daily mean of −27.5°C, without considering the effect of wind.  Even walking from the cabin to a runway bus may involve sufficient exposure to cause serious injury if passengers (and crew) are dressed for +20°C.  Most intercontinental flights pass over high latitudes, so a high-latitude emergency landing can't be that exceptional.

Are airlines required to have contingency plans to keep passengers warm in such an event?  There wouldn't be space to stock lots of bulky fur coats on a plane, but groundside there would be.

Taking FAA/USA as an example.

For north of 78th parallel, FAA operations are conducted in compliance with several regulations, including: FSIMS 8900.1, vol 3, Chapter 18, Section 4  Part B Operations Specifications: OpSpec B055 - North Polar Operations. The alternate airports must be able to receive the passengers of the diverted aircraft and to take care of the "physiological needs of the passengers and flightcrew for the duration until safe evacuation".

B055 requires the operator to demonstrate a recovery plan to extract passengers from a diversion airport prior to conduct commercial passenger operations. While it's the operator responsibility to provide the details, the general requirement answers your question:

  A recovery plan is required that will be initiated in the event of an
  unplanned diversion. The recovery plan should address the care and
  safety of passengers and flightcrew at the diversion airport, and
  include the plan of operation to extract the passengers and flightcrew
  from that airport.

As the plan should address the care and safety of people at the alternate airport, any protection against low temperature must be provided in order for the plan to be accepted by FAA. The plan must also demonstrate the ability to extract passenger from the airport within, if possible, 12h (which may be a challenge in Arctic region) and at most within 48h.

Extract of B055 (also discussed at PPRuNe, some copy-paste done from here):

Minimum Equipment List (MEL)

  Before receiving FAA authority to conduct polar operations, the MEL must indicate that the following systems/equipment is required for
  polar operations dispatch:

  3)    Communication system(s) relied on by the flightcrew to satisfy
  the requirement for effective communication capability.

  4)    Except for all-cargo operations, expanded medical kit to
  include Automated External Defibrillators (AED).

Training Program Requirements

  The following must be in the approved training programs:

  Training on special considerations, such as diversion decision making into austere airport environments to include aircraft
  performance, crash, fire, and rescue availability, and passenger
  support; and
  Flightcrew training in the use of the cold weather anti-exposure suit.

Special Flightcrew Issues for Long-Range Operations

  The operator needs to address the following special long-range
  flightcrew issues:

  A minimum of two cold weather anti-exposure suits will be required to be onboard so that outside coordination at a diversion airport with
  extreme climatic conditions can be accomplished safely.

Dispatch and Crewmember Considerations During Solar Flare Activity

  The operator must be aware of the content of AC 120-52, Radiation Exposure of Air Carrier Crewmembers, and provide crewmember training
  as stated in AC120-61, Crewmember Training on In-Flight Radiation
  Exposure.

En Route Polar Diversion Alternate Airport Requirements

  Operators are expected to give definition to a sufficient set of alternate airports for polar diversions, such that one or more can be
  reasonably expected to be available in varying weather conditions.
  The flight must be able to make a safe landing, and the airplane maneuvered off of the runway at the selected diversion airport. In the
  event of a disabled airplane following landing, the capability to move
  the disabled airplane must exist so as not to block the operation of
  any recovery airplane.

  In addition, those airports designated for use must be capable of protecting the safety of all personnel by being able to:
  (1) Offload the passengers and flightcrew in a safe manner during
  possible adverse weather conditions;
  (2) Provide for the physiological needs of the passengers and
  flightcrew for the duration until safe evacuation; and
  (3) Be able to safely extract passengers and flightcrew as soon as
  possible (execution and completion of the recovery is expected within
  12 to 48 hours following diversion).

Validation Flights

  An FAA-observed validation flight is required in which the operator exercises its reaction and recovery plan in the event of a diversion
  to one of its designated en route polar diversion alternate airports.
  The exercise of the operator’s reaction and recovery plan may also be
  completed prior to the validation flight.


Where I can get historical jet fuels prices? I would like to analyze jet fuels prices in 2014.

Where can I get jet fuel prices for 2014, only in USA and Russia?

As there are different types of fuels, it would be okay to get prices for one (believe, trends are the same) or for all types.

U.S. Energy Information Administration keeps tabs on most refined and crude prices including kerosene-type jet fuel. For those who hail from metric units' land, these are in dollars per gallon.