What does "POS ITERV WAS CHGD" mean on the ACARS page of a Boeing 737? During the whole flight, the message "POS ITERV WAS CHGD" appeared frequently on the ACARS page of the MCDU (Multipurpose Control and Display Unit). The aircraft is a Boeing 737.  I cannot find any reference in the FCOM (Flight Crew Operating Manual).

What does this message mean and why does it appear?

Your aircraft is reporting its position periodically over the Aircraft Communications Addressing and Reporting System (ACARS) to the airline operations centre (AOC).

Since there are costs related to sending these position messages, the interval in which these message are sent drives operating costs for the airline.

This patent from China Southern Airlines (original Chinese version here) describes the behaviour you have observed on the MCDU. Apparently it allows the AOC to change the position reporting interval over ACARS remotely. If the interval is changed, a "POS ITERV WAS CHGD" text is displayed on the MCDU scratch pad.

The relevant text from the patent (including translation & typesetting errors):

  ...

  [0087] PTIC message display unit, see FIG. 6, the module receives PTIC
  PTIC uplink triggering instruction, parsing PTIC variable, position
  determined by the adjusted multicast time interval T3, if the variable
  is valid PTIC, is given in M⑶U unit tip text message to inform the
  crew of the current position of the broadcast time interval has been
  changed, the present invention uses "P〇S ITERV wAS CHGD" text gives
  the unit prompts; the message is always displayed in MCUD the scratch
  area (Scratchpad) until a new the message will disappear after replace
  the unit or manually pressing CLR keyboard. ...


Strange plane-shaped object at UK airport A friend sent me the following image, spotted at an UK airport. Do you have any idea what that might be?

It looks a bit like MD-11/DC-10 transport case, but i have no idea. Is something like this used to transport airplanes?

That's a training rig for airport fire crews. They can usually be set on fire through whatever controlled means and the crews can practice approaching and working around aircraft.

In fact, after a cursory Google it's either the one at Heathrow or is near identical to it.


What WWI biplane is this model? What WWI biplane is this model?

(own work)

My first guess (but it is a guess) is an AirCo/de Haviland DH.4.

Reference: https://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=448


What exactly is engine design speed? Any further information is welcome, this is what I have learned so far:

Engines are designed to operate at a certain RPM (N1). The compressor consists of small 'wings' which are fixed in position, so the angle of attack will vary only by engine speed and forward speed. The engine design speed should be 85-95% N1 for most turbofan engines, this results in an optimum airflow through the compressor. Above or below a higher risk exists for an engine to stall.

Engine design speed is the shaft RPM and vane pitch which yields the rated thrust that the engine was originally intended to furnish. This will typically be quoted for takeoff at or near sea level at a standard ambient temperature (including a time limit to control maximum temperatures inside the engine) and for optimum cruise conditions at altitude (which will include specification of nominal fuel burn rate in pounds per hour).


For how long are state and federal aircraft registrations valid? How long is a state registration valid for and how long is a federal registration valid for?
and for state I mean North Dakota if any of you know where to look for that.

Federal registration is for three years, according to the FAA (the actual regulations are in 14 CFR 47.40):

  Aircraft registration issued due to renewal expires three years from the expiration date of the previous certificate.
  Aircraft registration issued to a new, import, or reinstated aircraft entering or re-entering the U.S. Civil Aircraft Register
  expires three years after the last day of the month in which it is
  issued.

State registration - if any - is up to each state so you need to check with the state where the aircraft's owner registered it.


Why do some aircraft have pods on their wing tips? By JetPix [GFDL 1.2 or GFDL 1.2], via Wikimedia Commons

Why do some aircraft have pods on their wing tips, like this Cessna 414?

Wingtip pods or winglets differ in installation reason from aircraft to aircraft. Here is a non exhaustive list of possible reasons:

Fuel tanks
Whitcomb bodies to enhance the area rule of the aircraft also known as Kuchemann Carrots
Vortex generators and relievers - used to enhance aircraft aerodynamics and modify fuel consumption
Mass balance - in particular on forward swept wing aircraft
Housings for sensors or landing gear


Why are some contrails longer than others? I've often noticed that planes flying on more or less the same track, headed in the same direction leaves different contrails. By different I mean how long they stay visible and the length of them. Why is this so? Is it weather related?

It is a mixture of factors. All else being the same:

a contrail at a higher altitude will last longer (the lower temperature slows the sublimation of the ice cristals)
a contrail formed in air with higher humidity will be bigger and last longer (more water is being turned into ice)

If there is not enough (relative) humidity, the contrail will not form at all. See for example this image:

Image from NASA

The contrails start forming on the east, near the clouds where you have a higher humidity, and do not form on the west, where no cloud is present and you have higher temperature/lower humidity.

  I've often noticed that planes flying on more or less the same track, headed in the same direction leaves different contrails.

What you observe might be airplanes flying at different altitudes and thus encountering different humidity/temperature combinations, giving birth to contrails with different histories.


If sweep delays compressibility, why does 747 cruise slower than A380? B747 has a sweep angle of 37 deg and A380 has a sweep angle of 33 deg. If the main reason for sweep is to delay compressibility effects and increase operating Mach number, why does B747 cruise at a lower speed than A380?

From Wikipedia, the cruise speeds of the both airplanes are fairly similar:

A380, nominal wing sweep angle 33.5 degrees, cruise speed Mach 0.85

Boeing 747: nominal wing sweep angle 37.5 degrees, cruise speed Mach 0.84 .. 0.9, depending on the model.

So those numbers would contradict the claim in your question, but align with your expectations.
There are several other things to consider. The nominal cruise speed of these planes is more dictated by efficiency, required power for a given speed, and fuel prices. The 747 is an older design, when fuel was cheaper, the general tendancy is that modern airplanes reduced the cruising speed slightly in favor of higher efficiencies.
considering the sweep, raw numbers:

cos(33.5 deg)= 0.83
cos(37.5 deg)= 0.79

So the difference of approx 4% here seems to reflect the difference in cruising mach numbers: the higher sweep of the Boeing 747 reduces apparent Mach number roughly by the same amount that it is flying faster.
Then, for both airplanes, and certainly for the A380, the wing aspect ratio is quite low. So there's a point to challenge how much the sweep actually angles differ, from an aerodynamic point of view. It may be very well that effective angles depend a lot more on local airfoil shapes, low aspect ratios, and other 3d effects than they depend on the nominal sweep angle.
All that said, the swept wing has more advantages than just reducing the apparent Mach number. There is

enhanced aerodynamic stability around the yaw axis (this may even help in the event of asymmetric thrust due to an engine failure)
enhanced mechanical stability of the wing itself under aerodynamic loads
trim properties in transsonic aero regimes

The final design is then a result of many different considerations.
Eg, IIRC, the wing span of the A380 had a limitation so it would "fit into standard airports", and there were likely some trade-offs in aerodynamics for that reason.


What does a white diagonal line mean on an Airbus ECAM DU? When my A321 powers up, the lower ECAM DU shows only a diagonal white line. What does it mean and what would be the fix?

Display Management Computer issue:

  If a DMC fails, all information is removed from the displays it
  controls and replaced by a white diagonal line to indicate a working
  display with a failed source. ECAM will detect the failure and provide
  a sequence of alerts.

  Due to the priority rules, the E/WD display will
  move to the lower DU if it was DMC1 that failed. The EIS DMC switch is
  used to replace the failed DMC with DMC3.

Source

Steps to clear warning:

  First select DMC #3 to isolate fault to DU or DMC. If DMC is at fault
  reset above associated circuit breaker for 5 seconds. If fault is with
  DU reset these (CAPT PFD/ND = G3/E1) (FO's PFD/ND = R3/R4) (Upper ECAM
  = E5) (Lower ECAM = R11).

Source

More in the maintenance manual at AMM31-60-00-710-001. (EIS start).


Why were the 747SP's trailing-edge flaps so much different than those of the -100/-200? I read several decades ago about how the 747SP's trailing edge flaps were substantially redesigned from those of the "original" 747-100/-200s.  The images on the 747SP Wikipedia page clearly show what appears to be an unslotted Fowler flap - contrast with the triple-slotted Fowler flap of the 747-100.

Why the major re-design?

Related sub-question:  The Wikipedia page also mentions "... the SP's heavy wings" as one of the factors contributing to its cancellation.  But, the SP had the same wing (modulo the trailing edge flaps) as the -100/-200.  How could its wing be considered "heavy" in this context?  (I'm thinking maybe it has to do with moments of inertia and/or size relative to the fuselage, but hopefully someone else here can clarify this.)

Wikimedia Commons (from the Wikipedia 747SP page)

The wing was relatively too big for the airplane after cutting bits of the fuselage off, which reduced weight by 11,000 lbs. The aircraft did not require the triple slotted high lift devices anymore: if the wing area is large enough the wing requires no flaps & slats but has relatively high cruise drag. All in all the total weight savings on the SP was 45,000 lbs. (Source)

The B747SP could not do completely without flaps, but the simpler flaps of the SP saved weight. The competition at the time was DC10 and L1011, which had lower wing area and one less engine, resulting in better fuel economy.

B747SP: 300,000 kg, wing area = 511 m$^2$, wing loading = 587 kg/m$^2$
L-1011: 231,000 kg, wing area = 320 m$^2$, wing loading = 722 kg/m$^2$
DC-10 : 263,100 kg, wing area = 368 m$^2$, wing loading = 715 kg/m$^2$
Source

In cruise, a smaller wing area means less resistance: higher wing loading gives better fuel economy, but creates problems at low speed which need to be solved with high-lift devices.


Why do modern jetliners provide Thrust Reversers at all in their design decisions? Let's start with the following knowns (please correct me if I am wrong about any):

The braking force provided by the wheel brakes is much larger than that by the thrust reversers
One is not allowed to does not take credit for reversers when calculating landing distance in most aircraft. (A few exceptions exist)
Thrust reversers add quite significantly to the weight and complexity of engines
An improperly deployed thrust reverser can be critically dangerous and hence many redundant systems must be provided to prevent unwanted deployment
Modern civillian aircraft never rely on reverse thrust during flight
In the history of aviation incidents quite a few have been related to reverser problems or procedure errors.

In the light of this why aren't more large civilian aircraft designed that use only wheel brakes + spoilers to do all their braking?

More specifically, suppose you had to re-assign the braking force provided by the reversers in the initial rollout to spoliers alone how much more spoiler area would one need to provide?

Overall, spoilers + wheelbrakes seem far more docile and benign than the complexity and risks associated with reverse thrust?

What gives?

PS.

Are the any modern large passenger jet aircraft that don't have reversers at all?

There are  a couple of reason for the presence of thrust reversers:

To reduce wear on the brakes.

To provide a margin of safety (for example in wet conditions).

In 1995, NASA carried out a survey on airlines Why Do Airlines Want and Use Thrust Reversers?. The results of the survey, though dated, give an indication of presence of thrust reversers.

The main reasons given by the airlines was to provide additional stopping force in adverse weather and to reduce brake wear.

The first question posed to the airlines was "why do we have thrust reversers?" (...) The number one reason given by the airlines was to provide additional stopping forces in adverse weather conditions (i.e. on wet, slushy or slippery runways). The airlines also use thrust reversers to reduce brake wear and to provide directional control and additional safety margins during an aborted takeoff (RTO).

According to the airlines, the thrust reversers were there because they wanted them there. This meshes with the fact that the thrust reversers are not used in calculating stopping distances during certification.

When the airlines were asked who they perceived as the principal organization behind the installation of thrust reversers on commercial transport aircraft, the airlines responded that they were. That is, the
aircraft manufacturers put the systems on board the airplanes because the
airlines want them.

Most airlines recommend using the thrust reversers early in the landing to minimize braking.

The airlines weigh the economic benefits of using the thrust reversers (and engine wear) against the use of brakes and the results seem to indicate a significant amount of money saved by using thrust reversers. The report notes:

... the savings in brake system costs due to the use of thrust reversers was estimated. The results show that the total yearly savings in brake system costs is about \$8.6 million, or an average of about $17,700 per airplane for airline 17.

Though this is almost certainly an exaggeration, the numbers indicate that the airlines would definitely prefer thrust reversers over increased braking.
In the end, the reverse thrust can be important in reducing the runway requirements in case of a wet runway. In 1999, a Qantas 747 overran the (wet) runway in Bangkok and landed up in a golf course. Qantas has used only idle reverse thrust rather than full power during the landing as per the operational procedure. The official accident report included data from Boeing 747-400 Flight Crew Training Manual, which stated that,

Immediate initiation of reverse thrust at main gear touchdown and full reverse thrust reduce brake usage, thus minimising brake temperatures.
To minimise wear of carbon brakes, minimise the number of brake applications. Use maximum reverse thrust and operate the autobrakes normally.
The importance of establishing the desired reverse thrust level as soon as possible after touchdown to minimise brake temperatures, tyre and brake wear, and to reduce stopping distance on very slippery runways cannot be overemphasised..

As a result, Qantas revised their operational procedures, requiring full reverse thrust. Brake wear is an important reason for having thrust reversers. For example, in Airbus A380:

... unlike the thrust reversers on most airliners, including the Boeing 747 jumbo, they do not stop the aircraft in a shorter distance than brakes and spoilers alone. They do, however, take some of the strain off the brakes and are useful if water or snow makes the runway slippery.

The BAe 146 lacks a thrust reverser; it makes do with an airbrake in the tail and spoilers all along the wing for braking (which should give an indication of how much spoilers is required to eliminate reversers). The 146 got away with that because of the low touchdown speeds (~90 kt) and the huge airbrake, which is not avialble in the other commercial airliners. For the same amount of spoiler area in other commercial airliners (in absence of airbrakes), they (spoilers) would occupy most of the wing surface, increasing weight and complexity. Some Embraer ERJ 145s also lack thrust reversers (they are optional).


What is the reason for not providing glide slope guidance on the western approach to Innsbruck? When approaching Innsbruck (ICAO: LOWI) from the east, you intercept a localizer (111.10) which also provides glide slope indication. I believe this should be used just for guidance and not for A/P controlled descent.

Making the western approach, you intercept another localizer (109.70) that guides you in the right direction before making the final circling procedures towards the runway. However, this one has no glide slope guidance, and you have to manually compare the current altitude and DME values to the ones in the profile given in the charts (excerpt below) and correct the descent accordingly.

I'm wondering why this is. The descent in the western approach is by no means easier than when coming from the east, see images below.

The approaches differ somewhat in that the eastern localizer gives guidance all the way to runway 26, albeit offset by 5 degrees, but the western localizer is placed far from the airport and is used to get to the start of the circling procedures to either runway.

Could this be the reason that glide slope guidance is omitted, or are there other reasons not to provide this support in the western approach?

Update:
I would like to expand and clarify this question to give it a more general touch. Are there regulations that control the appropriateness of g/s equipment when it comes to the particulars of the terrain or the vicinity to the runway? Are there other properties (geographical or other) that would limit its usability?

Eastern approach profile

Western approach profile

Looking at the charts, I can see quite a few good reasons for not providing glideslope for the West approach:

The East approach leads you (almost) directly to the runway threshold, the West approach leads you a few miles east of the airport.
The East approach has more terrain clearance. If you go only slightly below the glideslope for the West approach, you will be dangerously close to terrain.
The descent profile is steeper for the West approach: you are expected to lose 1500 feet for every 3 miles you travel. For the East approach it's 1320 feet for every 3 miles.

Number 1 is very important. If some pilot decides to blindly follow the ILS needle on a East approach, eventually he'll see the runway. If a pilot does the same on a West approach, eventually he'll crash his plane somewhere in the valley. The absence of glideslope reminds the pilot he has to pay attention to the vertical space.

Tracking the glideslope accurately is also pointless, as the pilot will transition to a visual approach and circle around anyway. It won't make big difference if you were a little bit off the initial descent.

For reference, East approach:

West approach:


What’s the difference between “approved” and “legal” procedure? I occasionally see these two words used in opposition; for instance [emphasis mine]:

  In the United States, aircraft usually join the pattern at a 45° angle to the downwind leg and abeam midfield. Although aircraft may legally join the pattern at any point, the AIM clearly states that the only approved pattern entry is the 45[° angle entry].1

In the referenced circular AC 90-66B CHG 1, the words “approved” and “legal” don’t appear except in other contexts.

So,

Is this just imprecise layman terminology in use on Wikipedia?
Or do the two terms have defined meaning somewhere?

My guess is that a pilot-in-command can deviate from “approved” procedure to other “legal” procedure whenever deemed necessary by exercising PIC authority, but deviation from “legal” procedure would be allowable only in emergency (“mayday”) or urgency/distress (“pan-pan”) situations? Or perhaps also if controllers direct or authorize deviation?2

I’m curious primarily about flying under FAA and ICAO regulations, but if this terminology differs in other jurisdictions, I’d be interested in that as well.

1 From English Wikipedia, “Aircraft traffic pattern”, retrieved 16 Aug 2019 20:30Z

2 Wording in the circular §8.2.1:

  The FAA does not regulate traffic pattern entry, only traffic pattern flow.

gives a clue in specifying that the 45° entry is not regulated.

The AIM is not regulatory, just best practices approved by the FAA. You should do what the AIM says, but as PIC you are free to ignore it.

The FARs are regulatory, so as long as you don't violate them, what you're doing is legal. You must do what the FARs say (unless you have an emergency, of course).

In the case of pattern entry, other pilots are expecting you to do what the AIM says (45 to downwind), so doing something different is probably unsafe--especially if you aren't in radio contact. But if there is nobody else in the pattern, that reason doesn't apply and it is safe to enter however you wish (straight in, crosswind, etc.). It is up to you as PIC to make this decision.

The same logic is true generally: if you understand why the AIM says to do (or not do) something, you probably understand when it's okay to ignore it.


Could someone please explain why the A320 doesn’t have an anti ice system for its vertical and horizontal stabilisers? I had come across in the FCOM that there is no anti ice system for the vertical and horizontal stabilisers while looking at the schematic diagram. I find it very strange that the other surfaces on the empennage do not have anti-ice systems.

On PPrune I found:

  The aircraft has been designed to account for that. (Simplistically,
  the tail is over-sized to compensate for reduced effectiveness when
  ice forms; it's easier/cheaper/simpler to make the tail a bit bigger
  and take a weight penalty than to install a whole extra anti-icing
  system on the tail, which is why that's the typical approach for
  higher speed aircraft)

To me this makes sense, as the weight penalty for making the tail a bit larger is not as big as the weight penalty for making the wing a bit larger.

Another thing that is different between wings and empennage is ice build up on the wing near the engine could suddenly let go and end up in the engine and cause damage. To prevent the ice buildup, anti icing is used. On the empennage this is no issue.


Why is the VFR traffic pattern area at some airports different from its IFR circling approach area? Take Half Moon Bay Airport (KHAF) as an example.

Under VFR, the traffic pattern is right pattern for RWY 30 and left pattern for RWY 12. This implies the downwind leg is to the EAST of the RWY 12-30, and therefore we should fly over the land at TPA 999'.
However, looking at the IFR plates, both RNAV (GPS) Y Runway 30 and RNAV (GPS) Y Runway 12 indicate we are required to circle WEST over the water at 800', since that "Circling NA east of Rwy 12/30".

I understand it is likely that we have more vertical room over the water since there are no obstacles there. However, I don't get the reason to require VFR traffic over the land. Is it for VFR/IFR traffic separation?

Some reasons that I came up with

Favors the water, against the land: Terrain/Obstacles, Noise Abatement.
Favors the land, against the water: Marine Sanctuary Protection.

It looks like you have a few different questions here. As a caveat, I know nothing about Half Moon Bay so these are (educated) guesses to some extent. Someone with personal experience at KHAF could probably give better answers.

Why is circling always west of the runway at KHAF?

Circling areas are planned according to the TERPS criteria (see section 2-7-1); the formulas are in the document, but the basic idea is to make sure that there are no obstructions to circling within a certain distance of the runway. It looks very likely that at KHAF the terrain east of the field rises too sharply to allow safe circling there: the minimum allowed in the TERPS is 1.3nm/1.5sm/2.4km, and Google Maps shows that there's definitely rising terrain within that distance.

Why is the pattern always east of the runway at KHAF?

I don't know for sure. Noise abatement is obviously a concern at KHAF but then as you said, why not put the pattern to the west, over the ocean? The most obvious reason is that Half Moon Bay is in the Monterey Bay National Marine Sanctuary and flying over national parks below 2000' AGL is discouraged. Another possible reason is to avoid directing light, single-engine aircraft to fly over water unnecessarily.

Why - in general - would a certain area be used for the pattern but not for circling?

There's no reason why one area should always be suitable for both needs. In particular, circling requires guaranteed obstacle clearance within a certain distance from the runway. VFR pilots should be able to see and avoid, but obviously that assumption isn't possible for IFR. If you fly a circling approach at minimums then you might even go back into cloud while circling (and then go missed); in that scenario you really don't want to have to worry about terrain or obstacles being anywhere nearby.


What limits the lifespan of helicopters? The lifespan of aircraft is generally limited by metal fatigue. This is true for fixed wing aircraft; is it also true for helicopters? What is the determining factor for helicopter useful life?

Helicopters are also subject to metal fatigue and there have been accidents attributed to it but the primary determination is component life times.  All of the engine, transmission and rotor parts are lifed and most of the control mechanisms.  Depending on the helicopter, there will be many more lifed components.

Some helicopters also have fixed intervals between major overhauls by the manufacturer.  For example, the R22 is effectively rebuilt to an "as new" standard by Robinson at 2,200 hours.

Corrosion might also play a part.  There may be a time when it is just not economical to continue to repair and service the airframe.


How are the Tupolev Tu-95's blades shaped? The Tupolev Tu-95 "Bear" seems like an awfully cool piece of innovation with its unusual contra-rotating supersonic-tipped props.  From what I've been reading it sounds like it's been the only mass production airplane to use props at those speeds (there were apparently a handful of American examples as test aircraft but NASA abandoned the project?).

I'm curious what profile of blades they used.  I know there are lots of supersonic-capable airfoil shapes out there, but it's not clear which if any of these were used for the Tu-95 props, or even whether a fixed wing supersonic blade profile is appropriate for a prop.  Any ideas?

The propellers were designed by OKB-120 headed by K.N. Zhdanov, type AV-60N.  This type was used on a few other aircraft, but unfortunately I can't find any further details about it.  Can somebody visit one and inspect it?


Why does the P-51 Mustang takes so much altitude to recover from a spin? From this answer, it appears that the P-51 Mustang takes a lot of altitude to recover from a spin. The average is a 3000 feet to 6000 feet loss, with a loss of up to 7500 feet in one instance.

The recovery also seems lengthy. From the document quoted in the answer:

  The average spin [...] requiring 3-1/2 turns for recovery.

What makes the P-51 Mustang so difficult to recover from a spin?

Others can probably give you more precise info since I'm not a P-51 pilot, but I am studying aircraft dynamics in school right now, so maybe this will help.

Many fighter aircraft are designed such that they are very agile. This is especially true with roll dynamics, where modern fighters are even designed to be inherently unstable. They can then roll faster since the dynamics promote the roll. For roll stability, the wing design is often the main concern. Now, to spins.

I believe spins are mainly a yaw-plane event (though I'm sure there is some coupling of the equations). this means its a rapid rotation about the z-axis, the axis normally considered down. For stability, or desirable spin recoverability characteristics, the tail design is key. I don't know all the details or considerations behind the P-51's tail design, but any number of things could cause slow spin recovery, meaning you need to fall for a while (sorry, pilot!)

For example consider the distance between the tail's centroid and the overall plane's center of gravity. Imagine we added a lot more fuselage, basically extending the tail farther out. Now, with our extended tail, we have a different system. a really long tail might be too resistant to any yaw - basically it wants to got a certain direction, like an arrow.

Now, shorten the body instead, making like a short little squished P-51 with the tail right behind the pilot(shorten the arrow). while flying, the tail now might not help the plane fly very straight, at least not easily.

Finally, put the tail in front of the pilot and try to find anyone brave enough to fly it! No one will want to, because they won't make it home. its like shooting an arrow backwards, or throwing a paper airplane backwards- the dynamics of the vehicle just aren't favorable - any sort of deviation and the instability induces more deviation.

Thats only one part of tail design. You also need to consider size, number of tails, control surface size, and this doesn't even include the yaw dynamics that come from the rest of the plane in a spin.

I apologize if you already understood all that, but maybe it would help with my key idea. That is, that the reason it takes so long to recover from a spin is due mainly to its tail design. I don't know specifically how they designed it, or what design goals they were looking for, but because of what they chose, maybe considering manufacturing ease, structural considerations, aesthetics, drag, turn performance, weight, heck, maybe they just sketched it up and tried it, they ended up with a plane with this yaw plane recovery performance. It might be bad, but maybe their other design goals were met and they chose to live with it.

Other aircraft with better spin recovery performance will likely have different tail features like larger control surfaces, different tail volume... Overall, their tail design will give it better yaw stability and authority (control power available) to recover sooner.

Its late, and I'm sure I've missed things. I hope others can chime in and fix anything I may have mistaken. Let me know what I can add to improve my answer


Is GOCE a satellite or aircraft? This vessel (GOCE) is in orbit and maneuvers by using air similar to a plane to create lift and turn. The solar powered ion thrusters powers it continuously inside the atmosphere for years. Is this technically a plane, satellite, or a missile?

Source: https://space.stackexchange.com/a/33202/18879

A satellite is an object in orbit. A satellite keeps a constant altitude if it is traveling at the correct orbital speed for their altitude. Otherwise it will be in an elliptical orbit where the altitude is constantly changing. In any case, satellites are (almost) in free-fall

An airplane travels at much, much lower speed than orbital speed. Airplanes keep their altitude because their wings produce lift.

Satellites in lower orbited are subject to atmospheric drag, albeit to much smaller extentd than planes. GOCE was orbiting Earth at an - for satellites - very low altitude (224 km). There is hardly any atmosphere at this altitude, but at an orbital velocity of 7.8 m/s (51337 kts), atmospheric drag is still a problem.

Therefore the structure of GOCE was particularly designed for low drag. The wings were flat without camber. They did not produce any lift. GOCE used ion thrusters to compensate the atmospheric drag and maintain orbital velocity.

Photo: ESA

Photo: ESA

Missiles are self-propelled guided weapons. I can assure you that GOCE was not a weapon.

[TL;DR]: GOCE was a satellite, because it orbited an astronomical body. It was not a plane, because its wings did not produce lift.

GOCE´s 20 month mission ended on November 11, 2013 with the planned destructive re-enty into the atmosphere. It measured Earth´s gravity field and acquired a precise model of the Earth geoid:

Image: ESA


What climb rates can the Airbus A320-200 achieve and which climb rates are commonly used for normal flight operations? In relation to AirAsia flight QZ8501 officials have been quoted as saying:

  "It is not normal to climb like that. It's very rare for commercial planes, which normally climb just 1,000 to 2,000 feet per minute. It [climbing at 6,000 ft per minute] can only be done by a fighter jet."

Two parts of that statement struck me:

The rate of 1,000 to 2,000 feet per minute is stated as "normal", not "maximum"
The claim that only fighter jets can climb at 6,000 feet per minute.

My question is then:

What is the maximum climb rate that an AirBus A320-200 such as the one involved in this incident could achieve with out stalling? (Including configurations and operations outside of "normal")
If it is less than 6,000 feet per minute on the A320-200 can any commercial passenger carrying aircraft in operation today exceed 6,000 feet per minute? (I'd assume Concorde could, but that's no longer in operation)

There's a lot of nonsense being banded about regarding this flight.
First up, we are not talking about sustained, powered climb rates. If you're travelling at Mach 0.85 and pull up vertically, in theory (if your plane didn't break) you'd climb at an initial rate of nearly Mach 0.85 (your original speed minus the airspeed loss when pulling up).... That's near enough 57,000 feet/minute.
If you're at high speed and willing to trade speed for altitude, an Airbus A320 is physically capable of climbing at much higher rates than 6000 feet per minute.... At least until it runs out of airspeed.
A fighter is the only aircraft which would be likely to perform a sustained 6000ft/minute climb rate in normal use, but they're also capable of much higher rates of climb.
The maximum rate of climb you'd see in an A320 in normal use is in the 2000 ft/min range, but that's because it's the highest reasonably efficient rate of climb. That's not the maximum the aircraft is capable of under power (which is more in the region of 4000 ft/min), and is absolutely no indication of that maximum unsustained climb rate.
It would eventually stall at any unsustainable rate of climb, but then again, so would any aircraft even at a sustainable rate... Keep climbing and before too long you run out of atmosphere.
Either way, there is nothing to say that climbing above the sustained climb rate for an aircraft is unsafe or, necessarily, unusual. You trade airspeed for altitude, sure, but if you need to be higher at that moment in time, there's plenty of time to accelerate again later.
From Airlines.Net:

The three are roughly the same at 10,000', at about 2500 fpm. (Maybe a bit more for a light A319, and less for a full A321)
Normal climb rates from 10,000' to about 30,000 are as follows:
A319, 3000 fpm to about 1500 at 30,000'
A320, 2200 fpm to about 1000 at 30,000'
A321, 1400 fpm to about 500 at 30,000'

TL;DR - The official is spouting nonsense s/he doesn't understand. A fighter is the only aircraft likely to be able to (or wish to) climb at a 6000 ft/minute SUSTAINED climb rate, but almost any aircraft can climb at that rate for brief durations in a zoom climb - converting airspeed/momentum to altitude


Could fly-by-wire protect against a takeoff tail strike? If the takeoff weight is underestimated, rotation will be done too early and may result in a case of tail strike.

One example of such mistake is a 747-400 (F-HLOV) in 2006 (case 8 in this study). The crew entered ZFW for TOW (100 tons lower), VR was underestimated by 32 kts.

Boeing documentation mentions every aircraft can be subject to tail strike, at different degrees. Airbus documentation for tail strike prevention doesn't mention any specific protection from FBW.

(source: The Aviation Herald.)
UA B744 tail strike on Sydney takeoff (photo may not be the actual May 7th 2010 T/O).

I wonder why such basic mistake may be done. Weight could be sensed in some way by the instrumentation, and crew entered values should be challenged if really different.
To prevent the crew from being forced (or tempted) to rotate the aircraft beyond the maximum safe angle, isn't that possible to monitor the T/O progress and in case of low performances alert the crew, and provide an opportunity to reject the T/O.
Airbus FWB embeds many security systems (compared to Boeing), this is surprising that they cannot prevent such T/O tail strikes. I'm sure there are good reasons, just asking to understand the difficulty.

Edit: Based on the answer from Marky Mark, who references the EK407 case, I checked a study published in the aftermath of EK407 tail strike: Take-off performance calculation and entry errors: A global perspective and noted this recommendation for 'TOPMS':

  While the above recommendation does not preclude data entry and
  calculation errors relating to take-off performance parameters from
  occurring, Transport Canada (Department of Transport) agreed that a
  take-off performance monitoring system(s) (TOPMS) would provide a
  significant safety benefit. However, before regulatory authorities
  establish a requirement for the fitment of TOPMS, a certified system
  would need to be developed (Transport Canada, 2010).

  Basically, a TOPMS, which assists pilots in determining whether to
  continue or reject the takeoff, can be defined as (Brown & Abbasi,
  2009, p. 7).

Are TOPMS now in place?

On Airbus aircraft, the guidance law provides attitude protection on take-off which should prevent a tail strike. However, this is not fool-proof and it remains up to the PF to maintain the correct nose-up angle.


Why do airline schedules start in March and October? Is there any specific reason as to why airline schedules for the summer season start around 27 March and winter season around 27 October? Thanks.

The main reason for new schedules in March and October is the Daylight Savings Time changeover.

It is a MAJOR headache for airlines all over the world. Schedules have to undergo extensive restructuring during the switch over from summer daylight savings time to winter standard time. Maintaining code-share connection times is the biggest priority.

What makes this all very difficult is the fact that many countries and localities do not observe daylight savings time, or have different dates for the switch-over. This is especially true for flights between northern and southern hemispheres.


What are the types of NOTAMs and how do USA NOTAMs differ from the ICAO definitions? I'm looking for a complete list of the types of NOTAMs that can be found in the USA and under the ICAO definition. I looked at this question and it gives me a good starting point, but I'm not clear on how NOTAMs vary between the USA and when ICAO is used. Or maybe the USA is using "the ICAO way."

Is there a document that could help me compare where there is overlap and where there is a difference between how NOTAMs are defined in the USA and internationally. I assume there are ICAO definitions for NOTAMs that are used internationally.

If there are specific definitions for NOTAMs for countries other than the USA, that would fall outside the scope of my question here but might be an interesting additional subject matter for a very thorough answer.

There are significant differences between US domestic NOTAMs and international NOTAMs, please note that US NOTAM Office issues NOTAMs in both formats (NOTAMs susceptible to affect international flights being issued in international format). Canada is also issuing domestic NOTAMs in the same format than US.

encoding is different, US domestic encoding is described in FAA order 7930.2R (https://www.faa.gov/documentLibrary/media/Order/7930.2R_basic_dtd_1_5_17_(2).pdf), international NOTAM encoding is defined by ICAO doc 84000
Domestic NOTAMs are mainly split between D NOTAMs (about airports and navigation facilities) and FDC NOTAMs (about airspace, procedures or regulations), there are also military NOTAMs with more subtypes.
there is to my knowledge no document describing in detail all differences between both encodings, although the FAA order 7930.2R is quite detailed and provide information on both types and some list of differences.
other documents are useful, for example https://www.faa.gov/documentLibrary/media/Advisory_Circular/150-5200-28F.pdf that provides guidance on using the NOTAM system for reporting airport facilities changes or outages and for
utilizing the Runway Condition Assessment Matrix for airport condition reporting

There are many differences between both formats, for example:

domestic NOTAMs are easily recognized as they start with an exclamation point !
the international NOTAM encoding is more structured. For example, a Q field will summarize essential NOTAM information, including affected FIR, vertical boundaries, geographic coordinates. In US NOTAM, geographic coordinates is described in the text of the NOTAM and then less easily decoded automatically.
the Q code also store the type of affected facility and the state of the facility. US encoding for facility types is different.
domestic NOTAMs are using standardized phrases defined in FAA document but not recognized by ICAO standard, the FAA order 7930.2R list them.


What runway is used in a 90 degree crosswind? If an airport has runway 09/27 and the wind is at 180 or 360, which runway is used? Is it possible for both ends to be used depending on the amount of traffic?

One would basically follow the same guidance as if the winds were calm:  If the field is tower controlled the controllers will pick a runway.  There may be a primary runway direction preferred in these circumstances for noise abatement, traffic routing, (i.e. Instrument Approach or Standard Instrument Departure procedures favoring one runway over another) or other considerations, otherwise they might consider whether the winds are forecast to shift to favor one or the other and base their decision on that.

At a non-tower controlled airport pilots would be expected to monitor a common traffic frequency and follow what others are doing.  And if you are the first or only person there, lucky you... take your pick!


How close to the White House did the Space Shuttle Discovery "fly"? The CNN article For 747, transporting a shuttle is no heavy burden shows the shuttle Discovery on top of a "shuttle shuttle", a special 747 used to shuttle the space shuttles around.

How close to the White house did it fly? Did there need to be any special arrangements to fly so close to this highly sensitive airspace (especially post-9/11)?

Note: Presumably this is a NASA aircraft rather than a military aircraft (e.g. Marine 1) so the flight planning for this "fly-over" may not be exactly the same as those for landing a helicopter on the White House lawn.

According to this article they cruised through DC at an altitude of 1,500 Ft. Based on the pictures you can see here and here and here and lastly here of the flight and some of the locations it banked at its course seems to have taken it right around the prohibited flight area noted in Carlo's answer which you can see on the sectional here:

(source)

Foreflight does a better job of overlaying that on a street map. Assuming they kept a reasonable margin if we drop a ruler on it Im showing ~0.6 NM

(source: own images)

As for special clearance they were flying the the SFRA and would need to follow the rules on that as everyone else. Im sure the course was prearranged as the FAA prefers transitions more than loitering in the SFRA. The SCA also had a fair number of limits to its flight regime as discussed in this podacast the weather would have also needed to be optimal for the flight to occur.


Does EASA allow using a portable GPS for RNAV capability? Assume an older IFR-certified aircraft with the classical equipment, that is two VOR/ILS receivers with plain CDIs, ADF and DME, but no GPS. It can be flown IFR, but many routes can't be used, because they use fixes that can't be found with this simple equipment.

If a suitable portable (that is, not built in nor connected to the aircraft systems) GPS unit is available in cockpit, and has appropriate aviation maps loaded, it it allowed to plan or accept an RNAV route that can only be flown using the GPS? What features and certifications does the GPS unit need to be usable this way?

Note that I am not thinking about any RNP procedure nor a RNAV approach (the ILS is there for approach in IMC), just normal en-route navigation over fixes defined by coordinates only. That way, the GPS is not critical—if it fails, I can always request vectors or rerouting over a navaid.

(If it differs over the world, I am most interested in European situation)

The answer, broadly is no, handheld GPS units can not be used for IFR RNAV routes (or approaches for that matter). To know if a specific GPS unit is legal for IFR navigation you need to check up on a variety of paperwork, thats covered in this answer. Strictly speaking if you could find a certified unit it would be legal but there are no current units (to my knowledge or searching) that are.

If we look at the regulations and bounce around a bit we can see why. AC 90-108 tells us about the use of RNAV systems and states that one bust be compliant with installation instructions in AC 10-138D of which there are many different regulations. The AC does not actually specifically state that the unit must be panel mounted but in a round about way it does:

The definition of display which is used widely in the document does state it must be mounted to the panel,

  Display. Within the context of this AC, a display is a device mounted
  in the aircraft instrument panel to convey course guidance navigation
  information to the aircrew for controlling the aircraft along the
  intended route. Displays may also be used to convey other information
  as well.

There are also lots of regulations about wire mounting to avoid issues and failures as well as other mounting regs. If you are interested its worth going through the document.

See Pondlife's comment bellow for more info on panel mounted GPS'

  just normal en-route navigation over fixes defined by coordinates
  only. That way, the GPS is not critical—if it fails, I can always
  request vectors or rerouting over a navaid.

In order for the GPS to be non critical you must fly at altitudes serviced by other nav-aids. The reason GPS routes are coming into use is that they, in some cases, allow flying at lower altitudes that may be beneath ATC radar or out of range of nav-aid coverage. In the case of a failure of a GPS unit you would then be with no means of navigation and terrain avoidance.


Is it possible to (electronically) disable an ejection seat? I'm currently reading "2034: A Novel of the Next World War" and my question may have minor spoilers:
One part of the plot comes into motion, when a F35E (the E is probably fictional) is hacked and maneuvered into a hostile airspace. The pilot wants to escape the inoperable F35 by activating the ejection seat, however, the hacker also made the ejection seat inoperable.
Now I'm wondering if this would be possible. Can ejection seats be deactivated? And if yes, why? I wasn't able to find something about this, which may indicate, that this is a bad idea to begin with. I found this answer and I would conclude, that there are indeed systems which can manipulate the behavior of an ejection seat, but nothing about completely disabling it.

I am not familiar with the current F-35 ejection seat, much less what design changes, (real or fictional...) might be made by the year 2034, but of the three ejection seat aircraft I flew in the 1990s, none were electronically actuated such that it might be possible to hack into and disable the seat.
While they are mechanically complex, the means of actuation for most seats is actually fairly simple; relying on springs, firing pins, cartridges, and rocket motors.  It would be a very poor design decision in my mind to manufacture a last ditch fail-safe system like an ejection seat that is vulnerable to EMP, or is connected to a hackable network.


Why is the airflow in airline cabins downwards? Air is distributed from overhead outlets and flows downwards towards the floor. Since the exhaled air is hotter than the air around, and tends to concentrate towards the ceiling, wouldn't it make more sense to pump air from the floor upwards towards the ceiling?

Temperature stratification is a vexing problem on lots of airliners.  The big challenge is you need a distribution system that is effective when cooling (on the ground and at low altitude when the weather is hot) and heating (as soon as the outside temperature drops to the point where there is a net heat loss that can't be made up by passenger body heat, the ECS will be producing inflow that is warmer than ambient).  At cruise where the  outside temperature is generally -10 to -40C, you are in heating mode, where inflow temperature is above ambient.
The objective is to get a circulation going (air falling along the side walls, and rising at the center aisle) to keep the air mixed and prevent temperature stratification in the small space, with the added factor of a large heat emission from the passengers to cope with. Distribution systems strive to do this.

So you would think that most of the time, you want the air coming in at the floor so there is a natural convective circulation favoring heat from below (most of the time incoming air is warmer than ambient).  Problem is, you have the heat of the passengers, which is significant, rising into the ceiling.  You generally want to measure temperature for regulation purposes at somewhere around passenger head level, and if the heat comes in at the floor, there is a tendency for heavy stratification as the sensor is remote from the incoming heat source and it creates a very long response loop (sense, adjust, wait for the result, adjust again, etc.).
The CRJ200 suffers badly from this problem because the airflow is from Dado panels along the sides at the floor like a home heating system (a design carryover from the Challenger corporate jet, which had different distribution requirements).  The temperature sensor is up by the overhead bin.  When the sensor called for more cooling, or even just less heat, the Environmental Control System would dump in all kinds of cold air, which didn't want to rise being colder than ambient, so it would have to, in effect, fill the bottom of the cabin space with cold air (or really, less hot air) until the "coldness" reached the sensor up at the bin.  Anyone who's ridden in the CRJ200 knows well the cold feet problem with that airplane, even at altitude where it's -30 outside.  What helped a lot was moving the sensor down near the floor to the inflow region to reduce the response loop, and a modification was created to do that which was quite effective, but few airlines bothered with it and having the sensor near the floor is generally suboptimal from a design perspective.
On the later CRJ versions they went with the more common airliner arrangement.  Air is injected up at the overhead bins somewhere and most of it is shot at the sidewall panels, to get a waterfall sort of flow down the sidewall panels, inboard along the floor and up the center aisle(s) (some air may also be injected into the space between the bins to prevent stagnation there).  This works reasonably well even when in heating mode where the air being injected down is warmer than ambient, and allows the temperature sensor to be in a good location with a reasonably short response loop, so variations of this type of distribution system are the most common.


Can a vacuum cleaner create sufficient vacuum to operate the artificial horizon? Inspired by this question about breaking the glass of instruments, I was wondering if a sufficient level of vacuum can be achieved by using a vacuum cleaner on the inlet, or simply sucking through a straw connected to the vacuum inlet, in case the artificial horizon's vacuum pump failed?

The answer is a qualified yes: It's theoretically possible, but wholly impractical to provide a pressure source to your gyros from within the cockpit, at least the way you're describing.

Air-Driven gyros require a relatively constant pressure differential somewhere between 4 and 6 inches of mercury to operate correctly (this can be "suction" or "pressure", but as vacuum/suction systems are more common let's stick with that term). We can split the difference and say we want to supply 5 inches of vacuum (which is usually right in the middle of the "green arc" for most vacuum gauges) - this is sufficient suction to keep the rotor spinning at an appropriate RPM so the instruments function as expected.

Because a constant vacuum is required we can kill off one of the options: You won't be able to suck air through a straw to do this -- you would be constantly over-speeding or under-speeding the gyro rotor as you produce either too much vacuum (inhaling) or not enough (when you have to let go of the straw to exhale).
The variable pressure would vary the rotor speed, and your instruments would be totally unreliable within a few breaths, defeating the purpose of the exercise.

A household vacuum can provide the necessary pressure differential (these fine vacuum-rating folks tell me that "An average vacuum will have a [suction] rating of around 80 inches of water", which Google tells me is around 5.9 inches of mercury. If you could hook the vacuum up to the aircraft's system downstream of the vacuum regulator (where the main vacuum pump hooks up) you could theoretically power your gyros normally.
There are some caveats to using a vacuum cleaner idea besides the obvious "How are you going to hook the vacuum up to the system?" question:

The vacuum cleaner specifications are presumably at or near sea level - they might not be able to provide adequate suction at higher altitudes.
Powering the vacuum cleaner in this scenario is left as an exercise for the reader (most aircraft with air-driven gyros don't have household AC power in the cockpit - you could install an inverter, but vacuums pull quite a lot of power, so you'd need a high-amperage circuit to supply it. The draw from the vacuum may exceed the capacity of the plane's electrical system, and to remedy that we're getting into complicated major alterations...)

There are other more practical alternatives to an engine-driven vacuum pump to consider if you're worried about the reliability of your vacuum source:

Precise Flight makes a standby vacuum system that ties into the engine intake.
For normally-aspirated engines this works well as long as the engine is operating at part throttle: The manifold pressure differential is sufficient that it can supply suction for your gyros.  The downside is that you can't guarantee a stable vacuum source: at full throttle there will probably not be sufficient suction to operate the gyros (particularly at altitude).
Pneumatic venturi tubes can be used to supply vacuum for aircraft in flight.
These are bolted on to the airframe and use the slipstream air moving through a venturi to create the necessary vacuum. In extremely slow flight these may also fail to provide adequate vacuum.
Electric standby vacuum pumps are a popular option as they offer you the ability to keep using your main vacuum instruments regardless of throttle position or airspeed. The primary drawbacks are weight, space (for the installation), and power to run the motor.
Electric gyro instruments are a popular option (though somewhat expensive): They provide a backup for the air-driven system using an independent power source.


Has an aircraft carrier ever assisted a civilian passenger flight? Has an aircraft carrier ever assisted a civilian passenger flight? I am trying to find an example of this. It could be as extreme as a small plane landing on aircraft carrier in an emergency. A simpler example would be a civilian passenger plane requesting navigational assistance from an aircraft carrier over VHF communications.

It has happened before.

There are definite cases of light civilian aircraft landing on a carrier, the most well known was in April 1975 when South Vietnamese Air Force Major Buang Lee landed an O-1 Bird Dog on the deck of the USS Midway trying to escape with his wife and 5 children from the fall of Saigon to North Vietnamese forces.

Landing aboard an aircraft carrier presents several difficulties, namely limited landing roll and available deck space.  A Nimitz Class carrier is just shy of 1100 feet in total length and 250 ft at its widest point.  The designated landing area or LA is approx 75 x 650 ft.  The ship is capable of steaming at 30+ kts so it can develop quite a bit of wind over the flight deck reducing the effective unarrested landing roll.

Then you need to stop the aircraft once it's on the deck.  Carrier based fixed wing jets use tailhooks designed to work with the arresting gear and reduce the landing roll to about 330 feet.

The largest carrier aircraft in service were the Douglas A-3 and the Grumman C-2 and E-2, each one about the size of a regional jet.  The largest aircraft which I am aware of which made a successful unarrested landing was a Lockheed C-130.

Large commercial aircraft like a Boeing 747 or an Airbus A-380 simply cannot fit on the deck without the wings clipping the island or other deck antennas, etc, not to mention requiring landing rolls of over 3000 ft even in the most extreme short field attempts.

So HAS a carrier aided a civilian passenger flight via recovery operations?  Yes but only with small aircraft.  COULD a carrier aid in recovering larger commercial aircraft?  Possible depending on the size of the aircraft, its loadout and fuel state and performance capabilities.


What is the feasibility of a Coanda/Magnus effect wing airplane? It seems the EU granted some hundreds of thousand € to a non-engineer, to study a cargo airplane with a turning cylinder in the leading edge, to produce increased lift by the Coanda/Magnus effect also used in the Flettner rotor sails for ships. As the concept seems having been discarded because of the important gyroscope effect of the turning barrel: anybody commenting about technical reasons for this revival of a discarded concept?

A lot of research grants are wasted on scams or projects making exorbitant claims. See it this way: The people who judge an idea grant-worthy need to spend the money they have available somehow, and if they were clever enough to pick winners all the time, they would not work in a government bureaucracy.

On the other hand, who is to judge what idea is really good before it has been tried? You have to accept some losses if you want to move outside of safe bets - only then can new ground be broken.

NASA funded a researcher for more than three decades who was only working on joined wing projects. It's easy to see that they are a non-starter, but this guy built his career on that particular hoax.


Where can you find symbols (like these) that aren't on the legend? I see a lot of these fan like symbols:

...on the Nav Canada Alaska Highway - Fort Nelson to Northway, 1:500,000 VFR Navigation Chart, but they're not anywhere on the map legend.

I presume they're marshland as they look a little similar to symbols I've seen on hiking maps, but I don't like assuming when making flight plans!..

Is there some universal reference somewhere that I don't know about? Are they indicating marshland, or are they something else entirely?

You can find this symbol in the  "FAA Aeronautical Chart User Guide"

on page 30.

It shows as "Swamps, Marshes, Bogs"


Is there a way for the helicopter rotor to get its power half by wind, half by engine? Imagine a gyroplane, if something happen mid-flight (when the plane is basically an autogyro and the engine provides no power to the helicopter rotor) and just the wind generated by forward flight can no longer turn the helicopter rotor enough to provide enough lift, could the engine partially take over? Like using the engine to provide just enough power, with the rest provided by the wind, so the helicopter rotor could spin enough?
I don't want the plane to autorotate downward. I want the plane to keep flying, but using the engine to increase the rpm. If the incoming wind could turn the top rotor in a certain rpm, could we increase the rpm using the engine? In my memory, rotodyne could do this because it uses a tip jet, but what if we use normal piston or turbine engine?

The problem is that as an autogyro, the air is going through the rotor from below, and as a helicopter, the air is coming from above and it has to be one or the other.
In any case, gyroplanes don't have a problem of low rotor rpm as long as you keep the rotor loaded (and you always keep the rotor loaded).  If you slow down, the rotor rpm doesn't decay, the machine just descends steeper.   You can slow a gyro to zero airspeed, and it will maintain most of the rotor rpm on its own and autorotate straight down, although the vertical speed may get pretty high. If you have a landing gear that can tolerate a 500 fpm descent, and start from only 20-30 feet or so, you can land like that.  This is why some small autogyros don't even bother with a rotor rpm gauge.
So to get low rotor rpm, you'd have to unload it to take away the aerodynamic forces driving the blades around by pitching over to go zero G or close to it, and at that point an engine might be useful to keep the rpm from dropping, but you'll have probably already chopped the tail off from the blades flapping down (low G maneuvers in gyros are to be avoided at all costs - as with 2 blade helicopters, for different reasons), and you'll already be on your vertical trip to your final resting place anyway.


What is the history and process of designing new waypoints and airways? I am interested in what goes into designing new airways and navigation fixes, especially on international routes. For example, after WWII, there were no established international air service. Now, we have waypoints (defined by coordinates), VORs, high and low altitude airways etc. connecting across continents. So at some point in history, somebody decided to add a new airway and a set of fixes to the charts. But exactly how?

Who decide where and what to put on the chart? Is there a panel with representatives from major airlines? Or, if government authorities are involved, what happens to waypoints above international waters?

In systems theory, emergence is the "phenomenon whereby larger entities arise through interactions among smaller or simpler entities such that the larger entities exhibit properties the smaller/simpler entities do not exhibit."
I think this best describes how the airspace design came to be from nothing.
In the beginning...
There was air mail. The pilots had hard time finding their way despite the US Postal Service installing lighted beacons connecting the major routes.
Then came a 20-something year old chap by the name of Elrey Borge Jeppesen. He made a cheat sheet that everyone wanted. The aeronautical charts and the AIM's precursor was born. He even included farmers' telephone numbers for weather reports.
The Department of Commerce then funded a better airway system. First there was the four-course radio range, which gave way to VOR and NDB. NDB is now extinct in the wild, and VOR is vulnerable. GPS gave birth to the free route airspace.
(SkyVector) Airways black hole in Europe (Free Route implementation).
Who draws the map?
Everyone. Each country designs its airspace, but since airspaces share borders (even over water), countries also work together. Article 68 of the 1944 Convention on International Civil Aviation says:

Each contracting State may, subject to the provisions of this Convention, designate the route to be followed within its territory by any international air service and the airports which any such service may use.

Or, as the Australian Department of Infrastructure and Regional Development puts it:

Before an airline can operate international services to another country, the government must first negotiate a treaty level agreement with the destination country's government. These treaties are known as bilateral air services agreements.
The result is that international aviation is regulated by a complex web of over 3000 interlocking bilateral air services agreements.

Map of bilateral air services agreements.
International waters
(Source)
In civil aviation, the Flight Information Regions (born c. 1947) share borders. They are not limited to 12 NM offshore like territorial waters. In the Mediterranean Sea for example, Egypt and Greece share a border. So does Scotland and Norway across the North Sea. Along the shared border are waypoints shared by both countries, they form the entry/exit points to/from each county's national air system.
Airways that cross borders form regional networks, they have different prefixes from airways that never leave an FIR. See: ICAO Annex 11.
Really, who draws the map?
The air navigation service provider (ANSP) of each country, by working with the national aviation authority (NAA), other countries, airlines, ICAO, IATA, etc.
An example would be the FAA redrawing the map for the NY/NJ/PHL airspace.
Each ANSP or NAA will have an airspace design unit responsible for the analysis, design, and simulation of the airspace system, among other tasks. Guidelines and regulations exist on the local and international levels for every aspect of the route and sector design. An example would be ICAO Annex 11.
A typical team and process (via icao.int):

This process takes 280 days to complete.
The bigger the scale, the more cooperative the process becomes, for example check this airspace design webpage for the EU.
(Source) Software for airspace design.
Demand and technology
It's supply following demand. You don't see many airways above the Tibetan Plateau for example. And of course the technological advances are a huge driving force. A bend in an airway due to a mountain range shielding a VOR can now go away thanks to GPS, RNAV, RNP, etc.


What are the drawbacks of being a helicopter and fixed-wing pilot at the same time? Are there any drawbacks if someone who is a fixed-wing pilot, learns to fly a helicopter, or vice-versa? Specifically, are there instinct actions in one category that are dangerous in the other?

Does this differ if someone is experienced in one category (e.g. 1000+ hours), versus a student learning both within a short period of time (e.g. less than 6 months in between)?

In case of an engine failure, the fixed wing pilots natural reaction is to push forward to lower the nose, then look for the correct glide airspeed. A helicopter pilot in most engine failures should pull back (although not agressively) to load the disc and restore, or increase rotor RPM.  Maintaining rotor RPM is the only way to get to the ground safely so flaring is an instinctive reaction trained in.  You don't look for airspeed or rotor RPM.  You dump the collective and flare, then have a look at airspeed and RPM.  Pushing forward will reduce rotor RPM which in some flight phases and some helicopters might not kill you but in many helicopters at altitude may well kill you.  In addition, a stall buzzer will prompt the fixed wing pilot to push the stick forward and increase power, which in a helicopter means pulling the collective.  In a helicopter the low rotor RPM buzzer sounds just like a stall warning but pushing the stick forward and pulling the collective will almost certainly kill you.

Another action that has to be instinctive is to stick in a boot full of right pedal (counter clockwise rotor) which is totally alien to a single engine fixed wing pilot in an engine failure and completely the opposite of what a twin engined fixed wing pilot might do, who will naturally "step on the failed engine".  In a helicopter, that can get you into a very bad attitude rapidly from which it might be impossible to recover.

Negative G in an aircraft is not a problem. In a 2 bladed helicopter, you must gently pull back to reload the disc.  Pushing forward has a real risk of a blade chopping off the tail or hitting the canopy. It might also cause "mast bumping" which can cause the rotor to separate from the aircraft.  Too many helicopter pilots have been killed this way. Most helicopter pilots avoid -ve G.  The main point here is that you do not push the stick forward to level out from a climb.  The instinctive reaction for a helicopter pilot is to to pullback as soon as they feel the slightest hint of rising out of their seat.

In a helicopter, to accelerate, you push the stick forward then increase power to maintain altitude or climb.  In an aircraft, you increase power, then push the stick forward to maintain altitude.

A running landing, and not a hover landing, requires you to push the stick forward to level the skids.  A fixed wing tricycle gear pilot wants to pull the stick back to flare which again, might chop off the tail.

Keeping trim (balance) is a function of power and not direction of turn.  It is perfectly possible to make a properly executed balanced turn in a helicopter with the opposite pedal pushed in.

Helicopters can slow down with a nose down attitude and you take off by pushing the stick forward to accelerate.

I'm sure there are others which I've forgotten but I think these are the main things and, most importantly, as I've shown, trying to fly a helicopter like a fixed wing can be deadly.

In summary, flying helicopters is very different to flying fixed wing and you need different responses which need to be intuitive, especially in emergencies.

My gut reaction response is that it is easier to transition from helicopter to fixed wing and that the lower time pilots will find it easier because the years of experience and muscle memory are not there.


How does a Missile Lock Work? When we say that a missile has been locked on a target (lets assume a fast moving target, and that the missile is mounted on a fast moving plane), we assume that once the missile has been locked onto the target, it will actually hit the target after firing (Irrespective of the subsequent changes in the position, velocity and acceleration of the target). How does this system work?

Short Answer:

This will be very generic...

It depends on what type of missile it is: either IR or radar-guided.

With IR missiles, the missile is caged and locked at missile boresight.  The missile is commanded to the aircraft cueing system.  When the target enters the missile's FOV, the pilot uncages the seeker head, at this point you will hear a loud, "whiney" audible tone.   The missile then transfers to track mode.  The pilot pickles... the missile batteries become operational, fins are unlocked, autopilot takes over, midbody connector is retracted, then ignition is commanded.

With radar-guided missiles, it depends on the missile and what type of radar they have.  Usually the radar is slewed to a target and locked up.  When the pilot pickles, the missiles is either receiving data from the aircraft via datalink or is in active mode with the missile's radar tracking the target.  Eventually the missile's radar will take over and track the target.  The datalink can be terminated early by the pilot if the missile's radar can take over allowing for some pretty cool tactical stuff.

Long answer:
There is A LOT more to it, but this is very basic.  Tread very lightly with questions like this.  A lot of the stuff (especially numbers) with regards to weaponry and modern threats are classified.  And even though some of the stuff isn't classified, it's still OPSEC and shouldn't really be discussed on an internet forum.


How does the mounting location of a jet engine affect aircraft performance? Different jet airplanes mount the engines in different ways.

For example:

Under the wing

To the fuselage

How does the engine location affect aircraft performance?  Is one better than the other?

Engine location performance-affecting factors:

1. Mounted in the wing root

low asymetric yaw on engine failure, less rudder required: less drag
no engine pods: less parasitic drag
engines closer to CG, less downforce needed from the tail:  less drag
very little reverse thrust available
Little space for high-bypass-ratio engines

2. Mounted in pods under the wing

high asymetric yaw on engine failure requires larger rudder: drag penalties
engines provide bending relief on the wing, allowing better wing design (thinner wings): less drag
at high incidence angles the pods can prevent spanwise flow: less drag and better stall characteristics
full thrust can impose a large, undesirable, pitch up moment (think stall recovery)
less freedom in roll on cross-wind landings
Location ahead of the wing's elastic line helps to dampen flutter

3. Mounted inside the tail or on pods on the rear fuselage

low asymetric yaw on engine failure, less rudder required: less drag
wing design is freed from the need to accomodate engines, allows for more complex wing designs: better performance throughout the flight envelope
heavy engines so far aft of the fuselage require wings mounted further aft, and a higher tail to support that: more drag
Lower landing gear required, especially in case of short fuselages

That's about what I can come up from memory, maybe someone can merge all answers into a comunity wiki kinda post..


What is the difference between an Non-Directional Beacon and a Compass Locator Beacon? What is the difference between a Non-Directional Beacon and a Compass Locator Beacon?

Normally "Compass Locator Beacons" were co-located with the outer marker for ILS approaches. A "compass locator beacon" is an NDB beacon specifically to drive the radio compass.

A radio compass was a lot simpler instrument than the ADF that worked off of the NDB beacons. Typically it just had a needle that pointed left/right to direct the pilot to turn towards the station. They operate on the same frequencies as ADF/NDB and can be tuned with an ADF receiver.

Radio compasses used the old "loop antennas" that you see on old aircraft pictures. The pilot, co-pilot, or navigator would rotate the antenna by hand (the older radio navigation system required the pilot to turn, so rotating antennas were a step up) to be able to find the bearing to a particular station.

ADF (the "automatic" part of the "automatic direction finder) eliminated the need to rotate the antenna to get the direction to the NDB.

So to answer the question, the NDB and the compass locator beacon are technologically the same, it is the equipment in the aircraft that changed.

See NDB Nav History for more details


What's the difference between positive and negative pressure relief valves? In cabin pressurisation systems, I thought that the negative relief valve is automatically opened if outside pressure becomes greater than inside pressure.

The positive pressure relief valve opens in case the cabin pressure is too high in comparison to outside air Pressure. This happens if the pressure differential is higher than 8.85 psi / 0.61 bar (Airbus). It is most likely to happen in malfunction of the outflow valve (stays closed).

The negative pressure relief valve opens most likely during descent, when the cabin altitude is still at 8,000 feet (normal condition) but the aircraft itself is lower than that. That means that the pressure outside of the aircraft is higher than inside. The valve opens at a differential pressure of -1 psi / 0.07 bar.


What is this extension at the tip of the Supermarine Southampton's wing? Looking at this Wikipedia image of the Supermarine Southampton flying boat, I noticed what at first looked like a small wheel. But then I thought it couldn't be, as a wheel would be pointless in a flying boat (not to mention, it appears to be only under the right wing).

Any idea what it could be?

Source: Supermarine Southampton Flying Boat - Nightime 'Landing' (YouTube)

It's a standard flare bracket – controlled from the cockpit,[1]:76 it holds a burning flare to illuminate the water surface at night when landing.[2]
This particular streamlined design is most likely based on the 1922 patent by Holt Harold Edward Sherwin.[3] It's a clamshell device; when open, the two halves help reduce the heat going up. Those flares are also re-ignitable. The earliest design, also by Holt, was filed in 1917.[4] They are also known as Holt flares.

See item 18 in the front and lower-wing views above.[1]

Provision is made on the rear spars of the bottom outer main planes for the attachment of the standard flare brackets. The flares are controlled by push buttons on the port side of the pilot's instrument board.[1]:76 [emphasis mine]

The Air Navigation Directions (...) require aircraft to be equipped with landing lights (lamps or wing-tip flares) for flights by night (...) The construction of the flare brackets and their position on the wing of the aircraft must be such as to prevent the flame from the flare overheating the wing or aileron fabric when the aircraft is in flight or standing on the ground.[2] [emphasis mine]

Source: twitter.com; cropped

In the crop above, the object at the leading edge is a navigation light, the one below at the trailing edge is the flare bracket.
(My guess, with the engines near idle for landing, there wasn't enough electrical power for bright lamps, or they were heavy and/or unreliable back then.)

1: Great Britain. Air Ministry. (1929). The Supermarine Southampton Boat Seaplane, Mark II. (Metal Hull) Two Lion Engines ... Air Ministry. Issued November, 1929. London: H. M. Stationery Off.. (hathitrust.org)
2: (1939), "A German Long‐Range Flying‐Boat: Some Particulars of the Latest Dornier Seaplane to be put into Service on the South Atlantic Route", Aircraft Engineering and Aerospace Technology, Vol. 11 No. 9, pp. 357-369. https://doi.org/10.1108/eb030544
3: Sherwin, Holt Harold Edward. "Landing light or flare for attaching to aircraft." U.S. Patent No. 1,423,326. 18 Jul. 1922.
4: Sherwin, Holt Harold Edward. "Flare for use on aircraft." U.S. Patent No. 1,360,527. 30 Nov. 1920.


Does it make sense having a MiG 19 fuselage 'area ruled'? If the MiG 19 fuselage diameters followed the Area Rule, instead of being a constant size cigar, perhaps transonic performance will be improved; someone answered to this question elsewhere indicating the airplane is already somehow area ruled, from the swept back wing, the place of canopy, but the B-58 'Hustler' fuselage is actually 'Area Ruled', you can have a look at it. Think in some USA aircraft cases where Area ruling greatly improved results.

Maybe a little, but not really worth doing.
Area ruling is not a precise science. The exact cross-section used to calculate the area depends on the Mach number, so the best you can do is pick some problem speed and area-rule for that. Also, junctions and other features do not always blend smoothly, so the ideal area profile as you work along the plane is not achievable. You end up making compromises.
And even then, unless your design already has a problem, area ruling will not magically push your plane faster. For example the English Electric Lightning had a similar straight-through fuselage design yet was capable of Mach 2 plus.
The MiG-19 was one of the fastest "pre-area rule" types in large part because it had among the fewest problems with sharp changes in area. The kind of re-contouring that Convair undertook between the YF-102 and YF-102A would not need to be nearly so drastic on the MiG-19 and would not bring anything like the same benefits.
The Mig-21 is in some ways what you suggest, a developed MiG-19 with area ruling (and a few other little tweaks!). Prototypes were originally built with swept and delta wings, and the delta only then selected for production.


Should I log flying lessons from the start? I've recently started taking flying lessons and was wondering if I should begin logging my flying hours immediately?

I'm aware there are minimum hours for each license certification, so I'm assuming I should be noting down my flight time right from the start but my instructor hasn't really said anything about it yet.

Yes, you should be logging from the start. Now for the first few lessons, it'd be ok to not have your own logbook yet, but you should get one. Hopefully your instructor has kept his up to date, and can build your logbook in terms of flight times since you started.


How long is a clearance void time valid? You're picking up your IFR clearance on the ground and you get a 10 minute void time from now.

What phase of flight is that 10 minute void time clearance good until?

..your wheels are up?
..a certain altitude?
..on course?
..your initial call to ATC?
..or is it from when ATC gives your position report and says "radar contact"?

Since you didn't state jurisdiction, I'm assuming US.

From the AIM:

  1. Clearance Void Times. A pilot may receive a clearance, when operating from an airport without a control tower, which contains a
  provision for the clearance to be void if not airborne by a specific
  time. A pilot who does not depart prior to the clearance void time
  must advise ATC as soon as possible of their intentions. ATC will
  normally advise the pilot of the time allotted to notify ATC that the
  aircraft did not depart prior to the clearance void time. This time
  cannot exceed 30 minutes. Failure of an aircraft to contact ATC within
  30 minutes after the clearance void time will result in the aircraft
  being considered overdue and search and rescue procedures initiated.

The requirement is to be airborne prior to the clearance void time. You need to contact ATC within 30 minutes of the void time either in the air or to notify them that you did not depart.


How did the two F35 planes get from Fort Worth to Williamtown? I am curious how the the F35 that recently arrived in Williamtown Australia arrived there.
Were they transported at any point, or were they flown the entire way?
How many stops did they make?
Did Australian pilots land them in Australia? If so did Australian pilots take off in them from Fort Worth?

The two aircraft had been delivered to the RAAF at Luke in September and October and delivered to Williamtown via Hickam Air Force Base in Hawaii and RAAF Base Amberley, south-east of Brisbane.

From Defense News.


Why don't big airliners have bigger doors? Reading this question I saw this picture in MikeFoxtrot's answer and noticed how easier it would be to board the plane using that huge door:

I understand that for single aisle planes you wold need to form a single line anyway, but for two aisle planes having a wide door could speed up the boarding process a lot.

So, is there a reason why it is not done? What is the limiting factor in the door size?

Multi-aisle commercial aircraft adopt a multi-door boarding strategy rather than a single-huge door (see the A380 or the B747, both use two doors). This helps under the structural viewpoint: the presence of a door (cargo or passenger that might be) induces design problems that are amplified if the compartment has to be pressurised.

A door interrupts both frames and stringers and weakens the overall aircraft structure. A huge door interrupts many more frames than a small one and two small ones can be set apart from each other to have some continuous frames between the two, restoring some rigidity.

The complex closure systems ensure that part of the stresses are carried by the door material, but it will never be perfectly transmitted as it would be without a door. As mentioned before, the stresses are heightened if the compartment is pressurised (as when passengers have to be transported).


What is the weight that is used to balance an aircraft called? I remember I was reading about balancing an airplane a few days ago, and i came across a type of weight that is added to balance the airplane. But, I do not remember what it was called.

Also could someone tell me the approved location of these weights on a Boeing 747-400?

747s in everyday operation typically use fuel for ballast when needed. Ballast fuel is considered to be part of the zero fuel weight and you are not allowed to burn it, although obviously if you were about to run out of fuel, it's available.

Ballast fuel is carried in either the center tank or distributed evenly in the four main wing tanks. Individual carriers have different ideas insofar as their preference for either center tank or wing tank ballast fuel. Also, after the TWA 800 explosion back in the late 1990s, there were as I remember special rules for a time on carrying ballast fuel in the center tank.

Should you wish to explore the effects of ballast fuel on the CG of a 747-400, go to 747.terryliittschwager.com and select the first aircraft N402YY. When the aircraft comes up, you'll notice that the BALLAST FUEL radio buttons at top center have the Center Tank selected. If you put 100000 lbs of fuel in and then 1000 lbs of ballast, you'll see the zero fuel weight CG change from 30.6% MAC to 30.8% MAC.

Ballast fuel is more often necessary for 747s that were originally passenger airplanes and then converted to freighters than otherwise. The problem is that the heavy structure added for the large cargo door aft of the wing brings the basic operating weight CG farther aft then before the cargo conversion. 747s originally manufactured as freighters do not have this problem as they have additional structure for the nose cargo door in addition to the side cargo door structure.


Do flight attendants have a regulatory responsibility to risk their own lives to save passengers? A documentary about the collision at Tenerife seems to imply that the Pan Am flight attendants left the aircraft without helping a single passenger?  Is this correct? If so how is this possible? Are flight attendants required by regulation to place their own lives at risk to save passengers?

In training, flight attendants are given lots of emergency training, but always with the caveat that they are under no obligation to put themselves in danger.  Emergency procedures should proceed up until the time a flight attendant feels they are in danger, then they are to evacuate the airplane themselves as quickly as possible.

There was a long standing joke among flight attendants when I was working, which was the most important emergency instruction you can give:  Follow me!  Funny, but not really.  It keeps things in perspective.  Not commonly known is that any emergency responder today operates under the same conditions.  You are not being paid to put yourself in danger beyond what your training will accommodate.


What is the purpose of the selected altitude/airspeed in ARINC 429? What is the purpose of the selected altitude and airspeed fields in ARINC 429?

Both labels are used to transmit the altitude and airspeed that are dialed into the Mode Control Panel of the autopilot. They are not necessarily the current altitude/airspeed, instead they are the target values that the autopilot is steering to.


What is the difference between ACARS and ADS-B? What is the difference between ACARS and ADS-B?

For weather information in-flight or pre-flight which one is used?

One can easily get lost in the alphabet soup that is datalink.

Both ACARS and ADS-B provide datalink applications – which can be broken down in terms of CNS: Communication, Navigation, and Surveillance.

ACARS is used for:

Communication: includes uplinking (ground → aircraft) weather data upon a downlink request to the company/service provider – not a public service
Navigation: if you consider flex-routing
Surveillance: position reports in the North Atlantic for example (CPDLC over ACARS).

ADS-B is used solely for Surveillance; broadcasting (OUT) own location – and can include ownship surveillance by receiving (IN) traffic information.

If this IN setup is via the UAT frequency, then the aircraft can also receive weather information using FIS-B (free service). Its only relation to ADS-B in this particular instance is the UAT frequency, and it is more of a general aviation (and low-flying commercial) service.

Source: https://www.faa.gov/nextgen/programs/adsb/pilot/#fisb


What are the accident rates for kit built aircraft vs. normal aircraft of the same model? I know that some manufacturers both sell kit and finished version of their aircraft. For a fair comparison of accident rates, i was wondering:

What are the accident rates for kit built aircraft vs. normal aircraft of the same model?

Are the home-builds less safe than the company finished aircraft?

The Australian Transport Safety Bureau did a report titled:

Amateur-built aircraft Part 2: Analysis of accidents involving VH-registered non-factory-built aeroplanes 1988-2010

This report specifically covers this and found that the accident rate was three times higher in kit built -vs- similar factory build aircraft:

  What did this report do

  The ATSB investigated the safety history of amateur-built aircraft in
  Australia through analysis of accident data held in the ATSB’s
  occurrence database from 1988 to 2010. Comparisons were made between
  accidents involving amateur-built aircraft and those involving similar
  factory-built aircraft to help identify whether the rate and types of
  accidents differed between these two groups of aircraft.

  What the ATSB found

  Amateur-built aircraft had an accident rate three times higher than
  comparable factory-built certified aircraft conducting similar flight
  operations between 1988 and 2010. The fatal and serious injury
  accident rate was over five times higher in amateur-built aircraft, in
  particular due to relatively more serious injury accidents. The pilots
  of amateur-built aircraft involved in accidents were significantly
  more experienced overall than factory-built aircraft accident pilots.
  However, they were significantly less experienced on the aircraft type
  that they were flying at the time of the accident.

  Over half of the accidents were precipitated by mechanical events,
  which were mainly complete or partial engine failures. Following the
  amateur-built phase one test period, mechanical failures were still
  significantly more common when compared with factory-built aircraft. A
  quarter of accidents were from loss of aircraft control. Structural
  failures were not common precursors in amateur-built aircraft.
  Collision with terrain and forced landing accidents were more frequent
  in amateur-built aircraft. Collisions with terrain, hard landings, and
  runway excursions were more likely to result in a serious injury from
  an amateur-built aircraft accident than for factory-built accidents.

On the other hand, the EAA says that homebuilt aircraft have an accident rate of less than 1% higher than the general aviation fleet in their FAQ, but this didn't compare homebuilt to factory built in similar models:

  How Safe Are Amateur-Built/Homebuilt Aircraft?

  Studies by FAA and the National Transportation Safety Board (NTSB)
  show that Amateur-Built/Homebuilt aircraft have an accident rate less
  than one percentage point higher than the general aviation fleet. In
  fact, the accident rate for Amateur-Built/homebuilt aircraft is
  dropping. The total number of registered homebuilt aircraft is
  increasing by about 1,000 per year, while the total number of
  accidents has stayed virtually the same. Another good barometer of
  safety is insurance rates. Companies that insure both homebuilts and
  production aircraft charge about the same rates for owners of either
  type of airplane. That indicates a similar level of risk.


What are the effects of adding power to a 45 degree banked aircraft? In a recent question it was proposed that adding excess power to an aircraft in a level 45 degree banked turn would cause it to pitch up into a rolling climb.

This case was compared with level flight using a positive static stability (CG forward-tail down force) model.

In level flight, adding excess power will initially cause an increase in speed, followed by increase in tail downforce,  followed by a pitch up, followed by speed stabilization and climb.
Pitch controls speed, power controls altitude.

Roll 45 degrees and do a level coordinated turn around a point. Add in power.
What I am seeing is a turn around a barber pole with no change in roll, an ascending spiral.

If we added more pitch,  leaving the throttle, rudder and ailerons where they were, a slower upward spiral with steeper barber stripes?

The plane does not seem to roll, the wing is always pointed to the same pole.
Is there any rolling motion WRT aircraft performing these manuvers?

The key is that you qualified the turn as coordinated.  If the turn continues coordinated after the application of more power, then the aircraft will climb due to increased energy being converted to altitude.  Unless you decide to "lower the nose" and turn at a faster airspeed.


What is the most critical takeoff shear margin condition for a Type IV anti-ice fluid? Type II and the more common Type IV anti-ice fluids use non-Newtonian thickening agents so that they can stay put during ground operations, yet shear stresses on the fluid during the takeoff roll cause the fluid to come off the wings, leaving a clean wing behind that can provide proper lift at rotation.  However, if the fluid itself fails to detach from the wing, it can degrade the aerodynamic performance of the wing just like any other contaminant.

Under what conditions of liftoff/rotation speed, aircraft design, temperature, and precipitation is the margin between "shear forces available to get the fluid off the wing" and "shear forces required to thin and remove the fluid" the least?   You can assume that the fluid in use is a standard SAE Type IV fluid applied as per SAE ARP 4737.

Under the following conditions, we can't take off:

Temperature below -10 degrees C, and
Small Hail or ice pellets (i.e. METAR "PL" reported), and
Rotation speed below 115 knots

To operate with PL reported, we have to have Type IV anti-ice applied, and under those conditions of temperature + precip, they (yeah, "they") have determined that you need at least 115 knots to be sure the fluid adequately shears off.  There are various ways to drive an increase to your VR speed; it takes a pretty light 737 to rotate at 115 knots.  Other aircraft, of course, might normally rotate well below that speed.

I suspect that this limitation is probably applicable across the US airline industry, but the charts I have are specific to one carrier, so I won't generalize beyond that.

This (PL, -10C) is the only place in all the de-ice/anti-ice charts that we have this 115 knot limit.  With all other forms of precipitation, we have a holdover time and the requirement to visually check the fluid for failure; if it has failed, then we don't take off but rather go back & get it washed off & re-applied.  In the case of PL, there is neither a visual check nor a holdover time, but an "allowance time" after which you have to assume fluid failure & go back to start over.  (With PL, you can't visually identify fluid failure -- so you have a conservative time, and after that you're just done.) Speculating, I'm assuming that the nature of the ice pellets is such that they can, in sufficiently cold temperatures, generate the conditions where the fluid needs a particular speed to shear off that some of our operations might not reach -- thus the 115 knot limit.  Whatever can happen with the other precip, presumably can't keep the fluid from shearing off at whatever our lowest possible VR might be -- which I don't know offhand.  Again, for aircraft with a slower VR, you might get those sorts of situations with combinations of precip & temperature that we wouldn't worry about.

Not a complete answer to your question, but hopefully this data point may be helpful.


Can microbursts occur at high altitudes? I was wondering whether a microburst can occur at high altitudes?

Strong downbursts of air are possible at high levels also, for example in Cumulonimbus-clouds. However I wouldn't characterize them as microbursts, since the change of airflow direction is an equally dangerous and defining factor in microbursts.

(source: weather.gov.hk)
The head/tailwind parts don't exist at higher altitudes and you would experience the downdraft merely as turbulence.