Why do you need to provide your arrival airport when you close a VFR flight plan? I file VFR flight plans all the time, now that 1800wxbrief.com makes it so easy to open and close them.

Opening is easy, just click the activate button, but when it's time to close the flight plan, you have to type in your arrival airport.  Of what value is that particular piece of information to FSS?  Is there a historical reason why they request it?

My understanding is that providing multiple pieces of information related to your flight plan when communicating is to ensure that the correct flight plan is being manipulated.

It seems odd that it would be required on an electronic format, but what if your N-number is N1234RF and a person closing the flight plan types N1234EF?

There is potential to close the wrong flight plan.  Now the likelihood of both of those N-numbers having an active flight plan to the same destination and having someone fat-finger it at the same time is much less likely, obviously.

Also, "if you are flying to multiple airports this function provides a chance to confirm which of the flight plans you are using. Ex. a student pilot flying from their Home airport to airport A, taking a break then flying onto airport B before flying back home." - Dawn Breaker

So it is just a cross-reference for accuracy.


How is the 737 main landing gear protected from weather? I really like the 737, it is perhaps my favorite airliner. One curiosity of this aircraft (afaik, it is the only commercial airliner) is that the main landing gear has no cover:

Here is another picture from the inside:

In this situation, how does the aircraft protect the gear mechanism from weather/freezing?

Aircraft icing is not caused by ice in clouds- it is formed by supercooled water droplets (Source). They freeze on impact with a surface that has some location with zero flow velocity, most often on the leading edge of the wing.

  Ice accumulates on every exposed frontal surface of the aeroplane – not just on the wings, propeller, and windshield, but also on the antennas, vents, intakes, and cowlings. It builds in flight where no heat or boots can reach it. It can cause antennas to vibrate so severely that they break. In moderate to severe conditions, a light aircraft can become so iced up that continued flight is impossible. The aeroplane may stall at much higher speeds and lower angles of attack than normal. It can roll or pitch uncontrollably, and recovery may be impossible. Source

The gear as such as is not worse off than normal landing gear. The B737 has wheel caps visible in your first photo to cover towards the outside, and is not allowed to fly without them. If icing had been a problem, the same concern would extend onto landing gear doors being frozen shut. Landing gears bays are unpressurised and very cold normally anyways.


What regulations or procedures address runway-taxiway interference for aircraft with large wingspan? Are there cases of airports where a large wingspan aircraft on a taxiway can interfere with another aircraft on the runway?

Or do the airport design parameters take care that the largest wingspan aircraft on a taxiway will still never infringe on a runway's safety zone?

How about taxiway-to-taxiway interference? Is that precluded by design itself for worst case combinations or can there be cases where two large wingspan aircraft on two taxiways may interfere?

If so, is it the pilot's duty primarily or the tower's  to ensure that interference does not occur due to conflicting wingspans of aircraft on different taxiways?

Are taxiways with potential for such interference separately indicated on the airport taxi charts?

Yes this can and has happened with what is considered a "super-jumbo" like the A380 or the 747-8 (Aircraft Design Group VI aircraft).

The FAA must issue waivers to airports to legally accept these types of aircraft due to spacing rules that are in place. A lot of larger airports built quite a few years ago didn't have the foresight to handle aircraft of this size, so special precautions have to be taken when handling those types of aircraft. For class VI aircraft, an airport must have taxiways that are 100' wide and runways that are 200' wide. Note though that an A380's wingspan is 262', so even on a 100' taxiway, the wings hang over 81' on either side.

Usually ground controllers get special training to handle the larger aircraft and maintain separation, but its even a problem for the ground crew before talking to ground control because there are quite a few notable incidents of aircraft being backed into other aircraft.

Here are some interesting reads:

Miami International A380 Preparations
Los Angeles LAX A380 Operational Plan


What is the belly pod on this Beech A200 Super King Air? In this photo of N46L, a Beech A200 Super King Air owned by Dynamic Aviation, there is a large pod attached to the belly with what looks like two largish ports or windows on the underside.  What is it, exactly?  It looks similar to a synthetic aperture radar pod or video surveillance package, but I was curious if anyone could ID it precisely.

The full photo is available at http://www.jetphotos.net/viewphoto_new.php?id=7118680.

Short answer
It seems to be a US Army CEASAR pod, a communication intercepting and jamming system for electronic warfare, which has been flown in Iraq and Afghanistan. CEASAR is derived from AN/ALQ-227 EA used by US Navy on the EA-18G Growler.
The aircraft is equipped with missile detection and countermeasures. Two sensors are below the cockpit windscreen, two other on the aft fuselage. The chaff is released by a dispenser aft of the pod.
N40R is N46L's sister aircraft, and it also carries a CEASAR pod. The A200 variant used may be a C12-A or a C-12C (this is the model number visible on N40R fuselage). They are also known as Huron and HC-12.
High definition photo of N46R:

Photo by Keith Newsome on photobucket (source)
Detailed answer below.

About CEASAR
From Stars and Stripes:

The CEASAR, which stands for communications electronic attack with
surveillance and reconnaissance, is a rectangular metal box that holds
technology capable of both knocking out cell phones and radios and
intercepting transmissions, while an electronic warfare officer
onboard speaks directly to troops on the ground. It’s precise enough
to cover friendly soldiers while jamming insurgents, but not knocking
out communications for an entire village near a given operation.

From matthewaid.com:

Contractors Continue Flying CEASAR SIGINT Aircraft in Afghanistan
The CEASAR system mounted in these contractor-owned and
government-operated (COGO) aircraft is based on the Raytheon
AN/ALQ-227 EA system as fitted to the US Navy’s (USN’s) Boeing EA-18G
Growler electronic warfare (EW) aircraft. It is designed to provide
both a communications jamming and an intercept/monitoring capability.

CEASAR UAV replacement
Flying CEASAR on a modified A200 was already very much cheaper than using a pod on a fighter. However like for other functions, military are looking at using unmanned aircraft. The NERO pod has been designed for this purpose.
From Defense Systems:

NERO jams aboard a drone in Army test
The Army recently tested a jammer called the Networked Electronic
Warfare Remotely Operated, or NERO, attached to a Gray Eagle unmanned
combat aircraft at the Great Salt Lake Desert at Dugway Proving
Ground, Utah.

Missile Warning System AN/AAR-47
Closer view (N40R):

It detects infrared or radio sensing from a missile and commands a response, e.g. release of chaff or flare using the countermeasures dispensing system aft of the pod.
Two other sensors are located on the aft fuselage.
Sensor detail on another aircraft:

(source)

About the aircraft
From FAA, King Air A200, CN BC-1 thru BC-61 are variant C-12A used by US Army.
From JetPhotos.net this aircraft is used under call-sign Grizzly 23:

Registration: N46L
CN: BC-56
'Grizzly 23' taxies for departure to Wick.this is one of a number of
aircraft owned by Dynamic that operate on behalf of the US Army.

There are two C-12 aircraft equipped with CEASAR. The other is registered N40R, with call-sign Grizzly 12:

(source)
Huron are seconded or being replaced by Dash 8.


How do single engine airplanes handle changes in torque? In multirotors, there is a regulation of torque from the rotors which keeps it stable. However, in single engine airplanes, there is only one engine with one propeller.

How is the aircraft able to stabilize itself in such a case?

Single engine airplanes experience torque proportional to the amount of engine power used. Pilots mitigate this torque by applying engine power smoothly and gradually. Since the torque on most planes will be applied to the airframe in the counter-clockwise direction from the point of view of the pilot, the pilot further mitigates this torque by applying Some right rudder when applying engine power. Aircraft manufacturers mitigate torque by offsetting engine placement and control surface neutral positions slightly. Quick applications or reductions in engine power will still cause the torque to be noticeable enough to create a left turning tendency.


Where can I find reliable data on maximum turn rates for jet fighters? I'm looking for reliable data on maximum instantaneous turn rates for jet fighters, something coming from reliable sources, ideally official flight manuals or specifications. I can't seem to find anything. I've seen reports of turn rates around 35°/s for some fighters (F-22, Typhoon, Rafale) but I don't know whether those can be trusted: https://defenseissues.wordpress.com/2014/01/11/comparing-modern-western-fighters/

If possible I'd like to have data on fighters with exceptionally high maximum turn rates, but really, anything would be welcome. Even information on old, retired fighters would be nice, and I guess that's more likely to be declassified. Failing that, a lower bound would be useful.

I don't know if turn rates make much sense for helicopters, but that information would also have some value.

Imformation on the F-22, particularly performance and mission systems data remains classified, as with the F-35 airplane.  To the best of my knowledge there isn't much technical data available to the public on those subjects.

Now flight manuals for older fighter aircraft are readily available to the general public.  PublicIntelligence.net is a great source for these documents, as they have them for the F-14, F-16, F/A-18E/F, AV-8B, A-10, just to name a few.

Janes/IHS is not a great source for this stuff; their entries are more on the level of intelligence briefs and encyclopedia entries and are not likely to contain the information you ar looking for.


Can someone explain Exemption 3585? Exemption 3585 allows 121 carriers (and perhaps others) to dispatch to destinations in certain cases with weather below minimums.

What are the forecast weather minimums to be dispatched under exemption 3585?  When is it required to have a second alternate listed on the release?  What are the forecast weather requirements at the two alternates?  What is the regulatory basis for this exemption?

Exemption 3585 is an exemption to 14 CFR 121 dispatch requirements for weather originally requested by Peoples Express.  Lots of airlines have requested similar approval, and here is an example on regulations.gov for Air Transportation International.

The exemption that they asked and were approved for was:

  ...an exemption from §§ 121.613, 121.619(a), and 121.625 of Title
  14, Code of Federal Regulations (14 CFR) to the extent necessary to
  dispatch airplanes under instrument flight rules when conditional
  language in a one-time increment of the weather forecast states
  that the weather at the destination, alternate airport, or both
  airports could be below the authorized weather minimums when other
  time increments of the weather forecast state the weather conditions
  will be at or above the authorized weather minimums.

In other words, if there is a conditional or temporary weather condition that is below minimums at the destination or the alternate airport at the flight's ETA1,2, where the flight could not normally be released, they can depart under the 3585 exemption as long as a second alternate that is above required minimums3 is filed in the flight plan and enough fuel is carried to reach the furthest alternate plus the required 45 minute reserve.  There are a few other requirements too (training, manual and OpSpec revisions, etc.) but you can take a look at the letter to see them.

The exemption must be requested of and approved by the FAA for each air carrier that wants to use it.

1 The forecast weather conditions at the destination airport must not be less
than one-half of the lowest weather minimum visibility value established
for the instrument approach procedure expected to be used at the
destination

2 The forecast weather conditions at the first alternate airport must not be less than one-half of the alternate weather minimum ceiling and visibility values
specified in ATI’s operations specifications for that airport

3 With respect to the second alternate airport listed in the flight release
pursuant to this exemption, the METAR, the appropriate time increment of
the TAF, or any combination thereof for that airport must indicate in the
main body and remarks section of the METAR or TAF that the forecast
weather conditions will be at or above the alternate airport weather
minimum ceiling and visibility values specified in ATI’s operations
specifications for that airport


Why are two-stroke engines nearly unheard of in aviation? Almost all aircraft piston engines are four-stroke engines, with one power stroke per piston every other crankshaft revolution and a great deal of intricate moving parts which are only too happy to break.  Two-stroke engines, in contrast, have a number of features that would seem to make them excellent choices for aviation use:

They have one power stroke per piston per crankshaft revolution, twice as many as a four-stroke engine, and also have far fewer moving parts, making them smaller and lighter than four-stroke engines of the same piston size and count; these two factors add up to give them a phenomenally high power-to-weight ratio, much better than that of a comparable four-stroke engine.
The same mechanical simplicity that contributes to their high power-to-weight ratio also makes them cheaper to build and sell, and (all else being equal) more reliable than four-strokes.
Most two-stroke engines are lubricated by mixing lubricant into the fuel rather than using a traditional oil sump; this allows them to operate happily in any orientation, including upside down.

The sole disadvantage of two-strokes is their greater fuel consumption and emissions, but:

Good design can reduce this problem to insignificant proportions;
Higher fuel costs could easily be offset by the reduced maintenance costs of a more reliable engine1 and the ability (due to the engine's greater power) to use fewer engines per aircraft, and;
When it comes to piston-engined-aircraft emissions, there are far worse concerns.

Yet, despite these advantages, to the best of my knowledge, only one two-stroke aircraft engine has ever entered mass-production (the highly-unusual Junkers Jumo 204/205/207 series), with a second (the Rolls-Royce Crécy) being cancelled during static-fire testing.

Why are two-strokes essentially nonexistent as aircraft engines?

1: Especially given that maintenance costs are often (though not always) a greater expense than fuel costs to begin with (scroll to page 20); the linked document is discussing jetliners, but the preponderance of maintenance costs would be much more pronounced for piston-engined aircraft, as piston engines are considerably more efficient and considerably less reliable than turbine engines (the latter due mainly to their massive mechanical complexity).

Several issues:

As you mentioned, high specific fuel consumption.  About to that of turboprops, but without the reliability. If you're going to live with that SFC, you might as well as go with turbines.

Poor reliability.  They are very sensitive to tuning and timing.  A 4 stroke piston aircraft engine will run with all kinds of things wrong with it.  Cam lobes worn down to nearly nubs.  Loose valve guides.  Horrible compression.  They can have compression readings that will cause most mechanics to ground them, but they will still make rated horsepower (Continental did testing to find this).  They are very "under-tuned", like a tractor or industrial engine.  You want this in aviation.  About the only thing that will make a 4 stroke aircraft engine blow up in your face is something like a thrown rod from a spun bearing or a cylinder that cracks open, and that requires bad maintenance or criminal neglect in the vast majority of cases.  2 strokes, in the ultralight world where they are widely used, have a reputation for letting go at any time (the only 2 stroke aircraft engine that even comes close to 4 stroke reliability is the Rotax 582 - but only close, and they're only reliable for a few hundred hours).

2 strokes require pressed together cranks with ball bearings because they have to depend on lubrication from oil mixed in with the fuel charge. So you can't have a forged one-piece crank (radials get away with ball main bearings but there is only one or two crank throws, and they still have dedicated oil lubrication).  With the only oil coming from what's diluted in the fuel in a 2 stroke, piston ring lubrication is marginal and ring life is poor.

Which gets us to longevity.  Although it has an official TBO of 2000 hours, if you take decent care of it, a Lycoming O-320 will run 3-4000 hours.  The plain bearings in a 4 stroke only see wear on startup; there is zero wear once they are pressurized because there is no metal to metal contact, and if you never shut it down and changed the oil on the go, the bearings would theoretically last forever.  Ball bearings lubricated with diluted oil have a finite life, and that and the barely lubricated rings limit longevity. You would never dream of a 2 stroke lasting that long in any galaxy in this universe.

2 strokes are popular in the ultralight world almost totally because they are cheap and have a superior power to weight ratio. You almost get a turbine's power to weight, and minimal cost, and that's worth living with the crappy reliability.  Ultralights get away with it because they crash going 30 mph not 70.

Problem is, a lot of the issues are baked into the configuration and can't be designed out.  Combine with with a business that is conservative by necessity, because your life depends on the conservatism, and it's no surprise.


Is the Valsalva Maneuver safe? The Valsalva Maneuver is where a pilot or passenger pinches their nose, closes their mouth, and then attempts to exhale through their nose. It is used to equalize or clear a buildup of pressure in the ear.  I'm always nervous when I do the maneuver, though. I'm afraid I'm going to damage my eardrums in some way.

Can performing the Valsalva Maneuver do damage to the ears, or is it entirely safe?

Yes, it's safe. It's taught to scuba divers as a standard method for equalizing air pressure, with the general caveat that it should never take too much effort and if you feel any pain or discomfort from doing it then you should stop diving and consult a doctor. Since pressure changes in the air are much more gradual than those underwater, it shouldn't be difficult at all to equalize in an aircraft.


What is this thing on the engine of a Cessna 500 Citation I? I've noticed something on the engine of this bizjet. Could somebody explain what that is?

Source (image modified to indicate location of fairing).

Those are the fairings containing the mechanisms for the engine's reverse thrust system. See this photo (copyrighted) of the similar reverse thrust "buckets" deployed on a Citation 550.

See this example of a similar thrust reverser system deployed on a different aircraft type:

Image source, public domain

See also Wikipedia's article on Thrust Reversal systems.


DP confusion. Do I turn left or right if not told? Please take a look at the MIA5 depatarture from KOPF:

MIA5 Page 1

MIA5 Page 2

The instructions seem in conflict. Specifically, suppose you are taking off RW 270R and want the WINCO transition.

The textual instructions are:

climb heading 273°, thence....
....maintain 2000 or higher altitude
and expect vectors to appropriate transition. Expect further
clearance to filed altitude 10 minutes after departure.

OK - that
    is straightforward essentially runway heading to vectors to WINCO.

However, there is a third text segment on page 2 regarding the WINCO transition:

"From over DHP VORTAC on DHP R-322 to WINCO INT"

DHP is a LEFT turn from OPF and would take the airplane directly across the KMIA departure / arrival paths; WINCO is a right turn. Which is it? What do I do in lost comm? Why do they have "from over DHP" I would expect the instruction to be "climb heading 273° to intercept DHP R-322 to WINCO"

Also, if I load that procedure into Garmin Pilot, it just shows a path direct from OPF to DHP then to WINCO which I know is wrong.

The ROUTING is DHP 322 radial to WINCO.  So that's the course line that you'd intercept when so instructed.  There is no reason to actually start at DHP, and since you'll be flying the heading off the runway, the leg from the field to DHP in the Garmin is immaterial.  You can expect that they'll either clear you to WINCO, or (for a non-RNAV aircraft, most likely)  that they'll clear you on a heading to intercept the DHP 322 radial to WINCO (and thence as filed), so you'd cycle the active leg from the {OPF to DHP} leg, to the next leg, which is {DHP to WINCO} (which is the same as the DHP 322 radial), and then you'd intercept that active leg.

Nothing in those instructions is telling you to fly to DHP, nor should you expect that you'd get a clearance to do so.

To answer the question in the title, until you're told otherwise, you fly the initial heading in the text instructions.  You're on vectors, so don't turn until told to do so.

If you go lost comm, then AVE-F would tell you that you're on Vectors to WINCO, so get yourself there as best you can, probably by turning direct if you're RNAV equipped, or flying the radial if not.

EDIT: Note, though, that in the normal (with comm) case,the DP instruction is NOT to fly heading 273 to intercept the radial; it is to fly that heading.  That's your only CLEARANCE.  ATC will turn you to intercept on whatever heading they want you on.  Only in the case of lost comm would you turn to WINCO upon reaching the 322 radial.  In all other cases, follow ATC instructions.


"Gross" and "net" planned runway length for the Haifa airport My city's mayor was just boasting on how she'd gotten an approval for an airport runway of length "2100 m gross, 1900 m net length", and that this would be enough to connect the city - Haifa - to hubs all across Europe.

I'm not sure what she meant exactly, but I looked up some aircraft runway requirements, and found this, with no distinction between "gross" and "net" length. Now, some of the Boeing 737 models can fit the "net" length she mentioned, and so can Airbus A319's - but A320s or A321s fall right between the "net" and "gross" lengths.

So, my question is:

Is there such a thing as "gross" vs "net" runway length? If so, what counts into the gross but not the net? Clear space between the tarmac and the perimeter fence maybe?
Was the mayor making an empty boast or can the information about that runway be interpreted so that what she said is correct?

Gross and net are not aviation terms for runways. Many runways have extra space on either end to be used as stopways, giving extra stopping distance in case of an overrun.

I'm going to hazard a guess and say that the gross length is the total paved area of the runway and the net length is between the thresholds that is usable for takeoffs and landings.


Destiny of Unused food after flight What happens to the unused food after a flight? Does it get all destroyed (on-site or off-site) or is there some alternative use (e.g. Charity ) that it gets put to. Does the incoming food truck cart it off with the carts or is it handled by the Janitorial / Clean Up crews.

On shorter sectors can some items be used on the next flight with the carts only being "topped up"?

PS. Obviously, I'm referring to the perishable items with short shelf lives. Not talking about peanuts and other packaged items that last with longer shelf lives.

The crew eats the food, no doubt. Just joking. The unused food is off loaded from the airplane into catering trucks and is discarded. It seems a bit sad but the reality is, any food that is leftover from a flight is considered “contaminated” so is discarded. This includes meals that passengers didn’t finish as well as entire carts full of food that were never used.

  So what is being done to help eliminate unnecessary waste? With
  limited space on flights, some airlines have started to make small
  changes by only loading 95% of the required meals on each flight with
  the expectation that some passengers will opt not to eat. Other
  airlines have started charging around $10 a meal, recognizing that
  less food is consumed when meals are only available for purchase
  rather then complimentary. In the past, some airlines have even
  donated their unused food to shelters and charities to help make a
  difference. Unfortunately due to incidents where food poisoning
  occurred, the liability became much too high and is no longer
  practiced by airlines. (Source)


Why don't commercial aircraft use all-movable tail surfaces like my RC plane? Many conventional RC planes use control surfaces at the tail just like the image below:

You can see there is a part in front of each surface control that never moves and only the surface control itself moves.

So, I built an rc plane without that part in front of the surface control. Take a look below:

This plane I built flies really well (no aileron). So I was wondering: why commercial aircrafts or even rc planes dont use this type of rudder/elevator without the part in front of it? See: making the control surface the way I did reduces drag since you dont have a fix part at the tail that does nothing, it reduces weight cause you just need the control surface and nothing more and it is also way easier to build. I cant understand why commercial aircrafts and rc planes dont make use of this exactly same type of rudder/elevator!

Could you please tell me the reason?

What is better and easier for small-scale models is not necessarily better for larger aircraft.

First, you can't say that the fixed part "does nothing". The tail is primarily a stabiliser; without it, a normal airplane will not fly at all. Only then it is a control surface, which allows it to fly well and how you want it.

Consequently, the size of the tail is primarily driven by stability considerations. For control, you need a certain amount of it and not too much more. If you have an all-moving tail, you may find that you need to move it only very slightly, or else control will become too sensitive. This is not necessarily easier to do.

From design point of view, the all-moving tail requires that the whole stabiliser was attached to a single shaft. On a small RC plane you can afford to make it of a simple wire. On a large aircraft, this translates to something bigger than your suburb water supply pipe: stabilisers of planes like A380 or An-124 are larger than wings of some airliners. Apart from the scale problem, this makes it a single point of failure, which makes it still heavier to be reliable.

Another design problem is nice aerodynamic coupling between the moving tail and the fuselage. Often designers have to invent something like this (A330):

Source

Overall, it is usually easier and lighter to make a conventional tail and attach an elevator (and rudder) to it.

Nevertheless, quite many airplanes have an all-moving stabiliser. There are several different reasons for this.

To accommodate a large range of centre of gravity (CG) locations, i.e. load distribution, and/or different aerodynamic configurations (e.g. flaps). This requires a large amount of control. But this control is typically 'slow': the load or configuration doesn't change in fractions of a second. So the tail is split between the slow all-moving part providing the so-called trim, and the fast conventional elevator. Most airliners have such arrangement, like the A330 from the above picture. But the largest ones, the An-124 and -225, don't use it: too hard. They entirely rely on the elevator.

There is rarely such a demand for the vertical tail: airplanes are more or less symmetrical, so rarely will you find an all-moving vertical stabiliser like this.
To provide easier load balance for small airplanes with reversible control, i.e. those where the control surfaces are moved by the pilot's muscle force. If you make an elevator on normal hinges, it may be quite hard to move it at high speed. Various tricks are used to make the force comfortable (which should be 'just right', not too much, not too small). But one of the straightforward solutions is to make the whole tail move about a carefully chosen axis. For smaller GA aircraft, the scale problem is not too bad yet, so many designs use this approach, for example, Piper PA28

Source

(The thing you see at the trailing edge is not a traditional elevator, it is the anti-servo tab that provides the 'just right' force).
Normal elevator control efficiency. Sometimes, airplanes just need more control than the normally-sized tail can provide. This primarily applies to agile supersonic aircraft. There are several reasons for it:

Agile manoeuvring obviously needs more control;
At supersonic speeds, pitch stability (and thus control effort) increases significantly;
Elevator efficiency falls. The thing is, at subsonic speeds, the normal elevator redistributes the airflow over the tail such that more air is affected than just the area of the elevator assumes. The relation is $\sqrt \frac{S_{elevator}}{S_{tail}}$, so if you have elevator occupying half the tail, its efficiency will not be just $0.5$, but $\sqrt 0.5 \approx 0.7$ compared to the all-moving stabilator deflected to the same angle. But at supersonic speeds this doesn't apply, and the relation is just linear. So all-moving surfaces make more sense. Occasionally, you can even find an all-moving vertical tail, like on Tu-160 (note it has all-moving horizontal tail as well):

Source


What is flight inspection, as provided by Cobham Aviation Services? At about midnight, I saw a small plane (a Diamond Twin Star) take off from Heathrow, on flightradar24. It then proceeded to fly in irregular loops around North London, at low altitude, 1700ft. The plane had registration G-COBS, and seems to be owned by "Cobham Flight Services", which provides "flight inspection services". Their web page advertises how good they are, without explaining what they do.

It seemed unusual, as such small planes don't normally use Heathrow, and flying low over a city at night also seems unusual. What was the purpose of a flight like this?

From their website,

  Cobham conducts commissioning, return-to-service, engineering and
  periodic flight inspections in addition to trials work on a range of
  systems including, CAT I/II/III ILS, MLS, PAR, DVOR, NDB, U/VDF,
  TACAN, DME, AGL and PAPI and PSR/SSR.

  The specialist capabilities include procedure validation, ADS-B and
  MLAT-systems, ship borne navaids, FI programme management, technical
  investigations, communication tests and trials, windfarm trials,
  flight inspection advice, and training.

  Cobham has formal approvals from UK CAA Safety Regulation Group (CAP
  670), UK MoD, INAC (Portugal), ENAV (Italy), British Standards
  Institute (BS EN ISO 9001:2008), Germany BAF, and Air Safety Support
  International OTAR for UK Overseas Territories.

It looks like they test airport/en-route equipment such as approach systems and ADS-B systems etc. This can presumably be done in any aircraft equipped to fly/test those approaches and systems.


Do small airplanes have AC power? I know that DC power is essential for avionics and that in medium and big airplanes AC (28 V, 400 Hz) is used with DC (28 V).

Small airplanes have a starter-generator that provides DC, but do they have an inverter too, to provide AC? If yes, then why use AC, and in which systems? And when is AC 26 V used?

I have worked on large and small aircraft.  You will find a 400hz power bus only on large aircraft. The reason is the greater quantity of poles in the generator and hence weight. Smaller aircraft use a 28v DC system for the avionics.


Dynamic modes at supersonic speed Our teacher gave us an assignment where we have to study the longitudinal stability of an X-15. I have to study it at 353.9 m/s which is Mach 1.2. Another group has to study it at 235.9 m/s so Mach 0.8.

I made a Matlab code computing the eigenvalues of the A matrix because I have to plot the phugoid and the short period modes. With my speed I get :

Eigenvalues [at 353.9 m/s]:
  -0.6094 + 3.1782i
  -0.6094 - 3.1782i
  -0.0775 + 0.0000i
   0.0473 + 0.0000i

While with the other speed I get:

Eigenvalues [at 235.9 m/s]:
  -0.4093 + 2.1175i
  -0.4093 - 2.1175i
  -0.0070 + 0.0649i
  -0.0070 - 0.0649i

In the second case, it is clear that the phugoid is the -0.0070  ± 0.0649i and the short mode is  -0.4093 ± 2.1175i. While in the first case, what can I deduce ?

Is there a dynamic mode which is cancelled by the supersonic speed?

EDIT: The A matrix is the coefficients of the longitudinal motion equations:

At 353.9 m/s:
 your phugoid mode is unstable as well as degenerated (Poles lie on real axis and has damping ratio 1).
while at 235.9 m/s:
phugoid mode has become stable as well as oscillatory and has some damping and frequency.

so, nothing has been canceled its just phugoid mode poles changing positions.
you can check it clearly by plotting root locus using rlocus command on MATLAB.


What are the "panels" on the wingtips of the Panavia Tornado? I am wondering about the purpose of the panel marked with the number 156 in this picture:

The same black panel can be seen on the wingtips here:

And also here:

What purpose does this panel serve? It could be just a construction technique, but in that case why would they cut a hole in the larger panel just to cover it up with the smaller black one?

From another cutaway drawing:

    57: Wing tip antenna

Found here, but the original source is unknown.


Gliding: why pulling the stick back in a spiral dive would tighten the turn? I have recently done my spiral dive recovery lesson in a glider ASK21.
The instructor taught me to level the wings first, then ease out of the dive by pulling the stick back. He said that pulling the stick back would only tighten the spiral and not help with reducing the speed.
Why is that? Should the nose not pitch up and reduce the speed?

The effects of rudder and elevator get mixed when the aircraft flies at a roll angle. See it this way: When you pull the elevator at a roll angle of 60°, it will mostly (86.6%) work like a rudder would for a level airplane.
Why those 86.6%? When looking at the aircraft in an earth-fixed reference system, the additional tail force from an elevator deflection will produce a side load component proportional to the sine of the roll angle (which is 86.6% at 60°). The vertical component which would help to get the nose up is only 50% at a roll angle of 60° because it is proportional to the cosine of the roll angle.
Coordinated flight at higher roll angles is almost like flying a loop sideways. You will only lift your glider's nose in the reference system of the glider and tighten the loop. The reference system that counts more here is the one in which gravity acts, and you should lift the glider's nose up in this system.
Not knowing this subtlety ended the life of several early aviators until it was found out in 1912 that the rudder is what lifts the nose in a spiral dive. Of course, it is even more efficient to first roll wings level and make the elevator work properly again.
The horizontal-loop thing works in reverse, too: Rüdiger Kunz, the designer of the Standard Austria, was always fond of telling the story that happened on occasion of the first flight: At some point, the pilot started to fly loops. After the third, he asked Herr Kunz over the radio: "Notice anything?" - "Yes, you're climbing" was his answer. Thereupon the pilot replied: "That's how you can circle in thermals, too!"


Why and when to use flaps? On a commercial airliner, what is the purpose of the flaps? I understand that depending on which direction they move in, they can be used to decrease airspeed, but I don't know when flaps are used. Are flaps used before takeoff, after takeoff and on approach?

Flaps change the camber of the wing's airfoil. This in turn changes the zero-lift angle of attack, increases the maximum lift potential and, in case of fowler-type flaps, the wing's area.

Airliners use flaps on both take-off and landing, and most of the time they are only partly deflected. Full deflection is only set on final approach to reduce the landing speed as much as possible.

When simple camber flaps are used, the drag increase is negligible for small deflections (±10° for a 20% flap), and they can be used for both take-off and landing. Other types of flaps are designed to increase drag (split flap, Zap flap) and should be used only for landing. If flight speed stays constant, a flap deflection will only change induced drag if it redistributes lift over the wingspan. Modern gliders use camber flaps inboard and flaperons (a combination of aileron and flap) outboard, and changing flap settings will not affect induced drag.

Generally, the purpose of flaps is to shift the minimum airfoil drag to the desired lift coefficient $c_L$. Especially laminar airfoils have a pronounced range of lift coefficients with low drag. The pilot should attempt to stay within this region of minimum drag, and flaps give him/her the means to achieve this. See below for an example of an airfoil at a Reynolds number of 1 Mio.

Flaps for lift increase work the same way, but change camber much more. Normally, they need to be combined with leading edge devices (slats) which change camber at the airfoil's nose to unfold their full potential. Below are some examples for flaps, in combination with proper leading edge devices. Note that the solid outline of the fowler flap is the position for landing, while the dashed outline is the position for take-off. $\delta$ is the relative chord of the flap.

Junkers flaps were the best way to control big aircraft in the days before more elaborate force compensation mechanisms were developed, and split- and Zap flaps were very popular in the 1930s. They are still used on smaller aircraft today. The simple Fowler flap is used on the C-130, and airliners use slotted flaps like the ones in the lowest two rows of the table above.

Besides increasing drag, powerful flaps change the pitching moment of the wing by shifting the center of lift backwards, which requires sufficient tail size and control power. On airliners, the incidence of the full horizontal tail can be adjusted in order to create enough downforce to counteract the pitching moment. Note on the picture of the An-70 below that the stabilizer has a slat which operates in the opposite direction to that of the wing.


Why not increase the number of Flight Data Recorders and add jettisoning capability? With some Flight Data Recorders gone unrecoverable during crashes , what's the argument for not changing their locations, like wings or engines?

Given their utility after accidents, why not increase the redundancy even more by placing separate boxes in each engine for example.

I understand that military aircraft have jettisoned Recorders  that signal their location for recovery. Could this option be considered with Jettisoned Engines even before the crash in case of Extreme Load or excessive vibrations ?

The simplest argument to me is that no location on the aircraft is particularly special when it comes to locating black boxes in this sense. The recorders that aren't found are either in exceptionally remote locations or underwater - I don't see anything special about an engine that makes it more likely to be found than the wreckage of the fuselage.

No matter where you place them, there are going to be circumstances where they can't be found.


How do airlines choose what food to serve? I'd imagine there are probably reasons behind the choice of food that airlines serve, and I'm wondering what those reasons are?

I guess that Air India probably serves more curries than American Airlines, but what other considerations are taken into account? Presumably weight is one.

1. Money

Meals are available at different prices. Most US airlines know you aren't choosing them on the basis of cuisine and pick the lowest priced meal they can get away with. Other airlines eg Emirates, Singapore compete by offering high customer services and so invest more money in better food and service.

2. Culture

Airlines which are mostly flying a home market will adapt the food to the traditions of the country. EL-AL aren't going to be serving bacon cheese-burgers and Air India used to do very good veggie curries.


Does the DC-3 have a prop sync? I'd like to ask if the DC-3 has a prop sync.
I found nothing about prop sync in the DC-3 operations manual, in the running specs, design features, or in the chapters about its engine and propeller. I've read the Wikipedia article about prop sync (which  didn't mention it) and this What is propeller / engine sync and how does it work? (which was great, but didn't speak of the DC-3). I've used this last link (which highlights the instrument) to check pictures of the cockpit and didn't see anything that looked exactly the same, but I don't think the instruments would look exactly the same in aircraft of different manufacturers (Junkers and Douglas). I assumed it didn't, but being that it's a twin-engine (which qualifies as a multi-engine) turboprop aircraft I'd have thought it'd make sense to have one. Can anyone help?
Thanks

Judging from this video, it does not have an automatic prop sync. When throttles are advanced you can hear the harmonic beat of the twin propeller blades, and during the climb the instructor seems to manually set the levers to reduce the harmonic set the correct manifold pressure. He may or may not have an indicator to help him, but judging from the sound effects there is no automatic synching taking place.

And here is an old C-47 cockpit procedure training film, on how to fly the aircraft. Nothing on synchronising the propellers.

That beautiful engine sound is not produced by a turbine by the way.


Has any Cessna Denali ever flown yet...? With all the articles and hypes around the new Cessna Denali with its GE catalyst turbo-prop engine, I am wondering has any prototype of this plane made it into the air yet?

I understand that the performance figures can be partly calculated but am wondering how they can be so specific about its speed, range, load, and fuel consumption? Thank you.

According to Flying Magazine's September 2018 profile of the Denali:

  The Denali’s first flight is expected early next year, with an entry
  into service during the first half of 2020.

As for the performance figures you mentioned, the same article says:

  The Denali will weigh less than 12,500 pounds to prevent the need for
  a type rating, but at the moment, Cessna hasn’t released a gross
  weight number, nor any performance figures. Those won’t be made public
  until after the Denali’s first flight next year.


What is the largest (size) solid object ever dropped from an airplane to impact the ground in freefall? What is the record for the largest single solid item that has ever been dropped from an airplane at free fall to the ground?

Here, "free fall" means falling vertically, or nearly vertically falling allowing some leeway for expected horizontal movement such as the ground speed of the plane doing the drop, winds, or unintended Magnus effect among other things, and allows for normal atmospheric air resistance.
The object being dropped should be payload, not part of the vehicle doing the dropping.
The object should not be designed with the intent to generate lift. For example, the above mentioned Magnus effect would disqualify if a machine was purposely built to spin with the intention of generating lift. This includes things with wings, parachutes, landing thrusters, etc.
The object must have hit the ground in an uncontrolled descent in the past. In other words, satellites in free-fall orbit around the Earth do not count unless they fell to the ground and then got re-launched into orbit again (unlikely).
Objects that burn up in the atmosphere do not reach the ground as a single solid object, so they do not count unless any possibly remaining fragment that may reach the ground is still the biggest object to be dropped and reach the ground in its destroyed state (unlikely).
The item does not have to have been intentionally dropped. For example, if it were dropped with a parachute, but the parachute failed to deploy, that counts.
Bombs easily count as long as they don't have a parachute, thrusters, wings or any other design factor that is intended to generate lift.
Last, but not least, "largest" means greatest volume, not heaviest.

I can't think of anything dropped from an aircraft larger than the US Space Shuttle when it was dropped from a specially modified 747 during the testing phases of development.


Why have different flights with the same flight number? It's not uncommon for two distinct flights to have the same number.  For example, DL10 consists of a narrow-bodied jet flying from Denver to Minneapolis–St Paul and then, two to three hours later, a wide-bodied jet flying from MSP to London Heathrow1; AA55 splits Manchester–Chicago–Orlando. This question gives another example and asks how ATC would deal with the situation where one of these flights is delayed leading to both being in the air at once.

But that begs the question of why one would give the same number to two flights in the first place. I understand that, historically, it was common for a long-haul flight to make several stops for refuelling but it's a long time since that was common and, here, we're talking about completely different aircraft and not just a refuelling stop.

What advantage is there to an airline in assigning the same number to two flights like this?

1 At least, it did when I posted the question in early October 2017. Now, a month later, it's a narrow-body from Kansas City to Minneapolis and then a Minneapolis–Heathrow flight. On some days, there's about 45 minutes between the two; on others, a little over three hours.

As far as I know, this practice is mostly just limited to very large airlines in the U.S. The reason for this is that the airlines are so large that they'd literally run out of flight numbers in some of the allocated ranges. Usually the 9000 range is reserved for special flights (e.g. repositioning flights, or, as discussed in the answer to the linked question, when a different callsign is needed,) but other ranges are also reserved for things like codeshares onto the flights of partner airlines and for flights operated by regional carriers instead of by mainline.

For example, this post from this flyertalk thread lists the following ranges used by Delta observed by a frequent flier on that airline:

  GoJet: 6000s
   Endeavor: 3000s
   Shuttle America: upper 2000s to lower 3000s.
   Compass: 5000s
   SkyWest: 4000s, 7000s
   Mainline: 0001-2999

From personal experience, I've noticed that partner airline codeshares on Delta are usually up in the 8000 range (maybe also part of the 7000 range?) Delta has a lot of partner airline codeshares, so quite a lot of the flight numbers go to this. Delta mainline operates a lot of flights. According to Wikipedia, Delta mainline and its regional carriers operated 5,400 flights per day as of October 2016. Having only 3,000 flight numbers available to mainline means that they'd almost certainly not have enough if they didn't reuse some of the numbers.

In total, according to Delta, their route network, include partner airline flights, totals over 15,000 flights per day. There are only 10,000 possible flight numbers and, when the reserved 9000 range is removed from consideration, only 9,000 possible flight numbers (or 8,999 if "Delta Flight 0" isn't allocated, which I expect it isn't.) As more and more of Delta's partner flights are given codeshares to Delta flight numbers, it would be very easy to exhaust the entire range of possible flight numbers.

An additional reason (possibly more relevant historically than today) is that it allows the airline to have a "direct" service to a city it doesn't actually fly to non-stop. Nowadays, people commonly use the term "direct flight" to mean "non-stop flight," but that's not the technical use of the term in airline-speak. The term "direct flight" really just means "we have a flight that gets you from A to B, but it might stop in C and D along the way."

Back in the day, this made more sense, as it wasn't as common for aircraft to have enough range to connect cities non-stop. So, a flight from New York to Seoul, for example, would typically stop in Anchorage to refuel before crossing the Pacific. Going even farther back, the first trans-Pacific flight (from San Francisco to Manila) had stops in Honolulu, Midway, Wake Island, and Guam. Since almost all of the passengers were going from San Francisco to Manila (not to, say, Wake Island or Midway, which were previously uninhabited,) it made sense to have a single flight number rather than using a different one for each segment. Nowadays, however, due to the much longer range of aircraft, there's not as much need for 'direct' flights with stops.

Pan-Am's SFO-MNL route via HNL, Midway, Wake, and Guam


Why are there 4 hands on the throttles of this B17 during takeoff? I watched a video of a a B17 taking off, and as you can see on the attached image, there are 4 hands on the throttles: the PF's right hand, both PNF's hands, and even the F/E has his hand under the throttles.

What's the reason for that? I understand the policy of the PNF having his/her hands on the throttles (as explained in this answer, for instance), but what about the F/E, what is he holding?

If you look at the throttle quadrant without all the hands involved, you can see more detail:

Source

At the bottom, the 4 levers control the pitch of the propeller blades. The FE is holding them to ensure that they are at full pitch for the entire take-off run.

The large levers in the middle are the throttles which (partly) control the manifold pressure (and power) that the engines are producing. Two pilots have hands on the throttles to ensure that all 4 engines are producing full take-off power.

But there are 4 more levers that nobody has their hands on, which control the waste gates for the turbocharged engines. These open or close the waste gates, and allow the turbo to make power. There are another 4 levers on older consoles that control the mixture settings. The levers shown above may be the mixture levers, its difficult to tell from this picture because it looks like the quadrant has been upgraded.

If you want to see a good video on how all these levers work, here is a really good YouTube video describing how to fly a B-17, start from about the 2:30 second mark, but its an interesting watch.


Would there be a restriction on my Sport Pilot license if I do my checkride in an aircraft without rudder pedals like the Ercoupe? I am training in an Ercoupe 415-C (C-85) that has no rudder pedals. I've read various stories about people taking a checkride in such an aircraft having a restriction on the license and having to take another checkride in a different aircraft to have the restriction removed. I've also seen this referenced as a myth that does not happen in real practice.

My questions:

Does this restriction really exist, or is it a myth?
Does it depend on the examiner?
Does it apply to sport pilot (where I would have to have an endorsement for another model anyways), or just private?
Would I have to take another checkride to have it removed, or could
it be removed with a CFI's endorsement?

The restriction you're talking about does exist, but there's no explicit wording for it. It's described in FAR 61.45(b)(2):

  An applicant for a certificate or rating may use an aircraft with operating characteristics that preclude the applicant from performing all of the tasks required for the practical test. However, the applicant's certificate or rating, as appropriate, will be issued with an appropriate limitation.

One of the most fundamental tasks in the Sport Pilot PTS is maintaining coordinated flight (you won't find it as a discrete task, but if you look at the PTS the phrase "while maintaining coordinated flight" occurs multiple times), and an Ercoupe without rudder pedals relieves the applicant of that responsibility because the aileron/rudder interconnect basically does it for you.

I'm not sure exactly how this works for Sport Pilots, but as you cannot demonstrate to the examiner that you can "maintain coordinated flight" they could reasonably apply the same restriction to your Sport Pilot certificate as they would to a Private Pilot certificate ("Limited to aircraft without rudder pedals").  You would need to demonstrate to a DPE or Examiner that you can operate an aircraft with rudder pedals at some later date to remove the restriction (it is a restriction on the certificate so the only way to remove it is to have the certificate amended/reissued/replaced).

The easiest way to avoid the entire issue is to prepare for and take your practical test in an aircraft with rudder pedals. You can do everything in the Ercoupe and then switch to the Cub for a week to brush up on systems and polish your maneuvers in that plane and get used to using your feet.


Can anybody give an example about Clearance Expiry Time? Clearance content is included: callsign, flight path, clearance border(destination aerodrome, available report point, controlled airspace border), flight level along the route or for a specific part of the route, etc. and end time of clearance or clearance expiry time. Can you give an example of a clearance expiry time? How does it end, is there any specific time that is notified by air traffic controller to pilot to pass some specific point? How is it said? can you give me a clearance example?

The current version of the AIM says:

  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.

  EXAMPLE− Clearance void if not off by (clearance void time) and, if
  required, if not off by (clearance void time) advise (facility) not
  later than (time) of intentions.

Let's say you're using a GCO or telephone to contact an ARTCC for your clearance out in a low-population area with little infrastructure making it impossible to contact ATC from the ground via standard radio equipment.  After you receive your clearance, you will hang up the call or change frequencies and break contact with ATC.

Due to the break in communication, they will end your IFR clearance by assigning a void time in case you don't get airborne as soon as expected.  If you delay beyond your void time, you would need to call and get a new clearance that you would expect to have issued with a new void time.  The void time is short enough that the implied intention is for the aircraft to receive the clearance while stopped at the runway's hold short line already prepared for takeoff.


How to select a Lead In Fighter Trainer in the presence of both single engine and twin engine fighter jets? A major part of fighter pilot training is learning the handling of the aircraft itself. On the other hand, automatic controls on modern fighter jets take away a lot of the pain and hassle. I am curious about the extent to which such ease of use plays a role in choosing the Lead In Fighter Trainer (LIFT) platform for an airforce.

Usually, it is assumed that the manufacturer supplying fighter jets will also supply the LIFT platform. But an airforce could buy jets from multiple vendors. It would be extremely cost ineffective to buy a different LIFT platform for each type of fighter jet. So airforces should try to standardize the LIFT platform they use.

Assume an airforce buys both single and twin engine fighter jets, from two different manufacturers. Neither aircraft has a twin seater version, so the first time pilots fly in them, they don't have an instructor sitting behind them giving instructions. Obviously, the aerodynamics and general handling of a twin engine fighter jet ought to be quite different from a single engine fighter jet. Now in making a decision on standardizing the LIFT platform, would this airforce take into account the presence of both single and twin engine fighter jets in its inventory? Would it procure two different LIFT platforms, one for training pilots towards single engine fighters, the other for training pilots towards twin engine fighters? Or does it make any practical sense for the airforce to choose only a single engine LIFT platform, or only a twin engine LIFT platform? What would be the pros and cons of such a decision?

Fighter lead-in isn't about becoming an expert in the training jet, it's about learning the fundamentals of flying tactical aircraft -- air combat maneuvering, strafing, bombing, etc.  So the difference between the aircraft flown in LIFT and the aircraft that the pilot will go to next isn't all that important.

I've never heard of any issues the US Air Force had with students flying AT-38's (2 engines) in fighter lead-in training then going to F-16 training.  The unique aspects of operating the single-engine F-16 are all covered during the F-16 course, and there are LOTS of differences between that and the AT-38.  Removing one of those differences, the # of engines, wouldn't be worth adding a whole new aircraft to the LIFT course -- a very expensive proposition for negligible gains.

So no, the number of engines in the eventual aircraft vs in the LIFT trainer is immaterial.


How should I read these climb and descent profile notations? I use a tool called SimBrief to build virtual flight plans for a desktop flight simulator. As I've been getting more familiar with procedures, I've also been exploring more advanced settings in the builder as well as some parts of the OFP output.

One thing that I can't figure out even after consulting the tool's docs is how ascent and descent profiles are represented: for example, for a 737-800 on a medium-haul route, one of the available ascent profiles will be 250/280/78, while one of the decent profiles is 78/280/280.

How should these be read?

For the climb profile, the first two values are indicated airspeed -- below 10,000 and above 10,000 feet MSL, and the final value is a Mach fraction. So 250/280/78 would be a climb of 250 knots below 10,000', 280 knots above 10,000', and transition to a climb of Mach .78 somewhere in the high 20's or low 30's (i.e. at the point where 280 KIAS = M 0.78).

For the descent profile, it is the reverse, initial Mach number from Cruise altitude until reaching the transition to indicated airspeed, then the IAS above 10,000', then the IAS below 10,000'.

The 250/280/78 climb profile is very standard for the 737 NG and Max aircraft; most airlines fly them at something fairly close to those speeds, using a Cost Index which starts there and then the FMC applies an adjustment for headwind or tailwind.  In a stiff headwind, the climb speed will increase up to maybe about 310 KIAS (as a ballpark) and Mach .80; with a strong tailwind the speed will go down to maybe 270 and Mach .76 (again, ballpark - exact Cost Index being used affects these adjustments).

The typical descent profile looks similar, although at least in the US we'd never use 280 knots below 10,000' -- it would always be 250 below 10.  If the country you were flying in didn't regulate that, you might do 280 down to close to pattern altitude, but I don't know what countries would allow that, and what you'd gain in time saved (not much) you'd pay for in terms of risk if you hit a big enough bird on or near the windscreen.

But that's what those numbers are almost certainly referring to.


Why did it take so long for helicopters to be developed/in use? The Sikorsky_H-5 was made in 1943 but used an engine released in the 1930's. It seems to me that the used that applied to helicopters, specifically in warfare, could have applied much earlier. Things like SAR, Medivac, spotting and ground support would all have been useful in the Second World War.

The useful payload and the robustness of rotorcraft were not sufficient for the rough conditions on the front. Only when turbines were available with their much better power-to-weight ratio and high reliability did helicopters offer a real advantage to the military.

The de Cierva autogyro line was begun in 1920, but de Cierva focused on building unstallable GA aircraft, not weapons. The same can be said for Henrich Focke, who improved on de Cierva's designs (which he built under license) with the Fa-61, which is considered the first practical helicopter.

The only helicopters to be used by the military were the designs of Anton Flettner who used two intermeshing rotors with considerable success, the transport helicopter Fa-223 with two rotors on outriggers and the Sikorsky R-4. The Flettner 282 and the Fa-223 were ordered by the Luftwaffe, but development took a long time, with many new problems to be overcome. In the end, they came too late to be used in any quantity.

The Sikorsky design was unstable and needed considerable pilot attention. Just watch how poor Igor is working the stick to keep the VS-300 straight! It also needed years of refinement before it could be used by the military. This was the R-4 which saw limited use for rescue missions from 1944 on.

Just because something can be demonstrated once does not imply it is ready for widespread use.


Could the Boeing 747's 'hump' be improved aerodynamically? Couldn't the Boeing 747's aerodynamics be improved by extending the hump further back, or sloping it back more gently? Wouldn't this make it more aerodynamic and therefore fuel efficient and faster?

The 747-300/400 has a longer hump than the original 100/200. Surprisingly, this longer hump had lower aerodynamic drag than the 200 hump: at higher mach numbers compressibility starts to cause serious drag increase. The speed at which this "drag divergence" occurs depends on the variance of cross section area of the plane. If the cross section of the plane would be a constant value, drag divergence speed would be closest to mach 1.

The longer bump on the 747-300 resulted in a more constant cross section and therefore higher drag divergence number => higher cruise speed.

Could it be made more efficient aerodynamically? Yes, by trying to match the Area Rule as closely as possible.

Source


What is the best route for my 18 year old son to become a pilot with a major airline? What is the cheapest and most effective way for my 18 year old son to become a commercial pilot with a major airline?

Look for a community college with an aviation program, they're quick and VERY affordable. I attended Iowa Lakes Community College, I was able to get my Private, Commercial, Instrument, Multi-Engine, and Instructor ratings in 2 years for $38k. DO NOT send him to a large university like UND, the programs are insanely overpriced and they take 4 years solid. At Iowa Lakes, you can get done as fast as you can, people have gone from student to instructor in a year, it all depends on you, at universities you HAVE to stay all 4 years which is a killer in an industry so heavily reliant on seniority. I have the exact same ratings as a kid coming out of UND only I have 1/4 his debt and I'm probably already a captain at a regional when he first gets to the airlines. Airlines are REALLY hurting for pilots, this is absolutely the best time to be a pilot.


How can I convert a Peruvian pilot's license to one that will let me work in the USA? My fiancé just became a U.S. resident. He's originally from Peru and is a helicopter pilot with some airplane experience as well. He has more than 8000 hours flying helicopters and around 150 airplane hours. He's an instructor pilot in Peru and currently works for the Peruvian Air Force.

I would like to know what does he has to do in order to work in the United States. Is there a different certification he has to get in order to fly either a commercial plane or an helicopter? Where can i get more information about it?

Well, first step would be a validation of his PPL, resulting in a US PPL based on the foreign one and only valid with both present. This can be done at an FSDO (Flight Standard District Office) for free. It can be done by mail as well. Also many flight schools experienced with foreign students can arrange it at a fee (usually in the 50 USD range). Going through a flight school may be the fastest way - for a CPL he needs one anyway. (Reference)

A foreign CPL (and everything else but a PPL, so like an FI) cannot be converted or validated. He will have to go through full process as described in 14 CFR 61.123. This needs signing up to a flight school/instructor. So while his hours will be accounted for, he need to do at least an extensive check ride (usually more than one - as procedures may differ) to convince the instructor to be ready for the practical test, as well as going through all knowledge tests required - and fulfil the language requirement as well.

A (good) school may also be the best place to get more in depth information, as this case may hold many individual details to be considered.

I guess the worst part might be to (re-) learn the standard phrases used in the US vs. what is used in his country of origin. 8000 hours means a lot of experience and deep entrenched radio phrases :))


Does Autopilot make planes safer? Statistically, are planes with advanced autopilot functionality less likely to be involved in fatal crashes? Answer only with actual statistics, not your personal opinion.

Using e.g. Boeing's annual commercial aviation safety statistics, one can essentially show that with each new aircraft generation, the accident rate reduces. This answers your question about statistic involvement, but doesn't really confirm a causal relationship, since it's not only automation but e.g. also human machine interface (flight deck) design and system architecture that improves. However, I would assume there are quite probably at least some safety improvements due to automation in there. One would need to go about analysing the accident factors to prove this.

As an interesting aside touching on this topic, a former colleague of mine flying commercial jets recently offered his first-hand view on different aircraft automation levels in his blog.

While not a comprehensive answer as such, I hope the links allow you to pursue this a bit further.


Second career as an avionics technician I will soon be retiring from my first career as an electrician on large construction projects. Planning on becoming an active private pilot again and I am
basically an aviation nut. I am curious as to what certifications are needed to be employable at an avionics shop ? What would be the best/quickest route to get there?

This answer assumes you live in the United States. You should consider attending a Part 147 program at an Aviation Maintenance Technician School approved by the FAA. Some avionics technicians also get themselves an Airframe mechanic's rating from the FAA because a good percentage of what a line avionics technician does has to do with components of the airframe. (As a side note, military experience as a line avionics tech is considered sufficient to qualify to take the tests for the Airframe mechanic rating). You can also become certified through a repair station, but that may only qualify you to perform specific work. You should definitely also get the FCC radio-telephone operator certification or Aircraft Electronics Technician (AET) certification from the National Center for Aerospace and Transportation Technologies.


Is it possible for a person to fly with mechanical wings attached to his torso? I’ve seen several adaptations of this concept in fiction from the tales of Icarus to Falcon in the MCU. But is it possible in reality for an average human to be able to fly through the air by wearing these gadgets?

If it is possible, then how would this work?

You could reasonably call a hang glider "wings strapped to the torso" for this purpose -- hence the answer is "yes, sort of."  With a well designed glider, one can launch from sloping ground and soar on slope lift or thermals, limited by oxygen requirements and fatigue.  Hang gliders have done cross country flights running to many hours, stayed up literally dawn to dusk on ridge lift, and flown high enough for the pilot to require oxygen (and then some, I believe the altitude record is around 18,000 feet).

None of this, of course, is powered by the pilot, using either arms or legs, but this is clearly "wings strapped to the torso."

Add a small engine and you get a modern ultralight/microlight, or something like Rocketman's jet powered wings.  The latter, especially, is still pretty clearly "wings strapped to the torso."


How many cabin crews are needed for an A350-1000? How many cabin crews are needed for an A350-1000?

It depends where you are flying, i.e. which countries rules apply. In the US for example, the minimum cabin crew is determined by the seating capacity:

  For airplanes having a seating capacity of more than 100 passengers—two flight attendants plus one additional flight attendant for each unit (or part of a unit) of 50 passenger seats above a seating capacity of 100 passengers.

(CFR 121.391 (a) (4))

The A350-1000 can seat up to 480 passengers, which would then require 10 flight attendants. Typical seating is however only 369 according to Wikipedia, which would only require 8 flight attendants.

In Europe, EASA defines the minimum number of cabin crew in the Type Certificate Data Sheet (TCDS):

  For the A350-1000, the minimum required cabin crew number established during the aircraft
  certification process is 8, irrespective of the Maximum Operational Passenger Seating Capacity
  (MOPSC).

  [...]

  In accordance with the operational requirement ORO.CC.100-Number and composition of cabin
  crew, if the MOPSC for the specific aircraft exceeds 400, the minimum required cabin crew number
  becomes 9.

(EASA A350 TCDS)

So here 8 or 9 flight attendants are required, also depending on the seating capacity.


Does Airbus buy Boeings and vice versa? I read somewhere that Airbus developed the A350 in response to the B787. In general, how much do Boeing and Airbus know about each other's aircraft? And how do they learn about the detailed designs of those aircraft? Do they buy each other's planes and study them piece by piece?

When a manufacturer is making an aircraft to compete with another manufacturer's products, they have the public marketing material to go off of, as well as what their customers tell them the other aircraft can do, and what they are looking to buy. The general performance capabilities and costs are what is most important at the high level of making a competing product.
More in-depth study does help for detailed information, and there are multiple ways that this can happen.
Manufacturers will end up with airplanes from other manufacturers through trade-ins. Just like with car dealers, they may offer to buy older aircraft from a customer as part of the sales deal for new aircraft. Unless they are headed for scrap, these aircraft are generally worth more intact on the used market than dismantling them but it certainly allows closer study.
Manufacturers can also look for parts on the spares market like any other buyer, and get specific parts of interest that way.
Information can also be found in safety bulletins or accident reports if a certain system or component is involved.


What is RTOW and how is it different from MTOW? Please explain what is RTOW, and what is the difference between RTOW and MTOW. Is there a link between the RTOW and the Weight and Balance Manual?

Google gives you the answer without even clicking any links:

https://www.google.com/search?q=RTOW

  MTOW is a hard limit regardless of other considerations and is tied up
  with the basic aircraft certification basis.RTOW is the limiting
  takeoff weight calculated for a particular runway under particular
  specified conditions

Maximum Take Off Weight - The maximum weight in which an aircraft can ever take-off, under any circumstances.

Regulated Take Off Weight - The maximum weight in which an aircraft can take off from a particular runway under specific conditions (winds, weather, specific aircraft configuration, etc,). For example, runway 29 at KXYZ airport with ambient temp of 20° C. This can get as specific as you wish.

Of course $RTOW \le MTOW$.


Would a chain strip built in the airport taxiways, help airlines in saving money and time during taxi? I am referring to the mechanism used in aircraft carriers, which help in catapulting fighter aircraft. What I had in mind is a milder version of the same concept. It would massively save cost, due to it being operated by electric power, save energy and time of the pilots, less exertion.

Would such a system be feasible?

Airports already have several ways to move aircraft along taxiways

Aircraft engines (least economical but always available)
Tugs (often used for pushback from terminals)
Aircraft wheel-motors (some makers are at least planning for electric taxi)

A system of fixed chains along a complex network of intersecting taxiways would be expensive to install and maintain and might be unreliable (e.g. icing up in cold weather).

See also

Does it make sense towing airplanes to the head of airstrip by external means?


Have bi-wings been used without creating more drag? As I understand from answers I've read here 1, 2, 3, biplanes create more lift with less wing span when compared to single wing aircraft, because the combined wings have greater surface area overall.

However this is usually at the expense of added drag as both wings are accelerating the same air downwards causing interference and creating inefficiencies. Also the wings commonly have supporting wires/structures between them causing more drag.

With that said biplanes do have some desirable characteristics like shorter roll response. I also realize when looking at how nasa calculates for the drag coefficient, wing aspect ratio is a major factor in their equation:

With this information it would seem to me if you could separate the wings of a biplane far enough apart that they don't cause much interference, you could possibly get a better performing aircraft with the same wingspan.

I almost imagine it being as simple as making the tail a full sized wing and giving each wing a thinner aspect ratio. However I've never seen this done before or even attempted. Is there a reason for this? Would the wings still interfere too much with each-other.

Moving the wings vertically apart would mean more and heavier supporting structure, but also a higher pitch moment of inertia. Since this grows with the square of the vertical expansion, a biplane with a lot of distance between both wings will be hard to control and very sluggish.

The real advantage of a biplane is reduced induced drag because less structure needs to be lifted. When cross-bracing enables the top wing to work as the compression member and the bottom wing to work as the tension member of a truss, a very lightweight structure becomes possible, especially when the size of the aircraft grows.

If all you have to power your airplane is a heavy, inefficient piston engine like those at the beginning of the last century, and you can tolerate that your aircraft won't fly fast or far, a biplane is indeed the lowest-drag solution.


If I am transiting a class delta airspace on a VFR flight and am coming up to a class bravo boundary without a bravo clearance, what will happen? Kind of an edge case, but will the class delta controller ask me to "say intentions"? Or maybe let a bravo controller know I could be entering without permission?

Because you're in Delta space, you are necessarily talking with a Delta controller.They will likely do one of two things:

Either:

give you a vector to keep you clear of Bravo:
N45WTF:  Turn left 40 degrees
coordinate with the Bravo controller, and the Delta controller may give you clearance:
N45WTF:  Climb and maintain 3,500.  Squawk 3462, Cleared into the Bravo, contact Center on 118.9


What information is recorded in aircraft sensor and maintenance logs? I was wondering what the sensor and maintenance logs in an aircraft look like and what are the values logged? Like maybe the engine temperature, altitude, exhaust temperature, etc. I know the data is logged in the black box, was wondering if it is available to the owner of the aircraft to any cloud service for further analysis or something. I'm talking about fighter planes and commercial aircraft.
I am looking for variables like the speed of the turbine (N1 and N2), altitude, pitch, roll, vertical acceleration, air temperature, exhaust gas temperature, etc. Came upon a Vox video where they showed about 60 variables.

For the F-35, it captures possibly too much. Not just every aspect of the physical operation of the jet, but all the other things the jet can do.
Capturing details on all the radar and sensors that may be trying to track it, route, speed, altitude, G's etc, etc.
The specific details of what is captured and available for download is not generally public info.
The Autonomic Logistics Information System (ALIS) system is going away, to be replaced by Operational Data Integrated Network (ODIN) in late 2020.
https://www.thedrive.com/the-war-zone/31861/replacement-for-f-35s-troubled-alis-cloud-based-brain-rebranded-odin-and-is-still-years-away

The Pentagon says that a replacement for the F-35 Joint Strike
Fighter's long-troubled cloud-based computer brain is finally coming.
The U.S. Air Force, Marine Corps, and Navy have said that the existing
system is one of, if not the most significant factor in the abysmal
mission capable rates for their respective F-35 variants and a major
contributor to the growing sustainment costs for the aircraft.
Unfortunately, the upgraded system is not expected to be in widespread
use until 2022 at the earliest.


What is the rotor speed of an EC135/H135 helicopter? I need the Eurocopter EC135's rotor speed to estimate its natural frequencies. I checked the helicopter TCDS but I only find there percentage values. For example for the P1 variant: 104% Max and 95% Min. This is percentage of what? In other helicopters I normally get concrete values in RPM.

The main rotor speed (100%) of the EC-135 is 395 RPM.


Artificial horizon - "horizon bar" or "symbolic airplane adjust" (Student pilot, ~ 22hrs training)
On a box-standard AI in a C172 there is a knob that allows you to move the symbolic airplane up and down. I've never managed to ask what it is for, but have now been intrigued enough to google it. An RC Allen instrument manual points out that it "adjusts the Symbolic Airplane to compensate for viewing parallax. Adjust Symbolic Airplane so that it is visually aligned with the horizon from pilot’s normal sitting position."

Two questions:

My best guess is that I could/should adjust it during the run-up along with the "instruments check" item on the checklist. However, is the Cessna always sitting correctly for that to be exact (or exact enough)? If there is a slightly different pressure in the nose wheel oleo the nose wouldn't necessarily point to the horizon, or when there is a slight slope of the taxiway/run-up area. Would it be better to (re-)adjust it in level flight?

Why do more modern AIs no longer appear to need that? The viewing parallax is still there, why isn't the button?

Instrument parallax has to do with viewing position of the pilot compared to the instrument. You adjust the symbolic airplane to the horizon bar on the outside of the instrument, not the part that moves, so you don't have to wait for it to spin up or find flat ground. I do it as part of my pre-start instrument checks, after adjusting my seat.
All mechanical AIs should have an adjustment mechanism, but many modern ones are digital, with a flat screen. You can't have parallax error with a screen because there is no distance between the needles and the reference measurements.


Does the F-22 (or any other stealth aircraft) carry chaff? Considering it is nearly undetectable on radar, it seems like it wouldn't have to worry about radar guided missiles; in addition to this it is sure to have sophisticated jamming capabilities. So why carry chaff? Just weight.

It certainly seems so.

Stealth aircraft are not invisible to radar, only less visible.  Under certain conditions the adversary will be able to get a radar lock:

At close distance
With very high (focused) radar energy
At certain angles of incidence

Given these risks and the low weight of chaff, it wouldn't be be wise to not carry it.

One source that claims the F-22 carries chaff: http://science.howstuffworks.com/f-22-raptor8.htm

  It releases flares to confuse heat seekers and sends out chaff, small pieces of reflective material, to disperse radar waves and confuse a radar-guided missile's tracking system.

It's even been used in the field, according to The Washington Post:

  the [F-22s] shot flares and even chaff — clouds of metal meant to confuse radar systems but possibly used in this case as an additional visual warning.


Are the guns on a fighter jet fixed or can they be aimed? Are the (built-in) guns on fighter jets fixed, or can they be elevated up and down or panned right and left for aiming?

In other words are fighter jet guns aimed by pointing the whole aircraft at the target or can they be aimed independently?

They are fixed, and many attempts were made over the years to have an aiming capability - and all failed. That should tell you something.

The earliest aereal combats used indeed handguns which were pointed at the adversary by the pilot. But it soon became obvious that only the rapid fire of a machine-gun will give the pilot a realistic chance of hitting a fast-moving target.

During the Italo-Turkish war of 1911 and 1912, the Italians used aircraft in war for the first time. Since the Ottoman Empire had no air force yet, the Turks engaged European aviators who flew their own aircraft, taking a handgun along to shoot at the Italians.

The same was tried in the opening months of WW I, but it soon became obvious that only a machine gun was effective. Before gun synchronisation was invented, pusher designs were fielded, some of which carried a dedicated gunner in a seat ahead of the cockpit.

Vickers F.B.5 "Gun Bus" (picture source)

Of course, the much smaller and nimbler Fokker single-seaters with gun synchronisation made such designs soon obsolete.

When Great Britain prepared for WW II, the firing power of bomber turrets impressed the Generals so much that they ordered several dedicated fighters with a gun turret mounted right aft of the cockpit. The resulting Bouton-Paul Defiant was again too slow and easily outmanoeuvred by the single-seaters, and the Blackburn Roc and the Hawker Hotspur were even worse. The Defiant's only successful role was as an early night fighter; when attacked by day it could only join others in a Lufbery circle to defend against being shot down itself.

Bouton-Paul Defiant F. Mk.I (picture source). Note the retractable belly-mounted antenna masts which gave the gunner a free field of fire in the upper hemisphere.

Another attempt was made by the MiG design bureau in the 1950s. In a dogfight the pursuer needs to get inside the circle of its opponent in order to score a hit with a fixed machine gun. The Russians thought: Why not pivot the gun into the circle, so the pursuer can fly the same circle as its opponent and still shoot at it? A MiG-17 was modified accordingly, but flight testing soon revealed that the recoil from the machine gun would push the nose of the fighter down and outside of the circle when the gun was not aligned with the longitudinal axis of the fighter, so this idea was dropped very soon.

Now I need to mention that rarely are the guns completely aligned with the longitudinal axis; instead, they point slightly up to compensate for the ballistic bullet drop at the expected distance of the target. Also, wing-mounted guns point slightly inward, again to ensure the bullet path is straight ahead when it catches up with the target, a procedure called gun harmonisation. This also means that interceptors will have their guns pointing up slightly more than those of air-supremacy fighters. One particular case involved the MiG-15: Being designed to fight large B-29 formations, the guns were badly aligned for fighting the F-86 Sabre during the Korea War. The MiG-15 armament consisted of two 23mm guns and one 37mm gun with very different ballistics. In order to ensure that the path of all bullets would meet at the right distance for fighting bombers, the 23mm guns pointed more up, and when used against the much smaller F-86, the Russian and Chinese pilots opened fire at a shorter distance so that the 23mm bullets would fly over the target while the 37mm bullets went below it. This was a major reason for the poor kill ratio of the MiG-15 vs. the F-86 despite the MiG's better performance.

Gun harmonisation on a jacked-up P-47 (picture source)

Modern high-off-boresight missiles with helmet-mounted cueing (or sight-controlled missile targeting) have turned that longtime dream of shooting at what the pilot is looking into reality, and the gun is carried largely as a low-priority weapon of last resort.


Flight Levels shall be transmitted by pronouncing each digit separately. And how should be FL200 transmitted? It is a huge doubt I have, because I have seen on CAP 413, FL 200, transmitted as flight Level two hundred, and how should then transmit it on Europe (out of UK) and on The USA airspace?

Your confusion is understandable, since, back in 2016, a number of countries changed this phraseology as ICAO published the 7th edition of Annex 10. In the EU specifically, EU regulation 2016/1185 applies, which states that, generally speaking, each digit should be spoken separately, but with some exceptions:

Flight levels shall be transmitted by pronouncing each digit separately except for the case of flight levels in whole hundreds.

Example: Flight Level Two Hundred (instead of "Flight level two zero zero").

The altimeter setting shall be transmitted by pronouncing each digit separately except for the case of a setting of 1 000 hPa which shall be transmitted as “ONE THOUSAND”.

Example: QNH One Thousand (instead of "QNH one zero zero zero")

All numbers used in the transmission of transponder codes shall be transmitted by pronouncing each digit separately except that, when the transponder codes contain whole thousands only, the information shall be transmitted by pronouncing the digit in the number of thousands followed by the word “THOUSAND”

Example: Squawk seven thousand (instead of "Squawk seven zero zero zero")
Source: SKYbrary
The UK have obviously implemented this EU regulation, which is why you find the new phraseology in CAP 413.


Will afterburner work at settings less than full dry thrust? Dry thrust is normal jet engine power without using an afterburner. Max dry thrust is the engine's most powerful thrust level without afterburner.

But what if the engine is at half power, or even idle power? Can you safely engage afterburner at that point?

I'm interested in turbojets and turbofans. Both can have an afterburner. I'm wondering if it's possible to engage afterburner on both of them at a time when the engine is not already at full dry thrust.

Edit: one reason it might not work is that idle thrust might not be powerful enough to ignite the fuel in the afterburner.

The reason I ask is for emergencies. Jet engines need several seconds to spool up from idle to full thrust. If you could engage afterburner from the get-go, you could be up to max speed much quicker.

Afterbuner simply injects fuel directly into the jet pipe (i.e. beyond the turbine) in order to greatly increase thrust. The way throttle levers are normally set up, afterburner is engaged once the lever is advanced past maximum dry thrust, but I can't imagine why, theoretically, you couldn't set one up to be engaged at less than maximum dry thrust.

Mind you, it would be awfully inefficient to do so, as thrust output is exponential, with most of it being delivered in the top 5% of the RPM band; engaging afterburner while you still have a lot of dry thrust available would just be a massive waste.

What's more, jet engines are much quicker to respond today, and, in addition, landing approaches are not performed at idle thrust; the main benefit of flap settings greater than 20 degrees is that they slow the aircraft down, allowing for steeper approaches. In jet aircraft, this also allows the engines to be kept spooled up above flight idle, specifically in order to reduce response times in the event of a go around.
In other words, throttle might be reduced to flight idle for the initial descent, but the final approach will use a higher thrust setting.

The benefits of adding afterburner to civilian transport aircraft are usually massively outweighed by their costs (see the Concorde and Tu-144).


What flight and route information do pilots need for flight? A pilot needs some information before and during flight like METAR, TAF, NOTAM's, Charts, Frequencies, and so on. I want to build someday ,when I have enough time, a website, for private use (Flight Simulation), and maybe when I get the project to work good for public too, that displays all of that data. One should be able to input Departure and Arrival Airport and then get displayed all the Information named above about those two airports. The real question:

What do pilots still need except the above named? Have I forgot something. What would you implement, what would you like to have that makes your pilot (real or flight sim) life easier? Do you know a nice option in the GARMIN G1000 that could be implemented. But please only possible things. An artificial horizon is nice and would be even possible more or less but is very hard to program and is useless for flight simulation.

I might be able to help a little, I am a professional software developer and also a recreational pilot in Australia.

Starting firstly with the requirements for such a site.  Data for different countries is often sourced from different locations, so you would need to investigate that.  I can only speak for Australia, but we have a web service that we can log into which provides us with weather briefings (METARs, SPECIs and TAFs, as well as ATIS for some Class C airports) and NOTAMs, and which also allows us to submit flight plans.  There are a few apps available which link in with this system, and you could definitely get yours to do the same.

Charts are again something that will differ between regions, and you will need to source these.

On to flight planning itself, you've mentioned the basic things you need.  I only file VFR flight plans, so I can only speak for those.  I start by finding my origin and destination on my charts and ensuring I have all the charts required for the flight, and that they are all up to date.  I have a look for any PRDs (prohibited, restricted or danger airspace) along a direct route, and plan around them by selecting waypoints that will take me on a track away from them.  I avoid controlled airspace where possible and look for major landmarks that I can use as visual cues along the way.  If your system could tell me straight away what PRDs I'll be breaching, whether they are active (from the NOTAMs), and if so, plot a course away from them, that would probably make it stand out from the crowd.

Once I have my route, I look at the LSALT (lowest safe altitude) along it (by looking at the terrain elevation and any obstacles), and work out my cruising altitude, conforming to the hemispherical level rule (odd altitude for track 000-179, even altitude for 180-359, plus 500 feet for VFR).  Again, your system could look at the terrain in the area and suggest an altitude for me which conforms with this rule.

Once I have my exact route (both horizontal route and vertical route), I work out my TOD and TOC (top of descent and climb), mark those on the charts, and then work out my fuel burn by looking at the forecast winds at each level and calculating how much head/tail wind I will have, plus any offset I need to counteract any crosswinds (which may affect my groundspeed if the offset is large enough).  There are a few apps out there now that will do this all for you, so I would expect you would want your system to do the same.  If you're serious about this project, I would recommend getting your hands on a wizz wheel and learning how to use that.  That'll give you a good idea about how the calculations work, and you should be able to make a few algorithms from that.

To give you an idea, below is my flightplan from a few days ago:

Then it's a matter of filing the flight plan and going for a fly.


Is it possible that derated thrust takeoffs are safer than normal takeoffs? The reason for my arguments here are (assuming that you have sufficient runway distance):

That with less thrust, less force should also be required to hold the aircraft as desired, and possibly the aircraft should be easier to control and fly when the engine fails than if it does so with the thrust set to full blast.

An engine event, such as a bird strike, might (?) be less likely to have catastrophic consequences for e.g. the turbine blades when they are not running at full thrust and their design limits.

Never having actually commanded an aircraft, are any of these ideas correct?

The reasons presented at ground school for the benefits of de-rated thrust takeoffs were twofold:

less chance of catastrophic engine failure during takeoff
less overall wear between overhauls

It is from this standpoint that reduced thrust takeoffs are safer.

As you point out, these are only authorized when the weights, temperature and runway length allow, but for the EMB-145 virtually every takeoff we did was eligible for reduced thrust.

You point about ease of control with an engine out is countered by engine out procedures which involve setting max thrust on the remaining engine (for two-engine ops).  During takeoff roll in the EMB-145XR, this puts the other engine at 117% power.  With the exception of flying near $V_{MC}$ (for light twins) the extra thrust is a benefit and not a hindrance to control and if this is at or after $V_1$ you'll want the thrust to go flying.

Your question about a bird strike is going to go one of two ways:

the bird hits the N1 fan and goes through the bypass ducting
the bird hits the N1 fan and is ingested into the N2 compressor stages

In either scenario a reduced thrust vs full thrust takeoff is not going to make a huge difference, but scenario 2 will be far more destructive to the engine than scenario 1.


Why are jet engine fan blades painted? I came across this extremely interesting article with details on a 2018 United Airlines Boeing 777  engine failure, which is also related to the more widely-publicized failure a few days ago: http://aerossurance.com/safety-management/ndi-failures-b777-pw4077-fbo/ . Amongst others, it contains the following:

The records for the TAI [Thermal Acoustic Imaging] inspection in July 2015 as well as an earlier
TAI accomplished in March 2010 revealed a thermal indication in the
same location as where the LCF crack occurred. The records for the
fractured fan blade’s July 2015 TAI inspection was
annotated ‘paint’ that, according to the inspector, was consistent
with him accepting the indication because he thought it was an issue
with the paint.
Flaking paint was a regular issue, affecting perhaps 25% of blades,
requiring either a touch-up or a complete re-paint.

which begs the question: why are fan blades painted? The only reason I can think of is so that damage from small objects (or birds) sucked into the engine is easier to see? But, if I read the article correctly, the paint can also mask more serious issues - in this case, the inspector thought that the TAI indication was due to flaking paint, which is apparently common, when in fact it was a defect in the blade. So maybe it would make sense to leave the blades unpainted?

The final report notes:

At the time of each TAI [thermal acoustic imaging], the inspectors attributed the indication to a defect in the paint that was used during the TAI process and allowed the blade to continue the overhaul process and be returned to service. [emphasis mine]

The paint being referred to is used for the inspection. Its function is to improve the emissivity of the object.


How do services like Flightradar24 and FlightAware track flights? Do they use the same data sources/aviation services? If so, how do they differ?

https://www.flightradar24.com/how-it-works - taken from the FR24 website. They use ADS-B - hence the reason the majority of General Aviation stuff doesn't show (unless it has a mode S transponder).