Do carrier-less militaries maintain carrier qualifications on allied boats? "How do jet fighters get to war?" made me wonder if there was any cross-training for carrier operations between allied nations. While the equipment could be different (see "Do carrier-less militaries retain the equipment for carrier operations?"), do nations that don't operate carriers have pilots with training on it?

For example, are any Australian pilots qualified to land an F/A-18E/F on an American carrier, even if their own plane can't do it?

Example of use would be in an emergency, i.e., land their F/A-18's on a US carrier even though they won't be able to takeoff, and the aircraft will likely need to be shipped.

The problem with the carrier landing is currency and recency of experience

  Example of use would be in an emergency, i.e., land their F/A-18's on
  a US carrier even though they won't be able to takeoff, and the
  aircraft will likely need to be shipped.

The approach to landing on a carrier is a specific technique, wherein an angle-of-attack approach is flown all the way to the deck(and a very firm landing) with the intent of landing on the centerline and catching the 3-wire.  An acceptable approach catches any of the wires (there are 4).  The counter intuitive(for someone not trained in CV landings) advance-throttles-to-full- power-upon-landing ensures that if the wires are missed (Bolter!) one goes around and tries again if there's enough gas.

An approach to an airfield typically does not entail this, but instead includes a higher speed approach, and a flare which reduces the impact force on the aircraft (but of course requires a lot more runway).

If the pilot of the F-18 has never had the initial qualification on a carrier(which takes hundreds of field landings and a Carrier Qualification flight), making that approach becomes a non-trivial exercise in risk assessment.

If you aren't trained for it, why are you doing it?

Is the captain of the ship willing to risk a mistake that will damage dozens of aircraft on the deck and perhaps kill a few people?
Is the pilot willing to risk the approach that he or she is
untrained for, with the known lethality of failed attempts?

The severity of failure can be seen in youtube videos of ramp strikes on carrier approaches.  I suppose the pilot could ask, but the Captain of the Ship and his Air Boss might refuse permission.  See risk analysis above.  During a shooting war ... who knows what people might try?
Here's an A-7 ramp strike that's a vivid example.

To demonstrate the complexity of the matter:

The USN requires both an initial qualification and currency in order for its pilots, who land on carriers as a matter of standard operating procedures, to do a certain number of landings per quarter/per year/etc in order to remain current. If you aren't current you have to get recurrent to land on the Carrier.

But what if that pilot had a PEP tour?

The US and Australia, among other navies, have a "Pilot Exchange Program" where we trade officers who fly in our services.  Part of building alliance relationship.  So, if this Australian pilot had done a PEP tour in USN hornets, and been a carrier qualified pilot, he may not be recent or current, but he knows the basics of how to fly a successful approach.  It's still a risk assessment issue since the Captain of the Ship, his Air Boss, and this pilot know that he isn't current, and that his kit may be out of configuration compared to USN hornets, so that he's flying a degraded or visual only approach.

He can ask, but a decision to try it will take the safety of the pilot, his aircraft, and everyone/everything on that carrier's deck into consideration first.  (Low probability, but on a given day, who knows?)


Why and how were "eybrow windows" helpful in tight turns? It is written in some answers that "eybrow windows" were helping pilots in "tight turns". How did this work? These tiny windows seem located right above the head, so I would not expect to see anything else than the sky right above through them, regardless if turning or not.

In a (steep) turn, airplane is actually flying partially upwards relative to the cockpit directions. It is simply because the turn is (usually) flown with more-or-less constant altitude, but the airplane is significantly banked, so plane of motion intersects cockpit in the same, bank, angle.
So these windows are located approximately in the direction where you are just going. As long as you see only sky there, everything is fine and as it should be. :) But would there be an another airplane, you really want to see it while there is still time to avoid a collision. Whatever you see through front window during a steep turn is either not on your flight path at all or about to collide with nose in nearest following seconds.


What degree of elevator deflection is required to takeoff? I've always wondered how much the elevator actually needs to deflect in order to cause rotation on takeoff for a large airliner. On videos I can rarely see the elevator moving at all.

I'd really like to know what the degree required is for a 777, but if someone can provide this for another airliner that would be ok. I presume that it depends on takeoff speed, which is of course variable, but let's see what you can come up with.

It depends. Mostly on two parameters:

What is the position of the center of gravity? A more forward position would require a bigger downforce at the tail, so deflection angles would be bigger. On the 777-200, c.g. positions from 14% to 44% of MAC are allowed.
What is the trim setting of the stabilizer? Depending on the setting, more or less deflection is needed to set the whole horizontal tail to the right downforce for rotation.

Further parameters are flap settings, take-off mass, rotation speed and desired rate of rotation, but the first two are the most important.

Since I do not have the official Pilot's Operating Handbook for the Boeing 777, the virtual version has to do. Sadly, it contains very little information. The more seedy corners of the internet have maybe more substantial content, but here you are on your own.

The Boeing 777 has a computer based weight and balance system, called Accuload, which will compute the proper take-off trim setting, therefore, no discrete values can be given. With the recommended trim setting, the pilot will apply forward pressure on the control column until roatation speed ($v_R$), relaxing control forces to neutral for smooth rotation.

If you would take off with the trim setting for cruise, the elevator would need to be deflected by approx. -10° (trailing edge up) in a simulation with typical parameters. Please note that this is not the regular take-off procedure, and the actual deflection angles are much smaller.


Can a F-4 Phantom II pilot control weapons? In the F-4 Phantom II, can the pilot in the front seat control the weaponry as well, or do they only fly the aircraft?

And can the weapons officer in the back fly the aircraft in emergencies, e.g. if the pilot is unconscious?

Can the pilot in the front seat control the weaponry as well, or do they only fly the aircraft?

Yes, the pilot in the front could control all weapons.

  And can the weapons officer in the back fly in emergencies, like, pilot is unconscious or something?

This is more complicated. The USAF F-4's did not have controls for the RIO's (now called WSO's), but the Navy/Marine F-4's did.


How can I take 360° panoramic pictures in an aircraft or helicopter? I would like to receive some answer or advice on how to create 360 panorama images.
My plan is to use Cessna or Helicopter.

This is as much a photography question as an aviation one. The type of aircraft you might want depends on the type of picture you want.

If you want a picture from low altitude, showing the area nearby, a helicopter or a quadcopter (depending on local regulations) would be ideal. This would let you hover in one spot, and rotate to cover the full panorama. The movement of the aircraft could easily be compensated for in processing the photos. A quadcopter holding a position by GPS should be very stable for long enough to take the photos.

If your picture is at a higher altitude, focusing more on things further away, a small plane could work. Many general aviation aircraft can fly fairly slow. With only more distant objects as the subject, a plane in a turn at under 100 knots should be slow enough that the perspective change would be negligible.

If you could get something like a simplified version of Google's street view setup, and send it up on a quadcopter, that would probably give the absolute best result.

See also this more general question:

What is a good plane for aerial photography?


How to calculate the amount of weight my plane can takeoff with? This is how I approached this problem-

My takeoff run is limited. So, depending on my configuration I calculated the maximum possible velocity I can attain in my groundroll. I assumed that at the end of the run my lift should be greater than the weight I want to carry. So I computed the lift I generate at the end of the groundroll. I got the CL value from xfoil for my angle of incidence. Would this method give me a rough estimate of the total weight my plane can carry?

Yes, you can do your equations at OEM (Operating Empty Mass) and get your ground distance. Then you can calculate the same for different mass values (your OEM+your payload), and generate a distance vs mass. Since you know how much distance you have (including any safety factors), you can see what mass you can take off with. Or work backwards from the same equation, set the maximum distance you allow, and work back to your mass value.

Keep in mind this will not tell you whether the airplane is structurally strong enough to carry that weight, only if it can take-off with it. Structural calculations are a bit more complex than this. Also, you might want to do similar calcs for landing distane as well!


What portion of an Instrument Proficiency Check must be in the airplane? I was asked this question by the Chief Instructor at my Part 141 school. I've looked all over and I can't seem to find an answer to this question. We often use the AATD which is a Redbird full motion but I've not heard anything about a specific portion being in the airplane whether or not you did it all in a sim, or a mixture of simulator and airplane. Can anyone elaborate on this? Thank you in advance.

This is explained in the Instrument Rating ACS (page A-18):

  Instrument Proficiency Check

  If a person fails to meet the experience requirements of section 61.57(c), a pilot may only
  establish instrument currency through an instrument proficiency check
  as described in section 61.57(d). An FSTD may be used as part of an
  approved curriculum to accomplish all or portions of this check. If
  specified in its LOA, an AATD may be used to complete most of the
  required Tasks. However, the circling approach, the landing Task, and
  the multiengine airplane Tasks must be accomplished in an aircraft or
  FFS (Level B, C, or D).A BATD cannot be used for an instrument
  proficiency check. Please see the Task Table in Appendix 5 for
  additional information. (Appendix 5, Instrument Proficiency Check
  Table).

To summarize:

If the simulator is an approved FFS, you can do the whole IPC in it
If the simulator is an approved AATD, you can do everything except circling, landing and multi-engine tasks
Otherwise, you need to use an aircraft


Does a runway have to be closed for not having markings due to resealing work? Is it required to close a runway if the paint has been removed for resealing the asphalt?

Not Necessarily

While some regulations or guidance material may call for some or most runways to be closed during maintenance or construction work, such as marking removal for asphalt reseal, this is certainly not always the case.

If markings are non-standard, faded, or removed, for any reason, the condition should be documented in a Notice to Airman (NOTAM) so that pilots and other interested parties will be aware of the condition and prepared for the non-standard situation.

An example of such a NOTAM includes this one from Randolph AFB (KRND), where some markings on runway 14L/32R are missing dues to removal and repaint during maintenance or construction work.

  RWY 14L/32R SURFACE MARKINGS NON STD ; SOME MARKINGS MISSING DUE  TO
  REMOVAL AND REPAINT.

Note that runway 14L/32R is not closed during this work. However, the parallel runway, 14R/32L, is closed:

  RWY 14R/32L CLOSED


What is "picture flying" and does the FAA define it? What is "picture flying" and does the FAA define it in any of their literature?

Here is an example situation. You are instructed to depart using a SID. The SID states that at 1.5NM from ABC VORTAC a left turn should be made to heading 360. Your FMS allows you to draw a 1.5NM ring around the fix on your moving map, so you draw the line. When the little airplane is at the line, you make the turn. Anecdotally, I have been told this constitutes "picture flying" and isn't a legal way to comply with instructions from a SID or other procedure. The legal method would be to tune the VORTAC and make the turn when the DME reads 1.5NM.

One could make the argument that the DME is as inaccurate as the visual estimate from the picture flying. Aircraft climb at different rates and the angular distance affects the straight-line distance across the ground, especially if the instructions are something like, cross 20NM from ABC VORTAC at 10,000 feet.

Any definition or clarification from FAA publications or letters would be appreciated.

I can't prove a negative, but as CrossRoads pointed out, the phrase "picture flying" isn't used on faa.gov. At least, neither Google nor faa.gov's own search engine turn up any hits.

I searched a bit further and I did find one specific match in a Bendix advert in the Feb 2, 1953 edition of Life:

  Picture flying is the name pilots give to flying with OMNI-MAG. Merely by watching the pointer the pilot always knows where he is,
  where he is going, and how to get there

There's no real technical detail in the advert (it's actually an advert for Bendix television sets!) apart from mentioning that the OMNI-MAG uses VHF radio, but based on the picture it looks like a VOR receiver.

So, given that the FAA seems not to use the phrase at all and the only exact hit I could find was from 1953, I suspect that "picture flying" is an obsolete phrase for following a visual course indication. Before VORs, pilots used audio signals from a four-course radio range and the advert even mentions that they won't have to listen constantly any more.

That makes me think that the phrase arose around the time that radio navigation moved from audio to visual signals, to indicate that the pilot could now look at a visual indicator rather than just listen. That transition happened in the 1950s, so it would fit with the advert's publication.


How to best recover from an excessive descent? Suppose I found myself in a rapid, steep descent, perhaps right after breaking a spin. E.g. a 60 degree nose down with 100kt and accelerating rapidly, on a Cessna 172.

What might be an ideal recovery strategy, other than trying to guess/feel the optimal back pressure on the yoke? Obviously, if I pull back too hard I risk overloading the wings (to the point of collapse?) whereas if I pull back too gently I risk gaining too much speed, losing too much altitude, etc. Among other considerations, would it be advisable to enter a slip to (greatly?) increase the drag?

Sideslips at high G and/or high speed aren't a good idea structurally.

Absent a G meter, airspeed and judging G load is all you've got.  If I found myself going straight down at 100 kt, I would try to keep the speed below maneuvering speed, 128 kt, but if I felt I was applying too much force and risked an accelerated stall, I would let it go faster and if the air was smooth I'd let it go up to Vne if necessary.

And in a really extreme case, if the choice was exceeding Vne or maybe pulling the wings off, I'd take my chances exceeding Vne.  If you have to exceed a parameter, it's safer to go too fast than to pull too hard, because there is ample safety margin for flutter, and you know how much you are going over.

Of course, without a meter, with G load it's all judgement.  The yield G limit for normal category is 3.8, so what can be really useful is go with your instructor and practice 60 degree banked level turns to become familiar with the sensation of 2Gs, which will at least give you a reference point.  Even better if you can get a ride in an aerobatic airplane and learn what 4 Gs feels like and try to stay below that when the time comes.

The other big thing is knowing whether you are in a dive inverted or right side up.  This is a problem for pilots who get flipped over by wake turbulence and end of upside down in a 45 degree dive, and instinctively pull right around in a split S through 90 degrees and rip the wings off.  In an inverted dive most airplanes will accelerate past Vne in a heartbeat.

If you are in an inverted dive like that you have to roll the plane right side up before pulling out.  Recognizing it takes training and professional pilots often get upset training in aerobatic aircraft to develop the correct reactions.


SR-71 flew 2193 mph. How can this mathematically be Mach 3.3? Virtually every time I read about the Lockheed SR-71 (including other threads on this forum), I see that its speed record is listed as approximately 2193 mph.  The same blurb will invariably say this is "about Mach 3.3".

But when I search for how fast Mach 1 is, the number that almost always comes up is 767 mph.

Now 767 * 3.3 comes out to 2531, well above 2193.  If I take 2193 and divide it by 767, I get Mach 2.85

I doubt I've stumbled on something new here.  So what am I missing? How can 2193 mph be Mach 3.3 when 767 mph is Mach 1?

The SR-71 was only capable of Mach 3.3 flight at altitude. You can see the limitations in the pilot's operating handbook(POH) for the aircraft:

At higher altitudes the relative speed of sound is lower. If we use this handy NASA calculator in a standard atmosphere the relative speed of sound at 70,000 ft. is 660 MPH making your 2193 MPH equal to Mach 3.321

Its also important to note that the word "about" is often used as the SR-71 was flown to a maximum compressor inlet temperature(CIT) not a maximum Mach when doing a 3.3 run. According to the POH

  Mach 3.2 is the design Mach number. Mach 3.17 is the maximum scheduled
  cruise speed recommended for normal operations. However, when
  authorized by the Commander, Speeds up to Mach 3.3 may be flown if the
  limit CIT of 427°C is not exceeded.


How far along was JFK Jr. in his instrument training? I read up a little more about the infamous and tragic incident. JFK Jr. had over 300 hours logged, and about 36 in the Saratoga, half of which was solo. It's not like he was a newly minted VFR pilot and supposedly his CFI thought he was an "excellent" pilot.
However, there was very little information on how far along he was in his instrument training. Did he just get the minimum requisite time under the hood? Did he begin pursuing IR training?

From the NTSB accident report:

Pilot Training
On October 4, 1982, the pilot started receiving flight instruction. Over the next 6 years, he flew with six different CFIs. During this period, the pilot logged 47 hours, consisting of 46 hours of dual instruction and 1 hour without a CFI on board. The pilot made no entries in his logbook from September 1988 to December 1997.
In December 1997, the pilot enrolled in a training program at Flight Safety International (FSI), Vero Beach, Florida, to obtain his private pilot certificate. Between December 1997 and April 1998, the pilot flew about 53 hours, of which 43 were flown with a CFI on board. The CFI who prepared the pilot for his private pilot checkride stated that the pilot had "very good" flying skills for his level of experience.
On April 22, 1998, the pilot passed his private pilot flight test. The designated pilot examiner who administered the checkride stated that as part of the flight test, the pilot conducted two unusual attitude recoveries. The pilot examiner stated that in both cases, the pilot recovered the airplane while wearing a hood and referencing the airplane's flight instruments. After receiving his private pilot certificate, the pilot flew solo in his Cessna 182 and received instruction in it by CFIs local to New Jersey. He also received instruction at Million Air, a flight school in New Jersey, and flew their airplanes. During calendar year 1998, the pilot flew approximately 179 hours, including about 65 hours without a CFI on board. On March 12, 1999, the pilot completed the FAA's written airplane instrument examination and received a score of 78 percent.
On April 5, 1999, the pilot returned to FSI to begin an airplane instrument rating course. During the instrument training, the pilot satisfactorily completed the first 12 of 25 lesson plans. The pilot's primary CFI during the instrument training stated that the pilot's progression was normal and that he grasped all of the basic skills needed to complete the course; however, the CFI did recall the pilot having difficulty completing lesson 11, which was designed to develop a student's knowledge of very high frequency omnidirectional radio range (VOR) and nondirectional beacon operations while working with ATC. It took the pilot four attempts to complete lesson 11 satisfactorily. After two of the attempts, the pilot took a 1-week break. After this break, the pilot repeated lesson 11 two more times. The CFI stated that the pilot's basic instrument flying skills and simulator work were excellent. However, the CFI stated that the pilot had trouble managing multiple tasks while flying, which he felt was normal for the pilot's level of experience.
The pilot attended this training primarily on weekends. During this training, the pilot accumulated 13.3 hours of flight time with a CFI on board. In addition, the pilot logged 16.9 hours of simulator time. The pilot departed from FSI for the last time on April 24, 1999.
The pilot continued to receive flight instruction from CFIs in New Jersey in his newly purchased Piper Saratoga, the accident airplane. One CFI flew with the pilot on three occasions. One of the flights was on June 25, 1999, from CDW to MVY. The CFI stated that the departure, en route, and descent portions of the flight were executed in VMC, but an instrument approach was required into MVY because of a 300-foot overcast ceiling. The CFI requested an instrument flight rules (IFR) clearance and demonstrated a coupled instrument landing system (ILS) approach to runway 24. The CFI stated that the pilot performed the landing, but he had to assist with the rudders because of the pilot's injured ankle. (For additional information about the pilot's ankle injury, see Section, "Medical and Pathological Information.") The CFI stated that the pilot's aeronautical abilities and his ability to handle multiple tasks while flying were average for his level of experience.
A second CFI flew with the pilot between May 1998 and July 1999. This CFI accumulated 39 hours of flight time with the pilot, including 21 hours of night flight and 0.9 hour flown in instrument meteorological conditions (IMC). The pilot used this CFI for instruction on cross-country flights and as a safety pilot. On July 1, 1999, the CFI flew with the pilot in the accident airplane to MVY. The flight was conducted at night, and IMC prevailed at the airport. The CFI stated that, during the flight, the pilot used and seemed competent with the autopilot. The instructor added that during the flight the pilot was wearing a nonplaster cast on his leg, which required the CFI to taxi the airplane and assist the pilot with the landing.
The CFI stated that the pilot had the ability to fly the airplane without a visible horizon but may have had difficulty performing additional tasks under such conditions. He also stated that the pilot was not ready for an instrument evaluation as of July 1, 1999, and needed additional training. The CFI was not aware of the pilot conducting any flight in the accident airplane without an instructor on board. He also stated that he would not have felt comfortable with the accident pilot conducting night flight operations on a route similar to the one flown on, and in weather conditions similar to those that existed on, the night of the accident. The CFI further stated that he had talked to the pilot on the day of the accident and offered to fly with him on the accident flight. He stated that the accident pilot replied that "he wanted to do it alone."
A third CFI flew with the pilot between May 1998 and July 1999. This CFI accumulated 57 hours of flight time with the pilot, including 17 hours of night flight and 8 hours flown in IMC. The pilot also used this instructor for instruction on cross-country flights and as a safety pilot. This CFI had conducted a "complex airplane" evaluation on the pilot and signed him off in the accident airplane in May 1999. According to the CFI, on one or two occasions, the airplane's autopilot turned to a heading other than the one selected, which required the autopilot to be disengaged and then reengaged. He stated that it seemed as if the autopilot had independently changed from one navigation mode to another. He also stated that he did not feel that the problem was significant because it only happened once or twice.
The CFI had made six or seven flights to MVY with the pilot in the accident airplane. The CFI stated that most of the flights were conducted at night and that, during the flights, the pilot did not have any trouble flying the airplane. The instructor stated that the pilot was methodical about his flight planning and that he was very cautious about his aviation decision-making. The CFI stated that the pilot had the capability to conduct a night flight to MVY as long as a visible horizon existed.

So he had enrolled in a school to earn an IR training, and he had completed 12 of the 25 lesson plans, meaning he was about half way through training. His total experience, as of the log book that was available, was 310 hours, 55 hours at night. He had 36 hours in the accident aircraft (9.4 at night). About 47 of his hours took place between 1982 and 1988, he did not fly between 1988 and 1997. The NTSB report does not contain his total IFR hours.


Can civilians buy military aircraft? Say one wanted to buy a retired F-14, or F-5, or a BAE Hawk. Could I do it?

Obviously this would mean stripping out radars, weapons, rwr, and any other sensitive equipment, but after this, would it be possible?

Is there some kind of procedure for this?

EDIT: What is the typical way aircraft are released for sale? Is it common?

You could, if the aircraft is available for sale somewhere, and there are no other legal compliance problems. Paul Allen has a nice collection of military aircraft at his Flying Heritage Collection, and there are certainly quite a few other people with both flyable and unflyable military aircraft. There are also private companies which will let you try out their planes, such as Australian Jet Adventures

Here is a web site which tracks military planes in private ownership around the world:

http://www.warbirdalley.com/


Can one fight medical rejection due to depression noted 14-15 years ago? My husband's dream was getting his private pilot's license which he just got in August.

He was diagnosed with depression about 14 years ago and in medication less than a year. He has been great since - no depression or meds.

He did his physical this summer and got the all clear - he answered everything truthfully. Fast forward - he passed his tests and flight and has been flying since. Today in the mail he gets a letter from FAA saying his medical is rejected because he had a history of depression.

can he fight this and how?
how long is a depression bout from early 20s going to follow someone in life?

There are Aviation Medical Examiners (AMEs) who specialize in special issuance medicals. It is probably best to use one of them instead of your regular AME. This type of special issuance may require a battery of psychological tests and it may get expensive. But the good news is that once he has his special issuance, he can fly under Basic Med, so he only has to jump through the hoops once.

I know of two who are regular participants on pilot message boards and they are well-respected.

Bruce Chien, MD http://www.aeromedicaldoc.com

L B Fowler Jr MD lbfjrmd@gmail.com.

Edit: I just ran across a fairly long post on Pilots of American that addresses a similar issue with a good (but time-consuming and expensive) outcome.

  I wanted to share my story of a difficult SI in the hopes that it will
  give others some insight and perhaps courage to not take 'no' for an
  answer.

  I had been diagnosed with mild depression during my senior year of
  high school 25 years ago. The psychiatrist I had been sent to put me
  on Zoloft (Sertraline), which I guess helped. I stayed on it via my
  family doctor for the years afterwards, not really giving it much
  thought, and never realized the difficulty it would cause in working
  towards a PPL someday. …


How do redundancies work in aircraft systems? I've read about many aircraft systems having redundancies. For example, both Boeing's 787, and Airbus's A380 have a triple-redundant FCS. In this case, it makes sense to act upon the majority's decision. If all three components disagree, how is it decided which one wins? Is there any record of disagreement amongst redundant systems in airplanes?

The primary differences I have compared to the question about Airbus's control systems (How does the Airbus flight computer's voting system work?), is verification for non-deterministic systems, as well as optics for visibility. Given that the entire systems run in parallel up until the verification component (from sensor input, onwards), there will be some, obvious delta in their "decisions." -- Although, most of the time, this isn't perceivable, is there any visibility into what's going on with the FCS?

Triple-redundant systems have four independent members, so if one fails, a two-to-one vote of the remaining three is still possible.

One system    = No redundancy.
Two systems   = Simple redundancy.
Three systems = Double redundancy.
Four systems  = Triple redundancy.

However, often the term "triple redundant" is used when the system has only three members. And if all three disagree, two of them must be faulty already, so this is a case of multiple failures.

In case of Airbus, besides the three main FCS computers two backup systems are available to help isolate the faulty one. Inside, each has two channels which run software written by a different team, run on a processor different to the one in the other channel and which are supplied by two different suppliers.  This helps to reduce systematic errors, when all together would fail because of a common malfunction.

Airbus flight control system diagram (picture source). Only the first system of each is expanded; the boxes for system 2 and 3 look the same on the inside. Input is from the side sticks, and output goes to the hydraulic valves at the control surfaces. The voting happens first in the comparator step (between the two channels) and again in the filters (between the single systems).


How (and when) does Heathrow alternate arrival paths? I've noticed that flights over Richmond (particularly arrivals) seem to have significantly reduced over the last few weeks. This is based on looking at Flightradar, as well as listening to the noise levels overhead.

I believe that Heathrow ATC alternates runways, holding patterns, and directions, but I'm finding it difficult to understand how and when these changes happen.

When do these flight path pattern changes happen, and potentially when will flights overhead Richmond might increase again?

Heathrow has an extraordinarily elaborate runway alternation programme, designed to spread out noise as evenly between its different neighbours as possible.

Daytime runway alternation follows a daily cycle and a fortnightly cycle. Alternation starts at 6am and continues till the last aircraft departs at the end of the day.

In the morning we use one runway for take-offs and the other for landings. At 3pm – roughly halfway through Heathrow's working day – we swap over
We continue this morning and evening pattern of runway use for the rest of the week
The following week we switch completely. What we did in the evening during the previous week, we now do in the morning. And vice versa

Regarding planes over Richmond (which is situated under the approach path to runway 27L):
During the week starting 8th of April, the programme states that 27L was used for landings from 6:00 until 15:00, resulting in a lot of traffic over Richmond during the morning, but little to none in the evening.
During the week starting 15th of April, the programme states that 27L is used for landings from 15:00 until the end of the day.
During the week starting 22nd of April, they will switch over again to land on 27L from 6:00 to 15:00.
You can read much more about the programme here.


Why is the intake of the 757 (RR) engine slanted? I'm sitting looking at a 757 with Rolls-Royce engines and just noticed that the intake is slanted forward by 5-10 degrees. Anyone know why?

(wikimedia.org)

This is the case frequently, as the aircraft doesn’t have the same pitch angle on ground while accelerating, or at rotation, or at climb or at cruise. So the intake slant is calculated to the best appropriate as an average. As a summary this is not specific to this engine on this aircraft


What are the differences between PNL and PNR messages? What are the differences between Passenger Name List (PNL) and Passenger Name Record (PNR) message in CRS systems?

PNR is a passenger's/party's record.

PNL is the full list of all the PNR's.

Example:

7 01SMITH/JOHN...

John Smith is a party of 1, that's the PNR entry. And he is number 7 on the PNL.


If an aircraft cannot fly above 300ft, is it an aircraft? I saw a question here that inspired one of my own. If an larger, person carrying aircraft, say some sort of hovercraft, could not fly above 300 ft would it be allowed to fly? Here in Australia, 300ft is the minimum height for an aircraft to fly over a town, so if an aircraft simply could not go any higher would it be allowed to fly at all? Or only in certain circumstances?

There is actually a legal Australian definition for aircraft, in Part 1 section 3 of the Civil Aviation Act:

  aircraft means any machine or craft that can derive support in the atmosphere from the reactions of the air, other than the reactions of the air against the earth’s surface.

So those drones you can buy from the store are aircraft (and if you knock one out of the sky because it annoys you, you are technically bringing down an aircraft and could be punished). However the latter half of that definition suggests hovercrafts are not aircraft.

Also, the minimum height over populated areas in Australia is 1000ft, and 500ft over non-populated areas (CAR157)


Why did the pilot flying pull back in the moments after the auto-pilot disconnected on AF447? In the AF447 disaster, one of the elements that contributed to the crash was an "excessive" nose-up input shortly after the disconnection of the auto-pilot.

This caused the aeroplane to climb and lose airspeed, precipitating the ultimately fatal stall.

Why did the pilot flying pull back (excessively) on his stick? Did the investigation find probable causes?

He was at the same time correcting for turbulence-induced roll. Would a nose-up input in such circumstances be appropriate?

If so, how easy is it for a pilot to make an excessive input of that kind without realizing it, and what would normally prevent that from happening?
If not, is there any explanation for why he might have made it?

Most of the crew's actions in the incident are comprehensible, even if they were incorrect responses. They make sense in the context of the situation, and it's possible to have a fairly clear picture why they made the judgements and decisions they did.

Is there a good explanation for that initial nose-up input, that makes sense of it too in the context?

It's not accident speculation when it has been investigated.
The full accident report is available online with a very adequate summary on Wikipedia.
There are many reasons, but from the human factors study:

The final BEA report points to the Human Computer Interface (HCI) of the Airbus as a possible factor contributing to the crash. It provides an explanation for most of the pitch-up inputs by the pilot flying (PF), namely that the Flight Director (FD) display was misleading.
The pitch-up input at the beginning of the fatal sequence of events appears to be the consequence of an altimeter error.

The crew present in the cockpit at the time of the pitot blockage lacked experience/training, and were bombarded with conflicting warnings and indications.
As I've been reminded in a comment, they were also in darkness over an ocean with no external visual references.

A note on how human factors studies can relate cause and effect. There is a certain reaction time that we are unable to exceed, roughly it's 200 milliseconds for a trained person anticipating an event. It's longer otherwise and there are many studies on that. When a control input is put up against the various indications, and taking into account the reaction times to the different aural and visual warnings, then scientifically the probable cause can be known within reason.

From page 42 in the BEA report:

The drop in Mach also impacts the SAT and thus the true air speed and the wind speed.
In the following table, the case an A330-200 flying at FL 350 at Mach 0.8 in standard atmosphere with a 30 kt head wind is given as an example to illustrate the consequences of pitot icing that would result in a drop in Mach from 0.8 to 0.3.

During Pitot probe de-icing, the same variations occur in the opposite direction.

From the table, you can see how the BEA may have assessed that the likely reason for the initial nose up reaction by the pilot flying was to correct a ~300' altitude error.
They also say (p. 157):

The report specified that the stall was caused by inappropriate crew reactions to erroneous speed and Mach displays that resulted from blockage of the Pitot probes through atmospheric icing. The report stated that contrary to standard operating procedures, the crew had not switched on the Pitot probe heating.


What happens if only rudder is applied in a turn without ailerons? Do the two have to be applied together all the time? Fresh newbie in glider flying. I was told the joystick (aileron) and the pedal (rudder) should always be applied together when making a turn. My question is, what happens if I only pedals the rudder without applying the stick (aileron)? How is it different from applying only the aileron but not the rudder? And are there times when we should apply just one of the two?

To turn – any vehicle, not just an airplane – you need to generate corresponding centripetal force.

When you only apply rudder, the plane will turn a bit, but because unlike boat it has no keel, it will not generate much centripetal force, just fly somewhat sideways, which is called a skid. It will produce more drag this way.

Now any well designed plane has yaw-roll coupling, which will cause it to bank into the turn anyway. It is caused by the slight increase in speed of the outside wing, and the dihedral most wings have resulting in increase in angle of attack, thereby increasing lift on the outside wing. So you can make the plane turn with just the rudder, but it will be inefficient, and it will be slower as the yaw-roll coupling will take its time.

On the other hand if you apply just the aileron, the plane will bank into the turn as usual. However, there will be some slip, as the deflected ailerons cause an adverse yaw – the aileron deflected down, which is on the outside wing, causes more drag – so the plane will actually turn a little less than it should. Like skid, that will cause extra drag.

What you want to do is bank into the turn with ailerons, and use rudder to compensate the various drag asymmetries to keep the slip-skid ball centered. That will give you least drag. Different planes will need slightly different application of rudder.

There are cases where you will want to apply ailerons and rudder in different combinations (as mentioned in comments below):

On the ground you steer with rudder, while using aileron to prevent wind from tipping the plane sideways – the landing gear provides the centripetal force in this case.
During cross-wind landing, you need to align the plane with the runway, but as it flies relative to the air, it tends to drift sideways. You need to make it fly sideways relative to the air instead by banking into the wind while using opposite rudder to prevent turning.
The same combination applies during cross-wind take off, aileron into the wind to prevent wind from tipping you over sideways and rudder to compensate for weathervaning.
You can also use bank with opposite rudder to increase drag if you are too high and fast on the approach – this is called forward slip. Just don't let the airspeed decay too much, because stall in slip or skid is more likely to result in a spin.


How do VTOL aircraft like the V-22 Osprey not tilt? How do aircraft like the V-22 not tilt under an unbalanced load? if they are only supported by 2 forces on either side a large weight in the back should cause it to lean backward when stationary, should it not? its hard to put this into an image but here goes nothing:

A large weight in the back would surely cause it to lean; original image source

If you think about it, your question applies in exactly the same way to a conventional helicopter. You might expect that it would pitch nose-down if the weight is forward, and nose-up if the weight is aft. In fact, it's even worse for a conventional helicopter, because with only one rotor it would roll (tilt left-right) as well as pitch.

The answer is the same for the Osprey as for a conventional helicopter: the pitch is controlled by cyclic control of the rotor. As the rotor spins, a mechanism inside it changes the angle of attack of the blade (the pitch of the blade) as it rotates. This change can cause it to generate more lift when it's at the rear than at the front (or vice-versa, or left-to-right). This creates a turning moment about the centre of the rotor disk, which counteracts the moment of the unbalanced weight.

You only get so much of a moment with it, though. The aircraft needs that moment in order to change its pitch to manoeuvre. If you had to use the full range of blade pitch (the maximum cyclic control) just to counteract the unbalanced weight, you wouldn't be able to pitch the aircraft any further in that direction. For this reason, the maximum moment of rotorcraft (how far the centre of mass can be away from the centre of lift) is typically smaller than for airplanes.


What, exactly is "on the MEL"? The MEL, minimum equipment list, defines whether fault of some equipment on the aircraft prevents it from being dispatched for flight or not.

However, sometimes (e.g. in comments to this question) there is misunderstanding regarding what it means to say something is on the MEL. So, when I say something is on the MEL, does it mean that:

the aircraft can't be dispatched without it, i.e. the list contains the required items, or
that the aircraft can be dispatched without it, i.e. the list contains the optional items?

This answer suggests the former, but I've heard/read it used in the other way, so I would like some clarification.

The MMEL and MEL list items that can be inop while still dispatching the aircraft, it also lists any required restrictions of that system being inop.

I think FAA Policy Letter 34, which is the preamble for all MMELs, gives some of the best information:

First they set the basis of an MEL, that every system/function of the aircraft must be operation to dispatch. This restriction can be superseded by the MEL:

  The following is applicable for authorized certificate holders operating under  Title 14 Code of Federal Regulations (14 CFR) Parts 121, 125, 129, 135:  14 CFR  require that all equipment installed on an aircraft in compliance with the Airworthiness Standards and the Operating Rules must be operative. However, the Rules also permit the publication of a Minimum Equipment List (MEL) where compliance with certain equipment requirements is not necessary in the interests of safety under all operating conditions.

Then they tell you that MEL includes items that are allowed to be inoperative along with any limitations:

  The FAA approved MMEL includes those items of equipment related to airworthiness and operating regulations and other items of equipment which the Administrator finds may be inoperative and yet maintain an acceptable level of safety by appropriate conditions and limitations

  The individual operator's MEL, when approved and authorized, permits
  operation of the aircraft with inoperative equipment. Equipment not required by the operation being conducted and equipment in excess of  14 CFR requirements are included in the MEL with appropriate conditions and limitations.  The MEL must not deviate from the Aircraft Flight Manual Limitations, Emergency Procedures or with Airworthiness Directives.  It is important to remember that all equipment related to the airworthiness and the operating regulations of the aircraft not listed on the MMEL must be
  operative.

The image below is from the 767 MMEL, as you can see it lists items that can be inoperative and the limitation. Some items carry many restrictions, such as anti-skid or a pack, others carry none, such as reading lights. The MMELs are available on the FAA's website, so it can be an interesting read.

I do not know why the terminology is backwards, I assume it comes from a time aircraft were much less complex and an list of required items was realistic. But if it only listed items that were required for flight, you could end up with hundreds of systems inop, with no direct requirement to repair them. PL-34 addresses this a little bit:

  The MEL is intended to permit operation with inoperative items of equipment for a period of time until repairs can be accomplished.  It is important that repairs be accomplished at the earliest opportunity. In order to maintain an acceptable level of safety and reliability the MMEL establishes limitations on the duration of and conditions for operation with inoperative equipment.

and

  Operators are responsible for exercising the necessary operational control to ensure that an acceptable level of safety is maintained. When operating with multiple inoperative items, the interrelationships between those items and the effect on aircraft operation and crew workload will be considered.

Basically the take away from this is that an operator can not issue every MEL in the book and dispatch the aircraft. For example, it may be okay to MEL one AC pack or one AC pack temp control valve, but it would not be okay to MEL one pack and the temp control valve on the other pack.


Can pilots land an aircraft with only the use of throttles? Presuming that all other means of controlling an aircraft are unavailable to a pilot, can a pilot land a commercial airliner safely by using only the throttles and are pilots trained to do so?

Not safely, no. According to the Wikipedia article on UA Flight 232, with only throttle control, it is impossible to "control airspeed independent from sink rate", because there's no control of angle of attack.

In 232's case, that meant:

  On final descent, the aircraft was going 220 knots and sinking at 1,850 feet per minute, while a safe landing would require 140 knots and 300 feet per minute

I.e., even going 50% above safe landing speed the descent rate was 6 times too high. This is nowhere near safe, and it was something of a miracle that 185 out of the 296 souls aboard survived.

After that accident, the NTSB decided training for such a case wasn't practical.


What does "CC (Charlie Charlie)" mean when pilots reply to ATC? I heard a pilot replied "CC" to ATC instruction.

I can't remember the exact situation, but does anyone knows what it means?

Short answer

This wording comes from the common meaning of letter C to be Correct/Yes, early standardized and used at sea since 1857. Under the Commercial Code of Signals (1857-1902), the C flag, in addition of representing the letter itself, had the meaning of Yes/Affirmative. This code has been improved and extended into the International Code of Signals (ICS). While the visual representation changed, the meaning was preserved.

Today's version of the C flag (previous version)

From the 2003 ICS:

  Signals for flags, radiotelephony, and radiotelegraphy transmissions.
  C: Affirmative—YES or “The significance of the previous group should
  be read in the affirmative”.

The pilots you heard were saying affirmative.

Longer answer

Codes have their origin in the need to abbreviate everything at a time the communication channels were limited, as for nautical flags, Chappe, Morse, Aldis, etc. Nineteenth and early twentieth centuries saw appearance of codes (flags, lights, telegraphy, Q, X and Z) in order to federate many isolated practices, in particular in commercial telegraphy (Marconi) and railroads. Codes have many resemblances as they have borrowed good practices and common usages from each others.

In radio communications, letter C has been early used in consistence with the ICS, to mean correct, like when acknowledging a readback with a single C, meaning this is a correct readback.

Example

Discovered by @ymb1, this accident report includes a transcription of the pilot (CA) controller (MA) exchange:

  CA: Roger, we will appreciate it if you can alert, er,
  fire, er, er, er.
  MA: Do you request a full emergency please? A full emergency?
  CA: Affirmative, that's Charlie Charlie
  MA: Roger, I declare a full emergency.

later:

  MA: Confirm runway one four?
  CA: Charlie Charlie.

And this other document, still from @ymb1:

  Do you have ATIS information Delta?
  Charlie Charlie we have Delta.

...

  Ok our stand 41 AF028.
  Understand B 41.
  Charlie, charlie.

Details

Charlie-Charlie is a fancy substitution for a standard affirmative and accepted non-standard words roger and wilco.

Standard phraseology is meant to prevent confusion, and has been improved after incidents/accidents where the communication between parties played a role. In a conversation listed above, we can imagine how information can be  easily misunderstood:

  Do you have ATIS information Delta?
  Charlie Charlie we have Delta.

ATCO are not required to know the ICS, though in many countries, an important part of civil aviation ATCO have had a military career, and are likely to know the meaning of letter C in many codes.

More

More on signals, and how to use flags: ICS, US edition, revised 2003.
More on codes and abbreviations: Origin Of Ham Speak -  Fact, Legends And Myths (AC6V)


What kind of container should be used for storing a disassembled Cessna 172? I need to store a damaged aircraft away rather than leave it exposed to the weather and elements on a tie-down at an airport. It is a Cessna 172. If I remove the wings and horizontal stabilizer (from the tail), I can fit all lengthwise into a 40 foot shipping container.

However the span of the landing gear is just over 8 feet and won't allow fitting width-wise into a standard container. I suppose the landing gear can also be removed, but not desirable. Are there extra-wide containers suitable for storing small aircraft?

A "dry van" (nonrefrigerated) 53 foot trailer, commonly towed as a "tractor trailer" sports an extra 3 inches of inside diameter (8 foot 3 inches) to go with 9 feet 3 inches in height.

You could also build a custom crate either onsite (storage shed) or portable (on a flatbed).
Transporting it to a local barn or unused building is also possible, better than leaving it to the elements.

I would look into local storage options, with the wing removed, there should be many.


Do stealth designs have canard configuration? Do stealth-focused aircraft have canard configuration? I believe canards have a negative impact on the radar cross section.

So far, no operational stealth aircraft has had a canard wing as the canards do affect the radar cross section.

However, a few experimental and under development under development aircraft have canards, like the Chengdu J-20.

"J20 2" by V587wiki - Own work. Licensed under CC0 via Commons.

The Sukoi PAK-FA, on the other hand uses movable Leading Edge Root eXtensions(LERX), which are much more stealthy and are shown drooping down in the following figure.

Source: defenceindustrydaily.com

There are a few major drawbacks with the traditional canard designs:

Planform alignment Most of the canards are in aircraft for stability and aerodynamics requirements an as such are not amenable to planform alignment, as their characteristics are sensitive to their shapes and sizes. For example, compare the planform alignment in case of F-22 and Eurofighter Typhoon.

Source: forum.keypublishing.com

Some low observable aircraft, like the Boeing X-36 did  have planform alignment, it is simply that it is difficult to achieve.

"McDonnell Douglas X-36 planform" by NASA/Dryden Flight Research Center - http://www.dfrc.nasa.gov/gallery/photo/X-36/HTML/EC97-44165-151.html. Licensed under Public Domain via Commons.

Canard Angle Most (not all) of the canards have an anhedral or dihedral due to aerodynamics requirements, which means that they are not in the same plane as the wing and reflect radar waves in other directions, increasing RCS. The following image shows the (mis)alignment of canards with the aircraft.

Source: forum.keypublishing.com

More reflecting surfaces Having canards basically means there are two extra surfaces to reflect the radio waves and increase RCS.
Interaction with fuselage and wings The diffracted (radio) waves from the canards can impact on the wings and fuselage and get reflected back, which can increase the radar cross section.


Why do BWB designs typically put the engines in the rear? A Blended Wing Body aircraft looks something like this:

In fact, every true BWB concept model I've seen puts the engines in the rear. Why is this? Can't they be hanging from the wings on pylons?

I'm envisioning a large cargo aircraft, if that maters. In fact I'm considering turboprop engines for even better fuel efficiency, so you could theoretically put one of them on the nose.

Is there something about BWB geometry that greatly favors rear engines? Wikipedia says the body can generate its own lift. Does that mean the airflow is faster over the top and therefore you get greater intake mass flow at the top of the tail area?

The airflow over the top of a BWB accelerates as it would do over the top of any airfoil, and by the time it reaches the wing's trailing edge, its speed has slowed back down, so any engines fitted at the back would see no advantage, from that point of view (although they might indeed have a beneficial effect on the wing's boundary layer).

There are at least two non-aerodynamic reasons for putting the engines at the rear of a BWB. The idea is for BWBs to be more environment-friendly than traditional jetliners, in terms of higher fuel efficiency and lower noise emissions.

In general, the fuel efficiency of a turbofan increases with the engine's diameter (compare the engines of the new A320 neo vs the old ceo), and you would expect a future BWB to have even larger engines than today's ones, which would be difficult to fit under an already thick wing.

Secondly, the engines at the back are also significantly quieter than under the wings, since the body of the aircraft shields people on the ground from the noise produced by the air intake (a major portion of the total noise emitted by a jet aircraft).


What makes wing strakes desirable? Some planes have this large protruding part at the wing root. If my understanding is correct, it's a wing strake and it improves lift at high aoa via vortex induced lift on the rest of the wing. I have 3 questions.
1:If that's true, what are it's downsides?
2:This seems like a desirable thing, why don't more planes have it?
3: What does it have to do with canards? Every single canard aircraft has them, Rutan planes, Velocity planes, basically every canard plane I've ever known has them, and no conventional plane I can think of has them. What's the connection here?

The strakes (or root extensions) only have a secondary purpose aerodynamically. Mainly, they solved a particularly vexing problem on the Rutan canard designs (Vari-eze and its offspring), where the wings were swept and the operating C of G  was forward of the wings due to the canard configuration; where to put the consumable load, the fuel, where it can be as close as possible to the C of G.
You couldn't put fuel in the main wings farther aft, because depletion of fuel moved the C of G forward too much, and the Vari-eze already suffered from C of G and main gear placement issues due to the pilot forward, forcing Rutan to use the kneeling camel nose gear arrangement to avoid a tail skid to hold the back end up when empty (a really big problem when there's no tail to speak of, just a propeller).
There was no room in the fuselage for a tank of significant size and still have space for any baggage.  That left the sides of the fuselage ahead of the wing leading edge. He could have just put blisters there for fuel tanks, but that makes drag with no other benefit. The root extensions were an obvious and much more elegant solution.  Minimal drag increase, and a beneficial aerodynamic effect at high AOA, and plenty of fuel volume that changes the balance very little when depleted.
The presence of the strakes moves the mean area of the wing forward somewhat, but minor adjustments to the configuration take care of that.
"Regular" airplanes can put fuel in the straight wings and don't need strakes of that size and if they are used, there are strictly to improve stall behaviour. Some homebuilt owners, like the Thorp T-18 guys, have experimented with small leading edge strakes to improve high AOA behaviour, but these were only about the size of your hand and are just being used as vortex generators (can't find a pic of one so far).


Why was the FDR of flight ET409 extracted from ocean transported dry instead of in water? I was more than sure that FDR (as good as any other electronic device including magnetic strip, i.e. HDD), after sitting for a few days under the sea or ocean, must unconditionally be transported wet (i.e. inside some water container) to simply not let magnetic strips to get dry. The answers to this related question confirm this.

Yet, I have just saw a reconstruction and investigation of Ethiopian Airlines Flight 409 crash and noticed that:

FDR (found and extracted first) was transported dry, enclosed in an empty box,
CVR (found and extracted few days later) was transported in a box filled with water.

Is this just a "bug" in movie or can FDRs be transported dry after extracting them from sea / ocean?

As posted on Avherald, Lebanon's CAA released the final report in January 2012, detailing the investigation and its findings. The link on Avherald is broken, the current site for the CAA can be found here. The front page still links to a page on the report, where it can be downloaded.

Section 1.11 describes the recovery and contents of the flight recorders, and describes both recorders as being "immediately packed in water.".

See this fragment:

  The DFDR was recovered from the Mediterranean Sea by the Lebanese Navy divers and turned over to the IIC in presence of members from the IC on 7 February, 2010. The DFDR was immediately packed in water to prevent/delay the onset of corrosion and transported to the BEA laboratory in Paris France under the custody of the IIC accompanied by a Lebanese and an Ethiopian IC members.

And this one:

  A thorough hand search of the sea bed was then carried out the Lebanese Navy divers who finally succeeded in retrieving the CSMU and handing it over to the D/ICC in the presence of members from the IC on 16 February. The CSMU was immediately packed in water to prevent/delay the onset of corrosion and transported under the custody of the D/IIC and an Ethiopian member of the IC to the BEA laboratory in Paris France, for readout on 16 February, 2010.

While this could be inaccurate, it's much more likely that the reconstruction missed this point.


For a large commercial plane on landing, does the L/D ratio increase, decrease, or not change much? Consider a large commercial aircraft coming in for landing. The exact part I'm interested in is the flare (where the aircraft noses up yet does not actually go higher above the ground), with flaps extended, but before any ground effect comes into play.

Compared to normal cruise, does the Lift-to-Drag ratio increase, decrease, or not change much at all?

Increasing angle-of-attack increases both the lift and the drag, but probably not by the same proportions. I'm not really sure which way the curve goes for a typical airfoil.

Also, there's a really harsh complication: the flare also results in the engines pointing upwards too. This means that some "lift" is generated directly by the engines' vertical component of thrust. It's not really lift; a more accurate way to say it is the wings don't need to produce as much lift as before, because the engines do a direct part in helping to counteract gravity.

So that might suggest the L/D in fact decreases, which seems so counter-intuitive.

Actual numbers for the L/D at both stages of flight would be the most rock-solid answer possible. But I wonder if the L/D's cited by the manufacturers are derived from a simple wind-tunnel test (at different AoA and flap configuration) or if they actually take into account the upwards-pointing engines and their typical thrust during flare (which would be best measured as a percentage of aircraft weight at that point, and the mess gets messy).

In the flare you are already in ground effect. Maybe we should compare the final approach with cruise.

The answer is simple: L/D is far worse in approach configuration. The wing buys the increased lifting capacity with a relatively higher drag increase. This is not all bad: If the L/D is too high, a precise landing becomes much harder. Also, some more drag allows you to run the engines above idle, so spooling up for a go-around takes less time. Generally, you want the L/D to be between 5 and 10 for landing. Too much, and the approach becomes too shallow for a precise selection of the touchdown point, and too little and you lose too much energy in the flare, so you decelerate too fast in that final phase where sink speed is reduced.

Compare that to the L/D of modern airliners in cruise, which is around 16 for designs like the Boeing 747 and above 20 for the Boeing 787 or the A350.

You can study this cheaply in gliders. Take one with powerful flaps, like the ASW 20 or the ASH 25. Try to land them with all flaps and spoilers fully extended: You will never get to a smooth touchdown, but drop on the wheel somewhere before the flare is complete. Then try to land them with flaps set for slow flight and no spoilers: You need a loooong runway to do so.

The lift contribution of the engines during the flare is very moderate. They do not run at full power, and even if they did, their combined thrust would be only maybe 30% of the aircraft weight. Since they don't point straight up, but only by about 10°, the vertical component would be only 5% even at full thrust. In reality, they run at a little above idle, and their lift contribution is only 2% at most.

Flap type effectiveness comparison (picture source). The L/D is only for maximum lift, not at 60% of it which would be more representative for an approach lift coefficient, but the trend to lower L/D with higher maximum lift coefficient should be obvious.


Why is induced drag less on a high span wing? I have a basic question and sorry if it is a well known fact.

I understand that the induced drag is due to the tip vortices changing the effective angle of attack (downwash).

I searched some website and they mentioned that for high span wings the disturbance caused by tip vortices is less and hence, less induced drag.

Now the confusion arises.

As per the lifting line theory, the tip vortices strength will be as same as the bound vortex.

Does this mean that the induced drag is reduced only for a high span wing when having same bound vortex strength as a low span wing?

[For simplicity we can assume a elliptical lift distribution]

You start from wrong assumptions, which explains your doubts. The line

  the induced drag is due to the tip vortices

is as true as saying that wet streets cause rain. Also, the opinion that the

  tip vortices strength will be as same as the bound vortex

is wrong. Unfortunately, many authors don't understand the topic themselves and copy what others have written before without thinking the issue through. Ideally, you would forget about all what you have heard about vortices and lifting lines, but since you ask I will try to explain potential flow theory a little.

In potential flow theory, lift is caused by vortices which are caused by the movement of a wing through air. These vortices run along a closed line: Within the wing they form the bound vortex, then they leave the wing backwards as trailing vortices and are connected at the point where the movement started by the starting vortex.

Now comes the important part which most authors conveniently leave out: There is no single vortex; instead, potential flow assumes an infinite number of infinitesimally small vortices which form out of nowhere when lift is increased or speed is reduced. Consequently, no single vortex leaves the wing at the tips, instead, a sheet of vortices leaves the wing at the trailing edge. The change in strength of the bound vortices over span is equivalent to the strength of the vortices leaving the wing, so the vortices fade out towards the tips.

My advice is: If you do not want to operate or to write a potential flow code, do yourself a favor and forget all that. It is much better to interpret lift as the consequence of a pressure field around a wing which accelerates the air flowing around this wing downwards. Induced drag is simply the component of the resulting pressure forces parallel to the direction of movement, while the perpendicular component is lift. Please make sure to follow at least the last link; it gives a very good explanation what induced drag really is.

Tip vortices are the consequence of air filling the void above the downward moving air behind the wing. They are not originating from the wingtips, but the consequence of the vortex sheet rolling up (if you want to stay in that picture). Note that the distance between the cores of the vortices is much smaller than the wingspan. For an elliptic wing of span $b$, it is actually only $\frac{\pi}{4}\cdot b$

A higher wingspan allows to capture more air for lift creation, so less downward acceleration is needed. Lower downwash speed also causes a less powerful trailing vortex. Note that the mass of air affected by the wing grows with the square of the wingspan!


How are these Airbus A350s flying in formation without being affected by wake turbulence? The first photo in this article appears to depict three Airbus A350s flying closely in tandem at approximately the same altitude.

I thought that a large jetliner would leave a trail of wake turbulence behind it that would be unsafe for several minutes.  Is there something special about the Airbus A350 that makes this formation possible?  Am I misinterpreting the photo?

The V formation in the second photo seems much more reasonable.

You are right that wake turbulence would be a danger when flying behind another aircraft like that.

The perspective of the photo makes it hard to see the actual position of the trailing aircraft relative to the ones in front of it. Pilots do this sort of thing in airshows when they fly in formation. The trailing aircraft are generally slightly below the ones in front of it. This allows good visibility of the plane they are following. At the higher speeds that these jets are flying at, the wake vortex will not drop enough to impact an aircraft fairly close behind and below.

See this old photo of the Thunderbirds. From this perspective, it is easier to see that the trailing aircraft is also below the flight path of the leading aircraft.


Why does London have so many airports? London has six international airports: Heathrow, City, Luton, Southend, Stansted, and Gatwick. It might even have eight international airports if you count Birmingham Airport and Southampton Airport.

Why does London need so many? I think two airports is enough. Plus, they are put in bad locations. So, is this for a practical, or some kind of other reason?

Why does London need so many? I think two airports is enough. Plus, they are put in bad locations.

As others have mentioned, London is a huge connection point for several parts of the world as well as being one of the big financial cities in the world.

During WW2 a huge number of air bases in the UK were built or expanded by the allies, and post-war several of them were used as civil airports. Several of the ones you mention has roots in this:

Southend was built during WW1, closed after and reopened in the 1930s
Gatwick was built as a civilian airport between the world wars
Stanstead was built during WW2
Luton opened just prior to WW2
Heathrow opened between the world wars as a civilian airport

Several of them saw expansions by the military during WW2, getting improved infrastructure and bigger capacity. Once the war was over, the airfields were available to civilian and commercial use.

  So, is this for a practical, or some kind of other reason?

It is not as if the city of London planned where to put each airport. They were there when the need for additional capacity appeared; in some cases the airports initially served local municipalities and cargo airlines, later to be used by charter and other airlines when the airports closer to London were full. The same thing is done today with budget airlines choosing to operate out of airports further from the population centers where the operational costs are lower for the airline.

The only apparent exception to all this is London City Airport, the only of the airports mentioned built after WW2. It was built in the 1980s as part of a bigger plan to revitalize a part of London; by having a small business airport close to the city it could attract new investors and companies.

  I think two airports is enough.

By numbers alone, London could get by with two Atlanta-sized airports. But to do this you need room to build and the political will to spend money on expanding an airport rather than allowing airlines to use other airports further away.


What causes an airplane to rhythmically bounce during taxiing? Some time ago, I was on a commercial flight and while the airplane was taxiing around, there was this rhythmic bouncing. Here is a video I made of the takeoff. You can notice the bouncing at the taxi and takeoff roll of the video. What causes that rhythmic bouncing? Is it a result of uneven wear on the tires?

For the sake of anyone who wants to know in case it helps, the airplane was a Boeing 757-200.

If you are old enough to remember, the bias-ply automobile tires used in the 1960's would develop a flat spot when left sitting overnight. The flat spot would quickly go away when you started driving.

Many of today's aircraft tires still use bias-ply tires and are also subject to flat spotting.

Source: The Boeing 737 Technical Guide


Why are there so many moving parts used in the landing gear? This short clip of the landing gear on a Hawker 850XP being retracted seems extremely complex.

I'm curious to know why there are so many moving parts but as a layman I'm struggling to make sense of it all.

So what exactly is going on here and why?

One of the key points (circled in red) above shows the part that locks the gear in the extended position and requires that the linkage up top (circled in blue) is actuated to release the gear.

At the end of the clip you can see a glimpse of the linkage bar at the top returning to its previous position. That way if the gear is dropped by gravity it will lock itself once fully deployed.

If you strip those parts all that's left is a basic 4-bar linkage and a connection to the gear door.


Why does Turkish Airlines avoid Israel when going to Amman, but not on the return leg? (flightaware.com)

Last week I was browsing Flight Aware when I came across a Turkish Airlines flight from Istanbul (Turkey) to Amman (Jordan). I noticed that the flight path clearly makes an effort to avoid Israeli airspace. My instinct was that Turkish airlines had some diplomatic issues with Israel and had to avoid their airspace.

Today I came across this post asking what the busiest Turkish Airlines route is, and turns out that the answer is Istanbul to Tel Aviv (Israel). That made me curious about my initial finding. I posted this as a comment on that thread and fellow user @MichaelSeifert pointed out that the return flight, THY813, flies right over Israel.

This leads me to believe that there are some restrictions on flights entering Jordan. Does anyone know anything about this issue or have other similar examples?

There are no issues overflying Israel to Jordan:

From the Israeli AIP:

Prior permission is not required for commercial scheduled
flights by aircraft registered in countries that are parties to the
International Air Services Transit Agreement (IASTA) or
where the relevant Israeli bilateral Air Services Agreement
allows overflying the State of Israel or making stops for non-
traffic purposes.

The prohibited airspaces on the shorter route allow flights above 6000 feet (per the AIP).

There are two airways that are used. Each is one-way.

(skyvector)

Amman arrival procedures allow flights coming via waypoint SALAM on the Israeli side (the OSAMA arrival). See SALAM and OSAMA above.

The AIP confirms airway P51 (eastbound to Jordan) is used.

There is a whole section titled 'Procedure for IFR flights to and from Amman (Jordan)', nothing stands out, just to have two-way communication established with both ends.

As far back as flightaware allows, it's consistent. So that rules out airspace closure for military exercises, etc., and also similar threads exist on airliners.net as far back as 2012.

Conclusion:
What all that hints at, is that the reason is in the fine print of the non-publicly-available air service agreement between the nations and carriers involved.
Note: the site that hosts the eAIP of Jordan is not loading, so I couldn't check the Jordanian side.
Also, it's not a diplomatic thing: Pegasus Airlines 1710 (Turkish) and Royal Wings 6558 (Jordanian) when flying from Turkey to Amman, overfly Israel (shown below).


How long do airliner tires last? Can this be improved? I imagine that the tires on commercial jets wear out pretty fast with all those squealing landings as the tire suddenly has to spin up from zero to the speed of landing.

2 questions:

How many landings does any average commercial airliner tire last before it is discarded?

Before landing, why not have a small motor assembly on the landing gear to spin up the tires to the correct speed? Surely this would avoid the degrading tire burn. The tire might last a lot longer and might even offset the cost of the motor assembly.

I've heard that airliners' tires will last about 200-250 depending on how many hard landings are made. Bizjet tires will last longer, and light aircraft tires will last indefinitely, depending on how gentle you are and what kind of surface you're landing on. I had one start cracking around the wall and just looking unsafe long before the treads ever started to wear.

As for the spin-up idea, it's been proposed many many times, but generally always rejected due to weight and maintenance costs. However, now that fuel is by far the main expense in an airliner's trip, companies are looking for any way to reduce fuel burn. As it turns out, taxiing an airliner burns quite a bit of fuel. They've already started turning one engine off for long taxis, and I think that electric wheel motors will be the next big thing.

The motors have gotten light enough and strong enough that they are a now a viable option. They can be powered by the APU or by a set of batteries (which are also now becoming light enough, see the 787 when they get the kinks worked out). So when they get around to putting them on aircraft for taxiing purposes, you can bet that they'll be spun-up right before landing.


What is the propeller efficiency, $μ_p$, of modern propellers for light sport aircraft? Roskam's book on preliminary design gives a value of 0.7 for "homebuilt" aircraft and 0.8 for general aviation. What explains this difference in propeller efficiency? The content of Roskam's book is fantastic but some of the constants that he gives may be a bit dated as was the case for specific fuel consumption which was given as 0.7 for homebuilt aircraft when a modern engine like the Rotax 912UL has a sfc of 0.47.

On a search of Wikipedia, it is written that modern propellers can have an efficiency of 0.9.

Propeller efficiency is mentioned a lot here on Aviation SE, but lacks a good explanation. Here we go:

A propeller accelerates the air of density $\rho$ which is flowing through the propeller disc of diameter $d_P$. This can be idealized as a stream tube going through the propeller disc. This stream tube starts with air at ambient speed and a wide diameter d$_0$. As the suction ahead of the propeller accelerates the air in the streamtube, it starts to speed up and the stream tube contracts. In the propeller plane we witness a jump in pressure p: Here, energy is added to the flow, so Bernoulli does not apply momentarily. Past the propeller the air in the stream tube accelerates further and the tube contracts to the diameter d$_1$ when the pressure inside has dropped to the ambient pressure (dashed line in the pressure graph below):

The air speed ahead is $v_0 = v_{\infty}$ and the air speed aft of the propeller is $v_1 = v_0 + \Delta v$. The propeller effects a pressure change which sucks in the air ahead of it and pushes it out. Since the mass flow must be equal ahead and behind the propeller, the stream tube diameter is bigger ahead of the propeller and smaller downstream. In reality, there is no neat boundary between the air flowing through the propeller and that surrounding it, but for computing thrust this simplification works well if the airspeed is identical across the cross section of the propeller disc.

The efficiency $\eta$ of thrust creation is the work done on the mass flow through the propeller $W = m\cdot\Delta v\cdot v_0$ relative to the impulse change of the air $\Delta I = m\cdot\frac{v_1^2 - v_2^2}{2}$:
$$\eta^{opt} = \frac{2\cdot v_0}{v_1 + v_0} = \frac{v_{\infty}}{v_{\infty} + \frac{\Delta v}{2}} = \frac{1}{1 + \frac{\Delta v}{2\cdot v_{\infty}}}$$
This equation assumes that air is uniformly accelerated straight backwards. To be more precise, you need to add the swirl losses, since the air receives a rotational component $\omega$ from the propeller, spinning with the angular velocity $\Omega$, as well:
$$\eta^{opt}_{Prop} = \frac{1 - \frac{\Delta v\cdot \left({v_{\infty} + \frac{\Delta v}{2}}\right)}{d_P^2\cdot\Omega^2}}{1 + \frac{\Delta v}{2\cdot v_{\infty}}}$$
Still, we have not included friction losses yet and our prop spinner and engine nacelle are also not included. Now we must enter into a definition what propeller thrust is: Is it just the lift acting on the propeller blades in forward direction, or is it the remaining forward force after the additional drag of the airplane components in the slipstream of the propeller has been subtracted?

To avoid lengthy computations, charts can be used where the efficiency is plotted over a range of parameters.

To cut the discussion short: Generally it is safe to assume a top propeller efficiency of 0.85 (85%) with big, slowly spinning propellers (1000 to 1700 RPM). If the twist distribution along the blade does not match the local angle of attack distribution (say, if the propeller is optimized for high speed, but operated at slow airspeed, like during take-off), efficiency can easily drop to 0.7 (70%). Things become worse if the pitch of the blades is fixed. See below for a typical example of a variable pitch propeller. Each of the curves is for a different pitch setting, the x axis shows the advance ratio (the ratio between airspeed and circumferential speed; here off by a factor of 1/$\pi$), while the y axis shows the efficiency.

Efficiency chart of a variable pitch propeller. Source: McCormick B.W. Aerodynamics, Aeronautics & Flight Mechanics. John Wiley & Sons, Inc., 1979.

What can be seen from the equations above is that it is more efficient to accelerate lots of air a little than to accelerate a little air by a lot. This means that small propellers on ungeared engines, spinning at high RPM, are at a distinct disadvantage; this is why Roskam assumes only 70% for them and only 80% for GA propellers.

The 90% you name has to my knowledge only been scratched at by some very efficient (slow, large, contra-rotating) propellers operating under ideal conditions. To play it safe, I would choose a slightly smaller number for them.


Why did wings start to be made with aluminium skin instead of fabric? Why did engineers start designing planes with aluminium skin on the wings instead of fabric covering? While the force of lift acts on the skin, to my knowledge it is not subject to high stresses

Wings and fuselages are subjected to twisting loads as well as bending so they need to be torsionally stiff.  Prior to aluminum, the options were to make the wing/fuse with a frame of spars and ribs with fabric to provide the aerodynamic contours, braced with struts and/or wires to provide the torsional stiffness as well as resistance to bending, or, to do away with the struts and brace wires and make a monocoque structure (like an eggshell) with a plywood skin to provide torsional stiffness (with the spar beam inside for bending).  If you wanted to go fast, you had to do away with all the bracing so plywood monocoque was the way to go.
When "duraluminum" came along after WW1, it was realized that as well as replacing sitka spruce for spar beams and ribs, it could also replace plywood for a stressed skin monocoque structure.  You could build an airplane in the 1930s using plywood stressed skins bonded to wood ribs and spars, or aluminum stressed skins over aluminum spar beams, and have pretty much the same performance.  You could make your egg about of plywood, or aluminum sheet, and it was pretty much the same egg.
There were so many manufacturing and durability advantages to aluminum (no glue, no wood rot etc etc), it was a no brainer to switch, once the metallurgy started to become understood well enough to use it as an engineering material, and plywood skinned wooden airplanes faded quickly.


What is the make and the model of this seaplane? What is the model of this seaplane?

This is a Progressive Aerodyne SeaRey, a kit aircraft. Also on:

Wikipedia and
Youtube.

About 500 of this make had been built up to 2011 according to the Wikipedia article.

(Source: Light Sport Hangar Flyin')

This one is seemingly registered in the Philippines ("RP"), I read that at some point experimental aircraft had been grounded in the Philippines, but don't know if this was temporary only.


What is a radar fix? Sometimes fixes found on approach plates are labeled radar. What are these radar fixes and how to they differ from fixes usually found on approaches?

Since this an FAA instrument approach procedure, this answer is specific to the FAA.

The RADAR label indicates that these fixes are marked on the approach controller's screen and he/she can advise the pilot when the aircraft is over the fix.

The use of Radar for arrivals and approaches is outlined in FAA JO 7110.65, Chapter 5, Sections 9 and 10. FAA Order 8260.19, paragraph 8-2-5(a) states that "Radar vectoring may be provided through any approach segment up to and including the final approach fix."

You'll note that the approach plate does NOT indicate RADAR REQUIRED because it is not the only method of determining or defining the fixes. In this particular approach, arrival at a fix can be determined THREE different ways: with Radar, LOC with DME (or GPS lieu of DME), and LOC with VOR radial. Per 8260.19, paragraph 8-6-6h, all IFR aircraft are assumed to have at least one VOR receiver, thus no equipment requirement note is required for this particular approach.

In practice, I've found that ATC will not call out crossing a fix unless you specifically request the service, though they will usually identify your position prior to hand-off (e.g. November 1234, two miles from SHAGY, contact tower on 120.5).


Could a single engine pilot land a passenger jet? (from Airplane) I'm assuming that almost everyone on this website has seen the movie Airplane at least a few times...

Last time I was watching it I was wondering how plausible the actual act of having a single engine prop pilot, with a lot of training (maybe comparable to a modern day aerobatic pilot), land a quad engine passenger jet?

I can relate to you the true story of my uncle who successfully landed a large WWII aircraft with no flight training.

He was the flight surgeon on board a large aircraft that got heavily shot up.  Hostile fire killed or severely injured every crew member.

He moved the pilot out of his seat, and contacted a control tower.  With the expert help of the control tower operators, he successfully landed the aircraft.

After the war, he had a private practice in his home where he saw patients.  For patients too ill to come to him, he performed house calls.  He continued to perform house calls until a short time before he passed.

I have always thought his life story would form a compelling foundation for an inspiring movie.


What is the difference between LP fuel valve and LP fuel shut off valve? In the Airbus A320 FCOM in some places "LP fuel valve" is mentioned (in Fire and Fuel System chapters) whereas in the engine chapter "LP fuel Shut off valve" is mentioned.
Is there any difference between the two?

The "LP fuel valve" and "LP fuel Shut off valve" are the same valve just being named differently in different sections of the FCOM.
The valve is located in the wing leading edge and is also sometimes referred to as “spar valve” by engineers who also work on Boeing aircraft.


What is the minimum recommended cruising altitude to avoid bird strikes? I was surprised to see geese flying some 200 ft above my aircraft at 2000 ft MSL.

I obviously would like to avoid them but I am based too close to the New York City Class B, where there are much bigger, heavier, and faster birds:)

In order to avoid having to get clearance from ATC, I need to fly under the layered minimum altitudes by a safe margin of the upside down cake of the class B airspace.

What is the minimum recommended cruising altitude to avoid bird strikes?

AIM 7−4−1. Migratory Bird Activity
a. Bird strike risk increases because of bird migration during the months of March through April, and August through November.

b. The altitudes of migrating birds vary with winds aloft, weather fronts, terrain elevations, cloud conditions, and other environmental variables. While over 90 percent of the reported bird strikes occur at or below 3,000 feet AGL, strikes at higher altitudes are common during migration. Ducks and geese are frequently observed up to 7,000 feet AGL and pilots are cautioned to minimize en route flying at lower altitudes during migration.


To what FAA office or personnel should one direct an inquiry about the reasons behind the airspace design at a particular airport? The airspace design process is extremely complex.  See for example this FAA document, Order 7400.2M.

To what FAA office or personnel should one direct an inquiry about the reasons behind the design of the airspace around one particular airport?

I'm seeking real-world, practical insight as to why the unusual airspace configuration we see at KACV and KTVL was selected, over the common configuration that we see for example at KONP and KCEC.

I'm specifically seeking information about why the airspace was designed that way, not about how it is being handled now in actual practice by ARTCC etc.

These two airspaces are rather unusual and it's unlikely that a satisfactory answer will be obtained just by perusing the FAA documents giving general guidance on how to design airspace to handle existing/ proposed instrument procedures, etc.

However any kind of actual "paper trail" relating to the design of the airspace at these two particular airports could possibly be helpful, if it were not too "dense" to interpret -- how might that be obtained?

But I'd prefer to speak to an actual person, if he/she had some relevant insight on the design process for the airspace at either of these airports.

Although guidance concerning my specific case is most welcome, also I'm seeking an answer crafted in such a way as to be helpful to anyone seeking  to answer a similar question for any airport in any region of the nation-- how to go about locating an appropriate person or FAA office to direct such a query toward?

By reading your linked FAA Order and finding references for responsible offices and a little follow-on search, I found this link to the Office of Mission Support within the Air Traffic Organization.

Airspace analysis appears to be within their purview:

  Mission Support Services oversees the Air Traffic Organization’s
  activities in:

  Aeronautical Information Manual (PDF)
  Aeronautical Information Services
  Air Traffic Organization Environmental Reviews
  Air Traffic Procedures Advisory Committee (ATPAC)
  Instrument flight procedures production/charting
  Metroplex
  New York/New Jersey/Philadelphia Airspace Redesign
  Obstruction Evaluation/Airport Airspace Analysis (OE/AAA)
  Performance-Based Navigation (PBN) Implementation And Usage Dashboard
  Pilot Web

They provide the following contact information:

  Address
  FAA National Headquarters
  1028 - 10A
  800 Independence Ave., SW
  Washington, DC  20591

  Phone: (202) 267-8261


Has the Boeing 737 MAX MCAS system successfully prevented a stall or approach to stall condition outside testing? The Boeing 737 MAX MCAS system has been in the press a lot as it has been implicated as a possible cause of 2 fatal crashes. The MCAS system was put in to prevent a wing stall caused by excessive Angle of Attack. My question is, outside of testing, has the system ever operated as intended and prevented a stall or approach to a stall?

We don't know - until we hear about such a case!

A positive answer would require

a trace of MCAS action
sufficient evidence that the pilot could not have handled the (near) stall without MCAS.

This information could come from

a pilot who

notices the trim interference, and
perceives the situation as dangerous, and
reports the event

or

a flight data recorder that is analyzed, and

corrective MCAS action is found, and
it is evident from the data the pilot(s) did not / could not control the situation.

[ Am I missing any other way how MCAS could leave a trace? ]

A well-trained vigilant pilot can handle (near) stall situations in most cases.

MCAS is designed not only to get out of a stall, but to prevent the airplane from stalling in the first place. That means that
 the plane should never get into a critical stall situation, if MCAS does its preventive work.

All that just to say, it would be possible to answer "yes" as soon as there is knowledge of one averted incident, but it is impossible to conclude "no" from the absence of information.

I am very well aware that I wrote this theoretical answer while sitting in an arm chair, and I will happily remove it as soon as anybody with hands-on knowledge can provide more satisfying information.


Can leaning provide more power when running at full throttle? Looking at this graph I see that a piston engine provides less than best power when the mixture is richer than best power, and this is expected indeed.

I know that at full throttle, more than the required fuel is provided to the engine in order to achieve better cooling.
Also, I know that - especially on supercharged engines - the amount of "cooling" fuel is quite high, that is, the engine is not surely providing its best power when at full throttle.

If an engine is rated 300hp when at 29 inches of manifold pressure (MAP) and 2700RPM at full throttle, does it mean that it is actually capable of providing more power if leaned to the best power mixture? It seems to be that it should be able to provide around 8-9% more power. Of course, I would expect it to suffer some serious damage.

Yes. The engine will produce its optimum amount of power for throttle setting when leaned to the correct stoichometric mixture.   The primary risk during operation at peak EGT/TIT is of course the high temperature during operation and greater wear and tear. Engines are usually operated approximately 50° rich of peak for max performance or 50° lean of peak EGT for economy operations, depending on the model of engine, flight regiment, etc.  Rich mixtures are preferred to keep the engine cool and minimize detonation risks, but it can also foul the sparkplugs with lead deposits, reducing engine efficiency, power and causing engine roughness during operation.  Excessively lean mixtures can sip gas during cruise but risk fuel starvation or put the engine at a high risk of detonation resulting in severe damage.  For these reasons, the leaning range I stated above is the most widely used.

Normally aspirated engines are often leaned prior to high-performance operations at high altitude‘s, such a short take offs from a mountain airstrip, etc.


How do I find all the frequencies for my local TRACON? I'd like to program my hand held radio with all frequencies that I can expect to need around my area.  Specifically, I'd like to find an official list of all the frequencies used by the local Tracon facility.

Looking in the Chart Supplement for the primary airport, I get a list of frequencies for approach and departure at that airport.

If I look at charts for airports around the periphery, I can find other frequencies not listed in the supplement for the primary airport.

My example is Salt Lake City.  Outlying airport is Provo Municipal from which you can reach Salt Lake Approach on 118.85.  I'd guess terrain prevents collocation of the 118.85 antenna with the others.

I'd also be interested to know if there are maps available for ATC sectors within facilities.

There are sector maps available, and each facility updates them periodically.  They are published.  My understanding is that sectors are joined and separated frequently, even based on the minute to minute workload.
(I have a set of charts showing High, Low Center and tracon sectors. I haven't found a public source for those charts yet.  Here is a set of maps, but I would like to provide direct FAA maps.  https://ivaous.org/academy/index.php/controllers/procedures-and-organization  )

The chart supplement and AFD are good places for common frequencies, however most facilities have additional frequencies.  They might be used for certain events, emergencies, when VIPs are being handled, during extreme congestion and when there are problems with the primary frequencies.  I do not know of a good source for those backup frequencies, which is published.

There are radio reference listings of ATC frequencies, however, they are not always accurate.  While the may show the station frequency assignments, they may not show the true facility usage.

As an example, here is a compilation of Boston Air Route Traffic Control Sectors. https://en.wikipedia.org/wiki/Boston_Air_Route_Traffic_Control_Center#Low_Altitude_Sectors_2

Addendum:  FAA Facility Transmitting Authorization (FTA) would be the document, prepared for each facility, which would list all the frequencies that facility is authorized to use.  The genesis and use of the FTA is covered in this FAA Order: https://www.faa.gov/documentlibrary/media/order/6050_32b_with_chg_1_and_2_incorporated.pdf

  For FAA-owned systems, this number will be the Facility Transmitting
  Author ization (FTA) number assigned by FAA Spectrum Engineering. For
  non-federally-owned systems, this number will be the Federal
  Communications Commission (FCC) license number or “call sign” assigned
  by the FCC.  For military-owned systems, this number will be the
  National Telecommunications and Information Administration (NTIA)
  serial number assigned by the FTIA.

So if you are trying to obtain frequencies for a military base, which may be working with local FAA facilities, you will also need to get the NTIA/FTIA data.

The FTA is public information, but I am unaware of an Order or publically accessible database for the FTA.  When I see an avionics inspector later today, I will ask her if she knows where FTAs can be looked up.


What is the name of the system that replaced stairs for disembarking aircraft? Back in the day, or in old airports, or airports that have not upgraded their systems, passengers disembarked in aircraft using stairs, through rain and or snow and extreme weather, sometimes having to delay disembarking because of bad weather in turn delaying themselves, the airport and the aircraft schedule. Today there is a new weather proof system where passenger disembark the aircraft and find themselves in the air conditioned airport, devoid of all the unfavorable extremes, devoid of delays.  What is the name of this system and when was it introduced?

(throughouthistory.com)

Shown above is a telescopic corridor at London Gatwick airport c. 1930's (I had to make it interesting).

For today's system, the name you are looking for is jet bridge. It's also known by other names. There is also a rarer system called mobile lounge.