Why do the spoilers move in this video? In this video when the aircraft is turning left(2:25) the spoilers on the wing move. What causes them to move?

Two reasons that are really one reason. In short: Because lift.

In this case though, it's "to get rid of lift". The spoiler's job is to reduce the amount of lift the wing experiences. This can be done symmetrically, on both wings at the same time, to increase the rate of descent or keep an aircraft from lifting back off the ground when in ground effect, or in this case, it can be done asymmetrically, or only on one wing.

In order to turn, an aircraft has to create an imbalance of force, more on the side outside the turn, less on the inside of the turn. The wing to the inside of the turn needs to drop, but it doesn't really want to...it has lots of air pushing it up (when it doesn't, you will have a very bad day)!

The spoiler in this case is just acting as an extension of the aileron. By moving upward with the aileron itself, it spoils the airflow over the top of the wing a bit, reducing the lift, and causing the wing to drop a bit, raising the other wing. It also acts as a larger surface area for the incident airflow to impart force on, which also pushes the wing down.

On the other side, the aileron is doing the opposite, increasing the wing's effective camber, at least near the tip, and increasing lift. Flaps do the same, but also are usually used symmetrically to increase lift on both wings. In some airplanes, you can have a 'flaperon', which can also be used as an additional control surface while also doing it's flap-thing.


How much cheaper would flying be if we made it less safe? Comment: I know this doesn't represent reality, it is a hypothetical scenario.

I have the impression safety measures are non-linear in cost, i.e. that reducing the accident rate by one percent costs more than the preceding percent. We often go to great lengths (and costs) to eliminate very unlikely events from happening.

Let's just assume that we would tolerate the fatality rate of aircraft to be 10 times as high as it currently is. Flying would be even more  attractive and cheaper than going by car (replacing cars on more distances) and would still be statistically safer, so there would still be less fatalities overall.

Is there an estimate on how much the ticket price for end passenger could decrease if we allowed for this to happen? The usage case would be the average commercial aircraft on for instance a 2-3 hour short haul flight.

For instance:

Reduce number and frequency of maintenance checks.
Dispatch aircraft to their destinations under less stringent Minimum Equipment Lists.
Have lower pilot requirements.

Lets completely remove liability from the picture. The airlines are simply not responsible for anything that happens to the passengers, and as a result they don't care. Seatbelts, oxygen systems, escape slides - who needs them? Flight recorder? In the trash. FAA staff are cut to 20% of current levels and are mainly concerned with keeping things running smoothly (their pay is docked across the board when flights are late) and the NTSB is defunded.

Daily operating costs go down a bit. We've removed a couple of hundred kilograms of safety equipment and that will make a small dent in the fuel bill. But only a small one. The mini-Starbucks installed where the over-wing exits used to be weighs about the same. Costs related to FAA-mandated paperwork are eliminated, but only temporarily.

There's less training for the cabin crew, but we can replace the evacuation training with sales training to bump up profits from regular and duty-free sales. Hooters re-enters the air carrier industry and does quite well, as cabin crew can be transferred directly from the restaurants skipping all that troublesome FAA qualification business.

But we find that maintenance costs don't go down. Costs plummet for the first year, but then go back up as management realizes that an airplane on the ground because it won't start costs a lot more in losses than maintaining it properly to begin with. And the one that crashed on takeoff was a complete loss on the airframe ($100mil and up) along with a dent in sales for the following 6 months.

Flight recorders are reinstalled as they are actually rather useful to predict if something is going to break. It can then be replaced by the night shift. The FAA paperwork we stopped doing is also quite useful for deciding wether or not to overhaul the wheel bearings with winter-weight grease, as we wrote down when it was last done.

The flying public will see maybe 10% reduction in fares. Remember that a very large percentage of ticket costs are taxes. For example, flying out of the UK costs up to £194 just for taxes. Wether the public will accept a large decrease in oversight for a small decrease in fares, or wether the long-term accident rate actually goes up or down will be a very interesting social experiment.


Why Air France 447 could not reduce angle of attack? I just finished reading this article and couldn't understand why in 3 minutes and 30 seconds even though there was no reliable speed data, pilot could not level the plane? Isn't the angle of attack reported by a gravity based tool like in off-road vehicles?

Summed up Question: When it's unclear what is happening with the aircraft, isn't it safer to put it in level position and medium speed? (Sorry for rudimentry language here)

I just finished reading this article and couldn't understand why in 3
  minutes and 30 seconds even though there was no reliable speed data,
  pilot could not level the plane?

If you look at this video by the French accident investigation bureau (BEA) you can see what happened.

The problem started when the speed indicators failed temporarily because of icing of the pitot tubes. The aircraft was flying through the intertropical convergence zone (ITCS) where severe thunderstorm activity can build up to high altitudes.

Instead of maintaining attitude and thrust setting, which is a normal procedure when speed indication is lost, the pilot flying (PF) brought the nose up. The aircraft started to climb but at the same time lost a lot of speed (trading kinetic energy for potential energy). Eventually the airspeed dropped so far that the aircraft stalled. By the time the aircraft entered the stall, the pitot tubes where de-iced and all speed indicators were working again. From the moment the aircraft stalled it started to sink. The PF tried to maintain a nose-up attitude, eventually using full aft stick. We can only guess to the reason why; it is likely that he was disoriented and had no confidence in the instruments after the failure. Yet it goes against basic flying instincts to pull the nose up in a stall.

The aircraft is naturally stable and will automatically drop its nose in case of a stall so it took some effort by the PF to keep the nose up. The horizontal tailplane then stalled as well which removed a lot of the nose-down tendency. The result was that the aircraft was in a nose-up attitude for the most part of the descent.

The angle of attack remained therefore too high and the aerodynamic stall persisted all the way down. If the crew would have brought the nose down they would have increased the speed, lowered the angle of attack and recovered from the stall. Once recovered from stall they could then level off the plane.

It may have contributed to the confusion of the crew that the airspeed was below 60 knots during portions of the descent. As they accelerated through 60 knots, the stall warning re-appeared.

The stall indicator systems makes use of alpha vanes which need some airflow over them to work. By inhibiting the stall warning below 60 knots the system is prevent from giving nuisance warnings on the ground. Such a speed is not normally encountered during flight, even not during a stall.

Another contribution to the accident may be that the pilot-not-flying (PNF) cannot see what stick inputs are given by the pilot flying. If it would have been in a different aircraft with coupled yokes, the PNF may have realized what was going on.

  Isn't the angle of attack reported by a gravity based tool like in
  off-road vehicles?

The angle of attack is the angle between the chord of the wing and the incoming airflow. It is not related to gravity.

  Summed up Question: When it's unclear what is happening with the
  aircraft, isn't it safer to put it in level position and medium speed?
  (Sorry for rudimentry language here)

Initially only the speed indicator failed. If the crew would have remained at the same attitude and power setting the aircraft would not have stalled. That is the standard procedure in such a case ("thrust and attitude")  That may not have been the proper reaction in this case. The aircraft was encountering severe turbulence and the fastest way out may have been to climb. But after the stall warning sounded all speed indicators were back to normal and the aircraft was flyable.


Do test pilots on commercial aircraft wear a parachute? I was watching a video of the first A350 flight. At 0:35 one of the pilots appears to be wearing a helmet and what looks like a parachute. Is that true? Do pilots on maiden flights wear such a kit, so that in case of an emergency they can evacuate the airplane?

To the best of my knowledge, all commercial aircraft being tested have their pilots take on parachutes and hi-vis clothing in addition to creating a possible means of egress on all important flights, such as the first flight and high-speed tests.

Since getting the cabin doors open is practically difficult, the solution I think most producers use is to built a chute down the front cargo entrance which can open.

Bombardier produced a pretty extensive film for their new CSeries.

Here's the solution employed on the Concorde:


What are the crewing requirements for a B787 flying LAX to SIN? I’m wondering what the crew size, and rest requirements for the flight crew of a Boeing 787-9 flying LAX to SIN (Flight number UA37).

I can't provide a specific answer but rest times are contract matter and airline specific. Also, most curiously, you won't find rest crews on private jets.

Depending on the airline you will have anything between 3 and 5 pilots on longer flights (anything above 8h). Three being the most common. Start and landing are handled by captain and co pilot, in between the aircraft is flown by a "cruise pilot" of a lower rank.

Rest crew regulations can cause problems, if there is a delay. Even a small delay may cause to require a standby crew, which will incur a further delay.

As a rule of thumb, airlines have around 10 flight crews per aircraft to allow for relief crews, training, holidays, ...


What's the name for this part on a Cessna 172P? I am trying to figure out what the name for this part is.

I believe that's the door seal, but all seals I am looking at, seem to be glued to the outside now.

It’s part of the interior trim, which has come dislodged from the fuselage side near the door.


In the early days of flight, were there any cockpit control schemes other than the modern one? Back in the early days, what kind of control schemes were invented for aircraft, other than the modern one? (pedals to yaw, yoke to pitch and roll).

I'm only interested in control schemes that can be done from the cockpit and control relatively small surfaces. So no weight-shifting, no wing-warping.

Hypothetical examples: 2 yokes (1 for each aileron and elevator), a steering wheel?, one-axis yokes?

The Dunne D.8 used a pair of levers, each controlling one elevon.


Who is responsible for getting approval of cabin layout? There are many aircrafts. There are many layouts. Even same aircraft model can have many layouts. Emirates offer in-flight shower while other airlines do not. Toilets locations may differ from different airlines. Seat pitches can be widely different for competing budget airlines etc.

Who is responsible for getting all these layouts certified? Is there any guidelines or regulations about it?

Edit: there are aircrafts in every continent I know of. Any jurisdiction is fine. Best if you can compare between their differences. Just general idea of your familiar is good enough.

I can answer for the FAA as that is the jurisdiction I am in and familiar with. The FAA (and I assume the other similar organizations) have a variety of guide lines for airplane interiors and its generally on the owner/operator to get them certified. However manufacturers may elect to get an interior configuration certified so that they can sell complete aircraft. As for regulations there are plenty of them, you may want to check this out as well as this and also this. The FAA generally looks at evactuation times (how long it takes every one to get out of the plane in the event of a crash) as well as certain aspects of the seats and restraints. Generally speaking they also look at the materials for their flamability.

One of the biggest interior policies of recent years was the move to "16G Seats" over the older seats. However as long as the seat is an approved 16G seat it can be used.

This is a nice summary of some of the research the FAA has done on cabin safety and its components.

As far as I know the FAA will let you submit just about any layout as long as it passes their flame, evac, and safety regulations. With the popularization of large private planes interior options are pretty much limitless.

On larger planes there are some things that may be fixed like the bathroom and galley since that requires plumbing and electric to be run but its more than likely they can be moved if requested.

There have even been talks of standing room only sections of airplanes but the regulators put a hard no to that as of now.


How does one address a first officer in conversation? If I am just deplaning a commercial flight and I see the captain (4 bars on the epaulet) and want to thank him/her for a safe and enjoyable flight, I would say "Excuse me, Captain, thanks for the nice flight".

However, if I were to encounter the first officer (3 bars), how should I address him or her? "Excuse me, First Officer...?"

Presumably not "Hey co-pilot!" :)

Call the FO 'Captain' anyway.

Both crewmembers are equally rated in the aircraft.
The FO might have more time in the aircraft than the captain or even have been a captain at a previous airline, but is sitting in the right seat because of low seniority at this carrier.
Nobody minds being referred to by a higher title.
You're a passenger, no one expects you to be able to read the bars on their uniform anyway.


Will I have to do a checkout ride at a rental place if I'm already familiar with the aircraft type? I've done my training and checkride on Piper Archer (PA-28A). Will a rental place make me take an checkout ride with an instructor if I wanted to rent the same plane model?

Generally they will make you do a checkout with their own instructor, at least this is the situation I have always encountered when renting from various places. Generally speaking, when you go to a new rental place they will audit your log book, put you in their system and make you fly with one of their instructors for a few reasons:

While your license was issued, presumably legitimately and your log book may be full of hours that are presumed to have occurred they still want to make sure you can do what you say you can.
Generally their insurance will require it. At least this is what I have always been told by FBO's/Flight Schools. Both of the places I fly out of, even require a recurrent 90 day checkup with an instructor to be able to keep renting (no matter how much you fly).

One thing to note is that none of these are FAA regulations, so you are legal to fly the PA-28 as long as you have your bi-annual and TO/LD requirements filled. The rental shops can how ever impose other rules as they see fit (mine does not allow flights to grass strips with the rental planes).

Note: some rental shops may also have differing gap policies on their insurance. It's worth asking about this up front and seeing if you need to carry any gap insurance.


What is the correct way for pilots to say the time? While listening to Air Crash Investigations, the pilots used the 24-hour format in a different way than we do.

Example: 07:57 hrs would be said as oh-seven-five-seven hours (which makes it a little confusing as one might think of them as co-ordinates) instead of saying 7-hundred and 57 hours.

What is the correct way for pilots to say the time?

"Zero seven five seven" is the correct way to state the time, pronouncing each digit separately per the table below.

Aircraft call signs are sometimes grouped instead of annunciating each digit, for example United 6330 would be "sixty three thirty" instead of "six three three zero".
 Otherwise, headings, time, coordinates, and all other numbers used in aviation radio communication are generally spoken individually, digit by digit.

It is important to note that in aviation the need for clarity overrides common English usage.  For example, while it is common to pronounce the number zero as "oh" in the everyday world, aviators are taught that zero and O are distinctly different:  One is a number, and the other is a letter of the alphabet.  They should never be substituted for one another, or used in the wrong context.

Finally, the example you offered is incorrect because it isn't "seven hundred and fifty seven hours", past time zero, rather it is "seven hours and fifty seven minutes".  (Except it isn't said like that...)


Which system on the 737NG decides the use of roll spoilers? Which of the 737NG systems decide to use roll spoilers? FMC? Some other flight surface controller? Does it trigger when airspeed is low?

That would be the "spoiler mixer". See this document, refer to pages 3, 4 and 20.


In a dogfight, can a pilot shoot down a parachute? Forgive me if my question sounds more like a rule of engagement for aerial combat than aviation technique. I was wondering that is it ok, in a dogfight, for a victorious pilot to shoot a defeated pilot's parachute to kill him. Are there any records of this type of event?

You question is a question of rules of engagement. Shooting down a downed pilot in a dogfight is not only not OK, but also illegal.

According to Article 42 of Geneva Conventions,

  No person parachuting from an aircraft in distress shall be made the object of attack during his descent.

Of course, war is war and this kind of attacks have been practiced by pilots of almost all air forces, though it should be noted that in most cases, this practice was specifically prohibited by their high commands.


Why aren't there direct flights connecting Honolulu, Hawaii and London, UK? London is by far my favorite city, and many people in Honolulu apparently feel the same. An old poll (5-6 years ago) said that 50% of polled people would go to London on that flight if it existed. The airlines are quite definitely aware of this, as Hawaiian Airlines responded a year later by saying they would make a direct flight. But it never happened, and no one has heard anything from them on the issue since. (This was more than four years ago.) I have considered the following:

Capabilities of planes (More than capable of making the flight)
Popularity of flight (The poll)
Flight restrictions (None)

After my pondering, I have concluded that there should be no problems connecting the two popular destinations. So why are there no flights? They would mean certain profit for the first airline to offer the journey. (They could charge whatever they wanted to.)

Simply, because no airline has determined the route makes economic sense.

A poll doesn't necessarily translate into a ready market of passengers. Sure, lots of people might check a box on a survey saying they'd like to see such a thing, but does that really translate to thousands of people actually a significant sum of money for the service? Would enough of them travel frequently enough at a high-enough price point to make the service worthwhile? There's no guarantee of "certain profit," and considerable money could be lost investing in such a route if it turns out not to be a success. A few reasons why it might not be a slam dunk:

Some passengers already travel between London and Hawaii, through connecting flights. A non-stop flight might cause more people to fly this route, but it would also cannibalize existing business from the connecting flights, meaning you'd need to get further customers to make up the difference.
LHR-HNL is about 7,200 miles. As you note, this should be within the capabilities of long-range aircraft, but we'd still be talking about a flight on the order of 16 hours. This is quite the distance. Would enough passengers want to travel this long between the cities? To put it another way, are passengers willing to travel that long also willing to endure a bit longer of a journey by making it a connecting flight?
The airline operating the route needs aircraft capable of such long flights. If they don't already operate a suitable aircraft, they need to acquire some and train pilots and mechanics and ground staff, an operation that takes years and hundreds of millions of dollars.
Hawaii is generally considered a leisure destination, and it's generally a fairly expensive one at that. Londoners have access to lots of rather inexpensive flights on low-cost-carriers to beach resorts within at most a few hours flying time. Many are in low cost of living countries where accommodation is fairly cheap. Tenerife, Greece, Southern Spain, Mallorca, Cyprus, and a number of Eastern European destinations are all rather accessible, and operators frequently offer packaged trips. Such destinations may not be exactly the same as all the splendor of Hawaii, but they're much cheaper and don't require 16 hour flights to get there.
Will the route be popular with business travelers? Keeping such a service profitable is far easier if you have a regular stream of business travelers between the two cities, especially if they're willing to pay for premium cabins and last-minute bookings. Ultra-longhaul flights without a large supply of business travelers just don't work.
Landing slots at Heathrow, the most logical place for such a flight due to its connections, are in very short supply and thus quite valuable. This further increases costs.
Ultra-longhaul flights work best when they're connected with an extensive route network, so they can receive feeder passengers from and carry passengers to other connecting flights. That's why they generally serve major airline hubs. Honolulu, because of its location, isn't an ideal high-density hub. Its main links are to other Hawaiian and Pacific islands, along with the US West Coast and East Asia, generally to cities that are already served by direct flights to London. As such, adding such a flight would not be that useful in helping an airline build its network. In addition, if Hawaiian were to operate the route, it would need to develop partnerships with European airlines to build a route network there (so as to facilitate booking, of say, HNL-LHR-CDG), a process that could involve lengthy and expensive negotiations.
Is there significant air cargo demand? A very profitable cargo route may help make up for lower passenger demand, but is there a lot of demand to ship cargo between the two cities? The amount of cargo payload you can take also depends on the aircraft you choose. Some aircraft do have the range to make the flight, but would have payload restrictions, which reduces profitability. Larger aircraft may have more capacity, but may be harder to fill.

Also, according to this forum post, a service was operated in the early 80s (with a fuel stop), and it was rather unpopular and thus unprofitable.

All that said, ultimately, all we can do is speculate. Airlines study potential routes extensively, but they don't release their internal numbers. If one thought it made economic sense, they would introduce the new service.


What aerodynamic characteristics arise from trailing edge sweep angle? I drew 3 wing planforms, each with the same leading edge sweep. But they have different trailing edge sweep.

Let's just assume for the moment that all those wings have the same surface area, so that they all have the same total lift. What would be the different aerodynamic characteristics due to the trailing edge sweep angle?

Note: let's leave out considerations of control surfaces. Obviously the first wing would have the easiest implementation of control surfaces, but I want to focus on what the static wings do.

I looked into this and that related question. IMHO they're not quite the same thing as what I'm asking here.

One aerodynamic behavior appears at high angle of attack : dihedral or anhedral wake, which affects (in some weird mixture) both roll and yaw stability. Forward swept trailing edge is much more stable than backward swept trailing edge.

Some jet fighters (let's say F-22) and most aerobatic airplanes (let's say SU-31) adopted forward swept trailing edges in order to increase stability at high AoA.


Does Qantas have an above-average safety record? There is a widespread belief, at least within Australia, that Qantas has, or had, an above-average safety record. For example, AirlineRatings.com recently listed Qantas as the world's safest airline, which was reported on by the Australian Broadcasting Corporation and Fairfax Media. Personally speaking, it seems like aircraft incidents with Qantas or JetStar get more coverage than those involving other airlines, but I can't verify that.

I'm skeptical of the belief that Qantas has an above-average safety record, let alone being the safest airline in the world.

From the Wikipedia article List of Qantas fatal accidents, I know that Qantas hasn't had any fatal jet airliner incidents, and the last accident it had was in 1951. However, I don't know whether aircraft accidents are so rare that an airline can have a better average than others because of chance alone.

I'm not doubting that some countries have safer airlines than others. If offered the choice between Qantas and Air Koryo, I'd definitely choose the former. I also don't doubt that some countries are safer to fly in than others - for example, planes in Australia don't have to deal with snow very often. However, I don't expect that to be a major factor. So I'm ultimately interested in a comparison between Qantas and airlines from countries that are comparable to Australia.

Did Qantas have a perception of having an extraordinary safety record before the 1988 movie Rain Man, where the titular character said that Qantas never crashed?

Is there enough data to say that Qantas is the safest airline in the world, or even say that it's safer than similar airlines, such as the ones Raymond refused to get on in the movie?

Defining and Measuring 'Safety'

These ranking depends how you define safety. Here is your problem: You can easily do this by widely publicised facts, such as well documented fatal accidents. Fatal accidents occur much much too seldom to with any statistical confidence to say how safe an airline is.

What you would much rather do is go by accidents and incidents (the little things that occur everyday and give you a feeling for how stuff is done and handled). For instance: hydraulic leaks, loss of separation to other aircraft or electrical problems prompting a return. A small selection of these are reported on the popular site Aviation Herald, but this is (emphasis) only a small subset that happen to come through. Some western countries with the objectively the best safety are over-reported since they are just better at documenting. You'll find heaps of entries on 'fume events' on Airbus aircraft from Germany for instance.

These are considerably harder to collect, since how they are classified and reported changes by country and aviation agency. Some publish for common good, other ones barely collect them. For this reason, the way these 'rankings' do it is by fatal accidents and other easy to get parameters. This is eventually what comes through to newspaper sites with little detail on how they were put together.

The parameters measured by AirlineReports:

Is the airline IOSA certified?
Is the airline on the European Union (EU) Blacklist?
Has the airline maintained a fatality free record for the past 10 years?
Is the airline FAA endorsed?
Does the country of airline origin meet all 8 ICAO safety parameters?
Has the airline's fleet been grounded by the country's governing aviation safety authority due to safety concerns?
Does the airline operate only Russian built aircraft?

Most of these are bare minimums that can be expected from an airline, but do not really go to any distance to show who stands out. For any more detailed sense and purposes (how media are using it), I'd call this useless.

Also note that this does not include the liability question for fatal accidents- who was at fault? You can finally also (albeit unlikely) have a completely safe airline that does not have a single certification.

Qantas

Qantas has had two very serious incidents with a Boeing 747 and A380. They also had a serious incident on involving A330 losing altitude. This does not really IMHO award them as the 'safest airline' for the past few years, since this is considerably more than a lot of other airlines have experienced.

However, for all practical sense and purposes, they are as safe as any other airline. The chances of anything happening are just so incredibly remote that it's not worth the trouble of thinking about it. Getting a connecting flight to fly with another airline will probably be less safe than just flying them directly.

As for the maintenance matters, Qantas owns JetStar and they appear to use the same maintenance facility for their aircraft. A further difference is the training where there appear to be overlaps as well, so there are only small differences on perhaps the most important parameters differing the two.


Are CVR and FDR reset after every flight? Recording the thousands of parameters and voice conversations must take a huge amount of storage, and so I am wondering, how frequently is this data "deleted", so it can be used again?

For example, after every successful flight, is the CVR and FDR data deleted or it records maybe 10 flights or so, and then is reset?

No, they are not reset after each flight, but as commented, the FDR and CVR are on a loop, and just keep recording over the old data. For US registered aircraft, FAA Regulation "14 CFR 91.609" covers flight data recorders and cockpit voice recorders.

It states for flight data recorders:

  (c) 1. No person may operate a U.S. civil registered, multiengine, turbine-powered airplane or rotorcraft having a passenger seating configuration... of 10 or more that has been manufactured after October 11, 1991, unless it is equipped with one or more approved flight recorders that .... are capable of retaining no less than 8 hours of aircraft operation.

And:

  (c) 3. All airplanes and rotorcraft subject to (the above)... manufactured on or after April 7, 2010, must ... retain at least the last 25 hours of recorded information...

For cockpit voice recorders:

  (h) 2.  All airplanes required by this section to have a cockpit voice recorder and a flight data recorder, that are manufactured before April 7, 2010, must by April 7, 2012, have a cockpit voice recorder that also ... retains at least the last 2 hours of recorded information ...

There are not "thousands" of parameters.

The CVR must record the following 25.1457 (Cockpit voice recorders):

  (1) Voice communications transmitted from or received in the airplane by radio.
  (2) Voice communications of flight crewmembers on the flight deck.
  (3) Voice communications of flight crewmembers on the flight deck, using the airplane's interphone system.
  (4) Voice or audio signals identifying navigation or approach aids introduced into a headset or speaker.
  (5) Voice communications of flight crewmembers using the passenger loudspeaker system
  (6) all datalink communications

So, probably 6 or so channels.

For the FDR, wikipedia states "There are 88 parameters required as a minimum under current US federal regulations (only 29 were required until 2002), but some systems monitor many more variables."

So, if the flight lasts less than two hours, there will be at least the whole flight on the CVR. But if the flight is longer than two hours, you only have the last two hours.


What is this tube-like thing protruding from under an A330's wing? I took a flight for a business travel and I saw something new for me on the wing. I highlighted that part in a red circle in the picture below. The aircraft is an Airbus A330-200.

What is it and its function? I know the anti-shock bodies and static wicks, but what's that?

As a contrast, there isn't such a thing on this other aircraft, an A320, except a static wick.

It is the port for mid-air fuel jettison.

(Image credit: http://opilotoprofissional.blogspot.hk/2011/08/consideracoes-sobre-overweight-landing.html)

The A330 is a long range airliner, capable of serving flight routes that are 10~12 hours long. It is equipped to dump fuel while in-flight to reduce its landing weight.

The A320 is not a long range airliner, thus there is no need to install such equipment on it.


How can a part 91 operator gain authorisation from the FAA to perform RNAV (RNP AR) approaches? How would an individual pilot operating under Part 91 in a light aircraft with a future "glass cockpit" setup (maybe Garmin will add it to the G2000?) capable of coding and flying RNAV (Area Navigation) and RNP (Required Navigation Performance) approaches with the necessary precision and accuracy (incl. Radius to Fix legs) go about gaining authorization to fly them?  Or would such a system require a blanket authorization from the FAA that says that "all users of such-and-such system flying under Part 91 are authorized to fly RNP approaches using the procedure in the system manual"?

I have no practical experience with FAA RNP AR authorization but the guidelines for obtaining RNP AR authorization from the FAA are described in FAA Advisory Circular 90-101A (FAA PDF). The whole process to go through is described in that document. It specifically mentions Part 91 and Part 91K (fractional ownership) so it should be possible to obtain permission for individual pilots.

However, it will not be easy for an individual pilot to meet the requirements.

You will have to perform a high number of RNP AR approaches under a provisional authorization in VMC or increased minima before final authorization is granted.

Luckily the FAA made provision for operators with a small fleet:

  NOTE: In unique situations where the completion of 100 successful
  approaches could take operators an unreasonably long period of time
  due to factors such as a small number of aircraft in the fleet,
  limited opportunity to use runways having appropriate procedures,
  etc., consideration of a reduction in the required number of
  approaches will be on a case-by-case basis. The FSDO/CHDO will
  coordinate with FAA HQ in consideration of an operator’s request for
  reduced interim authorization requirements.

You will need to arrange proper training:

  Initial training: With no prior RNP AR approach experience,
  each pilot
  must complete at least four RNP AR approach
  procedures: two as pilot
  flying and two as pilot
  monitoring.These four RNP AR
  approaches shall employ the uni
  que AR characteristics of the
  operator’s approved procedures (i.e., RF legs, RNP missed). You must fly two approaches to the DA and two approaches must result in an RNP missed approach procedure. Two of the above approaches will include interrupted approaches resulting in one approach with vectors to resume the approach and one approach resulting in a hold at an initial approach fix (IAF) or transition
  fix.

And in addition to the a qualifying aircraft the operator must have a program to ensure data the navigation database stays up to date and is of sufficient quality.

You will also need to implement a monitoring program to review your RNP AR approaches and detect any negative trends. Results from this program will need to be shared with the FAA on a monthly basis.


Have there ever been any JATO bottles using only kerosene? I've been reading about the early rocket work during WW2. They tried all sorts of fuels, hydrogen peroxide, hydrazine, red fuming nitric acid...

Just in the scope of JATO/RATO, has there ever been one working just with kerosene? The airplane would accelerate normally to sufficient airspeed such that enough oxygen was flowing, then the JATO would ignite. This would then boost the aircraft very rapidly up to a high altitude.

I think this could be called an afterburner all by itself (without the turbojet lol), or maybe even a ramjet all by itself. Whatever you call it, it has no moving parts other than a fuel pump. So I am wondering if this concept was ever tried during WW2 or shortly thereafter.

(P.S., surprised there is not JATO tag, nor RATO tag. I will create it but also use "takeoff" for visibility purposes.)

A RATO unit's purpose is to give a high impulse very quickly, it does this by combining a fuel with an oxidizer causing rapid combustion in a chamber, and forward thrust from the equal and opposite reaction. Kerosene is a fuel, but without an oxidizer you don't have a rocket, you have some lamp oil burning. If you wait until the airplane is moving then it's lamp oil burning in a wind, giving you no benefit.


How many commercial jetliners are equipped with ADS–B? The Wikipedia page for Automatic Dependent Surveillance – Broadcast (ADS–B) explains that the aircraft surveillance technology is being phased-in around the world currently, with some due dates in 2017 and 2020 and so on. I see organizations like FlightAware.com are deploying their own ADS-B receivers and are crowd-sourcing data from homemade receivers as well. That leads me to wonder…

How many commercial airliners are currently equipped?

Any reports or estimates by airline or by country/region?

Also: Are private jets being equipped? Are small aircraft being equipped?

The majority of commercial airliners are currently equipped. I don't have the latest statistics, but for Europe over 80% of the airliners were equipped with 1090 Extended Squitter ADS-B two years ago. The percentage in the USA was similar but a bit lower.

That doesn't mean that all those aircraft are compliant with the European rules that mandate ADS-B for these aircraft from 2020 onwards. To be compliant, the aircraft need to have ADS-B version 2 (EUROCAE ED-102A / RTCA DO-260B compliant transmitters) and the installation in the aircraft has to meet certain criteria. At this moment (May 2016) I estimate the percentage of rule compliant airliners to be less than 20%. I haven't run statistics on my own dataset for a while, I may update this figure over the summer.

In Europe, all aircraft heavier than 5700 kg maximum take-off mass or a maximum cruise speed exceeding 250 knots true airspeed are subject to the ADS-B rule.
Therefore private jets and some small propeller aircraft will need to equip with ADS-B as well. In addition many people voluntary equip their aircraft with ADS-B; it is not uncommon to see ADS-B equipped gliders in Europe.

The situation in the US is a little different. The FAA mandate requires aircraft flying in certain airspaces to equip with ADS-B. In my view this makes more sense since it will prevent a mix of equipped and non-equipped flights in one airspace.

In the USA, two types of ADS-B are allowed. The 1090 ES is required above 18 000 ft, below that altitude Universal Access Transceiver is also allowed. This causes all kinds of interoperability problems that can only be fixed at high cost.

The FAA mandates aircraft in the 48 contiguous states (and D.C.) that operate in class A, B, or C airspace or class E airspace above 10 000ft (class E airspace below 2500 AGL excluded) to be ADS-B OUT equipped by January 1st, 2020. The mandate itself can be found here and the associated Advisory Circular (AC90-114) can be found here.

This means many more aircraft are subject to the rule. I have no recent information on what the implementation status is.


Why do propellers on aircraft have a slight offset angle? Single-engine aircraft (one propeller on the 'nose')

Why do propellers on aircraft have a slight offset angle? I have picked up this information that the rotational axis of the propeller is not aligned with the roll axis of the aircraft, but I don't know why and by how much it is off. I also don't know the direction in which the propeller's rotation axis pointing (other than 'roughly' in roll axis direction).

Is the direction of the propeller's rotation axis important?

Does the direction of the propeller's rotation have any influence on it?

How big are these angles between aircraft roll axis and propeller rotation axis typically?

Is this concept only useful for propellers?

The direction of rotation of the propeller introduces an asymmetry which designers try to mitigate by adding more asymmetries. Specifically, a right-turning tractor propeller (clockwise from the pilot's viewpoint) will swirl the propeller wake in the same direction which adds a negative sideslip angle on the vertical tail (which sticks up into the upper half of the wake only). By pointing the axis of rotation of the propeller slightly to the right (right sidethrust), this sideslip angle can be reduced.

Other means of correction like an incidence on the vertical tail would not work equally well: Once the engine is throttled back, such an incidence would require to re-trim the aircraft.

On multi-engined aircraft a sidethrust can help to reduce rudder input in engine-out cases. Here each wing engine points slightly away from the fuselage so its thrust will pull the aircraft into a helpful sideslip when the opposite engine has failed.

The propeller axis can also point slightly down in order to move the thrust line closer to the center of gravity, reducing thrust-related trim changes, and to reduce the P-factor effect (sideways shift of the thrust vector) at high angle of attack. This is called downthrust. One example would be the RR Griffon-engined version of the Supermarine Spitfire: When the new engine was installed, its lower thrust line required 2° more downthrust.

This is one of the few topics where the English version of Wikipedia stays schtum; only the German version has an article on it (Motorzug and Motorsturz).


What prevents fighters from being fitted with jetliner-style bleed-air wing anti-ice? In a comment, John K points out that:

In any case, military fighter aircraft have to avoid icing, which is kind of odd for those that are considered "all-weather" interceptors..

This, to me, raises the question of "why would you omit wing anti-ice from a supposedly 'all-weather' aircraft?"  Especially on a larger fighter like a F-15 or Su-27, it seems to me that the weight penalty for a couple of piccolo tubes, two butterfly valves, and a bit of extra bleed ductwork would be fairly minimal relative to the weight of the aircraft and payload, or am I wrong on that?  Or are there aerodynamic or engine-performance reasons that prohibit fighter jets from using bleed-air anti-icing, or some other anti-ice system for that matter?  I've also heard the saw that "fighters don't need anti-ice because they can simply fly fast enough to use ram rise to deal with icing", but could there be other reasons they couldn't fly in icing, such as not having heated pitot/static systems or inlet anti-ice functions?

Most fighters have enough thrust to power through icing conditions, so anti-icing or heat is limited to inlet(s) and pitot probe(s). That said, at least one F-16 flight manual, to use one example, says the following about flying in known icing conditions:

Flight in areas of icing should be avoided whenever possible. If icing
conditions are anticipated or cannot be avoided, turn ANTI ICE switch
to ON and PROBE HEAT switch to PROBE HEAT. Frequently check the
aircraft leading edges for indication of ice buildup. Make all
throttle movements slower than normal when in potential icing
conditions to reduce possibility of engine stalls and/or stagnation.
Consider diverting to an alternate field if required to avoid icing
conditions.

The F-14 also had the same systems, engine inlets and pitot probe heat. No other anti-icing systems on the aircraft.


Reduction in Service Ceiling / Change in RVSM I did some research and minimum vertical separation used to be 2000ft but it changed to 1000ft in 2002 and they want to change it to 500ft on american territory. Is this correct? Why they wouldn't change it to 500ft on European territory also ?

2nd question:if aviation is evolving yearly, then airspace is getting more and more crowded. there is Concorde who has retired but used to fly at 60.000ft for example, why instead of designing new aircraft to fly higher, they would reduce the service ceiling ? I heard that from an engineer but I don't find an explanation. Statistically, they are reducing the service ceiling. Can anyone give an opinion? example? Thanks.

1(a). Yes, in the US, below 18,000 feet and above 3,000 feet, airspace seperation is 500'.

3,000' and above to 18,000 feet:
IFR traffic, eastbound fly at odd thousands
VFR Traffic, eastbound fly at odd thousands + 500'
IFR traffic, westbound fly at even thousands
VFR traffic, westbound fly at even thousands + 500'

(I always figured that was because "east is even" would be too easy to remember.  JUst like Nav lights, red is in the left because "red on the right" would be too easy to remember. Red/Green is likely a carryover from boating tho.)

1(b), I don't know about Europe.

2 I believe service ceiling is more a factor of jet engine efficiency and aircraft drag.  Piston engine's need to be turbocharged or turbonormalized (make sea level power at altitude) to make the high teens need to make air denser for the engine to make power - if you can get up there, the drag drops a lot and you can go a lot faster.  Jets are big compressors in essence and can make all the dense air they need to burn jet fuel with.

Why don't more jet arcraft fly higher? Maybe it's not worth it drag reduction-wise, or time savings enroute-wise, to climb higher and then to descend back down.


What's the difference between 'Go Around' and 'Pull Up'? We use on the standard RT (radio telephony) Go Around. But what's the difference between Go Around and Pull Up?

Going around is a process, pulling up is an action. When ATC tells you to go around or you say you are going around it means you are initiating a set of actions to abort an approach. Pulling up is a single action, i.e. increasing the angle of attack in order to climb, and would be part of a go-around procedure.

Pull up is a non-standard phrase, in most parts of the world at least, but you might hear it as 'pull up and go around' in Canada. It also might be used in urgent situations to urge a pilot to act to avoid an obstacle or collision.


What materials form the structural elements of the Boeing 737? What materials form the structural elements (leaving the spars, ribs etc) of the B737?
It was tough to get any information on the kind of composites used on the 737 structure. Hoping to get some information on that.

Most of the Boeing 737's structure is made in aluminium. Composites are used for smaller parts like the ailerons, the wing-to-body fairings and the tail cone.
It looks like all of the control surfaces are composites.

Medium capacity airliner series. Aluminium alloy wing structure, upper skin and tail plane, with graphite composite elevator, rudder and ailerons. Glass or carbon fibre-reinforced plastic nosecone, fairings and fin tip. Single or split-scimitar double winglets.

more composite components:
The nosecone, wing and fuselage fairings, fin tips, the fairings of the flap actuators and other non-stressed components are constructed from glass and carbon fibre reinforced plastics (GFRP and CFRP). The rear of the engine nacelles are constructed of graphite, Kevlar and glass fibre composites.
In February 2000 an advanced carbon graphite winglet developed by Boeing became available as an option on the 737-800.


Will portable Stratus ADS-B In receivers operate normally from the passenger cabin of a commercial airliner? Are ADS-B In receivers such as Stratus or Stratux permitted to be used along with other portable electronic devices at cruise altitude on commercial airliners? Will they receive GPS and ADS-B signals in the passenger cabin to be able to track progress on ForeFlight, for example?

Source: Appareo

The receiver will work in the cabin but the reception is really poor. GPS will only work if it has enough satellites in view, so a window seat is best. The signal is severely attenuated by the windows.

I have brought ADS-B receivers with me on various flights but in my experience you will not get a proper ADS-B signal from aircraft further than about 20-30NM away.

Whether it is permitted or not depends on the airline and the country of operation.


What steps have been taken to rule out instrument failure due to blocked static ports or pitot tubes? In the case of Aeroperu Flight 603, a fatal crash was caused by duct tape that was accidentally left over some or all of the static ports on the underside of the fuselage after the aircraft was cleaned. As the static ports are critical to the operation of virtually all of those flight instruments that provide aerodynamic data regarding airspeed, altitude and vertical speed to the pilots and to the aircraft's computers, this bit of duct-tape caused the total failure of multiple basic flight instruments.

Another crash was caused for a similar reason: pitot tubes that were blocked by an insect led to flight instrument failure, and later, a tragic crash. This was Birgenair Flight 301.

These accidents happened in the mid-1990s. Today, two decades on, are there better systems in place to ensure that static ports or pitot tubes don't get blocked, causing instrument failure?

Edit 1: In both these flights, the pre takeoff checks missed out on the blocked static ports/pitot tubes. Human error clearly happened at this stage. Question is, have an steps been taken to make the flight instruments proof to this particular human error?

The best thing way to mitigate an issue like this is to draw attention to during the preflight check. Its becoming common to use covers that have a nice big red "Remove Before Flight" tag on them. These should be used as much as is practically possible (storage, cleaning, maintenance etc.)

Something like this would do nicely.

(source)

Similarly the aircrafts paint may be done in such a way to make the port stand out.

(source)

Caps/Covers for both static ports and Pitot Tubes are generally a good idea and can help prevent a clog that occurs while the plane is on the ground. As with anything diligence during preflight is key to avoiding this issue.

Most larger aircraft pilots call out "airspeed alive" during their takeoff roll as a way of confirming the Pitot system is working. If the air speed indicator does not read, the general procedure is to abort the takeoff.

Some aircraft may also be equipped with a radar altimeter which can help mitigate serious issues by providing an altitude system not based on the static system. However this only works at lower altitudes.


What should I expect to happen when I get on a skydiving flight I am schedule to go on a short flight (skydive)* on a Cessna 208B Grand Caravan during an international visit to some friends. I found the serial number of the flight, here is it's record.

Since privately owned aircraft within skydiving community are known not to be maintained as well as commercial operations and sometimes these pilots have very little flying hours, is there anything I as a passenger can do to improve the safety of the flight? For example, what pre-flight checks should the pilot make before taking-off?

Note* Related to this question.

is there anything I as a passenger can do to improve the safety of the flight

You should do exactly what your told, when your told and make sure you keep well clear of spinning propellers. You will have a marshall or the pilot themselves guiding you when airside - do exactly as you're told!

  what pre-flight checks should the pilot make before taking-off

If it's the first flight of the day the pilot will do a walk around of the aircraft. They will check the general airframe, as well as some specific things

The static ports being clear
Pitot covers/control locks all removed (those little red dangly things that say "remove before flight")
Control surfaces have free movement and their connecting rods are secure
Tyres & brakes satisfactory
Fuel is sufficient and uncontaminated
Propeller(s) undamaged
Oil sufficient in engines
... and a load of other things!

Before each take-off the pilot will also run the engine up and run it at idle. Just before take off they will perform some pre-takeoff vital actions. You will probably not notice any of this, but I assure you they'll be doing them - they may take mere seconds.


What is this piece on the Bell 206? I asked this question which led to another question of mine, What it the long rod just past the top of the nose of the Bell 206B helicopter and what is it's purpose?

If you are referring to the angled pieces above the front window, and below the nose; they are referred to as the WSPS (wire strike protection system). Designed to shear a line before it wraps around the landing skids or rotor.

Related post: Is special equipment required to perform high-voltage line inspections?


Why use a single engine plane instead of a multi engine one for a long range flight record? Tupolev ANT-25 was designed specifically for setting flight range records. In 1937 two flights from Moscow, Soviet Union to USA via the North Pole happened - one covered 9130 kilometers and finished in Vancouver, Washington and another covered 11500 kilometers and finished near San Jacinto, California.

ANT-25 had a single V-12 piston engine. This sounds kinda not very redundant - should a single engine fail while the plane was crossing Arctic there was good chance the flight would end there and maybe the crew would not be rescued because simply reaching there would be problematic.

Why was a single engine airplane selected for this specific task where reliability was very important?

As said in the comments, in a distance record aircraft you want to keep the drag and mass of your aircraft as low as possible. The previous and next record were flown in single engines too and risk assessment was a bit different back then.

Using a single engine for such long distances wasn't the only ANT-25 characteristic you wouldn't see in a normal airplane: the engine was underpowered (only Russian production engine available?) and for record flights the whole aircraft was even lack-stripped in order to weight less.

For emergency landings in the arctic they had skis, tents and other gear stored in the wings.

In the case of having to land on water they would jettison part of the fuel and inflate some kind of balloons which were inside the wings. That way the wings could be used as floating bodies and prevent water from entering. After water-ditching with retracted landing gear the aircraft could apparently stay afloat for a long time.

If you're interested in further details this biography of Pavel Sukhoi describes the project thoroughly in one of the chapters.


Why do many ram air inlets have this shape? I often see this particular shape for ram air inlets.

Here on an older 737

It's stretched on the newer 737's but still the same basic shape

A also see it a lot on cars.

1979 Camaro Z28

Lamborghini Countach

Is there some aerodynamic advantage to this shape, and if so why?

Those are called NACA inlets or NACA ducts. As wikipedia mentions:

  When properly implemented, a NACA duct allows air to flow into an internal duct, often for cooling purposes, with a minimal disturbance to the flow.

So yes, there is an aerodynamic advantage.
As for the "why", if you're in the mood, you can have a detailed look at the original report (I'm not able to properly summarize it).


Do lighter-than-air aircraft communicate with ATC? Do lighter-than-air aircraft communicate with ATC? If not, how do they avoid running into other aircraft?

Short Version:

No aircraft is required to talk to ATC, except in certain situations.  Whether or not they have a radio, all pilots are required to continuously watch outside the airplane for other aircraft and to avoid them visually, much like someone driving a car avoids other cars by looking for them.

Long Version:

Aircraft are required to communicate with ATC only in certain situations.  14 CFR 91 contains the requirements:

91.126 - Within 4 miles and 2,500 ft of an airport in Class G Airspace
91.127 - Within 4 miles and 2,500 ft of an airport in Class E Airspace
91.129 - Within Class D Airspace
91.130 - Within Class C Airspace
91.131 - Within Class B Airspace
91.135 - Within Class A Airspace
91.155 - In weather conditions less than VFR
91.183 - While operating IFR
91.511 - More than 1 hour flight time or 100 miles from shore (overwater)

Many of these can be  waived with prior coordination with ATC.

Outside of the above situations, no radio is required.  In fact, there are still many airplanes that don't even have an electrical system, much less a radio, and they are perfectly legal to go fly around.

On the other hand, if they do have a radio (even a hand-held radio) it can greatly add to the safety of flight if they remain in contact with ATC since they can point out traffic that they might not have seen as quickly otherwise.

Now, whether or not the pilot is talking to ATC, they are required to "see and avoid" other aircraft, and certain aircraft have the right of way over other aircraft.  As you can imagine, an unpowered balloon can't really get out of way of a 747, so it is the responsibility of the more maneuverable aircraft to turn to avoid hitting the less maneuverable one (see 91.113 for more details).

They are also required to remain a certain distance away from clouds (91.155).  This is so that one aircraft doesn't come out of a cloud, possibly at a very high speed, and run right into another aircraft because they didn't have time to avoid them.  If they are far enough away, then the pilots will have time to see and avoid each other.


Why does the MH370 ATC transcript never mention QNH? When is QNH given to aircraft? Looking at the ATC transcript from MH370, I noticed that nowhere is the QNH communicated to the aircraft. That seemed odd to me... it seems that every time I talk to a tower or airways they tell me what the QNH is in their location.

So, is it normal for airliners to not be told what the QNH is before takeoff? Or in communications with DEPARTURE or RADAR?

Airline pilots generally get the QNH from the airport ATIS or similar. If they don't get it from there, ground control will give it before taxi.

Above the transition level (11,000 feet (3,350 m) in Malaysia, 18,000 feet in the US), the altimeter is set to the standard pressure (29.92 inHg, 1013 hPa), also referred to as QNE. It doesn't take that long to climb through this point, so they would keep the departure QNH set until reaching the transition altitude. They won't need to set it again until they begin their descent near their destination.

So after setting it before taxi, the next time they would need it is on approach before they descend below the transition level. Again, they can get the ATIS from their arrival airport for QNH. If not, the approach controller will give them the QNH.


Which aircraft can fly at FL600 or above? I would like to know some examples of aircraft (specific models) which can fly at FL600 or higher.

I am interested in aircraft which can or could fly at that altitude on a regular basis (service ceiling included). Space exploration or launcher systems are out of the scope.

As far as I know, commercial airplanes cannot fly that high so I can only think of jet fighters, aerostatic balloons, and rocket-powered aircraft.

Commercial Airliners:

Both Concorde (service ceiling FL600) and the Tupolev Tu-144 (service ceiling FL660) could reach FL600. Most airliners have a service ceiling of around FL410 though.
Business Jets:

According to this article the highest service ceiling for various business jets is at FL510, so none can reach FL600.
Military Reconnaissance Aircraft:

The Lockheed SR-71 Blackbird had a service ceiling of FL850 and routinely operated above FL600. Many other aircraft in this category (e.g. MiG-25, Tsybin RSR, U-2, RB-57F, M-17 and M-55) can also fly above FL600.
Military Fighter Jets:

Most fighter jets have a service ceiling below FL600, but there are a few that can fly higher (e.g. F-15 and F-22 with service ceilings of FL650, the MiG-25 again, and  MiG-31 with the highest service ceiling of FL820+ for a fighter).
Experimental Aircraft:

Wikipedia has a list of altitude records, often by experimental craft. The 60,000 feet limit was surpassed around the end of the second world war with the advent of rocket and turbojet engines. Two notable achievements:

The rocket powered X-15 reached space twice. In 1963 it climbed to 67 miles, nominally corresponding to FL3530. Note that the X-15 did not self-start.

The glider (!) Perlan II has a service ceiling of FL900 and actually reached 76,124 feet. It utilizes standing waves forming at mountain ranges which under certain conditions can extend into the stratosphere. From wikipedia: "A sailplane at 90,000 feet altitude flies in approximately the same aerodynamic regime [...] to be experienced by a moderate size aircraft flying near the surface of Mars."

High altitude balloons and rockets can of course fly higher.


What are the US flight planning regulations for an alternate airport? As I read 14 CFR 91.169 literally, I understand an alternate airport listing waiver can be granted if the destination airport

Has at least one instrument approach procedure from an authorized source.
reports/predicts within ETA ± 1 hours, ceiling 2000 or higher, 3 SM or greater (1-2-3 Rule)

Q1) So one case, If we plan an IFR flight to an airport without any IAP, even if the whole area is SKC, we are legally required include an alternate airport?

As for the alternate airport qualifications, I get the following following flow,

Is there any weather reporting or forecast service at this airport?

Yes, Go to Step 2

No, return Unqualified Alternate.
Does the weather good enough for basic VFR descend from MEA, approach and landing at ETA?

Yes, return Qualified Alternate

No, Go to Step 3.
Does the airport have an IAP?

Yes, Go to Step 4

No, return Unqualified Alternate.
Is your airplane WAAS-equipped?

Yes, include GPS approaches in your candidate IAP pool. Go to Step 5

No, remove all GPS approaches from your candidate IAP pool. Go to Step 5.
Remove any IAP with unmonitored or inoperative equipments from your candidate IAP pool. Go to Step 6.
Find the alternate minimums for each IAP in your candidate IAP pool from Step 5, or if no alternate minimum is published apply 600-2 for precision approach and 800-2 for non-precision approach. Go to Step 7.
Compare the your lowest minimums from Step 6 with the weather report or forecast at alternate airport. Is your lowest minimums greater than the weather minima?

Yes, return Qualified Alternate.

No, return Unqualified Alternate.

Q2) Does this flow reflect the current FAA alternate airport requirements?

Q3) In an actual approach to the alternate, can we first attempt an approach that is different from the one we used to satisfy the alternate weather minimum planning requirement? (the one selected from Step 7 for lowest minimums). Technically, The IAP to use is not a required part of a flight plan.

It is important to point out that what follows only applies to flying under §91. Operations under §135 have a different set of requirements for alternates than those specified here in §91.169. Your question includes the general-aviation tag, which is poorly defined (at no fault of your own); the tag description given on this site includes all civil aviation other than §121 airline flights, but many definitions exclude charter, or even all §135 flying. In what follows I will assume flight operations conducted exclusively under §91.

Q1:
Yes, that is correct. An alternate is always required on the flight plan unless—among other things—the first airport of intended landing has an instrument approach prescribed under §97 or otherwise authorized.
Weather conditions also determine that exception.

Q2:
This is mostly true, but needs some corrections and clarifications.

There is no requirement for the airport to have weather reporting or forecast based at or provided specifically for that airport. The regulation merely requires "appropriate weather reports or weather forecasts". This could include weather information such as Area Forecasts or even TAFs or METARS for nearby airports.

Yes, this is accurate.

Yes, this is true when understood within the programing–type flowchart logic you use. However, just to be clear, lack of an IAP alone does not disqualify the airport as an alternate—see #2 and §91.169(c)(2).

No, not necessarily. AIM 1-1-18(b)(5)(c) clarifies that operators with non-WAAS equipped GPS systems can plan to use a GPS approach at either their destination or the alternate, but not both:

(c) For flight planning purposes, TSOC129() and TSOC196()-equipped users (GPS users) whose navigation systems have fault detection and exclusion (FDE) capability, who perform a preflight RAIM prediction for the approach integrity at the airport where the RNAV (GPS) approach will be flown, and have proper knowledge and any required training and/or approval to conduct a GPS-based IAP, may file based on a GPS-based IAP at either the destination or the alternate airport, but not at both locations. At the alternate airport, pilots may plan for:
(1) Lateral navigation (LNAV) or circling minimum descent altitude (MDA);
(2) LNAV/vertical navigation (LNAV/VNAV) DA, if equipped with and using approved barometric vertical navigation (baroVNAV) equipment;
(3) RNP 0.3 DA on an RNAV (RNP) IAP, if they are specifically authorized users using approved baroVNAV equipment and the pilot has verified required navigation performance (RNP) availability through an approved prediction program.

Note: TSOC129 and TSOC196 are the non-WAAS TSOs (as opposed to the WAAS TSOs: TSO-C145 and TSO-C146)

Yes, this is seen in AIM 1-1-18(b)(3)(b):

Ground-based facilities necessary for these routes must be operational.

Yes, this is true.

Yes, though I would say equal to or greater.

Q3:
Yes, the filed alternate—and the approach used to qualify it—are for legal filing purposes. In the actual flight, another appropriate approach, deviation airport, or approach at the deviation airport can be selected as needed.


Is it possible to takeoff without flaps extended? related questions:

landing wihtout flaps
takeoff with full flaps

My question focus on passengers jets (goes from Embraer E-jet family to  Airbus A380). I don't know why pilots would attempt to takeoff without flaps but lets say they will.

Considering all the other parameters are good enough (no crosswind, long runway, aircraft light enough,...) and the pilots are aware of this unusual takeoff configuration and adapt their action accordingly (including increasing $V_r$ and $V_2$), is it possible for any passenger jet to takeoff and stay airborn (not like the flight spanair 5022) without extending flaps?

Yes take-off without flaps is possible. The Airbus A300 and Boeing 767 are approved for such take-offs and it is being done regularly. It results in a better climb gradient, especially with one engine out. The one engine out climb gradient is an important and sometimes limiting factor in take-off calculations.

One important constraint is the length of the runway.

Another limitation, perhaps less obvious, is the maximum rolling speed of the wheels. The tires are rated to a limited speed which may be exceeded by a flap-less take-off.


What are the flight rules for crop dusters? Crop duster aircraft operate much differently than most other aircraft. Are there special rules that apply to their operation? Specifically, are there rules about how close they can fly to structures, terrain, or vehicles?

14 CFR Part 137 regulates agricultural aircraft operations, with §137.51 discussing operation over congested areas, including:

  The crop duster must operate “with maximum safety to persons and
  property on the surface” and the crop duster must have obtained prior
  written approval from the FAA and notice of the intended operation
  must be given to the public. Further, the crop duster must submit a
  plan to the FAA that considers the flight obstructions and plans for a
  possible emergency landing.

Of utmost importance is the section regarding the flying of restricted category civil aircraft such as agricultural aircraft:

  Sec. 91.313 — Restricted category civil aircraft: Operating limitations.

  (a) No person may operate a restricted category civil aircraft— (1)
  For other than the special purpose for which it is certificated; or

  (2) In an operation other than one necessary to accomplish the work
  activity directly associated with that special purpose.

  ...

  (e) Except when operating in accordance with the terms and conditions
  of a certificate of waiver or special operating limitations issued by
  the Administrator, no person may operate a restricted category civil
  aircraft within the United States—

  (1) Over a densely populated area;

  (2) In a congested airway; or

  (3) Near a busy airport where passenger transport operations are
  conducted.

  ...

More information is available in this FAA document.


Can anyone tell what kind or even which airplane this is? As stated in this post on the Dutch Police website (Google Translate English version) this morning (12th june 2018), they are looking for all available information concerning the image below. All help is appreciated!

[Update] Additional information: the picture was presumably made on the 16th of January 2018 at 20:57 local time. They are looking for any information about airplane type, carrier or maybe even flight number.

It may be an A318 with cabine plan like this one for Avianca:

My guesses are:

the emergency light line stops around row 6, with the (red?) curtains around row 4.
the seats arrangement is approximately 3 rows of business class then economy class.
best guess would be 2x3 seats per row, with central screen every three row.
cockpit door is slightly not centered to the left

So it can fit with this type of plane.

Sorry,  I can't guess the company. The curtains seems red, but the cabine does not fit with AirFrance (and Hop) neither British Airways.

EDIT

According to the video posted by @Florian in comments, Avianca is a good guess for the company.
Following the comment of @jean, and considering the shadows on the seats, it may be taken during daylight (in flight or on the ground) but for sure not during night.


What does "Clear Of Clouds" mean in reference to Class B Airspace in the United States? Does "clear of clouds" mean you cannot touch a cloud or does it mean that that Class B airspace must not have any clouds in it?

That specific phrasing means that you can't touch a cloud. See the VFR minimums in 14 CFR 91.155, where it says:

  no person may operate an aircraft under VFR when the flight visibility
  is less, or at a distance from clouds that is less, than that
  prescribed for the corresponding altitude and class of airspace in the
  following table [...]

The table lists the "distance from clouds" in class B as "clear of clouds".

You can also find it in the AIM section 3-2-3 on class B airspace, and in other sections about SVFR, visual approaches etc. where a requirement for those procedures is to remain clear of clouds.

The actual cloud cover in the class B airspace is reported by METARs and ATIS.


Could a kerosene fueled jet engine run on methanol without significant modifications? Could a kerosene fueled jet engine run on methanol without sacrificing performance other than specific impulse? Would it require changes to the fuel injection/turbopump system? Would the combustor require a redesign? Consider both turbo engines and ramjets
(this question was previously posted on space SE due to a mixup, I've deleted it now)

You couldn't have any aluminum components in the fuel system because methanol dissolves aluminum (F1 race cars remove and purge their fuel systems right after racing).  Ethanol would be much better in that regard.

It would take changes to the fuel controller to change the air/fuel ratios used with less energy density.

Other than that, I don't think it would be a big problem.  I've been told that the Honeywell/Lycoming turboshaft in the M1 Abrams tank will run just about on any liquid hydrocarbon.. gasoline, kerosene, diesel, booze, rubbing alcohol...


Does Green Dot Speed Calculation include banking Angle? I'm wondering, whether the Green Dot- speed calculation in the Airbus PFD does account for the actual bank angle of the aircraft.
Green Dot Speed is the speed for the best lift to drag ratio as it is stated in Safety first SPECIAL  EDITION: Control Your Speed Series.
In that edition, it is stated, that the Green Dot-speed is a function of aircraft weight, which is quite obvious.
I wonder however, whether the current roll angle is also accounted for as the hodographs like given in Avrenli, Kivanc, und Barry Dempsey. „Is “Green Dot” Always the Optimum Engines-Out Glide Speed on the Airbus A320 Aircraft?“ The Journal of Aviation/Aerospace Education and Research, 2015. suggests:

Any ideas how to get those numbers for Airbus aircraft?

The Green Dot speed is very stable on the PFD, unlike for example VLS which is a function of G (bank included), mach number and speed brake position.
According to Flight Crew Ops Manual(s) green dot speed varies only as a function of aircraft weight and altitude. For A320 a very crude formula is given: below 20000ft 2 x weight in tons + 85kts, above 20000ft add 1kt/1000ft.
Based on experience I would say FCOM is accurate on this matter. It wouldn't be the first time the whole truth is not revealed to the pilots, though :)


Are there any civilian planes with seating arranged in a round area? Recently, I heard Airbus want to make an aircraft that looks like a UFO.  Is there currently any civilian passenger plane designed with the seating in a round area rather than the traditional design with a long aisle?

The simple answer is no.

Why a round seating design is not feasible? We need to look at a few aspects.

Real Estate
An airplane fuselage is rectangular (roughly speaking) in shape (when viewed from top). Airplane seats are rectangles. If you place rectangular boxes in a circle, you can fit lesser number of boxes than if you place them in a rectangle of the same area.

Airlines have just one goal to achieve, i.e. make money. Yes they take people from point A to point B too but if demand arises for joyrides, airlines will not be hesitant to start that.

By fitting more people in lesser space (not in inhumane positions mind you, governments don't allow it), they make sure that their profits soar.
Loading/Unloading Passengers
In a circular configuration, people will be a lot more confused to find their seats. People are already so confused and disillusioned when boarding a regular airplane that flight attendants have to guide every single person about where the seat is. Don't believe me? Notice how the flight attendant will snatch the boarding pass from your hand if you try not to show it.
Servicing Meals
Trolley carts used in airplanes are designed for straight aisles. In case of circular aisles, it would be very hard to maneuver them because flying airplanes do get bumps every now and then.
Evacuation
In case passengers need to be evacuated, a circular design would not be very practical. Since all people will not facing forward, simple emergency instructions, e.g. move to the front/back/left/right of the airplane can be confusing and will waste time. Locating an emergency exit will be harder too than in a normal airplane.
History
People are used to the conventional design. The present design is in use for over half a century. In addition to airplanes, trains, buses, cars and buggies have the same configuration.

I am not sure how that (and some other) news channel found about Airbus's new design. Airbus does disclose the future innovations it is working on, and flying doughnut is not mentioned there. It could be that is it on paper only at the moment. The patent information mentioned in your referenced article cannot be found with United States Patent and Trademark Office, or at Google Patent Search.


How much earlier/later is sunrise/sunset at 40,000 feet? If I'm over New York City, and sunrise is 6am, I will see the sunrise earlier when I'm at 40,000 feet on the plane.
I think that latitude plays a role here, but using NYC as an example, how much earlier/later (later for sunset, as I will see the sun for a longer period at that height) are these events on a plane than on the ground?

There's two parts to the answer.  One is the extra angular distance to the sun you get from altitude and the other is the time that it would take to traverse that distance.

For the angular distance, besides the surface geometry, there's some additional effects of refraction.  I'm going to ignore that on the assumption that there will be some refraction both at the surface and at altitude, so it will mostly cancel out (and it's harder to calculate it).

From the surface we see the sun cross a line of 90 degrees to the vertical (horizontal), from 40,000 feet it would be $\sin^{-1}(\frac{R}{R + 40,000 \text{feet}})$ or 86.5 degrees.  From altitude, we see around an extra 3.5 degrees.

The time you get from that extra distance depends on the season and the latitude.  If you were doing it over the arctic circle in december, you might get hours or days more sunlight.

If you have time to look it up, check the civil twilight calculator for your location.  That's the time when the sun is 6 degrees below the horizon.  That means you'd see sunset at that altitude about the midpoint of civil twilight.

Otherwise, you can make a broad guess that most places in mid-latitudes have a civil twilight that lasts about half an hour.  So at altitude, you get about 15 more minutes.  Maybe a couple minutes more near solstices, a couple minutes less near equinoxes.


Does anxiety increase the likelihood of developing motion sickness? In general, does a person's anxiety or "fear of flying" have an effect on his likelihood of experiencing motion sickness during flight?

I am wondering if providing some ground education to first-time flyers would have a positive impact on their experience by reducing anxiety levels and, therefore, the chances of needing to use regurgitation collection devices.

Assume all other factors such as specific G-forces and accelerations experienced, temperatures, meals eaten, etc. are controlled or disregarded.

It's different for everyone, but I'd expect stress/anxiety to be a contributing factor for many, which is an ultimately self-defeating cycle; if you "know" you're going to get sick, you'll be anxious about that, and that'll make you sick.

The trigger for me is inadequate ventilation. I'm fortunate enough to rarely get motion sickness, but when it does happen it's usually because I'm in a hot, still cabin without a good source of fresh air.


Once you have passed the oral portion of a checkride, do you have to retake it ever again? I recently attempted to take my Commercial/ME/Instrument checkride. I passed the oral exam portion, but shortly after the engine started running rough. After making it through about 3-4 maneuvers and tasks, the DPE and myself called safety of flight and brought the plane back in. He did a discontinuance on my app for a new rating, but did check me off on the tasks performed. He stated that the tasks performed have a two month shelf life.

My question is, does the oral exam have the same shelf life since I passed it?

The reason this is a concern is that I have a deployment with the Guard in about two weeks. If the plane doesn't get back up and running, I'm hosed. My shelf life on the checkride stuff expires on 5/31 and I won't be back home from my deployment until early to mid-June.

Unfortunately, yes.  It is part of the checkride and if you don't finish it within the required time you will need to take the entire checkride again.

The commercial PTS shows the areas of operations that are included in the checkride, and the oral itself is given throughout the entire process.  What most people consider "the oral" is the examiner asking questions during the "preflight preparation" portion of the checkride.  This is where they ask the most questions because in all reality, this is where you as a pilot should be asking the most questions.

There is a note in the beginning of the PTS which talks about this:

  Examiner Responsibility

  The examiner conducting the practical test is responsible for
  determining that the applicant meets the acceptable standards of
  knowledge and skill of each Task within the appropriate practical
  test standard. Since there is no formal division between the “oral”
  and “skill” portions of the practical test, this becomes an ongoing
  process throughout the test. Oral questioning, to determine the
  applicant’s knowledge of Tasks and related safety factors, should be
  used judiciously at all times, especially during the flight portion of
  the  practical test. Examiners shall test to the greatest extent
  practicable  the applicant’s correlative abilities rather than mere
  rote  enumeration of facts throughout the practical test.

  ...

As a small aside, you don't really get two months, but rather 60 days.  This is covered in 14 CFR 61.43:

  §61.43 Practical tests: General procedures.

  ...

  (f) If a practical test is discontinued, the applicant is entitled
  credit for those areas of operation that were passed, but only if the
  applicant:

  (1) Passes the remainder of the practical test within the 60-day
  period after the date the practical test was discontinued;

  (2) Presents to the examiner for the retest the original notice of
  disapproval form or the letter of discontinuance form, as appropriate;

  (3) Satisfactorily accomplishes any additional training needed and
  obtains the appropriate instructor endorsements, if additional
  training is required; and

  (4) Presents to the examiner for the retest a properly completed and
  signed application.


How do helicopter pilots practice auto rotation? How do helicopter pilots practice auto rotation, and specifically, the landing phase?

Timing the flare as ground is approaching seems critical to a successful auto rotation landing. Yet I can't figure out how this can be practiced safely.

It seems that you already understand what an autorotation is but for the benefit of other readers, I'll recap what the flare  is all about.

There are two really critical parts of an autorotation.  The entry and the flare.  If you get the entry wrong, then there is no autorotation.  You become a passenger all the way to  the scene of the crash.

If you get the flare very wrong (not enough speed when you flare or flaring far too high), you become a passenger all the  way to the scene of the crash.

If you make a mess of the flare, perhaps plenty of speed but too early, or too late, or not enough speed but flaring at a good height, then you will survive.  You might not get to use the helicopter again and you might spend some time in hospital but you're not going to  hit the  ground with enough energy to ruin all your mushy internal parts.

The reality is that most GA and low hour pilots faced with a real autorotation have a high chance of messing up the flare, and the subsequent touch down, damaging themselves and the machine but surviving.  The accident statistics and reports confirm this.  Chopping off the tail and rolling over are common outcomes of real autos.

In training and practice, the idea is that you walk away and get to use the helicopter again.

So, what height is the "right" height for the flare?

The POH emergency procedures section will also detail the height but, it will use slightly vague words such as "about 50 feet".  This is because most practice autorotations end with you at 50 feet with around 60kts airspeed and the nose straight - "the ideal autorotation".  The are many factors which affect this, mainly weight and wind (ideal ones always finish into wind).

Take a look at the "height velocity" diagram for a typical GA/sport helicopter.

(Source Rotorwandwing.com)

The shaded areas show the combinations of height and velocity from which a successful safe landing cannot be accomplished in autorotation.  When you flare, you are going to be close to the ground.  You have no choice in that!  When you start the flare, you want to be well away from the shaded areas of the diagram.  A normal autorotation aims for an entry into the flare with 55-65 kts airspeed.  Look at the diagram again and note that being at around 40-50 feet at that speed is well away from the shaded areas - bang in the middle of the "safe corridor".  This is the area you are aiming for.  At this point, you have enough energy, both kinetic and potential, to land safely.

You can see why flaring too high, too low or with not enough speed can lead to a bad weekend if you make a mess of it or, a permanent removal of flying privileges if you get it really wrong.

Hopefully this gives you a good idea of what the "right height" means.

When doing ab-initio training, you are gently led into autorotations. Your instructor will demonstrate one to you very early.  If you are clearly confident and not nervous, maybe on the first lesson which my instructor did.  Indeed, at my school, every single dual flight included at least one demonstrated or practice autorotation so you get a feel for the height early on.

You will also, perhaps every time (I think this is true in the US) finish an autorotation with a power recovery.

I chose that video because there's a good illustration in it of how to judge the height - and given that "about" is as good as the POH gives you, it's all about judgement.  In this video, you can see everything.  Watch it and look straight ahead.  Do not look at the ground, let your peripheral vision do the work. Notice how as you get closer to the ground, it seems to be coming towards you at a constant rate then suddenly, it seems to rush towards you - the "ground rush"?  That's when you start the flare.  You already know from the power recoveries you've practiced and the demonstrations what the correct height looks like so you know roughly when to flare but that sudden ground rush is the sure sign that now is the time to start slowing down.

What you are aiming for is to arrive at 0 rate of descent at or just above the ground so that a little bit of collective can be used to cushion the touch down.  With some wind on the nose and good airspeed, it is possible to bleed off most of the descent rate and ground speed with the flare.  A skilled pilot might not even use collective until the last couple of feet for a really gentle 0-0 touchdown.

There are a lot of different kinds of autorotations and some advanced ones don't use flare at all - or very little flare from low speed.  Really skilled pilots in light helicopters can go more or less vertically down with just enough airspeed to keep translational lift.

In summary, good judgement which is arrived at from the POH reinforced with demonstrations and practice.

Note to other rotary pilots:  I know that using the HV diagram is not how it's trained but it's useful in my opinion to understand what the correct height is.


Do any modern airliners have a non-flat floor in the passenger cabin? Are there any non-flat (sloped or stepped) passenger cabins in modern commercial planes? E.g. the floor at the back of the cabin is a few centimeters higher than at the front?

Some Airbus aircraft have this characteristic, in the rear section of the cabin floor. You can see this in the following image. The rear passenger windows slope up following the floor slope.

A340 line drawings; image from wikimedia.org

This image of the upper cargo deck of A330 MRTT upper cargo deck (which would be the cabin floor in the passenger version) shows the upward slope.

A330MRTT cabin floor; image from thinkdefence.co.uk

Apparently, this is a common trait in A300/310/340/330's to allow more containerized cargo in the rear.


Why is best angle/rate of climb indicated in airspeed? I understand the difference between best angle of climb $V_{x}$ and best rate of climb $V_{y}$. When I take off I would aim to maintain one speed or another depending on what I want.

But I don't understand why it's measured in airspeed, instead of pitch angle, which would seem more intuitive.

Because determining Vx and Vy has to do with the specific aircraft, specific power output of the engine, thrust from the propeller, etc, which is often a function of pressure altitude and airspeed.

Remember that Vx represents a situation where the aircraft has the MAXIMUM EXCESS THRUST meaning a situation where the difference between the maximum thrust available and and the thrust required to neutralize drag force and maintain straight and level flight is the greatest.

Images courtesy of BoldMethod

Vy on the other hand is the point where the aircraft has the MAXIMUM EXCESS POWER available to it, translating into the greatest change in altitude for a given period of time by simple conservation of energy considerations.

Images courtesy of BoldMethod

The airspeed where Vx occurs increases as the pressure altitude increases.  Conversely Vy decreases as pressure altitude increases.  This is due changes in power and thrust outputs with increasing pressure altitudes.  Vx and Vy eventually equal each other at the aircraft’s absolute ceiling, since there is neither any more excess thrust or power available here for climbing.


Why are end-fire glideslopes less useable for low-minimum approaches than image-type glideslopes? In this answer to an earlier question of mine regarding the predominance of image-type glideslopes (which bounce the lower glideslope beam off the ground rather than transmitting it directly up and out) over end-fire glideslopes (which use a separate antenna installation for the lower beam and don't need to bounce it off the ground), @UnrecognizedFallingObject pointed out something surprising about the differences between the capabilities of the two types of glideslope:

Note also that there are multiple flavors of image-type glideslope antenna (null reference, sideband reference, and capture effect), and some are more tolerant of poor site conditions than others. Furthermore, even though endfire glideslopes can work in situations where an image-type glideslope cannot, they have their own limitations as well. For instance, while well-sited image-type glideslopes can provide the tight tolerances required for a CAT IIIb ILS, end-fire antennas are limited to CAT II operations under ideal conditions, and systems designed for the most adverse sitings are apparently limited to CAT I usage.  [Emphasis added.]

Given that both an image-type and an end-fire glideslope transmit the upper glideslope beam in the same manner, and that an end-fire glideslope transmits the lower beam directly up and back along the approach path, while an image-type glideslope has to bounce it off the ground first, it seems that the end-fire glideslope should have the easier time avoiding distortion or interference, as the end-fire glideslope's lower beam

is not reliant on reflection from the ground, eliminating the potential for beam distortion from irregularities in the ground surface, and
spends much less time in close proximity to the ground (as it starts moving upwards as soon as it leaves the antenna, whereas an image-type glideslope's lower beam is transmitted downwards, descends to ground level, bounces, and only then starts moving upwards), greatly reducing the potential for interference from terrestrial sources like airport vehicles or local wildlife,

which would, at first glance, indicate that the end-fire glideslope should be more able to provide tight ILS-III tolerances than is the image-type glideslope.
Yet, apparently the opposite is the case (and, frustratingly, the FAA document linked in the abovequoted answer makes no mention of this problem) - why?

End-fire CAT III is available.
A 1990 paper[1] mentions that the slotted cable end-fire system is able to provide the highest levels of performance for any runway. One of the references is the WAC Model 105 from 1986. And indeed the product page confirms the CAT III option. I was also able to find the Leonardo Model 2100.
But, there's truth to what @UnrecognizedFallingObject wrote, at least for the US.
A 2008 assessment[2] of how the US evaluates the G/S performance has found that the current methodology does not account for the end-fire signal structure, the requests for waivers is in most cases declined, the rewriting of the standards would be too costly, and for the FAA to "have the latitude to apply alternative analysis methods". The assessment also reached out to Rockwell Collins, an auto land manufacturer, to understand how auto land systems utilize the G/S, since information about this is very limited (commercially sensitive information). And it turns out past the threshold the auto land system does not use the G/S, which is in favor of the end-fire evaluation issue – "In other words, the specific computational method used to estimate RDH is not important as long as it is representative." [bold emphasis mine]
Of note in that report from 2008:

As of this writing, all endfire glide slope systems operating in the U.S. are certified only for Category I use.

1: Watts, C. B. "Applications of slotted cable antennas in the instrument landing system." IEEE Aerospace and Electronic Systems Magazine 5.5 (1990): 16-20.
2: Edwards, Jamie S., Michael F. DiBenedetto, and FAA Aeronautical Center. "ASSESSMENT OF THE EFFECTIVENESS OF THE RDH/ARDH EVALUATION METHODOLOGY FOR THE ILS GLIDE SLOPE." (2008). (PDF)


Are engines automatically stopped in an emergency landing? This answer made me wonder if engines are stopped automatically after an emergency landing as soon as one of the exit doors are opened.

  (...) if the engine is still running, you're about to run forward into the area where you're at risk of being sucked into the running engine.

I'm not sure how high the risk would be to be sucked in or being blasted away by the jet-blast, I guess a lot of the emergency landings are because of engine failure so they aren't running anymore.

Maybe as an added extra - how long does it take for an engine to spin down to a safe RPM (so that it won't suck in people or blast them away)?

There is no automatic shutdown. However, shutting down the engines is part of the evacuation checklist done by the flight crew.

It's happened before that the controls link was severed and an engine could not be shutdown, such as in Qantas Flight 32.

  Upon landing, the crew were unable to shut down the No. 1 engine, which had to be doused by emergency crews until flameout was achieved.

Normally the captain would then instruct the cabin crew to not use that side of the plane. Same thing happens when there is a fire on one side, in that case the captain would also steer the plane so that the good side is upwind.

Aircraft are tested to ensure all occupants can evacuate with 50% of the emergency exits not working (glass half-full: 50% of the doors working). See: How are evacuation tests made as realistic as possible?

About how long it takes for the engine to stop producing thrust, it's about 5 seconds. If there is no or little thrust, there is no suction to worry about. Also note that figure is for a spool down from full thrust (not from idle thrust, which is to be expected after landing).

(Source: Jet Transport Performance Methods)


Can a jet stream make a subsonic plane fly at a supersonic speed relative to the ground? If a plane flies with a jet stream, its speed relative to the ground is the sum of the speed of the jet stream and the speed of the plane relative to the air in the jet stream. If the speeds that are added together are subsonic, can the resulting speed of the plane relative to the ground become supersonic? If it can, does the plane create a sonic boom on the ground?

Yes, the ground speed of a subsonic aircraft could be larger than the speed of sound. As an example, during the record time for a subsonic Atlantic crossing a Boeing 747 reached speeds of up to 1327 km/h:

Experts are hailing a British Airways flight as the fastest subsonic New York to London journey.
The Boeing 747-436 reached speeds of 825 mph (1,327 km/h) as it rode a jet stream accelerated by Storm Ciara.

(BBC)
The speed of sound at sea level is usually around 1235 km/h. The speed of sound is however temperature dependent and will be lower at high altitudes, therefore the ground speed in this case was higher than the speed of sound, regardless of the altitude.
This does not make the aircraft supersonic. A supersonic flight implies that the TAS (True AirSpeed) is higher than the local speed of sound. This was never the case for this 747 flight.

If it can, does the plane create a sonic boom on the ground?

No, a sonic boom can only be created locally by an aircraft flying faster than the local speed of sound. It is unrelated to the ground speed.
Consider the following illustration of a sonic boom:

(image source: Wikipedia)
You can see a line of sound waves currently hitting the person standing on the ground. This is the sonic boom you would hear.
I modified this image for subsonic flight:

You can see that the circles never intersect and can therefore never form a line of sound waves. If the aircraft is in a tailwind, the sound waves would be emitted in the same way, they would just move faster across the ground as a whole, but there is no relative difference between them (and the aircraft). Therefore, there is still no sonic boom even when the aircraft's ground speed is faster then the speed of sound.
Note however that the wind speed would change with altitude. The jet stream does not extend all the way to the ground. This would distort the circles when they get closer to the ground, but it cannot create a sonic boom.