What do the abbreviations on this Jeppesen Dataplan mean? Attached is a screenshot from a flightplan created with Jetplan. Can someone help with decoding the format? What do the abbreviations mean in the table header?

I understand the following:

FLT = Flight Level *100

T = ?

WIND = Wind speed & direction

TAS = True Air Speed

S = ?

GRS = ?

MCS = ?

DST = Distance to next waypoint

DSTR = Distance remaining

ETE = estimated time en-route

ETR = estimated time remaining

FU = fuel used?

FR = fuel remaining?

FF/E = ?

GRS = Groundspeed

MCS = Magnetic Course

FU = Fuel burned that leg (100s)

FR = Fuel Remaining

T = OAT in degrees C, apparently without the sign.

S = Shear value (measure of turbulence) forecast

FF/E = Fuel Flow per Engine per hour

With thanks to @mins for filling in the gaps!


What's this hole on the ATR-72? There is a hole on the belly fairing circled in yellow. I guess is an air intake but I tried searching some info and couldn't find anything.

Source

It is the ram air intake for the air conditioning system. There are two of them, one on each side.
Here is an image from the ATR-72 FCOM:

ATR-72 Air conditioning System, image from 737ng.co.uk
Details from the same document:

The air conditioning system is supplied by air processed through two packs which regulate air flow and temperature. The two packs are installed in the main landing gear fairings and operate automatically and independently.
The left pack supplies the cabin and cockpit air conditioned; the right pack supplies only the cabin air conditioned.

Also, as @Jonathan Walters points out, the intake is a good example of NACA inlet (or NACA scoop) and are found in a number of aircraft, for example Boeing 737.


What happens when the surface ends at the laminar zone of the boundary layer? When a body travels through any fluid, due to viscosity of the fluid a boundary layer is formed around the surface of the body which separates the velocity of the fluid inside the boundary layer(near the surface of object) to velocity of the fluid.The boundary layer consists of three zones laminar, transient and turbulent zones respectively.

Is it compulsory for all the three zones to exist in a boundary layer? If we consider a small smooth surface, is it possible that the surface ends at the laminar zone of the boundary layer and there is no turbulent zone in boundary layer over the surface? And if it is possible will there be a low pressure zone at the end of the surface or something?

Then you get a fully laminar boundary layer without transition. This can happen at very low Reynolds numbers, especially if no steep positive pressure gradients are encountered.

A steep pressure rise can lead to separation, and if the boundary layer does not change to a turbulent one, this separation can be final, with no re-attachment of the boundary layer. Then the attached flow ends before the body ends, but still the boundary layer is fully laminar.

It is not compulsory for transition to happen. If the flow is stable (either due to a negative, stabilising pressure gradient or due to very low Reynolds numbers), the boundary layer will stay laminar for its full length.


What's the EPNdB for large turbofan engines for stage 5 noise regulations? I'm trying to estimate the Effective Perceived Noise (EPNdB) of the GE9x. GE Aviation says that it will be within 8 dB margin of the stage 5 noise regulations, can anyone confirm that?

What the FAA is calling "Stage 5" is the ICAO Chapter 14 regulations. These do no go into effect until 2017 or 2020, but that means it would be applicable for future engines such as the GE9X.

The cumulative EPNdB margin for Chapter 14 is Chapter 4 +7, or Chapter 3 +17. The exact EPNdB value depends on takeoff weight.


Does the transponder need to be on in the upper limit of Class B airspace? Is a transponder needed to be turned on to operate above the upper limit of class B airspace?

Yes:
If you combine the two sections provided by SMSvonder Tann and Raaj Tram you get:

  14 CFR 91.215 - ATC transponder and altitude reporting equipment and use:

    (b)(4) All aircraft in all airspace above the ceiling and within the lateral boundaries of a Class B or Class C airspace area designated for an airport upward to 10,000 feet MSL; and

    (b)(5)(I) airspace of the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface; and

You can't fly over B or C without a transponder.

There are some specific exceptions for aircraft not originally equipped with an electrical system.


Do ICAO specifications have the force of regulation? ICAO, the International Civil Aviation Organization, has specifications for the conduct of civil aviation throughout the world. Such things as the language to be used between controllers and pilots, aircraft calls signs, and a host of other things are covered. At the time of my retirement in 1999, the ICAO specifications were merely recommendations, they did not have the force of regulation in the U.S. or, to the best of my knowledge, in any country in which I operated. Is that still true? Is there any country that says, essentially, that if ICAO says it should be so, the country treats that as a regulation.

According to About ICAO from their own site:

  ICAO works with the Convention’s 191 Signatory States and global industry and aviation organizations to develop international Standards and Recommended Practices (SARPs) which are then used by States when they develop their legally-binding national civil aviation regulations.

So ICAO continues to develop standards and recommendations without the force of regulation.


How are airline pilots assigned routes? Are there easy and tough ones? How are routes given to airline pilots? Is it based on the amount of flying experience they have or just random or based on availability?

Also, can routes be classified into tough and easy? If so, what are some examples? In not, then are all routes equal? Doesn't more traffic in a particular area correspond to a harder route?

The answers to your questions vary greatly depending on the individual airline, type of equipment, what kind of flying they do, as well as contractual and union (if any) work rules. The one thing that is generally the same and as noted in the previous answer and comment, is that scheduled lines of flying are published to the crews, and a bidding system based on seniority is used to assign those lines.

  Also, can routes be classified into tough and easy?

What one pilot considers tough another may consider easy. A better way perhaps to think of it is that what one pilot considers desirable, another may not, and that will be reflected in how the individual pilots bid.

Some examples (but certainly not exhaustive): Young pilots with families would typically bid away from Christmas flying. I, however, not being a fan of Christmas and with all my children grown, deliberately bid to work on Christmas to open a no-work-on-Christmas line for someone else. In the northern hemisphere winter, I would bid into Australia, South America, or Africa because I don't like the short days of winter. In the northern hemisphere summer I tended to bid into places where I stood a good chance of getting to a beach. A lot of pilots bid simply to maximize income. And there were those who bid to maximize overnights at a place where they had an ongoing personal relationship.

Whether or not a pilot gets to actually fly a line as published is another matter. If you're flying for a scheduled airline that does no on-demand charter work, and you're going from one company station to another company station, chances are good that you'll get to fly the line as published. If, however, you're flying for a company that does on-demand charter work, the probability of flying the line as published goes down as the percentage of charter work goes up, and this is especially true with a mixed fleet of passenger and cargo aircraft. I flew for two commuter airlines, and I almost always flew my awarded bid line as published. Then I flew for two 747 carriers, both of which did a lot of on-demand charters. In the 12 years of flying for the 747 carriers, I rarely flew a line exactly as it was published. If was a matter of when you would have to depart from your line, not if.

There are companies that do nothing but on-demand charters. In those cases what you're bidding is not where you're going to fly, but which days you will be on-call.

  Doesn't more traffic in a particular area mean more tougher?

Some would consider it tougher, some more fun. A higher workload certainly, but I always felt that was more fun. There's something addictive, at least for me, to running approaches in high-density traffic. It's quite exhilarating really.


Can you identify this aircraft photographed during solar eclipse 8/21/2017? The following sequence of shots was taken about 9.5 minutes before the start of the eclipse, 1:12pm EST.

Shooting in burst mode off of a tripod - all 3 shots taken within 1 second. Burst mode is 14 frames per second, so it's reasonable to assume that these 3 photos were taken 1/14sec apart.

Exif:
Camera: Canon EOS1DX
Lens: Sigma 150-600mm Contemporary.
1/8000s, f/29, ISO 100, focal length 600mm. No filter.

First image: the aircraft is seen above the sun - no contrails.
Second image: completely different trajectory and a contrail (?)
3rd image: the aircraft is gone.

Zoomed in:

Based on the second picture and the list of US military jet, I would guess F-22 Raptor, and since this kind of aircraft usually fly by 2, the jet in the first picture is maybe a second F-22.

As for the timing of the shots, the trail we see in the second pic not appearing in the 3rd is telling me they were shot with at least a couple of seconds interval. That would also explain why each jet appears only in one pic.


Did British aircraft fly at a specific speed while returning from missions during WWII? I remember reading a whole lot ago (so I am currently unable to find the reference, sorry) that during WWII, British aircraft would return from missions at a specific speed that was unattainable from German aircraft, i.e. it was either too fast for some, or too slow for others.

This had the immediate benefit of enabling radar operators to distinguish friends from foes without the need of any additional equipment or method, they would simply compute the aircraft speed and determine if the aircraft was British or German.

Is it true? What was that speed?
Why wasn't there a German aircraft capable of flying at that speed?

Ground speed
Real time wind components were not available to the pilots. They wouldn't have been able to tell the ground speed. Especially over the English Channel on a calm or foggy day where a drift meter is not very useful (if equipped).

[A drift meter] indicates the aircraft's drift angle due to winds aloft, and can be used to calculate the ground speed.

If they flew at an agreed true airspeed, then the controllers wouldn't have been able to tell that true airspeed.
Early IFF
Looking into the history of IFF and radar in WWII, it's apparent from early on radio IFF was used. It started with the pip-squeak system.
Mistaken identity
In the Battle of Barking Creek a radar issue caused a friendly fire incident where returning British fighters were attacked. According to Wikipedia, as of 2010 the final report has not been declassified yet.
Another one was the air attack on the fortress of Koepenick, the Germans thought there was an air raid en-route, they launched fighters, only to mistake their fighters for the raid, only to send more fighters, etc. And there was no raid, just the Americans were returning from a bombing mission and judging their direction of flight aurally led to this confusion. The German fighters started to run out of fuel and landed.

Göring freely admitted the laugh was on him, that he had sent the Luftwaffe on a mammoth tour of their own air space.

Navigation
Wind and ground speed aside, if we say it was a certain route combined with speed, that would require a level of area navigation that just wasn't there in WWII.
Logistics
Logistically, when an operation is launched, the air command has an idea of when to expect its return.
Speeds
Comparing the Focke-Wulf Fw 190 with the Supermarine Spitfire, the German Fw 190 was faster. 426 mph compared to 370 mph.
As for slow speeds, slow flying on the return leg is just calling for the surviving planes to be caught up with and shot down.

I'm calling it myth busted.


What prevents a government from selling/leasing publicly owned airports? When an airport is open to the public, it is generally owned and operated by a government entity. If the local government leases or sells the airport, this would generate significant amounts of revenue.

What are the legal impediments which discourage a local government (who owns a public airport) from leasing or selling their airport to a private entity?

One possible impediment might be the grant assurances that come with accepting Federal aid to improve the airport.

In short, if the local airport accepts money from the Federal government to improve the airport, that money is often granted "with strings attached" - requirements that the airport remain open, etc.


What kind of identification code is this format? (AAA0000) From what I understand, an aircraft's registration number is its ICAO code in the pattern found here: Wikipedia: Aircraft registration, but I have seen references to aircraft using a 3-letter code (I'm assuming it's an airline code) followed by a 4-digit number. (Example: PAK0032) What kind of a number could that be?

That format is the flight id. The first three characters are the ICAO operator code which identifies the airline. The rest of the characters are unique to that flight. The first character after the ICAO operator code is always a number, after that both numbers and letters are allowed. The maximum length of the flight id is 7 characters.

The flight id is transmitted to Mode S radars by the transponder and also broadcast on ADS-B. It is used to correlate a flight to a flightplan.

The flight id is also the basis for the callsign used in radio communications. The ICAO three letter code represents the airline's callsign, the rest of the code is pronounced in the ICAO alphabet.


How are V speeds spoken? How are V speeds spoken? --Research for my novel.

Is it the V and the number or letter notation or is there something more to it?

The Wikipedia Page on V Speeds does not delve into the subject matter.  I did search the search box, prior to submitting, but nothing has come up.

Please don't get angry by my question or restrict my learning.  I can always go to a better source--I got a message some of my past questions were not well received.

It Depends on the speed, and in some cases the context it is being announced or discussed, different pilots may also call things out differently depending on op specs or simply the way they are trained.

V1 is typically announced as "V One"

I typically announce V4 as "Trimming for XXX Knots"

Vfe for me is typically "in the white arc, deploying flaps"

Vr is typically announced as just "rotate"

Vx and Vy are usually discussed as such or some times as "pitch for best angle" or "pitch for best rate"

Some of the V speeds are never really announced but important to know. V speed numbers help define the operational envelope of an aircraft but are not always announced or even relevant to announce. For example unless you are in a really bad situation its unlikely you are ever going to announce Vne out loud but its a very important speed to know (and avoid).


What do winglets do to increase aircraft performance? It seems like a lot of the newer airliners have winglets or wing fences. How do they improve aircraft performance?

they reduce the wingtip vortex and the associated drag by deflecting the air that wants to escape over the tip back down

(source: wikipedia)


Why don't both black boxes hold the same data? As I understand, there are two black boxes on-board an aircraft. One black box, the Cockpit Voice Recorder holds the cockpit conversations and the other, the Flight Data Recorder holds essential flight parameters.

But why are the two black boxes holding separate data?
Why don't both black boxes hold copies of both the FDR and the CVR data for extra redundancy in case the other box goes missing or is completely damaged by the crash?
Are there any technical reasons for why this isn't possible or hasn't been attempted yet?
Is there any benefit of having the CVR and FDR in separate boxes?

Black Box(s) is a misnomer, you have correctly mentioned their actual names.

  Why are the two black boxes holding separate data?

They have different purposes.

Flight data recorder: This is an electronic device employed to record any instructions sent to any electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters.

Cockpit voice recorder: This device is used to record the audio environment in the flight deck of an aircraft for the purpose of investigation of accidents and incidents.

  Why don't black boxes hold copies of both the FDR and the CVR data for
  extra redundancy?

Since they record different data, they are different. They are built different.

Differences:

FDR

Time recorded: 25 hour continuous
Number of parameters: 5 - 300+

CVR

Time recorded: 30 min continuous, 2 hours for solid state digital units
Number of channels: 4

Similarities:

Impact tolerance: 3400 Gs /6.5ms
Fire resistance: 1100 deg C /30 min
Water pressure resistance: submerged 20,000 ft
Underwater locator beacon: 37.5 KHz
Battery: 6yr shelf life, 30 day operation
Both recorders are installed in the most crash survivable part of the aircraft, usually the tail section.
Each recorder is equipped with an Underwater Locator Beacon (ULB) or pinger to assist in locating in the event of an over water accident.

  Are there any technical reasons for why this isn't possible or hasn't
  been attempted yet?

It has certainly been attempted.

  Is there any benefit of having the CVR and FDR in separate boxes?

Probably the reason is that different teams investigate the data obtained from them as they have to recreate the scenario before the accident.

Regulatory Details

CVR: Due to the highly sensitive nature of the verbal communications inside the cockpit, Congress has required that the Safety Board not release any part of a CVR tape recording. Because of this sensitivity, a high degree of security is provided for the CVR tape and its transcript. The content and timing of release of the written transcript are strictly regulated.

FDR: Newly manufactured aircraft must monitor at least twenty eight important parameters such as time, altitude, airspeed, heading, and aircraft attitude. In addition, some FDRs can record the status of more than 300 other in-flight characteristics that can aid in the investigation. The items monitored can be anything from flap position to auto-pilot mode or even smoke alarms.


Does the ditching switch allow an A320 to float indefinitely? I watched a documentary yesterday about the Hudson River ditching of US Airways Flight 1549. In the documentary, one of the investigators explained that the reason the water was entering so quickly was because the FO did not have time to hit the 'Ditching' switch the A320 is equipped with. This switch closes all vents etc. to prevent water from entering the cabin.

If an A320 or similar is ditched and the switch is activated in time, does that totally prevent water from filling the cabin (in a best-case scenario)? I'm thinking if one ditched in the Atlantic and had to wait for hours for help, would it be possible to stay afloat for so long?

The answer is no, not totally, but it would really slow things down. I don't think anybody knows the precise answer because only flat water ditchings seem to result in the airplane stopping in the water in one piece (such as 1549 and a similar one in Malaysia) and flat water incidents (like Malaysia and some airport overruns) are usually in shallows where the ditching valve is moot.

But assuming an A320 was able to ditch on open ocean swells without breaking somewhere, certainly it would float for a much longer time, but not forever. Pressure hulls are never absolutely fluid tight; door/hatch seals leak a little bit, and there may be tiny leaks through various entry points below the water line like bleed air shutoff valves, fay-sealed skin laps, rivets, control cable pressure bulkhead fairleads, etc (the older the airframe the leakier).

Wing dry bays may be sealed off with a tape made for the purpose but they are not usually totally water tight.  Water can migrate into the fuel tanks through the vents.  Full fuel or nearly full fuel would be a bonus, fuel being buoyant.

You certainly would have a lot more time to get onto the rafts (perhaps Airbus has estimated the theoretical sink time by calculation), but it would sink eventually (it would take quite a few hours, maybe even a day or two), and you aren't going to be staying on board any longer than necessary regardless.

(Now, if you ditch in a composite foam sandwich sailplane, well you've got yourself an unsinkable boat right there, and if you took a paddle along, you could actually go places.  If I'm in a glider that gets low over rough forested terrain, and there are lakes around, I'm putting it in the water and paddling it to shore with whatever I have at hand).


What names are used for certified "mechanics"? While watching a documentary on the the UK Red Arrow aerobatic team, mechanics were sometimes called "tradesmen", "technician", or "engineer".

In the US they are commonly called "aircraft mechanics" or an "A&P".

What other designations are used for certified aircraft "mechanics"?

image source

From Wikipedia:

  An Aircraft Maintenance Engineer (AME), also Licensed Aircraft Maintenance Engineer (LAME or L-AME), is a licensed person who carries out and certifies aircraft maintenance. The license is widespread internationally and is recognised by the International Civil Aviation Organization (ICAO).


Is it possible (not practical) to create a liquid nitrogen jet? Would it be possible (though not practical) to create a jet that runs on liquid nitrogen that is heated, creating the expansion effect? I believe nitrogen takes up 674 (about) times as much space in gaseous form as in liquid, but if it were somehow evenly heated, could it provide a similar effect to combustion without the carbon emissions?

At best, the mechanical energy you can release by evaporating liquid nitrogen would be about its heat of vaporization, which is 5.56 kJ/mol or roughly 200 kJ/kg. (Converting this energy to useful thrust probably requires you to use the expanding nitrogen to drive a turbine that drives a fan or propeller, but that's a Simple Matter of Engineering, at least comparatively).

The chemical energy density of jet fuel is about 46 MJ/kg.

Even if we suppose the efficiency of your nitrogen engine could be a bit better than that of hydrocarbon-burning engines, this still mean that you would need to carry about a hundred times more nitrogen (by weight) than jet fuel for the same result.


Fuel price actually used in the industry I know it's a bit off-topic but I guess some of the terminology used in the aircraft community is the same as in marine transportation.

I know that both aircraft and marine vessels use fuel. But if I'm looking at the fuel prices on a commodities exchange, I guess the price is a bit different from the actual prices someone must pay for fuel used in the industry.

Do you have a name/term for fuel prices used in the industry, like fuel industrial price or something like that?

Jet Fuel is not listed on the commodities exchange, at least not according to this list. For what its worth small boats use regular car gas or diesel fuel and some larger ships are powered by fuel oil but they use boilers as opposed to a reciprocating engine like on smaller boats. Small boat gas tends to command a higher price because it can not because its any different than car gas. This is largely because you cant pull a big boat and take it to the gas station to fill it up every time you need fuel. AvGas for piston pounders is 110 or 100 octane low led. This is every similar to car gas (but higher octane and leaded). It is more expensive since it is taxed differently. Jet Fuel is effectively kerosene.

In the end of the day these are all crude oil byproducts so if you are looking for a commodity price the price of crude oil will effect the price of aviation fuels the same way it effects the price of car and boat fuels. Crude oil prices are about as close as you are going to get.


What happens during a solo checkride and how do I put myself in the best position to be successful? What happens during a solo checkride and how do I put myself in the best position to be successful?

Also, why is it 2 hours? Is there a reason it would be longer than the flight you're used to if you usually fly 1.5 hours?

It's pretty simple.  You will be asked to demonstrate everything you've learned.  The Grade II is evaluating you and is also evaluating your instructor's teaching skills.  The two hour block probably includes extra time allowance if the check instructor wants to give you remedial or supplemental training before signing you off (assuming you are acceptable), and the actual flight may be the full 2 hours or quite a lot less.

Just relax and do what you're told to the best of your ability and don't worry about it. To best prepare, go through all the things that you may have to recall from memory, especially emergency memory items or sequences or mental check lists, and drill drill drill that stuff on the ground while at home or while driving until you can't stand it any more, then do it some more.  You want to be able to spit out procedures or numbers automatically without thinking, under pressure, with distractions, and to do that it just takes repetition (have a friend shove you and yell at you while you recite everything - you'll know right away if you have things internalized sufficiently).

I cannot stress that aspect enough.  If you have everything that needs to be memorized fully burned in to your brain beforehand, it will massively reduce the stress of the flight itself and you'll find you are better able to free your brain to concentrate on flying and it's only a matter of having the physical and judgement skills in place or not.

The other thing to add is that instructors and examiners love students who show up well prepared, who have obviously taken a lot of time and effort to learn what they need to learn, who can spit out answers to verbal questions immediately without having to mull the question over (to a reasonable degree).  The result is that they will tend to cut you a bit of slack on little screw ups you make during the evaluation or test if it's obvious you are putting in the work, and obviously, aren't dangerous.  In the end they just need to be satisfied you won't kill yourself, and a lot of that comes from a general feeling of comfort the examiner gets from the overall experience of flying with you and knowing what you have put into it.


How does a tiltrotor yaw while in vertical flight? Conventional helicopters have a tail rotor or equivalent to counteract rotor torque. The pilot's rudder pedals control the force generated by the tail rotor (e.g. by changing its pitch).

But the V-22 Osprey lacks a tail rotor: it has rudders on its twin vertical stabilisers. Rudders wouldn't seem to have any useful effect when in vertical flight, because there's no horizontal airflow for them to deflect. The AW609 appears to lack even a rudder, in the photographs I've seen: the vertical stabiliser appears to be one piece in a fixed shape.

Co-axial helicopters such as the Ka-50 can yaw by varying the torque of one rotor compared to the other, but it seems unlikely to me that the same mechanism would work well when the two rotors are at opposite ends of the wings. The effect of differential torque would be much smaller, and it would have huge secondary effects (such as adverse roll). For that reason I don't think the Osprey can work that way.

So what mechanism controls the yaw on a tiltrotor?

The V22 Osprey yaws by tilting one rotor backwards from the vertical and one forward by moving the swashplate up on one side and down on the other causing a cyclic change to the rotor blade angles of attack.  This is accomplished using the pedals in just the same way as a helicopter.

Since the rotors are tilted from the vertical, this introduces a horizontal component to the thrust vector.  The rearwards titled rotor produces a horizontal thrust component to the rear and the forwards tilted rotor produces a horizontal thrust component to the front.  This produces a turning moment, using the wings as the lever, around the centre of gravity and therefore the aircraft yaws.

The secondary effects will be as expected.  Since some of the thrust vector is no longer vertical, a little more power will be required to maintain height and I expect that there will be a pitch change although I'm not familiar enough with the aerodynamics of this type to figure out which way and how big.


Are remarks in the Chart Supplement (A/FD) "regulatory" or "advisory"? StallSpin's answer on the recent question about VFR traffic patterns has got me thinking about the "Remarks" section of the Chart Supplement (formerly the Airport/Facility Directory).

We are all taught in training to review the Supplement entry for airports we intend to visit (part of FAR 91.103's "become familiar with all available information" requirement), and to comply with any restrictions noted - typically things like "no touch-and-go landings", "Standard traffic pattern required of all aircraft", "Prior Permission Required for jet aircraft", etc.

Aside from it being The Right Thing To Do, and avoiding the possibility of local fines/sanctions, are the remarks in the Supplement "regulatory" such as to require compliance, or are they advisory where compliance is encouraged but not mandatory?

A required rule in the airport/facility directory is required. It is a very good idea to check the AFD entry online (or on paper) before you fly to a new airport. It just takes a second and you can learn important things, such as "NO DEPS AFT 2230" or "PPR FOR TKOF ON RY 15. CTC FBO 970-920-2016" (Aspen).


What are these markings on the A380 wing? There are some "markings" over the wings and the horizontal stabilizer. Could somebody explain what they are?

The darker areas denote where it is safe to step. Stepping outside of these areas could cause damage to the aircraft.

Here's a closeup of the warning:

(This happens to be a photo of Qantas Flight 32 after its un-contained engine failure)


When does a pilot and when does a co pilot start/land? I am wondering if there are certain rules about when a pilot and when a co pilot starts or land a plane. As far as I understand a co pilot's job is to support the pilot. Do they talk to each other during the flight and decide that spontaneously or is the decision already done long time before a flight and how?

You've asked a many-faceted question, the answers to which depend a little on FAA regulations in the U.S. but mostly on the policies and culture of individual airlines. Also, it's the captain's airplane, which means he/she may have, should we say, his/her own way of doing things. How much that might vary from the airline's "standard" can vary greatly, especially when you compare what would be typical in, say, the U.S. versus other countries, and especially third world countries. You could write a small book on this topic. A few items I can think of offhand follow.

All four of the airlines I flew for (two commuters and two 747 carriers) required the captain to do the engine starts. These days there is FADEC, so it's an automated procedure. Pre-FADEC, somebody had to move the lever that introduced fuel to an engine and, in the case of a hot-start, had to cut off the fuel and handle the heat properly. Failure to do so meant you might trash a multi-million dollar engine.

At all four of my airlines, the usual procedure was for the captain to fly the first leg and then alternate with the f.o. after that. At the two 747 carriers, however, new captains were required to do all the landings for their first 100 hours.

The second commuter I flew for had a rule that when the nose-wheel steering of the aircraft (SA-227 Metroliner) was inoperative, the captain had to taxi the aircraft.

The second 747 carrier I worked for had a rule requiring the captain to do all the taxiing. I ignored that rule as I felt it was unnecessary and ill-advised.

There were rules that required the captain to do approaches when the weather was below certain minimums.

The standard way of doing things was always well covered in initial and recurrent ground schools, simulator training, and CRM (Cockpit Resource Management) classes and sim exercises. IOE (Initial Operating Experience) for new cockpit crew as well as later periodic line checks by check airmen provided continuing standardization.

During a flight, the pilots continually talk to each other as required, and on long flights typically a fair amount of visiting, although below 10,000 feet only essential conversation is the rule. There is an old joke that goes something like, "When pilots are in the cockpit, all they talk about is women. When they're with women, all they talk about is flying." Obviously it's a sexist joke and is, I hope, disappearing with increasing numbers of women in the cockpits. It was never really true anyway.

Concerning verbal communication, both 747 carriers, as a part of Cockpit Resource Management had a procedure for handling subtle incapacitation of a pilot. If at any time you did not get a verbal response from your fellow pilot when a response would normally be expected, you were to turn to him and say distinctly, "Are you okay?" If they didn't answer, you were to take control of the aircraft.


How does Boeing Deliver single aisle jets to South east Asia? I am not sure if they can fly on full tank gas to their destination (say India or Thailand), but how does Boeing deliver single aisle jets to these destinations. I read somewhere about the process of delivery, but I am more interested to know what kind of skip hop flights do they take for delivery? Any way we can track new outgoing aircraft?

Magic. More specifically, science.

Even regional aircraft are generally designed with 3,500+ nmi range with some load, and more without. It's more than enough to travel to anywhere in the world, given some refueling stops.

In fact, even WWII combat aircraft, which had a fraction of modern airliner range (though it took a big dip once we went from props to jets), were able to travel to both Europe and Japan for duty.


How will the Boom SST not require an afterburner? The company Boom is developing a supersonic airliner (SST).

In one of their blog-entries1 they state they would not need to use after-burners because they use modern turbo-fan engines.

Does this mean they will use a variable geometry exhaust?
Is there another (efficient) way to become supersonic with turbo-fan engine?
Which turbo-fan engine are they planning to use?

1: blog.boomsupersonic.com/why-we-dont-need-an-afterburner-a4e05943b101

1. Will they use variable geometry exhaust?
According to Wikipedia, with references, they plan to use variable inlet/exhaust. So yes, which is similar to the Concorde.
2. Are there other ways?
In theory, the variable cycle engine (VCE), which according to them they won't go for due to the R&D cost. Those engines are also heavy and very noisy, even by the 80's standards.
3. Which turbofan are they going to use?
For the scaled demonstrator they built, they are going for a turbojet, the General Electric CJ610 from the 60's. At the present time, we don't know is the right answer. But the technology can be analyzed.
The inlet of a  supersonic turbojet slows down the oncoming air so it can be compressed and then accelerated by combustion out the back. And as you hinted, a converging nozzle is needed for the supersonic regime. This is the classic accelerate a small amount of air by a lot.
The propeller and the fan (in the turbofan) are the opposite, they accelerate a lot of air by a little. And it's easy to visualize why. The optimum blade tip speed is around Mach 1.0 give or take, so the average velocity of the air behind the fan after gaining energy will not be much faster, but it will be a lot of air (also note, away from the tip it's slower). This is where I don't get it, why have an inlet that slows down the air, only to accelerate it by a little bit, instead of accelerating it by a lot?
They also note that the engine they will settle on will have higher maintenance cost, which hints at running at extreme power levels. This is to be expected as the previous paragraph shows. This answers how the no-reheat. The aim seems to be noise reduction, not economics (wait for it).
Onto some true context:
They compare a fare of \$5,000 to the Concorde's \$20,000 (adjusted for inflation). What they don't say is that the Concorde's original fare was around £1,000, and it only increased because the management realized the rich who flew the Concorde didn't even know how much they were paying.
Adjusted for inflation from 1981, we are looking at an original fare of \$5,500. The reason is simple, to this date, the Concorde's engine remains the most efficient, when you factor in the speed.
Note: I was being very conservative when I said £1,000, in 1980 it was actually £600. And BA was reporting profits on the NYC route.

In short, they already said they can't afford the R&D of the VCE technology, so don't expect something new, it will be present day transonic technology used in the wrong flight regime, which explains the high fare.
Note on the Concorde afterburner:

The reheats are turned off shortly after take off. The reheats are turned back on, for around 10 minutes to push the aircraft through Mach 1 and on to Mach 1.7 where they are no longer required.

Addressing comments:

I would think that higher maintenance costs could be completely attributable to the small market that this engine will have.

If they don't have financing for VCE R&D, then they should settle on an engine with parts commonality to existing models to reduce the maintenance cost.

Existing turbines in reliable daily operation all around the world make enough [thrust] to power the Boom jet.

In the supersonic regime, if they don't use a turbojet or at the very least, a low BPR turbofan, they're wasting fuel, but yes, they will be keeping the noise down. I just didn't like the false marketing of a low-fare. Engine manufacturers would not have been chasing VCE's if medium BPR was the solution all along. The problem with supersonic flight and the low speed of the turbofan exhaust can be understood from this NASA page. The faster the freestream, the faster the exhaust needs to be.


Which airplane designs have the greatest longevity? What airplane designs have been around the longest, from first flight through last retirement from active commercial or military service?

My guess is that the DC-3 will win, since it has been around since before WW II and is still in service, although there are enough other designs out there I'm not familiar with that I'll be interested to see where I may be wrong on that. (Russian designs come to mind as an obvious source of possibilities.)

Can anything out there beat the DC-3? What's the runner up?

(The wikipedia page on the DC-3 says its first flight was December 17, 1935.)

This is a community-wiki mashup of the other answers - I thought a table would be useful.

Date Introduced
Aircraft Type
Commercial Service (2015)

1909
Bleriot XI
Flown by Shuttleworth collection UK, entrance fee.

1932
JU-52
Sight seeing flights by Ju-Air, Switzerland.

1932
Tiger Moth
Flight experiences, e.g. Cheltenham UK.

1934
Dragon Rapide
Sight seeing flights, London.

1935
DC-3
Many commercial flight-experience/other operators.

1935
PBY Catalina
Still used in aerial firefighting role.

1938
Piper Cub
Many still in private/GA use and in flight schools.

1947
AN-2
Still in widespread use in 2020.

1952
B-52
76 still in service with USAF. Projected service to 2045?

1952
Tu-95
In service with Russian air force. Projected service to 2040?


What are the options for installing ADS-B OUT in a Cessna Citation to meet the regulations? So I have a friend that works for a company that owns a Cessna Citation. His company is looking to comply with the ADS-B regulations. He has been given the task of making a business case for actually doing this, but so far the only thing he's turning up is companies that want to sell the Garmin solution (GTX-345).

The specific questions:

Are there other manufacturers of ADS-B equipment that are recommended (by AOPA, FAA, or any other respectable group)?
What companies (again, respectable) would do installations? Maybe towards the Northeast since that's where he is located.
What sort of considerations do you have to look out for in upgrading to ADS-B? I am assuming it's a transponder replacement that you end up doing, but it also has to tie into a bunch of other equipment. What are the gotchas?

It depends on what kind of Citation you are talking about.

I found a presentation by Textron(ppt) that discusses ADS-B installation for various models. Textron is focussing on creating Service Bulletins (SB) for installation of ADS-B on recent models (up to 15-20 years old).

For the Cessna Citation a SB is available for the following models:

Pro Line 21

CJ1+: SB525A-34-90
CJ2+: SB525A-34-41
CJ3: SB525B-34-26
CJ4: SB525C-34-09 R1
Encore+: SB560-34-163
XLS+: SB560XL-34-76

Sovereign

Primus EPIC: SB680-34-33 R1

Citation X

Primus 2000: SB750-34-58

For the following
Cessna Citation SB's are under development (when the presentation was given)

Ultra, Encore, XL, XLS

Primus 1000; expected Q2 2016; Prerequisite: Universal FMS with SBAS LPV

Mustang

G1000; expected Q2 2016

It is possible to install another transponder than advised by Cessna. However if it hasn't been done already, you have to go through a Supplemental Type Certificate (STC) process for that which makes it rather expensive. It also wouldn't be supported by Cessna, which will impact the resale value of the aircraft. You may offset the cost of the STC by offering it to other Citation operators, but then you are suddenly in a whole different kind of business.

Other considerations to take into account are support of future operations, mainly LPV approaches using the same GPS receiver.

Since all offers seem to prefer the Garmin GTX, I assume the aircraft is a Cessna Citation CJ1 or CJ2 with a non-Collins FMS. Cessna has a STC for this aircraft that is based on the Garmin GTX.


What is a Second Segment Weight Limit? I am very interested in the principles of take-off performance optimization.
During my research I found an interesting picture, showing the software used by a European carrier.
However, the output presented shows a value I do not understand:

In the lower right corner, the following values are shown:

PTOW: 68.5
Field Length: 73.2
Sec. Segment: 71.0
Obstacle: 68.5

I do not understand what the Second Segment limit stands for.
I know about the different phases of the take-off run, however I am not aware how the Second Segment could be limited by any other weight than the Obstacle Clearing weight.

The second segment of the takeoff is defined as (source: skybrary.aero):

  Second Segment - begins when the landing gear is fully retracted. Engines are at takeoff thrust and the flaps/slats are in the takeoff configuration. This segment ends at the higher of 400' or specified acceleration altitude. In most cases, the second segment is the performance limiting segment of the climb.

The minimum climb gradient is defined for each segment of the takeoff (same source):

  Each segment of the one engine inoperative takeoff flight path has a mandated climb gradient requirement. For example, a gross second segment climb gradient capability of 2.4%, 2.7% or 3.0% is required for two, three and four engine aircraft respectively. Similarly, the required gross gradients for the fourth segment are 1.2%, 1.5% and 1.7% respectively.

I'm not familiar with the performance tool you show, but I would assume that the given value is the maximum TOW, which still ensures this required climb gradient can be met with one engine inoperative, so in your example a maximum of 71.0t allows 2.4% gross climb gradient for the second segment.


Can you fly a plane in a wind tunnel? There are very large wind tunnels out there. Wouldn't it be very efficient to test new airplanes flying them "on the spot" inside of these tunnels? That is, in free flight - not mounted to a pylon? One could presumably omit the test pilot and remote control them, get excellent visual feedback and have a completely controlled environment. Has this been done? If not, why?

It would actually miss the point of wind tunnel testing. A free flying model could only be subject to air stream in speed and direction so that the forces are balanced. A fixed model on the other hand can be subject to air stream of any direction and speed and the forces measured. It is important to measure the forces under those conditions too.


How long should a boarding pass be preserved, after the trip? Is there any FAA mandate on the same to make any claims later? Ok, i'm not sure if this is relevant to AviationSE, but my query is as a passenger.

How long should a passenger preserve their boarding pass after their trip? This is with view for making any kind of claim on the Airline, be it for lost luggage, or injury during the trip, or any thing else. Is there any relevant FAA guideline or rule on the same?

If you have arrived approximately in time, picked-up your undamaged luggage, passed immigration and customs and doesn't want to use an airtrain (or something similiar) you should be able to safely discard it.

Personally I tend to keep them as holiday memory, so I miss the old style tickets/boarding-passes from the 90ies :)


What is the up-to-date disposition towards narcolepsy in the U.S.A. for obtaining a pilot license? Citation: What medical conditions does the FAA consider disqualifying?

In the past, I recall this page having listed narcolepsy, but I find no mention of narcolepsy anywhere relevant on the FAA website anymore. Can anyone enlighten me as to whether I am just missing it somewhere, or if there is knowledge of this specifically having been changed? It would surprise me greatly if this were not a disqualifying condition, but I want to find official information on it.

In the FAA Guide For Medical Examiners there is only a single direct reference to narcolepsy

Under the Obstructive Sleep Apnea QA section it states

  Does this process involve other sleep disorder conditions? (E.g.
  Period Limb Movement Disorder, narcolepsy, central sleep apnea, etc.)?

  No. This process is for obstructive sleep apnea only. If it is clear
  that the airman suffers from a different sleep disorder, DEFER and
  submit any supporting documentation for FAA decision.

This would indicate that if you suffer from any sleep disorder conditions your medical should be DEFERed

Earlier in the document it states:

  Medical conditions that chronically interfere with sleep are
  disqualifying regardless of whether a sleep aid is used or not.
  Examples may include primary sleep disorders (e.g., insomnia, sleep
  apnea) or psychological disorders (e.g., anxiety, depression). While
  sleep aids may be appropriate and effective for short term symptomatic
  relief, the primary concern should be the diagnosis, treatment, and
  resolution of the underlying condition before clearance for aviation
  duties.

Narcolepsy is a sleep disorder and would potentially fall under this definition and thus prevent your from getting clearance.

In these cases its usually best to get the advice of an FAA AME.


Do pilots pilots keep track of their groundspeed, by head? For VFR nav. flights, do pilots have to keep track of their groundspeed, by head (done so by considering wind speed, wind direction, crosswind, tailwind etc.)?

And the purpose of this, is to check that you are on par with your pre-planned flying time?

That depends on what you have in the cockpit, most planes these days fly with some kind of GPS be it a full blown panel mounted IFR certified unit or just an iPhone app. All of the ones I have encountered either by default or with minimal effort will display your ground speed for you and there is really no need to manually compute it.

The main purpose of ground speed is to ensure that you actually arrive at your destination with more than vapors in your tank. Let's say you need to travel 100 nautical miles in a Cherokee. You have 1.5 hours of fuel on board which is legal for a VFR flight. You unexpectedly hit a 55 Kt headwind at altitude. You trip is now going to take you a little over 2 hours assuming you cruise out at 100 Kts/Hour. Knowing your ground speed ensures you have the information you need to know that you will need to land ~50 miles into the flight and gas up.

When flying IFR its also important so that you can provide ATC an appropriate time deviation if you are not going to make a way point when expected.

On a similar note, most decent flying apps will do fuel computations en route for you as long as you provide a performance profile.


How do you encode a radial to radial turn in ARINC-424? I am building my own ATC simulator and for that purpose I need to include several instrument procedures. I have a problem with that particular one:

My problem is on KEA transition, the leg between "RDL 256 KEA" and "RDL 192 ATV" how should the transition be encoded in terms of ARINC-424 path terminator sequences.

Specifically it's the turn from the one leg to the other that bothers me: "RDL 256 KEA" seems to terminate on either 27 DME KEA or RDL 187 ATV. But then what? There is a 20 DME ATV on the next leg that spoils everything. CD (or Course to DME) is not a specific route over the ground so the previous turn won't be able to intercept it. I could either omit the CD part or insert another CR (course to radial) before the CD leg but then I'm not doing what the map says, I improvise. So my question is am I conceiving this wrong, or the IAC is ambiguous in this particular point?

So you fly the KEA transition like this:

Track RDL 265 KEA until crossing RDL 187 ATV or 27 DME KEA
Start a right turn and intercept RDL 192 ATV
Fly RDL192 until intercepting final

As egid said, RDL 187 ATV is a lead radial which is a radial used only to tell you when to start a turn.

As far as 20 DME ATV, it is actually only used for the PELAG transition so you can ignore it in this case.


Could a pilot incapacitate other crew/passengers by manipulating cabin air quality/pressure? Could a pilot of an airliner incapacitate everyone outside the cockpit by somehow triggering a loss of cabin pressure while simultaneously disarming the airplane's oxygen masks, manipulating the air circulation system to induce hypoxia, or some other means?

For example, would it be a credible theory that the pilot de-pressurized the 777 flying Malaysia Airlines Flight 370 and flew it off somewhere?

The answer depends on what kind of aircraft you're talking about, and how much control the crew has over the pressurization systems.

For example, in theory you could very well reduce or completely shut off the air to the cabin on a 777. This could also be done by a single crew member alone. The pilots have full control of this system should say the one of the engines produce bad air to that cabin and would needed to be switched off.

As for the oxygen masks- these are for emergency descent use and have a generator that runs out after about 15 minutes. The crew bottles last a bit longer I think, but these will also have a limit, and doing any attempt to break through the bullet-proof cockpit door in those conditions I'd imagine would be very difficult, since I'm not sure you're still picking up the amount of oxygen you normally would.

For a similar situation (though not a deliberate attempt) you can read up on Helios Airways Flight 522.

For an idea of how the pilot masks look, see this video.

Source: SmartCockpit


Is "right-of-way" based on aircraft size? I was speaking with an ATP-rated pilot the other day, and he said something that sounded odd: basically the bigger aircraft has right of way once airborne.

Can anyone shed some light on this? As far as I understand, ATC coordinates the landing/departing aircraft; at least at my airfield where there was MD80's, B738 and G/A.

The size of an aircraft plays no role in identifying who has right of way.

The general rule is that for same-class/type (powered or non-powered) aircraft, the aircraft coming from the right has right-of-way and should be yielded to. This is irrespective of the size within the same type, but a question of manoeuvrability. For different types of aircraft, a powered aircraft will have to yield to non-powered aircraft. For more details see the related question below, ICAO Annex II, FAR 91.113 or another explanation in the Skybrary.

Technically, this means that where separation between IFR and VFR traffic is not provided and aircraft on both flight rules can operate, a Boeing 737 would have to yield to any powered or non-powered aircraft coming from the right.

In most jurisdictions you will find a passage that also details that aircraft should give way to other aircraft that are established on final approach, so a strong situational awareness in the vicinity of airports and airfields is required. Whether separation is provided between IFR and VFR within a traffic pattern, is based on the jurisdiction and the airspace class. In most cases of smaller general aviation aircraft and larger/faster general aviation or commercial aircraft operating at uncontrolled airfields, the smaller aircraft will yield to the faster traffic already on the final approach path out of courtesy or due to good airmanship. It is easier and also cheaper for a smaller general aviation aircraft to perform a 360° turn than for e.g. a Learjet on final approach.

See related question: Which way should you turn to avoid another aircraft?.

See also this YouTube video: Airplane Right-of-Way Rules - Author: Humble Aviation


Can BOTH instrument rated pilot under the hood and safety pilot log PIC time in IFR flight? This question is somehow related to question: Can a non-instrument rated safety pilot log PIC during an IFR flight? , but the scenario is different.

Scenario

Pilot A and Pilot B are BOTH instrument rated. Pilot A wants to fly under the hood to practice and Pilot B will be the safety pilot. They will be flying in an IFR flight, in VMC conditions.

Question

Can both pilots log PIC time? Pilot A would be logging PIC time for being the sole manipulator of the controls, and Pilot B would only log PIC as a required crewmember/safety pilot when Pilot A was under the hood.

I believe the key to this scenario is in the FAA Counsel Office's interpretation to Speranza (2009)

Quoting from the FAA's interpretation letter:

  The FAA has previously stated that there is a distinction between logging PIC time and acting as a PIC. See Herman Interpretation. To act as a PIC (i.e., the pilot who has final authority and responsibility for the operation and safety of the flight), a pilot must be properly rated in the aircraft and be properly rated and authorized to conduct the flight. In your example of an IFR flight, being properly rated and authorized would include having an instrument rating. Accordingly, only Pilot A may act as the PIC, and Pilot A has final authority and responsibility for the safety of the flight regardless of who is manipulating the controls.

They also clarify the circumstances under which Pilot B may log PIC time for this flight, and what that means for Pilot B logging PIC time:

  Accordingly, Pilot B may log PIC time for the portion of the flight during which Pilot B was the sole manipulator of the controls.
  . . .
  However, Pilot A may not log PIC time for the portion of the flight during which Pilot B is the sole manipulator ofthe controls, and is logging PIC time, because there is no provision for this logging in §61.51(e). Section 61.51(e)(1)(iii) allows the pilot acting as PIC to log PIC time only if more than one pilot is required under the type certification of the aircraft or the regulations under which the flight is conducted, and only one pilot is required for the flight in your example. Although Pilot B properly may log PIC time for a portion of the flight as discussed previously, Pilot B could not act as PIC and was not a required flight crewmember for any portion of the flight under the aircraft's type certificate or the regulations under which the flight was conducted.

(Emphasis mine in both quotations.)

So, because the flight is conducted under instrument flight rules you must hold an instrument rating (be "properly rated and authorized" to conduct the flight) in order to act as PIC and log PIC time on that basis, regardless of the weather conditions (VMC/IMC) under which the flight is conducted.

A key difference between your case and the one in the interpretation is that both of your pilots have instrument ratings. Since the safety pilot in your example holds an instrument rating they are rated for the aircraft and authorized to conduct a flight under Instrument Flight Rules, therefore they can act as PIC, and would be eligible to log PIC time for this flight (as a required crewmember under FAR 91.109).

This would, as best I can tell, revert to the same logging situation as a safety pilot under VFR: For any portion of the flight in which the safety pilot is also manipulating the flight controls the pilot under the hood would be unable to log PIC time, and for any portion of the flight where "Pilot A" is not under the hood they safety pilot would (generally) be unable to log PIC time.


Why is it advantageous to vary sweep angle with relative thickness? In the answer to this question, Peter Kampf stated that:

"In the majority of cases it is aerodynamically advantageous to vary sweep with relative thickness, but it is not structurally and economically efficient."

Why is this the case?

Here's a high speed reason:

TL;DR: They counter each other's effect on the wave drag

Thickness versus wave drag

Basically, a thicker airfoil has a bigger curvature, and will accelerate the airflow around it more. This leads to more lift for the same speed. However, at cruise speed, closer to M=1, sonic effects will occur. This will lead to increased drag.

This can seen from the figure below, with increasing $t/c$, the value of $c_d$ is higher, and the rapid increase associated to wave drag starts earlier. The value of $M$ at which this occurs is called the Drag Divergence Mach number, $M_{DD}$.

Source: NASA supercritical airfoils: A matrix of family-related airfoils

Sweep versus wave drag

When a sweep angle is present, we can decompose the velocity in two components, of which only the one perpendicular to the chordline ($V_\bot$) is effecting lift (and thus wave drag).

By increasing the sweep, we can reduce the value of $V_\bot$, allowing the airfoil to experience a lower value of $M$, thus delaying the drag rise.

Source: Wing Shape Multidisciplinary Design
Optimization

Combined effects

As you can see, for wave drag, the two counteract eachother. If you have a certain value of $t/c$ and a certain $\Lambda$, this will lead to a certain $M_{DD}$. If for some reason, you want to increase the value of $t/c$, the wave drag increase will come earlier, leading to a lower $M_{DD}$. To maintain the same $M_{DD}$, you could counteract the effects of a larger $t/c$ by increasing $\Lambda$.

This is clearly shown by the emperic Korn-Lock-Mason method, which states:

$$ M_{DD} = \frac{K_A}{cos \Lambda} + \frac{t/c}{cos^2 \Lambda} +\frac{c_l}{cos ^3\Lambda} $$

This also shows the effects of lift on the value of $M_{DD}$.


What is this part on a Cessna 172 engine? Can any one tell me what this tube with the red is? This is a photo of a 1977 Cessna 172 engine. Looks like the tube is directly connected to the top of the crankshaft.

NOTE: Revised in response to poster comment: The engine is a Lycoming O-320 D2G, part of the series that replaced the disastrous H2AD engine which that '77 172 originally came with, in 1981 (the H2AD was '77 to '80). The H2AD engines (I have to think some joker at Lycoming put the AD designation in as a gag — it had a number of ADs against it), among other problems had a very small valve lifter contact face that would spall very quickly and trash the camshaft (on the plus side, you can remove the lifters without splitting the case).  Most 77-80 172s have had their H2AD engines replaced with Ds, which went back to the old lifter design, which also applies to the airplane pictured.

Anyway, the fitting is tapping into an oil gallery that supplies the valve lifters and has a plug at each end.  Someone has removed the plug at the front and installed the elbow to run oil pressure back to a cockpit indication, possibly because the port normally used on the accessory case is being used for something else.


Why does the Pressure ratio across the compressor increases when the mass flow rate is reduced? I am learning about Rotating stall in Axial Flow Compressors. So, when we throttle the compressor then there is Pressure Rise and later after the peak pressure rise tip stall starts to appear.
But I am trying to figure out the relation between mass flow rate and pressure rise.

The simplest way to understand this is to refer to Bernoulli's Theorem.  When the flow of a compressible fluid (in this case air) speeds up, the density of the compressible fluid goes down (and vice versa).  Pressure is directly related to density, so pressure also goes down when flow rate (velocity) goes up.

Mathematically, Bernoulli's Theorem is expressed $\rho \times v =$ constant.

Here, $\rho$ is density, $v$ is velocity.

Look at a diagram of a Venturi tube, and it will make sense.


Can I fly "into" the Grand Canyon? I haven't looked at the Grand Canyon on a sectional yet, but I know that it is definitely big enough (by far) so that someone could fly a plane under the level of the rim and stil meet all of clearance requirements for VFR flight.

Is it legal, and safe to take an airplane into the canyon?

The answer is: no, normal flights are not allowed under the canyon rim.

If you look at the sectional chart, you see this notice:

Searching through the CFR (Title 14, Part 91) brings up this Special Federal Aviation Regulation No. 50-2 - Special Flight Rules in the Vicinity of the Grand Canyon National Park, AZ.

Ther is also Supbart U of Part 93.

The Subpart U regulations seem to be the most current applicable regulations (please correct me if I am wrong).

The rule applies to everything under 18,000 feet MSL within an area around the park (like the chart says).

  Except in an emergency or if otherwise necessary for safety of flight, or unless otherwise authorized by the Flight Standards District Office for a purpose listed in 93.309, no person may operate an aircraft in the Special Flight Rules Area within the following flight-free zones:

It then describes the four zones: Desert View, Bright Angel, Toroweap/Shinumo, Sanup Flight-free Zone. You can't fly through these, but between them are "corridors" in which you are allowed to fly above a certain altitude. See this map for locations of the Flight-Free Zones and corridors.

There are also minimum sector altitudes for different areas, including the corridors, which are going to be the main thing preventing you from flying very low. The altitudes are different for commercial air tours versus transient and general aviation.

Also:

  no person may operate an aircraft within 500 feet of any terrain or structure located between the north and south rims of the Grand Canyon.

There are also noise limits depending on the aircraft type.

For some info on the background of these rules, see this NPS study.


What floatplane is this model? What floatplane is this model?

(own work)


Which aluminium alloy is used in the Boeing 747's fuselage? Which aluminium alloy is used in the Boeing 747's fuselage?

The primary alloy for the original 747 is 2024-T3, which is not the strongest or otherwise perfect, but a well-established convenient choice. Second is 7075-T6, used for major load-bearing parts.

7075 is stronger, but less workable and less tough than most; it comes closer to the edge for aluminum, so to speak.
6061 follows for for less-loaded or some more complex parts, where it's a staple, being overall the easiest to use out of common Al alloys. This is not nearly an exhaustive list, just the main alloys.


How does an airspeed indicator look from the inside? How does a typical GA airspeed indicator look from the inside and how does it work?

The Indicated Airspeed (IAS) is measured based on the difference between the static air pressure (measured via the static port) and the ram air pressure (measured via the pitot tube). A typical GA airspeed indicator looks like this:

(source: Wikimedia)

The difference in the pressures causes the diaphragm to flex. This flexing is then mechanically translated into a rotation of the indicator. See this question for the full details: How does the mechanical linkage of the airspeed indicator convert dynamic pressure to KIAS?


On which axis do we measure angle of attack and airspeed? The lift value depends on the relative airspeed of the plane. That's what every website says without anymore explainations.

But as we are talking about lift, are we talking about the relative speed ONLY on the axis of the chord line of the airfoil ? Or the relative speed, not related to any particular axis ?

Now about angle of attack (AOA ):

Is the AOA measured on a specific axis ? Or is it the absolue angle between the airspeed Vector and the chord Line ?
Or with other words : does AOA = 20° when the plane is on a 20° side slip ?? That's seems wrong to me but if we relate to the words of wikipedia for example thats what is being said.

Airspeed is always the total magnitude of the free-stream incident on the wing/airplane. In zero sideslip, angle of attack is exactly the angle between free-stream and body x-axis (could be chord for an isolated wing). In non-zero sideslip, it's nuanced; see below.

By industry standard (Ref. Etkins, Dynamics of Flight; Stevens, Aircraft Control and Simulation), the angle of attack ($\alpha$) and the angle of sideslip ($\beta$) are defined as Euler rotation from the coordinate axis attached to the free-stream such that the speed vector is $\begin{bmatrix}V_a & 0 & 0\end{bmatrix}^T$, where $V_a$ is the airspeed magnitude, to the body frame (where x-axis aligns with the chord):

$$\begin{bmatrix}u_a \\ v_a \\ w_a\end{bmatrix} = \begin{bmatrix}\cos\alpha\cos\beta & -\cos\alpha\sin\beta & -\sin\alpha \\
\sin\beta & \cos\beta & 0 \\
\sin\alpha\cos\beta & -\sin\alpha\sin\beta & \cos\alpha
\end{bmatrix}\begin{bmatrix}V_a \\ 0 \\ 0\end{bmatrix}$$

where $u_a$, $v_a$, $w_a$ are the incident speeds in the body frame.

Simplify, and we have:

$$\alpha = \tan^{-1}\frac{w_a}{u_a}$$

$$\beta = \sin^{-1}\frac{v_a}{V_a}$$

(Image Ref. Etkins, Dynamics of Flight)

Note that when sideslip is small (whereby $\cos{\beta}\approx1$), we can reduce the above to:

$$\alpha \approx \sin^{-1}\frac{w_a}{V_a}$$

Therefore, taking angle of attack as the projected angle between chord and free-stream is pretty darn good.


What maintenance actions are required after a bird strike? Does the SRM or AMM detail what Inspections to do following a bird strike? Do the engineers have to examine the bird remains too and report it to someone?

Depends on the nature of the strike. If a glancing strike—e.g., off the top of the windscreen, or the upper surface of a wing—maybe none is needed. Other strikes could take out the windscreen (some have, in fact).


Why do (or did, until very recently) aircraft transponders wait to be interrogated before broadcasting beacon signals? An aircraft’s transponder transmits signals that announce (at the very least) the aircraft’s identity, altitude, and direction of motion (plus, for most newer aircraft, a whole slew of other useful information); this is what allows secondary surveillance radar (SSR), the backbone of modern air traffic control, to function,1 and what makes it possible for aircraft’s TCAS to see other nearby aircraft and (if necessary) warn their pilots not to collide with them.2

For a long time, I thought that this worked by having the transponders broadcast this information in the blind, in case there was a radar or TCAS within range who might want to know about the aircraft attached to the transponder.  I’ve recently learned, however, that most aircraft transponders “speak only when spoken to”, not transmitting their information until they hear a radar or TCAS shouting “Anyone there?” into the deep blue sky (although ADS-B, which works essentially how I thought all transponders worked, is being rolled out, and will soon become mandatory in the U.S. for many aircraft) - and that this transmission is sent only to the shouter, and not to anybody else who might have an interest in the matter.3

I don’t get why most (or, until very recently, all) transponders don’t broadcast unbidden; it’s obviously feasible (otherwise we wouldn’t be able to have ADS-B), and would eliminate the need for those big, expensive SSR transmitters (ATC would just need a small, cheap receiver, plus a primary surveillance radar4 dish for detecting birds, weather, detached aircraft parts, aircraft with broken-or-otherwise-nonfunctioning transponders, and aircraft without transponders [such as most balloons and gliders], and as a backup in case the aforementioned receiver blew up/contracted malware/got stolen by space aliens).  So why do, or, at least, did, aircraft transponders have to be interrogated by a radar or TCAS before they spill the peanuts?5

1: Which, in turn, enables controllers (for instance) to stack multiple aircraft at different altitudes in close horizontal proximity to one another without risking a mid-air collision (whereas most primary radars can’t determine the altitudes of their targets - since they can measure the azimuth and slant distance of a target, but not its elevation angle - and, thus, can’t be used for vertical separation of targets), to warn aircraft if they sink dangerously low (same reason), to immediately identify new targets appearing on their screens, and to associate said targets with radio transmissions from said aircraft without having to ask the transmitter to make a 360º turn for identification purposes.

2: I’m sure there are a lot of other things transponders are useful for as well, but that I’ve forgotten to include.

3: For instance, this means that an aircraft has to have an operational transponder in order for its TCAS to work - it can’t just sniff out transponder signals sent by nearby aircraft in response to interrogation by other radars and/or TCASses.

4: Radars that detect targets by physically bouncing radio waves off them and listening for the echoes.

5: Like spilling the beans, except that aircraft serve (and spill) peanuts instead.

The Secondary Surveillance Radar system provides range in a method similar to primary radar: by measuring the time between the transmission of the interrogation signal and reception of the reply. The range is proportional to the time difference, minus a constant that allows for the aircraft transponder to perform processing.

This would not work if transponders replied without a interrogation.

Azimuth is traditionally found by observing the direction of the SSR antenna the moment this occurs, though some modern systems utilize the time delay between multiple receiver locations (multilateration).


What is the difference between a pitot tube and a pitot-static tube? What is the difference between a Pitot tube and a Pitot-static tube? If an aircraft fitted with Pitot tube and static holes on the fuselage, is it necessary to consider the static pressure measurements to calculate the airspeed?

A pitot probe strictly measure ram air pressure, commonly called "pitot pressure" or Pt pressure. A pitot tube measures pitot pressure and pitot pressure only. A separate static port is required to measure static pressure (Ps) and will usually be located on a section of the fuselage where airflow is minimized.

A pitot-static port is a combination pitot AND static port. That is, the tube itself has an opening for detection of Pt pressure and one or more openings for static pressure. In this case, there generally is no static port on the fuselage since it's built into the pitot-static probe.

TLDR: the only difference between the two is that a pitot-static probe is a pitot probe with static ports whereas a pitot tube is strictly just a pitot tube. :-)

Edit: Not sure if the original question was edited after my answer or if I missed the second part in my original response... Static pressure is required to know indicated airspeed because as altitude increases, airspeed increases due to less air resistance.


Did WWII fighters have inverted airfoils for horizontal stabilizers? Like would for example the P-47 most likely have symmetric, normal or inverted airfoil as horz. tail?

Is my analysis correct?:

It has a CG at 25-32% MAC according to manual. Since AC on wings is usually located around 25% MAC it safe to assume the CG is aft of AC. Since the setup is that way, it would be normal to have horizontal tail producing positive lift.

Also; did typical WWII planes have inverted airfoils as horizontal stabilizers?

What about general aviation planes today?

From the Longitudinal Stability (Pitching) chapter in the FAA Pilot's Handbook, two things stand out to me:
One:

Regardless of the airfoil shape, nose-heavy airplanes like WWII fighters will almost always have downforce on the horizontal stabilizer.
Even if the airfoil is not inverted, it will be attached at a negative angle of attack.

Compensation for this nose heaviness is provided by setting the horizontal stabilizer at a slight negative angle of attack.

Cutaway drawings for the P-47 seem to suggest they're not inverted, example:
(Source)
Two:
Unless it's a T-tail, the propwash combined with the downwash results in downforce on the horizontal stabilizer.
(Source)

P.S. Do not rush to accept, wait for votes or wait for our resident aerodynamicists to answer.


How to turn a fighter jet? I am not a pilot - just a student & play Ace Combat  sometimes

So I turned off the flight turn assistant in the Ace Combat flight simulator/game & now I have to manually control bank & pitch to turn. I also like to use a little yaw for stabilizing myself.

If I am not wrong - both pitching & rolling are controlled by the control yoke in jets. So, when going for a right turn from level flight, what does the pilot do:

Push the yoke a little right (attain 90+ degree rightward roll) and then pull the yoke towards him (to pitch up - i.e. actually execute the right turning arc). OR
Pull the yoke in a diagonal way i.e. towards SouthEast (assuming pilot was initially heading north) or 4'o clock - and the flight's internal computers break down yoke movement movement into respective pitch and roll magnitudes.

Just curious.

I think you are making things too complicated on yourself. To the best of my knowledge, fighter jet controls will in principle behave the same way as almost any other aircraft- they will in general actuate surfaces the same regardless of orientation. A left/right movement controls roll, a backwards/forwards movement controls pitch.

You would push the stick sufficiently to the right to bank until you reach the desired turn rate. You would have to maintain a little right stick to maintain the bank angle.
As you do the above, pull back a little to ensure that the vertical speed remains zero. You also need to add a little rudder to create a coordinated turn.

See the following images taken from here and here:


What is the physical scale of the turbulence that affects large passenger planes? What magnitude of displacement of air in turbulence conditions is large enough to affect (i.e. be noticeable in) an airliner?

Are there any minimum limits, so that even fiercely turbulent air below a certain displacement is not noticeable?

Summary

There are in effect no minimum levels of displacement that will not have noticeable effects. Even very small displacements, of an appropriate period and spectrum, can affect a large aircraft. Scale alone is not a limiting factor.

In more detail

Question 2: Are there any minimum limits, so that even fiercely turbulent air below a certain displacement is not noticeable?

The title addresses "large passenger planes" and not passengers, or passengers with vestibular anomalies, etc.

Generally mountain wave is considered "fiercely turbulent" as the updrafts and downdrafts can exceed the climb and descent capability of an aircraft.  However, the "frequency component" of the mountain wave can be very low, at times creating no human perception of motion. Yet the turbulence causes loss of control by virtue of exceeding the aircraft's capabilities of counteracting an upsetting force.

So in this instance, it is possible to have an extreme situation, and actually loss of control, by turbulence which is imperceptible by a human without instrumentation.

Question #1: What magnitude of displacement of air in turbulence conditions is large enough to affect (i.e. be noticeable in) an airliner?

The aircraft, and it's contents (including people) act as a system. The system can dampen the effects of some forces and cause amplification of other forces.

A tiny, repeated push to a child on a swing, can result in very large displacements of the swing, and is a good example of a form of resonance or amplification of the effects of a small push.  The pushes have to have the right periodicity, matching the resonance of the swing to be effective.

The above is an example of a resonant system, but we also have around us systems which dampen energy, such as the suspension on a car.  Driving a car over a bump in the road might create a very mild sensation in the car, but if we were riding on a solid wheel hitting the same bump at the same speed the resulting bump could be injurious.

So to only ask about displacement is akin to only asking about sound pressure of music. The frequency (notes) help create the music, and the periodic occurrence of the frequency energy also helps create the music (like beat). A drum strike can be very loud or a triangle very soft, but they are both noticeable in music, in part due to our perceptual training, but also due to the human auditory system.

So for an aircraft, a displacement at one frequency may have essentially no impact on the flight path, due to the systemic response of the aircraft. Furthermore that displacement may or may not be detectable by a human riding in that aircraft.
 To answer your broad, but limited to displacement question, becomes impossible to do so accurately if you choose to limit the dimensionality of the system you are seeking analysis of. (reference your comment)


Is it possible to create a direct supersonic airflow to a turbofan's afterburner in order to enhance the performance or reduce the fuel consumption? so I found out that SR-71 Blackbird is using what's called "turboramjet" and I find the idea a bit appealing since they say with such engine, the Blackbird is more fuel efficient at it's top speed. I know that the mechanism for such engine is extremely complicated, but what's on my mind is not making an engine like Blackbird's, more to the point of having a direct supersonic fresh airflow to the afterburner to keep the fuel consumption slightly lower thanks to more oxygen to keep the afterburner effectively burn(because I heard somehwhere afterburners burns 3 times more fuel than dry thrust, I hope this can reduce it to only twice or even 1.5 times original dry thrust fuel consumption and have the same performance). Is it possible to do such thing? what would be the main problem to such engine/design? can it produce more thrust/more efficient in fuel consumption? and for the sake of calculations, let's say the turbofan engine in question is GE F-414-EPE, on afterburner, in supersonic speed.

The J-58 took compressed air from the compressor at stage 4 and piped it directly into the flow aft of the turbine. This cooled the exhaust stream that entered the afterburner, so the starting temperature there was lower and the density higher, which increases efficiency and thrust. Note that the intake of the SR-71 slowed the flow down to Mach 0.4, so all internal flow was subsonic. Only when the hot exhaust gas in the afterburner expanded again would the flow speed increase to supersonic speeds again.

This is only possible because the intake would already compress the air by a factor of nearly 40 when flying at Mach 3.2. This precompression scales with $$p_0 = p_{\infty}\cdot\frac{(1.2\cdot Ma^2)^{3.5}}{\left(1+\frac{5}{6}\cdot(Ma^2-1)\right)^{2.5}}$$
so the precompression is much lower (less than 6) for a typical F-414 maximum speed of Mach 1.8.

($Ma$ = Mach number, $p_0$ = ram pressure, $p_{\infty}$ = atmospheric pressure).

The gains in efficiency scale with the ratio of starting and exhaust temperatures (measured from absolute zero), so the increase in efficiency is much lower than what you seem to hope for.

Make sure that flow speed at the entry of the afterburner is decidedly subsonic. Supersonic flow at the start of the afterburner section will only delay ignition until the flow exits through the nozzle. All afterburners have rings inside, called flameholders, which cause local separated flow, so some burning gas is always present to ignite the newly arriving fuel-air mixture.


In the United States, is there any way I can fly without a medical certificate? I live in the United States. I haven't been able to get a medical certificate yet, but I'm interested in flying airplanes (or maybe other kinds of aircraft). Is there any way I can fly without having a medical certificate? What are my options here?

There are lots of options for flying without a medical certificate in the United States. Most of the regulations about medical certification are in 14 CFR Part 61, Section 23.

Note that even if an operation does not require a medical certificate, it's still illegal to fly if you have a medical condition which would make it unsafe for you to fly.

Your options for flying without a medical certificate are:

Fly with an instructor, or someone else as the pilot in command (FAR 61.23(a))

You usually need a medical certificate to act as the pilot in command, but you don't need a medical certificate to merely handle the controls!

This means that you can take flying lessons without a medical certificate, as long as you have an instructor with you. The instructor will act as pilot in command, but you will get to do some (or maybe even all) of the flying.

This also means that if you have a friend who's a pilot (with a pilot's license and a medical certificate), and you and her are in an airplane together, she can let you do all of the flying! She will need to act as pilot in command, meaning that she's responsible for ensuring that everything is done safely, and for taking control of the aircraft if need be. But she can have you do the flying.

In case you're working towards a pilot's license, flying lessons received from a certified flight instructor can be logged as pilot time. If you're flying with a friend who's not an instructor, you cannot log that time.

Fly a glider or a balloon (FAR 61.23(b))

You don't need a medical certificate at all in order to fly a glider or balloon. Even without a medical certificate, you can still:

Get a solo endorsement from an instructor and fly by yourself.
Get a pilot's license and fly with passengers.
Get a commercial pilot's license and fly for compensation.
Get a flight instructor certificate and give flying lessons. (In a balloon, you only need a commercial pilot's license to give flying lessons; there is no flight instructor certificate for balloons.)

If your goal is to get an airplane pilot's license, pilot time in balloons and gliders can be counted towards that license! To get a private pilot's license for airplanes, you need 40 hours of pilot time; some, but not all, of that time is required to be done in airplanes.

Fly a light-sport aircraft (FAR 61.23(c)(1) and (2))

If you have an aircraft whose maximum takeoff weight is 1,320 pounds or less, it's probably a light-sport aircraft. If you fly a light-sport aircraft under the sport flying rules, then you can satisfy the medical requirement using a driver's license instead of a medical certificate. If your driver's license has any limitations, then those limitations also apply to your flying.

However, there's a caveat. In order to fly a light-sport aircraft using a driver's license instead of a medical certificate, you must satisfy either of the following conditions:

You have never applied for a medical certificate.
After the most recent time that you applied for a medical certificate, you were issued the certificate, and that certificate has never been suspended and revoked.

This means that if you're a licensed sport pilot, and you don't have a medical certificate, and you apply for a medical certificate, the privileges of your sport pilot's license go away until the medical certificate is issued!

Time in light-sport aircraft can be logged as pilot time.

Fly under BasicMed (FAR 61.23(c)(1) and (3), and 61.113(i))

If you've had a medical certificate in the past, but it's expired, you can still fly if you meet all the requirements for BasicMed. The main requirements are:

You must have a driver's license.
If your driver's license has any limitations, then you must also obey those limitations while flying.
You must have held a medical certificate at some point after July 14, 2006.
Your doctor must do a medical examination and sign off.
Your most recently issued medical certificate must not ever have been suspended or revoked.
Your most recent application for a medical certificate must not have been denied.
You must comply with the operating limitations in FAR 61.113(i).

Fly an ultralight aircraft (FAR 103.7(b))

If you're brave enough to fly an ultralight aircraft, good news! You don't need a medical certificate (or even a pilot's license) to fly a Part 103 ultralight aircraft.

Time in ultralight aircraft cannot be logged as pilot time.


Is it possible to build a turbojet engine with aluminum cans? (Soft drink cans) I'm interested in building a working model of a turbojet engine, but I don't have a lot of supplies. So I'm wondering if it's possible to use aluminum cans for construction, for every body part. While we're on this topic, would the heat melt the aluminum?

No, you cannot make an entire model jet engine out of aluminium.
Most fuels burn at 1000+C and aluminium melts at around 660C: Even if you keep the burning contained in airflow (thus away from the walls) the heat transfer will still damage the aluminium.

You could make the majority of the engine from it, though: Just as long as you find something more suitable for the 'hot' parts.


Why is the lower deck of the Airbus A380 curved like a single deck airplane? I recently traveled on the lower deck of an A380 and the section where the side walls of the fuselage and its roof top meet is curved just like any single deck airplane.

Credits: Wikimedia Commons

If there is a deck above me (which there definitely is) then why does the lower deck have to be curved near the top? Shouldn't it be straight on the sides?

Shouldn't it be straight when there is one more deck above it?
I'm sure that it's just the interior that is curved and the external structure is indeed straight but does it serve any important purpose?

Details:

Airline:  Emirates
Aircraft: A380-800
Seat: Row 58

Here is what i saw:

Notice that even the roof is curved, is there a structural reason for that as well? On the side wall one of the rows has an extra covering on it, I'm almost sure that is to cover one of the brackets as mentioned in the answer below but even without that the whole cabin is curved.

The cabin interior is curved to accommodate, among other things, the brackets holding the upper deck floor beams.

These brackets are a structural feature that transfers the weight of the upper deck to the fuselage with considerably less reinforcement that a straight T-joint. The bracket acts as a small truss element, creating a triangle with the deck and the fuselage that partially turns bending loads into axial ones.

Here is an actual production cutaway, noticeably different from wiki's simplified representation of the A380's cross-section:

It would be possible to only wrap the interior lining around the brackets themselves, not along the whole length. But they're not the only thing there (although others could be rerouted; structure requires testing), and this curve saves a bit of weight, so Airbus curves the whole interior by default. An airline could request something different if they wanted to.


Are these two aircraft too close to each other? One aircraft is taking off and another is quick to land after it. Are they within safe limits?

They're not too close

They (almost certainly) are not closer to each other than is allowed.

It would be quite extraordinary if a pair of airliners at an airport were allowed by air-traffic control to approach each other in violation of limits, which not only include the distances of time and space demanded by safety, by additional margins as well.

If there had been a violation of those limits, it would have recorded as a matter of course and investigated.

On that basis I think it's safe to say that it's extremely unlikely that approach limits were violated.

The camera doesn't lie, but YouTube doesn't tell the truth either

A second point is that it is extremely hard for human beings to judge distances, positions and speed in three-dimensional space.

Frankly, it's a wonder that we're ever able to play table-tennis, but the fact is that when you're looking at a pair of aircraft you have little chance of accurately judging what they are doing in relation to each other.

That's especially so when the aircraft are on YouTube. I bet even a champion wouldn't be able to play table-tennis on YouTube...


What is this strange looking aircraft? This website describes twin-tail aircraft. It has a photo of a strange-looking aircraft with a twin tail, and turboprop engines, resembling a C-130 Hercules.

There was no registration or tail number on the aircraft. I looked around at other images trying to find the name, but it did not feature the same aircraft. The aircraft looks fictitious.


Can an ICAO contracting state charge money for NOTAMS? does anyone know of any written icao rules where they state if a contracting state is allowed to charge money for the dissemination of NOTAMS? are products like notams and Local Aeronautical Circular messages supposed to be free for everyone? so that safety can be guaranteed ?

Extract from ICAO Annexe 15 (Aeronautical Information Services):

3.5 Cost recovery

Recommendation.— The overhead cost of collecting and compiling aeronautical information/data should be included in the cost basis for airport and air navigation services charges, as appropriate, in accordance with the principles contained in ICAO’s Policies on Charges for Airports and Air Navigation Services (Doc 9082).

Note.— When costs of collection and compilation of aeronautical information/data are recovered through airports and air navigation services charges, the charge to an individual customer for the supply of a particular AIS product, either in paper or electronic form, may be based on the costs of printing paper copies or production of electronic media, and costs of distribution.

NOTAMS are issued gratis (free) as the information can be essential to the safe conduct of flights. The raw NOTAM is available to any member of the public, anywhere in the world online via the country's AIP (Aeronautiical Information Publication/Services) documents which are of a standard format. You'll probably have to register at no cost as a user though.
Click here for the FAA site
A company could charge a fee for processing the info thus obtained so as to tailor the NOTAM list and filter it in a manner suitable for a particular Operator. Or they could put it into a more user friendly format. It maybe noted that briefing areas have (computer) terminals dedicated to this linked to the official NOTAM server, and these terminals can have powerful filtering capabilities already provided by the issueing/distributing authorities.
ICAO lays down that safety related info should disseminated in such a way that there's no undue hindrance for the end user. Think of it this way - could the authority refuse this info to the pilot if it so happens that the subscription was not renewed on time due to any mundane reason?


What is the relationship between angle of attack and wake turbulence? It is said that when the preceding airplane is heavy, clean, and slow, wake turbulence is much hazardous due to greater angle of attack is requried. However, why does increasing angle of attack result in increase in wake turbulence? (or wing tip vortices)

It is not the angle of attack - downwash intensity grows with lift squared and inversely to the squares of wingspan and speed. Please read this answer on how wake turbulence forms. Now let's look at the parameters you listed:

Heavy: Yes, the heavier the aircraft, the more lift needs to be created. Induced drag grows with the square of lift.
Clean: Not really. With or without flaps the amount of lift is the same. Only the lift distribution over span might be different, but this does not make much of a difference for the wake.
Slow: Absolutely! Induced drag is proportional to the inverse of speed squared.

What is missing from the list is wing span which lets induced drag grow with the inverse of its square. The angle of attack is only indirectly responsible for induced drag because lift is (within limits) proportional to the angle of attack.


Are there regulations for the minimum amount of toilets per passenger? Are there any rules or guidelines that define the minimum amount of toilets per number of passengers on an aircraft? I know there are similar rules for cabin crew, emergency doors etc.

It seems to be varying per airline the amount of toilets (similar aircraft type)

(this answer is specific to US laws and regs for domestic flights)

No, there are not. And, in fact, it is perfectly legal to fly with ALL of the toilets broken and unusable. No restrictions on flight time, either. The airline is required to notify all passengers that the flight has no working toilets. (I'm not sure if any compensation is required for passengers electing to not board the flight).

The Department of Transportation does provide the following in their Aviation Consumer Rights rules:

(in the section discussing tarmac delays): While the aircraft remains on the tarmac lavatories must remain operable and medical attention must be available if needed.

Although it's obviously not possible to make the lavatories available during a tarmac delay if the lavatory is broken, there are no rules prohibiting the flight from departing if the lavatory is broken.


Why is the Su-27 so much larger than the MiG-29? I was watching the following video of the Russian Knights and Swifts aerobatic teams flying together in formation. The contrast in the size of their airplanes is striking.

Why was the Su-27 designed to be so much larger than the MiG-29?

Do the two planes have very different missions?

The Su-27 and Mig-29 were the result of high-low concept subscribed by both the USAF and Soviet Air Force (VVS) in the 1970s. Basically, this involved the development of two different fighters, a high performance medium weight fighter crammed with every advanced technology (which made it expensive) and a low cost light weight fighter to make up the numbers.

In this direction, the USAF announced the FX (Fighter eXperimental) program, which resulted in the McDonnell Douglas F-15 Eagle (designed to counter the misunderstood Mig-25), followed by the LWF (Light Weight Fighter) competition, that gave birth to the General Dynamics F-16 Fighting Falcon.

The Soviet equivalent of these programs was the PFI( Perspektivnyi Frontovoy Istrebitel, Perspective Frontline Fighter), which called for a high performance multirole aircraft to counter the new generation US aircraft and the LFI (Lyogkiy Frontovoy Istrebitel, Light Frontline Fighter), which called for a low cost fighter with respectable ground attack capabilities.

The PFI was required to operate 250-300 km beyond the frontline, with sizeable internal fuel and a comprehensive Communications, navigation, avionics and weapons suite. The LFI, on the other hand was required to operate 100-150 km beyound the frontline, while being easy (read cheap) to build and maintain and capable of using semi-prepared strips while carrying limited armament (initially limited to a couple of medium range AAMs and gun).

In 1972, the VVS tasked the Sukhoi bureau to build the PFI, resulting in the Sukhoi Su-27, while the Mikoyan bureau got the LFI, resulting in Mikoyan MiG-29.

F-15 and F-16; image from sunketh.wordpress.com

Basically, Su-27 is to Mig-29 what F-15 is to F-16; hence the size difference.