Is it ATC's responsibility to ensure read backs are correct? I have experienced this a few times in the last couple of months. When the ATC assigns me a squawk code and I enter it in the transponder, a few minutes later when I try to reconfirm the squawk code, they give me a new code. I know that they can see me on the radar anyway, just may not identify me positively. I noticed this more on an inbound flight to a towered airport.

This happened yesterday too. I was assigned to squawk 6451. I replied to confirm it and entered it in the transponder. While holding short for takeoff, when I asked the controller to reconfirm the code, he said that it is 6455.

What is the controller's responsibility if they confirm an incorrect read back? Since this happened to me several times, I am concerned if such incident can impact safety, traffic advisories or aircraft separation?

A controller, should be on the lookout for all incorrect readbacks. But controllers are human, and can easily miss them, or say things in correctly. Incorrect squawk codes are often more of an annoyance versus an actual separation issue. It'd become an issue if they didn't take action when it was noticed that there was an incorrect code airborne, and let you truck on your way and not perform appropriate handoffs or inform others of any issues with your flightplan/target.

Most of the time, an incorrect beacon code will be flashing on the scope, if it's not assigned to someone else, and the controller will look through their list to find the correct code. If you tag up under someone else's code, then it becomes more of an issue, as they have to realize it's incorrect, suspend the datablock, and flightplan(or most likely drop it out of the system and reenter it) (flightplan issue is often delegated to others in the operation), and hunt for your correct code.


What does "the other's right" refer to in 14 CFR Part 91.113? There's a part in 14 CFR Part 91.113 (regarding airborne right-of-way rules) that's been confusing me:

Converging. When aircraft of the same category are converging at approximately the same altitude (except head-on, or nearly so), the aircraft to the other's right has the right-of-way.

Specifically, I don't fully understand the phrase "the aircraft to the other's right" - it would seem both aircraft will either perceive themselves as being to the left or right of the other meaning either both aircraft or neither aircraft would have the right of way. This is obviously not what is intended in FAR, so could someone give a more intuitive explanation of this? Thanks!

You wrote that:

it would seem both aircraft will either perceive themselves as being to the left or right of the other meaning either both aircraft or neither aircraft would have the right of way.

But that's only the case if the two aircraft are approaching head-on, or nearly so, and the FAR you quoted already accounts for that situation:

Converging. When aircraft of the same category are converging at approximately the same altitude (except head-on, or nearly so), the aircraft to the other's right has the right-of-way.  [Bolded emphasis mine.]

If the aircraft aren't approaching nearly or actually head-on, one aircraft will be unambiguously on the right:

As an extreme example, take the case of two aircraft "approaching" each other on side-by-side parallel courses in the same direction.  Obviously, in this situation, one aircraft will be on the right (and have the right of way).

(Red and blue are each a different scenario.)

Now consider two aircraft approaching each other on perpendicular courses (with a 90° angle between the two).  One aircraft's pilot will need to look to the left to see the other aircraft, and the other aircraft's pilot will need to look to the right to see the first aircraft.  The aircraft whose pilot has to look left is the aircraft on the right, and they have the right of way; the other aircraft is to the left of the first aircraft, and will have to give way.

Even if there's a 135° angle between the two aircraft's flightpaths, one pilot will still be seeing the other aircraft noticeably left of the center of their windscreen; this pilot's aircraft is on the right, and has the right of way.  The other pilot will have to look through the right side of their windscreen to see the first aircraft; the other aircraft is on the left, and has to give way.


Is a hold short expected when given taxi directions to a runway? When a ground controller gives taxi instructions to a runway, are pilots expected to hold short by default if an explicit instruction to hold short isn't given?

Yes.  A taxi clearance enables you to taxi an aircraft through a controlled movement area within the terms of the clearance given by ground control.  Entering an active runway requires an explicit and separate clearance from the tower to do so.

In addition, crossing any runway which intersects your taxi path requires an explicit clearance from ground control to do so.  This clearance can be included in the original taxi clearance or a separate clearance wile your aircraft is currently taxiing.  If you reach the hold lines of an intersecting runway, you must hold short unti you are cleared to cross by ground control.


What is the maximum amount of flight hours an aircraft can have a month? The reason I ask this question is because I am a programmer and developing ETL processes to calculate reliability of products that are installed in aircrafts.

I have been getting A lot of bad data from the OEMs.

I have been told by an engineer at my organization that the maximum number of flight hours an aircraft can have is 400 hrs a month.

Is this accurate per FAA regulations?

I don't think there is any regulation on max flying hours, just regulations on maintenance intervals.

The "A" check is the most frequent check, and according to Wikipedia:

  This is performed approximately every 125 flight hours or 200–400
  cycles. It needs about 20–50 man-hours and is usually performed
  overnight at an airport gate or hangar. The actual occurrence of this
  check varies by aircraft type, the cycle count (takeoff and landing is
  considered an aircraft "cycle"), or the number of hours flown since
  the last check. The occurrence can be delayed by the airline if
  certain predetermined conditions are met.

The other checks include:

B check - every 4–6 months, requiring about 150 man-hours and is usually performed within 1–3 days at an airport hangar
C check -  every 20–24 months, requiring about 6000 man-hours, taking 1 to 2 weeks to complete
D check - major maintenance check, occuring about every 6 years, requiring 50,000 man hours, generally spanning a couple months.

Note that all of these times are approximate, depending on the exact maintenance plan filed by the airline and the aircraft type. Also cycle count may be factored into the maintenance intervals in addition to flight hours so aircraft that do many short-haul flights may have more frequent maintenance.

So in any case, only looking at the A checks, if you can land, refuel, service, and get back in the air in 2 hours between 10 hour flights, the plane could stay in the air for 20 hours/day. Every 6 days, it will need some downtime for the A checks, let's say the airline puts enough  people on it to get the check done in 5 hours. So that's 125 hours per cycle: 120 hours flying, 5 hours in maintenance. They can fit 4.83 of these cycles in a 30 day month so the aircraft could be flying up to 580 hours in any given month (but that last A check gets deferred to the next month, so that means less time in the air that month.

With longer flights (which reduces the overhead from turnaround times) and tighter turnaround times, the flight hours per month could be higher. If you really want the maximum for a month, then if you assume 125 hours per maintenance inverval and that the plane is kept in the air as long as possible with 0 turnaround time, that's around 690 flying hours out of 720 total hours in a month.

Of course, this makes a big assumption that the A check interval really is 120 hours, and that the time to do the maintenance is 5 hours, in the real world both numbers will vary based on aircraft, airline, and maintenance staffing levels.

Plus, over the longer term, you need to factor the other, less frequent but also more time consuming maintenance checks (B through D checks), as well as allow downtime for unexpected repairs.


Does weight affect the fuel burn calculations in a light GA airplane? When calculating fuel burn in say a Piper Archer, I usually just use the conservative estimate of 10GPH, but, does the weight of the aircraft affect my fuel burn?

Assuming I have full fuel and am taking off a max takeoff weight, will I still burn the same amount of fuel in 4 hours as I would if I took off with only myself in the plane and full fuel?

The engine doesn't care how heavy the airplane is (or how well it is flying), but you might.

As long as you are cruising around at a particular altitude and power setting, then the engine is going to consume fuel at the same rate.  A heavier airplane will require increased lift, which will induce greater drag, and will have a lower forward airspeed as a result of that same power (assuming it is not so heavy that it prevents you from maintaining altitude).

If on the other hand you have a particular airspeed you want to maintain, then the power needed for that speed will depend on weight.  Lower weight, less power necessary, less fuel flow required to supply the power.


Can I log my military training time as PIC, if I have a PPL? It's my understanding that instrument and commercial training time can be logged as PIC, after you have a PPL.  I received my PPL in a standard C-172.

I was about to go through and log all my military training time (in the T-6 and T-38) this weekend, and was wondering if I can log all that as PIC?

This questions specifies that you must be be rated in the category and type to do so.  I'm not really sure what that means.  Of course I don't have any FAA ratings other than my PPL in the 172.

So, can I log my T-6 and T-38 time as PIC for my civilian records?

Thanks!

For FAA purposes you can log PIC time in the T6 because you hold a license in the airplane, single engine, land category and class.  However, the USAF might not see it that way.

Since you do not have an FAA license for the category and class multi engine land, you can only log PIC time for your solo flights in the T38.


In the US, do ultralight aircraft have tail numbers? Just wondering if ultralight aircraft in the United States have tail numbers like the larger general aviation aircraft have?

Assuming that you mean an ultralight as defined in part 103, there is no requirement to be registered or have a tail number. 14 CFR 103.7(c) says:

  Notwithstanding any other section pertaining to registration and marking of aircraft, ultralight vehicles are not required to be registered or to bear markings of any type


Will manned aircraft have to defend ground targets against unmanned aircraft in the future? Given that current Unmanned Combat Aerial Vehicle (UCAV) development is mainly directed towards the strike role, is it most probable that a future manned vs unmanned combat aircraft scenario will involve manned aircraft attempting to defend ground targets against attack by UCAVs?

Some advantages of UCAVs over manned aircraft in the strike role:

The enemy doesn't gain hostages when they get shot down over enemy territory
The numbers that can be deployed are limited by the rate at which they can be turned out on automated production lines, not by the time it takes to train a combat fast jet pilot to a high standard (about 5 years minimum)
The UCAV can potentially be much smaller than a manned aircraft, if a reduction in range is acceptable, reducing the radar signature and vulnerability to air defence systems
As a result of 3, the UCAV can potentially be based nearer the area of operations and launched by catapult or using a rocket booster, leading to a shorter reaction time

In a scenerio where manned aircraft are intercepting UCAVs it is probably reasonable to assume that the UCAVs will have an advantage in numbers. UCAVs engaged in tactical missions will probably operate at low level and rely on superior manouverability and short range missiles to defend against attacks by manned fighters.


Does the Air Force (United States) help design their own planes? I know that companies such as Lockheed Martin and Boeing design and build planes for the US Air Force. However, when I was thinking about this, I realized the Air force has no part in designing the thousands of aircraft they own (or am I wrong). Does the Air force basically act as a consumer or do they help in the process of designing the jets? (I know there is a job of an aircraft mechanic but they act as maintenance people and don't design the jet.)

While the Air Force (or other military unit) does not design their own jets, they do release specifications and have contests (e.g. the ATF that selected the F-22). This is basically the way it works (and not just for fighter procurement):

A design specification is released, these include things like range, mission, weapons.
A "paper" design is submitted from companies like Boeing and Lockheed Martin. These may be based off of existing designs or "clean sheet" designs.
The military funds the development of one or two prototype aircraft from a number of paper designs.
The military evaluates each design against the specification and selects a "winner".
A larger contract is awarded

So it's not really up to companies like Boeing or Lockheed Martin to come up with their own designs and sell that to the military. They work under strict program requirements to develop something "to spec" and then demonstrate the capability. The military has a hand in the design process as this goes along, so they are not entirely "out of the loop".
The secondary market is different though. Boeing may sell (with the approval of the US Government) these aircraft to certain foreign military groups. These work more like selecting something from available stock in the dealer lot.


What is the average deviation from the PAPI glide slope at the threshold? If one approaches with three red and one white light what will be the average deviation from the standard threshold height of 50 feet?

If one approaches with three red and one white light what will be the
  average deviation from the standard threshold height of 50 feet?

Short answer

It depends on the location of the PAPI (and its slope). For a 3° PAPI at 1,000 ft (305 m) from the threshold, three red lights means you cross the threshold between 43 and 49 ft.

PAPI heights at runway threshold

Explanation

There are different ways to calculate this. One is to start from the distance of the change from  red to white for the third light, which is given in this table (line B):

Source

The right side is for APAPI, let's ignore it. d2 is the distance from the PAPI (not from the threshold) an aircraft flying at a height of 1,000 ft sees the system switching from 3 red lights to 2 red lights.

If at this point the aircraft starts following the B glideslope, it will maintain this 2/3 red lights limit until landed. It will have lost 1,000 ft over a distance of d2.

A simple application of Thales theorem, about proportionality, says:

height at threshold = 1,000 * d / d2

where d = distance PAPI to threshold.

Example:

PAPI slope 3°
d2 = 3.33 NM = 6,167 m
Distance PAPI to threshold = 305 m

so height at threshold = 1,000 * 305 / 6,167 = 49 ft

If we do the same calculation for the other light transitions, we get: 60, 55, 49, 43 ft respectively.

Actual height

To elaborate on CVn's comment: A PAPI isn't corrected for parallax error. The sensor being the eyes, and having a difference between eyes height and wheels height, the PAPI glide path is always higher than the landing wheels.

In particular when the glide path crosses the threshold at 50 ft, the wheels are a bit lower, the actual height depending on the particular aircraft configuration and attitude. This error comes in addition of the glide path inaccuracy itself (+/- 3 ft at the threshold between lights + angular setup error). A PAPI is not a precision instrument, and the landing has to be done visually.

Larger aircraft performing precision landings are fitted with radar-altimeters located on the belly, well below the pilot eyes and close to the main wheel. Their raw value is usually corrected, by adjusting the aircraft installation delay beyond what is required for line length cancellation, to indicate the main wheels height.

This improved precision allows for lower decision heights (the point where the pilot is not allowed to pursue the landing if the runway isn't in sight).


How will the altimeter read in air colder than ISA? When flying in air which is colder than ISA (International Standard Altitude), how will the altimeter read compared to true altitude?

My manual says the altimeter will over read - why?

Air expands as the temperature increases and it compresses when the temperature decreases.

image source: aviationweather.ws

When it is colder than ISA, the air column is compressed and therefore you are flying lower than the altimeter is indicating. In other words: the altimeter will over read in cold air.

So to fly safely over an obstacle at a cold day, you have to add extra margin to the obstacle's height, because your altimeter will show a higher altitude than your true altitude.


How is a propeller diameter for given application determined? let's say I need 1000 N of thrust for a given aircraft and flight velocity. I have available a fixed pitch propeller with a given shape, and thus given performance to advance ratio curves. Let's say the propeller diameter is 2m.

Now, what would determine if this is the best diameter for the application on hand? What if the blade shapes were scaled up to 4m? Wouldn't this generally be better for efficiency as the RPM would decrease and the air acceleration required would be lower? Other than practical factors like clearances, stability, etc., what aerodynamic reasons are there to stop increasing the diameter at a certain value?

Let's start over with the basics.

In any application, the prop tips have to be maintained subsonic or else propulsion efficiency will suffer and noise generation will become extreme. Therefore, for any given prop diameter, there is a do-not-exceed RPM value associated with the sonic limit: big props have to turn slower, smaller ones can turn faster.

(Prop diameters are also limited by ground clearance considerations but for small planes like a Cessna 172 or a Cherokee 160, the need to keep the prop tips out of the grass can be accomodated readily.)

Next you have to match the prop with the best power operating point of the engine turning it. For 4-stroke gasoline engines of typical design this will be around 2500 RPM at which the engine is producing roughly a half horsepower per cubic inch of displacement. You then pick the maximum allowable prop diameter to keep the tips subsonic at 2500 RPM.

Next you assume the minimum number of blades for a start (2) and select the pitch angle at that diameter which will absorb the full output of the engine running at 2500 RPM. If two blades will not load the engine enough to hold it at 2500RPM at full throttle, then you add another blade and repeat the process.

For engines of less than about 180HP, the right answer is a two-bladed propeller of fixed pitch. For engines bigger than that, the right answer is generally a two- or three-bladed propeller with variable pitch.

One way to beat the sonic limit while getting more power out of the engine is to gear the engine down so it is spinning faster, and thereby generating more power, while still maintaining the prop tips subsonic. This also lets you further reduce the prop tip speed and go for a larger diameter prop if you have the ground clearance available, which will generally be more aerodynamically efficient than a smaller one- but running the engine faster shortens its service life and the cost to rebuild a geared engine has to include the cost to rebuild the gearbox itself.

For light aircraft in the homebuilt class or for ultralights, a less-expensive alternative to the geared engine is one with a rubber-belt reduction drive. This lets you use lighter and simpler 2-stroke engines which have a best power point of around 4500 RPM and still maintain the prop tips subsonic.


Can I use dual time for the 10 night takeoffs and landings required in 61.129? For the 5 night VFR hours and 10 T/O at class B/C/D required in 14 CFR 61.129(a)(4)(ii), can you mix/match solo and dual instruction (as PIC) time for these hours and landings? In other words, are they combinable? I may reach all 5 solo but definitely have more than 5 night dual (as PIC).
Also, does being under the hood dual with CFI count? I would expect not since you're not flying "the traffic pattern" (i.e. right base, straight in, etc.) but just wanted to get consensus.

No being under the hood does not count as "night flying" see this question for the FAA's definition of night flight.
You dont need to be alone in the aircraft for these TO/LD's while the FAA definition of "solo flight" which this question covers could apply it does state that an instructor can be present

(4) Ten hours of solo flight time in a single engine airplane or 10 hours of flight time performing the duties of pilot in command in a single engine airplane with an authorized instructor on board (either of which may be credited towards the flight time requirement under paragraph (a)(2) of this section), on the areas of operation listed under § 61.127(b)(1) that include -

(ii) 5 hours in night VFR conditions with 10 takeoffs and 10 landings (with each landing involving a flight in the traffic pattern) at an airport with an operating control tower.


What's the name of the runway equipment referred to in this video? In this Air Crash investigation video clip (31:06), a beacon system that tells the pilots whether the aircraft is laterally aligned with the designated runway is mentioned. What's its official name?


What happens when I tell ATC to "mark the tape"? You can find anecdotal mention of this phrase among pilots you may talk to as well as postings on various forums.  The idea conveyed is that telling a controller to "mark the tape" means they will make take some action to note the current time for the audio recording of his seat, which can then be referred back to by someone.  As many anecdotes you can find about this, you'll find just as many saying this phrase is essentially an old wives tale, and means absolutely nothing.

Given a situation with a controller that I'd like to bring to the attention of his superiors, or perhaps just with him over the phone, does using the phrase "mark the tape" do anything?  If it does nothing, what is the proper procedure I should use to review something with a controller or their supervisor (e.g. noting time and frequency, asking for a phone number)?

These days, with digital recording, it's likely that nothing special happens.

"Mark the tape" is a holdover from when ATC recordings were actually on tapes - you could ask a controller to "mark" a tape to hold it and prevent it being recycled for another recording while your request for a copy of the tape is being processed. (Anecdotally I've been told some facilities had tape rotations as short as 15 days, and a FOIA request letter could easily take longer than that to make it to the facility).

Today much (probably most) of what is said on the frequency is recorded digitally, direct to hard drives, and kept around "essentially forever" as one of our local controllers put it when this came up at a recent event.  Basically the virtual "tapes" stick around for as long as the facility's recording machine has disk space to store them, and since audio files aren't that big facilities can store recordings a lot longer than they did in the days of tape.

All that's really needed to pull a record to review it with a controller/supervisor is the date, time, facility, and frequency (and your aircraft callsign would probably be helpful too) - e.g. "April 4, 2014 - JFK Local Control for Runway 04R (119.1) - United 123 Heavy".

"Mark the tape and give me a phone number" survives as non-standard phraseology that lets the controller know that you will likely have a bone to pick with someone when you get on the ground and gives them the opportunity to tell their supervisor that an annoyed pilot will be calling the facility in the near future (and hopefully give the supervisor time to listen to the tape).
The useful part is really getting the facility phone number so you know who to call when you land.


Can ramjets reach higher thermal efficiencies than gas turbines? Since a ramjet isn't constrained by turbine inlet temperature like a gas turbine is, it seems to me that it should be able to achieve a higher thermal efficiency, given that it's operating at a speed that results in a comparable compression ratio. Is this true?

The Carnot condition notwithstanding, whether a ramjet actually operates at a higher "hot end" temperature than a turbojet is questionable, as well as whether a comparable percentage of thermal energy in the exhaust stream is converted to kinetic energy.
Further, just because there's no turbine, doesn't mean there's nothing in the hot part of the engine that can melt -- combustion chamber walls are made of real material, as is the flameholder, and due to cost of exotic metals, likely aren't as heat resistant as first stage turbine blades.  Even a very simple, low-powered ramjet (see YouTube) can operate at a temperature that makes the hot section glow from heat; one capable of propelling a high speed aircraft will presumably run even hotter, requiring tradeoffs in efficiency to prevent thermal damage.


When is a runway considered to be wet or slippery for 135 or 121 landing performance considerations? For the purposes of following FAA regulations, when is a runway considered to be wet or slippery in the context of landing performance calculations? Specifically, what definitions or guidance on meaning for the terms "wet" or "slippery" should a pilot or dispatcher use in making the determination required by §135.385 or §121.195 as to the runway condition?

14 CFR 135.385 gives the following regulation pertaining to §135 operations of Turbine powered Large Transport Category airplanes:

  Large transport category airplanes: Turbine engine powered: Landing limitations: Destination airports.

  (d) Unless, based on a showing of actual operating landing techniques on wet runways, a shorter landing distance (but never less than that required by paragraph (b) of this section) has been approved for a specific type and model airplane and included in the Airplane Flight Manual, no person may take off a turbojet airplane when the appropriate weather reports or forecasts, or any combination of them, indicate that the runways at the destination airport may be wet or slippery at the estimated time of arrival unless the effective runway length at the destination airport is at least 115 percent of the runway length required under paragraph (b) of this section.

Likewise, 14 CFR 121.195 gives the following regulation pertaining to §135 operations of Turbine powered Large Transport Category airplanes

  Airplanes: Turbine engine powered: Landing limitations: Destination airports.

  (d) Unless, based on a showing of actual operating landing techniques on wet runways, a shorter landing distance (but never less than that required by paragraph (b) of this section) has been approved for a specific type and model airplane and included in the Airplane Flight Manual, no person may takeoff a turbojet powered airplane when the appropriate weather reports and forecasts, or a combination thereof, indicate that the runways at the destination airport may be wet or slippery at the estimated time of arrival unless the effective runway length at the destination airport is at least 115 percent of the runway length required under paragraph (b) of this section.

These regulations are effectively identical.

How is this determined? Does the FAA offer a definition (I have not found any such definitions in 14 CFR)? Does an AC give the appropriate definitions? Is the Operator expected to make this determination or to include a definition in the accepted or approved GOM? Should pertinent aircraft manufacturer's data be considered, for example if the AFM includes a definition of "wet runway"?

I am especially asking for any cases where the AFM does not give approved wet or contaminated landing data. Note the difference between approved and advisory AFM data. However, I am interested in knowing any and all ways in which the determination required by these regulations is complied with.

I also could not find a definition for wet or slippery by the FAA, only for a contaminated runway:

CONTAMINATED RUNWAY− A runway is considered contaminated whenever standing water, ice, snow, slush, frost in any form, heavy rubber, or other substances are present. A runway is contaminated with respect to rubber deposits or other friction-degrading substances when the average friction value for any 500-foot segment of the runway within the ALD fails below the recommended minimum friction level and the average friction value in the adjacent 500-foot segments falls below the maintenance planning friction level.

(FAR/AIM Pilot/Controller Glossary, emphasis mine)
My Boeing 737 FCTM does however define:

A slippery surface is any surface where the braking capability is less than
that on a dry surface. Therefore, a surface is considered “slippery” when it
is wet or contaminated with ice, standing water, slush, snow or any other
deposit that results in reduced braking capability.

(Boeing 737 NG FCTM 2.13 Ground Operations, emphasis mine)
This sounds quite similar to the FAA definition of contaminated runways, so I would assume the same definition applies to wet or slippery in §121 and §135 operations as well.
The FCTM further says:

Slippery Runway Landing Performance
Slippery/contaminated runway advisory information is based on an assumption of
uniform conditions over the entire runway. This means a uniform depth for
slush/standing water for a contaminated runway or a fixed braking coefficient for
a slippery runway. The data cannot cover all possible slippery/contaminated
runway combinations and does not consider factors such as rubber deposits or
heavily painted surfaces near the end of most runways. With these caveats in
mind, it is up to the operator to determine operating policies based on the training
and operating experience of their flight crews.

(Boeing 737 NG FCTM A.27 Landing Roll - Factors Affecting Landing distance)
So it seems to be (at least in part) up to the operator to provide clear definitions on when exactly a runway should be considered slippery.

The Flight Safety Foundation has collected some more definitions, although from Europe, not the US:

Dry Runway
The European Join Aviation Authorities (JAA) defines dry runway as "one which is neither wet nor contaminated, and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain 'effectively dry' braking action event when moisture is present."
Damp Runway
JAA says that a runway is considered damp "when the surface is not dry, but when the moisture on it does not give it a shiny appearance."
Wet Runway
JAA says that a runway is considered wet "when the runway surface is covered with water, or equivalent, less than specified [for a contaminated runway] or when there is sufficient moisture on the runway surface to cause it to appear reflective, but without significant areas of standing water."
Contaminated Runway
JAA says that a runway is contaminated "when more than 25 percent of the runway surface are (whether in isolated areas or not) within the required length and width being used is covered by the following:

"Surface water more than 3.0 mm [millimeters] (0125 in [inch]) deep, or by slush or loose snow, equivalent to more than 3.0 mm (0.125 in) of water;

"Snow which has been compressed into a solid mass which resists further compression and will hold together or break into lumps if picked up (compacted snow); or,

"Ice, including wet ice."

(FSF ALAR Briefing Note 8.5 - Wet or Contaminated Runways)


When are pilots required to have approval to conduct practice approaches? I would like a clarification about requesting practice approaches.

I have seen pilots at uncontrolled airports shoot practice approaches such as VOR, SDF, etc. without needing approval; obviously.

Am I correct in thinking that a practice approach approval is only required to be explicitly requested when being controlled by ATC via flight following or approach/tower control?

I know this may seem like a silly question, so I will describe a scenario so that readers understand the context of why I am asking a little bit better:

A VFR flight passes through class C airspace, and contacts approach control prior to entering.  On the other side of said class C airspace, a few miles out of the boundary line, there is a destination airport where the pilots would like to shoot a practice approach, which is a non-controlled airport outside of the boundaries of "ATC-contact-required" airspace.  Do the pilots request a practice approach, or do they request to terminate radar service and then go ahead and shoot the approach?

Maybe the answer lies in the content of the approach depending on whether or not initial fixes or a missed approach segment would lead a flight into "ATC-contact-required" airspace.

Usually airports with approach controls will have it printed on the approach plate. Take for example the non-towered field Menominee-Marinette Twin County:

The approach control frequency is highlighted in the chart. This is who you receive approach clearance from. KMNM is outside of KGRB (Green Bay) airspace by a good 40 miles, but KGRB approach control is responsible for the airport.

So the short answer is: Look at the approach plate for the responsible frequency/agency for the airport.

I think the other part of your question is more along the lines of "If I'm shooting an IFR approach, am I required to get clearance via ATC?" This I'm not 100% sure about but I would guess that the answer is "yes" since you don't want to interfere with traffic shooting real approaches.

The Aeronautical Information Manual has advice for conducting practice approaches in section 4-3-21 (Page 204):

  (a) ...Practice
  instrument approaches are considered to be instrument approaches made by either a VFR aircraft not on an IFR flight plan or an aircraft on an IFR flight plan.
  To achieve this and thereby enhance air safety, it is Air Traffic’s policy to provide for separation of such operations at locations where approach control
  facilities are located and, as resources permit, at certain other locations served by ARTCCs or parent approach control facilities.

(Emphasis mine)

Furthermore, it goes on to say...

  (b) Before practicing an instrument approach, pilots should inform the approach control facility or the tower of the type of practice approach they desire to make and how they intend to terminate it, ...
  (c) At airports without a tower, pilots wishing to make practice instrument approaches should notify the facility having control jurisdiction of the desired
  approach as indicated on the approach chart.
  (e) VFR aircraft practicing instrument approaches are not automatically authorized to execute the missed approach procedure.

But as I say in my comment, the AIM is a guideline, not a rule and I don't think there is anybody stopping somebody from doing an instrument approach without controller notification, however because ATC isn't providing traffic separation at that point, it could be considered negligent of the pilot to not request ATC clearance. Besides, a good portion of conducting practice approaches is talking to ATC.


Does TSR (Time Since Repair) Need A Reset After A Clean/Inspect/Test Workscope? So I am a little unclear on what the regulations recommend.

Say you have a component that has a Restoration (Ignore the nomenclature) workscope but it is strictly an Inspection/Cleaning/Testing process. The FAA/EASA tags would say Inspected/Tested.

Does that mean the TSR/CSR (Time Since Repair / Cycles Since Repair) need to be reset to zero? Or would the TSR/CSR continue as-is because there was no Repair work carried out? Any assistance would be appreciated.

In an MSG-3 based maintenance program there's no such thing as "overhauled" as in "put back in new condition and reset to zero".  Line Replaceable Units will be qualified operationally and structurally under an endurance/fatigue test program and will normally have a structural life limit where a unit carries structural loads of some kind.  If there is no applied life limit the part can be theoretically run forever (or at least the certified life of the airframe), because under MSG-3, components can be run indefinitely until some form of inspection or test in the field detects a degradation beyond a limit.  Think functional test, leak test, NDT, visual inspection etc.

What happens with LRUs is they may fail or some internal parts may fail during endurance testing. The part was designed to run 80000 cycles, was tested to 120000 cycles (1.5 scatter factor margin for mechanical parts), and say a bearing and thrust washer failed during the testing at 60000 cycles of testing. Those parts will be replaced and the endurance test continued to the end.

But now when it's certified, there will be a need to send the unit in at 40000 cycles (1.5 scatter factor applied to 60k) to "restore" it to its pre-test failure condition.  The unit has to go in, be disassembled and reassembled and any parts that are out of serviceable specs replaced, but the parts mentioned in the restoration task must be replaced, serviceable or not.

Sometimes, a part with a grease charged gearbox will have a restoration applied because the grease was found to be breaking down during endurance testing, and the grease is the only component that must be replaced.  The restoration task in the maintenance program will say specifically what has to be done, as in "replacement of the grease" or "replacement of the Main Ballscrew Thrust Bearing and Washers, PNxxxx and xxxx" (Operators get mighty mad when they send some part in for replacement of grease or 40 dollars worth of needle bearings because the Maintenance Program requires it, expecting a 2000 dollar bill, and the unit comes back with half the guts replaced and a 15000 dollar repair bill because other parts were damaged or worn out prematurely).

When an LRU goes in for repair not related to the maintenance program (like a random breakdown), whatever parts are replaced will be those that are out of service limits or are considered needed for the unit to pass an outgoing Acceptance Test Procedure (functional test in a test rig).  When it comes in for repair, it will get an incoming Acceptance Test done (the same rig test), and if it passes, it may go right back out No Fault Found unless the operator specifically demands it be torn down anyway. In any case, a repaired part does not come with any reset to a Life Limit, but it MAY reset the restoration interval if the restoration requirements were met during the repair.

The Life Limit applies to the root housing (the structural part with the serial number) and when a unit gets to the life limit in total hours/cycles it is scrap even if it was fully "rebuilt" 5000 cycles ago when it was sent in for a repair (so you generally try to avoid doing that).

Anyway, under this type of maintenance program, what needs to be tracked are total hours/cycles since manufacture to which the LRU's Life Limit applies, and hours/cycles since Restoration, (and hours/cycles since functional test, or some inspection obviously) where the maintenance program has a Restoration task applicable to an LRU (like a screw jack that has to go in every 30000 cycles to get a set of bearings changed).

So.. if you had a part with a tag that has "time since repair" on it, that information is not sufficient, and has no real effect on anything, because the only mandatory removal interval under MSG-3 is the Restoration task and the Life Limit.  If a screwjack's tag says it was repaired at 20000 cycles, and there is a 30000 cycle Restoration in the maintenance program, you're going to have to send it back in in 10000 cycles (when it gets to 30k) unless there is language in the shop paperwork that states that parts mentioned in the  Restoration were replaced, or there is a statement something to that effect.  If that's the case, you can now run it to 50k, the next 30k interval.

Then when it gets to the life limit, it is trash even if it just went in and had a complete and total "overhaul" done where everything but the gearbox was replaced, following a random breakdown in the field. An LRU that breaks down a few thousand cycles short of its life limit will normally go in the trash.


How do you calculate the optimal cruising speed of an airfoil? I am working on a school project (aircraft design).
I would like to know how to calculate the cruising speed of a given airfoil. For example, if I have a NACA 5613-35 airfoil (that is the NACA 4 digit modified series), what is the the cruising speed at which this airfoil has the best aerodynamic properties?
Another way to ask this question: If I want my aircraft to have a cruising speed of 120 knots, how do I choose an airfoil to fit the cruising speed requirement?
I tried looking it up on google and on some other aviation forums, but I did not find the answer.
Thanks in advance and have a great day!

The cruising speed is only one parameter. For optimum flow conditions, you need to look at the Reynolds number and the lift coefficient at which the airfoil shows its best behavior and then tailor the aircraft to achieve those numbers at its design operating speed. Normally, a higher Reynolds number is better, but at low speed (= low Reynolds numbers) airfoil performance drops off a cliff. It is important to stay above this limit in order to get good performance.
This tailoring is done by selecting the wing area in order to achieve the right wing loading (the ratio of airplane mass to wing area) and the wing's aspect ratio (that is the ratio between span and chord) to arrive at the lowest possible drag. Selecting too high an aspect ratio (wing becomes too slender) will drive up the mass of the wing structure and reduce its Reynolds number. Conversely, picking too little wing span will give you plenty of wing chord, but induced drag will be higher than necessary.


Does an airfoil drag coefficient takes parasite drag into account? Im trying to understand why does L/D MAX, (the top of the polar curve that computes CL & CD ratio for any airfoil) is also the lowest point of the total drag curve.
Im guessing the reason is that CD curve is not just about induced drag as I thought.

Airfoil drag is "parasitic" (or better: everything but induced) drag.
It consists of shear drag and pressure drag, the latter mostly from local flow separation. Both are only present when viscous flow is assumed. Airfoil drag is for the wing section without taking tip effects into account, presuming an infinitely wide wing. This kind of theoretical wing has no induced drag (d'Alembert's paradox).
L/D max is the point on the polar curve where the angle to the origin of the coordinate system is steepest. This is not the point of the lowest drag coefficient! Maybe you mean the point of lowest drag for a full airplane – but that is another story, with more than just the airfoil polar. Now induced drag is part of overall drag and due to its inverse relationship with speed, a distinct minimum can be found when lift is held constant.

Drag polar of the NACA 23012 airfoil (picture source, colored comments own work)


Clarification on the SEA-TAC VFR map I've been looking at the SEA-TAC VFR map, and something caught my eye...

On this map one can see that the SEA-TAC airport has a class B designation in a strange inverse-rhomboid  shape, surrounded by, depending on the direction, class C or D airspace.
This is confusing to me, and I am looking for clarification.
Specifically:
There is no Ceiling or floor stated for the class C space. What are the proper ceiling/floor elevations for the class C airspace?
There is also no ceiling or floor for the class D space. What are the proper ceiling/floor elevations here?
The center of the map also says "see NOTAMSs/SUPPLEMENT" for class D eff hrs. I didn't get any supplement with this digital map.. where would I find this information?

Your question is flawed because you have labeled the airspace incorrectly:

The thin circular magenta line you have labeled class C is actually the edge of the 30 mile mode C veil around SEA.

The shaded magenta line you have labeled class D actually depicts the area where the class E floor is 700’ AGL.

If you want to see how class C airspace is normally depicted, look North to NAS Whidbey Island.
If you want to see how class D airspace is depicted, come halfway back to Paine Field in Everett.  (There is also class D around SEA, BFI and RNT, but they overlap each other and the chart is pretty busy in this area, so Everett is a cleaner example.)


What was the first jet-powered supersonic aircraft? Just to clarify: I am explicitly not referring to the Bell X-1, or any other early experimental supersonic aircraft that were rocket-powered. I'm curious as to the first supersonic aircraft powered by an air-breathing jet engine, as well as (if possible) the technological innovations needed to transition from rocket-powered to air-breathing supersonic flight.

One ME-262 Pilot claims to have exceeded Mach 1 in a dive, but the conditions are disputed due to compressibility and later tests that find the aircraft uncontrollable above Mach .84. The first U.S. fighter plane to exceed Mach 1 in level flight is the F-100 Super Sabre.

For research on how the sound barrier was broken as it results to aircraft design is to read Wikipedia: Sound Barrier.

Wikipedia also has a good read on Supersonic Aircraft that lists aircraft by manufacture date.

As for technological innovations, I would suggest reading about the turbofan engine, specifically inlet design since the air must be slowed sub-sonic before entering the compressor stages.


What are the protrusions on the sides of the fuselage of the F-16I? I've noticed that the F-16I has these protrusions on the sides of its fuselage. What purpose do they serve?

They are Conformal Fuel Tanks.

See http://israeli-weapons.com/weapons/aircraft/f-16i/F-16I.html:

  Conformal Fuel Tanks (CFT) - These tanks are manufactured by the  "Israel Aircraft Industries"  and increase the aircraft's amount of internal fuel by 50%. Their purpose is to significantly prolong the aircraft's flight range and ability to remain in the air. The tanks are installed the plane's back and conform to it's figure.

Israel does not have any heavy bombers, so they need the fighters to be capable of striking deep in enemy territory and since they can't be accompanied by tankers there, they need additional fuel.

As jwenting mentioned in comment, unlike most conformal tanks that are removable on the ground, these are fitted permanently.


Why is the 737 MAX 7 selling so poorly? The 737 MAX 7 is the smallest of the four major variants in Boeing's 737 MAX product line; it is intended as the successor to the highly-successful 737-700, and features a higher fuel efficiency, considerably greater capacity, and increased range compared to the 737-700.  Yet it is selling very poorly, with only 58 orders so far - and 23 of those 58 orders, from MAX 7 launch customer Southwest Airlines, have been deferred until the mid-2020s, raising the possibility that Southwest might cancel those 23 orders entirely.

Why are the airlines which enthusiastically jumped at the -700 balking at its successor, despite its being the longest-ranged 737 ever (the MAX 7 can fly for 7,130 kilometres before it needs to refuel), thanks to its increased fuel efficiency, and having a capacity of 138-172 passengers, as compared to the -700's 138-140 passengers?

There are two reasons: the market changed, and seat economics favor larger aircraft.

The NG models were designed in the early 1990s, before much of the dramatic change in the air transport market wrought by deregulation and ascendancy of LCCs. Southwest for example, was using high frequency of narrowbody aircraft to attack the network carriers and drove the extinction of widebodies in domestic US air travel. Since the early nineties, airline traffic has more than doubled depending on how you count, and there is a maximum frequency that is appealing to travelers. If you have four flights a day on a particular route and you double traffic, you might decide that six is enough and use larger aircraft.

This is what Southwest is now doing, replacing -700 aircraft with Max8s. The Max8 acquisition and operating cost is only about 10% higher than the -700, but its passenger capacity is 25% greater. The math makes the smaller aircraft unusable, given that market demand now supports the larger aircraft. Ryanair came along later than Southwest and went straight to the lower seat cost of the larger aircraft. This is why even smaller aircraft like the Cseries are in trouble, forcing Bombardier to sell half of the program to Airbus for nothing.


Rolling take off compared to take off from a standstill When ever I fly I choose flights with the most take off and landings. After going down the taxiway and turning onto the runway sometimes the flight crew ramp up the engines up while holding the airplane from moving with the brakes, then let off the brakes and the plane shoots down the runway like a rocket sled on on wheels. Other times the plane will go down the taxiway, turn onto the runway and without stopping ramp up the engines and head down the runway. What is the difference in these two techniques? Is it pilot choice?

There are a few things that may be going on.

Generally the foot on the breaks, full throttle, spool up, release and roll is derivative of a short field takeoff. In other words you need all available runway and all available power to get off the ground safely and clear your runway end obstacles. This is dictated by airplane performance and runway conditions/length.

Roll on, roll into full throttle and go is more or less standard. In some cases this may follow an ATC clearance like

  123AB Cleared for takeoff 22 depart no delay

This generally means there is either someone inbound for a landing but theres time for you to go, or there is a long queue on the ground and the controller wants you to get going. Stopping on the runway to spool up your engines takes time and at a busy field that can be in short supply.

Its important to note that in any case the pilot should line the aircraft up with centerline prior to applying full throttle.

The aircraft can also be instructed to, "line up and wait" in which case its cleared to enter the runway and wait on the numbers until cleared. This may occur at an airport that offers parallel runway operations and the aircraft is waiting for a plane to land on a parallel runway.

EDIT: I found a possible dupe, noted in the comments. Its a bit different so ill leave this answer here and let the community decide.


What types of antennae do aircraft have and what are their functions? What types of antennae do aircraft have and what are their functions? Examples are HF-, VOR- and SATCOM-Antennae.

The Boeing 787 has just about every kind of antenna I can think of. Here's a chart of all their locations and purposes.

From Boeing 787 Systems Manual


What is the minimum separation between two landing A380s? I have always assumed that landing separation depends on wake turbulence limits depending on weight class.

However I see that no minimum separation needed for the A380 as trailing aircraft (and in a few other cases):
http://www.ais.gov.hk/HK_AIP/aic/AIC22-12.pdf

In practice, what distance or time separations used in these cases, where wake turbulence isn't the limiting factor?

In general, the heavier an aircraft is, the greater the wake it produces but, it is also less affected by the wake of other aircraft.  In particular, an aircraft can always resist the wake turbulence of a lighter category aircraft.

It was found that the A380 was not affected by wake turbulence from any aircraft in front, including another A380, down to the minimum RADAR separation used on approaches which is 3NM.

The RADAR separation used on any particular approach might be greater, but not less than this minimum therefore, there is no need to apply wake turbulence separation to a following A380 and the required RADAR separation for the approach is applied.


Why would an airport use an L/R runway combination and a second number instead of L/C/R? At KPHX, there's a Runway 25L/R and a runway 26. What would the reasoning be for using this instead of what seems to be the more common L/C/R designation?

There is flexibility on the numbering of parallel runways based on a number of factors as described in FAA advisory_circular/150-5340-1J -page 4 (see excerpt below). In the case of KPHX for example, there is the main terminal between runways 8/26 and 7R/L-25R/L.  Also, when approaching from the east the threshold for runway 25L is a significant distance from the threshold for runway 25R (about 2500 feet inset).
I would guess that minimizing possible pilot confusion factored into the decision not to have a "center" runway designation.


What are CP-like codes or designations after SAS or Scandinavian flight attendant names? While browsing through Wikipedia I came across this photograph:

It's description says (emphasis mine):

SAS DC-9, interior of cabin, service on board. Air hostess Kirsten Andersen and Birthe Bymose both CPHCV serves lunch to Elisabeth Pinske CPHKA and Torben Wittrup CPHZC-S. 1960s

I was wondering what these codes are used for or that is their meaning.

I emailed the SAS museum in Oslo to inquire about the acronyms in this photo description. It took awhile, but I finally got the following reply:

I'm a retired SAS-captain volunteering at our museum. These codes are
IATA communication codes. CPH is Copenhagen airport, CV is the name of
a SAS-sub group, the cabin attendant's group there. So if I were to
send a old fashioned telex to that group, I would include a NAME with
address CPHCV. Similarly, my former address would be my NAME, OSLOA.
These addresses were used within almost all airline companies, an
external message to me would be addressed NAME, OSLOASK, where SK
denotes SAS.
CPHKA is the address of the administrative SAS-department in charge of
all SAS stations within Denmark. CPHZC-S is unknown to me, but -S
indicates a further sub-division.
We used to have mail departments at all SAS stations, and this type of
addressing was extensively used on envelopes and in phone-directories.
These days, we still have mail departments, but these are greatly
reduced since e-mail has taken over communication.
You'll find more info on internet:
https://en.wikipedia.org/wiki/IATA_airport_code and:
https://www.iata.org/en/services/codes/
Best of luck with your studying.
Leif Leren, at the SAS-museum at OSL.


Are commercial pilots ranked or graded differently based on the size of the aircraft they fly? I am not sure whether "rank" or "grade" are the most suitable words for this question. If someone know which the most suitable, please edit this question.

I mean, is the rank of a pilot of, say a Boeing 737, different than the rank of a Boeing 747? And the equivalent to my pilot of Airbus A320 and the pilot Airbus A380 are ranked differently? If different, which one is higher?

This question is related to the airplane's passenger capacity, not to the most advance technology installed in one particular airplane.

To the extent that there is any sort of "rank" amongst airline pilots, seniority comes first.  The most senior pilot gets his choice of aircraft, schedules, vacations, and so on; the next most senior pilot gets his choice from everything that's left, and so on until the most junior pilot gets what's left over that nobody senior to him wanted.  So the pilot hired a month before I was is senior to me, and I'm senior to the pilot hired a month after I was.  Not that this translates into "rank" the way that a lower ranking officer in the military salutes a higher ranking officer -- I'm on a first-name basis with anybody I fly with, and I've flown with the most senior pilot in our company, and if not the very most junior pilot, pretty close to it.

At some airlines, larger aircraft pay more to fly than smaller aircraft, so one could contemplate a "ranking" of sorts in that regard.  The pilot who transitions from the 737 to the 767 gains an increase in pay rate in doing that, so you might infer that 737 pilots are lower "rank" than 767 pilots.  Of course, the most senior pilot on the 737 at that carrier has his choice of schedules, while the most junior pilot on the 767 has a schedule that most would see as less desirable.  So I don't think there's too much stock to put into any idea that just because Allen is flying the 767 and Bill is on the 737, Allen is necessarily a higher "rank".  Especially if he's flying to Timbuktu on weekends in that jet, while Bill enjoys his pick of layovers in San Diego in the winter and Boston in the summer.

And, some airlines don't have different pay rates for different equipment.  This makes for less training burden, as pilots aren't switching aircraft to keep moving up the pay ladder as much.

Some guys will find any distinction that they can to make themselves feel special, or superior, or whatever, but for the most part that isn't all that common.  "You're on a bigger airplane than I am, but I'm flying weekdays and you're stuck on weekend reserve."  Or, "You have a better schedule, but my airplane is bigger than yours."  Honestly, who cares?  We're all pilots, we all started at the bottom, we'll all retire at some point between "here" and #1 on the list, and where "you" are on that progression compared with where "I" am right now doesn't really matter all that much.

Of course, the one very real "rank" distinction, on the flight deck at least, is Captain and First Officer.  But between airplanes, not really so much in my experience.


Did any VTOL aircraft implement an airfoil with engine-blown exhaust? Did any VTOL aircraft implement an airfoil with engine-blown exhaust?

Near as I know every attempt to do so has never worked out.   It’s a very enticing design on paper but has always been a disappointment in real life. One of the best examples was from the 1970s. Designed as a supersonic replacements for the AV-8A Harrier, the Rockwell XFV-12A attempted to use this scheme for a vertical lift system.   Unfortunately it never met the design metrics, and the program was ultimately canceled.

Source: boxartden.com


Can aircraft other than rockets go to space? I always wondered if it was possible for planes and other aircraft to leave the Earth's atmosphere. Normal commercial transport airplanes can fly pretty high, but then they need air to get the speed boost from. Reactive engines seem like a better idea, but I don't know how much importance air has for them.

Is it possible to get to space from Earth's surface using a non-rocket aircraft?

Depends on what you mean.

Get to high altitude? Yes you can. It is really inefficient to get there, but some aircraft already do it.

Achieve a stable orbit and be able to maintain control? No, at those altitudes you do not have enough oxygen to keep your engines running, you have to bring your own (and thus use a rocket)

For the sake of clarity, some definitions:

reaction engine: includes both rockets and jets. The engine pushes some mass in one direction and by reaction it achieves thrust in the opposite one.
jet (engine): is used to refer to airbreathing engines. The aircraft carries the fuel, but not the oxidizer; that is taken from the surrounding atmosphere.
rocket (engine): is used to refer to non-airbreathing engines. The (space)craft carries both the fuel and the oxidizer. No atmosphere is needed.
space: above 100km of altitude.
go to space:

staying in space:

Images from xkcd


Why are F-15s usually taking off with afterburners? If there's no emergency, is it a big waste of money for military aircraft to take-off with afterburners? Why are they doing it, what are the advantages?
Like here:

To be sure to not use more runway than available.
It is also good to have runway to spare in case take-off has to be aborted.
Look at this image as an example from another fighter. Notice the two X-axis. The top MIL is for without afterburner and the bottom FULL AB is with afterburner. Notice how the numbers for the MIL is almost double that of the FULL AB axis. That means much (a little less than the factor difference between the two numbers) more runway required for same conditions. And in case your wondering, that number depends on runway temperature and altitude above sea-level beside from thrust setting.


What is the procedure for restarting an F-16 in the air? If there is a flameout on the F-16 in the air, what is the procedure for restarting it?

I'm sure this is an elaborate checklist, so I'm only asking for an overview of the key parts, especially I'm interested in to what extent the pilot has to manually operate this process.

Is it required to manipulate fuel? Ignition? Temp? Air source? Does it involve the JFS system? Battery?

This https://www.quora.com/How-do-you-start-the-engine-on-an-F-16-Fighting-Falcon provides a nice little overview of how to start an F-16, with some pictures. However, it doesn't explain exactly how the engine is ignited in the first place. JFS, then engage throttle to allow fuel in, and magically it ignites? Surely it doesn't ignite just from pressure alone when driven by the JFS? It feels like a crucial step is missing in that overview and that step would probably allude to how to restart the engine.

It seems that in the event of a flameout, on at least block 50 F-16's Can fighter aircraft glide? the EPU (Emergency Power Unit) kicks in which provides power and hydraulics. Prior to this, the battery supplies power (but I imagine it must be turned on manually, as there is a switch for this!) and the hydraulics appear to work for some time even without the EPU, JFS or the main engine.

However, I know nothing about how the engine actually gets restarted. What does the pilot need to do, and why?

As a bonus question: Why doesn't this guy attempt to restart the engine? Did they already try, and give up?

There are a lot of questions rolled into one here, and I can't answer specifically to the F-16, but a turbine engine needs the same three elements from the basic fire triangle to run:  Fuel, Air, Ignition.  The element missing from the sequence description linked in the question is ignition.

The igniters are like spark plugs, and they are probably energized during actuation of one of the other mentioned switches.  Most likely the JFS switch has a secondary function of energizing the ignitors since it is engine start specific.

Airstarts are not an overly complex procedure, in fact for a single engine aircraft like the F-16 they need to be brief and committed to memory because fighters don't have the best glide ratio.

Fuel - Make sure the throttle wasn't inadvertently shut off, likely the checklist will call for placing this in the idle position.  (you need fuel flow, but don't want to dump too much gas into an engine that isn't lit yet!)  Perhaps there is a step to turn on a boost pump or switch tanks.

Air - Airborne this comes from outside ram air pressure, as measured by airspeed.  The minimum airspeed required envelope will vary with altitude, but most pilots will have a number committed to memory that will provide reliable airstarts across a broad range of altitudes.

Ignition - There will likely be a separate igniter switch for airstarts.  Press and hold until lightoff is achieved, then advance the throttles smoothly and resume flying.  The airstart ignitor switch is generally located on the power control lever for convenience.  If single engine, an alternate electrical power source may be required first in the form or activating a Ram Air Turbine or other source of emergency power to provide a spark if the generator is disabled.

The process isn't really any different from lighting a natural gas stove or propane grill that has a piezoelectric lighter - You turn on the gas and hold the button down or press repeatedly to make the igniter spark until it lights, then release the button and adjust the flame.  (in fact when testing the airstart igniters on the ground before flight you listen for a clicking sound to indicate they are sparking!)

So, in its simplest form a generic airstart checklist for a tactical jet would look something like the following example:

AIRSPEED - Maintain 200 KIAS minimum.
THROTTLE - Idle.
AIRSTART BUTTON - Press and hold until light off.
If no relight by 5000 feet AGL - EJECT


How close do you have to be to an underwater black box to detect it? The news keeps talking about the black boxes on aircraft that end up in water, and one thing that keeps coming up is the underwater locator beacon that transmits a signal for 30 days if it gets wet.

What kind of signal does it transmit and what kind of range does it have?  I'm guessing that the depth of water that it is in will affect how far away that it can be detected, but by how much?

This excellent explanation is taken from Avionics News in 2006:

FDRs are equipped with an Underwater Locator Beacon (ULB). If you look at a picture of an FDR, you will almost always see a small, cylindrical object attached to one end of the device.

If a plane crashes into the water, this beacon sends out an ultrasonic pulse that cannot be heard by human ears but is readily detectable by sonar and acoustical locating equipment.
There is a submergence sensor on the side of the beacon that looks like a bull's-eye. When water touches this sensor, it activates the beacon.
The beacon sends out pulses at 37.5 kilohertz (kHz) and can transmit sound as deep as 14,000 feet (4,267 m). Once the beacon begins "pinging", it pings once per second for 30 days.

Newer FDRs can now transmit as deep as 20,000 ft.
The following table is taken from a fascinatingly detailed article on Hydro International about the retrieval of black boxes. It shows the radius you can pick up the signal of a pinger from:

Notice that if pingers were replaced with more powerful transponders, the range could be drastically improved!
The article also points out, that in very deep water:

under normal conditions, the existing pinger would not be detectable from the surface in depths exceeding 2km


What do I do with fuel, distance, and time to descend and climb, on nav log? So I've got my navigation log mostly filled out. All that's left to do is determine fuel to climb and descend. I go to my Archer POH (Pilot Operating Handbook) and use the time, fuel, and distance to climb and descend charts. Got about 1.5 gal for both descent and climb. 8 min and 6 NM for climb, 8 min and 18 NM for descent. What do I do with these numbers?

Realize that both the climb and descent are taken from the en-route section.

I always calculate climb first and determine where I will reach top of climb on the sectional chart. I then calculate descent and figure out when I need to descend on the sectional chart. The distance in between is my en-route section.

From reading your question, it seems you calculated en-route from departure airport to destination airport. You don't want to do that.


What missile defense systems would be used against hypersonic glide vehicles? What missile defense systems would be used against hypersonic glide vehicles and cruise missiles (like Avangard or Sky Star)? What challenges would nations face developing them?

From an aeronautical point of view, an interceptor normally must be faster than the target it is seeking to reach. Therefore, existing missile defense systems are ineffective against hypersonic aircraft, because the target is moving at least as fast as the would-be interceptor.
Of course, if the target moves in a unchanging straight line, then it is theoretically possible for the interceptor to reach it, so long as it is positioned in front of the target. For this exact reason, all hypersonic missiles are designed to make irregular movements in any situation where an interceptor may be present.
For straight line paths, there is a cone of viability where an interceptor needs to be in order to intercept the target. The slower the interceptor is, the smaller this cone becomes. In the current (2020) strategic situation, the cone of intercept for existing hypersonic weapons is so small that the probability of intercept is impractically small, even for high value targets. This is one reason why there is a great effort currently to develop laser-based defensive systems.


Non-fueled, bladeless, minimally-noisy aviation engine --- Science fiction or real theoretical science? As a non Aeronautics expert I ask if non-fueled (electric?) vehicles which are minimally-noisy only science fiction or a real theoretical scientific concept aimed for close or very far future development?

I ask if there is any theoretical science that tries to describe how such a thing would be possible in the future...

Characteristics of such a vehicle:

Some non-fueled thrusting; if electrical, than an enough powerful battery or enough powerful solar energy exploitation mechanism
Fireless
Bladlessness: No jet, no propellers/rotors or turbines
Wingless
Silent or almost silent: Not the regular noise. Something very very quiet - at least 75% of the noise will be air molecules rotating solely from the whole objects' motion, but not from the engine itself.

This flying object may or may not be able to fly both in earth's atmosphere and out of it.
Bob Lazar's flying saucers maybe?

Electric propulsion using ion thrusters is already in use for space applications. Today's ion thrusters deliver very high specific impulse at low power (typically in the order of 10 to 1000 W). Lower or higher outputs are possible and subject of current research and development.
Ion thrusters work great in the vacuum/free fall environment where low thrust over long durations is useful, and electric energy can be generated on the spot with solar panels.

The usage of ion thrusters in the atmosphere is possible, but there are major challenges:

planes require a lot of thrust during take-off
the propellant does not contain the energy to drive the thruster
the atmospheric pressure changes all the working paramters. Existing ion thrusters for space are not useful in the atmosphere.

Today, ion thrusters are not ready for aviation and it might never happen, but there is some research going in this direction. Personally I do not believe that ion thrusters are useful for low altitude, but I can well imagine a scramjet engine for high altitude using ion thrust technology. In any case, even an ion thruster without any moving parts cannot be silent when working in the atmosphere. The particles expelled at very high speed will create a lot of noise, similar to a welding torch.


Does the compressor stationary vane have stagger angle? Does the compressor stationary vane have stagger angle? ( stagger angle is the angle between chord of the blade or vane with engine's longitudinal axis )

The stationary compressors are responsible for guide the air particles flow to the next compressor or stage with an even air flow on the engine's longitudinal axis, taking under consideration angle adjustments in order to avoid air turbulence with may cause a compressor stall.

So, depending of the engine project, the answer is yes. The angle can variate, being static or even with self-adjustment.


Should one use mainly the rudder or the ailerons combined with rudder to go back to center line on short short final? My pattern work is improving but there is one thing I consistently miss: I have a very hard time staying aligned with the runway on short final, say after passing the airport fences. When the nose points left or right, should I correct primarily with rudder or with ailerons using rudder just as usual to stay coordinated?
Cross wind is not a factor at this point because I miss even when wind is calm.

Rudder.  It is amazing how much even a tiny puff of wind can move the nose off line.
If you are on "short short", just clearing the fence, your momentum will carry you onto the runway even if you are almost sideways. (But this is not good for the landing gear).
Most important here is to round out correctly at the proper airspeed (the earlier you get your approach speed right the better).
It is not unusual at all for the nose to move offline, keep flying the plane all the way down using rudder corrections to hold the nose to the line.
Only if your plane drifts towards one side or the other do we need ailerons, and this is how we do a crosswind landing:  aileron holds drift, rudder holds line.
A light GA aircraft will usually pivot faster than it will drift.
The physics is that the torque turning it requires less force than to move the whole thing sideways.
But air is rarely completely calm, so be ready to use your rudder and ailerons and continue using them until the wheels stop.


Why is there a compressor in an air cycle machine? I'm a curious high school student. Why is there a compressor after the first heat exchanger in an air cycle machine? I've read that compressing the cold air is for the cause of efficiency because compressing hot air uses much more work than cold air, and the effect of this is that the compressed air temperature increases. But if so, why compress at all when the air itself is going to be cooled again in the second heat exchanger?  Why not leave the compressor and place the turbine as it is from the ACM?

If I understand your question correctly, you don't really understand how the ACM works.

The idea of an ACM is to create 'cool' air. Especially on the ground (imagine landing on your tropical holiday destination), this means that the air must sometimes be made cooler than the outside (ambient) temperature. The second law of thermodynamics (and in this case, the law of common sense) states that you can't just cool your air against the warm ambient air, so you will need to do some special tricks.

In this case, the special trick is compression. You compress the air, which will make it quite hot (increase the temperature) (search for adiabatic compression on the internet). Then, this hot air can of course easily be cooled against ambient air, which happens in the second heat exchanger. In fact, the hotter the air after compression is, the more heat is exchanged in the second heat exchanger. This means the heat exchanger can be made smaller, which is especially useful since air-to-air heat exchangers are inefficient and thus relatively big.

Now, you expand your air again, which will cool it (decrease the temperature). However, since you already cooled it down in the second heat exchanger, it will now be cooler than when it originally encountered the compressor! This makes sense, since you removed energy from the air in the second heat exchanger. So, this way, you can cool the air down further than would have been possible by a heat exchanger (search for reverse Brayton cycle on the internet).

So, this system has two advantages:

It is possible to cool down air beyond ambient temperature, so it functions as 'airco' on the ground or at low altitude.
It is possible to cool hot compressed bleed air with a relatively small, light heat exchanger for pressurizing your cabin while not cooking your passengers medium-rare.


Do the four engines of a BAe-146 make it efficient? The BAe-146 is a small aircraft that can seat approximately 80 passengers, but it has four engines. Does having four engines instead of two affect the way it performs or is it more efficient or less efficient than if it were to have only two engines? I understand that it helps lessen noise during takeoff in populated areas, but is it more/less efficient in terms of both aerodynamics and fuel?

Do the four engines make the BAe efficient? No! Does it affect performance? Yes it does. The BAe 146 occupied a niche for Hot & High airfields, in that it can continue the takeoff when an engine fails: one failed engine out of four leaves 75% of full thrust. So take-off performance with a failed engine is better on a 4-engine aeroplane.

The engines themselves were quite clever designs: the Lycoming ALF 502 with a relatively high bypass ratio and a geared fan. The bypass ratio of 5.7:1 is higher than the 5.0:1 of the Trent 700 used for the A330. By comparison, the Fokker 100 used the Rolls Royce Tay, with a bypass ratio of 3.0:1 and the proven core of the RR Spey.

 Photo from the wiki.

But was the BAe 146 efficient because of the four engines? For an aircraft of a given weight and a given thrust requirement, the design considerations for number of engines would be:

Four engines are each smaller than two engines. Turbine engines do not scale down well. All else being equal, purchase price starts to be the limiting factor when reducing the size: half thrust engines are not half the price.
4-engined planes have worse fuel economy than an identical sized twin engine, due to decreased efficiency of a smaller turbine, and increased drag from more engine pods and a larger vertical tail area.
In cruise, a typical single aisle airliner uses a third of the take-off and climb thrust. So once in cruise, one out of two engines can provide all the thrust required to continue the flight, and have less yawing moment than a failed outboard engine of four. Picture and quote from this document:

  Specifically, current subsonic airliners require about three to five times more thrust to take off than they do to cruise, and the power produced by a high bypass ratio turbofan engine at constant throttle setting varies in much the same way.

Twin engine turbofans actually have a third engine on board: the APU. It can power the systems with full redundancy after an engine fail, and is normally shut off in flight, like the no.1 engine of a P-3 when loitering. Note that the propeller blades of the P-3 can be made to feather, providing much less asymmetrical drag than a windmilling turbofan.

So the advantages of four engines are mainly the consequences of an engine fail in the TO/climb phase: a four engined aircraft could opt to continue the flight, while the twin engine would have no more redundancy and a much harder time climbing to altitude. But all else being equal, four engines have twice the chance of failure than two engines...

The BAe 146 had a relatively wide and stubby fuselage, designed for 6-abreast seating but often configured for 5-abreast due to awkward headroom for the window passengers. This added to the drag penalty of the type over that of a comparable size aircraft like the Fokker 100, which is still a sought after aircraft for feeder airlines in Australia, the limiting and most expensive cost being engine overhaul. The BAe 146 has twice this cost...


When did inflight smoking become (widely) prohibited? Currently in my mid-'30s, I can still clearly remember the time when half of the plane's passengers were smoking throughout a long-haul flight. I know commercial flights became non-smoking sometime in the late '90s but I can't remember the exact timeline and the Wikipedia article is remarkably lean in details.

When did the major airlines start forbidding inflight smoking? How long did it take for the new policy to spread across most of the airlines? Can we expect this length of transition period to apply to other significant policy changes (e.g. the use of small electronic devices being allowed during take-off and landing by some airlines, provided they are in flight-safe mode)?

There is an interesting timeline here which includes other transportation service as well.

According to this New York Times article, the FAA banned smoking on all flights under 2 hours beginning April 23, 1988. According to the timeline, Northwest and British Airways make all domestic service smoke free shortly after.

On February 25th, 1990, the rule is expanded to all domestic flights under 6 hours, which includes all but 28 of 16,000 flights.

In 1992, ICAO urges its members to go smoke free by July 1, 1996. Delta went smoke free on all flights starting in 1995. TWA, United, and American follow suit in 1997. In 1998 even more airlines go smoke free.

This federal rule bans smoking on all flights to and from the US and is effective June 4, 2000. It mentions that all domestic and 98% of international flights were already in compliance.

td;dr The FAA banned smoking on all flights under 2 hours in 1988, and it escalated from there. Within 10 years, almost all airlines were smoke free.

I think that smoking had the advantage of being a health issue, whereas electronic devices are more just convenience and comfort. Barring any emergent safety issues, it seems easier to allow people to do something new (use electronic devices) than stop them from doing something (smoking). Considering the proliferation and advancement of inflight entertainment systems, I would expect airlines to be fairly quick about allowing the use of devices, especially since some already do (I know American and United do).


Why are airports like Roswell and Fresno so popular for flight tests? I recently visited Roswell, NM, and was surprised at how many flight tests have been performed there.  Even the fatal Gulfstream flight test crash happened there. My research shows that a lot of flight tests happen at places like San Bernardino, Roswell, Fresno, and  Moses Lake. My research turned up only simplistic explanations for why these airports are so popular like "Boeing chose the San Bernardino facility because of three factors: hangar size, availability and weather." (Source: The Sun News)  Is that really all they consider in determining flight test locations?

I've heard that you can't do flight tests at just any airport, though I haven't been able to find any relevant legal restrictions.  The airport choice doesn't even seem to be just the obvious factors like weather, runway length, and GA availability.  (I also don't care about specialized testing that would require unusual airports like long runways or specific temperatures.) There are a few dozen low-volume long runways in the arid American West and similar regions.  Why are just a few so popular?  Are there any FAA (or EASA) restrictions on doing flight tests at any old airport?

You can do flight tests from almost any airport, but it helps if:

The weather is dry and stable,
the field is not too far from the factory,
there is a large unpopulated area nearby, and
you have support facilities available.

The support facilities were installed by the Air Force, and the other factors were already taken care of by Mother Nature in the case of places like Fresno or Roswell. Given that the distance from Los Angeles, a major aviation industry hub, to Fresno is only a bit more than 200 miles, flight testing in predictable weather and over the open terrain west of Fresno becomes very attractive. If you look at Lancaster, the next town near the vast Edwards Air Force base, the driving distance to Los Angeles is only 70 miles. This should help to explain why Edwards is today the main Air Force test base. Once you have a long runway and some experienced flight test engineers in place, other manufacturers will also converge on this location in order to make their flight testing more predictable and effective.


How to set frequency and distance in ARINC 429? How can I set frequency & read distance in ARINC 429?

For example can you give an example to tune a 1105.5 MHz and read 25786 ft.

LABEL | INFORMATION CONTAINED IN LABEL | FORMAT | SPEED
------+--------------------------------+--------+----------
035   | DME Frequency                  | BCD    | Low Speed
202   | DME Distance                   | BNR    | Low Speed

The first thing you need to understand is that DMEs are not tuned by their actual frequency but by the frequency of the paired VOR/VHF Com, ILS, or MLS frequency.  For the vast majority of operations, this means a VOR or ILS frequency. This frequency as well as mode settings are coded in the Label 035 as shown below:

And the text from reference to Section 4.1.2:

So you wouldn't attempt to tune 1105.5 MHz. First, it's not a valid DME frequency, as DME channels are assigned to whole MHz.  1105 MHz is valid, but would be tuned by the paired frequency of 113.40 or 113.45 MHz (VOR) or 5067.6 or 5067.9 MHz (MLS). You don't need to know the actual DME frequency as the DME knows the pairing and the DME ground stations are charted using the paired frequency. The snapshot above includes an example of coding to different frequencies.

The unit you mention in the comments is a two channel DME.  DMEs are available with up to 5 channels. Tuning of a specific channel is done using bits 11-13 (DIR FREQ 1-5).  Labels are sent sequentially. The DME expects a minimum of 5 labels per second and any one channel label must be received at least once per second.

The DME distance is output on label 202 as an unsigned twos complement fraction as shown in the following from ARINC 709:

There are 16 significant bits. Bit 28 is equal to 256 NM and each successive bit is half the value the previous. (e.g., bit 27 = 128 NM) The LSB is Bit 14 and is approximate 0.008 NM.

The distance and frequency labels are output from the unit in blocks so you can correlate distances to stations.


How common are gear-driven or belt-driven superchargers in modern aircraft? How common are gear-driven superchargers in modern piston-engine aircraft, either alone or in combination with exhaust-driven turbochargers? What are some examples of modern aircraft that use them? Is it a technology that essentially went extinct in the aviation context with the last of the piston-engined fighters, bombers, and large airliners? Such that turbocharging alone (or other variants such as turbonormalizing) is the preferred technology for piston-engine aircraft now?  (Besides the old standby of normally aspirated engines of course.)

How about belt-driven superchargers-- do any aircraft have them?  If so, which ones?

Feel free to consider homebuilt aircraft, experimental aircraft, lightsport aircraft, and automotive conversion engines in your answer.

Edit: in light of a recent comment, I'll add that I'm asking about devices that are used at least in part to increase thrust and power by feeding pressurized air to the engine, rather than only to pressurize the cabin.

Lycoming offered mechanical superchargers in some of their large 6 and 8 cylinder opposed engines like the GSO-480 but such engines have been out of production a long time.

I would say the only mechanical superchargers to be found on any engines manufactured today would be found on Russian or similar Eastern European radial engines like the M14P.

I'd be pretty shocked to hear of a homebuilder incorporating a mechanical supercharger, but maybe somebody will find an example. In any case, if you're going to do it, so much easier to do it with a turbo.  The thing that makes turbocharging difficult to work seamlessly in cars, the power lag issue, isn't a problem with aircraft, so a turbo is a no-brainer that can be done by the homebuilder on just about any engine if they really want it.  To incorporate a mechanical drive system on an engine not designed for it would be quite a daunting task.


How fuselage creates lifting force when plane flying on a side? On a question "How plane able to fly on a side" people answer that it's because fuselage shape crate lifting force and plane should have enough thrust.
But that seems vague to me.
How fuselage creates lift ? Wing shaped that way that more air goes under it, so there more pressure below wing than above it. But fuselage is the same from both sides, so how it able to create lift after rotated on side ?

The photo that you posted already gives quite a few hints on how this can be possible:

The aircraft is flying at a sideslip angle (the nose pointed slightly up), so a part of the thrust vector is counteracting the weight.
It seems like the aircraft is not exactly perpendicular to the surface, so a part of the lift vector is still counteracting the weight.
The vertical stabilizers produce some "lift" in this situation due to the sideslip angle mentioned in 1. Note that these typically have symmetrical airfoils, so without the sideslip angle, these would not create any force.
The aircraft might be descending in a controlled way. In that case, not all of the weight must be carried.

As an example, look at the high sideslip angle here:

            . There you can also see the rudder being deflected for trimming.


How much power is generated by a Ram Air Turbine (RAT)? For long range, wide body planes A380 and B777, what is the power generated by RAT (Ram Air Turbine)? And which all are the systems which the RAT drives?

According to the Flight Crew Operations Manual of the Boeing 777:
Hydraulics

The RAT, when deployed, provides hydraulic power only to the primary
flight control components connected to the center hydraulic system.

Which leaves out:

Nose gear
Main gear
Steering
Brakes
Flaps
Thrust reversers

Electric
The RAT powers both C1 TRU and C2 TRU, which powers the captain's and first officer's flight instruments, respectively.
The RAT can supply electrical and hydraulic power simultaneously. However, if the RAT is unable to maintain its RPM, the electrical load is shed and provided by the main battery, until RPM is satisfactory.


How to find capture area of an engine inlet? I tried to relate intake pressure recovery in terms which do not involve efficiency of an inlet and capture area, i was able to formulate pressure recovery without intake efficiency but now i need to find a way to formulate capture area of inlet without without use of intake efficiency and pressure recovery is it possible ? if yes please share.

It is not so hard, actually.
You need to know the speeds ahead and inside the intake. You can deduce their ratio from the pressure recovery factor, and normally the Mach number inside the intake is between 0.4 and 0.5, so this, combined with your design flight speed, is a good starting point.
In supersonic flow the air is rammed into the intake face, producing a shock. This will be a straight shock in case of a pitot intake or an oblique shock in case of an intake ramp. Use the appropriate shock tables to find the corresponding speed and density ratios.
For subsonic flow you can use a Gedankenexperiment: Your intake is flying through a densely packed array of stream tubes. Some of them will end up inside the intake, others will be pushed aside as they come close to the intake lip and will flow around it. The speeds in those tubes varies between flight speed well ahead of the intake and your eventual intake speed inside the intake. In between, things change continuously in subsonic flow or via shocks in supersonic flow. Now assume that all the air which passes through the intake will have to pass through their corresponding stream tubes, both ahead and inside the intake. No air is allowed to cross between tubes. If the air inside the intake flows faster than flight speed, the flow in the tubes will be accelerated as they approach the engine face, so the intake has to ingest a lot of tubes to keep mass flow the same. Conversely, if flight speed is higher than intake speed, some of the tubes will be pushed aside to get a match between the mass flows ahead and inside the intake. Don't forget to adjust stream tube area for density changes: The change in stream tube cross section has to be inversely proportional to the change in air density as the air inside the steam tube changes speed, like this:
$$\frac{\delta\rho}{\rho}=-Ma^2\cdot\frac{\delta v}{v}$$


Should the aircraft logbook be with the aircraft, or should it be on the ground? Should an aircraft logbook stay inside of the airplane, or on the ground with maintenance?

This is depending on which country the airplane is registered in, as the requirement to carry the logbook can be implemented per country, e.g. Germany requires the logbook to be carried onboard the airplane.[LuftBO §30 Abs. 5]


Are fireworks a hazard to aircraft? Tonight's fireworks got me wondering:  With all of the firework displays happening at the same time, how do they keep aircraft away from them?  Is there any risk of collision or blinding the pilots?  Is there anything that pilots need to do differently when fireworks are in the area?

In canada and I assume in a similar way in the United States, fireworks are treated like any other obstacle such as a communication tower, building, or crane. The location and elevation of the firework activity is assessed for impacts to any instrument procedures, airways, minimum altitude areas, etc. and NOTAM to temporarily amend affected procedures will be issued prior to the activity to advertise the changes and their effective periods.

Having said that, this doesn't address the VFR side of things. Operating near fireworks is essentially the same see and be seen idea. NOTAM get issued here all the time for the fireworks activity themselves and they would include a radius from the centre point. Simply avoiding the area is usually sufficient.


Why is the MD-88's front starboard door smaller than its port one? Having been on a few airplanes of the MD-80 family, I noticed that the front starboard doors of the planes were smaller than the ones on the port side. Why may this be the case?

This may also be the case with the rest of the DC-9 and B717 family as well, but I don't remember that clearly anymore about those other planes.

The larger port side doors are for extra convienience during boarding. Passenger boarding is always done on the port side (left) while the starboard side doors are only used for servicing the galleys or as an emergency exit.


What is an aircraft magneto? I know that magnetos are related to the engine and that on many planes, they are used to start the engine. But what exactly do they do in the engine?

A magneto is a gear driven electric generation device connected to the crankshaft of the engine. It supplies the ignition system (spark plugs) with power.

Each engine has two magnetos. Each cylinder has two plugs. Each magneto supplies one plug in each of the cylinders. This makes the ignition system redundant. If a magneto fails, the other magneto can sustain the engine.

Since the rest of the aircraft's electrical system is supplied by a belt driven alternator/generator, the engine is electrically isolated from any other electrical issues. If you lose electric power in the cockpit, your engine will still run. If you have to shut off electricity because of a cockpit fire, your engine will still run.

The scale of the image below is a little distorted. I had to get my phone pretty close to the oil filter for sufficient lighting.

MAGNETO #1 mounted below and to the side of the oil filter on the back of the engine

STARTER mounted under the front of the engine, connected to the flywheel only when in use

ALTERNATOR mounted under the front of the engine, connected via an accessory belt to the crankshaft


Why are there extra restrictions on constant-speed propellers? Constant-speed propellers are far more efficient than non-constant-speed propellers, allow the engine to be made considerably simpler (due to removing the need to continuously adjust the ignition timing based on how fast the shaft is rotating at any given moment), and, unlike traditional variable-pitch propellers, don't require the pilot to manually adjust the propeller pitch.

However, according to Wikipedia, propellers with constant-speed mechanisms have considerably tighter restrictions on them than other propellers:

  A pilot requires some additional training and, in most jurisdictions, a formal signoff before being allowed to fly aircraft fitted with a CSU [constant speed unit; the part of the propeller mechanism that makes it a constant-speed propeller]. CSUs are not allowed to be fitted to aircraft certified under light-sport aircraft regulations in the United States.

Given that a constant-speed propeller performs its pitch adjustments automatically, without the need for pilot intervention, and that constant-speed propellers perform better, not worse, than other propellers, why all these extra requirements and restrictions?

The engine is the same, not simpler. There is one additional level of complication to the system -- the constant speed propeller has a number of extra parts.

The pilot needs to handle one more lever, selecting the speed. And needs more training in order to remember to put it at the right setting in various flight conditions -- not to mention how to handle an emergency when the constant speed unit falls (you need to prepare for every possible situation).

All in all, more training and more complicated systems sets up the requirements for restrictions.


Where can I find a worldwide General Aviation incident/accident ocurrence reports database? I enjoy reading reports about aviation incidents and accidents. There are often interesting technical details and I believe that this practice increases the safety of my flights.

To keep up to date I have set up a browser add-on which informs me daily about changes in the web-pages of several aviation safety agencies: NTSB, TSBC, IAC, BEA, AAIB, CIAIAC, BFU, SUB... This way I get to know about new occurrences and the publication of reports. However, depending on how each web page is structured, this method creates false positives, works only partially or doesn't work at all.

Is there any worldwide database or source informing about aviation occurrences and the publication of the corresponding reports?

I know about the Aviation Herald, but it only only deals with new occurrences on commercial aircraft. I'm especially interested in General Aviation and the publication of final reports.

No such official worldwide consolidated general aviation accident database exists. Most countries have their own, many smaller countries have none.

The closest you will find to a consolidated aircraft accident database is the one maintained at the Aviation Safety Network's web site. However, this database does not qualify as an answer because it only covers airliner, military transport category aircraft and corporate jet aircraft safety occurrences since 1919, and then again only if the aircraft had 12 seats or more. Most other sites advertising such databases also have similar exclusions.