How autonomous are commercial passenger airliners? Average layman here. Assuming the latest generation of planes/avionics rolling out of the factory today, how autonomous are commercial passenger jets? Obviously, autopilot has been around for decades, but what are the limits of its capabilities? Can it take off and land by itself? What can be done remotely, if anything?

Watching a typical airliner-crew-is-dead-what-can-we-do-now movie caused me to think of this question.

They're not really autonomous, they're mostly automated.

I'll lift this description from Wikipedia despite being written for cars (emphasis mine):

  Autonomous means self-governance. Many historical projects related to vehicle autonomy have been automated (made to be automatic) due to a heavy reliance on artificial hints in their environment, such as magnetic strips. Autonomous control implies satisfactory performance under significant uncertainties in the environment and the ability to compensate for system failures without external intervention.

While most autopilots will fare fairly well under "significant uncertainties in the environment" (read e.g. "severe turbulence"), they are not equally capable "to compensate for system failures without external intervention". Even the Airbus' autopilots revert authority to the pilots if the system degrades.

Even knowing the destination airport, they need a pilot to insert the flight plan into the flight computer, they cannot compute it by themselves.

They cannot take evasive action in case of dangerous situations, but they can only warn the pilot (see EGPWS and TCAS RAs).

They cannot even properly recognize bad weather (say, a thunderstorm) and eventually plan diversions around it.

They could not land an aircraft by themselves, as they generally lack control over the aircraft configuration.

What they can do is blindly follow the flight plan given, so they are automatic, but not autonomous.


Is ultrasonic noise from small turbines painful to pets? A question on another SE site prompted me to search for 'Aircraft engines untrasonic noise dogs', but with not much success.  The OP's dog barked like crazy at turboprops, but was not bothered at all by 'louder' noises from light GA planes with piston engines, even when led next to them as the engines ran up on the ground.

Does anyone know how much ultrasonic noise does a small turboprop put out?  I suspect that it may be worse, in proportion, to that from the large turbofans on airliners since the hp shaft revs so high on those little engines.

Maybe that noise that is merely an annoyance to humans is actually painful to dogs etc?

This answer lists a number of RPM values for different aircraft engines. A typical small turboprop engine, the PT6, runs its core at 45,000 RPM and the power turbine at 30,000 RPM, which should produce sounds in the ultrasonic region.

The picture below shows a cutaway of a PT6 (source); if you count the blades and take the result times 3 (the cutaway spans 120°), the high pressure turbine disc shows 54 blades and the power turbine 42 blades.

Each time one of those blades runs through the wake of a stator blade ahead of it, it will create a pressure change with a frequency of 30,000·42/60 = 21 kHz and 45,000·54/60 = 40.5 kHz. At idle power, the speed is a bit lower, but not by much.

So, yes, the dog might very well have heard a noise inaudible to humans.


What is this protrusion on the door? There's something below the door on almost every commercial aircraft. What is inside that box? The protrusion can be seen from the interior of the aircraft.
Source

It contains the evacuation slide. From airspacemag:

  An escape slide sits inside a carbon fiber pressure cap covered by a casing of material similar to the aircraft interior walls—that big square box at the bottom of an airliner’s interior door.

Here's an image from Boeing:

Image from Boeing.com

According to Boeing, the positioning of evacuation slides inside the doors reduced the deployment time.

  By 1963, improvements in materials and inflation systems reduced the weight and bulk of the slide system, making it practical to move the slides out of the ceiling to the lower inboard face of the cabin doors (see fig. A). This location resulted in a still more efficient escape system, reducing the time needed to ready an escape slide from between 20 to 50 seconds to between 18 and 24 seconds, including door opening time.


What are these small engine inlets on the Super Hornet? Does anyone know what these two small variable inlets on top of the engines are used for on the Super Hornet?

Source: navy.mil; cropped

These are the auxiliary air inlets for the ECS (Environmental Control System):

(image source)

They provide air to the primary heat exchanger (A18), which is then exhausted via the ram air exhaust (A20, the tubes visible behind the inlets in your picture).


What is the maximum decibel noise level of a stage 4 rated engine? I was just wondering if anyone is able to help me. I need to find out, what is the maximum decibel noise level of a stage 4 rated engine (as defined by the Federal Aviation Administration)?

Some more information: I need this information because the General Electric Honda HF120 engine has a noise level rating of stage 4. This is a small turbofan engine that is designed to be used on small business jets, such as the HondaJet. I have tried searching all day, but I cannot seem to find anything.

Thank you for your time and any help would be greatly appreciated.

I have found an answer. This datasheet (easa.europa.eu) lists the noise levels for an aircraft with the engines and the stage 4 limits:


What are these red lights next to an airport runway? What are these red installations at the end of the runway? They shine bright like a laser but I don't think they would install those near an airport.

These are VASI lights, which stands for Visual Approach Slope Indicator. When approaching a runway to land, an aircraft follows a specific glide slope. Usually, that slope is around -3 degrees.

These VASI-lights help the pilot visually verifying that they are not too low and not too high. There are a total of four lights, representing two bars.

Now you only see two reds on the VASI, but there is also another color, that you will never get to see, except if you sit in a cockpit of a plane: White. Using this two colors, the VASI tells pilots if they are approaching the runway too high or too low.

The VASI works analog, so it does not know how high a plane is and it's position and changes lights accordingly. Both red and white light at the same time and by using a lens-mechanism, the pilots gets to see the correct lights.

There are three color codes of a VASI:

Source

When both the VASI-bars are red, as in your picture, the plane is too low and needs to pitch up. Red and white means on glidepath and two whites mean too high and the pilot needs to descend faster.

There's also a mnemonic to remember the (very easy tbh) color codes:

  White over White, you're high as a kite.

  Red over White, you're alright.

  Red over Red, you're dead.

  White over Red, unsaid.

(White over red is no color code actually, because you would have to fly inverted to get it, that's why it's "unsaid".

Here's how a VASI-light looks close-up:

Source


How does ATC handle arriving/departing runways that cross? Forgive my total lack of aviation knowledge. I just flew out of SFO and was fascinated by the fact that pairs of planes alternated between departing on 28L + 28R (simultaneously) and arriving on 19L/R.

My question is this: What amount of micromanagement from ATC exists to keep taking-off planes on schedule and not running into the landing planes, especially in cases where runways cross? How much information does the tower give to the taxiing planes?

Thanks!

Chapter 9 - Departure Procedures and Separation of the FAA Order titled "Air Traffic Control" covers the procedures that are used for aircraft departures, including those cases where they have intersecting runways.

There are numerous procedures that they follow that are specific to intersecting runways, including:

3-9-4 - LINE UP AND WAIT (LUAW)

If the tower has an airplane Line Up And Wait (taxi onto the active runway but not actually takeoff) because of another airplane that is landing or taking off on an intersecting runway, they must inform them of the other airplane and why they are not taking off.

3-9-7 - WAKE TURBULENCE SEPARATION FOR INTERSECTION DEPARTURES
3-9-8 - INTERSECTING RUNWAY SEPARATION

This probably covers most of what you are asking about, and has some great pictures showing when they are allowed to clear another airplane for takeoff in different situations.  For instance, they can't clear an airplane for takeoff with another airplane landing on an intersecting runway until after they have passed their runway.

Note that there are similar procedures in Chapter 10 - Arrival Procedures and Separation

In short, there are lots of extra procedures that must be followed when using intersecting runways simultaneously, but they also get a lot of operational benefits when they can do it so are able to get a lot more airplanes on and off the ground in the same amount of time.


Does wind provide lift for hang gliders in the air? Basically, if there are no thermals, but a strong wind, is there a way to use that wind to gain altitude?

Yes, it's called ridge lift. From Wikipedia:

Ridge lift (or 'slope lift') is created when a wind strikes an obstacle, usually a mountain ridge or cliff, that is large and steep enough to deflect the wind upward.
If the wind is strong enough, the ridge lift provides enough upward
force for gliders, hang gliders, paragliders and birds to stay
airborne for long periods or travel great distances by 'slope
soaring'.

https://en.wikipedia.org/wiki/Ridge_lift
If you happen to be in the San Diego area on a nice summer day. Go to the Torrey Pines glider port above Black's Beach in La Jolla and just north of the Scripps Institution of Oceanography. The onshore wind striking the bluff overlooking the beach is forced upwards and provides plenty of lift for hang gliders working their way back and forth.
You can see images of people doing that at the Torrey Pines Gliderport website or just Google "torrey pines gliding images" for additional images.


Topics for high school chemistry project (IB Chemistry IA)? I have to do an IB Chemistry IA and I wanted to relate it somehow to aviation; however, I can't do anything super complicated though because I'm only a high schooler. Here are some possible topics along with research questions...

Fuels - comparing qualities, response to different variables/environments
Aluminum alloys - strength testing, response to different weather, idk
Antifreeze - how it works, how to strengthen, etc
Paint - UV radiation corrosion, high temperatures

This list could go on and on, but I'm curious what you all think is a good idea. All a topic really needs is just a chemical reaction(s) that can be extensively studied and extended. Also it's important to note I don't actually have to do any experimentation, I just have to find information online in papers and databases. Sorry if these ideas sound ridiculous/outlandish, this is my first time attempting to tackle aviation from a scientific perspective. Thanks for any help.

I'd do aluminum corrosion. Long term, it's the number one lurking monster in any airline's back closet.

There is interesting chemistry, not just in oxidation processes, but how the different alloy compounds used in making the aluminum have different effects on corrosion susceptibility. For example, the alloy 2024 has copper in it, which makes it its own battery and it corrodes readily in moisture, so it is normally supplied with a pure aluminum coating as a protective layer (alclad).

Besides 2024, 7075 is the most common alloy in commercial aviation and has zinc, which makes it corrosion resistant, but it's resistance to fatigue cracking is not so good.

The alloy 6061 has silicon in it which makes it inherently corrosion resistant and you can weld it, but it's not as stiff or strong as 2024.  6061 is popular with homebuilt aircraft because it's cheaper and easier to form.

Then you have the issues of placing aluminum adjacent to other materials.  Aluminum isn't super happy being next to stainless steel (like using stainless hardware against bare alumimum in a moist environment - this is a big problem with sailboat masts) and really doesn't like being next to carbon fibre (on a jet design I was involved with, the floor beams were made of aluminum with carbon honeycomb floor panels and an inadequate barrier between them - it was a disaster in service and the rotted out beams had to be replaced with titanium ones).

Hard to beat as a topic with chemistry and a bit of drama potential to spice up your paper (corrosion is a very painful experience for an airplane owner).  I'd title it "Aluminum Oxide Never Sleeps".  If the teacher is old enough, he/she will get the gag.


What is this plane doing flying back and forth near Sydney at night? As I write this, a mystery plane is going back and forth over south Sydney, Australia:

The plane took of at Bankstown, flies straight from West to East and back, with a distance between paths of about 600m. It maintains a steady height of ca. 4100ft at a speed 120kts.

It is a Cessna 404, but flightradar24 provides no call sign or any other ID.

I noticed the plane ca. 00:30 on 10 May 2018, as it was at its 8th "lap", and took the above screen shot. It may have gone on for a while, perhaps for an hour or more.

As it's night, no markings on the plane are visible. It has the usual white flashers on the wing tips and the top of the rudder, and the red and green marker lights. The plane is quiet loud (prop), but that's most likely only because it's night and there's no other sound sources in my suburb.

Does anyone have an idea what that plane could be, and what the purpose of such flights could be? Obviously, they (whoever they may be) waited until after the curfew of Kingsford Smith (23:00) to not get in the way of commercial traffic.

Might be similar to this question, but I have no way of knowing whether it is the same. Italy and Australia are different countries. E.g., to my knowledge, Europe doesn't permit Police planes or helicopters above urban areas without reason. Australia does.

With a path like that its most likely surveying something. There are a handful of 404's registered in Australia for areal survey, you can find them on this list.


What is the Difference between mogas and avgas? Could anybody tell me the primary differences between mogas and avgas?

Chemically speaking, The difference in the fuels is the inclusion of lead-based additives that increase the Octane rating of the fuel, which are otherwise banned for use in other settings due to the negative effect on air quality. The other common use of leaded fuels I can think of is in auto racing, which also doesn't particularly prioritise air quality. Unleaded high-octane fuels do exist for aircraft engines, but those engines have to be certified to use those fuels, a long and expensive process. This is why they are less common.

Octane rating itself measures how resistant the fuel is to detonation.

Engines run at a specific level of compression. Simplistically, More compression produces more power, which is important in smaller piston engines. But having too high a compression ratio causes the mixture in the cylinder to detonate on it's own before the proper point in the timing cycle where it should be ignited by the spark plug. This is called 'knocking'.

In the best case, the result is increased fuel consumption as the ECU (ironically) throws more fuel into the mixture to reduce the possibility of detonation (at least in fuel-injected car engines this the case). In the worst case, the result is damage to the engine as uncontrolled detonation can put large unwanted loads on the crankshaft and the con-rods. Power output will be reduced in any case, which can be a massive issue for heavily laden aircraft attempting to climb in high or hot conditions.


Can I log the flight as the authorized instructor on board? Commercial long cross country I was an authorized instructor on board for my students long commercial cross country. Do I log any of that flight time?

Answer solved,

https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/2014/kuhn%20-%20(2014)%20legal%20interpretation.pdf

Short terms, yes.


What is the type of nozzle used on the MiG-21 and MiG-27? Generally supersonic fighters have convergent - divergent nozzles. What is type of nozzle used in MiG-21 and MiG-27?

Also please explain that how in a convergent nozzle where the max velocity in the nozzle is limited to one mach , how can the ac still go supersonic??

Mig-21F, the first version of Mig-21 to be called as such, used a Tumansky R-11F-300 engine, which had a (variable) convergent nozzle. Later versions used Tumansky R-13-300, which was similar to the R-11 and Tumansky R-25-300 which had variable convergent nozzles as well. The Mig-27 used the Tumansky R29B, which has a convergent-divergent nozzle according to the manufacturer's site.

In theory, the aircraft speed is not limited by the exit speed, but the extra speed imparted to a mass of air by the engine (more the $\Delta v$, more the thrust). Basically, there is nothing that prevents an aircraft with convergent nozzle from attaining supersonic speeds, albeit the system is very ineffecient.

If the designer is ready to accept a weight and fuel consumption penalty, he/she can use a supersonic convergent nozzle. Though this is ineffecient, for short duration, this would be acceptable.
Another point to note is that the high exit temperatures means that the sonic velocities in the exhaust are nuch higher than the freestream ones. This means that the difference in speed is there, though the mach number may be less.


Is it possible to get a list of Cl/Cd values for various NACA Airfoils? There are a lot of links which give the shape of the airfoil for any given set of camber thickness, position and max. thickness values, but I would like to know if it is possible to get the Lift vs. Angle of attack graph, i.e., in turn lift curve slope, and also Cl/Cd values for every NACA airfoil specified.

Actually, I needed the values to begin the designing of a basic propeller blade for my project.

I have tried searching a lot. It would be really helpful if anyone could help me proceed.

Perhaps the most important resource for airfoil data is the NACA (the predecessor of NASA) Report No.824 Summary of Airfoil Data by Abbott, Von Doenhoff and Stivers.

This report contains the description, generation and experimental data like variation of lift, drag and moment coefficients with angles of attack for a number of NACA airfoils.

You can also see NACA report No. 460 The Characteristics of 78 Related Airfoil Sections from the Tests in the Variable Density Wind Tunnel by Jacobs, Ward and Pinkerton.

Also, Aerodynamic characteristics of a large number of airfoils tested in the variable-density wind tunnel by     Pinkerton and Greenberg.

These are similar to the first report, but older.


Is it possible to get a purely VFR job with colour blindness? I'm 23 years old and I have red-green colour vision deficiency. I'm currently working in engineering but I have my PPL and I've been interested in commercial flying for a very long time. I've always assumed I'll be unable to get the medical needed to follow a flying career anywhere.

I wonder if there are any opportunities for flying purely in VFR, i.e. Bush flying and that sort of thing, where all flying takes place during daylight hours? Are there any airlines or other flying companies that I'd have a chance with?

Thanks, any input is really helpful :)

PS: my location is the United Kingdom.

There is another test, called the Farnsworth Lantern test, which you can take.  Not many aviation medical examiners have the lantern, so you might have to ask around, but if they have it and you can pass with that, you meet the medical criteria.

The waiver that Terry discusses is the SODA (or statement of demonstrated ability).  I had to get one for nearsightedness when I got my Class I, which consisted of a trip to the local flight standards office, a checkride with the FAA inspector who agreed I could fly just fine with my fully corrected 20/15 but uncorrected >20/200 vision.  There are plenty of airline pilots floating around with waivers of this type.


What is the reason Light Sport Aircraft (LSA) minimum speed is limited? I saw an explanation about Icon A5 Light Sport Airplane (LSA), it is said that according to FAA regulation, its stall speed NOT LESS than 45 miles per hour (mph) or around 39.1 knots or around 72 km per hour (kmph). Which is mean, its minimum speed is that 45 mph. I was curious that minimum speed is limited.
Than my question is, what is the reason FAA limits the minimum speed of an airplane? Is that stall speed limitation also applied to another type of airplane?

Photo source:
Edit: Some conversion from mph to knot was not clear. Should be 45mph or 39.1 knots.
Edit 2: I added the minimum speed not less than 45mph.

The FAA mandates a maximum to the stall speed, not a minimum. The minimum speed must not be higher than a given value.
The minimum speed is limited in order to reduce the risk and severity of accidents, especially during landing. The same was used in FAR 23 where a speed limit of 61 knots was mandated for singe-engined aircraft and multi-engined aircraft of 6000 lbs MTOW or less (§23.49 (6)c).
A slower stall speed translates into a slower approach speed and shorter landing distance. Both help to prevent accidents by giving the pilot more time to get the landing right and come to a stop without crashing. Also, the energy involved is smaller so if something goes wrong the accident is more survivable.


Can static electricity affect navigational instruments? Is it possible for navigational instruments to get affected by static electricity or electrical discharges like lightning? If so, how does this happen?

This will depend on the system, but the over all answer would be Yes at least to some extent. When talking about VOR/VORTAC/DME/NDB/GPS or any other nav system that relies on both a device in the plane as well as a device elsewhere we must consider how these devices talk. In this case we are talking about radio waves (em propagation), and lighting does produce an EM field so it has the capability to interfere.

That being said "interference" has both a technical term and a reality IMO. On paper, yes this may interfere with the signal but in reality lightning is fast and isolated so its momentary interference may not interfere with the operation of the device over a usable amount of time or may cause a momentary drop out.

Local INS (Inertial Navigation Systems) if you have it would remain generally unaffected.

There is another issue that presents itself if the lighting is very very close to the aircraft and will be more of an issue with composite aircraft. For what it's worth, if the whole skin of an airplane is conductive (as with metal skinned aircraft) it will act as a pretty solid Faraday cage. This will vary from plane to plane but is generally true. Thus if the lightning generates a strong enough EM pulse the interior of the plane will be protected from it. On a composite based plane you potentially expose yourself to flux related power surging. It should be noted that the critical electronics are protected from this kind of damage.


Are there special safety considerations when flying to/in Atlantic Canada? I'm considering a trip to Nova Scotia from New York in a Cessna 172 or a Piper Archer. The trip is about 3.5 - 5 hours long and could involve some small open ocean portions. Since Nova Scotia has variable weather, high wind, and is pretty rural, I'm interested in knowing if anyone has any recommendations, warnings, or resources for flying to Nova Scotia or Newfoundland.

I know this questions is pretty broad, so I welcome any suggestions for narrowing the scope. I've just had a hard time finding anything on the internet about making a trip to the area.

Plan for unexpected weather amid limited options for dealing with it.  I've flown a number of times between Newark (EWR) and Halifax NS (YHZ), Moncton NB (YQM), and St Johns, NL (YYT).  It can be quite foggy and windy and in the cold months braking action can become a factor.  A lack of options can be problematic.  When we flew EWR-YHZ we often chose EWR as an alternate and I've turned around as late as talking to Halifax approach as braking action become NIL and we didn't have gas to wait it out.  Going out to YYT we'd only have enough gas to get to Gander (YQX) if we couldn't get a good approach in at St Johns.  I flew a capable jet under IFR with Cat II approach capabilities so your concerns will be slightly different down low and VFR.

Although you are VFR, I'd play by IFR rules as alternates and fuel is concerned.  Plan enroute alternates and carry enough gas to get to your destination and get to your second choice with some gas to spare.  The weather can turn quickly and the fog in any of the maritime airports can be thick enough to turn even IFR GA planes away.  Have a plan to be able to get on the ground somewhere else.  Also consider how fatigue will play into your decision making once you are out there.


What is your favorite aviation joke? This is funny!
Please post jokes, pictures, cartoons, videos related to pilots, air/ground controllers, aircraft mechanics, flight/cabin/ground crew or anyone/anything related to aviation.
Rules

Any material should not be offensive, rude or insulting to any group.
If that material requires proper attribution, please verify that by posting it here, no copyright rules are being violated.
You can add your own personal story as a joke. However, this is not the Aviation Blog. We are quite active over there and will be very happy if you want to contribute. Please come visit the chat room Readback, and ping the owner of the room for permissions.
This post is not for rep generation, hence all posts should be wiki. Mods are watching, and one of them has a cattle prod (yes, the electric one).
The material you are posting should be strictly related to aviation.
Make sure that the post is readable, and properly formatted.
Brevity is a virtue.

Please remember:
Before flagging it as off-topic, or too broad, or low quality (really, doesn't that depend on you), please refer to this discussion behind the motive of this post. More information is present in the links in that question and the comment which follows.

Pilots Vs Maintenance Engineers
After every flight, pilots fill out a form, called a “gripe sheet” which tells mechanics about problems with the aircraft. The mechanics correct the problems; document their repairs on the form, and then pilots review the gripe sheets before the next flight.
Never let it be said that ground crews lack a sense of humor. Here are some actual maintenance complaints submitted by pilots (marked with a P) and the solutions recorded (marked with an S) by maintenance engineers.
P: Left inside main tire almost needs replacement.
S: Almost replaced left inside main tire.
P: Test flight OK, except auto-land very rough.
S: Auto-land not installed on this aircraft.
P: Something loose in cockpit.
S: Something tightened in cockpit.
P: Dead bugs on windshield.
S: Live bugs on back-order.
P: Autopilot in altitude-hold mode produces a 200 feet per minute descent.
S: Cannot reproduce problem on ground.
P: Evidence of leak on right main landing gear.
S: Evidence removed.
P: #2 Propeller seeping prop fluid
S: #2 Propeller seepage normal – #1 #3 and #4 propellers lack normal seepage
P: DME volume unbelievably loud.
S: DME volume set to more believable level.
P: Friction locks cause throttle levers to stick.
S: That’s what they’re for
P: IFF inoperative.
S: IFF always inoperative in OFF mode.
P: Suspected crack in windshield.
S: Suspect you’re right.
P: Number 3 engine missing.
S: Engine found on right wing after brief search.
P: Aircraft handles funny.
S: Aircraft warned to straighten up, fly right, and be serious.
P: Target radar hums.
S: Reprogrammed target radar with lyrics
P: Mouse in cockpit.
S: Cat installed.
And the best one for last.
P: Noise coming from under instrument panel. Sounds like a midget pounding on something with a hammer.
S: Took hammer away from midget.
(Source)


In what manner does the Cockpit Voice Recorder timestamps? See here the transcript of ending moments of Aeroflot Flight 593 . The Wikipedia writes :

  (N.B.: All timestamps refer to the flight data recorder time, not GMT or local time.)

What do 2265,2266...2300.....2393..2400 mean? Maybe, they don't mean seconds since CVR can record for only 30 minutes i.e. 1800 seconds..

As described, it is the flight data recorder time. The linked video in that Wikipedia article shows it as seconds. I could not find after how much time Flight 593 crashed, but 2400 seconds equal to 40 minutes.

An FDR typically records around 90 parameters, and certainly can and does monitor all of them all the time, even when several parameters change within a single second.

For the purpose of transcript for this accident, the article on Wikipedia (which is far less technical and detailed than an NTSB investigation report) omits all the entries from FDR recordings which are neither relevant to the story, nor interested to the reader. For example, the reader will care less the input from different sensors between 2303 and 2314.

Since the recording time of a CVR (30 minutes - 2 hours) is less than an FDR (25 hours), they are synchronized for an investigation. This is described here (PDF), for the investigation of Flight 1549:

  The CVR and FDR data were synchronized to one another by comparing the
  FDR “Key VHF” parameter with radio transmissions as heard on the CVR
  recording. By comparing the CVR elapsed time (time since the beginning
  of the CVR recording) for radio transmissions to the corresponding FDR
  Subframe Reference Number (SRN) for “Key VHF”, a relationship between
  the CVR elapsed time and the FDR SRN time can be developed.


Is it legal to land in bad visibility conditions without ILS? Korean Air Flight 801 crashed during bad visibility conditions in Guam because the ILS was out of commission and the pilot thought it wasn't.

My question though is why he even tried to land there in the first place. Wouldn't an airport be closed during bad visibility conditions in that scenario? Or is it possible to land without ILS in bad weather conditions?

I seem to remember someone talking about a step-chart or something like that as an alternative to ILS, is that what would be used in a case like that?

The answer is "Maybe".

An ILS is actually comprised of two signals - a localizer (which lines you up with the runway) and a glideslope (which guides your vertical descent).
If the glideslope is out of service (as it was when KAL801 was flying its approach) you fly a localizer-only approach, which requires visual contact with the runway at a higher altitude.
In this case as shown on the plate below the ILS can be flown down to 531 feet (in red); the Localizer-Only approach can only be flown down to 1440 feet (in green).

So as long as the crew had the minimum visibility and cloud height requirements (and observed the altitude restrictions on the approach) they could legally fly into the airport on a localizer-only approach

In the case of KAL801 there were a few contributing factors to the accident (go ahead and skip to page 142, unless you really like reading NTSB reports):

The glideslope may have been receiving false signals.
The crew should have disregarded the glideslope indication anyway as it was NOTAM'd out of service, but it's possible the crew followed the needle anyway.
The DME fix for the approach is not located at the airport.
This may have caused the crew to believe they were closer to the airport than they actually were.
Because of (1), (2), or some other reason, the crew flew below the Localizer-Only minimum altitude.
This is ultimately why they hit the hill -- they were too low during the approach.
Had they been at or above the localizer-only minimum altitude they would have cleared the obstacles.


What is the relationship between fuel mixture, throttle setting and engine temperature? I'm trying to understand the relationship between mixture, throttle, and engine temp.  In this article from AOPA, it states

... a lean mixture of 16 to 1 is not going to burn as hot as a rich mixture of 8 to 1. ... an engine [runs] hotter on lean mixtures.

This seems in general contradictory but what I'm gleaning is that there are some instances in which a leaner mixture will result in a higher engine temp and other instances in which a richer mixture will.  Perhaps this comes down to throttle?
Could someone clear up for me what are the "primary points" so to speak with regards to engine temp that I should be aware of?
Further, does there exist a general graph somewhere with mixture, throttle, and engine temp on the x, y, and z axes, respectively?  I might expect to see local maxima at full lean, full rich, and stoichiometric and local minima at I don't know where.

This image from Lycomings leaning instructions is likely what you are looking for:

The misnomer may be that leaning always increases the temperature of the engine. If you start at full rich or something above peak lean temp, leaning the engine will cause the CHT and EGT to rise until it hits its peak. If you continue to lean beyond this the temperature will start to drop again, and rapidly, but so will the power generated and at some point you run the risk of simply cutting the engine out so generally you want to lean to "peak EGT" since thats as low as you are practically going to want to go (unless you want worse fuel economy while flying slower).
If you look at the chart you will see below peak EGT your specific fuel consumption will also start to increase again.
Broadly speaking you can also see that increasing the mixture within its general operating range has a cooling effect on the engine.
If you are flying GA planes I would say the primary points in regards to engine temp is simply:

Keep an eye on temps and don't overheat the engine.
Lean slowly and carefully, keeping an eye on EGT or CHT for warm up which may not be immediate while leaning

If the gauge is creeping up, richen the mixture and consider reducing your angle of climb to increase airflow over the engine.


Will VR make large professional simulators obsolete? I believe that with the new breed of low latency VR displays such as the Oculus Rift, as well as associated control peripherals, the days of the large simulator are numbered. Crews can train together from different locations and each can be on their own moving chair, much cheaper to actuate than a full-hydraulics cockpit.

Will VR based solutions replace simulators with physical displays for FAA certification purposes?

Based on the variety of tasks that are performed in a simulator that VR would have great trouble accurately replicating, I think the answer is likely, no.  There IS a role for "simulators" that are more accurately referred to as "procedures trainers" in that they are non-motion, but this has nothing to do with VR, as those don't use all that much visual display anyway.  Networked wargaming is a great capability that VR can add to military simulations, but that's an addition to, not a replacement of, traditional simulators.

In a full-motion simulator, there are several things about the simulator that contribute to aircrew training, and the visuals are one important part.  The replication of the entire cockpit, including every switch, lever, display, keypad, and so on is another.  When I go to the sim and practice emergency procedures, each control reacts exactly as it does in the aircraft: where I look and where I reach to put my eyes and then my hand on each control, how hard I need to pull to get the desired effect, and so on.  And where I'm reaching with my sitting height and arm's reach is ever so slightly different than another pilot does.  We both get the same control, but it's farther below a tall pilot's eye line than a short pilot's. (Slightly over-simplified, but the basic point remains.)

We also do a fair amount of manipulation of the Flight Management Computer while in the simulator, which involves typing.  Not to say that typing isn't possible in VR, but it's not exactly the same as typing on a physical keyboard.  And we're using the same physical checklists and iPad EFB's that we do in the aircraft; not sure how well VR can mimic those.

So when you consider all the parts & pieces that make up the modern simulator & its considerable cost, the physical replication of the cockpit probably isn't something you're going to be able to remove in favor of VR.

For basic flying training, some of these sorts of factors are less important, as the basic flying skills you learn on one trainer transfer quite well to another trainer, even with a different cockpit layout.  But for basic flying training, not only the visual but also the vestibular and "seat of the pants" elements are more important.  While VR goggles like Occulus Rift are probably cheaper than several large display panels for providing the out-the-window visuals, these days high quality visual displays aren't the most expensive part of most simulators, and VR can't simulate the seat-of-the-pants sensation of accelerating, stopping, turbulence, and the like without some sort of motion actuators -- hydraulic or electric.

Now, for networked purposes (i.e. wargaming where Air Force elements from multiple bases across the country or globe can participate without the time & expense of getting to, say, Nellis AFB for a Red Flag), VR has amazing potential.  But to the extent that each pilot still has his own realistic cockpit & switches, what's driving the big gains is more the network than the VR... you can network an existing visual display with about the same hardware as you'd network the Rift devices.  To the extent that the "reality" of the precise cockpit can be sacrificed, then the VR probably makes for fabulous gains -- units practicing their tactics, rather than precise switchology. Sometimes that's a perfectly acceptable tradeoff; other times, not so much.

But until the tactile feedback of VR is good enough that I can use it to practice putting my hand on a lever, pulling it out of its detent in "this" direction with "this much" force required for "this much" travel, then pushing it down "this far" with "this much" force until it hits the stop "here," I really doubt that VR will replace the high-dollar flight simulators used in military and airline training.


Why are thrust reversers so unreliable? I see many questions regarding the unreliability of thrust reversers. Why are these components so faulty across all airplane models and manufacturers?

Is there a technical challenge to making the the thrust reversers as reliable as other aviation systems? Are the A380's electronic thrust reversers more reliable than the traditional mechanical or hydraulic reversers?

It's not so much that thrust reversers (TRs) are more unreliable than other components of the plane. However, they have a very important impact on the airplane's performance. Hydraulics, flaps, and even engines fail regularly. But engines and hydraulics can be backed up by redundant systems, and an airplane can still land without flaps. But engineers learned from Lauda Air Flight 004 that an airplane may not be controllable if the TRs deploy in flight.

So in the interest of safety, the TRs have additional precautions. The reasons for not aborting a landing after they are deployed are discussed in your first linked question. Reliability is also not the only reason for having no TRs on the A380 outboard engines, as discussed in the second linked question.

So to answer your question, there is indeed a technical challenge in making the TRs reliable: they absolutely must not deploy in flight. This means many safeguards are put in place, and they are designed to fail by not deploying if there is any doubt about whether it is safe. A TR that won't deploy is more desirable than a TR that deploys when you don't want it to.


On the 737NG, after deployment of spoilers automatically after landing, do the spoilers automatically go back down? So, I was just wondering whether the spoilers on a 737-800, after automatic deployment when landing, will go back down automatically, or need manual input by pilots for the spoilers to go down.

The spoilers on the 737 after auto deploy will re-stow automatically based on TLP (thrust lever position). This is a function for a rejected landing which will automatically lower the boards & retract the levers for go around... most pilots after taxi off the runway quickly advance the throttle to let the actuator reset the system in leu of pushing the lever forward (it has a clutch in the linkage to allow manual positioning as well)


How long does it take for an FAA licence to be delivered? Would anyone have an idea how how long it takes for a licence to be posted out.

The airmen search tells me my ATP processing was completed at some point last week. So the licence has been finalised.

Do they post the licences straight away and do they use Fedex or DHL, normal or priority?

I live in Australia. And need to present this licence at an interview in a weeks time which is why i ask. Are there means of expediting or tracking the licence in the mail?

Between the flight school and the fsdo losing my paperwork and forgeting signatures and corrections being sent to the wrong FSDO offices, its taken me about 5 months to get this licence processed. Ive missed out on some job offers already because the companies would not accept temporary licences. Id rather not miss out on this one.

If anyone has a clue, it would be most appreciated. I know fedex says its about 5 working days economy mail and UPS says 7 working days economy mail. But i have never delt with either.

Thank you kindly

The FAA has, at least in the recent past, been backlogged with some forms and certificate issuance has been one of those items. My private pilot certificate took nearly 3 months to arrive (hence, my temporary certificate almost expired). I had to make several calls to my DPE (Designated Pilot Examiner), who then reached out to the FAA in Oklahoma City to see what was wrong. It turned out a computer glitch had erased my knowledge test report. After several times around, this was fixed and my certificate showed up within several weeks. In the USA they always send it via First Class Mail (uncertified, no tracking number). Last August (2016) my new certificate showing my instrument rating showed up just a month or so after the checkride, so much faster. If you have a question, don't hesitate to reach out to your DPE - they are very helpful and can get things moving again if they're stuck. Also, make sure you keep all test reports and other documents until you receive your certificate in case they somehow get lost in the system. And when you get your new certificate - don't forget to sign the back or it is not legally valid!

Regarding your interview - your temporary airman certificate is valid for all purposes until the expiration date. You can bring this to an interview as it is as valid as the plastic card. I don't know if a company is allowed to reject you because you only have a temporary certificate while your plastic one is being prepared - I'd look into this and maybe ask an attorney as that doesn't seem like it would be legal to me since the certificate is valid.

Cheers!


Why is the APU located in the tail for almost all commercial aircraft? I know there are planes whose APU (Auxiliary Power Unit) is located elsewhere, but for the most common commercial jet aircraft (A320, B737, B747, A330,...), the APU is located in the tail.

Is there a good reason for that (place, weight, airflow,...)?

Dead space... Not much room in the tail to put other stuff, and it fits. Plus it has a nice empty space just outside for the exhaust pipe to exit without the hot gasses hitting anything.

Put the APU in the nose and you need a long pipe somewhere to get rid of the exhaust. More weight, more space, etc.
Put it in the wing and you're looking at uneven weight distribution (you want it at or near the centerline).
Leaves the tail area as a logical place, and there just happens to be space there as well in most aircraft.


Aircraft thrust calculation I had a question regarding thrust calculation for an aircraft during cruise. For an aircraft flying at a constant cruise altitude and a constant Mach number (level unaccelerated flight), what exactly is the weight we use in the equation T = W/(L/D) while calculating the thrust?
What I understand is that since the mass of the aircraft is continually reducing due to constant fuel consumption, therefore the lift requirement will change. Assuming a constant L/D ratio, that implies the drag will change leading to a constant change in the thrust. Therefore the cruise thrust is not a constant value. So how can we apply the above equation for a calculation of the thrust anyway? Is it a thrust at some specific point during the cruise?

The equation refers to instantaneous thrust in unaccelerated flight. The weight in this equation is instantaneous weight.
Indeed, this weight changes over time. This is for example the reason we have to use the  Breguet range equation instead of just divide thrust by thrust specific fuel consumption to calculate the range of an aircraft.


Can you fly a light GA airplane into a major hub? What operational considerations are there if you do? I did my training around the Seattle area, and was told that landing at SeaTac Airport (the region's major International/Commercial airport), while not strictly forbidden, was definitely frowned upon because it can slow down and interfere with the big planes on schedules. To discourage GA aircraft from using the big airport, they have a variety of landing fees, ramp fees, and prior-approval requirements.

But later, I moved near MCI, and was told that landing at the big airport was no big deal.  That they're actually happy to have little planes there.

If you fly small GA planes, do you land at the major airports in your area?

What advanced preparations can you make to minimize your impact on the "big boys", and remain a good airspace citizen?

Can you?  Absolutely, and air traffic control will treat you (almost) like any other airplane.  You are supposedly handled on a first-come-first-serve basis (reality is slightly different with different aircraft speeds, etc.).  Do the airlines like it if you slow them down?  No, but it's part of the system and the way that it works.

Very often, there are multiple runways at bigger airports, and sometimes there are even shorter runways that are dedicated for airplanes that don't need to land on the same one as the "big boys".  Even if not, they will work you in.

Now, that being said, very often there is a better option.  As you said, there are usually high fees at the big airports, so landing at a smaller satellite airport can often save you money and save you time because you won't have to taxi as far or sit and wait in line to get out.  An extra 15 minutes by car can be better than an extra 30 minutes while taxiing.

As far as being prepared, it isn't really much different than smaller airports other than the fact that ATC is much busier.  They don't have the time/tolerance to keep repeating instructions to you, and expect you to be "on your game".  When they rattle off taxi instructions like "Cessna N1234, taxi to the ramp via Alpha, Tango, Echo, and Xray. Hold short of runway 23." they expect a quick readback and for you to follow instructions exactly because they need to move on to the next guy.

It will also help everyone out if you don't fly your final approach the way that most people are taught for an entire 10 mile final:  very close to your actual landing speed.  In fact, you are usually landing on a runway that is 4X+ the distance that you need and you can slow down fairly quickly (especially compared to a jet), so if you can fly an extra 20 (or 80) knots as long as possible, it will be greatly appreciated and keep traffic moving.  Make sure that you leave yourself enough time to slow down at the end and above all else, be safe.


What is the throttle setting of a piston aircraft during cruise? I am learning to fly nowadays, I am sorry if this sounds like a dump question.

What is the throttle setting of an aircraft during cruise flight?

After stabilizing the flight after climb do i need to turn down the throttle?

Broadly speaking its what ever you chose it to be. You should always refer to your aircrafts POH for the information specific to your airframe and engine. Beyond the POH there may also be supplemental engine information from the maker.

Generally take off and at least initial climb out occur at full throttle. Then at when you reach your cruising altitude you will throttle back to your cruise power setting and level off.

For example lets take a look at the charts for a PA-28

You can chose your desired power setting based on a desired fuel burn

Then refer to this chart to see your airspeed.

You can then use these numbers for your flight planing, or work backwards to achieve a target airspeed.

For a trainer these numbers tend to be not all that large of a range. My Archer will do a full power climb out at 2650RPM then throttle back to about 2450RPM for cruise. Higher performance aircraft may have larger ranges as well as more complex operating limitations. Some engines have time limits on which they can be at full throttle and most have thermal operating limits if you decide to dance on the mixture lever. Turbo or super chargers may also add an additional level of management to prevent over boosting. Modern digital engine analyzers allow for a level of precision previously unachievable.

AOPA has a decent article on power management over all, you can find it here.

Pro Tip: A lot of small trainers print the engine performance data on the inside of the sun shade so you dont need to thumb through the POH in flight.


What do the radiation patterns of ADS-B transmissions on large airliners tend to look like? In the recent article Flightradar24 gears up for a new wave of flight tracking I've read about FR24's experimental Wave Glider ADS-B receiver - essentially a self-propelled, solar power buoy as a remote ground station.
What do the radiation patterns of ADS-B transmissions on large airliners tend to look like? In particular, the transmissions that would be received by satellite or surface ADS-B receivers collecting traffic information.
Are there any examples of these radiation patterns published? Are there guidelines, best practices or regulations that apply to the directionality of the radiation?
An example of a general requirement might be EASA's CS-ACNS:

CS-ACNS.D.ELS.060 Antenna installation
(See AMC1 ACNS.ELS.)
(a) The installed antenna(s) has (have) a resulting radiation pattern which is (are) vertically polarised, omnidirectional in the horizontal plane, and has (have) sufficient vertical beam width to ensure proper system operation during normal aircraft manoeuvres.
(b) Antenna(s) is/are located such that the effect on the far field radiation pattern(s) by the aircraft structure are minimised.

which only addresses directions above/below horizontal to the extent that they apply to "normal aircraft maneuvers." There may be more.

Below I've added a similar but different gain pattern as an example of the kind of data I am looking for. However it is the gain pattern for a downwards-looking ADS-B receiving aboard a satellite, showing good reception from below (nadir: $\theta,\phi \approx 0 $). What I am looking for is a similar type plot, but for the radiation from an aircraft.

above: Photo of FR24's ADS-B receiver aboard a Liquid Robotics Wave Glider platform. Photo credit Flightradar24.

above: Example from this paper of an receiver's gain pattern. In this case it is an ADS-B receiving antenna system, aboard a satellite, showing gain optimization looking straight down (nadir).

In airliners, like in most aircraft, the ADS-B transmission come from the ATC radar transponder. The transponders in aircraft with an Maximum Takeoff Mass exceeding 5700kg /12500 lbs are required to have antenna diversity. This means that the aircraft will have a top and a bottom antenna connected to the transponder.

ADS-B transmissions are sent out of either the top or bottom antenna, the selection of which should be random with a 50-50 distribution.

Radar and TCAS replies are sent out the antenna on which the incoming interrogation was strongest.

The antennas are vertically polarised and have an approximately omnidirectional radiation pattern in the horizontal plane. In the vertical plane, most radiation energy will be focused 45 degrees around the horizon. They have a cone of silence.

The aircraft structure blocks and reflects part of the radiated energy. This is causing the far field pattern to be not uniform and varies from aircraft to aircraft. On the lower antenna the main effect is of the fuselage and the engines. On the top antenna the fuselage, the tail and the wings/winglets are the main obstacles.

On small aircraft this is more of a problem, especially when the transponder antenna is between large fixed gear struts.

This study contains an antenna pattern of the top antenna of an aircraft


What are these silver stripes on Cosmic Girl for? Cosmic Girl (a 747-400 used for launching things into space)1 has a network of silver-coloured stripes on its empennage, starting at the (closed-off) last cabin window, and going aftward and upward from there, with branches running onto, and up, the vertical tail; there also appears to be a similar stripe emanating from the (also-closed-off) third cabin window behind the second main-deck exit door and running downward onto the wing root:

(Image originally by Crishazzard at Wikimedia Commons; modified by me.)

What are these stripes for?

1: It actually had that name before it became a rocket launcher - it didn’t get it from Virgin Orbit.

It's aluminum "speed tape" being used to run wires around the outside of the fuselage, possibly for load cells or some other kind of sensor related to whatever is being tested and that was impractical to run internally.  If you zoom in the image and look carefully at the vertical strip to the right and below TEST, you can make out a dark line in the middle of the tape that is a shadow from the wire bulging out.  Strictly temporary.

It looks like two window panels have had their acrylic panes removed and replaced with aluminum blanking plates with holes for passing the wire out through the pressure hull, making it a simple job to return to the normal configuration.


Electrical systems in light aircraft How does the electrical system in a light aircraft such as a Zenith CH-750 or Cessna 150 work compared with electrical systems in larger aircraft? Are the system is different than the electrical system on a common car?  Do we need static electric discharge system?

Typically light normal category aircraft make use of either a 14 VDC or 28 VDC electrical systems powered primarily by an engine driven alternator. This provides power to one or more power bus bars which provide electrical power to the various aircraft systems requiring it.  Below is an example light aircraft electrical system from a Cessna 172S.

One notable deviation from automobile electrical systems is that the engine spark plugs receive electricity from a separate pair of magnetos which produce their power independent of the main electrical system for reasons of redundancy.


What practical alternatives are there to 100LL in 2021? As a prospective student pilot in Southern California, I would like to avoid 100LL. Since the FAA 100LL phase-out is stalled, what other alternatives are there? Continental has a line of Diesel engines such as the CD-135, are supplemental type certificates available / retrofits common? What about "mogas?" Does the answer change if someone is looking to purchase an aircraft?

Right now, Mogas is the only alternative fuel because the unleaded avgas program still seems to be going nowhere, although the industry testing program is supposed to restart this year.
You could put an aircraft diesel engine in your plane if you're rich, and run it on Jet A, but if you can afford that, you can probably afford other alternatives as well.
The most practical thing for a prospective owner to do is to buy an airplane and incorporate the Petersen Mogas STC (it's just a paperwork/placard mod for a lot of high wing airplanes, but physical parts may be required in other cases), and run the plane on mogas when possible, and avgas when not.
Overall, Mogas is better, because the tetraethyl lead in avgas used to get its octane rating is just bad news all around (the lead combustion byproducts contaminate the oil, leave crud in the cylinders, etc.) Mogas's main caveats are higher Reid Vapor Pressure (it boils more readily) and long term storage.  Mogas is more volatile and needs fuel stabilizers if a fuel supply is left for more than few months.  The volatility also means more susceptibility to vapour lock.
On airplanes with gravity feed fuel systems, vapour lock is less of a problem because there is positive fuel head pressure all the way from the tank to carb.  On low-wing pumped-fuel airplanes, there is pump inlet suction, which to the gas is like going up a several thousand feet depending on how hard the pump sucks, so on a very hot day with a hot engine, there is a chance of vapour lock and it can be prudent to install cooling shrouds on fuel system components like engine driven pumps (you'll know it's happening as the fuel pressure fluctuates).  I was having incipient vapour lock indications on my plane during heat waves (only on the ground) and installing a cooling shroud for my engine-driven fuel pump seems to have solved it.
Those issues aside, any 80 octane engine will be MUCH happier running on Mogas than 100LL, so if you can do it, it's a no-brainer.


How do I choose the correct NACA airfoil for my requirements? How do you find the correct NACA airfoil to use when you already know the requirements?

All of the research I have done on this has shown how to determine what kind of camber/chord/aspect ratio etc. only, but not how to actually pick the proper NACA airfoil. I would like to know if there is some website or program where you can easily find the correct airfoil given different circumstances. Then I would be more sure of having the correct airfoil when performing my tests. I understand I could just eyeball it, but I would like to be able to find the exact lift that my wings would produce, and that would only come from knowing the exact NACA airfoil.

It doesn't necessarily have to be a NACA airfoil, but it should be some type of airfoil where data can be taken from it.

I also could be approaching this from the wrong way, as I do not have an experienced mentor, so if using NACA is unnecessary or outdated please let me know because I really am at a loss of how to select the proper airfoil.

So you know your wing planform and look for the right airfoil.

You need to be more specific with your requirements, and yes, NACA airfoils will most likely not be the best choice. But since there is plenty of literature on them, they are a good start.

Please answer those questions first:

What is the maximum airfoil thickness you can afford? A thicker airfoil makes for a lighter wing with more internal volume for flaps and fuel. However, if you want to operate your design at high subsonic speeds, thickness needs to be controlled.
What is the lowest cruise lift coefficient and the highest lift coefficient for a clean wing and with flaps down? Does your design need flaps at all?
If the aircraft is small: What Reynolds number is flown at which lift coefficient?
What is the desired stall behaviour? Docile (as preferred for training aircraft) or snappy (as preferred for aerobatic aircraft)?
What construction technique is used for the wing? Wooden frame and fabric? All metal with countersunk or exposed rivets? To be built on a jig or on a flat table? Composite, in a mold or positive over a foam core? All of them have subtle consequences for airfoil selection.

Generally, you look at all requirements and then select or design the airfoil according to the desired pressure distribution at different angles of attack and Mach numbers. Once you tell us more, I can become more specific.


Does the F-4E Phantom II have a weather radar? Here's the cockpit of the F-4E:

The Main Panel NO7 says "Radar Scope" and when you put your mouse cursor on that "magician globe", the X-Plane 8.15 tooltip says "Weather Radar". So, what is that overly "oversized weather radar scope"?

The F-4 radar was a low PRF pulse radar, designed to search for, acquire, and track other airborne aircraft, and then provide guidance for Aim-7 Sparrow air-to-air missiles. It also had a ground mapping capability, and a capability to detect and display severe weather, but it was primarily designed for air-to-air combat.

Later models of the F-4 had an more modern radar, (installed in the German F-4F for example) which was a high PRF pulse Doppler system, and had improved capabilities, but I don't know whether they still had a weather mapping capability. I would be surprised if they did not.


Why should a Piper Seneca not take off after an engine failure below 100MPH? In the Seneca (PA34-200) AFM, in the ENGINE FAILURE DURING TAKEOFF section, it is noted that if engine failures occurs during takeoff ground roll and 100 MPH has not been attained, the pilot must abort the take off and if attained the pilot must continue. Since Vmc is 80 MPH, why was 100 MPH chosen as the cutoff point for go/abort?

  ENGINE FAILURE DURING TAKEOFF
  The single engine minimum control speed for this airplane is 80 mph (CAS) under sea level standard conditions.

  a. If engine failure occurs during takeoff ground roll and 100 mph (CAS) has not been attained, CLOSE BOTH THROTTLES IMMEDIATELY AND STOP STRAIGHT AHEAD. If inadequate runway remains to stop, then:
  (1) Throttles - CLOSED.
  (2) Brakes - apply maximum braking.
  (3) Master switch - OFF.
  (4) Fuel selectors - OFF.
  (5) Continue straight ahead, turning to avoid obstacles as necessary.

  b. If engine failure occurs during take-off ground roll or after lift-off with gear still down and 100 mph (CAS) has been attained:
  (1) If adequate runway remains, CLOSE BOTH THROTTLES IMMEDIATELY, LAND IF AIRBORNE, AND STOP STRAIGHT AHEAD.
  (2) If the runway remaining is inadequate for stopping, the pilot must decide whether to abort the takeoff or to continue. The decision must be based on the pilot's judgement considering loading, density altitude, obstructions, the weather, and the pilot's competence. If the decision is made to continue, then:
  (a) Maintain heading and airspeed.
  (b) Retract landing gear when climb is established.
  (c) Feather inoperative engine (see feathering procedure).

Original image of text.

I finally found out an answer which makes more sense to me . By test pilot , vmca masured with a lot of citation and one of them Is 5 degrees angle of bank towards the live engine . So it means that we can't have that 5 degrees because we are still on the ground.
for each 1 degree , our speed decreases 3 knots .So 5 degrees = 15 knots which is equalls to 20mph !
 80+20 = 100 mph !
This was the best answer I have got until now.


Does the "follow" instruction give an aircraft clearance to turn onto a taxiway and/or cross a runway? Consider this ATC instruction from a ground controller:

  N123, continue down Alpha, turn right at Kilo, hold short of RWY36.

  N456, follow N123.

Does this instruction mean N456 can turn right at Kilo without further ATC instruction?

What about:

  N123, continue down Alpha, turn right at Kilo, cross RWY36.

  N456, follow N123.

Must N456 hold short of RWY36 and await clearance to cross the runway?

The controller is required to give explicit clearance for crossing a runway.  "Follow" is not clearance to cross a runway.
From the ATC phraseology:

7-3-2
d. When an aircraft/vehicle is instructed to “follow” traffic and
requires a runway crossing, issue a runway crossing clearance in
addition to the follow instructions and/or hold short instructions, as
applicable.
EXAMPLE−
“Follow (traffic), cross Runway Two−Seven Right.”
or
“Follow (traffic), cross Runway Two Seven−Right, hold short Runway
Two−Seven Left.”

The AIM doesn't spell this out as explicitly.  AIM 4-3-18-5

A clearance must be obtained prior to crossing any runway. ATC will issue an explicit clearance for all runway crossings.

The explicit requirement for runway crossings is somewhat new (2010 I think) and was the more interesting part.  I neglected the question about crossing taxiways:

Does this [follow...] instruction mean N456 can turn right at Kilo without further ATC instruction?

Yes.  Also from 7-3-2

a. Note 1. The absence of holding instructions authorizes an
aircraft/vehicle to cross all taxiways that intersect the taxi
route.

That said, I would not expect the only instruction from the controller to be "follow (traffic)".  I would expect to be cleared to a specific destination as well.

"N456, taxi to 36.  Follow N123"


Did older Airliners use a pitot-static system? Aircraft like the B707, how would the aircraft gather speed and altitude data? And if they used pitot static system by that time, was there ever anything else that gathered the speed data?

They used the same kind of pitot probes and static ports as modern aircraft, but prior to the 70s they didn't use Air Data Computers  that processed the pitot static information in a central location for electronic distribution to other systems that needed the data (that had to wait for the Integrated Circuit and Microprocessor revolutions of the 60s).

Prior to that the pitot and static pressure was routed directly to the instruments and devices that needed to measure it, so you had the plumbing itself routed to both the pitot static instruments and electronic devices that needed it, pretty much like with light aircraft, but with way more plumbing.  The adoption of ADCs reduced the plumbing requirements to just that required between the probes and ports and the ADCs.

Computations and conversions of pressure data (like deriving Mach#) were done by analog mechanical or electronic means directly within the instruments themselves.

So, an airplane like a 707 in the late 50s would have lots and lots of low pressure pneumatic plumbing running up behind the instrument panels and to various analog computing devices in the avionics bay.


What is MCAS trying to fix on B737 MAX? New sources such as Seattle Times and Aviation Week provide a pretty good overlay of the MCAS function on B737 MAX. However, I'm unclear as to the issue that MCAS is attempting to fix. From what I can gather, the larger nacelle led to a shortening of the pylon height, leading to altered aerodynamics at the wing/pylon/nacelle junction. At high AOA, this leads to a higher pitch-up moment than on the NG (dispelling other popular theories, it has nothing to do with the thrust line or nacelle CG).

In Seattle Times, it talks about shock formation at the junction, indicating that this is not a low Mach problem. However, transonic regime is usually not limited by stall but by deterrent buffet. Can someone with the knowledge clarify? If it is a stall issue, is it a lack of stall identification (lack of distinct pitch down) or is the aircraft experiencing a pitch-up without MCAS?

From The inside story of MCAS: How Boeing’s 737 MAX system gained power and lost safeguards by Dominic Gates and Mike Baker:

During flight tests to certify an airplane, pilots must safely fly an
extreme maneuver, a banked spiral called a wind-up turn that brings
the plane through a stall. While passengers would likely never
experience the maneuver on a normal commercial flight, it could occur
if pilots for some reason needed to execute a steep banking turn.
Engineers determined that on the MAX, the force the pilots feel in the
control column as they execute this maneuver would not smoothly and
continuously increase. Pilots who pull back forcefully on the column —
sometimes called the stick — might suddenly feel a slackening of
resistance. An FAA rule requires that the plane handle with smoothly
changing stick forces.
The lack of smooth feel was caused by the jet’s tendency to pitch up,
influenced by shock waves that form over the wing at high speeds and
the extra lift surface provided by the pods around the MAX's engines,
which are bigger and farther forward on the wing than on previous
737s.
(...)
Under the proposal, MCAS would trigger in narrow circumstances. It was
designed "to address potentially unacceptable nose-up pitching moment
at high angles of attack at high airspeeds," Boeing told the FAA in a
proprietary System Safety Assessment reviewed by The Times.

Another article from The Seattle Times published in March makes mention of a high speed stall:

Designed to activate automatically only in the extreme flight situation of a high-speed stall, this extra kick downward of the nose would make the plane feel the same to a pilot as the older-model 737s.

This indeed points to a stick-force-per-g test, as @Jimmy mentions in a comment. Since the B737 has a fully irreversible hydraulically actuated flight control system, with an artificial feel that is proportional to dynamic pressure but not to load factor, the obvious mechanism for "lack of smooth force feel" would be having to release the column to some extent due to extra nose-up moment that the aircraft generates.
It is very plausible that the added lifting surfaces from the engine pods create a larger pitch-up moment than the 737NG has in the same circumstances. I'm not really sure how the supercritical airflow over the MAX wing differs from that of the NG to create extra pitch-up.
All of that is the original limited cure for the stick-force-per-g tests. If this was the only thing that needed to be fixed, all would probably have remained well. But the first linked article also mentions:

The flight-test pilots had found another problem: The same lack of smooth stick forces was also occurring in certain low-speed flight conditions. To cover that issue too, engineers decided to expand the scope and power of MCAS.

As you can see, The Seattle Times is my source of information as well...there is no additional information on what were the "certain low-speed flight conditions".


How is the camera positioned for these plane-to-plane Schlieren images of shock waves? These two popular press articles discuss the use of schlieren photography to image shock waves of jets during flight using a special schlieren camera on a third plane.

Gizmodo: NASA Captures First-Ever Images of Intersecting Shockwaves From Two Supersonic Jets
Ars Technica: NASA visualizes supersonic shockwaves in a new, awe-inspiring way

NASA's Glenn Research Center page on Schlieren photography is instructive but doesn't give a clue how this is done. Where is the camera relative to these target aircraft, and what's behind them?

This NASA page shows a diagram of traditional Schlieren photography but in that case a special light source is behind the plane, and the present photos are "in the wild" rather than in a laboratory setting.

Where is the camera relative to these target aircraft, and what's behind them?

Straight from NASA themselves:

  NASA flew a B-200, outfitted with an updated imaging system, at around 30,000 feet while the pair of T-38s were required to not only remain in formation, but to fly at supersonic speeds at the precise moment they were directly beneath the B-200

and (alternative link)


Is there an aircraft that can go supersonic at sea level without using afterburner? Is there an aircraft that can go supersonic at sea level without using afterburner? Quick look through the "supercruise" capable aircraft might be helpful in narrowing down the possibilities, though I haven't seen anything specifying the top speed without afterburner and at sea level simultaneously. If I remember correctly, the F-15 is not capable of doing that; this gives you an idea, however, it's not the fastest jet in the world, so I'm still looking for the answer.

According to Wikipedia, the BAC TSR-2 was capable of supercruise (no reheat) at Mach 1.1 at 200 feet (~60 m) altitude.  The TSR-2 first flew in 1964.  The English Electric Lightning had demonstrated supercruise several months earlier, but only at higher altitudes (above 20,000 feet, appr. 6 km).


Why does GR mean hail in a METAR? Wouldn't you think they'd choose HL instead?

That might confuse pilots who frequently see SS (Sandstorms),
 DS (Dust Storms) and VA (Volcanic Ash).

The French word for hail is grêle which is abbreviated GR.  METAR is an international standard so you will see some non-English words included in the METAR.


Why does the F-35 Lightning II have only 1 crew when the F/A-18 Hornet had 2? Many successful fighter aircraft, eg F/A-18 Hornet, have 2 crew (pilot and navigator), which (from my albeit limited research) gave great benefit in complex situations especially involving ground defences.

The F-35 Lightning II is supposed to be multi-purpose, but has only 1 crew - why?

Do the advanced electronics compensate for the lack of a navigator?
Would the design (aerodynamics/frame) be compromised by adding another seat?
Something else?

Why does the F-35 Lightning II have only 1 crew when the F/A-18 Hornet had 2?

According to program officials involved in the development of the F-35, the F-35 is a single seat aircraft because:

  New advances in avionics and sensor fusion technology, which can
  allow  a single pilot to perform missions that previously required two
  crew members.

Given the fact that the F-35 is build around the concept of
Network Centric Warfare there is less cockpit workload for most strike missions. Consequently, the need for a co-pilot is a lot less.
The single-seat configuration also maximizes commonality between the
three variants of the F-35 thereby keeping development costs low.
The survivability of the F-35 includes limiting the probability of   detection. Ergo, a two-seater version can very easily increase the RCS of the F-35 thereby compromising its stealth capabilities

West 2014: Joint Strike Fighter: What Do the Pilots Who Are Flying It Today Have to Say?

That said, one major drawback that remains on the one seat design is the demand on one pilot to assimilate and decide on all the information available.


Can light aircraft be equipped with yaw damper? The smallest aircraft I know of that has a yaw damper is the Pilatus PC-12.

From an engineering standpoint, how hard is it to make a light-weight solution for a light single engine plane?

The system in mind would also automate the corrections for all left turn tendencies, and coordinate the turns.

The reasoning for it is a no-hands-and-feet autopilot flying, plus the other benefits in takeoff rolls, etc.

The components I'd imagine would be needed:

Slip indicator digital output;
IAS digital output;
Logic board;
Rudder control-tab powered by an electric actuator.

Yes.  The Garmin Perspective avionics suite for the Cirrus SR-22 is equipped with a yaw damper in its GFC-700 AFCS.

The King KAP140 autopilot also offers a yaw damper function for aircraft with a servo controlled rudder trim.


What is different between a B737 and B757? Both are single aisle, 3 by 3 seating planes.  Both are vaguely similar in length (with appropriate models).  But they have fairly different ranges.

For similar sized airplanes, why the big difference?

Although the 737 has grown over the years, the 737 and 757 remain in different size classes. Both models can be ETOPS certified, although the 757 is more often used in long flights.

At the time the 757 was introduced (in the 80's), the 737 classic series was current. For the 737-400:

Passengers: 146
Length: 119 feet
Wingspan: 95 feet
Wing area: 1135 sq feet
MTOW: 138,000 lb
Takeoff distance: 8000 feet
Range: 2160 nm
Thrust: 2x 23,500 lbf
Max fuel: 5,311 US gal

The 757 was significantly larger. For the 757-200:

Passengers: 200
Length: 155 feet
Wingspan: 125 feet
Wing area: 1951 sq feet
MTOW: 255,000 lb
Takeoff distance: 6500 feet
Range: 4100 nm
Thrust: 2x 43,500 lbf
Max fuel: 11,489 US gal

The 757 is about 35 feet longer, seats about 50 more passengers, and flies about 2,000 nm further (roughly twice as far). The extra range is due to the larger wingspan and longer fuselage, being able to carry more fuel. For this reason, the 757 is used on longer and busier routes, while the 737 is used on shorter, less busy routes.

In the 90's, both models were updated. The 737 was significantly upgraded, including new wings and a new engine, which increased its efficiency. The 737 NG series eventually included the 737-900ER model, currently the largest 737 model.

Passengers: 180
Length: 138 feet
Wingspan: 117 feet
Wing area: 1341 sq feet
MTOW: 187,700 lb
Takeoff distance: 9843 feet
Range: 3235 nm
Thrust: 2x 28,400 lbf
Max fuel: 7,837 US gal

The 757-300 was also introduced. This was a stretched version of the 757-200.

Passengers: 243
Length: 178 feet
Wingspan: 125 feet
Wing area: 1951 sq feet
MTOW: 272,500 lb
Takeoff distance: 7800 feet
Range: 3595 nm
Thrust: 2x 43,500 lb
Max fuel: 11,489 US gal

Although the more efficiency gains of the new 737 bring the range up to nearly that of the 757, the 757 remains significantly larger.


What is this white-tail, short upper deck 747 I just saw? It was seen taking off from a US Air Force base, which is part of Air Mobility Command.  A great deal of their operation is departing or returning troops from abroad, so it gets a lot of rare visits from oddball commercial aircraft.

This 747 had the short 3-window upper deck area, so it was a -100,-200 or SP, and it wasn't an SP.    It was a "white tail", entirely white except for some numeric markings.

No USAF marking, that's not a surprise since the Air Force has six 747-100/200s: all accounted for by four NEACP planes (why would they come to an AMC base?) and two VIP transports (and they have a distinctive paint scheme, so, I wouldn't be asking).

It did not carry the distinctive markings of several Arab state head-of-state aircraft, the NASA paint scheme, nor the Las Vegas Sands Corp. scheme, nor Earnest Angley Ministries.   It did not have any funny engines on it.  Kalitta Air doesn't fly them anymore.

I have to assume none of the nine in Iranian service would be visiting a USAF/AMC base.

I'm sorry, I tried to get a photo, but could not safely stop.  What could this airplane be?

All factory freighter 747s have short upper-decks, that includes the -400F and -8F. Some don't, but those are converted from passenger 747s that had the stretched upper-deck.

It could have been a 747-400F contracted by the military, plenty of those come in all-white, such as N404KZ:

source

I don't know on what basis the military prefers contractors over C-5s, etc., but an example of a civilian 747 contracted by the Air Mobility Command that crashed is National Airlines Flight 102.


Why does carburetor icing require manual attention by the pilot? Why is it carburetor icing has to be handled manually by the pilot, at least in a helicopter? I am hoping very soon to take my PL/H lessons, I have a little understanding of mechanics and how things work and this is one subject that puts the willies up me as a potential student helicopter pilot. Why can it not be an automatic response built into the engine? After all, this is the 21st century.

Also, I am assuming every motorized engine is the same, so why does a helicopter require a manual response to carb icing but a motor vehicle doesn't? Do we not notice it because the vehicle is on the ground?

Not every motorized engine is the same: For example, you would be hard-pressed to find a carbureted car these days.

The most similar kind of land-vehicle engine you'll find would be a motorcycle engine, and those do in fact suffer from carburetor ice:
- A discussion of carb icing on the Ninja 250
- A thread about carb ice on Bike Talk Forums

Older cars with carburetors were also susceptible to carburetor ice, and eventually included measures to avoid or mitigate it.
This could include passive changes such as mounting the carburetor in a warm part of the engine compartment (usually above the block, in a downdraft configuration), semi-active changes like "heat risers" which would feed warm air into the intake (usually behind the throttle plate, but occasionally in front of it), or fully-active systems like automatic "heat flaps" and "Time/Temperature switches" which do the same thing as the carburetor heat control in an airplane but without the driver's input or control.

These systems aren't usually fitted to aircraft as they add both weight and complexity, and can come with their own disadvantages (such as reduced power if the carburetor heat flap is in the "on" (heating) position during takeoff or on a go-around).

So why don't we hear about ground vehicles suffering from carburetor ice as much? Three main reasons:

Carburetor ice is most likely to form at low power settings.
Your car or motorcycle probably doesn't spend much time at or near idle power unless you're stuck in traffic: A few seconds coasting to a stop and then you accelerate away again.
Carburetor ice is less dangerous when you're on the ground.
One of the most common times you'll have a carburetor ice problem is during an approach/landing, with the engine at or near idle power for an extended period of time (this is why many aircraft call for carb heat during landing). Having your engine die at this point is a pretty serious problem, especially if you need to execute a go-around.
The analog in a car or motorcycle is having your engine stall after spending an extended period idling (standing or stopped in traffic). Having your engine die when you try to accelerate away is inconvenient and will probably make other drivers honk their horns at you and say unkind things, but it's unlikely to kill you.
There's nothing the driver can do about it.
A driver doesn't usually have a "carburetor heat" handle to pull (except possibly in very old cars), so you can't turn around and say "Your engine stalled because you didn't do this." On top of that because the problem is usually more inconvenient than dangerous on the ground it's not likely to make news: "Driver had to sit on shoulder for 30 minutes while their carburetor thawed out. Hundreds inconvenienced by rubbernecking traffic." is simply not as newsworthy as "Airplane crashed!"


How do plane landing-gear tyres roll before take off? How do plane tyres roll? Are they equipped with special engines like cars or are they rolling using the plane flying engines? Or can both methods be found with different constructors?

Normally, aircraft wheels are rotating freely around their axle, unless the brakes are activated. The ground roll was a convenient time for engine warm-up in the days of piston aircraft.

However, rolling on the ground using jet engines is very inefficient; fuel consumption could be reduced if the aircraft uses other means of propulsion on the ground and only starts the engines right before take-off. Therefore, electric propulsion using hub motors is actively studied. The batteries could be charged (partially) during landing, when the hub motors are switched to generator mode, and the rest of the power could be provided by the APU.

Pushing back from the gate using jet engines is unwise, so a tug is used to move the aircraft to a position from which it can continue the ground roll to its take-off position. These tugs push a bar which is linked to the nose wheel of the aircraft. Towbarless (TBL) tugs scoop up the nosewheel and lift it off the ground, allowing more-secure control and faster maneuvering.

Conventional tug Goldhofer F110E (picture source)

Boeing 777 being pulled by Goldhofer TBL aircraft tug (picture source). They are really hard to see when you are sitting in the cabin.

Towbarless tug detail (picture source)


What are the implications of a Memorandum of Understanding during an aircraft order process? The term "Memorandum of Understanding" often pops up when airlines are about to order aircraft.

I'm a little confused as of the importance it carries:

Does it contain any details if the agreement is broken?
Does it state when and where aircraft will be ordered? Or is it just "we will order from you"?
Does it contain any details on any discounts/benefits or similar? I imagine these would in some form be put down on paper before starting negotiations with which company to order from.

A Memorandum of Understanding (MOU) isn't an aviation term or practice, it's a general business/legal term for a 'pre-contract' of some kind. Before two companies commit to a legally binding and perhaps very expensive contract, they'll often prepare an MOU to make sure that everyone involved has the same understanding of what will be in the contract. That way, there shouldn't be any big surprises or fundamental disagreements when the real contract is prepared.

In the context of aviation, that could be things like how many aircraft will be purchased and when, or what the price is anticipated to be, or anything else that both side consider important. That means that the information in an MOU could be very interesting for other parties ("can you explain why our competitors are paying you $50m less per aircraft than we do?"), so they're usually confidential.

Another common use for MOUs is for PR/Marketing purposes. If two companies are discussing a joint business venture they might come up with an MOU and use it to generate market interest or even raise capital ("I know we're a small company but we have an MOU with Boeing to jointly research alternative fuels").

Given that background, I don't think it's likely that you'll get any specific answers to your questions. An MOU could include all the things you mentioned but only a real contract is enforceable.


How to join a traffic pattern when passing overhead? I can't seem to find a definite answer to the question on how to enter a traffic pattern when joining from the opposite end of the pattern. No matter who I ask, I'm getting a different answer every time, and they all seem convinced it's the only way to go.

So I'd like to ask a broader audience here.

Let's say runway 36 is in use, right traffic and you approach from the west. How do you enter the pattern?

I'm convinced "B" is the right way (safest at least) but recently I heard an ATC conversation where the pilot was instructed to cross overhead and join downwind. He used method "B" but the controller didn't like that because it took too much time.

What is the correct way? Is there a difference between controlled and uncontrolled airports? What about the procedure when approaching from other angles? And is there a difference between the U.S. and other parts of the world?

EDIT:

On March 13 2018, the FAA released the following Advisory Circular regarding this matter: AC-90-66B.

What is the correct way?
Is there a difference between controlled and uncontrolled airports? What about the procedure when approaching from other angles?

Well I'll address your second quesition first: There is ABSOLUTELY a difference between controlled and uncontrolled fields. At a controlled field you do what ATC tells you to do (and if there's any ambiguity you ask them to clarify what they want you to do).

At uncontrolled fields in the USA the standard way to enter the VFR traffic pattern is a 45-degree intercept to the downwind leg. The FAA's pronouncements on the issue can be found in AC 90-66A.
A brief and relevant excerpt:

a. Prior to entering the traffic pattern at an airport without an operating control tower, aircraft should avoid the flow of traffic until established on the entry leg. For example, wind and landing direction indicators can be checked while at an altitude above the traffic pattern. When the proper traffic pattern direction has been determined, the pilot should then proceed to a point well clear of the pattern before descending to the pattern altitude.
b, Arriving aircraft should be at the appropriate traffic pattern altitude before entering the traffic pattern. Entry to the downwind leg should be at a 45-degree angle abeam the midpoint of the runway.

(Emphasis Added)
You will find a rich variety of opinions (a polite way of saying "hidebound arguments") among pilots on the correctness of various other entries, but the 45-to-downwind is what's expected by most pilots in the US, and it is generally the safest way to enter the pattern (you will be where everyone else expects you to be, and you will have plenty of time to look at the pattern and figure out how you're going to sequence into it).
The 45-degree intercept assumes that you are on the side of the runway where you will be flying your downwind leg. If you are on the opposite side you need to position yourself to maneuver for a 45-degree intercept. I am personally a proponent of the technique illustrated below:

Cross midfield 500-1000 feet above pattern altitude.

At airports where there are multiple pattern altitudes specified, such as a "jet pattern" above the light aircraft pattern, cross at least 500 feet above the highest pattern altitude to ensure traffic separation.

Proceed away from the airport and clear of the traffic pattern before descending.
Make a descending turn to intercept the 45-degree entry

Ideally time your turn and descent such that you're at pattern altitude when you intercept the 45-degree track. If you expect to need more time to descend plan for a longer entry.

Enter the traffic pattern on a 45-degree-to-downwind.

Note that this is subtly different from your "Option B" (which has the descending turn leading directly into the downwind) in order to comply with the advisory circular's instruction that you should be "well clear of the pattern before descending".
I cribbed the pattern entry graphic from Alliance Airways, with some minor modifications, as it was the best illustration of the technique I could find.


How do I get an airworthiness certificate for a prototype aircraft? If I were to build a plane of my own design as a prototype for possible sales, what steps would I need to take to get an airworthiness certificate from the FAA? If it's truly a certified aircraft and not a homebuilt?

You can't legally fly any aircraft heavier than an ultralight unless it is certified. Your prototype will be certified as Experimental Category in one of these classes. The certification is awarded based on inspection during construction, on completion, and after a flight test period. The design is not subject to FAA approval.

If you want to manufacture aircraft for sale, you need approval of the design. This is called a Type Certificate. For smaller general aviation aircraft the appropriate regulation is Part 23 which states the requirements. There are also Advisory Circulars which provide clarification on approved means for satisfying the design requirements.

To avoid the expense of inspecting and flight testing every aircraft as is required for the experimental category, manufacturers instead obtain a production certificate. This reference is for larger part 21 aircraft. The production process is approved rather than inspecting each aircraft as it is produced. Each aircraft is still flight tested, but this may take an hour or less as compared to an Experimental flight test, which is 40 hours.

Reading these four references will give you some limited understanding of what you are asking. Here is an 2012 swag at certification costs. Part 23 was estimated at $$25m for design and testing, then another $25m for certification. This does not get you a production certificate.


What is a gold seal flight instructor? What is a gold seal flight instructor and how does it differ from a usual flight instructor? Does it offer any additional privileges or prestige?

A gold seal flight instructor is obtained by having a ground instructor certificate and within the previous 24 months have a pass/fail rate of 80% or above and recommending at least 10 applicants.

It is a way for the FAA to recognize the best instructors in the industry.  You do not get any special privileges with the gold seal.

See AC 61-65 for more details.


Do high-speed ailerons help with the roll rate control in non-FBW? Do inboard high-speed ailerons help with the roll control by decreasing the moment arm as a secondary benefit? As in make it harder to exceed the roll limits when at high-speed.

I know the main benefit is to avoid aileron reversal. Also I'm aware discussing tailoring the stick forces in depth will be too broad. So I'm not after an in-depth analysis. Just if that secondary function is indeed a reason.

Comparison of high-speed aileron placement on Airbus and Boeing is shown below. In an Airbus with fly-by-wire (FBW), the stick commands a roll-rate. And all the Airbus FBW heavies—including the A380—do not feature far-inboard ailerons like the Boeings. In other words, if FBW did not exist, could Airbus have still been able to not have mid-wing ailerons?

Airbus (top) source; Boeing (bottom) source.

No it does not reduce the aeroforces: the hydraulic actuators that deflect the inboard aileron have as much of a force to apply as the ones at the outboard aileron. Force for deflecting a flight control surface is a function of dynamic pressure, surface area and of surface deflection.

As you state in the question, the inboard aileron reduces wing twist which could produce aileron reversal at high dynamic pressures, particularly problematic with relatively thin wings and high wing sweep angle.

The reduced moment arm affects the aircraft response upon aileron deflection. The problem with the ailerons is that a deflection equates to an end roll rate, as opposed to the elevator and rudder where a deflection results in an end angle. Many aircraft have a slow roll oscillation in cruise that the autopilot compensates for. If it must do that with an outboard aileron at M=0.85, the strong response of the outboard aileron makes it hard to not overcompensate. I have seen the inboard ailerons on a B747 do a slow deflection dance in cruise, while the aircraft roll angle stays perfectly still.

Slow roll oscillation in cruise was a problem with the F100 for a short while, the gains in the autopilot could not be set low enough to obtain a constant zero attitude. Not really a problem, only in the perception of passengers looking out of the window. It was ultimately solved using different logic but unfortunately I don't know how they did it.


How does a G1000 equipped with a GDC 74 calculate IAS from dynamic pressure? How exactly does a G1000 system equipped with a GDC 74 air data computer calculate the indicated airspeed that is displayed on the PFD from difference between the total and static pressure (i.e. dynamic pressure) measured from the pitot-static system?

The reason I ask is because I want to reverse the calculation and convert KIAS back to dynamic pressure, i.e. $ q $ as defined below:

$$ q = \frac{\rho u^2}{2} $$

My objective is to calculate dynamic pressure from the KIAS value that is logged to the data logs written to the top SD card by the MFD. The problem is that there are multiple ways to perform this calculation -- i.e. does the G1000 display an indicated airspeed that is uncorrected for instrument and position error (IAS, in the traditional sense) or corrected for instrument and position error (CAS)?

I'm not sure if it is the same for all G1000 installations, but according to this Integrated Flight Deck Pilot's Guide the flight data logging feature records both IAS in knots and TAS in knots.

Do you have the Pilot's Guide for your aircraft? It would likely indicate the values saved in there as well.


What's the name of this light airplane? The propeller of this light airplane almost looks like a triangle, so I'm interested in knowing its performance but I need help in identifying this plane because I don't even know her name.

Looks like the "Homebuilt Hornet, one-off wonder plane" on the cover of the March edition of the Australian Sport Pilot Magazine.

The article can be found on pages 34-37.


What do the terms "Landing Since New", FC, and FH mean on a Landing Gear RDAS? Could anyone able to tell me the "Landing Since New" Meant? and what is the FC and FH in here?

Thanks

Landing Since New - The definition is probably provided in Page 2 of the RAS.

This basically means the number of hours spent Landing from the time the aircraft was brand new . Based on this figure the blades will have to be removed.

FH - Flight Hours - Basic unit for measuring length of time in service/before maintenance becomes due. The flight hour (FH) represents one hour of flight

FC - Flight Cycles - One Take Off and Landing


How to interpret 14 CFR Part 61 Requirements 61.129 on instrument training time? For part (3)

  (i) - Ten hours of instrument training using a view-limiting device including attitude instrument flying, partial panel skills, recovery from unusual flight attitudes, and intercepting and tracking navigational systems. Five hours of the 10 hours required on instrument training must be in a single engine airplane;

Can this time be previous instrument time, or does it have to be specific to the commercial certificate?

Same thing with the night take off and landings at a towered airport.

  (4)(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.

The experience requirement for a commercial rating need not be acquired during training for a commercial rating.