texts: What replacement wings are available for old F-16s?

texts:
Eventually, material fatigue will force any aircraft to either be grounded or have its wings rebuilt, or replaced. And please, correct me if I'm wrong.

For the F-16, if one were to replace its wings, what alternatives are there?

Are wings for the F-16 still made, as they were in the 1970s, or does multiple modern alternatives also exist? Can you buy e.g. carbon fiber wings for the F-16? What about other composite materials?

If not, why not? Is the performance different negligible and not worth the cost compared to the original wing?

As a bonus question: If there are indeed more high performance wings, such as carbon fiber wings available for the F-16, how does the performance of the aircraft overall, and especially in a dogfight get affected? I imagine all such studies are classified, if they exist at all, but if they are public, I'd love to see such a study.


texts: What is the process to remove frost off an airliner?

texts: My aunt recently was going on a flight home and she boarded the flight, but her flight was delayed due to frost on the aircraft. She noticed this crane like device above the aircraft wing during the removal process. How do they remove frost off an airliner?


texts: What are the consequences of falsely and/or unnecessarily declaring an emergency?

texts:
I'm curious as to what would happen to a pilot should they falsely declare an emergency to expedite their landing.

By 'falsely' or 'unnecessarily' I mean that the hypothetical pilot is not experiencing anything abnormal, has adequate fuel onboard, is in perfect VFR conditions, and all souls on board are conscious and in good health. In other words, lying about an emergency status to make their landing more convenient or expedient.

Obviously the absence of a real emergency (and the pilot's knowledge of this) would have to be proven (after all, if the pilot even feels like the safety of the flight is compromised, they can and should declare an emergency and be given full benefit of the doubt), but let's assume for our purposes that the pilot simply admits upon landing that there was no emergency and they were aware of that fact, and that information eventually makes its way to the FAA.

Would the pilot lose their license, be grounded for a time, or face civil punishment? Is it addressed on a case-by-case basis, or is there a prescribed punishment? Has this ever happened before?

I'm interested in the consequences for either private pilots, commercial, or both. Though I'm sure the difference with commercial pilots would be reprimand or termination from the airline, on top of whatever civil punishments exist.


texts: What size/engine/payload aircraft would be needed for carrying two passengers and a motorcycle?

texts:
I'm not even in the realm of knowledge of aircraft so don't chew me out on lack of terminology please.

My objective is to fly myself and a 300-pound motorcycle to destinations to ride from there.

I weigh 185 lbs, the motorcycle weighs 300-400 lbs, any secondary seating and other interior furnishings would most likely be removed to reduce weight, and, obviously, all the necessary components would stay. As a side note, the aircraft needs sufficient enough door to get a small motorcycle in. Let's not even talk about how unsafe this might be; this is all hypothetical.

How large, or what class, of an aircraft would be needed for such a task to be completed?


texts: What are the effects of dihedral on net lift of a wing?

texts:
I read somewhere on the internet that dihedral decreases wing lift,so my question is will dihedral decrease the lift of an airplane wing since the wings are attached to the fuselage  at an angle ? If yes,will anhedral also decrease the lift produced by the wings?
If dihedral/anhedral decrease wing lift,is the decrease in lift negligible im comparison to thesame wing(with thesame area,aspect ratio) but without dihedral?


texts: What is the difference between Cruise and Service ceilings?

texts: I am looking at aircraft performance data. There are charts for "Cruise Ceiling" and "Service Ceiling."  What is the difference?  (The cruise altitude is lower.)


texts: On the V2533 engine, what protections do the FADECs provide against uncommanded unstow?

texts:
An uncommanded reverser unstow at high power is quite a problematic event for a flightcrew to handle, at minimum.  As a result, engine and airframe builders put protection mechanisms in to prevent this -- such as auto-restow functions, and on the CFM56-5, code in the FADEC that automatically rolls back the engine to idle upon detecting an uncommanded unstow.

However, I have not seen any documentation for the A320 family with IAE V2500 series engines that details what the FADECs on those engines do in case of an uncommanded unstow of the reversers.  (The A320 FCOM on Smartcockpit only covers the CFM56-5 equipped versions of the A320 family.)

Can anyone fill me in on this?


texts: Is it possible to fly using a small engine?

texts:
I'm currently a high school student trying to build an ultralight aircraft from scratch (I'm self taught and still learning from educational videos), but I don't have much savings (about RM 2.5k, which converts to roughly 587 USD), so I could only afford a small engine.

Is it possible to achieve a certain propeller's efficient rpm by using gears while still using a small engine? Like those gearboxes found in cars to increase rpm.


texts: How do RC airplanes create thrust without using propellers or rockets?

texts:
I haven't wondered how RC planes create thrust until now. I know some literally use rockets, but what about the small ones, that don't use propellers? How in the world do they manage to create thrust in the air without propellers, or rockets?

Also, how do they control aileron? Does an RC plane have a rudder? Do RCs have to be registered with local aviation authorities (if in Canada)?


texts: What are the fatigue regulations in the US and Australia for military transport helicopters/rotorcraft?

texts:
For transport category military helicopters, what are the fatigue regulations as specified by the US and Australian regulatory bodies?

I've managed to find that FAA has 14 CFR 29.571 (Fatigue Tolerance Evaluation of Metallic Structure) but this could just be for civil helicopters.


texts: How does one interpret the satellite data on flight MH370?

texts:
There seems to be a problem with some of the data released by the satellite company Inmarsat.

Specifically, the handshake at 00:10:58 on 7/03/2014.

In the left column the difference in time-stamp between the ground station initiating the request and the receipt of the return signal from the aircraft is given as 1.928 seconds. However, the prior handshakes at 19:41, 20:41, 21:41, and 22:41 took 1.996, 1.997, 1.998, and 1.999 seconds.

This would imply that the round trip distance between the ground station and the aircraft changed by about 13,000 miles in 1.5 hours.  What gives?


texts: How can lift on a canvas covered airplane wing in level cruising flight be explained without introducing Bernoulli ? Both upper and lower surfaces are bulged out,which indicates lower than ambient static pressure on both surfaces.


texts: Why does TAS increase as altitude increases and why does my C-152 POH seem to contradict this?

texts: I remember learning and memorizing that TAS increases as altitude increases, however I don't understand why. Especially since my C-152's PoH seems to indicate the opposite in the cruise performance section. Can someone please explain what I'm misunderstanding here?


texts: What is the ratio of standby crews to flying crews?

texts:
Section 4.O of the FedEx Collective Bargaining Agreement discusses how pilots are to be compensated for being on standby. From what I can tell they basically get paid a "trip guarantee" that is close to the same as had they flown the leg, even though they may not get any flight time (right?).

That made me wonder: How many standby crews does an airline schedule for a given number of flights? Is it 1:10? 1:50? Does it differ between passenger airlines and cargo airlines?


texts:
Military Training Routes (MTRs) with no segment above 1,500' AGL shall be identified by four number characters (IR1206/VR1207)

MTRs that include one or more segments above 1,500' AGL shall be identified  with three number characters (IR206/VR207).

What is the meaning of segment in MTRs?

What is the difference between three and four?


texts:
I thought there was a limit but I can't remember and can't find it anymore.

So with an US PPL, what would be the maximum takeoff weight that an aircraft would be allowed to for me to still fly it?

It'd be great if anybody could point out the appropriate FAR, too!


texts: What exactly did this mechanic sabotage on the American Airlines 737, and how dangerous was it?

texts:
An American Airlines mechanic sabotaged a 737 in Miami

An American Airlines mechanic accused of sabotaging a navigation system on a flight with 150 people aboard at Miami International Airport was denied bond by a federal judge on Wednesday after prosecutors suggested he may have links to a Middle East terrorist organization.
Abdul-Majeed Marouf Ahmed Alani, a 60-year-old veteran employee, told investigators after his arrest earlier this month that he disabled the system because he was upset over stalled union contract negotiations with the airline and wanted to generate some overtime for maintenance on the plane. He said he meant no harm to anyone, and the July 17 flight was aborted before takeoff after an error alert appeared on the navigation system.

His defense attorney said it wasn't as big a deal as they were making it out to be

But Alani’s assistant federal public defender, Christian Dunham, said the prosecutors were exaggerating the evidence. He pointed out that there was a second navigation system still working on the plane so his alleged sabotage could not have caused it to crash.
“We don’t believe he intentionally endangered the safety of people” on that flight, said Dunham, who sought a pretrial bond signed by Alani’s family members in California and Florida. “I think the government is blowing this out of proportion.”

What was it he sabotaged, and how serious would it have been if it had taken off?


texts: What is the input range of common fly-by-wire controls?

texts:
What's the range that typical fly-by-wire controls (let's take A320 and B777 as examples) allow inputs in?

The A320 controls in the y-axis of the side stick (forward/backward axis) the g load - what's the minimal g load you can input when pushing the stick fully forward / the maximum when pulling it fully backwards? Is this a fixed value or does it depend on factors like speed (IAS / TAS / ...), attitude, altitude / air density or anything / ...? Or is it just the maximum value that the flight controls could give you at any moment?

Same for roll rate, what's the maximum you can command there? And for the B777, it's basically the same question except for the yoke instead of the sidestick.

Also, is the relation between control input (side stick movement / yoke movement) and controlled variable (g-force, roll rate, ...) a linear curve? I.e., if the side stick gives you at the neutral position 1g and e.g. 1cm backwards it gives you 1.1g, does 2cm backwards give you 1.2g?


texts: How could an airliner as big as B777 make a U Turn on ground?

texts: I just heard about this 4 month old incident, where a United Airlines B777 made a U-turn, while it was on way to runway. What is the turning radius required to make such a U-Turn? Also, is so much space available near the taxi area at the IGI Airport? At last, is this a common practice for airliners to do?


texts: Why are there no parachutes to carry the aeroplanes in case of serious accidents?

texts: Sometimes I wonder why the manufacturers do not design a big parachute to carry the aeroplanes when serious accidents occur. Perhaps the high cost is the reason?! But is it more expensive than a human life!?


texts: What's the smallest 3-blade propeller for this motor?

texts:
I've got a 15470 brushless 35kw motor from China
How do I find the smallest 3-blade propeller I can use for this motor?

Here are it's specs,
Max Power: 35KW
Max Amp: 400A
Max RPM: 8500
Max Volt: 120v
Torque: 75Nm
Resistance: .94

I've looked into eCalc but it's for determining power / thrust, etc and not finding prop size.
Any help would be appreciated!


texts: As of June 2019, can a DPE in the United States renew a CFI's certificate based on completion of a FIRC?

texts:
Flight instructors need to renew their CFI certificates every 24 months. One of the ways to do that is by completing a FIRC. In the past, you had to take your completed FIRC to the local FSDO and have an inspector approve it.

Lately, I've heard rumors that FSDOs are so overworked that they're not doing CFI renewals any more, and are sending them to DPEs instead.

Is this rumor true? Can I take a completed FIRC to a DPE in June 2019 and re-up my certificate?


texts: Does an AD terminate by issuing new one?

texts: When an AD superseded by a new one, Does the operator still retain the instruction of superseded AD even though the AD include repetitive action?


texts: What is required to fly privately from a region with high levels of the ebola virus (Nigeria) to the UK?

texts:
My dad will be flying us in a private aircraft from Nigeria back to the UK.

I know that he has been in touch with someone from the UK about this, but since I wasn't present for the conversation I'm not sure what was discussed.

What precautions and declarations should a pilot make when coming from a heavily infected area? We will be landing at a private airport so the current screenings done by major airports will not be considered.


texts:
Lower altitude means higher air density, which means more liff, which means a glider can maintain a given glide slope at lower airspeed.
As a rule, aircraft tend to have higher peak L/Ds at low airspeeds, due to a reduced parasitic drag coefficient.
So, for a given design, I would expect the best glide airspeed to increase with altitude, and best L/D to decrease, and best glide slope to steepen.


texts: Are Aircraft yokes self centering in non-auto pilot mode?

texts:
In a typical car steering wheel if you release it while the car is in motion, it will return to its center, neutral position.

What's the corresponding situation in an airplane? Is a yoke self centering? Or does it stay put until corrected by the pilot inputs? Let's stick to non autopilot modes to simplify the basic behavior.

The forces on the control surfaces ought to be high when deflected from their default position, right? So I'm assuming that offers a restoring torque? E.g. with the rudder if you take your feet off the pedals then it centers, I think.

Some additional points:

As a simplified case what happens on the ground when the aircraft is stationary. If I deflect the control surfaces to their extreme position & release the yoke would they all return to the neutral position? Is the restoring force gravity or spring loading?
The answers on the other question seem to focus on ailerons but what about elevators?
Does the rudder typically self center with more alacrity than the other surfaces? Why?


texts: What are the benefits of using Krueger Flaps?

texts: I mean why using Krueger flaps in some aircraft instead of using slats all over the leading edge?


texts: Can anybody confirm which aircraft is in this picture?

texts:
Image Source

Does anyone know what airplane is shown in this picture? It looks like the Republic F-84, but I'm not sure because the front landing gear is under the nose on the F-84 and this one is further back.


texts: What data does ACARS send back to base? Can it be used to track a plane?

texts:
An aircraft's Aircraft Communications Addressing and Reporting System uses line of sight HF via ground stations or satellites to communicate with its base station.

This system allows for three types of messages to be sent:

Air Traffic Control
Aeronautical Operational Control
Airline Administrative Control

  Aeronautical operational control and airline administrative control messages are used to communicate between the aircraft and its base. Various types of messages are possible, for example, relating to fuel consumption, engine performance data, aircraft position, in addition to free text.

So, questions:

Can ACARS be turned off? Would this generate a warning at the base station?
Can ACARS send postion, altitude and heading information automatically?
Can ACARS be repeatedly pinged to track an aircraft's position and heading? Would this require any intervention by the pilots? (posted separately)
Is this system standard on commercial airliners?
What data do Airlines collect from the ACARS, if any at all?


texts: When to turn from crosswind to downwind to base in a circuit?

texts:
I was told by my instructor that my circuit spacing is inconsistent. I do not know how to look at the runway and use it to judge when to turn downwind and base. As a result, my base leg is sometime high and sometime low.

How do you determine when to turn at different leg in a circuit?


texts: What is this item on the nosewheel of the Sukhoi PAK-FA?

texts:
I noticed a small item on the rear side of the nose wheel in multiple images of the Sukhoi PAK-FA, shown below.  The item in question appears to be a grille wrapping around the back of the tires and I cannot think of any reason to put something like this on an aircraft's landing gear.  Does anyone know what function it serves?

Image credit Dmitry Zherdin.  Obtained via Wikimedia Commons.

Image credit Alex Beltyukov.  Obtained via Wikimedia Commons.


texts: How do long-haul pilots cope with boredom?

texts:
Imagine you're in a large jet on a long route on a major airway -- say, for example, you're in a 747 going LHR-JFK at night. It's dark, you're over the Atlantic, and ATC has cleared you to just keep on heading along at FL330 (or equivalent) for another ~1500 nautical miles.

As it has throughout much of the flight, the autopilot is effectively flying the plane. There's nothing on the weather radar, no adverse meteorological effects expected, and ATC ensures that aircraft are well separated. In short, other than occasionally changing radio frequencies, there is very little for you to do.

Just a week ago, you were in the simulator, practicing spin recovery, instrumentation inop procedures, engine failures epsilon before V1, and all sorts of other fun things that required your attention. In your spare time, you're a private pilot and enjoy flying VFR at lower altitudes with the occasional bit of aerobatics mixed in, and practicing what to do in all sorts of rare eventualities at odd attitudes. In other words, you like flying planes. Now, your job is to check that the sophisticated flight computers are still flying this plane, and that ATC have done their job properly. They are, and they have. For the next few hours, you're going to be doing nothing but sitting in a chair watching blackness roll past. You can't even talk to the guy next to you about the weather -- there isn't any!

How do long-haul pilots cope with boredom on long, uneventful segments? Is my above scenario completely not plausible (aside from the lack of weather) -- is there always something meaningful to do during a 7+ hour long flight? I would expect that pilot boredom or distraction would be a safety-critical situation, yet I cannot imagine a situation that involves two humans sitting in chairs in a small room for a long period of time where they will not be bored or distracted at some point.

Do airline transport pilots ever "hope" for "something interesting" to happen?


texts: What advantages would a triangular shaped spy plane have over a an SR-71?

texts:
This is a picture of the supposed SR-72 Aurora. What kind of advantages would this have over the SR-71, in terms of its triangle design? Paper airplanes have the same shape, and fly really well.

The SR-71 design that I am comparing it to.


texts: How does the Airbus ECAM / ND transfer work?

texts:
On the Airbus A320 a knob on the switching panel says ECAM/ND XFR (Electronic Centralized Aircraft Monitor / Navigation Display Tranfer) and it transfers the either the Engine/Warning Display (E/WD) or the System Display (SD) onto the Navigation Display (ND). The ND gets its information from the Air Data Inertial Reference System (ADIRS) and IT and the ECAM gets its information from the system sensors.

Both ADIRS, IRS and system sensors information get sent to the Display Management Computers (DMC), and I'm just wondering if im correct but when you switch SD or E/WD the DMC when it is processing the data for, in this example the system sensors, it sends the system sensors data to the ND?

And the other way around when you switch the ND to the ECAM. When the DMC is processing the data, in this example ADIRS and IR data, it will send the ADIRS and IR data to the ECAM?

So my question is, is it during the processing the data phase that the DMC sends the data to thd correct display?


texts: Could airline tires be deflated in mid-flight to reduce weight?

texts: As a means of weight reduction to reduce fuel consumption, could the tires on an aircraft’s landing gear be deflated once airborne then re-inflated just prior to landing?  Is that feasible and safe?


texts: Are we expected to fly distanced leg (instead of timed leg) in holding pattern in GPS approaches?

texts:
The standard inbound/outbound holding leg are 1 min leg each (no wind condition). I noticed that a distance (4 nm in the following example) is noted in many GPS approaches. Do we need to fly the leg as 4 nm, or the number conveys other meanings?

E.g. http://flightaware.com/resources/airport/TCY/IAP/RNAV+(GPS)+RWY+12/pdf


texts: What is the regulation related to weather radar use?

texts:
I think most commercial aircraft have a weather radar located in the nose cone, like this:

(Source: PhotoBucket, by intelmani5)

It's well known that radar emissions can be harmful, e.g. one could get their eye burnt like an egg in a microwave oven.

However I don't know:

About the typical frequency, power and duty cycle (time in transmission mode vs time in reception mode).
Whether there is a risk for a harmful radiations exposure.

My question is: Based on current radar specifications and regulation, is there an overall ICAO (or local, e.g. US or EU) regulation forbidding the use of the radar on the ground to prevent radiation exposure for people close to the aircraft nose (or conversely to be ON at certain phases of the flight for cumulonimbus detection)?


texts: Is there other option than a Chinook to transport 2 cars simultaneously?

texts: If a civilian wants to fly between homes several hundred miles apart AND carry 2 cars with him what are the options other than a chinook?


texts:
We know that the wavy lines on the canopy are detcord, to shatter the glass in case of ejection.

Why are they wavy?


texts: What is the icing probability required for an AIRMET?

texts: For an icing AIRMET to be issued, moderate icing must be forecast over an area of at least 3,000 square miles. What probability of moderate icing is required before that AIRMET will be issued?


texts: How do Air Traffic Controllers determine which planes take off in a certain order?

texts:
Does it depend on the weight of an aircraft? If two planes requested take off permission and taxied out to the runway at the same time what would determine which plane takes off first (is it to do with weight or flight path?)

If you have an A320 and an A380, which would take off first?


texts: Can I get an EASA Class 1 medical with high astigmatism?

texts:
I have high astigmatism (5 dioptres) and myopia which is under the limit. Is it possible to acquire a class 1 medical? If I recall correctly it's up to the ophthalmologist if he will judge me able to get the certificate?
If not is there something equivalent to the FAA SODA? I know about a medical flight test but I have no idea how it works and if it's possible to do it in order to acquire a class 1 medical.


texts: Why is the Su-27 so much larger than the MiG-29?

texts:
I was watching the following video of the Russian Knights and Swifts aerobatic teams flying together in formation. The contrast in the size of their airplanes is striking.

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

Do the two planes have very different missions?


texts: After looking into aircraft report data at Aviation Weather Center, I realized that PIREP is usually reported inside of US; on the other hand, AIREP is typically reported outside of US. I was wondering if there is any specific/particular reason why AIREP is not available at US territory?


texts: What Inertial effects should be considered to achieve blade stability on a Variable Pitch Propeller tailoredby aerodynamic loads?

texts:
I am developing a self adjusting variable pitch propeller tailored by its pitching moments due to aerodynamic loads setting the blade rotation axis in an offset from the aerodynamic center as shown below.

At the moment i am trying to attain static and dynamic stability of the blade due to mass/Inertial effects. I have created a sketch as shown on the following figure, based on my so far understanding on inertial effects which represents a blade airfoil section and the centrifugal force (OR NOT??) acting on a mass particle.

Mass: ρdxdy*dr

Offset from Pitch Axis x

Offset from longitudinal Axis y

Force: (ρdxdy*dr)*rω^2

Component along the x-axis: (x/r)*Force

Pitch Moment: y*(x/r)*Force

And now comes the difficult part. I suppose that here i need to consider the theory of three dimensional kinetics of a rigid body and angular momentum, however i am confused on defining the coordinate systems on the blade as well as which exact moments and products of Inertia have to take into account. If i am not wrong, here a fixed coordinate reference system and one that rotates with the twisting of the blade have to be defined.  The question is where the coordinate reference system has to be defined; on the blade axis of rotation, C.G, or somewhere else?

Finally i have informed that  to compute the blade's dynamic stability, i will need also to consider blade flapping (i.e., motion of the blade out of plane with the rotation of the propeller), and pitching (or twisting) and this is another part i am struggling too!


texts: What is the relationship between thrust and engine RPM in a turbojet?

texts:
I understand that, to increase the thrust of a turbojet engine in flight, it is necessary to increase fuel mass flow rate. This throttling then increases the exit velocity of air and gives increased thrust (if this was wrong, please also explain how is the thrust practically changed in cruise).

How does the engine RPM vary in this process?

Is there an equation which binds together spool RPM to the thrust?


texts: How would an IACRA suspension affect future applications?

texts:
An interesting question over on the new UAV.SE site asks

  Is it possible to get a FAA Part 107 drone license if one has had a pilot license revoked or suspended?

The answer appears to be that it's not immediately fatal to the application (they would undoubtedly warn you not to bother if you've had a suspension or revocation), but they do ask about it.

In general, how does an IACRA suspension and/or revocation affect future applications of any type?


texts: Why were DHL611 and Bashkirian 2937 on a collision course?

texts:
This is about the crash over Lake Constanz/Überlingen on July 1, 2002. The planes were on a collision course, the automated TCAS told one to climb and the other to descend, but air traffic control gave the opposite order to the Russian plane and they crashed.

My question is, why were they on a collision course? I have not seen anything indicating they were off course. Don't planes flying different directions fly at different altitudes? And aren't there paths in the sky that planes are supposed to stay in?

What about flight plans? Does anyone check to see if two planes are on a collision course?


texts:
I thought it was HF antenna  the What is the purpose of that?
What kind of nav aid use HF frequency?


texts: Why does this GPS approach say "RADAR REQUIRED"?

texts:
As I was looking at the approach charts for KCXY while answering this question, I realized that the GPS "overlay-style" approach to RW8 also requires RADAR.

Since the HAR VOR isn't even shown on this Approach, and it has an IF, why should RADAR be required?

Note that the RNAV (GPS) RWY 26 approach to this airport does not require radar.


texts: Do any ejector seat designs include controllable thrusters?

texts:
Are there any ejector seat designs with built-in thrusters, or boosters, which the pilot can deploy to maneuver himself out of, or away from enemy territory?

A use case might be that after the parachute is deployed, the ejected pilot uses the thrusters to change direction or propel himself in a different path.


texts: What prevents a passenger from hijacking a private jet?

texts:
I was reading another question on this site when I saw this answer.

As you can see in the photo I copied below, this private jet has no cockpit door. On commercial aircraft the bullet-proof cockpit door is seen as the last line of defense against would-be hijackers.

What security measures are in place to prevent unauthorized passenger access to the controls of private jets? Even though they are smaller and carry fewer people, a G650 or BBJ pointed in the wrong place can do a lot of damage.


texts: Could winds of up to 150 km/h impact the structural loads on a Boeing 777?

texts:
From 15 October 2016, AI 173 from Delhi to San Francisco started flying over Pacific. Jet streams over Pacific helped Air India in reducing the flight time by 2 hours, despite increasing the travel distance by 1100 km. This also made AI 173 the world's longest flight, with total distance of over 9300 miles (15,000 kilometres). It completes the journey in 14.5 hours, with average speed of 1040 km/h; 560 knots.
(Adapted from here.)
As many people are wondering, could winds of up to 150 km/h impact the structural loads on the B777-200LR? Is it ever likely to be dangerous?


texts: Why don't the newest versions of Mi-35Ms have retractable gear?

texts:
Older versions of Mi-35 Hind helicopters had wheel boxes so that they could retract their wheels while flying.

Why don't the newest versions of Mi-35Ms have wheel boxes?


texts: What is the Eights on Pylons maneuver intended to demonstrate about a pilot's skillset?

texts:
This maneuver has the common requirements such as clearing the area, and it has the unique requirement among maneuvers to determine the pivotal altitude and select appropriately spaced pylons as references for the maneuver.  However, unlike others, this maneuver has no altitude, heading, bank (other than not to exceed 40 degrees), or airspeed tolerances to determine satisfactory performance standards.

Without these tolerances, what is actually intended to be proven of the pilot's ability upon successful performance of this maneuver?

This is the ACS page for commercial airplane eights on pylons:


texts: How can larger wingspan decrease the strength of wingtip vortices?

texts:
In the last paragraph from the link below, it states that Vortex Strength is inversely proportional to Wingspan. Why is this?

http://avstop.com/ac/flighttrainghandbook/wingtipvortices.html

EDIT: From https://howthingsfly.si.edu/aerodynamics/vortex-drag: "The farther a vortex is from the main body of the wing, the less influence it has on the wing."
Again: why?


texts: What happens if a crew complies but does not read back ATC instructions?

texts: For example, a commercial airliner is inbound and is in the traffic pattern; ATC instructs the aircraft to reduce speed to 160 knots, which the airliner does. ATC notice the aircraft has complied but never read back the instruction. Would the air traffic controller file some type of complaint against the crew?


texts: If all engines fail in a Boeing, how heavy are the flight controls?

texts:
Consider a large airliner with no Fly-By-Wire controls, such as a Boeing 747 or 767. All the engines have failed, the Ram Air Turbine is deployed, and the plane is gliding.

How heavy are the flight controls in this situation?

What about Boeing 777 and 787, which are Fly-By-Wire aircrafts?

EDIT: Regarding the question "how heavy", I would like to get a number, or if that's not possible, a description from a pilot whether it is physically exhausting to hold the controls.


texts: Can helicopter rotor produce infrasound?

texts:
While watching a Mil Mi-17 helicopter takeoff I experienced strange thing. The helicopter produces a lot of noise even when just starting the engines.

But shortly before taking off the high-pitched sound of the jet engines changed somehow (I guess changing the tilt of the rotor blades) and I felt some sort o pulsing "sound" which I felt rather with my belly than with my ears. Really unpleasant experience.

Could it be infrasound?


texts: Could a GE90-115 engine generate enough suction to ingest a typical passenger vehicle?

texts:
We all know that a jetliner can generate enough blast behind it to toss around cars, light aircraft, and even the occasional school bus, and also can generate enough suction to inhale (and promptly destroy) unwary ground crew.

However, if some foolish ground person drove a car (let us assume it's a typical passenger car of exactly 1 ton weight) into the intake hazard area of a GE90-115 engine during a full power runup, would that engine generate enough suction to pick the car up and attempt to ingest it? Or would they have to get so close to the intake that they'd notice that they'd better put the pedal to the metal and get out of Dodge before they went for one last, most unfortunate ride?


texts: AIP, AIC, NOTAM, ANO (UK): How do they relate to Annex 15 of Chicago Convention?

texts:
I've recently started studying for my Air Law and Meteorology exam and am trying to get my head around some of the basic literature / legal documentation structure.

As I understand it the Chicago Convention outlined a series of ICAO Articles that are available in detail as Annexes. These are introduced into law in the UK via the Air Navigation Order.
I'm having some confusion understanding the AIP and how this relates back to the ANO, if at all. Not only this but also what the main differences between an AIP, AIC and NOTAM are.

Is anyone able to help by concisely explaining how these entities relate to one another and how they differ so that I can build a mental image before studying each further, I would greatly appreciate it.


texts: Why do wall-to-wall airfoils in wind tunnels produce no (or infinitesimal) downwash?

texts:
There are several induced drag explanations out there saying that tip/wake vortices “come from” downwash and downwash “comes from” lift. I’m using quotes because the concept is that there are no cause and effect events but simultaneous events that occur in a flow.

Essentially, these explanations describe how the flow turns downwards immediately after leaving the trailing edge of a finite wing; examples in stackexchange can be found here and  here.

Apologies if I describe the above incorrectly, feel free to correct me.

What I want to ask is if someone can “adjust/adapt” these explanations to describe what happens on an airfoil placed wall-to-wall in a wind tunnel that has no (or extremely small) induced drag. I’m not talking about theoretical infinite wings and mathematical explanations, I’m looking for a physical description similar to the ones given above for finite wings.

The only difference between wind tunnels and free flight (in THIS case) is that in the wind tunnel the upper and lower surface flows can interact only at the TE while in free flight they can interact (touch, blend, etc.) at the TE and at the wing tip.

In this NASA page, it is said that “The wing tip vortices produce a downwash of air behind the wing which is very strong near the wing tips and decreases toward the wing root.” Although this is not technically correct (see wake vortex), the importance of exposing the wing tip to the flow seems to be underestimated in the explanations above so I’m looking for an explanation of the wall-to-wall airfoil behaviour through the above explanations.

About Peter Kampf’s reply:

Now I think we’re getting somewhere…

Wake vortex is certainly more important than tip vortices, this is why I used the word wake with tip when referring to vortices. Perhaps I wasn’t very consistent/clear with that (like the NASA page) so apologies for any confusion.

You correctly say that the effect of the wake vortex is reduced by the tunnel walls and there are no tip vortices, which means induced drag is greatly reduced for a wall-to-wall airfoil (essentially a side effect taken care of by grating). If it was possible to add infinite size end plates with zero drag on real aircraft wings (acting as wind tunnel walls), the induced drag would be greatly reduced.

This is all I’ve been trying to say, that the only explanation for the induced drag increasing drastically when we move from a wall-to-wall model (2D) to a finite wing (3D), is that the wing tip is exposed to the flow.

Yes, a vortex sheet leaves the wing.
Yes, there's no spanwise spillage of lower flow towards the upper flow.
Yes, tip vortices do not create induced drag.

However, the free stream air “sliding” next to the wing tip (where the tunnel wall would be) definitely interacts (pushes, gets pushed, blends, etc.) with:

The upper and lower flows (vortices) as it travels the chord of the wing.
The “combined” upper/lower flow (vortex sheet) at/after the trailing edge.

so the more the wing tip is “walled”, the effects of this interaction get weaker and consequently the induced drag gets weaker....

The explanations correctly say that wingtip vortices do not create induced drag but, at least that’s how I understand it, neglect the importance of the physical exposure of the wing tips to the air flow that causes the “interaction” described above.

Thanks to everyone for bearing with me, I’ve never written about aerodynamics in a forum…


texts: What restrictions apply in international airspace?

texts:
What restrictions are there on a flight in international airspace? For example, if you fly into the Pacific Ocean more than 12 miles (or whatever the distance is) offshore, are you free to fly any speed (such as faster than sound), at any altitude, or in any weather? Are FAA regulations in effect?

Is anybody really "in charge" of this airspace? If not, how do airliners keep organized on intercontinental flights?


texts: If someone can identify this aircraft, please tell me which aircraft this is?


texts: What is the lowest-speed bogey a jet fighter can intercept/escort?

texts:
Jet fighters are made to cruise at a high subsonic speed, even at a supersonic speed (supercruise?). It means that they can be flown comfortably at relatively high speeds.

Jet fighters are often used to intercept aircraft, whatever the reason (assistance, escort from national to international airspace, check an unresponsive aircraft,...).

General aviation aircraft can cruise at a slow speed compared to jet fighter. Moreover, if needing assistance, it may fly even slower. I imagine it is possible that a GA aircraft needing assistance cannot fly at a speed above the stall speed of a jet fighter. I know that some countries dispatch choppers to intercept slow aircraft to handle such situation.

I imagine the military doesn't fly their jets at stall speeds when close to another aircraft (a margin is needed).

Is there a speed below which a jet fighter cannot intercept another aircraft? Otherwise, how do they do it? (I imagine you can orbit above another aircraft but it is less convenient to guide it safely to an airport)


texts: What is the maximum altitude a manned plane that flies subsonically can reach? Subsonic airplanes can't go as high as super- and hypersonic ones of course, so record holders are the latter ones. But ironically, the altitude record for leveled flight is set by the subsonic NASA Helios propeller aircraft at ~97,000 ft. However that's an uncrewed and weird-looking one. Can manned airplanes that fly subsonically go above the Armstrong line (60-63,000 ft) and higher (either in leveled or in parabolic flight), considering realistic fuel limitations? How high can subsonic airplanes go compared to supersonic ones?


texts: Why doesn’t the A320 family suffer from the same design constraints regarding engine placement/landing gear length as the Boeing 737 family?

texts:
This answer gives a pretty good description about the design issues which lead to the problems of the Boeing 737 Max (basically the same as in a video I watched a while ago):
The landing gear of the 737 is fairly short. One benefit at the time was that this eased baggage/cargo loading by hand. The JT8D engines for which the original 737 was designed were slim enough to fit under the wings.
However, these engines performed poorly when compared to later generations. Unfortunately, later generations of engines such as the CFM56 are also larger in diameter, so Boeing had to resort to various tricks to squeeze modern jet engines underneath the wing, while still ensuring sufficient ground clearance.
Increasing the height of the landing gear, thus adding enough ground clearance in order for the bigger engines to fit underneath the wings, was not an option. As the landing gear retracts into the fuselage in flight, its length essentially is limited to the distance between its mount points on the wings, minus some clearance.
Mounting the landing gear further outward on the wing would have required a structural redesign to cope with the increased torque from the landing gear. Retracting the landing gear with the wheels in “tandem” (one behind the other rather than both next to each other), or shortening the gear upon retraction (either by a telescope mechanism or an extra hinge) would also have been major design modifications, which would have been costly and taken extra time to develop.
Therefore, Boeing opted to reduce the engine diameter as far as they could (which helped a bit but not enough), and move the engine further forward and higher up on the wing. Because the latter alters certain handling characteristics, they added an electronic system known as MCAS to compensate for that. As this change was not clearly communicated, pilots were not aware of it, which eventually lead to two crashes and the grounding of the entire fleet.
What none of these two sources addresses: the 737’s main rival, the A320 family, was designed two decades later and had the larger engines from day one, along with sufficient space underneath the wings to accommodate them.
So how does the A320 design address this? Longer landing gear with attachment points further outward on the wing (which I assume is fairly easy to do on a new design but comes at a significant cost when upgrading an existing one)? Or something else?


texts: What factors determine magnitude and orientation of induced velocity at propeller blade?

texts:
• Magnitude
What factors determine magnitude of "Vind" (induced velocity)?
• Orientation
If we take analogy with induced velocity at wing,isnt "Vind" must be prependicular to Vr?
• Induced velocity is almost always neglected
I notice that blade theory very rearly use Vind into consideration.For example effective pitch and advance ratio not include Vind, pretend like blade is "ideal".
I can see that Vind increase axial velocity  and decrease circumferential velocity,this reduce real AoA what blade section see.
Is Vind very small compare to V and Vt,so this is reason why it is neglect in most cases?
Θ real angle of advance


texts: Does the F-4E Phantom II have a weather radar?

texts:
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"?


texts: Was wood used in the construction of the TU-144?

texts:
This image the Yegoryevsk crash of the TU-144 CCCP-77111 appears to show a part of the wreck made of wood:

(picture source)
The inside looks like wood slats with rafters. Wood is sometimes used in airplane construction and has pretty good constructive properties, so I don't want to dismiss the idea a priori as crazy. Was it the case?


texts: In an international airport, is there specific set of laws for the international area?

texts:
When travelling in an international flight, you pass a border with passport check at both the departure and the arrival airports. It means you spend time in an international area. What are the applicable laws in this area? The one from the country the airport is located in? A special set of international laws?
Are you juridically out of any country (as if in international waters)? Is there special status with flights between countries with special immigration agreements (e.g. Shengen area)?


texts: What in-flight weather info is available to commercial pilots?

texts:
This question was asked yesterday about sources of wx info. The answers focused on sources for pre-flight planning. As weather changes constantly pilots need current wx info en route, especially on long flights.

The wx radar aircraft are equipped with can show what they are approaching for the next several miles, but often pilots need to know what is in their path much further ahead than what onboard radar can show.

This question asks about in-flight wx info via cellular connection. The answers all allude to the unreliability and possible illegality of cellular use. However, in the comments several people suggested sources available through satellite and FIS-B.

I was reading this blog post relating to the recent Delta flight which suffered severe hail damage after flying into a storm. The author decries the lack of weather info sources available to commercial pilots in-flight. He says, "a pilot flying a single engine Cessna 172 can have significantly more weather information available to them in the cockpit than the crew of this A320 had." The author of the blog post is advocating for airlines to provide this info.

With many airliners now equipped with wifi it seems a pilot could have access to any number of ground-based NEXRAD radar services through a tablet or their EFB. What is there preventing commercial pilots from using these services? Is there an FAA rule that prohibits this or do airlines have rules as to where they can get their weather info?


texts: How are large cargo aircraft loaded at airports?

texts:
Passenger aircraft are accessed at gates, or using buses. While they are parked waiting for passengers to board, the area they use is billed by the airport.

I was wondering what is the procedure for loading large cargo aircraft, whose payload must be moved slowly, using relatively complex equipment, and fastened to the airframe carefully.

Source

This takes time and if the area used is also billed, the cost could also climb a lot.

Do shipping companies have specific reserved areas to do that? Are these areas specifically reinforced?
What kind of fees are paid to the airport?


texts:
Almost every passenger cabin in a commercial aircraft is white with a little bit of grey. Why are they in these colors?

Source


texts: Are radar bars centered around the horizon or do they move with aircraft pitch?

texts:
Say I am in a military aircraft with a non-AESA radar.
The radar is set to scan 4 elevation bars, so when I fly level, 2 above and 2 below the horizon.

If I pitch 20 degs up, will it continue to scan around the horizon or will the bars move up with the aircraft pitch?


texts: Are there regulations about carrying cargo on passenger seats?

texts:
We see that passenger aircraft have recently made cargo flights so that the supply chain does not decrease due to the Covid-19 crisis.

It is seen that the cargo boxes are loaded on the passenger seats by fastening them with a strap or rope.

https://twitter.com/AHoensbroech/status/1243095677485436928?s=09

Are there any regulatory restrictions (firefighting, smoke detection, aircraft weight&balance etc.) or guidance on carrying loads on the main deck of wide-body passenger aircrafts without removing the passenger seats (there will be no passengers on board)?


texts:
If I understand correctly, heading is usually measure relative to the pole (either magnetic or true). Traveling at a constant heading can't be approximated as travelling straight ahead when near the pole. The extreme case being heading to 180° and crossing the south pole.

Althought there are not many aircraft in this situation as explained in this question, using the heading may not be relevant.
How is the navigation handled is such area? Is the heading used?


texts:
Do modern aircraft employ accelerometers or other similar equipment to measure g-forces on the aircraft? I could imagine this being used as an inspection/service indicator, particularly after hard landings. Or do hard landings and other forceful flight regimes typically not pose any significant structural concerns?

Update. Related on determining hard landing inspections:

From Aero Magazine on Boeing conditional inspections

Section on AMM changes:

  Boeing is modifying the 737 AMM, section 05-51, and will revise the AMMs for other Boeing-designed airplane models, to include these vertical acceleration values (table 1). For Douglas-designed airplanes, similar values are being generated and will be available in the AMMs in early 2001. The values are intended as thresholds that can be used to help determine whether a hard landing inspection is necessary. If the flight crew concludes that it has experienced a hard landing, the AMM conditional inspections should be performed even if the acceleration readings do not exceed the values added to the AMM. The vertical acceleration values are to be used by operators, in addition to or in lieu of flight crew judgment, to initiate conditional maintenance inspections.

Source: Aero Magazine


texts: Can briefly explain the principle behind the inversion on this power required curve?

texts: I’ve noticed on several graphs in the “Advanced Pilot’s Flight Manual”, that power available is lower for any given speed at 10,000 feet as compared to sea level flight. The power required curves intersect at the sea level best rate-of-climb (BROC) speed. Can someone briefly explain why more power is required at 10,000 feet when below this BROC speed and less power is required at 10,000 feet when above it?


texts: Why is there a a nose-up pitching tendency during a forward slip in a Cessna 172?

texts:
Why is there a tendency for the nose to pitch-up during a forward slip in a Cessna 172 (According to the TC Flight training manual)?
Quote:
"If full rudder is used, considerable aileron pressure may be needed to maintain the bank. There will also be a tendency for the nose to pitch up as a result of the banked attitude and rudder input"


texts: Do military pilots have flight & rest hours regulation?

texts:
I have read that civil pilots have stringent regulations regarding flight hours and hours of rest between flights.

What about military pilots? Does it change between wartime and peacetime? Between type of aircraft (transport vs combat)?


texts: How does ATC handle arriving/departing runways that cross?

texts:
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!


texts: How are aircraft controlled that have no forward view out of the cockpit?

texts:
Modern aircraft tend to have quite reasonable cockpit visibility. But throughout history there were some that had literally no visibility directly forward.

The best known example is probably Ryan Spirit of St. Louis:

but there were others like Supermarine S6. Granted, they were all special purpose planes. But still, how did the pilot align with the intended runway and ensure the runway is clear? There was no ILS to help him, so it still had to be done visually. And how did he avoid obstacles and other aircraft?


texts: Is it ATC's responsibility to ensure read backs are correct?

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

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

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


texts: What is the purpose of the pressure relief door fitted on the PW1127G-JM engines of the A320NEO?

texts: Hey guys many times during my exterior walkaround I noticed on the A320NEOs that they have this pressure relief door and our SOP for the exterior walkaround states to check that this door is closed. However I would like to know what is the purpose of this door? As it's not mentioned in the FCOM.


texts: How could I match the surrounding traffics displayed with their radio communication

texts: If I have a traffic display I could see the traffics in proximity of my aircraft and meanwhile I could listen to their voice communication. So how could I match the traffic shown in the display with the corresponding voice communication? My understanding is that if I have a ADS B in system and the other aircrafts have mode-s transponder, I could know their call sign thru the ADS-B data, is that right? But how about I just have a TCAS or I have the ADS-B in transponder but other aircrafts do not have a Mode-S transponder?


texts: What can ground personnel do in the event of in-flight depressurization?

texts: If the pilots, crew and passengers had all passed out from an unexplained result of gradual de-pressurization, and ground personnel were somehow aware of this scenario, would there have been anything that could of been done to save the plane and people before the fuel ran out?


texts: How heavy are modern cantilever monoplane wings?

texts:
Aircraft need to reduce weight in order to reduce induced drag.  The modern shallow cantilever beam wings carry a massive weight penalty, as most of the material is wasted inefficiency absorbing the bending moment. However, with advancements in materials,  their mass has reduced to the point that parasitic drag benefits outweigh induced drag losses.
But I would like to know how much structural efficiency still influences wing design. Compared to the total empty weight of the aircraft, how heavy are the wings if modern cantilever monoplanes? This includes large airliners and small GA planes. An example of a design from each class is sufficient.


texts: How long does a runway have to be for an Airbus A380 to takeoff?

texts: I have seen several Airbus A380's takeoff on large runways, but how small can a runway get for an Airbus A380 to takeoff fully without overrunning?


texts: Is the "confirmed allocation" string in "A Scandal in Belgravia" a real airline practice?

texts:
(This is a repost of this question on Movies SE. I hope to get better answers here.)

Irene Adler shows the following text to Sherlock:

007 Confirmed allocation
4C12C45F13E13G60A60B61F34G34J60D12H33K34K

He immediately guesses that "these are seat allocations on a passenger jet", claims it must be a Boeing 747 and then recalls a specific flight which takes off at 6:30 PM the next day. Note that only 14 seats are listed. A Boeing 747 can carry about four hundred passengers. The flight takes off tomorrow evening.

Do airlines really document or communicate seating allocations in this way? Shouldn't there be more seats "confirmed" (whatever that means)?


texts:
In the US, will the tower likely think my aircraft has been hijacked if I taxi with the flaps down?
Related:
Why are flaps retracted when an aircraft is parked on ground?
https://fsims.faa.gov/wdocs/orders/ps_orders/a_7110.49d.htm


texts: Is it possible to eliminate induced drag completely?

texts: According to Wikipedia an airfoil of infinite length would create zero induced drag. Therefore, would it be possible to make a wing that creates no drag if you ignore viscous effects (skin friction) by walling it off on the wingtips to prevent vortex formation? Or is there another drag creating mechanism?


texts: Who decided that the Boeing 737 MAX planes that were airborne when the grounding was issued cannot enter and land in EU air space?

texts:
On March 12th, 2019, EASA grounded the Boeing 737 MAX series by publishing their Emergency Airworthiness Directive 2019-0051-E (AD):

  Effective Date: 12 March 2019, 19:00 UTC

   [...]

  Required Action(s) and Compliance Time(s):

  From the effective date and time of this AD, do not operate the
  aeroplane, except that a single non-commercial ferry flight (up to
  three flight cycles) may be accomplished to return the aeroplane to a
  location where the expected corrective action(s) can be accomplished.

The PDF document was created at 17:12 UTC and went into effect practically immediately. The AD does not specify any particular instruction for actions concerning flights already airborne.

Of course there were a number of long-haul flights en-route, that clearly started before the publication, and were scheduled for landing in the EU hours after the effective date/time of the AD. Closely related questions have already been asked on Avitation SE:

What happens to an airborne plane when its type is grounded by an authority?
Why would a flight no longer considered airworthy be redirected like this?  (Smart Wings QS 1201 was scheduled for DXB 15:30 UTC - PRG 23:20 UTC)

After March 12th, many people were convinced that EASA has forbidden entry or landing for the 737 MAX in EU air space. I cannot read that from the directive or any other reliable source.

We all agree that operation of a plane shall not be finished mid-air. The AD could not be followed literally for flights like QS 1201. Unless this case is covered by a different applicable document, EASA failed to give a clear directive.
Emergency ADs shall always serve the purpose of aviation safety. I cannot see how diverting numerous flights on very short notice can be safer than allowing landing at the planned destinations.

For comparison, this is how the FAA worded their AD on March 13th in this corresponding part:

  This Order is effective immediately. This Order prohibits the
  operation of Boeing 737 MAX airplanes by U.S. certificated operators.
  This Order also prohibits the operation of Boeing 737 MAX series
  airplanes in the territory of the United States. Boeing 737 MAX series
  airplanes covered by this Order, if in flight at the time this Order
  is issued, may proceed to and complete their soonest planned landing,
  but may not again takeoff.

  Special flight permits may be issued [...] including to allow non-passenger carrying flights, as needed, for purposes of flight to a base for storage, production flight testing, repairs, alterations or maintenance.

FAA's AD covers the case of airborne 737 MAX explicitly. On the contrary, the EASA AD requires interpretation at this point, and therefore this is my question:

Who had the right and duty to interpret this AD and to decide what should happen with the B737 MAX in flight?

Was it ATC in the role of an executive authority?
Was it the Airline that is risking its certification or wanting to minimize storage fees?
Was it the PIC who is risking a hefty fine?
Or am I missing something entirely?


texts: Is there a good resource for ACARS messages?

texts: Is there a good place to find out all the types of data that ACARS can send and receive? I've seen high level descriptions, but I'm looking for the data that actually gets fed from or to the Flight Management System.


texts: What is the purpose of the serrated trailing edge spoilers on the B52?

texts:
At around 50 seconds on the linked video you can see the serrations on the trailing edge of the B52's spoiler.

What purpose does it have, and what gives it advantage/disadvantage over the standard spoiler? I've only seen serrated trailing edges on wind turbine blades.


texts: Is there an FAA rule or Advisory Circular with regard to blood donation?

texts:
Is there an FAA rule or Advisory Circular with regard to flightcrew member blood donation?  For example, how many hours or days is required or advised before a pilot may act as a crewmember?

I'm interested in finding the source of legitimate FAA policy or guidance for flightcrew members.  If the answer is, there is no FAA rule or advisory circular, I'd also be interested in specific examples of FAA-approved air carrier policy.

It seems 24 hours is the generally accepted waiting period to recover from possible hypoxia related to a donation.


texts: Do manufactures list the maximum speed of an aircraft based on its theoretical maximum speed or dive speed?

texts:
I know that the absolute maximum velocity of an aircraft is based on the thrust available. However the aircraft is usually limited beforehand by other speed limits such as dive speed and Mach Never Exceed velocity.
So when researching the maximum velocity of an aircraft, is the max speed listed the absolute max speed or the dive speed as that would make the most sense since its the structural limit. The example I am specifically thinking of is the C-130J Hercules which according to this brochure (linked below) from Lockheed, is around 365 kts.
https://www.lockheedmartin.com/content/dam/lockheed-martin/aero/documents/C-130J/C-130Brochure_NewPurchase_May2020_Web.pdf


texts: What is done to prevent the tail hook from bouncing off the carrier deck?

texts:
At 2:20 of this video, it appears that the tail hook of the F7U-3 bounces off the flight deck a couple of times before catching a wire. Does this still happen with more modern fighters or has something been done to prevent this from happening?

Note: at some point after this, there is a fatal ramp strike incident.


texts: Is there any civil aircraft that decelerates with a parachute?

texts:
Some previous generations military aircraft decelerate with a parachute to decrease landing distance:

Israel Aircraft Industries Kfir landing with a parachute (source)

It this something found on any civil aircraft today?


texts: Can the autopilot (or stall avoidance system?) of the B737 MAX 8 be overridden by sheer force?

texts:
A New York Times article from today about the Lion Air Flight 610 crash claims that in order to control the airplane the pilot

  could have braced his feet on the dashboard and yanked the yoke, or control wheel, back with all his strength.

Thanks to T.J. Crowder's comment I realize there is not only the autopilot but also a (new?) stall avoidance system installed on this new line of B737s.

Is it true that either one can be overridden by a simple application of sufficient force to the yoke? If so:

What is the respective underlying mechanism for the systems?
What force would be necessary, respectively?
Are both systems designed such that they can be overridden simply by applying an unusually strong force, or would that be just a violent and "unofficial" way to control the yoke despite the systems' best efforts?1

I understand that the main flight controls of this recent incarnation of the Boeing 737, the MAX 8, are still hydraulic. Does that play a role in the "override by sheer force" possibility?

1
A design which would allow a pilot to eventually control the plane just by applying excessive and unusual force (as opposed to perform a complicated series of button presses and/or touch screen actions to disable either system) would in my opinion make a lot of sense as a "panic mode".


texts: Why aren’t any JP-1-type (extreme-narrow-cut) fuels in use today?

texts:
JP-1 was the first U.S. military standard jet fuel (hence the 1 in the designation), with its specifications issued in 1944; it was an extremely narrow-cut, high-alkane kerosene, not far from what would later become RP-1.  As a result, it had both a very low freezing point (-60C maximum) and a very high flash point, a combination that is the Holy Grail of the aviation-fuel industry.  Its only drawback was that it was hard to produce (since, to quote John D. Clark in Ignition!, “not many refineries in the country could produce such a product with their available equipment and crudes”), and therefore expensive and in chronically short supply, which prompted the development of wide-cut fuels (first the extremely-wide-cut JP-3, followed by the somewhat saner JP-4) and the gradual disappearance of JP-1 (although, judging by mentions in various aircraft accident reports, it apparently was still being produced into the 1970s).

On the other hand, those were 1940s/50s refineries that had difficulty producing JP-1 - and what would be tough beans for a 1940s refinery would be no trouble at all for a 21st-century refinery, thanx to the polymerisation/cracking/hydrogenation/witchcraft/etc. techniques originally developed to turn all the heavier, less-profitable petroleum fractions (and the gaseous, hard-to-store ones) into gold, I mean gasoline, which could easily be adapted to turn even the most recalcitrant crudes into extreme-narrow-cut, JP-1-type fuels (especially given that RP-1 is an even tighter kerosene than JP-1, albeit not by much, and yet we haven’t had any trouble getting ahold of that in the vast quantities needed for launching things into space); so why haven’t we returned to JP-1 and similar fuels, which have freezing points rivalling Jet B combined with flash points that blow away (pun intended) even Jet A?


texts: What is the purpose of classifying fighters?

texts:
Fighters are classified by generation, as explained in this answer. Given this Wikipedia sum up, some fighters are not clearly in a defined generation, especially for 4th generation subclasses. Thus people may not agree on a list of fighters that belongs to a generation.

Some of the previous generation (generation 4, 4+, 4.5, 4++) are still actively produced (e.g. Rafale, F/A-18E/F)  while the F-22 (definitely 5th generation) is no longer in production.

Airframe designed a long time ago (e.g. the F-15, F/A-18) still receive updates that make it competitive on international market (the section about potential operator of the F/A-18 on Wikipedia give an overview for the F/A-18), even in front of 5th generation fighters (at least in Canada for the F/A-18 and the F-35)

Another capability we cannot rely on to define generation is stealth. The A-12 and more precisely its variant YF-12 was stealth supersonic aircraft with weapons (AIM-47) inside internal bays, but was not a 5th generation fighter.
Moreover, since ECM can be fitted on a fighter, this fighter expose some stealth feature.

Given those facts, it seems that since the 4th generation, knowing a fighter is classified as a specific generation does not provide information about its production year, its capabilities nor its competitivity in front of other nation's fighters.

In short, since the 4th generation, generation does not provide reliable information about capabilities, features nor designed or production year.

What information does the generation of a fighter give? How useful it is to know a fighter belongs to a specific generation?


texts: Are nose wheel tyres designed differently from the main wheel tyres?

texts: For the heavy large Jumbos like the Airbus A380 and the Boeing 747-800, considering nosewheel tyres are not subjected to the excessive heating caused by braking from the disks and brake pads, and frictional heat on the outer surfaces caused by contact with the tarmark surfaces and braking, are nose wheel tyres designed and manufactured differently from those of the main gear and do they cost more or less.  Considering they are not fitted with brakes, What is their temperature at landing after and are there instruments to measure this? If not why not?


texts: Is implementation of CPDLC mandated by EASA?

texts: Is CPDLC (Controller–pilot data link communications) mandatory by EASA? I have not heard any update that Airlines are using CPDLC. While talking to some of the pilots I heard that they have been instructed to switch the System due to satellite cost. What is the real scenario?


texts: Is there a way for pilots to report difficulties and challenges experienced during a flight, to the next flight crew?

texts: My question is reflected in the title - is there an official, international system for commercial pilots to report difficulties and challenges faced during a flight to the next and future crew? Ideally, such a system should also require the next crew to review recent entries into it. Does something like it exist and if so, how strictly is it followed?


texts: What is the maximum speed for regulation of sonic boom noise?

texts: If fuel cost and fuel efficiency were not the issue, what is the maximum speed (air speed and ground speed) that business jets or airliners could travel at without exceeding the maximum noise and sonic boom allowed or as regulated in the USA, Europe and the rest of the world.  I need to know why there are no faster business jets and for business class airliners given that private and business fliers are prepared to pay a premium


texts: Why are the strings on paramotors so long?

texts: I don't completely understand why the strings on paraglider/paramotors (connecting the vehicle/person to the parafoil) are so long. Couldn't they be made shorter to reduce the amount of space used? It just seems like an unnecessary feature. Sorry if I'm missing something elementary.


texts: How does pressure increase in a multistage compressor?

texts:
Given the overall pressure ratio of a multi-stage compressor, how can I calculate the increase in pressure at each stage?

Does pressure increase linearly at every stage, or does it increase logarithmically or exponentially?

Intuition tells me that pressure increases logarithmically since the latter stages of a compressor can't compress the air as much as the first stages, but intuition hasn't served me so well in thermodynamics...

Thanks!


texts: What other materials apart from conventional nickel and steel superalloys can be used as a first stage turbine blade material?

texts:
Steel and nickel chromium alloys have been prominent and most used as turbine blade material although there are other materials such as tantalum carbides, tungsten and many more which I have no knowledge of. But these materials are not being used or even planned on being used in the near future why is that?
Do the cons of these materials beat the pros of the ni-cr superalloys?


texts: Why is the horizontal stabilizer forward of the vertical stabilizer on the P-51?

texts: Why is the horizontal stabilizer forward of the vertical stabilizer on a P-51? Are there other airplanes that are like this?


texts: There are many airplanes that claim to be the fastest piston, private jet, airliner, but what is the all time fastest airplane? How fast does it travel?


texts: What options do the crew have when passengers go berzerk?

texts:
In one recent incident with an American Airlines flight from São Paulo (GRU) to New York (JFK or LGA, dunno), the crew decided to land in Brasilia (BSB), Brazil because one couple was fighting (source in Portuguese).

In this case, the crew decided to make a landing in an airport outside their flight plan, and remove the fighting passenger couple from the aircraft. Because of Brazilian regulations on the crew working hours, the aircraft was then grounded for the day.

In the scenario where:

passengers aboard an international flight (during flight) begin fighting between themselves (the shouting at each other, possibly bare-fist only kind of fight) and refuse to heed the flight crew's warnings and requests (but not in a life-threatening way), what other options could the crew have besides the one used in the incident above?


texts: Do fighter jets experience a reaction or recoil force upon firing a missile?

texts: When fighter jets fire a missile, do they observe any kind of reaction force due to firing the missile? If yes, how is this observed by the pilot? If no, why not?


texts: What is the status of "Notes" in ICAO Annexes?

texts:
As per the forward to ICAO Annex 11, the status of a "NOTE" in any annex is - "Notes included in the text, where appropriate, to give factual information or references bearing on the Standards or Recommended Practices in question, but not constituting part of the Standards or Recommended Practices."
So, does it mean, a note given in the Annex does not hold any authority as it is not a part of the SARPs ?


texts: Under what conditions is a flight attendant required on an aircraft?

texts:
Not all airplanes with passengers are required to have flight attendants.

What are the regulations that cover this and when are they required?


texts:
Is there some reasonably accurate ballparking formula to allow for quick conversions between IAS and TAS as a function of pressure altitude and difference of ground temperature relative to standard atmosphere? That is,

E.g. "for each 1,000ft subtract X%, for each degree F/C subtract Y%" so that if I'm at 8,000ft and ground temperature is 10 C, I simply subtract 8X% and add 5Y% to get a good approximation.

My idea is to have a quick ballpark to start working with, in case there is no time to start fiddling with the flight computer, or in cases where the error would be insignificant for practical purposes.


texts: How do you hold at a non-towered airport?

texts:
Let's say, hypothetically, that you enter the pattern for a small, non-towered airport (my local one, 3DW, may be a good example.)  But as you get into the pattern you find out that the runway is occupied by another craft and, for whatever reason the runway will probably be occupied for another 20 minutes, much longer than it will take you to complete the pattern.  So you'll have to delay landing.

But you've already entered the pattern, so what should you do?  Is there a standard holding pattern for small airports that incorporates parts of the pattern (maybe some little loop where the base leg and downwind meet)?  Or do you just fly away form the airport a bit and make up your own holding pattern?


texts: When airspaces adjoin vertically, which airspace class does the shared flight level or altitude belong to?

texts:
Airspaces have a lateral and vertical boundary, which results in airspaces adjoining other and thus having a shared vertical boundary. Which airspace class do these shared vertical boundaries belong to?

Example:
Dortmund's (EDLW) control zone is a class D from GND/SFC to 2500ft MSL, on top of this control zone is a TMA airspace class D from 2500ft MSL to 4500ft MSL thereafter class E from 4500ft MSL to FL100and above that we have class C airspace from FL100 to FL660.

(Image Source: www.skyvector.com - Map Data: skyvector, ARINC, OpenStreetMap)

If an aircraft wants to occupy 2500ft MSL, 4500ft MSL or FL100, which airspace class are they in?


texts: How are pitching and rolling moments transferred from rotor to the body?

texts:
When a rotorcraft pilot moves pushes on the cyclic control stick, the swashplate tilts so that angle of attack of the retreating blades increase and of the advancing blades decrease, which creates forward pitching moment on the rotor (shifted 90° due to gyroscopic effect).

Now the first reaction is that the blades flap up aft and down forward, tilting the plane of rotation forward. But which is then the dominant effect that makes the helicopter body to follow the pitch?

Is is the blades pulling on the hub due to centrifugal force trying to align it with their own plane of rotation,
or is it that the lift vector tilts with the rotor so its action line no longer passes through the centre of gravity?


texts: Do airliners adjust altitude for latitude?

texts:
According to this NASA article, the troposphere extends from about 5 miles at the poles to about 9 miles at the equator. Though the height of the troposphere is defined by the height of the tropopause as per this Aviation SE question.

I'd expect that the air pressure at the top of the troposphere would be similar at 5 miles above the poles as it would be at 9 miles above the equator.

As the altitude of an airliner increases, the angle of attack necessary to produce the same amount of lift also increases. Eventually an altitude is reached where the angle of attack necessary to produce sufficient lift is also the stall angle of attack. This pretty much defines an airplane's service ceiling. (Certainly, there are other factors, but this is a pretty big one.)

This suggests that the service ceiling would be lower at the poles than at the equator. Does this mean that an airliner flying a polar route would fly at a lower altitude than one staying in the temperate or tropical regions?


texts: Would fuel quantity indications be affected by extended flight at nonzero bank angles?

texts:
If flying with a 20kt crosswind requiring yaw input as well as roll input to maintain course, would the fuel indicators show different loads depending on the roll angle of the aircraft (in this case, an MH-53e)

Clarification: With a left bank angle of 15-20 degrees would it appear that the right side fuel cells were using fuel faster with a quantitative fuel quantity system?

Thank you sir. That is a better way of saying it.


texts: Are there safety countermeasures for test flights that simulate crashed flights?

texts:
This question is based on this episode of Air Crash Investigation concerning crash of Lauda Air flight 004.

It discusses a test flight that simulates the crashed flight (41 minutes and 20 seconds into the video), in order to determine the effects of a sudden unintended reverse thrust deployment at higher altitudes and speeds, than those of the original test flight (which tested the deployment with the Boeing 767 at around 10,000 feet).

However, since there seemed no preventives or recourses for this test flight, was this test flight as dangerous and likely to crash as Lauda Air Flight 004? If so, was it a forlorn hope or suicide mission?

ACI did mention that this test flight was conducted with the 4-engined DC-8, instead of the 2-engined B767, so is ACI implying that the greater number of engines on the DC-8 was a corrective?


texts: How much wind force is required to push/rotate a 737 sideways while parked?


texts: How are go-arounds safe with close parallel runways?

texts:
Some airports operate simultaneous take off and landing on parallel but close runways. By close, I mean like the pairs of runways at LAX.

What if a landing aircraft makes a go-around at the same time as another aircraft takes off? How is separation maintained? Would it be enough for the missed approach procedure to specify turning away from the departure runway?


texts: Could an ultralight hypothetically takeoff without power on if it were windy enough?

texts: I don't know if takeoff would be the right term, but the wing should generate lift with any headwind.


texts: Why didn't Boeing make the Sky Interior for the Boeing 777?

texts:
Generally, Boeing has attempted to make the interiors of their aircraft as similar as possible, with one "unified" interior across different aircraft (i.e. based on a single "look and feel" for you UX enthusiasts), such as the older (but still fairly new) "Signature Interior" (debuted with the Boeing 777) and the newer "Sky Interior" (debuted on the Boeing 787).
When a new interior style was created, it seems like Boeing generally tries to copy that same interior to other aircraft. For instance, the Signature Interior was also used on earlier 737 NG and later 747-400 and 767 aircraft (with a retrofit offered), and the Sky Interior was used on later 737 NG (conflicting information about retrofits), 737 MAX, and 747-8.
While it seems from the above that Boeing is pushing new interiors onto older aircraft, including the 737, 747, and 767, this doesn't seem to be the case for the 777; even those coming off the assembly line today still have the original Signature Interior. Why didn't Boeing make a Sky Interior for their 777?
To make it clear what I'm talking about, here are some images and descriptions of each interior:
Signature Interior

Source: Airliners.net
Notes:

Middle section overhead bins and passenger service units appear integrated with the ceiling.
Side passenger service units are angled.
Overhead bin open handles can only be pulled one way.
The interior fittings are beige.

Sky Interior

Source: Lufthansa Magazin
Notes:

Middle section overhead bins and passenger service units appear attached to, rather than integrated with, the ceiling.
Side passenger service units are almost completely horizontal.
Overhead bins have open handles that can be pulled either way.
The interior fittings are white.

Keep these mind's answer points to a Ukraine International Airlines marketing material that advertises the "Sky Interior" for their 777s. However, clicking through the link shows a picture of their 777, but it has the same Signature Interior as above.


texts: Could vortex generators be used to preserve aileron authority during a stall?

texts: I know that using aileron input in the approach to a stall is generally inadvisable; what if vortex generators are placed at the wingtip (where the ailerons sit), meaning that the ailerons will still have roll control authority available even when the rest of the wing is stalled? In this case, would aileron input be permissible?


texts: What happens if an engine fails between V1 and V2?

texts:
What happens if an engine fails between V1 and V2 on a modern twin airliner?

As I understand it, at V1 you have enough runway remaining to safely stop and abort the takeoff. V2 is the lowest single engine flying speed.

If an engine is going to fail, surely it will be at the worst possible time.


texts: How to calculate the airspeed for maximum specific range?

texts:
Given the following parameters for a small business aircraft:

Wing surface: $S=30m^2$
Lift Drag Polar in clean configuration: $C_D = 0.022 + 0.047 {C_L}^2$
Maximum Lift Coefficient $C_{L_{max}}=1.35$
Static sea-level Thrust: $T_0 = 12KN$
Thrust variation with altitude: $\frac{T}{T_0}=\frac{\rho}{\rho_0}$
Aircraft weight: $W = 50 KN$
Thrust specific fuel consumption (constant): $C_T = 0.7 N/Nh$

I need to calculate:

the optimum lift coefficient for maximum specific range
the airspeed for maximum specific range when operating at the specified weight and sea level conditions.

For $C_{L_{opt}}$ I have found a value of 0.395 using the lift drag polar and the fact that $C_{L_{opt}}= \sqrt{\frac{1}{3}C_{D_0}\pi A e}$.

I am then assuming that the airspeed for maximum range is given by $V=\sqrt{\frac{W}{S}\frac{2}{\rho}\frac{1}{C_{L_{opt}}}}$.

In my calculations, I am using $W=50000/9.80665=5098.581 KG$ and $\rho=1.225$, which gives me a value of $V = 26.504 m/s$

However this seems not to be the correct answer. What am I missing?


texts: How significant is antenna drag on light GA aircraft?

texts:
Antennas sticking out of an aircraft obviously increase profile drag, but the folks who design antennas have done a lot to improve aerodynamics: High performance aircraft can have antennas mounted inside of fiberglass components like wingtips, and flush-mounte antennas are available for transponders and DME equipment.

For slower light GA aircraft more aerodynamic antennas are also available (e.g. blade-style transponder antennas are available which produce about 80% less drag than older spike-and-ball style antennas), measured at 250 MPH.

Since the average light GA aircraft has a VNE below 250 MPH and isn't generally covered in antennas, how significant is the antenna drag on a typical light GA airframe?  For example, would stripping the ~6 pounds of antenna drag from your average Cessna make an appreciable difference in airspeed?


texts: What are these engine inlet devices used for?

texts:
While looking at the Boeing Chinook CH-47 for this question, I noticed the screens in front of the engines, and found similar devices in other photos:

Source: left -- right

What are these devices used for?

A recurrent question here is about protecting turbine engines against bird/FOD ingestion. It seems that a screen can be used, at least at low speed.

It is the case? Is it used for this purpose?


texts: Which modern passenger aircraft has the simplest, most automated systems?

texts:
I'm looking for an aircraft meeting the following criteria:

Manned (no drones, etc.)
Has or had a production run (no prototypes, design-only, etc.)
Capable of carrying multiple passengers who are not crew-members (no single-seaters or 2-seaters where both people are required to be part of the crew)
Modern avionics, either designed that way or significantly retrofitted if older base model
Has the fewest configurable knobs/switches/buttons/etc. in the cockpit that are related to the main flight systems like the engines, APU, electrical system, hydraulic system, control surfaces, brakes, etc. Note that computerized touchscreen displays that expose complex configuration of these systems should be counted against the aircraft's complexity, unless the computer automates the configuration of the system by default. Ignore cosmetic things like knobs to let you change the brightness of the lighting; and don't count the FMS, or displays or indicators that give the pilots information about the flight status, either.

Answers don't have to point out THE absolute best craft fitting these criteria currently available; if you have broad experience with systems complexity in a lot of modern aircraft, and you can think of one off the top of your head that is especially clean and simple compared to the rest (either due to automation or just fewer systems to deal with), point it out in an answer.

Bonus if you can explain what is automated or taken care of for the pilot without them having to worry about it under normal conditions, but if you're going to explain this, only focus on automation that is unusual or new or unique to the aircraft, not things that are automated on most/all current aircraft.

Here's the question stated in another way: To take an aircraft from cold and dark, into the air and land it again in normal, uneventful conditions, which aircraft meeting the criteria above can accomplish this with a minimum of input from the pilot?


texts: What thrust is used for thrust to weight ratio?

texts:
Performing some preliminary calculations for an aircraft design I have and was wondering what thrust I should use to calculate thrust to weight? The thrust calculations I have, vary due to speed (since in general force is a change in linear momentum) and so the faster the aircraft is traveling, the lower the thrust I have is. Should I use the initial thrust when the aircraft is initially accelerated, an average thrust of some sort or a different thrust estimate altogether?
These are two different equations I have used to estimate thrust (For propellers)


texts: Calculating the Thrust vs RPM Relationship of a Brushless DC Motor

texts:
hope everyone is doing okay.
I am conducting a project with my friends for an Unmanned Aerial Vehicle. We are first using MATLAB - Simulink to design and simulate the quadrotor. We completed the Kinematics part of it now we are about to incorporate the rotor dynamics of the design.
We are going to be using Emax CF2822 1200kV Brushless Motors. We want to model this motor on Simulink as well. We have a general Brushless DC-Motor equation which yields RPM as its output. However, since we do not have the motors with us at the moment (we are awaiting for our funds for this project to be deposited), we are searching through the internet to find some experimental data. However, there is not too much to look at. We are going to be using 10x4.5 propellers and this setup has only the following data:
Prop: 10x4.5, Cell Count: 3S, RPM/V: 1200kV, RPM: 6100, Thrust: 745 grams, Max Current: 14.5A.
I looked for similar setups with similar motor characteristics on the internet, however I was not very successful at finding similar setups which had the potential to help the process. I am just wondering if the above data would be sufficient to have an approximate equation/relationship for the RPM vs Thrust characteristics? When I looked on the internet, I mostly saw that the relationship was non-linear about the mid-parts and kind of linear at the end parts.


texts: What methods exist to detect airframe icing, and how do they work?

texts: What are the primary methods used to detect ice on an airframe, and how do they work on at least a high level?


texts: Is there any logic (operational convention or heuristics) for quantifying risk of loss of separation between two aircraft in the terminal airspace?

texts:
Is the risk just directly proportional to the loss in separation? Is a large duration of LoS but with a very small amount of loss of separation considered risky?
I am trying to quantify the risk of loss of separation in terminal airspace beyond just the violation of separation thresholds specified by FAA. Are there any historic datasets on LoS incidents available?


texts: Why do we call moving an aircraft on the ground "taxi"?

texts:
We all know what "taxi" means to general public -- a car which carries you from A to B in exchange for your paying a fare.

"Taxi" also means to drive an aircraft on the ground. Why do we call it that? What's the reason & history behind the term?


texts: Where can I find a worldwide General Aviation incident/accident ocurrence reports database?

texts:
I enjoy reading reports about aviation incidents and accidents. There are often interesting technical details and I believe that this practice increases the safety of my flights.

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

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

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


texts: Why don't 747s use unreliable, but cheap, jet engines instead?

texts:
I'm a neophyte who was reading a little bit about jet engines, and the economics behind them. In particular, I was curious about what makes jet engines so expensive compared to piston engines.

A recurring theme that came up, again and again, was the cost of quality control, and related factors like product liability. Jet engines are designed to be ultra-reliable under conditions of high stress, and understandably that drastically adds to the cost of manufacture and design.

However, what doesn't make sense is why these standards are so universally high, even in the case of jets on multi-engine craft with redundancy. It would seem that you definitely want reliability on a single-engine craft, a multi-engine that can't fly when it loses an engine, or even a two engine craft.

But for a four-engine aircraft like a 747, why pay so much for ultra-reliability? A 747 can stay at cruising altitude with only 2 engines. Modern jet engines have a failure rate of about 0.01 per 1000 hours. A 747 could use engines with a failure rate of 1 per 1000 hours, and still achieve the same safety profile as an aircraft with only 1 engine of redundancy. (Assuming engine failure rates are independent)

I'd assume that relaxing the jet manufacturing process to allowing 100X less reliability would drastically reduce costs. It seems like we could be manufacturing very cheap four-engine aircraft by allowing for high-failure rate engines. What am I missing here?


texts: What information is recorded in aircraft sensor and maintenance logs?

texts:
I was wondering what the sensor and maintenance logs in an aircraft look like and what are the values logged? Like maybe the engine temperature, altitude, exhaust temperature, etc. I know the data is logged in the black box, was wondering if it is available to the owner of the aircraft to any cloud service for further analysis or something. I'm talking about fighter planes and commercial aircraft.
I am looking for variables like the speed of the turbine (N1 and N2), altitude, pitch, roll, vertical acceleration, air temperature, exhaust gas temperature, etc. Came upon a Vox video where they showed about 60 variables.


texts: Why is thrust available constant with speed for turbojet engines, when it varies with speed for turboprop engines?

texts: Similarly, why is power available (nearly) constant with speed for a propeller engine, while it varies for a jet engine?


texts: How do airports generate "indirect" income?

texts: How do airports generate "indirect" income i.e. income from things other than aviation operations (landing, FBO services, repairs)?


texts:
From other answers I've gathered that stall occurs when the air flow separates from the wing surface. And also that this starts at the back of the wing and progresses forward as AOA increases.

Is this process not uniform? What causes the buffeting just under the stall AOA? Is it simply the turbulence behind the point of separation?

Also, what factors, such as speed, altitude or air density affect the amount of buffeting?


texts: Can Airbus A400M take-off from the beach fully loaded?

texts: I've recently saw this footage. Airbus A400M tactical capabilities on natural surfaces by performing take-off, landing and taxiing manoeuvres. I wonder if she could take-off fully loaded from that surface ?


texts: Does the FAA consider flights that generate content for profitable YouTube channels displaying airborne video to be commercial operations?

texts:
Is there any guidance from the FAA such as an Advisory Circular, Letter of Interpretation, or other document that directly clarifies the scenario below?
If a pilot creates aerial video content while acting or logging as pilot-in-command and profits from advertising revenue through a service such as YouTube on which that video content is hosted, would that cause the flights during which the videos were recorded to be considered commercial operations by the FAA?
Note: Videos made by costs-shared-pro-rata passengers are not within the scope of this question.


texts:
Flying home from the Denver ComiCon, on a 737, I saw an angled flange on the engine. Could you describe its purpose?

Photos by CGCampbell licensed CC0


texts:
Although I have a rough idea of what it is...

In my mind from growing up watching hundreds of hours of Seconds from Disaster / Air Crash Investigation, trimming an aircraft is turning a dial that changes the airplanes "forward" direction. So maybe it changes the control surfaces so that the plane is flying straight forward even though the rudder for example is at some deflection angle that isn't 0.

However if I was asked to define trim I couldn't exactly say what it is, what situations I would use it for or how it's achieved.


texts: What is the difference between a concourse and a pier?

texts:
Both are narrow buildings with aircraft parked on both sides, so what is the main difference?

(image source)


texts: Can someone explain to me why these planes just don't turn about their center of gravity?

texts:
Look at this one:

The thrust force from the engine should generate some clockwise moment, right? Why won't it turn and just crash then? I guess the wings generate some sort of anti-clockwise moment? Can someone explain this?


texts: What are the slides that ATCs use for tracking departures and arrivals?

texts: I've seen ATCs use little slides with flight numbers for tracking arrivals and departures - is there a term for them and are they still used today with modern ATC terminals?


texts: What is the CDSU for a governor with magnetic trim?

texts:
The governor is a spring-loaded, flyweight-operated, hydraulic control valve whose driving gear is in mesh with the differential output ring gear through the scavenge pump gear. The governor senses CSDU output speed and controls the oil pressure to the control cylinder, maintaining a constant output speed of 12,000 revolutions per minute.

This I have understood from this picture but I want to know the operation in detail.

What is the purpose of the CSDU?


texts: Do high-wing aircraft represent more difficult engineering challenges than low-wing aircraft?

texts:
Generally, it's easier to make things strong in compression than in tension.

In a low-wing plane, the weight of the aircraft is on top of the wing; in a high-wing aircraft, it hangs from it.

It seems to me (I'm not an engineer) that the area of attachment in the latter case has to do a lot more difficult work (suspending the rest of the plane by its bolts) than in the former (bearing the weight from below).

And since in a high-wing aircraft all the structure is in tension (everything is hanging from something above it), presumably it's not just the wing and its attachment points that are affected, but most of the fuselage that has to withstand this tension.

Are these intuitions true, and if so, what are their engineering implications?


texts: Can a small plane be floated off of an aircraft carrier?

texts:
Would it be possible to float a small plane (say a Cessna 150) off of the deck of an aircraft carrier without the Cessna achieving any forward motion with respect to the aircraft carrier? If not a Cessna 150, is there a standard GA aircraft that could do it?

EDIT:  Per a comment from ratchet freak: the takeoff would be done via lift from the wings, not via an engine duct (VTOL), like a Harrier.


texts: How can I find the CG of a model aircraft based on its dimensions?

texts: Given the dimensions and gross weight of an RC model aircraft, how can I find the center of gravity? Can I calculate it, or perhaps there's some way to approximate it?