texts: In a tailwheel plane, which design elements affect the propensity for a ground loop?

texts:
In comparisons between conventional gear vs. tricycle gear aircraft, it is generally explained that the CG location relative to the mains is a necessary condition for ground-looping. But there's very little more explanation than that.
I'd like to know more about the design traits which affect the propensity for a ground-loop. The following is an uninformed list of some things which I could see affecting a taildragger's ground handling, but I wouldn't hazard a guess as to relative importance.

CG location
Gear width
Gear shape
Gear springiness
Tire pressure
Tread traction


texts: How difficult is it to design a high bypass turbofan given a military derived core?

texts: Suppose one of the big-threes is given a military low-bypass turbofan core, how difficult would it be to produce a design centered around this core that matches the competitive performance of a similar brand-new design? What parts are new aside from the fan? Does it need a new LP compressor and LP turbine? Can you safely crank up the overall pressure ratio, confident in the fact that the original design's tolerance for supersonic flight would mean the HP compressor has the ability to take the heat of higher compression subsonic flight and hence needs no modification at all?


texts: Do dark conditions due to high-altitude smoke prevent ultralights from flying?

texts:
According to FAR103, you have to operate ultralights between sunrise and sunset, or between the times laid out in the Air Almanac (if you're in Alaska.) This means that the FAA has determined that certain lighting requirements exist for ultralight pilots, but has laid them down in a time-defined manner, instead of a lighting-involved one. Under normal situations, this is fine - you don't get enough eclipses, volcanic eruptions, or alien invasion fleets blocking the sun to make rules based upon luminosity.
At the moment, there are a number of arguments breaking out about whether Ultralights can fly in my area. It's just after noon, but because of the fires in California, high-altitude smoke and clouds are bringing lighting conditions to being comparable to 30 minutes post-sunset.
If the sun is up and pilots stay clear of clouds (and smoke plumes), and - of course - we're not violating a TFR, is the assumption that we can fly without a 3-mile visible light, or is there something in the FAA regs that deal with this situation?
To reiterate - we're not flying anywhere near the fires, we're not flying in a TFR zone or other controlled airspace, and we're not flying within a mile of a cloud or smoke plume.
Thanks...


texts: Where do I find a complete Volmet frequencies list for Europe?

texts: Is there any website or ,even better, book to buy to get such frequencies?


texts: What were the safety recommendations following the Aeroperú Flight 603 crash?

texts:
I just watched the Mayday Air Crash Investigation about Aeroperú Flight 603 and two questions that weren't answered are:

Who was responsible What caused the ATC to relay false altitude information to the pilots
Has anything changed since then to prevent that from happening again?


texts: What military aeroplane seen at Prestwick is this?

texts: I saw this plane flying out from Prestwick airport yesterday but what is it?


texts: What turn rates are expected by ATC when given expedited turn instructions?

texts:
One can reasonably expect that for a normal turning instruction (such as a radar vector), ATC will expect you to make a standard rate turn, or perhaps a half rate turn in the high altitude environment.

However, when ATC gives an "expedite turn" on a radar vector or equivalent instruction such as the "Traffic Alert, Turn Left Immediately" used for PRM approach breakouts, what level of performance are they expecting the pilot to demand out of their airplane? A 1.4g (45deg bank) steep turn? A 2g (60deg bank) steep turn? Maximum sustained Gs, even if that means using afterburner in a fast jet?  Get on this heading ASAP even if it means trading a bit of altitude for energy?  Does it depend on whether a light aircraft, a heavy jet, or a fast jet is being vectored around?


texts: How do i find a supercritical airfoil for my preliminary design?

texts:
The following information is available but i don't exactly know where to get the information about SC Airfoils from. Do Airbus , Boeing use secret airfoil that they don't disclose?
Cruise Speed = 240 m/s or 0.7 Ma; Chord length = 5.5 meters
Using online tool to get the Reynolds number gives a very high number of about 85 million. Using the standard setting for kinematic viscosity of $1.4207E-5$.
1.How do I find a SC airfoil for a transport jet of about 150 Pa @ 0.7 Ma?
2.Why are my Reynold's number so high? It should be around 25-30 Million.


texts: Why is air traffic control done manually by humans?

texts:
I'm not a pilot but have a software developer background, so forgive my aviation naivety.

From what I understand there have been numerous issues and almost-issues relating to human air traffic controllers. Not to mention there is considerable cost and complexity required for this delicate system to work perfectly all the time.

My question is simply why do humans manually attempt to guide all aircraft in real time? Has computerized air traffic control ever been suggested, and maybe even attempted? What was the problem?

Before anyone says that air traffic control is computerized; that's not what I mean. I mean fully computerized, with digital communication between the aircraft and a central computer on the ground which continuously updates the aircraft FMS, OANS (On-Board Airport Navigation System) or similar, and autopilot with all the required information and directs aircraft as needed with optimal real time sorting and queuing.

As for more simple aircraft without FMS, OANS or other suitable systems, perhaps they are better suited for having human guidance for the foreseeable future. A speech to text interface to a computerized tower would probably be disastrous.

It seems, (probably naively) to me, that this would eliminate a lot of latency, a lot of cost, and a lot of complexity. As an aside, this appears would also give the pilot contextual awareness if desired (I cannot imagine this would be useful during normal operations), as the OANS would be able to display everything the tower can see.

Having it explained to me briefly what exactly the tower does that cannot be handled by such a system would probably enlighten me somewhat.

My own reasoning for why this isn't a good idea:

The only thing I can think of is, I can imagine that sometimes information is relayed to the tower that requires some use of context and best judgment that would be hard to implement in full in software. Perhaps there is an emergency, and the pilot needs information about advice for some ad hoc emergency landing.

However, if this is the problem, the extreme cases where a human is preferred, why not keep a few humans around, similarly to how aircraft without OANS would perhaps need humans, just in case one is needed. The vast majority of the mundane work that seems (again probably naively) incredibly better suited for a computer to deal with, be handled by, a computer?


texts: May an emergency aircraft land on a closed runway?

texts:
Let's say that you're on approach to a remote airport to refuel (for arguments sake, Funafuti International Airport, Tuvalu), with 1-2 hours of fuel remaining in your aircraft. Contacting ATC to request permission to land, they tell you that the only runway is closed for an unspecified reason and will not reopen for ~2 hours.

The nearest airport is 295nm away, so you agree to hold, hoping the runway is soon reopened. After waiting a little while, the runway is still not reopened, so you declare an emergency.

Is the airport required to reopen the runway? Does the fact that the nation is not a part of The Chicago Convention change anything?*

Supposing ATC refuse to reopen the runway, is the pilot permitted to land anyway?

Let's presume the aircraft is not certified for ditching.

Searching Google, I found that at least one emergency aircraft has landed on a closed runway.

* 2020 update: in Nov 2017 Tuvalu became ICAO's 192nd member state (icao.int).


texts: Why doesn't the A320 have a dorsal fin like the 737?

texts:
The A320 doesn't have a dorsal fin, but the 737 does. If the 737 is more or less a similar aircraft, why doesn't the A320 have a similar dorsal fin?

By Bill Larkins [CC BY-SA 2.0], via Wikimedia Commons


texts: Why do some airplanes have a vertical rudder hinge while some others are canted?

texts: I was thinking that canted rudder hinges are used for modern aircraft while the vertical ones are used for old slow airplanes. But it seems that I was wrong since the SST Tupelov Tu-144 and the Concorde also have that vertical (or almost vertical) rotational rudder axis. Then my question is, what is the advantage and this advantage of such a rudder? Which one is better?


texts: What happens if an aircraft declares an emergency while there is another aircraft ahead cleared to land?

texts:
Lets assume this situation: In a controlled airport, two aircraft are approaching for landing. #1 is about to touch the runway (let's assume it is within 1~2 miles from touch zone).

Then #2 declares a emergency.

Is there any rule that require that the first airplane starts a go around, either by its decision or by controller's?

Some assumptions:

There is enough separation from #1 to #2. If #1 was allowed to land and it successfully does, that will not significantly interfere with #2 landing.
Airfield has just one runway.
I'm limiting this to a international accepted, US and/or Brazilian rule.

My concern is that if some incident occurs with #1 on landing, like a gear collapsing, that may render the runway unsuable, causing trouble for the trailing aircraft in emergency.

Speaking in other words: Is an aircraft cleared to land even if another is approaching in a emergency situation?


texts: How to convert IAS/CAS to TAS up to Mach 3?

texts:
Someone had recommended that I use this formula to convert KCAS/KIAS to KTAS:

https://www.experimentalaircraft.info/flight-planning/aircraft-navigation-speed.php

If you scroll down to "True Airspeed, TAS," you will see this formula:

=KIAS*SQRT(SEA LEVEL AIR DENSITY/AIR DENSITY OF DESIRED ALT)

So, enetered into an Excel spreadsheet cell, the formula would look like this:

=100*SQRT(1.225/0.905)

100 is the KIAS, 1.255 is air density at sea level, and 0.905 is air density at 10,000 feet.

This formula gives us 116 knots for KTAS.

This formula works for low airspeeeds, but as airspeeds get higher, the KTAS that is given is not accurate. As I have learned, this formula does not take into account "compressibility," and therefore the KTAS will not be accurate at higher airspeeds.

I am interested in a formula that I can enter into my Excel spreadsheet that will give an accurate KTAS for all airspeeds up to Mach 3, and altitudes up to 100,000 feet.

Is there one particular formula that will work?


texts:
I'm sitting here in a coffee shop on the local river and I noticed it was just wide enough to facilitate a landing. There is no chop on the river, but it does move pretty switfly, and there are bridges and whatnot that would quickly come into play. However, there are some pretty slow-moving, unobstructed rivers out there.

Does anyone land floatplanes on rivers for reasons other than emergencies?


texts: How do airlines manage routes when respective aircraft undergo B,C or D checks?

texts: While playing some airline management simulation games, I found all these checks to be some real kind of mess. If suppose I have a fleet of about 10 A-320s then if one them goes for any check, then I would end up losing about 10% of my earnings. How do real world airlines make up for these absent aircraft? Like, consider an A380. It takes more than 2 weeks for a C Check to complete (>1 month for a D-Check), and it certainly translates into a big financial loss. How do airlines operate such routes routes in the mean time?


texts: How accurately do I need to maintain my altitude while VFR-on-top?

texts: Is holding altitude as stringent a requirement when flying VFR-on-top? If the deviation exceeds say 200 feet off a given VFR altitude (i.e. 5500’ heading eastbound) is this as big of an issue for ATC?


texts: Where is the control loop of the actuator closed?

texts:
When electro-hydraulic servo-actuators are used for the actuation of control surfaces in aircraft, linear variable differential transformers (LVDTs) are used for position or velocity feedback. There is a control loop that compares the actual position with the commanded position.

Where is the loop closed? In the flight control computer or in a module near the actuator? By this, I mean where this comparison is taken place?
What are the pros and cons of each of these methods and which one is usually used in modern aircraft?


texts: How to get an accurate time of arrival to the en-route alternate airport during flight planning?

texts:
I was thinking about accurate criteria of selecting en-route alternate (ERA) weather from ground (planning stage) especially for ERA 3% contingency flight plan.
As we all know we should care about one hour before to one hour after of arrival time into destination hence the main question here how we should know what is the estimate time of arrival into destination i.e. 1400Z.
Personally what I am doing as a airline pilot is crosschecking the nearest waypoint to that "ERA" thence I can tell inaccurate estimate.
Is there any idea how we can get accurate estimate of en-route destination during planning stage (on ground) that can give us exact ETA of destination?


texts: How should I read these abbreviations on the Airbus 320 MCDU?

texts:
Often I have seen some abbreviations on the Airbus MCDU such as CI, CF, etc. They are explained in this question: What do the different types of approach abbreviations used on the A320 MCDU exactly mean?
How will I call them when forming my approach briefing? Is there any manual that trains pilots on these abbreviations? I need a quick guide to understand how to interpret these?


texts: What simulation software do airlines use?

texts: What simulation software do airlines use for training purposes? Do they use software like P3D, FSX, X-Plane, or FlightGear? Or is it a custom? What about aircraft? Do they source them from groups like PMDG or is this also custom?


texts: What are the maximum possible stabilizer and elevator deflections for the A320?

texts:
For research purposes I would like to know the maximum deflection angles (in both positive and negative direction) of the A320-200's stabilizer and elevator.

I am trying to analyse what flight conditions are trimmable.  The outputs I get are deflection angles.  I need to know whether those angles are within the ranges of maximum deflection.


texts: What do the remarks of this metar mean? "RMK SC1SC5AC1 AC TR SLP116"

texts:
Here's the current METAR from CYYZ:

CYYZ 140700Z 26011KT 15SM FEW025 BKN045 BKN080 M05/M08 A2984 RMK SC1SC5AC1 AC TR SLP116

Does anyone know what each section of text of the remarks section means?


texts: What is the fuel burn rate for climb of a C-130J Hercules?

texts:
I am trying to graph the payload range for a C-130J Hercules and I need an approximate value for fuel burn rate which I cannot seem to find online. Does anyone know approximately how much fuel a C-130J hercules would burn to climb 1000 ft?
This would be under atmospheric conditions and at standard speeds. The fuel burn rate of any other similar aircrafts is also appreciated. I am just looking for an educated estimation.


texts: How to reduce the noise of the supersonic passage(bang)?

texts:
as you know the transonic phase is often associate with the bang.
The principal cons of the transonic phase is the noise,it's why there is not supersonic passenger aircraft( cause the end of the concorde).Nasa (x59) and Boom(xb-1) do research to reduce this noise at door slam.
How is it possible? I know that we need a aerodynamic plane respecting the aera rule and have a thin fuselage. Have you" wind tunnel" images?or theorical explications?

Edit: for those who want i found more information about the bang on this vidéo. (2:35 to 4:45)


texts: What is autofeather and when is it used?


texts: Are HUD systems available for light GA aircraft?

texts:
Some other questions about HUDs and how they work got me thinking. Military aircraft have had reflector sights since before WWII, and full HUDs since the mid-70s. The very same display layout, sans targeting recticles, is fairly familiar to pilots of glass-cockpit aircraft, the primary difference being the representation of the artificial horizon (which, because the display is not a HUD and so not transparent, uses the blue/brown background from the analog instrument).

True HUD systems are starting to make their way into commercial airliners, and the technology is even seen in various cars (primarily luxury brands) as a situational awareness tool. So the question is, what types of reflector-sight flight display systems are available for light singles? I would assume a glass cockpit is a prerequisite to generate the digital display, but given that concession, it seems fairly straightforward to have a monochrome version of the PFD projected onto a glass plate instead of or in addition to the display on the LCD monitor. Has anyone marketed this? Are there disadvantages of having a HUD in a GA aircraft that I'm not thinking about? This sounds like a natural next step now that even entry-level LSAs are foregoing the traditional analog 6-pack for glass displays.


texts: Where are US FIS-B UAT ground facilities located?

texts:
In the US there are Flight Information Services Broadcast (FIS-B) transmitters strategically located to provide WX, NOTAMS and other flight information utilizing the ADS-B infrastructure. ADS-B has two physical layers, being the Universal Access Transceiver (UAT) and a 1090 mHz Extended Squitter (1090 ES). FIS-B utilizes the UAT, which are located at 978 mHz.

These UATs are intended for ADS-B use, as well as FIS-B, and additionally Traffic Information Service (TIS-B). They are primarily designed to service traffic below FL180. While they are not deployed to cover all locations, some design goals of the system include having CONUS enroute coverage.

The FAA publishes a coverage map, however, it has apparently not published a list of ground UAT sites. It would be possible to scrape UAT sites and develop a database of ground facilities, however, no one has published the results of doing so, at least that I am aware of.

Having such a list would be helpful to operators such as pipeline, geophysical, agricultural and other operators who tend to fly low, yet may still wish to have FIS-B (and perhaps TIS-B) services, or at least predict where they might be available.

Furthermore, the FAA has said that there is no security provision restricting the disclosure of UATs for FIS-B.  However, they have declined releasing a list of such ground facilities.

Where are the FIS-B UAT ground facilities, and has anyone compiled a list and published it for general access?


texts: How do I interpret electrical system indications in a G1000 C-182?

texts:
I recently switched to a G1000 equipped aircraft C182 and trying to figure out the specifics of the G1000 and how it works in the 182.

One that I can't really figure out with the manual and the POH  is the Electrical System

I have the following Indication (in flight around 30 min after takeoff)

M        BUS      E
28.0     VOLTS    28.0

M        BATT     S
+1.5     AMPS     +0.3

Does this mean that the main and the backup battery delivery 28 Volts?

The + Amps mean that the alternator is charging the batteries ?

I noticed that the BATT Amps (M) never goes to 0 is that normal? I remember from the old analogue gauges that at some point they stay in the middle/0.

What are normal/acceptable values for BUS/BATT in a C182T?


texts: Why haven't helicopter CAT III procedures ever been developed?

texts: Why is there no helicopter equivalent to air transport CAT III ILS?  This PPrUNe thread discusses that some helicopter manufacturers have tested coupled approaches down to very low visibility minima (perhaps even zero-zero), but it seems that even with the current capability levels of autopilot technology and ILS ground station sophistication, there's no way for a helicopter to land in minima below RVR 1200'/DA 100' (i.e. the "half minima" rule applied to a standard ILS, or a COPTER ILS procedure).


texts: How to plot the pressure distribution over an airfoil?

texts: I have found only the description of this pattern with experimental graphs.Could anyone please tell me the mathematical formula required to plot the distribution?


texts: What's the name of the runway equipment referred to in this video?

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


texts:
I've seen almost every aircraft land back gear first to evenly distribute the landing load between more struts.

However, I recently saw this video of a NASA Super Guppy Nose-Wheel land gear first at Mansfield-Lahm Regional Airport:

            .

I couldn't think of any reason a pilot would want to do this so is there any reason as to why they would want to land nose first opposed to the conventional way that I don't know of?


texts: Is it possible to hack an airplane while it's moving (in general)?

texts:
I recently searching Airbus Careers section, and I can say that I saw too many Cyber Security job positions. It was saying in the job description that there is a need of having knowledge about avionics and of other related sections. It was not focusing on Computer Science part.

My question is this: Is there a way that someone can hack an airplane? I mean each airplane is moving. How can someone "touch" a moving airplane, have the time to identify it and then to hack it?

Also, the airports are having really specialized machines and systems in order to communicate with an airplane. How can someone, without having specialized machines, can hack an airplane?


texts: How can we avoid running out of airport abbreviations?

texts:
As far as I know, airport name abbreviations are a 3 letter name. For example:

MEL for Melbourne/Australia airport
LAX for Los Angeles/USA airport
YYZ for Toronto/Canada airport

And that means all the options we have for naming are 26 * 26 * 26 = 17,576

Sometimes these match the IATA code, but not always. IATA codes are also 3-letter codes, but are not assigned to every airport as shown in this answer. But what about all of the other airports in the world? Will the world ever run out of "regular" airport codes?

A simple Google search about the number of the airports worldwide shows there are 17,678 airports. So are they going to extend airport codes to 4 letters or use numbers 0,1,2,...9?

Even by starting to use numbers they may reach a point where they run out of options. What is the approach to fix that ?


texts: Do Airbus aircraft fitted with ACT have additional fuel system controls?

texts: Do Airbus aircraft fitted with ACT (Additional Center Tank) have a push button that controls the fuel transfer to the main center tank? If yes, where is it located?


texts: What regulations govern the quality management system for producers of aircraft components?

texts:
I am looking for FAA documents and regulations regarding the quality management system for producers of aircraft components.
Specifically I would like to know what is a production certificate .

Furthermore may I download those regulation somewhere ?


texts: Is there any public database available by Airlines/OEMs listing all field issues?

texts: Do we have any public database available by Airlines/OEMs listing all field issues for various parts o an aircraft? I know every MRO maintains some but not sure if Airlines maintains that and if its publicly available.


texts: What do I request when contacting tower of an airspace I'm transiting over?

texts: I'm a student pilot who has just begun dual cross-country with my instructor. However, he has not been explicit when I've asked him about radio comm with tower/approach/radio during the flight. If I enter an airspace (say, Class D) and contact the tower, but I do not intend to land there, what would my initial call to the tower be? And what are the differences in requests for approach/departure and tower?


texts: How often is a passenger jet aircraft painted?

texts:
I just read an article (published in 2012) telling the special livery for British airways' A320 to celebrate the Olympics game is made to last one year. I assume this mean those aircraft are painted once per year because painting is not free and thus it is reasonnable to change the livery only when painting is already schedule. But because this is a special livery, it may last less than other painting. As this is only assumptions, my question is the following:

How often is an Airbus or a Boeing painted (even without changing the livery)? Does it significally change from on airline to another? Does a special livery change this frequency?


texts: How much can 3 fans 7 inches in diameter and each a generating 160 cubic feet per minute airflow rate lift?

texts: I'm working on a hoverboard project and am having trouble finding out the maximum weight these fans could lift.


texts: Does acceleration increase linearly on a takeoff roll?

texts:
I'm a relative novice when it comes to aircraft performance and was wondering if someone could both answer the following and maybe direct me to some good source material.

If I wanted to model a take-off roll, can I assume a constant acceleration up until the wheels-up point?  If not constant, is there a reasonably good function that could model the velocity curve on takeoff?


texts: Why does the Lockheed D-21B have three air data probes?

texts:
The Lockheed D-21 has three air data booms / pitot intake tubes: one on the nose and one on each wing. (Images here and here.)

All three appear to be pitot-static tubes. Anyone know what purpose having three of these served?


texts: What are these devices on or adjacent to an airport taxi-way?

texts:
Can someone identify and provide some description of the objects marked in this photograph?

Especially those marked with yellow and red seem to be placed in the middle of a road and that seems to be making the road unusable. How can a plane or airport car go that way, if there are some devices placed in the middle? What am I missing?


texts: Is it dangerous to do a skidding turn to lose altitude without increasing airspeed?

texts:
I was taking some lessons in a light sport aircraft in South Africa a few years back, my instructor taught me something which I had never seen or heard of before or since. We went through an emergency scenario in which we had to make an emergency landing in a field (not really landing but just going through the motions, of course). I found a place to land and started my descent, but had to loop back around after I passed it. The instructor then told me to give full right rudder with left aileron to quickly descend without gaining airspeed.

Wouldn't this qualify as a recipe for creating a spin and possibly killing myself? Should I actually implement that skidding turn in an emergency to land if need be?


texts: Where to do the Run-up and Safety on the Return Flight?

texts:
At my home airport, we do the run-up on the ramp, but I guess each airport has its own preference.

What is the "standard" run-up location? If I recall from my training early on, you can do it at the runway if you angle yourself against the departure end. If this is correct, how do I know that I've angled myself in a way not to blow any debris into an aircraft behind me. And if I do the run-up at the end of the runway, don't I risk obstructing an aircraft that wants to takeoff behind me but has to wait for me to do the runup?


texts: When did inflight smoking become (widely) prohibited?

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

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


texts: Could the Boeing 787-9 near vertical takeoff demonstration be performed by Airbus A350 aircraft?

texts:
I am an aviation enthusiast. A couple of months back I came to know about the difference between piloting Boeing and Airbus planes here.

What are the main differences piloting Boeing vs. Airbus aircraft?

The very first comparison says this:

  Boeing trusts more the pilots: they can supersede the autopilots
  commands by exerting enough force on the controls

  Airbus trusts more the autopilot: if the system is fully functional it
  will always have priority over the pilots (but they still have room
  for "non-standard" maneuvers, e.g. commanding bank angles beteween 33°
  and 60°)

Also another answer stated this:

  Airbus aircraft limit pilots' capabilities in situations that require
  extreme action to be taken; the computer may prevent the pilot from
  pushing the plane past its safe ranges, which could be necessary in
  case of an emergency.

  Boeing aircraft leave ultimate control mostly to the pilot.

Now relating the above points with the recent near vertical take off by Boeing 787-9 in the Paris air show 2015:

Is this near vertical take off is an example that "Boeing aircraft leave ultimate control mostly to the pilot"? If Airbus aircraft trust the autopilot more, would they allow this type of takeoff as it is done by pilot by pushing the engines to extreme? Also, is it some kind of mockery by Boeing to Airbus?

For those who haven't yet watched the video, here is the link:


texts:
I was recently flying on an United Airlines A320 and noticed a narrow section between the overhead storage bins with a placard labeled "Lifeline Extension Belt" on it. It was over the wing exit row. What exactly is a lifeline extension belt?

Unfortunately I didn't get a picture, but what I'm referencing can be seen in these photos (not copied here since they are copyrighted):

https://www.flickr.com/photos/oliverporter/7653848312 (on the top-left)
https://www.flickr.com/photos/49111993@N00/13890509784 (narrow section is visible rising from the forward exit to the overhead compartment, no placard)


texts: Approximate Cost of Food & Beverage Preparation & Storage Equipment on A350

texts:
What's the approximate price for all the food and beverage preparation & storage equipment on the A350? If you don't know the answer for the A350, I'm interested in hearing knowledgeable estimates with a 90% confidence interval range.

I'm asking for a research project I'm doing.

In response to the critique that the question is too broad: Food and beverage storage and preparation equipment on large wide-bodies is supplied by just 1 or 2 global suppliers. I wouldn't expect the price to be different by geography since it's all typically denominated in USD. But, if it makes a difference, let's say we are talking about the US market.

For an example, I believe I know the following from prior research:

All the galleys in each A350 cost about \$1-1.3 million USD per A350 aircraft,

All the business class seats likely cost about \$2.6 million in each A350 assuming \$70-80 thousand USD per business class seat multiplied by an estimated 35 business class seats for airlines that choose a 2-class configuration of the A350.

All the oxygen systems in each A350 is roughly \$100-150 thousand.

Assuming a 2-class configuration of the most popular version of the A350, what's the approximate total value of all the food and beverage storage and preparation equipment?  If there are important distinctions or configurations I'm not clarifying, I'd ask you to assume the configuration that is most common since that would be most reflective of the overall market.


texts: What is the significance of a squawk code?

texts: I've been looking for a detailed explanation for how the transponder works and the importance of a squawk code.


texts: Why so much throttle work on navy fighter during final approach?

texts:
• Look at his left hand: why so much throttle work while flying? What is he doing?
• Is the throttle response very slow?
It seems to me that the fighter don't accelerate so much when he gives full throttle.
• I read that landing on carrier is extremely difficult, does that mean that navy fighter pilots are even more skilled than acrobatic pilots (Red Bull Air Race)? Or is this a subjective topic?


texts: Could a quadcopter fly if its propellers were encased in cylindrical tubes?

texts:
Picture a standard quadcopter, with regular old propeller guards, which are generally just circles around the propellers. Now, take the propeller guards and stretch them so that they're cylinders surrounding the immediate cross-section of propeller blades, as well as some distance above/beneath them.

Now I am fairly certain that it would be able to go up/down. But would it be able to turn? I know it is a relatively vague question, but after thinking about it for some time, I really have no idea. I might just modify the propeller guards on my cheap little drone to see if this works.


texts: Why does Chicago O'Hare have a penalty box?

texts:
I was reading What information does a pilot have about aircraft operating on an intersecting runway? and noticed this on the map:

(airnav.com)

Why is a "penalty box" marked on the map? What is it? What is it used for?


texts: Can an aircraft operator hire a Commercial Pilot to fly their aircraft under part 91?

texts:
Here is the scenario. Joe owns a Cessna 172. Joe hires Tim to fly him in his 172 from A to B. Tim is a Commercial Pilot. Is this legal?

So far, everyone has said yes to this question, but not one person I have asked can cite a regulation or regulations for me.

Here is my chain of Logic:
Part 61.133(a)(1)(i):

  (i) Carrying persons or property for compensation or hire, provided
  the person is qualified in accordance with this part and with the
  applicable parts of this chapter that apply to the operation; and

Alright, let's see which part(s) apply to Tim.

Looking at 119.1(a)(1):

  (a) This part applies to each person operating or intending to operate
  civil aircraft - (1) As an air carrier or commercial operator, or
  both, in air commerce; or

Now let's see if any of those apply to us. Perhaps "commercial operator".
1.1:

  Commercial operator means a person who, for compensation or hire,
  engages in the carriage by aircraft in air commerce of persons or
  property, other than as an air carrier or foreign air carrier or under
  the authority of Part 375 of this title. Where it is doubtful that an
  operation is for “compensation or hire”, the test applied is whether
  the carriage by air is merely incidental to the person's other
  business or is, in itself, a major enterprise for profit.

Okay. This Tim seems to be operating as a Commercial Operator.

Now look at 119.23(b):

  (b) Each person who conducts noncommon carriage (except as provided in
  § 91.501(b) of this chapter) or private carriage operations for
  compensation or hire with airplanes having a passenger-seat
  configuration of less than 20 seats, excluding each crewmember seat,
  and a payload capacity of less than 6,000 pounds shall - (2) Conduct
  those operations in accordance with the requirements of part 135 of
  this chapter, except for those requirements applicable only to
  commuter operations; and

Well we want to be under part 91, so let's look at the exception provided as 91.501(b).

91.501(b):

  (b) Operations that may be conducted under the rules in this subpart
  instead of those in parts 121, 129, 135, and 137 of this chapter when
  common carriage is not involved, include - (4) Flights conducted by
  the operator of an airplane for his personal transportation, or the
  transportation of his guests when no charge, assessment, or fee is
  made for the transportation;

Number 4 seems to apply! Awesome!

But let's take a look at 91.501(a):

  (a) This subpart prescribes operating rules, in addition to those
  prescribed in other subparts of this part, governing the operation of
  large airplanes of U.S. registry, turbojet-powered multiengine civil
  airplanes of U.S. registry, and fractional ownership program aircraft
  of U.S. registry that are operating under subpart K of this part in
  operations not involving common carriage. The operating rules in this
  subpart do not apply to those aircraft when they are required to be
  operated under parts 121, 125, 129, 135, and 137 of this chapter.
  (Section 91.409 prescribes an inspection program for large and for
  turbine-powered (turbojet and turboprop) multiengine airplanes and
  turbine-powered rotorcraft of U.S. registry when they are operated
  under this part or part 129 or 137.)

What is a Large Aircraft.
1.1:

  Large aircraft means aircraft of more than 12,500 pounds, maximum
  certificated takeoff weight.

Okay, a Cessna 172 is not a Large Aircraft or turbojet multiengine. And this is not a Fractional Ownership Program since that requires 2 aircraft in the first place.

So, from my understand, Tim cannot fly for Joe since 91.501(a) says this part does not apply, BUT wait. 91.501(b) says it is allowed.

How is this intrepreted? Does 91.501(b) apply only to large aircraft and such on a fractional ownership program? What am I missing?

Everyone I know says it is allowed, but the rules seem to be different. Any help is appreciated.


texts: How is engine thrust measured in flight?

texts:
When aircraft engines are evaluated in a test flight, how is the thrust of the engine measured?

You would need accurate thrust numbers to calculate the real-world specific fuel consumption (i.e. not in a controlled environment like an engine on a test bed).

I'd assume it is nearly impossible to measure thrust indirectly with any accuracy since so many factors are involved (wing shape, wind, air density, lift, ...).

So I guess there should be a way to measure thrust directly, probably in the engine pylon.

So how is engine thrust measured in flight?


texts: What's a typical first lesson of glider flying like?

texts:
What is a typical first lesson for glider flying like? Does it usually include a pre-flight mini lecture on basic theories at all, or if not pre-flight, do instructors usually spend some time on the ground teaching related theories at some point of the lessons?

I understand it may appear as primarily opinion-based to some, but input from instructors or past-students with a similar experience would fall under 'specific expertise' and thus I think insightful answers are possible.


texts: Are there examples of passengers' Micro SD cards or USB flash drives surviving crashes?

texts: Are there any well-documented cases of Micro SD cards or USB flash drives surviving 100% hull loss crashes? I'm asking about cards held by passengers, not ones that are part of the aircraft's systems.


texts: What are good resources on causes of private aircraft crashes?

texts: I'm working on getting my PPL, and I would like to read more about the specific causes of small private aircraft (single or twin prop, primarily) crashing, especially those that were caused by pilot error. Are there any good books or other resources on this matter? A decent amount of searching hasn't turned up much -- it seems like the data from private charter jets is often combined with that of the aircraft I'm interested in.


texts: Can light aircraft be equipped with yaw damper?

texts:
The smallest aircraft I know of that has a yaw damper is the Pilatus PC-12.

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

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

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

The components I'd imagine would be needed:

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


texts: Can a single seater airplane fly with 50 lbs of thrust

texts: An airplane with 10 sq meters of wing five meters fuselage and including one person. can it fly with 50 lbs of thrust? And the max weight  is 400 lbs


texts: What are the rules in the UK about attaching a GoPro camera to the outside of an aircraft?

texts: Is it fully legal to have a GoPro attached to the outside of the aircraft during flight, in the UK? I've heard mixed answers, but I don't want to try it until I've got confirmation.


texts: What is the relationship between the design lift coefficient and the section lift coefficient of a NACA5 airfoil?

texts:
I would like to know the relationship between the design lift coefficient Cli, of a 5-digit NACA airfoil, with the expression Cli = 0.15*L according to Wikipedia. And the section lift coefficient of an airfoil.
I was doing a CFD project and was planning to compute the section lift coefficient of different airfoils, and comparing them to the L (1st digit of a 5-digit NACA airfoil) of the specific airfoil, but I don't know which is the relationship between the 2 values.


texts: Why does the A320 have an anti skid system and how does it work?

texts: Can somebody explain why do A320 aircraft have an anti skid system? What is its purpose? And a brief explanation on how it works.


texts: Which fixed-wing aircraft has the highest number of required flight crew members?

texts:
Most modern airliners require two pilots to operate. Older airliners require a flight crew of three: two pilots plus one flight engineer.

Has there ever been an aircraft where the number of required flight crew members is extraordinarily high, for example five or six?

To clarify the question:

"required flight crew member" is the number required by relevant regulations, not the number needed to physically operate the plane. If that number is not met, the plane could not legally have taken off
gunners / weapon operators of military aircraft who are not necessary for a safe flight are not included
flight attendants are not included


texts: Can two opposite localizers to a single runway be on simultaneously?

texts:
In case of a single runway with two separate ILS systems (one in each end, facing localizers) operating on two different frequencies, can both localizers be on and transmitting at the same time, or must one be switched off if the other is on?

Please refer to ICAO recommendations if possible.


texts: What are the procedures for radio malfunction

texts:
I was reading this question Do airline pilots ever risk not hearing communication directed to them specifically, from traffic controllers? and there is a answer mentioning radio malfunction

  If it's a real radio problem, there are procedures for both sides to follow to keep everyone safe.

How do pilots / ATC work together if radio does not work?


texts: Why is the 60-year-old NK-12 more fuel efficient than Europrop TP400?

texts:
If Wikipedia is correct the 60 years old NK-12 is more fuel efficient than the Europrop TP400, the engine for the Airbus A400M transport aircraft.

For the NK-12MV a specific fuel consumption of 0.219 kg/kW-hr is given.

The TP400 has a specific fuel consumption of 0.238 kg/kW-hr according to Wikipedia.

Am I interpreting these specifications wrongly?


texts: What are the effective span and lifting properties of a circular wing?

texts:
Today I read an article on FlightGlobal about the Bell air taxi demonstrator. It includes some paraphrased quotes from the Bell VP of innovation, Scott Drennan, among which the following stood out:

  The ducted fans will provide lift during hover, forward propulsion and lift during forward flight, says Drennan. That forward lift will not come from the fans being tilted slightly down, but from the ducts, which act as aerofoils – "circular" wings, engineers call them.

This sounded odd to me for a variety of reasons. I realize this could be the effect of the journalist miss-hearing or miss-quoting the VP, so I'd like to focus on the aerodynamics at play here.

The Bell Nexus air taxi is a quad tiltrotor design with small engine pylons, so cruise lift must come at least in part from the ducted fans, either via downward thrust vectoring or through "duct lift", and the latter presents a slew of issues.

Therefore, the question: what would be the effective lift achievable by a circular wing, or duct without a fan installed in it, in forward flight? In particular, how close would it come to the performance of a regular slender wing of a span equal to the duct diameter. Let us limit the discussion to low-subsonic flight.

Bonus points: what would be the bonus or malus of having a fan installed in such a duct or circular wing, adding its own component to the circulation around the duct walls?


texts: How to stabilize the aircraft flight after dropping boosters?

texts: I want to make aircraft model with boosters, but i don't know how to stabilize it. Аfter dropping the boosters, the center of mass of the aircraft will change, and I would also like to know whether it is necessary to stabilize it at all? Also during the flight on its own engine with fuel consumption, its mass will also change, whether in this case it is necessary to stabilize it? I need methods/ways or sources of info about it (maybe books, articles). Thanks for your attention.


texts: What kind of propellers are generally mounted on the Aeriane Sirocco?

texts: I'm curious what propeller is used for the Aeriana Sirocco. Online I see lots of pictures of propellers with three blades, but none with only two and I cannot find many clear pictures of the proppeler. Are there any Aeriana Sirocco aircraft flying around with (wooden) propellers with only two blades?


texts: Where are "standard taxi" instructions published?

texts:
Example: at KATL (Atlanta), the ground control sometimes gives taxi instructions as "standard taxi"; Where is that defined?

  Delta 2732 27-Right Lima Charlie "Standard Taxi."

In that case, from a south ramp, the aircraft is noticed taxiing on Lima to 27R at intersection LC.

The question is, how did the pilot know that "standard taxi" meant going on taxiway Lima? Where are "standard taxi" instructions defined/published?


texts: If I have multi-engine land, can I learn multi-engine sea directly?

texts:
Let's say I hold PPL privileges for Multi-Engine Land. Now I want to start my seaplane training.

Can I begin my training directly on a multi-engine seaplane? Or, do I have to get a license for Single-Engine Sea first before I can proceed to multi-engine?


texts: How much electrical power is available in a Gulfstream G550 and from which power sources?

texts: I'd like to understand what electrical power sources are available (engines? APU? GPU? Other?) on a larger jet like the G550, and how much power they can provide, depending on whether the airplane is flying at cruise speed or on the ground. I'm curious about how much electrical load can be added to the aircraft and how.


texts: How much air, by mass, enters an average CFM56 turbofan engine cruising per minute?

texts:
How many kg of air enters an average CFM56 turbofan engine cruising per minute?

I have looked everywhere and cannot find it or figure out how to find it, if you could either tell me or give advice on where or how to find it I would appreciate it. Thanks


texts: Why didn't the A330neo and A320neo share the cockpit of the A350?

texts:
Recently Airbus presented its lastest projects A330neo and A320neo.

I'm sincerely surprised about the cockpit, in that it is essentially the same of the original A330, while I was expecting that renovation would affect not only the engines, installations, and lights but also the cockpit instrumentation taking inspiration from the new bigger screens of the A350.

I know that in this way the training for pilots is much easier, but at the same time I think that if a new cockpit is developed for a new plane (taking into consideration that "Type Rating" is anyway considered the same), it should be because of more safety, readability, and situational awareness.

In the past Boeing completely updated its cockpit inside the B747-400 and B737NG models from the original mechanical/analog gauges to the new glass cockpit. In those cases, surely the necessary training was very hard for pilots so, why not now for minor updates?


texts: What prevents miltiary jets and turbo-props from being refitted with a turbofan?

texts: What prevents military jets and turbo-props (such as P-3 Orion) from being refitted with a high bypass turbofan?


texts: Are tracked landing gear systems still in use and development?

texts:
In the 1940's and 1950's, there were several tracked landing gear systems developed for the purpose of allowing landing on soft ground and/or using particularly heavy aircraft such as the B-36.

Are any such systems still in use and/or development?

(I have been searching and found quite a few examples but none in recent decades except for a proposal that suggests that it would be feasible to deploy modern improved tracked landing gear on C-130's, C-17's and 747s.)


texts: Do large non-pressurized metal planes have a maximum fatigue cycle?

texts:
For example the DC3. The way I understand it, the only thing that "ages" the airframes of DC3 is the landing/takeoff cycles and the accompanied periodic force loading/unloading. Do planes such as this really have a meaningful definition of lifetime of its airframe?

As a side note, is loading/unloading cargos on the floor another kind of cycle too?


texts: What is the difference between IAN and LNAV/VNAV?

texts:
Is there a real difference or benefit in using Integrated Approach Navigation (IAN) instead of LNAV/VNAV for a non-precision approach (NPA)?
Both give you lateral and vertical guidance during an NPA. Is IAN more precise?


texts: What is the relation between a helicopter's length and rotor diameter?

texts:
I was looking at a couple of helicopters on Wikipedia (specifically the Boeing A160, the Robinson R22, and the Sikorsky S-46) and I noticed the main rotor diameters seem to be pretty similar to the helicopter length (see below).

Is there a reason for this, or is it just coincidence? I thought it might be that helicopters are just long enough for the tail rotor to not interfere with the main rotor, but that doesn't seem to work out, because the rotors aren't quite centered over the helicopter.

Helicopters' length and main rotor diameter legend:

                Length     Rotor Diameter
Boeing A160      35'0"        36'0"
Robinson R22     28'8"        25'2"
Sikorsky S-64    70'3"        72'0"


texts: How dangerous was this approach of a Dash8 Q400 really?

texts:
There is a video going viral here of a Dash8 landing during a recent media hyped storm:

According to the description and imagery it is a Dash8 Q400 (registration D-ABQD), Eurowings flight EW9203. It did land during a storm with alleged 110km/h (60 kts) crosswind on Düsseldorf airport.
According to https://www.flightradar24.com/data/flights/ew9203 it landed at 12:13 local time on 18.01.2018, runway 23L or 23R. Within the video it is claimed that there is wind up to 110km/h whereas other sources from other places claim more like 80-90kmh (43-40kts), it probably varied by the minute.
Wind direction seems to have been mostly from west, with storm typical quick variations.
The crosswind limit for the Dash8 Q400 seems to be 32knt, quite below any of the cited wind speeds, however given the angle difference (230 to 270) a cited wind speed of ~50knt would have been just within the limit.
TL;DR
If there was the possibility of going to another airport (I have no idea if there was), should the pilot have diverted to a less windy area for safety reasons?


texts: Can a human be blown away by jet engines of an A380?

texts:
Can a human be blown away by jet engines of an A380 at full throttle? If so what is the largest object that it can blow away and cause significant damage? Can it blow away another parked Airbus A380 and cause damage?  Can it perhaps blow away the A320 and cause damage?

If so what is the safest parking distance between aircraft, with regards to jet air at full throttle.  What are the safest recommendations?


texts: What does Elon Musk mean by "electric jet"?

texts: Elon Musk has said that he has a design for a vertical take off and landing super sonic electric jet. I was under the impression that jet engines work by burning fuel, expanding volume and thus creating force. How can this be done electrically?


texts:
I came across this extremely interesting article with details on a 2018 United Airlines Boeing 777  engine failure, which is also related to the more widely-publicized failure a few days ago: http://aerossurance.com/safety-management/ndi-failures-b777-pw4077-fbo/ . Amongst others, it contains the following:

The records for the TAI [Thermal Acoustic Imaging] inspection in July 2015 as well as an earlier
TAI accomplished in March 2010 revealed a thermal indication in the
same location as where the LCF crack occurred. The records for the
fractured fan blade’s July 2015 TAI inspection was
annotated ‘paint’ that, according to the inspector, was consistent
with him accepting the indication because he thought it was an issue
with the paint.
Flaking paint was a regular issue, affecting perhaps 25% of blades,
requiring either a touch-up or a complete re-paint.

which begs the question: why are fan blades painted? The only reason I can think of is so that damage from small objects (or birds) sucked into the engine is easier to see? But, if I read the article correctly, the paint can also mask more serious issues - in this case, the inspector thought that the TAI indication was due to flaking paint, which is apparently common, when in fact it was a defect in the blade. So maybe it would make sense to leave the blades unpainted?


texts: Why is the MD-80 magnetic compass behind the first officer's seat?

texts:
I was watching this video about the MD-83 magnetic compass and I found it interesting that it's designed the way it is. I'm not sure which of the airplanes in this series featured this strange arrangement, but it was the case on at least the MD-80 and MD-83.

The magnetic compass on these machines was located behind the first officer's seat and a series of mirrors were used to make it visible to the pilots.

Why was it built this way? Were there any advantages to it? Did they go back to a more conventional design in later models?


texts: Do aerodynamic forces depend on the materials of the wing surfaces?

texts: I think that statement is true, but in the book "Fundamental of aerodynamic", page 35: the aerodynamic forces R don't depend on the skin material, 5 variables are mentioned but none of them is relate to skin material of wings. So why is that???


texts: Studying bird flight and insect flight: Would studying aerodynamics of airplanes be useful?

texts:
Would studying the aerodynamics of airplanes be useful, if one wants to study bird flight and insect flight?

For instance, would studying a gliding paper plane and a gliding unpowered airplane be fundamentally the same?

I've read that aerodynamic laws for airplanes are different from aerodynamic laws governing bird and insect flight, but I forgot where I read this from -- possibly from an academic journal paper, if I remember correctly.


texts: How would exhaust heat recovery into the combustion chamber affect the efficiency of a jet engine?

texts:
So, a jet engine basically sucks in air, heats it up and spits it out, right?
The hotter the air gets, the faster the exhaust velocity and thus the more efficient (Higher specific impulse).

Now my question is how this all gets affected if you use a heat recovery system, either a heat pump or a simple heat exchanger. Let's ignore the annoying practicalities of metals melting and all that stuff and just look at the theoretical side.

If you recover heat from the exhaust and put it back into the combustion chamber how does this affect the efficiency of the engine? If we were to apply the heat into the combustion chamber using a heat pump, pumping heat from the exhaust into the chamber could we get even higher efficiencies? While "Yes/No" answers would suffice I would be much more interested in a thermodynamic explanation and possibly even some estimations of the theoretical efficiency which could be reached using the Carnot cycle for pumping the heat.

Onto the practical, has anything like this been experimented with? To my knowledge we don't have heat pumps capable of operating at 2000 degrees Celsius and pumping heat quickly enough to compare to any type of engine, but maybe someone has experimented with simple heat exchangers like how rocket engines use regenerative cooling (for different purposes though, but still similar to this).


texts: How to calculate the amount of weight my plane can takeoff with?

texts:
This is how I approached this problem-

My takeoff run is limited. So, depending on my configuration I calculated the maximum possible velocity I can attain in my groundroll. I assumed that at the end of the run my lift should be greater than the weight I want to carry. So I computed the lift I generate at the end of the groundroll. I got the CL value from xfoil for my angle of incidence. Would this method give me a rough estimate of the total weight my plane can carry?


texts: Is there some technology which will help in stall recovery?

texts:
Although rare, it seems that there has been a number of cases where airliners have crashed as a result of a high altitude stall. I tend to picture this as entailing a long, uncontrolled descent where the plane never has proper flow over control surfaces to re-establish flight.

Is there any type of deployable technology that could force a plane into an attitude from which it could re-establish control? I am thinking of something like a drogue system that would force the nose down and dampen spin that could be jettisoned later.


texts: Why does the F-4's rear seat have a weather scope eyepiece?

texts:
In the front seat. The pilot has a flat screen radar scope that shows both the planes and the weather.

But on the rear seat. The weather scope has an giant eyepiece. Perhaps glare protection?

(angelfire.com)


texts: When buying airliners what is the difference between "orders", "options" and "purchase rights"?

texts:
I've often seen announcements by aircraft manufacturers or operators along these lines "Qantas announced today that they will buy 10 A380's and have taken options on another 10".

What does it mean to "have an option"? I mean what level of contractual obligation exists between the manufacturer and the operator? Has a non-refundable deposit been paid - if so what sort of proportion of the eventual cost?

Does "having an option" mean much more than the manufacturer hopes you'll order those planes and has pencilled you in on the manufacturing schedule?

I also came across this on Virgin Atlantic's website:

  Virgin Atlantic announced in March last year that it was ordering 15
  of the 787-9 Dreamliners - with options on ordering another eight
  787-9s and purchase rights on a further 20 aircraft.

I've never heard of "purchase rights" so I'd be interested to know about the significance of "purchase rights" as well.


texts: Does distributed propulsion create unwanted lift at cruise speeds, requiring a negative angle of attack?

texts:
Does distributed propulsion create unwanted lift at cruise speeds?

The great thing about slats and slotted flaps is that you can "turn them on" when you need high lift at takeoff, and "turn them off" when you don't need high lift during cruise.

So what about distributed propulsion by using 4 engines with props covering the majority of the wingspan? You can't turn off the extra lift off if you're trying to cruise as fast as possible.

I understand distributed propulsion adds a clmax of about 3.

Typically, you only need a Cl of 0.5 during cruise, but most GA planes cruise at about 75% power, almost at full power as on takeoff, so wouldn't a cl total of say 1-2 be generated with distributed propulsion?  That's 200 to 400% higher lift than needed.

To get rid of this extra lift and drag, wouldn't you need to lower the nose until the wings produce a " negative induced cl" of about -.5 to -1.5, adding the "distributed propulsion cl" of 1-2, for a total desired cL of about 0.5?

Is this correct, at least conceptually? Or does lift due to distributed propulsion trend to zero at a zero AOA? i.e. it's just additive if the wing is producing lift above a zero AOA


texts: Can an unserviceable component be fitted on a serviceable aircraft for a maintenance check?

texts:
I was doing some reading on aviation regulations and I wanted to understand from an expert whether the following situation is allowable or not. I have reviewed EASA continuing-airworthiness guidelines but am still unclear as this is a bit of a unique scenario.
Appreciate if you can shed some light on whether this situation is permissible or not.

A component fails and is removed from Aircraft A and declared unserviceable (with an "unserviceable" tag).
A similar component is removed, via robbery/cannibalisation, from another aircraft (Aircraft B) undergoing maintenance activity (A or C check), and provided to Aircraft C, which has a similar failure.
There is now a "hole" in Aircraft B, since the component has been robbed/cannibalised to support Aircraft C for the latter's maintenance requirement.
The original failed component (from Aircraft A) which was declared unserviceable (with an "unserviceable" tag) will be used to support the maintenance check inspections/tests for Aircraft B.
These tests are to inspect/test aircraft systems, and the "hole" needs to be plugged to carry those out.
The unserviceable component will eventually be removed from Aircraft B as unserviceable (with the "unserviceable" tag).


texts: Is it taken by both pilots and flight attendants? How frequently? What is the main purpose of it? Is it mandatory?


texts: Why has the IO-390 not replaced the IO-360?

texts:
Having looked at the IO-390 vs IO-360, one can not help but notice that very few STCs have been done, and even fewer OEMs have fitted this engine in place of the IO-360 used in many airframes.  180 or 200 gross HP vs. 210 guaranteed net for the extra weight of dynamic crank counterweights - to me that would be a no brainer.

Why is this engine having such a struggle for acceptance?


texts: Is it correct that a jet fighter can be used as a non-lethal (sonic) weapon?

texts:
Imagine you have a crowd of people, who want to go to a certain territory (e. g. close to the border). An airplane flies over them such that when it reaches supersonic speed, there is a loud bang. People hear it, it hurts, and for several days they are deaf. That noise scares them off, and after some time most of them recover (i. e. there is no permanent injury to their ears).

I heard this story from a source I don't trust.

Can this be true? Could you, in theory, protect the border of a country from intruding crowds by simply flying over them (provided the crowds can't down the plane)?


texts: Are the GPWS callouts recorded with real people or computer generated?

texts: I absolutely love the tone of the GPWS callouts in the Boeing 737NG, and I was wondering whether the callouts where computer generated or a recording of a brilliant voice actor.


texts: What is happening with this aborted flight?

texts:
I live near Southend airport in the UK (SEN, EGMC) and noticed a strange behaviour of a cargo jet that does daily trips to Spain.  It started out on runway 05, took a normal departure until it turned around 5 minutes later.  Then it started circling the airport at 4,000' three times, before descending to 2000', switching direction and finally landing on runway 05.

The flight was obviously diverted back to Southend (it did leave an hour later) but given time was 0030-0100 local time, and it was quite noisy, can anyone think of a reason why it would repeatedly circle round a built up area so many times?

https://www.flightradar24.com/data/aircraft/g-powp#24941d80

edit:

There was a report on a local facebook group that it had lost communication, but its squawk didn't change to 7600


texts: What is this propeller found underwater in the English Channel?

texts: I need some help identifying this piece.


texts: Will a self balancing wing using an Eppler 186 airfoil still generate a Clmax of about 3+ with slats and slotted flaps?

texts:
Will a self balancing wing using an Eppler 186 airfoil still generate a cl of about 3+ with slats and slotted flaps?

Although the NACA2415 used in the pegasus wing for the Zenith 701 has a low Cm, the Eppler 186 has an almost zero Cm at an AOA of about 3 deg.

Just wondering if there is some aerodynamic reason why it couldn't generate a Clmax of about 3, the same as the NACA2415?

Of course, it would only be self balancing in cruise, without the slats and flaps deployed.

I understand not all airfoils see the same increase in Clmax, due to the leading edge, etc.


texts: What is the difference between Distant (D) NOTAMs, Local (L) NOTAMs and FDC NOTAMs in the US?

texts: I would like to know the difference between Distant (D) NOTAMs, Local (L) NOTAMs and FDC NOTAMs in the US. Is their meaning obsolete or still in use by the FAA?


texts: Can an Iranian citizen attain ATP in the United States?

texts: I know that you can be a pilot in the U.S. as a foreigner. However, are there any special regulations regarding citizens of Iran because of political issues?


texts: Why do the British not produce anymore aircraft?

texts: Minus Airbus which is a group of companies, why does the United Kingdom not produce aircraft anymore ie, the VC10.


texts: What is "required navigation performance" or "RNP"?

texts: I understand that this is some sort of on-board navigation monitoring and alerting...what is it used in? Do the Garmin G500s, G1000s, or the G430s use it? Where can you find it? I know nothing about this and I am trying to figure out what it is.


texts:
I have a hard time understanding the physics behind the pneumatic erecting system in an attitude indicator. According to my book and the linked image, the applied force is “precessed 90 degrees” (anti-clockwise seen from above) and thus re-aligns the gyro. I understand how the pendulous vanes change the exhaust of the air, but since this part is stationary, i.e. not rotating, how can the net force be precessed?

https://savageplane.files.wordpress.com/2017/06/pendulous-vanes-figure-10-101-screenshot-from-2017-06-06-171632.png


texts: What are the differences between top and bottom mounted airbrakes?

texts:
What are the differences between airbrakes on the top side of jet aircraft (like on the F-15) compared to those on the lower side (like on the A-7), in terms of effectiveness and pitching when they are deployed?

From Wikipedia.

From Reddit.

Would pitch authority be better in one than the other?


texts: How does the A320 FMGC (autothrust, autopilot) decide which radio altimeter readings to use?

texts:
How does the A320 (or other Airbus FBW aircraft, for that matter) decide which radio altimeter reading to use (say, for FMGC functions like autothrust), or whether to reject the radio altimeter data altogether and throw an ECAM to the pilots?  It's certainly not a full voting system, considering that the A320 only has two radio altimeters, not three...

(For the curious: I ask because the flight profile from the ACA 624 mishap bears some resemblance to what would happen if the power rolled back on very short final without the crew noticing.)


texts: How much noise does flow separation cause?

texts:
I recently found the following image showing the different sources of noise in vehicles. I notice that Aerodynamics is actually quite a big part of vehicle noise, as shown below by the blue line:

Image source

I can imagine this is partly because of the flow going over the car. However, I think a part of this noise also comes from separating flows (for example at the rear window).

I was wondering if it is possible to reduce the aerodynamic noise of vehicles by applying separation control.

As such, I'm wondering:

How much noise does a separating flow generate?

I'm guessing this highly specific to the local geometry and velocity, but I would already be very happy with some examples.


texts: How do acrobatic pilots avoid pulling too many G’s and passing out?

texts: I just watched a video of a acrobatic pilot doing stunts, it involved a type of stall, not sure which one though. Long story short he overcompensated(?) which caused him to pass out, and then he crashed in the lake. Honestly I’m surprised this doesn’t happen more often. What kind of safety measures do they take when pulling off maneuvers that come close to the ground and would require a fast change in angle of attack?


texts: Is it possible to use a split rudder as an air brake?

texts:
This question (which is the first result for a Google search for "Split rudder aircraft", btw), talks about some of the advantages of the split rudder, including the fact that the lower rudder is smaller for finer adjustments while flying.

If the rudders were equal size, or if there were three pieces, two of them being equal to the third, could they be used as an air brake?

Would there be advantages to doing so vs building in a dedicated air brake?


texts: In a non-symmetric turn, how do the side slip angle and thrust side slip angle affect the equations of motion?

texts:
I'm doing a problem on Flight Mechanics in which a banked turn is performed. The center of gravity of the aircraft is always within an horizontal plane.

In order to write the dynamic equations, I have to assume some simplifications and conditions. One of them is the following:

  The thrust’s sideslip angle is equal and with opposite sign than the aeroplane’s sideslip angle, that is:
  ($\nu = −\beta$).

  Side slip angle ($\beta$) is defined as the angle made by the velocity
  vector to longitudinal axis of the vehicle at the center of gravity in
  an instantaneous frame.

  Thrust side slip angle ($\nu$) is defined as the angle made by the
  thrust vector to longitudinal axis of the vehicle at the center of
  gravity in an instantaneous frame.
  https://en.wikipedia.org/wiki/Slip_(aerodynamics)#Sideslip_angle

Then, I have to write the dynamic equations for the symmetric flight and for the non-symmetric flight.

My questions are:

In my opinion, the condition written above should not be accounted for the symmetric flight, so $(\beta = \nu = 0)$. Is this affirmation correct?
For the non-symmetric case, I have drawn the following scheme of velocity and thrust. But I'm not sure if it's correct because it doesn't make sense, despite that is what the condition says: $(\nu=-\beta)$. Is the scheme correct according to the condition? (The scheme is the top view of the aircraft.)


texts: Where can I find numeric maps of aerodromes?

texts: I desperately need a map of an airport aerodrome like the ones used for tracking the movements of aircraft similar to the picture below and I don't know where I can find these ones :


texts: Can instruments be fixed via a swift punch?

texts:
I remember reading a book about private piloting techniques, (I can't remember the title; it has been so long; perhaps I can check my library history or something to see later), and I saw something bizarre.

The author was discussing instruments, and what to do in case of failures. He wrote something about how, in the case of a failure of a critical instrument, in a situation where you really need it, that one should punch out (or otherwise destroy) the glass of the gauge, to allow air into the system.

What?

Is there any way something like this could be useful, or at least theoretically logical? Can anyone deduce any sense out of this?


texts: Does auto pilot take into consideration the altitude, speed, and the difference in heading change, to calculate the degree of bank?

texts:
Or is there a “standard” that the auto pilot follows at all times?

By “standard” I mean the aircraft will bank at x amount of degrees each time regardless of the following mentioned? The more you bank, the sharper the turn is, correct?


texts: What are the differences between various simulator levels?

texts:
I've heard of level A, B, C, and D simulators, (as well as FTD and AATDs) but know nothing about them.

What criteria is used to certify a sim as a particular level?


texts:
I do not understand when the Compass around a VOR is and is not present on maps.

For example, around Kansas City:

VOR OJC has been deactivated for quite some time now.  But its compass is still present on the latest map revision. (the frequency has hash-marks through it, indicating the deactivated status.

Why hasn't the map been updated to remove the compass?

VOR RIS is still active, but does not have a compass around it.

Why isn't the compass on this active VOR?

Are there any general guidelines for when a compass is present on the map?


texts: Why do we have a booking code and a ticket number?

texts: As per subject why is this done? Doesn't it make operations more confuseing as we have to references for every single passenger? A ticket number seems to be unique so why is this not used for all passenger references?


texts: What is this second smaller runway next to London City Airport?

texts:
I was looking at London City Airport (EGLC) on Google Maps today when I noticed the remains of a very small runway marked 10/28 just across the water from City Airport's main runway. It can be seen here.

To my surprise I couldn't find any mention of this small runway after searching online and looking into the history of the airport. Using the Google Earth historical imagery feature the earliest image I could find that included the runway was 2008, so I assume it was built some time between 2006 and 2008.

Can anybody tell me what this short runway is for?


texts: Why does X-Plane 11 show the SR-71 at 200 knots but Mach 3 at 80,000 ft?

texts:
So I noticed on X-Plane 11, the SR-71 reaches Mach 3 at 80000 feet, but the equivalent airspeed is only around 200 knots. What explains this difference between the mach number readout and the EAS readout?

Edit: the reason I ask is because other questions such as How did SR-71 spy, flying at 80,000 ft and 3500 km/h? indicate the SR-71 flew at 1910+ knots at 80000 feet, but I'm not sure if this is with a conversion of some sort or not, i.e., is this simply a simulator problem or an accurate representation of airspeed and mach?


texts: Does the FDR record data about the cockpit door lock system?

texts: Does the flight data recorder record whether the cockpit door lock was deliberately used to lock someone out?


texts: Can an airliner provide ground level cabin pressure, temperature, humidity etc?

texts:
Apart from the cost angle, which seems to be the biggest factor in airlines, is it technically possible to bring cabin atmosphere (includes pressure, temperature, humidity) etc. at par with ground level, at the cruising altitude of most airliners (say 35000 ft).

I just want to understand what stops airliners from providing this kind of comfort to the passengers. I am assuming there might be issues of hull integrity in order to maintain higher cabin pressure etc.


texts: Can a contra-rotating helicopter simply tilt its entire rotor set instead of using a cyclic?

texts:
I was reading this interesting question and, per answer #1, a normal helicopter cannot do it because gyro effects would probably mean the body of the heli would tilt more than the rotor.

So now I think about contra-rotating helicopters, like the Ka-50. They don't need tail rotors, because the contra-spin cancels out reaction torque (except when they want to yaw, for which they extend little things at the blade tips of one rotor, producing more torque there and therefore opposite yaw).

Anyway, can't a contra-rotator just tilt its whole hub instead of using traditional cyclic (swash plate, scissors link, which in fact are a lot more complex for a contra-rotating helicopter).


texts: How does one develop artificial stabilization for aircraft uncontrollable without it?

texts:
In an answer about the F-117 Peter Kämpf writes

  F-117 (...) is unstable and uncontrollable without artificial stabilization.

I wonder how such an aircraft comes to existence, specifically how one develops the program without which the aircraft can't be flown.

How one establishes (presumably in a wind tunnel using a scaled model) that the plane will not be stable or controllable, but it can be helped by an artificial stabilization system well enough to be flyable? How does one develop the system itself? How it is determined that the stabilization system has became mature and reliable enough to permit test flights?

Sorry about the question being somewhat blurred, I realize I don't even know what exactly to ask about. Any suggestions or reasonable edits welcome (in worst case I can roll the edit back).


texts: What is the reason for different engine configurations seen on Solar Impulse?

texts: In various images of the Solar Impulse aircraft, I see the engines mounted in different positions along the wing.  Am I looking at SI 1 vs SI 2, or are the mount positions capable of reconfiguration depending on conditions/experimentation?


texts: Can we build a bigger aircraft than the A380

texts: Can we scale up from the A380 airbus to accommodate more passengers


texts: Why is ARTCC room lighting in the US dim?

texts:
I have made several trips to US ARTCC centers and they had very dim lighting. I was told the lighting, carpet and wall colors where all decided on by the (PATCO) union contract with the FAA.

This week I was watching a BBC documentary and the British air route control room (NATS) was brighter than a normal office.

What is the justification between the two lighting preferences.

Dimly lit ARTCC room, even the display and control area use dark trim.

Brightly lit British NATS room, note the bright display and control area.


texts: How is the direction of the hydraulic fluid changed so that the cylinders and pistons can move backwards and forwards?

texts: How is the direction of the hydraulic fluid changed, so that components and actuators (cylinders and pistons) can move backwards and forwards?


texts: When does the mandatory minimum climb gradient during an Instrument Departure Procedure end?

texts:
While studying FAA's Instrument Procedure Handbook, I noticed these minimum performance requirements for obstacle clearance, when a SID or ODP is absent for a particular runway:

-- Cross the departure end of the runway (DER) at least 35ft AGL.
-- Climb to 400ft above the DER before turning.
-- Maintain a climb of at least 200ft per nautical mile (FPNM) until reaching minimum IFR altitude.
The minimum IFR altitude is 1000ft above obstacles, or 2000ft in mountainous areas.

I was wondering if the last rule, regarding a constant climb with a minimum climb gradient of 200 ft/NM (if no other is specified) until reaching minimum IFR altitude, applies also in case of SIDs, or it is up to pilot's or ATC's judgement to establish a minimum climb gradient for a particular, arbitrary portion of the SID route.
In other words, if for a particular SID it is mentioned "climb gradient of X ft/NM until Y altitude", then after reaching Y altitude is the pilot allowed to fly with whatever climb gradient he deems necessary, even if it is less than 200 ft/NM?
p.s. I have to give some credit to this question, though it is not a duplicate since it asks if a minimum performance applies in case of the absence of a SID or ODP. I am asking if a minimum performance (especially the last rule regarding the minimum IFR altitude) applies when the pilot is following a SID.


texts: Is there a website which highlights airport locations on a map?

texts:
Is there a good website which shows airports (both public and GA)? I can look it on Google and Bing Maps (as shown in the image below). Shown the picture, I have zoomed in a lot to see airport icons (bottom left and top right). I feel that the icon on Bing (right) can be easily spotted than the one on Google (left). Even if I zoom out one level, Bing still shows both airports but Google doesn't.

When I search on Internet, mostly A/F Directories are returned. Wikipedia also has a thorough list but I don't like plotting them on a map to find their proximity.


texts: Does lift-to-drag ratio asymptote to 4 (or 6) at high Mach numbers?

texts:
The Kuchemann equations for L/D at high mach numbers, approximately verified by wind tunnel tests, were:
$$\left(\frac{L}{D}\right)_{max} = \frac{4\cdot(M+3)}{M}$$
and, for wave riders
$$\left(\frac{L}{D}\right)_{max} = \frac{6\cdot(M+2)}{M}$$
As you can see, these equations asymptote to 4 and 6 respectively.
If my understanding of the matter is correct, at ultra high Mach numbers, air begins to behave more like rays of radiation. Hence, L/D would simply be:
L/D = 1/tanA

where A is angle of attack.
Hence, the corresponding angles of attack for the two asymptotes would be 14 degrees and 7.5 degrees, respectively.
Is there any physical evidence for the above asymptotes (and perhaps the AoA values)?


texts: Mathematical model used in free route airspace

texts:
As a new researcher in an air traffic institute, I am currently looking into mathematical models - promising or otherwise - that are used in modelling free route airspace.

What is a good place to begin?

Thanks in advance.


texts: What is the average time and distance needed to reach cruising height?

texts:
I am trying to compare trains with airplanes and the distances where taking a train is more viable than an airplane. I guess this would depend on the type of plane, but the Airbus 320 seems like a common enough plane in Europe so I have something along that type in mind.

As far as I know, it would be a good model for airplanes to separate the takeoff and landing phase, where they cover less ground and does take appreciable time on shorter hauls and the cruising phase. I found average speed for the latter but I don't know how much time takeoff takes and how much ground the aircraft can cover during this. Same goes for landing, so my question is, how much time do these take and how far does the aircraft get during these?

I'm also assuming that when looking at city center to city center travel times, taking a plane has about a three hour overhead (airports are far and it takes quite a long time to get in, security check and all), but if anybody actually knows some statistics on this I'd be much obliged :)


texts: If I'm cleared to land without any specific instructions on how to enter the pattern, what should I do?

texts:
I learned at an uncontrolled airport. I thought I had controlled communications down pretty well, but I upset the tower controller today.
Situation:
I was coming from the southeast, and tower told me “clear to land runway 5”. He didn’t tell me what leg to fly or anything. It wasn’t busy. So I stayed straight for the left crosswind. He said I should have never crossed the field. I continued left downwind, base, and final.
I know I should have asked for clarification on how he wanted me to enter. Maybe he was also expecting me to have maneuvered to the west side of the airport for a right base.
I could use some coaching on this. What do you all experienced pilots think?


texts:
I've started working to make airport files for an online ATC game, and my first airport is Newark Liberty (DP: https://flightaware.com/resources/airport/KEWR/DP/all/pdf).  What I already understand is that there are various climbs valid for different runways, and that the SID directs each aircraft to its first fix.  What I don't understand is how the climb is determined for each aircraft.  I also want to know how often airplanes use the SIDs, as I sometimes see planes on Flightradar not following the climb paths.

Thanks, this has confused me for a week or two.


texts: What causes this surface texture, and how does it affect flight characteristics?

texts:
The picture on this answer to "What is this plane seen in Mobile, Alabama?" shows a B-52D Stratofortress with a very irregular surface texture.

(Source)

Were they like this when they were new, or is it just because this is an old aircraft that serves as a display piece? Would a surface like this cause issues with airworthiness?


texts: Fuel jettison in Top Gun, is there any reason to do this other than show-boating?

texts:
20 years of watching Top Gun and I only noticed this today, after almost an annual repeat!

At 00:29 in this video, you can see what seems to be condensation swirling in the wake vortices.

Up until today, I thought this was just a cool shot catching some serious condensation under a high-G maneuver. However, if you look closely, you can see that it's actually a fuel jettison! At 00:38, it's very obvious.

I'm guessing that this is nothing more than show-boating and it sure did produce a cool shot.

Fuel jettison/dumping is used to reduce landing weight in emergencies but, is there any tactical/ops reason to do this?


texts: What is the difference between Body Pitch Rate and Inertial Pitch Rate?

texts:
ARINC 429 specifies two series of attitude rate labels for ADIRS/AHRS/IRS systems:

Body

326 : Body Pitch Rate
327 : Body Roll Rate
330 : Body Yaw Rate

Inertial

336 : Inertial Pitch Rate
337 : Inertial Roll Rate
340 : Inertial Yaw Rate

What are the differences between these two sets of values? I'm assuming the Body labels are in reference to the airframe, but do the Inertial labels use a different reference?


texts: What is the slowest fixed-wing airplane?

texts: It's easy to find information about the fastest airplanes, in different categories (e.g. X-15, SR-71, the Concorde etc), but what is the slowest one? Which powered, manned airplane is capable of sustained level flight at lowest velocity?


texts:
What Is This in The Top of IL-86VKP?
What Is This in The Top of IL-86VKP?


texts:
I'm intrigued by the Lockheed SR-71's take-off procedure, as it seems different to that of civilian aircraft. I would like to know what are the major differences in take-off procedure, and why?

For example, most aircraft begin to take off like the following: engine one on, warming up. Engine two on, warming up, etc. But is this the same for the SR-71 what was its take-off protocol?


texts: What mechanism did the turbine reversers of early high-bypass turbofans use?

texts:
Nearly all jetliners nowadays use fat, efficient high-bypass turbofans (turbofans with a bypass ratio greater than or equal to 5:1).  As the vast majority of a high-bypass turbofan’s thrust comes from the air blown past the engine core by the fan, rather than from the superheated air and exhaust gasses coming out the core’s tailpipe, thrust reversers on these engines generally only redirect the bypass air (saving on maintenance costs and reliability, as the reverser never has to come in contact with the hot, corrosive core exhaust); as such, these types of reversers (usually cascade-type reversers, where the entire rear portion of the fan cowling slides rearwards, although some smaller aircraft use clamshell-type reversers, where several discrete petals open up in the fan cowling to redirect air forwards) are often known as fan reversers (as the air they redirect has passed through only the engine’s fan, and no other rotating parts of the engine).

However, very early high-bypass turbofans (GE TF39/CF6, P&W JT9D, RR RB211), used primarily on the first generation of widebodies (747 Classic, DC-10, L-1011, A300B1/2/4), also included separate turbine reversers, which redirected the engine’s core exhaust.  Apparently, they were unreliable and required frequent maintenance (due to their frequent exposure to the core’s superheated, corrosive exhaust gasses), they were yet another complicated mechanical system on an already-very-complicated airplane, and they provided little additional stopping power on top of that provided by the fan reversers (due to the core of a high-bypass turbofan providing only a small fraction of the engine’s total thrust); as such, most airlines deactivated the turbine reversers on their fleets after a few years.1

The only reference I have handy at the moment that actually points out the turbine reversers is this diagram of the DC-10-30’s wing-mounted (#1 and #3) engines and pylons.  Unfortunately, I do not have access to a copy of the DC-10 Structural Repair Manual, so this is all I have to go on regarding its turbine reversers:

(Image by McDonnell Douglas, via the BEA [page 102, discussing a part which came loose from a different part of the CF6-50 engine, later resulting in damage to another aircraft]; modified by me.)

Other than clearing up the location of the turbine reversers (which wasn’t that much of a mystery to begin with), the diagram provides essentially nothing else in the way of information.  What sorts of mechanisms were used for the turbine reversers on these early high-bypass turbofans?  Did they use a target-type mechanism (the kind that one immediately thinks of when one hears the term “thrust reverser”, with the two big bucket doors swinging out into the airstream behind the engine), like those nearly ubiquitous on the older airliners equipped with turbojets or low-bypass turbofans?  Clamshell doors?  Something else?

1: I can think of one other potential problem; the core exhaust of a high-bypass turbofan is considerably hotter, less dense, and oxygen-poorer than the bypass air, and, thus, would tend to be more prone to causing engine surges were it to travel far enough forward to be reingested into the engine intake.  Even redirected bypass air (heated solely by the compression imparted by the engine’s fan) can easily cause an engine to surge (this is one of the reasons why the use of reverse thrust is not recommended at low speeds, the other biggie being the danger of the engine ingesting loose debris kicked up by the reverser airflow), and the much-hotter and somewhat-less-oxygenated core exhaust would presumably be even more surge-promoting were it to enter the intake; however, I do not, as of yet, have any solid evidence that this was a problem in practice, so this is pure speculation on my part (which is why it’s in a footnote, rather than the question itself).


texts: Do airliners stall first at the wing tip?

texts: One of the disadvantages of the sweepback aircraft is the tendency of a stall to occur at the wingtip first. Various high lift devices are added by design to the wings of the sweepback aircraft like Boeing and Airbus airliners to prevent or delay stalls, yet what happens if the aircraft actually stall? Do they stall at the wingtip first or at the wing root? Do the wings of these aircraft feature washout? If they do, is the washout great enough to prevent a wing-tip-first stall? How much washout do they have in degrees?


texts: What is the most efficient design for a human powered aircraft limited to 30mph at 100ft?

texts:
What is the most efficient design for an aircraft limited to a maximum velocity of 30mph at a maximum altitude of 100ft?
The objective is to minimize drag and weight.
The payload would be 1 human, and my budget is approximately 100,000 dollars (more can be done) for materials I was thinking airloys (because they are light and strong). The end goal is to go more than 74 miles on flat train using human power.

My guesses are aircrafts shaped like a sail plane or a Ground Effect Vehicles (GEVs).


texts: Who decides whether an airline docks at a jetbridge or parks at a remote stand?

texts:
A trip I took led me to wonder how airports/airlines decide when to allocate a gate and when to board out on the apron.

Yesterday, I flew TLV-IST-BOS on Turkish Airlines. At the start of the trip, I briefly wondered if we were travelling to Istanbul (IST) by bus. The airplane was parked far from the gate.

We got to IST, and, once more to ride the bus. In this case, we parked at jetway, but we were sent down the stairs and onto a bus. Turkish sure is a big, legacy airline at IST.

And, to complete the process, our A340 for Boston was parked half-way to Europe, and reached by a bus.

What determines all this? Bad luck? Plane size?


texts: What is this aircraft from ca. 1925 (crash included)?

texts:
I recently found the following family pictures from ca. 1925 and have been trying to identify the aircraft in them:

A second picture of the same aircraft was taken shortly after the first one:

Both of the occupants supposedly walked away unharmed - my guess is that confident look in the first image didn't linger.

Judging by the inscription on the top of the second image they were taken in Lausanne, Switzerland.

Bonus Question: Does the registration number of 85 mean anything in particular? For example, is this the 85th aircraft registered in Switzerland? Or the 85th aircraft of this type made by the manufacturer?


texts: Why does the B-29 have eight oil needles?

texts: In the image above, quiet flyer and I realized that there are 2 needles in every oil gauge, and there are 4 oil gauges. Well, why in the world are there 8 needles in total? And the optimal range arcs and redlines of each oil gauge is different. Why would that be? Oil is oil, I can't see how the optimal range arc for some oil in one gauge is different from the optimal range arc for some oil (same oil, oil is oil, the B-29 does NOT run on multiple oils. It isn't an eco-plane and it drops bombs. It has no need for more than one oil) Any thoughts would be great. Solving questions concerning something like dials and maximum speed with flaps extended for such an old plane have answers that are hard to come by, since they would have had to note this stuff down on paper and not electronically, and the people who built them are either very, very old; or unfortunately dead.


texts: Can we apply landing minimum with ALS when ALS is available with low intensity only?

texts:
Can we apply landing minimums with ALS when the ALS is available with "low intensity" only?

For example, the following NOTAM is issued at KABQ:

  !ABQ 05/270 ABQ RWY 03 ALS OUT OF SERVICE EXC LOW INTST ON CONS
  1705302145-1706151800EST

In this case, is the applied landing minimum for ILS RWY03 VIS 1/2 or VIS 3/4?

I'm talking about part 121 operator.


texts: Do helicopters ever dump fuel before landing?

texts:
In my answer to this question about fuel dumping I included the following rhetorical question:

  Or if you're dumping fuel from a helicopter (does that ever happen?)
  it could hover over a tank on the ground, pump out the fuel and then
  land.

Two commenters said that helicopters should never need to dump fuel because if they can take off with a full fuel load then they can land again. Makes sense, but this news story refers to a helicopter dumping fuel in order to land, although it's only one article and the general (non-aviation) press is notorious for misreporting aviation incidents.

So, can/do helicopters ever dump fuel as a safety measure before landing?


texts: How should the maximum output force of the actuator be chosen?

texts: If the hinge moments of the control surfaces of an aircraft are given, how should the maximum output force of the actuator be chosen? Is there any standard or reference?


texts: How to start to get in the field of aviation with degree of Computer Science?

texts: I am a 3-year computer science student and really want to go into the field of aviation, but not able to figure out what should I do at this point of time so as to have a career in this field.


texts: Has there ever been an commercial airplane with rear-facing seats?

texts: Has there ever been a commercial airliner that the seats have been facing rearwards? It sounds like rear-facing seats would be significantly safer. In addition, the procedure for rear-facing bracing (https://en.wikipedia.org/wiki/Brace_position), seems significantly simpler and more obvious than traditional methods.


texts: How much thrust and fuel are required to get a B767 moving from a complete stop?

texts:
How much thrust is involved, and how much fuel is burned, to get an aircraft like a Boeing 767 - or something similar - moving from a complete stop?

Recently, I was on a 767 that took the "scenic route" around the DFW airport trying to get to a gate.  We were on the tarmac for an unusually long time, and had multiple stops and starts.  I was curious how that might have affected fuel costs as opposed to a shorter time on the tarmac and a more direct path to our gate.


texts: Are the Sudan Airways A300-600 (ST-ATA & ST-ATB) stored in Khartoum?

texts: Does anyone know what happened to the last two A300-600R from Sudan Airways? They should be stored but where or are they already dismantled?


texts: Why is a small amount of smooth ice over the top of the wing more dangerous than an accumulation on the leading edge?

texts:
According to a Gleim study guide,

  "Generally speaking, smooth ice on top of the wing is more dangerous than heavy accumulated icing on the leading edge."

Is this true? If this is true, why?


texts: When can I descent below the MDA if the approach light system does not have red terminating bars?

texts:
Specifically, I'm a little confused about Sec 91.175(c)(3)(i) which states:

  The approach light system, except that the pilot may not descend below
  100 feet above the touchdown zone elevation using the approach lights
  as a reference unless the red terminating bars or the red side row
  bars are also distinctly visible and identifiable.

From what I understand, I'm allowed to descend up to 100ft above the touch down zone elevation (TDZE) if I'm able to see and identify the red terminating bars on the approach light systems (ALS).

However, what happens when the ALS does not have the red terminating bars (for e.g. MALSR and MALSF)? Do I maintain my MDA even if I have part of the ALS in sight?