texts: Why do pilots sample the fuel before a flight?

texts:
I was reading this checkup writeup and it says the pilot took fuel samples before the flight. So I Googled and found out, there are several fuel samplers/testers available.

Now I am wondering: Why is this necessary? Is it a mandatory procedure or do you just do this if you don't trust the supplier?

I can also imagine, that you check for water or contamination. However, we never do that with our cars.

Or am I completely off track?


texts: Are measures taken to deliberately increase the fuel burn rate to lower the landing weight?

texts:
Just recently the Air Canada flight AC837 from Madrid to Toronto had problems with the gear right after take-off and they decided to abort the flight and go back to Madrid. It was a B767-300 (C-GHOZ) which, AFAIK, cannot dump fuel so they circled approximately four hours southeast of Madrid in order to burn the fuel before landing:

(Source: Flightradar24, https://www.flightradar24.com/data/flights/ac837#23be1953)

Four hours is quite a long time and I wonder if the pilots actively do something to increase the rate at which fuel is burnt to somehow speed up the whole process. Like running the engines at full thrust and/or putting speed brakes/flaps in place. I don't know if they retracted the gear (which dramatically decreases the fuel consumption), but I doubt so because its damage was the whole reason for the circling.

If it matters: they circled approx. 1h @4500 ft and then approx. 2h 45m @7500 ft before heading back in Madrid.


texts: Do you have to lubricate the shock strut?

texts:
I have a school report about the lubrication on the shock strut and I was wondering if there is a specific type of lubrication they apply it on.

This is for Cessna 150-152


texts: How are modern jets modified to takeoff/land on a dirt runway?

texts:
I've been reading a lot about the Soviet and Russian military aircraft, and it seems a lot of them are built to work on dirt runways, or modified to do so.

How is this accomplished? Is it a simple thing to modify aircraft in this way? Is it just a matter of strengthening the undercarriage and upgrading the tires for more stress? Or is something harder involved, like maybe strengthening the fuselage frame?

NOTE: let's exclude worries about foreign objects going into the engines. Right now I'm only interested in the difference between paved and dirt runways as far as landing gear and strength are concerned.


texts: Do glow plugs face fouling? I understand that spark plugs foul on occasion, do glow plugs face the same issue?


texts: If a pilot's plane suddenly and unintentionally becomes inverted, what is the pilot's best course of action?

texts: If a plane was suddenly inverted through no action of the pilot, say wake turbulence from a much large plane (think 747 vs. Learjet), should the pilot first try to right the plane or get the nose pointed in the correct position so that the wings start producing lift again?I would think that a pilot would instinctively try to get the plane righted, but I wonder if this would be the best course of action, especially if there's not a lot of space between the plane and the ground. In trying to do so, the pilot could lose precious seconds that would otherwise be spent avoiding the ground. Though possibly counterintuitive, it seems like it would be best to get the plane flying, even though it's inverted, and then get it right side up.This brings up another question: are pilots trained how to handle an inverted aircraft? But I think it's a separate question.


texts: What does "Information " in ATC transmissions mean?

texts: When listening to ATC broadcasting (at least for ULLI), phrase "Information <Charlie|India|whiskey|etc.> on board" may be heard. Charlie, India, Whiskey, etc. refer to "C", "I", "W" but what do these codes mean? What kind of information is this?


texts: In India, what is the difference between "local flying area" and "airspace"?

texts: Can anyone define what is a "local flying area" and an "airspace" and what is the difference between the two? It would be good if the definition is as per Indian rules.


texts: What is the angle $\epsilon_{cl}$ in this diagram?

texts:
Here is an image showing the geometric significance of $\epsilon_{cl}$. To me it looks like the angle between the tangent of the underside of the trailing edge and horizontal (V infinity).

Here is a formula for $\epsilon_{cl}$:
$$ \epsilon_{cl} = \frac{1.62 C_{L_w}}{\pi A} $$
$C_{L_w}$ is the coefficient of lift of the wing and $A$ is the aspect ratio.


texts: Can you identify this old cockpit canopy?

texts: I stumbled across a cockpit canopy in the woods. What type of markings should I be looking for to identify this? And where exactly should I be looking for markings to identify this piece? Here is a photo of what I found.


texts:
ICAO Annex 14 recommends that "Runway centre line lights shall be provided on a runway intended to be used for take-off with an operating minimum of an RVR of the order of 400 m or higher when used by aeroplanes with a very high take-off speed, particularly where the width between the runway edge lights is greater than 50 m." (section 5.3.12.4).

I wish to know whether aircraft are categorized by take-off speed (like they are by approach speed), or which aircraft fall in the category of having very high take-off speed.


texts: What is the cooling air exhaust velocity for the piston engine of a propeller driven aircraft?

texts:
Piston engines of propeller driven aircrafts need to be cooled. There are engine cowlings which accomodate the inflow of air to "wash" over the engines within them and which is then exhausted out into the freestream.

The model in question here would be a single block engine in the cowling of a tracktor configuration propeller aircraft. The airflow enters the cowling, washes over the engine, and then exits into the freestream.

The question is:

What would be a good estimate for the velocity of this air stream exhausted into the freestream?


texts: How are airliners secured on the ground during hurricanes?

texts:
Say a major hurricane is expected to hit. Given that the weather is known beforehand, what can be done to avoid damage to the airliners sitting on the tarmac?

Fly every plane away - not very economical, considering that commercial operations cease at the last minute.

Move all planes into a hangar - a Boeing 747 takes a huge hangar to park. It may be possible to move all GA planes inside, but certainly not airliners.

Planes are designed to interact with winds; the wings is meant to generate lift, and the sideway forces on a vertical stabilizer is meant to swing a plane around. What procedures would minimize the stress put in the airframe by the 100+km/h winds?


texts: I need help to identify a group of planes, can someone help me?


texts: What materials are used for the gas bags in hydrogen airships?

texts:
I heard that to construct a hydrogen blimp or airship, the gas bag must be coated with aluminium, which got me confused: doesn't it add significantly to the weight? Is aluminium really used, and is there a specific reason to use it?

I'm also interested in knowing what is the best lightweight material in general for building an airship/blimp bags.


texts: I am studying Aircraft mechanics currently, and in our academy we have some aircraft engines and different types of them, and I need please your help to know the reference of one of them, and if it is possible the engine manual of it, because it is essential for us to study it deeply.


texts: How does the F-35's roll posts work, and how does its engine turn down 90 degrees?

texts: I've heard about the F-35's roll posts but I don't get how they work and how its engine turns downwards 90 degrees, any ideas?


texts:
Consider the following hypothetical scenario:

An MQ-1 Predator pilot sees an Su-27 closing in from straight ahead for a kill. The pilot prepares to write up his 10th loss of the week when he has an idea: He targets the Su-27 with the laser designator and fires two AGM-114 Hellfire missiles.

Would this work? Can Hellfire missiles be used effectively as air-to-air weapons?


texts: What are various specifications of Engine oil used in Piston and Turbine engine aircraft?

texts: I only know of two types MIL-O-7808 and -23699. Is there anything else ?


texts: What is this? Multiple small cracks in passenger window

texts: I have seen this many times in typically older aircraft passenger windows and on a recent flight from Sydney to Melbourne I took the following pictures. It appears as if there are small cracks in the window or one of the laminate layers used to construct the windows. Could anyone shed some light on what is the cause and if there is any risk?


texts: When do controllers assign a squawk code to VFR aircraft in Canada?

texts:
In all of my previous flying experience the controllers provided a squawk code only when I requested flight following. On a recent flight from Buttonville, Ontario (CYKZ), the controller provided a squawk code on the ground. I asked if she was providing a squawk code because she was going to provide flight following as well. She said the flight following will need to be requested after she hands me off to Toronto City Center.

Then why was the squawk code provided? Was the controller anticipating the need for a squawk code? Are all airports in the Toronto region required to provide squawk codes to departing flights?


texts: How to navigate onto VOR RWY 18 approach at KDEC?

texts:
Maybe a dumb question.  I've seen a few places where a VOR approach doesn't have an obvious (to me) way to get lined up inbound without radar vectors.
Say you don't have GPS and you're navigating with VORs.  You'd like to do the VOR RWY 18 approach to KDEC, and you're coming from somewhere north of the AXC VOR the approach is based on, like the BMI VOR for example.  How would you get yourself established on this approach without radar help?
It seems reasonable to me to fly (off-airway) R-180 outbound from BMI and intercept the approach course of R-349 inbound to AXC.  However I'd heard (though don't have any regs to back it up yet) you can only transition from enroute to an approach based on a fix that appears on both charts.  So I suppose you can't essentially vector yourself this way with the off-airway R-180.  Is this true?  If so, I'd be super grateful for a FAR/AIM reference if you know it!
So then what fix appears on both the enroute chart and the approach plate?  Only AXC is on both.  But if you fly directly to AXC from BMI then you're facing the wrong direction.  You'd be incoming on roughly R-352 and then need to turn around and fly outbound on R-349.  A HILPT would be just the thing on an approach, but here we wouldn't be on an actual approach yet and I haven't heard of them being used outside approaches.  Would you do a HILPT at that depicted hold, or just hang a uey here, or is neither really right?
As I said, maybe a dumb question, but it's stumping me.  Thanks for the help!


texts: How do instructors simulate instrument failure in basic training aircraft with glass cockpits?

texts:
While working towards my private pilot's license in the United States in 2004-2005 (in a steam gauge only airplane), I very much remember my instructor covering one or more instruments to simulate failure and recovery techniques.  He used covers which are commonly available in pilot shops:

I don't remember the examiner asking me fly under such conditions, but this type of failure is covered in the FAA PTS both for private and commercial.

Now that more and more pilots are training with glass cockpits, I was wondering how covering instruments the same way would work.  For reference, let's take the Garmin 1000, standard in the Cessna 172 Skyhawk, which I have to guess is one of the most common civil aviation trainers:

I am, of course, assuming it would be much more difficult to cover the altitude indicator, airspeed indicator, artificial horizon, etc. on a glass cockpit display, not to mention being a questionable practice on a multi-thousand dollar LCD screen.

Then it occurred to me that perhaps the glass cockpit manufacturer would just provide the ability to temporarily disable specific instruments.  But (at least for the G1000) I did not find this feature in the manual.

To summarize, my question is, how do flight instructors/examiners simulate the loss of one of the "six pack" flight instruments in an airplane with a glass cockpit?


texts: Why do the ratio of proppeler plane over jet engine seems to have change in Bucarest airport during the covid19 crisis?

texts:
I live in a village very close to an (intl) airport: Bucharest "Henri Coanda" International Airport.
Now, due to lock-down caused by covid pandemic, I noticed - at least today when I spent most of the time outdoors - that all planes that flew over/around our location were propeller, none of them was a jet-plane.

Companies that normally operate flights on this airport: KLM, WizzAir, Alitalia, Delta, Aegean, Air France, Tarom, etc.

The main types of aircraft that normally operate on this airport are: A318, ATR42/72, B737, etc.

Do you have any idea why only propeller-planes these days?
I don't think it's a coincidence or just an impression, so I guess there must be some logical explanation.


texts: Do stealth designs have canard configuration?

texts: Do stealth-focused aircraft have canard configuration? I believe canards have a negative impact on the radar cross section.


texts: To a pilot, does turbocharging differ from supercharging?

texts:
When it comes to operating an aircraft, what are the practical differences between a turbocharged engine and a supercharged engine? I'm aware of the mechanics - turbochargers being exhaust-driven, while superchargers are mechanically driven - so I'm looking for the differences in how pilots need to treat the systems:

Do power settings need to be set differently?
Are temperatures more of a concern with superchargers?
Is it easier or harder to overboost a supercharger? If you do, are there waste gates?
Do engines with superchargers need a cool-down period before being shut off?
Any other operational differences that would be meaningful for pilots to know.

Similarly, what are the ownership implications of any differences? Does one cost more to maintain than the other due to the way they are constructed? Will a supercharged engine have a lower TBO because of the mechanical aspects of the system, or will it be the same as a turbocharged engine?


texts: What is the proper technique for using rudder pedals with toe brakes?

texts:
I just had my first flight lesson the other day and I had some issues with using the rudder pedals and toe brakes for taxiing.  For example, how do you steer and brake at the same time when making turns?  I also sometimes inadvertently press the toes brakes when trying to steer the plane. Is there any advice that you can give me to help me coordinate steering with toe brakes? I find that steering the plane on the ground with the rudder pedals is quite foreign to me, I have never had to use this level of foot coordination before.

I am flying a Piper Cherokee with steerable nose wheel and toe brakes.  Also does anyone else have this problem or is it just me?


texts: Since they are essentially an annular wing, how much do they contribute if at all to an aircraft's total lift? Would the effect of this lift be noticeable enough to help cancel out the drag they produce?


texts: Telluride (KTEX): Why is the localizer antenna located where the glideslope should be?

texts:
Telluride (KTEX) in Colorado, USA:

Source

As visible, the localizer antenna for RWY 09 is located where the glideslope antenna is usually found, abeam the touch down zone. The localizer is normally seen at the end of the runway, aligned with the runway center line.

Why was the localizer moved close to the TDZ at Telluride airport?
What is the practical impact for the pilot to have the localizer beam distant from landing path?


texts: On a axial flow turbo fan or turbo jet engine what comes first the rotor or the stator?

texts:
I've been let to understand that one stage consists of a row of rotors and stators. But I'm not sure which comes first? Does the front fan blades make the first part of the stage (rotor) with a stator section behind? And so on.. Or on a fan engine with a booster the first stage is the stator and then rotor (after the fan blades).
Secondly do all engines have inlet guide vanes? I'm assuming not or we would physically see them in front of the the big fan engines or do they appear later on.. Maybe in the HP section?

Hope this makes sense and any images with an explanation would be appreciated.

Thanks


texts: Definition of aircraft longitudinal axis?

texts:
I know that longitudinal  axis connect nose and tail, but at what exactly point?
What definition says?
I have a glider and I want to draw with pen longitudinal axis to measure angle of incidence  for wing and stabilizer, but I don't know where exactly I need to draw longitudinal axis.

Is airflow parallel with longitudinal axis during cruise, for well design real aircraft(to reduce fuselage pressure drag)?


texts: Could someone give me a simple working of a propfan? Also I've heard the 2 sets of blades in a propfan rotate in opposite directions. Is this true? And if so why?


texts: What is the difference between a rating and a certificate?

texts:
I did some research on what it would take to become a private pilot. I am totally green to the aviation world, so bear with me on my question.

I see the licenses also referred to as certificates but I also see the term "rating" listed on many things like "twin-engine", "turbo-prop", etc.

So what is a "rating" vs a "certificate"? Am I over-thinking this?

I'm referring to US regulations.


texts: What are the flight training options for a private pilot's license in the US?

texts: In the USA, what training options does a student pilot aiming for their private pilot license have?


texts: Why do most airliners have underwing engines, while business jets have rear-mounted engines?

texts:
Why have modern airliners converged on a configuration with two or occasionally four underwing engines, while modern business jets have converged on a configuration with two or occasionally three rear-mounted engines?

I am of course aware of the many past airliners with rear-mounted engines, with the DC-9 and MD-80 and later derivatives continuing into production until rather recently, but it still seems fair to say that the underwing configuration dominates modern airliner design.

Meanwhile business jets exclusively use the rear-engine design, unless one counts small airliners put into business service such as the Boeing Business Jet.  Does the underwing engine design simply not scale down well to something the size of a smaller business jet?

Here's a related question with good answers but still doesn't really answer my question-- How does the mounting location of a jet engine affect aircraft performance?

One key factor now occurring to me is that business jets are boarded with self-contained airstair doors/ steps so a fuselage sitting high off the ground would be problematic.  Airliners with long fuselages perhaps may need rather long landing gear to provide adequate ground clearance for rotation anyway-- although the DC-9 / MD-80 with its wing and landing gear far to the rear did sit rather low to the ground-- still in the airliner situation perhaps there simply is not as much benefit to having a low-sitting fuselage as there is in the business jet situation.

Of peripheral interest is this Wikipedia article on "airstairs", pointing out some cases where full-blown airliners are equipped with airstairs.  One of the more interesting lines is:

  The most unusual airstair design was found on the Lockheed L-1011,
  which was a full-height airstair which was stored in a cargo
  compartment and allowed access from the right aft passenger door to
  the ground. This design was ultimately so large and heavy, and it took
  up valuable cargo space, that it was rarely used.


texts: Is excess power always increasing with a decreasing altitude at iso-mach?

texts:
For an aircraft with a jet engine, let's say the power margin at M1.5 at an altitude Z1 is x.
Is the power margin at a lower altitude Z1-H at M1.5 always greater than x ?
From my point of view, there are two adverse effects going on :

For the same Mach at a lower altitude, IAS is greater, drag is greater, and thus the thrust necessary for SLF is greater (power margin reduces)
At lower altitude, the thrust produced by the jet engine increases (and so does the power margin)

Is there a general rule for jet engines to answer the question or is it highly engine-specific ?
Thanks


texts: Is it normal for the flaps to move like this?

texts:
I noticed this particular portion of the flaps moving differently from rest of the wings. In the attached picture, the middle flap is raised. Is this considered normal?

The landing and takeoff in this flight was normal, but the flaps moving like this made me a little (lot) uncomfortable! I've added a video, as well.

Video on Youtube


texts: Why is flutter a function of true, not indicated, airspeed?

texts:
I am learning about gliders in preparation for an exam. It says in the textbook I am reading that for a glider, you use indicated airspeed for most relevant speeds (stall speed $V_s$, best glide speed $V_{BG}$ etc). However, $V_{NE}$ should never be exceeded in true airspeed. As far as I can tell, this is because flutter depends on true airspeed rather than indicated airspeed. (Let me know if this assumption is wrong, because that would make the title wrong.)

Why is this the case? Is flutter somehow related to the speed of the air molecules, rather than to the energy provided by them?


texts: Why don't some airlines assign seats to passengers?

texts:
Why don't some airlines (for example Southwest in US) assign seats to passengers? How does it help them? Doesn't it delay the boarding (passengers going back and forth inside the plane to grab their favorite seats)?

Are there any studies to show that this is a better method? Or is there any technical reason why some airlines does this while others do not?


texts: Is gravity less on an airliner at cruise altitude?

texts:
Is the force of gravity less on an airliner at cruise speed and altitude? I'm not talking about a special reduced gravity flight with a parabolic flight path, just a typical long distance flight.

Seems to me there should be less as passengers are further away from the centre of the earth, and also possibly a tiny effect from the speed the plane as it travels round the curve of the earth (altitude remaining constant) but does anybody actually know how much less?


texts: What is the maximum number of infants allowed on a flight?

texts:
Is there any authority regulation which limits the maximum number of infants allowed on a flight?

Some airlines set a limit at 10% of total seats, some airlines have a different limit. Normally, the number of extra oxygen masks is much higher than 10%.


texts: Please provide some expert commentary to the aborted flight of the German chancellor

texts:
This week the German chancellor's plane (an Airbus A340-300) had to abort the flight due to loss of communications. The newspaper write they only had a satellite phone left1:

  Die Kommunikationssysteme waren ausgefallen, sodass kein Kontakt zum Boden möglich war. [Der Pilot] musste deshalb per Satellitentelefon mit dem Flughafen Köln/Bonn die ungeplante Landung vorbereiten.

  The communication systems failed, contacting the ground wasn't possible.  The satellite phone had to be used to prepare the landing.

  Man gehe derzeit von einem Fehler in einer elektronischen Verteilerbox aus, die sowohl die Funkanlage als auch das System zum Ablassen des Kerosins steuere, hieß es von der Luftwaffe.

  Currently an error in a distribution box is most likely.  The box services the radio as well as the fuel dumping system.

Is the antenna for the satellite uplink an integral part of the air plane?  As suggested here for WiFi.  I assume satellite phone doesn't work from inside the plane without an external antenna, is this correct?

Maybe this is nitpicking, but when the satellite phone is build into the airplane, with the necessary tracking, why is this not considered part of the communications system?

How come that seemingly crucial yet quite simple two way radio can fail and is not powered by some very basic passive turbine?  How much power is approximately required by the radio?


texts: How does the ground effect affects longitudinal stability?

texts: I recently learned that the ground effect increases the effective AoA of the wing and thus increases lift, how does that translates in to the tail plane and it's stabilizing effects? does it reduce/increase stability?


texts: What is the 'fuel cost' of a pneumatic braking system vs. a hydraulic one, in terms of weight?

texts:
A pneumatic braking system has indisputable advantages over a hydraulic braking system for large and heavy aircraft in terms of braking force and secondary perhaps in terms of weight (pipes and hydraulic fluid). However it requires engine input to compress the air and generate the pressure and force required for braking, all of which use fuel.

What is the cost of a pneumatic braking system from a fuel point of view as opposed to hydraulic in relation to weight for a large Jumbo like the Airbus A380 or Boeing 747 if one had to consider using hydraulic brakes for any of these aircraft?


texts: Why are so many tail-strike incidents not verified until later inspection?

texts:
One often reads of a "suspected tail-strike" at take-off (for example suspected because a controller has seen something from the tower, or because a cabin crew member sitting at the back of the plane has felt a jolt or heard a noise).

What puzzles me is why this must remain merely "suspected" until an inspection.

As an example, a 737 suffered a tail strike that appears to have at least been considered a possibility by the crew. Apparently doubting that it actually had occurred, the flight crew continued to their destination; had there been a clear indication, they presumably would not have.

Aircraft are festooned with external sensors and measuring devices; I would expect aeroplanes susceptible to tail strikes to have sensors measuring movement of, deformation of or contact with a plane's skid plate, to provide a cockpit alert, so that there need not be any doubt.

Since this often doesn't appear to be the case, there must be good reasons why such systems are not usefully employed - what are they?


texts: How can I find information about the aircraft with registration / tail-number N58644?

texts: I am trying to find information on aircraft N58644 which doesn't show on the N number listing. This is a BT-13A converted to civilian use from the 40s or 50s. Any ideas where I can get any information since the FAA doesn't show it?


texts: What exactly is an ATC clearance and how is it requested?

texts:
What exactly does it mean to get an ATC clearance?
I’m asking the question because I read point 8015 of the Standardised
European Rules of the Air (SERAs), which states that ATC clearances are requested by submitting a flight plan. I always thought that this was done by a radio-request when asking for start-up (at least for IFR-flights)...
And what does it exactly mean to get certain ATC instructions during the flight (for example in the case of vectoring)? Are these amendments to the initial clearance or do I mix something up?


texts: Is the US certification process for airliners shorter or longer than in other countries?

texts:
I was researching information regarding the competitiveness of different government certification organizations (FAA, EASA, etc) and the processes (Amount of time, costs, etc) to get their nations aircraft certified and flying.

Is the certification process to get a US jet manufacturer's product into the hands of its customers shorter or longer than other countries?

From what I've found so far it seems GAMA and other US aviation entities are trying to help shorten/simplify this process in the US. This leads me to believe we are at a competitive disadvantage, but I haven't really found any data to back this up. Any direction helps.

Countries/manufacturers that I have been comparing to the US are: Bombardier (Canada), Embraer (Brazil), Dassault (France), and Airbus(France).


texts:
Most (all?) aircraft have a Pitot Heat Switch which must be turned on in certain conditions.

Seems Pitot Heat is one of those things you don't want to forget to switch on when it's needed, or worse, not recognize you need it on and take action based on false readings.

The pre-flight checklists I've read always say something like:

Pitot Heat - As Required

Why not always have it on? Or not have a switch and it just comes on with the aircraft's other power systems?

Is there a downside to it being always on?


texts: How do contrails compare between piston-powered aircraft and jet aircraft?

texts:
Based off this question, I got interested on how contrails compare between jet engines and piston powered engines.

Seeing images like these from WWII, I am wondering what the significant differences are in the contrails made by the two different kinds of engines.

Image Source


texts: For a Part 61 IFR rating, how much can be done alone on a simulator?

texts:
Per Wikipedia:

Requirements for Instrument Rating in the United States are listed in section 61.65 of the Federal Aviation Regulation[2] are:

50 hours of Pilot in Command cross country
40 hours of simulated or
actual instrument time
15 hours of flight instruction towards
Instrument Rating

Does this mean that 40 hours could be done on a simulator alone or does that overlap with the 15 hours with the instructor?


texts: How to correct a roll due to turbulence?

texts:
I fly a Piper Cherokee 180 (PA-28-180) in an area that has frequent turbulence. When turbulence causes the aircraft to roll to one side I usually try to correct by using aileron and rudder in the opposite direction of the roll.

However my flight instructor says that I should use rudder only to correct for the roll. I can get the wings level by using only rudder but it seems to me that using aileron and rudder would be the most effective method. Can someone please explain to me why I should use only rudder in this instance?


texts: How does the head-up display on a spitfire work?

texts:
It turns out that the Spitfire from World War 2 had a head up display.
Does anybody know how it worked exactly?

All I could find was this picture, but no explanation:

Source

The source does not explain what it does.

Seeing as it is projected, it would only be of use if it were dynamic, that's why I'm asking.

How could they have something like that back in the day?

Edit: Not a duplicate, not all sights were gyro sights.


texts: What component of an aircraft is most likely to fail?

texts:
Given how rare airplane component failures have become today, I'm curious, are there still any components which are commonplace on aircraft, but still see a high failure rate? If so, why are these components used?

If not, are there any specific regulations to prevent this kind of thing?


texts: What is the purpose of the Boeing SCAP module?

texts: The Boeing SCAP module will be used to calculate the takeoff and landing performance data. But what exactly does the Boeing SCAP module contain and how is it used to calculate takeoff and landing performance for the aircraft?


texts:
From the USAF c. 1955 training film No Sweat, there is a technique called 'steer'. By pressing the PTT button for a few seconds, the tower controller is able to determine the pilot's bearing.

What airport equipment was used to get the bearing of the signal?
Did it work with HF, VHF, and UHF? Or only one of those?
Was this technique available to the civilian/commercial pilots flying to civilian airports?

I've searched for USAF manuals and Flying Magazine issues from that era, but came up empty.


texts:
I read this question about diesel-electric (DE) helicopters, which sparked the following question:

Are fully electric helicopters suitable for military operations?

They are more silent, and electric motors are lighter than combustion engines. Would the only drawback be battery weight?


texts: What the weather condition can affect for flight?

texts:
What is the most disturbing weather conditions for flight?
On another word: what more dangerous for takeoff/landing: wind, precipitation or something else?


texts: Is there a benefit to having the motors for a multi-rotor copter on the top vs the bottom of the frame?

texts:
There is a new quadcopter being launched on Indiegogo that has the quadcopter motors positioned on the top of the propellers as opposed to being positioned on the bottom.

Is there any advantage to this or is it just for looks?


texts: Why is the take off speed and distance reduced by head winds?

texts:
A headwind of 20 knots and a true airspeed for the take-off safety
speed being 120 knots, the ground speed is only 100 knots.  Getting to a true ground speed of
only 100 knots will require less distance.

Anyone can explain to me is that mean that the distance for take off will be less and also the take off speed will be less?
�


texts: What is the difference between centripetal and centrifugal force?

texts:
In a homework problem I was asked:  In a balanced banked turn an increase in angle of attack will :?

Answers are :
1/ reduce indused drag.
2/ increase centripetal force .
3/ increase centrifugal force .
4/ have no effect on the turn.

Obviously answer 1 and 4 are wrong but what about centripetal vs centrifugal force?  What is the difference between the two?


texts: Are there risks if the side joystick must be handled with a pilot's weaker hand?

texts:
Suppose that a first officer were left-handed and a captain were right-handed. Both are NOT ambidextrous. Even after training, what if their weaker hands' control and  degree of versatility
remain worse than their dominant hands'?

In other words, in commercial (and not just military) cockpits, joysticks (on the side) must be grasped with only one hand. But does this fact presuppose or require perfect ambidexterity?


texts: How does the location of a propeller affect an aircraft's stability?

texts:
Some aircraft possess propellers on front of the fuselage, like the Cessna 172, and some aircraft have propellers located at the rear of the fuselage, like the Velocity 173RG-E.

How does the propeller's location affect the aircraft? Why don't we see back-propeller planes more often than front-propeller planes?


texts: How precise must a pilot be when flying a holding pattern?

texts:
When ATC asks a pilot to fly a holding pattern, he expects the airplane to stay at the required altitude in the sector of the holding pattern.

For the vertical direction, the question is straightforward: how much can the aircraft deviate from its assigned altitude?

For the horizontal direction, the question is more tricky: can the pilot fly a larger than standard holding pattern (lower turn rate, straight legs twice as long as expected)? What happens if on the contrary the pilot flies the pattern in less than 2 minutes?

Bonus question: what prevents the pilot flying an 8-shape instead of an oval one if he stays inside the holding pattern area?

EDIT: my question is really about the limits. It is obvious that a deviation of few millimeter or less than 10 seconds is OK, but at what point does it start to be not allowed (in other word, what is the precision required)?

To better understand the problem I want to address, my comprehension is that as long as you stay in the assigned sector, separation is ensured without any ATC intervention. Thus, I see no added value to be as precise as possible as long as you stay in the assigned sector. You may circle closer to the holding point, the separation will still be assured. But what happens if you fly farther away but still in the assigned sector? And what happens if you fly a non standard shape but still inside the assigned the assigned sector?


texts:
I have read people's stories that they landed their small planes (e.g. C172) on bigger airports. They strongly recommended landing at a higher speed and without flaps as the runways are quite long, and there is traffic behind them.

Hence, if I want to land an airplane at higher than recommended landing speed (e.g. VS0):

How fast can I go?
What is the procedure to do this?
What consequences are there (good or bad)?


texts:
Why do older planes not have a middle hand luggage compartment?
Where are the oxygen masks for the people in the middle rows?

L-1011 Interior:

777 Interior:


texts: Is there a "maximum" airplane count in the visible sky at a given location?

texts:
At night, I look at the planes in the sky and count them. I can normally spot between 2-5 planes, never more.

As the visible sky is always a constant area and there are security distances and aerial ways, is it possible to use a formula/approximation to determine the maximum number of visible planes in the sky?

Assume horizon to horizon visibility.

EDIT - Note to all those who spent some time for me

I didn't imagine this question would be such broad... this was just a though I had last night in my garden.

So, I have no idea how to be more precise... I learned some things of your comments, I am now reading some articles to learn what all that means (new words, moreover in English), and I will enrich the question some further day.

Thanks to all !


texts: Which language is used to develop new aircrafts' avionic systems AI?

texts:
As an airframe and powerplant maintenance student, I also want to get an avionics license. My main goal is working on artificial intelligence of aircrafts avionics. However I'm concerned about the right language which I should work on. I've been learning Python with OOP for a long time (it was someones advice) but I think I should switch to C++ or Ada.
Honestly, I want to continue with Python but nowadays I have almost no motivation about it. Any advice for my roadmap? Thanks a lot!


texts: What ATC entities does a commercial airliner communicate with?

texts: As a private pilot, I am familiar with tower, ground, approach and departure control, but I am aware that there are other entities like clearance, pushback and center. If I were flying a commercial airliner, what is a complete, ordered list of entities (and a brief description of roles) I might talk with over a flight between two class B airports?


texts: What aircraft manufacturer uses an HSI with DME, VOR, and G/S in one Instrument?

texts: Which aircraft manufacturer uses a horizontal situation indicator (HSI) with DME, Glide Slope, VOR, and ADF in one Instrument?


texts: Why there is such a strong correlation between the range of an airliner and its passenger capacity?

texts:
Why we rarely see an A320 (or equivalent aircraft) on a long route with all premium business seats or an A380 (or equivalent aircraft) with high density seating and on a short route?

On top of that, it is a much easier task to design a long range light aircraft and a short range heavy/high capacity aircraft, so why have no airliners (as far as I know) ever been designed with these characteristics in mind?


texts: What does the letter J mean at the start of an FAA instrument approach chart identifier?

texts:
To identify a specific Instrument Approach Chart in either the FAA Terminal Procedures Publication (TPP), or the Department of Defense (DoD) Terminal Low Altitude (TLA) Charts, the FAA uses what they refer to as an internal numbering system.

This identifier on any given approach chart is found in the center of the top margin information area and includes two letters, A and L, followed by three or four numbers, followed by the approval authority for the chart, i.e.: AL-571 (FAA).

Found in the FAA Terminal Procedures Chart Users Guide and the general information legend in both the TPP & TLA, the "AL" stands for "Approach and Landing", however, on a high altitude approach chart, the AL is proceeded by a "J", i.e.: JAL-685 (FAA).

Does anyone know what the "J" stands for?

The chart users guide does not identify its meaning nor can I find any reference that addresses it. My assumption is Jet...but I would prefer to confirm what it stands for.


texts: What are those things at the wing tip of an aerobatic aircraft?

texts:
See:

The radially placed needle-like things that resemble a snowflake in the first picture.
The triangular structure in the second picture.
In the third picture, the object placed on only one wing
In the last one, it's also placed on one wing but this one is perpendicular.

What are those things?


texts: Do ailerons on opposite wings move together?

texts:
It seems nicely symmetrical that opposite ailerons would be locked togther, so that when the left wing's ailerons move up, those on the right wing would move down, by the same amount and at the same speed.

Is this in fact generally the case on aeroplanes? Or can they be moved independently, or at different rates or to different positions (and what advantage would that offer)?

Finally, are there any aeroplanes on which they can be moved in the same direction?


texts: Can you identify this scrap cockpit section I found in a scrapyard?

texts:
I recently found a scrap cockpit in a scrap yard, and I'm hoping there's enough remaining to identify the aircraft type from pictures.
Unfortunately, all are taken through fencing as I don't have access to the compound.
Imgur Link


texts: How many aircraft can airline put in hangar?

texts:
Another question talks about aircraft movement in and out of hangar.  Most hangar I see at commercial airport I see one aircraft per hangar.

This makes me wonder how many aircraft can be kept in the hangar depth-wise(ie nose-to-tail direction)? Is larger hangar common?

Note: please do not include special hangars such as those at Airbus or Boeing facility in main answer but side note about those are welcomed.


texts: Can a passenger drone perform auto-rotation?

texts:
(Source)

The Dubai Drone is an Ehang passenger drone planned to start commercial services in July 2017.

If there is a failure, can such an electric multi-copter auto-rotate a landing?

I'm wondering, if an electric motor would even allow auto-rotation, and if the autopilot could handle it? Are there regulations for devices like that?


texts: What happens if a pilot uses left rudder during a turn to the right?

texts: What happens if the pilot turns to the right using ailerons but then simultaneously applies left rudder? I'm asking about a large aircraft e.g. Boeing 747-800 or Airbus A380, or any other aircraft. If there are any negative effects, what mechanical or other measures are in place to avoid this (besides strict training)?


texts: What is the difference between RAIL and SFL lights?

texts:
What is the difference between Runway Alignment Indicator Lights (RAIL) and Sequenced Flashing Lights (SFL)?

Both of them are same in terms of flashing light.


texts: Can you be paid to taxi an aircraft if you don't have a commercial license?

texts: From a strictly legal standpoint, in the US (I'm also interested in Canada) can you (not should you) accept compensation to taxi an aircraft if you don't have a commercial pilot's license? If I was a mechanic with just a private license, could I charge for my time while taxiing an aircraft?


texts: What would happen to the rudder on an A320 if both FAC systems failed?

texts:
What would happen to the rudder of an A320 if both Flight Augmentation Computer (FAC) systems completely failed during mid-flight? Would the auto pilot immediately pass control back to the pilots or if they  failed would that be it? Would it be impossible for the cockpit to communicate with the mechanisms which control the rudder or is manual operation possible in an A320?

Also, I know this maybe a more difficult/impossible questions but what would cause the malfunction of one of the FAC computers? Are there any likely scenarios or previous cases?


texts: Can I be a pilot now considering the new advancements in color vision lenses and glasses?

texts: I have always wanted to be a pilot but I am red/green color deficient. I passed all other physicals and can easily tell the difference between red and green. I only discovered I had a deficiency after I failed the Ishihara Plates Test (the one with circles of dots with numbers). So I opted for Military Police instead of flight school. However, now color vision contact lenses and glasses are available with a 100% success rate after testing with the Ishihara Plates Test. Does this open any new doors for color deficient applicants in flight schools? I can't find anyone that has answers. Thank you.


texts: What are the advantages and disadvantages of an oblique wing over a swing wing?

texts:
This question asks about the benefits of an oblique wing over a delta wing, but I am more interested in the benefits of an oblique wing compared to a swing wing.

Wikipedia states:

  This is a variation on the classic swing-wing design, intended to simplify construction and retain the center of gravity as the sweep angle is changed.

But I'm pretty sure there are a lot more advantages or disadvantages, in terms of stalling behavior (forward swept side inboard first, aft swept side outboard first), aircraft control etc.

Related: What are the advantages of a forward-swept wing over a rearward-swept wing?


texts: Can an aerodrome in class G airspace be controlled?

texts:
Can an aerodrome be controlled, even if the only associated airspace is classified G?

E.g. can such an aerodrome have a control tower with the authority to give takeoff and landing clearances and taxi instructions?

I know the opposite is possible (uncontrolled aerodromes in class D airspace for example).

I am not asking about AFIS aerodromes, since AFIS is not an air traffic control service.

Please provide examples and/or references to ICAO SARPs or national regulations.


texts: How do airliner manufacturers come up with typical capacities of their planes?

texts:
Instead of providing the maximum capacity of a particular model, airliner manufacturers often provide official typical capacities, like 280-366 seats for A350 series and 350/400seats for Boeing 777x series.

The question is: How do they generate this number?


texts: What is the typical cruising altitude for a civil airplane?

texts:
I'd like to know the interval of altitudes airliners usually cruise at (and its reasons)? And if there are international restrictions about this?

Also I read somewhere that recently about a restriction that airliners should not fly bellow 26000 ft over egypt. How hard that restriction would be?


texts: What are the repercussions of flying an aircraft with an invalid N number on the side?

texts: I have requested a new N number for my airplane a few months ago. Thinking the change would come through I had my airplane painted with the new number. What will happen if I fly it without the number being authorized?


texts: How do I calculate new minimal speed for a glider when I put water into the tank?

texts:
Lets say a glider weights 400kg and has a minimal speed of 70km/h.

When it has additionally 100l water, so in total 500kg, what is the new minimal speed?

I would argue, that in order to reach the same point in the polar diagram, we have to scale according to

$v_2 = v_1 \cdot \sqrt{m_2/m_1}$

because drag and lift forces scale quadratic with speed.

The result would be 78km/h.

However, in the theory we learn

$v_2 = v_1 \cdot m_2/m_1 = 87km/h$

Q: Isn't that wrong?


texts: How are sensors in the wheels connected to power and data buses?

texts:
In this question the sensors to measure the tyre pressure are described.

But how do such sensors receive the electrical power they need, and how are the signal values transmitted back to the relevant computer systems?

Since the wheel rotates, one would presume that transferring power and data electrically with the reliability needed for aviation use would pose specific demands on the technology.


texts: Can anybody give an example about Clearance Expiry Time?

texts: Clearance content is included: callsign, flight path, clearance border(destination aerodrome, available report point, controlled airspace border), flight level along the route or for a specific part of the route, etc. and end time of clearance or clearance expiry time. Can you give an example of a clearance expiry time? How does it end, is there any specific time that is notified by air traffic controller to pilot to pass some specific point? How is it said? can you give me a clearance example?


texts: Is it a good thing that ailerons remain deflected and the stick is hard to move?

texts: The aileron stick of my homebuilt ultralight is stiff (hard to move) and the aileron itself can remain in its deflection angle hands free, is that a good thing?


texts: Is it possible to control a drone with a link mediated by the cellular phone network?

texts: If that were possible, it would allow an operator to control the drone from a very remote place, and without resorting to satellite radio links, as military drones do...


texts: Aerobatics in "firm" IMC -- how would one do it?

texts: Assuming you are aerobatically trained, IFR rated, have an aircraft that is rated for the aerobatic maneuvers you are planning to perform (let us assume that it is acrobatic category, even), and the aircraft in question is type certified and equipped for flight under IFR, how would you plan out and safely execute a set of aerobatic maneuvers in IMC (think solid cloud, but without serious up/downdrafts, icing, or lightning hazards) while flying under IFR?  Can you define a "box clearance" in an IFR flight plan, akin to a VFR aerobatic box, only defined by coordinates or intersections instead of ground reference points?  How feasible is it to carry out the Aresti catalog maneuvers by reference to flight instruments alone?


texts: Why can't we use APU bleed air for wing anti ice on the A320?

texts: The question says it all. While reading I came across this that we can under no circumstances use APU bleed air for supplying wing anti ice? Any reason?


texts: Mechanical vs Pneumatic Stall Warning Systems

texts:
Light Cessna aircraft - at least the high wing single engine line - have commonly made use of a solid state pneumatic stall warning system.  The system is fairly unique to Cessna airplanes and makes use of the fact that negative pressures form over the leading edge of the wing near the critical angle of attack, causing a reverse flow of air through the warning system and causing a horn in the cockpit to sound.  Most other light aircraft make use of a movable tab with activates an electric switch when depressed by airflow near the critical AoA, causing a chime, horn or other aural cue in the cockpit alerting the pilot to an impending stall.  Here's the question:  What are the pros and cons of each of these systems?  From brainstorming, I can come up with the following:

Pneumatic Stall Warning Systems:

Pros:

Solid State; has no moving parts which can break or become immobilized or altered by neglect, damage or airframe icing.
Does not require electrical or other sources of power from engine or elsewhere to work.

Cons:

Orifice can become blocked by FOD or airframe icing, causing the system to become inoperative.

Mechanical Stall Warning Systems:

Pros:

Simple operating and mature technology.
Can be electrically heated to prevent immobilization by airframe icing, though this is not always the case depending on the aircraft.

Cons:

Moving parts which can break.
Tab can be bent by maintenance or neglect, causing system to operate erroneously and give false readings.
Can be immobilized by airframe icing, rendering the system inoperative.

Can anybody think of other pros and cons for each of these systems?


texts:
This plane's ground speed looks slower than a person's walking speed, maybe 10km/h!? It can not be possible that an airflow of 10km/h around wings keep plane in the air.
What is the key for such a slow flight?
a) head wind
b) blast from propeller make additional lift at wings
or
c) maybe propeller upward thrust component help to lift plane in the air


texts: Why are two-stroke engines nearly unheard of in aviation?

texts:
Almost all aircraft piston engines are four-stroke engines, with one power stroke per piston every other crankshaft revolution and a great deal of intricate moving parts which are only too happy to break.  Two-stroke engines, in contrast, have a number of features that would seem to make them excellent choices for aviation use:

They have one power stroke per piston per crankshaft revolution, twice as many as a four-stroke engine, and also have far fewer moving parts, making them smaller and lighter than four-stroke engines of the same piston size and count; these two factors add up to give them a phenomenally high power-to-weight ratio, much better than that of a comparable four-stroke engine.
The same mechanical simplicity that contributes to their high power-to-weight ratio also makes them cheaper to build and sell, and (all else being equal) more reliable than four-strokes.
Most two-stroke engines are lubricated by mixing lubricant into the fuel rather than using a traditional oil sump; this allows them to operate happily in any orientation, including upside down.

The sole disadvantage of two-strokes is their greater fuel consumption and emissions, but:

Good design can reduce this problem to insignificant proportions;
Higher fuel costs could easily be offset by the reduced maintenance costs of a more reliable engine1 and the ability (due to the engine's greater power) to use fewer engines per aircraft, and;
When it comes to piston-engined-aircraft emissions, there are far worse concerns.

Yet, despite these advantages, to the best of my knowledge, only one two-stroke aircraft engine has ever entered mass-production (the highly-unusual Junkers Jumo 204/205/207 series), with a second (the Rolls-Royce Crécy) being cancelled during static-fire testing.

Why are two-strokes essentially nonexistent as aircraft engines?

1: Especially given that maintenance costs are often (though not always) a greater expense than fuel costs to begin with (scroll to page 20); the linked document is discussing jetliners, but the preponderance of maintenance costs would be much more pronounced for piston-engined aircraft, as piston engines are considerably more efficient and considerably less reliable than turbine engines (the latter due mainly to their massive mechanical complexity).


texts: Does it make sense having a MiG 19 fuselage 'area ruled'?

texts: If the MiG 19 fuselage diameters followed the Area Rule, instead of being a constant size cigar, perhaps transonic performance will be improved; someone answered to this question elsewhere indicating the airplane is already somehow area ruled, from the swept back wing, the place of canopy, but the B-58 'Hustler' fuselage is actually 'Area Ruled', you can have a look at it. Think in some USA aircraft cases where Area ruling greatly improved results.


texts: How does the RQ4-Global Hawk improve stability?

texts:
I have seen several videos recorded from an UAV in which the stabilization of the camera is almost perfect. Cameras are installed in a gimbal, of course, but do new drones introduce some new technology in order to improve the stability?

We can take, for example, the RQ-4 Global Hawk (first flight in 1998) and the Chendgu HQ (First flight in 2012). Note that the HQ-4 Xianglong's airframe topology its quite similar to the RQ-Global Haw, however it has a special wing configuration.


texts: What are the differences between a helicopter engine (turboshaft) and an aircraft engine (turboprop)?

texts:
Given the fact that most helicopters nowadays use turbo shaft engines and many aeroplanes still use turboprop engines (which are essentially turbo shaft engines with a propeller), how do you differentiate between a helicopter engine and an aircraft engine? What are the differences between the two?

p.s. I am not looking for differences in turboprop and turboshaft, but differences in helicopter and plane engines


texts: Why we had two empty rows on busy Ryanair flight Boeing 737-800 and no one was allowed to seat there?

texts:
Back in 2012 I flew from Tenerife South airport to London Stansted with Ryanair airline. All the tickets for this flight were sold out. But 3rd and 4th row on this Boeing 737-800 were empty (12 empty seats) 1 & 2 row are for customers who paid for the seats. The interesting think that no one was allowed to seat there. One lady before departure occupied one of the empty seat in the 4th row. Cabin Crews told her that aircraft will not depart unless she will go back to her seat. At first lady refused to go back and started complaining. We were waiting for her to change the seat and then we departed.
I did ask the steward why is there two empty rows but had no clear explanation from him


texts: Is the FF (Fuel Flow) the fuel consumption index?

texts:
I am creating a program to calculate the fuel needed to fly and I need to know the fuel cost of the plane. In the boeing 737-800 (PMDG), on the display that shows the plane's systems, there is the FF (Fuel Flow) field. I think that is the fuel consumption index.

However, using a stopwatch, the value there appears to be incorrect. Advancing the throttle to keep the FF at 5, about 10 pounds was spent in 8 seconds. I expected 10 pounds to be spent in 2 seconds (5 pounds * 2 seconds = 10 pounds).
My question is: does the FF indicate the plane's fuel consumption? If so, does it indicate pounds per second? If not, how can I know the fuel consumption?


texts: What are the advantages/disadvantages of ultrasonic in aircraft structure inspection?

texts:
What i mean by structure is (different composite materials and aluminum).

What are the cons in terms of time required to test the full body of the aircraft (B747 for example) in C and D checks ?


texts: What are the STOL features on the Pilatus PC-6 Porter?

texts: What's so special about the Pilatus PC-6 Porter that makes it a world-leading STOL aircraft? How do its features work?


texts: What local facilities are required for me to get flight following services?  It seems that if I'm 100 miles from any control tower then I won't be able to get flight following.  How close does a control tower need to be for me to be able to get flight following?  And is flight following available when only Class D towers are close by, or do I need to be close to a Class C?  Class D airspaces usually do not have approach and departure control, so I'm not sure if flight following is available when only Class D airspace is nearby (no class C).


texts: Do fuel reserves take into account the possibility of a constant headwind?

texts:
I'm concerned about safety rules for commercial flight in North America. There is supposed to be a fuel reserve of "30 minutes" if I remember correctly. This seems to imply an extra 30 minutes of flying time, but this is not perfectly clear.

Specifically, for example, does this 30 minutes include the worst case scenario of a headwind during the entire flight? If so, what is the max headwind speed used in the calculation?


texts: Backup airspeed indicators (lack thereof)

texts:
This recent aviation.SE question asks why isn't GPS used as a backup speed indicator. The answers given mention that GPS cannot indicate airspeed. However, there are other methods to indicate airspeed. At the very least, a small anemometer and vane might be deployed in a fashion similar to how a ram air turbine is deployed. Or at the very least, deploy the ram air turbine and measure the RPM or voltage.

Another creative method might be to release a small red sponge ball, and have a camera/sensor mounted in the top of the tail (where the A380 already has a camera) determine the vector that it flys away. Image processing for this type of work has been available for years already.

Of course, these solutions would only be deployed when necessary. I wager that using the ram air turbine to determine the airspeed could be done in software with no added weight or mechanical components added to the vehicle. Assuming that the vehicle already has a camera in the tail (such as the A380), adding the ability to deploy a small sponge ball would be less of a retrofit than adding cellular telephone service.


texts: What rules would allow a pilot to refuse a passenger's boarding?

texts:
I would like to know about any rules that would authorize a pilot to refuse to allow a specific passenger from boarding his plane (i.e. mental instability, obvious sickness, drunkeness, etc.).

Hypothetically, if someone were being 'forced' take a flight they did not want, what would be the options for the passenger to be refused boarding? I am only interested in the rules for a pilot.


texts: Why does the Pilatus PC-24 have such a large "Airplane Support"?

texts:
The PC-24 has, under the fuselage, a kind of huge support to hold the wings.

If we compare with the Citation CJ4 or the Phenom 300, this difference is quite significant. Why??


texts: How does an outflow valve work mechanically?

texts:
Under Environmental control and oxygen systems chapter of Aircraft Maintenance and Repair book by M. Kroes, there's an topic of working of the outflow valve

The diagram is of a valve that also works an altitude limiter and positive pressure relief valve. What I don't understand is the working of this valve from the diagram.
The text explanation states, when cabin pressure reduces below a preset value the bellow expands and it moves the poppet and introduces reference chamber air in the case, effectively closing the outflow valve. How is the outflow valve connected tp the bellow chamber?

If the cabin altitude
exceeds the preset limit, the bellows expands enough to press
on the small poppet just to the right of the bellows. This opens
the reference chamber to cabin air pressure and causes the outflow valve to close. The valve remains closed as long as the
cabin altitude is above the setting of the bellows. This operation
can be overridden by the positive pressure-relief control system

Above is the explanation from text.
Also, why are outflow valve openings so big?
And, do all the pressurised sections of the aircraft have separate outflow, or are they connected to a single unit via lines from the pressurised sections?


texts: Can an engine that is extinguished by foam be returned to service?

texts:
During the Qantas 32 accident, one of the engines could not be shut down as the control cable from the cockpit to the engine is cut. The fire crew eventually shut down the engine by shooting fire-fighting foam into the engine.

In such cases, can the engine be returned to service following an inspection? Or, does foam damage the engine to the extent that it is more economical to simply buy a new engine?


texts: Are “zero-bag fares” really profitable for airlines?

texts:
Any extra weight costs the airline in fuel. So, if none of the passengers carry any extra luggage (be it checked in or cabin luggage), will it lead to lesser fuel for the airline, thus lesser expenses, which would justify the lower  “zero-bag fares”.

Or, do the airlines have to meet some minimum weight criteria anyway to make any feasible fuel savings.


texts: Why don't smaller powered airplanes have better lift-to-drag ratios?

texts: Many airliners have LDRs near 20, and it sounds like the electric Eviation Alice may have an LDR of 24 at 240 kts, but many small planes typically have LDRs of only 8-10.  It seems like they could easily increase the ratio with e.g. larger wingspans with higher aspect ratios and save a lot of fuel - why don't they do this? What are the tradeoffs? Are there any commercially successful 4-20 PAX planes that have LDRs over 20?


texts:
Is the Bill Of Sale required for deregistration?

What are the FAA and EASA regulations applicable?


texts: How many aircraft types can a 135 pilot be assigned to?

texts:
Is there a limit to how many aircraft types a §135 operator may assign a pilot to fly? In other words, could a pilot type rated to fly—for example—a Learjet 75, Citation X, and Challenger 300 be assigned by the §135 certificate holder to fly all three of these types in §135 operations at any given time? Would that pilot be limited—for example—to only two types at a time for the purposes of §135 flight operations? I am not considering flight assignments that are to be conducted under §91. Is there a difference if the pilot is assigned as PIC or SIC?

I ask because my understanding has been that a §135 operator may assign a pilot to a maximum of two aircraft types at a time. However, I cannot find any documentation or discussion to support this.

Edit: To be clear, I am not asking about how many type ratings an FAA certified pilot is allowed to acquire in total (the answer to that question is: no limit). I am asking about what §135 operators are authorized to do, as far as assigning flight crew to various aircraft types.


texts: Why are flaps retracted when an aircraft is parked on ground?

texts:
I found this question. One of the answer tell the flaps are generally retracted after landing. I assume this mean flaps are retracted when the airplane is on the ground between flights.

Flaps are extended for landing and then extended again for take off. Not taking care of their position while on ground (no need of them) and putting them in the required position before take off may save (few) flaps actions (something like putting them from landing to take-off position instead of landing position to fully retracted and then from retracted to take-off position).

Is there some good reason to retract the flaps on ground? Does this good reason varies from a type of aircraft to another?


texts: Doppler shift in appendix G of ATSB report for the MH370 incident

texts:
Two people provided answers to my previous questions:

What is the nominal frequency of the satellite communications terminal on MH370?
How does one interpret the satellite data on flight MH370?

And they referred me to Appendix G. "Explanatory Notes on BTO and BFO Analysis".

Now I have questions about Appendix G.

The report (Appendix G) says that the Doppler shift from the satellite (down-link) to GES depends on the satellite movement with respect to GES, since the satellite is not exactly stationary.  But in Table 6. the Down-link Doppler frequency varies, from the satellite to GES depending on the aircraft Latitude. Why should the Aircraft Latitude affect the DeltaFdown Doppler frequency shift?
And another question is about the Down-link doppler-shifts, from the Satellite to GES, given in Table 5. The listed Doppler-shift in frequency is -75.1 Hz for UTC time 17:07. However, I can only derive this frequency using the satellite velocity for UTC time 16:55:00?  The calculated frequency differs slightly from the one in the report.


texts:
I have a Cessna 210 with inertia reel seatbelts.  The spring coil on the retention wheel broke.

FAR 43, Appendix A (C).14 allows for owner replacement of seat belts
FAR 43.13.(b) requires that it be restored at least to its original
or properly altered condition.
and FAR 21.9.(a).5  allows a part produced by an owner / operator to be installed

so... can I as owner / operator:

repair the spring and re-install the seatbelt
or
purchase a used seatbelt with a working coil spring (but no good webbing) and replace the coil spring?


texts: Could an aircraft be tied down, then throttle up and release for takeoff in order to use a shorter runway?

texts:
Could airplanes, in theory, be designed to takeoff by first tying the tail to a post, throttling the motors to full power, and then letting loose?

Could it even take off while tied, if the cable is attached to a point that's higher than the tail of the aircraft?


texts: How is maximum rate of climb defined in aircraft specifications?

texts:
In common aircraft specifications a "rate of climb", or "maximum rate of climb" is specified. For example the wikipedia page for a Spitfire, or C172.

However my intuition is that the rate of climb depends wildly on various things. Aircraft weight, altitude and so on. Furthermore, you could potentially fly at maximum airspeed, and then pitch up 90 degrees, and climb until you begin to stall. Sure you wouldn't be able to last long, but for a short period you'd have a very high rate of climb.

So the question really is, when aircraft specifications detail "rate of climb", is there some implicit context for when that rate of climb is applicable? Is it optimized for climbing in the most time or distance efficient way for X distance or something?


texts: Does altitude affect how you interpret the attitude of the aircraft?

texts:
I understand that for any specific aircraft, at a constant power setting, you can use the aircraft's attitude as a proxy for airspeed.

For e.g. In aircraft X, when the dashboard is 1 inch below horizon, at power setting X, means the aircraft will be flying at around speed X.

My question is, if you are much higher in terms of altitude, won't your attitude based on visual reference e.g. How many inches away is your dashboard to the horizon, be different when you are much closer to ground?


texts:
I am beginner and I want to understand the advantage of a tapered wing tip front edge beyond reducing the mass. How does this minimize or effect vortex drag, etc. Can someone help me to visualize this scenario please?
I have captured the screenshot from the video on YouTube.


texts: Do seaplane bases ever have marked "runways" or approach lighting?

texts:
Some seaplane bases have prescribed areas for landing, but are the landing areas marked by buoys or lights? If so are "runways" outlined in the water or just a general area?

Do they have IFR approach procedures?


texts: Could placing a fan jet further in front and closer to the wing create undesired pitch motion from its exhaust?

texts:
So far in discussion of the Max 8 people have mentioned CFM LEAP cowling size and 737 tail design as possible factors in the need to develop a MCAS system to control tendency to pitch up at high AOA.

Since the tail has much more leverage than the wing (much longer lever arm), is it possible that the high bypass exhaust blast is affecting the tail at high AOA by pulling more downwash onto it by Coanda effect? At first I though the may be affecting the back of the wing, but then realized the 737 Max 8 is very close coupled (tail close to wing) and may be susceptible to stronger downwash effects.

I wanted to be sure before suggesting a larger horizontal stabilizer or considering lengthening the fuselage.  Is it possible?  Has it ever been seen before?


texts: Is deicing fluid harmful to the environment?

texts: How harmful is the fluid applied on aircraft to the environment? Is there any way to collect this waste fluid to minimize this, if in fact it is harmful?


texts: Why was the boat mounted this way on the underside of the wing on the "Landseaire" flying yacht?

texts: After seeing the below image of the "Landseaire" flying yacht here I was curious to know why the small boat mounted to the underside of the plane was mounted the way it was.  At least to me (and @Dave who mentioned it in his answer containing this picture), I found it interesting that the boat would be mounted "backwards" and also so far from the body of the aircraft.  Can someone explain why this position and orientation was necessary or why it was chosen?


texts: How do pilots determine the takeoff distance of an aircraft?

texts: While making a flight plan, depending upon the weight of the aircraft, I'm assuming pilots determine the takeoff distance. How do they do so (is there a formula to calculate the takeoff distance)?


texts: Are there any civil programs that uses S1000D?

texts:
For civil programs, aircraft documentation (especially maintenance) used to follow ATA 100 or ATA iSpec 2200.

S1000D, on the other hand, is mostly used in military programs, but civil program may use this specification and clearly should supersede ATA-like documentation.

I found this document that talks about S1000D implementation in civil aviation, but it is quite old.

For now, do you know of any civil program (in production or currently in development) that effectively uses S1000D? Which version do they use?

To my knowledge, the only civil programs currently writing documentation in S1000D are Airbus A350 and Boeing 787. Are there any other ones?


texts: In the compressor characteristic, how do I calculate the minimum flow?

texts: I have a small question, how do I determine the minimum flow point on the compressor characteristic? I.e. what is the safety margin on the curve?


texts: What does the last digit mean in a Piper Arrow model number?

texts: The Piper Arrow's model is PA-28R-201. At first, I thought that 201 means horsepower but the Arrow's HP is 200 so I figured that's not the case. What does it stand for?


texts: Why did the pilot in this EC135 crash change the throttle setting after encountering wake turbulence?

texts: I’m confused in this accident why the Eurocopter EC135 pilot decided to manipulate the throttle after encountering wake turbulence - I can’t think of a reason for this. Could someone please explain why a pilot would do that?


texts: What is the traffic pattern altitude at KSQL?

texts:
According to some online sources (https://skyvector.com/airport/SQL/San-Carlos-Airport and https://www.airnav.com/airport/KSQL) TPA at San Carlos Airport is 800 ft AGL. However, reading the Chart Supplement / AFD entry (pg. 205 of Chart Supplement Southwest US, pg. 207 of the PDF version available here: https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/dafd/), I don't see it explicitly noted so I would assume it's the standard 1000 ft AGL. The Garmin Pilot app also concurs with my reading and lists it as 1000 ft.

I know from being a student pilot based out of KSQL the altitude is in fact 800 ft. But how would you arrive at that short of asking tower or airport management? Am I missing something or could this be an error on the part of the FAA (perhaps because 800ft used to be the standard TPA - related question that mentions this: How do I determine the VFR pattern altitude at an airport?)?


texts: How do I find how much it costs to park a B747 at an airbridge in Perth?

texts:
I need to park my B747 at Perth for 1 hour. How much will it cost me? You may assume I have 200 fare paying passengers. I must use an airbridge for those 60 minutes.

To be honest, I don't really own a B747 (yet), but am having trouble figuring out the costs for this. I've found some example costs for various airports around the world, and some landing fee documents on the airport's site, but they're a trifle confusing to decipher.

Perth's commercial fees appear to be here.


texts: How much lift can be generated by the intake lip of a duct?

texts:
How to calculate the extra lift gained by the intake lip of a duct? Aside from improving efficiency by preventing tip vortices, if a duct has a bell-shaped intake, this lip around the edge creates extra lift because the incoming air sticks to and curves around it which lowers it's pressure. This pressure difference between the duct lip surface and the surrounding air is what causes the extra lift.

The concept was used on the US military's Hillier Flying Platform with some success however, I cannot find any information on how to calculate the exact amount of lift generated by the duct lip for a given flow characteristic through the duct.

I made my own model but I have no idea if it's accurate, hence the need for experimental data to check it against.


texts: What is the purpose of these "stickers" in the F/A-18 Super Hornet fuselage?

texts:
Photos source: screenshot from youtube video ->

I think they can be used as fuselage reference points in flight testing, but I'm not sure.

Are they part of NATO standard symbology?


texts: Could this propeller work on a quadcopter and decrease the sound?

texts:
I came across a video yesterday that showcased a propeller design that looked very interesting. I am a regular drone flyer and I constantly look for exciting things to try out. Would this design in theory work and if so, would the sound of the propeller decrease by a lot? I was planning to 3d print them out and test them but i wanted to share the video with more experienced people first to see if i would waste my time or not/hurt the engines by using them.

Video

My idea is to put it on my quadcopter that has 2300kv motors and works well with 5" props.


texts: Why did this pilot have his single-engine license revoked?

texts:
5 minutes into this video, a commercial Indonesian pilot is shown performing a very tame version of a parabolic flight path as performed by zero-gravity flights, in a Cessna 172.

This video has over 11 million views currently and due to the 'wrong' people presumably having seen this footage, the pilot has had his single-engine license revoked. There is currently a petition to have his license re-instated and the coverage in Indonesia is widespread.

What actual laws or regulations did he break? Seems like he performed the maneuveur safely to me.

Link to news story (translated to English)


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


texts: Why aren't there more passenger helicopters?

texts:
I've observed helicopters being used often

in the military
for medical flights
for other special use purposes, such as sightseeing and news reporting

Why aren't there any commercial passenger transport helicopter flights? Or are there any examples of this? Are airplanes simply that much more efficient?


texts:
I was wondering why the F-35 engine is exposed. The F-22, F-16 and the YF-23 Black Widow have the exhaust nozzles of their engines blended flush with the fuselage.

(YF-23 Black Widow)

(F-35)

The YF-23 Black Widow clearly has two engines which are indented into the plane. However the F-35 has one engine which is exposed at the back. So I have two questions:

Why does the F-35 have only one engine unlike the older models?
Why is the F-35's engine exhaust nozzle clearly more exposed to bullets and rockets than older models?


texts: What is the difference between frequency wild AC system and other AC systems?

texts: What is the difference between a standard AC system and an "AC wild" system? How does the latter work?


texts: If the EPU (Emergency Power Unit) on a modern fighter jet fails, will the aircraft drop out of the sky?

texts: If the EPU (Emergency Power Unit) and batteries plus engines fail on a modern fighter aircraft, basically they will fall out of the sky, there is no dead stick landing - is this correct?


texts: Propeller Characteristics at Different Altitudes

texts:
Assuming I have a propeller with a given diameter (D), pitch, blade twist, and number of blades, I can theoretically analyze discrete airfoil sections in XFOIL and come up with lift and drag polars for the airfoil sections, for a given Reynolds number. Using the new information along with the pitch and twist (to give angle of attack for each section), the overall thrust and torque for the propeller blade can be solved for given operating conditions (RPM and airspeed). Even more accurately, the induction airflow factors can be accounted for to adjust the velocity vectors and angles of attack experienced by the airfoil sections on the blade, and an iterative solution can yield more accurate thrust and torque data for the propeller. Doing this at different operating conditions (RPM and airspeed) can give many data points, allowing for a generation of a thrust, torque, and efficiency curve vs advance ratio. I have done all of the above for a certain propeller.

However, if I wanted to change my flight altitude (and thus air density would be different), my Reynolds number could be vastly different for the same operating conditions. Does the thrust, torque, and efficiency curves for the propeller still hold up? Or does the different Reynolds number mean that if I solved the airfoil sections thrust and torque data again, they would yield different dimensionless data as a function of advance ratio?

I'm happy to provide more details. Looking forward to figuring this out!


texts: Is it normal for a Boeing 757 engine to bounce under its fairing?

texts: Earlier this week I was on a 757 flight from SFO to JFK and the right engine was bouncing under the fairing under mild turbulence, and really moving 2+ cm under moderate turbulence. Is that in any way normal or cause for concern? Here's a video of the bounce with very mild turbulence. To see the bounce, zoom into the seam where the nacelle meets the fairing: https://drive.google.com/file/d/1QpegQ0FOUhJrp8vqMrshtCdBQDyJTWO0/view


texts: Is the passenger capacity of the A350 really only 250 pax?

texts:
I read online that the capacity of an A350 was 250 passengers, but I took the max cabin width and length of an A350-900XWB, and I ended up with a 400 passenger capacity in a 4-class layout.

Economy was a 3-3-3 configuration, with 2.48 feet seat pitch
Premium was a 2-4-2 config. with a 3 feet seat pitch
Business was a 2-2-2 config. with a full 6 feet seat pitch
First class had a wide 1-2-1 configuration with a full lie flat bed to make for a 7 feet seat pitch

Yet, I still got a capacity way higher than 250 of 234 economy seats, 54 premium seats, 42 buisness seats, and 16 first class seats, and the total for 346 passengers + 8 crew! Yes, I included washrooms for all classes, emergency exits, and the galleys. What does the capacity of 250 really mean?


texts: Why do some airplanes have simultaneously a straight wing and a swept horizontal stabilizer?

texts:
I'm sure there are many other examples like this one: Embraer EMB 120 with an almost straight wing and an obviously swept horizontal stabilizer.

Why is there a difference in sweep angle between the main wing and the horizontal stabilizer, since both surfaces fly at the same speed?


texts: How to design the blade twist angle in propeller design?

texts:
I am designing a scale propeller for small UAVs and I have computed blade twist distribution for the blade airfoil sections. While I was modelling the propeller I have set the angles to twist about the trailing edge of each section so that this point is collinear. However, the final result looks a bit weird.
I would like to ask whether I have to consider any other point of the airfoil to set for the twist angle (Maybe leading edge or C.G). Below is a screenshot for the final model.


texts: What is the proportion of active aircraft from CASL (commercial aircraft sales and leasing)?

texts:
I recently discovered the existence of CASL and I understand they buy a lot of new aircraft (e.g. BOC aviation ordered more than 80 B737's and about 40 A320's few weeks ago). I imagine those aircraft are used for temporary operations (e.g. during scheduled maintenance or waiting for an aircraft to be delivered) by regular airliners, charters, lines with demand growing faster than expected, etc.

Given the number of aircraft they buy, a significant part of the traffic must be operated by these aircraft. Is there some statistics about the number of aircraft and/or the number of flights performed with an aircraft owned by leasing companies compared to flights performed with aircraft owned by airlines themselves?


texts: Why do double-ended ILS runway share the same frequency from both sides?

texts:
Let's find a runway where there are localizer-related procedures at both ends, e.g.

KMRY: 110.7 for both ILS RWY 10R and LOC/DME RWY 28L
KLAX: 108.5 for both ILS OR LOC RWY 06L and ILS OR LOC RWY 24R

However, this doesn't align with the ILS back course concept. When I fly one procedure, how can I can tell that I am not on the back course of the other? Getting down to instrument interpretation, for an HSI, how to set the front course? In a traditional VOR, is it positive or negative sensing?

POST EDIT:
Tried in a SIM, it seems that when well above the slope, it shows back course. When I get lower, it shows front course.


texts: What are the pros and cons of using shielding as opposed to liquid cooling the skin of supersonic aircraft? This is in light of the fact that most shielding materials used in aircraft, like ceramics, are very heavy. Could a radiator with 100 liters of water possibly weigh less?


texts:
On a trip a few weeks ago traveling out of Charlotte (CLT), I took this picture of a vehicle at the airport.  Our plane was fueled as we were about to board but due to various factors, boarding didn’t occur until almost five hours later.  As we were finally about to board, this vehicle arrived and connected a tube to a port in the vicinity of the fuel input port.  My question is this:  what was the vehicle doing and what circumstances necessitate the usage of it?

Edit: Although not immediately obvious without zooming in, the yellow pieces visible are the ends of a spool around which the hose is wound.  It is not one single large tank as it appears from a distance.


texts: Would a coaxial propeller with the second prop slower and larger improve speed?

texts:
Looking at various propeller designs, I started wondering about these limitations:

Large propellers at high speeds have tips going supersonic
Scimitar props attempt to keep prop tip from going supersonic
Counter-rotating props absorb more power at smaller sizes

This made me wonder if a coaxial prop had a larger prop spun at slower speeds and a smaller prop spun at high speeds would increase thrust better, or do other designs already deal with that problem?


texts: Can a weather balloon move horizontally?

texts:
How does a hobby weather balloon control its flight path? Just it just keep rising straight up vertically, always at the mercy of the winds, being swayed side to side?

Unlike a rocket/drone, it does not have an engine/motor that can be controlled remotely. So if I want the balloon to hover over a particular area and send me images (a particular section of a forest to watch for wildlife activity), how do I do it?

All weather balloons seem to be aimed towards gaining altitude and taking NASA like images, but is there a way to move a balloon horizontally and not just vertically


texts: Has anyone been able to verify ADS-B works without radar?

texts:
I know that one of the biggest advantages of ADS-B is "supposed" to be that it will directly communicate between equipped aircraft without ground support. Has anyone actually seen that in action? That is, seeing another aircraft on an ADS-B display where radar coverage is impossible, say, a remote valley surrounded by mountains with no radar station near.

Obviously both aircraft would need to be ADS-B equipped for this to work.


texts: I've been trying to get my head around wing design and have been following a few YouTube videos. When people talk about aspect ratio (AR) on a wing and give a value (Piper PA28 having an AR of 5.7) what is the 5.7? Is it wingspan length? Square metre of coverage? Or something else? I'm confused.


texts: When are pilots required to have approval to conduct practice approaches?

texts:
I would like a clarification about requesting practice approaches.

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

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

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

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

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


texts: Why is there no numbering system for more than three parallel runways?

texts:
If an airport has three parallel runways - a good example being Schiphol (EHAM/AMS) - the parallels are usually labeled "left", "center", and "right", and in case of Schiphol they are 18/36 L/C/R.

However, if there are four or more parallel runways, one or more have to be given a different number. For instance, ORD has five parallel runways heading 93.6-273.6 and their designations are 9/27 L/R and 10/28 L/C/R.

Why couldn't these runways all have the same number and add a second letter - I, M, or O (for Inboard, Midboard, or Outboard) so the number can accurately indicate the runway's heading? Under this system, ORD's 10R/28L could become 9LO/27RO.

Is it because the I and O could easily be mistaken for a 1 and 0?


texts: What is this part which is mounted on the wing of Embraer ERJ-145?

texts:
Take a look at the yellow parts which are mounted on the wing of an Embraer ERJ-145. What is it?

Two closer images:

From bottom:


texts:
A sidestick is spring-loaded to the centre position.

If there were servos under the stick, connected to the other side stick, so instead of being spring-loaded to centre, it was spring-loaded to the position of the opposite stick.
Then each pilot would get feedback on what the opposite pilot was doing, and the application of opposite stick actions could be prevented.

Is that feasible?

EDIT:
As this apparently is existing technology, then is there a reason Airbus is not using it?


texts: What does "wraparound" mean in the context of flight controls?

texts: In the references regarding the flight control (for example in F-16) I see the word "wraparound". For example "Rudder coil wraparound", "IBU pitch wraparound", "IBU lateral wraparound"or "AMUX bus wraparound failure". What does this word mean in this context?


texts: Could flight control be achieved by rotating a wing entirely?

texts:
In a typical airplane, one of the main flight control mechanisms are the ailerons/flaperons, which allows one to tweak the lift/drag profile of both wings independently.

I was wondering about the feasibility of achieving similar flight control by means of rotating an entire wing around its lengthwise axis. As I understand it, such tweaking of the aoa would have very similar flight control characteristics as regular ailerons.

Obviously this is a somewhat awkward design mechanically; the point where the wing meets the fuselage is one of the most heavily stressed parts of the airplane, so to add a pivot there takes some consideration. But I am thinking here in the context of an RC plane; where i think just nesting two carbon tubes at the center of lift will work fine.

Some potential advantages are that while the static loads on the articulated part will be high, the forces required to actuate the mechanism could be lower or approach zero, assuming the center of lift can be held reasonably constant. Also, ailerons are aerodynamically awkward and draggy when not in neutral position; moreso than an airfoil tilted tilted from its optimal L/D. Mostly I am just curious though, what something like this would look like in practice.

I cant seem to find anything on google about a design like this, but surely someone must have tried this before? If not, there must be good theoretical reasons I am missing why we should expect this to be a disaster. Is there a search term anyone is aware of that would lead me to similar designs?


texts: Would an 8% reduction in drag outweigh the weight addition from this custom CFD-tested winglet?

texts:
I'm writing an essay at school about why there is so much variation in winglet design. I am analysing all the primary types of winglets used today in the aviation industry. I'm constructing them in Solidworks (CAD software) and then running them through the in-built CFD. The winglets which gave me the lowest drag were those of the 737MAX. I then went on to design my own winglet and see how it compared - I took on a sort of compund spiroid/MAX winglet mix - according to the numbers fom Solidworks, the drag force with this winglet is 8% lower than that of the MAX winglet.

Now, OBVIOUSLY I am not better than the a team of hundreds of Boeing engineers with this design I stumbled upon, so I was wondering what the reasons would be for Boeing/an aircraft manufacturer not to use this type of winglet. I understand the consequences of weight on the wing root moment/structural reinforcements, etc... but I feel an 8% reduction in drag would outweigh the weight addition from this winglet?

Test parameters:

The wing is the same as that of a 737NG, with the winglet stuck on the end

TAS: 280kts
Air density: 1.2kg/m^3
Airflow: Incident at normal to fuselage direction
AoA: ~1.5 degrees

Images of the CFD and winglet itself are attached


texts: Does the cyclic in a helicopter re-center automatically?

texts:
Just wondering if the cyclic in a real helicopter re-centers like a joystick for a computer?

I'm pretty sure the controls in a fixed wing re-centers due to natural physics if the plane is in dynamically stable flight, without the detent (extra force required to overcome fine-grained controls at the center).

Do the controls in a helicopter re-center in the same way? Not sure because I consider helicopters to be fundamentally unstable. I'm also curious about the center detent (if there is one) in a helicopter.


texts:
During World War 2, my uncle was a navigator for a B-17G bomber based in the UK. On return from a bombing run over Frankfurt, the crew was forced to bail out over Belgium at 3000 feet altitude. My uncle and 3 of his crewmembers were rescued by Belgian resistance members and hidden for 8 months when Allied forces liberated western Belgium.
In the Escape and Evasion report the pilot gave on his return to 8th Army HQ, he wrote that the crew bailed out because "No 2 and 4 engines had runaway superchargers, lost oil. Would not feather with full oil pressure."
Could someone help me out here in understanding what's the likely causal sequence of events here? Why would the plane experience a "runaway supercharger?" Was that the cause of lost oil, or was it the other way around - some sort of oil loss causing loss of control of the supercharger?
Or was it that the propellers for 2 and 4 engines wouldn't feather properly (due to mechanical trouble or maybe flak damage?) causing the engine to overheat and burn oil?


texts: How does the size of each stage vary in a high pressure compressor?

texts: Is it true that in the high pressure compressor the stages and blades on the stages get smaller as it goes on?


texts: How to handle the formula for computing net thrust of closely coupled engine systems for an engine with a nacelle that has non-circular dimensions?

texts:
I am working on a paper and I wish to use this equation for calculating the thrust of an engine in a nacelle:
$$ Fn= \displaystyle \oint V_x\rho\vec V\cdot\vec n \ dA + \displaystyle \oint(P-P_{\infty})\vec n_x \ dA - \displaystyle \oint \vec \tau_x \ dA$$

This equation was given for a simplified case: the common circular nacelle. However, I would like to apply it to the flattened bottom nacelle as on the 737.

I have attempted to fit an equation to this by adjusting the parameters of a cardiod in polar coordinates. I'm having some trouble changing the above to polar integrals, however I'm not sure as to how this conversion would affect the rest of the equation. I could apply the rectangular form instead and keep the above integrals, but I don't think there is a away to express y explicitly in terms of x; it must be done implicitly and so that integral wouldn't really be possible.


texts: What does a dot inside two parenthesis mean on a weather depiction chart?

texts:
Earlier today, a friend asked me what this symbol (referring to an airport in Canada) on a weather depiction chart represented.  I didn't know. (Full chart available here)

What does a dot inside parenthesis mean on a weather depiction chart?


texts: Like the one above. Is it just so that you can hinge closer to the leading edge of the aileron? Why did the designers of the ATR-72 elect to use this feature?


texts: What aircraft was used as Air Force One for the flight between Southampton and Shannon?

texts:
On Wednesday 5th June 2019, The US President flew from Southampton Airport, UK to Shannon Airport, Ireland on Air Force One.

However, since SOU is more of a small regional airport, more used to seeing Dash-8s, the runway isn't very long so the aircraft used wasn't the usual B747-200, it was this much smaller aircraft.

Can anyone identify the type? My guess would be a B737-600?


texts: Do leading edge flaps increase the critical angle of attack?

texts:
So from my understanding, trailing edge (TE) flaps increase wing area + camber, effectively increasing the coefficient of lift for a fixed AOA which leads to higher lift at a fixed airspeed and AOA. This allows an airplane to fly at lower speeds + lower AOA to maintain lift.

But does the same also apply to leading edge (LE) devices like slats or flaps? I know that a slat moves to allow underside air to flow over the top and prevent airflow separation, leading to a higher critical AOA. Do LE flaps also increase the critical AOA? Also, it seems that both slats and LE flaps affect the wing camber, increasing it. Does this mean that their deployments lead to higher coefficients of lift for a fixed AOA like with trailing flaps?


texts: What is the purpose of this interesting pattern of class E airspace in northwest Alaska?

texts:
Perusing SkyVector today I noticed this airspace pattern:

It can be viewed in more detail here.

What immediately jumped out at me is that

there are no charted airports in any of this airspace;
the RNAV routes crossing through this area are also class E, so in reality the airspace is not actually divided, but the VOR airway crossing in the northwest of the area gets different treatment; and
there is little discernible pattern to the airspace based on terrain, landmarks, or politics (e.g., it is more extensive to the north than to the south of the intersection, there is a very small extra bit in the southeast corner).

My best guess is that this airspace exists to facilitate IFR/VFR separation where three RNAV routes intersect, but that doesn't necessarily explain all the points above. I'm hoping that someone familiar with the area and/or better at searching FAA publications can lend some insight.