texts: In the event of a crash over thick snow or a forest, would it be safer inside the aircraft or free-falling?

texts:
I just saw this question about humans surviving terminal velocity free-falls, sometimes even with little injury depending on the surface conditions, particularly over forests, hills, or thick snow cover.

That made me wonder, if a passenger of:

a large commercial aircraft, perhaps a Boeing 737
crashing from 5000 meters or higher
above a large forest or thick snow

had the choice between free falling and buckling up to crash with the aircraft, which option would offer him the greatest chance of surviving?

I'm thinking the plane might offer lower falling speed, and physical protection, but also pose the dangers of giant engines, explosions, and crushed metal / shrapnel. Perhaps the answer is that over a forest, the free fall could be safer, and over snow the plane could be safer, but that's pure speculation on my part.


texts: Where can I find the planned and flown paths for certain flight routes?

texts:
Are there official definitions of air traffic corridor pathing? Specifically European & Mediterranean routes.

I'm working on an application that needs this input data to perform an analysis. I and others in my company have been unable to find anything, and I really don't want to have to derive something approximating it myself if I don't have to.

Edit: Since what I'm asking for doesn't seem to be very clear I'll try a different way.

When an commercial jet starts a flight from one airport to another. I assume it had a generally predetermined path (or options of paths). These are not straight shortest path between two points on an ellipsoid so the data at OpenFlights.org isn't helpful, as it is not accurate enough. Obviously though no one can fully predict exactly where an aircraft will be in the future because that changes in respect to many different unknown variables, but I need something more like this, which was done tracking one commercial jet from one airport to another which includes no amount of variation, and it takes a long time to do this live.

Ideally I could get the general routes that these individual flights tend to follow, but to get an approximation of the actual routes between airports would be a whole lot better than I am know.

In a perfect world there would be lat/lon/alt/ pairings of the paths with some sort of standard deviation on those points. I doubt that exists but anything that could get me closer to that would be excellent.

Paying for something is not necessarily a problem, as long as I can prove it to my boss that it is what we need.


texts: Why does the Beech Staggerwing have its low wing ahead of the high wing?

texts: Why does the Beech Staggerwing have its low wing in ahead of the high wing? What are the aerodynamic ideas behind this? Other biplanes of the era had the opposite, low wing behind the high one.


texts: Turbofan engine start - Why does ignition occur so early?

texts:
In another thread, two key steps of starting a turbofan (ignition and fuel introduction) are given as follows:

  With increased N2 rotation, ignition will be turned on. [...]
  With further increase in N2 rotation, fuel flow will be introduced.

For some engines I saw that ignition is typically turned on at about 15% rotation, and fuel is introduced at about 30%.

I understand that the value for fuel introduction (therefore light off) is given by the need to further power the engine as early as possible, but not too early or the system will be disrupted. However I don't understand why there is a precise moment for ignition. My questions are:

Between 15% and 30% rotation, ignition will be on without any fuel. Why doesn't ignition instead occur just before fuel introduction?
Conversely, why wouldn't ignition occur earlier? Is there a physical requirement of the compressor turning at a certain speed before ignition can be on?

Thank you for your answers.


texts: Why are the colors of the MiG-15's attitude indicator inverted?

texts:
Why are the colors of the MiG-15's attitude indicator inverted (blue on the ground side, brown on the sky side)?

Source: http://www.warbirdalley.com/mig17.htm


texts: What is the most severe engine failure for modern turbofan?

texts:
Today I read again something about the Southwest Airlines Flight 1380 and the related engine failure resulting in one passenger being sucked out of the window. As I understood it was a fan blade out incident and normally the engine are certified for it.
Are the engines certified for all failure possible ?
If not what would be the most sever engine failure possible on modern engines ?


texts: Advantages and disadvantages of air intakes above fuselage/wings in jet fighters?

texts:
I found some jet fighter designs that never went into production. All of them have air intakes above the fuselage or wings (albeit not in the same manner).

I'm trying to assess if there'd be any point in making planes like those.

There are almost no real-life examples of small planes with similar placement of air intakes, so maybe it would be too disadvantageous? I know only of A-10 and F-117, but they are both ground attack aircraft. Some say those designs would be prone to engine failure while doing sharp maneuvers with high angle-of-attack in a dogfight. On the other hand, isn't air travelling faster above wing/fuselage?

What do you think? Would there be any point in manufacturing planes like this in real life?


texts: Why are modern aircraft wings often pointed instead being more rectangular?

texts:
When viewed from the Z axis (above or below), why are modern aircraft wings often pointed as they get towards the wingtips instead of maintaining the same surface area for their entire length?

This seems to be a design change in the last 50-60 years, as earlier designs typically featured more rectangular wings.

Extra points if you can explain why some rectangular wings feature rounded tips, with the maximum protrusion halfway between fore and aft of the wing.  This design was very common for biplanes.


texts: IFR requirement for altimeter question (i.e. +/- 75 feet)

texts: What if the ATIS/AWOS/ASOS results in a very low or very high altimeter setting (i.e. barometric pressure)? Surely this setting will result in an altimeter setting way outside the envelope of the +/- 75 feet related to field elevation? Since each inch of Hg results in 1,000' change...what am I missing w.r.t. the altimeter check?


texts: Why do some cargo aircraft have windows?

texts:
There are some cargo aircraft that have windows which are not covered. Look:

On the second deck above where it says "Hong Kong Asia's World City" the aircraft has 3 uncovered windows. Source: Airliners.net
Also here:

Source: Airliners.net

On the upper deck of the Martinair 747 the windows are not covered. My question is: if the aircraft is used for cargo, why do they leave the windows uncovered?


texts: How does the FAA BasicMed affect the safety pilot for somebody flying under the hood?

texts:
When one pilot is practicing instrument flying with a view limiting device (a "hood"), a licensed pilot needs to be along to watch for traffic (the safety pilot). There are several scenarios where none, either, or both are instrument rated, and the flight could be held in IMC or VMC. In this case neither pilot is instrument rated and are just following VORs in visual flight rules.

BasicMed applies to certain aircraft, so lets assume we are talking about your ordinary general aviation IFR capable aircraft with 4 seats and 150 knot cruise speed, while flying VFR.

The FAA states this in their FAQs:

  Q25:  Can I use BasicMed to act as a safety pilot, rather than holding
  a medical?
  A: Only if you’re acting as PIC while performing the
  duties of safety pilot.  The statutory language prescribing BasicMed
  said it only applies to people acting as PIC. BasicMed cannot be
  exercised by safety pilots who are not acting as PIC but are required
  crewmembers.

I find this confusing, aren't safety pilots acting as PIC because they are required crewmembers?

This question suggests that a BasicMed pilot can only be a safety pilot in VMC:Logging PIC time during IFR flight in VMC.

So my question is this (because it pertains to my present situation): Can I be a safety pilot for a non-instrument rated pilot when I have my BasicMed physical, as long as the flight is in VMC? Can I log PIC time while the pilot under the hood is flying? I should, because I am the PIC as safety pilot.

It would be nice if the FAA gave more clarification, and examples for all the practical scenarios pilots would experience. The safety pilot issue itself confuses a lot of people, now we have BasicMed regulations to add to the confusion.


texts: What's the maximum range an A350-900 can reach at TOW of 250,606 kg and full payload?

texts:
When the TOW (takeoff weight) of an A350-900 is 250,606 kg (because of runway length limitation), with maximum payload, what is the maximum range it can reach using the chart above?

It is easy to figure out for a Boeing 787 since Boeing provides different brake release slopes, as shown below, unlike the A350 chart.


texts: How does the 737 MAX MCAS differ from stab trim in other 737 variants?

texts:
I have the following questions:

MCAS will not cut out from excessive control column movement as non-MAX 737 aircraft stab trim does. Is that correct, and is this cutout permanent or does it  re-engage after the control column forces/movement are relieved?
MCAS can adjust the stabilizer to its hard stops whereas non-MAX 737 aircraft have soft limits. Is that correct?
MCAS operates the trim wheel motor in approximately 10 second bursts with 5 second pauses. What do non-MAX 737 aircraft do?


texts: Why should one not slip a Cessna 172 with flaps extended?

texts:
The POH strongly recommends not slipping the AC with full flaps...why?

It seems natural in a crosswind approach to
allow the horizontal lift component to cancel the airmass movement across the centerline.


texts: How can jet engines be more efficient than propellers?

texts:
If jet engines are smaller in diameter than propellers, is it fair to say that propellers accelerate a lot of air a little while a jet engine accelerates a little air a lot? Basically, a jet engine accelerates the air flowing through it by more than a propeller engine of the same thrust, right?

If so, propellers should be way more efficient because, by accelerating a larger mass of air, they're able to generate more force (thrust) while performing less work (change in kinetic energy of the accelerated air) due to the fact that force is proportional to $\Delta V$ but energy is proportional to $\Delta V^2$, but both are proportional to mass.

So, if this is true, shouldn't propulsion systems try to maximize the mass of air that it accelerates in order to minimize the $\Delta V$ required? This is, after all, the whole concept behind using large wings to stay aloft (they can grab onto a large mass of air).

So how can jet engines be more efficient than propeller engines? What other factors contribute to the efficiency of the propulsion system besides just the mass and velocity of accelerated air? And similarly, why aren't propellers way larger than they typically are? Because by this logic airplanes should have propellers the size of helicopter rotors.


texts: Where is the midspan airfoil located on the 737?

texts: The 737 has a root airfoil, two midspans, and one outboard. Is the midspan located under the fuselage or between root and tip?


texts: How to do Weight & Balance for Cessna 172?

texts:
What is the best method to do Weight & Balance for a Cessna 172? (If it's possible with a small tutorial!)

Thanks


texts: What construction standards are used to increase impact survivability of passengers in case of a crash landing?

texts:
There are several equations on the site about effectivity of passenger seats and restraints, and how beneficial they would be in case of a crash landing:

This question about lack of shoulder restraints
This question about possible decrease of fatalities when using a shoulder harness.
This one about the best brace position.
This one on turning the seats backwards.

The latter one is the only one of the four that cites any research and quantifications on increasing survivability rates in a crash.

What are the requirements imposed on airliner seats and restraints in order to make sure that preventable deaths from impact are actually prevented? What research has been conducted to improve safety standards in the last few decades?


texts:
There is something above the engine on the tail of this MD-11:

What is that?

Source


texts: Why do NY ARTCC Standard Operation Procedures have different altitude limits than the NY Class B airspace?

texts:
The NY Class B airspace is defined, officially, as seen in this document, which can be found in the VFR Class B Graphics in the FAA website. In this graphic (and in the corresponding shapefile, Class Airspace), the flight altitude limits can clearly be seen, for example 70/30 in the "outer ring", meaning, below 7000 FT and above 3000 FT.

However, in the specific SOP definitions for the NYARTCC, here, different altitude limits can clearly be seen, for example in the DEP 4L LAND 4L/R.

Why are these two limits incompatible? Which ones are technically "officially" valid?


texts: What would an inlet look like on a hypersonic aircraft? Would it be fixed or movable?

texts: What would an inlet look like on a hypersonic aircraft? Would it be rectangular or like a cone (assymetric). Would it move and if so how?


texts: Is it allowed to log actual instrument under IFR in VMC when VFR would be prohibited?

texts:
Flying with an IFR clearance near IMC but with visual references where VFR would be prohibited I have the following questions:

Are you technically even in VMC if you are that close to a cloud? Technically flight is not strictly by reference to instruments, but VFR would be illegal.
Can an instructor log instrument time? (a PPL would not be allowed to fly through tiny holes in a cloud)
Does an instrument student need foggles or can it be logged as "actual"?
Are you still required to see and avoid (obviously still a good idea)

Example: you are 100ft above a cloud and 1000ft horizontal in class E airspace under IFR. You can technically see but need the IFR clearance to be legal.


texts: Regulations regarding cleaning of water cooking equipment on planes?

texts:
Inspired by this question over at MiYodeya, does anyone know of specific practices or regulations regarding the use and cleaning of water urns on commercial planes?

Specific questions would be

are water urns on planes only used for water?
are they washed? (or do we saw that they don't need to because they only contain water)?
are they washed in dedicated washing machines for water urns or with other food containers/dishes?

These might seem weird questions but some Jewish travelers who observe Jewish dietary laws (i.e., eat kosher) will decide whether they can drink coffee on planes based on these answers.


texts: How do symmetrical airfoils generate lift?

texts: It is widely understood that the curved shape of a typical airfoil (such as a Clark Y) causes a pressure difference that creates lift. How do symmetrical airfoils do this when the top and lower surfaces are the same shape and length?


texts: How does the Aerobridge dock with an aircraft?

texts:
What mechanism is employed by the Aerobridges to dock with the aircraft. I am not looking at how the plane docks but how the aerobridge manages to attach itself over the door of the aircraft? Is it some vaccum tech or what? From outside, one can only see the bellows/ flexible diaphragms.

What I am looking for is actually - how two non-conformal surfaces can be "joined" in order to create a sealed "lock" (assuming its closed from all other ends). This came to my mind and now I am trying to understand this as the situation is almost the same.


texts: Why did the pilot inform ATC that he is going to autoland?

texts: I was listening to ATC and I heard the pilot say that they are going to autoland. What is the purpose of providing this info to ATC?


texts: What is that ceiling compartment of a Boeing 737?

texts: Does somebody know what that big box in the roof of the 737 cabin is?


texts: How does the forward speed of an auto-gyro relate to the rotation speed of the rotor during auto-rotation?

texts:
In my other question I was looking for a relation between the forward speed and the thrust (lift) of an auto-gyro.

I have come to the conclusion that for an auto-gyro in auto-rotation the forward speed will rotate the rotor and with that regulate its rpm. The faster an auto-gyro flies the faster the rotor rotates resulting in a higher thrust.

What I hope to accomplish is forward braking where the auto-gyro flies faster than needed to provide sufficient thrust, resulting in a higher rotation speed which will then result in more thrust and lift the auto-gyro up. This additional thrust isn't needed as the same level is required. By braking the rotor, using a generator, the rotor speed is reduced till the point it is still able to maintain level using auto-rotation. For this theory I need to understand the relation between the forward speed and the rotation speed.

But it is still not completely clear how this forward speed relates to the rotation speed. I hope someone can explain it to me or point me into the right direction.

I might be completely wrong and came to the wrong or inconclusive conclusions if so don't hesitate to tell me.

Thanks in advance!


texts: Is it true that airlines won't let pilots drink diet soda?

texts:
I watched a documentary called Hungry for Change that claimed pilot associations advise avoiding diet soda due to the aspartame sweetener inhibiting motor skills and killing brain cells.

Is this true?


texts: I’ve been exploring the FMC(flight management computer) on the PMDG 777 and noticed that under the route section you can insert VIA and TO points. From what I’ve learnt this is where you would insert SIDs and STARs. What are SIDs and STARs? And how are they different?


texts: Is the total lift of a quadcopter the sum of the lift from each propeller?

texts:
In this diagram each rotor R1,R2,R3,R4 has an individual lift force of 490 N. All combined, does the total force on this aircraft equal to 1960 N?

The aircraft in question is similar to a quadcopter.


texts: What astronauts and/or pilots had their "own" T-38 for transportation and practice?

texts:
It appears that the T-38 was used as a means of transportation for certain personnel. Astronauts, and certain pilots? It appears it was also used for training in some cases.
From some articles regarding astronaut training, it seems that some of them had their "own" T-38, that they could more or less use arbitrarily for transportation and training.
I'm curious what pilots and/or astronauts had access to T-38's, and to what degree they had their "own" plane. What were the limitations surrounding their use? Could an astronaut of the Apollo era, take the T-38 for a recreational trip to some other airport?
I'm thinking of articles such as this:

Yes, the jets were used for transportation to training sites.

and this

After the announcement pilots could fly the F-117 during daytime and no longer needed to be associated with the A-7, flying the T-38 supersonic trainer for travel and training instead.


texts: What is this plane shown on the 'Blended wing body' Wikipedia page?

texts:
(wikimedia.org via wikipedia.org)

What is the second plane from left, between the 757 and the B-2?


texts: Is there a recommended self-study syllabus or set of books for UAV design?

texts:
I'm junior software engineer (C/C++/Assembly) in a UAV project. After working there for some months I decided that it would be very interesting to start my own project. So, my goal is to design my own UAV from scratch at home. The main problem is lack of knowledge: I don't know anything about aerodynamics, engines, mechanics and so on...

It's not a problem for me to find materials on the web. The difficulty is that I don't know which disciplines to take and in which order. I understand that you should be good at calculus, differential equations, solid mechanics, aerodynamics and so on.

So, the main question is: which books/resources would you recommend and in which order?

P.S. I have found some stuff on MIT OpenCourseWare but the information there is old and not complete. Books are much better. For example I found this one very helpful, but rather complicated.

Update: I decided to extend my question. So, let's try to structure all themes, that are needed.

Base:

Math.
Mechanics.
Dynamics/Kinematics
Aerodynamics.

Specific:

Engines.
Automatic Systems.


texts: What navigational aid(s) would WWII bomber pilots have used while flying in instrument conditions?

texts:
In my furthering attempt to understand the accident mentioned in this post, I've become interested in how WWII Bombers would have flown on instruments.  In the accident report, the pilots states:

  After passing Naknek en-route Elmendorf Field, we tried to go through Bruin Bay Pass but the Pass was closed. We climbed to about 7500 ft. and were between two layers of overcast. The layers began to converge ahead of us and before we knew it we were on instruments. Icing was severe and the antennas were lost in a very few minutes. Static was so bad on the loop antenna that the Anchorage range could not be heard. We thought our position was further East, over Cook Islet, until Co-Pilot, Lieutenant Donaldson, saw a mountain just off our wing tip and shouted to me. At almost the same instant we struck the mountain. After we got into the overcast everything seemed to happen so fast we couldn't do anything about it.

As a PPL and a budding instrument pilot, I am, of course, fairly well versed on how VORs and ADF/NDBs work.  However, It is unclear to me whether when the pilot refers to the "Anchorage range" and the "loop antenna" whether he is talking about either one of these instruments/station types.  He also mentions not being able to "hear" the range, which I would guess is similar to identifying a station with morse code the way VOR/ADF is identified today, though again, that is a guess.

Since the B-18 was much less common than the B-25 or B-17, there is much less written on them.  I did find this article, but it does not go into detail on the types of instrumentation.

I've also tried to find a decent picture of the B-18a instrument panel, but so far this one is the best I've come across:

The instrument between the compass and the turn coordinator looks a bit like an ADF, but I think the image is too fuzzy to tell for sure.

I've also seen this very informative set of answers though I don't think they answer my specific question.

So again, my question is, what navigation aid(s) would these pilots have used while flying on instruments?


texts: Why don't helicopter change altitude based on variable rotor RPM as opposed to the collective?

texts: AFAIU, helicopter rotors turn at constant RPM and changes lift based on the collective.  Why no have a variable RPM heli?


texts: Would it be possible for a aircraft to deliver a payload into space using a turbojet-rocket hybrid? Merits are that they don't have to carry tons of oxidizer like a rocket would have to. It still may need to carry some but only when the atmosphere gets so thin. But even there is a lot of weight saving which means huge savings in fuel cost. Can Projects like the Skylon Space Craft really work or are they just fantasy?


texts: Is under the cockpit used to access avionics on the ground or something like that ?


texts: What are the advantages and disadvantages of autogyro aircraft?

texts: What are the advantages and disadvantages of autogyro category of aircraft?  Is there a maximum speed an autogyro can attain?


texts:
I recently got the polar curve of an aircraft with the method of Anderson. But this method is too old.

Does someone know a recent method for the polar curve without using CFD?


texts: Why Western fighters' afterburner glow is reddish orange while Eastern Bloc fighters' is blue?

texts:
Recalling what little physics I know, this could be explained by two factors:

The blue color is given by the characteristic EM radiation of C-H bond breaking, C- and H- radicals forming and recombining with O- radicals to form CO2 and H2O. This is independent of temperature and is the reason why a new gas oven's flames are blue.
The orange color is definitely the characteristic blackbody radiation wavelength of about 1500K, ~1200 degree Celsius. Now the problem is what the source of this blackbody radiation is. The way I see it it's possibly from three sources:

The hot afterburner inner wall,
The soot produced by partial combustion, or
The incandescent exhaust itself.

If the above recap is correct, this means either

the Western afterburners either run a lot dirtier than Eastern afterburners, which is unlikely because F35 and F22 have orange afterburner flames and they must be running squeaky clean to not have their afterburner inner walls coated with soot (amorphous carbon) thus having a huge IR signature because of the high emissivity of carbon, and we do not see black smoke coming from any jet since F4,

or

Western afterburners are a lot hotter than Eastern afterburners, to the point that the blackbody radiation color, which is dependent on temperature, dominates the radical color, which is independent of temperature. This seems to be the logical conjecture, given that the Russians have always been pretty poor on metallurgy.

Does anyone have authoritative knowledge on this subject? This rumor seems to be circulating on the internet forever.

EDIT: OK, the exhaust may seem a little purplish, that is caused by the emissive characteristic of H2O.

EDIT: Or maybe the Su27 and Mig29 just had a cold start and the inner walls of their afterburners still cold?

EDIT: On closer inspection, the orange color seems to be solely coming from the glowing afterburner inner wall, as opposed to the exhaust, although the exhaust is glowing also. This seems to confirm my guess that Western afterburners run hotter.

EDIT: OK, I've spoken to some guys from one of the ex-soviet design bureaus. One of them said the blue color is the result of cold afterburner and Sukhoi afterburner design, the fuel being dumped at acute angles into the center of the cylinder using a few big injectors.


texts: Aerospike nose cones for supersonic jets?

texts:
Not to be confused with aerospike nozzles. This is about the big pin-like rod in front of ICBM nose cones.

This answer (from Space) about aerospike nose cones notes that one of the potential advantages of the aerospike nose cone is to considerably decrease noise from the supersonic boom. In this comment the author evokes projections for the Concorde, dropping noise from 110 dB to 60-70 dB, that is 15 to 30 times quieter.

Noise from the supersonic boom, as the story goes, is what ultimately killed the Concorde: most nations forbid overland flight because of it, limiting it to ocean flights. So there would be clearly benefits from this.

Have there been any supersonic planes using this design that flew? Are there projects to do so that are currently active? Otherwise, why not?


texts:
In MSFS2020, I frequently hear terms like "Cleared to ACO transition" and I can set an ACO in my flight plan.  What exactly is an ACO and its obviously not a unique point because they seem to be everywhere?
It was for KCAK (Akron-Canton Regional Airport) but I thought I saw the same thing for KCLE as well, maybe I was mistaken. But the MSF2020 ATC says ACO transition.


texts: What is the legal definition of separation as it relates to ATC?

texts:
ATC provides "separation" for all aircraft in class bravo airspace. What is the legal definition of separation?

Is it the same or different than the see-and-avoid rule (FAR Part 91.113(b)) where all pilots are supposed to keep their plane from hitting another plane?

If two planes in class bravo airspace were radar identified with a mode C transponder and they hit each other in VMC, who would be responsible for the collision? The pilots or ATC?


texts: How do engine manufacturers minimize damage from bird strikes?

texts: What are the ways that engine manufacturers currently minimize the damage caused to engines in a bird strike?


texts: Can I become a reserve fighter plane pilot in the Indian air force?

texts:
I am a B.Tech Computer Science student in India. Soon after my studies I will get a job somewhere in computer science field. I am interested in technology, and things like Artificial Intelligence that is why I joined this technological field. But, I have huge interests in flying aircraft and also some other fields. When I was young, I wanted to be a pilot.
We have reserve army in India, so do we have reserve air force also?
If yes, how can I become reserve fighter pilot in it?
What is the procedure for it?
In this way my two other dreams will also fulfill that are flying and
serving nation in part of the year.
So as a conclusion, in major part of year I want to work in technology (AI in computer science) and in remaining part of year, I want to serve the nation as reserve fighter pilot.


texts: How do I obtain the max endurance altitude?

texts:
There are excellent explanations of the physics that determine maximum endurance speed here, here, and here.

I was thinking of aircraft that have to be "on station" without an indicated altitude and then wondering: Is maximum endurance not a function of both density altitude and speed?  If so, what are the relevant variables and equations?

(I imagine that maximum L/D is a function of Mach number, so that might conveniently account for the effect of change in air density with altitude.  But from the answers on max endurance speed I see that there are already differences between jets and props which, when air density is added, will result in further differences between turbo-props and piston props.)


texts: How does increasing the aspect ratio decrease the drag over the wings? Wouldn't the various types of drag affect over the wings in proportion to the increasing aspect ratio?


texts: Will the frequency 122.000 MHz no longer be used for Flight Watch after October 1st 2015?

texts:
The Flight Service Program Changes announcement from the FAA includes

  On October 1, 2015, the FAA will consolidate Flight Watch services into routine flight services inflight frequencies to eliminate unnecessary duplication of service and provide greater convenience for pilots. These services provide inflight weather information to pilots. After that date, these services will be available on the same frequencies that pilots use to open and close flight plans and to receive updates on NOTAMs or Temporary Flight Restrictions (TFRs). Dedicated Flight Watch frequencies will be decommissioned.

What are the “dedicated Flight Watch frequencies,” plural? The mnemonic drilled into my head was Flight Watch on 122.0, with the zero shaped like the face of a wrist watch.

The only frequencies I, a student pilot, have ever used for opening and closing flight plans has been RCO. The wording above is not specific, so does that mean instead of one dedicated frequency, you have to know the local RCO frequency to call Flight Watch?


texts: What is this aircraft with elaborate folding wings?

texts: I noticed this plane in the background of this car advert. Can anyone identify it? I'm assuming that may have been used on an aircraft carrier, hence the elaborate folding wings?


texts:
I was reading this thread and in the answer, the person wrote "For example, the turbine blades are replaced after a set number of turbine cycles and/or after a set number of hours, which are lesser than the others."

What is the main reason for replacing the turbine blades?
is it the fatigue or deterioration of TBC?


texts: what is the mechanism of hydro-mechanical system in power control unit that uses follow up feedback?

texts: I read somewhere that the follow up system aids in actuator deflection in specified position by controlling hydraulic fluid to the actuator , but how?


texts: What class airspace is depicted in the magenta colored area southeast of the Lake Havasu City, Arizona AIrport?

texts: What class airspace is depicted in the picture below within the wide magenta colored bar southeast of the Lake Havasu City, Arizona Airport (on the Phoenix, Arizona Sectional Chart)?  What are the vertical boundaries of this airspace?


texts: Are the jet blast fences positioned other way around in this video?

texts:
I was watching the following video, showing a 757 landing on Skiathos, Greece.

If you take a look at the 8:26 mark, you'll clearly see that all jet blast fences are positioned with their support toward the apron.

Can someone who knows better than I do confirm for me that this is the wrong way to position jet blast fences?

Here's an image, for those who can't/won't watch the video:


texts: What is this number in the bypass ratio?

texts: Here is an example of a bypass ratio 9:6:1. 9kg goes around the core and 6kg goes into the core, but what is the 1 for.


texts: How high can I fly a kite above my farm?

texts:
This idea is inspired by this question.

Suppose the OP decides to fly some kites or helium balloons above his farm to keep other pilots from flying near it. Regulation-wise, how high can these objects go?


texts:
I am a glider pilot and instructor with a master’s degree in actuarial mathematics. I teach aerodynamics every winter for upcoming glider pilots.

As you surely know, the aerodynamic center is the location where the aerodynamic moment remains constant regardless of the angle of attack – the leverage of the lifting force acting through the center of pressure gets larger for decreasing angles of attack while the force acting through this location gets smaller.

Although I find it easy to understand the mechanisms behind the aerodynamic center, I struggle with understanding how it can exist? How can we be sure that there is such a point in the wing? I know that by definition it is a fixed point, but will it be exactly fixed in practice or just approximately fixed?

Is it not possible to construct an airfoil which will somehow have a discontinuity in center of pressure leverage but delivering the same lifting force in the two situations, yielding non-constant moment around the aerodynamic center?


texts: What does the Airbus A340 Primary Flight Display look like during startup?

texts:
I'm developing a simulator addon and I'd like to accurately show what the A340 Primary Flight Display (PFD) shows during its startup sequence.

I'm looking for any images, photos, documents or movies that show the display from a cold and dark start until it's fully operative. That might include different states like a boot screen, self test and so on.

I can easily find information on what the PFD looks like once startup is complete, but what is displayed before that point?


texts: Would "Mad" Mike Hughes' steam-powered rocket have been certified airworthy by the FAA?

texts:
Daredevil 'Mad' Mike Hughes died after his homemade rocket crashed on 22 February 2020. The cause appears to be the premature deployment of the parachute used for a safe return. He was hoping to reach 5000ft.

In the U.S., Title 14, Code of Federal Regulations, Subchapter F, Part 91.7 states:

  "No person may operate an aircraft unless it is in an airworthy
  condition"

The FAA defines an aircraft as "A device that is used or intended to be used for flight in the air" and has extensive information on certifying home-built or experimental aircraft. The original rationale, I presume, being that an aircraft is a danger not only to its occupants but people on the ground too.

They also say

  the owner or operator of an aircraft is primarily responsible for
  maintaining that aircraft in an airworthy condition

... but what is not made clear is whether it is an offence to operate fly your own aircraft without FAA airworthiness certification.

With regard to Hughes' home-built rocket, the FAA definition of aircraft surely qualifies this device as an aircraft, (although,  owing to its speed, not an ultralight which have their own waivers). Further, there was no intent or pretence to go to space, so the SpaceX / NASA rules don't seem to apply here.

It seems to carry no registration, nor the mandated "EXPERIMENTAL" marking one would expect if it were - however, it is noted that in the US an aircraft does not have to be registered to be certified airworthy (although they usually are).

Should this sort of aircraft fly with an airworthiness certification? And if it didn't, why not?

NOTE - this is neither the place nor the time for a discussion of the wisdom of Mr Hughes' venture.

source

.


texts: Can the new multi scan weather radar on the A320 see low level cumulus?

texts: Is it true that in the new multi scan weather radars fitted in the A320, low level cumulus clouds are not picked up?


texts: What happens at the wings when the yoke is pulled backwards?

texts: What happens at the wings and vertical stabilizers when the yoke is pulled backwards or forward on typical airliners like the Boeing 747-800.  Is it any different for smaller similarly shaped aircraft like private jets?


texts: Why does the local speed of sound decrease with temperature and not pressure?

texts: I presume I'm missing something here but from looking at charts indicating the value of Mach 1 at different altitudes it seemed to reduce the higher in the atmosphere you went which I presume is related to reduced temperature and not pressure related which to me seemed counter intuitive. Thanks, hopefully you can clear this up


texts: Are glider winch launches rarer in the USA than in the rest of the world? Why?

texts:
I had heard before that winch-launching gliders was a relatively rare practice in the USA, while quite common in the rest of the world.

My data is mostly anecdotal, but I do know gliding clubs in Europe that exclusively use winches.

A recent post in The Hangar reminded me of this: Tanner claims their club owns the first winch launcher sold by Tost to a USA customer, and that they have not used it in years.

As far as I know general aviation scene in the Asia-Pacific region takes after that in the US, but I have no concrete knowledge.

Is winch launching relatively rarer in the USA than in the rest of the world? If so, why? How does it compare to other regions?


texts: Do some aircraft now have "full aircraft" parachutes?

texts:
I was intrigued to see this mentioned in passing,

http://robbreport.com/aviation/cirrus-aircrafts-vision-sf50-personal-jet-completes-flight-testing-video

Is it true that some new products now have this?

Do they actually work, are there any demo videos, who pioneered it, in what situations is it actually useful, etc?


texts: How large are the CF-100 Canuck wingtip fuel tanks?

texts: How big are the CF-100 Canuck's wingtip fuel tanks and what is the maximum fuel capacity they can carry?


texts: Would supersonic bi/tri/multiplane wings have less lift interference drag than a subsonic version?

texts:
Biplane wings interfere with each other, reducing the total lift often to about only 20% more than a mono wing of the same chord and span.

But at supersonic speeds - say, Mach 2, where Mach angle is 30 degrees, the wings (now provided with supersonic airfoils, before anyone asks) would have to be 0.5 chord-lengths apart for their shockwaves to interfere.

So, am I correct in saying that for a given chord-length separation, drag due to airfoil interference on vertically stacked multiplane wings interference decreases with Mach number?


texts: What is the hierarchy of aviation regulatory bodies?

texts:
What does the hierarchy of the aviation bodies look like?

Does it look like this:

International: ICAO

Continental: EASA,ECAC,...?

National:?


texts: Can you fly a glider in a cloud on primary instruments?

texts:
Assume you enter a cloud with no visibility of the horizon. Your glider is not equipped with an artificial horizon, turn speed indicator or the like.

You must fly within safe limits, using air speed, ball, yarn, compass, variometer, altimeter and what basic instruments are available.

Is this possible, and how difficult is it? Can most "normally skilled" pilots do that without extensive previous training?

For example, if you just correct the yarn with the ailerons, the speed with the elevator and keep rudder neutral or fly a fixed compass heading, is that likely to keep you flying safely until you're out of the cloud?

Edit:
I now remember an old "story". I am not sure I remember it correctly though. What is certain is that in the "old days" some instruments were sometimes sealed before a competition, in order to (try to) make it impossible to go into clouds. I think it was the turn speed indicator and also the compass? But some pilots were caught cheating by bringing a small compass in their pocket.
OK, I am not sure I am telling this story correctly. (Nowadays they check GPS logs and compare to cloud base altitude.) If I remember correctly, these pilots were willing to fly in clouds and also curve using only primary instruments.


texts: Is there any source of live ATC audio with subtitles?

texts: I'd like to know if there is a way to hear ATC and pilots' communications, with subtitles.


texts:
Related question: do planes have keys?

Let's say I happen to spot a fine-looking plane at my local airport and decide the owner probably wouldn't mind if I borrowed her for a little while - what stops me from stealing this plane? On commercial jets, the cockpit door is locked, but as I understand smaller planes don't have cockpit doors. The linked question suggests that single-engine planes have ignition keys, but twin-engine planes don't. Are the outer doors (cabin doors) locked? What else restricts me from walking up, climbing in, and flying away? (Other than the fact that I don't have the least clue how to fly a plane.)

(This is about all types of planes.)


texts: How does deploying flaps change the gradient and rate of descent?

texts:
My understanding is:
Using the gradient formula "(T-D)/W x 100", we can see that with the deployment of flaps, the gradient would reduce (due to the drag added). And since Rate of Descent (RoD) = gradient x Ground Speed (GS), the RoD will naturally decrease.
However, when doing questions, it is apparent that the gradient increases rather than the reduction I expected.
Can anyone provide some explanation on it? Am I using the wrong formula or viewing it in the wrong way?


texts: Does the transponder need to be on in the upper limit of Class B airspace?

texts: Is a transponder needed to be turned on to operate above the upper limit of class B airspace?


texts: Stick in center console, how to easily write down clearances and other similar information?

texts:
I write with my right hand. I can make sort of intelligible scrawls with my left hand, but that is much slower for me.

The airplane I'm training in is a single-engine prop plane with the control stick (not yoke) in the center console, between the seats, rather than directly in front of the pilot. (For those curious, it's an Ikarus C42B. Here and here are some photos of what the interior looks like; your favorite search engine will show you many more, including all kinds of variations to the panel layout.)

Sitting in the left-hand seat, this means that my right hand is operating the control stick, which also has the PTT and trim controls plus the main brake handle. (I typically keep my left hand on the throttle lever, which in this aircraft is between the legs of each pilot. Yes, this means there are two throttle controls and one control stick.)

This combination presents an obvious obstacle when trying to write down things like clearances, as I'll have to either:

use my left hand to write, resulting in difficult-to-read scribbles (certainly not ideal), or
use my right hand to write, requiring reaching over with my left hand to the control stick (awkward), or
use my right hand to write, letting go of the control stick and trusting that the aircraft will fly reasonably straight and level (requires much trust in the aircraft)

Any practical tips on how to handle a situation like this? (Surely I can't be the only person in this situation.)

The aircraft is equipped only for VFR; no autopilot of any kind, no IFR instruments, etc. So I'm only interested in VFR during VMC, but with the possibility of some turbulence and possibly in controlled airspace. (If I somehow manage to end up in IMC, ATC will just have to put up with me until I'm back in VMC...)

Since there seems to be some confusion, here are some examples of the kind of information I'd like to be able to write down:

taxi instructions
landing instructions, including e.g. runway in use
altimeter settings (e.g. QNH value, transition level or transition altitude)
frequencies
reporting positions and altitudes ("report 3,000 feet climbing", "report BAZ")
instructions for where to enter or exit controlled airspace, or where to transition from one controlled airspace to another ("cleared entry via FOO, 2,500 feet or below")
transponder codes, especially when assigned a code different from the local default VFR code (1200 in the US, 7000 in Europe, ...)
cleared altitude or flight level

There's probably much more that I'm just not thinking of right now. While some of this is in a relatively relaxed environment on the ground, some of it needs to be handled in the air.

One of these days I plan on trying to simply let go of the stick for a few moments (after trimming for level flight) to see how well the plane actually maintains straight and level flight on its own with at most rudder inputs, but other than that, I'm having trouble coming up with ways of actually handling this situation. How do other pilots do it?


texts: I was wondering about how often can one fly a privately owned plane? Is it somehow like owning a car where you just light up the ignition and just drive away? Obviously, there are a lot of regulations and rules... but say I have my plane parked in a hangar in a nearby airport. Can I just drive up to that airport and take my plane for a spin anytime I want (after coordinating with the control tower)?


texts: Are there any privately owned V-22 Ospreys?

texts: Could someone buy a V-22 Osprey and convert it to a luxury interior rather than a military one? Has anyone done that? Are there any images available of a private Osprey made to be luxurious inside? What does the interior of the US President's Osprey look like?


texts: Is there a "pounds per hour" reading that could have signaled the fuel leak to the pilots of Air Transat 236?

texts:
Watching a documentary and reading up on the Air Transat 236 incident, I would have thought that even with the tech available in 2001, it would have been simpler to spot a fuel leak, even with the strange warnings going on. Don't aircraft have a "pounds per hour" real-time display that indicates rate of fuel expenditure?

If so, would such a device have been taken to have malfunctioned or showing incorrect information, or would the difference it showed at the time of the leak be unnoticeable? It is said that the pilots were checking fuel balances half hourly or so before the first alarm. Would a "pounds per hour" display be a good up-to-the-second indicator, that even if the last fuel check was ok, there was now a steady problem? Would it remove be necessary to make any other calculations or do any other guesswork? Was this figure/display not available on this flight?


texts: What are these lumps on the top side of the wings of military aircraft?

texts:
There is an online video game called War Thunder that lets you fly various planes from roughly the 30s to the late 50s. It has some pretty detailed models, and I've noticed these lumps on the wings of many planes. The planes are partly modelled on the interior and can be seen in what's called X-ray view. I've noticed that many of these lumps are placed right above where the base of the plane's gun/cannon is. This has led me to believe that they might be placed in these positions to cool the guns as air is swept over these lumps. But it turns out that in many cases these lumps aren't placed where the guns are and seem not to have this purpose. Here are some pictures of what I've talking about, I have circled them in black.

Examples of where they appear over the guns:

Focke-Wulf 190

Hawker Tempest MkII

Brewster F2A Buffalo

Sukhoi Su-6

Examples where these lump wing features don't appear above the gun/cannon:

Supermarine Spitfire

Grumman F4F Wildcat

Gloster Meteor

de Havilland Venom

Note that the last two planes are jets and have their guns mounted completely in the centre of the plane, on the nose (ie., there are no guns in the wings). Also, I've noticed that for planes that have no guns mounted in the wings only British planes (in the game) have these, namely the two jets.

I'm am wondering what the function of these things are, and what they are called, if anything? Do they serve an aerodynamic function or are they maybe to cool other parts within the wing?


texts: I have seen this dome on the top of some 737-800 airplanes and am curious to know  what is it for. Is the a communication antenna for the satellite connection and in-flight internet that some airlines are providing?


texts: Why is "NO STEP" used instead of a grammatically correct spelling?

texts:
There are commonly "NO STEP" signs on airplanes where damage could be caused if a maintenance worker inadvertently put weight on a delicate part of the fuselage.

However, the grammar of this appears to be off. It should either be:

No Stepping -- akin to No Smoking, as it is the activity that is prohibited

or

Not a Step -- this is not a step (noun)

Does anyone have any sense of why the grammar of this sign is incorrect? What is the history of it? Does it hark back to the military?


texts: Where are the circuit breakers on the 787?

texts:
(787 left, 777 right)

Normally found aft of the overhead panel, where are they on the Boeing 787?


texts: Why do modern airliners have only two engines?

texts:
In this terrific question we see the advantages of four engines over two. Namely:

Engine out capability: Losing an engine means losing only one quarter of the thrust, rather than half.
Ground clearance.
Drag: Increased yaw control with four engines in an engine-out scenario means that the vertical stabilizer can be smaller, thus reducing drag.
The wing is loaded more evenly.

If that is so, then why don't new commercial airliner designs use four engines?


texts: Why do cruise missiles look different than subsonic jet aircraft?

texts:
They both fly. They both carry loads.

Why do cruise missiles look too different from subsonic jet aircraft?


texts: Why did the Junkers Ju-52 have corrugated external surfaces?

texts:
Every time I pass by Munich I have to pay a visit to the Deutsches museum, in particular to the aviation wing.

Among the other aircraft on display, there is a Junkers Ju-52. A different photo taken from a different website illustrates well what caught my attention:

Why are the external surfaces of both wing and fuselage corrugated?
Were the designers hoping to achieve some performance improvement through this choice? Are there any papers/documents about this?


texts: Why are lavatories located near the exits of an airplane?

texts: Is there some scientific or technical reason to locate the lavatories near the plane exits? Wouldn't it create problems during evacuation, if the swing open doors gets unlatched etc on forced landing or some minor crash etc.


texts: Which current commercial flights have the highest ETOPS ranking?

texts: While the Airbus A350 is technically certified for ETOPS-370, what are currently the highest rated commercial ETOPS flights? Which airline actually operates flights under ETOPS-330 or ETOPS-370 rules today?


texts: How much aerodynamic heating do jetliners endure?

texts:
At cruise altitude (~ 33,000 ft) and cruise airspeed (~ 500 mph) how much do present-day airliners heat up due to air friction during their journey? Probably not much because there's still ice on the window outside when you're at cruise altitude, but by how many degrees is the plane's hull warmer than in case the plane stood still at that altitude (therefore, compared to the minus 56°C at the tropopause)?
I'm also curious about the Concorde which flew up to 60,000 ft high and at more than 1300 mph. To the air friction there also comes the heating due to supersonic flight, so all in all how much warmer did the Concorde get during its supersonic cruise?


texts:
Situation: I’m at the uncontrolled small airport (one runway and one taxi way).  The runway in the direction I will be taking requires backtaxing. I’m ready to taxi, I check the radio and get ‘clear and loud’ back.  I pull up to hold short lines, check the downwind, base and final, announce that I’ll be starting backtaxing and pull up to the runway (i.e. facing the final). To my horror I discover that there is an aircraft that must have just turn final. I execute 180 and exit the runway. The other aircraft lands and I re-enter the runway, backtaxi and take off. After I land I find a message from the owner of the flight school/club that own the place I used. He says that the airport called him, saying that I taxied in the line of approaching aircraft, but I couldn’t be reached on the radio. In fact, I did not hear anything during the entire episode (either from the airport, or the approaching aircraft). During my flight (1.7 hr) I used the radio repeatedly without any problems.
I am, of course, hugely embarrassed about the whole episode/incident. I’m a new pilot (130 hours) and I love the place where I rent the planes. I haven’t yet heard from the owner of this school/club (other than the initial voicemail), but I wonder if you could help me to answer the following: (a). what likely legal consequences will I face and (b) even if I don’t face any legal  consequences, is it likely that I will be banned from renting this school/club planes in the future.


texts: Checkerboard painted on fuselage of Boeing test aircraft

texts: What is the purpose of the four square block checkerboard painted on the aft fuselage of Boeing's flight test aircraft?  It is either break in markings for fire rescue or some sort of optical measurement for speed, distance associated with flight testing, I believe.


texts: Is TGA analysis required for composites used in low speed subsonic aircraft?

texts:
I need to analyse the temperature drop effects on glass-fiber reinforced polymer (GFRP) used in aircraft subjected to icing, how can  it be done?

Does thermogravimetric analysis (TGA) help or is it only for high temperature material?


texts: Can the pilot stop airflow between cockpit and cabin?

texts:
During normal operation the entire fuselage is pressurized equally:

  An aircraft fuselage does not contain separate compartments with different pressure values in each. The entire vessel is pressurized equally from the forward pressure bulkhead to the aft pressure bulkhead. This normally includes the cabin, cockpit, and lower-deck cargo holds. (source)

If my understanding of physics is correct, this means that there must be airflow between the cockpit and the cabin (otherwise a pressure difference would occur). The airflow equalizes the atmospheric pressure in the cockpit and cabin.

Question: Can the pilot completely stop the airflow between cockpit and cabin, i.e. hermetically sealing off the cockpit from the cabin ?

3 scenarios for which this question is interesting:

fire
If there is smoke in the cabin, the pilot would need to prevent the smoke from entering the cockpit.
hull breach
Does cabin depressurization (due to a hull breach for example) directly lead to cockpit depressurization? Or can the pilot prevent this by stopping the air outflow from the cockpit to the cabin?
MH370
One working hypothesis in the MH370 mystery is accidental or deliberate cabin depressurization. Assuming the latter, is there any way the perpetrator in the cockpit could prevent the cockpit depressurization ?

I would appreciate if your answers included these 3 scenarios. Since the third scenario deals with a B777, please use this type as an example. Technical airflow diagrams very welcome!

Concerning scenario 1 (fire), my research into this question seems to suggest, that the cockpit is indeed designed to be sealed off in case of fire. I could not find the relevant information for a Boeing-777, but here is a description of how smoke entered the MD-11 cockpit in the Swissair 111 crash and how it was supposed to be prevented (smoke barrier, etc):

SR 111 Investigation Report:

  Airflow patterns in the MD-11 are affected by the aircraft configuration. In the forward portion of the aircraft, this configuration includes the valve position of individual air outlets in the cockpit and throughout the cabin, and the position of the louvres in the bottom part of the cockpit door. Also, all MD-11s are equipped with a smoke barrier installed laterally across the aircraft in the attic area above the cockpit aft wall (see figure 3). Inspection of Swissair MD-11s showed that the smoke barrier was sealed relatively tightly in some aircraft, while in others there were gaps in the barrier at the edges and at the seams where conditioned air ducts pass through the barrier. These gaps allowed air to flow past the smoke barrier. The holes in the barrier, designed to permit the engine fire shut-off cables to pass through the barrier, would also be a path for smoke to pass between the cabin and cockpit.


texts: How can wingtip vortices affect the direction of the relative wind in front of the leading edge?

texts:
I have a question on aeroalia's answer on this post (Why does the vortex created by wing affects its own angle of attack?).

If I'm not mistaken, wingtip vortices are generated behind the trailing edges of the wings and, even if we assume wingtip vortices somehow can reach the front area of the wings, it would only be able to affect the relative wind in front of the leading edge on the far outboard of the wings close to the wingtips, because after all it's wingtip vortices. Then, how could it be said that the upwash from the wingtip vortices changes the direction of the entire relative wind?


texts: Why don't black boxes have their own GPS?

texts:
In too many cases of unfortunate incidents, hunting for FDR (or CVR also) is a major challenge.1 There are many or all answers recorded on that device.

Why a locator (GPS linked) cannot be included in the black box? It has its battery which runs for several days and very rigid outer shell.

Ordinary cell phones are GPS enabled which pinpoint their location with the accuracy of a couple of feet. So why there cannot be a more sophisticated technology added to the black boxes?

1: I am aware that most of FDRs/CVRs are eventually recovered.


texts: How can I avoid flight simulator software reinforcing bad habits?

texts:
While looking into getting into flying I've seen in several sources that using flight simulator software typically creates and reinforces bad habits. Most articles say that it reinforces "instrument" flying which is not practical.

Is there some other action I should incorporate into learning to fly that would maybe help me avoid focusing too much on the instruments? Or would the simple introduction of things like pedals, flight sticks, etc be enough help to avoid this issue?


texts: How does early rotation increase the likelihood of a tail strike at take off?

texts: This question indicates that an early rotation can cause a tail strike. What are the (pre-)flight dynamics that would cause this to happen vs what happens when rotating at the proper time?


texts: Was the Boeing 747 designed to be supersonic?

texts:
I heard a rumour that the Boeing 747 was originally designed for supersonic cruising.

Is this correct? Are the airframe and wings able to cross the sound barrier without damage?


texts: Why don't all commercial aircraft transmit GPS data in real time?

texts: It seems strange that trucks and taxis can be set up to transmit GPS data in real time but aircraft cannot.  Wouldn't this be a useful function and feasible to implement?


texts: What material are High Pressure Compressors made of?

texts: What material are GE engine High Pressure Compressor (spools) made of ? i.e. aluminum, titanium ?


texts: When sharing an airplane, what liability does the owner bear?

texts:
What liabilities apply to the owner of an aircraft who allows other pilots to use his aircraft for not-for-profit and non-commercial use?

Example: An aircraft owner has a friend that wants to use his aircraft on a semi-regular basis (20-40 hours/year). His friend is willing to pay a fair share of maintenance, hangar, fuel, etc.

(Liabilities not limited to insurance, but also regulation, maintenance, etc)


texts: Can you log both XC PIC time and simulated instrument time together?

texts:
Are you permitted to log both XC PIC time as well as simulated instrument time (during the voyage over) whilst with a qualified safety pilot? I am pursuing my IR and would like to know if doing this is a useful strategy to build some hours in both required categories.

(I realize both pilots cannot log PIC XC time. Only one pilot can perform the necessary landing 50+ nm from the origin airfield in order to get the time there.)


texts: Looking at some photos, I saw that a lot of planes are very dirty (on the fuselage, not inside or in the cabin), and it is said that the dirt on the fuselage affect performance. Also insects affect the aerodynamics of the plane, so, do airlines ever clean their planes?


texts: What will happen to wing Vortices on supersonic aircraft?

texts: Having looked at the new Aerion AS2 design I wondered whether anyone could tell me what happens to wingtip vortices at a cruise of Mach 1.4 with the strange wing shape of the AS2 design? I know that induced drag (very closely associated with wingtip vortices) reduces with velocity, and that many supersonic aircraft work by vortex lift using delta wing configurations, but the AS2 has bizarrely conventional stubby wings. can anyone help?


texts: What should pilots do if they observe illegal activity onboard an aircraft?

texts:
So Justin Bieber was in the news again a couple of days ago:

Pilots on Justin Bieber’s Plane Had to Wear Masks Because of Pot Smoke

What are pilots legally obligated to do in a situation like this where the passengers (allegedly) are doing drugs or any other illegal activity?

Notify ATC, call 911, or land immediately?  Are any of these required or can you tell them to stop and if they comply you are good?

Are there any good recommendations on how to handle the passengers?


texts: In a dogfight, can a pilot shoot down a parachute?

texts: Forgive me if my question sounds more like a rule of engagement for aerial combat than aviation technique. I was wondering that is it ok, in a dogfight, for a victorious pilot to shoot a defeated pilot's parachute to kill him. Are there any records of this type of event?


texts: What triggers the trim horn and the "stabilizer motion" aural callout on the MD80?

texts:
I got conflicting or incomplete responses from various sources:

  There is an internal rate monitor looking to see the stabilizer is
  actually moving .08°/sec or -08°/sec.

https://forums.tfdidesign.com/index.php?/topic/2509-bbetty-stabilizer-motion-warning/

  The trim horn will sound each 1/2 degree of constant pilot use, but
  the stabilizer motion call will sound when the auto pilot moves the
  trim 2 degrees within 30 seconds.

https://forums.x-plane.org/index.php?/forums/topic/123539-cockpit-sounds/

  The CAWS will provide an aural warning (tone and voice) when the
  horizontal stabilizer deviates one degree or more for a given length
  of time. The warning will be on until the horizontal stabilizer sensor
  goes off.

https://www.airliners.net/forum/viewtopic.php?t=751253

Which one is correct?


texts: How much thrust do you lose by putting chevrons on a engine?

texts: The chevrons on a 787 are there exactly to decrease a type of drag that makes the engine louder, but the chevrons form vortices causing more drag. How much thrust is lost from the vortices on the chevrons?


texts: Can a Bombardier CRJ derate the takeoff thrust?

texts:
I have recently been flying a Bombardier CRJ 700 in a simulator and wondered how to derate the engines for takeoff.

I know how the takeoff thrust derating is selected in Airbus and modern Boeing aircraft via the (M)CDUs (see also How do pilots set the exact amount of thrust needed for a reduced power takeoff?) and I have also seen panels for setting engine modes including a flex temperature in aircraft like the MD-80 or the Avro RJ. However, I could not find anything like this on the CRJ (at least not in the simulator).

Can the CRJ even derate the thrust for takeoff? And if, how does it work?

I saw the thrust levers have detents labelled SHUT OFF, IDLE, CLIMB, TOGA, MAX POWER:

(image source)

I assume TOGA would result in less thrust than MAX, but how is this selected?


texts: Why does Google's Wing drone have dimples?

texts:
The question What operational aspects of Alphabet's Wing drone delivery service will be the same as that of an airline? includes a cropped photo of a google drone from FAA Certifies Google's Wing Drone Delivery Company To Operate As An Airline.

It is a winged aircraft with two long rows of vertical electric motors and propellors, and two more forward pointing motors for thrust, one on each wing.

The nose of the spacecraft is large and hemispherical and appears to be covered in small hemispherical dimples.

Question: Why the dimples?

Images below have been cropped, zoomed and substantially sharpened to enhance the visibility of the dimples.

Google's Wing Drone

  Customers who took part in Wing's drone delivery test program in Virginia approach their package after it was dropped on their lawn. Credit: Wing Source


texts: How can I calculate ambient air pressure from flight data?

texts:
I am playing around with data collected during a flight. I would like to find out the (real, not ISA) ambient air pressure for each data point, since it is not reported in the spread sheet containing my flight data.
I have the following data for different time points, but do not know how to (if even possible) derive from this the ambient air pressure:

Mach

Density altitude

Pressure altitude

Airspeed ktas and kcas

Static air temperature

Total air temperature

Geometric altitude

Pressure at the ground / surface pressure

I would be thankful for a solution or any tips for literature helpful to solve this.
Under the following link I found a formula I could rearrange but I believe this would return the pressure in the standard atmosphere...
https://www.weather.gov/media/epz/wxcalc/pressureAltitude.pdf


texts: Is air to air refuelling possible at "cruising altitude"?

texts:
When an aircraft uses air to air refuelling are there constraints on the maximum altitude this can take place at?
For instance I'm guessing that a Boeing Globemaster when on a long journey would cruise at 8,000m or higher (Wikipedia says service ceiling is 14,000m / 45,000'). Is there any reason why air-to-air refuelling can't take place at that sort of height?
I'm wondering whether there's something about the lack of air pressure that makes it problematic to transfer fuel or the speeds that must be used for the transfer are not viable at very high altitudes.


texts:
How can I encode an altitude (ft) in ARINC429? I didn't understand if I just need to transform it in binary number and then use the "Bipolar Return-to-Zero".
Like for example with an altitude of 25 000 ft.


texts: Is this wording that appears in the legend of the "Chart Supplement" re "airspace" actually used in any entry in the Chart Supplement?

texts:
On page 26 of the legend for the February 25 2021 issue of the "Chart Supplement" for the NE region of the US, in reference to airports where Class D airspace converts to surface-level Class G airspace when the tower is closed, it is stated that the "Airspace" entry in the Chart Supplement will typically read

AIRSPACE: CLASS D svc ‘‘times’’ other times CLASS G with CLASS E 700´
(or 1200´) AGL & abv

I've never noticed any entry in the Chart Supplement that refers to the status of the airspace at 700' or 1200' AGL.  For example, on page 30 of the same Chart Supplement, for the "IGOR I SIKORSKY MEML" airport (KBDR) at Bridgeport CT, the "Airspace" entry in the Chart Supplement simply reads

AIRSPACE: CLASS D svc 1130–0300Z‡; other times CLASS G

The VFR sectional chart shows us that the airspace at this airport will become Class E above 700' AGL when the Class D airspace is not in effect, but there is no reference to this in the "airspace" entry in the Chart Supplement.
So is the notation (quoted above) that appears in the Chart Supplement legend ever actually used in any entry in the Chart Supplement?
Does the legend refer to a new change in notation that has simply not been implemented yet?
Or is it a holdover from an older notation format that has since been simplified?


texts: Why would some flights use props instead of jets?

texts:
Two years ago I flew from Tel Aviv, Israel to Tromso, Norway via Riga and Oslo. The Tel Aviv-Riga leg was flown in an A320, and the Riga-Oslo and Oslo-Tromso legs were flown in prop planes, Fokker airplanes I think.

What considerations are used to determine what type of plane will fly for a particular journey?

Obviously the choice would be limited to whatever aircraft the carrier has available, but given reasonable choice of any aircraft that seats the required amount of passengers, what considerations are used to decide on props or jets? Runway size? Fuel efficiency for short / long trips? Weather or temperature (both current and typical)?


texts: why are airplane propellers always undersized?

texts:
While calculating propeller static thrust by using a famous Prop-power-calculator.xls (by Pé Reivers),
I've noticed that no matter what "stock" configuration I put into the calculator, I do always get the propeller power required half or third of the engine power available.

I.e.:

Zivko Edge 540: Lycoming AEIO-540-EXP 300HP@2700rpm engine, HARTZELL
76" prop @ 11.5" pitch
Calculator given performance: 51HP, 154Kg thrust
Piper Sport: Rotax 912ULS 100HP@2400rpm engine, Woodcompo 67" prop @
10" pitch
Calculator given performance: 17HP, 88Kg thrust

!NOTE - calculator is for 2-blade props, while above planes have 3-blade props. However, that doesn't change the mismaching in numbers a lot.

Above engine RPM's are with reduction applied (i.e. 1:2.43). That means the actual HP available is two-fold!.

I would imagine everything shouldbe the other-way around(?)

Reduction rates of 1:0.5, RPM's * 2, engine power / 2
Or propeller driven directly by the shaft
Or prop diameter increased (not to practical perhaps)
Or pitch inreased
Or number of blades increased?
Or all of above?

What am I missing here?


texts: What exactly is the airspace above CYYZ (Toronto)?

texts:
I'm planning my first real life cross country trip from KFRG to CYKZ. I'm trying to understand the Toronto Airspace:

Is a Canadian Class C airspace the same as a US Class B airspace?
Toronto Pearson International (CYYZ) inner blue circle has this marking 125/25 and the number 25 within a broken square bracket:

I believe this means that the airspace above CYYZ is broken into two parts: class B and class C. Does anyone know the reason for this? I have not seen this structure in the US.

The sectional for this area has the following note:

  TORONTO CLASS C AIRSPACE FOR FLIGHTS BELOW AT AND BELOW 12500' MSL SEE
  TORONTO VTA CHART

I actually purchased a Toronto VFR Terminal Area (VTA) chart but it's even more confusing than the normal sectional. What exactly am I looking for on the chart?


texts: Is it plausible to forget the cockpit unlocking code?

texts: Is it plausible for a pilot inside the cockpit to be incapacitated and that at the same time the pilot locked outside simply doesn't remember the code or the procedure for entering the cockpit?


texts: What's the precision of a modern Inertial Measurement Unit, and how is it obtained?

texts:
This recent comment reports that:

  the IMU on new (plane) would localize the aircraft to within 3 feet
  after a cross-country flight, without any GPS input other than the
  starting location.

I somewhat doubt about this statement, at least for an IMU based solely on inertial measurement: over the duration of a flight, I fear much more error accumulates.

So what's the precision of a modern Inertial Measurement Unit over say the duration of a flight, and from what sources is that obtained? If some source (in particular, GPS) becomes unavailable, how does it degrade that accuracy?


texts: What area is used to determine the horizontal and vertical tail volumes of a vtail?

texts:
What area is used to determine the tail volume of a 45 deg vtail?

Is the same entire area of the vtail used to calculate vertical and horizontal tail volume?

or do you use the projected areas in the x and y directions for horizontal and vertical tail volumes, respectively?

or other?


texts: What are the differences between ACARS and CPDLC?

texts:
What are the differences between Aircraft Communication, Addressing and Reporting System (ACARS), and Controller Pilot Data Link Communication (CPDLC)?

Can anyone please let me know in short, what is the difference between ACARS and CPDLC? So far, I have learned that both use data link communication. A ground station is necessary for ACARS and I am not sure weather ground station in necessary for CPDLC or not. ACARS can works on VHF and HF frequency also on SATCOM. Does CPDLC also works on these or it requires different system to work on? CPDLC gives the messages on a digital display. Does ACARS also provide information on a digital display or it is like fax machine where information come out on a paper from the machine.

I become confuse while figure out the differences between ACARS and CPDLC. Can anyone help me out?


texts: How does a ring paper airplane fly for a long distance?

texts:
My friend showed me something which he called the glider. At a first look, it looks like it will crash, but it flew quite well:

I was surprised to see it go about 25 meters (82 feet), as it was nothing but a big ring made out of paper. I thought of how it could fly, but I had no idea. I knew that it could go through air with least resistance, but it wasn't supposed to fly.

Can someone explain me the logic of how this flies?


texts: What are the pros and cons of sealing the gap between the wing and the aileron?

texts: I read somewhere that sometimes gap between the wing and aileron is sealed and this is done to reduce drag. But somewhere else I read that "slotted" ailerons allows for better aileron effectiveness. So which design is beneficial? Is it possible to find an optimum solution or one design exclude other one? And second question - which type of drag unsealed ailerons generate?


texts: Why aren't there direct flights connecting Honolulu, Hawaii and London, UK?

texts:
London is by far my favorite city, and many people in Honolulu apparently feel the same. An old poll (5-6 years ago) said that 50% of polled people would go to London on that flight if it existed. The airlines are quite definitely aware of this, as Hawaiian Airlines responded a year later by saying they would make a direct flight. But it never happened, and no one has heard anything from them on the issue since. (This was more than four years ago.) I have considered the following:

Capabilities of planes (More than capable of making the flight)
Popularity of flight (The poll)
Flight restrictions (None)

After my pondering, I have concluded that there should be no problems connecting the two popular destinations. So why are there no flights? They would mean certain profit for the first airline to offer the journey. (They could charge whatever they wanted to.)


texts: Do airports use automated ground operation systems?

texts: I'm interested to know if any airports use an automated ground operation system guide planes between gates and vise/versa from/to landing strips/tarmacs.


texts: What is the explanation of the apparent staining inside this airliner window [photo]?

texts:
On a recent flight, I noticed a pattern of staining or dust particles inside the window, on the plastic reveal within the cavity.

It looked as though a long-term and consistent pressure differential between the cabin and the cavity had drawn a stream of air into the cavity, resulting in what looked like a sooty stain.

And even more oddly, as you can see in the picture, right opposite the vent, the mark is very concentrated, as though formed by a high-pressure stream - which I presume isn't actually the case.


texts: How do hot air balloon pilots avoid collisions?

texts:
There are many places in the world where hundreds of hot air balloons are flown in close proximity to each other. How do the pilots steer them away from each other to avoid mid-air collisions?

Wind blows all of them in one direction and I'm sure there are plenty of calculations done by these expert pilots prior to taking off, but I am also sure that not all the balloons will react to wind at exactly the same rate.

What happens when they are getting too close for comfort? Do they have horizontal movement control?

Credits: NewYorkUpstate.com

Ironically this image already has one collision in it on ground.


texts: Do the ICAO and IATA codes for an airport ever change?

texts: Do ICAO and IATA codes ever change for airports in time? If they do, how often does it occur? I am developing an app for airports and I am thinking of setting the uniqueness of an airport through ICAO or IATA codes.


texts: Is there a standard word or phrase in the English-speaking world to describe the angle between the fuselage and the flight path / relative wind?

texts:
Is there a standard word or phrase, or several alternative commonly-used words or phrases, in the English-speaking aviation world to describe the angle between the longitudinal axis of the fuselage, and the flight path/ relative wind/ undisturbed free stream airflow?

Also, is one particular greek letter commonly associated with this angle in engineering texts and papers, much as "alpha" is commonly used to describe what the English-speaking aviation world usually calls "angle-of-attack"?

Basically the angle we are asking about is conceptually much like angle-of-attack, but modified to mean the angle-of-attack of the fuselage rather than the angle-of-attack of the wing.

Note: this question is asking about an angle that we would see when looking at the fuselage and flight path in a side view, as the aircraft flies with the wings level.  This question is not asking about a yaw angle or sideslip angle.


texts: What benefits does Automatic Dependent Surveillance bring to continental ATC over Mode S?

texts:
In particular, to the extent that there are mandates for it in USA and Europe?

I checked various posts here and official descriptions (e.g., faa.gov), but I can't figure out the following:

For continental (non-oceanic) usage, what benefits does ADS(-B) provide to ATC that is not possible with Mode S SSR?

I came to a dead end at How can ADS-B replace primary radar when FlightRadar24, using ADS-B, is so inaccurate? In particular:

  ADS-B can and will replace a number of secondary radars, but not all of them.

By not all of them, I reckon those in congested areas will not be replaced, say the New York/New Jersey/Philadelphia Airspace. One could say to provide cheap coverage elsewhere where radars can't reach (too low targets), or not enough traffic to sustain the cost, but then for the FAA mandate, for example, outside Class A, B, C, and E (above 10,000 ft), one is not required to have ADS-B. (What is ADS-B and who needs it?)

I understand that there are plenty of beneficial uses for ADS: [Cheap] online tracking that benefits the operators and general public alike, and situational awareness for any GA pilot willing to spend money on ADS-B IN. But my question is about the benefits to ATC, that Mode S can't provide.

Edit: I found one usage (benefit?) in the post Is ADS-B intended to replace other traffic management systems?:

  A more advanced usage of ADS-B will be flight deck based interval management (FIM) where ATC will be able to instruct aircraft to 'follow that plane XX seconds behind for landing on runway YY'.

Technologically, this is cool. But why the complication? Terminal airspace design that utilizes RNP routes, combined with requested times of arrival relayed to each aircraft, can accomplish the same, and is already a thing. Why let the separation be the responsibility of many, versus a few, i.e., bigger chance of something going wrong.

I'm thinking there must be more to it, even if not yet implemented.


texts: How can a single misplaced screw so massively increase a stealth aircraft's radar cross-section?

texts:
In this comment on one of the answers to an earlier question of mine, @CarloFelicione points out how even the tiniest of imperfections can make a stealth aircraft much more visible to radar:

  A screw not properly seated on a maintenance panel can make the plane show up like a barn door on a radar. Not the size, it’s the reflectivity that matters

How is it possible for a single loose screw to increase a stealth aircraft's radar cross-section that dramatically?  Why does it show up like a barn door, rather than like, well, a screw?


texts: Did these weather conditions require the airline to cancel a flight?

texts:
[I do not believe this question duplicates a previous question, which involves different conditions and circumstances]

I'm interested in the airline's response to a query of mine about why a flight was cancelled due to weather when destination airport had visibility of at least 12 SM. I asked them and the airline wrote back, attaching relevant METAR and TAF reports.

The destination airport was Victoria International (CYYJ) which is not category III (maybe cat II?). All METAR reports indicated 12SM visibility with the lowest ceiling FEW170. The airline acknowledges that the actual conditions were clear. The flight was scheduled to depart 0716 ZULU, 33 min. duration, 2 alternates with CAT III available at 16 min (Vancouver, CYVR) and 33 min (Seattle, KSEA) flying time.

The aircraft was a Dash 8. A competing airline flew the same route with a CRJ 15 minutes before the scheduled departure without incident. This was the only cancellation at YYJ that evening (there were perhaps a dozen arrivals, mostly Dash 8s or Q400s but there was an A320 and at least one 737).

First question

The airline claims a TEMPO condition of 1/4SM made it illegal to dispatch. But the TAF at 335Z said TEMPO 1 1/2SM BR SCT002, not 1/4SM. The bases prediction was P6SM SCT250 but there was also a PROB40 for 1/4SM and fog (FG).

Is a PROB40 for fog and 1/4 SM visibility enough to cancel? Is the airline required to cancel at that point? The 335Z TAF also had RMK next forecast by 0600Z, 1 hour before departure.

Second question

The new TAF issued at 538Z did not have TEMPO but had PROB30 (I can't find PROB30 in my TAF/METAR definition list, as PROB40 is supposed to be 30-50%, right?) for 1/4SM and fog (FG) again with what appears to be a main prediction of P6SM FEW150 SCT250. Was this enough to reasonably cancel?  Was the airline legally required to cancel on this basis?

Update: a poster asked me if I could post the full set of TAF and METAR reports, as received from the airline. Here they are (assuming no typos on my part because I received these hard-copy not electronic):

Scheduled flight departure from SEA  Zulu 7:16  Flight duration: 33 min. Arrival YYJ

METARS for YYJ:

  0700Z  27004KT 12SM FEW170 BKN250 01/01 A3043
  0600Z  27004KT 12SM SCT250 M01/M01 A3041
  0500z  27004KT  15SM FEW250 00/M00 A3041

TAFs for YYJ:

  CYYJ 1005338Z 1006/1106 VR03KT  P6SM FEW150 SCT250
  PROB30 1006/1016 1/4SDM FG VV002 FM101800 29008KT P6SM FEW004 SCT100
  FM102000 35005KT P6SM SKC RMK NXT FCST BY 101200Z

  CYYJ 100335Z 1003/1024  VRB03KT P6SM SCT250
  TEMPO 1003/10-18 1 1/2SM  BR SCT002
  PROB40 1005/1016 1/4 SM FG VV002 FM101800 29008KT P6SM
  FEW004 RMK NXT FCST BY 100600Z


texts: Is procedure turn considered published approach course?

texts: Procedure turn is not completely lined on the chart and only marked with the barbed arrow. Is it still considered a segment of a published approach course? Can you report to ATC that you're established on the course when you're flying PT?


texts: Why would Boeing be under review if crew-error is determined to be the cause?

texts:
The captain on Lion air's flight 610, re-trimmed the aircraft through 21 MCAS activations. The first officer, who was given control of the aircraft, got 5 more. Although it is speculated that neither pilot executed the required stabilizer trim procedure, the report does not specifically state whether or not that procedure was actually run. Source

The captain on Ethiopia Airlines flight 302, tried engaging the auto-pilot, on the faulty side as well, and despite that being the first step for the procedure, to disengage, he tried multiple times to do otherwise, then skipped over the second step, which was to disengage auto throttles, this allowed their airspeed to build up around 390. I’m sure this didn’t help the nose down force, but ultimately, they re-engaged the system which allowed MCAS to drive the nose down further. Boeing's CEO stated these failures to follow procedures is what led to the crash. Source

The question, then, is this: if the crashes each resulted from pilot error, why is Boeing under so much scrutiny?


texts:
Watching flying videos and listening to LiveATC, you will sometimes hear a pilot cancel IFR approach.

Why does the ATC care if you are on IFR or VFR? So long as you get on the ground safely, it seems like it wouldn't matter if you were looking at instruments or out the window.

Surely the "radar service" is still running for other aircraft, so it seems it's merely a formality to indicate how a craft was navigating in the event there's an accident. Is there another reason I'm not thinking about?


texts: Are run-ups required for multiengine piston aircraft?

texts: Are run-ups required or advisable on multiengine piston aircraft?


texts: What is the correct technique for working on an airframe with a pneumatic rivet gun?

texts:
I currently work as a trainee AME and want to eventually start specialising in sheet metal / composite repairs as I've heard the money is really good for these specialist skills. I've bought myself a pneumatic rivet gun to start practicing some basics and have an array of sets for the rivet sizes and types.

My question to any aircraft structural engineers / experienced sheet metal workers in this forum is how to stop getting the smiley faces on the solid universal rivet head? I'm putting enough pressure on the gun to stop it bouncing and the bucking bar is setting a good rivet tail but on some of my rivets I have this smile crease / dent at the bottom of the rivet head. Does this mean the gun isn't in line enough with the rivet? I'm always trying my best to keep the gun 90 degrees to the sheet metal. Or am I doing something else wrong? I've been told I'm using the correct set and air pressures so I'm sure it's my technique letting me down on some of these rivets. Although less mistakes are happening when I get someone to hold the bucking bar so I can use two hands I still have the same smiley face problem on some. Any tips and tricks would be much appreciated.


texts: Why does gas turbine engine have pressure oil supply tube and the scavenge oil tube?

texts: What is the function of pressure oil supply line tube and the scavenge oil tube on turbo shaft engine?


texts: I've looked everywhere but I can't find a good diagram of the inside mechanics of helicopter. I know what swashplate does but I want to how it is moved by the stick. Can someone pls give me a good video or diagram so I can understand what is going on. :)


texts:
I'm reading the UAVSAR data format and in File Naming Convention section is said that if we take a typical file name:

Dthvly_34501_08038_006_080731_L090HH_XX_01.slc

as the name that follows

Dthvly_34501_08038_006_080731_L  (090)  HH_XX_01.slc

The three digits that are in parentheses, is the steering angle.
And for the above file name, we have:

  Dthvly is the site name, 345 degrees is the heading of UAVSAR in
  flight, with a counter of 01, the flight was the thirty-eighth flight
  by UAVSAR in 2008, this data take was the sixth data take during the
  flight, the data was acquired on July 31, 2008 (UTC), the frequency
  band was L-band, pointing at perpendicular to the flight heading (90
  degrees counterclockwise), this file contains the HH data, this is the
  first interation of processing, cross talk calibration has not been
  applied, and the data type is SLC.

What is steering angle?

Please explain very simply because I'm not very familiar with aviation concepts. I just want to have a sense and intuition about of the aircraft steering angle.


texts: How to calculate the stability derivative of Pitch Moment with respect to AOA rate?

texts:
How to separate the stability derivatives: $C_{M\dot \alpha}$ and $C_{Mq}$.

I can imagine a $q=const, \dot \alpha=0$ movement like this

But what a $\dot\alpha=const, q=0$ movement would be look like?


texts: Why does the use of reverse thrust in flight on the DC-8 cause areas of separated/reversed airflow over the wing?

texts:
The DC-8 is one of only a few jetliners that can safely use reverse thrust in flight; even so, reversing the inboard engines (the outboard engines can only be reversed on the ground) while flying still produces extensive airflow disruption over the wing’s upper surface in the vicinity of the reversed engine(s), as detailed in this excellent PDF documenting a series of flight tests carried out by NASA on their DC-8-70.  A significant area of separated flow extends from leading to trailing edge (wider at the trailing edge) whenever the inboard engines are reversed below approximately mach 0.88, and becomes very large (covering over a third of the upper wing surface) below approximately mach 0.6; additionally, at mach numbers of 0.6 and below, an area of full-on reverse airflow appears over the trailing edge, in line with the inboard engine.

This would make perfect sense if the engines extended aft of the trailing edge, in which case the reversers would blow air forward and over the wing, but that isn’t the case for the DC-8; instead, the DC-8’s tailpipes (even on the DC-8-50 and -60, with their long, cigar-shaped JT3Ds) are placed under, or just behind, the wing’s leading edge.  If anything, one would expect the use of reverse thrust on a DC-8 to strengthen the airflow over the wing, instead of disrupting it, due to all that forward-blowing air piling up around the engine and under the leading edge and helping to partially block air from passing under the wing, forcing it to go over the top instead.  So why does in-flight thrust reversal on a DC-8 instead produce large areas of airflow separation (and, at lower speeds, even airflow reversal)?


texts: Is anyone able to identify this vintage aircraft please?

texts: I have this plane on an art glass print in my home.  A lot of people ask what the plane is and I have been unable to identify it.  Any ideas?


texts: The aerobatic aircraft I've seen don't have any flaps or air-brakes, besides they're taildraggers so I guess they usually have to do stall landing or three point landing but I don't understand how the pilot controls the approach speed or just how they slow down.


texts: What is the fundamental physics behind L/D decreasing as AoA increases beyond the optimal point?

texts:
Why does lift over drag decrease with AoA past the optimum AoA?  Is it because the backwards vector for a given lift force on the wing is now larger for a given air particle compared to lower AoA?

For a single air particle interacting with the wing at higher vs lower AoA does the higher AoA cause a larger change in the velocity of the air particle?

Are there other factors involved?


texts:
How do rotorcraft (helicopters, and other rotary aircraft etc.) achieve lift?
I mean, obviously the rotor. But who knows the specifics?

What are the physical, mechanical requirements of a rotary blade (propeller?) to achieve sufficient lift to carry

its own weight and
the weight of the vehicle?


texts: Is a monobloc variable incidence wing viable (updated)?

texts:
Could this be a viable way to control roll on an aerobatic airplane, using some sort of tab to control a monobloc variable incidence wing? Both wings are mechanically linked together in order to only allow roll ( like conventional ailerons are )

Advantages could be a very high roll rate (deg/sec) and low effort on stick (get rid of ailerons aerodynamic compensators)


texts: Can commercial airliners fly over central Antarctica during winter?

texts:
For example, if an airline decided they wanted to run year round flights on the great circle from Perth to Buenos Aires with a commercial airliner (e.g. A380 or B747), would they be able to do so? Or would it be too cold to fly?

I'm aware that there are a few sightseeing flights during the summer over Antarctica, but the winter temperatures in central Antarctica are lower than anywhere else on Earth (with surface air temperatures occasionally reaching around −90 degrees Celsius).

Edit: To clarify, by "winter" I mean the coldest time of year, i.e. roughly May to September.


texts: In a press release for a new Boeing "wingman" (BATS) drone being built in Australia, a closeup of this Australian AWACS flying in formation was provided. What would be some of the specific uses for the antenna farm located all over the fuselage?


texts: Why do countries not bound by US law comply with the FAA's originate airworthiness directives?

texts:
I'm not an aviation or private international lawyer, but

is it true that countries unbound by US law, i.e. most if not all countries outside the US, still comply with the FAA's directives?

If so, is the cause merely political and/or public outcry and pressure? Doubtless non-Americans would be worried if their nation state's airline still flew airliners, Boeing or not, against the FAA's directives.


texts: Are being +30 and having a Ph.D. considered as barriers to become an air traffic controller in NAV CANADA?

texts:
The requirements to apply to the training phase of NAV CANADA (to become an air traffic controller) are listed here, in which no upper bound corresponding to the age and the education level of a potential applicant is noted.

Does that mean an over-30 Ph.D.-holding person has also chance to be picked for such position (or he may be pruned off the list of successful candidates because of being old and over-qualified)?

PS. Any potential similar piece of knowledge associated with other aviation control bodies is also appreciated.


texts: Does heavy air pollution improve takeoff performance?

texts:
As you all probably know by now, aircraft have much better takeoff performance when and where the air is denser; this is why flights need to either use longer runways or jettison passengers and cargo on hot days (hot air is less dense than cold), and why a disproportionate number of the world’s longest runways are at high-altitude airports (air is much less dense at high altitudes than low).

Do aircraft see a similar performance boost at airports with heavily-polluted air, laden with dense gasses such as carbon dioxide, sulfur oxides, nitrogen dioxide, hydrogen chloride, nitric and sulfuric acids, and heavy hydrocarbons, plus lots of soot and tar particulates which raise the air’s mass much more than they do its volume?  Or is the benefit of having denser air swamped by the engine-performance penalty of having air with a lower oxygen concentration (a considerable quantity of said oxygen having gone into the formation of many of the aforementioned dense gasses)?


texts: Would shooting the tyres prevent a takeoff?

texts:
In the movie Fast & Furious 6, among other questionable parts of one scene, they try to prevent a very large aircraft from takeoff.

As opposed to whatever they tried, how effective would it be in preventing takeoff to shoot the tyres?


texts: What can a new student pilot do on their own to prepare for class and instruction?

texts: What is the best way to start for beginners learning to fly? I have a class set up and a instructor but not for another week or two. I just want to know if there is anything extra that I can start now, so it will become easier. I have started reading about the basics to get my mind going.


texts: Can Private Pilot training, funded by employer, count as company hours?

texts:
My employer would like me to get my Private Pilot License, and is funding the remainder of my training. The intention is to have me do my training on company time.

I am an engineer, and sit in the copilot seat of aircraft we test while collecting data. A commercial pilot actually flies, but for safety's sake, they would like me to have my private license while doing testing.

Could this potentially breach the commercial limitations of a Private Pilot license, as I am "technically" receiving compensation (my salary) while flying on company time? Or, as this salary is already being paid to me for my actual job duties, would the salary not be considered a contributing factor?

(For example, plan is to instead of working 40 hours/week, I would work 30 hours/week, and fly for 10/hrs/week)

If this would be a violation, would the solution to instead be to continue working 40 hour weeks, and accomplish those 10 hours outside of company time?


texts: In high-altitude piston aircraft, what type of forced induction (boost) is used? Turbocharger or supercharger?


texts: Why complex landing gears are used instead of simple, reliable and light weight muscle wire or shape memory alloys?

texts:
Muscle wires actuators are really simple, have a high power density and are reliable. Landing gears on other hand are used only twice per flight while taking off and landing (if everything goes well though). During flight these machines are not useful and there are numerous gear up landings because of landing gear failures.

What is so complex in landing gears?

Why are electric motors/hydraulic actuators used instead of muscle wire actuators in landing gear which are simple, light weight, reliable and cheap?
(If there are electric power requirements, that can be achieved by supercapacitors.)


texts: Why do aircraft with turboprop engine have black painted anti-icing system?

texts:
Everyday as I watch aircraft with turboprop engines, a question pops up: Why do aircraft with turboprop engines have black painted anti-icing system?
For instance: