# All Questions

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31 views

### my teachers said that turbofans were rejected

Today, my propulsion teacher said that turbofan were disliked by the general population because they were noisy and looked cheap in comparaison to turboprop. He said that the main reason they were ...
12 views

### Any has a link for fmgs ,ecam or mcdu trainer?

I want a link for ecam or mcdu trainer for A320
29 views

### is there a link between thrust and the speed of the plane

my propulsion teacher showed us the thrust equation where we substract the velocity of the air leaving the engine by the velocity of the air going in the engine.He said that if the plane is moving , ...
14 views

### how often is cabin air replaced

One of the A320 pilots told me that there is an icao rule that air should be replaced every 90 seconds? Is this true ? can someone give me a supporting article for the same
57 views

### What is this instrument?

I am looking to sell this instrument, but it has no part numbers or any other identifying marks other than it says "Kollsman" on the back. Anyone know what it is and what it might be worth?
34 views

### How much is thickness of air layer with zero velocity at wing surface?

How much is thickness of air which is not moving(zero velocity) at surface of wing and can be higher than height of roughness? Because everything wich is inside this layer(V=0) will not contribut to ...
48 views

### Would the IA 58 Pucará III “Fenix” be a good training aircraft? [closed]

The title is mostly self-explanatory but here is why I am asking the question. I see that most new training aircrafts use turboprops now, the Pucará does too. The Pucará looks agile enough to handle ...
77 views

### Is using a DERATE for Takeoff actually reducing the power of the engine?

When one chooses a DERATE for takeoff (TO-1 or TO-2 in the case of a B737), does the system actually reduce the available thrust of the engines, or is it computing a N1 that corresponds to the reduced ...
16 views

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

For an aircraft with a jet engine, let's say the power margin at M1.5 at an altitude Z1 is x. Is the power margin at a lower altitude Z1-H at M1.5 always greater than x ? From my point of view, there ...
63 views

### Clarification on the SEA-TAC VFR map

I've been looking at the SEA-TAC VFR map, and something caught my eye... On this map one can see that the SEA-TAC airport has a class B designation in a strange inverse-rhomboid shape, surrounded by,...
80 views

### How does the F-16 achieve negative stability?

F-16 has negative stability at subsonic conditions. How is this achieved? To me it looks like a very streamligned, very normally shaped aircraft. Is the Center of Mass actually behind the Center of ...
41 views

### How can a touchdown zone RVR report for one runway be different than the rollout report for the runway going the opposite direction?

I saw an RVR report in KSEA where 16C was 800 1200 1800 (touchdown zone, midpoint, rollout), and 34C was 1800 1200 300. I always thought the same scatterometers used for the rollout side on runway as ...
28 views

### Is there an exact solution for induced velocity during vortex ring state?

In plots such as these, the section between -2 and 0 has no exact solution. As shown in the first image, the other two formulas are known, but not during vortex ring state because, as seen in the ...
93 views

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

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

### Is skin friction also pressure drag looking at microscopic level?

Roughness in boudary layer is taller than height of air which is not moving ,feel oncoming airflow in boudary layer, at front side must be high pressure at rear low pressure etc,so net force is to the ...
16 views

### When do my EASA ATPL exams expire? [duplicate]

so I finished my ATPL exams in July 2019 and started in April 2018 . I just want to know in EASA when do my atpls expire ?
78 views

### Why does a jet's combustion energy propel the engine forwards rather than acting equally in all directions to create zero thrust? [duplicate]

I'm a novice. I have high school physics and I've seen many explanations of how a jet engine works. To paraphrase: Fans compress air into a chamber where combustion energy is created, which spews ...
113 views

### In the USA, how much more expensive is 100LL compared to Jet-A1?

I have never flown an aircraft before and do not have any clue of what the fuel prices are. I was doing some research recently and found that some websites say Jet-A1 costs about 1.5 - 2 dollars per ...
56 views

### What effect do urban wind conditions have on operating tiltwing aircraft and gyrocopters?

From this research it seems there are quite a lot of strong wind in suburb residential area and around high-rise buildings. High-rise buildings would also create wind tunnel effect and eddy winds. ...
57 views

### What is the speed of gas in the core of a jet engine?

Coming from a slightly related question, I want to know what is the speed of the gas in the core of a jet engine, after combustion but before the first turbine stage. I'll just pick a random example: ...
5k views

### Why don't flights fly towards their landing approach path sooner?

For example shown here, the flight is heading to the centre of the airport, until it gets close when it then moves into it's landing path. This is an inefficient use of time, fuel and emmissions, why ...
21 views

### What is the fan pressure ratio in a turbofan?

What is it and how does it affect efficiency and thrust?
42 views

### 747 should have been bought at first [closed]

We all know that at first the 747 failed because supersonic travel was coming up and wanted to save money for the Concorde but the 747 is fast and efficient and affordable so they should accept both ...
221 views

### I'd like to know the name of this aircraft

I recognize it but can't recall the name, if anyone can tell me that would be great.
137 views

### Why is the fuel:air ratio of a turbojet engine not around ~1:15 (the stoichiometric ratio)?

Also, what is the maximum fuel:air ratio possible in a combustion chamber of a jet engine?
111 views

### Does Betz's Law apply to jet engine turbines?

Betz's Law says the extractable power from wind is only 59% (16/27) of its original power. $$P_{max} = \frac{16}{27} \frac{1}{2} \rho A v^3$$ Rho is the gas density, A is the cross section area of gas ...
506 views

### Why did Concorde have a 8000 ft airport elevation limit?

According to the Concorde Flying Manual Volume II(a) - 1 Operating Limitations - page 01.01.02 the take-off and landing airfield altitude is minimum -1000 ft and maximum 8000 ft. Why is Concorde ...
2k views

### Why is the maximum endurance for a piston aircraft at sea level?

The Canadian Flight Training Manual stated this when talking about maximum endurance: For reciprocating engines, maximum endurance is achieved at sea level. The book does not explain further as to ...
52 views

### Pitching Moments CG vs CP vs AC

Probably the question will be a little bit confusing but I'll try my best to make it clear. Due the position of the CP with respect of the AC, symmetrical airfoils don't produce pitching moments, but ...
106 views

### Why does part 135 require a maintenance log on board the aircraft, but part 91 does not?

During a dispute within friends, it came to my attention that in 135.65 the maintenance log copies must be present in the aircraft, and that 91.407(b) and 91.417(c) have similar rules, but, meanwhile, ...
16 views

### pqr computed from ENU and NED axis, are they the same? [closed]

I derived the rotation matricies from inertial to V1, to V2, to body for ENU, as follows. (x -> pitch axis, y-> roll axis, z-> yaw axis) If I compute p, q, r using the following definitions, ...
157 views

### What is an Air-Filed Flight Plan? Are aircraft capable of filing flight plan when in flight?

ICAO Doc 4444 mentions to input AFIL in the departure field of flight plan if it has been filed in the air. What is an Air-Filed flight plan? Can aircraft crew file a flight plan in-flight? If yes ...
88 views

### Has anyone tested or flown permeable wings to increase efficiency?

See this article: Aerodynamic Performance Improvements Due to Porosity in Wings at Moderate Re Was wing porosity ever tested/used for real aircraft? source: The aerodynamic efficiency parameter ...
129 views

### Why is there an altitude limitation on operating the slats/flaps on the A320?

As per the FCOM limitations chapter there is an altitude limitation of 20000 feet for operating the flaps/slats on the A320? Why this specific altitude?
55 views

### Calculation of temperature correction for altimeter

I try to calculate the correction of cold temperature for altimeter , i use for this the equation 24 of the Engineering Sciences Data Unit (ESDU) publication but it give me very high number . if i ...
90 views

### How does outflow valve work?

As we know that outflow valve normally closes during climb and cabin altitude also increase but why does outflow valve open if we have selected manual pressurisation and increasing cabin altitude !
110 views

### Do mechanical attitude indicators have rotation limits?

Do mechanical attitude indicators have limits to the rotations they can display? Wondering since gyros suffer from gimbal lock when two axes become aligned (e.g., at 90 deg pitch, if you were doing ...
224 views

### Why does Boeing 247D have reverse slope windows when they were removed from the D models?

Have a look at this article on a famed example of the 247D, DZ203, the first aircraft to make a completely blind landing. The first image is the aircraft during its flights with the RAF, which places ...
88 views

### Do raked wingtips reduce drag of a hang glider?

https://rakedwingtip.wordpress.com/ Do they realy reduce drag or improve performance? If so, how?
51 views

### Is there a database of aircraft 3D models that are accurately created [closed]

I was just wondering if there was such a thing as the title describes. I am trying to work on a machine learning algorithm that generates aircraft designs based on what it learns from current designs, ...
35 views

### Do Air Passenger Number statistics on a route refer to both directions of flight?

Looking at the air passenger data for specific routes, I was wondering if this data referred to just one direction of the route, or both directions? For example (see link below), Philadelphia's most ...
140 views

### What aircraft has a sustained bright orange light visible at night/early morning?

This morning around 6 a.m. in Durham, N.C. I was sitting on my porch and saw a bright orange light, I thought it was Mars it was so orange, but it was very bright. After looking at it for a moment it ...
40 views

### why is rhumb line bearing for this question 270 as the answer?

An aircraft leaves position "G" in lat 40 degree South and flies the following Rhumb Line tracks and distances: ...
81 views

### If an aircraft has two altimeters what is the allowed difference between them?

If an Altimeter must be within +/- 75 of known field elevation, and the aircraft has two altimeters, one could be +74 while the other could be -74 and both would be within 75 of known field elevation, ...
76 views

### Deicing Rod for Propellers

Similar to a card hitting the spokes of a bicycle, the card is soft enough to knock the dust off the spokes with no damage. What material would be best to impede the propellers to chip off the ice. ...
192 views

### Why are the Antonov An-124 horizontal stabilisers directly behind the wings?

With the wings being on the same plane as the horizontal stabilisers, turbulent air from the wings would interfere with the airflow over the elevators making them flutter. Surely putting the ...
147 views

### Why does the Tu-134UBL have a sharp/pointed nose cone?

Russian/Soviet aircraft design has always intrigued me, and even more so when coming across this photo of the Tupolev Tu-134UBL with its pointy nosecone. Having looked up the performance ...
66 views

### How does push forward work? [duplicate]

From Facebook video shows a BA aircraft being pushed forward into a hangar. I wonder how it works? Do they rotate nose wheel 180 degree to push it or there is attachment point for the tug to push ...