# All Questions

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### Why is there no alternative mechanism to extend and lock the landing gear in case of failure? [closed]

As we know, most passenger planes have redundant systems in case of failure of a mechanism. For example, in case of failure, that specific thing can be operated by another alternative method, ...
40 views

### When modeling a shear flow for dynamic soaring, is the coefficient always a constant?

Is a wind shear model for dynamic soaring always given by the velocity vector field: F = < cy, 0 >, where c is constant? I've tried modeling c to introduce a decay in magnitude of the wind shear ...
121 views

### How is a stolen aircraft returned to its owner?

Once the authorities figure out where a stolen GA aircraft is, do they get the owner to come take it back? do they fly it back to its home airport? How exactly does the owner get his hands back on it?
88 views

### Why there are multiple classes in same plane? [closed]

This question always baffled me, why most conpanies do not have different planes for each ticket class ? There are obvious benefits to this system: Better paying customers can fly more reliable/newer/...
79 views

### Can I fly the LNAV MDA when the GPS is set up for LPV?

I am going to do my CFII checkride in a few weeks and my DPE wants to do RNAV approaches to satisfy the Non-Precision and Precision approaches tasks on the PTS/ACS. According with the Instrument ACS ...
42 views

### Why no runway markings at south end of 18/36 at FRA? [duplicate]

Perusing Google Earth I just now noticed that the north/south runway at Frankfurt am Main Airport (FRA / EDDF) does not have the usual markings at the south end of runway 18/36 - no "piano keys&...
157 views

### During WWII, what did internal bomb bays and turret layout look like on flying boats?

I am writing an alternate WWII story, and I was wondering if you fine fellows on this site could help me. I am trying to make a fantasy bomber version of the USN Boeing C-98 Clipper, AKA the Boeing ...
221 views

### What is the reason why dihedrals are used when building a plane? [duplicate]

How does dihedral affect flight characteristics of a plane? I know it increases stability, however is it the only reason why it is implemented? If so, aren’t there more effective methods to stabilize ...
107 views

### Can a company without an AOC hire out pilots to another company that does have one?

Is it legal for a company that does not hold an Air Operator Certificate (AOC) (company A) to hire out a pilot a second company that does have an AOC (company B)? Company B would be the one actually ...
180 views

### Why is the landing gear lever not set to OFF on the ground?

Several older airliners (e.g. Airbus A300, Boeing 737 until the NG series, Boeing 747 until the -400 series) have landing gear levers with three positions: UP, OFF and DOWN. OFF (or NEUTRAL for Airbus)...
251 views

### What are the differences between battens and ribs?

What are the differences between battens and ribs?
37 views

### Commercial aircraft can withstand up to 3.8 (sustained) G's. Can an airliner withstand more G's if the G forces are momentary (ie Turbulence)? [duplicate]

If yes, how many (momentary) G's found in turbulence could an airliner withstand? Since the G rating comes from static/sustained G's, rather than turbulence G forces which are momentary/not sustained.
59 views

### Can I make an emergency landing in Area 51? [duplicate]

In an emergency situation, it is permitted to land the aircraft anywhere. But does that include military bases such as Area 51? If my plane crashes and I determine that the safest place to land is ...
42 views

### Do modern airliners have a higher Gust Load Limit than an older airliner of the 50's or 60's?

I ask this because the BAC 1-11 had a Gust Load Limit of ~66 fps, and it had a structural failure in a thunderstorm. Many websites say aircraft design has improved since then, so has the Gust Load ...
23 views

### When can we apply the typical section in aeroelastic modelling?

I'm currently delving into the field of aeroelasticity. It has been quite challenging so far to find study material that is both thorough and relatively easy to understand. But, unto my question. As ...
122 views

### Can a modern airliner handle turbulence forces of +5/-3G?

In the BOAC Flight 911 accident the 707 likely experienced around positive 5G and negative 2-3G. The wings of the 707 were only about as 50% as flexible as the wings of airliners today. How would a ...
152 views

### How far along was JFK Jr. in his instrument training?

I read up a little more about the infamous and tragic incident. JFK Jr. had over 300 hours logged, and about 36 in the Saratoga, half of which was solo. It's not like he was a newly minted VFR pilot ...
45 views

### Velocity induced by a straight vortex filament

Consider a straight vortex filament as shown below. At each point, there's a point vortex of strength $\it T$. Consider that a point $P$ is there on the outermost circle of flow induced by the vortex ...
393 views

### How ribs angle change wing overall shape? [closed]

How ribs angle change wing overall shape?
103 views

### What advantages are there to operate a corporate flight department under Part 135 as a separate entity instead of in-house as a Part 91?

This question specifically involves FAA regulations in the U.S. Some U.S. corporate flight departments will set up a separate business entity for their flight operations to limit the liability of the ...
99 views

### When is an aircraft considered dispatched?

When is an aircraft considered to be dispatched? Before an aircraft is dispatched certain pieces of equipment must be operational on an aircraft. If some equipment is found to be inoperative, a ...
110 views

### Could I hold both an EASA license and a UK CAA license?

With all the ongoing mess with Brexit at the moment, I'm trying to figure out the wood from the trees so to speak. However there seems to me a bit of mass confusion with it all. I'm just wondering if ...
197 views

### Will this specially shaped can produce any lift?

I am wondering if a specially shaped can will produce any lift as it moves through the air. Please reference the drawing below: This drawing is showing a hollow can that has been cut so that it will ...
2k views

### Why angle of attack is always shown against the relative wind parallel to horizon?

I have a question about Stall, which I have difficulty to understand. According to the theory, stall happens when : 1- Speed is slow then a certain limit. 2- Angle of attack is greater than a ...
93 views

### Why RNAV SIDs and STARs are RNAV 1 instead of RNP 1?

I am studying for my CFII check-ride and I was wondering to know why SIDs and STARs are not RNP 1 but RNAV 1? Let's start with the following two definitions RNP - Required Navigation Performance: It's ...
118 views

### What exactly is an ATC clearance and how is it requested?

What exactly does it mean to get an ATC clearance? I’m asking the question because I read point 8015 of the Standardised European Rules of the Air (SERAs), which states that ATC clearances are ...
171 views

### Why don't airlines place some physical separator between passengers in the planes to prevent the spread of COVID-19?

Why don't airlines place some physical separator between passengers in the planes to prevent the spread of COVID-19? A bit like the following, but adapted for cabins and viruses: (image source)
233 views

### Does angular momentum contributes in lifting a helicopter? [closed]

I want to know whether it is possible to make a helicopter with blades that rotate counter-clockwise (CCW) seen from below. I have difficulty understanding the angular momentum in this situation. As ...
193 views

### What causes air to move to combustor?

I know the pressure is highest at end of compressor. But what forces air to move low to higher pressure? Am i missing out something? I have heard seals are used to prevent leakage of air from ...
108 views

### What does the * (asterisk) next to radio and nav aid frequencies on Jeppesen charts refer to?

For Bournemouth, all radio frequencies and LOC IBMH are marked with an asterisk - * Many other airports also have these markings, such as: Southampton, Alderney, Jersey, Guernsey, Exeter... However, ...
299 views

### What is the maximal altitude at which an emergency slide can be deployed?

If I understand correctly, the mechanism to inflate an emergency slide relies on a tank of inert gas and on an "aspirator" that sucks ambient air. This aspirator works thanks to depression ...
433 views

### Why are some parts of the wings not protected by the wing anti-ice system in the B737?

This picture is an explanation on the wing anti-ice system of the B737. As you see from it, the system doesn't protect the outboard leading edge slats and the leading edge flaps from icing. Anybody ...
149 views

### Should I log flights on separate lines if I park the plane between legs to different airports? [duplicate]

I flew one leg of a cross country, landed, parked, and turned off my engine. I flew the same plane home an hour later. Are these two separate flights and should be logged as such, or can they be ...
153 views

### Why is the critical angle of attack lower in ground effect?

Why is the stalling angle of attack lower in ground effect? Does ground effect more increase pressure on lower side of wing (cushion effect) or more decrease pressure on upper side, or both? So which ...
88 views

### How to find the angle of attack?

I'm trying to calculate the angle of attack (AOA) using aircraft some data. From what I understand the AOA is just the angle between the aircraft's forward unit vector (out the nose vector) and the x-...
90 views

### What is the difference between mist and haze in terms of relative humidity?

I am an aviation meteorologist and I struggle to distinguish the two of them.
166 views

### Has any commercial airliner ever flown inverted? [duplicate]

Has any commercial airliner ever flown inverted, either intentionally (extremely unlikely) or during an upset?
1k views

### What pitch attitudes are common during an emergency descent for an airliner?

What pitch attitudes are common during an emergency descent? I assume it would be a fairly nose-down attitude, but I can't imagine how steep would feel to the passengers. Suppose a gradual ...
663 views

### Why can't we see the downwash/wake roll-up behind 2D/wall-to-wall airfoil tests? [duplicate]

Why we can't see the downwash/wake roll-up behind any wall to wall airfoil wind tunnel video? To make that happen, the air behind the center of the airfoil must go down and the air at the side walls ...
145 views

### What is the difference between a waypoint and a significant point in an airspace?

I know ATS routes are made up of waypoints, but what are Significant Points used for? Is there a difference, or are they really just two names for the same thing?
94 views

### Why would my electric turn coordinator suddenly stop working?

The electric Turn Coordinator in our Cardinal stopped working and we would like to understand the cause. It simply doesn't move at all, it remain fix. The red flag is not on, I have double checked the ...
253 views

### Why did the altimeter in an F-16 jump suddenly as it passed through Mach 1?

In this video, Destin — the creator of YouTube channel Smarter Every Day — rides in an F-16 with a USAF Thunderbirds pilot. If you start watching the video at the 11:06 mark, you will see what happens ...
49 views

### How does a hybrid airship take-off?

A hybrid airship generates lift from a combination of lighter-than-air buoyancy, and aerodynamic lift. Some figures suggest that up to 40% of the lift comes from aerodynamic lift (wikipedia). So how ...
47 views

### How does an accessory drive hydraulic system power a crop duster pump?

Aerial agricultural spraying uses pumps, which are usually powered electrically from the starter/generator. Now I have read, that these pumps can also be powered by an accessory drive hydraulic system....
49 views

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

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?
157 views

### How is flight envelope protection implemented in Dassault Falcons?

In normal laws, envelope protection is implemented differently on Boeing and Airbus fly-by-wire systems, as highlighted in this question. I don't want to reopen a debate about which one is better (...
100 views

### How do AHRS systems meet the “gyroscopic” requirement of 14 cfr 91.205.d?

EDITED Among the instruments listed as required for IFR operations in the US FAR is are various "gyroscopic" instruments, including those for the turn coordinator, attitude and heading. In ...
474 views

### How safe are extreme aerobatic flights?

Statistically, how safe are extreme aerobatics flights like this one?