# Linked Questions

20 questions linked to/from What is compressibility drag?
11answers
38k views

### How do wings generate lift?

Just the basic question that every aviation enthusiast must be curious about: exactly how does a wing generate lift?
3answers
21k views

### Why is the Tu-95 so efficient despite having propellers that spin faster than the speed of sound?

I've ready many, many times that propellers are not efficient near the speed of sound because it's so hard to get a tip-speed above Mach 1. Then I came across this: It's the Tu-95 "Bear", a ...
3answers
8k views

### Is it dangerous for a supersonic aircraft to fly at exactly Mach 1?

If a plane that is designed for supersonic flight, say the Concorde, kept flying at exactly the speed of sound, would there be any danger in that? If so, what could get dangerous at constant Mach 1 ...
4answers
55k views

### What happens when an aircraft breaks the sound barrier?

What happens when an aircraft breaks the sound barrier? Why can't it break the sound barrier near the ground?
4answers
12k views

### What is the propeller efficiency, $μ_p$, of modern propellers for light sport aircraft?

Roskam's book on preliminary design gives a value of 0.7 for "homebuilt" aircraft and 0.8 for general aviation. What explains this difference in propeller efficiency? The content of Roskam's book is ...
3answers
11k views

### Why does the J58 engine of the SR-71 have a diffuser after the inlet spike?

I heard that the diffuser allows the compressed air after the inlet spike to "spread out". What does this mean? If this means expansion, wouldn't it be beneficial to have it compressed before entering ...
2answers
7k views

### Why is an F22 slower than an F15?

An F22 has a higher thrust to weight ratio. The F22 has around ~70,000lbf thrust from its F119 engines, where as the F15 has around ~48,000lbf thrust from its F100 engines. But every metric I can ...
2answers
1k views

### Acceleration of a supersonic aircraft after breaking the sound barrier

People on the physics stackexchange recommended I ask here, so I am pasting my question regarding supersonic aircraft. I stumbled upon an interesting plot; in particular, the dependence of wave drag ...
4answers
901 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 ...
2answers
2k views

### What causes the reduction in speed across the shockwave?

Wherever I read about shock waves, it is mentioned that there is a reduction in speed across the shock wave. Can someone please explain what happens at the molecular level, i.e. the physics of the ...
2answers
534 views

### What is the aerodynamic purpose of an Acorn?

This is an IL-62. On the tail of the aircraft, there is a large cone, protruding out of the vertical and horizontal stabilizer which is called acorn. I am trying to figure out what is the aerodynamic ...
1answer
2k views

### How does compressibility affect the critical angle of attack?

Why does the critical angle of attack reduce with increasing mach number or What is the effect of compressibility on critical angle of attack?
3answers
175 views

### Why should Mach wave angle be less than wing sweep angle?

This is from my lecture notes: I see that this is so you can have subsonic flow over the wing planform, but why is this desirable? And are there more reasons? I can think of heat being an issue if ...
2answers
366 views

### The wing has a pressure gradient along the AB direction, is there a pressure gradient along the CD direction?

The wing has a pressure gradient along the AB direction, is there a pressure gradient along the CD direction?
1answer
656 views

### What makes the loss of a flap track fairing strongly increase fuel consumption on Airbus planes?

Inspired from this question about the loss of a flap track fairing. In the answer by Thunderstrike, a part of the configuration deviation list of an Airbus A320 is linked. In it, it says: One ...

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