40 votes
Accepted

Why are birdlike airfoils not used?

Early biplanes did use similar airfoils. Not as extreme as the Eppler 376, but still very thin and highly cambered. When Otto Lilienthal started his glider experiments, he tried to copy storks. He ...
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29 votes
Accepted

Could a big plane glide significant distances, same a ordinary glider (1000 km or about)?

No, there's no way an airliner can glide 1000km, this is because its wing is designed for fast cruising speeds, and it's much heavier compared to the lift generated than a glider. Gliders are light ...
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  • 50.2k
27 votes

Why aren't any wingsuits able to sustain flight?

I'm aware that under zero power it is a glider, but there are gliders that sustain flight and have enough lift to climb etc. This statement is a bit incorrect. Gliders don't climb like aircraft as ...
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  • 96.3k
20 votes
Accepted

During an engine failure should I deploy 10° of flap or keep it clean?

You keep it clean: adding flaps adds drag. You can see this in Section 3 of the Cessna POH, which includes a Maximum Glide (distance) diagram. In the C172S POH that I checked, it notes that maximum ...
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  • 70.4k
19 votes
Accepted

What would be the best alternative during a dead-stick approach?

Attempting a tight turn, while low and slow, is an almost certain recipe for disaster. Your first option of landing with a tailwind is possibly preferable - there is no inherent danger landing with a ...
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  • 25.8k
19 votes
Accepted

Why aren't any wingsuits able to sustain flight?

There are very small jets that for hype-related reasons are called wingsuits. As current jet technology (and propeller technology) is easily capable of producing (from a human-portable frame) enough ...
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  • 436
19 votes

Why aren't any wingsuits able to sustain flight?

As an ex-hang-glider pilot... Two other answers have covered the basic concept of gliding - namely that you're constantly descending, and to stay aloft you need to be in air that's rising faster than ...
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  • 2,284
16 votes

What was the Space Shuttle's glide ratio?

As far as I know the space shuttle is no longer in use. However, the glide ratios (more than one in different configurations) can be found on the Wikipedia page: Space Shuttle Wikipedia page. There ...
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16 votes

Could a big plane glide significant distances, same a ordinary glider (1000 km or about)?

First, the 1000 km glider trip requires three prerequisites: Excellent weather for the whole of the trip. Strong thermals caused by lots of sun, a high cloud base and an unstable atmospheric thermal ...
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16 votes

Do jet aircraft have a better glide ratio than propeller aircraft in general? If so, why?

"Glide performance" is measured by "Lift-to-drag ratio": In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the amount of lift generated by a wing or vehicle, divided by ...
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  • 25.8k
15 votes

Why are birdlike airfoils not used?

This is more an addendum than an answer, regarding "birdlike" airfoils. Ignoring the fact that birds can modify geometry, chord and camber of their wing when required, what can at best ...
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  • 4,143
14 votes
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How is the glide ratio affected when converting a wheeled plane to floats?

As glide ratio is the same as the L/D ratio, the increase in drag due to the addition of floats will reduce it. The Beaver's POH gives the effect of addition of floats in the glide ratio: DHC-2 ...
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  • 98.7k
13 votes

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

There are plenty of smaller power planes that achieve those numbers; motorgliders. And motorgliders with L/Ds in the high teens and low 20s are pretty efficient cruisers. So the real question is; ...
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  • 107k
12 votes
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What was the Space Shuttle's glide ratio?

The NASA website quotes an approximate ratio of 1 The shuttle was designed with a low L/D ratio (~ 1) because during the descent the spacecraft must be slowed from about 17,300 mph to about 250 mph ...
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11 votes

How does the Boeing 787 Dreamliner's glide ratio compare to other airliners?

As discussed here, glide ratio is related to the L/D (lift-to-drag) ratio of the plane. When talking about commercial aircraft, "glide ratio" is typically used to mean the ratio with engines ...
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  • 69.8k
10 votes
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Where can I find (or how can I calculate) the glide ratio for a PA-28-181?

If you were to take off from an airport at 2,000' ASL on a standard day, and climb to 7,280' ASL you would be exactly 5,280' above the ground which means exactly 1 statute mile above the ground. If ...
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  • 32.4k
10 votes

For maximum glide range, should I minimize glide angle or AoA?

The furthest glide is by definition the lowest glide angle! So if that is one of your design inputs, you should definitely go for that. But seriously, reducing weight and form drag gets you the ...
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  • 58.8k
9 votes
Accepted

How can the glide ratio in a balanced turn be estimated?

I get a variation of the glide ratio with $\frac{2}{\bigl(\cos\varphi + \frac{1}{\cos\varphi}\bigr)}$ for circles flown with a bank angle of $\varphi$ when compared to straight flight at the ...
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9 votes

Do jet aircraft have a better glide ratio than propeller aircraft in general? If so, why?

A few reasons: if we're talking glide range from altitude, then jets certainly can glide longer! They fly MUCH higher than most props do, even turboprops! Second, propellers are draggy when they're at ...
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  • 2,414
8 votes
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Does full nose up trim yield best glide in Cessna 172/152 for a given load?

That ground instructor is giving you bad information. You can not make a blanket statement like "full nose up trim" and expect it to be valid for any and all situations. You are correct that the best ...
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  • 32.4k
8 votes

How can planes with the same stall speed and power-to-weight ratio have such different takeoff field length, climb rate, glide ratio, etc?

Are we comparing apples to oranges again? The differences in take-off length are far too big with such similar performance numbers, and I agree that they should be closer together - if we are really ...
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8 votes
Accepted

Could a commercial plane like Airbus A320 glide with no working engines from 11000 meters?

All standard fixed wing aircraft are able to glide. The key measure of performance in gliding is the glide ratio which is related to the lift-to-drag ratio of the aircraft. The glide ratio of a clean ...
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7 votes

What would be the best alternative during a dead-stick approach?

It depends on a number of factors including the aircraft type, its associated glide/descent ratio at max L/D, where the a/c in relation to the landing site, your current absolute altitude, other ...
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7 votes
Accepted

What are the engine-out implications of giant turbofans?

Both-engine-out glide performance isn't accounted for and isn't a certification requirement (of any airplane that I'm aware of). Airliners have good glide performance as a happy side effect of design ...
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  • 107k
7 votes

For maximum glide range, should I minimize glide angle or AoA?

Well, well, well. Time to go to ... the well. "Balsa toss gliders" can be a lot of things, but they are a great place to start. If they are thrown for distance design criteria will be ...
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6 votes

How to calculate the Glide Ratio from Drag & Lift?

The glide ratio for a given angle of attack is the ratio of lift to drag. Both of these are proportional to the respective coefficients (with a proportionality constant of $\frac12\rho v^2A$), so the ...
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6 votes

What is a mushing glide?

Why is it called a mushing glide? The aircraft is not cleanly cutting through the air. It is "mushing" through the air at a high angle of attack creating lots of drag and a slow forward airspeed. ...
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  • 32.4k
6 votes

Does it help to climb in case of a partial engine failure?

Agreeing with @Antzi, high engine speed when combined with some sort of small scale physical damage or corrosion is a typical failure mode for propeller engines. Combining that logic with the fact ...
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  • 370
6 votes

Why aren't any wingsuits able to sustain flight?

Because the glide descent ratio of a wingsuit is around 2:1 vs a well designed sailplane exceeds 40:1. This very gradual descent rate allows the sailplane to take advantage of normal, commonly ...
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6 votes
Accepted

How does retracting flaps help extend the glide of an aircraft?

Some answers presume that raising flaps reduces lift. That is wrong.* All it does is to increase angle of attack, until the change in flap setting is so severe that the airplane stalls. Only then ...
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