Can any plane glide unpowered? (unless it is a brick of course)

[iDan122]

Because my mother claimed she saw some tv show where they told about "some airplane crash" where the plane "fell down like a brick" and that that certain type of plane "couldn't glide".

I am 99% sure I am right that any plane can glide, but her stubbornness now made me wonder...

[SargeRho]

Every plane can glide. Some have to fly faster than others though. I think the reason the Space Shuttle landed at such high speeds is because it wasn't the best glider.

[sal_vager]

Some planes glide better than others of course, a ASK 21 will go a lot further than a 777 and is light enough to take advantage of thermals for lift.

A plane can fall like a brick if it's suffered structural damage though, such as if its tail has broken away.

The space shuttle wasn't that bad considering, but because it could not regain any energy it lost during the descent it always came down with excess speed, so there was a margin for error, that's why it had to make all those S shaped turns, to scrub off the extra energy.

Here's a good article on flying the shuttle in x-plane, it gives you an idea of how hard it was

[Ralathon]

You can make anything glide, some just have a worse descent angle than others.

What your mom probably meant (Or misinterpreted) is a stall. If a plane angles the nose too far from the direction of travel the air no longer follows the wing's curvature. This causes a dramatic increase in drag and a severe loss of lift. So your plane will suddenly drop out of the sky until the pilot corrects the mistake.

[Tarrow]

Pretty much any aircraft with wings can glide, it's a trick of minimising the altitude drop whilst not shedding enough velocity to drop into the region where the aircraft will stall. Stalling (and the resulting nose drop) is not going to be fun if your control surfaces (or rather the engines that're powering the hydraulics that move them) are having issues.

There's at least one case where a 767 pilot has managed a glide ratio only 20% less efficient than a hang glider. Check out a flight referred to as "The Gimli Glider" - a 767 with both engines & most electronics out due to a fuel miscalculation - ended up landing on a runway in the middle of a drag race event.

[mrfox]

There has been multiple instances where commercial airliners had to glide after losing all engines.

http://en.wikipedia.org/wiki/List_of_airline_flights_that_required_gliding

[Charzy]

Depends on the plane. An actual glider, like an ASK 21, will glide for ages depending on whether or not it can find thermals or other types of lift about.

On the other hand, you have things like Flexiwing Microlights like this which will indeed fall like a brick (they're also too small to carry a parachute, so if the engine fails you get badly injured or die).

[Brethern]

Most planes are designed to have a 15:1 glide ratio. For every fifteen feet the glide they drop a foot. The only way I know of one dropping is if it stalls.

[Chris P. Bacon]

even helicopters are built to be able to 'glide' (autorotate) in case of an engine out... as long as you have sufficient forward air velocity over your lifting surfaces, no matter what kind of rotor or fixed wing craft you have, you will glide... Now that doesn't mean you will always be in control of the craft.. there are special cases like the b-2 which requires engines for yaw control in flight.

[KASASpace]

Every plane can glide. Some have to fly faster than others though. I think the reason the Space Shuttle landed at such high speeds is because it wasn't the best glider.

The Space Shuttle WAS a flying brick, or at least it was referred to as such.

[Rokker]

Because my mother claimed she saw some tv show where they told about "some airplane crash" where the plane "fell down like a brick" and that that certain type of plane "couldn't glide".

I am 99% sure I am right that any plane can glide, but her stubbornness now made me wonder...

All planes CAN glide, however there are a number of things that can cause said gliding to be impossible. Is there anything more about the even that you know of, name of the event, circumstances around it, what the tv show was, anything like that?

Depends on the plane. An actual glider, like an ASK 21, will glide for ages depending on whether or not it can find thermals or other types of lift about.

On the other hand, you have things like Flexiwing Microlights like this which will indeed fall like a brick (they're also too small to carry a parachute, so if the engine fails you get badly injured or die).

No it does not. Ultralights can too glide, they are literally built out of gliders. They will glide, especially since, at least from when I last checked, the average ultralight glide ratio is something like 8:1 which isnt actually all that bad. All planes can glide, not necessarily glide well, but they can glide.

Edited April 20, 2014 by Rokker

[Nuke]

didnt the mythbusters have marginal success with concrete gliders?

i think the rule of thumb is that the higher the glide ratio, the better the glider. most planes are capable of gliding in an emergency. a plane at altitude has a lot of potential energy it can use to land safely, you can do a flare manuver to temporarily lower your descent rate, usually right before touchdown. however if there is no where to land in the radius at which the glide slope intersects the ground, then you are sol, though belly landings are still an option.

Edited April 20, 2014 by Nuke

[Brun]

The Space Shuttle WAS a flying brick, or at least it was referred to as such.

That's because its glide ratio on final approach was about 4.5:1. In the early phases of reentry it was even worse, closer to 1:1. Those are atrociously bad glide ratios compared to regular aircraft, hence the flying brick nickname.

[KASASpace]

That's because its glide ratio on final approach was about 4.5:1. In the early phases of reentry it was even worse, closer to 1:1. Those are atrociously bad glide ratios compared to regular aircraft, hence the flying brick nickname.

Yeah, I know. That was my point, it could glide, and it effectively had bad glide ratios, so most things probably can glide.

[Rokker]

Yeah, I know. That was my point, it could glide, and it effectively had bad glide ratios, so most things probably can glide.

Well, the shuttle could glide because, despite it having a terrible l/d ratio, it still had an l/d ratio above 1. It may not have been a good glider, but it was still a glider. However, things such as ICBM re-entry vehicles might not be considered able to glide because their l/d ratio is below 1.

[KASASpace]

Well, the shuttle could glide because, despite it having a terrible l/d ratio, it still had an l/d ratio above 1. It may not have been a good glider, but it was still a glider. However, things such as ICBM re-entry vehicles might not be considered able to glide because their l/d ratio is below 1.

Well, reentry vehicles are usually not equipped with wings, and aren't really designed to fly, they're designed to fall.

[Rokker]

Well, reentry vehicles are usually not equipped with wings, and aren't really designed to fly, they're designed to fall.

Well, you said "most things probably can glide"

[KASASpace]

Well, you said "most things probably can glide"

Yeah, "most things" as in aircraft.

And, it really depends on what is meant when you say "glide".

[K^2]

The ability of an airplane to glide is defined by the ratio of its lift coefficient to its drag coefficient, called the glide ratio. Both of these are a function of air speed and air density. The best glide speed is usually equal to the airplane's V_Y speed, which also gives best rate of climb. So if you are trying to land an airplane unpowered, you shoot for V_Y. Airplanes with good glide ratio are relatively easy to land with no engines. A typical light airplane will have a glide ratio in the 8-10 range and unpowered landing is often part of standard training. High performance gliders can have glide ratio of over 60. These can stay in the air pretty much indefinitely with a good pilot, thanks to thermals. An airliner, typically, has much lower glide ratio. A 777, as an extreme case, has a glide ratio of only 4. (Actually, a 777 has a glide ratio of almost 10 at cruise altitude, but that's due to it being designed for flight at low density and high speeds. At low altitudes, it's only marginally better than a brick.) A wing suit has glide ratio of about 2.5-3. Helicopter in auto-rotation is also about 3, but helicopter can flare a lot better than an airplane can due to energy stored in the rotor, so they can do a soft landing unpowered, despite being very bad at "gliding". A 777 with all four engines dead is typically considered incapable of unpowered landing. It needs at least 1 engine running. Though, under ideal conditions, a survivable landing is possible with that glide ratio.

Well, the shuttle could glide because, despite it having a terrible l/d ratio, it still had an l/d ratio above 1.

Technically, so does the brick. If you add a small tale to keep brick's orientation stable, it can do better than 1.

Edited April 20, 2014 by K^2

[Rokker]

Yeah, "most things" as in aircraft.

And, it really depends on what is meant when you say "glide".

Indeed it does, I like to consider anything with an L/D ratio of over 1 to be gliding since in most other cases it would at least appear to be simply dropping

The ability of an airplane to glide is defined by the ratio of its lift coefficient to its drag coefficient, called the glide ratio. Both of these are a function of air speed and air density. The best glide speed is usually equal to the airplane's V_Y speed, which also gives best rate of climb. So if you are trying to land an airplane unpowered, you shoot for V_Y. Airplanes with good glide ratio are relatively easy to land with no engines. A typical light airplane will have a glide ratio in the 8-10 range and unpowered landing is often part of standard training. High performance gliders can have glide ratio of over 60. These can stay in the air pretty much indefinitely with a good pilot, thanks to thermals. An airliner, typically, has much lower glide ratio. A 777, as an extreme case, has a glide ratio of only 4. (Actually, a 777 has a glide ratio of almost 10 at cruise altitude, but that's due to it being designed for flight at low density and high speeds. At low altitudes, it's only marginally better than a brick.) A wing suit has glide ratio of about 2.5-3. Helicopter in auto-rotation is also about 3, but helicopter can flare a lot better than an airplane can due to energy stored in the rotor, so they can do a soft landing unpowered, despite being very bad at "gliding". A 777 with all four engines dead is typically considered incapable of unpowered landing. It needs at least 1 engine running. Though, under ideal conditions, a survivable landing is possible with that glide ratio.

Technically, so does the brick. If you add a small tale to keep brick's orientation stable, it can do better than 1.

Way to go Overly-Technical Guy who actually sorta avoided answering the actual question.

Edited April 20, 2014 by Rokker

[jwenting]

didnt the mythbusters have marginal success with concrete gliders?

yes. Make the concrete layer thin enough, and the ratio of surface area to volume high enough, and it'll glide. Didn't get very far, but it flew, sorta.

[mrfox]

The ability of an airplane to glide is defined by the ratio of its lift coefficient to its drag coefficient, called the glide ratio. Both of these are a function of air speed and air density. The best glide speed is usually equal to the airplane's V_Y speed, which also gives best rate of climb. So if you are trying to land an airplane unpowered, you shoot for V_Y. Airplanes with good glide ratio are relatively easy to land with no engines. A typical light airplane will have a glide ratio in the 8-10 range and unpowered landing is often part of standard training. High performance gliders can have glide ratio of over 60. These can stay in the air pretty much indefinitely with a good pilot, thanks to thermals. An airliner, typically, has much lower glide ratio. A 777, as an extreme case, has a glide ratio of only 4. (Actually, a 777 has a glide ratio of almost 10 at cruise altitude, but that's due to it being designed for flight at low density and high speeds. At low altitudes, it's only marginally better than a brick.) A wing suit has glide ratio of about 2.5-3. Helicopter in auto-rotation is also about 3, but helicopter can flare a lot better than an airplane can due to energy stored in the rotor, so they can do a soft landing unpowered, despite being very bad at "gliding". A 777 with all four engines dead is typically considered incapable of unpowered landing. It needs at least 1 engine running. Though, under ideal conditions, a survivable landing is possible with that glide ratio.

A typical airliner, 777 included, has a much better glide ratio then light aircraft - over 15 generally.

Glide ratio is constant as long as the aircraft is properly trimmed for gliding - it does not change as a function of altitude, it only varies as a function of angle of attack.

And for powered aircraft, best l/d always occurs below Vy, the only time the two values equal to each other is at the absolute ceiling of the aircraft - where climb rate equals zero.

Lastly, a 777 has only 2 engines under the best of circumstances! And the ability to glide to a landing has less to do with an aircrafts glide ratio and much more to do with its overall energy state - the space shuttle lands unpowered just fine even with its horrible glide ratio.

Edited April 20, 2014 by mrfox

[luizopiloto]

some fighter jets cannot glide very well... like that F-117 one...

[Rokker]

some fighter jets cannot glide very well... like that F-117 one...

Glide well, no, glide, yes.

[iDan122]

ThAnks for the answers guys! I knew I was right

I know how badly the shuttle glides, when I am waiting for something I just play F-Sim space shuttle landingsim on my phone.its quite realistic for an iphone game...