Airplane Question

[jronald]

Question: How fast would the following airplane glide with no power

Givens: 28:1 glide ratio, ceiling of something over 70k feet. Known glide of over 175 miles. Rumored glide 1000 miles

Suspected: Around 125 miles per hour?

Ron

[rkawakami]

I don't know if there's enough information to determine the speed. And I'm assuming that you are talking about "ground speed", as opposed to "air speed". Certainly if the airplane is vectored straight down (a possibility at flight level 700 and no power ), it will be going more than 125MPH.

[craigmontHunter]

I don't know the speed, but I know that it could go 371 miles with the given information
(28 ft forward for each 1ft down)
(28 * 70 000 = 1 960 000ft)
(1 960 000ft/5280ft/mi = 371.21miles)
For the speed, the best that you could come up with for the information given would be that it:
- was starting from rest (not possible)
- had a constant acceleration (a componet of gravity) - would mean that it would keep accelerating
- the speed when it hits the ground (which would be higher than real life - terminal velocity and air resistance)

I am too lazy right now (and I have physics work to do) to solve this, but if I have time, I could give you the maximum speed it would reach with no air resistance (which would cancel the glide ratio)

[jronald]

Terminal velocity is about 125 miles per hour, that should be straight down. From 70k feet up, you have got to assume it would "slow down" to that speed prior to impact. NOT THE QUESTION
Under power it flies at about 500 miles per hour, once again, not the question.

Un-powered, clearly not in a stall, how fast would it glide. Lets assume to reach maximum distance. Obviously if the runway were closer, the speed could increase to attain right place at any time.(heck your without a engine!)

Ron

[bill bolton]

Question: How fast would the following airplane glide with no power

It would depend a very great deal on the weather conditions.

Cheers,

Bill B.

[jronald]

No jet stream, although I suspect that a 200 mph tail wind could account for the 1000 miles glide.

What does a glider fly at?

Ron

[RealBlackStuff]

This might help: http://www.scribd.com/doc/39450374/Airspeed-Gliders

[rkawakami]

So will this: http://www.youtube.com/watch?v=y2R3FvS4xr4

[jronald]

The world record, on a sail plane/glider was just short of 120 mph for about 1100 miles. The glide ratio was roughly double one compared to the other, so Im not sure its applicable.

Ron

[jronald]

Ray
Your twisted

Ron

[craigmontHunter]

If you are talking about a real glider, then yes, as long as thermals were found, the glide could be indefinate, allowing for a longer than calculated range. The average glider goes at about 120mph, but it all depends. A glider could not get to 70k feet though - the record is 50 699ft, and that was achieved by going over the andes. (seehttp://www.technologyevangelist.com/200 ... oes_i.html)Yes, a jetstream could account for the longer glide, but if it is a real glider situation, thermals and wind currents would have made the greatest diffrence.

Ray's Video was the best help

[jronald]

If we are going west to east, and a known glide time was in excess of 3 hours. South of the Tropic of Cancer but North of the equator Japan would be some 2800 miles away, even at engine speed of 500 mile per hour with the engine, 3 hours would only equal 1500 miles. At the "time" of this question Korea/China and Russia were the hot spots. Curious, where the devil this plane was coming from.

Ron

[rkawakami]

Ray's Video was the best help

A little OT:

If you liked that, somebody actually took the time and made some calculations and came up with the definitive answer: 24MPH.

ref: http://www.style.org/unladenswallow/

[craigmontHunter]

If we are going west to east, and a known glide time was in excess of 3 hours. South of the Tropic of Cancer but North of the equator Japan would be some 2800 miles away, even at engine speed of 500 mile per hour with the engine, 3 hours would only equal 1500 miles. At the "time" of this question Korea/China and Russia were the hot spots. Curious, where the devil this plane was coming from.

Ron

Is this airplane the U2 spyplane (the only plane I can think of with a 28:1 glide ratio and a ceiling of ~70k ft), then it had a range of >5000 miles, so it could easily make it 2000 miles one way before turning around. Since there is no context to the question, it is impossible to tell, but U2s did fly from China for a time.

see: http://en.wikipedia.org/wiki/Lockheed_U-2

[jronald]

Very late 1964 or early 1965.
Im assuming it was the U2, still left with my first question how fast was the glide. I dont think I will ever know why it broke East and headed over the pacific. We had friendly countries a whole bunch closer. Push comes to shove it could have gone to Japan, to glide a minimum of 400 miles and hit a speck of sand with a minimum of 1000 miles of water surrounding it?!?!?!

Figuring the jet stream, its very likely the glide was 1000 miles. 200 mph X 3 hours
125 mph X 3 hours = 375 miles about 400
125 mph + 200 mph jet stream = 325 mph
3 hours x 325 mph = 975 miles

1000 miles is not the 2800 I mentioned from Japan. However I dont think it was headed West to East, although with the prevailing winds and the US in the East bound direction, there would be know reason for it to be West bound.

Strange tale. I can not get the math to add up.

Ron

[mediasponge]

If the objective is to glide the longest distance from a starting point (engine flame-out?) at 70,000 feet, the pilot would most likely maintain the attitude of the plane such that its airspeed was just above stall speed. Stall speed depends on air density, and therefore altitude. I don't believe thermals have much effect until you are only a few thousand feet from the ground, so dropping from 70,000 would depend more on the jet stream and prevailing winds. If you know the plane, you can probably look up stall speed, or landing speed and go from there. You need to give up potential energy (altitude) to gain kinetic energy (airspeed) at a rate that offsets drag. Drag increases with air density, so you would probably need to descend faster the closer to the ground you got.

Ever watch a Space Shuttle landing? That's the ultimate glide from altitude aircraft. It goes up like a rocket and comes down like a glider. A glider with the glide ratio of a Coke machine! At hypersonic speeds, the Shuttle has a glide ratio of 1:1. Closer to landing, it's around 4:1.

Here's a real aircraft oddity: The Boeing Condor. I've seen it. It's in the Hiller Aviation Museum. The wing span is about 200 feet. It flew around 67,000 feet altitude, the airframe is carbon fiber and cardboard, empty weight is only 8,000 lbs, and it's completely robotic!

[craigmontHunter]

An legally, all you need to pilot the space shuttle is a glider license (I had some friends who were wondering a while ago )

[jronald]

The shuttle is not a glider, unless we are considering a brick a glider.

I found this:
High-aspect-ratio wings give the U-2 some glider-like characteristics, with a lift-to-drag ratio estimated in the high 20s. To maintain their operational ceiling of 70,000 feet (21,000 m), the U-2A and U-2C models (no longer in service) must fly very near their maximum speed. The aircraft's stall speed at that altitude is only 10 knots (19 km/h) below its maximum speed. This narrow window was referred to by the pilots as the "coffin corner". For 90% of the time on a typical mission the U-2 was flying within only five knots above stall, which might cause a decrease in altitude likely to lead to detection, and additionally might overstress the lightly built airframe.[5]

Which means the formula just got really complicated...............
As the U2 descends, it would slow, and still stay airborne.
After he flamed out, and nosed over the speed had to have been 499 mph (about) as it descended he lost speed but gained distance. He glided further the lower he got? Without CFIT? Well not really CFIT, but you get the idea.

By the way, at Sea Level the U2 will fly @ 81mph.

Ron

[mediasponge]

An legally, all you need to pilot the space shuttle is a glider license (I had some friends who were wondering a while ago )

I'm sure NASA security is going to require a little more in the way of credentials before letting you climb in there.

[mediasponge]

I heard a U-2 take off once. It may have spindly wings, and only one engine, but that thing is Loud with a capital L. That was back when the Russian spy satellite came down over Canada and the US was scrambling to find it. They launched a U-2 from Moffett Field every day till it was spotted.

[rkawakami]

NASA flew U-2 and later, ER-2, aircraft from Moffett back when I was working there in the mid-to-late '70s. Launches were usually at 11am and indeed were loud. My parent's house is across 101 from the field but by the time you heard the plane, it was almost too late to actually see it climbing.

[craigmontHunter]

I'm sure NASA security is going to require a little more in the way of credentials before letting you climb in there.

Theres the problem - if you could get your hands on a space shuttle, all you would need (legally) to fly it is a glider license. The issue is the practicallity - not everyone has acess to boosters and rocket fuel, and you would probably annoy quite a few people in you intterupted their commerical flights to land your space shuttle - normal gliding fields would not work.

[killer]

This might be slightly off topic but a few days ago we were on a Britten-Norman Trislander aeroplane between Guernsey and Alderney and it landed on grass.

[mediasponge]

All Soviet-era Russian fighter planes were capable of take-off and landing on grass. They were frequently stashed away in barns "just in case." In the US, only Naval aircraft capable of landing on carriers were built that stoutly. The US Air Force never saw a need for this.

Incidentally, the oddball plane in Mad Max: Beyond Thunderdome is real: Mad Max Plane

[killer]

We used to have vertical take off Harriers that could take off anywhere. They are now a thing of the past.

The amazing thing about sub-sonic harriers was that when tailed by an enemy aircraft they could stop in mid air and reverse the positions almost immediately.

[Nohbody]

We used to have vertical take off Harriers that could take off anywhere. They are now a thing of the past.

While technically true, the problem with VTOL is that it makes for a massive hit on their payload and/or combat radius to do so. VTOL launches are in general frowned upon because they reduce the ultimate effectiveness of the aircraft. Great, you can take off like a bird... but at the expense of having a bird's carrying capacity. Hope you don't mind throwing spitballs at the enemy, because you can't really lift anything much heavier after that bird-like take-off.