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Help with Plane Research, please?

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posted on Feb, 24 2006 @ 03:54 AM
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I've been looking everywhere for a formula on how to work out a thrust-to-weight ratio, to help with working out the thrust-to-weight ratio of a U-2 recon aircraft. If any of you know anything about this, then please reply.

Off topic here, how can a thrust-to-weight ratio of 0.8 - 1 power an aircraft to take-off speed? Wouldn't the thurst need to be above the weight to get the plane fast enough to T/O? Or am I missing something?

I know that such variables as air-pressure need to be controlled to give an accurate reading, but all I need is a roughly approximate answer.




posted on Feb, 24 2006 @ 04:03 AM
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No, it doesn't. It only has to get you fast enough for your wings to generate enough lift to overcome the weight of the plane.



posted on Feb, 24 2006 @ 04:30 AM
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The U-2 has huge wing aspect ratios, 10.6 to 1. Dunno how that comes into it. As I said, I'm aeronautically inept.



posted on Feb, 24 2006 @ 04:34 AM
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The U-2 wing generates a lot of lift at low speeds. It's bascally a glider that they put a powerplant into.



posted on Feb, 24 2006 @ 04:52 AM
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Uhm, thrust to weight ratio is straightforward.

Just divide the engine thrust by the aircraft weight (making sure to keep your units consistent!).



As for the aspect ratio, a higher aspect ratio wing will produce less induced drag, thus allowing a smaller powerplant to be used. Its limitation is mostly structural, forcing the aircraft to operate at slower speeds and lower g-limits.



posted on Feb, 24 2006 @ 06:12 AM
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Ahh, thankyou. I suspected it was that, or something similar, but wasn't going to risk it.



posted on Feb, 24 2006 @ 09:58 AM
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A thrust to weight ratio in excess of 1:1 is only required for vertical take off. As conventional planes use wings for lift rather than engines most aeroplanes don't come anywhere near 1:1. The engine only has to move it along the ground fast enough to induce wing borne flight. Think of yourself and a heavy object, like maybe a car thats broken down. It is much easier for you to push it along the ground, which you can do by yourself, than it is to lift it up, which you can't. If that doesn't help just ignore my ramblings



posted on Feb, 24 2006 @ 10:53 AM
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Yes that is correct, some fighter aircraft which have a higher T/W ratio of 1:1 will accelerate even if they go straight vertical. Most other planes would loose speed if they did that and then they would eventually stall.

Now even fighter aircraft that have a high T/W ratio will stall if they continue to go vertical because the higher they go the thinner the air and their engine performance will decline, this in turn would reduce thrust.



posted on Mar, 1 2006 @ 12:17 PM
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For U-2A/C/D:

Empty weight: 6464 kg
MTOW: 10 954 kg
Engine / thrust / T/MTOW ratio:

PW J57-P-37 46,70 kN 0,435
PW J57-P-31 49,82 kN 0,464
PW J75-P-13A 70,28 kN 0,654
PW J75-P-13B 75,62 kN 0,704

Note: Engine is equipped with hydrogen injectors to boost its power in high altitudes.




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