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Thrust question by Sootah
Started on: 08-07-2001 04:14 AM
Replies: 7
Last post by: Indiana_resto_guy on 08-07-2001 07:01 PM
Sootah
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Report this Post08-07-2001 04:14 AM Click Here to See the Profile for SootahClick Here to visit Sootah's HomePageClick Here to Email SootahSend a Private Message to SootahDirect Link to This Post
Now, if 1 lb of thrust is the force required to prople 1 lb of material 32 ft/sec would not 1 lb of thrust also be able to propel 32 lbs of material 1 foot in 1 second? Reprimand me severely if my logic is flawed. Assuming that you can even understand what I am trying to get at.

How many lbs of thrust would be required to lift an 800 lb aircraft up? By that I mean getting it moving fast enough that it could take off.

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fierospeeder
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Report this Post08-07-2001 04:41 AM Click Here to See the Profile for fierospeederClick Here to visit fierospeeder's HomePageClick Here to Email fierospeederSend a Private Message to fierospeederDirect Link to This Post
I havn't been in a plane or studied it for a long time.

I think its more complicated then that. First you have to determine the area of the wings and the curvature of it. The curvature causes higher pressures under the wing causing it to lift. Because the air on top has to travel farther then the air under the wings.

Thrust is mostly just a force to push the plane. A plane has 4 forces acting on it. thrust, lift, drag, and gravity.

If you changed the question into a rocket. Then it would be much easier to solve. Because you just need to find out the thrust to make the rocket go up, if you dont consider air resistance.

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SilverFieroV6
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Report this Post08-07-2001 05:21 AM Click Here to See the Profile for SilverFieroV6Click Here to Email SilverFieroV6Send a Private Message to SilverFieroV6Direct Link to This Post
As a pilot i can tell you that speeder is correct with regards to a plane haveing the four forces. A planes wing is flat on the bottom and curved on the top of the wing so the air has to move farther , and the air under the wing will produce the lift then.
Concering thrust and wieght a cessna 152 ( two seater single engine) is about 1650lbs, depending on instruments and what not on the plane. The plane has a lycoming 4cyl engine the is connected directly to the propeller. I dont know how much thrust that produces ( i even tried to find it in two of my manuals), but it is a little more complicate than just the thrust to making an airplane fly.


BTW what type of aircraft are you trying to fly that is 800lb???

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Indiana_resto_guy
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Report this Post08-07-2001 08:46 AM Click Here to See the Profile for Indiana_resto_guyClick Here to Email Indiana_resto_guySend a Private Message to Indiana_resto_guyDirect Link to This Post
The 152 Cessna 4 cylinder Lycoming engine will produce around 110 to 120 HP. (I think this is correct, not very familiar with this type AC)
Mainly in aircraft applications the lift (wing area) to weight ratio is the major consideration to HP & thrust required to get off the ground and maintain straight and level flight. The greater lift produced by the wing area the shorter the take off roll (full flaps) used in short field take offs.

Your logic is flawed in the aspect that your attempting to change the variable of gravity (32ft. per sec.) in exchange for the 1lb. of weight. That just won't work as you first need to calculate the static resistance (friction) to start the weight moving. The power for this is usually higher that the power needed to maintain the desired motion and speed. This depends on a great many things like the following, type of material to be moved and it's shape and contact area at the surface material, also the coefficient of resistance between the objects material and the surface material composition also comes into play.
Try this in your car if it's an automatic, put it in drive and release the brake, (no gas) then stop and do it again, this time give it a little gas and note the difference.

If you wish a more detailed explanation I'll go get my physics books. (Don't want to though!)

I to am a pilot and former military UH-1H senior crew chief.

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Sootah
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Report this Post08-07-2001 02:14 PM Click Here to See the Profile for SootahClick Here to visit Sootah's HomePageClick Here to Email SootahSend a Private Message to SootahDirect Link to This Post
It was merely a hypothetical question, I am aware of the 4 forces acting on the aircraft. I just had been bored and looked at all of the homebuilt aircraft sites. Many state how many HP their engines put out, but not how much thrust.
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Indiana_resto_guy
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Report this Post08-07-2001 02:58 PM Click Here to See the Profile for Indiana_resto_guyClick Here to Email Indiana_resto_guySend a Private Message to Indiana_resto_guyDirect Link to This Post
Basically the amount of thrust the engine will produce depends on the pitch of the propeller blade that it spins. The higher functional pitch, the greater the thrust.
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JSocha
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Report this Post08-07-2001 03:04 PM Click Here to See the Profile for JSochaSend a Private Message to JSochaDirect Link to This Post
 
quote
Originally posted by Indiana_resto_guy:
Basically the amount of thrust the engine will produce depends on the pitch of the propeller blade that it spins. The higher functional pitch, the greater the thrust.

Huh? And all this time, I thought that thing was just up front to keep the pilot cool. Because I was dang sure that if you were to turn it off, the pilot and any passengers would certainly start to sweat.

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Indiana_resto_guy
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Report this Post08-07-2001 07:01 PM Click Here to See the Profile for Indiana_resto_guyClick Here to Email Indiana_resto_guySend a Private Message to Indiana_resto_guyDirect Link to This Post
Naw, just like a rollercoaster ride, the rushing wind on the way down will keep you cool!
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