I Am asking about the takeoff power here not how the aircraft takes off.
What do I need if I want to calculate the power required by an aircraft to take off?
What parameters should I consider?
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$\begingroup$ Welcome to Aviation.SE! I edited the question to (hopefully) make it more clear. If you wanted to know something else, feel free to edit again. $\endgroup$– BianfableCommented Apr 30, 2020 at 19:24
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$\begingroup$ I believe you mean 'thrust' instead of 'power'. If so, this question will answer your question. $\endgroup$– SuperCommented Apr 30, 2020 at 19:26
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$\begingroup$ First you need to accelerate to take off speed within the runway length. Then you need to climb quick enough without decelerating. These two are the dominate factors for engine output at takeoff. $\endgroup$– user3528438Commented Apr 30, 2020 at 19:57
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1 Answer
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In the physics realm $Power$ = Mass x Acceleration x distance/time
To many it means "how much throttle" , which is how much fuel/time.
"Throttle" x prop efficiency = $Thrust$
This gives you a unit of Force that can be directly compared to glide data as follows:
Potential energy Mass x Gravity x altitude loss = $Thrust$ x horizontal distance flown
This rearranged to $Thrust$ = Mass x Gravity x altitude loss/horizontal distance flown
$Thrust$ = force required for straight and level flight, expressed in "pounds or Newtons"
So if your plane weighs 10 lb and glides 5:1, you need 2 lb of thrust for straight and level flight.
One would at least double, or even triple this for "takeoff power", depending on your performance preferences. Sufficient "takeoff power" will give a safe climb rate to avoid difficulties with downdrafts.
For example: my plane glides 5:1 at 60 mph or around 5000 feet/minute and loses 1000 feet/minute. At 10 lbs it was calculated to need 2 lbs of thrust for straight and level flight.
How much more thrust do we need to climb 500 feet per/minute. Again, the glide data provides a very good estimate, 2 lbs x 500 fpm/1000 fpm = 1 lb additional or 3 lbs total at 60 mph. Higher speeds with more drag, or lower speeds "behind the power curve" will require more than 3 lbs of thrust.
answered Apr 30, 2020 at 19:52