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Power needed to climb constant slope at constant speed 
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#19
Dec1112, 02:49 AM

P: 777

I saw the attachment, and indeed it appears that the plane loses power as it climbs, and I still suspect it is direclty related to decreasing air pressure. For an air breathing engine, less air means less power. Nevertheless, the power required to maintain the climb remains the same (it actually probably decreases). But since the "excess power" of the plane decreases, so does it's rate of climb. It's engine is getting weaker, as it's simply running out of breath. I don't know the formula for this but I'm guessing the air pressure is the driving factor. 


#20
Dec1112, 03:03 AM

P: 777




#21
Dec1112, 03:18 AM

Sci Advisor
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P: 12,275

For an aircraft which is using the air for lift then its design will be optimal for a certain air density. This could favour a very high altitude (as with the U2 spy planes) so the power needed to climb may be less at high altitude. Then the characteristics of a 'real' engine are almost bound to involve loss of power beyond a certain height. This may not actually be relevant to the original question  if the question is to be answered literally. I think the question needs to be broken down into parts, each of which stands a chance of being answered. 


#22
Dec1112, 03:56 AM

Sci Advisor
P: 2,470

Lsos is absolutely correct. If you define excess power as power over or under power required to maintain speed at fixed altitude or on level ground, then constant rate of climb will require constant excess power.
While the power requirement will change with altitude, the excess power requirement will remain the same. 


#23
Dec1112, 05:08 AM

P: 777




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