Gravity is the Main Source of Energy for a Heavier Than Air Aircraft

Gravity is the Main Source of Energy for a Heavier Than Air Aircraft

If one were to truly think about the energy consumption of an aircraft flying thought the air, one would quickly realize that dramatically less energy is consumed than would be expected.

When a plane is flying, say straight and level, the thrust generated from its engines must continuously transfer enough energy to overcome drag and create lift. The lift created must continuously counteract the gravitational weight of the craft. This would also be the case if the aircraft were pointed vertically and acting more as a rocket.

Very few aircraft are equipped or capable of sustained powered vertical flight (steady speed or even acceleration)--most if not all are fighter aircraft. The energy consumption of an aircraft in vertical flight is enormous and as a result is usually used in short bursts.

Now if an aircraft in straight and level flight should consume approximately the same amount of energy as one in vertical flight, what constitutes the difference?

I state that gravity is the additional energy source and also serves as the PRIMARY energy source of an aircraft.

Thursday, March 24, 2011

The 747 as Our Guide

A 747-400 weighs about 875,000 lbs. at takeoff. It is usually powered by 4 jet engines providing about 60,000 lbs. of thrust per engine. That is at most 240,000 lbs. of thrust or about a .274 thrust to weight ratio. In other words, the engines a best can only provide about 27% of the direct energy to support the aircraft in the air.

The remainder must come from the pull of gravity. Gravity does most of the work; pulling on the plane, causing airflow over the wings and the resulting lift. The engines then provide the additional thrust needed to generate the lift needed above what gravity produces.

Put another way, if a 747 were pointed straight up and fully powered, it could not rise much less maintain altitude. Horizontally, it still needs to transfer the same amount of energy to the air to support its weight, but is assisted (actually assists) by gravity.
Posted by at

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)