Designing for Endurance around Preselected Electric Powerplant

[Aerohandel]

Normally, when designing aircraft, we start by designing the structure based on performance requirements, then find an engine that matches your needs.

If given an electric motor, a propeller, and a battery pack, and the goal is to make an airplane that has the longest endurance, how is this achieved?

Obviously, you want low Lift/Drag. One might think that it would be best to design for the velocity at which the motor/propeller is most efficient, but it might be better to design the slowest and lightest possible airplane.

What is a good way to go about designing the airfoil?

 

[GregLocock]

What class is this for?

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[aerodog]

Aerohandel,

I always thought you designed the airplane around the engine (which sounds like that is what you are doing).

Once you select the engine, you do the best you can with what you have to work with in terms of meeting your performance goals.

aerodog

 

[rb1957]

i'd suggest looking in detail at your engine performance. there should be a couple of clear choices for max endurance, most probably the power output that minimises power consumption (that way you can keep powering the engine for the longest time, maximising endurance) ... if you want to maximise range this'll be a little different.

from this you'll know the speed you want to optimise on and the drag you can handle (since you'll know the power output, which is equal to Drag*Speed). now you'll be able to design the rest of the plane ... you know the drag, opt. speed, lift (depending on your wing Cl), airplane weight (lift - Lh, the h.stab. balancing force; you could think of a canard configuration so that Wt = Lw + Lh) ... everything is interconnected ... the difficulty is getting it all to work out !