Helicopter fuel economic
Hi all
First post wee
Good questions you are asking griffin.
Stupid question, DEMANDS stupid answers!
Here is a stupid one (if you ever doubted)...
The question about helicopter fuel economics, I have a few thoughts on that:
As pointed out bay sobek the rpm is “fixed” but whey is rpm fixed?
A good reason for that I can think of, is the speed of the rotor blade at its ends, (there may be several).
The speed of the blade tips dependents on the rpm of the disk and the length of the rotor blades.
Lets say our speed at end of blade tip Is 900 kph and you are flying at a speed of 300kph,
The blade tips will at some point rotate “white the flight direction” and the relative speed trough the air will be 1200 kph ? At this speed you are roughly at speed of sound.
Anybody seen an helicopter with a delta shaped rotor disk?
So you cant step on the “pedal” to increase the rpm to gain more lift, what to do?
You Increase the rotor blades AoA as solbek pointed out.
As higher you go the air gets thinner and the rotor blades at an given AoA produce less lift.
You then compensate by increasing the AoA, but can you do that forever?
A show stopper can maybe be engine power. But What if you had unlimited power?
The Higher the AoA more drag you produce, but thinner air makes opp for some off the efficiency loss? Is the blades(airfoils) efficiency at producing lift at different AoA equal?
http://en.wikipedia.org/wiki/Lift_coefficient
Maybe others answers pointed down this lines, or maybe its all gibberish.
Please comment/correct.
