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Old 04-28-2011, 11:24 AM   #1 (permalink)
ChrisGB
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Join Date: Feb 2011
Default Rethink on trottle/pitch curves on electric heli

I went out flying yesterday and crashed my 500 electric . The wind was blowing about 10knots but the 500 handled well in normal fig8 flights. The problem came in at landing time. Brought the heli nose into wind slow FF to heli pad. 2Meters form the ground on it's way to the helipad it flipped right and crashed hard. At that time I had to bring the throttle down to 1/4 stick. When the heli flipped it was if I had no aileron stick control. At first I thought one of the aileron servo's failed, at home confirmed it did not.


My throttle/pitch curves I was using are TH-0%,50%,70%,85%,100% PI-30%,40%,50%,75%,100% which relates to -4,-2,0,+5,+10 degrees.

I had to drop the throttle stick to 1/4 to get the heli down from 15m. The wind just kept it in the air. @ 1/4 stick the blades are @ about -3 but the head speed dropped to 50% of 2200rpm or less. @ that speed and below you lose cyclic and tail control. The reason why it went to the right was the advancing blade created more lift when a gust blown over it, tilted right and just dropped down.

On Nitos you normally have a governor that keeps the head speed constant and you can use the full pitch curve range. On a TH curve like I had, you an only use pitch range when head speed is above 1800rpm which was effectively 50% and upwards.
On clam days this would not apply as I land the heli just below 3/4 stick.
I am going to change my Idleup1 to be more flat, running from about 70% to 100%. Only then can I realy use the pitch range from 0 to -4. I think of stating in normal mode, then once in hover change to Idleup1, Idleup2 stuntmode only

Any other pilot with the same kind of experience?
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