|Dec 26, 2009, 01:03 PM|
LeO C-30 maiden flight:first crash NEED HELP !!
This afternoon, I made the fist flight of my LeO C-30. Unfortunately the video camera failed, so I will try to explain what happened.
First, here are the specs of my gyro:
- 71' rotor span
- 3100 kg
- ASP 70 4 strokes
- 5° engine incidence down
- 5° rotor incidence
- 0° stabilizer incidence
- approx. 6° nose down attitude for center of gravity
- DC Head with triangle of fiberglass (very stiff)
- 2 15kg/cm torque metal geared servos with load sharing (delta mix on transmiter)
- 10° movement on each side on "elevator" and aileron.
- anti-clockwise rotor
- Aerobalsa blades
After pre-rotating the rotor with an electric drill (approx 1200 rpm) I start my take-off with 3/4 throttle. The gyro ran a few 10 meter then take off itself.
Immediately it took a very nose high attitude (almost vertical).
I tried to reduce the incidence of flight with some "down elevator" The gyro reduce to approx. 20° incidence and start to turn right.
It was impossible to stop the turn, with full stick to the left on ailerons.
I finally cut off the engine and the gyro fall on the right side wiht minors damages : right half-landing gear twisted, part of the stabilizer and one blade broken.
So what happened?
I think the center of gravity may be too backwards, and too much incidence on the rotor.
What is your opinion?
Please I need help with my fist gyro.
|Dec 26, 2009, 03:40 PM|
Joined Nov 2006
You mention that the fibreglass hinge material is very stiff. The rotor blades have to flex up and down easily every rotation, so in my case I use quite thin polypropylene code 5 plastic It is as flexible as as I can find but has adequate strength. This hinge material has never given trouble in the air, but has sometimes ripped apart due to a ground strike, possibly preventing damage to the blades.
|Dec 26, 2009, 04:13 PM|
In this forum, someone suggest me to use 1/8' fiberglass triangle. It is very stiff and don't flex.
I 've made a 1/16' triangle head, and it flex just fine, but I don't know if it is enough for a 3 kg autogyro.
|Dec 26, 2009, 04:18 PM|
If your plate was'nt flexible enough it would roll to the left (anti clockwise rotation)as soon as it left the ground.
From your explination it seems to me that you have not got enough nose weight. With my tractor gyros I hang them from the rotor spindle and they hang with a nose down attidude of around 14 degrees with an empty tank.
Do the rotors spin up ok without the drill?
|Dec 26, 2009, 04:40 PM|
I've made static test with the rotor in my hand. It rotate well in the wind and accelerate quickly when I start running; I don't feel torque in my hand.
Blades have -2° incidence.
But, during the take off, the rotor seems to rotate slower than during my tests ( But I ran quite fast and the wind was quite strong too, rotor noise was impressive)
The gyro went into the air by itself, without any action on the stick.
It don't goes on a roll, but turn to the right, nose up.
I've put the same center of gravity like the plan, but I increase the rotorspan, so effectively, the CG was a bit backwards I think.
|Dec 26, 2009, 05:16 PM|
It is very likely!
Why not try holding your autogyro into wind? (with the radio on!!) when the blades are up to full RPM the gyro should go 'light' in your hand/hands, you will be able to tell whether the nose wants to pull up or it pulls to the right. You can then trim to suit, but please be careful as 72" rotors can hurt if they strike someone
|Dec 28, 2009, 10:00 PM|
G'Day Red Baron.
That's a fine looking machine you have there .I myself am flying a 'C30' although it is a smaller 'E' powered profile model.I had similar problems on my first flight.causing the model to spiral in and damage several parts .I think that it is easier to fix the problem of the model not lifting ,rather than the model jumping into the sky at a great speed and having to correct the problem very quickly.
I am sure many people will have many reasons for your situation and I hope you may find something in my ramblings.
The hang angle on my model is approx 12 deg [it started at 8deg]
The mast is at 4 deg [started at 6 deg] and the motor down thrust is at 6 deg.
The biggest modification I made was to the incidence on the tail plane.on my first attempt to fly it was at O deg ,now that has been gradually changed to +4 deg..when I first flew the model jumped into the air as if I was holding 'up' elevator. I believe the tail plane incidence was my biggest problem.I see you have -2 deg on your blades? I don't know if that may be adding to your situation,all my blades have always been at 0 deg
You said before that you would be using Aerobalsa blades ,is that so? Aerobalsa blades are very well made and very efficient .I have used them and found that they have generated more lift than I needed and I found the controls to be super twitchy.Now that may just be me ,as they are very popular and I would not say a bad word about them. I have cut down my Aerobalsa blades to reduce the diameter.I have found that a flat trailing edge works better for me.
[ Please feel free to disregard the ramblings of a mad man]
Good Luck and Happy Landings
|Dec 29, 2009, 04:15 PM|
Thank you for sharing your tips; Yes I use Aerobalsa blades on the C-30, and they seems to give a lot of lift. I would reduce a bit the diameter of the rotor, because the 70 ASP seems to have not enought power: he flawn very slowly at full power.
The interesting in your answer is the positive incidence of the tail, but before eventually applicate this big modification, I will try to reduce rotor incidence, and increase hang angle (actually 6°).
To be continued...
|Dec 29, 2009, 06:29 PM|
Hi Red Baron
Yes I know the tail plane is a major modification,and I would not make it until making other mod's so I believe you are going in the correct direction with the rotor and hang angle.Don't worry to much about the speed of the model at full power..autogyros can handle it O.K.
Lot's of luck
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