autorotation landing system

[txradar]

Can anyone explain how the autorotation landing system works that is advertised on the walkera 68B.

Thanks \\

Joe

[chaos]

Just in general, autorotation refers to keeping the blades spinning without the benefit of a motor. A one-way bearing is used to effectively disconnect the rotor from the drive train to eliminate any drag from that. To keep the blades going you have to have some amount of negative pitch on the blades, usually around -3 degrees and obtained simply by reducing the stick position, and you want some forward speed. Near the ground, the nose is pulled up to slow the heli, then you get it level and use up the inertia in the blades by pushing the collective up in order to set it down gently. Of course this final maneuver near the ground has to be timed correctly so that you don't run out of rpm before landing.

[Aztek1701]

Hi txradar,

Chaos has provided a good description there. It sounds to me like Walkera is advertising "autorotation" as some kind of unique safety feature that will protect your heli automatically. Unfortunately as chaos has pointed out, bringing a heli down in autorotation is a skill on its own and a beginner is likely stuff up an autorotation landing resulting in a broken heli.

Also, you should know that most (if not all) collective pitch model helis can auto but small electrics such as the Walkera and the T-Rex dont do it at all well because the blades dont have enough mass to keep spinning for long.

A far more practical "landing system" for a small electric is a battery alarm which alerts you to a low battery condition before its too late and the need to Autorotate is removed.

Take Care.... Azzy

[hawkman]

The alarm is a great idea for electrics....auto practice is a must for other heli which are powered by nitro, petrol or gas turbine engines.

If you have a simulator you can practice doing autos....they are a difficult thing to get right but once you get the idea they are not so bad.

The more skilled heli flyers can do autos all the time.....I have pulled off a few now but the risks of breaking the heli are quite high.

First time I did an auto I smashed the heli.....I was practicing the descent...didnt like what I saw and missed the throttle switch (thottle hold for ic engines puts the engine to idle....leaving the rotor to freewheel) my heli was written off.

Second time, new heli, saw a good touchdown....I relaxed but the rotor hit the boom....one dented boom....one broken blade....I was pleased though because I could at least touch down....it wasnt pretty but the heli was still in one peice.

Third time...success!!!!! heli touched down and gracefully skidded and spun 180 degrees....wow!!! looked good even if the final move was an accident


The worst thing to happen is this.....how many times do you fly around and come into land....notice how you will hover about looking for that ideal spot on which to land.....with a full blown emergency auto you dont get that luxury....you have to do a controlled descent followed by a nice smooth landing....straightaway...

dithering will see a broken heli...beacuse once the rotor rpm is lost the heli will fall like a stone.....and break.


To practice....try zooming about....and then come into land....nice and steady....but without dithering about....its quite hard to do then first few times, but you will get it...use a simulator first.

Hovering just slightly above the ground is ok....but just inches though....no more....the thing to watch for is this:

as the heli descends and the landing is about to take place...you will tend to pull the nose up.....the rotor disc goes back.....if you touch down rear first the rotor disc is still at its last attitude.....the boom comes up and if the blade speed isnt high the rotor will droop....and hit the boom....thats a 'boomstrike' not pretty but your heli will live to fly again...with parts and some straightening out

as you touch down in an auto....get into the habit of putting the collective pitch UP....and gently push the cyclic forwards...this should keep the disc clear of the boom.

If the ground is rough the heli might tip over....its usually ok....this has happened many times to me.


Its rare that you have to auto for real....good maintenance and landing your heli early, if you think theres a problem, usually saves the day....but if you have a sim...do get into it....and when you fly for real....try as I said before...do that landing without thinking too much.

Good luck


Rob

[dooleyje]

I agree that the smaller helis do not auto well. But it can be done. I always set my helis for -3or4degrees normal mode and -5 or so in idle up 1 and -10 in 3d IDLE UP. It helps to land TO HAVE SOME NEG PITCH AT MID STICK. In auto to keep you head speed up as it comes down is to give it full neg pitch. This keeps the blades rotating. hOLD IT DOWN TILL YOU REACH A POINT ABOUT 5 FT FROM GROUND AND PUSH THE STICK UP TO ABOUT 3/4 POS. PItCH AND KEEP PUSHING UP AS IT COMES DOWN. Every bird will be different. My FAI machine will auto and can do a 720 degree circle and land like it had the motor running. In competition you also had to perform a spot landing during the auto. Of course this is a 12lb bird with heavy FAI blades.
My Ergo is not as good but it will do it. I had to learn how on every bird I've had.