RC India

Hi,

I came across this usage -"washout during forward-flight" in a discussion about an RC heli? What exactly is it? I am familiar with the washout for a fixed-wing (increased root incidence angle for an early stall). How is it applicable in helicopter forward flight?

Hi,
Please insert the link of the discussion of washout during forward flight. That will be helpful for understanding the situation.
Thanks

Thanks for the suggestion @newpg202.. These are some links.

"https://www.helifreak.com/showthread.php?t=410245#post4114770"

This is the first one. "Washout in the helicopter" appeared in the answer given by 'Raggedyman'.

Also in the below-given post, there is a mention of "washout control arm". The post mentions about tail rotor servo arm I suppose.


Thanks,
ROM

Hi ROM,
I am referring to a write-up from the website rchelicopterfun.com by Mr. Jhon Salt from Canada.

"The sole purpose of the washout assembly is to rotate the top half of the swashplate with the head so it remains properly phased with the rotor head while still allowing the full range of up/down & tilting movement/articulation of the swashplate."

It is a mechanical component that is very common in fbl helicopters. But it is not present in DFC heads.

Now the helifreak phrase "washout during forward flight", in my understanding is related with the mixing of cyclic and collective pitch inputs to keep the helicopter from overpitching during forward flight. The rotary wings where the lift force is not evenly distributed along the blade length, don't also need a washout design like fixed wings, which prevent the fixed wings from unwanted roll in case of stall and keeps it stable.
Thanks

Hi newpg202,

That clears it...So the washout assembly is the 'control arm set' (as we call 'it') that locks the upper swash with the rotor head and phase the swashplate with the rotor.
Thanks a lot, mate!

Regarding 'the mixing of collective and cyclic during forward-flight' - Is it a passive process? I was in an understanding that, the flight controller takes care of the over-pitching during forward-flight. Please correct me if I am wrong.

Still, I wonder why it is called 'washout assembly' though..

Regards,
ROM

Hi ROM,
You are right, a control arm set and it is also know as swash driver. I think it is the most appropriate nomenclature.

Most of the RC helicopters are designed for Aerobatic maneuvers. And thus need stabilization in roll, pitch and yaw axis. On a conventional fly bar design, the flybar takes care of the roll and pitch stabilization, where the head lock gyro control the yaw axis. Now the modern flybarless head design uses 3 axis gyro stabilization for the three axis. The collective is not equipped with any stabilization and fully under control of the pilot (some flybarless unit uses 6 axis stabilization system, but there also nothing used for collective stabilization, only autopilot flight controller can manage collective). In that scenario, at high collective input a cyclic input has potential to stall the blades, though today's flybarless controller uses some travel limit setting to avoid such incidents. It is my experience, hope it may help.
Thanks.

Thanks newpg202...Its been a great help!! :)