5150flyer

IMO, the stock Hitec servo arms that come with the HS -79__ etc… are not strong enough.

In all the AW build instructions that I have seen, they show Hitec servos using the stock included servo arms. Last week I saw an AW 50cc Yak lost due to one of these arms failing. The servo stripped the arm threads which resulted in aileron flutter and then a spin. Happened on the 83rd flight.






Edited for formating issues to remove html JR

JOHNS3D

My Feedback: (5)

well i think the manual can sometimes be an ilustrative way to build an airplane...... is our goal and task search and do the best based on others experience. I can say that most of the people with 50cc airplanes use other arms like SWB from default. I just use the hitec hd arm on the throttle.

TIA

Use these.

http://www.airwildhobbies.com/MoreIn...&level=2&id=21

bodywerks

My Feedback: (4)

I have also seen where the end user douses the screw with locktite before installing it - well, those karbonite arms get eaten alive by nearly every type of loctite!!! I have seen those karbonite arms used successfully in 40% airframes for countless flights. Unfortunately, aircraft manufacturers cannot package common sense or experience. Otherwise, that plane may not have crashed

5150flyer

Can you explain to me how a lack of common sense or experience has anything to do with a servo arm failing. It happened to an individual with 19 years experience in the hobby whose primary experience is in competition level pattern flying.

I have replaced all my Hitec servo arms with SWB (Airwild is good too) and that is my suggestion. You can use the plastic ones.

bodywerks

My Feedback: (4)

Did it break or did the splines strip? I have only seen splines strip when a screw backs out or when loctite is used. I don't use loctite at all. I use rtv on the screw threads then I dab RTV over the top of the screw after I tighten it - 100% maintenance free and never a single problem. I have never seen the Karbonite arms break as a result of flight loads, but if the ball links are installed such that they put undue tortional load it might cause a problem. I'm Still running the plastic arms on the ailerons and elevators of my 100cc AW 260 with hundreds of very hard 3D/extreme aerobatic flights with not a single problem whatsoever. These are also the same servos and arms that I used for over a year-and-a-half prior on two different 100cc planes.
Just sayin'

JOHNS3D

My Feedback: (5)

5150 maybe it was a bad luck.... thats why most of the people use SWB arms...or other brand but not the stock ones....i dont see a problem with the normal ones...but risk a $2k airplane is better to invest just like $40 bucks more in arms.

mikeiiijr

I have used the stock servo arms on my Hitec servo's for my 42% Aeroworks Ultimate for a year now with no problems at all. I always check before each day of flying that my servo arm screws are not backing out and I have found them loose before. I would imagine that if they did come loose before a flight that the teeth could strip or break the arm in half due to the play in the arm.

5150flyer

I have found this thread educational and I have some comments:

[*]For you guys flying 100cc and bigger - you have the smothness of a twin and redundant servos on each surface. 50cc planes have neither, so the issue maybe more critical.[*]"Did it break or did the splines strip?" The servo arm was broke, 90% was gone when we saw it on the ground. The screw was also missing.[*]The RTV idea is great.[*]The Hitec arms seem good to me, but doesn't plastic get brittle over time? These arms were 4 years old, but only used on 85 flights.[*]I did buy and install SWB arms on my QQ Yak. $10 each and they are a challenging to install. Removing them will be even worst.[*]My Da50 thumps hard at certin RPM's near idle and I have often wondered how hard that must be on the servos etc...[/list]

Ferocious Frankie

My Feedback: (7)

I have been using the stock Hitec servo arms for more than 3 years with no problems whatsoever. I don't use loctite on the screws.

bodywerks

My Feedback: (4)

However, can't fault a guy for wanting to invest in aftermarket servo arms, either.

FrankFuss

It is never completely wrong to eliminate any possibility of a failure, however remote or imagined, if the cost is not ridiculous. If I crash, I want it to be because of some stupid pilot error, not anything else. Besides, those little red aluminum servo arms look pretty.

Mark Dennis

My Feedback: (4)

The Stock servo arms that come with the Hitec servos are extremely strong and from what I have seen over the years hold up very well. I've used them on all my planes that use/used Hitec servos and never had a problem with them stripping or breaking. Not saying that your friend didn't have an issue with the arm but could it have been the other way around? Did the aileron flutter and then the splines strip? That's the thing about control surface flutter, it is so sudden and violent that it will cause that type of destruction instantly. I also use loctite on ALL my servo screws and have never had the arm eaten up by the loctite.

That being said thank you for offering the constructive criticism on our manuals, we are always happy to hear from customers about how we can better improve our products, from the manuals to the airplanes themselves.

Mark