Check that A-Arm!

[JustPlaneChris]

I think I remember someone posting a similar advisory a while back, but I couldn't find it offhand. So here's another one:

Check your A-Arm for free-play as part of your pre-flight checklist!

For the last several outings, I've had some weird drifting (either forwards or backwards) from my F50 while in a hover. I blamed this on a recent servo gear replacement, and figured my swash wasn't quite level. I even checked it once and turned a few links to get it level. However, a few flights later the drift was back.

After flying it this weekend, I decided to go over the whole setup, and I found the problem: With the radio powered on I was able to rock the swash fore-aft several degrees! The reason? BOTH of the screws that clamp the A-Arm to the shaft were loose. Very loose. I removed them, cleaned them really well with alcohol, and re-applied liberal amounts of threadlock upon reinstallation.

I figure I used up quite a few Karma points avoiding disaster with this one. It is definitely something I'll wiggle more often to make sure it's still secure.

[Slyster]

Thanks Chris I'll check mine before my next flights.

[zorax2]

Dumb question - What is an A-Arm?

[JustPlaneChris]

The manual calls it the "Elevator A Arm Assembly". It's that A-shaped part and the other bit that connects to the rear of the swashplate and pivots on the rear control rod that goes through the frame.

What was loose on mine are the two M3x5mm cap screws that secure the elevator arm to the control rod. Luckily they were still tight enough that it couldn't rotate past the flat spots on the shaft, but they were loose enough to cause slop and control issues.

[Grok]

Yeah. Don't have a Fusion yet, but this is something I check weekly on my 550.

[AeroMattics]

Thanks for the heads up. I just checked both of mine which were ok, but I'll continue to monitor them.

[airbound]

I have had to tighten them once so far--103 flights.

[sansone]

thanks a bunch..
will check mine today

[im4711]

good catch - but not just the elevator arm should be checked. On regular basis the other small screws should be checked as well.

[s0laris]

check the elevator bell crank set screws too.. they have a habit of backing out

[Ah Clem]

Chris, Solaris,

Thank you.

I will check both on my ship before I fly it again.

This type of information regarding preventative actions/maintenance could save a great deal of money and time.

[JustPlaneChris]

Originally Posted by Ah Clem

Chris, Solaris,

Thank you.

I will check both on my ship before I fly it again.

This type of information regarding preventative actions/maintenance could save a great deal of money and time.

Indeed, I consider myself very lucky to have found the issue before it came completely loose.

I've had a few questions about what exactly was loose, so here's a picture from the manual to clear up what screws were wiggly.

[spence46]

Just found mine loose today also, probably going to use red this time.

[tonyxwing]

Here was the thread. My buddy just finished his build and the same thing happened to him too. So make it a best practice to check them before every flight.

https://www.helifreak.com/showthread.php?t=314163

[SkyIsTheLimit]

Does anybody know a way to tighten the screws without disassembling the half heli?

[Brandon Gaither]

Originally Posted by s0laris

check the elevator bell crank set screws too.. they have a habit of backing out

+1

I've seen this happen repeatedly. I started putting a set screw on both sides of the elevator bell crank.

[Arcturus97]

Originally Posted by Brandon Gaither

+1

I've seen this happen repeatedly. I started putting a set screw on both sides of the elevator bell crank.

Same here - I had a crash this summer, I found the elevator set screw loose afterwards. I can't prove if that was cause or effect; but now I have two set screws, one of each side of the elevator bell crank.