What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Appalling Rotax Exhaust Springs

mike newall

Well Known Member
Sponsor
2 RV12's

Both shed exhaust springs within 10 hours of new despite lathering with silicone as per plans.

Just lost another 2 on start up today. The ramp lads presented them to me when I got back. They just crack at the base of the curly bit and fall off.

These OEM springs are just garbage and need flagging up via MOR or similar.

I am doing that now in the UK
 
I've been flying my RV-12 for 4 1/2 years, almost 700 hours. Not sure exactly but I think I've broken two springs. I've replaced probably 3 or 4 that have shown wear, I keep those just in case I break one without a spare.
 
"Knock on wood": 5.5 years and 850+ hours on original OEM exhaust springs on my 912ULS. Instead of filling the interior of each spring with silicone per plans, I ran three beads of silicone down the exterior surface of each spring after initial installation. I am not sure whether any of this matters much since I typically unfasten/refasten each spring during each annual CI to clean and reapply exhaust pipe joint anti-seize compound. I also run some loose safety wire through the center of each spring to retain the pieces should a spring fail. Seems to work for me.
 
Last edited:
Yeah, forgot about that. I use a single bead of red silicone down the outside of each spring and a loose safety wire down the center ...
 
You might try balacing the prop. Breaking the springs is one sign of a vibration problem.

Vic
 
I installed GPL STAINLESS STEEL EXHAUST SPRING FOR 912 SERIES from Aircraft Spruce - $4 ea. Springs were slightly longer than stock so requires bending the welded tabs to get correct stretch. I filled the center of the spring with high temp silicone. Springs have been fine for 400 hours...
 
Another 500+ hours and 7 years flying without a broken spring. A precaution I always take is to never use anything to remove the springs that will scar or gouge the spring hooks. IE, no pliers, Vice grips or screwdrivers! These springs are highly stressed parts and even the smallest surface scratches are stress risers that can lead to hook failure. I use a circular cross section hook tool I made from 3/32" stainless wire.
 
Agreed!

Another 500+ hours and 7 years flying without a broken spring. A precaution I always take is to never use anything to remove the springs that will scar or gouge the spring hooks. IE, no pliers, Vice grips or screwdrivers! These springs are highly stressed parts and even the smallest surface scratches are stress risers that can lead to hook failure. I use a circular cross section hook tool I made from 3/32" stainless wire.

Just to clarify, I use the vise grips to pull on the soft brazing rod tool looped around the spring hooks, not to pull on the springs themselves.
 
This is a snap of the springs..... They have been on for 12 hours !

IMG_9183_heic-M.jpg
 
The Aircraft Spruce springs are 304SS, which has poor resistance to chloride. So if you're in a salt-air environment, you may want to look for 316SS springs, or have some made, or make them yourself.
 
Back
Top