I've installed a K&S 46/50 muffler on my Raptor 50 V2. It worked fine so far until yesterday. The muffler was suddenly broken while I was having inverted flight tail in circle. I enclosed a few pictures. The muffler was ejected just like a bullet shouted out from a gun.

Why ?

I am using OS 50 Engine and Coolpower 30%. The OS engine was installed only a month ago. The needle setting was one and half turn. Each flight last only 7 - 7.5 minutes. It should not be lean.

What do you think ?

Here is the muffler ......

It looks to me that you just got a bad muffler. That should be under warrentee.

Yes, I gusses.

It is rare to see a muffler broken without having collision. []

No it is not that rare. Their are some heli airframes that are harder on mufflers then others. Some airframes resonate/vibrate more then others (your Raptor 50 is one for that - see the article from Mike Mas about it in Rotory Magazine, which is a magazine that is very pro-Raptor) at the high frequency of the engine. This causes premature failure (metal fatique) in many mufflers at the flange area (specially with the latest longer and larger hi-volume units) unless the muffler is also supported at the rear by a seperate muffler support.

What also weakens this area is the high temperatures right at the exhaust outlet. Because this heli has plastic lower frames (they do not dissipate any heat from the engine) the engine cooling is more critical, so it is easy to be unwittingly running the engine hotter then you would in a heli with a more rigidly designed lower metal frame (they help dissipate heat).

Most hobby shops that have staff that are adequately informed on helicopters will know this and also sell you a rear support if you are using such a muffler on a R50.

Thanks, Syclic

It's been very useful.

I decided to buy a new muscle pipe II LR for my raptor. I'm not sure if I can found a rear support for that. I'll try.

I'm glad to tell all of you that K & S Japan would replace my muffler with a new one. They told me the problem was probably from the vibration. They advised me to adjust the helicopter free from vibration before flying again.

What should I pay attention to in order to adjust the helicopter free from virbation ? In general, what is the main cause to vibration ? Is it the main Shaft Or is it something else?