Tail Pipe damage in helicopter

[peeush]

This is about a 'tail pipe' damage that occurred in a medium lift twin engined helicopter. This component is not the exhaust pipe of the engine, but a part of helicopter airframe and is positioned at the end of engine exhaust to facilitate smooth outflow of the exhaust gases. In fact it is a rolled, welded metal sheet for the purpose.

Now the meat part.

There was a one inch crack detected at the end of this pipe during a turn around servicing (the welding had given away). The discussion was "How bad things would get if the helicopter was flown back to the repair depot with the known fault still existing". Though legally I agree that it cannot be a good decision, nevertheless following implications were considered, had the decision to fly back to repair depot was accepted:-

1. Owing to in-flight vibrations and pulsating aerodynamics this crack may have propagated resulting in exhaust gases contacting the helicopter structure and thereby leading to a possible fire hazard.

2. Turbulent air flow so developed in the downstream of the tail pipe may result in upstream instability leading to an unstable operation of the engine.

That's how far I could see.

Any more possibilities, comments on the implications please.

Thanks for the read anyway.

[sycamore]

P,there are usually limits in the Tech.manual as to how long /how wide/where a crack is, as to what you can do in the circumstances.It usually may/will require a suitable hole being drilled at the `head` of the crack to prevent it spreading,or maybe a piece of metal/steel being riveted/bolted over the crack to effect a temporary repair to allow it to be ferried to an engineering base.It may even be able to do a temporary weld,but it depends on the type of metal,and what is allowed in the Tech manual..Try the `Engineers` Forum for `non-pilot advice..!!

ed..It may also be possible to start,take-off and in safe flight ,run the affected engine at idle,then bring it up if needed for landing....

[ShyTorque]

Don't forget that anything falling off the aircraft can damage the tail rotor, which is a helicopter pilot's nightmare.

[peeush]

Thanks Sycamore....... I must admit that this is exactly what we did... drill a hole at the 'head'. And, as advised for validation of my speculations, I would post it in the Engineers' forum.


Thanks a ton for your time.