As a new operator of an RR250, this thread got me thinking enough to ask my shop a few questions. They said that with a properly maintained engine, there is little possibility of a drain valve sticking closed. If the compressor is washed correctly at the intervals recommended by RR, the washing solution also cleans the drain valve of deposits which might cause sticking, and washing allows confirmation that the valve is not stuck closed. Shop owner says he cant recall the last time an engine maintained by his shop required valve replacement, but he said he sees this problem often enough on helicopters that are brought to his shop for the first time. He didnt say that a stuck valve couldnt happen with the recommended wash schedule, just that it is unlikely.
