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#1405498
An unfortunate incident occurred to a friend today.

His maintenance organisation have recently done a serious amount of work on his aircraft and done a great job. As part of the work, new engines were installed. Ground runs were all good and the aircraft was to be test flown.

Unfortunately on carrying out power checks, the rpms dropped and the throttles seemed ineffective, with serious lagging of rpm movement, and high manifolds, even with what seemed like high throttle positions. The engines were shut down and then it was obvious....the props had feathered themselves - later ascertained due to too high dry air pressures in the prop system.

The engines were probably run at very high manifolds 24-26" briefly but not continuously while troubleshooting tried to make sense of what was wrong. So the engines have probably been subjected to high loads upon them.

The lesson to be learned is (with fully feathering CS props) if you have had work around the engines, props, govenors (even if ground run and told all is okay) and you get really odd, low, rpms, high manifolds and throttle control that feels like it is sluggish or not controlling the engine properly.....STOP! You may have unexpected feathered props.

This now looks resolved (with the correct air pressures), but it is not clear if there is any hidden engine, or airframe damage or stresses that have been caused.
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By Instructor Errant
#1405518
Anon wrote:...new engines were installed.... So the engines have probably been subjected to high loads upon them...it is not clear if there is any hidden engine, or airframe damage or stresses that have been caused.


I feel your pain.
By Aprocek
#1407720
Was this 'test flight' done by an experienced airworthiness test pilot?
By Aprocek
#1407772
...my point being that some years ago, the cadre of airworthiness pilots, responsible for CofA air tests, was always known to maintenance organisations, and thus was on hand for this type of flying. They would be aware, too, of this type of novel problem, and prepared to deal with it. Moreover, such a pilot would be able then to tell the owner that, after all the money he's spent on his new engines, the aircraft is (or is not) performing as it should. Obviously, if it's not, remedial action is necessary.

None of this seems to happen any more. Which, I think, is to be regretted.

Of course, when an aircraft is sold, a proper test may be carried out, but by then, it may be far too late to get the maintainers to put something right, without further expense.