The advice below landed in my Inbox this morning;
The CAA is advising owners of Gipsy Major engines ensure routine checks are carried out by a company/person experienced on this engine type, if low compression is noticed in the engine when turning the propeller by hand or the engine is found to be running rough. Owners are also advised to ensure they are using the most appropriate fuel at all times.
The new guidance follows an emerging trend, identified by the CAA’s Safety Performance and Risk team, of rough running engines, and engine failures, involving Gipsy Major engines.
Now, it's 52 years since I sat behind a Gipsy Queen, admittedly one with very few hours left to the next overhaul, as it rumbled away on route to Sharjah. It strikes me that it's a bit late to find out that if the prop rotates rather too freely when turning it by hand it's time to summon someone who knows what that indicates. Running rough is a rather loose term; what might sound sweet as a Gipsy Queen flies overhead sounds, I can assure you, quite rough from just behind it with another 50 miles of Mediterranean or desert to the nearest airfield. I could add the advice not to take a Gipsy Queen with you into a cloud, at least if it's installed in a Prentice, because that tends to stop the mags working perfectly (or even at all, which provides useful forced landing practice). As well as the advice not to bother with a mag check on the ground, it will fail in a tail-dragger. So long as you can get something approaching full power you take off and check the mags, if you're brave enough, at 1,000 ft. It astonishes me that there are any Gipsy Queens flying outside museums.