Gentlemen,
This is an alert for a potentially serious problem with the Continental IO/TSIO-550 engine/Hartzell 78” Scimitar propeller combination commonly used on Lancair aircraft. Please appreciate that this is from a very small data sample, and analysis is on-going, but it’s important enough to share what we now know.
Lancair (N619SJ) owner Bob Rickard called last week to advise that he’d discovered a major crack in his crankshaft at the propeller flange and wanted to alert other owners flying the above engine/prop combination of his problem.
Bob has been chasing a random vibration in his airframe since he bought the aircraft three years/approximately 500 hours ago. The “standard suspects” of prop balance/run-out, engine mount/isolators, engine contact with the cowling, etc. had been systematically ruled out over time. In frustration, and unwilling to just ignore it, Bob ordered a new MT 4-blade to replace the Hartzell, remaining very uncomfortable with the vibration and unable to think of any other possible fixes. Part of Bob’s discomfort was based on the fact that he’d talked extensively to Ed Smith who had similar vibration issues with the same engine/propeller combination. (Ed’s N9JE experienced an in-flight crankshaft failure/departure of the prop in 2010; Ed successfully dead-sticked the airplane onto a beach.)
Bob’s recent discovery of the cracked crankshaft was made when the Hartzell was removed for replacement with a new MT prop. At the time of removal/discovery, the engine had just more than 100 flight hours since major overhaul. The crankshaft had been checked for cracks at overhaul, and the actual eddy current test results were still available showing no cracks or irregularities at that time. Bob believes that the crack developed within the last 100 flight hours as a result of long-term exposure to harmonic vibration, and that this vibration could be a result of an incompatibility between his big-bore Continental and this specific Hartzell prop. He notes that although this is an “FAA approved” engine/propeller combination, he has talked to other airplane owners flying this combination who have/are experiencing similar vibration issues.
We understand that Continental and the FAA have been notified of this problem, but we have no additional information at this time. LOBO expects to publish a more detailed report on this in the next monthly newsletter, but both Ed Smith and Bob Rickard felt this discovery was worth making immediate notification about. Specifically, any unusual or new engine vibration should be cause for immediate attention. Bob considers himself very lucky to have caught the crack before in-flight failure.
We’ll devote a few minutes to share what we know/answer questions at our LOBO Safety Forum to be held at 1300 in Forum Pavilion 2, Monday, 29 August, at AirVenture. Bob Rickard won’t be available to discuss this at our safety forum, but you can email him at r.rickard@rcginc-us.com. LOBO would also appreciate an email or call (rpastusek@htii.com 757-286-4802) if you are experiencing similar problems.
Thanks,
Bob Pastusek
For LOBO