ROCHESTER, NY, USA
N5494J
CESSNA 310R
THE PILOT HEARD A LOUD 'BANG' AFTER HE APPLIED FULL POWER TO BEGIN THE TAKEOFF ROLL. HE THEN NOTICED THAT THE RIGHT PROPELLER HAD SEPARATED FROM THE ENGINE. METALLURGICAL EXAMINATION OF THE PROPELLER HUB REVEALED THAT THE HUB SEPARATED AS A RESULT OF FATIGUE CRACKING THAT INITIATED FROM THE HOLES FOR THE STUDS USED TO ATTACH THE HUB TO THE CRANKSHAFT FLANGE. A SUBSTANTIAL AMOUNT OF FRETTING WAS NOTED ON THE MOUNTING FACE OF THE HUB, INDICATING POSSIBLE LOOSENESS BETWEEN THE HUB AND CRANKSHAFT. THIS IS LIKELY DUE TO INADEQUATE PRELOAD ON THE STUB AS A RESULT OF INADEQUATE ASSEMBLY TORQUE ON THE NUTS.
On October 11, 1994, at 1835 eastern daylight time, a Cessna 310R, N5494J, operated by Northland Aviation Inc., and piloted by Raymond Jacqus, aborted the takeoff at the Rochester Airport, Rochester, New York. The pilot was not injured. Visual meteorological conditions prevailed and an IFR flight plan had been filed for the flight operating under 14 CFR 135. The pilot heard a loud "bang" after he applied full power to begin the takeoff roll. He then noticed that the right propeller had separated from the engine. Six pieces of the three bladed feathering hub, part number E- 5887, other internal and external components from the right propeller were sent to the NTSB, Material Laboratory, Washington, DC. Three stud holes, a second dowel pin hole were not submitted for examination. Metallurgical examination of the propeller hub revealed that the hub separated as a result of fatigue cracking that initiated from the holes for the studs used to attach the hub to the crankshaft flange. The fatigue initiated in about the third thread root from the bottom of the holes. The examination revealed combined fatigue cracking initiated from stud holes, labeled "1" and "2" and propagated almost all of the way from one blade socket to another. Examination of the portions of the hub mounting face revealed the presences of "extensive fretting damage." There were no defects found in the hub that may have contributed to the cracking.
Inadequate maintenance which resulted in undertorqued bolts, fatigue cracking of the hub, and the separation of the propeller assembly from the engine.
Source: NTSB Aviation Accident Database
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