Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Engineer
Flight Crew Last 90 Days 150; Flight Crew Total 18000; Flight Crew Type 750
Aircraft Equipment Problem Critical
Aircraft Aircraft Damaged; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed
Aircraft
After reaching cruise altitude of 6;000 MSL and setting cruise power I heard a bang and the aircraft exhibited a medium to high rate of vibration in the floor. I verified engine operation was good and looked for any missing [aircraft components]. Not being able to find the problem I canceled my IFR flight plan with Approach and turned toward a nearby suitable airport. I slowed to 120 MPH and begin a 500 foot per minute descent. As the aircraft remained controllable I determined I could be on ground at same time if I continued to back to my departure airport. Upon landing the vibration got worse as aircraft was in flare. On landing rollout I noticed the left spinner was moving about one inch side to side and so I shut down the left engine. The prop stopped with a damaged blade end up. I taxied single engine to the hanger and secured the aircraft.Post flight inspection revealed four inches of one of the left prop [blades was] missing. The left side of the aircraft; just forward of the prop center line; had damage with a dent and cracked gel coat to the fiberglass nose at the battery jumper connection. There was no known prior impact to the blade or history of prop damage.
A PA30B; Twin Comanche; pilot canceled his IFR clearance and returned to his departure airport after experiencing significant vibration ultimately found to be the result of the loss of several inches of one left prop blade which had broken off and struck the fuselage.