With regard the Whyalla accident;
The ATSB surmised that the left engine failed due bearing failure, which in turn the crankshaft failed. The ATSB tried to pin this on LOP operation when in fact their own report states the majority of Whyalla pilots were leaning to 50F ROP, with occasional leaning LOP as part of an experiment. Even if the accident day the pilot leaned 50F LOP the bearing had failed 50 operational hours previously and was doomed to fail that flight. The engine oil temperature had been trending high and even exceeded 245 prior to the accident day, this was hinting at something going wrong. It apparently was fixed a day or two before the accident.
The exact reason for the right engine failure is still unknown but the best guess was that the pilot pushed the power up with the RPM and mixture still set for cruise, this in turn resulted in severe detonation and cylinder melting. We do not know what method of leaning he used, it is still and forever will be speculation.
The other Chieftains in the fleet were checked and no faults found other than trend data maintenance associated with high temperature operation. Was this due to a few hours operating LOP or the majority hour operating 50F ROP. I know of two other Chieftains (of the 15 or so) that suffered crankshaft failure, neither of these were operated LOP and failed in almost identical fashion to the MZK.
The ATSB acknowledged that leaning in the climb may result in mild detonation, this would not have led to bearing/crankshaft failure or piston melting considering the climb power setting they were using. However Whyalla had an initial climb procedure to lean with power settings 38-40" higher than the recommended POH procedure.
Last edited by 43Inches; 14th Apr 2014 at 23:32.