Lumps
16th Aug 2014, 12:28
Apologies if this particular aspect of the Mojave PGW accident has been discussed before, I searched and could not find..
So what went wrong in that engine that precipitated the chain of events:
Spectral analysis of the recording indicated that the propeller RPM of the affected engine was varying from about 2,350 RPM to greater than 2,600 RPM, which exceeded the specified maximum rotational speed of 2,600 RPM.
However, the engine manufacturer advised that the surging RPM that was audible in the background to the pilot’s transmissions was ‘consistent with uneven fuel distribution to the cylinders’. The propeller manufacturer advised that it had ‘yet to find a causal factor in surging that was clearly identified as being from the propeller or governor, especially for a report of a large RPM excursion’. On that basis, the Australian Transport Safety Bureau (ATSB) concluded that it was likely that the surging was related to an uneven fuel distribution problem, rather than to a propeller/governor problem.
How on earth does uneven fuel distribution to the cylinders cause engine rpm to exceed its maximum governed speed? If that's what Lycoming told the ATSB intern that rang them then I bet they were giggling when they hung up the phone. ALL their engines have uneven fuel distribution when they leave Williamsport.
That answer, if indeed anyone actually asked Lycoming, is pure piss taking. How embarrassing. I think this shows what Lycoming thinks of the ATSBs top engine brass, after their imaginative analysis of the Whyalla accident some years ago.
So what went wrong in that engine that precipitated the chain of events:
Spectral analysis of the recording indicated that the propeller RPM of the affected engine was varying from about 2,350 RPM to greater than 2,600 RPM, which exceeded the specified maximum rotational speed of 2,600 RPM.
However, the engine manufacturer advised that the surging RPM that was audible in the background to the pilot’s transmissions was ‘consistent with uneven fuel distribution to the cylinders’. The propeller manufacturer advised that it had ‘yet to find a causal factor in surging that was clearly identified as being from the propeller or governor, especially for a report of a large RPM excursion’. On that basis, the Australian Transport Safety Bureau (ATSB) concluded that it was likely that the surging was related to an uneven fuel distribution problem, rather than to a propeller/governor problem.
How on earth does uneven fuel distribution to the cylinders cause engine rpm to exceed its maximum governed speed? If that's what Lycoming told the ATSB intern that rang them then I bet they were giggling when they hung up the phone. ALL their engines have uneven fuel distribution when they leave Williamsport.
That answer, if indeed anyone actually asked Lycoming, is pure piss taking. How embarrassing. I think this shows what Lycoming thinks of the ATSBs top engine brass, after their imaginative analysis of the Whyalla accident some years ago.