Hi SpazSinbad. The vibrations within the restricted RPM ranges were not physically detectable by the pilot. The "dual only" aircraft were known as "growlers" - often very loud growling noises. I think that these were the result of further compressor modification to reduce the restricted RPM ranges - they didn't do that. Some of the growlers did have pilot detectable vibration levels.
I recall flying one where the vibration and noise became so intense that the engine was shut down, and it quickly seized. Forced landing back at Pearce. Cause engine front bearing failure.
I recall an engine disintegration just after takeoff at Williamtown. Successful ejection. At the time the standard power setting after a pairs takeoff 10500.
Last edited by zzuf; 28th Oct 2021 at 06:55.