shrike wrote:
Dan Jones wrote:
It was reported that the Stearman threw a propeller blade just after take-off (like less than 100' in the air or so). The one bladed prop then caused the engine to leave. The engine departing then caused the c of g to abruptly move aft, well beyond any kind of manageable limits. And all of this happened in about half a millisecond. Both guys were pretty badly hurt but they were damned lucky to have survived at all. I flew mine once after that happened and couldn't even begin to relax. The next day I pulled the prop (same kind) and sent it out for teardown and a complete NDT inspection.
That's why there is an AD dating from 1949(?) to disassemble and NDT both the Army and Navy versions of the prop every 100hrs of operation. Some prop shops have given up on them. We'll do a Magnaflux only inspection, and leave the reassembly to the owner.
That AD actually applies to a different prop (different manufacturer). Those props have steel blades whereas these have aluminum blades, though I am probably going to put my prop on a 100 hr NDT cycle just for my own peace of mind after this anyway.
And shrike is quite right, and I'll quantify that a little;
One evening a few years ago I took my airplane out with it's wooden prop on it and went out and established some numbers. At 1800 rpm I had a cruise speed of 85 mph (stall is 55 mph), an initial rate of climb after take off of 200 ft/min (that's TWO hundred, not twelve hundred), and wide open in level flight she would just nudge 100 mph. I came back in, landed, and my buddy and I pulled the wooden prop, installed the metal one, and I was back up in about forty-five minutes. Initial rate of climb was now 600 ft/min, she cruised at 95 mph, and wide open she'd indicate about 112 mph. You want to talk about a revelation...
That wooden prop has hung on the wall in my shop ever since.
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