:eek: Those people might be airplane steerers, but they sure as hell aren’t pilots.
When I was 12 an F-4 pilot from NAS Miramar gave my mom a BuWep flight jacket to give to me. (Mom worked at Gibbs Flight Service.) The nameplate had my name, and underneath it, AIRPLANE DRIVER.
And Continental, Franklin, P&W round engines Kinner, Jacobs, Ranger inline inverted and some which are a bit rare.
I don’t know about dry vacuum MOTORS but dry vacuum pumps in my experience are just fine with a few backward hand turns when rotating a prop backwards. I have never lost a pump even when an engine runs backward for a second or so on shut down.
They are more delicate than a wet vacuum pump but …
I agree, always be very careful around propellers, of any kind.
I have no experience with Rotax engines. Do they even have valves of the traditional kind?
I am a big guy so Ultralight Airplanes and I don’t mix much.
Is Dave following this thread?
Head injuries suck, glad to see he’s recovering well.
But yeah, he was probably turning the prop to adjust the timing or something and it popped. I know there are certain procedures for tuning car engines that require you to manually turn the crankshaft, but cars don’t have a different ignition system.
Y’know how lawnmower manuals tell you to disconnect the sparkplug wire before mucking about underneath? That’s because lawnmowers have always-on magnetos, and if you turn the blade to scrape off a bit of goop behind it, it MIGHT fire the engine, and on a mower the sharp bit is on the leading edge.
Reminds me of the possibly-apocryphal story about a guy walking through the danger arc of a running prop, somehow miraculously going between the blades, and upon realizing his mistake, turned around and went back the way he came and … well, apparently you only get one miracle a day. :eek:
I mentioned it to him, but he’s not much of a message board kinda person. He appreciates all the kind words and thoughts though!
Pretty much has to be apocryphal.
About the slowest idle I’ve ever seen is 600 RPM = 10 revs per second. On a 2-bladed prop that’s 20 blade passages per second = one chop every 50 milliseconds. A non-obese person is about 12" deep. To pass between 2 chops he/she has to be traveling at least 12" per 50 milliseconds = 20 feet/second = 13+ mph. That’s a dead sprint for an ordinary athlete. When sprinting we’re thicker than 12" due to arm swing & leaning forward.
If it ever happened at all (which I doubt) I’d sooner believe somebody walked *under *a prop on a big airplane and happened to pass through the arc at a low point in his/her gait, *juuust *clearing the bottom of the prop. Most folks’ heads bob up & down an inch-ish during the course of a complete step. On the return trip he/she missed the low spot and got the top of their brain Cuisinarted.
How’s Dave doing?
Happiest guy on earth right now, since he was cleared to fly again yesterday and went up for a 90 min tool-around on his own today 
Excellent news! Congratulate him on the reinstatement of his medical, and his flight. 
Way to go Dave. That saddle still fits see.