Propellor Vibration

There was a discussion about prop vibration recently, and I found this link that helps to explain.
Sorry I couldn't post it as a link, ain't smart enough


http://www.epi-eng.com/propeller_technology/propeller_vibration_issues.htm

Looks like Steve made me smarter automatically!

Thank you for posting. That is a very informative clear explanation. It is likely that the pilot who has a serious vibration problem will not be telling us about it.

skywagon8a said:

...It is likely that the pilot who has a serious vibration problem will not be telling us about it.

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can remember 2 people around here that lost a tip of 82" borer props.... ye haw... they said it was just like they were told it would be, shaking so bad you can't see a thing through the windshield and you are shutting it down and landing where you are at....now.. by looking out the open side window...

they both did ok, think one got a gear leg in the unplaned landing in the alders, and did more damage kicking at his boot cowl cause he was pissed off.... of course the wings were fresh cover a few months earlier.... and prop was not that old....

mike, Do you happen to know if the prop that "was not that old" happened to have a stone nick in the leading edge?? That could have done it.

Damn now I need to start carrying a extra prop in my survival gear.

skywagon8a said:

mike, Do you happen to know if the prop that "was not that old" happened to have a stone nick in the leading edge?? That could have done it.

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most likely... both during hunting seasons.. both guide/transporter doing all off airport stuff...

DW said:

Damn now I need to start carrying a extra prop in my survival gear.

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no, hacksaw.... for the long blade....

I've got that new catto so my brush saw should work.

The Catto is wood isn't it? Wood is not susceptible to cracking like aluminum.

I watched a friend throw a blade off a Formula One at Reno a long time ago, just before the last pylon. It snapped off 6" or 8" out from the hub at about 4300 rpm and way over 200 mph. Ripped the engine off the motor mount almost instantly and covered the front of the canopy with oil. No foreward viz. The only things holding the engine onto the airplane were the oil line and one of the two safety cables. The other snapped. The engine laid down against the right landing gear. The pilot thought he had blown the engine - no clue about the prop. It took more or less a 45 degree descent to keep it flying with all the drag. Flared and hit the runway hard, on the centerline, crowd dead center. Spun 90 degrees and came to a halt. Then he had the nerve to open the canopy and stand up. Saturday only show.

I watched another friend throw about 18" of one leading edge of her Tiger Moth prop on takeoff. A quick return due to the extreme vibration and a downwind landing. No damage except the prop. And her heart rate!

Another friend threw a couple of feet off the leading edge of a prop on his full-size SE5-A replica on half-mile final to Santa Monica one day. We really couldn't see anything until the prop stopped after landing, and we saw the damage. The pilot only knew it was vibrating horribly and was afraid he wouldn't make the airport. You should have seen the look on his face!

Wood doesn't fatigue like metal. It does crack and break. Two experimental props, (one metal, the other wood) one certificated wood. All looked fine at preflight. No one was sitting on a parachute, so they were all committed to the ride. All three of them were pretty lucky.

Tom

I assume that the certificated wood prop was the one on the Tiger Moth? Leading edge tipping has been known to come off due to moisture getting into the screw holes and causing the wood to deteriorate.

Yes, the certificated prop was on the Tiger Moth.