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Debris Strike
#1
Still working my way into a rotor-craft mentality and it occurred to me that rotor wash debris is another important thing to think about while flying.

Seeing many Mosquito pilots doing hover practice I was wondering how high you have to be to avoid getting ground debris being sucked into  the rotor wash circulation and potentially going through the rotor disk.

I imagine even paper might be cause for concern.

I imagine birds would stay away due to the noise, but a rotor bird strike would likely be a very bad thing as well.

Any comments on safer hovering heights and what sort of things have started flying in the rotor wash.

I have read of things like plywood sheets and carpets becoming airborne in the rotor wash.

Also just dirt starting to circulate could be a problem as you may loose visual ground reference and end up spatially disoriented and I'm thinking if you recognize that situation developing, getting some altitude and moving away might be the quickest safest way out of a potentially bad situation.
Ray
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#2
I had a bird strike on the main rotor, I had no idea what happened when I landed found bird guts right in middle of one blade no damage.
Birds will climb and dive around you when flying sometimes 



chuck
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#3
(02-21-2017, 06:49 PM)Chuck308 Wrote: I had a bird strike on the main rotor, I had no idea what happened when I landed found bird guts right in middle of one blade no damage.
Birds will climb and dive around you when flying sometimes 



chuck

I have not seen how the blades are constructed but its good to know the blades can withstand some punishment. 

Had the bird hit near the tip which travels at 385mi/hr I wonder what would happen to the rotor?

I suspect the birds tissues get torn up before any damage to the rotor would occur.

At midspan the rotor is traveling at 192 mi/hr

PI(factor for Circumference of a circle) x 20'(rotor Diameter) x 540rpm(Rotor rpm)x60(Minutes per hr) / 5286'(feet per mile) = 385mi/hr
Ray
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#4
The easiest way to avoid possible debris strikes is to be aware of your surroundings. Although sometimes unavoidable like bird strikes, a piece of plywood flying around is a very bad hazard and you should remove the debris before it becomes an issue. I would be more cautious of what the tail rotor could be damaged by. A kneeboard that flys out of the cockpit could do enough damage to cripple the heli. Often I will fly with the left door on (R22) so as to avoid any debris flying out of the cockpit. You never know what your passenger has in their pockets or purse that could fly out!
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#5
Living in a very sandy area, I do several things to lessen the chance of damage to my blades. I wet the area down before I take off, this helps a lot. Hovering at about 4 feet also reduces rotor wash. Still, stuff does happen. Was hovering in the front yard and a plastic bag floated up from nowhere, my heart skipped a beat, then the rotor cleanly went through it, no damage. My solution is going to be the creation of a proper helipad. Another summer project, right after the wife's shower and vanity upgrade.
Got to keep priorities straight.
Dave
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