View Full Version : AS350 - 3R Vibration
OverTq
20th Nov 2007, 13:43
One of our Squirrels has developed a marked 3 R vibration, which we have not come across before. Head, tail and drive-shaft are all OK, and can't think what could be causing this. Any ideas, please?
wrench1
20th Nov 2007, 13:48
OT,
Check the tuning weights under the floor per the work cards.
W1
OverTq
20th Nov 2007, 13:54
Thanks wrench. They are regularly checked, and show no sign of the cracking problem, Also, they don't seem to have shifted from their original position.
alouette3
20th Nov 2007, 15:21
This might make absolutely no sense ,technically ,but check the condition of the uni ball.
Alt3.
Fred Bound
20th Nov 2007, 16:24
Have a look at the condition of the rubber bushes on the 'dog bone' link under the transmission. It's a bit of a bugger to get out and in, but it's accessible, just, above the fuel tank.
We had 3r with a 350 in low autos/low power descents caused by these bushes.
Good luck.
Hawkrx
20th Nov 2007, 22:16
OverTq;
Have a good look at the windshield screws, loose screws are a primary cause of a sudden pronounced 3per. Also would have a look at the MRH Frequency adapter bearings, landing gear springs, vertical fin attachment screws, M/R blade trim tabs, AVA attachment screws, and Fuel tank strap tension. Double check your inflight NR set to 390 to get the smoothest ride. Best of luck, I know chasing a phantom 3per can be a real pisser :ugh:. -HawkRX :cool:
OCTANE100
21st Nov 2007, 06:17
Hawks is on the money....
A couple of additional ones I have come across are the MGB support struts rod-end bearings worn (it takes only a tiny bit of wear to make a real rumble which you may pick up as a 3 per) and wear on the (bottom primarily) rod-end bearing of the M/Rotor Hyd servos.
By far the most common is the M/R freq adapter spherical bearings....
I wouldn't start adjusting the hammers until you are totally out of other options.......Have you inspected the airframe around the attachment for cracking..?
The lower br'g on the M/R vib absorbers ok ? top shaft attachment screw (to the weight)is still in place?? Can also do a dimension check on the springs if the aircraft has a few hours on it....
Cheers:ok:
OverTq
21st Nov 2007, 08:24
Thanks guys - the aircraft is only recently off a C check, but will get the 'spanners' to check those things you've suggested.