help, Strong vibrations on Enstrom 480
 

A friend is working on a Enstrome 480 and after they had the rotor blades of it has very strong virbations. The cyclic is moving nearly an inch back and forth. 0.48 IPS @5:22 we got it down to 1.6 ISP @1 mesured with vibres2000 plus, but the vibrations are still there. They bled the hydraulic dampeners but no improvement. Any sugestions? Please sent me an email. [email protected] Thank you Freightdog

Isn't that normal? :)

Seriously - presumably it was OK before they took the blades off. Were they the same blades that went back on? If so, sounds like somebody knocked something.

Phil

Call the factory in Menominee there such a lively bunch they will help you out there not like Eurocopter or Augusta they will genuinely want to help not fob you off

Good vibrations
 

Most probably put blades back in wrong order or bent tab or two.
Get someone who knows about Enstroms to fix it, or you will end up chasing around and it will most probably get worse.:E

In Africa it is a little bit more difficult. You can not just call 1800-help-Me. When you are a pilot/Mechanic you like to help other aviators if you can. It is an older machine.

Not sure about the phone service where you are, but you can actually do this with an Enstrom helicopter. Call the factory in Menominee, MI. (See here for details: Contact « Enstrom Helicopter Corporation ) Ask for Bayard DuPont. If he is not the right guy, he will direct you to the right person. Enstrom does this kind of support very well in my experience.

I think the T&B can be easily disrupted on 480s.

Needs an engineer who understands the procedure, with correctly calibrated equipment, and an experienced 480 pilot who can sense when it feels just right.

Properly set up, it should be smooth and comfortable, although the 'B' models are always a bit smoother, especially through the cyclic.

Try swapping the dampers to see if the clock angle changes for a start.

What work has been done to the blades while they were off?

Email Enstrom detailing everything you've done, they should be able to point you in the right direction.

If its damper you will have a pretty significant vib level at blade passing frequency and also at 2R.

I have emailed you, if you haven't got it pm me, I have a bunch of ideas. If I am reading your post right, you have 1R Vert reading of 1.6 i.p.s.?? or is it 0.16 i.p.s.? If 1R is 0.16 then my supporting questions and other data requests will make sense.

:ok:

Thank you for your support. After some searching they found the blade sheet and I bent the inboard and outbord tabs back to factory specs and this improved the situation a lot. A few testflight later the helicopter flys well again. I had to do a 100 hr on one of my ships so the assistance for my hangar neighbors took a little longer. The Enstrom is a very nice helicopter and I like flying it. fly safe dc3freightdog

Don't just focus on blade track and phasing.....check all flight controls with bellcranks, bearings, rod ends and hardware.:ok:

And you do know that you are to use the outboard tab for "stick shake" inboard tabs for ride quality in forward flight.And the p/c links for track picture are very very sensitive. Im talking dont make a whole flat adjustment, more like half to 1/4 flat adjustments.