Shimmy: front wheel fairing damaged

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Shimmy: front wheel fairing damaged

Message  MCRider le Dim 26 Oct 2014, 15:46

Hello,

Today I had a problem with my MCR 01 ULC: During the landing roll I had a strong nose wheel shimmy. It was so strong that the wheel fairing was damaged. The landing was quite normal exept that it was with 17° flaps instead of 30° (because I expected a gusty wind with a significant crosswind component - but actually there was little wind). Landing was on a hard runway in very good condition. For training purposes I have landed with 17° flaps and even with retracted flaps in the past without problems. The shimmy started before braking - braking made it stronger but did not cause it. The nose-wheel fairing had been repaired a while ago but there was no obvious damage before the flight. There is no noticeable play in the nose-wheel steering. Tire pressure was checked a week ago.

After removal of the fairing (by cutting it in half - it was damaged anyway) I did a high-speed taxi test and one more flight and landing (to get home) - both without any noticeable problem.

Does anyone have an idea what the cause might be and what to do against it? Dyn'Aero has a shimmy damper option. Why?

Regards
MCRider

MCRider

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Re: Shimmy: front wheel fairing damaged

Message  heulin le Dim 26 Oct 2014, 19:13

Hi MCRider,
Did you check de full extension of the nose strut, when someone push down the tail???
Because normaly the angle of stearing is limited when the strut is full extended after the wheel is unloaded by take off.
Grease could help the shock strut to work properly, or new shock strut sandow for locking down the strut when unloaded.
Just my mind for the moment

Best regards

Serge





heulin

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Re: Shimmy: front wheel fairing damaged

Message  CHARLIER le Dim 26 Oct 2014, 19:32

Hi,
The anti-shimmy damper ‘was born’ with the 4s and I do not think it is really necessary (mandatory) for the ULC.

Would you, please, check if the cable adjustment is correct ? (if the springs are extended to the right value of 60mm)
(see MOUNTING INSTRUCTIONS - INTERCONNECTION CABLE INSTALLATION)

My 0.02 EUR Surprised)
Good luck.

CHARLIER

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Re: Shimmy: front wheel fairing damaged

Message  MCRider le Dim 26 Oct 2014, 21:04

Thank you for the help.

@Serge: I had the opposite problem in the beginning. Sometimes the nose-wheel steering stayed locked even after the wheel came down, especially during really smooth landings. This even caused a small accident. The plane did not follow the rudder inputs and so I increased the pressure, when the nose-wheel unlocked a sudden turn was the result. Unfortunately I did not know the problem until then and it was on a very narrow runway.

@CHARLIER: I will check the cables and springs asap (it will take a while before I have the time).

I have to mention that it is a factory-built aircraft (probably the last one completed by the "old" Dyn'Aero)...

MCRider

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Re: Shimmy: front wheel fairing damaged

Message  Alain Baudry le Mer 29 Oct 2014, 00:37

Hi MCRider,

Another hypothesis could be that the breaking of the fairing occurred first, and that the shimmy was a consequence of this breaking…

That would explain why the shimmy disappeared after the fairing's removal...

Alain

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Re: Shimmy: front wheel fairing damaged

Message  MCRider le Jeu 30 Oct 2014, 13:33

Another hypothesis could be that the breaking of the fairing occurred first

Checking the wheel fairings is part of my pre-flight check. So there was no obvious damage or looseness before the flight...

MCRider

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Re: Shimmy: front wheel fairing damaged

Message  MCRider le Ven 20 Fév 2015, 16:50

I think that I have found the cause: The wheel was balanced with two 5g weights glued to the rim (done like that by the factory). One of the weights is missing now. During landing (I am still flying without wheel fairing because I did not find the time yet to mount the new one) there are notable vibrations in the front wheel. Checking the photos I took after the incident I found that the weight was already missing. So probably the weight fell off during the landing and the vibration caused the shimmy.

MCRider

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Re: Shimmy: front wheel fairing damaged

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