Shimmy: front wheel fairing damaged

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

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

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 )
Good luck.

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

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

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...

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.

i had a shimmy event on my MCR01 Sportster last weekend. vibration was very strong and nosewheel fairing got damaged at the lower attachment

is the first time it happens, i recently greased the front wheel strut (it was basically seized) and replaced the sandow, probably the friction in the seized strut acted as damper, now that there is no friction shimmy occurred

i think the shimmy can be caused by too much weight on the nosewheel. the following takeoff i kept the nosewheel light and no shimmy.

i like the antishimmy modification but it requires removing the tank and i really really would if possible avoid that...

hi,
the best solution on MCR sporter is the installation of the right front wheel.
3 front wheel solutions are possible:
small wheel like as BANBI from Michel Colomban; but difficult to run on grass
big size, like as the first MCR, with several shimmy pb
medium size. light wheel from tost
ref 064991 tire 260x85 tost aero
ref 064292 tube 260x85
i use it from 2007 and never pb.

Nice flies

Hello GIL,

I ever have heard about the small Banbi wheel (the first mount), but I never heard about the second kind of wheel.
On my Sportster, the front wheel has the same size than the two main gear wheels. Is-it the medium or the big size ?

Mini

Translation :

Bonjour GIL,

J'avais déjà entendu parler de la petite roue du Banbi (première monte), mais je n'avais jamais entendu parler du deuxième modèle de roue.
Sur mon Sportster, la roue avant a les mêmes dimensions que les deux roues du train principal. S'agit-il du modèle moyen ou du grand modèle ?

Mini

Bjr Mini
si la roue avant est identique à celles du train principal, il s 'agit bien de ce que j' appelle la grande roue.
en raison de sa taille et surtout de son poids, elle est victime de shimmy ( j' ai payé pour ça en 2007, avec rupture du train avant)
lors du changement du train avant, Dynaéro m' avait recommandé soit d'installer le vérin anti shimmy, soit d 'installer la roue intermédiaire
d 'origine allemande car issue d 'un planneur. elle est très légère, très solide et ne nécessite pas d' anti shimmy.
seul inconvénient, je ne trouve pneu et chambre que chez tost ( ref sur le message précedent). le prix est tout à fait correct.
je recommande sans hésiter.
bons vols

Thank you GIL !

With the big wheel, and without shimmy-damper, I never encountered any problem, neither on concrete or on grass runways.
The excess of weight goes in the right direction, because our MCRs are rear-centered, and bigger size increase the gap between the propeller and the ground, decreasing risk of ground-strike.

I sometime encountered small vibrations short after take-off, caused by balancing defect of the front wheel.

Mini

Traduction :

Merci GIL !

Avec la "grande" roue, et sans anti-shimmy, je n'ai jamais rencontré de problèmes, sur piste en dur pas plus que sur herbe
Le poids supplémentaire va dans le bon sens, parce que nos MCRs sont centrés arrière, et la grande taille augmente la garde à l'hélice, limitant le risque de choc avec le sol.

J'ai parfois rencontré de petites vibrations juste après décollage, causées par un défaut d'équilibrage de la roue avant.

Mini

Bonjour à tous,

j'utilise depuis l'origine de la construction une roue avant de 260 et n'ai jamais constaté le moindre shimmy (870 heures de vols au total).
J'achète pneus et chambres chez Glider Equipement :
pneu :
http://glider-equipment.nl/catalog/product_info.php/tost-aero-tire-3004-260x85-064991-p-1068
chambre :
http://glider-equipment.nl/catalog/product_info.php/vredestein-tube-3004-260x85-90%C3%82%C2%B0x90%C3%82%C2%B0-tr87-238819064292-p-1384

Alain

Bonjour Alain
Maintenant que j'ai les trois roues de la même taille 11x4.00-5, aurai-je besoin d'une autre jante pour le pneu 260-85?

merci
gm

Alain Baudry a écrit:Bonjour à tous,

j'utilise depuis l'origine de la construction une roue avant de 260 et n'ai jamais constaté le moindre shimmy (870 heures de vols au total).
J'achète pneus et chambres chez Glider Equipement :
pneu :
http://glider-equipment.nl/catalog/product_info.php/tost-aero-tire-3004-260x85-064991-p-1068
chambre :
http://glider-equipment.nl/catalog/product_info.php/vredestein-tube-3004-260x85-90%C3%82%C2%B0x90%C3%82%C2%B0-tr87-238819064292-p-1384

Alain

le shimmy n' arrive qu 'aux autres, et puis brutalement , à environ 400h, après un kiss, au roulage sans prévenir. c 'est terrifiant.
cela a provoqué la rupture du train avant ( soudure de la platine da la fourche).
c ' était avant le BS obligatoire de renfort de cette soudure.
un conseil pas bien cher, faire équilibrer la roue avant ( garage moto) et finies les vibrations après décollage.

GIL a écrit:le shimmy n' arrive qu 'aux autres, et puis brutalement , à environ 400h, après un kiss, au roulage sans prévenir. c 'est terrifiant.

Ah, c'est pour ça... Je ne fais jamais de kiss !

Bonjour Gianmarko,
Oui, pour monter un pneu de 260, il te faut une jante spécifique et aussi une nouvelle fourche ainsi qu'un nouveau carénage.
Avec ce nouvel ensemble tu bénéficieras aussi d'une traînée réduite, et donc d'une meilleure vitesse.
Alain