Undercarriage "noise"?

Lately I have been able to hear a "noise" when taxiing on grass ground. I lock the brakes and discovered this "sound" which can be clearly heard in the video, when I push forward and back on the plane. I suspect the silent blocks in the undercarriage suspension. The silent blocks don't look so bad and only show small movement / wear when I pushing to make the sound.
The "sound" is worst in the passenger seat side and I can "feel it knock" in the undercarriage wheel boom  



Does anyone have a clue to what is wrong?

I hope not I need to replace the silent blocks. Its so lot of work. Wings off, flaps system off, lift the plane, wheels off, wheels boom out

(I have a 4S with oil-pneumatics undercarriage so this is just an advise) To me this is not a « knock » noise but rather an « unscrewed » one but one having an ULC would have a better answer may be…

Have a thorough check to the M6 screws locateted at the rear of the landing gear horizontalsupport plates.

Good luck

Luciano

Hi,
Your video recording with good sound quality let me think about some plays.
first : i'm not a mechanics, my english could  be not very precise.
 Visually silent blocs seem not to be in bad condition . When they are bad ( often the inners deteriorate first and are swollen) play movements are more on yaw axis.
In your video visually play seems to be very limited. I 've already use to hear this noises on my plane and i operate on grass too with a vla .
There are plates to cancel axial play beetween silent bloc and extremities of steel bar .They are also "glyco dur" rings that may have wear . when knocking with the type of movement you did you can ear axial movement of steel bars  and perhaps...
And as luciano said inspect m6 at the rear of the horizontal plates they may sometimes brake.
On the right side, the upper edge of the rear of the carbon blade seems to be very close or in contact with the 6 mm bolt. If the thightening of the  4 bolts ( 2 m8 and 2 m6 ) are not sufficient the carbon blade may slide or ( but i'm not sure) squeak in the aluminium plates or along upper rear carbon edge with micro movements. with the bolt tension the plates may be curved in time so that the blade slip a little. I have already deposit my landing gear three times. Two times for silent bloc refection and one more to change the carbon blade(  at  tot 900 hours ) that had a defect ( delamination) near a wheel spindle . That was a lot of work each time but the job has been done .
So you should for instance just watch sound and play ( to évaluate play you can touch parts with your finger during mechanical stimulations) and visually inspect your silent blocs in order to detect degradations along flights. Play and knocking in carbon plane  structur is very noisy so you should be informed, and expect if possible next annual  or next 5 years revision.

f w

First, Thank you guys for the good inputs . I was afraid that this year flying season was over for me, if the silent blocks had to be changed (long time job for me).

After reading your answers very carefully and looked a lot on the main landing gear installation instruction on application.se-aviation.fr

I wanted to see if it was enough to "move" the undercarriage leg in center of the silent blocks, maybe the leg had moved a bit over the years as francky described can happen.

First step was to lift it up so I could move the undercarriage leg freely. A small lift had to be built of an motorcycle lift:


After getting the undercarriage leg fairing off and looked into the undercarriage holes in the fuselage, could I see what francky described that the leg was moved backward and was touching the M6 bolt: (maybe the noise/sound is coming from this touching?)


When the undercarriage leg bolts are loosened are there lot of "play" between the leg and bolts, and between the leg aluminium supports and the silent blocks: (lot of adjustment space  )


In the main landing gear installation instruction is it clearly described there must be play (Jeu in French ) between the leg aluminium supports and the silent blocks:


I chose to center between the leg and bolts and between the leg aluminium supports and the silent blocks. I found a bag of "plastic spacers" (for adjusting windows, doors and kitchen cabinets) in different thicknesses in the local hardware store, perfect to the job.




When I was satisfied with the centering, everything was tightened according to the installation instruction. After that the plane was lowered down from the lift and the test:  


Now I will keep an eye on the leg moves again and of course the silent blocks have to be replaced at some point, but I think/hope they will last a little longer.

Happy Flights!

Hello flyverjonas,

Congratulations to you for solving problem, and many thanks for the feedback, usefull for the communauty.

Have good flights !
Mini