Aw139 track and balance. Help!
Hello all.
2 weeks ago we started have vertical vibration on M/R on FPOG only about 0.4 IPS and sometimes 0.5Ips . There is no recommend adjustment show on HUMS report.
But as soos as the pilot pull the collective up during the ground run all vibrations disapear and when he lower the collective the vibration back again.
also when pilot move the cyclic left or right ,fwd or aft all vibration disapear and when he put the cyclic to center the vibration back.
as i said on the top the vibration only on ground when the pilot select the flight mode only. (On idle mode no vibration). Also on hover,cruise ,fast cruise no any vibration.
Another thing to mention. If the piolt hover the aircraft and then land all vibration disapear as well and will not come again all the day even if he shut down the engines and start again at same day no vibration will show but when we park the aircraft overnight and try to start it on the morning the vibration will come again and will not stop unless the pilot hover the aircraft and then land.
More than 10 years working as engineer on aw139 but the first time i had this issue.
Any advise what can cause this problem?