Aw139 track and balance. Help!
Thread Starter
Joined: Aug 2019
Posts: 4
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From: Dubai
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?
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?
Joined: Mar 2011
Posts: 518
Likes: 50
From: London/Atlanta
I suggest that you put this question to the manufacturer, I m pretty sure you have plenty of manufacturers backup in your location.
Also welcome to this forum, we don’t get to hear from many in the Middle East.
Also welcome to this forum, we don’t get to hear from many in the Middle East.
Thread Starter
Joined: Aug 2019
Posts: 4
Likes: 0
From: Dubai
I already checked the main landing gear shock absorber (oleo) for the main L/H and R/H + the nose. I found the pressure within the limit according to the chart on IETP. I also checked the Tires pressure all within limit.
Last edited by Eng.; 5th August 2019 at 16:21.
Joined: Nov 2016
Posts: 41
Likes: 1
From: Near the surface
Indeed, check oleos, check tire pressure, check main rotor dampers.
Do you park it outside overnight? Temperature differences have effect on the dampers as well. Usually a 10 minute ground run should bring everything to an operational condition.
If this does not work, our engineers turn to the log cards and start comparing balancing mass and pitch rod settings with the current conditions. (Sometimes the trim tabs, however, considering your situation these can be ruled out - i.e. fast forward flight only).
Please let us know if the situation has resolved and what action led to a possible solution. Good luck!
Do you park it outside overnight? Temperature differences have effect on the dampers as well. Usually a 10 minute ground run should bring everything to an operational condition.
If this does not work, our engineers turn to the log cards and start comparing balancing mass and pitch rod settings with the current conditions. (Sometimes the trim tabs, however, considering your situation these can be ruled out - i.e. fast forward flight only).
Please let us know if the situation has resolved and what action led to a possible solution. Good luck!
Thread Starter
Joined: Aug 2019
Posts: 4
Likes: 0
From: Dubai
Indeed, check oleos, check tire pressure, check main rotor dampers.
Do you park it outside overnight? Temperature differences have effect on the dampers as well. Usually a 10 minute ground run should bring everything to an operational condition.
If this does not work, our engineers turn to the log cards and start comparing balancing mass and pitch rod settings with the current conditions. (Sometimes the trim tabs, however, considering your situation these can be ruled out - i.e. fast forward flight only).
Please let us know if the situation has resolved and what action led to a possible solution. Good luck!
Do you park it outside overnight? Temperature differences have effect on the dampers as well. Usually a 10 minute ground run should bring everything to an operational condition.
If this does not work, our engineers turn to the log cards and start comparing balancing mass and pitch rod settings with the current conditions. (Sometimes the trim tabs, however, considering your situation these can be ruled out - i.e. fast forward flight only).
Please let us know if the situation has resolved and what action led to a possible solution. Good luck!
The problem HUMS system read the vibration but not recommand any adjustments. Something strange!
Thread Starter
Joined: Aug 2019
Posts: 4
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From: Dubai
But maybe somebody had this problem before and can give us some information.
Avoid imitations
Joined: Nov 2000
Aviation Qualifications: ATPL
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From: Wandering the FIR and cyberspace often at highly unsociable times
I've flown other types of aircraft that suffered vertical bounce problems caused by SAS/autopilot/gyro faults.
Joined: May 2002
Posts: 43
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From: tomorrowland
ENG, I believe that the problem are the elastomeric bearings. When they are cold, at first start in the morning, one may have a different rigidity and this could be the cause of the vibration because a blade goes out of track. When they became hot the rigidity is equal and the track is restored.
You may check the MR track at first start and then when the vibration has disappeared.
You may check the MR track at first start and then when the vibration has disappeared.
