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RPM fluctuation during decending

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7b engine: #2 engine rpm fluctuation about 1% during decending and when goes through the weather. NTS gap is OK and plunger looks good. 

Any experience about this?

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if by weather you mean cloud or rain, changes in air density going into compressor will be

detected by fcu cip & cit probes. as the throttle is already pulled back, a weak valve housing

may not be able to hold the rpm steady. 1c-130h-2-71jg-00-1 gives rpm 1.5% total travel

with throttle below flight idle, and 1.0% with throttle above x-over and more than 8000"lb

torque. valve housing change is the quicker fix, but you may end up changing fcu. as an

after-thought, check the time on dome quad-seals. 

 

 

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Thank you pjvr99. By weather I meant cloud. Every time during decending rpm travel 99.5 to 100.5 at all modes with frequency. Fuel flow and tit stable and no fluctuations. 

Did you mean bellow crossover 1.5 total travel allowable? If it is can you send me a screenshot or if you can send me to pmostafiz@gmail.com.

If fuel flow and tit stable, should I go to Fcu?

I am thinking about V/H. 

What is your opinion?

 

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1 hour ago, pjvr99 said:

if by weather you mean cloud or rain, changes in air density going into compressor will be

detected by fcu cip & cit probes. as the throttle is already pulled back, a weak valve housing

may not be able to hold the rpm steady. 1c-130h-2-71jg-00-1 gives rpm 1.5% total travel

with throttle below flight idle, and 1.0% with throttle above x-over and more than 8000"lb

torque. valve housing change is the quicker fix, but you may end up changing fcu. as an

after-thought, check the time on dome quad-seals. 

 

 

Thank you pjvr99. By weather I meant cloud. Every time during decending rpm travel 99.5 to 100.5 at all modes with frequency. Fuel flow and tit stable and no fluctuations. 

Did you mean bellow crossover 1.5 total travel allowable? If it is can you send me a screenshot or if you can send me to pmostafiz@gmail.com.

If fuel flow and tit stable, should I go to Fcu?

I am thinking about V/H. 

What is your opinion?

 

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yes, thats it. if your rpm flux is only +-0.5 you appear to be within limits. however, if the crew is

uncomfortable you will have to do something. out of curiousity, did you do a fuel governing

and pitchlock check?

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9 hours ago, pjvr99 said:

if by weather you mean cloud or rain, changes in air density going into compressor will be

detected by fcu cip & cit probes. as the throttle is already pulled back, a weak valve housing

may not be able to hold the rpm steady. 1c-130h-2-71jg-00-1 gives rpm 1.5% total travel

with throttle below flight idle, and 1.0% with throttle above x-over and more than 8000"lb

torque. valve housing change is the quicker fix, but you may end up changing fcu. as an

after-thought, check the time on dome quad-seals. 

 

 

 

1 hour ago, pjvr99 said:

yes, thats it. if your rpm flux is only +-0.5 you appear to be within limits. however, if the crew is

uncomfortable you will have to do something. out of curiousity, did you do a fuel governing

and pitchlock check?

Fluctuations allowable, above crossover: 1.5

Below flt idl: 1, what is allowable range of below crossover?? Because during decending throttle remain in-between flt idl and crossover.

I did not do pitchlock Ckeck. Can you describe for my understanding why it is important as everyone rpm stable and only fluctuates during decending. 

Thanks

 

 

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20 hours ago, pmostafiz said:

7b engine: #2 engine rpm fluctuation about 1% during decending and when goes through the weather. NTS gap is OK and plunger looks good. 

Any experience about this?

Hello, at that time ur prop is in normal governing mode or in mechanical mode? If fluctuation is in both modes then change v/Housing filter and then valve housing. Most probably cause of valve governor. Regards

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15 hours ago, Ahmer said:

Hello, at that time ur prop is in normal governing mode or in mechanical mode? If fluctuation is in both modes then change v/Housing filter and then valve housing. Most probably cause of valve governor. Regards

Every time during decending rpm travel 99.5 to 100.5 at all modes ( Mechanical and normal mode even synchrophaser off) with frequency. Fuel flow and tit stable and no fluctuations. Rpm stable at level flight and on ground. 

 

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Posted (edited)
43 minutes ago, pmostafiz said:

Every time during decending rpm travel 99.5 to 100.5 at all modes ( Mechanical and normal mode even synchrophaser off) with frequency. Fuel flow and tit stable and no fluctuations. Rpm stable at level flight and on ground. 

 

If fluctuation is in all modes,Most probably cause of valve housing. 

Edited by Ahmer

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