F-16 #4 Eng Bearing Leak

Operating an F-16 on the ground or in the air - from the engine start sequence, over replacing a wing, to aerial refueling procedures
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tomahawk_breezy

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Unread post11 Sep 2021, 08:46

First time posting on here and am hoping there is someone who can help troubleshoot this issue.

We have a Block 40, F-110-GE-100 that will leak out of the number 4 bearing only after we swing the landing gear. After every leak, MFE scopes the motor and the carbon seal is bad. (But only after jack and swing) We have R2 the motor 7 times in 6 months and everytime, the same issue comes up.

We figured it was a bad batch of carbon seals from Hill going in these motors, so we canned and known good motor and it didnt leak after the run. It wasnt until it was C3 for a NLG wouldnt retract issue that we jacked it, swung it and it leaked again.

A twisted airframe could be a possible cause but we havent had Depot come laser boresight the jet yet.

Im not engines, and dont have too much knowledge on it but, myself, another crew chief and eng troop are pretty invested in trying to find something since the engineers havent had much luck either.

Looking for any insight into what could be the issue.

Appreciate any help. Chop!
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f119doctor

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Unread post11 Sep 2021, 15:35

I know nothing about the F110 engine oil system, but a couple of places you might check:
1. Is the breather overboard adapter blocked somehow?
1a. Is the gang drain open to overboard? Is something else leaking and being forced up the #4 drain?
2. Is the throttle rigged correctly? Don’t know if it is possible, but running sub-idle can induce compartment leakage.
3. On the F-16 (at least on F100) the engine nozzle goes open at idle with the landing gear handle down. Is the nozzle open at ground Idle? Your gear swing comment is pointing in this direction.
P&W FSR (retired) - TF30 / F100 /F119 /F135
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j79-17

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Unread post12 Sep 2021, 22:16

How exactly is this being isolated to a #4 bearing oil leak? I assume no oil consumption and they are borescoping the LPT.
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f119doctor

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Unread post13 Sep 2021, 16:24

j79-17 wrote:How exactly is this being isolated to a #4 bearing oil leak? I assume no oil consumption and they are borescoping the LPT.

There is a gang drain on the F-16 where several fuel and oil leak sources are plumbed together to exit the airframe. I don’t know if the F110 has a #4 compartment drain going to the gang drain that could be isolated when excessive leakage is noted going overboard.

On the F100, there was a #4 compartment vent that exited the side of the diffuser case, under the fan duct. If you had excessive consumption, you could look at this vent with a boroscope for signs of oil, but it was not a normal post flight inspection item.
P&W FSR (retired) - TF30 / F100 /F119 /F135
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j79-17

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Unread post15 Sep 2021, 01:07

F110 Doesn’t have an external #4 area drain. I suspect they are seeing wet 1st stage LPT blades. If it is just a couple of blades at the 6 o’clock position that is a static leak and I would talk to Tinker. I doubt highly that it has anything to do with the landing gear. Just my 2 cents.

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