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RGB failures


mechanic80
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A number of RGB's have failed due to quite a handsome size of metal chunks detected by magnetic drain plugs..what could be the possible reasons for this cause...

oil used is 23699 and is changed properly.

Propeller dynamic balancing is also done properly.

engine used is T-56-A-15

unable to find a good reason for these overhauled RGB's.:confused:

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I heard yrs ago the they were having problems with the -7 and -15 engine, it had to do with the engine only having I think 2 support bearing in the engine and it was causing vibrations into the gear box and causing problems. I was also told in 2003 by a Rolls Royce field unit in England doing work on the Brits J models that that were having the same problems with the RGB on the J model that they had yrs before with the -7 and -15. The fix was they had to put a extra support bearing some were in the engine to get rid of the vibration and it fix the RGB problem.

This is what I was told so it is what I can only go by.

One other thing to look at is hook up the vibration kit to the engine and check things out and check the read out for a freq that not suppose to be their.

Hope this helps you out.

Herc 308

Darrell

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Where are you checking the vibrations? There are several methods of doing a vibration check. There is the single Velo on the RGB, a single accelerometer on the turbine, the torquemeter runout (finding a lot of these bad), and a multipoint harness (never done one, but the Tech Data exists). The RGB Velo doesn't always catch everything.

The only other thing I can think of is check your supplier of RGB's. If it is Rolls Royce, I have no idea. If you are getting refurb units from third-party companies, you might want to check into their credentials. They may not have purchased the proper tech data for RGB overhaul, or are using unapproved materials or parts during the rebuild. Even through legit channels, we managed to recieve a large batch of engines with bad Prop Brakes causing many engine removals, even on a brand new motor. It happens.

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  • 2 weeks later...

"mechanic80 well the RGB oil pressure is 150 - 250 psi"

Well, it depends on the oil pump installed. Some operators still use the 130 to 250 limit. Problem is 130 is good for the old pump but 20 PSI low for the new pump. Hence my question..... The new pump should be installed on most engines.

A paper was published about the issue in 99 i think... Basically at 130 there is not enough of a "film" covering the RGB parts and failures result. This paper also addresses the oil pressure flux limit and range.

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  • 2 weeks later...
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I know we have had some come through here and we have only a couple of Hundred hours on them and they fail and we do DR'S and Depot really has no answer for them. I just feel they (depot) are using refurb parts that have been refurbed one to many times. I know here at my base we can't get into the front half just the rear case but most failures seem to be in the front section. I know we are just getting into the 135 day torque meter runs and feel once the info gets processed we will be changing more RGB'S I know years ago on the early -7's we ran the Torque meter Run out tests as we had no mid bearing that caused us problems.An engine Mechs work is never done.

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