Generator shaft nut

Mark Harwood · Post by **Mark Harwood** » Tue Sep 25, 2007 1:06 am

Just removed generator as it was the source of oil puddle under 9183A. I am sending it back to shop that O/H last year. My local mechanic pointed out that it had a fiber lock nut and he would rather see a drilled shaft with castle nut and washer. I spoke with someone at O/h shop who said the older delco's came with fiberlock nut. Is this OK? Can the shaft be legally drilled to use castle nut with pin? Mark

Post by **GAHorn** » Tue Sep 25, 2007 2:27 am

The TCM Overhaul Manual states on pg 54 (with regard to installing the drive gear onto the gen shaft):

"(5) Insert special 5/16" washer over generator shaft, screw on 5/16" shear nut and secure with 1/16 x 3/4 cotter pin."

Just becasue your shaft is not drilled for such a pin does not mean it is not properly modified, however. I suspect your mechanic is following the general recommendations of not using fiberlock nuts on engines due to heat, but the generator on these engines are specifically called for installation with fiberlock nuts per the Ovhl Man. and the IPC.
I would not worry about a fiberlock nut in this location, but if the shaft is already drilled I'd install the shearnut and cotter. (I would not drill a shaft however. What would be the basis of approval for that modification? It'd be better to install a MS21042 all-metal locknut before drilling the shaft, IMHO.)

Mark Harwood · Post by **Mark Harwood** » Wed Sep 26, 2007 12:05 am

Thanks George. I spoke with someone at Aerotech today who said he had never heard of a problem with a fiber lock nut on this generator. He claims that many people use the old nut that came off the generator. Is that an accepted practice?

Post by **GAHorn** » Wed Sep 26, 2007 8:25 pm

As long as a fiberlock nut cannot be turned by the fingers, then one re-use is common. (But they are so cheap, why do it? Use a new fiberlock. That's what's on mine for the last 7 years.)
A Cessna service center (although not one I respect at N. Las Vegas) tried to convince me to use only plain nuts with lock washers to mount my new generator, or to use all metal lock nuts on mine. I made them install what is illustrated in Cessna manuals.....fiberlock nuts.
I've had absolutely no problems with using them in that locations.

Mark Harwood · Post by **Mark Harwood** » Wed Oct 10, 2007 10:09 pm

My generator is a Delco Remy part #1101887, It has a 3/8 shaft that is not drilled, and has a fiber-lock nut on it. My mechanic can find no documentation for this generator going on a c 145. All his paerwork shows 5/16 shaft drilled with a pin. Is the generator I have OK for a c145? Before we sent the gen back to repair shop we removed gear to see if o-ring was installed. There was not. I now have gen back.I spoke to Quality Aircraft Accessories who replaced the seal. I asked if they put an o-ring in it and he said they did not. He said that generator does not call for one? He also said the generator had very little oil in it when he received it. That does not explain the puddle under the plane. The engine is new and clean and dry above the gen with lots of oil leaking off the lower generator mounting nut. We are pretty sure oil is coming from generator. Any one else have or seen this generator? Is it legeal for c145? Should it have inner o-ring? Mark

Post by **GAHorn** » Wed Oct 10, 2007 10:18 pm

The approved generators listedf on the TCDS are:
1101880 and 1101898 (35 Amps) eligible only with dampened crank.
1101879 (25 Amps) only with special gear TCM PN531325)
1101876 (12 Amps) was original standard.

1101887 is a 25 Amp generator. I do not have any info on which aircraft/engine it has approval for.