Mailing List lml@lancaironline.net Message #8603
From: Scott Krueger <sky2high@hotmail.com>
Subject: LNC2 Hartzell Prop, torque, safety wire tip, spinner back plate info
Date: Mon, 19 Feb 2001 08:10:17 -0600
To: <lancair.list@olsusa.com>
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For direct replies, use Sky2high@aol.com

LNC2's with a Hartzell prop probably have drilled prop mount bolts with a
nut that is fixed to the bolt with a roll pin. These bolts are buried in a
depression which limits access for tightening and makes safetying hell.

Because of certain experimental piloting techniques and blind taxiing, I am
on hub #2, blades 5 and 6. From my experience I can relate the following:

1.  A standard Craftsman crowsfoot is not strong enough and will destroy the
"nut" over time.  Get a hi quality Snap-On crows foot or be dumb like me and
buy the special crowsfoot from Hartzell for $300, or see your local mechanic
for help.

2.  A prop mechanic showed me his technique for safetying:  After torqueing,
choose the hardest nut to get the wire thru; remember its position; back it
off a bit to get the wire thru; return the nut to its torqued position and
safety it to an adjacent easier nut.

3.  Safetying tip: After you have made the last pull on the twisting safety
pliers, grab the pliers and, while twisting the pliers, describe a circular
arc with the tip of the pliers (about 180 deg).  This results in a nice
tight wire grip at the origin.  If its at the pig tail, this technique also
starts a curl so that you can cut off the excess and then easily form the
loop that prevents you from being cut by the sharp end.  Practice this --
you will like it.

After 300 hours, I have not seen any damage to the web between the bolts
from the tight safety wire.

Spinner back plate:

1. The back plates are slightly cupped by the manufacturing process and can
be work hardened and crack in service.  The doubler plates should be
installed and the rivets should be bucked, not squeezed.  Note:  I had the
outside squeezed rivets shear after some use and a prop mechanic said bucked
rivets are less likely to fail.  Since he bucked in all the rivets, I have
not had a failure.

2. Remember that the back plate mounting nuts are to be torqued to only 22
ft. lbs.  This is important.

3. Hartzell uses silicon to seal joints.  The bolts that are replaced by
longer bolts to mount the spinner back plate are devils to work with because
of the tight fit and silicon squeeze out in the holes.  I don't have a good
suggestion here.  I lubricated the bolts and holes and hammered them in.

Scott Krueger
LNC2 - N92EX

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