PS Magazine - TB 43-PS-710
PS, The Preventative Maintenance Monthly
ISSUE 710
JANUARY 2012
24
PS 710
JAN 12
Dear Sergeant Blade,
While out in the field, I spent days helping out with re-shimming the flex
pack on a Black Hawk, and some thought the oil cooler mounts were out
of alignment. I noticed the flex packs failed their last inspection. When I
pointed out the correct way to do shimming checks, some disagreed. When
I performed the procedure correctly, all the flex packs that failed then
checked out OK.
Here’s the long and short of it: WP 0700 00 of TM 1-1520-237-23-7
for the UH-60A/L and WP 0656 00 of TM 1-1520-280-23-7 for the
UH-60M tells you to do a shimming check, but it doesn’t tell you
how
. This
can result in it being done wrong, which results in multiple shimming check
failures.
To avoid re-shimming flex packs unnecessarily, here’s the solution. Step
3 of WP 0700 00 (UH-60A/L) and WP 0656 00 (UH-60M) tells you
what to do to get the right reading when using a feeler gage, NSN 5120-
01-335-1666, and a straight edge. A good tool to use as a straight edge
is a steel machinist rule (6 inch), NSN 5210-00-971-8827. (An alternate
straight edge is the machinist rule, NSN 5210-01-335-9236.) However,
as noted above, the
how
is not given.
Some mechanics place the straight edge along the flange surface and
the flexible couping while holding the straight edge by either end, then try
to measure the deflection gap with the feeler gage. The problem is that
placing too much pressure with your finger at either end of the straight edge
creates a gap and gives an erroneous reading with the feeler gage.
To do the check right, place your finger in the middle of the straight edge.
You’ll get a better reading with the feeler gage.
Do the test and inspection like so:
Charles Pope
AMCOM LAR
Afghanistan
Dear Mr. Pope,
Sounds like you’ve got a good one here.
One small adjustment—like where you
put your fnger—can really make a big
diFFerence in preventive maintenance.
UH-60A/L/M
Series…
Drive Shaft Shimming
Check Done Right?
I know why the
flex packs are
failing inspection
on the black
hawks.
okay.
whatcha
got?
what
are
you talking
about?
what’s
wrong
with the
way we’re
doing it?
easy there,
soldiers!
listen
to what THE LAR
has to say.
his way might
just end up
saving
you a lot
of trouble.
we’ve done it
this way for a
long time!
you
mean
there’s
another
way?
it comes
down to
doing
shimming
checks
the right
way.
let me
show you.
Drive Shaft check the
right
way
By putting
your
finger in
the center
of the
straight
edge, the
feeler
gage
gives an
accurate
reading
By putting
your finger
only on
one end
of the
straight
edge, it
will make
a gap on
the other
end
.016 gap is at the end
0.00 Gap
Drive Shaft check the
wrong
way
710 24-25.indd
1-2
12/6/11
1:59 PM
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