Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Wed, 30 Oct 2002 19:52:21 -0500
Message-ID: <redirect-1848927@logan.com>
From: "Bob Jude" <bobjude@charter.net>
Subject: LNC2. GM28 replacement
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This subject has turned into a frustrating experience for me and I would
like to hear what other LNC2 owners have to say about it.
Since 1994 I have been doing my Annual Condition Inspections, using the
check list in the Lancair Pilot Operating Handbook as a guide.  On page
VIII - 21 of the Handbook, it states "Check nose gear gas spring for 100#
minimum to compress".  To me this means that if the spring can be compressed
and held in with less than 100# of force, it should be replaced.  I recently
purchased a new GM28 from Lancair, measured the force required and found it
to be less than 100# (brand new).  After talking to Alan, Mark and Vern at
Lancair, they are of the opinion that 100 plus or minus a few pounds is OK.
I know these springs don't go bad suddenly, but leak down gradually over
their lifetime.  So if you start out at 95 pounds, it will probably be just
a few months before the spring is too weak to lock your nose gear down
during free fall, even at very low airspeeds.  If you slow down to about 90
MPH, your gear will may lock down but I think it should
lock down at higher air speeds in order to provide a little safety factor.
In my view, the minimum specification of 100# established by Lancair back in
1994 is a good number and as far as I know has not been officially changed.

Vern agreed to accept return of the first GM28 and send me another.  I
measured the second one today and found that it is no better than the first.
Now what?

In the mean time, having a bad feeling about the situation, based on GM28
replacement history in my airplane, I started looking for an alternate
source for gas springs.  I think I found a good replacement.  Only time will
tell about the service life time.

My GM28 replacement history is as follows:
First unit came with kit (1989)  --  Replaced after 12 months of service
plus 5 years of shelf time  -- probably good
Second unit -- Replaced after 44 months of service --  a good one
Third unit  --    Replaced after 28 months of service --  not bad
Forth unit  --    Replaced after 11 months of service  -- not good
Fifth  & sixth units  --    Bad when purchased (less than 100#)

To me this looks like a deteriorating situation.

The alternate source that I am going to try is as follows:
________________________________________________________
Thank you for placing your order with McMaster-Carr Supply Company.

  Qty   |    Part Number/Description        |   Price       | Shipping Info
+-------+-----------------------------------+---------------+--------------+

    1 EA    9416K155 - Gas Spring With        $9.90 EA                Monday
            Threaded Ends 3.94" Stroke
            Length, 120 lb Force, M6 Male
            Thread

    2 EA    9416K84 - Zinc Eyelet End         $1.25 EA                Monday
            Fitting For M6 Thread Gas Spring
            With Threaded Ends

The two end fittings need to have a bushing pressed in to them with 1/4 inch
ID.
Also, the top end fitting can be trimmed in length a little in order match
the extended length of the AVM unit.
You can specify the compression force in 10# increments.  Not sure, maybe
110# would be the best choice.
The end fittings can be re-used if you need to replace the gas spring so,
the follow-on replacement cost will be $9.90 instead of the current $35 plus
shipping.  At McMaster Carr, you can order on-line and get next-day
delivery.

I would like to hear from other LNC2 flyers on this subject.  Where am I
going wrong?