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Sagging Engine Mounts on TSIO-550E
(LIVP)
"When I first saw her, she was beautiful. Now,
after two wonderful years together, I've noticed that she's sagging up
front, not quite as perky. I've decided to send her to an expert
to get them lifted a bit, get her back into a more youthful
look."
Now that I've gotten your attention....
When I receive my fast build TSIO-550E from Lancair, it was
mounted on my engine mount ready for install. After install, I
adjusted the cowling to fit the spinner position in X-Y-Z. All
seemed perfect. After two years and 160 hours, I have seen the
engine sag and the spinner's top edge drop ~0.5 inches below the
previous perfectly aligned edge of the cowling up front. Others
have noticed this, including my HPAT instructors, and say this is very
common.
During my annual (these last two weeks), I could see the engine
mounts' vibrator isolators up front sagging, a bit distorted,
compressed from the weight. Clearly, the weight on these mounts
and their brief aging have caused this. I understand that other
aircraft using this engine and these quality isolators have gone to
six contact point engine mounts to carry the load better, reduce the
sagging. I've spoken to Lancair (Ross) who also said this was
common, and agreed with my plan to add engine mount washers to the
engine side of the virator isolator. I plan to add three washers
on the engine side, each 1/8th inch thick, to the front mounts.
The bolts (7/16th, 20-thread) will need to be lengthend. Torque
is standard 450-500 inch-pounds.
As a footnote, the current bolts do not reach fully into the
engine side mount. The aluminum threads with its helicoil is
plainly visible if one looks into the threads from behind. Ross says
this is normal, and none fill the thread side of the mount. I
will be sure to have a bit more helicoil engagment with the new
bolts.
If others have experienced this, please share your
thoughts.
The archives don't have much about engine mount sagging.
Here's some related advice from 2003 for an LNC2:
Nah! You're torqeing down on the steel sleeve
that slips over the bolts
inside the rubber donuts, not the rubber directly. When that's tight -
steel
washers on the outside of the rubber donuts against the steel sleeve,
the
rubber is compressed the required amount - bolt torque has little to
do with
it, unless you deform the sleeve. The mounts and bolts I used (don't
know
about others) required the use of a cotter pin so an exact torque is
moot
anyway since you need to align the castle nut slot with the hole in
the
bolt.
Incidentally, if you're still in the building process, put a washer or
two
on the top engine mount bolts and then align the spinner and cowl.
When the
inevitable droop occurs, you can then remove washers as required to
line
things up
again.
Just sharing an observation and plan.
Jeff Liegner
New Jersey
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