Tim Ong attempted to modify the struts to use thinner 5606 fluid but it was unsuccessful.

 

I also ran some viscosity tests on Belray 30W and several other fork oils in an effort to find another oil that had better temperature characteristics.  I included some premium fork oils that claim to be stable at high temperatures.  None of them performed very well.  I used a Zahn cup to measure the viscosity.  All of the oils lost about half of their viscosity (measured in time) in only 30 degrees F.  Belray 30W took 2:00 at 60F, 1:00 at 90F, and :32 at 120F.

 

My shimmy incident happened when I was doing training.  I believe my strut was much warmer than usual.  I had just completed a half hour of slow flight, then some go-arounds, then the shimmy happened during the rollout on a no flap landing.  Combine being a little high, a little fast, a little long, a little more braking than usual, and a rough runway.  Wham!  Shimmy!  I got off the brakes and the shimmy stopped and I rolled out with very light braking into the overrun area.

 

Lancair has also developed some "higher toleranced" parts and a couple modifications to the struts to make them more durable.  I sent my strut in for servicing and they did the mods, about $400.  I've only got about 25 hours on my airplane since the rebuild.  I had no damage to my engine mount but the severe rock 'n roll caused my baffling to hit my cowl and I got a crack that had to be repaired.

 

The jury is still out on how much better they perform with the modifications.  I know of two ES struts that have failed within a short time of being serviced, one had shimmy, the other severe leaking.

 

I do the greased plate test before every flight now.

 

Mike Easley

Super ES