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During my 20th hour of flight, performing an emergency gear drop test, I could not get a "down and locked" indication for the right gear.  No amount of slipping would turn on the green light so I engaged the pump and ultimately got the green.

A later inspection revealed that the right main actuator push rod was bent into a frown shape (a smile would have been as bad).  I'll never know if the gear had hung up (the previous hundred retractions/extensions were all good) or a high pressure surge bent the rod because:

1. The Aerotek cylinder rods are pretty sloppy when extended.  That is, the center of the extended assembly can be displaced about .5 inch from straight in-line; and,
2. The ram was about .375 inch short of bottoming out in the cylinder when the gear was down and locked, so there was still some push to go to full extension.

It is easy to see that this combination, high pressure and some slight cocking, could bend the push rod with potentially disastrous results, such as one gear leg partially extended/retracted and jammed if it was even slightly bent on a prior extension.

The Lancair assembly manual I used (Circa 1990) only makes reference to the careful adjustment of the up-stop sleeve so that the gear is not retracted through the wing upper surface.  However, final adjustments should provide that, on extension, the cylinder is bottomed out.  This will assure that attach points won't be broken and rods won't be bent.

BYW, I bought Wolstenholm (S & F 99 award winning Lancair IV-P) replacements from Lancair which are sturdier at extension.  They were adjusted to fully extend down and I used longer up-stops for the retraction phase.  No problems after 120 hours of operation.

Scott Krueger
N92EX


[I'm a little surprised none of our IV gang has chimed in on this one...
I understand that there was (is?) a problem with their flap actuator which
is virtually identical to what we get to battle with while setting up
the gear cylinders on the 360... the difference is that if their flap
actuating cylinder doesn't bottom out they stand the risk of damaging the bellcrank-like component to which the cylinder attaches.  Has there been
an update to that component recently?  Bill Maddox told me he had to
have the pushrod shortened on his IV-P flap cylinder to keep from breaking
that part at full flap extension.          <Marv>    ]

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