Check your Landing Gear Retraction Lever Strut (Mod 51)
after 10 years in service and some 800 hours with as many landings, my Landing Gear Retraction Lever Strut (Mod 51) had an oval oversize hole at the bottom end (14mm; for the MS 20392-5C37 bolt which is 9,5 mm) and it finally broke at the top (just below the AN 3 bolt probably due to some misalignment due to the play at the bottom...
no play at the top AN 3 bolt, however!
The three screws on the Landing Gear Retraction Lever at the top seem to hold (no play)....
I'm still searching for an explanation; my aluminum angle was probably not strong enough: material thickness: 1,5 mm; L-profile: 20 mm x 8 mm
also the strut is not absolutely straight and there is some sideways flexibility which may have favored the play...
Klaus
budyerly(at)msn.com
Guest
Posted: Tue Jul 13, 2010 4:23 pm Post subject: Check your Landing Gear Retraction Lever Strut (Mod 51)
<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Klaus and others,
Please send me pictures of your elongations or failures of the strut for me to analyze. If you can provide the type material and thickness also.
Normally 6061 common aluminum angle of 1.6 mm or 1/16 inch is plenty strong enough.
Elongation of the hole at the bottom indicates slight movement of the gear lock ,retraction mechanism (most probably in the down position) due to not staying perfectly vertical with the gear down and eventually the stresses from bending, as Klaus said, or from the latch slot gear retraction arm interface bending, and or the three bolts elongation has caused fatigue of the material or too much force on the aluminum angle strut.
We will need some look see time to evaluate should if we go to steel or a specific material/dimensions, time change, or what.
In the mean time, if everyone can look at their Mod 51 landing gear retraction lever strut brace if over say 500 hours and look for wear, as soon as you can, and low time planes on your next annual, then send me updates, I'd appreciate it.
Many thanks,
Bud Yerly,
Europa Tech Assistance.
Jerry,
You are not alone and not living dangerously, as it seems you have a well built
reliable gear. However the non mandatory mod 51 arm helps keep the stress down on
the three bolts in the retraction arm. Eventually, through trailering, rough air,
rough airstrips and countless landings you may experience trouble. If the arm
flexes at the connection to the LG08 it may be difficult to lower the gear and it
may require you to unload the aircraft to near negative G to flop the gear handle
out of the slot. On takeoff, you may find that the gear will not lock up properly.
Extending the gear may leave the LG08 mechanism at less than vertical. Looseness at
this joint will progress rapidly through normal use as the gear has no over center
lock per say and will bend at its pivot points slightly both up and down,
exacerbating the problem.
Even with mod 51, if the gear is not perfectly vertical from LG8 down, the gear
handle takes the load. That dog leg in the gear handle with the bends will flex
over time, causing a higher than anticipated tension load on the Mod 51 diagonal
brace. We'll have a material and proper dimensions to use for the arm soon. We all
used Home Depot aluminum on previous builds and I should have questioned it, but I
fly a trigear and rarely get a monowheel of significant age in the shop. No one
reported the problem so it was unknown to me until now.
I would recommend one look at his retractable gear carefully on his annual, and at 5
years or 500 landings do a full inspection and rebuild. Call me conservative in a
liberal world, but the bushings and landing gear block take a beating and are never
cared for (I hate that dirty hole..). All the retractable gear certified planes I
have experience with require not just a retraction check but a complete check of the
bearings and bushings annually, slop and play are defined in the maintenance manual
for the aircraft. Why shouldn't we do the same thorough inspections and replace
known wear points at a specific time to preclude future problems.
Klaus and I discussed time changing out the following:
At 5 years or 500 landings,
Replace the bungee.
Wheel bearings KLNJ 1 1/2 They are sealed bearings, and I haven't seen a failure
but why wait until they break.
Brake pads (inspect caliper for corrosion)
Upper and lower bushings AIC 060816/AIC 060820. Inspect annually for play and
replace if detected and replace at 5 years anyway.
Inspect Mod 51 arm for wear and replace as necessary
Inspect shock absorbers and rubber block. If it hops like a bunny, change the
shocks, if it sits low, change the block. I don't know how low, low is, but the
block is about 70mm on an empty mono, so if it has lost 10 mm in height since new,
it probably needs replacing.
Look at the long bolts Euro 26 and pins LG 04 for deformation, replace as necessary
Change the outrigger legs, inspect the pivot points and the locking mechanism for
corrosion and wear. Remove and replace as necessary.
Replace the outrigger tires/wheels if worn.
I do not have a checklist for how I check the mono gear for play, and frankly just
look at the mechanics as I do not own one... I support the aircraft, push on the
lower arm and watch the mechanism when down, especially the locking arm. Look at
the LG 04 pin and support for cracks and wear. Any deformations of the gear
requires replacement. Then partially retract the gear and check for play in the
joints, wiggle the arms to check for play, and pivot points for play (nasty dirty
job), and finally lock the gear up and check movement of the gear mechanism by
pushing up on the gear and using my bore scope to see if there are problems. I have
never removed the mod 51, but I have also never worked on a high time mono. As for
the outriggers, I have to look at the book if I have to take one apart just to
figure how to put it back together. I make sure that the gear leg locks down and
that the flap moves through the proper number of degrees before unlock. I was not
familiar with the Europa Club bushing mod many of you had on the outriggers until
Jim Butcher led me through one. I have only seen the standard factory build. If
there is a comprehensive checklist other than the FAA condition inspection, I'd like
to see one for my own education.
