REFLECTOR: Nose Gear Almost Up

[Chuck Jensen]

Dave,
 
Well, mine works a little differently, but I don't know exactly how/why
its different.  Normally, during the retract cycle, my nose gear comes
up first (about 95% of a full retraction, then the mains go through
their clean-n-jerk, then the nose gear "jumps" up the last few inches of
travel, which triggers the sequence valve to close the doors.  
 
Just before leaving on a trip to the Midwest on Sunday (racing ahead of
Dennis), I cycled it on the ground.  The nose gear 'jumped' all the way
up to its final position, then settled back down to about 75%-80% of the
up position and never moved again.
 
The next time I cycled it, I applied a small amount of force against the
nose wheel as it came up, so that it could not bounce.  It went up to
its 95% tentative position, then finished the retract cycle with doors
closing just fine.  The next 6 cycles went perfect.  To say the least, I
was 'watchful' with each of 4 retracts during the trip, but everything
worked flawlessly.
 
I'm in favor of flawless functioning, but I did NOTHING different for
the retract cycles that failed and the ones that worked as designed,
hence I'm clueless as to what was wrong, why it was wrong and what to
fix to prevent it from happening in the future.  The intermittent,
non-repeatable problems are always the worst, but thanks all for a
couple ideas.  Actively looking at something is better than not even
have something to look at.
 
Chuck
 
 
> Most time, but not all the time, the XL RG nose gear  raises to its up
> position, then the mains come up, then the nose gear travels the last
few
> inches into its 'up' resting position which triggers the nose gear
doors to
> close.  The problem is, in the air, about 50% of the time the nose
gear
> comes up, the mains comes up, but the nose gear never finishes its
last few
> inches of 'up' travel, thus the nose gear doors never fully close.
> 
> I've tried cycling the gear and resetting the hydraulic system, but no
> change.  It rare that the hydraulic motor ever has to cycle on for a
second
> or two to keep the hydraulics up to pressure.  Any ideas why the nose
gear
> isn't popping up into its final resting position?
 
Absolutely. 
 
There are two issues at play here:
 
1) The sequence valve is extremely difficult to push, so prevents the
nose
gear closing as it should before the mains go up. The fix for this is to
relocate the sequence valve to within 2" of a pivot point in the NG
retraction
mechanism. In that location, the gear will retract and the doors will
close
slick as grease BEFORE the mains come up. 
 
2) The hydraulic system shuts off before reaching high enough pressure
to
activate the sequence valve at its present location. If you don't mind
the
nose door slamming shut at the end of the retraction cycle, simply
increase
the high pressure limit on your hydraulic pump until it always retracts
the
nose gear. The extra hydraulic pressure probably won't damage anything,
and
anyway this is how 98% of builders adjust it. 
 
Either of these two methods will get your nose doors to close. I prefer
relocating the sequence valve, as that's at the root of your problem.
But most
builders look nervously for the nearest exit when I explain this...
 
 
Dave
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