Manual Gear Uplock Block Wear

[Jerry 5TJ]

What are the wear limits on the uplock block? 

Photo is of "C" model with 4000 hours, apparently the original uplock block.  Taken in flight, the view is from below and shows how the steel top of the Johnson bar has worn a groove in the aluminum block's ramp.   The hole is worn oval, and the end of the locking pin appears worn to a bevel, too. 

It feels secure when I latch it, and give a big "heave ho" test on the handle as part of the GUMP check. 

Questions for the forum:

(1) Is there a wear limit specified anywhere in Mooney literature?

(2) If/when the block is changed, does the gear rigging tension change much?

 

FYI -- the rectangular tab visible in the center of the uplock hole is the gear safe light switch.  It toggles a microswitch to light the red and green gear indicator bulbs.

[MooneyMitch]

I do not know if there are specific measurements, but from your photo, it is definately time to replace your top block.  LASAR produces the replacement.  What you are close to experiencing is having the bar disengage when it is in the gear down/locked position.  When this happens, and if you are not quick enough to grab the bar and relock it, you can experience a gear collapse on the ground. 

After many hours of use, the once round hole does elongate, as verified in your photo.  In addition, please check the gear up floor block as well.  It can and does suffer from the same degredation.  LASAR produces that block too. 

Jolie ["mooneygirl"] can speak from experience on this topic.  I hope this helps you.

[Seth]

I replaced mine last March and it made operating the Johnson bar very smooth.  It had the same groove, and after 41 years, it was time to replace it.  It's time to replace yours as well.

[HRM]

Quote: jerry-N5911Q

FYI -- the rectangular tab visible in the center of the uplock hole is the gear safe light switch.  It toggles a microswitch to light the red and green gear indicator bulbs.

[Jerry 5TJ]

Regarding the lock -- Attached is another image that shows the pin lock better.

When the thumb button is pressed the “J” shaped pin moves to the right.   The pin moves out of the locking groove on the Johnson bar's handle.  That allows the sliding handle to move down, towards the viewer in the image, and the bar can swing towards the floor.

The “sliver” to the right in the earlier image is beyond and above the block, It is a piece of the lower panel trim, and is not part of the downlock block assembly. 

So, in answer to one question -- the pin is the locking mechanism, not the “sliver” thing.

Re prices -- I did get a price for the uplock block from LASAR, and it was about $250 for the part (don't have the quote in front of me, so that's an approximate figure).  That price is for the machined aluminum block, it does not include the button, slide locking part, or the microswitch assembly.   I was told you salvage those parts from the old unit and reuse them.

Since the new block will hold the Johnson bar in a different location (albeit slightly) the landing gear preloads may change.  At the least, it seems prudent to check them after installing a new downlock block, and before lowering the Mooney back onto its “feet.” 

[N6843N]

I repaired mine. Nothing like having a TIG, mill, and lathe in the garage.

[Immelman]

Jerry,

When I bought my airplane my '66 j-bar socket looked similar. LASAR replaced it. They also replaced the thumb latch. You mention their kit does not include the thumb latch. In my case I remember they replaced both because the thumb latch was worn as well. I'd suggest having a look at that (if you can) and checking with LASAR about including it in what they sell you.

Also, when this part is replaced you may be changing the j-bar position ever so slightly with the gear locked down. As I recall, this can have an effect on the gear 'pre-load', which may require adjustment after replacing this part. Don't skimp on that.