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  Uplock Roller Cable & Bracket Watchouts

 

 

The uplock system in our Beech landing gear has been with us for some time. It's essentially a mechanical blocking arm that was engineered by Beech to keep the landing gear from coming out of the wing under a high G load.

 

Bonanza owner and BT-er Rick T. has this picture and narrative:

 

When the cable breaks (due to lack of proper tension - from a missing spring)....the up lock arm can continue to rotate up.....till it contacts the upper skin. When the arm contacts the upper skin....it either pokes a 1" hole....or flops back.

 

 

There are varying opinions on whether this system is really necessary or not. Nevertheless it is on many of our airplanes and we have to deal with it.

 


 

Here is a narrative from a very experienced Bonanza owner, John W, of Texas. While in the process of changing out an uplock cable during annual:

 

"In the throws of an annual. I have been installing a new uplock cable in the left main gear well. That requires adjusting the rigging which is under way. In the photo is a squiggly arrow pointing at the attach bolt for the turnbuckle at the end of the cable. That bolt head needs to be on the aft side. Once the gear is up, the bolt head just barely clears a rib. If it was the other side (castle nut) it would likely catch. Just a point of emphasis. Anyway, for those with keen eyes, the turnbuckle has not been safety wrapped yet as I'm still adjusting tension.

 

The bracket that holds the end of the cable as well as the uplock block is made of aluminum and, unfortunately, it has no bushings where it rotates about a bolt. In the photo, you can see there is a crack extending out from the elongated hole although that crack does not reach the edge. The bracket failed where the rotation point simply elongated over time.

 

In other words, the hole got too large and the bolt head could slip through (with help from a small crack). I share this because one typically cannot see under the bolt head so as to determine the condition of the bracket hole without removing it for inspection. I will be installing new brackets on both mains.

 

I replaced an uplock cable on my prior Vtail. Not a fun job at all. Anyway, I had a lot of trouble getting the uplock block to move into position correctly at the end of the retract cycle. Try as I may, If I approached to book value of the cable tension (which is REALLY high at 52 + and minus nothing) the block would move into place too early and end up assisting in the lifting of the gear leg. That's not good. I queried a number of sources that I trust and all came back with the same answer ... don't get too wrapped up in that high number.

 

I believe the sequence of adjustment should be to screw the turnbuckle into the end of the cable to a point where the witness hole is well covered yet there are threads still visible. Then route the cable in the gear well ( that will change tension by just adjusting the routing a little) and then get to where the block moves into position correctly with w .010 to .020 gap between the block and gear flange. Now, after everything is working OK, go check the tension on the cable. If it is around 40 to 45 pounds, I've heard from many sources that this is just fine. But as you say, I would never personally vary from the book tension. No, not me. 

 

 

 

 


 

 

Below is a picture of a damaged Uplock cable which was hiding under the tubing

 

 

 


 

Here are pics of the bracket in serviceable condition

 

 

 

 

 


 

 

Below is a comment from Old Bob who forgot more about Bonanza design and maintenance than any of us will ever know (grins)

 

"One thing I have found is that the mechanism will last longer if the tension on the cable is a bit below the 52 pounds specified. It might work just as well at only 35 or 40 pounds, but, of course, that would not be legal even though it would reduce wear."

 

"Old Bob"

 

So remember, varying from book tension is illegal and it will REDUCE the wear on your mechanism.

 

HERE is the Beech Instruction for the uplock system.

 

Below is an image of the uplock cable and bracket system for clarity

 

 


 

Here is an image of later model Baron 55/58 landing gear that includes a DOWN LOCK as well. It is believed Beech added this feature to guard against side loads of their heavier birds and this can also be found on the Duke gear as well.

 

 

 

 

 

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