Have broken U-bolt at gear strut, '78 DeCat. Have been looking at related posts of those with some experience replacing.

[JAK]

Welcome any further detailed and specific advisory and recommendations anyone cares to share on the replacement job from those who have successfully done that.

>>> Replace broken gear strut U-bolt '78 Decathlon -- Procurement of new / removal of broken U-bolt / installation of new / issues of which to be cognizant, if any <<<

 

[Big Ed]

I also have a 78 Decathlon, and replaced my U bolts with the new style bar bolts. It is not a hard job.

Buy the bar bolts and hardware from ACA. Call the factory and ask for Chad in parts. He will make sure you get the right parts. The hardware pricey, but this is one area where you do not want to skimp. Numerous 7's and 8's have suffered gear collapses and prop strikes from the old style U bolts over the years.

You will need a jack adapter. I bought 2 from ACA so I could do both legs at once. The Cessna style gear leg jack adapters do not work for this project.

Other tools required are a 12 point 9/16 socket, a hex key socket to fit the bolt head, a torque wrench with a 9/16 box wrench extension, and a selection of pry bars. The inboard bolts can get frozen in the frame holes and are a mofo to work out due to lack of clearance to drive them out.

You will probably have to poke a hole in the belly fabric to get the hex socket on the inboard bolt, so have the materials on hand for a patch. Some have said they did not have to do this, but I don't see how.

The bolt take a special washer with a hollowed out inner edge to accommodate the fillet on the bolt head. Make sure the right side of the washer is against the bolt head.

You may have to trim the boot cowl a bit to provide clearance around the end of the bar. No big deal, just snip a quarter inch notch in the edge of the aluminum sheet.

Overall, not a terribly difficult project, just sweaty and some banged up knuckles.

Here are some pics.

 

[Big Ed]

Oh yes, and pay attention to tightening sequence. Loose fit both bolts. Tighten the outboard bar bolts until the gear leg barely touches the frame, then tighten and torque the inner thru bolt, then torque the outer bar bolts.

 

[Bob Turner]

All good advice. I do not remember any jacking problems.

I do remember getting the NAS bolts for $28 each from Genuine, when ACA list price was $130 each.

As Ed says, that washer under the head is critical. Weren't the original bar kits supplied with AN-7 bolts?

The U bolt is incredibly weak, and probably not 63,000 psi steel. They probably just heated up some steel rod, threaded the ends, and called it a day. Do not fly with U bolts. Opinion.

 

[Big Ed]

To clarify the jacking comment, you cannot remove a gear leg while simultaneously supporting the aircraft by that same gear leg. Ergo the Cessna-type adapter will not work for this application. You must lift the aircraft by some other point, such as the lower lift strut attach point using the ACA adapter.

 

[Bartman]

i'd add to Ed's comments that the most basic, light duty bottle jacks aren't quite adequate for the job. there are heavier duty jacks but you just have to make sure the jacking column fits into the adapter he's talking about. blocks of wood under the jack help by decreasing how much the jack has to extend to lift the plane but the other wheels should be chocked to keep it from moving while the gear leg is off which is why i'm more fond of doing one leg at a time.

just my two cents.

 

[Bob Turner]

I understand. Yes, I made an adapter to jack at the strut. I think you could replace the U bolt without jacking if you were careful. For safety, hook a hoist to the engine mountand take some of the load off.

 

[Big Ed]

Do not fly with U bolts.

Very important point!

 

[Hiperbiper]

Actually;
Flying withe u bolts is fine.

Don't LAND with U bolts.

Chris

 

[Bob Turner]

So, are AN-7 bolts legal with the bars? I know that originally they were ok on the inner attach point, but needed to be checked often.

 

[Big Ed]

So, are AN-7 bolts legal with the bars? I know that originally they were ok on the inner attach point, but needed to be checked often.