Jacking up a Bearhawk

[Blackrock]

So today, I changed out the main landing gear bolts. They had about 800 hours on them. Two were slightly bent, and all showed some wear so it was time. For just changing tires up to 8:50's, I have used a floor or bottle jack and lifted each wheel individually. When I switched to Bushwheels, there wasn't enough clearance between the jack and the tire. To solve that, we (Russ, Andy, and I) made up a spreader bar that goes between strut attach points on both wheels thus allowing more clearance for the jack since it can be moved inboard. We jack both sides at the same time to lift the plane. I don't have any photos of that right now, but will add some maybe tomorrow.

That is all good unless you want lift the plane to work on the landing gear bolts. In the past, I have used a sling around the engine mount and lifted the plane with an engine hoist. That is what I was going to do today, but I really didn't want to uncowl the engine for that. So my son Tyler and I used the engine hoist to lift it just outboard of where the wing strut attaches to the main spar. This isn't for the faint of heart, and I considered it a bit risky at first, but it worked very well and allowed us to change the bolts easily. The plane was on 29" Bushwheels when we did this and the opposite wheel was well chocked. A few photos of the jacking arrangement are attached.

[Mark Goldberg]

I think I like better hoisting from the engine mount. This looks a little precarious although it might have been fine.

Mike - did you look at the fuselage gear attach holes when you changed out those bolts? Mark

[Blackrock]

Hi Mark, yes this looks precarious and is to some degree and I don't necessarily recommend it, but it is an option. I agree with you that using the engine mount method is the preferred way to go. The only difficulty I've had with that is the plane wants to roll to one side or the other so securing the plane so that cant happen is important.

I did look at the holes and they are in good condition.

[Blackrock]

Using a spreader bar to lift the BH for a tire swap and while we are at it, replace the break pads.

[jaredyates]

I never thought to use the engine hoist to push from the top... With a little bit of fabrication it could be made less precarious. I'm imagining an 8" square plate with a little tongue welded to the middle. I could grind a slot in the top of the arm of the hoist, and then that tongue could engage with the bolt that usually holds the chain. That, combined with a high-traction pad on the plate, would really reduce the risk from movement.

[Blackrock]

Jared, what you describe would indeed be much safer.

[bearhawk2015]

I highly recommend you don't jack up your plane this way. When I was finishing my airplane and was adjusting my shock struts I did something similar and it didn't work out very good. The problem is with the tail, as you lift one side it causes the tail wheel to tilt over just a little bit and when it tilts the tail wheel wants to turn sideways and when it turns sideways the whole airplane will rotate and fall off your jack, even if you chocked it and the brakes are on this can happen. The only semi safe way to jack the airplane this way is if you have the tail wheel secured to the floor or have something very heavy on either side of the tail wheel to keep it from moving sideways.

[Battson]

You are a braver man than I, Mike!

Are you using standard AN bolts or NAS bolts?? I know some seem to like the idea of NAS, however I have concerns that the bolts will damage the fuselage attachment points, rather than failing first. I also wonder if NAS bolts would fail with a fracture rather than displaying obvious bending and necking first.

I plan to change all my gear bolts this year, at the next 100hr check (500hrs TT). I plan to be replacing like for like with AN bolts, at this stage.

[N942VT]

I use the spreader bar method, or a six foot nylon stap around the lower gear fitting and an engine hoist.

[Blackrock]

I highly recommend you don't jack up your plane this way. When I was finishing my airplane and was adjusting my shock struts I did something similar and it didn't work out very good. The problem is with the tail, as you lift one side it causes the tail wheel to tilt over just a little bit and when it tilts the tail wheel wants to turn sideways and when it turns sideways the whole airplane will rotate and fall off your jack, even if you chocked it and the brakes are on this can happen. The only semi safe way to jack the airplane this way is if you have the tail wheel secured to the floor or have something very heavy on either side of the tail wheel to keep it from moving sideways.

2015, thank you for sharing your experience. I see how what you describe could happen and I probably just got lucky that time. Sorry you had that happen and hope nothing was damaged too badly.Next time, if there is a next time, I try that, I think I'll lift the tail onto an elevated table, and secure it so it can't roll. The wings will be level fore/aft or close to it that way so less chance of movement that direction, also.

N942VT, I'll have to try the sling approach sometime. Looks like it would work well.

Jon, Yes, AN bolts since, like you, I'd rather they yield than than experience a brittle failure. The 500 hour mark seems about right. I was planning to do mine then, but just never got around to it and it was bugging me enough, I just went ahead and got it done. FWIW my bolt sizes were two AN6-15's, two 22's, two 24's and two 25's.

Mike