Has anybody made a jacking cradle?

[GAHorn]

Probably not for short periods, but he hazard is that anything hydraulic should not be trusted for holding the aircraft up for actual work-in-progress unless it can be "locked" in position.

In every case, never jack an airplane outdoors...always do it in an enclosed hangar only.

[jrenwick]

Probably not for short periods, but he hazard is that anything hydraulic should not be trusted for holding the aircraft up for actual work-in-progress unless it can be "locked" in position.

In every case, never jack an airplane outdoors...always do it in an enclosed hangar only.

Agreed! When I use my engine hoist to hold something for more than a few minutes, I cut a piece of angle the length of the extended hydraulic piston and tie-wrap it or hose-clamp it to the piston. If the hydraulic pressure lets go, the angle will carry the load. I also double up on the straps that go through the engine mount. I'd sure hate to drop an airplane!

[Mark Harwood]

Today I removed the tie-down rings and replace them with 5/16 X 4 grade eight bolts with 1 1/2 " inches of washers so the head of the bolt sticks down and fits in the concave divet in top of jack. I jacked on one side a few inches but never got the wheel up. I just did not feel good about the stability of the plane,although it would be similar to the link George posted in this thread. I would hate like heck to drop it. Would jacking both sides at the same time be better? I was thinking one side at a time would keep the plane more stable with only one leg up? Would there be any advantage to having the tail up? I have an engine hoist in in the hanger and wheeled it over and plan to try jacking and hoisting at the same time. John, Do you use a spreader bar when you hoist at upper engine mounts. Are you using some kind of strap to go around these mounts? Thanks, Mark

[jrenwick]

Hi Mark,

No, I haven't used a spreader bar -- just a heavy cargo strap under the upper two engine mount tubes, suspended from the hook at the end of the boom of the engine hoist. I'm very serious about backing up the engine hoist's jack with a piece of angle to stop it falling if the pressure goes away -- I don't trust these Chinese tools that much!

It helps to place a weight (a bucket of water or scrap hardware or a sandbag) on the floor and tie it to the tie-down point of the lighter wing. Adjusting that tie-down lets you lift one wheel or the other, or both, once the nose is hoisted up.

The more I think about it, and reading your post, I like this solution more and more as compared to wing jacks. With wing jacks, I'd be scared to death of one of them coming off the jacking point and going through a wing.

Best Regards,

John

[cfzxo]

I still have the lifting eyes in the carry through spars from when my plane was on floats.I have a spreader bar and lift it up completely, then place a sturdy padded sawhorse under gearbox and then lower on to it to take the strain off lifting eyes. It helps stabilize the plane when removing gear legs or wheels etc. I know that when I had the eyes installed it didn't seem like that big of a cost, but that was quite a while ago. It might be the perfect solution for piece of mind if your roof structure is strong enough to carry the weight.
Bill CFZXO 170-B

[wingnut]

I've never lifted an airplane by the engine mount, and will never try. If you try, use a speader bar, because there are no stiffeners or cross braces on the firewall to keep the upper tubes from pulling toward each other and wrinkling the firewall. Don't ever try to lift the aircraft by the engine lifting eye. I've seen the results of this from some one who tried. The case busted.
For wheel bearing maintenance or removing one gear leg, we have a piece of 3/4" plywood, approx 18"x24" with some 4" thick foam glued to it. We made some brackets that are attached to the bottom of the plywood and will bolt to a cherry picker (where the chain or hook attaches). You place it under the main spar, just outboard of the lift strut and can lift one wing at a time.
When we are doing major repairs and need to lift the fuselage (with wings off), we have a spreader bar (in Arkansas it's called a single tree, for field dressing a C170) and lift the entire fuselage from the front spar, remove the legs and then lower onto a cradle. Never trust hydraulic jacks for long term support.
Wish I could post pics of this stuff, but I don't have the proper equipment and/or knowledge to do that

[GAHorn]

I've never lifted an airplane by the engine mount, and will never try. If you try, use a speader bar, because there are no stiffeners or cross braces on the firewall to keep the upper tubes from pulling toward each other and wrinkling the firewall. Don't ever try to lift the aircraft by the engine lifting eye. I've seen the results of this from some one who tried. The case busted....

Good words.

... I jacked on one side a few inches but never got the wheel up. I just did not feel good about the stability of the plane,although it would be similar to the link George posted in this thread. I would hate like heck to drop it....

Lift BOTH sides SIMULTANEOUSLY when jacking by the wings. Going back-and-forth one wing at a time can make the airplane shift off the jacks if done much more than an inch or so at a time, and if one wheel leaves the pavement sooner than the other the entire aircraft can slip sideways if the lifting points and jacks are not secure with each other.

If you've never jacked an airplane previously, you might want to go to the local airport and observe the shop's procedures at least once.

If you're only doing wheel and tire work, then I suggest not jacking the entire aircraft anyway. Just do one side at a time, and use the Cessna jack-adaptor or a couple pieces of ply-wood clamped onto the gear-leg with a C-clamp and an automotive jack. Don't forget...don't trust a hydraulic jack not to leak down. Place a block of wood or other support under the axle when you get the wheel off.

[Mark Harwood]

Doing pponk so weight has to come off legs. I am leaning toward lifting both wings at the same time as well as lifting on engine mount with strap and spreader bar. Probably set it on a cradle as soon as it is up before doing the work. I am thinking that the 2 X 4 with carpet on front spar just outward of strut would be less likely for the plane to slip off. Do you need to contour the 2 X 4 as the wing is not flat there? will the skin flex and cause the paint to crack? George, I have seen other planes jacked, but not tail wheel. I wonder if getting the tail up and the wings closer to level would be better? I have discussed the jacking with three local mechanics and had on older carreer FAA guy call one of his mechanic friends. The answers are split as in this thread. Some would never jack at wing some would not lift at engine mount and so on. I have been assimilating all these opinions and will hopefully have positive results. I have a little time as My tight 90 degree drill is not here yet. My skis arrived (thanks John) and the lake is frozen so I gotta get a wiggle on!! Mark

[GAHorn]

If I were doing a gear-leg removal (such as Pponk mod) I'd lift the tail and put it on a padded box or support first. I'd then jack at the wings, at the tie-down rings, or just outboard the strut beneath the spar using a 2x4 beneath a square of thick plywood padded with carpet. I'd use the tripod stands I showed earlier. Personally, I would never use the engine mount.

Here's a pic of how one guy mod'd his airplane to accept jack pads a-la C-210. This shows that it's an appropriate place to jack the aircraft. Just spread the pressure a bit if you use plywood/carpet.

170JackPoint.jpg

[Bill Hart]

I've never lifted an airplane by the engine mount, and will never try. If you try, use a speader bar, because there are no stiffeners or cross braces on the firewall to keep the upper tubes from pulling toward each other and wrinkling the firewall. Don't ever try to lift the aircraft by the engine lifting eye. I've seen the results of this from some one who tried. The case busted.
For wheel bearing maintenance or removing one gear leg, we have a piece of 3/4" plywood, approx 18"x24" with some 4" thick foam glued to it. We made some brackets that are attached to the bottom of the plywood and will bolt to a cherry picker (where the chain or hook attaches). You place it under the main spar, just outboard of the lift strut and can lift one wing at a time.
When we are doing major repairs and need to lift the fuselage (with wings off), we have a spreader bar (in Arkansas it's called a single tree, for field dressing a C170) and lift the entire fuselage from the front spar, remove the legs and then lower onto a cradle. Never trust hydraulic jacks for long term support.
Wish I could post pics of this stuff, but I don't have the proper equipment and/or knowledge to do that

I know we are talking 170's here but the Mooney recommended method of jacking for gear swings says to use the engine lifting eye. Sounded strange to me but it works well. On a Mooney. On my 170 I use high wing jacks and lift the tail on a stand that I have. Any member who's in the Atlanta area is welcome to use them.

[GAHorn]

Bill, isn't the Mooney procedure intended only to support the nose-heaviness during the gear swing, while the main aircraft weight is supported by main-jacks? (I can't imagine actually relying upon the engine lifting eye, even on a Lycoming, to support a 2,000 lb airplane.)

[Bill Hart]

Yes you are correct in that the main weight is held up by wing jacks but it sill looks scary to me. It is however very stabile, I would think that there would be some movement when climbing up on the wing but it is rock steady.