What’s up with the jack stands?

Trippster · #1 02-20-19, 08:23 PM

We bought our 337 in December and bought the jack stands and jack pads from aircraft spruce. Today we were trying them out while changing a tire, but this doesn’t look right to us. Really don’t want to swing the gear with this setup unless one of y’all can confirm this is how it looks or tell us what’s wrong. Thanks.

kilr4d · #2 02-21-19, 03:32 AM

My jacking points go in straight and stay straight. Something seems off there. Where's the nearest inspection cover?

JAG · #3 02-21-19, 06:43 AM

That is not right...can't tell from the photo where this is exactly but jack point is located on the fwd spar. It should not buckle or be at an angle like that - the spar is solid. Could you take a photo from another angle - from wing tip looking inboard?
Jeff

JAG · #4 02-21-19, 10:47 AM

I just pulled up a picture of my 1966 337A jack point. The dark circle is where the screw and washer is inserted into the jack point, which is along the rivet line for the wing spar. Looking at your picture is a little different, as the rivet heads are raised (AN470) and not flush like mine (AN426). This could be due to a previous repair, or a different model. Either way, it looks to me that the jack point on yours is in the incorrect position, and aft of the spar. The double row of rivets running span wise is likely the spar location. Your jack pad should not be behind the skin lap, but in front of the skin lap (for reference).

Was there any repairs made in that area, and the hole for the jack pad incorrectly located?

Jeff

SteveG · #5 02-21-19, 10:48 AM

Can't add much except to say that this is seriously deranged. The central axis of the jack pad should be very nearly vertical when threaded into the spar. This condition, at least as it appears in the photo, should be impossible if assembled correctly. Is the bottom skin actually as buckled as it appears? What does the starboard side look like with its jack pad in place? Threading a longer rod into the wing would dramatically illustrate any misalignment. Not only would I not jack the aircraft until I understood the problem, I wouldn't fly it either.

hharney · #6 02-21-19, 09:01 PM

I see you bought the jack pads from Aircraft Spruce, I have never used these type and they look totally different from the factory pads that are used on Skymaster. Not sure that is the problem but I think those pads you have are made by Bogart and they may say they work for Skymaster but I have never seen these used. I looked for a photo of the factory units but nothing comes up. I won't be home until Monday but maybe someone else has a Photo

Part number 1400110-2

JAG · #7 02-25-19, 09:04 AM

Here is a picture of my jack pad installed on the RH Wing. I am not sure if these are Cessna Original jack pads, but they are crap. I am going to purchase a set of those yellow Bogert pads for my bird. With the shape of the jack pad ball, they will fit better in my jacks (Alpha Jacks) and be much safer.

Jeff

Ed Coffman · #8 03-01-19, 06:06 PM

Here is one of our aircraft on jacks. We just leave the jackpads on all the time.

Trippster · #9 03-02-19, 10:01 AM

Quote:

Originally Posted by Ed Coffman

Here is one of our aircraft on jacks. We just leave the jackpads on all the time.

Ed,

Thanks for the pictures. Your jack pads are the same as the old ones we had before we bought the yellow Bogert pads. I'm also glad to see that the location of your pads is the same as ours. We may try putting the old pads back on and see how they line up with the jacks. This is really strange.

JAG · #10 03-02-19, 02:16 PM

Tripp,
I would recommend looking inside the wing at the structure before you jack again. Something does look right in the first picture you uploaded how the jack pad is at an angle. Just a thought.
Jeff

CO_Skymaster · #11 07-12-23, 07:45 PM

I'm planning to purchase some jack stands for my 337A, so I can rotate the gear and get to the nose strut pressure inlet so I can charge it. I know where the jacks on the wings go, but what are all of you using to support the tail and if it is another type of jack, do I need two for both tail booms. I am nervous about doing this, although I suspect after doing it a few times it will get better, but are there any procedures I should know about before trying it?

Karl

edasmus · #12 07-13-23, 03:27 PM

Just came from my shop as my plane is getting it's annual inspection. My plane is on jacks per the photo. Only the co-pilot side boom is supporting the tail. There is no jack on the other boom. This is my 20th annual inspection with this shop. I have never seen both booms supported. Just my experience but I do not know for certain what the accepted practice is.

FYI, 58 pumps to manually extend the gear.

wslade2 · #13 07-17-23, 12:38 AM

For tailboom I took a countour copier from hardware store and made replica of underside of boom at the support location. I then test fitted cardboard template from that. I used the cardboard to draw a cutout on multiple squares of plywood. Ended up with about a 3 inch thick “U” of plywood that I then throughbolted some 2x4 legs. I lined the “U” with some foam rubber doormat. I made the whole set up short enough that I could put a hydraulic jack underneath it. Made two of these, one for each boom. Jacked them up with the plane.there was some running around from jack to jack. Did have to put some blocks underneath due to not enough reach of the jacks, so be ready for that.

The plane will try to tilt backwards as you raise the underwing jacks. I use the bogert jack adapters on the spar jackpoint screw hole at the wing. And yes there is jack point ball on belly behind nosegear.