Van's Air Force
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Wing Jack warning!!!
- Thread starter Jackm
- Start date
N402RH
Well Known Member
This is what the top of my purchased aircraft wing jacks look like.
I have been using these for years to lift my RV-4 and RV-10 without any problems.
There was a local maintenance facility that had a Global Express fall off the jacks a few years ago if that makes you feel any better.
Rob Hickman
N402RH RV-10
I have been using these for years to lift my RV-4 and RV-10 without any problems.
There was a local maintenance facility that had a Global Express fall off the jacks a few years ago if that makes you feel any better.
Rob Hickman
N402RH RV-10
Sorry for your troubles
Jacking planes is always a little scary even when you have the right equipment. In 39 years as an aircraft mechanic, I never had one slip off the jack but it sure could have happened. I own Bogert Aviation and one of the things we do is build jacks and jack pads for a wide variety of aircraft. I don't currently build a jack specifically for the RV series but from the sound of it, it's a problem worth spending some time on. I do have jack pads for the Mooney M20 series that are mounted with a single bolt like some of you are trying to do except it has a ball nose that is designed to fit the top of a wing jack. http://bogertaviation.com/component...ge/product/Mooney_Jack_Pads_4d5c03b35dea2.png
I think the best thing would be to lift at the bottom of the gear leg near the brake. The wings would be in no danger and the aircraft would be stable and safe. The jack is no problem, we just need to work on the jack pad.
Jacking planes is always a little scary even when you have the right equipment. In 39 years as an aircraft mechanic, I never had one slip off the jack but it sure could have happened. I own Bogert Aviation and one of the things we do is build jacks and jack pads for a wide variety of aircraft. I don't currently build a jack specifically for the RV series but from the sound of it, it's a problem worth spending some time on. I do have jack pads for the Mooney M20 series that are mounted with a single bolt like some of you are trying to do except it has a ball nose that is designed to fit the top of a wing jack. http://bogertaviation.com/component...ge/product/Mooney_Jack_Pads_4d5c03b35dea2.png
I think the best thing would be to lift at the bottom of the gear leg near the brake. The wings would be in no danger and the aircraft would be stable and safe. The jack is no problem, we just need to work on the jack pad.
This week we started our first annual on our RV10. We had inspected the wheels and brakes and decided to replace the tires and brake pads and service wheel bearings all in one shot after initial inspection. During the build we had the RV10 up on the stands numerous times with these wing jacks with no problems.....Well today we had a problem..... and it was my fear from the the moment we started using these a year ago. The airplane was just a inch off the tires...a loud snap and a crunch with no danger but it could been much worse as I was working on removing the cotter pin to remove the wheel retainer nut. I didn't think I was creating any movement to the airplane but who knows....I was a Dumb *** for not watching close. The reality is it happens fast and safety is a concern.
I am not exactly sure what went wrong but a few thoughts so this doesn't happen to others if you are using the same system.
1. Do Not lift both sides up at same time, Block the tires on opposite side and nose to prevent the aircraft from moving the aircraft.
2. Do Not lock the homebuilt pipe cap to the stud bolt...oversize the hole and leave the nut above the pipe cap slightly loose to allow the cap to pivot as you lift and lower the aircraft...mine was tight.
3. Use Grade 8 bolts for the stud and keep cap as close to wing skin as possible.
The fix is somewhat simple with installing a stall warning inspection kit in the place of the hole.
This ruined my day but no one got hurt...hopefully this prevents any future incidents.
Jack points that lift on a gear leg are fine if all you need to do is service a tire/wheel, but an important part of a condition inspection on an RV is checking the condition of the gear itself (looseness of leg in socket, etc.).
This is pretty difficult to do if the airplane is being supported by the gear leg.
This is pretty difficult to do if the airplane is being supported by the gear leg.
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Confession time
Back in the hanger tonight and I just couldn't leave it alone. I been thinking why this never happened before and why it never happened the 20 other times I lifted the aircraft.....so investigation began and re enacted the crime.
Here's what happened I think...I am sure ... I had lifted the aircraft earlier that week to inspect only...I lowered the wing jacks but left them in place. I lowered the right side last ( left side was problem) On Saturday I went to jack the plane again... thinking the ram end was still in cap... I thought I even checked it but it was not in the cap so I was jacking on edge of the cap.
It crashed only 2 or 3 minutes after jacking so I am sure the force on the edge of the cap rolled the bolt and ultimately sheared it. This makes sense because the cap was on the ground after it broke and if it was over the ram it would not have been able to twist and come off.
If you look close you can see marks on cap to support this.
So this supports my original post that I was a dumb idiot. It also reminds me that if you don't check and double check... things can or will go wrong.
I apologize for creating a false theory that our lift points are insufficient.
Back in the hanger tonight and I just couldn't leave it alone. I been thinking why this never happened before and why it never happened the 20 other times I lifted the aircraft.....so investigation began and re enacted the crime.
Here's what happened I think...I am sure ... I had lifted the aircraft earlier that week to inspect only...I lowered the wing jacks but left them in place. I lowered the right side last ( left side was problem) On Saturday I went to jack the plane again... thinking the ram end was still in cap... I thought I even checked it but it was not in the cap so I was jacking on edge of the cap.
If you look close you can see marks on cap to support this.
So this supports my original post that I was a dumb idiot. It also reminds me that if you don't check and double check... things can or will go wrong.
I apologize for creating a false theory that our lift points are insufficient.
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BillL
Well Known Member
Excellent post failure analysis!
Jack, thanks for looking deeper, we all should have thought about why the cap was not introduced through the skin. Thanks for looking at this with an objective eye and giving more evidence of the causal chain. I had wondered why a little wiggling would cause that to fail, unless the floor stands were wobbly. They should not wobble, an inherent (potential) weakness of a plywood base. It seems, though that you are on to a better design with that bolted plate. If the bolt were still used and the fence were built into the plate, then if it jumped off the bolt, then the plate would still provide enough area to handle the load without damage. The plane should be able to withstand some reasonable tugging while on stands.
Although there have been other threads on jacks, yours has revealed the concept of failure modes that have an unpleasant result. Thankfully, nothing fell on someone. I was pinned under a car once, and in another incident had a floor jack head fail and flop over, I was almost clear but the 4" drop bruised my shoulder as I was reaching around to bleed some brakes. It could have been worse, deliberately not reaching over the wheel, which would have surely broken my arm. I learned my lessons and always wiggle the cars after lowering to the jack stands, but while the jack(s) is (are) still underneath.
Jack, thanks for looking deeper, we all should have thought about why the cap was not introduced through the skin. Thanks for looking at this with an objective eye and giving more evidence of the causal chain. I had wondered why a little wiggling would cause that to fail, unless the floor stands were wobbly. They should not wobble, an inherent (potential) weakness of a plywood base. It seems, though that you are on to a better design with that bolted plate. If the bolt were still used and the fence were built into the plate, then if it jumped off the bolt, then the plate would still provide enough area to handle the load without damage. The plane should be able to withstand some reasonable tugging while on stands.
Although there have been other threads on jacks, yours has revealed the concept of failure modes that have an unpleasant result. Thankfully, nothing fell on someone. I was pinned under a car once, and in another incident had a floor jack head fail and flop over, I was almost clear but the 4" drop bruised my shoulder as I was reaching around to bleed some brakes. It could have been worse, deliberately not reaching over the wheel, which would have surely broken my arm. I learned my lessons and always wiggle the cars after lowering to the jack stands, but while the jack(s) is (are) still underneath.
rleffler
Well Known Member
The one thing I just noticed comparing Jack's cap to the custom milled cap that I'm using is how it mates to the wing.
The pipe cap in Jack's photo has a nut to hold the bolt in place and is the interface to the wing, or the nut isn't threaded all the way in, putting all the stress on the bolt.
My cup is threaded, so there is no nut on top. The top is also flat and we've put a piece of rubber on it as well. I screw the bolt in until it and the cup is snug to the bottom of the wing. So I not only have the bolt, but also the two inch diameter of the cup snug against the wing bottom.
I think the advantage is that it minimizes some of the shear stress on the bolt. The bolt I use also has a round head which pivots in the depression in the jack ram. There is room within the cup to accommodate small angle changes, but it also serves as protection to keep the jack ram from slipping off the pivot point.
I'm sure that there are still potential failure modes with the solution I'm using.
I don't have photos handy at the moment of just the cups. With the freezing rain and show, it will be awhile before I can get to the hangar to take some.
The pipe cap in Jack's photo has a nut to hold the bolt in place and is the interface to the wing, or the nut isn't threaded all the way in, putting all the stress on the bolt.
My cup is threaded, so there is no nut on top. The top is also flat and we've put a piece of rubber on it as well. I screw the bolt in until it and the cup is snug to the bottom of the wing. So I not only have the bolt, but also the two inch diameter of the cup snug against the wing bottom.
I think the advantage is that it minimizes some of the shear stress on the bolt. The bolt I use also has a round head which pivots in the depression in the jack ram. There is room within the cup to accommodate small angle changes, but it also serves as protection to keep the jack ram from slipping off the pivot point.
I'm sure that there are still potential failure modes with the solution I'm using.
I don't have photos handy at the moment of just the cups. With the freezing rain and show, it will be awhile before I can get to the hangar to take some.
Walt
Well Known Member
If I'm not mistaking though, the tie down is not flush against the bottom wing skin on any of the RV models if built according to plans (I know this to be the case on the 2 seat RV's, don't recall on the 10) so if you screw the "jack pad" up against the wing you will bend the skin.
This makes using adapters like this not really an effective option.
This makes using adapters like this not really an effective option.
Ron RV8
Well Known Member
I noticed this on the plans while building... I could not visualize any design reason since tightening the tie downs, or lift points, would bend the skin.
Mine are flush!
JonJay
Well Known Member
If I'm not mistaking though, the tie down is not flush against the bottom wing skin on any of the RV models if built according to plans (I know this to be the case on the 2 seat RV's, don't recall on the 10) so if you screw the "jack pad" up against the wing you will bend the skin.
This makes using adapters like this not really an effective option.
I used these for many years, as supplied by Vans. Only recently did I notice one of them had a slight bend to it. I switched over to a bolt. I don't know what the shear strength of that plastic is, but it must be way less than any grade of steel bolt.
If someone made a steel version of these plastic devices, I would buy it right now. They fit perfectly into the socket on top of my jacks.
Walt
Well Known Member
These are from Bogert Aviation and have a steel stud but they are 5/16 for the Mooney, I contacted Richard at Bogert Aviation (Bogibar) to help us come up with a better/similar adapter for the RV.
Mike S
Senior Curmudgeon
The 10 also has a gap between the skin and the end of the tie down mount plate.
However, the hole in the skin---at least on my plane---is large enough that the nut will pass through, and can be snug against the tie down mount. That would eliminate the bending stress at that point.
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I use these with similar modified concave hydraulic jack ends as Ron_RV8 but I put an additional short vertical pin in the hole. I countersunk the hydraulic jack end slightly deeper into the modified concave to fit the pin. The vertical pin is LOOSE and only restricts lateral movement if for some reason the ball unseats. The lift load is on the ball not the pin. I made the pins from old drill stock. The ball end is $25 from Cleveland Tool. Less drag than the standard tie down ring and you can leave them in place.
I have and like these ball ends. They work great most of the time for tie downs, exceptions are airports that have frayed or taped 1/2 in ropes installed for tiedowns. I carry carabiner hooks for these times so I dont have to use my 3/8 inch tiedown ropes. Sure wish these had been made a bit larger with 5/8 inch holes since most airports have larger ropes. Oh well.
To keep,this related to jacking, my jack has the top of the ram concaved and I ground the head of my 3/8 inch grade 8 bolt round so it nests into the ram. Gives it plenty of swivel motion and secures it from slipping out of the ram.
douglassmt
Well Known Member
My jack top
I looked at my jack top last night and noticed that I did it a little differently. I screwed the pipe cap on top of a coupling that fits loosely over the ram and overlaps several inches. The bolt is loose in the cap, but has a stop nut that I tighten through the hole in the skin to the bottom of the wing tie down. So, when jacking up the bolt can pivot freely in the pipe capto adjust its angle as the wing comes up. I will be watching more carefully now to make sure it doesn't bind, but this has worked well. Any critiques are welcome.
I looked at my jack top last night and noticed that I did it a little differently. I screwed the pipe cap on top of a coupling that fits loosely over the ram and overlaps several inches. The bolt is loose in the cap, but has a stop nut that I tighten through the hole in the skin to the bottom of the wing tie down. So, when jacking up the bolt can pivot freely in the pipe capto adjust its angle as the wing comes up. I will be watching more carefully now to make sure it doesn't bind, but this has worked well. Any critiques are welcome.
JonJay
Well Known Member
Thanks Walt. They looked so similar to the Van's plastic ones.
JoeBlank
Well Known Member
Back in 2007 or so I wrote a blurb for the RVator on building your own wing jacks out of 2x4?s cribbed together and then using some deck screws to mount a inexpensive bottle jack on the top. This work pretty well for years but it ALWAYS made me nervous when the aircraft as up in the air as Jack?s event illustrates. As I stated then, you want to ensure that there are no crosswinds in the hanger?
Last year I got to thinking and fooling around (dangerous, I know) with using a shaft inserted into the maingear axle and lifting that with a floor jack. I felt that this was much safer and far less risky that the wing jack method. This procedure works great for changing tires, brakes, and perhaps might be useful in an emergency in the field. In this particular case, I found that an old RV tailspring is the exact diameter needed to fit the axle. It flexes a bit under load but appears to be safe enough to lift one side at a time. Simply spin the axle nut off, insert the spring, jack it up, slide the wheel off onto the spring shaft, and set the axle down on some wood blocks. Reverse the process to reinstall. I feel much more warm and fuzzy without the airplane up on the wing jacks too. So if you can steal your neighbors tailspring you have an easy way to jack up your aircraft with much less risk.
As Scott alluded, at some point though you gotta get the weight off of the gear leg during the condition inspection to check for wear/play. So this trick won?t work for that but you can use it to limit the need/risk to use wing jacks for all of the maintenance?
YMMV?
Last year I got to thinking and fooling around (dangerous, I know) with using a shaft inserted into the maingear axle and lifting that with a floor jack. I felt that this was much safer and far less risky that the wing jack method. This procedure works great for changing tires, brakes, and perhaps might be useful in an emergency in the field. In this particular case, I found that an old RV tailspring is the exact diameter needed to fit the axle. It flexes a bit under load but appears to be safe enough to lift one side at a time. Simply spin the axle nut off, insert the spring, jack it up, slide the wheel off onto the spring shaft, and set the axle down on some wood blocks. Reverse the process to reinstall. I feel much more warm and fuzzy without the airplane up on the wing jacks too. So if you can steal your neighbors tailspring you have an easy way to jack up your aircraft with much less risk.
As Scott alluded, at some point though you gotta get the weight off of the gear leg during the condition inspection to check for wear/play. So this trick won?t work for that but you can use it to limit the need/risk to use wing jacks for all of the maintenance?
YMMV?
I like Joe's method. Our new lift pad is much safe than our original cap which hit the trash last night. It still uses the 3/8 bolt with a sleeve inserted into the rubber pad so weight is applied through the bolt and not on wing skin...but in event of bolt issues the pad will be the fail safe...the same pad can be used under the wing spar.
The whole issue here though is you cannot fix stupid
The whole issue here though is you cannot fix stupid
JonJay
Well Known Member
A couple of studs welded to the bottom corners of the engine mount and a jacking system similar to what I use on the Bucker and you couldn't knock the thing off with a wrecking ball.....
If I was building again, I might do this. However, for the one or two times a year I need to jack her up, I am fine with the tie down.
If I was building again, I might do this. However, for the one or two times a year I need to jack her up, I am fine with the tie down.
Walt
Well Known Member
Richard and I have been collaborating on this project and I think we (Richard really) have come up with the ultimate jack pad adapter for the RV. They consist of 2 mating pieces, one for the wing and the other for jack. The best feature is the nice deep swivel balls so there will be no chance of the aircraft slipping off the jack pad.
I think it's a winner!
The adapter will fit up to a 1.25 inch ram and has two set screws to hold it to the ram. The jack pad is 2 inches in diameter and is nicely padded so that it can pick up some of the load against the spar (if your tiedown goes all the way to the skin) but even if it doesn't its still a great feature. The stud is 3/8-16 grade 8 thread. They made the stud long so that you could trim it to the correct length depending on how deeply you tapped your tie downs.
If you're interested in purchasing a pair contact Richard at Bogart Aviation.
[email protected]
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Master Designs
Well Known Member
I've been using the dished bottle jack extensions from Bogert Aviation and the tie down ring from Cleaveland Tool for a couple of years now and it works GREAT! Plus, I have cool tie downs to carry in the aircraft.
http://bogertaviation.com/index.php?page=shop.product_details&flypage=garden_flypage.tpl&product_id=15&category_id=8&option=com_virtuemart&Itemid=23
http://www.cleavelandtool.com/Stainless-Tie-Down-Ring/productinfo/RVTR4/#.VTfNrqbR8dI
http://bogertaviation.com/index.php?page=shop.product_details&flypage=garden_flypage.tpl&product_id=15&category_id=8&option=com_virtuemart&Itemid=23
http://www.cleavelandtool.com/Stainless-Tie-Down-Ring/productinfo/RVTR4/#.VTfNrqbR8dI
RV3bpilot
Well Known Member
Jacking up the tire
After seeing the hole in the bottom of the wing when the tie down bolt broke and the jack went through the wing skin I was determined not to do the same. My new method of jacking up the wing is simple, I just laid a piece of rubber over a 2X4 so that it would not move after placed under the wing, also the rubber leave no marks or scratches. Then I placed a small floor jack on a sturdy wooden stand and jacked up the wing. The 2X4 was placed along the line of the main wing spar. I did remove the tie down bolt because I wanted the lifting point to be in that area, far enough away from the wheel for easy access.
After seeing the hole in the bottom of the wing when the tie down bolt broke and the jack went through the wing skin I was determined not to do the same. My new method of jacking up the wing is simple, I just laid a piece of rubber over a 2X4 so that it would not move after placed under the wing, also the rubber leave no marks or scratches. Then I placed a small floor jack on a sturdy wooden stand and jacked up the wing. The 2X4 was placed along the line of the main wing spar. I did remove the tie down bolt because I wanted the lifting point to be in that area, far enough away from the wheel for easy access.
My engine came from an aztec that slipped off its wing jacks and totaled the plane.
After hearing that story I have been hesitant to use wing jacks, so I bought the Flyboy jack points. I was all ready to install them and do some wheel work when I read the instructions that say in order to install them, I needed to jack up the plane at the wing. :-(
I looked at the gear for about two hours and finally came up with this method. It only takes about 3 minutes to string up the webbing, and uses equipment I already had in the garage. It's super stable since it is hanging from the jack, and not at risk at breaking any metal.
After hearing that story I have been hesitant to use wing jacks, so I bought the Flyboy jack points. I was all ready to install them and do some wheel work when I read the instructions that say in order to install them, I needed to jack up the plane at the wing. :-(
I looked at the gear for about two hours and finally came up with this method. It only takes about 3 minutes to string up the webbing, and uses equipment I already had in the garage. It's super stable since it is hanging from the jack, and not at risk at breaking any metal.
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rocketman1988
Well Known Member
Except it won’t works with the leg fairings installed…
