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Jacking Aircraft Safely
By Tony Bingelis (originally published in EAA Sport Aviation, November 1994)
The letter starts out . . . "I’m in need of jacking technique and hardware. Basically I need to lift one wheel so I can remove the wheel and tire. What I currently do is ‘painful’ and time consuming. Once the aircraft fell off the jack. I use an auto hydraulic jack and a bolt at the aircraft (wing) tiedown hard point. Any (inexpensive) suggestions?"
Sure. Let’s explore a few of the more common jacking problems in detail.
Attempting to jack a homebuilt or, for that matter, any aircraft is not difficult and yet it can result, as this gent learned, in some anxious moments - if not serious consequences when due care is not exercised.
His is not the first airplane to have fallen off its jack(s). It is the sort of thing that can happen in the hangar next to yours and you may never learn about it.
Mishaps like this occur, most unexpectedly, during routine maintenance and inspection work. And they have been known to happen to experienced aircraft mechanics, and to homebuilders as well . . . more often as a consequence of poor jacking technique rather than bad luck.
The consequences resulting from careless jacking can be devastating.
The worst one imaginable is somebody getting hurt when the aircraft and a poorly placed jack part company.
Almost as bad is the consequence of a punch hole in the wing when an airplane slips off the jack. This sort of calamity is most likely to happen after the airplane has been jacked up and somebody is attempting to climb on board, or is doing some sort of work that causes the airplane to rock.
SOONER OR LATER YOU’LL HAVE TO DO IT
Jack up your airplane, that is. This need arises anytime you have to:
1.Rotate the tires to reduce tire wear.
2. Replace a worn tire.
3. Work on the brakes.
4. Lubricate the wheel bearings.
5. Repair a flat.
6. Adjust wheel alignment.
7. Perform a gear retraction test (that’s right, Wilbur, only retractables need this).
WHAT KIND OF JACK?
Aircraft jacks are costly. However, since most of us are not in the maintenance business, we have no need to spend big bucks on jacks specially designed to accommodate a large variety of heavier aircraft.
The typical homebuilt rarely weighs over 1200 pounds empty. Jacking such a lightweight object can be done easily with the smallest of commercially available hydraulic or mechanical jacks.
There are all kinds of commercially available jacks.
The two most practical for our purpose are relatively inexpensive. One is a small 2 ton hydraulic jack costing about $12, and the other, a long ram 3 ton hydraulic jack priced as little as $39.99. A good source for all kinds of jacks is Harbor Freight Tools of California.
The smallest hydraulic jack stocked by most auto parts stores is the common 2 ton hydraulic jack often selling for less than $15. This size hydraulic jack can handle any homebuilt jacking need.
The problem with these small inexpensive jacks, however, is their limited extension range. Most of them can raise an object only a meager 5" or so.
Therefore, it will be necessary to build some kind of a stand or sturdy box to position your jack up high enough for it to make contact with the jack point on your aircraft.
In determining how tall to make your jack stand, consider sizing it to be used as close inboard as is practical. This will allow you to make most of the limited jacking extension the hydraulic jack has for raising a wheel off the ground.
Another serious shortcoming is that most hydraulic jacks have a rather small base. This makes them very unstable and tipsy when extended.
A simple fix for this deficiency is to attach a large base plate (at least 12" x 12") to the bottom of the jack. If made of 3/4" plywood, bolt it through a couple of holes you can drill in the base of the jack (Figure 1).
A more permanent method would be to arc weld a large 1/4" thick steel plate to the bottom of the jack.
These jack base modifications will do much to eliminate any tendency for the airplane to rock while it is jacked.
JACK POINT LOCATIONS
Special jacking points can be built into the fuselage. My Emeraudes had handy jack points built into each side at the firewall.
More common than the fuselage jack points are the jack points commonly located in the wings of low wing aircraft.
Normally, these are the wing tiedown points which double as jack points. This change over is accomplished by removing the tiedown ring and screwing in a short bolt in its place to serve as a jacking hard point. To ensure greater stability, the bolt head, backed by a jam nut, may be modified. Simply grind the corners of the bolt head to round it off to better fit the jack recess.
Some landing gear legs, such as the Cessna spring gear types, can double as jack points. This is accomplished by clamping an adapter, or block, directly to the gear leg. The jack is then positioned under it for the jacking.
Jack points for a high wing aircraft are more difficult to utilize because the wing is so high above the ground. Special long reach jacks are available, of course, but are very costly. It is probably more practical to construct a taller stand and use a smaller long ram hydraulic jack.
As the manufacturer of your own homebuilt, it is your responsibility to provide safe jacking points for your aircraft.
BEFORE YOU DO IT
Before jacking, always chock both the front and back sides of the opposite wheel tightly! (Figure 2)
Do the same with the tailwheel, or nose wheel if your airplane is so blessed.
The simplest and safest jacking effort is where only one wheel must be raised off the ground. Fortunately, this allows you to accomplish most of your landing gear maintenance needs.
Jacking both wheels at the same time puts you at greater risk because you cannot chock the main gear. Nevertheless, you can and should chock the nose wheel or tailwheel as the case may be.
The jacking problem becomes more complicated when you are faced with the need to "rotate your tires" in an attempt to get better wear and a longer life out of them.
This is because most of us prefer to jack up the entire airplane for the job so that both wheels are off the ground.
Nevertheless, this is a worthwhile and commendable practice . . . especially if you are the one buying the tires.
Tires usually wear on one side more than the other. The only thing you can do to minimize this wear is to, occasionally, remove both wheels. You can then demount each tire and turn it around on its wheel before reassembling it and installing it on the opposite gear leg.
You cannot merely move the right wheel over to the left gear leg without demounting the tire. That tire would still wear on the same side. You have to disassemble the wheel and turn the tire around on the rim before reinstalling it in order to change the wear pattern.
It is also advisable to switch the wheels to the opposite gear legs for more equal tire wear. The reason for this is because most pilots, for one reason or other, tend to land (touch down) on one wheel slightly before the other.
In my case, I think it is because I tend to look out the left side of the airplane more often and I therefore seem to touch down on that wheel sooner than on the other.
If you only have one jack, you can still rotate your tires but it involves more work.
1.Jack up one gear and remove that wheel. Then lower the jack to allow the axle to rest on a block of wood.
2. Next, move the jack over to the other gear and jack it up so you can remove that
3. After completing the tire demounting operation just described, you can reinstall the wheel and lower the jack. Move the jack to the opposite side, jack it up and reinstall the other wheel to complete the job.
A FLAT TIRE AND NO JACK . . .
What to do? There you are on an airstrip with no facilities.
Well, for one thing, you have to remove the wheel so you can take the tube out and get it patched somewhere.
The problem is, how do you get the wheel off if you have no jack and no access to one?
If your airplane is a homebuilt (they are smaller and lighter than Bonanza class store boughts) and it is a biplane or a low wing job you can substitute a strong back for a jack. The assumption, of course, is that there is someone else who is willing to give you a hand (or a back).
Here’s where you first learn if your emergency tool kit has the tools you need. You do have a small emergency tool kit, don’t you?
In it should be the tools necessary to remove the wheel pants, the axle nut cotter pin, and a pair of slip-joint pliers (vise-grips or monkey wrench) for loosening and removing the axle nut.
Next, if possible find a rock or a block of wood or something you can slip under the axle after the wheel is removed.
To raise the wheel off the ground is not difficult if you have someone who is willing to use a little back muscle to bodily raise the wing high enough so you can slip off the wheel. Prepare the wheel for removal before raising the wing.
So much for the strong back jacking technique. Replacing the wheel afterward is just as simple a procedure.
More difficult, probably, would be locating a tire or a replacement tube if you can’t effect the necessary repair on the spot.
In performing a retraction test, it will be necessary to weigh down the tail of the aircraft to get the nose wheel off the ground.
An alternate means is to use a specially weighted tail stand that you can attach to the tail tiedown ring.
Use whatever means is dictated by the manufacturer. If it is a homebuilt, you will have to, in the absence of any guidance, decide which method is safe and suitable for your aircraft.
HOISTING VS. JACKING
Why not hoist the airplane instead of jacking it?
That is not a good idea for a number of reasons:
1. You would have to remove the top cowling.
2. When the entire aircraft is hoisted it is difficult to keep it from swaying while you are trying to work.
3. The hoisting eye on the engine was not intended to support more weight than just the engine. You may over stress and crack the crankcase if you try to lift the entire airplane from that single hoisting eye.
If you feel you have to hoist the entire weight of the airplane, at least try to distribute the load by installing a second hoisting eye. Use a load leveler arrangement to distribute the weight equally between the two hoisting eyes.
Ordinarily, hoisting the airplane is necessary only when installing and removing the wings - or the landing gear - or maybe loading the airplane onto a trailer.
There is no harm in using a hoist as a stabilizing safety precaution when the aircraft is raised up on jacks.
If you shop around you will find an amazing variety of jacks (air/hydraulic jacks, screw jacks, floor jacks, long ram jacks, scissor jacks, etc., etc.) at fairly reasonable prices . . . many of these selling for under $50 can be adapted for your particular need.
Check out your favorite auto parts place, trailer and camper sales outlets, and don’t forget Harbor Freight Tools.
You can save yourself several hundred dollars by making your own special jacks for running gear retraction tests . . . assuming you have such a need. Take two small (2 or 3 ton) hydraulic jacks and mate them to automotive jack stands as shown in one of the photos and, voila, you are in the high tech jacking business.
As is usually the case, it may be necessary to weight down the tail to get the nose wheel off the ground. For this purpose you can make a steel tail stand that has a couple of angles bolted across the bottom. Connect this stand to the tail tiedown and load it with a couple of cinder blocks to provide enough weight to pull the tail down. This will give you the nose wheel clearance you need.
Hopefully, these jacking suggestions will trigger your own ideas and ingenuity for handling your special jacking requirements.
I might add these words of caution:
1. Avoid jacking under windy conditions.
2.Don’t trust any jack. After raising the aircraft, lock the jack with some sort of positive locking device.
3.If extensive work is to be done, it would be wise to place a solid support under the raised wing (a saw horse, crate, barrel. . . whatever).
JACK SOURCES AND INFORMATION
- Auto Supply Stores
- Trailer and Camper Outlets
- Harbor Freight Tools 1-800/423-2567 (ask for free catalog)
- "Sportplane Construction Techniques" by Tony Bingelis (pages 260-264, order from EAA @ 1-800-843-3612 stock # F01395)