Foreword
I am not an A&P! If anything I write here can be interpreted by anyone as contrary to the "book", than, the book way is the way I did it. I came late to the airplane world, nut I did not live 58 years in a bubble before that time. Everything you experience in life can be used with common sense to make sense out of new experiences.
I have been blessed with an A&P-IA who will let me do anything that needs done on our bird. He is always there to look over my shoulder and impart his knowledge and advice, as well as to insure that I do it right. My experiences working on my airplane, my discussions with Dave and the ongoing threads on the various aviation forums I attend tell me that many are afraid to "mess" with their plane.
If you have enough mechanical ability to remember "righty tighty, lefty loosy", you can perform the maintenance tasks allowed to the PP-ASEL, and give real assistance to the A&P on the more complex tasks.
Do not be discouraged by the maintenance manuals. Most of them are sketchy at best. It almost makes me beleive that they were written to preserve the aura of mystery that surrounds the A&P. But the oil change instructions that simply say "drain old oil, remove filter, replace filter, refill oil" were not written to discourage you from doing it. They were written with the assumption that the person doing it had enough common sense to locate the drain plug and provide a way to get the oil into a bucket instead of all over the inside of the cowling.
When it came time to replace my main gear donuts, I could not find enough details anywhere to give Dave nor I enough sense of the task to understand it's magnitude. As we did it, I made notes and took pictures and published them here. The response from the Musketeer owners was gratifying. The idea then came to do the same for other maintenance functions that I perform or participate in.
The manuals are sketchy. These musings are not intended to go to the level of "unlatch cowling, open cowling, secure cowling in the open position, etc,". If they did, someone would nit-pick over some item that was not in the order they do it. Or someone might contemplate litigation over an omitted or misunderstood item. Some items will be omitted for other reasons:
- They are obvious.
- The order is immaterial.
- Exactly how to do it would be a matter of personal preference.
Do's and Don'ts of tire changing!
As you can see from the first picture, I needed to change a tire. This is another one of those things that you as an owner can legally do. But don't do it by yourself until you have done it under the eye of someone with lots of experience first. It is a simple job, not unlike changing a tire on your car, but with different tools and on a smaller wheel. There are some serious pitfalls to avoid.
Take it off
It is always best to jack the airplane while on a flat, hard surface. The same applies to your car, but often, you don't have any choice. Normally, your plane is in a hangar or on a ramp for this procedure which implies a flat, hard surface.
Next, remove the bolts holding the inside pad of the brake assembly. Now, remove the wheel nut and slide the wheel off the axle.
In the picture, note the wheel cover with the wheel nut and cotter pin on it and the brake pad and bolts laying on the other side of the jack.
Disassemble
Remove the valve core from the valve stem and allow all the air to escape. You can't re-use it anyway.
To remove the old tire and tube, you must separate the wheel halves. You will need an open end wrench and a socket wrench with a short extension. The bolt heads should be on the side with the brake disk (assuming a main, not the nose wheel) and will not have enough room to get a socket over them. Remove the three nuts, pull the bolts and lay them aside, along with the brake disk.
Finish pulling the halves out and throw the old tire and tube away. Now, you have the parts as shown here, two wheel halves and a brake disk. Take them along with the new tire and tube to the place where you have an adequate air supply.
Re-assemble
Take the new tire and dump a liberal amount of talcum powder (Baby powder will do) in it. This will allow the tube to be inserted and positioned more easily. Rotate and shake the tire until the entire inside is covered with the powder. Then put the tube in. Get it fully inside the tire with no bunching and the stem aligned with the red spot on the tire. Make sure the tube wants to stick out on the side with the spot. If not, remove the tube, flip it over and re-insert it.
There is a shoulder on one wheel half and a lip on the other. (You can see them in this picture. the bottom half slips into the upper half.) These must be correctly mated before the bolt holes will align properly. When you have this done, replace the brake disk and drop all three bolts in through the brake disk. Put all the nuts on finger tight and recheck the alignment of the shoulder and lip (small hands will go through the bearing so you can feel for proper alignment). Pull the stem all the way through if it didn't come voluntarily. Carefully tighten the bolts without allowing the alignment to slip
Blow the tire up to around 50 PSI and check for good seating to the rim, all around and on both sides. Allow the air to escape and re-install the valve core. Now inflate to normal pressure and check the valve stem for leakage.
Put it back on
Re-packing the wheel bearings is a judgement call. How dirty is the grease? How long has it been since they were last re-greased? Did you get some stuff into them during this procedure? Repack if necessary.
Slide the wheel back onto the axle and put the nut on finger tight. Re-attach the brake shoe to the back side. Tighten the wheel nut until the wheel no longer spins freely. Then back it off to align the holes with the slots in the nut. Replace the cotter pin. Re-install the wheel cover and lower the plane. Remove the jack and clean up. Then go home and lick your wounds.
Donuts!
Preface
I am not an A&P! Do not take this page as gospel. The maintenance manual is very sketchy for our birds, so I am merely trying to add some detail to the instructions therein. If what I say here seems to disagree with the manual, the manual is correct and that is the way we did it.
This covers only the main gear donuts. I didn't change the nose gear donuts as they were apparently done at the time the nose was rebuilt some 2000 hrs ago. The nose still sits at nearly the specified height and can be bounced, so I saw no need to replace them.
Preparation
Pre-compression
The donuts must be pre-compressed before installation. The setup for this is at your discretion, but this is what I used. I got 2 pieces of 5/8 threaded rod with washers and nuts. The inside diameter of the donuts is 1", so get as close as you can or you may have problems maintaining alignment. Much smaller than 5/8 and you may strip the threads on the nuts before you reach full compression.
- Nut
- Washer
- Plate
- 8 Donuts
- Plate
- Washer
- Nut
Unless your house is a meat locker, room temperature is warm enough. Begin tightening the nuts slowly, no more than a 1/4 turn at a time. As the stack compresses, let it sit longer between tightenings.
If you have a smaller diameter rod, the donuts may slip out of alignment. If this happens, loosen the nuts and re-align, rotating the donuts that slipped a half turn before re-tightening. Re tighten, but not to the point where they were when they slipped. Let them sit longer between tightenings to minimize a reoccurrence. We were worried initially about a portion of the donuts sticking past the edges of the plates. When we loosened the stack to re-align it, we found no scoring on the donuts and they came back to "flat" before we were ready to re-tighten the stack.
You will need to compress the stack at least 1", more is better.
The day before you need them, put them in a normal refrigerator. They will need to cool at least 24 hours.
Manpower and parts
This is essentially a one man job. There is a lot of "third hand" assistance needed, for advice, steadying something or simply supervision and criticism. But your A&P can do it himself with you supplying the third hand or supervising you.
With this in mind, unless the shop is awash in manpower, do it one leg at a time. This means jacking only one wing at a time which is much safer.
I would recommend that you pre-order the two pairs of pins for the pivot pins. Unless you are very lucky, you are going to bend the ones on the donut pivot (Which MUST be removed) and there is no easy way to get the pin out of the main pivot. [part numbers: main pivot retainer pin, MS20392-1C61. donut pivot retainer pin MS20392-1-41]
I would also recommend that unless you know they have been replaced since your bird was new, that you replace the abrasion washers. [Part number: Abrasion washer 169-810000-119. Tulsair has them.]
Removal
Preparation
Pull your Mouse's pants leg down, Clean out any debris on top of the casting (I found an old dirt dauber nest on one side of mine. Disconnect the brake line where it comes out of the wing and cap the stub. Cap the line from there to the brakes if you can, but don't worry about it as you will have to flush that before bleeding it anyway.
Remove the wheel cover and axle cotter pin and loosen the axle nut. Remove the inside brake pad. Now jack the wing up enough to remove the wheel. Lay the wheel under the swing arm for safety and cover the hub to keep dirt out of the bearings.
Removing the Jo-Bolts
I saw several methods for removing the Jo-Bolts discussed, but as the shop manual says in at least 2 places to grind the heads off, that is what the A&P decided to do. We taped around the bolt head to protect the flange as much as possible and went to work. We had an air grinder with a 3" cutoff wheel and an electric grinder with a 5" cutoff wheel and used both of them. Do not attempt to "cut" the head off, there is too much risk of damaging the leg if you get too close. Hold the cutoff wheel perpendicular to the leg and just eat it away. It only takes about 10 minutes per bolt.
Stop working on the first one when the shaft separates from the remainder of the head. Do the other one then drive both shafts into the leg. I would venture the odds of the leg falling off as soon as the bolts are gone as astronomical, but that is why the tire is sitting under it as shown in this picture. It cannot come all the way off until you move the tire.
Removing the assembly
Push the pants leg back up a little so you can grasp the leg firmly. Push the tire out of the way and wiggle the leg off. The entire assembly even with the brake assembly weighs less than 10 lbs., so removal is easy. If available, blow out the entire area under the casting with an air hose and take it to the bench for disassembly.
Disassembly
Remove the pants leg and set it aside. If you had to loosen the fitting where the hydraulic line goes down the leg to get access to the Jo-Bolt, remove it and set it aside. Remove the nut on top of the stack. It is 1 7/16" self locking, so someone must hold the leg down while you take it off. Inside should be at least one steel washer and a rubber washer (referred to as the abrasion washer in my service manual). Throw the 2 Jo-Bolt ends away (unless you just have to keep things like that as souvenirs) and set the washers and nut aside.
Once the pin is removed, remove the pivot pin. A deep well socket works well here to protect the zerk fittings. The swing arm can now be moved far enough to remove the donut stack. There is a plate on the bottom of the stack which must be separated from the bottom donut.
Reassembly
Since you must install and load the donuts quickly once they are removed from the refrigerator, have everything ready to go first. Clean all the parts as desired. Clean the pivot pin holes and pivot pins completely. A little Scotch-Brite works well. Test fit the pivot pins to insure that they will go back in easily. Work with them until they do. The donuts will not slide easily onto the shaft. We found that a can of white grease and a brush helped. Have the 1 7/16 socket, extension bar and breaker bar or long handled ratchet close by. You will also need the third hand, so have him/her close. Put the spacer back on the shaft. Remember, once you remove the donuts from the refrigerator, you need to get them on without stopping.
Remove the donut stack from cold storage and release whatever is holding them compressed. "Screw" each donut past the threads on the shaft and slap some grease on the shaft. Push the donut all the way to the bottom. After all 8 donuts are on and as far down as you can get them, insert the shaft into the casting. The hole in the casting is only a little bigger than the shaft and the donut flanges are almost as big as the inside of the casting, so lining up the hole and shaft may take some doing.
Place the rubber abrasion washer on the shaft. If you are using a new one, a little grease on it will help. Once it is completely on the shaft, put the steel washer(s) on and use the socket and extension to force them to the bottom (the third hand will be holding the assembly down for you). I have small hands and could start the rubber washer and hang the steel washers, but I could not start the nut. Put the nut in the socket. You may have to pad it up with some paper towel to keep it from going to the bottom of the socket. Get it started, but make sure it is not cross threaded.
You will need to place the swing arm back into the donut pivot to hold the stack while you tighten it up. Then tighten the nut to the required dimension. The position shown in the picture above is nearly correct, so get close to that before you even start to check with the ruler. Now, you can relax a minute.
Reinstallation
You are now ready to re-build your Mouse. Do a little preventive maintenance here before you start. Re-pack the wheel bearings if it has been a while. Check the air in the tire. Re-grease the pivot pins, remember they have been subjected to cleaning while they were out and the inside of the bushings have been cleaned.
Replace the Hydraulic line if it was removed. It is easier to start the fitting with the pants leg off. Do not tighten it up. Re-install the pants leg and push it all the way down. Test fit the Jo-Bolts. You may have left some deformation of the hole edges when you drove the old ones out. The compression part should slip in easily but the barrel part will be a force fit.
Insert the leg into the wing bracket and push it up into position. Visually check that you can align the holes and slide the tire under the leg. Insert both Jo-Bolts and tap them all the way in. Now, install the Jo-Bolts using whatever tool you have available. The hard part is done.
Re-connect the hydraulic lines and tighten them up. Re-install the wheel, axle nut and cotter pin. Get the plane off the jacks. Bleed the brakes and re install the pants leg and wheel cover.
Clean up the tools and work area, pull the bird out into the sunshine and give it a bath. And then a test flight.
Now you are done
