TECH TIP: Maintaining a Production Airplane – Part Two
In part one of our discussion on maintaining a production airplane, I provided an overview. We will now discuss the actual maintenance items that you can legally perform on your production airplane as the aircraft owner.
Item number 1—“removal, installation, and repair of landing gear tires.” This preventive maintenance item usually will be outlined in your service manual. Here are a few general suggestions. The primary concern is proper jacking of the aircraft. This is found in your manual. Wheel pants and brake lines should be properly removed and noted for reinstallation. After removal of the wheel, completely deflate the tires before dismounting. Always use caution when removing valve cores. Break the beads of the tire before loosening the wheel bolts using a bead breaker. Do not use a pry bar, tire iron, or any other sharp tool to loosen tire beads.
Prior to mounting the tire, dust the deflated tube with talc and insert it into the tire. Then inflate it until the tube is just rounded out. Install the valve core, line up the tube and tire balance marks. Inflate, deflate, and then reinflate to the recommended pressure. If you are unsure as to how freely the wheel should rotate when reinstalled, have a mechanic show you. Do not use old cotter pins. NOTE: These items and procedures will vary considerably depending upon your type of aircraft.
Item number 2—“replacing elastic shock absorber cords on landing gear.” The bottom line with this procedure involves having the right tool. If you do not have the proper tool to do this job hire someone else to do it. It appears simple but can be very complex.
Item number 3—“servicing landing gear struts by adding oil, air, or both.” Again, follow the instructions in the aircraft manual for proper strut inflation. Be sure you wipe down the bottom of shock struts with a rag and MIL-H-5606 (hydraulic fluid) to keep them clean. Use the right kind of oil. A number of struts use nitrogen instead of air for inflation. The use of nitrogen prevents corrosion. Usually your FBO will have a nitrogen bottle you can borrow or rent. Be cautious when placing the air or nitrogen fitting onto the strut fitting—make sure your hands are out of the way in case the strut totally deflates.
Item number 4—“servicing landing gear wheel bearings, such as cleaning and greasing.” You must first thoroughly clean the bearing using Varsol or a similar type cleaner. Inspect the bearing for corrosion and wear. Keep track of which bearing goes with which wheel side and keep them together. Use a quality wheel bearing grease. Then place the grease in the palm of your hand and force the grease into one side of the bearing until it comes out on the other side. A tool is also available that will accomplish this task.
Item number 5—“replacing defective safety wiring or cotter keys.” Always use aircraft quality safety wire of the size specified. That will usually be .032 or .041 in diameter. Ensure that placement of the safety wire will cause the item to be tightened. A good pair of safety wire pliers is a must for proper safetying. Cotter pins should be of proper size and after placement in the castle nut they should be bent over so they lock in place.
Item number 6—“Lubrication not requiring disassembly other than removal of nonstructural items such as cover plates, cowlings, and fairings.”
Your aircraft manual should contain a lubrication chart outlining points and types of lubrication. Note that you may only lubricate areas not requiring disassembly of structural items.
This particular preventive maintenance item also allows the pilot or aircraft owner to change engine oil. This is, of course, one of the most important tasks you can perform. It is usually very simple to do and is usually accomplished in conjunction with item number 23 that allows changing of the oil filter. I will specifically address that later. Occasionally, you will encounter an Airworthiness Directive that may apply to changing your oil. Check that out before beginning. Change the oil and replace the filter, or check the oil screen, at time intervals recommended by the manufacturer. Always ensure that the oil is replaced and that the proper type and weight of oil is used. Do not forget to safety the drain plug. After you have completed the oil and filter change, wash down the engine and the run it to check for oil leaks. Anytime you have your engine cowling removed check for all types of leaks and problems. In particular, check the fuel system, oil system, exhaust system, cooling air, induction air, and electrical. A thorough inspection of all areas should be accomplished. If you desire you can send an oil sample for an analysis. In order to be effective, this should be done on a regular basis. A history must be established by taking a sample from the same area at a regular time interval. An occasional analysis will tell you very little.
Item number 7—“making simple fabric patches not requiring rib stitching or the removal of structural parts or control surfaces.”
To do this item, you must first determine what type of fabric covering system was initially used. You should repair the surface using the same type of system and the repair procedures outlined in that manual. A simple repair means a small repair. The covering manual should specifically address repairs and how to make them. If you are unable to find any information the Poly-Fiber System manual has a good presentation on fabric repairs. AC43-13 also talks about making fabric repairs. You are not allowed to remove a control surface or repair in any area requiring rib lacing without a mechanic’s supervision. Remember, however, that it is perfectly acceptable for you to perform such a maintenance item under the direct supervision of a certificated mechanic.
Item number 8—“replenishing hydraulic fluid in the hydraulic reservoir.” The most important consideration for item number 8 is the use of the proper fluid. MIL-H-5606 is by far the most common type of hydraulic fluid used in smaller aircraft. It is used in the brake systems and hydraulic systems. Use of any other type of fluid will cause a lot of problems with seals, O-rings, etc.. Follow instructions in your service manual.
In the next issue I will list and discuss the remaining preventive maintenance items that can be accomplished without a mechanic’s license. As a review, FAR 43.3 (g) states “The holder of a pilot certificate issued under Part 61 may perform preventive maintenance on any aircraft owned or operated by that pilot which is not used under FAR Part 121, 127, 129, or 135.” This applies to production aircraft operated with a standard airworthiness certificate. Aircraft certificated under a special airworthiness category such as “experimental” fall under a different set of rules that we have previously discussed in earlier issues of Sport Aviation.
You also may legally restore, rebuild, or maintain your production airplane under FAR 43.3 (d). This regulation allows an individual, not holding a valid mechanic’s certificate, to perform the rebuilding tasks under the supervision of a certificated mechanic.
Always have the proper manuals and tools available to perform the maintenance. Document the performed maintenance in the aircraft logbook. Proper maintenance begins with a very thorough pre-flight inspection of your airplane. Perform this inspection as outlined in your aircraft service manual.