Thursday, August 30, 2012

Preventive Maintenance

FAR Part 43, Appendix A, Paragraph C - Preventive Maintenance
1. Removal, installation, and repair of landing gear tires.Know the proper jacking procedure for your aircraft as outlined in the service manual.
 The aircraft should be jacked in an enclosed hangar.
 If the aircraft must be jacked outside, take into consideration wind and proximity to taxiway; consider how the removal of wheelpants will affect other systems;
Know the type of brake system and how it may affect wheel removal and installation;
Removal and installation of the wheel-retaining nut requires a special touch. You should know how freely the wheel should rotate after being installed. Replace the old cotter pin with a new one of proper size;
2. Replacing elastic shock absorber cords on landing gear.Shock absorber cords, commonly called bungee cords, are found on many types of airplanes.
3. Servicing landing gear shock struts by adding oil, air, or both.It is allowed the adding of oil and air to air-oil or oleo struts. However, many manufacturers recommend the use of nitrogen instead of air, which helps to prevent the possibility of corrosion. It’s also a good idea to keep that dirt and grime removed from the bottom of the shock strut by wiping it down using a clean rag with some MIL-H-5606 on it. This will help to increase the life of the strut.
4. Servicing landing gear wheel bearings, such as cleaning and greasing. 
Cleaning must be done thoroughly, using a cleaner such as Varsol.
Inspection -  inspect the roller and inner and outer races for deterioration.
Greasing -  Take a nice dab of grease and put it into the palm of your hand. Force the grease into the side of the bearing until the grease comes out the other side. 
5. Replacing defective safety wiring or cotter keys.Always place safety wire in a manner to cause the item to be tightened. Use approved safety wire of the thickness specified.
6. Lubrication not requiring disassembly other than removal of nonstructural items such as cover plates, cowlings, and fairings. refer to the lubrication section in the service manual for the type of lubricate and how to apply it.
Engine oil change is one of the simplest tasks that pilots are allowed to do under the privileges of preventive maintenance.
Check for any airworthiness directives that apply when changing engine oil.
Another good idea is cutting the oil filter open and rinsing the filter element in a bucket of Varsol or a similar material. Use a magnet to extract ferrous particles, and save them for later examinations. 
Type of Contamination/ Quantity/ Suggested Course of Action. Small, shiny, nonmagnetic flakes of metal and/or hairlike magnetic slivers. Fewer than 40 pieces (total) of filter after 25 hours: Place aircraft back in service and recheck screen. As above, 40 to 60: Clean screen, drain oil pieces (total) refill. Run engine on ground for 20 to 30 minutes then recheck screen. If clean, fly aircraft 1 to 2 hours and recheck. If still clean, check once more after 10 hours. As above, _ or more teaspoon: Remove engine from service. Investigate to determine cause. Chunks of metal, magnetic and nonmagnetic, the size of a broken pencil point or greater. Any quantity: Check sump for other pieces. Bore scope cylinders to check for possible valve and/or Nonmagnetic plating averaging approximately 1/16 inch in diameter. May have copperish tint. _ teaspoon or more: Ground aircraft and investigate. If cause cannot be found, mail particles to engine manufacturer for analysis. Same as above, but minus copperish tint: Propeller action may be impaired. _ teaspoon or more: Ground aircraft. Mail material to engine manufacturer for analysis. Nonmagnetic brass or copper-colored material resembling coarse sand in consistency, _ teaspoon or more: Ground aircraft and investigate. If origin cannot be found, send particles to engine manufacturer for analysis. Any piece of metal (of any kind larger than a broken pencil point, any quantity: Ground aircraft and send particles to engine manufacturer for analysis.
7. Making simple fabric patches not requiring rib stitching or the removal of structural parts or control surfaces. In the case of balloons, the making of small fabric repairs to envelopes (as defined in, and in accordance with, the balloon manufacturer’s instructions) not requiring load tape repair or replacement.Remember: no rib stitching or control surface repair.
8. Replenishing hydraulic fluid in the hydraulic reservoir.MIL-H-5606 is the common type of hydraulic fluid used in light airplane brakes and hydraulic gear systems. Use of other than recommended fluid can cause damage to seals, O-rings, and other parts of the system. Be sure you add only the same kind of fluid as that already in the system; follow instructions in the service manual.
9. Refinishing decorative coating of fuselage, balloon baskets, wing tail group surfaces (excluding balanced control surfaces), fairings, cowlings, landing gear, cabin, or cockpit interior when removal or disassembly of any primary structure or operating system is not required.
10. Applying preservative or protective material to components where no disassembly of any primary structure or operating system is involved and where such coating is not prohibited or is not contrary to good practices.

Advisory Circular 43-12a : 

Preventive Maintenance

1 comment:

Dick Olson said...

Steel bearings are usually preferred in industrial usage; let it be chrome or stainless steel, specifically due to their last longing ability.
babbit bearings