TECH TIP – Maintaining a Production Airplane, Part 3

Vintage Aircraft Association | Jun 16, 2016 | Technical Articles

by Ron Alexander, VAA 27150

This is the final in a series of articles naming the maintenance items you can legally perform as an aircraft owner. The first 8 items are discussed in the previous article.

Item number 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.”

Simply put, you are allowed to repaint any part of your airplane as long as you do not remove or disassemble any control surfaces or primary structures. You need to check in your aircraft manual to see if the control surfaces have to be balanced when they are painted. If so, you need to leave the painting of these surfaces to the professionals.

Item number 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.”

Item number 11—“Repairing upholstery and decorative furnishings of the cabin, cockpit, or balloon basket interior when the repairing does not require disassembly of any primary structure or operating system or interfere with an operating system or affect the primary structure of the aircraft.”

You should be careful not to disassemble any control systems, throttle linkages, fuel shutoffs, etc. to enable you to make these repairs. You can remove side panels and seats, and headliners for repair as long as you remain within the guidelines of not interfering with any primary structure or operating system. All materials used for repair must meet the FAA burn requirements. When you purchase the material be sure to obtain a statement from the supply house that states the material is FAA approved.

Item number 12—“Making small simple repairs to fairings, nonstructural cover plates, cowlings, and small patches and reinforcements not changing the contour so as to interfere with proper air flow.”

Again, you must use approved materials and procedures. You should check with a licensed mechanic if you are unsure as to whether or not the repair is simple.

Item number 13—“Replacing side windows where that work does not interfere with the structure or any operating system such as controls, electrical equipment, etc..”

Note, this does not mean a windshield. A certificated mechanic must replace windshields.

Item number 14—“Replacing safety belts.”

Replacing safety belts and shoulder harnesses is a critical maintenance item. It obviously affects your safety. Be sure to purchase only approved belts for your make and model and be aware that spacers and washers may be needed in the installation. Refer to the service manual for proper procedures.

Item number 15—“Replacing seats or seat parts with replacement parts approved for the aircraft, not involving disassembly of any primary structure or operating system.”

Again, disassembly of operating systems and primary structures is the limiting factor. Also, you should ensure that all parts you use are approved. Do not try to reinforce your seats or modify them in any way. You can only replace parts or the entire seat with exact replacements for your make and model of airplane. You should check your work carefully before putting the aircraft back into service. As an example, you do not want the seat to slide full aft during take-off because you forgot to reinstall a stop.

Item number 16—“Trouble shooting and repairing broken circuits in landing light wiring circuits.”

Notice, this does not apply to any lighting systems other than landing lights. If you are not familiar with electrical circuits and how to check them out, then leave this to a knowledgeable mechanic. You can get in over your head fast on this item. Be sure you replace any wiring with proper sizes and connectors.

Item number 17—“Replacing bulbs, reflectors, and lenses of position and landing lights.”

This is less intimidating. Replacing a bulb is a lot simpler than replacing electrical wiring. This also includes the anti-collision lighting. Check the aircraft service manual for proper bulb size and rating. Don’t forget to properly seal any lens covers that are removed.

Item number 18—“Replacing wheels and skis where no weight and balance computation is involved.”

The replacement wheels and skis must be approved. You also should have someone double check your work prior to flying the airplane.

Item number 19—“Replacing any cowling not requiring removal of the propeller or disconnection of flight controls.”

It should be apparent that only a certified mechanic can remove any critical component of the aircraft including flight controls and propellers. You as the owner or operator are not allowed to remove the propeller. You can however, remove and replace any cowlings or cowl flaps.

Item number 20—“Replacing or cleaning spark plugs and setting of spark plug gap clearance.”

Prior to undertaking this preventive maintenance task, you should be sure you have the proper tools. That includes a deep socket, torque wrench, spark plug holder, round wire gauge, and a spark plug gap setting tool. Proper replacement and cleaning of plugs is as follows:

1. Remove the shielded terminal connectors.
2. Pull out the terminal sleeve assemblies in a straight line.
3. Loosen the spark plug with the proper size deep socket seated securely on the plug.
4. Place the plugs in a tray with numbered holes.
5. Inspect the plugs for cracked insulators, eroded electrodes, or damaged threads. Any of these conditions is cause for rejection.
6. Do not reuse obviously worn plugs.
7. Degrease the plugs and then thoroughly dry.
8. Use an abrasive-blasting machine designed for cleaning spark plugs and clean them completely. Clean the threads using a wire wheel with soft bristles.
9. Check the gap of the plugs using a round wire gauge. The setting should be found in your service manual. If the gap is too large, it is closed using a special gap setting tool. If the gap of a four-prong or two-prong spark plug has been closed beyond limits, no effort should be made to open the gap.
10. If for any reason you accidentally drop a spark plug on the floor, do not use it.
11. Test the plugs.
12. If you need to replace a spark plug, check your service manual for the proper type and number.
13. Rotate the spark plugs according to the manufacturer’s recommendation.
14. Install the plugs using an anti-seize compound and a new gasket.
15. Tighten the plugs using a torque wrench to the proper value.
16. Connect the ignition lead to the spark plug by inserting the terminal sleeve in a straight line into the barrel.
17. Tighten the terminal nut by hand then snug with a wrench.
18. Run the engine and perform a magneto check to ensure proper installation and performance.

Item number 21—“Replacing any hose connection except hydraulic connections.”

With this item, replace any hoses only with hoses made of the same material as the one being replaced. Do not overtighten hose clamps.

Item number 22—“Replacing prefabricated fuel lines.”

The key is “prefabricated”. In other words, the fuel line must be already fabricated and approved for your make and model aircraft.

Item number 23—“Cleaning or replacing fuel and oil strainers or filter elements.”

This goes along with item number 6 that allows you to change your engine oil. The filter element should also be replaced or cleaned. When you replace your oil filter you should examine the old filter element for signs of metal. This can be accomplished by using a special tool to cut open the element. Remove the element from its housing and visually inspect the material trapped in the unit.

Once again, use only approved filters. Use a new gasket when you reinstall a filter housing. You should hand tighten the housing until the unit makes contact with the surface. Check your service manual for the proper torque value and then tighten the unit accordingly. Be sure to replace any safety wire. It is advisable to clean the engine and then run it to check for leaks.

There are several AD notes ( Airworthiness Directives ) that apply to oil filter changes. You can change the oil and filter but only a certificated mechanic can comply with and sign off the AD note. Check with your aircraft mechanic for any applicable AD note.

Item number 24—“Replacing and servicing batteries.”

You are aware by now that all parts must be approved for your particular aircraft make and model. This also applies to the battery. When removing the battery, always remove the ground cable first. Check for corrosion on the cables and in the battery box. You can clean your cables and battery box by using baking soda mixed with water. After cleaning, flush with clean water. Do not allow any baking soda to enter the battery. You are also permitted to charge your battery and to add distilled water. Only charge the battery after removing it from the aircraft. If a battery cannot be restored to a fully charged condition, it must be replaced. A hydrometer can be used to test the battery.

It is also legal for you to remove and replace your ELT battery. The battery expiration date must be visible on the outside of the transmitter and also entered in the aircraft maintenance record.

Item number 25—“Replacement or adjustment of nonstructural standard fasteners incidental to operations.”

You are allowed to replace any fasteners that are nonstructural. This includes screws, bolts, nuts, and even rivets that attach nonstructural fasteners. Be careful where you purchase hardware. Be sure you are getting aircraft quality hardware that can be traced through a lot number back to the manufacturer. Another possible problem area is corrosion created by contact of dissimilar metals. When you replace nonstructural screws you should take steps to preclude this type of corrosion. When steel comes in contact with aluminum it will set up electrolytic or dissimilar metals corrosion. When replacing screws place a washer, sealant, grease, or metal primer between the aluminum piece and the steel screw.

Item number 26—“The installation of anti-misfueling devices to reduce the diameter of fuel tank filler openings provided the specific device has been made a part of the aircraft type certificate data by the aircraft manufacturer, the aircraft manufacturer has provided FAA-approved instructions for installation of the specific device, and installation does not involve the disassembly of the existing tank filler opening.”

Item number 27—“Removing, checking, and replacing magnetic chip detectors.”

If your engine is equipped with a magnetic chip detector, you should comply with the manufacturers’ recommendation for its proper use.

Item number 28—“Removing and replacing self-contained, front instrument panel-mounted navigation and communication devices that employ tray-mounted connectors that connect the unit when the unit is installed into the instrument panel, (excluding automatic flight control systems, transponders, and microwave frequency distance measuring equipment.) The approved unit must be designed to be readily and repeatedly removed and replaced, and pertinent instructions must be provided. Prior to the unit’s intended use, an operational check must be performed in accordance with the applicable sections of FAR Part 91.”

Item number 29—“Updating self-contained, front instrument panel-mounted Air Traffic Control navigational software data bases (excluding those of automatic flight control systems, transponders, and microwave frequency distance measuring equipment provided no disassembly of the unit is required and pertinent instructions are provided. Prior to the unit’s intended use, an operational check must be performed in accordance with applicable sections of FAR Part 91.”

So, you can remove a front instrument panel mounted navigation or communication radio for repair or replacement. You can also update the software in a GPS as an example. Testing of the unit after replacement is required.

To review, the holder of a pilot certificate who owns or operates the airplane can perform the maintenance items listed above. These items are considered to be preventive maintenance on the aircraft and do not have to be supervised by a licensed mechanic. The pilot must also make a log book entry stating the work that was performed and the date it was performed. The pilot’s signature and pilot certificate number must be a part of the entry. If the pilot encounters a problem that goes beyond the scope of preventive maintenance as defined above, then a certificated mechanic must complete the maintenance item.

Preventive maintenance begins with a thorough pre-flight. Do not be in a hurry to perform your pre-flight. Write down any discrepancies that you observe so they can be fixed. Always do a post-flight inspection. Performing preventive maintenance on your production aircraft affords you the opportunity to learn more about the mechanical aspects of the plane. This knowledge facilitates the safe operation of the aircraft. The more you know about your airplane the safer you can fly it.