vided to absorb the landing loads. A number of different shock absorbing devices are used by aircraft manufacturers. A few will be discussed here.
general condition, cleanliness, stretching, and fraying. Shock cords must be kept free of gasoline and oil, both of which deteriorate rubber products. Follow the manufacturer's recommendations regarding life limits of the replacement of shock cords.
Perform a close visual inspection of the main landing gear for cracks in the vicinity of welds. Examine attachment fittings for condition and elongation of bolt holes.
Wrinkled fabric or metal skin detected in the area of the attachment fittings should be referred to a qualified mechanic or repair station for detailed inspection and analysis.
Spring steel shock absorbers require little maintenance. Check for cracks in the fuselage attachment brackets and the axle attachment area. Inspect the strut in the step attachment Excessive play between fittings may be detected more readily if the wheel is off the ground and the landing gear shaken vigorously in a fore and aft direction, as well as up and down. If noticeable clearance is detected at any of the attachment points, the bolts should be removed and inspected for wear or distortion. Defective bolts should be replaced immediately and distorted bushings and fittings repaired or replaced as recommended by the manufacturer. Since there will be considerable movement at the bearing surface, it is essential that they be inspected carefully and lubricated properly at frequent intervals.
Inspect shock struts for cracks, bowing, and security of attachment. Check braces and fittings for general condition and possible defects.
Inspect the nosewheel assembly for general condition and security of attachment. Examine linkage, trusses, and members for evidence of undue wear or distortion. Ensure that all bolts, studs, and nuts are secure with FIGURE 4-13. Fixed nose gear check points.
no indication of excessive wear and that they are properly safetied. If a shimmy damper is installed, ensure that it is operating satisfactorily and that the steering mechanism is properly rigged.
FIGURE 4-14. Oleo-type landing gear checkpoints.
FIGURE 4-15. Steerable tailwheel inspection points.
Inspect oleo-type shock absorbers for cleanliness, leaks, cracks, and possible bottoming of the pistons. Check all bearings, bolts, and fittings for condition, lubrication, and proper safetying.
Following the manufacturer's instructions when replenishing fluid and air pressure charge in the shock absorber.
Steerable tailwheels should be inspected for bearing adjustment, lubrication, clearance, and range of operation. Check for proper steering action and security of attachment.
Landing gear that retracts into the wing, nacelle, or fuselage structure should be cleaned and checked frequently for defects and proper operation. Particular attention should be given to locking mechanisms, drag struts, shock strut, stops, linkages, and alignment. Be sure the shock strut is properly inflated and the piston is clean and oiled. Examine fairing doors for satisfactory operation, proper rigging, and for loose or broken hinges. FIGURE 4-17. Retractable main gear checkpoints.
Retractable Landing Gear FICURE 4-16. Inspection chart-retractable landing gear.
FIGURE 4-18. Landing gear retracting.
When new or retread tires are installed, a landing gear retraction test should be performed to check for proper clearance. Improper tire size may cause the gear to hang up in the wheel well.
Check main gear, nose gear, or tail gear uplock and downlock mechanisms for general condition and proper operation.
Refer to the manufacturer's service instructions for proper lubrication of retractable landing gear.
Inspect the power sources and the retracting mechanism of the main gear, nose gear or tail gear for general condition, defects, and security of attachment. Determine that actuating cylinders, sprockets, universals, chains, and drive gears are in good condition and within the manufacturer's tolerance. Clean and lubricate using cleaning fluids and lubricants recommended by the manufacturer of the aircraft.
Inspect the aircraft structure to which the landing gear is attached for distortion, cracks, and general condition. Be sure that all bolts and rivets are intact and secure.
Any items not within required tolerances should be referred to qualified maintenance personnel for correction and readjustment.
FIGURE 4-20. Retracting mechanism checkpoints.
If the landing gear is electrically operated, inspect motors for defects and security of attachment. Ensure that wiring is in good condition, properly routed, and secured to prevent interference with movable members. Determine that protective rubber or plastic caps are properly installed over all wire terminals FIGURE 4-19. Retractable nose gear checkpoints. requiring such protection.
FIGURE 4-21. Typical electrical retraction installation.
FIGURE 4-22. Electrical retracting motor and wiring.
If the landing gear is hydraulically operated, inspect all actuators for general condition, leakage, and operation throughout their full travel. Determine that lines, reservoirs, accumulators, and valves are securely attached and free of leaks. Be certain that the lines are free from chafing and securely attached to the adjacent structure. Check entire gear operation, using normal hydraulic pressure.
Inspect warning system microswitches for cleanliness, condition, security of attachment, and proper operation. With the aircraft on jacks, check landing gear warning horn system with electrical power "ON," by retarding throttle (s) with gear retracted. Check wiring for routing, freedom from chafing, and general condition.
Water accumulation in microswitches may freeze at altitude, making switches inoperative.
Only qualified personnel should attempt any adjustments to the microswitches.
FIGURE 4-24. Gear attachment structure checkpoints.
Other Gear Inspect the skin for general condition, evidence of corrosion, or loose rivets and screws.
Check the structure for defects or cracks.
FIGURE 4-23. Warning microswitch installation. FIGURE 4-25. Float installation inspection points.
Inspect float attachment fittings for condition, cracks, and defective welds. Check struts and bracing for proper attachment, alignment, and safetying. Due to the rigidity of float installations, a thorough inspection should be made of the fittings and adjacent structure where the struts are attached to the fuselage.
Drain or pump any accumulated water'from each float compartment.
Skis should be inspected for defects or damage and for security of rigging and main axle attachment fittings. Special attention should be given to the ski pedestal. Periodically inspect the ski bottoms for tears or cracks. If installed, check hydraulic system for leaks and proper fluid level. Inspect for FIGURE 4-26. Ski installation inspection points.
condition and proper rigging of all devices restraining the skis from digging into the snow.
Section 5. WING-CENTER SECTION FIGURE 5-1. Inspection chart-wing-center section.
Determine the condition of the wing and center section by carefully inspecting fixed surfaces for signs of deterioration, distortion, and loose or missing rivets and screws, especially in the area of fabric or skin attachment to the structure. Inspect fabric or skin for tears, cuts, or other defects; and examine condition of protective covering. Inspect fabric at windshield for deterioration and security of attachment.
External distortion in any area may be an indication of internal failure. Inspect the interior through available inspection doors or holes. If internal failure is suspected and no inspection doors or holes exist, contact a certificated maintenance facility to make the necessary inspection and repair.
Inspect the internal brace fittings (struts or brace wires) where they attach to the wing structure, for distortion, cracks, or any other defects. Inspect clevis pins or bolts for wear, cracks, worn or damaged threads, and any other defects.
If any rigging adjustment of the external bracing has been accomplished, particular care should be taken to ensure that there is a sufficient number of threads holding in the adjusting terminals. Most terminals are provided with a test hole in the shank for making this inspection. If safety wire can be inserted through the test hole, the terminal is not being held by the required number of threads.
Another method of ensuring that sufficient threads have been screwed into the barrel or female fittings is to count the threads on the 53
male fitting. If more than three threads show, the connection MAY not be satisfactory.
Determine that wing attachment fittings are not distorted, cracked, or damaged in any way, and that bolt holes are not elongated. Check wing attachment bolts for general condition and security of attachment. If wing attachment bolts are loose, determine the reason for looseness. Tighten to the torque values specified by the manufacturer if no other defect exists.
Be certain that hydraulic lines are free from cracks, kinks, dents, and leaks, and inspect for security of attachment and wear due to chafing. Ensure that hydraulic actuators are securely mounted and not leaking.
Any defects noted in the hydraulic system should be corrected, by a properly qualified mechanic.
If the condition of the fabric is doubtful, the advice and assistance of a qualified person should be sought. Samples of the fabric may be taken from portions of the aircraft MOST affected by the elements and forwarded to an accredited testing laboratory for examination.
On fabric-covered surfaces, check drainage grommets for security of attachment and obstructions. Drainage grommets are reinforced openings usually located near the lowest point at the trailing edges of wings and tail sur- FICURE 5-2. Indication of defective fabric.
faces. These openings provide for drainage of moisture and circulation of air to dry interior surfaces. Seaplane drainage grommets are identified by a hood over the center cutout which minimizes effect of spray during takeoff and landing. This type of grommet is sometimes used on landplanes in that part of the structure subject to splash from the landing gear when operating from wet or muddy fields.
FrOURE 5-3. Wood structure inspection points.
FIGURE 5-4. Metal structure inspection points.
Remove all inspection plates and fairings, and open all access doors so that internal inspection may be made. Examine the internal structure for condition of spars, ribs, compression members, rib lacing, and any internal form of skin attachment. -Inspect spars and ribs for cracks, damage, and deterioration.
Check the condition of glued joints and the protective finish on all internal structure.
Inspect compression members for security, cracks, kinks, bends, and condition of finish.
Inspect drag and antidrag wires for proper tension, attachment, protective coating; and corrosion. Check all fittings attached to spars or ribs for security, protective coating, and corrosion. Check all forms of internal skin attachments for proper security.
Any defect or questionable item in the wing structure should be brought to the attention of qualified maintenance personnel.
Inspect movable surfaces (ailerons, flaps, and trim tabs) for proper operation. Check for loose or pulled rivets, distortion, and loose fabric or skin attachment. Examine hinges and horns for security of attachment, breaks, bends, loose or worn pins, proper lubrication, and safetying.
No repairs, refinishing, or repainting of balanced control surfaces (ailerons, elevators, rudders, and trim tabs) may be accomplished unless the surface is rebalanced. Control imbalance may cause a dangerous vibration or flutter condition. Rebalancing may only be accomplished by certificated personnel.
FIGURE 5-6. Control bellcrank checkpoints.
Examine the control mechanism for freedom of movement and proper operation. Inspect bellcranks for cracks, alignment, and security.
Check cables for proper tension, fraying, wear, and proper routing through fairleads and pulleys.
Inspect hinges for breaks, cracks, distortion, and security of attachment.
Refer to the manufacturer's recommended procedures for lubrication.
FIGURE 5-5. Lightning damage-flap, lower surface.
FIGURE 5-7. Fuel tank vent.
LEAD WSA12 VENT GALS FICURE 5-8. Fuel cap, vent, and placard and signs of leakage. Ensure that filler caps are secure and the vent is in the proper loca- tion and free from obstructions. Check fuel lines and connections for leaks, cracks, security are properly routed to the outside air. of attachment, and chafing. Be sure overflow and drain lines are not kinked or broken and Inspect fuel tanks for security of mounting caution against using the wrong grade of fuel, kinked or otherwise distorted can cause fuel make sure a legible placard is located at or near the fuel tank filler neck. starvationi and engine stoppage. As a pre- distortion, and security. Make sure static vents Improperly placed vents and lines that are Inspect pitot tubes or masts for obstructions, 57