21) Main Landing Gear Wheel Alignment

Have you noticed uneven wear of your main landing gear tires? There are small thin shims between the axles and the main landing gear legs that align the tires properly. The Cessna Skymaster Service manuals contain procedures to check for proper wheel alignment. However, the problem is that it is a trial and error process and only 1 or 2 different size shims may be needed out of the 6 different size shims. Cessna only has a few of the shims in stock.

We at Commodore Aerospace Corp have developed a kit that includes most of the shim sizes and configurations. We send the customer our kit that has 2 of each of the shim sizes and the customer can try different shims without having to guess which ones they need. We charge a nominal fee to send the kit. Once the proper size shims needed is determined, then the remainder of the kit is sent back and we then only charge for the shims used.

Shim Part #s:

• 0441139-5, -6

• 0541157-1, -2

• 0541111-2

• 1241061-1

Suggested Trouble Shooting 1979 337H for Main Landing Gear problems by Commodore Aerospace Corp and Larry Good. 8 May 2018

1. Fill power pack with hydraulic fluid.

2. Connect a pressure gauge to outlet pressure line, with master switch on pressure should be 1500 lbs.

3. Without operating the landing gear system, if power pack cycles to maintain the 1500 lbs pressure more than one time per 5 min. interval, check for air in the system and bleed accordingly.

4. If after air bleed, and the power pack still cycles more than once every 5 min., check for internal leakage in the main landing gear actuators by opening the non-pressurized line on the actuator. Should not be any hydraulic fluid leakage more than just static fluid leakage from the open line. Any significant leakage flow will require actuator o-ring replacement or overhaul.

5. Main gear actuator is a rack and pinion type and there is a possibility of a sheared/damaged tooth at the end of the stroke. With aircraft on jacks, check total rotation of each gear leg in degrees and compare with other gear.

6. Check main gear leg saddle clamp (p/n1512247-1 & -2) for damage or distortion and clamp bolts (p/n 1541043 & NAS146-33) and mount bolt (p/n NAS1307-20) for damage or distortion which could allow gear to move during retraction or extension. Clamps should fit flap to surface of gear leg, there should be no clearance between bottom of clamps and top surface of gear leg.

7. With aircraft on jacks, check down lock ball/pin (p/n 1541006-1 &-2) clearance against bottom of gear leg surface at stop pad. Should be able to lift gear leg when it is in down locked position, .010” to .020” by manually lifting up on gear leg. If gear lag can only be moved up .005” as shown in Fig 5-35(Cessna 1974-1980 Service Manual), clearance is too tight and may not allow down light switch to activate until weight is on the gear after touchdown.