AD 77-13-21 covers the landing gear system on the Piper PA-24, PA-30, and PA-39. On the surface, it sounds straightforward. In reality, it’s a reminder that landing gear tolerances can drift quietly over time in ways you won’t catch until the aircraft is fully disassembled and measured.

Part A requires a full teardown at 1,000-hour intervals. That means checking for worn bushings, incorrect bolts, stress points that were never properly radiused, hidden pitting or bends in the oleo cylinders, mis-rigged drag links, and over-center rigging that’s simply not where it should be. If it’s out of limits, it comes off the airplane.

Part B is just as important: main landing gear bungee cords must be inspected every 500 hours and replaced every 500 hours or 3 years, whichever comes first. Any fraying, soft spots, or breaks mean immediate replacement.

The lesson is simple: the Comanche gear is strong, reliable, and predictable — but only when geometry, measurements, and inspection intervals are treated with discipline.

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