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Replacement of piston pin and plug assemblies to preclude the possibility of disintegration of the piston pin plugs, failure of pistons, and complete engine failure.
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Required inspections of the ailerons, aileron balance assembly, and aileron rigging for looseness or wear, and required repair or replacement of parts as necessary.
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Replacing leaky fuel tank with one made of stainless steel or aluminum alloy before the next flight.
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In order to prevent the seat belt anchorage from failing during crash landings, it has been found necessary to modify the seat installation as follows.
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Directions to prevent failure of the seat back which could result in loss of control of the airplane.
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Inspection of control cables for continual fraying and failure in the control column assembly.
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Due to the possibility of a defective fitting on the upper end of the control column shaft in the aileron control system, the system should be tested to a load of 94 pounds.
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Prevention of a degradation of the induction system icing protection or partial engine power loss.
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Replacing the original muffler on the serial numbers listed above with a new muffler.
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Failures of the exhaust stacks have occurred in the area of the cabin heat muffs, causing hazardous carbon monoxide contamination of the cabin when cabin heat is used.