AD 57-15-01

57-15-01 AERO COMMANDER: Applies to All Models 560A, 560E and 680 Serial Numbers 231 Through 559.

Compliance required as indicated.

A. Failures have occurred on the upper retaining pins on the main landing gear. These pins react the rebound loads when the main gear lower piston reaches its limit of extension with respect to the upper cylinder.

1. Until Item 2 has been accomplished the following inspections should be performed daily.

(a) With aircraft on ground remove center scissor bolts right and left main gears and inspect for evidence of shearing. These bolts normally carry zero shear load and evidence of shearing is an indication of upper bearing retaining pin failure.

(b) Inspect center scissor bushings for evidence of cracking or elongation due to shear loads being applied on center scissor bolts.

(c) Check area where scissors attach to strut and housing for evidence of scissor to strut or scissor to housing contact due to overextensionof strut assembly. This is further evidence of upper bearing retaining pin failure.

If any of these indications are present, the upper bearing retaining pins must be replaced at once. Contact the Service Department, Aero Design & Engineering Co. for parts and detailed instruction to accomplish replacement.

2. To be accomplished by October 1, 1957. The present design incorporating two 1/4 inch retaining pins should be modified to incorporate four 3/8 inch retaining pins. Four pin kits and drill fixtures for installing the pins, as well as information as to where the modification can be accomplished, may be obtained from the Service Department, Aero Design & Engineering Co.

(Aero Design & Engineering Co. Service Bulletin No. 43, dated June 18, 1957, also covers this subject.)