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NEW SERVICE LETTER DEFINES
MLG STRUT REPLACEMENT

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Strut


The main landing gear on most piston and turboprop Twin Commanders is large, long, stout, and unusual in that the tire rotates 90 degrees as the gear retracts so that when fully retracted it is parallel to the ground and fully enclosed in the aft portion of the engine nacelle. On extension it rotates back to normal position for landing.


The design that makes the rotation possible uses inner and outer strut bodies, and a torque link that attaches to the landing gear truss and the upper part of the strut assembly. As the main gear retracts rearward, the torque link rotates the strut inner body approximately 90 degrees. This rotates the fork and wheel assemblies and allows the wheel to lie flat within the wheel well when retracted.


As is often the case on long production runs, the parts used for the main landing gear structure on different models evolved over the years. Beginning with production of the 500A piston Twin Commander, and continuing through the last 695A Model 1000 turboprops, Aero Commander and, later, Rockwell Commander and Gulfstream employed two different designs for the main landing gear strut inner strut. One type of strut inner body was used on earlier, lighter-gross-weight models, while a second strut inner body design was used on the later, heavier-gross-weight models.


(The earliest piston-powered Twin Commander models with the large, so-called �bathtub� engine nacelles did not have rotating main landing gear tires. Any Twin Commander fitted with 400-139�all dash numbers�main landing gear strut inner body can use the later-style strut inner body.)


New-production replacement strut inner bodies for earlier, lighter-gross-weight models are no longer available, but that is not a problem for owners and operators�the later-model strut inner body can be used on earlier-model aircraft. That has been the accepted policy for years, but recently a foreign-government aviation regulatory agency asked for written guidance confirming that policy.


As a result, Twin Commander Aircraft is developing Service Letter 386 to provide instructions, parts numbers, and authorization to use the later-type main landing gear strut inner body on most piston and turbine-powered Commanders up to and including the 695A.


The new service letter will come into play during a five-year 3,000-hour landing gear inspection if and when the service center determines that the main landing gear strut inner body is worn, damaged, or out of tolerances and must be replaced. That work can now be accomplished using the later-style strut inner body.


The Custom Kit specified in SL 386 includes the new strut inner body, scissors, and necessary hardware.


For more information on SL 386 and main landing gear issues, contact an authorized Twin Commander service center.




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