Robert Don Grace

I think the AD was written correctly; it should not be changed. AD 2004-05-01 R1 applicable to DHC-3 Otters, with STC No. SA3777NM (A.M. Luton PT6A-34/-135 convergin) already addresses this issue for these aircraft by making STC SA01059SE mandatory. STC SA01059SE effectively reduces the wear and play in the trim tab system by reducing the vibration and flutter. The AD should not be changed to include aircraft with STC SA01059SE because this STC embodies a second control rod in the center of the trim tab, stronger built trim tab, and better closer tolerance hinge. The ICAs for STC SA01059SE already require inspecting the trim tab hinge, control rod, and attach brackets for wear. AD 2004-05-01 R1 talks about further evaluation and possible action for other DHC-3 aircraft. I believe that AD 2011-05-02 is the further evaluation; and the possible action for other DHC-3 aircraft should be based on the inspection results reported to the FAA. If you leave the AD as it is the “inspection results reported to the FAA” will only apply to aircraft with original factory installed or factory replacement parts, in there original configuration. This is the data you are looking for. If you change the AD the “inspection results reported to the FAA” will be a mix of data from aircraft with the new improved redundant control rod trim tab configuration and aircraft with the factory configuration. If you mix the reported inspection results from both configurations it will not give you true findings for either configuration. It will: Make aircraft with the original factory configuration look like there is not as much of a problem in this configuration. AND Make aircraft with STC SA01059SE look like the STC is not effective; it will look like there is a greater problem for aircraft with STC SA01059SE than there really is. Robert D. Grace Phone: 907-225-3850 Cell: 907-617-0802