Texas Turbine Conversions, Inc.

Texas Turbine Conversions, Inc., objects to the language of this AD for several reasons: The AD implies, if not stating directly, that the STC of Texas Turbine Conversions, Inc., on the DHC-3 Otter is not in compliance with the regulation 14 CFR 23.1505(c). The DHC-3 Otter was certified under the Civil Air Regulations, CAR 3, in the 1950’s. In order to allow changes and improvements to the aircraft in later years, companies seeking STC’s were not required to make changes to the aircraft so that they would satisfy current regulations for aircraft being certified now (Pre Product Change Rule). The FAA and the applicant would come to a reasonable agreement as to which regulations would need to be complied with for the STC considering the changes to be made. A list of the regulations requiring compliance was prepared in a Compliance Checklist for the STC engine conversion on the DHC-3. In the case of this STC, Texas Turbines was required to comply with many regulations, particularly those relating to the current power plant requirements. However, the company was not required to modify the airspeed limitations as originally established by De Havilland when the Otter was certified or comply with 23.1505(c). Recently, Texas Turbine Conversions and the FAA discussed the possibility of voluntary limits on the airspeed as would be required by 23.1505(c) to provide an extra margin of safety. This did not seem to be a problem as the feedback from the company’s operators indicated that operations were normally done in the green arc for fuel savings. Texas Turbine agreed to send out a service bulletin to operators requiring that the airspeed indicators be remarked with a red line at the top of the green arc. These discussions and Texas Turbine’s agreement were not the result of finding any failures or damage to aircraft from operations at higher speeds. The company has not had any reports of any problems from a structural or fatigue standpoint as a result of the all