73-16-06: Induction Air Box Flapper Door

73-16-06 PITTS: Amdt. 39-1699. Applies to S-2A airplanes, Serial Numbers 2001 through 2059 certificated in all categories. Compliance required as indicated. To prevent the possibility of a power loss due to the failure of the induction air box flapper door, accomplish the following: (a) Within the next 50 hours time in service after the effective date of this airworthiness directive, unless already accomplished, install stiffener, Pitts Part Number 2-7112- 16, to the induction air box flapper door assembly, Pitts Part Number 2-7112-7, in accordance with Pitts Service Letter No. 2. Access to the induction air box flapper door assembly may be gained by removing the lower engine cowl. (b) Until the modification specified in paragraph (a) above has been accomplished, visually check the induction air box flapper assembly, Pitts Part Number 2-7112-7, for cracks in the welded areas upon the accumulation of 50 hours time in service or within 5 hours time in service, whichever is later, and thereafter at intervals not to exceed 5 hours time in service from the last check. The checks required by this AD may be performed by the pilot. If the flapper door in the area of the weld is found to be cracked, remove the flapper door assembly from the alternate air box, and add stiffener, Pitts Part Number 2-7112-16 in accordance with Pitts Service Letter No. 2, before further flight. (c) The installation of the stiffener, Pitts Part Number 2-7112-16, in accordance with Pitts Service Letter No. 2, will eliminate the necessity for the repetitive inspections required in paragraph (b). Pitts Service Letter No. 2, dated June 26, 1973, pertains to this subject. This amendment becomes effective August 13, 1973.