72-05-01 GATES LEARJET: Amdt. 39-1397. Applies to Model 23 airplanes, Serial Numbers 23-003 thru 23-089, except those airplanes which have been modified to incorporate the Gates Learjet Model 24 Flap System.
Compliance: Required as indicated, unless already accomplished.
To prevent loss of flaps:
1) Within 25 hours' time in service after the effective date of this AD on those airplanes with 4,000 or more hours' in service,
2) Within 150 hours' time in service after the effective date of this AD, but no later than 4,025 hours' total airplane time, whichever occurs first, on those airplanes having between 3,851 and 3,999 hours' time in service, and
3) Within the next 150 hours' time in service after the effective date of this AD on those airplanes having between 2,350 and 3,850 hours' time in service, accomplish the following:
Replace the flap actuator rod end with a new part in accordance with Gates Learjet Service Bulletin 23-231, dated February 17, 1972, or any equivalent part approved by Chief, Engineering and Manufacturing Branch, FAA, Central Region.
NOTE: The type design data and the airplane service manual are being revised to specify a mandatory retirement life of 2,500 hours for the flap actuator rod end for applicable aircraft.
This amendment becomes effective February 29, 1972.