72-15-03 LEARJET: Amendment 39-1489 amended by Amendment 39-1597 is further amended by Amendment 39-1959. Applies to Model 24 (Serial Numbers 24-178 thru 24-268) and Model 25 (Serial Numbers 25-020 thru 25-114) airplanes.
Compliance: Required as indicated, unless already accomplished.
To prevent failure of spoiler actuator attachment bolts, accomplish the following:
A) On aircraft with 500 or more hours' time in service, within 25 hours' time in service after the effectiveness of this AD, replace the spoiler actuator pivot bolts (P/N NAS 464P4-32), nuts (P/N AN320-4), and cotter pins (P/N MS24665-7), in accordance with procedures in Gates Lear Jet Service Bulletin SB No. 24/25-237 dated July 7, 1972.
B) On aircraft with less than 500 hours' time in service upon the effectiveness of this AD, the spoiler actuator pivot bolts, nuts and cotter pins identified in Paragraph A must be replaced in accordance with the Gates Lear Jet Service Bulletin identified above, upon the accumulation of 500 hours' time in service. (If the aircraft has between 475 and 500 hours' time in service upon effectiveness of this AD you must replace the specified parts within the next 25 hours' time in service.)
C) The spoiler actuator pivot bolts, nuts and cotter pins identified in Paragraph A of this AD must be replaced upon accumulation of each 500 hours' time in service thereafter.
D) When the spoiler actuator installation is modified per Gates Learjet Aircraft Modification Kit AMK 73-1 and Service Bulletin 24/25-237B dated January 15, 1973, further compliance with this AD is no longer required. Any equivalent modification must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region.
Amendment 39-1489 became effective July 28, 1972, to all persons except those to whom it was made effective earlier by telegram or letter issued July 11, 1972.
Amendment 39-1597 became effective March 2, 1973.
This Amendment 39-1959 becomes effective September 19, 1974.