AD 78-16-03

78-16-03 LEARJET: Amendment 39-3278. Applies to Learjet Model 23 (Serial Numbers 23-003 and up); Model 24 and 24A (Serial Numbers 24-100 through 24-180); Model 24B and 24B-A (Serial Numbers 24-181 through 24-229); Model 24C, 24D and 24D-A (Serial Numbers 24-218, and 24-230 through 24-328); Model 24E, 24F and 24F-A (Serial Numbers 24- 329 through 24-356); Model 25 and 25A (Serial Numbers 25-002 through 25-066); Model 25B and 25C (Serial Numbers 25-061, 25-067 through 25-201, 25-204 and 25-205); Model 25D and 25F (Serial Numbers 25-206 through 25-253); Model 35 (Serial Numbers 35-001 through 35- 066); Model 35A (Serial Numbers 35-067 through 35-194); Model 36 (Serial Numbers 36-001 through 36-017); and Model 36A (Serial Numbers 36-018 through 36-040) airplanes.

COMPLIANCE: Required as indicated unless already accomplished.

To preclude a failure of the refrigeration condenser fan:

A) Before the next flight, remove or lower the tailcone access door, disconnect the aircraft batteries, and inspect the refrigeration condenser fan part number that is rubber stamped on the blade. If the refrigeration condenser fan installed has a part number other than 6608059-3, no further action is required. (The blades on P/N 6608059-3 fans are not tapered in thickness from the hub to the tip.)

B) If Part Number 6608059-3 refrigeration condenser fan is installed, before the next flight fabricate a placard which reads "DO NOT OPERATE REFRIGERATION SYSTEM UNDER ANY CIRCUMSTANCES ON THE GROUND OR IN THE AIR." Install this placard as near as possible to the refrigeration system control switch and operate the airplane in accordance with this restriction.

C) When the Part Number 6608059-3 fan is replaced with either a P/N 6608059-1, 6608059-2 or a P/N 6608059-4 fan, the above required placard may be removed and the airplane returned to normal service. (The blades on the -1, -2 and -4 fans are tapered in thickness from the hub to the tip.)

D) Any equivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region.

NOTE: Gates Learjet Service Bulletins SB23/24/25-284, dated 7/13/78, and SB35/36- 21-3, dated 7/12/78, or later approved revisions, provide inspection and fan replacement procedures, physical characteristics of the fans, and replacement part credit information.

This amendment becomes effective August 17, 1978, to all persons except those to whom it has already been made effective by air mail letter from the FAA dated July 21, 1978.