AD 72-02-01

72-02-01 CESSNA: Amendment 39-1379. Applies to Models 411, 411A, 421, 421A and 421B (up to and including Serial Number 421B0147) airplanes.

Compliance: Required within the next 50 hours' time in service after the effective date of this AD, unless already accomplished:

To prevent possible propeller separation in flight as a result of rough engine operation, accomplish the following:

A) Check the torque on the propeller attachment nuts by applying 80 to 85 ft. lbs. torque. Nuts which do not move when the proper torque is applied should not be further tightened. If any nuts are found loose (70 Ft. lbs. torque or less), complete the detailed inspection required by Cessna Service Letter ME71-16 Supplement No. 2, dated January 7, 1972. (See Note)

NOTE: A special adapter, Cessna P/N 5090006-5 for Hartzell propellers or P/N 5090006-9 for McCauley propellers, or equivalent, is required to accomplish the above torque check.

B) Modify the engine tachometer by incorporating a yellow arc restricting continuous engine operation for Models 411 and 411A airplanes between 2100 and 2350 rpm, and for Models 421, 421A and 421B airplanes between 1950 and 2225 rpm.

C) Install appropriate operational placard on the engine tachometer with the following wording: "AVOID CONTINUOUS OPERATION IN YELLOW ARC"

D) Replace existing Airplane Flight Manual pages with the following FAA/DOA approved revised Airplane Flight Manual pages, or later FAA/DOA approved revision, as appropriate:

1. Model 411 - Revision No. 12 dated December 7, 1971.

2. Model 411A - Revision No. 4 dated December 7, 1971.

3. Model 421 - Revision No. 8 dated December 8, 1971.

4. Model 421A - Revision No. 4 dated December 8, 1971.

5. Model 421B (Serial Numbers 421B001 through 421B0147) - Revision No. 4 dated December 1, 1971.

E) Equivalent methods of compliance with this AD must be approved by Chief, Engineering and Manufacturing Branch, FAA, CentralRegion.

Cessna Service Letter ME71-16 Supplement No. 2 dated January 7, 1972, pertains to this subject.

NOTE: This does not preclude continued recheck of propeller attach bolt as required by FAR 91 and specified for each 100 hours' time in service per Cessna Service Instructions.

This amendment becomes effective January 18, 1972.