AD 77-25-02 ACTIVE

77-25-02 ROCKWELL INTERNATIONAL: Amendment 39-3091. Applies to Sabreliner Model NA-265-70 Serial Numbers 370-1 and 370-7, and NA-265-80 Serial Numbers 380-1 through 380-58, certificated in all categories.

Compliance required as indicated.

To prevent deactivation of the engine fire detection system and/or crossed wires in the engine fire detectors to cockpit warning light, accomplish the following:

Prior to the next flight after receipt of this telegram, unless already accomplished,

A. Ensure that a proper ground exists between the engine fire detector element (Edison Cable P/N 244-12482) couplings and the engine, and

B. Ensure that proper continuity exists between the elements and the fire detector control units in accordance with Rockwell International Sabreliner Service Bulletin No. 30 dated November 2, 1977, or later FAA approved revisions, or accomplish tests and modifications as follows:

1. Disconnect electrical power from airplane.

2. Openand remove engine access doors as required.

3. Locate and remove existing MS 21105-4 clamps securing fire detector element couplings to engine. (Ref. Aeronca Dwg. No. 234-22029 Rev. A).

4. Install new clamps (P/N AN 742-H3) on each fire detector element coupling. Tighten clamp fasteners.

5. Using a Volt/OHM meter (Simpson 260 or equivalent) set to read OHMS, connect negative (-) lead to AIRFRAME GROUND and positive (+) lead to fire detector element coupling. Check that meter reads one OHM or less. Remove Volt/OHM meter leads.

6. On RH engine, disconnect fire detector element from ONE coupling. Apply external power to airplane.

7. Using a suitable jumper wire, attach one end of jumper wire to inner conductor of receptacle, and the other end of jumper wire to ground. Check that the right hand "Fire Pull" handle lights illuminate. Remove jumper from receptacle inner conductor and insert in center conductor of fire detector element. Check that right hand"Fire Pull" handle lights illuminate. Remove jumper wire.

8. Connect and tighten fire detector element to couplings (element disconnected in Step 6). Lockwire coupling.

9. On LH engine, disconnect fire detector element from ONE coupling.

10. Using a suitable jumper wire, attach one end of jumper wire to inner conductor of receptacle, and the other end of jumper wire to ground. Check that the left hand "Fire Pull" handle lights illuminate. Remove jumper from receptacle inner conductor and insert in center conductor of fire detector element. Check that left hand "Fire Pull" handle lights illuminate. Remove jumper wire.

11. Connect and tighten fire detector element to coupling (element disconnected in Step 9). Lockwire coupling.
NOTE: If the requirements of Step 7 thru Step 10 are not met, check fire detector wiring in accordance with Rockwell International Sabreliner Wiring Diagram Manual, Report No. SR-73-26.

12. Press "Fire Det Sys Push To Test"switch. Right and left "Fire Pull" overheat and fire-warning indicator lights should illuminate within one second after switch is pushed. Make sure both lights in each assembly illuminate. Release test switch. Both lights should go out within 5 seconds. Remove electrical power from airplane.

13. Close and/or install engine cowling.

C. Equivalent modifications may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region.

D. Special flight permits may be issued in accordance with FAR's 21.197 and 21.199 to authorize operation of an airplane to a base for the accomplishment of the modifications required by this AD provided the following is accomplished:

1. Interim addition of a positive ground between the engine fire detector element couplings and the engine to ensure proper operation of the engine fire detection system, and

2. Check the fire warning system to ensure that the fire warning light operates correctly for the engine/engines involved.

This amendment becomes effective December 12, 1977, for all persons except those to whom it was made effective by telegram dated November 4, 1977 which contained this amendment.