67-26-01 BRITISH AIRCRAFT: Amdt. 39-482 Part 39, Federal Register September 15, 1967. Applies to Model BAC 1-11 200 Series Airplanes.
Compliance required within the next 10 hours' time in service after the effective date of this AD, unless already accomplished.
To prevent unwanted rudder actuation as a result of yaw-damper control valve drift when electrically deenergized, comply with either paragraph (a), (b), or (c).
(a) Install a placard as near as practicable to the yaw-damper control switch, reading as follows: "Yaw Damper must be operating at the time of takeoff and at all times during flight." In the event of failure of the yaw damper during flight, the flight may continue only to the next scheduled stop. Repair yaw damper or comply with paragraph (b) before further flight, except that the airplane may be flown in accordance with FAR 21.197 to a base where the repair can be performed.
(b) Positively deactivate the yaw damper in accordance with British Aircraft Corporation Instruction SS316 or an FAA-approved equivalent, and install placard to indicate that the yaw damper is deactivated
(c) Adjust and modify the yaw-damper control as follows:
(1) Adjust the yaw-damper actuator Boulton Paul Part No. P185-45-10 to provide one degree bias between the torque motor and the rotary hydraulic control valve of the unit in accordance with BAC 1-11 Service Bulletin 27-PM 3291, or later ARB-approved issue, or an equivalent approved by the Chief, Aircraft Certification Staff, FAA, Europe, Africa and Middle East Region.
(2) Modify the Elliotts Company torque motor type 130/6P to incorporate Boulton Paul Modification Nos. P185/11 or P185/15, in accordance with BAC 1-11 Service Bulletin No. 27-PM 3191 or later ARB-approved issue or an equivalent approved by the Chief, Aircraft Certification Staff, FAA, Europe, Africa and Middle East Region.
(3) Apply sealant, Midlands Silicones LTD, cold-cure silastromer K9160, or an FAA-approved equivalent, to the inside surfaces of the torque motor mounting access plates on final assembly and plug the 5/32 inch diameter dowel access hole, if present in the mounting, with a suitable aluminum alloy plug, in accordance with BAC 1-11 Service Bulletin No. 27-PM 3193 or later ARB-approved issue, or an equivalent approved by the Chief, Aircraft Certification Staff, FAA, Europe, Africa and Middle East Region.
(d) When the adjustments and modifications set forth in paragraph (c) are accomplished, any placards installed in accordance with paragraphs (a) and (b) may be removed.
This amendment effective December 5, 1967.