AD 68-20-08

68-20-08 SIKORSKY: Amdt. 39-633 as amended by Amendment 39-665 is further amended by Amendment 39-1141. Applies to S-61A, S-61L and S-61N Type Helicopters.

To assure proper adjustment of the Automatic Flight Control System (AFCS) accomplish the following:

A. Prior to next AFCS flight inspect all AFCS electrical connectors for electrical integrity, pin alignment and perform a functional test of the AFCS system including amplifier and amplifier rack connectors Cannon Part No. DPJ-98-33S-B or DPJM-98-33S-B and box mating connectors Part No. DPJ-98-34P-A.

B. Prior to the first AFCS flight each day accomplish the following checks:

1. A pitch stick sensor check on the ground with electrical and hydraulic power "ON" as follows (a) engage the AFCS (b) place C.G. trim knob to center of its travel (c) select "P" on null indicator switch (d) move pitch cyclic stick to center the null indicator (e) verify that forward stick motion deflects the needle to the right.

2. A roll stick sensor check on the ground with electrical and hydraulic power "ON" as follows: (a) Engage AFCS (B) select "R" on null indicator (c) move roll cyclic stick to center the null indicator (d) verify that left stick motion deflects the needle to the left.

3. A pitch and roll AFCS hard-over check on the ground in accordance with Sikorsky Service Bulletin No. 61B65-1 Paragraphs B-1 thru B-4 dated April 12, 1967, or later FAA approved revision or alternate check approved by the Chief, Engineering & Manufacturing Branch, Eastern Region.

4. Yaw Hard-over check on the ground as follows: (a) position null indicator switch to position "Y" and position pedals to full right position (b) position yaw channel disengage switch to "ON" and yaw hard-over switch to "LEFT". Verify that pointer on null indicator also moves hard-over and pedals start motion to the left (c) verify that it is possible to push right pedal to override hard-over condition (d) position hard-over switch to "RIGHT" and pedals to the full left position. Verify that the pointer on null indicator moves hard-over and pedals start motion to the right. (e) Verify that it is possible to push left pedal to override hard- over condition.

C. After the effective date of this AD as amended and prior to the next AFCS Flight, if not already accomplished, with AFCS "OFF" measure the adjustment of the auxiliary servo linkage, by placing dial indicators at the output of the servo and at the bolt located in the sloppy link to ascertain that the adjustment of the linkage is .010" or less in the "AUX-ON" and "AUX- OFF" positions. Perform stick jump test to further verify these measurements. Perform these checks in the roll attitude, pitch and yaw functions.

D. Within the next 1200 hours time in service and thereafter at 1200 hour intervals of time in service, accomplish the following:

1. Perform AFCS hard-over check according to Sikorsky Service Bulletin No. 61B65-1 dated April 12, 1967 paragraph B-5, or alternate check approved by the Chief, Engineering and Manufacturing Branch, Eastern Region.

E. Compliance with this AD is not required if the AFCS installation is disconnected.

Amendment 39-633 was effective August 17, 1968.

Amendment 39-665 was effective October 10, 1968.

This Amendment, 39-1141, is effective January 14, 1971.