64-24-03 GENERAL DYNAMICS: Amdt. 824 Part 507 Federal Register October 23, 1964. Applies to Model 30 Series Aircraft Which Have Been Altered in accordance with Either American Airlines Fleet Campaign Directive No. 194K or General Dynamics/Convair (990) Service Bulletin No. 27-66 Dated December 6, 1963.
Compliance required within 300 hours' time in service following the effective date of this AD unless already accomplished.
American Airlines Fleet Campaign Directive No. 194K and General Dynamics/Convair (990) Service Bulletin No. 27-66 describe emergency electric stabilizer trim system circuit change which interlock the "up relay" and "down relay" coils. Under certain circumstances the emergency electrical stabilizer trim systems which incorporate these circuit changes could permit a runaway stabilizer condition to exist. To correct this condition, modify the aircraft emergency electric stabilizer trim system circuits in accordance with either paragraph (a) or (b). The circuit changes described in General Dynamics/Convair Service Bulletin No. 27-66, which interlock the coils of the "up relay" and "down relay", may be used when the changes described in paragraph (b) are accomplished.
(a) Restore the emergency electric stabilizer trim system circuits to the original Convair type certification design; or
(b) Replace the single pole, double throw, emergency electric stabilizer control "nose up"-"nose down" switch (S-246), with a double pole, double throw, momentary on, center position off, momentary on switch. Connect the added poles of the switch so that the power control relay (K-276) is energized with the "up relay" (K-124) and with the "down relay" (K-123) but is not energized when the switch is in the "off" position. This modification shall be accomplished in accordance with General Dynamics/Convair (990) Service Bulletin No. 27-66A dated April 22, 1964, or by an equivalent approved by the Aircraft Engineering Division, FAA Western Region.This directive effective October 23, 1964.