AD 70-15-19

70-15-19 BOEING: Amdt. 39-1051. Applies to 747-100 series airplanes which incorporate 60B00210-1 nose gear steering metering valve assembly. Compliance required as indicated. To prevent unsafe conditions resulting from malfunction of the ground steering system and to eliminate causes for such malfunction, accomplish the following: a. Within 10 hours' time in service after the effective date of this AD, unless already accomplished, either (1) establish and maintain pilot surveillance over landing gear steering inputs through an FAA-approved training program established by an operator which follows the recommendations in Boeing Flight Crew Training Bulletin No. 70-20, dated 14 July 1970, or (2) follow an equivalent pilot surveillance procedures approved by the Chief, Aircraft Engineering Division, FAA Western Region, or (3) install a placard with the following wording in clear view of the captain and first officer: Be alert for any unscheduled steering inputs during take-off and landing as indicated by unusual directional control problems or a chattering nose gear due to tire scrubbing. Take immediate positive action with the steering tiller to correct any suspected steering problems. Under no circumstances are circuit breakers to be pulled to deactivate steering or aural warning systems. b. Retain the placard or continue to employ the equivalent pilot surveillance procedure per a., above, until the airplane is modified per g., below. c. Within the next 25 hours' time in service after the effective date of this AD, unless already accomplished: (1) Test the inherent centering capability of the nose gear steering metering valve in the manner described by Boeing Alert Service Bulletin No. 32-2041. (2) Test the inherent nose gear centering capability provided by the tiller system, in the manner also described by Boeing Alert Service Bulletin No. 32-2041. d. Replace any nose gear steering metering valve prior to further flight if both of the test requirements of c(1) and c(2), above, are not passed, with valve P/N 60B00210-2 or with another valve P/N 60B00210-1 which has been tested and found to pass those test requirements. e. Inspect and correct any tiller steering system prior to further flight when the nose gear steering metering valve passes the test requirement of c(1), above, but does not pass the test requirements of c(2), above, in accordance with established B-747 maintenance procedures. f. A nose gear steering metering valve which does not pass the test requirements of c(1) but passes the test requirements of c(2) may be continued in service for a period not to exceed 300 hours after the effective date of this AD, provided the test prescribed by c(2) is repeated at intervals not to exceed 25 hours' time in service and the tiller system is corrected as necessary to assure continued satisfactory tiller centering action. g. Within the next 600 hours' time in service after the effective date of this AD, unless already accomplished, replace the nose gear steering metering valve, P/N 60B00210-1, with nose gear steering metering valve, P/N 60B00210-2, or with another valve approved by the Chief, Aircraft Engineering Division, FAA Western Region. This amendment becomes effective July 30, 1970.