AD 83-13-08

83-13-08 BOEING: Amendment 39-4678. Applies to all model 747 airplanes, except the 747SP, certificated in all categories equipped with either the Landing Control Logic Unit (LCLU) or Landing Rollout Control Unit (LRCU) automatic landing systems and either Collins Low Range Radio Altimeter (LRRA), Model 860F-4, or Bendix Low Range Radio Altimeter, Model ALA 51A. To prevent hard landing due to false altitude information from the LRRA to the autopilot, accomplish the following, unless already accomplished:

A. Within 15 days after the effective date of this AD, install a placard on the autopilot P10 mode control panel which reads as follows: "DO NOT USE AUTOPILOT BELOW 50 FT. ON WET RUNWAYS." The placard may be removed when either paragraph B, C, or D below is accomplished.

B. Remove Collins Model 860F-4 LRRA (P/N 622-3890-0XX), if installed, and perform Collins Service Bulletin 860F-4, Service Bulletin #8. Modified units become P/N 622- 3890-1XX. Install modified, orproduction equivalents, according to the Boeing Service Bulletin 747-34A2225.

C. Remove Bendix Series ALA 51A LRRA (P/N 2067631-05XX or -51XX), if installed, and perform Bendix Service Bulletin M-1632-(ALA-51A-34-56). Modified units become P/N 2067631-53XX. Install modified, or production equivalents, according to Boeing Service Bulletin 747-34A2226.

D. Alternate means of compliance which provide an equivalent level of safety may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region.

All persons affected by this proposal who have not already received the Service Bulletins may obtain copies upon request to Boeing, Collins Air Transport Division, or Bendix Corporation as appropriate. These documents may also be examined at the FAA, Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington.

This amendment becomes effective July 18, 1983.