Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, 25F, 28, 29, 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C airplanes. This proposed AD would require modifying the left- and right-hand standby fuel pump switches. This proposed AD would also require revising the Emergency and Abnormal Procedures sections of the airplane flight manual to advise the flightcrew of the proper procedures to follow in the event of failure of the standby fuel pump to shut off. This proposed AD results from a report of inadvertent operation of a standby fuel pump due to an electrical system malfunction. We are proposing this AD to prevent this inadvertent operation, which could result in inadvertent fuel transfer by the left or right wing fuel system and subsequent over-limit fuel imbalance between the left and right wing fuel loads. This imbalance could affect lateral controlof the airplane which could result in reduced controllability.