National Transportation Safety Board
Office of Public Affairs
The men and women of the Engineering Test and Evaluation Board can be justifiably proud of the work they have done over the past year and for the final report issued today.
The ETEB - made up of representatives from the Federal Aviation Administration, aircraft manufacturers, other industries and even foreign entitities - was the result of a Safety Board recommendation following our investigation of the crash of USAir flight 427. I think I can speak for my NTSB colleagues by saying that we are gratified that the ETEB essentially confirmed our findings in that accident report. The major finding of both reports is that the Boeing 737 rudder control system has numerous potential failure modes that represent an unacceptable risk to the travelling public.
The ETEB found dozens of single failures and jams and latent failures in the 737 rudder system, in addition to the single point of failure we identified in our accident report, that can result in the loss of control of the airplane. Although the failure mechanism that we believed led to the crashes of United Airlines flight 585 in 1991 and USAir flight 427 in 1994, and the near loss-of-control of Eastwind Airlines flight 517 in 1996, appears to have been eliminated through a redesigned rudder power control unit, the results of the ETEB echo our findings that failure modes still exist in the Boeing 737 rudder system.
While we are very concerned that some ETEB recommendations will not be adopted - particularly an independent switch to stop the hydraulic flow to the rudder and a rudder position indicator in 737 cockpits - we are pleased that both the FAA and Boeing Aircraft Company agree that there is a need for a redesign to the rudder actuator system. However, before the Board can determine if this will satisfy the goal of our recommendations, we will need to evaluate in detail the proposed design.
I hope this redesign and retrofit can be accomplished expeditiously so that the major recommendation of our accident report last year will be realized - a reliably redundant rudder system for Boeing 737s.
NTSB Office of Public Affairs: (202) 314-6100
The National Transportation Safety Board (NTSB) is an independent federal agency charged with determining the probable cause
of transportation accidents, promoting transportation safety, and assisting victims of transportation accidents and their families.