FAA proposes new rudder control for 737s

The Federal Aviation Administration (FAA) has published a proposal to mandate installation of a new, improved rudder control system in all Boeing 737 models within five years.

The proposed airworthiness directive (AD) would require Boeing 737 operators to install a new rudder system, which is currently being developed by Boeing, and make any additional changes to the aircraft needed to accommodate the new system, within five years of the AD effective date.

The order would affect about 2,000 US-registered airplanes at an estimated total cost of approximately $364 million. There are about 4,500 737s in the worldwide fleet. Comments on the proposed AD are due within 60 days.

‘This is the climax of a multi-year effort by government and industry to improve the excellent safety record of the Boeing 737,’ said FAA Administrator Jane F. Garvey. ‘Implementing a major design change in today’s airliners is never easy nor inexpensive – but we feel this is absolutely the right thing to do.’

The new design would increase the overall safety of the 737 by simplifying the rudder system and eliminating a range of previously known failure possibilities. The redesign also would make it unnecessary to have existing flight crew operating procedures and associated training unique to the 737 rudder system.

In mid-1999, the FAA established the government-industry 737 Flight Control Engineering Test and Evaluation Board (ETEB). The ETEB conducted a top-to-bottom analysis of the Boeing 737 rudder system, including possible ways the 737 rudder system could malfunction. The proposed AD is influenced by the ETEB findings.

The FAA already has taken many safety actions on the 737 rudder system. Last year, the agency mandated a simplified procedure for handling a jammed or restricted rudder and began training 737 pilots on the new methods. The FAA also made several maintenance changes to reduce the possibility of undetected failures.

The FAA had previously ordered other design changes that increased the safety level of the 737 rudder system. All US-registered 737s have improved rudder power control units, a more reliable yaw damper mechanism and a hydraulic pressure reducer that helps pilots maintain control if the rudder makes unintended movements.

A copy of the proposed airworthiness directive is available at: http://www.access.gpo.gov/su_docs/aces/aces140.html