Boeing Commercial Airplanes Group today announced enhancements to the rudder control system of its popular 737 twinjet as a result of work done in cooperation with the Federal Aviation Administration and the National Transportation Safety Board.
The announcement comes as the FAA released the final report of its Engineering Test and Evaluation Board after a year-long review of the 737 flight control system.
"These enhancements should be taken in context," said Carolyn Corvi, vice president and general manager of the 737 program. "The 737 family has been, and continues to be, among the safest of all jetliners; in fact its safety record is twice as good as the average for the world's commercial jet fleet.
"But we believe even this airplane can be enhanced. So we are simplifying flight crew procedures, increasing maintenance oversight, and modifying the rudder control system. We think these enhancements will improve an airplane that already has proven itself in more than 100 million hours of flight."
Crew procedures: The current cockpit procedures for dealing with jammed or restricted rudder operations have been clarified and simplified.
Maintenance procedures: Rudder system maintenance procedures on 737 Initial and Classic airplanes (-100 through -500 models) will be modified to match procedures developed for Next-Generation 737s.
Rudder system: The NTSB has recommended that the 737 rudder Power Control Unit (PCU) be made "reliably redundant." Boeing has developed a concept that ensures the reliability and fundamental safety that is built into the airplane.
"While the existing system is redundant and has proven itself reliable," Corvi said, "we have developed a new concept that eliminates the dual concentric valve that has been the subject of concerns in the past.
"It makes a major change to the system; however, it is based on proven current technology, will fit within the existing airplane structure and will be relatively simple to retrofit into the fleet."
Customers will be formally notified of the proposed crew procedure and maintenance changes in the near future. "We will work with the airlines and with the FAA to ensure timely implementation of these enhancements," Corvi said.
The proposed rudder modifications will be discussed with the airlines, suppliers and the FAA. "Given the nature of this modification and the need to ensure that the new system is service ready when it enters the fleet, we will be working very carefully with everyone concerned," Corvi said. "Our current, very preliminary, schedule indicates that the first airplane with the new system could be delivered mid-year in 2003, and that retrofits could begin in the third or fourth quarter of that year."
Pending further discussion with the FAA and Boeing customers, Boeing believes the retrofit can be accomplished during normal maintenance intervals, minimizing disruptions to flight or maintenance schedules.
"The 737 is a remarkably safe and reliable airplane," Corvi said. "It has been the workhorse of the world's jet fleet. Given this record, we want to be very sure that any changes we make to the system really do enhance safety. There is no rush to modify the rudder, and so we are going to proceed very methodically, making sure the system is robust and thoroughly tested before it enters service."
At the end of July 2000, Boeing had announced 4,736 orders for 737s and had delivered 3,740 to 300 operators in more than 100 countries around the world. A 737 takes off or lands somewhere in the world every 5.5 seconds, and approximately 1,000 of the twinjets are in the air at any given time.