737 Rudder Design Changes Mandated
On Oct. 7, the U. S. Federal Aviation Administration (FAA) issued an airworthiness directive (AD) mandating changes to enhance the 737 rudder control system -- expected changes that Boeing announced it was making on September 14, 2000. The modifications amplify three areas: flight crew procedures, maintenance procedures and control system design. These three steps make an airplane with an impeccable safety record even safer.
The design changes the FAA mandated today have been made in agreement with a National Transportation Safety Board's (NTSB's) finding that the current rudder system could be made more "reliably redundant." Boeing agreed with that recommendation, and Boeing engineers designed new hardware that provides two separate and independent control inputs to the main power control unit.
Within two months of its Sept. 14, 2000 announcement, Boeing issued cockpit procedures to its airline customers that simplify and clarify how to address a condition involving a jammed or restricted rudder. In less than a year, Boeing employed new rudder system maintenance procedures for Initial (737-100/ -200) and Classic 737s (737-300/ -400/ -500) that match procedures for the Next-Generation models (737-600/ -700/ -800/ -900).
The redesign has been completed and the shipment of kits to operators is proceeding as planned. The first airplane with the design change installed in-production was delivered January 21, 2003 -- six months earlier than first projected. Boeing is providing wiring provisions ahead of hardware (main rudder power control unit and supporting parts) availability to give airlines more flexibility to incorporate the redesign, and as kits are ordered, Boeing is fulfilling these orders per the operator's schedule.
The first wire provisioning kits were shipped to operators of Initial and Classic 737s in February 2002. Operators of Next-Generation 737s began receiving wire provisioning kits in August 2002. Boeing began shipping hardware kits to Next-Generation 737 operators in June 2003 and to Classic 737 operators in July 2003. Operators of Initial 737 models began receiving their kits in September 2003.
As of March 2006, 1,051 hardware kits have been shipped to Initial and Classic 737 operators and 696 hardware kits have been shipped to Next-Generation 737 operators.
"The 737 is a remarkably safe and reliable airplane," said Carolyn Corvi, vice president and general manager of the 737 program. "It has been the workhorse of the world's jet fleet. Given this record, we are assured that the rudder modifications add to its robustness, and make a safe system even safer."
At the end of February 2006, Boeing had orders for 6,160 737s and had delivered 5,009 737s to more than 200 operators in more than 100 countries around the world. A 737 takes off or lands somewhere in the world every 4.6 seconds, and approximately 1,250 of the twinjets are in the air at any given time.