By John Crawley WASHINGTON, Dec 12 (Reuters) - Boeing Co. <BA.N> and airlines are resisting a U.S. government proposal to require closer monitoring of rudder performance on 737 aircraft, years after two crashes prompted a design change and other measures. Industry and government correspondence show airlines and Boeing are comfortable with measures already in place to address rudder problems on the world's most popular commercial aircraft. The manufacturer and the airlines reject the Federal Aviation Administration's plan for them to update flight data recorders to capture new information by 2008. The redesign and extra monitoring were prompted by 737 crashes in Colorado in 1991 and Pennsylvania in 1994 that killed more than 150 people. Safety investigators found the accidents were likely caused by a mechanical problem with the 737 rudders, a movable tail-mounted panel used mainly to counter crosswinds during take-off or landing. Investigators said 737 rudders may experience a sudden uncommanded movement or movement in the opposite direction of what the crew intended. Boeing redesigned the mechanism. The correspondence and technical reports filed with the Transportation Department in recent weeks illustrates the degree to which the leading aircraft manufacturer and major carriers dispute the views of top aviation safety officials. The Air Transport Association (ATA), trade group for major U.S. airlines, said in a Dec. 4 report to the FAA that eight carriers under its umbrella operate more than 1,180 737s. More than 800 would not meet the basic requirements of the FAA monitoring proposal if it were finalized today, and most of those planes have already been fitted with redesigned rudder systems, the report said. The rest have gotten some variation of rudder upgrades since 1999 and will get the newly designed rudder system within two years. Airlines support extra monitoring for planes fitted with advanced recorder technology on the assembly line but oppose expensive recorder retrofits for the rest of their fleet. "In view of these ongoing measures, we believe the proposal is unnecessary to ensure the safety of Boeing 737 rudder control systems," ATA officials said in the report. But the FAA and the National Transportation Safety Board agree more oversight is needed to ensure Boeing's rudder redesign works as planned and any other problems are spotted. "Without more data, neither the FAA nor the NTSB can definitively identify the causes of suspected uncommanded rudder events," the FAA said. The work and cost to upgrade flight recorders varies with the aircraft age. Newer planes include advanced equipment while older models require retrofits. FAA estimates the cost at a total $225 million through 2020 of which more than half would cover retrofits. Airlines estimate the cost at nearly $300 million. In addition to the U.S. fleet, there are more than 5,000 737s registered to overseas carriers. Foreign regulators usually follow FAA safety mandates for U.S.-made planes operated by their airlines.
