FAA renews, toughens warning to Boeing 737 pilots

The airworthiness directive, issued Monday and effective Nov. 25, stems from a crash in which 121 people died on Aug. 14, 2005, when a Helios Airways 737-300 slammed into a hillside north of Athens, Greece.

Greek investigators determined that the pilots had lost consciousness because of a cabin pressure failure shortly after takeoff on a flight from Nicosia, Cyprus, and that the plane kept going on autopilot for two hours until it ran out of fuel.

Authorities say the cabin pressure control settings had been operated improperly and that an alarm went unheeded. Last Tuesday the attorney general of Cyprus said five people would face criminal charges for the crash.

The FAA's order applies to all Boeing 737s, the world's best-selling commercial jet with more than 6,000 orders since the model was launched in 1965 and 5,397 in use worldwide, and takes effect in 120 days. Public notice and comment requirements were waived "because an unsafe condition exists that requires the immediate adoption" of the directive, according to the notice.

Changes in the manuals must be made by each airline. The process is complex, varying by aircraft as well as the nature of the change, and new wording must be validated before it can take effect, FAA spokesman Les Dorr said.

FAA directives typically are reissued by civil aviation authorities in other countries.

Chicago-based Boeing Co. and FAA representatives said the cockpit warning horn serves a dual purpose. On the ground it indicates something is wrong with the plane's pre-takeoff configuration, such as the setting of the wing flaps. In the air it means a loss of cabin pressure, which can cause pilots to lose consciousness if they don't immediately put on oxygen masks.

The FAA directed on July 7, 2006, that flight manuals be changed to remind pilots to pay heed to the warning horn after takeoff, but "we have received continuing reports of in-service events involving failure of the flight crew to recognize and react property to valid cabin altitude (air pressure) warning horns," according to the latest directive.