FAA re-issues warning to pilots of Boeing 737 aircraft over in-flight warning horn

The Unites States Federal Aviation Administration (FAA) has re-issued an urgent airworthiness directive requiring that pilots of Boeing 737 aircraft be advised to pay attention if they hear an in-flight warning horn.

The in-flight warning horn indicates a loss of cabin pressure, which can cause pilots to lose consciousness if they do not put on oxygen masks immediately.

The FAA had directed on July 7, 2006, that flight manuals be changed to remind pilots to pay heed to the warning horn after takeoff. “But,” the latest FAA directive said, “we have received continuing reports of in-service events involving failure of the flight crew in recognising and reacting properly to valid cabin altitude (air pressure) warning horns.”

The Federal Aviation Administration is an agency of the United States Department of Transportation with authority to regulate and oversee all aspects of civil aviation in the US. The FAA is the single most influential governmentally run aviation agency in the world, with the European Aviation Safety Agency coming a close second.

The FAA’s new directive on airworthiness, issued on November 10, 2008, and effective from November 25, 2008, follows a crash in which 121 people died on August 14, 2005, when a Boeing 737-300 of Helios Airways slammed into a hillside north of Athens in Greece.

(Helios Airways was a low-cost airline operating scheduled and charter flights between Cyprus and many European destinations. Its main base was Larnaca International Airport in Cyprus. Helios Airways stopped flights on  November 6, 2006, after the company’s aircraft were detained and its bank accounts frozen by the  government of Cyprus.)

Greek investigators came to the conclusion that the pilots of the ill-fated Boeing 737-300 aircraft had lost consciousness because of a failure in cabin pressure shortly after takeoff on a flight from Nicosia in Cyprus, and that the plane kept going on auto-pilot for two hours until it ran out of fuel.

Investigators also found that the cabin-pressure control settings had been operated improperly and that an alarm went unheeded.

The Attorney-General of Cyprus had said a week ago that five people would face criminal charges for the crash of the Boeing 737-300 of Helios Airways.

The US Federal Aviation Administration’s latest order applies to all Boeing 737 aircraft, the world’s best-selling commercial jet with over 6,000 orders since the model was launched in 1965. According to Boeing Company, a total of 5,397 Boeing 737 aircraft are in use worldwide.

The media quoted a spokesman of the US Federal Aviation Administration as

Saying: “Public notice and comment requirements have been waived because an unsafe condition exists that requires the immediate adoption of the directive.

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.”

The cockpit warning horn serves a dual purpose, according to Boeing Company, based in Chicago, the United States. On the ground, the cockpit warning horn indicates that 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 do not put on oxygen masks immediately.