Install a placard

On some aircraft, the design of the cabin doors is such that the door can be pushed open when there is significant differential pressure between the pressurized cabin and the outside air. A placard or indication system on or near the door is recommended to warn flight crews of this hazard, according to an SAIB published July 8 by the FAA. This is advisory only, as an SAIB (unlike an airworthiness directive) says right on the letterhead, "Recommendations aren't mandatory."

The hazard can be deadly. A flight attendant was killed when he was ejected from the door of an Airbus A300-600 at Miami; he had pushed on the door when the airplane was still pressurized, and the force hurled him onto the tarmac (see ASW, Aug. 19, 2002). The FAA issued airworthiness directives to address this condition, but it maintains the SAIB is sufficient for about 39 different model aircraft. It said:

"We concluded that the majority of airplanes on which opening with significant differential pressure is possible are smaller transports, which have several mitigating features.

"They are low to the ground, have relatively small cabin volumes, and will thus equalize pressure very quickly.

"They are usually operated by persons familiar with the airplane. Even so, there is some potential for injury and we want to make sure you are aware of it.

"We expect that the situation would occur only rarely as there is generally only significant differential pressure on the ground following failure(s) in the cabin air pressurization or venting systems."

However, among the more than three dozen models listed in the SAIB is the Boeing 747 and the upper deck exits to same. (SAIB NE-05-75 may be viewed at http://www.faa.gov/aircraft/safety/alerts/saib/2003_2005/2005-4/)