by Joe Singleton in Washington DC

Calls for safety-critical assessments follow investigations into ‘preventable’ disasters

The US National Transportation Safety Board (NTSB) is calling for the US Federal Aviation Administration to amend procedures for addressing and documenting safety hazards and provide ongoing assessments of safety-critical systems.

The board’s recommendations follow the investigation of four crashes between 1999 and 2004 that “raised questions about the certification process used by the FAA to determine compliance with airworthiness standards”.

In its recommendations, the NTSB says the FAA should require that a list of safety-critical systems be drafted during type certification; provide for ongoing safety-critical assessments during the life of the aircraft; and consider the impact of human factors and structural failures in such assessments.

“The policy, practices, and procedures put in place for continued airworthiness do not ensure that the underlying assumptions made during design and type certification about safety-critical systems are assessed in light of operational experience, lessons learned, and new knowledge,” says the NTSB.

The NTSB’s recommendations follow several accident investigations where questions were raised into how a modified certification process could have prevented the disasters. These include the USAir Boeing 737-300 accident in September 1994 in which the NTSB focused on the rudder actuator; and the TWA Boeing 747-100 crash in July 1996, which was blamed on the centre wing fuel tank.

Other investigations noted were those into the Alaska Airlines Boeing MD-83 crash in January 2000, caused by the horizontal stabiliser screwjack assembly, and the American Airlines Airbus A300-600R accident in November 2001, which focused on the rudder system.

Source: Flight International