Flight International, 12-18 June, p8 reports on changes recommended by the US National Transportation Safety Board (NTSB), which has been a `full partner' with the Dominican Republic in the investigation of the 6 Feb 1996 Birgenair B757 accident. A blocked pitot is believed to have cause the erroneous airspeed readings on the captain's primary airspeed indicator. During the climb, "RUDDER RATIO" and "MACH/SPD TRIM" advisory messages appeared on the cockpit engine indication and crew alerting system (EICAS) display, as reported in the CVR transcript, and soon after that followed the stick-shaker activation and aircraft stall.

The NTSB says that the B757/767 EICAS doesn't warn pilots specifically of an erroneous airspeed indication. An air-data computer (the stabilizer trim and asymmetry module computer *) compares the several airspeed sensor inputs and at a difference of more than 10kts, the above advisories appear. Furthermore, the operations manual doesn't inform pilots that these two advisories together are indicative of an erroneous airspeed indication.

The NSTB has recommended to the FAA to require Boeing to revise the manual.

Footnotes

Back to `Incidents and Accidents'.

Peter B. Ladkin, 1999-02-08
	Last modification on 1999-06-15 by Michael Blume