BOEING 757 AND 767 pilots should be given better information about faulty airspeed indications and training to cope with them, the US National Transportation Safety Board (NTSB) has told the US Federal Aviation Administration (FAA).
The NTSB recommendation follows the 6 February Birgenair 757 accident in which all 189 people on board died when the aircraft stalled and dived into the sea shortly after taking off from Puerto Plata, Dominican Republic, bound for Germany (Flight International, 27 March-2 April, P13). A blocked pitot tube is believed to have caused erroneous airspeed readings, says the NTSB.
Investigators reported that the captain's primary airspeed indicator - one of three aboard - was not working properly. During the climb, "RUDDER RATIO" and "MACH/SPD TRIM" advisory messages appeared on the cockpit engine indication and crew alerting system (EICAS) display. Soon after that, the stall-warning stick-shaker activated, and the aircraft stalled.
The Safety Board says that the 757/767 EICAS does not warn pilots specifically of an erroneous airspeed indication. An air-data computer compares the several airspeed sensor inputs, however. When a difference of 10kts is detected, both the "MACH/SPD TRIM" and "RUDDER RATIO" advisories appear together.
The aircraft-operations manual does not inform pilots that the two advisories together are indicative of an erroneous airspeed indication. The Safety Board believes that the FAA should require Boeing to revise the 757/767 flight manual.
Source: Flight International