David Learmount/LONDON

Electronic flight instrument system (EFIS) failure is the main possibility under investigation by the Swiss Federal Accident Investigation Bureau (BEAA) as it examines the wreckage of the Crossair Saab 340 which crashed on 10 January, says the bureau's Basle headquarters (Flight International, 18-24 January).

Investigators have eliminated most other potential causes as a result of information from the flight data recorder (FDR) and cockpit voice recorder (CVR).

The CVR reveals that the pilots were communicating normally with each other from take off until the impact 2min later, despite the fact that the aircraft hit the ground in an extreme attitude at high speed. This implies that there was no sudden departure from controlled flight to alert the crew to what was happening.

When the aircraft hit the ground it was 70° nose down with about 130° bank (almost inverted), with an airspeed of 285kt (530km/h) and rate of descent of 27,000ft/min (130m/s), according to Crossair vice-president flight operations Capt André Dosé. He confirms that both engines were running at impact, there was no evidence of a propeller malfunction, and no master warning had sounded.

There are similarities between the Saab 340 loss of control profile, including the crew's lack of awareness as disaster unfolded, with that of the Korean Air Boeing 747-200F crash just after take-off from London Stansted in the UK on 22 December. The 747 had suffered a failure of the captain's attitude director indicator (ADI) (Flight International 11-17 January), determined because the ADI comparator warning sounded for the electromechanical instruments.

The Saab 340 has an EFIS, and the BEAA says: "They were flying with no visibility at night in cloud, but what was showing on their [EFIS] display panel? What was it that caused them to veer to the right and bank so sharply?"

The bureau is focusing on recovering EFIS components, which have non-volatile memory, to see if they reveal what the crew was watching as the aircraft banked and dived into the ground.

Source: Flight International