Inquiry details crashed Ethiopian 737's erratic flightpath

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Lebanese investigators have detailed the erratic course followed by the Ethiopian Airlines Boeing 737-800 which crashed off the coast of Beirut last year, showing that it failed to follow instructed headings before straying and entering a sharp left-hand spiral dive.

It also shows that the aircraft received a stick-shaker warning during its climb, and momentarily descended before climbing again, and receiving another.

In its newly-disclosed progress report on the accident, the Lebanese transport ministry adds that bank-angle warnings sounded 10 times during the flight, the first coming shortly after take-off.

The aircraft had originally been cleared to follow the Lateb 1D standard departure off runway 21 but this was changed just before take-off to an immediate right-hand turn direct to the Chekka (CAK) waypoint north of Beirut.

Air traffic control then ordered it to follow a heading of 315° and says that this was selected on the mode control panel. But the aircraft continued to turn right, eventually reaching a heading of 003°.

Air Transport Intelligence has previously been told that the aircraft had to be turned away from the inbound traffic flow to Beirut, although this is not specified in the ministry's report.

But the ministry states that air traffic control did order the aircraft to turn left to a new heading of 270°, and that this new heading was also selected on the mode control panel - but that the aircraft failed to level out on this heading as well.

Instead it continued to turn southwards, receiving the first stick-shaker warning as it climbed to around 7,700ft. The ministry says the angle of attack peaked at 32°.

The warning lasted 29s and the aircraft descended to about 6,000ft. It then climbed again, to 9,000ft and received a second stick-shaker warning, lasting 26s, before the aircraft turned sharply left and started descending again - a course which, at this point, was taking the aircraft eastwards towards high terrain.

It continued to descend in a sharp left-hand turn, the bank angle reaching a maximum of 118° as the aircraft pitched 63° nose-down. The jet reached a speed of 407kt during the dive and an overspeed warning sounded shortly before the aircraft struck the water.

 

ethiopian crash

 

ethiopian crash

 Ethiopian flight ET409 flightpath: 3D projection (upper) and 2D (lower)
 Source: Lebanese transport ministry

Cockpit-voice and flight-data recorder traces, as well as radar records, of the aircraft were all lost some 30s after the aircraft had reached 9,000ft. There were no survivors among the 82 passengers and eight crew.

Only preliminary findings - showing the aircraft was airworthy and the crew were licensed - are featured in the Lebanese ministry report into the 25 January 2010 accident, which adds that the twinjet took off without any known technical problems. The accident occurred in darkness, about 4min after departure.