Automated error messages from the flightdeck pointing to discrepancies in airspeed data
and the malfunction of five key computers are among a handful of clues available so far to experts investigating the deadly crash of Air France Flight 447

1 May 31, 22:04: Air France Airbus 330, with 228 people on board, departs Rio de Janeiro for Paris

2 June 1, 00:55: AF 447 overflies Natal at 10,670m and 450 knots and heads out over Atlantic on route UN873

3 01:33, INTOL waypoint: Scheduled radio contact with Atlantic Area Control Centre (CINDACTA) at Fernando de Noronha. Crew reports flying through severe turbulence. Expects to reach TASIL waypoint – entry point into Senegal airspace – at 02:20

4 01:48: Aircraft leaves CINDACTA radar coverage

01:51: Satellite data indicates AF 447 has crossed first of three storm clusters

01:59: Aircraft enters second, rapidly growing storm cell

02:05: Aircraft enters massive multicell thunderstorm with updrafts of freezing water and ice estimated at 100km/h. Facing 1,000km-wide line of storms pilot has no choice but to fly through them

02:10: ACARS automated message system indicates autopilot has disengaged. Three pitot probe systems show different air speeds. Margin of safety could have been as little as 95-130km/h, beyond which aircraft would stall or dive out of control

02:11-02:13: Air Data and Inertial Reference Unit – which shows basic instruments, airspeed, altimeter, attitude and position – and independent ISIS backup system both fail

02:13: PRIM 1 and SEC 1 faults indicate power to all three primary and two secondary flight control computers has failed

02:14: ACARS reports cabin in vertical speed, suggesting sudden loss of cabin pressure, either cause or consequence of plane breaking up in mid-air

5 02:20: Lack of report at TASIL waypoint prompts Oceanic Control to raise alert


WAYPOINTS

1,000km

All times GMT (also known in aviation as Zulu or Universal Coordinated Time)


Paris
Civilian air routes 
LIMAL
Mid-Atlantic Ridge
AFRICA
ATLANTIC OCEAN
SENEGAL
TASIL
Equator
INTOL
Natal
Fernando de Noronha
High-altitude route UN873
BRAZIL
Rio de Janeiro

Storm cells with moist updrafts rising to 15,500m and temperatures of minus 80 degrees C


Pitot probe
Pressure-sensitive instrument measures airspeed and altitude
Iced-over pitot probes can give false readings


Sources: Aviation Week & Space Technology, Forca Aerea Brasileira, Thales, Air France Communiqué
© GRAPHIC NEWS / GOLDEN SECTION GRAPHICS