Q FM Africa's Modern Radio
Germanwings co-pilot Andreas Lubitz is known to have suffered depression in the past
The co-pilot of the Germanwings plane that crashed in the French Alps in March appears to have practised a rapid descent on a previous flight, a report by French investigators says.
The report said Andreas Lubitz repeatedly set the same plane for an unauthorised descent earlier that day.
Lubitz is suspected of deliberately crashing the Airbus 320, killing all 150 people on board.
He had locked the flight captain out of the cockpit.
Lubitz appears to have practised programming a rapid descent on the outbound leg of the flight – from Duesseldorf to Barcelona on 24 March – the preliminary report by accident investigation agency BEA said.
It added that on several occasions – again with the captain out of the cockpit – the altitude dial was set to 100ft (30m), the lowest possible reading, despite instructions by air traffic control in Bordeaux to set it to 35,000ft and then 21,000ft.
It was also reset on one occasion to 49,000ft, the maximum altitude.
The changes apparently happened over a five-minute period at about 07:30 starting 30 seconds after the captain left the cockpit.
Analysis: Hugh Schofield, BBC News, Paris
If Andreas Lubitz “practised a rapid descent” on the outward leg of the Germanwings flight, then the obvious question is: why did no-one spot it and ground him in Barcelona?
The interim French investigation report explains that puzzle. Over the course of three or four minutes, Lubitz did indeed designate “100ft” as the selected flight level. He did this several times, while the pilot was out of the cockpit.
But this was just after the plane had already begun its descent. After each occasion that he chose “100ft”, he then corrected himself and entered the correct flight level. The course of the plane was not altered at all.
The picture that builds up is of a man steeling himself for the challenge he has set himself, building up the courage but at each point pulling back – until finally the pilot re-enters the cockpit and normality returns.
Had the return flight not crashed, no-one would have noticed these anomalies.
“I can’t speculate on what was happening inside his head – all I can say is that he changed this button to the minimum setting of 100ft and he did it several times,” BEA director Remi Jouty told Reuters news agency.
This conjures an image of the aircraft zig-zagging up and down while Lubitz pushed on a joystick, says BBC transport correspondent Richard Westcott.
But quickly turning a dial would not have led to dramatic changes on board, our correspondent adds, and the aircraft would have just kept descending as per instructions from air traffic control.
BBC