Two minutes and thirty-three seconds passed between the moment an Airbus A310 stopped doing what its crew believed it was doing, and the moment it hit a hillside in the Kuznetsk Alatau. Seventy-five people died.

The story is usually told as a simple morality tale: a pilot let his son fly the aeroplane and killed everyone. That is true as far as it goes, and it is not the useful part. The useful part is that the aircraft gave no indication whatsoever that it had handed control back, and that in the last thirty seconds the crew very nearly saved it.

Who was in the cockpit

The pilot-in-command, Andrey Danilov, was resting in the passenger cabin. In the left seat was the relief captain, Yaroslav Kudrinsky, 39, with 907 hours on the A310. Beside him was co-pilot Igor Piskaryov, 33. A fourth qualified pilot was deadheading and had been in the cockpit since shortly before.

Kudrinsky had brought his two children on the flight. The official report gives their ages as fifteen and thirteen — Eldar and Yana. He put each of them in turn in the left-hand seat, with the autopilot flying, and let them hold the control wheel.

It was against the rules and it killed them all. It was also, in the aviation culture of the time and place, not regarded as especially dangerous, because the autopilot was flying and a control wheel held by a child was assumed to be inert.

What the aircraft did not tell them

Here is the detail that most retellings get wrong, including some very widely read ones. The popular version says a warning light came on silently and the crew missed it. The official report says something worse.

There was no light. There was no sound. And the autopilot mode display carried on showing what it had been told to do.

What happened mechanically is this. Eldar held the control wheel against the autopilot for long enough that the force reached eleven to thirteen kilograms. That tripped a torque limiter in the lateral channel and declutched the aileron actuator — without electrically disengaging the autopilot, which carried on holding altitude in pitch.

Two aggravating details from the report. The declutch happened at a lower force than the eleven-to-fifteen-plus figure stated in the manual. And because two control wheels are mechanically linked, the force a pilot feels is split — so, in the report’s words, the pilot may not perceive the moment of disengagement at all.

The investigators judged the aircraft to fall short of the Soviet airworthiness standard then applicable, which required involuntary autopilot disengagement to produce a signal noticeable enough for pilots to detect it in time. Had such a signal existed, the report concluded, the crew could have caught it.

The first person to notice was the boy

The aircraft began rolling right at about two and a half degrees per second. Nobody in the left or right seat registered it for some seconds, at night, over unlit terrain.

The report notes plainly that the fifteen-year-old was the first to notice something he did not understand. By the time the adults reacted, the bank had gone past ninety degrees, and the autopilot — still holding altitude in pitch — was pulling the nose up into a steepening turn. The aircraft buffeted, stalled and entered a spiral.

They almost had it

This is the part that stays with you.

By 17:57:11 the airspeed had built back to 370 km/h and the rotation was slowing. The report is explicit: there is every reason to believe that if the elevator had been deflected even to neutral, the aircraft would have become controllable.

Instead the elevator was held fully aft. The nose came up, the speed bled off, and the aircraft entered a second stall.

They did recover it. At 17:57:56 the rotation stopped and the aircraft was flying again. But it was between three and four hundred metres above the ground, still pitched nose-up, and five seconds later it struck the hillside almost flat.

The A310 was aerodynamically stable enough to sort itself out. What it needed was for the person flying to stop pulling. That instruction — unload, let the aeroplane fly — runs against every instinct when the ground is coming up, which is why upset recovery is now trained rather than assumed.

A line pilot’s analysis of the accident sequence and the autopilot behaviour behind it.

The cockpit voice recording with English subtitles. Distressing.

What changed, and what did not

The investigation apportioned cause across the whole chain: an unqualified person at the controls, the override force, the crew’s failure to detect the declutch, the late recognition of the bank, the failure to disconnect the autopilot and push the column forward at the first buffet, no unusual-attitude training, and spatial disorientation at night.

Its recommendations asked the authorities, together with the aircraft designers, to find a way to stop the autopilot disengaging its aileron function without warning, and to amend the flight manual.

Two honest caveats. There is no public evidence that Airbus made a design change as a result — the manufacturer’s position at the time was that there was no evidence of any aircraft or systems malfunction, which was technically correct and beside the point. And while cockpit access rules did tighten, that was driven overwhelmingly by September 2001, not by this accident.

What did change is subtler and more important: upset prevention and recovery training is now a required, recurrent part of airline flying, precisely because a stable modern airliner in a stall will recover if you let it, and crews had never been taught to let it.

A reconstruction of the final minutes. Contains the cockpit voice recording.

The children were in the cockpit because their father was proud of his job and wanted to show them. That is the whole of it. Everything technical that followed — the torque limiter, the missing warning, the held elevator — happened because of an ordinary human impulse in a place where the system assumed nobody would act on it.

Sources: Official State Commission investigation report on F-OGQS (English translation, Flight Safety Foundation), Aviation Safety Network, Flight International (June 1994), Associated Press CVR transcript