French investigators have disclosed that the pilot of a Piper PA-34 light aircraft failed to heed orders from an air traffic controller intended to avert a conflict with an Airbus A320 climbing out of Baden-Baden.

Investigation authority BEA says the PA-34 pilot had only acquired the aircraft a few days earlier, and had recorded just 18h on it.

He was operating an instrument-rules flight from Heubach to Strasbourg on 22 October 2017, to familiarise himself with the aircraft.

BEA says he had previously accumulated just 2h in instrument conditions, and adds that he was not used to the conventional instrumentation of the aircraft as he had previously flown with electronic ‘glass cockpit’ displays.

As the PA-34 headed west it was cleared to descend to 8,000ft by Strasbourg air traffic control, in preparation for an ILS approach to runway 23.

The Air Berlin A320, departing Baden-Baden towards the south-west, was cleared to climb to 7,000ft and turn left to head north-east for Hamburg. Its crew was cautioned about the PA-34 flying 1,000ft above and 5nm to the east.

But BEA says the PA-34 continued to descend below 8,000ft. While the controller instructed its pilot to climb immediately back to 8,000ft – and received a correct readback – the aircraft did not ascend.

The controller ordered the A320 crew to make an immediate left turn to the north-east heading and, a few seconds later, told the PA-34 pilot to turn left to head south-west.

But although the A320 crew correctly obeyed, the PA-34 pilot turned the wrong way, “contrary to the clearance received”, turning right and heading north.

The controller asked the pilot what was happening, and was informed that he was experiencing difficulty with the autopilot. It reached 7,400ft before starting to climb back to 8,000ft, after further urgent instructions from the controller.

BEA says the proximity of the aircraft triggered a resolution advisory from the A320’s collision-avoidance system, and the jet started to descend.

The A320 passed beneath the PA-34’s flightpath, with about 750ft of vertical separation, before recommencing the climb to 7,000ft as the conflict was resolved.

BEA says the PA-34 pilot continued to experience problems with maintaining correct directions before eventually landing at Strasbourg about 10min after the airprox incident.

The pilot claimed to have encountered difficulty with the autopilot during the descent to 8,000ft.

“Being in [instrument] conditions, and still unfamiliar with the aircraft, he focused his attention on piloting, to the detriment of communications with the controller,” says the inquiry.

BEA says the “unexpected behaviour” of the navigation equipment “surprised” the pilot, but adds that his lack of familiarity with the newly-acquired aircraft and its navigation system, as well as his limited experience with instrument conditions, contributed to the incident.