Serbian investigators have revealed that the captain of an Embraer 195 pressured the first officer to accept an incorrect take-off calculation after taxiing onto the wrong runway intersection at Belgrade.

The Marathon Airlines aircraft – operating a service for Air Serbia on 18 February last year – subsequently took off from the D5 intersection of runway 30L, with insufficient length to become safely airborne.

It struck its tail on a grass surface during rotation and collided with the localiser antenna, suffering substantial damage before returning to the airport to land.

While Serbian investigation authority CINS had previously disclosed the intersection error – the jet was supposed to depart from D6 – its interim findings into the accident detail an extraordinary interaction between the pilots.

CINS says the captain was “showing a superior attitude” towards the first officer during informal conversations between the two while taxiing.

While progressing on taxiway A, running parallel to runway 30L, the first officer incorrectly assessed that the jet was already at the D6 intersection, and suggested reporting to the tower that they were ready for take-off. The aircraft was still at D5.

The tower cleared the aircraft to enter the runway via D6 but the captain – without checking visually – instead took the D5 turning and taxied onto the runway.

This left the aircraft with just 1,273m take-off distance rather than the 2,349m available from D6.

Although air traffic control identified the error and suggested a taxi route that would return the aircraft to the D6 intersection, CINS states that the captain refused.

Instead the captain performed a new take-off calculation, entering data with “significant discrepancies” to the entries of the first officer during the original calculation for a D6 departure.

These discrepancies included changing the runway and intersection, from 30L and D6 to the opposite-direction 12R and D5 – giving an available take-off distance of 2,266m. The captain’s entry for the take-off weight, 43.9t, also differed from the figure on the loadsheet.

“Failure to follow standard operating procedures led to different data being entered,” says CINS. “The absence of a standard departure briefing resulted in incorrect data being entered into the aircraft’s [flight-management system].”

The captain was “confident” that the runway was long enough, it states, and opted for a D5 intersection take-off.

CINS adds that he “put pressure” on the first officer to accept that the length was sufficient, and the first officer yielded without double-checking the performance calculation. The crew commenced the take-off without making changes to criteria including the aircraft’s configuration.

Even though the crew noticed, at the 80kt check, that the runway end was approaching, the first officer did not apply full thrust. After the V1 and rotation speed call-outs, the first officer pulled sharply on the control column, causing the jet to pitch 10° nose-up and leading to the tail-strike before the aircraft struck the localiser antenna.

Only after realising that the aircraft was not climbing did the first officer apply additional thrust with trim, enabling it to achieve a stable positive increase in height.