Brazilian investigators have finally disclosed that a taxi route error resulted in an Airbus A340-300’s overrunning the runway on take-off from Rio de Janeiro, whereupon it collided with lights and navigation aids before climbing away.
Investigation authority CENIPA detailed the circumstances in a 4 September document, released nearly seven years after the 8 December 2011 incident.
The crew of the TAP Portugal aircraft, bound for Lisbon, had been instructed to taxi for runway 10 which had already been effectively shortened by construction works that rendered the first 1,270m unavailable.
Take-off calculations showed that the remaining 2,730m was sufficient for a reduced-thrust ‘flex’ take-off, from the displaced threshold, at a temperature of 34°C.
To reach the displaced threshold the aircraft needed to taxi to the AA intersection. But the crew inadvertently taxied to the BB intersection, which lay some 600m further down the runway – leaving just 2,095m for the take-off run.
Airbus analysis showed that this distance was insufficient for the A340 to become airborne, even if it had used maximum take-off thrust.
“There was no possibility of success with the [flex] thrust regime selected by the crew,” says CENIPA. “Incorrect positioning on the runway was decisive.”
The inquiry highlights the layout of the taxiway system which, it believes, contributed to the blunder.
From taxiway N, which runs parallel to runway 10, intersection AA could be reached by following taxiway BB, then turning sharply left onto taxiway AA. But this 135° turn would have been awkward for an aircraft the size of the A340.
The inquiry says the layout of the taxiways might have “influenced” the crew to believe that following the BB taxiway would lead them straight to the displaced runway 10 threshold.
It points out that “large” aircraft were advised to follow a different taxi route – turning from taxiway N onto taxiway AA – but this advisory was “excessively generic”, and did not define specifically the large aircraft types which needed to follow this route.
“Clear instructions for A340-sized aircraft – requiring them to taxi via N and then via AA – could have prevented the incident,” says CENIPA.
While visibility was good, the departure occurred at 22:37, some 2h after sunset.
The A340 overran the runway, leaving tyre marks for 200m beyond, and striking approach lights as well as the localiser antenna situated 360m from the runway end.
Analysis of the length of the damage trail, says CENIPA, shows that the take-off would have been “uneventful” if the aircraft had used the additional 600m of runway available by departing from the displaced threshold.
“The pilots did not realise they had crossed the runway boundaries, because of the aircraft's nose-up attitude,” it adds. Neither could see the lights at the end of the runway.
None of the 255 passengers and 11 crew members was injured, although the aircraft (CS-TOD) sustained minor damage, with components of the approach lighting system discovered embedded in its landing-gear after arrival in Lisbon.
CENIPA had originally considered three hypotheses for the incident: unfamiliarity with the reduced runway length, an error in take-off calculation, or an aircraft configuration problem. But the inquiry says that all three were subsequently ruled out before investigators focused on the taxiing error.