Crews are being cautioned over the risk posed by slow rotation rates after serious take-off incidents involving long-haul aircraft operating at limiting conditions.

Colombian authorities have been probing incidents involving abnormally-long take-off rolls by Airbus A340s at Bogota, including one by an Air France A340-300 on 11 March this year.

Slow rotation has been identified as a significant contributor to the incidents, according to preliminary analysis by investigators.

The European Aviation Safety Agency has responded with a safety bulletin drawing attention to the risk of rotating too slowly during departure from runways where performance-limiting factors are present.

While EASA does not specifically mention the A340 events at Bogota, it states that the bulletin follows an incident involving a four-engined widebody departing a "limitative" runway while near its maximum weight.

The aircraft required a "very long" take-off run, says EASA, and was still below minimum required height when it passed the opposite-direction runway threshold.

Analysis of preliminary information shows that slow aircraft rotation was a "main contributing factor" in the incident, it adds.

Similar events had also occurred at the same airport involving another operator of four-engined widebody aircraft, says EASA, and slow rotation rates were present in a "significant" number of departures.

A source familiar with the investigation tells FlightGlobal that the EASA bulletin directly relates to the Bogota incidents.

EASA is recommending that operators and training organisations identify, through flight-data monitoring, whether rotation rates are a potential hazard, and take action to prevent unacceptable risks.

"These controls may include the provision of ad hoc training on rotation techniques based on [aircraft manufacturers'] operational documentation," it says. "The unintended introduction of additional risks [such as tail-strikes] should also be considered when analysing possible mitigating measures."

EASA says it has also identified another event which took place at a separate airport, also with a limitative runway, centred on a different four-engined widebody aircraft type.

This incident has lent further urgency to the need to address slow rotation rates, says the authority, although there are no current plans to issue an operational directive on the matter.

Source: Cirium Dashboard