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Rejected takeoff above decision speed caused Antonov An-74 runway overrun accident at Sao Tome

Staff Writer |
An Antonov 74TK-100 cargo plane, operated by Cavok Air, was damaged beyond repair in a runway excursion accident at São Tomé Island Airport (TMS), São Tomé and Príncipe.

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The aircraft had arrived on July 28, 2017 at 02:25 on a cargo flight from Stavanger (Norway), via Luxemburg and Ghardaia (Algeria). The following morning the aircraft was prepared for a repositioning flight to Accra, Ghana.

Sao Tome Tower initially cleared Cavok Air flight 7087 to taxi on runway 11 as favoured by the prevailing wind.

However, the crew requested runway 29 for departure. This request was approved by the controller and the aircraft was re-cleared to taxi to runway 29 for departure. Sao Tome Tower did not provide the flight crew with the information about possible presence of birds at the airport, in particular, on the runway.

At 09:05, the aircraft began the take-off roll. The first officer was the Pilot Flying (PF) while the captain was the Pilot Monitoring (PM). The engines and systems parameters were reported to be normal.

In the first half of the take-off run the captain noted five to six eagles getting off the ground and flying dangerously close to the aircraft.

He then requested the flight engineer to check if the flood lights were ON and to monitor the engine parameters. The crew asserted that they observed a rising and narrowing runway as the aircarft accelerated to a speed of 180 km/hr.

At that time the crew noticed a flock of eagles ahead. The captain took control of the aircraft and decided, after assessing the situation within 4 seconds that the best option for the crew was to discontinue the take-off.

At that moment, the crew heard a bang, which they suggested could be a bird strike. This was followed by aural and visual indications on the annunciator panel such as "Left Engine Failure", "Dangerous Vibration", and "Take-off is prohibited" and the captain immediately initiated a rejected take-off and instructed the flight engineer to deploy thrust reversers.

The rejected take-off was initiated about 5 seconds after sighting the birds, at a speed of 220km/h. According to the captain, his decision was necessitated by the consideration of losing multiple engines due to bird strike if the take-off continued.

The captain said he pressed the brake pedals completely immediately after initiating the rejected take-off, subsequently he assessed the braking action as not effective and he used the emergency braking at a speed of about 130 km/h.

On realizing that the aircraft would not stop within the remaining available runway length coupled with the presence of a ravine at the end, the captain intentionally veered to the right in order to extend the runway stopping distance and also avoid the ravine. The aircraft exited the runway at a speed of approximately 76 km/h.

As the aircraft’s speed decayed to 60 km/h and just before the aircraft exited the runway, the captain instructed the flight engineer to close the fuel emergency shutoff cock. The aircraft travelled a distance of about 95m from the exit point before plunging into the ravine.

In the process, the forward fuselage separated from the bulkhead located immediately after the cockpit section. The aircraft was destroyed but only one of the six crew members suffered minor injuries.

An investigation showed fragments of bird feathers in the engines, belonging to the Common Honey Buzzard.

The investigation determines that the cause of this accident as: Due to the presence of birds on the runway, the take-off was rejected at a speed above decision speed V1, which is inconsistent with CAVOK’s Standard Operating Procedures (SOP).

The contributory factors to this accident include but are not limited to the following:
i. Failure of the crew to deploy interceptors (speed brakes/spoilers). ii. Inadequate flight crew training on details of rejected take-off procedure scenarios.

iii. The omission of the take-off briefing in CAVOK’s Normal Operations checklist.

iv. Poor Crew Resource Management (CRM), especially in a multi-crew flight operation.

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