Cavok AN74 at Sao Tome on Jul 29th 2017, rejected takeoff due to flock of birds results in runway overrun

Last Update: December 6, 2018 / 18:19:09 GMT/Zulu time

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Incident Facts

Date of incident
Jul 29, 2017


Accra, Ghana

Aircraft Registration

A Cavok Air Antonov AN-74TK-100, registration UR-CKC performing a flight from Sao Tome (Sao Tome and Principe) to Accra (Ghana) with 6 crew, was accelerating for takeoff from Sao Tome's runway 29 when the left hand engine (D36) ingested a number of birds prompting the crew to reject takeoff. The aircraft overran the end of the runway and went down a slope before coming to a stop on soft ground. One crew member received injuries, the aircraft received substantial damage beyond repair.

Ukraine's Deputy Minister of Infrastructure Yuri Lavrenyuk reported the flight was attempting takeoff when according to preliminary information the right hand engine received a bird strike, the takeoff was rejected, the aircraft went past the runway end. All crew members received injuries.

Sao Tome's Civil Aviation Authority reported the aircraft rejected takeoff for some problem at about 11:00L (11:00Z) and suffered an accident. Five of the six people on board received injuries, one of them needed surgical treatment. The aircraft suffered substantial damage. An accident investigation commission has been formed.

The occurrence aircraft had operated to Sao Tome on Jul 27th 2017 from Stavanger (Norway) via Luxembourg (Luxembourg) and Ghardaia (Algeria) and was presumably departing for the return flight.

On Aug 18th 2017 Ukraine's NBAAI reported in their monthly bulletin, that the aircraft was accelerating for takeoff, when the aircraft rolled through a flock of birds causing both engines to fail. The crew rejected takeoff but was not able to stop the aircraft within the runway. All five crew members received injuries, the aircraft sustained substantial damage. The occurrence was rated an accident. The NBAAI have joined the investigation led by Sao Tome.

On Aug 17th 2018 Nigeria's AIB released an interim statement reporting the aircraft was about to depart for the return flight via Ghardaia and Luxembourg to Stavanger, however, was first planned to perform a tech stop at Accra (Ghana). The captain, first officer, flight engineer and two maintenance engineers on board remained unhurt, the flight navigator received injuries to his left foot and some minor bruises. A draft final report has already been sent out, comments and responses are due in 60 days.

On Dec 6th 2018 Nigeria's AIB released their final report concluding the probable causes of the accident were:

Causal Factor

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).

Contributory factors

The contributory factors to this accident include but are not limited to the following:

- Failure of the crew to deploy interceptors (speed brakes/spoilers).
- Inadequate flight crew training on details of rejected take-off procedure scenarios.
- The omission of the take-off briefing in CAVOK’s Normal Operations checklist.
- Poor Crew Resource Management (CRM), especially in a multi-crew flight operation.

The AIB reported an engine examination by the manufacturer found feathers inside the left engine which could be matched to a dead bird on the runway. The AIB wrote in the analysis: "It might have penetrated into the left engine as a result of being “overtaken” by the aircraft from behind on take-off during which part of its left feather was pulled out."

The AIB analysed:

According to the Captain, he saw five to six eagles get off the ground of the runway which flew dangerously close to the aircraft at the beginning of the take-off roll. At a speed of 180km/h, the crew asserted that they saw ahead of them a flock of eagles which were not seen initially getting off the ground from the runway.


The Captain took control of the aircraft and requested the Flight Engineer to check if the landing lights were ON and to monitor the engine parameters. The Captain further stated that he assessed the situation within 4 - 5 seconds and decided that the best option for the crew was to abort the take-off. The Captain immediately initiated a rejected take-off, instructing the Flight Engineer to apply the thrust reversers. The rejected take-off was initiated at a speed of 220 km/h, about 5 seconds after sighting the birds.

The decision not to continue the take-off could have been made when the flight crew observed that the runway surface appeared to be rising as the aircraft was accelerating towards the take-off speed, before they sighted the flock of birds. The investigator believes that the pilot intended to continue the take-off despite the birds seen and the runway factor.

According to the post investigation report received from Antonov State Enterprise Company, the pilot in command of the aircraft deliberately decided to abort the take-off at the speed exceeding the take-off decision speed V1, which was followed by the runway overrun, since an aircraft overrun during the take-off is obviously less dangerous than an aircraft impact at failure of two engines at the initial stage of the climb. Thus, the pilot's actions were motivated by a state of emergency and aimed at minimizing the consequences of the occurrence.

However, the Captain was hesitant on the decision to discontinue the take-off. This resulted in a delayed and inappropriate response to the situation. At that time, the aircraft rotation speed was attained, the captain called for rotation initially then he reversed his rotation call out and instructed the first officer not to rotate. At about 5 seconds after Vr (200 km/h), with the fear of losing multiple engines, the Captain was certain that a reject was imminent; he took control, initiated a rejected take-off and called for reversers at a speed in excess of V1 (20 km/h > V1) which is inconsistent with CAVOK’s SOP and AN-74TK-100 Airplane Flight Manual (AFM).

The braking action was initiated by the Captain at a time lead of 2 seconds as against the activation of the reversers by the Flight Engineer (FE) after the captain’s instruction. This delay in activation of the reversers resulted in the reduction of the braking effectiveness, hence increasing the unlikelihood of the aircraft stopping before the end of the runway.

During the cockpit examination following the accident, the investigators found the SPEED BRAKE/SPOILERS lever in the down detent position. This position would normally not deploy the system manually or automatically should the thrust lever be retarded to idle. Also, FDR data recordings did not physically indicate the deployment activation of speed brake/spoilers. The failure of the flight crew to activate the speed brake/spoilers during the reject procedures also increased the severity of the accident as a result of decreased effectiveness in slowing the speed of the aircraft within the shortest practicable distance. Had the flight crew used the speed brake/spoilers, it would have assisted considerably in slowing down the aircraft, therefore stopping capability would be enhanced and braking effectiveness would increase; enabling the crew to stop the aircraft before the end of the runway and also to achieve a successful rejected take-off (See Figure 15).

The AIB analysed:

Even with the delayed and moderate braking, and use of spoilers and speed brakes, the aircraft should have been brought to a full stop within the confines of the runway, if the RTO was initiated by V1. The combination of the reduced braking effectiveness and RTO initiation speed resulted in the runway excursion.

FPST 291300Z 18013KT 9999 FEW020 OVC040 26/21 Q1014 NOSIG=
FPST 291200Z 23004KT 9999 FEW020 OVC040 28/21 Q1014 NOSIG=
FPST 291000Z 14013KT 9999 FEW025 SCT040 27/21 Q1015 NOSIG=
FPST 290800Z 17004KT 9999 SCT025 25/20 Q1016 NOSIG=
FPST 290700Z 16006KT 9999 FEW025 BKN110 24/21 Q1015 NOSIG=
Incident Facts

Date of incident
Jul 29, 2017


Accra, Ghana

Aircraft Registration

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