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CAVOK Air 7087

Accident Case Study

In a training environment we are well schooled at removing our hand from the thrust levers at V1 and bravely continuing the takeoff no matter what happens. How about in real life?


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Photo: CAVOK Airlines 7087, Mikel Golego

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Accident Report

  • Date: 29 July 2017
  • Time: 0907
  • Type: Antonov An-74TK-100
  • Operator: CAVOK Airlines
  • Registration: UR-CKC
  • Fatalities: 0 of 6 crew, 0 of 0 passengers
  • Aircraft fate: Destroyed
  • Phase: Takeoff
  • Airport (departure): Sāo Tomé Island Airport (FPST), Sāo Tomé and Príncipe
  • Airport (arrival): Accra-Kotoka Airport (DGAA), Ghana

Narrative

[CVK/2017/07/29/F, ¶1.1]

  • On 29th July, 2017 at about 0905hrs, an Antonov aircraft Model AN-74TK-100, flight CVK7087, registration UR-CKC, owned by SWIFT SOLUTION FZC and operated by CAVOK Airlines LLC was departing Sao Tome International Airport to Kotoka International Airport, Accra, for positioning with six crew on board. The flight was on an Instrument Flight Rule (IFR) flight plan and Visual Meteorological Conditions prevailed. The aircraft exited runway 29 during a rejected take off. The Flight Navigator sustained an injury and the aircraft was destroyed.
  • On 28th July, 2017 at 0225hrs the aircraft arrived Sao Tome International Airport from Stavanger (Norway), via Luxemburg and Ghardaia (Algeria) as a Cargo flight. On 29th July, 2017 at about 0800hrs, the crew of CVK 7087 comprising the Captain, the First Officer, the Flight Engineer, the Flight Navigator and 2 Maintenance Engineers arrived the airport and commenced the flight preparation; pre-flight inspection, determination of weight and balance, computation of performance and take-off speeds. The crew received flight briefing/weather information and refuelled the aircraft with an uplift of 5,700kg.
  • At 0850hrs, the crew requested engine start-up clearance from Sao Tome Tower and it was approved. After completing the engine start procedures, engine parameter indications on both engines were normal. Appropriate checklist was completed and taxi clearance was requested by the crew.
  • Sao Tome Tower initially cleared CVK 7087 to taxi on runway (RWY) 11 as favoured by the prevailing wind. However, the crew requested RWY 29 for departure. This request was approved by the Tower and the aircraft re-cleared to taxi to RWY 29 for departure. Sao Tome Tower did not provide the flight crew with the information about possible presence of birds at the aerodrome, in particular, on the runway.
  • At 0905hrs, 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.
  • According to the Captain, "In the first half of the take-off run from the runway, from five to six eagles got off the ground of the runway and flew 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 aircraft accelerated to a speed of 180 km/hr. They stated further: "At a speed of 180 km/hr, ahead, a flock of eagles, which were not seen before this moment began to get off the ground from the runway." 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 (about 272.3m) 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 came to rest at a location with coordinates: N002o 2’ 51’’and E006o 42’07’’. The accident occurred in daylight at about 0905hrs.

Analysis

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Photo: Picture showing the wreckage, CVK/2017/07/29/F, figure 6

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[CVK/2017/07/29/F, ¶1.16.1] Fragments of bird feathers recovered from various locations of the left engine and photograph of a dead bird on the runway were sent to Institute of Zoology at the National Academy of Sciences in Ukraine for ornithological examination. The report suggested that the fragments correspond to the juvenile specimen of diurnal carnivorous bird of Falconiformes of the Hawk Family (Accipitridae) – CommonHoney Buzzard, Pernis apivorusL.

[CVK/2017/07/29/F, ¶2.2]

  • 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 at that time.
  • 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.
  • Post-crash inspection conducted by the BAGAIA investigation team could neither establish any physical evidence (traces of bird) nor its parts found on the engine or its surrounding to suggest any physical damage to the engine or its surrounding like the engine intake, engine nacelle, turbine, and turbine guide vanes.
  • Another comparative report of post inspection conducted on the two D-36 series 2A engines by the representative of the engine manufacturer (SE “Ivchenko-Progress”) revealed that some fragments of birds feathers were found at various locations of the left engine (fan blade, slot between the guide vanes, cavity of the lower engine mount strut main duct cowling of the engine core) respectively. These suggest that there was a bird encounter with the aircraft during the execution of the rejected take-off.
  • Further inspection of the fragments of feathers found at various locations inside the left engine was conducted by the Zoological Museum of the National Museum of Natural History of NAS, Ukraine. The report suggested that the fragments of feathers belonged to the dead bird found on the runway. 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 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.
  • 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.

[CVK/2017/07/29/F, ¶1.18.3]

  • Although the great majority of reported bird strikes have little or no effect on continued safe flight, a small number of encounters, usually with flocks of birds and especially flocks of large birds, can damage aircraft or their engines so badly that they cannot continue to fly.
  • Current aircraft certification standards therefore include requirements to demonstrate both airframe and engine resistance to bird impact. The standards which apply are those in place at the time of introduction of a new aircraft type or engine. Experience of Accident and Incidents has led to progressively tougher requirements although, as with most certification standards, with arrangement under which later derivatives of an initial aircraft type design can be manufactured under variations to the original Type Certificate; thereby avoiding the more complex procedures involved in gaining approval under a completely new Type Certificate. This implies that new requirements are not retrospectively applied to aircraft and engines that have been in-service. The Standards established by both the FAA and EASA are essentially similar but are not yet fully harmonized. However, new aircraft and engine types have to meet both standards so that more demanding of each applies in each instance. Assurance that certification standards have been met is achieved by various means including ground testing using dead birds, of specified weights and quantities, at representative impact speeds.

Cause

[CVK/2017/07/29/F, ¶3.2] 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).

[CVK/2017/07/29/F, ¶3.3] The contributory factors to this accident include but are not limited to the following:

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

See also:

Abort Authority

Panic!

V1

References

CVK/2017/07/29/F, Report of the Accident involving CAVOK Airlines CVK 7087 AN-74TK-100 Aircraft registered UR-CKC which occurred at Sao Tome International Airport, Sao Tome on 29th July, 2017, Banjul Accord Group, Accident Investigation Agency (BAGAIA).

Revision: 20190402
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