On 3 February 2022, a Boeing 737-200F (HK5192) being operated by Aerosucre on a non-scheduled domestic cargo flight departing from Puerto Carreño for Bogota as KRE157 in day VMC collided with an on-track obstruction almost immediately after becoming airborne. This collision involved the left wing and engine impacting a tree and the damaged engine ran down as the climb continued. A partially successful restart of the failed engine was achieved but with an excessive indicated temperature, this was followed by a decision to return to land which was accomplished without further event despite the relatively short runway. The damage to the aircraft was subsequently found to be relatively minor with the engine failure attributable to tree debris ingestion.
A CCTV record of the aircraft just after colliding with the (adjacent) tree. [Reproduced from the Official Report]
A Serious Incident Investigation was carried out by the Dirección Técnica de Investigación de Accidentes (DIACC), the agency responsible for Air Accident Investigation in Colombia in accordance with ICAO Annex 13 procedures. The FDR and CVR were both recovered from the aircraft and relevant data from the former was downloaded by the NTSB. Relevant CCTV footage of the moment of impact was also obtained. It was noted that the 57 year-old Captain - who was also the airline’s Director of Operations and had been acting as PF for the flight - had a total of 8,830 hours flying experience which included 762 hours on type and previous time on the AN32 and JS32. The 32 year-old First Officer had a total of 2,603 hours flying experience which included 812 hours on type and had otherwise been on light single and twin engine types and had included aerial work tasking. It was noted that “except for reading the operating procedures and checklists, all recorded communications between the pilots and between them and ATC were in Spanish".
The aircraft and crew (which in addition to the pilots also included an observing First Officer, a Technician and a Dispatcher) had arrived at Puerto Carreño earlier from Bogota and the inbound cargo had been unloaded. The aircraft was then loaded with 14,491kg of cargo for the return flight and fuel was loaded to achieve a total on board of 7,620kg which made the calculated total takeoff weight of 49,386 kg.
Taxi out for a takeoff from the 1800 metre-long, 20 metre-wide runway 07 (surface wind given as 060° 4 knots) was commenced and flaps set to 10°. With the speeds bugged as V1 130 KIAS, VR 132 KIAS and V2 as 137 KIAS, takeoff thrust was set and achieved as required. However, the aircraft only became airborne shortly before the end of the runway which meant the vertical profile was lower than the performance assumptions of the crew had indicated. As the landing gear lever was selected to ‘up’, 6/7 seconds after becoming airborne, the aircraft, passing approximately 35 feet agl, collided with the upper part of a 40 foot high tree located just to the left of the runway extended centreline some 239 metres past the end of the runway. Had the calculated performance been achieved, this position would have put the aircraft at 91 feet agl - see the illustration below.
The actual versus calculated vertical profile. [Reproduced from the Official Report]
An immediate indication of a failure of the left engine generator occurred accompanied by a complete loss of thrust from the same engine. After following the prescribed procedures whilst continuing the climb, it was decided to attempt a restart of the failed engine which was successful apart from an abnormally high temperature indication and a lower EPR than for the right engine. It was therefore decided to return to land which was achieved without further event.
The post-landing external inspection found “encrusted vegetation on the leading edge of the left wing, on the No. 1 engine and on various parts of the slats as well as residues of vegetation embedded on the fan cowling”. An internal inspection of the engine found ingested vegetation visible in the compressor and in the turbine section. Evidence of impact damage to one of the left wing flap guides was also found. An inspection outside the aerodrome perimeter where the impact had occurred found “a large amount of vegetation” which had clearly fallen from the aircraft onto a nearby road but it was confirmed that there had been no injuries to persons or structures on the ground.
Why It Happened
The Investigation began by obtaining assistance from the NTSB and Boeing in examining the validity of the takeoff performance calculation. A calculation based on the contents of the AFM applied to the actual conditions assuming an engine failure just after rotation, at an altitude of 35 feet agl should have allowed the aircraft to climb and reach a height of approximately 91 feet by the time it reached the location of the tree it hit whereas it did not, by a considerable margin, do so with both engines shown to have been functioning normally.
The crew were aware that the aircraft takeoff would be occurring at around the maximum permitted weight. However, the weight of the three additional occupants was not included in the calculations made and neither was any account taken of the fact that the air temperature was continuing to rise as the performance calculation was carried out. Accepting the crew assumption that the takeoff weight would be 227 kg less that the ramp weight used due to fuel used in taxiing, the takeoff was attempted at a weight of 49,240 kg. However, by the time the takeoff was commenced, the temperature had increased to 34°C which meant that the maximum permitted takeoff weight was actually only 48,980 kg, 260 kg less than the weight assumed during the performance calculation. Acceleration of the aircraft was therefore less than had been assumed it would be and this advanced the position where the calculated VR of 132 KIAS was reached. This increased the ground run prior to the aircraft becoming airborne and took the aircraft close to the end of the runway paved surface which “considerably limited the ability of the aircraft to clear the obstacle (the tree) ahead”.
CVR data showed that the on-board Dispatcher was aware of the increase in temperature and when they recalculated performance given the increase in both the actual temperature and the actual weight, complacency in respect of departing with the aircraft at a weight above that established in the performance charts was prevalent amongst the entire crew. It was established that the airworthiness of the aircraft and its components had no impact on the investigated event.
It was concluded that the wider context for what happened was to be found in ongoing systemic deficiencies in the company’s operational safety management. The Investigation of a similar takeoff performance event (although in that case an accident) involving one of the Company’s Boeing 727F aircraft taking off from the opposite direction of the same runway in 2016 had found very similar causes and contributing factors. After this accident, it was considered “clear that even when corrective actions were made at the time, as evidenced in internal audits, operational safety was not sufficiently strengthened”, and there had been a continued lack of adequate “hazard identification and risk management” which had created the conditions which allowed the investigated Serious Incident to occur.
The Probable Causes of the Serious Incident were formally documented as follows:
- Late Rotation, generated by the extreme conditions of weight of the aircraft and the prevailing density altitude led to a manoeuvre that did not allow the aircraft the angle of climb and height gain required to clear the obstacles in the takeoff trajectory.
- Execution of the takeoff with a weight greater than that determined during takeoff performance calculations and a difference in density altitude due to the increased air temperature caused the aircraft to travel a greater takeoff distance before becoming airborne with a consequent reduction in the margin of safety to overcome obstacles located in the trajectory. This caused the aircraft to collide with a natural obstacle immediately during the initial climb.
Four Contributing Factors were also identified:
- Overconfidence on the part of the crew, assuming that during the taxy out, there would a sufficient fuel burn to allow the takeoff to be carried out according to the performance calculations made.
- Low situational awareness of the crew and the operator's Office, which influenced the decision-making to continue the execution of the flight and of a takeoff under limited performance conditions.
- Weaknesses in the operational control and management of the ground operator's Office, by not carrying out an adequate briefing to the crew in which it was taken into account that atmospheric conditions (room temperature, above all) would change at the time of takeoff and that would affect the performance of the aircraft to carry out that manoeuvre.
- Absence of risk management by the crews and Security of the company, to anticipate the conditions that could affect the aircraft performance on a limited runway with high ambient temperatures.
Six Safety Recommendations were made as a result of the findings of the Investigation as follows:
On 17 February 2022:
- that Aerosucre establish a Standard Operating Procedure to limit 737 takeoffs from Puerto Carreño to the hours of the day in which the ambient temperature is less high, in order to thereby favour aerodynamic and engine performance and provide improved margins of manoeuvre safety. [REC. IMD 01-202205-02-DAY]
On Completion of the Investigation:
- that Aerosucre schedule the execution of permanent audits of the dispatch function to verify strict compliance with the provisions of the General Operations and Dispatch Manual regarding the verification of complete briefings by the crew. [REC. 02-202205-02-DAY]
- that Aerosucre establish a more effective control mechanism in the area of Operational Control of the company in order to supervise and ensure that the inclusion in manifests of weight and balance, the exact number of occupants on board and their corresponding weight, is confirmed. [REC. 03-202205-02-DAY]
- that Aerosucre provide, as a proactive action, special training in CRM to its crew members, to include the use of standardised phraseology and adherence to clean room policies, using the present case study as an example, in order to guarantee and strengthen the compliance with the guidelines established by the company and national regulations of the actions of the crew in the development of air operations. [REC. 04-202205-02-DAY]
- that Aerosucre carry out an exhaustive and detailed review of the management, operation and processes of the Operational Safety Directorate of the Company including the update and the improvement of:
- The Company SMS Manual
- The Mechanisms for dissemination of the SMS program to company employees and their familiarisation with its contents
- Operational Safety indicators
- The updating, use, management and timely dissemination of Reports of Risk/Operational events (IRO)
- The review of hazard identification and risk assessment
- The review of management, activities and compliance with the functions established in the Operational Safety Executive Group (GESO). [REC. 05-202205-02-DAY]
- that the Secretariat of the Aeronautical Authority of Colombia make this Investigation Report known to regular commercial cargo Air Transport Operators, so that they apply the recommendations as appropriate and that, in addition, the Report be taken into account to improve the Management Systems of Operational Safety. [REC. 06-202205-2 DAY]
The Final Report was completed and released in Spanish only in April 2023.