On 13 November 2020, a Boeing 727-100 (internally plated as 5Y-CIG but externally showing EY-724) was operating a non-scheduled international cargo flight from Nairobi to Kigali as TAK270 by Transafrican Air using the callsign designator of a former Russian operator Tatarstan Airlines (which had been required to cease operations almost seven years previously). After a late touchdown on the wet destination runway well to the left of the centreline following an ILS approach, it then partially exited the runway for approximately 1,000 metres before fully regaining it. The only occupants, the three man flight crew and two aircraft ground engineers, were uninjured but the aircraft and multiple runway edge lights were damaged.
An Investigation was carried out by the Aviation Accident and Incident Directorate (AAID) of the Rwanda Ministry of Infrastructure in accordance with the principles of ICAO Annex 13.
Despite attempts to establish which company was operating the aircraft at the time of the flight and who was employing the flight crew, this could not be definitively established. The only evidence of an AOC was one issued by the Tajkistan Ministry of Transport to an operator based in Dushanbe called ‘Waypoint Airways’ but no evidence could be found to confirm that this operator was active and all attempts to establish contact with the Civil Aviation Authorities in Tajikistan were unsuccessful.
It was noted that the externally visible aircraft registration was the Tajikistan registration EY-724 whereas the flight deck identification plate showed the registration 5Y-CIG (Kenya) and the operator of the aircraft as ‘Transafrican Air’. It was noted that an Investigation by the Kenyan authorities into a 2018 event involving the same aircraft when showing the external registration 5Y-CIG had recorded the operator at that time as Transafrican Air, although the same source showed the aircraft painted in the livery of an operator trading as ‘Lyca Cargo’ and based in Cotonou (Benin).
Prior to departing Nairobi on 13 November, the aircraft had not flown since 5 November when it had flown Entebbe-Nairobi-Juba-Nairobi. The holder of the aircraft CofA issued by the Tajikistan authorities was found to be a US-headquartered company called ‘Zone 4 International’ which had a base at Entebbe in Uganda. This company was also named on the aircraft Certificate of Registration as the aircraft owner with ‘Waypoint Airways’ as the operator.
Both pilots were DR Congo nationals and although it appeared that whilst both had formerly held licences issued by DR Congo which were the basis of licences issued by the Tajikistan Civil Aviation Authorities, the latter licences were invalid. The DR Congo authorities stated that they “did not recognise” the number of the licence carried by the Captain and added that they had never issued an ATPL to a person of that name. They also said that they had suspended the First Officer’s DR Congo licence in June 2017 “due to irregularities found on his file”.
The age and flying experience of the Captain, who was acting as PF for the investigated flight, could not be ascertained by the Investigation. The First Officer stated that he had a total of 2,300 hours flying experience of which 1,600 were on type. The Flight Engineer who was a national of both Argentina and Bolivia also had a licence issued by the Tajikistan authorities, in his case based on a licence originally issued by Bolivia. He stated that he had a total of 11,000 hours flying experience on type and also stated that the investigated flight was “his first flight for Zone 4 International”. It was concluded that the absence of valid flight crew licences alone meant that the flight had been operated unlawfully with “serious discrepancies” also present in respect of all other regulatory requirements for the operation of transport aircraft on international flights.
No data was available from the CVR or FDR since “Zone 4 International did not maintain a flight data analysis programme for the aircraft” but they had supplied detailed data from a GPS-based area navigation system which was installed on the aircraft which had provided data relevant to the Investigation. ATC R/T transcripts and a reliable eyewitness account of the landing were also available.
It was established that during a Cat 1 ILS approach to the 3,500 metre-long 45 metre-wide runway 28 at Kigali, the flight had been cleared to land by the APP controller because of the TWR controller’s inability to see the aircraft on short final due to poor visibility in moderate rain. The aircraft subsequently touched down approximately 1000 metres beyond the runway threshold close to the left hand edge (see the illustration below). The left hand main landing gear (only) then departed the runway and then the 7.5 metre paved runway shoulder and travelled parallel to it across taxiway ‘C’ before returning to the runway.
The initial aircraft ground track before (thick red line) and after (thin red line) touchdown. [Reproduced from the Official Report]
The aircraft left main gear was outside the marked runway width for 1,005 metres and off the adjacent paved runway shoulder for 577 metres. As taxi speed was reached, ATC advised the crew that “several” runway edge lights had been damaged and on request from the crew advised that the spot wind was 010°/14 knots (compared to the wind check given with the landing clearance which was 020°/11 knots). The aircraft was cleared to taxi to its allocated parking stand where all the cargo on board was unloaded with no evidence that the cargo had shifted during flight found.
In subsequent interviews, all three flight crew stated that the visibility during most of the approach was adequate with the runway in sight but at around touchdown they “were suddenly caught by heavy rain and crosswind from the right (and) as a result lost visibility and control of the aircraft”. The touchdown on the wet runway was reported to have been “soft or smooth” with no delay in deploying the spoilers and thrust reversers.
It was noted that the ATC windshear warning system had been activated about ten minutes prior to the previous aircraft, a DHC8-400 landing during a short period of heavy rain. However, by the time the 727 landed, this had changed to “light rain” although with standing water observed on the runway which had, according to a member of the airside operations team who was parked clear of but adjacent to the runway, “splashed up” when the 727 touched down. Soon afterwards, the rain stopped altogether.
Upon examination of the aircraft, damage to all six of its tyres caused by collision with a total of 15 elevated runway edge lights was found. The aircraft tailskid mechanism sustained significant damage with part of it found on the runway near to where the runway had been re-entered. An access panel on the No 2 engine was also found to be damaged. Examination of the left hand edge of the paved surface found that this had also been damaged.
It was found that Meteorological Office recorded weather radar data confirmed that a heavy rain shower had cleared the airport shortly before the 727 touched down with just light rain continuing briefly before stopping altogether as reported by witnesses.
An inspection of the runway surface shortly after the investigated landing found that the entire TDZ was covered with “a substantial layer” of accumulated rubber deposits from the tyres of landing aircraft. Although the airport operator stated that high-pressure water blasting using specialised equipment was periodically used to remove such deposits, it was not possible to find out on what basis this action was taken.
Why It Happened
Based on the available evidence, the Investigation considered various factors which might have caused or contributed to the runway excursion and concluded as follows:
- Pilot proficiency could not be assumed in the absence of any relevant evidence which could indicate this.
- Elements of a rushed/unstabilised approach were detected in a descent which was conducted 0.5° below the 3° ILS GS and an approach speed 10-15 knots above the applicable VAPP.
- Prevailing weather conditions, including an 11-14 knot crosswind component, were not considered to suggest that the approach and landing should have been “problematic for a well-trained and proficient crew”.
- Flight Management during the final stages of the approach could not be assessed in the absence of FDR data but it was considered that “since the flight came in low and fast and was drifting left of the runway centreline”, a go-around should have been initiated. It was also considered that damage to the tailskid mechanism was “a clear indication of an incorrect crosswind landing technique, resulting in an unusual high pitch-up and right roll attitude upon touchdown” which would have impaired forward visibility and corresponds to the pilots’ statements that they both “suddenly lost visibility during touchdown”.
- Viscous aquaplaning due to the combination of standing water, worn tyres and excessive surface rubber deposits was considered to have been extremely likely given the crew report of a soft/smooth touchdown on a surface with considerable rubber deposits which was further contaminated by standing water after the recent cessation of moderate to heavy rain. It was noted that the fact that all main gear tyres were “worn to the minimum acceptable limit” would have magnified the effect of this contamination. It was also calculated from the available evidence that despite one main gear travelling in mud, the calculated deceleration during the landing roll had been abnormally slow which itself could be taken as an indication of reduced wheel brake effectiveness.
- Rudder blanking (due to disruption of the airflow upstream of the rudder when reverse thrust is selected) was considered a possible factor in reduced directional control immediately after touchdown but it was not possible to be sure given that directional control would have also been compromised by the initially excessive nose up attitude.
Two Causal Factors were formally documented as follows:
- The crew not conducting a go-around when the aircraft had drifted to the left of the centreline on short final approach.
- Lack of proficiency of the Captain and First Officer resulting from:
- not being in possession of valid licences for the operation of the aircraft
- non-adherence to basic safety and quality standards by the aircraft operator Zone 4 International LLC
- deficient oversight by the Civil Aviation Authorities in Tajikistan, Uganda and Kenya.
Contributory Factors were also identified in respect of the decision to continue for landing when a runway excursion became unavoidable because of:
- an incorrect crosswind landing technique.
- subsequent skidding due to viscous aquaplaning once the aircraft was on the ground.
Seven Safety Recommendations were made as a result of the Investigation as follows:
- that the Rwanda Civil Aviation Authority (RCAA) and the Rwanda Airports Company (RAC) develop and implement a proactive method to assess the legitimacy of operators and their adherence to basic safety standards before allowing them to dispatch flights to destinations in Rwanda.
- that the Rwanda Airports Company (RAC) conducts regular rubber removal and have periodic friction tests for runway 10/28 at Kigali International Airport
- that the Investigation Authorities of Tajikistan and Kenya, in order to warrant effective drawing of safety lessons, ensure proper response to incident and accident notifications by the State of Occurrence as laid down in the ICAO Annex 13
- that the Civil Aviation Authorities of Kenya and Uganda verify the legitimacy of the AOC of an operator under their authority which operates an aircraft that is listed on a foreign Air Operator Certificate.
- that the Civil Aviation Authorities of Kenya and Uganda, in the event that an operator under their authority operates an aircraft carrying the registration of a foreign State, establish an agreement that regulates the oversight responsibilities between the State of the Operator and the State of Registration in accordance with Article 83 of the Chicago Convention.
- that the Civil Aviation Authorities of Tajikistan and Kenya resolve the discrepancy between the external Tajik registration mark EY-724 and the Kenyan registration 5Y-CIG on the identification plate in the cockpit of the Boeing 727 with MSN 21 19011.
- that the Civil Aviation Authorities of Kenya and Uganda resolve the ambiguity about the question of whether Zone 4 International (with a base in Entebbe, Uganda) or Transafrican Air (based in Nairobi, Kenya) is to be considered as the operator of the Boeing 727 with MSN 19011.
The Final Report of the Investigation was completed on 17 November 2021 and subsequently made available online.