What happened
On August 1, 2018, at approximately 13:52 UTC, a Piper PA-28 aircraft registered TU-GAD crashed into the Ebrié Lagoon near Marchoux-Bingerville, Côte d'Ivoire. The aircraft was operated by the Aero Club of Abidjan for a training flight involving circuit patterns with touch-and-go landings. The flight departed from Runway 21 at Félix-Houphouët-Boigny International Airport (Abidjan) at 13:34 UTC, carrying an instructor pilot and a student pilot.
The aircraft had completed two successful circuits without incident. At 13:44 UTC, air traffic control authorized the Piper for a third departure on Runway 21, instructing the crew to report on the left downwind leg and hold due to the arrival of a Boeing B77W (Boeing 777). The Boeing aircraft was descending through FL50 toward the ILS approach for Runway 21.
At 13:49 UTC, the Piper pilot reported seeing the Boeing traffic. ATC instructed the Piper to join the long final behind the Boeing and warned of wake turbulence. At 13:52 UTC, the Boeing landed on Runway 21 and exited via Taxiway Bravo. Shortly after, the Piper's radar contact disappeared at an altitude of 700 feet, approximately 1.8 nautical miles from the VOR/DME. The aircraft was found submerged in the lagoon; both occupants were killed.
The investigation
The Bureau Enquêtes et Analyses des Accidents d'Aviation de Côte d'Ivoire (BEA-CI) investigated the accident. Key facts established included:
- The instructor pilot held valid licenses and qualifications, with over 2,800 total flight hours.
- The student pilot held a valid student pilot certificate.
- The aircraft was airworthy and maintained according to regulations.
- Weather conditions were VMC with light winds (8 knots), which favored the persistence of wake turbulence vortices at low altitudes.
- Radar data indicated that the separation between the Piper and the Boeing was less than 2 minutes and 30 seconds when the Piper disappeared from radar.
The investigation examined the sequence of events, maintenance records, and pilot qualifications. It determined there was no evidence of mechanical failure or system malfunction in the Piper prior to the accident.
Findings
The Piper PA-28 TU-GAD crashed due to a sudden loss of control caused by entering the wake turbulence generated by the preceding Boeing 777. The atmospheric conditions on the day of the event, characterized by calm air, allowed the wingtip vortices from the heavy aircraft to persist at low altitudes and descend below the flight path of the Piper. The pilot likely underestimated the risk of encountering this turbulence and failed to maintain adequate separation. The loss of control occurred at an altitude that did not allow for recovery.
Safety action
The BEA-CI issued safety recommendations to:
- ANAC (Côte d'Ivoire Civil Aviation Authority): To ensure compliance with aeronautical regulations regarding operational documents and training materials through periodic validations.
- Aero Club of Abidjan: To conduct periodic awareness campaigns on wake turbulence for all pilots and to integrate wake turbulence as a specific module in pilot training curricula.
- ASECNA and ATS Services: To define strategic holding sectors for VFR flights within the Control Zone (CTR) and to ensure controllers strictly adhere to standard phraseology regarding approach sequences.