What happened
On 22 April 1999, a Boeing B727-23, registration ZS-IJE, was performing a scheduled international flight from Harare to Johannesburg International Airport. While cruising at FL 350, the flight crew received clearance to land on Runway 03 at Johannesburg. As the aircraft began its descent, approximately 90nm from the waypoint JSV, radar indicated the presence of two small convective cells near the destination airport.
To avoid these cells, the pilot adjusted the indicated airspeed to 250 knots and maneuvered the aircraft to the east of the original track. During this avoidance maneuver, the crew encountered light turbulence. Roughly 10 nm after passing the convective cells, the aircraft entered a region of intense atmospheric activity at FL 200. The aircraft experienced a powerful updraft, climbing at a rate of 1500 to 2000 feet per minute while maintaining an airspeed of 230 knots.
During this period of instability, the aircraft was subjected to severe turbulence and heavy hail for approximately 30 seconds. The aircraft transitioned into visual meteorological conditions about one minute later. Despite the intensity of the encounter, the aircraft reached Johannesburg International Airport safely, and no injuries were reported among the crew or the 58 passengers on board.
The investigation
The investigation focused on the atmospheric conditions encountered during the descent and the subsequent physical state of the aircraft. The crew noted that the onboard radar had not previously indicated any significant returns that would have signaled the presence of hail. The investigation examined the sequence of the descent, the pilot's maneuvers to avoid convective cells, and the specific impact of the updraft and hail on the airframe.
Findings
- The aircraft encountered severe turbulence and heavy hail during its approach to Johannesburg.
- The encounter with the updraft and hail occurred approximately 10 nm after the crew had maneuvered away from identified convective cells.
- While the flight landed without further incident and with zero fatalities, the structural impact of the hail was catastrophic for the airframe.
- The aircraft sustained damage so extensive that it was deemed beyond economical repair.