Synopsis
On 8 February 2005 at 1619Z, a Boeing B737-800, registration ZS-SJD, departed Johannesburg International Airport (FAJS) from Runway 21R on a scheduled domestic flight to Cape Town International Airport (FACT). The aircraft carried 2 pilots, 5 cabin crew, and 144 passengers. The surface wind was 120 degrees at 13 knots, producing a 90-degree crosswind from the left, with thunderstorm activity reported ahead of the runway.
Flight Details
During the takeoff roll, the captain observed that the aircraft accelerated slightly slower than expected at 70 knots indicated airspeed and suspected a flat tire. After becoming airborne, the aircraft began to roll to the right, prompting the captain to apply right rudder and 69.6 degrees of left aileron input to maintain directional control. The crew verified that no engine failure occurred, and the co-pilot adjusted engine power symmetrically. At the captain's request, the co-pilot declared a MAYDAY due to concerns about controllability near the ground. The captain then corrected the cross-control inputs, and the aircraft responded normally at approximately 1000 feet above ground level, climbing at 1100 feet per minute. The flight continued to Cape Town without further incident. There were no injuries and no damage to the aircraft.
Aircraft and Maintenance
The Boeing B737-800 was first registered on 6 December 2001. Its last Check A maintenance was certified on 7 February 2005 at 11,366.16 airframe hours; the aircraft had flown an additional 3.36 hours since that check. The responsible aircraft maintenance organization (J44/001) had been audited from 9 to 12 May 2004 with no major non-compliances identified.
Probable Cause and Contributory Factor
The investigation stated that the pilot induced approximately 4 degrees of right rudder and 69.6 degrees of left aileron wheel input (crossed controls) when the aircraft rolled to the right during take-off. This occurred with thunderstorm activities in close proximity to the airport. A contributory factor may have been that the crosswind component, combined with the thunderstorm activity ahead, allowed the pilot to over-react, aggravating the situation after take-off by providing the wrong rudder control input and creating a cross-control flight situation. The combination of control forces, roll-yaw coupling, and the presence of lateral acceleration in a cross-controlled sideslip condition can give the appearance of control problems or thrust asymmetry if the cross-control situation is not recognized.