What happened
The flight crew held for approximately seven to ten minutes upon arrival due to a thunderstorm and lightning activity over the airport. After another aircraft, a Beech Baron, landed, they initiated an Instrument Landing System (ILS) approach. The approach required an eight to ten-degree crab angle to compensate for crosswind conditions on final approach. The first officer was piloting the aircraft during this phase.
The first officer reported encountering wind shear at an altitude of 50 to 100 feet above ground level (AGL). He noted that only slight rudder input was necessary to straighten the aircraft. Following a normal touchdown, speed brakes and reverse thrust were deployed. However, the aircraft began to veer to the left, prompting the cancellation of reverse thrust.
The first officer applied rudder and brakes, but reported that braking effectiveness was nil. An attempt to re-engage reverse thrust was made subsequently. Despite these efforts, the aircraft departed the right side of the runway. Post-accident inspection revealed scrubbing marks along the runway surface from approximately 1300 to 3500 feet down the strip.
The investigation
Examination of the runway conditions indicated that the surface was not grooved. Additionally, the runway possessed a gradient of less than one percent. This gradient fell below the recommendation provided by FAA Circular AC No: 150/5325-2C, which suggests a minimum gradient for optimal drainage and performance.
Findings
The investigation highlighted that braking was nil during the rollout, contributing significantly to the overrun. The lack of runway grooving and the insufficient gradient may have exacerbated the situation, particularly given the wet conditions implied by the thunderstorm activity.