Jet It Honda Jet HA-420 accident

At the time of the approach and landing, a Braking Action Advisory was in effect and a field condition NOTAM reported slush on the landing runway. The airplane was flying 11 knots faster than the prescribed approach speed as it descended through 1,000 ft with the engines at idle. The pilots continued the instrument approach and visually acquired the runway environment about 100 ft above ground level. The airplane crossed the runway threshold 9 knots faster than VREF (landing reference speed), and touched down 893 ft past the touchdown zone at a speed that was 3 knots faster than the speed assumed by the airplane flight manual (AFM) landing distances. The airplane began to decelerate; however, the captain called for maximum braking when he detected the deceleration to be insufficient to stop the airplane on the remaining runway. He applied the emergency brake and steered to the left to try to stay on the airport property. The airplane skidded sideways, departed the end of the runway, and travelled tail-first over the edge of a steep incline, which resulted in substantial damage to the wings and fuselage. When the airplane descended below 1,000 ft on the final approach segment of the flight, the thrust levers were at idle, contrary to the operator’s stabilized approach requirement. The operator’s standard operating procedures required that if an approach became unstabilized below 1,000 ft, the flight crew was to initiate a go-around and missed approach procedure. The crew did not initiate a go-around, but instead continued the approach, which resulted in a fast and long landing. This increased the runway length required to stop from that predicated on a nominal touchdown location. Further exacerbating the long and fast landing was the captain’s decision during the landing roll to fully engage the emergency brake. Per the AFM, this action would result in the anti-skid feature not operating and would increase the wet runway landing distance by 100%. Postaccident examination of both main landing gear tires revealed evidence of reverted rubber hydroplaning, consistent with a locked wheel skid. It is likely that the full application of the emergency brake put the airplane into a locked-wheel skid and reduced the braking performance of the tires. Postaccident examination of the braking system revealed no evidence of any preimpact anomalies or malfunctions that would have precluded normal operation. Performance calculations revealed that the wheel braking friction coefficient achieved during the landing was lower than that implied in the wet runway landing distances recommended by the AFM and specified in the FAA Runway Condition Assessment Matrix (RCAM) guidance for wet runways, consistent with the findings in other wet runway landing overruns investigated by the NTSB. Performance calculations and postaccident simulations of the airplane’s stopping performance indicated that even with the longer-than-nominal touchdown point and 3-knot fast airspeed at touchdown, the airplane might have stopped before the end runway had it achieved the wet runway wheel braking friction coefficient implied by the AFM wet runway landing distance recommendation, and would have stopped about 850 ft before the end of the runway had it achieved the wheel braking friction coefficient specified by the RCAM. Conversely, even with the 3-knot fast airspeed at touchdown and the lower friction coefficient actually achieved during the landing roll, the airplane would still have stopped on the runway had it touched down at the nominal touchdown point.

Verbatim NTSB analysis and probable cause from the NTSB dataset