Iai GULFSTREAM200 N500AG incident near Jamestown, New York

Probable cause

The pilots’ failure to effectively use the airplane's primary (brakes), secondary (thrust reversers), and emergency braking systems to decelerate the airplane, which resulted in a runway excursion. Contributing to the accident was the pilots’ failure to conduct a go-around maneuver upon recognizing that the airplane had excessive airspeed while on final approach to the runway.

NTSB analysis

The pilot flying (PF) and the pilot monitoring (PM) were completing an airman competency check under the observation of a Federal Aviation Administration inspector. Following an uneventful flight, the pilots configured the turbofan-powered, transport-category airplane for landing on the 5,299-ft-long, dry runway. A review of the cockpit recorder (CVR) transcript revealed that, during the practice instrument landing system approach, the PM warned the PF that the airplane was approaching the runway at an airspeed 15 knots higher than its specified approach speed (Vref) as it descended to within 100 ft of the ground. The PM also warned the PF not to allow the airplane's airspeed to increase because the runway was "short." The airplane subsequently touched down within the airplane's touchdown zone about 1,000 ft beyond the runway threshold. The PM reported that he attempted to slow the airplane by applying the brakes and deploying the thrust reversers, but the airplane continued off the departure end of the runway and came to rest about 40 ft beyond its pavement.

The runway distance required for the landing was calculated using the airplane manufacturer's Airplane Flight Manual. It was determined that, given the airplane's loading and configuration and the weather and runway conditions, sufficient runway was available for the landing. The landing distance calculations were predicated on the airplane crossing the runway threshold at Vref and did not account for the use of reverse thrust during the landing roll. Postincident examination of the airplane's braking and thrust reverser systems revealed no evidence of any mechanical anomalies that would have precluded normal operation.

Although the PF reported in postincident statements that the braking action during the landing was "nil," a review of the CVR transcript showed that neither of the pilots mentioned poor braking performance during the landing roll nor did they attempt to activate the emergency braking system. Additionally, the operator's chief pilot, who had been seated in the cabin during the flight, reported that the braking system cycled several times during the landing roll and that, although the reverse thrust system appeared to activate, he did not "feel or hear" a pronounced application of reverse thrust. Although the electronic engine control system recorded a limited set of parametric data during the landing, airspeed was not a recorded parameter. Analysis of the recorded data revealed that, about 3 seconds after touchdown, the throttle lever angles (TLA) were positioned for deployment of the thrust reversers and that the thrust reversers subsequently deployed; however, the TLAs remained at an idle-thrust position. The TLAs did not increase to the maximum reverse thrust position until about 17 seconds later, at which time, both engines increased power for about 8 seconds.

Although the use of reverse thrust was not required for the landing, nor was the airplane's computed landing distance reflective of the use of reverse thrust, the PF's apparent delayed application of reverse thrust suggested that he may not have used maximum effort in his attempts to decelerate the airplane during the landing roll even after the outcome was in doubt. Additionally, although an exact account of the airplane's airspeed was not available for postincident analysis, the PM's airspeed callouts suggested that the airplane's airspeed while on final approach to the runway, and potentially throughout the touchdown, increased the total required landing distance. If the pilots had recognized this earlier in the approach, they could have conducted a go-around and avoided the possibility of a runway overrun. Alternatively, upon realizing that the airplane was not decelerating as desired, the pilots could have used all available means to slow the airplane during the landing roll, including the timely and complete activation of the airplane's thrust reversers, and if necessary, activation of the emergency braking system.

Text from the NTSB. Open the NTSB docket for ERA13IA294 for the full record.