Flight and Crew Information
The flight crew reported that the takeoff, climb, and cruise were uneventful. The No. 1 (left) thrust reverser was deferred per the minimum equipment list. The captain acted as pilot flying and check airman; the first officer was pilot monitoring completing operating experience training.
Approach and Landing
During the approach to Jacksonville Naval Air Station (NIP), the crew discussed two runway changes with air traffic control due to reported moderate to heavy precipitation near the field. They executed the area navigation GPS approach to runway 10, which was ungrooved with a displaced threshold 997 ft from the threshold, leaving an available landing distance of 8,006 ft. At 1,390 ft mean sea level, flaps were set to 30° and gear extended, but the speedbrake handle was not armed per the Landing checklist. At about 1,100 ft and 2.8 nm from the runway, the airplane was slightly above glidepath with on-target speed. Over the next minute, indicated airspeed increased to 170 knots (17 above target), groundspeed reached 180 knots with an estimated 7-knot tailwind. At 680 ft and 1.6 nm from the threshold, the airplane deviated further above the 3° glidepath, showing four white PAPI lights for the remainder of the approach. Eight seconds before touchdown, multiple enhanced ground proximity warning system alerts announced "sink rate" as descent rate peaked at 1,580 fpm. The airplane crossed the displaced threshold 120 ft above the runway (54 ft above on glidepath) and 17 knots above target speed, with a groundspeed of 180 knots and descent rate of about 1,450 fpm. It touched down about 1,580 ft beyond the displaced threshold (80 ft beyond the designated touchdown zone per the operator's SOP).
Accident Sequence
After touchdown, the captain deployed the No. 2 engine thrust reverser and began braking but reported not feeling deceleration and increased brake pressure. The speedbrakes deployed about 4 seconds after touchdown, likely triggered by right throttle movement into idle reverse after main gear spinup; this automatic deployment was delayed about 3 seconds compared to arming the speedbrakes before landing. The airplane crossed the end of the runway about 55 ft right of centerline, impacted a seawall 90 ft right of centerline, 9,170 ft beyond the displaced threshold, and 1,164 ft beyond the departure end of runway 10.
Post-Accident Evacuation
After the airplane came to rest in the St. Johns River, the flight crew initiated an emergency evacuation.