What happened
While operating on the takeoff roll for runway 18L, the captain was at the controls of the aircraft. The flight crew reported experiencing an airspeed stagnation, which was followed by a noticeable deceleration after the 'V1' callout had been made. Following this deceleration, the captain rejected the takeoff. However, the aircraft subsequently overran the runway.
The crew noted that the aircraft did not reach the computed V1 speed. According to USAIR procedures, the pilot not flying initiates the V1 call 5 knots prior to the computed V1 speed. For the specific takeoff conditions, the rotation speed (VR) was equal to V1, and the computed V1/VR was 132 knots, while V2 was 137 knots. The flight crew stated that the aircraft did not rotate during the roll; however, witnesses, including a tower controller, reported that the aircraft did rotate prior to the abort command.
The investigation
A review of the Cockpit Voice Recorder (CVR) indicated that the first officer called 'V1' and then 'R' (for rotate) before the takeoff was aborted. Data from the Digital Flight Data Recorder (DFDR) showed a small drop in airspeed of 1.92 knots at 128.63 knots, though the airspeed subsequently increased to 137.8 knots. An examination of the aircraft systems was conducted, but the investigation failed to explain the reported deceleration.