Incident Overview
A flight crew rejected a takeoff on runway 18L after observing an airspeed stagnation followed by a noticeable deceleration following the V1 callout. The captain, who was at the controls, initiated the rejection, but the aircraft overran the runway.
Crew Accounts and Procedures
The crew reported that the aircraft never reached the computed V1 speed. According to USAir procedures, the pilot not flying initiates the V1 call 5 knots prior to the computed V1. For the takeoff conditions, rotation speed (VR) was equal to V1.
Cockpit Voice Recorder and Flight Data Recorder Findings
Analysis of the cockpit voice recorder (CVR) revealed that the first officer called "V1" and subsequently "R" (rotate) before the abort was initiated. The digital flight data recorder (DFDR) indicated a small decrease in airspeed of 1.92 knots at 128.63 knots, but the airspeed then increased to 137.8 knots. The computed V1 and VR were 132 knots, and V2 was 137 knots.
Witness Observations
The flight crew stated that the aircraft did not rotate prior to the abort. However, witnesses, including a tower controller, reported that the aircraft did rotate before the takeoff was rejected.
Aircraft System Examination
An examination of the aircraft systems did not identify any factor that could explain the reported deceleration experienced during the takeoff roll.