BOEING 737United Airlines

United Airlines flight 716, came to a sudden stop while taxiing out of the gate area and trying to make a turn onto taxiway C at Phoenix Sky Harbor International Airport (PHX), Phoenix, Arizona. As a result of the abrupt stop, one flight attendant (FA) sustained a serious injury. The event flight returned to the gate and emergency medical services were called. Flight 716 was a scheduled passenger flight from PHX to Newark Liberty International Airport (EWR), Newark, New Jersey, with a planned departure time of 0700 MST. The flight crew reported that this was the first flight of the day. The captain was the pilot flying, and the first officer (FO) was the pilot monitoring. According to the flight crew, there were no operational pressures, and following a normal pushback and engine start-up, the airplane was positioned on Taxiway Z facing north, holding short of Taxiway C, where they contacted Airport Traffic Control Tower (ATCT) ground control for taxi clearance (see figure 1). Ground control issued the standard southbound taxi route, which they had reviewed during the pilot briefing. The captain confirmed the instructions with the FO that they would turn right on Taxiway C, then right on Taxiway S, holding short of Taxiway D. According to the flight crew, while taxiing at a speed below 10 knots, the FO noticed they were beginning to pass Taxiway C. The FO alerted the captain that they needed to turn right to enter Taxiway C. The captain applied the brakes to assist with the turning maneuver, using what he recalled felt like normal pressure. Initially, everything seemed normal, but shortly afterward, the flight crew indicated that they felt that the brakes responded more aggressively than expected, causing the airplane to come to an abrupt stop. Both crew members confirmed there was sufficient space to complete the turn safely. Figure 1. Image of the taxi route for flight 716. (Source: United Airlines) According to the forward FA’s, after the airplane had departed from the gate and was taxiing out to the runway, they had started showing the safety demonstration video. Shortly after that, the airplane came to an abrupt stop. Both FAs were in the forward galley at the time and were thrown into the metal counter and safety latches. Each reported experiencing sharp pain in the neck, back, and legs as a result of the sudden jolt. As the airplane entered Taxiway C, the flight crew received a call from one of the forward FA’s indicating that the other forward FA was injured and she needed to go back to the gate. The flight crew coordinated with PHX operations, ramp, and ground control to return to the gate. Paramedics met the airplane at the gate and transported the injured FA to the hospital where they were diagnosed with a serious injury. According to United Airlines, their maintenance personnel conducted a post-accident general visual inspection of the airplane’s brake system and reported no anomalies were found. The airplane was subsequently placed on jacks, and the wheels were manually rotated. No evidence of brake dragging or grabbing was observed during this procedure. The brake system was cycled multiple times while the wheels were spun, and no faults or irregularities were identified. A review of maintenance history for this airplane showed that there were two maintenance entries for the braking system in the previous 90 days. Both entries were due to broken clips and were not related to braking actions.