Incident Overview
Mechanics conducting engine tests in a Boeing 737 performed a high-speed taxi down Runway 26L. At the same time, a Cessna 172N, registration N737AV, was on final approach to land. The tower controller instructed the Boeing mechanics to exit the runway at midfield and "continue in the turn onto the parallel taxiway no delay off please."
Sequence of Events
One minute after the initial instruction, the mechanics requested clearance to proceed to the gate. The controller directed them to contact ground control. Following the turn onto the parallel taxiway, the Boeing came to a stop. The mechanics did not contact ground control until after the accident, which occurred 1 minute and 45 seconds later.
Meanwhile, the tower controller told the Cessna pilot to exit the runway at the same taxiway and then contact ground control. The controller stated that he cleared the Cessna based on the assumption that the Boeing would not stop. The Cessna exited the runway and stopped at the hold short line. The Cessna was then instructed to taxi northbound, crossing behind the Boeing.
As the Cessna began to move, the Boeing started powering up to resume taxiing. The jet blast from the Boeing resulted in substantial damage to the Cessna.
Statements from Mechanics
The mechanics reported that after turning onto the taxiway, they stopped and set the brakes while tuning the radio to the ground frequency. They said they then increased engine power to 40 to 50 percent N1 to begin taxiing again when they heard about "blasting the Cessna." At idle power, N1 was 21 percent.
Aircraft Specifications
A Boeing spokesman stated that break-away thrust for an empty Boeing 737 was 25 percent N1, while a fully loaded aircraft required 35 percent N1.