BOEING 737-8UNITED AIRLINES INC

The abrupt application of brakes during taxi, which resulted in a sudden stop and caused a flight attendant to sustain a serious injury.

the early rotation of the airplane to an angle at which the fuselage contacted the runway. Contributing to early rotation was the Captain’s reaction to the erroneous V1 automated callout, likely assuming that the airplane was at or close to the correct Vr at the same time. The erroneous automated callout was likely due to a keystroke entry error by the FO when manually entering takeoff data for a newly assigned departure runway.

The first officer’s improper control inputs after the airplane touched down. Contributing to the severity of the damage was the flight crew’s lack of recognition that the speedbrakes were not armed, which led to their delayed deployment.

The tractor driver’s failure to confirm that the tow bar head/handle was secured correctly to the airplane.

Brake application before all three landing gears were on the ground, which caused the failure of the right main landing gear tires and resulted in tire fragments impacting the fuselage.