N638DL

On October 4, 1993, at 1720 eastern daylight time, a Delta Air Lines Boeing 757-232, Flight 594, N638DL, collided with the runway during an attempted takeoff from International Airport, Fort Lauderdale, Florida. The scheduled, domestic, passenger flight operated under 14 CFR Part 121 with an instrument flight clearance. Visual weather conditions prevailed at the time of the incident. The airplane sustained minor damage, and none of the 95 occupants was injured. The flight departed Fort Lauderdale, at 1720 hours.

According to the pilots, during the takeoff roll, "the aircraft bounced forward and aft" (rearward), and as the airspeed approached 128 knots, the nose pitched up. At this point the pilot stated that he applied full power and continued the climb (see attached airworthiness release). Seconds later, a flight attendant seated in the rear of the airplane reported that she thought that the tail of the airplane struck the runway (see attached NTSB Form 6120.1/2 with crew statements). The flight returned to Fort Lauderdale and landed without further incident.

Examination of the airplane revealed a six-foot long scrape mark on the bottom of the fuselage near the aft pressure bulkhead. Further examination revealed a buckle in the lower panel of the pressure bulkhead assembly. Examination of the aircraft flight control systems failed to disclose a mechanical malfunction or component failure.

The aircraft digital flight data recorder (DFDR) was removed for data readout and evaluation. The recovered data disclosed that,

at 0039:30 elapsed time, at an indicated airspeed of 95 knots, elevator deflection began to change from a negative to a positive value. Three seconds later, at an indicated airspeed of 108.5 knots, pitch attitudes began to increase as well. At 0039:37 elapsed time, elevator deflection angles attained maximum values, and one second later, at an indicated airspeed of 126 knots, pitch angle reached a maximum value of +11.25 degrees nose up while the air/ground parameter changed to the "air" state. Pitch angle values then decreased concurrently with elevator deflection angle value. At 0039:41 elapsed time, the air/ground parameter changed back to the "ground" state. At 0039:42 elapsed time, at an indicated airspeed of 140 knots, the air/ground parameter changed to "air" and remained in that state for the remainder of the flight.

Data from the previous take-off was also examined. The data revealed that elevator deflection began to move from negative to positive values at an indicated airspeed of 136.5 knots.

Additional review of the DFDR data revealed no N1 engine speed changes until after the aircraft had established a positive rate of climb. Further review of the DFDR data did not disclose a pitch angle in excess of +10.0 degrees on the previous flight until the aircraft was well into the positive rate of climb; a corresponding reduction in engine N1 speed was also noted at that time. The previous flight liftoff occurred at 151 knots and at 6.855 degrees of nose up pitch.

A review of the final weight and balance data revealed the following computed takeoff airspeeds for Flight 594: V1-128, VR-130 and V2-135 (see attached V speed definitions).