N656DL

HISTORY OF FLIGHT

On June 2, 1999, about 2026 hours mountain standard time, a Boeing 757-232, N656DL, was substantially damaged during a hard landing at the Phoenix Sky Harbor International Airport, Phoenix, Arizona. The airline transport certificated captain, first officer, 6 flight attendants, and 119 passengers were not injured. The flight was operated by Delta Air Lines, Inc., on an instrument flight plan under 14 CFR Part 121 as Flight 491, a scheduled domestic passenger flight. The flight originated from the John F. Kennedy Airport in New York about 1831 eastern daylight time. Visual meteorological conditions prevailed during the landing at Phoenix.

Air traffic control cleared the airplane for a visual approach to runway 26R. The captain, who was handling the flight controls, reported that all phases of the flight up to the landing were uneventful. He described the landing as being "firm," and in the runway's touchdown zone, close to the centerline. There was a maintenance carry over (MCO) disabling the auto-spoiler deployment system, so the first officer manually deployed the spoilers upon touchdown. Thereafter, the airplane's nose pitched upward. The captain stated he then applied forward pressure to the control yoke. The captain additionally reported that he "felt a jolt" as the nose gear returned to the runway.

The first officer also provided a statement regarding the landing events. He concurred with the captain's statements. After landing, the airplane taxied to the gate. The event was originally reported by Delta as being a hard landing incident. However, a subsequent examination of the airplane revealed substantial airframe damage.

PERSONNEL INFORMATION

Captain.

The captain had about 17,000 total flight hours. His experience flying the Boeing 757 was about 1,446 hours. He had flown this type of airplane for about 185 hours during the preceding 90 days.

First Officer.

The first officer had about 8,000 total flight hours. His experience flying the Boeing 757 was about 1,007 hours. He had flown this type of airplane for about 52 hours during the preceding 90 days.

AIRCRAFT INFORMATION

The airplane was maintained by Delta on a continuous airworthiness program. Its total airframe time was about 32,594 hours.

METEOROLOGICAL INFORMATION

At 1956, Phoenix reported its surface wind was from 240 degrees at 10 knots, and the visibility was 10 miles. There were few clouds at 20,000 feet.

AIRPORT AND GROUND FACILITIES

Runway 26R is 11,001 feet long by 150 feet wide.

FLIGHT RECORDERS

The airplane was equipped with a digital flight data recorder (DFDR), which was removed from the airplane and read out by the National Transportation Safety Board's Vehicle Recorders Laboratory in Washington, D.C. Data for various parameters including altitude, indicated airspeed, magnetic heading, vertical acceleration, engine power, and control surface and airplane orientation (i.e. pitch, roll) was extracted. The parameters for the positions of the control columns and spoilers was not recorded.

The DFDR data indicates that approximately 3 seconds prior to touchdown, the pitch attitude started increasing in response to nose up elevator inputs. The aircraft was descending at 650 feet per minute at approximately 125 knots. When the aircraft was 33 feet agl and at 2.6 degrees pitch, the elevators start to be increased from approximately 0 degrees. The pitch of the airplane increased as the elevators are deflected to 8.5 degrees airplane nose up. The airplane reached a maximum pitch of about 5.8 degrees, a roll right attitude of 3 degrees. The airplane initially touched down (transitioned from air to ground) at an indicated airspeed of 124 knots, and reached a maximum vertical acceleration of 1.36 g's. The next DFDR sample of the air to ground parameter showed a transition back to "air" while the pitch remained close to 5 degrees and the vertical acceleration dropped to 0.6 g's over the next 2 seconds.

The second air to ground transition occurred 3 seconds after the first transition. The indicated airspeed was 121 knots, and the vertical acceleration quickly changes from 0.6 g's to 1.64 g's in 0.5 seconds. The elevator positions changed over the next second from plus 6 degrees to minus 16 degrees and reached a maximum of -20 degrees 1 second later. In response to the elevators, the pitch attitude rapidly decreased from 3.5 degrees to -0.7 degrees at a rotation rate of 4 degrees per second. As the airplane rotated nose down, a maximum vertical acceleration of 1.77 g's is reached as the longitudinal acceleration increases from zero to -0.28 g's. (See the Flight Data Recorder Factual report for additional details.) The Delta participant reported no evidence of any mechanical malfunctions during the landing event.

WRECKAGE AND IMPACT INFORMATION

The airframe examination revealed no evidence of a tail strike. The main landing gear was undamaged. A summary of principal airframe structural damage is as follows:

1. Buckled nose gear wheel well aft bulkhead; 2. Buckled skin on both sides of the nose gear wheel well bulkhead; and 3. Damage to associated underlying structure.

ADDITIONAL INFORMATION

The Safety Board did not take custody of the airplane.