ATL93IA135

The flight was cleared for a visual approach. When the flight reached the visual descent point on the approach, the flight crew transitioned to the VASI. According to the pilot the airplane was stabilized on the approach. As the airplane approached the touchdown point, the first officer advised the pilot of a higher than normal sink rate; the airplane touched down hard on the runway. The pilot stated that the airplane touched down sooner than expected. Examination of the airframe revealed structural damage between fuselage stations 1338 through 1351. The digital flight data recorder readout from the incident landing revealed when compared to the three pervious landings that the noseup stabilator trim was twice as steep, touchdown airspeed was 8 to 14 knots lower, noseup elevator deflection was two to three times larger, and the maximum pitch attitude at touchdown was two to five times higher. According to the MD-88 takeoff and landing booklet, the landing airspeed for the incident landing should have been 133 knots.

On July 27, 1993, at 1620 eastern daylight time, a McDonnell Douglas MD88, N948DL, operating as Delta Air Lines Flight 822, collided with the runway during a landing at Charleston International Airport, Charleston, South Carolina. The scheduled domestic passenger flight operated under 14 CFR Part 121 with a valid instrument flight clearance. Visual weather conditions prevailed at the time of the incident. The airplane received minor damage and the occupants were not injured. The flight departed Atlanta, Georgia, at approximately 1520 hours.

According to the pilot, the flight was cleared for a VOR approach to runway 21 into Charleston. When they reached the visual descent point on the approach, the flight crew transitioned to the Visual Approach Slope Indicating system (VASI). The pilot further said that the airplane was stabilized on the approach above the prescribed airspeed stated in the MD-88 takeoff and landing booklet. As the airplane approached the touchdown point on the runway the first officer informed the pilot of a sink rate, and the pilot applied power. According to the pilot, the aircraft touched down firmly on the runway sooner than he expected.

Examination of the aircraft tail section revealed compression damage aft of fuselage station 1338 through station 1351. The structural damage included the vertical displacement of the tail skid, and deformation of surrounding skin material.

Digital Flight Data Recorder (DFDR) Readout

The following comparative data was recovered from the DFDR for three previous landings:

* the noseup stab trim during the incident landing was approximately twice that maintained during the three previous landings,

* the touchdown airspeed during the incident landing was 8 to 14 KIAS lower than that of the three previous landings,

* the nose-up elevator deflections made during the incident landing were two to three times larger than those made during the three previous landing,

* the maximum pitch attitude at touchdown during the incident landing was two to five times larger than the maximum pitch attitude at touchdown during the three previous landings.

Summary of Incident and Prior Landing

***************************************************************** Comparison Item | Incident landing | Landing Prior to ***************************************************************** max nose-up stab| -10.9 | -5.8 trim, degrees ----------------------------------------------------------------- speed at | 120.5 | 134.8 touchdown, KIAS ----------------------------------------------------------------- pitch ,degrees, | +11.2 | +4.1 at touchdown ----------------------------------------------------------------- max nose-up, | 10 | 3 elevator during 3 seconds prior to touchdown,deg ----------------------------------------------------------------- Max Vertical Gs | 1.89 | 1.16 at touchdown ----------------------------------------------------------------- max flaps during| 28 degrees | 28 degrees final approach & at touchdown *****************************************************************

According to the MD-88 takeoff and landing speed booklet, at an aircraft weight of 122,500 pounds and 28 degrees of landing flaps the landing airspeed is 133 knots indicated (see attached copies from the MD-88 Takeoff And Landing Speed Booklet).