What happened
The flight operated between Honolulu and Lihue under daytime visual meteorological conditions. The captain authorized the first officer to act as the flying pilot for the route, which proceeded without mechanical issues until the approach to Lihue. The first officer established a 3-degree descent profile with stabilized engine thrust and a stabilized rate of descent.
Data from the digital flight data recorder (DFDR) shows that approximately one second before touchdown, the aircraft's rate of descent was roughly 384 feet per minute, which exceeded normal parameters, while the pitch attitude was 8 degrees nose up. The resulting hard landing and tail strike caused several passenger cabin oxygen masks to dislodge from their ceiling compartments and caused deformation to the aft empennage.
Following the event, the flight crew performed a post-flight walk-around and reported no visible damage to the airframe. The aircraft subsequently departed with passengers and completed several more flights.
The investigation
A follow-up maintenance examination revealed that the airplane's tail bumper compression indicator was in its normal horizontal position, having been compressed by approximately 2 7/8 inches. The design of the DC-9 specifies that a tail strike causing 3 or more inches of compression should move the indicator from a horizontal to a vertical position to alert personnel to the severity of the event.
Digital flight data recorder analysis indicated that the maximum vertical acceleration recorded during the impact sequence was 2.33 g's.