Negligence by maintenance technicians appears to have been the cause of an accident involving a Kitty Hawk DC-8-63 freighter during take-off from Seattle-Tacoma International Airport on 19 February.
Although the US National Transportation Safety Board (NTSB) is still investigating the accident, the investigator in charge tells ATI the agency understands that, after performing maintenance on the DC-8, mechanics did not secure the latches of the nacelles for the aircraft's number one and number two engines prior to its departure.
The maintenance mistake caused the entire nacelles of both engines to fall off the aircraft during and shortly after its take-off rotation, with the aircraft leaving nacelle debris on the SeaTac runway and part of one of the nacelles falling into a residential neighbourhood south of the airport.
Although the DC-8's pilots received very little indication from the DC-8's instruments and handling that anything might be amiss with the aircraft, they brought it back to SeaTac for a safe landing after air traffic control informed them that the DC-8 had shed debris on to the runway.
None of the three crewmembers known to be aboard the freighter was injured and no-one on the ground was hurt despite a piece of one nacelle falling into a residential area. The NTSB believes it is possible that - but does not yet know if - a mechanic was also travelling in the DC-8's flightdeck jump-seat, but if so that person was also uninjured in the accident.
NTSB investigator in charge Greg Nesemeier says "the basic scenario is that in the course of maintenance over several shifts", mechanics failed to secure the nacelle latches for the two JT3D engines slung on pylons below the DC-8's left wing.
Nesemeier says the NTSB is still gathering information from and conducting interviews with Kitty Hawk staff, so has not yet been able to determine the exact sequence of events.
However, the investigator is clear that the damage to the aircraft caused by the shedding of the nacelles was bad enough for the NTSB to determine that it met the FAR Part 830 definition of substantial damage required for the agency officially to consider the occurrence as an accident.
"There was a variety of damage to the left wing and the left horizontal stabiliser," states Nesemeier.
In addition to the scuffing, dents and scrapes to the wing and horizontal stabiliser that he says might be expected from such an occurrence, Nesemeier says the shed nacelles also caused "fairly significant holes" in part of the left wing and left horizontal stabiliser.
Furthermore, the nacelles blowing off caused a dent in the upper surface of the left wing, which Nesemeier says appears to "have dented in the rib to a depth of about a quarter of an inch". The incident also caused tears in the sheet metal of the leading edge and both the upper and lower surfaces of the left wing.
The NTSB investigator says that according to unconfirmed hearsay - the only evidence he has until the necessary interviews are conducted - the only indications of the incident that the crew of the aircraft received after the DC-8 took off was the illumination of a generator warning light and what seemed like a very slight list of the aircraft to the left.