What happened
Two distinct incidents involving the Boeing McDonnell Douglas DC-10 occurred at Amsterdam Airport Schiphol within a year of each other. On December 18, 1999, a DAS Air Cargo flight, operating N800WR, experienced an uncontained engine failure in its tail engine during the takeoff roll. The failure caused engine components to be ejected from the engine casing, penetrating the fan section cowling and striking the elevator. This resulted in severe damage to the engine and the aircraft' and forced an immediate aborted takeoff.
On September 7, 2000, a Continental Airlines DC-10-30, registered N15069, experienced a similar uncontained failure in its left engine during its takeoff roll at the same airport. In this instance, components from the low-pressure turbine were thrown through the engine nacelle. While the aircraft's fuselage and wing fuel tanks remained intact, the event necessitated an aborted takeoff.
The investigation
The investigation examined the mechanical failures of both engines. For the DAS Air Cargo incident, investigators focused on the bellmouth assembly, a component of the engine inlet located between the engine and the airframe. For the Continental Airlines incident, the inquiry centered on the structural integrity of the low-pressure turbine nozzle locks.
Findings
In the case of N800WR, the investigation determined that the most likely cause was the failure of the bellmouth assembly, which was sucked into the engine. Evidence suggested that a mounting bracket for this component had become detached, potentially due to improper installation during maintenance.
Regarding the Continental Airlines incident, the investigation established that the failure was caused by the simultaneous failure of all nozzle locks in the second stage of the low-pressure turbine. This allowed turbine segments to rotate out of place and be ejected from the engine. The failure was attributed to intercrystalline cracking caused by unforeseen thermal and time-dependent stresses (creep and fatigue) that the original component design had not sufficiently accounted for.
Safety action
Following the Continental Airlines incident, a safety recommendation was issued to the engine manufacturer, General Electric, to develop an improved nozzle lock design capable of withstanding fatigue loads. The manufacturer subsequently introduced a new design featuring a thicker diameter and a doubled number of locks in the second turbine stage. Since the implementation of these design changes, no further incidents of this specific nature have been reported.