Occurrence
On 22 November 1999 at 12:30 CET, a single-engine, two-seat Pilatus PC-9/B training aircraft departed from Kiel-Holtenau for a naval exercise in the Lübecker Bight (Baltic Sea). Operating as a target drone (ZD), the aircraft, occupied solely by the pilot, was to perform several approaches from different directions toward a German Navy supply vessel (tender). The PC-9/B approached the exercise object at low altitude above the water surface. Shortly before reaching the ship, the ZD executed a steep climb and immediately entered a tight right turn. During the departure from the tender, the ZD assumed a knife-edge attitude. While maintaining this bank angle, the altitude continuously decreased until the right wing contacted the water. The aircraft broke apart and sank immediately. The accident occurred at 12:47 CET under good visual meteorological conditions.
Investigation Findings
The accident site was located 1 km south of Grömitz in the Lübecker Bight, with the wreckage resting in 9 m of coastal water. Recovery efforts were initiated by the exercising ship, and the pilot was recovered deceased. The wreckage was transported to a hangar at Lübeck Airport for technical examination. It was determined that the ejection seat had not been activated but had broken out of the airframe. Witnesses, including individuals on the beach promenade and a fisherman, observed the low pass, abrupt pull-up, and the extreme bank angle of approximately 80-90°, which was maintained until water contact. Engine sound was reported as normal. Radar data from German Air Traffic Control (DFS) showed the aircraft reaching a maximum altitude of 3700 ft before descending for the approach; recording ended at 1900 ft. The aircraft's GPS unit had lost data due to saltwater damage.
Technical inspection of the wreckage revealed that the aircraft was intact at impact, with landing gear and flaps retracted. The power lever was near idle. All fractures and deformations in the mechanical flight controls were attributable to impact. The engine and propeller were complete and in good condition; propeller blade angles varied and showed bending consistent with power at impact. The engine's electronic monitoring unit recorded no faults. The vertical acceleration indicator displayed a current reading of +7g, with peak indicators near -5g and +10g; routine readings had never exceeded +5g. No cockpit instrument markings showed impact damage. The aircraft was not equipped with a radar altimeter.
Operationally, the flight manual (FOM) specified a minimum altitude of 100 ft above water for target profiling, with a legal minimum of 500 ft unless a waiver was granted. A waiver existed for the exercise area allowing descent to 100 ft. However, Navy trainers expressed a general desire for target drones to approach "as low and undetected as possible." No formal request for altitudes below 300 ft was documented; such flights were not part of the contracted performance scope.
Medical Examination
An autopsy conducted by the Institute of Legal Medicine in Lübeck determined that the pilot died from impact-related injuries. No evidence of alcohol or incapacitating drugs was found. Chemical-toxicological analysis revealed caffeine and acetylsalicylic acid; the latter was assessed as not likely to impair flying ability, though it may indicate minor pain or blood-thinning therapy. Histological examination of heart muscle tissue showed both a scarred, prior local inflammation or ischemia and evidence of acute insufficient blood supply. The pilot's last aeromedical certificate noted a pre-existing cardiac disorder. Review by the German Federal Aviation Office (LBA) revealed that since 1992, the pilot had been under specialist treatment for a cardiac conduction disturbance and arrhythmia. The cardiological expert concluded that the aero-medical examination center should have declared the pilot unfit in 1992, or at the latest by 1999. The pilot's medical fitness for target drone operations had not been properly evaluated. The BFU-commissioned expert opined that existing medical guidelines could ensure pilot fitness if consistently applied.