Serious Incident Involving F/A-18 Formation and Falcon 900EX Near Frankfurt

Overview and Identification of the Event On 4 December 2008, the German Federal Bureau of Aircraft Accident Investigation (BFU) recorded a serious incident in Class C airspace five nautical miles west of Frankfurt/Main. The event involved a Dassault Falcon 900EX and a formation of two McDonnell Douglas F/A-18 D aircraft. The investigation was closed summarily under § 18 FlUUG, presenting only the facts. No personal, material, or third-party damage was reported. ## Sequence of Events At 13:22:21 local time, the closest approach occurred at a vertical separation of 300 ft and a horizontal distance of 1.2 NM. The F/A-18 D formation was flying IFR from Norway to Switzerland at FL370. The lead aircraft reported a low oil pressure warning on one engine, which required shutdown to prevent overheating. At 13:19:46, the crew requested a descent clearance to FL280, but the controller denied it due to traffic, promising clearance in about three minutes. After further analysis, the crew decided to shut down the affected engine. They informed the controller at 13:21:29 that they could no longer maintain FL370. The controller provided traffic information about the Falcon 900EX, which was two miles away and 2,000 ft below. The crew acknowledged and reported visual contact. The controller asked if the formation was in an emergency; the crew replied, “not yet, no.” At 13:21:56, radar showed the formation descending to FL367 without clearance. The controller asked if they could level at FL365, but the crew replied, “negative, we need to descend now, sorry.” The controller then instructed the formation to turn right toward the west. The crew confirmed, “right west, descending.” When asked if they could level at FL360, the crew stated, “unable negative, we need to descend level 250.” The Falcon 900EX was on an IFR flight from Rotterdam to Munich, flying southeast at FL350 in visual meteorological conditions. At 13:21:49, its controller instructed an immediate right turn to heading 090°. The crew confirmed at 13:21:56. The controller then provided traffic information about the F/A-18 formation, which was at 10 o’clock, 1,000 ft high, and descending. At 13:22:10, the Falcon crew reported visual contact. At 13:22:21, the crew reported a TCAS Resolution Advisory to climb, deactivated the autopilot, and initiated a climb. At 13:22:40, the crew reported, “Traffic terminated…” All aircraft continued their flights. The F/A-18 engine fault was later determined to be a sensor problem. ## Personnel and Aircraft The F/A-18 D is a two-seat, twin-engine multirole combat aircraft with a bubble canopy for improved visibility. It is not equipped with ACAS. The aircraft were registered in Switzerland and operated by the Swiss Air Force. The lead pilot held a valid type rating since 1998 with approximately 1,000 hours of experience. The wingman pilot held a valid type rating since 1998 with approximately 160 hours of experience. The Falcon 900EX is a three-engine passenger aircraft with a capacity of up to 14 passengers, used for short, medium, and long-range flights. It was registered in Portugal and operated by a Portuguese airline. The pilot-in-command held a valid Flight Crew License issued by the Joint Aviation Authorities, Kingdom of Belgium, since 2007, with more than 5,000 hours of experience. The co-pilot held a valid CPL(A) issued by the UK Civil Aviation Authority since September 2008, with more than 2,700 hours of experience. ## Meteorological and Airspace Information The Falcon crew reported visual flight conditions. According to the German Weather Service, the tropopause was at FL340, with clear skies and good visibility above. The incident occurred in Class C airspace, where both IFR and VFR flights are permitted. IFR flights are separated from all other flights. General minimum separation standards are 5 NM horizontal or 1,000 ft vertical. Because the F/A-18 formation was not approved for Reduced Vertical Separation Minimum (RVSM), the minimum separation standards were 6 NM horizontal or 2,000 ft vertical. ## Additional Information In response to the incident, the Chief of Flight Safety of the Swiss Air Force issued a Flight-Safety-Bulletin in January 2009. It recommended that all crews declare an emergency and set the transponder to 7700 as soon as possible in the event of any malfunction that could affect the aircraft’s flightworthiness. The bulletin also stated that setting transponder code 7700 would be consistently practiced in all F/A-18 simulator exercises going forward.