What happened
On August 25, 1999, a mid-air encounter occurred near Buggingen, Germany, involving a McDonnell Douglas F4 Phantom and a COMCO Ikarus C42 ultralight aircraft. The ultralight was conducting a private flight from Bremgarten to a nearby landing site. Approximately six minutes after departure, while flying at roughly 2,050 feet AGL, the two aircraft crossed paths.
The F4 Phantom, performing a low-level training flight from Fürstenfeldbruck to Neuburg, approached the ultralight from the left. The crew of the jet attempted an evasive maneuver after spotting an object, but the aircraft passed the ultralight at a very close distance. Immediately following the pass, the ultralight entered the jet's wake turbulence and exhaust stream. The structural forces caused the wings of the COMCO Ikarus C42 to break off and the cockpit canopy to detach. The pilot of the ultralight successfully deployed the emergency system, allowing for a safe landing in a cornfield; however, the passenger sustained one minor injury.
The investigation
The BFU investigation focused on the visibility and reaction capabilities of both crews. Because the encounter occurred at 2,050 feet, the aircraft were operating in uncontrolled Class G airspace and were not monitored by air traffic control radar.
The investigation examined the flight parameters of the F4 Phantom, which was traveling at approximately 400 knots. While a 250-knot speed limit generally applies to flights below 3,000 feet, the investigation noted that military flight regulations for the Bundeswehr allow for higher planned speeds during low-level operations.
The investigation also assessed the visual limitations of the F4 crew. The pilot's view was partially obstructed by cockpit struts, and the Weapon Systems Officer (WSO) had even more restricted forward visibility due to his seated position behind the pilot. Calculations indicated that while the ultralight was theoretically detectable from 3,100 meters, the high closing speed of the jet left the crew with less than 13 seconds to react from the moment of potential detection.
Findings
- The primary cause of the accident was that the F4 Phantom passed the ultralight at an insufficient distance due to a delayed evasive maneuver.
- The crew of the F4 Phantom failed to identify the ultralight in time.
- The high approach speed of the F4 Phantom acted as a contributing factor to the lack of reaction time.