What happened
On May 1, 2005, an Aeropro FOX micro light aircraft, registration PH-3V9, was involved in an accident during a local flight departing from an ultralight airfield in Grubbenvorst. The aircraft was carrying a pilot and one passenger. Weather conditions were favorable, with visibility exceeding 10 km and light winds of approximately 3 knots.
Prior to takeoff, the pilot noted that the grass runway was wet and contained puddles. To assess the surface friction, the pilot taxied the length of the runway and observed significant resistance. After returning to the start of the runway, the pilot attempted the takeoff roll. During the acceleration phase, the pilot noticed that the aircraft's speed was increasing very slowly. Despite the approaching end of the runway, the decision was made to proceed with the takeoff rather than aborting. The pilot rotated the aircraft at approximately three-quarters of the runway length. Shortly after liftoff, the airspeed dropped rapidly, causing the aircraft to stall and roll over the right wing, ultimately crashing upside down in a nearby field. Both occupants escaped no injuries, though the aircraft sustained heavy damage.
The investigation
The Dutch Safety Board conducted a limited investigation due to the non-international certification standards for micro light aircraft. A key focus of the inquiry was the aircraft's weight and balance. Because no formal weight calculation had been performed prior to the flight, investigators estimated the total weight based on the pilot, passenger, fuel, and equipment.
This estimation placed the total weight at approximately 509 kg, which exceeded the maximum takeoff weight of 472.5 kg by roughly 36 kg, or over 7%. This overweight condition likely compromised both the aircraft's acceleration capabilities and its stall speed.