Overview
On the afternoon of 19 December 2003, an agricultural topdressing aircraft operating from a strip near Mairoa, approximately 10 nautical miles south-west of Te Kuiti aerodrome, crashed during takeoff. The aircraft, registered ZK-BXZ, was engaged in spreading lime on a property. The accident occurred in daylight at around 1500 hours NZDT at an elevation of 1150 feet. The exact sequence of events leading to the crash could not be conclusively determined.
Sequence of Events
The pilot began work at approximately 0630 hours, departing from Te Kuiti aerodrome to an agricultural airstrip about eight nautical miles to the west. There, he completed a 150-tonne lime contract that had been started by two other aircraft the previous day. Refuelling occurred roughly every hour, and the pilot took a break when about four loads remained. By 1400 hours, the job was finished, and he flew to the strip from which he operated until the time of the accident.
Upon arrival, the pilot performed a reconnaissance flight with the pilot of aircraft ZK-EMW, discussed their sowing plan, and agreed on a 1.1-tonne load with the loader driver. Take-offs were made to the south-west, landings in the opposite direction. The loader driver reported that operations were proceeding smoothly and the pilot appeared to be in good spirits, at one point miming wiping his brow, which the driver interpreted as a comment on the heat.
During this period, a third company aircraft, ZK-JAL, arrived and shut down because the loader driver could only handle two aircraft at a time. The pilot of ZK-JAL flew a briefing sortie with the pilot of ZK-BXZ before the latter's planned departure. After each take-off, ZK-BXZ would turn left onto a downwind leg and cross over the loading end of the strip on the way to the sowing area. ZK-BXZ operated inward from the eastern boundary, while ZK-EMW worked from the western boundary.
Fresh lime was being trucked to the strip and placed in a large bin from which the loader replenished the aircraft. The lime was dry and free-flowing. As each load arrived, the farmer mixed a cobalt supplement into the bin. A truck driver who held a Commercial Pilot Licence took several photographs of the aircraft landing and taking off.
One photograph showed ZK-BXZ leaving the end of the strip on what was likely its penultimate take-off, with ZK-EMW on final approach on the reciprocal heading. On that occasion, ZK-EMW passed over ZK-BXZ just after the latter became airborne. The next photograph showed ZK-BXZ approximately two-thirds of the way down the strip with 20 degrees of flap set on its final take-off, with dirt being thrown up by the wheels as it hit soft spots.
The pilot of ZK-EMW initially reported that on his landing approach, he flew over ZK-BXZ while it was still on its take-off run. He later disputed this and claimed that ZK-BXZ had just become airborne when it disappeared from view under his right wing. ZK-BXZ only flew approximately 170 metres, so the proximity of the two aircraft was very close if ZK-BXZ was already airborne. The close proximity is significant as it is possible that ZK-BXZ, being the lower aircraft, may have encountered wake turbulence from ZK-EMW. The weather conditions were favourable for encountering wake vortices from the aircraft passing above.
The first indication of the accident was a loud bang heard by the farmer, who was mixing cobalt in the bin. Initially thinking it was a truck tailgate slamming, he looked toward the end of the strip and saw a plume of smoke. He immediately went by motorcycle to investigate. Upon arrival, he found the aircraft well ablaze and could not approach due to the heat.
As the accident occurred, a fourth company aircraft, ZK-EGV, arrived at the strip. The pilot did not see the impact but flew over the burning wreckage on approach. After landing, he went on foot to the accident site but arrived too late to assist. The loader driver used his fire extinguisher but could not help the pilot. After the extinguisher ran out, the fire flared up again, and those present could only await the Fire Service.
Investigation
The official investigation found that the pilot was properly licensed, rated, and fit for the flight. The aircraft had received regular maintenance and appeared airworthy prior to the accident. The engine strip revealed no reason why it would not produce full power. The aircraft was operating at the limits of its performance for the given conditions. The accident was not survivable. Despite these findings, it has not been possible to determine a conclusive cause for the accident.