The aircraft track nearing OBVUP created a sharp closing angle on the OBVUP-GAGBU track. As the aircraft neared the OBVUP waypoint, the course track bar on the GPS would have moved very quickly toward the GAGBU waypoint. Due to the maximum rate of turn that an autopilot system allows, the aircraft would have flown through the OBVUP-GAGBU track before regaining course. To prevent this, a pilot would have to manually take control and initiate a steep turn. In an attempt to intercept the OBVUP-GAGBU course, an inexperienced pilot may try to follow the track bar using an increasingly steep bank angle. If this steep bank angle is left uncorrected, a spiral dive will result.
The PIC and owner started their day in Calgary at 0800 (0500 local) and had been travelling for more than 15 hours. The training in Buttonville was carried out under conditions of high heat and humidity. During the final minutes of the flight, it is likely that the PIC and owner were task saturated. Although fatigue is not supported by any factual information received, the lengthy day may have exacerbated the level of task saturation. When a pilot is task saturated, the increased load on the conscious brain raises the potential for unrecognized spatial disorientation and/or loss of situational awareness. Erratic flying consisting of multiple heading and altitude excursions while the aircraft is flown manually are indications that the pilot was possibly task saturated and disoriented. Spatial disorientation and the absence of a visible horizon have been identified as contributing factors to spiral dives. The radar track and the descent rate of the aircraft were indicative of a spiral dive. It is likely that the PIC and owner were both suffering some degree of spatial disorientation during the final portion of the flight. The crew was unable to recover control of the aircraft before contacting the surface of the water.
The investigation could not determine whether it was the PIC or the owner who was at the controls.
The PIC had arranged for a business meeting in Sydney on the morning of 06 August 2010. Self- imposed pressure to make this appointment likely influenced the crew’s decision to depart Buttonville despite:
their lack of experience on the aircraft type;
their unfamiliarity with the destination airport;
the night/IFR conditions; and
the lengthy day.
Due to the severity of the impact damage, the aircraft likely sank quickly and the ELT would not have transmitted a signal. 11 In 170 feet of water, attenuation would have masked the ELT signal if the ELT had withstood the initial impact.
By regulation, the first 406 MHz transmission from the ELT does not occur until about 50 seconds after activation.