The pilot had planned to fly direct from his property, Ocean View Farm, which is 92 km south-east of Esperance, to Jandakot. He obtained the area and aerodrome forecasts for the flight through AVFAX and submitted a SARTIME flight plan. The pilot's pre-flight planning, obtained from his copy of the flight plan, indicated that he would have 280 minutes of fuel available for the 182-minute flight.
The forecasts indicated that anticipated low cloud and fog would clear from 0900 onwards in the area south of Narrogin and from 1000 onwards north of Narrogin. Conditions at Jandakot were forecast to be suitable for visual flight after 1000.
The aircraft departed Ocean View Farm at 0850. At 1009 the pilot called Perth Flight Service requesting an updated weather forecast for Jandakot Airport. The amended forecast passed to him indicated that widespread low cloud was now expected to continue in the Jandakot area for some time with periods of reduced visibility in drizzle and low cloud.
Amended forecasts for the areas south and north of Narrogin were issued between 0915 and 0940 indicating that cloud, fog and drizzle would be worse than originally forecast. These amended forecasts were not requested by the pilot and, therefore, not passed to him.
Between 1030 and 1100, witnesses reported hearing an aircraft at low level in poor weather, south-east of Narrogin. Shortly after 1100 an aircraft was observed circling Narrogin townsite (38 km left of the direct track planned by the pilot) at approximately 100 - 150 ft AGL with landing gear and flaps extended. The aircraft passed in and out of the low cloud as it circled. Weather conditions at Narrogin at the time were a low cloud base (estimated to be 100 ft and observed to be down to the tops of trees in places), fog patches, no rain and a light and variable wind.
At approximately 1115 the aircraft crashed, in a near vertical attitude, into a farm paddock between the Narrogin townsite and the Narrogin airstrip.
The mode of impact, aircraft vertical, left wing low and yawing to the left, indicated that the aircraft was not in controlled flight at the time and the localised damage to the fuselage forward of the pilots' seats combined with the slight damage to the fuselage aft of the pilots' seats, indicated that the loss of control had occurred at low altitude. The generator and battery switches were found in the off position following the accident. The aircraft's automatic direction finder (ADF) was also found switched to the off position.
The flight plan, found in the wreckage, indicated the pilot's in-flight navigation procedures began to deteriorate after he passed abeam Lake Grace at 1004. The last entries made on the plan were his planned estimate abeam Kulin of 1042 and a copy of the amended Jandakot forecast given to him by Perth Flight Service. He also annotated that he had 30 gallons of fuel in each wing tank at that time.
The pilot's planning for the trip was comprehensive. He obtained the weather forecasts, prepared a flight plan and submitted flight notification to the Civil Aviation Authority.
The forecasts indicated that the weather would clear from 0900 onwards and, as he planned to depart at 0850 there was no reason for the pilot not to proceed with the flight to Jandakot.
The weather from Esperance to abeam Katanning was essentially as forecast.
The pilot requested the latest Jandakot weather at 1009 or about 20 minutes prior to encountering the poor weather conditions north of Katanning. It is possible that this request was precipitated by indications of poor weather ahead.
It is probable that the pilot, confronted with poor weather ahead made a decision to divert to Narrogin, an airport he was familiar with, instead of continuing to Jandakot. It is likely that the pilot was not aware of the full extent of the poor weather between his current position and Jandakot as he did not request an update, although he would have been able to see the general deterioration.
Witness information and the fact that the ADF was found switched off, indicated that the pilot probably descended to low level to remain in visual contact with the ground as he attempted to find Narrogin Airport.
Aircraft damage indicates that the aircraft probably stalled with a subsequent loss of control during the final landing manoeuvre.
Indications of an impending stall are normally provided by the aircraft's stall warning system. Once the pilot selected the battery switch off, the stall warning system would have been rendered inoperative. As a result, the pilot probably inadvertently removed an important indication that loss of control was imminent.
The passenger was not wearing the sash part of the seat belt at the time of impact.
Significant Factors
The following factors are considered relevant to the development of the accident.
- The pilot did not request all the weather information available to him before making a decision on whether or not to continue the flight.
- The pilot continued the flight into weather that was not suitable for visual flight.
- The pilot inadvertently disabled the stall warning system.
- The aircraft stalled at a low altitude from which recovery was not considered possible.