Collision with terrain involving PZL Warszawa-Okecie M-18A Dromader aircraft, VH-WHR, near Emerald Airport, Queensland, on 1 December 2017

What happened

On the morning of 1 December 2017, an M-18A Dromader aircraft (Pratt & Whitney PT6A engine), registered VH-WHR (WHR) prepared for an aerial agricultural spraying operation at a private airstrip, 9 km north of Emerald Airport, Queensland. The aircraft was operated by Central Highlands Aerial Services and was conducting a spray operation on an 81-hectare paddock (Figure 1, shown in green), about 6 km west‑south‑west of the airstrip.

Figure 1: Application area (green), accident site (blue) and track flown (yellow)

Source: Google earth, annotated by the ATSB

The pilot conducted a pre-flight inspection of WHR and found everything to be serviceable. He was also the last person to fly the aircraft, three days prior to the accident, and had not identified any problems.

The wind was reported to be 4‑6 kt from the northeast. The spraying operation was standard with no major hazards in or around the paddock ‑ the pilot had sprayed the paddock several times in the past conducting the same spray pattern flying east and west.

At about 0604 Eastern Standard Time,^[1] the aircraft arrived at the paddock and the pilot conducted several short spray runs in the south-western corner to ensure there was no overspray onto an adjoining paddock. He then conducted several back-to-back spray runs in the same corner (Figure 1) and at about 0614, he commenced a racetrack pattern over the remainder of the paddock.

At about 0620, a witness located about 1 km from the paddock observed the aircraft complete the ninth racetrack pattern run and commence a turn to the right to line up for the next run. The witness estimated that about three quarters of the way through the turn, while lining up for the next run, the aircraft rapidly pitched down and the right wing collided with the ground. The aircraft subsequently flipped, and came to rest inverted and facing in the opposite direction to the flight path about 20‑30 m from the initial contact point (Figure 2).

Figure 2: Accident site

Source: Police

At about 0622, the witness called emergency services and proceeded to the accident site. When the witness arrived at the wreckage, he found the pilot had exited the aircraft through the broken cockpit side window.

Ambulance officers treated the pilot before transporting him to hospital. He was admitted to treat his injuries, which included a fractured left leg, three fractured left ribs, bruises, cuts to his left side, and concussion. The pilot was wearing a helmet at the time of the accident and it was damaged from impact with the aircraft structure (Figure 3). The pilot had no recollection of the accident and no mechanical issue was identified that may have contributed to the accident.

Figure 3: Damage to the left side of the pilot’s flight helmet

Source: Police

While the track of the aircraft during the spray operation was recorded, other parameters such as airspeed, time, altitude, and aircraft attitude were not. Figure 4 shows the final four racetrack pattern turns back towards the west. The last inbound turn (shown in blue) was conducted at a smaller turn radius than the previous three turns in that direction. The track data finished about 460 m from the accident site.

Figure 4: Final four right turns from an easterly track (last shown in blue)

Source: Google earth, annotated by the ATSB

The pilot joined the operator in January 2015, gaining about 800-flight hours in WHR (with the installed PT6A engine) and flew the previous flight in WHR three days prior to the accident. He did not report any concerns with the aircraft.

The maintenance release for WHR was issued about 40 flight hours prior to the accident and no outstanding maintenance or defects were recorded.

Safety analysis

About three quarters of the way through a turn, as the aircraft was lined up for the next racetrack pattern spray run, the aircraft was observed to rapidly pitch down and collide with the ground. Analysis of the limited available recorded data showed that the final turn was flown at a tighter radius than the previous racetrack pattern turns. In combination, this could indicate that the accident was the result of an aerodynamic stall. However, there was insufficient information to determine if that occurred.

The pilot was unable to remember the final turn and could not provide a reason for the track variation or why the aircraft pitched down. No mechanical defects were noted with the aircraft, on the maintenance release, during the previous flight, or up to the section of the accident flight the pilot could remember. A post‑accident inspection of the aircraft by the operator did not identify any defects. From the limited available information, it was not possible to determine the reason for the accident.

The pilot was wearing his own personal flight helmet at the time of the accident. During the accident, the left side of the helmet struck the internals of the cockpit. Based on the degree of damage to the helmet, it probably prevented the pilot receiving more serious head injuries.

Findings

These findings should not be read as apportioning blame or liability to any particular organisation or individual.

• During a turn, and for reasons that could not be determined, VH-WHR pitched down and collided with the ground.
• The helmet worn by the pilot probably prevented more serious head injury.

Safety message

The International Civil Aviation Organization circular 85-AN/71 Safety in aerial work Part 1. Agricultural Operations discusses the importance of reducing serious head injuries by wearing a correctly fitting flight helmet. Pilots operating aircraft in agricultural operations are particularly vulnerable to accidents involving major or fatal head injury. The circular also discusses the need to select a helmet which provides effective protection and that is part of the pilot’s personal flying equipment as was the case in this accident.

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1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 Hours.