On 24 February 2013, the pilot of a Cessna 206 aircraft, registered VH-TOC (TOC), was conducting a private flight from Lake Nash, Northern Territory, to Mount Isa, Queensland, when the aircraft’s avionics system failed. The pilot commenced the radio failure procedure by squawking the transponder code of 7600 and transmitting blind.

The pilot overflew the Mt Isa Airport to assess the wind conditions and rocked the aircraft’s wings to alert any ground personnel of the communication failure, he then joined the circuit.

At around the same time, the Mount Isa airport safety officer (ASO) was preparing to conduct a runway and lighting inspection. The ASO turned on the vehicle’s radio and lighting. The ASO then activated the pilot activated lighting (PAL) and aerodrome frequency response unit (AFRU) systems.

The ASO broadcast a call on the Mount Isa common traffic advisory frequency (CTAF), advising that the vehicle was entering the runway and conducted a lookout for aircraft. As no response was received or aircraft sighted, the inspection was commenced.

By this time, the pilot of TOC was on the base leg of the circuit for runway 34 and observed a vehicle near the runway 34 threshold. He assumed the vehicle and would exit the runway, leaving the runway clear for him to land. The pilot continued to transmit his intentions blind.

As the pilot commenced the flare, he noticed that the vehicle had not yet vacated the runway. As a result of the vehicle being on the runway, the pilot initiated a go-around.

The aircraft passed 200-300 ft above the vehicle. The ASO heard TOC pass overhead and vacated the runway. The pilot of TOC conducted a second circuit and landed without further incident.

Mount Isa Airport Pty. Ltd. had planned to place yellow and black chequered safety stickers on the side and rear of the vehicle. As a result of this occurrence, that action was immediately implemented.

The need to conduct a go-around may occur at any point in the approach and landing phase, however, the sooner a condition that warrants a go-around is recognised, the safer the manoeuvre will be.

Aviation Short Investigation Bulletin Issue 19