The aerodrome circuit was active with a number of aircraft
conducting circuit training, or inbound for landing. Both runways
35 and 30 were in use. Runway 30 intersected runway 35
approximately 750 m from its threshold. The tower was staffed with
three controllers operating the aerodrome control (ADC),
coordination and surface movement control positions.
The ADC had instructed the crew of a De Havilland Dash 8 (Dash
8) to line up for a departure from runway 35. The pilot of an
American Aircraft Corporation Cheetah (Cheetah) had been instructed
to continue approach for runway 30. The ADC cleared the Dash 8 crew
for takeoff and then looked towards the final approach path for
runway 30 to monitor the approach of the Cheetah. As the ADC
completed the transmission to the Dash 8 crew, he saw that the
Cheetah was on short final and immediately transmitted an
instruction to the Dash 8 crew to hold their position. This
instruction was over-transmitted by the acknowledgment of the
take-off clearance by the pilot in command of the Dash 8. The ADC
commenced to issue a land-and-hold-short instruction to the pilot
of the Cheetah; however, seeing that the Dash 8 was starting it's
take-off roll, he ceased the transmission and issued a further
instruction to the Dash 8 crew to hold position. This instruction
was over-transmitted by the Cheetah pilot reporting that he was
initiating a go-around. The Dash 8 became airborne prior to the
intersection of the runways, however, the crew held their aircraft
at approximately 50 ft above ground level while the Cheetah passed
approximately 100 ft above and slightly behind the Dash 8.
The automatic voice recording of the radio transmissions from
the ADC during this period indicated that there were few or no
intervals between any of his transmissions. The pilot of another
aircraft that was operating in the circuit heard the hold-short
instruction. The crew of the Dash 8 reported that they did not hear
either of the hold-short instructions.
The ADC had formulated a traffic plan but this changed when a
turbojet aircraft he thought was going to conduct a full-stop
landing on runway 35, conducted a touch-and-go. The ADC had
instructed the crew of the Dash 8 to line up on runway 35 after the
approach of the turbojet aircraft, and had amended the approach of
the Cheetah to runway 30 to facilitate the departure of the Dash 8.
The ADC did not instruct the pilot of the Cheetah to report at a
position that would have enabled him to adjust the traffic sequence
if required. There was also a delay between the time the ADC
approved the Dash 8 crew to line up, and the eventual issue of the
departure instructions and a clearance. This delay was due to radio
transmissions from the pilot of the turbojet aircraft, as well as
the coordination of inbound traffic with the approach controller.
During this period, the Cheetah pilot had continued his approach to
runway 30. The ADC did not check the position of the Cheetah in
relation to the intersection of the runways prior to issuing the
take-off clearance to the Dash 8 crew. That was done as he was
completing the transmission of the take-off clearance to the crew.
As a final action to resolve the conflict between the aircraft, the
ADC proposed to issue a land-and-hold-short instruction to the
pilot of the Cheetah; however, the landing distance available (590
m) to the pilot did not meet the distance required (900 m) for
land-and-hold-short operations.
The Manual of Air Traffic Services details the radiotelephony
phraseology (RTF) to be used by controllers to cancel take-off
clearances or to stop a takeoff in emergency conditions. The ADC
used only part of the required RTF for the cancellation of the
take-off clearance. He did not use the RTF for an emergency
situation.
