Beech Aircraft Corp 1900D, VH-IMS

Local safety action

As at 24 June 2002, Airservices Australia had installed a tower
situational awareness display (TSAD) in the equipment room in the
Tamworth control tower complex so that appropriate maps can be
loaded and system performance monitored. Airservices Australia
expects to install the TSAD in the Tamworth control tower cabin in
September 2002. Although the TSAD is not used to apply separation
standards between aircraft, it should (when operational) assist
controllers with situational awareness in this complex air traffic
environment.

In an effort to control training in Tamworth controlled
airspace, the Tamworth ERSA entry, effective 13 June 2002, now
requires pilots planning instrument training at Tamworth, during
tower hours, to obtain approval from Tamworth ATC prior to
submission of the flight plan.

Although the crew was operating a regular public transport
operation, the cockpit of the B1900 was a training environment and
the Tamworth airspace was busy at the time of the occurrence. This
led to a complex and dynamic situation in which the crew of the
B1900 chose to continue descent, even though they were unable to
comply with the circuit entry instruction. Had the B1900 remained
at 4,000 ft until the crew could advise the ADC 1 that they could
not track as instructed, the aircraft would have remained
vertically separated with the traffic entering, and operating in,
the southern circuit. That would also have provided the controller
with time to evaluate the situation and issue alternative
instructions.

The crew reported that they were unable to advise the ADC 1 that
they could not comply with the circuit entry instruction due to
frequency congestion. However, they had an opportunity to inform
the controller when they acknowledged the clearance for the visual
approach.

The controller believed that there had not been an infringement
of separation standards between the B1900 and traffic inbound to
the southern circuit. However, no standard had been established
once the B1900 had left 4,000 ft on descent. The controllers did
not have enough time to sight the inbound CT4s and apply visual
separation because they expected the crew of the B1900 to comply
with the clearance as acknowledged. Consequently, visual separation
could not be applied because the ADC 2 had not sighted the inbound
aircraft and no other procedural separation standard, in accordance
with MATS, had been established between the B1900 and the inbound
aircraft.

The crew of the Beech 1900D (B1900) aircraft had been cleared by
the aerodrome controller (ADC) 1 to descend to 4,000 ft and were
instructed to join the circuit via a left base leg for runway 12L
(northern) circuit at Tamworth. The ADC 1 also instructed the crew
to report approaching 4,000 ft. The crew acknowledged the clearance
but later advised that they were unable to report approaching 4,000
ft due to frequency congestion. The ADC 1 had assigned 4,000 ft so
that a procedural separation standard of 1,000 ft could be
maintained with other aircraft until he could see the B1900 and
apply visual separation.

The crew of the B1900 subsequently requested confirmation of
their assigned level and reported their position when at 2NM north
of the aerodrome. The controller then sighted the aircraft and
cleared the crew to make a visual approach. The controller also
asked the crew if they would need to extend through the centreline
of runway 12L. The crew acknowledged the visual approach but did
not advise the controller that they would need to extend through
the centreline. The visual approach clearance authorised the crew
to descend below 4,000 ft.

The crew of the B1900 could not comply with the instruction to
join the circuit via a left base for runway 12L because the
aircraft was too high and too fast. The co-pilot was the non-flying
pilot and was undergoing command upgrade training. He had
acknowledged the clearance for the visual approach and had
previously acknowledged the instruction to join the northern
circuit via a left base leg for runway 12L. At the time that the
visual approach clearance was issued, the pilot-in-command was
aware that they could not comply with the circuit entry
instruction. He believed that the controller would have been aware
that they were unable to enter the circuit on a left base leg,
given their proximity to the circuit at that time and the height
and speed of the aircraft. He also believed that the controller
would have taken those circumstances, and the disposition of
traffic in the southern circuit, into account when issuing the
visual approach instruction.

The B1900 continued to descend and entered the runway 12R
(southern) circuit airspace which was under the control of the ADC
2. The ADC 1 notified the ADC 2 that the B1900 had entered the
southern circuit. The ADC 2 advised the ADC 1 that there was a
Pacific Aerospace Corporation Airtrainer CT4B (CT4) on a right base
leg for runway 12R. The ADC 2 provided traffic information about
the B1900 to the crew of the CT4. There were four other CT4
aircraft inbound to the circuit at that time but the ADC 2 had not
sighted them. The ADC 1 was unable to apply the required separation
standard, either 1,000 ft vertically, or a minimum horizontal
distance determined using the appropriate `Lateral Separation'
standard from the Manual of Air Traffic Services (MATS), between
the B1900 and the traffic inbound to the southern circuit. There
was an infringement of separation standards.

The ADC 1 reported that he had sighted the CT4 on right base. He
then instructed the crew of the B1900 to make a right turn and
track via a right base leg for runway 12L. He believed that the
B1900 was visually separated from that CT4 and that he could
maintain visual separation between the B1900 and that CT4 with that
instruction. He did not think that there had been an infringement
of separation standards between the B1900 and the aircraft inbound
to the southern circuit because all parties had enough time to
ensure that visual separation was not infringed.