Fairchild Industries Inc SA227-AC, VH-UUQ

Investigation number

200000869

Occurrence date

01/03/2000

Location

93 km SSE Mackay, (VOR)

Report release date

07/09/2000

Report status

Final

Investigation type

Occurrence Investigation

Investigation status

Completed

Aviation occurrence type

Loss of separation

Occurrence category

Incident

Highest injury level

None

Safety Action Analysis Summary

Local safety action

One of the operators involved in the occurrence issued a safety
article to crews notifying the limitations in the use of pilot
sight and follow procedure and reminding them to carefully consider
the situation prior to participating in the application of visual
separation.

Australian Transport Safety Bureau safety action

Following the review of a number of occurrences in which the use
of visual separation criteria was investigated, there was
insufficient evidence to support a recommendation. However, there
were a number of concerns in relation to the guidance, for the use
of visual separation procedures, provided to flight crew.
Consequently, the following was sent to the Civil Aviation Safety
Authority (CASA) on 27 October 1999:

"Subject: Aeronautical Information Publication Guidance for
Operations within CTA and GAAP Aerodrome CTRs The AIP ENR 1.1 - 32
paragraph 2 1. 1.1 details a pilot's responsibilities in relation
to operations in GAAP control zones including a requirement to:

"advise ATC if unable to sight, or if sight lost of, other
aircraft notified as traffic." The AIP ENR 1.3 - 2 paragraph 3.2.1
details the requirements for the provision of separation in
controlled airspace (excluding GAAP CTRs) and includes a special
provision of:

"under certain conditions, the pilot of one aircraft may be
given the responsibility for separation with other aircraft. In
this circumstance, the pilot is also responsible for the provision
of wake turbulence separation."

This latter entry would appear to be inconsistent with the GAAP
entry in that it does not provide any guidance or provisos which
require air traffic control to be advised by the pilot when they
have lost sight of a previously reported and sighted aircraft (or
one that they were following).

Any pilot requirements in relation to the application of visual
separation in the AIP should be consistent with the visual
separation criteria in the Airservices Australia Manual of Air
Traffic Services and should include:

the requirement for pilots to advise air traffic control when
they are unable to maintain sight of an aircraft, and
the issue of traffic information to the pilot of an IFR
aircraft that is subject to the application of visual
separation.

I therefore request that these aspects be considered for future
AIP amendments to ensure a consistent approach to the application
of visual separation, both inside and outside controlled airspace,
and between the AIP and the MATS."

CASA responded on 5 January 2000 and advised:

"I refer to your letter BS9710004 of 27 October 1999 in which
you requested that aspects of visual separation criteria contained
in MATS be considered for future amendment of AIP. In response to
your request, the following amendments will be incorporated in AIP
by the next amendment list. ENR 1.3 - 3 sub-paragraph 3.2.1 d. will
be amended to include:

the requirement for pilots to advise ATC when they are unable
to maintain, or have lost, sight of an aircraft, and
the advice that, where an aircraft has been instructed to
maintain separation from, but not follow, an IFR aircraft, ATC will
issue traffic information to the pilot of the IFR aircraft
including advice that responsibility for separation has been
assigned to the other aircraft."

Although the Keppel controller intimated to the crew of UUQ that
a minor reduction in airspeed would assist in the sequencing into
Mackay, the crew either did not appreciate the need for a speed
reduction or ignored the information. If the Keppel controller had
advised the Swampy controller that the crew of UUQ had been
forewarned of the likelihood of the imposition of a speed
reduction, or had the crew reduced speed when advised, the loss of
separation and subsequent situation may not have occurred.

The Swampy controller, despite not being endorsed for the
sector, was only required to use standards and procedures that were
commonly used on the Daintree sector. However, he did not issue the
required instructions to either crew to establish separation using
pilot visual separation procedures. The infringement of separation
standards may not have occurred if the controller had issued
instructions to either crew to follow the other aircraft and
confirmed their ability to do so, or alternatively, issued control
instructions to ensure that either vertical or radar separation was
maintained until at least one aircraft exited controlled
airspace.

The controller was probably more fatigued than he believed and
he may have endeavoured to operate with minimal restrictions and/or
control instructions in a situation which he thought was readily
appreciated by both crews. The time of the day (early morning) and
the resultant circadian disrhythmia may have also adversely
affected his performance. As a consequence of the small amount of
aircraft activity in the area at the time, the controller may have
also been lulled into being less situationally aware than
normal.

The lack of appreciation of the situation by the crew of UUG
following the Keppel controller's suggestion to reduce speed and
the acceptance by both crews of visual separation responsibility
when the forecast indicated IMC in the area, were indicators that
their performance may have also been sub-optimal. The limited
guidance available in the AIP in relation to the assignment of
separation responsibility to pilots does not clearly indicate pilot
and controller responsibilities in such cases. Provision of
additional information in the AIP would probably assist pilots in
their decision making regarding the safe conduct of a flight.

The perceived benefit of transferring separation responsibility
to pilots rather than imposing alternate air traffic control
standards and procedures requires careful consideration by both
controllers and pilots. This is more so the case for night
operations when en route or terminal weather conditions may not be
readily apparent. Additionally, any forecast that indicates that
instrument meteorological conditions may be encountered should be
an alert to crews and controllers to be wary of the use of visual
separation procedures. The issued forecasts indicated potential
instrument meteorological conditions for the Mackay terminal area
and it would have been prudent for the pilots to request alternate
separation procedures from the controller.

Two Fairchild Industries Inc S227 aircraft, VH-EEP and VH-UUQ,
operating under instrument flight rules (IFR) were inbound to
Mackay at approximately 0408 eastern standard time. EEP was from
Rockhampton, maintaining FL140 and was being followed by UUQ on the
Brisbane track at FL160. Near the descent point, approximately 55
NM south of Mackay, UUQ was above and abeam EEP when the Swampy
sector controller issued instructions for the crew of EEP to leave
control area on descent. The lower level of controlled airspace was
4,500 ft. About 1 minute later the crew of UUQ requested descent
and advised the controller that they had EEP in sight. The
controller instructed the crew to descend to FL140 and then to
FL130. As EEP was descending through FL130, as indicated by the
aircraft's Mode C altitude readout on the controllers' radar
display, the lateral distance between the two aircraft reduced to
4.5 NM while there was less than the required vertical separation
standard of 1,000 ft between them. The required radar separation
standard was 5 NM. There was an infringement of separation
standards.

The controller advised the crew of EEP that "traffic is UUQ".
That was acknowledged by the crew who also advised that they had
UUQ in sight. The air traffic system short term conflict alert
activated and the controller queried both crews with respect to
their ability to maintain their own separation on descent. Both
crews acknowledged and advised that they could maintain their own
separation. At this stage UUQ was ahead and above EEP. The
controller instructed the crew of UUQ to leave control area on
descent. Shortly after both crews reported transferring from the
Swampy sector frequency to the Mackay mandatory broadcast zone
frequency. As EEP was passing 7,000 ft it entered instrument
meteorological conditions and the crew lost sight of UUQ. The crew
of EEP contacted the crew of UUQ to establish the relative
positions of the aircraft and found that the UUQ crew had descended
their aircraft so that it was below EEP. The crew of EEP reduced
power and manoeuvred their aircraft in an endeavour to increase the
lateral spacing between them and UUQ. The aircraft subsequently
landed at Mackay.

Both the area forecast and the Mackay terminal area forecast
indicated the possibility of instrument meteorological conditions
below 10,000 ft during the period when the aircraft were expected
to be in the area.

The controller managing the Keppel sector, adjacent to the
southern boundary of the Swampy sector, controlled the aircraft
before the crews transferred to the Swampy sector. The Keppel
controller noted the similar groundspeed readouts from the aircraft
and queried both crews with respect to their respective indicated
airspeeds. The crews both advised their indicated airspeeds as 205
kts. The controller advised the crew of UUQ that as they were about
2 NM behind EEP and that the next sector would probably make them
second in the arrival sequence and, "if you would like you can
start to reduce speed back to about 20 kt groundspeed reduction
would probably fit you nicely behind". The crew acknowledged the
transmission and advised that they had that aircraft in sight and
were gaining on it.

The Keppel controller did not instruct the crew of UUQ to reduce
speed and was not responsible for arranging the arrival sequence
into Mackay. If the controller had issued such an instruction the
crew of UUQ would have been required to read back and comply with
the speed requirement. The Keppel controller informed the crew that
he would advise the next sector that they had EEP in sight and
subsequently told the Swampy controller. The Keppel controller did
not advise the Swampy controller that he had pre-warned the crew of
UUQ to possibly expect a speed requirement for sequencing. The
investigation did not establish why the crew of UUQ did not reduce
speed.

The crew of EEP was operating on the Keppel sector frequency and
heard the advice passed by the controller. The crew later reported
that they did not hear the response from the crew of UUQ but
expected that aircraft to be following them on arrival into
Mackay.

Due to the early hour, the Swampy sector was not busy and there
was little other traffic in the area. The controller at the Swampy
sector was endorsed and rostered for duty on the adjacent Daintree
sector, but was not endorsed for the Swampy sector. The rostered
and endorsed controller for the Swampy sector had left the position
for a break. In that situation it was normal practice for the
controller managing the adjacent position to monitor the radio
frequencies and communication links while the position was vacant.
If a radio or coordination call occurred, an appropriately endorsed
controller would be recalled to operate the position. Immediately
prior to and during the occurrence, the non-endorsed Swampy
controller did not recall the other controller. Although the
controller was not endorsed on the Swampy sector, the standards,
procedures and techniques used were common to both Swampy and
Daintree sectors. The controller should have been capable of
maintaining separation using either radar, vertical, lateral,
longitudinal or visual standards or a combination of these
standards. The controller later reported that he believed that
visual separation was being applied and consequently did not ensure
that radar or vertical separation standards were maintained while
the aircraft descended.

The Manual of Air Traffic Services (MATS 4-5-1) detailed how
responsibility for separation may be assigned to a pilot using
visual separation. For arriving aircraft above FL125 a controller
was to instruct the pilot of one of the aircraft involved to follow
and track behind the other aircraft, provided the pilot has
reported sighting the aircraft and at least one of the aircraft is
on descent. This was particularly so when the following aircraft
was faster. In this case, a controller should have confirmed that
the pilot was capable of following the slower aircraft. The Swampy
controller did not instruct either crew to follow the other
aircraft nor did he confirm whether the pilot of UUQ could follow
EEP. Prior to a controller issuing any control instruction
requiring a pilot to keep an aircraft in sight, the controller
should consider a number of aspects that may limit a pilot's
ability to comply. One of the aspects related to restrictions on
atmospheric visibility that may not have been apparent to the
pilot.

The Aeronautical Information Publication (AIP) contained a
number of references about the application of visual separation.
The references were different to what was in MATS. Also, the
reference that related to controlled airspace provided little
guidance to assist pilots in the application of visual separation.
AIP ENR13-3 paragraph 3.2.1.d stated, "under certain conditions,
the pilot of one aircraft may be given the responsibility for
separation with other aircraft. In this circumstance, the pilot is
also responsible for the provision of wake turbulence
separation".

Controllers were responsible for assessing their fitness for an
operational shift and if there were any doubts they were expected
to notify a supervisor. The controller managing the Swampy sector
had recently experienced some difficulties with obtaining
satisfactory rest during his time off at home and had also been
involved in a traffic incident the evening prior to the occurrence
shift. The controller later reported that at the time he believed
that he was capable of undertaking the shift despite his recent
experiences.

Human performance varies during the day, tending to correspond
with the body's circadian rhythm. Generally, the standard of human
performance of some tasks decreases during the early morning hours.
The reduction in performance is separate to that observed due to
sleep deprivation. Additionally, an individual's ability to
recognise the on-set of fatigue or a reduction in performance
diminishes with fatigue and low points in the circadian rhythm.

Aircraft Details

Manufacturer

Fairchild Industries Inc

Model

SA227

Registration

VH-UUQ

Serial number

AC-714

Operation type

Air Transport Low Capacity

Departure point

Brisbane, QLD

Destination

Mackay, QLD

Damage

Nil