Boeing Co 737-7BX, VH-VBT and Neico Lancair IV-P aircraft, VH-LDJ, 93 km NW Brisbane, Airport, 7 April 2004

Throughout this analysis it should be noted that the pilots of
both aircraft and the ATS controller involved in the occurrence
complied with the rules and procedures for operation in Class E
airspace associated with the NAS phase 2b, implemented on 27
November 2003.

The regulations, procedures and educational material associated
with that implementation stated that there was a shared
responsibility by pilots of IFR and VFR flights to see-and-avoid
each other in Class E airspace.

Prior to the implementation of NAS phase 2b on 27 November 2003,
both aircraft involved in this occurrence would have been operating
in Class C airspace. As such, they would have been subject to an
ATS airways clearance and would have been provided with separation
in accordance with Class C airspace rules and procedures. In order
for two aircraft to pass in close proximity at these flight levels
in Class C airspace, those rules and procedures would need to have
been compromised. As the pilots of both aircraft and the ATS
controller complied with the rules and procedures for Class E
airspace under NAS, those rules and procedures do not preclude an
IFR high performance, high capacity regular public transport
aircraft from passing within such close proximity as to generate a
TCAS RA on either known or unknown VFR traffic.

The controller's relatively low workload and other factors, such
as the Lancair pilot submitting flight notification details, and
broadcasting his departure from Maroochydore, assisted the ATS
controller to detect a possible conflict. Although there was no
requirement for the controller to pass traffic information to the
pilot of the Lancair about the location of the 737 under NAS Class
E airspace procedures, the controller provided traffic information
to both aircraft with respect to each other.

Part 5 of MATS also stated that controllers shall issue a safety
alert when, in the consideration of the controller, such an advice
was warranted to avoid conflict. In the circumstances of this
occurrence, the controller had provided traffic information to the
crews of both aircraft, and the Lancair pilot had broadcast that he
had the 737 in sight. Accordingly, the onus was then on the Lancair
pilot to avoid the 737. In those circumstances, the provision of a
safety alert, which may have included a suggested course of action,
may also have complicated the situation, if that suggestion was
contrary to what the pilots of each aircraft considered
necessary.

Provision of a safety alert, in the circumstances of this
occurrence, was not required. However, MATS did not provide any
guidance to controllers on the circumstances under which the
provision of a safety alert would be appropriate. Publication of
those guidelines may assist controllers to determine when a safety
alert should be issued.

In Class E airspace, the provisions of CAR 163A required the
crews of both aircraft to 'see, and avoid' each other. The 737 crew
were unable to see the Lancair despite their attempts to do so. The
Lancair pilot reported that he had the 737 in sight. When the 737
crew observed the position of the Lancair on the TCAS navigation
display, they commenced action to avoid a confliction prior to
receipt of both the TCAS TA and RA. In concert with that action,
they continued in their attempts to visually acquire the Lancair,
in accordance with Class E airspace see-and-avoid requirements.

In the circumstances of this occurrence:

• the ATS controller took more actions than those required by the
  published requirements for Class E airspace and MATS;
• the Lancair pilot took more actions than those required by the
  published procedures for Class E airspace under NAS;
• the early action taken by the 737 crew to avoid the conflict
  was not contrary to the published procedures for Class E airspace
  under NAS.

Despite those actions, the two aircraft came into such proximity
that a TCAS RA was generated in the 737.

Both aircraft were operating in Class E airspace that was
introduced as part of the National Airspace System (NAS) phase 2b
on 27 November 2003. (An ATSB research report titled National
Airspace System Stage 2b: Analysis of Available Data was
released in July 2004.) As no prescribed separation standards are
applicable in these circumstances, there was no infringement of
separation standards. However, ATS audio tapes, radar and TCAS
data, and information obtained from the air traffic controller and
the pilots of both aircraft were consistent and indicate that the
aircraft came into such close proximity that a threat to the safety
of the aircraft may have existed. Therefore, the incident has been
classified by the ATSB as an airprox event.

The incident at Canty IFR reporting point, on 3 December 2003
(ATSB report 200304963) was also classified as an airprox
event.

Unlike this incident north of Brisbane on 7 April 2004 and the
Canty incident, the occurrence near Launceston on 24 December 2003
(ATSB report 200305235) was classified as a serious incident due to
the lack of radar coverage in the Launceston area and the absence
of radio broadcasts from the pilot of the Tobago, which created an
unalerted see-and-avoid environment for the crew of the Boeing 737.
The air traffic controller also was unaware of the Tobago.

On 7 April 2004, a Boeing 737-7BX (737) aircraft registered
VH-VBT, operating under the instrument flight rules (IFR), was en
route from Townsville and descending for a landing at Brisbane. A
Neico Lancair IV-P aircraft registered VH-LDJ, operating under the
visual flight rules (VFR), was en route from Maroochydore to St
George, on climb to flight level (FL) 165¹. Both aircraft were operating in
radar Class E airspace at the time of the occurrence.

The Lancair pilot reported to the Air Traffic Services (ATS)
controller that he had departed Maroochydore at 0718 Eastern
Standard Time²,
although in accordance with the National Airspace System (NAS)
procedures, there was no requirement for him to do
so³. The controller
issued the Lancair pilot with a discrete transponder code to assist
with his situational awareness. Published NAS procedures stated
that:

In Class E airspace, IFR and VFR flights are permitted. IFR
flights are provided with an air traffic control service, are
separated from other IFR flights, and receive traffic information
on VFR flights as far as is practicable. VFR flights receive a
Radar Information Service (RIS)⁴ on request.⁵

Those procedures also stated that, for VFR aircraft operating in
Class E airspace, '…no flight notification was required…' and
pilots of aircraft conducting operations under the VFR were
required to monitor the appropriate radio frequency. The Lancair
pilot submitted flight notification details to ATS prior to
departure from Maroochydore, and reported that departure to
ATS.

In accordance with those procedures, the controller was not
providing traffic separation⁶ to either aircraft, and advised the
737 crew accordingly. Recorded ATS audio information showed that
the controller provided traffic information about the Lancair to
the 737 crew on three occasions between 0721:58 and 0725:08. At
0722:17, and again at 0725:38, the controller provided the Lancair
pilot with traffic information about the 737, although there was no
requirement for him to do so in Class E airspace. During the first
transmission at 0722:17, the controller advised the Lancair pilot
that the 737 was crossing traffic which would pass in about 15 NM
and was on descent into Brisbane. During the second transmission at
0725:38, the controller advised the Lancair pilot that the 737 was
'in your 2 o'clock at 8 miles now'. ATS radar data showed that, at
0725:38, the 737 was 8.8 NM from the Lancair. At 0725:47, in
response to that broadcast, the Lancair pilot advised the
controller that he had the 737 in sight.

As the 737 was passing through about FL157 at 0726:01, the crew
reported that they observed a traffic alert and collision avoidance
system (TCAS)⁷
traffic symbol on the aircraft's navigation display, about the
Lancair. They attempted to visually acquire the Lancair, but were
unable to see that aircraft. Recorded data from the 737's flight
data recorder (FDR) showed that, at that point, the crew commenced
manoeuvring the aircraft by reducing the rate of descent. At about
0726:18, the crew received a TCAS traffic advisory
(TA)⁸. The crew
reported that they were still unable to visually acquire the
Lancair and were uncertain of its relative position. Recorded FDR
data indicated that at 0726:34, the crew disengaged the autopilot
and commenced a right turn away from the Lancair. They subsequently
levelled the 737 at FL153 and then climbed to FL154. At 0726:40 and
at 15,420 ft the 737 received a TCAS resolution advisory
(RA)⁹ aural warning
instructing them to climb, in response to the proximity of the
Lancair. They subsequently climbed the 737 to FL166 and continued
the turn to about 15 degrees right of track. The duration of the RA
was 10 seconds and commenced when the Lancair was about 650 ft
vertically lower and about 0.7 NM to the left of the
737.¹⁰ Recorded ATS
radar data showed that, at about 0726:45, the Lancair altered track
8 degrees to the right away from the 737, just before passing
behind and below the 737. The Lancair pilot reported that he did
not experience the effect of wake turbulence from the 737. The
minimum distance between the two aircraft was about 600 ft
vertically at about 0.3 NM laterally.¹¹

The Class E airspace in which the 737 and the Lancair were
operating at the time of the occurrence was introduced as part of
NAS phase 2b on 27 November 2003. Prior to NAS phase 2b, that
volume of airspace was classified as Class C airspace. In Class C
airspace, both aircraft would have been subject to an ATS airways
clearance and would have been separated in accordance with
prescribed standards.

In Class E airspace, the pilots of aircraft operating under the
IFR and VFR were required to:

…maintain vigilance so as to see, and avoid other
aircraft.¹²

The NAS Implementation Group reference guide, distributed as
part of the NAS phase 2b implementation, stated that:

The other important change is that the pilot of a VFR flight
should not make broadcasts on ATC frequencies.¹³

It also stated that:

Pilots of VFR flights may monitor the ATC frequency to enhance
situational awareness.

Please do not make broadcast transmissions or engage in chatter
on an ATC frequency. The safety of others depends on you not doing
this.

Pilots are not precluded from responding to any ATC or pilot
transmission when they believe their safety is at risk from another
aircraft.

Part 2, Section 2, paragraph 2.2.4.1 of the Manual of Air
Traffic Services (MATS) stated that:

Before providing a radar service to an aircraft, radar
identification shall be established.

Although the controller did not advise the Lancair pilot that
the Lancair was radar identified, the controller issued a discrete
transponder code to the Lancair pilot and radar-identified the
aircraft before providing a Radar Information Service to the
pilot.

Part 4, Section 1, paragraph 4.1.1.1 of MATS contained
information regarding ATS controller responsibilities for providing
aircraft separation. The manual stated that:

Separation shall be provided by ATC using approved separation
standards and procedures.

In the circumstances of this occurrence, the ATS controller was
not required to provide separation to either aircraft in respect of
the other and there were no separation standards applicable in
these circumstances in Class E airspace.

Part 4, Section 1, paragraph 4.1.1.3 of MATS stated that:

Nothing in this chapter precludes a controller from using
discretion and initiative in any particular circumstance where
these procedures appear to be in conflict with the requirement to
promote the safe conduct of flight.

In the circumstances of this occurrence, the ATS controller
provided traffic information to the crews of both aircraft in
respect of the other, although under NAS procedures there was no
requirement for him to provide traffic information to the pilot of
the Lancair on the location of the 737.

Part 5, Section 1, paragraph 5.1.13 of MATS provided information
regarding provision of safety alerts. Paragraph 5.1.13.1 stated
that:

A safety alert shall be issued to an aircraft when a controller
is aware the aircraft is in a situation which is considered to
place it in unsafe proximity to terrain, obstructions, or other
aircraft.

The controller reported that, once the Lancair pilot broadcast
that he had the 737 in sight, there was no necessity to broadcast a
safety alert to either the Lancair pilot or the 737 crew. The
controller also reported that if that pilot had not broadcast that
he had the 737 in sight, his next option was to issue a safety
alert. MATS did not provide any guidance to controllers on what
might be considered '…unsafe proximity…', or when to issue a safety
alert.

The NAS Implementation Group reference guide contained
information for VFR pilots regarding separation from other aircraft
when operating in Class E airspace. Page 16 of that guide stated
that:

When you are flying in Class E airspace you are responsible for
separation from other aircraft. The onus is on you to look out and
see and avoid other aircraft.

Part 12, The Rules of the Air, Division 1, of the Civil
Aviation Regulations (CAR) 1988, contained information regarding
right of way, prevention of collision, operating near other
aircraft and responsibilities of flight crew to see and avoid
aircraft. More specifically, CAR 161 contained information
regarding right of way and stated that:

(1) An aircraft that is required by the rules in this Division
to keep out of the way of another aircraft shall avoid passing over
or under the other, or crossing ahead of it, unless passing well
clear.¹⁴

(2) The pilot in command of an aircraft that has the right of
way must maintain its heading and speed, but nothing in the rules
in this Division shall relieve the pilot in command of an aircraft
from the responsibility of taking such action as will best avert
collision.

CAR 162 (1) contained information regarding prevention of
collision and stated that:

When 2 aircraft are on converging headings at approximately the
same height, the aircraft that has the other on its right shall
give way…

Although not specifically referring to converging aircraft, CAR
162 also stated that '…each shall alter its heading to the right…',
and when referring to the aircraft other than the aircraft having
right of way, '…shall keep out of the way of the other aircraft by
altering its heading to the right…'.

CAR 163 (1) contained information regarding operating near other
aircraft and stated that:

The pilot in command of an aircraft must not fly the aircraft so
close to another aircraft as to create a collision hazard.

The 737 was on the Lancair's right and, in accordance with CAR
161 and CAR 162 (1), had right of way. The Lancair pilot reported
that he had the 737 in sight. While the crew of the 737 had
observed a traffic symbol on the TCAS display, they reported that
they did not see the Lancair, despite attempts to do so.

Information obtained from the crews of both aircraft, the ATS
controller, recorded flight data from the 737, ATS audio recordings
and radar data, was consistent and indicated that the crews of both
aircraft and the ATS controller complied with the published
procedures for Class E airspace under NAS.

Based on the factual data, and the definition contained in
Regulation 2.2 of the Transport Safety Investigation Regulations
2003, the incident was classified as an airprox
event.¹⁵

¹ 16,500 ft
with an altimeter pressure sub-scale setting (QNH) of 1013.2
hPa.

² The 24-hour
clock is used in this report to describe the local time of day,
Eastern Standard Time (EST), as particular events occurred. Eastern
Standard Time was Coordinated Universal Time (UTC) + 10
hours.

³ Aeronautical
Information Publication (AIP), ENR 1.1, Sections 3.4 and
18.3.2.

⁴ Radar
Information Service (RIS) is defined in Part 10, Section 1 of the
Manual of Air Traffic Services as:

An add-on ATC service within radar coverage, which
provides information to flights, not otherwise receiving a
separation service, in order to improve situational awareness, and
assist pilots in avoiding collisions with other
aircraft.

⁵ AIP, ENR 1.4,
Section 2.1.4 and pages 12-13 and 40 of the NAS Implementation
Group Reference Guide - How to Operate in the National Airspace
System, effective from 27 Nov 2003.

⁶ Separation is
defined in Part 10, Section 1 of the Manual of Air Traffic Services
as:

A controlled condition using defined standards to
prevent collisions between aircraft.

⁷ The Boeing
737-NG Operations Manual, Volume 2, states that:

TCAS alerts the crew to possible conflicting traffic.
TCAS interrogates operating transponders in other airplanes, tracks
the other airplanes by analyzing the transponder replies, and
predicts the flight paths and positions. TCAS provides advisory,
flight path guidance, and traffic displays of the other airplanes
to the flight crew. Neither advisory, guidance, nor traffic display
is provided for other airplanes which do not have operating
transponders. TCAS operation is independent of ground-based air
traffic control.

⁸ A traffic
advisory (TA) is generated when the other aircraft is approximately
40 seconds from the point of closest approach, dependent upon
aircraft altitude.

⁹ If the other
aircraft continues to close, a resolution advisory (RA) is
generated when the other aircraft is approximately 25 seconds from
the point of closest approach, dependent upon aircraft altitude.
The RA provides aural warning and guidance as well as manoeuvre
guidance to maintain or increase separation from the
traffic.

¹⁰ The recorded
ATS radar data and the 737 flight recorder data was consistent.
However, the accuracy of that information is dependent upon the
tolerances associated with both aircraft altimeters and the ATS
radar equipment.

¹¹ The horizontal
distance was determined using the radar positions that were
recorded every 5 seconds. By interpolating between those points to
derive a position every second, the minimum horizontal separation
was 0.3 NM, dependent upon the tolerances previously
mentioned.

¹² Civil Aviation
Regulations 1988, 163A - Responsibility of flight crew to see
and avoid aircraft.

¹³ Page 8 of the
NAS Implementation Group Reference Guide - How to Operate in
the National Airspace System, effective from 27 Nov
2003.

¹⁴ The
investigation was unable to locate a CAR definition of '…well
clear…'.

¹⁵ An airprox
event is defined in Regulation 2.2 of the Transport Safety
Investigation Regulations 2003, as:

…an occurrence in which 2 or more aircraft come into
such close proximity that a threat to the safety of the aircraft
exists or may exist, in airspace where the aircraft are not subject
to an air traffic separation standard or where separation is a
pilot responsibility.