Pitts Aviation Enterprises S-2A, VH-PTD

Investigation number

199900970

Occurrence date

10/03/1999

Location

Hoxton Park, Aero.

Report release date

21/06/2000

Report status

Final

Investigation type

Occurrence Investigation

Investigation status

Completed

Occurrence category

Accident

Highest injury level

Fatal

Safety Action Significant Factors Analysis Factual Information

Following this occurrence and a previous mid-air collision
between a Piper Archer and a Piper Tomahawk at Hoxton Park on 6
June 1998, the Bureau issued the following interim recommendations
on 8 June 1999:

"IR19990077

The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority increase the number of mandatory radio
broadcasts at non-controlled aerodromes to include a set of
critical location broadcasts for those locations where the risk of
collision is increased.

IR19990078

The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority extend the proposed radio requirements as
outlined in the Notice of Proposed Rule Making (NPRM9702RP) to
include both licensed aerodromes and any unlicensed aerodrome into
which fare-paying passenger services operate.

IR19990079

The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority amend current procedures/airspace for
aircraft operating into and departing from Hoxton Park in order to
reduce the potential for further aircraft collisions".

IR19990077

On 13 September 1999, the Civil Aviation Safety Authority
responded to IR 19990077 as follows:

"CASA agrees that additional mandatory broadcasts at
non-controlled aerodromes should facilitate alerted see-and-avoid
between aircraft operating in the vicinity of an aerodrome. CASA
will therefore take action to mandate the following additional
broadcasts at MBZ and CTAF aerodromes:

upon entering the runway for takeoff; and

upon joining the circuit."

ATSB classified the CASA response as CLOSED-ACCEPTED.

On 19 November 1999, the Bureau responded to the Civil Aviation
Safety Authority as follows:

"CASA's commitment to increase the number of mandatory
broadcasts at CTAF and MBZ areodromes is supported. The Bureau will
monitor the implementation of this recommendation. As such, could
you please advise the Bureau of the proposed date that this safety
initiative is likely to be implemented ?"

CASA amended the Aeronautical Information Publication (AIP)
Australia. The amendments effective on 2 December 1999, in section
AIP ENR 1.1, included new paragraphs 60.1 and 60.3.

Para 60.1 read as follows:

When approaching an aerodrome and before crossing the MBZ or
CTAF area boundary, all aircraft must broadcast the following
details on the MBZ frequency and, similarly, all radio-equipped
aircraft must broadcast on the CTAF:

callsign and aircraft type;

position (reported as distance with either the radial, bearing,
or quadrant from the aerodrome);

level; and

intentions

Para 60.3 read as follows

All aircraft operating into an aerodrome within an MBZ,
and all radio-equipped aircraft operating into an aerodrome within
a CTAF area, must broadcast on the MBZ frequency or CTAF when
joining the circuit.

IR19990078

On 14 July 1999, Airservices Australia responded as follows:

"Airservices does not wish to comment on this
recommendation except to agree with the remarks referring to the
potential for frequency congestion at non-controlled aerodromes
should this recommendation become mandatory."

On 13 September 1999, the Civil Aviation Safety Authority
responded as follows:

"Since fare-paying passengers may travel at any time to any
destination with a suitable landing area, CASA considers that
compliance with such a requirement by non-radio equipped aircraft
would be at best difficult, and would not impose it without a
clearly identified safety issue and justification.

"At the same time, the intended CASA action detailed in the
response to IR19990077 will go a long way towards satisfying the
intent of this interim recommendation."

ATSB classified the CASA response as CLOSED-PARTIALLY
ACCEPTED.

On 19 November 1999, the Bureau responded to the Civil Aviation
Safety Authority as follows:

"The Bureau agrees that the implementation of IR19990077 will go
a long way toward meeting the intent of IR19990078. In addition,
your reference to the difficulty of complying with such a
requirement by non-radio equipped aircraft in those cases where
passenger-carrying services do not operate in accordance with fixed
schedules, is also supported.

"However, a number of operators do conduct scheduled flights
into unlicensed aerodromes. In such cases, additional protection
for the passengers who commute on those services may be provided by
other means. Additional information would assist the pilots of both
radio and non-radio equipped aircraft to make decisions about their
intended activities that would reduce the risk of collision with
passenger-carrying flights."

IR19990079

On 14 July 1999, Airservices Australia responded as follows:

"Airservices agrees that the preferred situation would see
aircraft operating in the vicinity of Hoxton Park equipped with two
radios and with the suggestion that more appropriate position
reports in the circuit area would assist in situational
awareness.

"We are also aware of anecdotal evidence that pilots interpret
the requirements for radio calls in the MBZ differently which
itself can cause confusion and loss of situational awareness."

On 13 September 1999, the Civil Aviation Safety Authority
responded as follows:

"Special procedures to facilitate the safety of
operations are already in place at Hoxton Park. Given the
constraints imposed by the geographical proximity of other
aerodromes to Hoxton Park, and also in the light of the volume and
nature of aircraft operations at these locations, CASA would
welcome more detailed information from BASI as to how it considers
current procedures and airspace arrangements could be amended to
reduce the potential for further aircraft collisions."

ATSB classified the CASA response as OPEN.

On 19 November 1999, the Bureau responded to the Civil Aviation
Safety Authority as follows:

"The implementation of IR19990077 would, again, go some
way in addressing the concerns raised on IR19990079. The Bureau
understands the present airspace constraints imposed on Hoxton
Park; however, Hoxton Park's unique problems should be taken into
consideration in any future proposals for airspace changes in that
area. In relation to the procedural aspects, the Bureau believes
that there may be solutions that would reduce the risk of aircraft
collisions in the Hoxton Park area. The following suggestions are
offered, without prejudice, for your consideration:

"1. Pilots departing the Bankstown CTR boundary whose
aircraft are not equipped with dual radios, should switch
immediately onto the Hoxton Park frequency rather than delaying
that action until 3 NM from the CTR boundary, as currently advised
in the ERSA; "2. A defined airspace corridor with designated
altitudes for those flights operating directly between Bankstown
and Hoxton Park;

"3. Approach points for arrivals of flights from
locations other than Bankstown, be designated for Hoxton Park;
and

"4. Circuit entry procedures as currently outlined in
the ERSA, be more comprehensively defined.

"Therefore, the Bureau requests that IR19990079 be
reconsidered and that CASA provide advice on the outcome of any
further consideration at your earliest convenience."

Conspicuity trials

Approximately two months after the accident, the then Bureau of
Air Safety Investigation conducted a series of trials on the
conspicuity to a pilot on final approach of a light-coloured light
aircraft on the "piano keys" of runway 34 at Hoxton Park. The trial
was conducted in very similar weather conditions, and during the
same time of day, as the accident.

A brief description of the trials and their results were
published in Issue 23 of "Asia-Pacific Air Safety", September 1999.
In short, the Bureau found that under some conditions of light and
contrast, combined with an expectancy that a runway would be clear,
a pilot of an aircraft on final approach may fail to perceive an
aircraft on the piano keys at the threshold of the runway.

Why neither pilot saw, nor was aware of, the other aircraft
could be primarily due to communications and visual acquisition
limitations.

Without radio information, pilots only become aware of traffic
by "unalerted see-and-avoid", i.e. by visually scanning all
airspace surrounding their aircraft with no prior expectation of
seeing another aircraft.

If the pilots of two approaching aircraft have communicated by
radio, each pilot has some idea of where to look for the other's
aircraft and is expecting its arrival. This "alerted see-and-avoid"
process greatly increases the probability of each pilot sighting
the other aircraft in time to arrange separation.

A pilot operating at an uncontrolled aerodrome in an "alerted
see-and-avoid" environment such as a Mandatory Broadcast Zone (MBZ)
or CTAF, would expect other pilots to broadcast their position and
intentions. Consequently, pilots' efforts to scan the sky for
traffic might be less rigorous than they would be in the "unalerted
see-and-avoid" environment. If an aircraft is operating on an
unalerted basis in an alerted environment, other pilots can
incorrectly conclude that the absence of radio calls means that
there is no conflicting traffic. It is therefore less likely that
traffic approaching on an unalerted basis will be seen in an
alerted see-and-avoid environment than in an unalerted
see-and-avoid environment.

Communications

The investigation concluded that the requirement for only two
CTAF broadcasts was probably inadequate, even though the pilots
were free to make additional radio calls when appropriate. The
Pitts pilot reported that he made a broadcast when he was 5 NM from
Hoxton Park and again upon entering the crosswind leg for a left
circuit for runway 34. The reason the other three pilots did not
hear the radio calls from the Pitts pilot could not be determined.
He did not broadcast his position on the base leg or on final
approach which, in any case, he was not required to do. As a
result, the Sundowner pilot had little opportunity to take
advantage of alerted-see-and-avoid procedures at a time when he
would have been preparing to take off. If the Sundowner pilot had
not transmitted his intention to enter the runway and take off, the
Pitts pilot similarly had little opportunity to use alerted
see-and-avoid.

The Pitts pilot did not hear the Sundowner pilot's taxi call as
the Pitts was probably more than 5 NM from Hoxton Park when the
call was made. If so, the Pitts would not have been on the Hoxton
Park CTAF at that time. Consequently, the Pitts pilot would have
had to sight the Sundowner to become aware of its presence.

Vision

The Sundowner pilot's spectacles may have limited his ability to
see the Pitts by reducing the contrast between the yellow painted
Pitts and the environment. In addition, the relatively small
profile of the Pitts could also have made visual acquisiton more
difficult.

Trees obscuring traffic on left base for runway 34 prevented the
Sundowner pilot from effectively scanning that part of the circuit
while in the runup bay. However, while on the taxiway between the
runup bay and the runway threshold, he should have had an
unobstructed view of the final approach path.

The same trees may have obscured the Pitts pilot's view of the
aircraft in the runup bay. However, when the aircraft was on the
taxiway between the runup bay and the runway, there were no visual
obstructions affecting the view from final approach.

After the Pitts had lined up on final approach, the nose-high
pitch attitude of the aircraft at approach speed would have denied
the pilot, seated in the rear cockpit, a continuous view of the
runway threshold. In addition, briefly lowering the nose to obtain
an unobstructed view of the threshold would have given the Pitts
pilot limited opportunity to see the Sundowner entering the runway
or beginning its takeoff. He did not see the Sundowner before
committing his aircraft to a landing.

Sequence of events

The pilot of a Beechcraft Sundowner was preparing to depart
Hoxton Park Aerodrome for his first solo navigation training
exercise. The pilot of a Pitts Special S-2A had flown his aircraft
from Bankstown to the training area and then to Hoxton Park to
conduct practice circuits before returning to Bankstown.

The Pitts pilot reported broadcasting details of his entry to
the Hoxton Park common traffic advisory frequency (CTAF) area when
he was 5 NM from Hoxton Park, and when he entered the circuit area
on the crosswind leg for runway 34. He also reported that, in order
to maintain separation from a preceding aircraft in the circuit, he
had reduced speed and followed that aircraft.

Meanwhile, the Sundowner pilot had completed his pre-departure
checks in the runup bay. He then taxied his aircraft onto runway 34
and commenced the take-off run. At that time, the Pitts was on
final approach. The Pitts pilot reported that during the final
approach he had repeatedly lowered the nose of the aircraft for
short periods in order to provide a view of the flight path to the
runway threshold before committing himself to a landing. The last
time he had performed the manoeuvre was about 400 m from the
threshold.

As the Sundowner was accelerating along the runway, the Pitts
landed on top of it about 80 m from the threshold. Both aircraft
became entangled and travelled approximately 100 m along the runway
before slewing to the right then turning sharply left and coming to
rest on the runway. The propeller of the Pitts deeply penetrated
the Sundowner cabin and killed the pilot.

Another pilot operating in the circuit heard the Sundowner pilot
make a pre-taxiing radio broadcast on the CTAF. The investigation
could not establish if the Sundowner pilot made any further
broadcasts before the collision. The Pitts pilot later stated that
he did not remember hearing any radio transmissions from other
aircraft. Further, he reported that he had no idea that he had
collided with another aircraft until he vacated the cockpit.

Shortly before the accident, three other aircraft were operating
in the circuit area. Their crews later reported hearing each
other's radio traffic on the CTAF, but not hearing any radio
transmissions from the Pitts.

Wreckage examination

The Sundowner came to rest on a southerly heading, sustaining
deep propeller slashes to the left forward side of the cabin. The
fin was severed. The Pitts's right main wheel had penetrated the
Sundowner's left rear cabin. The very high frequency (VHF)
transceiver was tuned to 127.0 MHz, the CTAF, and later testing
showed that the radio was serviceable.

The wreckage examination indicated that the Sundowner was
serviceable before impact.

The Pitts came to rest on a heading slightly east of south. Both
right wings were detached and displaced 90 degrees rearward. The
VHF transceiver was tuned to 127.0 MHz and later testing showed
that the radio was serviceable. Test running of the engine showed
that it should have performed normally before the impact.

The wreckage examination indicated that the Pitts was
serviceable before impact.

Pilot information

The Sundowner pilot was 70 years old and held a student pilot
licence (aeroplanes) and a valid Class 2 medical certificate with a
requirement to wear vision correction. At the time of the accident
he was wearing multi-focal prescription spectacles, that corrected
his vision to 6/6. He had a total of 106 hours flying experience,
including 22 hours on type. He had completed a short dual check
flight earlier in the day, and had been cleared to carry out the
solo navigation exercise.

Autopsy and toxicological tests did not reveal any pre-existing
medical conditions, alcohol or other drugs that might have
prevented the pilot from safely operating the aircraft.

The pilot's yellow-brown tinted lens spectacle lenses were
designed to change colour in accordance with variations in
temperature and ultra-violet light exposure. (As temperature
reduced and/or the level of ultra-violet light increased, the lens
darkened.) This tint reduced light to the eye and changed the
colour of the environment. When viewed through the lens, the
contrast between the yellow painted Pitts and the blue sky would
have been reduced.

The Pitts pilot was 72 years old and held a private pilot
licence (aeroplanes) and a valid Class 2 medical certificate with a
requirement to wear vision correction. At the time of the accident
he was wearing vision-correcting prescription sunglasses. He had
been a pilot for about 38 years, and had about 2,700 hours flying
experience, including 491 hours on type.

Weather

The weather at the time of the accident was fine, with
visibility of 40 km and scattered cumulus clouds with a base of
4,500 ft above mean sea level. Wind conditions were light and
favoured landings on runway 34.

Aerodrome information

Hoxton Park was designated as a CTAF aerodrome. The radio
frequency for aircraft-to-aircraft communication was 127.0 MHz. The
only mandatory radio broadcasts required in accordance with CTAF
procedures were to be made when beginning to taxi and when inbound
to the aerodrome. Pilots operating within CTAFs would normally be
expected, upon hearing one of those broadcasts, to respond with
information on their position and intentions and to arrange mutual
separation.

According to the Aeronautical Information Publication, "Enroute
Supplement Australia" (ERSA), runway 34 was the preferred runway
for use in still wind conditions. Aircraft using runway 34 normally
conducted left circuits, resulting in traffic on the downwind leg
passing behind aircraft in the runup bay for runway 34. A copse of
trees about 10 m in height was located immediately to the
south-west of the runup bay. The trees obscured the view that
pilots in the runup bay would have had of aircraft on the left base
leg or of aircraft turning onto final approach for a landing on
runway 34. However, from the holding point on the taxiway between
the runup bay and the runway 34 threshold, and from most of the
taxiway, the view of traffic on final approach was
unobstructed.

The Hoxton Park CTAF was changed from 118.1 MHz to 127.0 MHz
with effect from 3 December 1998. Notice to Airmen (NOTAM) C9/98
(10 November 1998) publicised the change, but it was not published
in ERSA until the 25 March 1999 issue.

Aircraft Details

Manufacturer

Pitts Aviation Enterprises

Model

S-2

Registration

VH-PTD

Serial number

2022

Operation type

Private

Departure point

Bankstown, NSW

Destination

Bankstown, NSW

Damage

Substantial

Aircraft Details

Manufacturer

Beech Aircraft Corp

Model

Registration

VH-AYZ

Serial number

M-1580

Operation type

Flying Training

Departure point

Hoxton Park, NSW

Departure time

1215 hours ESuT

Destination

Goulburn, NSW

Damage

Substantial