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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.

 

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.

 
  1. The CTAF radio broadcast procedures did not provide the pilots with adequate opportunity for "alerted-see-and-avoid".
  2. Probably neither pilot saw the other aircraft.
  3. The technique of briefly lowering the nose on final approach did not allow the Pitts pilot to be certain that the runway was clear before he committed the aircraft to a landing.
 

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:

  1. callsign and aircraft type;
  2. position (reported as distance with either the radial, bearing, or quadrant from the aerodrome);
  3. level; and
  4. 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.

 
General details
Date: 10 March 1999 Investigation status: Completed 
Time: 1215 hours ESuT Investigation type: Occurrence Investigation 
Location   (show map):Hoxton Park, Aero.  
State: New South Wales  
Release date: 21 June 2000 Occurrence category: Accident 
Report status: Final Highest injury level: Fatal 
 
Aircraft 1 details
Aircraft manufacturer: Pitts Aviation Enterprises 
Aircraft model: S-2 
Aircraft registration: VH-PTD 
Serial number: 2022 
Type of operation: Private 
Damage to aircraft: Substantial 
Departure point:Bankstown, NSW
Destination:Bankstown, NSW
Crew details
RoleClass of licenceHours on typeHours total
Pilot-in-CommandPrivate491.02700
Aircraft 2 details
Aircraft manufacturer: Beech Aircraft Corp 
Aircraft model: 23 
Aircraft registration: VH-AYZ 
Serial number: M-1580 
Type of operation: Flying Training 
Damage to aircraft: Substantial 
Departure point:Hoxton Park, NSW
Departure time:1215 hours ESuT
Destination:Goulburn, NSW
Crew details
RoleClass of licenceHours on typeHours total
Pilot-in-CommandStudent/Passenger22.2106
 
Injuries
 CrewPassengerGroundTotal
Fatal: 1001
Total:1001
 
 
 
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Last update 13 May 2014