Separation occurrence involving Piper PA-44, VH-KZJ, and Cessna 172, VH-ZER, near Jandakot Airport, Western Australia, on 12 June 2025

The occurrence

At 1124 local time on 12 June 2025, a pilot conducting a navigation flight in a Piper Aircraft Inc. PA-44-180 (PA-44) aircraft, registered VH-KZJ, was inbound to the circuit area at Jandakot Airport, Western Australia. The flight was the third solo flight for the pilot in a twin-engine aircraft, and their first time operating VH-KZJ. At the same time, a Cessna 172 (C172) aircraft, registered VH-ZER, was also inbound to Jandakot Airport, with an instructor and student on board after conducting a training flight. 

The runway in use at Jandakot was 06L[1] and local procedures required aircraft to contact air traffic control (ATC) at specified approach points (in this instance Oakford and Russell) then track to Forrestdale Lake. From there, aircraft were to fly overhead the airport at 1,500 ft above mean seal level (AMSL) towards the north and join the circuit as directed by Jandakot Tower (Figure 1).

As the PA-44 was passing the inbound reporting point Russell, ATC passed traffic information on the C172 inbound to the circuit area via the Forrestdale Lake inbound reporting point (Figure 1). With the PA-44 being the faster aircraft, ATC instructed the PA-44 pilot to overtake the C172 on the right which was acknowledged by the PA-44 pilot by a callsign response. The pilot then reported at Forrestdale Lake with the C172 in sight. Both aircraft were at 1,500 ft.

Figure 1: Aircraft inbound tracks

Source: Google Earth with fight radar tracking, annotated by the ATSB

Despite the ATC instruction to overtake the C172, the pilot in the PA-44 reduced the engine power to circuit power, which resulted in the aircraft slowing down. As such, the PA-44 did not overtake the C172 prior to joining the downwind leg of the circuit.[2]

Observing that the PA-44 had not overtaken the C172 as they had anticipated, the controller changed their sequencing plan to have the C172 land first. The table below details the exchange between the pilots and controller and Figure 2 shows where these calls were in relation to the flight paths.

Table 1: Communication

Figure 2: Aircraft track with ATC clearances

Source: Google Earth with fight radar tracking, annotated by the ATSB

The pilot in the PA-44 reported that, as ATC was issuing its approach clearance, the traffic advisory system (TAS) in the aircraft began audibly alerting. The pilot later advised they were not familiar with the TAS and had never heard the audible alert before. They reported that as their attention was focused on the alert, they did not hear the sequencing part of the instruction to ‘follow the Cessna’. As such, they did not repeat this part of the instruction during the readback of their clearance and believed they were still cleared to pass the C172. 

They further advised they had always previously been required to read back the complete sequencing instruction and as they were not prompted for any further readback on this occasion, did not consider that they had not heard the instruction correctly.

The PA-44 continued to overtake the C172 on downwind by descending and accelerating, and then turning inside the C172. The pilot recalled that they thought the sight picture of the close overtake ‘did look a bit odd’, but did not consider questioning the controller. 

The instructor in the C172 was also an instructor of the pilot in the PA-44. When hearing their student’s interactions with ATC, they were concerned that the pilot may not have understood the intention of ATC. As such the instructor ensured they maintained visual contact with the PA-44 throughout the sequence.

Both pilots reported that they could see the other aircraft for the duration of the incident.

Context

Pilot details

The pilot of the Piper Aircraft PA-44 held a private pilot licence (aeroplane) and had a class 1 aviation medical certificate. They were undergoing training to obtain their commercial pilot licence (aeroplane) and had a total of 128 hours of flying experience, of which 22 were on the PA-44. They had flown 37 hours in the previous 90 days.

The instructor of the Cessna Aircraft Company 172 (C172) held a commercial pilot licence (aeroplane) with a class 1 aviation medical certificate. They held an instructor and instrument flight rating. They had a total of 1,200 hours of flying experience, of which 390 were on the C172. They had flown 155 hours in the previous 90 days. 

Aircraft details

The Piper Aircraft Inc PA-44-180 is 4-seat, low-wing, retractable-undercarriage aircraft with 2 piston engines. VH-KZJ was equipped with the Garmin G1000 avionics suite and optional traffic advisory system (TAS).

The Cessna Aircraft Company 172S is a 4-seat, high-wing, fixed-undercarriage aircraft with one piston engine.

Training

The operator advised that VH-KZJ was the only aircraft in its fleet fitted with the optional traffic advisory system (TAS) with the avionics suite (G1000) and it does not provide formal syllabus training on the TAS. A general awareness was provided during a dual flight, where the TAS system test was conducted as part of the PA-44 (G1000) Normal Checklist – After Start Checklist. 

Provision of separation in Class D airspace

In accordance with Aeronautical Information Publication Enroute 1.4-13 as both aircraft were operating under Visual Flight Rules (VFR) in Class D airspace there was no requirement for Air Traffic Control (ATC) to provide separation.

Readback requirements

Airservices Safety net – operating in Class D airspace highlighted the importance of correct readbacks from pilots to prevent frequency congestion. As part of this guidance, it referred pilots to Aeronautical Information Publication (AIP) General (GEN) 3.4.

AIP GEN 3.4 6.6 General Phrases provided the following phraseology when a pilot was assigned and required to maintain separation with a sighted aircraft: 

when a pilot is assigned and required to maintain separation with a sighted aircraft ATC are to use the phrase FOLLOW (or MAINTAIN OWN SEPARATION WITH [AND PASS BEHIND]) (aircraft type or identification) [instructions or restrictions].

Manual of Air Traffic Services (MATS) pilot readback requirements stated:

Obtain a readback in sufficient detail that clearly indicates a pilot’s understanding of and compliance with all ATC clearances, including conditional clearances, instructions and information which are transmitted by voice.

MATS further stated that readback discrepancies must be immediately corrected by the controller. 

The controller later advised that the ‘follow the’ instruction was not required to be read back as part of the [key elements] readback requirements in MATS (Figure 3), and therefore there was no reason to correct the incomplete readback.
Airservices Australia later confirmed it does not require ‘follow the’ type instructions to be read back.

Figure 3: Manual of air traffic services

Safety analysis

When the air traffic controller identified that the PA-44 had not overtaken the C172 as expected, they amended the PA-44 pilot’s approach clearance to require them to follow it as the second aircraft in the landing sequence. However, when the amended clearance was issued, the pilot’s attention was focused on the aural alert from the traffic advisory system and they did not identify the final part of the instruction to ‘follow the Cessna’. Consequently, and despite recognising that the sight picture was ‘looking a bit odd’, the PA-44 pilot passed the C172 as per the original clearance, resulting in reduced separation between the 2 aircraft.

Having missed the requirement in the amended clearance to follow the C172, the PA-44 pilot did not include the sequencing information in their readback. Although this was a key element of the revised approach clearance, the pilot’s incomplete readback was not corrected by the controller as they considered that the pilot was not required to read back that instruction. This was a missed opportunity to resolve the situation.

Safe circuit pattern operation relies on all the involved pilots having a common understanding of the aircraft sequence. Additionally, overarching guidance in the Manual of Air Traffic Services (MATS) required controllers to ‘obtain a readback of sufficient detail that clearly indicates pilots’ understanding of and compliance with all ATC clearances.’ Despite that, MATS did not explicitly require sequencing instructions to be read back as a ‘Key element’ of the approach clearance, providing no assurance that this safety-critical aspect had been correctly understood.

Finally, the situation awareness maintained by the instructor in the C172 ensured that adequate separation was maintained between the 2 aircraft as the situation developed, possibly preventing a more serious outcome.

Findings

From the evidence available, the following findings are made with respect to the separation occurrence involving Piper PA-44, VH-KZJ, and Cessna 172, VH-ZER, near Jandakot Airport, Western Australia, on 12 June 2025. 

Contributing factors

• The PA-44 pilot did not identify the final part of the amended instruction to ‘follow the Cessna’. Consequently, the PA-44 pilot passed the C172 as per the original clearance, resulting in reduced separation between the 2 aircraft.
• Although a key element of the revised approach clearance, the pilot’s incomplete readback was not corrected by the controller as they considered that the pilot was not required to read back the ‘follow the Cessna’ instruction.
• The Manual of Air Traffic Services did not explicitly state that sequencing instructions were required to be read back by a pilot, providing no assurance that this safety-critical aspect had been correctly understood. (Safety issue)

Safety issues and actions

Readback requirements

Safety issue number: AO-2025-033-SI-01

Safety issue description: The Manual of Air Traffic Services did not explicitly state that sequencing instructions were required to be read back by a pilot, providing no assurance that this safety-critical aspect had been correctly understood.

Glossary

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the pilots of both aircraft
• the air traffic controller
• Airservices Australia
• ADS-B data for both aircraft
• the operator of both aircraft.

Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report. 

A draft of this report was provided to the following directly involved parties:

• pilots of both aircraft
• the air traffic controller
• Airservices Australia
• the operator
• Civil Aviation Safety Authority.

Submissions were received from:

• the air traffic controller
• Airservices Australia
• the operator.

The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.

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