FACTUAL INFORMATION
A foreign Boeing 747 (B747) was being sequenced for landing on RWY 16 at Melbourne aerodrome by the Departures North radar controller (DEPN). After landing, the pilot in command of the B747 rang the Area Approach Control Centre (AACC) and queried whether the aircraft had received a clearance to land. A check of the tower audio voice recording (AVR) tape revealed that the Aerodrome controller (ADC) had issued a landing clearance but that the transmission had not been acknowledged by the crew of the B747. Further checks of the AVR for the DEPN position found that the DEPN controller had not instructed the crew of the B747 to transfer to the ADC frequency. The AVR also indicated that the crew did not query the DEPN for the need to transfer to the ADC frequency as the aircraft approached the runway. The crew of the B747 left the aircraft radio selected to the DEPN frequency during the landing. The Aeronautical Information Publication (AIP) stated that the clearance limit for an aircraft approved to make an instrument approach was the nominated runway, subject to further air traffic control instructions and a clearance to land. The crew of the B747 continued the flight beyond the clearance limit without requesting a clearance to land or further instructions. The AIP also stated that a pilot in command must not land unless the specific clearance "Cleared to land" had been received. The ADC would normally receive an acknowledgement of the receipt of a landing clearance from the flight crew. The ADC did not challenge the crew of the B747 when the clearance to land was not acknowledged. Three controllers normally staffed the control tower. On the day of the occurrence there were only two controllers on duty as one controller had been rostered to relieve at another location. Due to a misunderstanding a replacement controller was not nominated. The controllers on duty in the tower believed that staffing was adequate for the expected traffic and did not request a replacement controller. The two controllers were required to share the responsibility for the conduct of coordination while operating their respective positions of ADC and Surface Movement control (SMC).
ANALYSIS
The reasons for the crew of the B747 not querying the DEPN controller with respect to the need to change to the ADC frequency and for the DEPN controller not instructing the crew to change to the ADC frequency, were not determined. The ADC was distracted by coordination duties to the detriment of his prime function. Consequently, he did not ensure that the B747 was operating on the ADC frequency prior to issuing a clearance to land. He also did not challenge the crew of that aircraft to acknowledge receipt of the clearance.
SIGNIFICANT FACTORS
1. The DEPN controller did not instruct the crew of the B747 to transfer to the ADC frequency.
2. The crew of the B747 did not query the DEPN controller regarding transfer to the ADC frequency as the aircraft approached the runway.
3. The ADC did not query the DEPN controller with respect to the frequency transfer of the B747 when the aircraft was on final for the runway.
4. The ADC did not establish that the B747 was on the frequency prior to issuing a clearance to land.
5. The ADC did not obtain an acknowledgement of the clearance to land from the crew of the B747.
6. The crew of the B747 landed the aircraft without obtaining a clearance to land from the ADC.