Operational non-compliance involving a Boeing 737-377, VH-CZM, Wonthaggi VOR, Victoria, on 13 July 1995

When VH-CZM was transferred to the arrivals controller, the aircraft was observed to turn left at Wonthaggi and track 298 degrees towards BAYSI instead of 320 degrees towards Plenty. The controller subsequently radar vectored VH-CZM to Plenty. There was no breakdown in separation.

By replaying the communications tape, it was discovered that at 14.04.35 EST, the sector three controller had issued the following clearance: "Charlie Zulu Mike, STAR clearance Plenty One arrival, runway 34, maintain flight level 370."

The pilot read back: "Charlie Zulu Mike BAYSI One arrival, runway 34, flight level 370."

When the pilot read back a different clearance, the controller failed to notice the pilot's error. When the aircraft turned left, the pilot genuinely thought that he had been cleared for a BAYSI one arrival.

Significant Factors

The following factors were considered relevant to the development of the incident:

1. The pilot misheard the Plenty One clearance and read back BAYSI One.

2. The controller misheard the pilot's incorrect clearance read back.