Coulson Aviation and the relevant Western Australian Government Departments had not published a minimum retardant drop height in their respective operating procedures for large airtankers. Consequently, the co-pilot (pilot monitoring), who did not believe there was a minimum drop height, did not alert the aircraft captain (pilot flying) to a drop height deviation prior to the collision.
The amendment to the Coulson Aviation Flight Operations Manual to prescribe a minimum target drop height should adequately address this safety issue.
Coulson Aviation issued Operations Bulletin 23-1 with their revised minimum drop height of 200 ft on 8 February 2023. On 19 July 2023, they issued a Flight Operations Manual Policy with a 200 ft minimum drop height. This was incorporated into their fixed-wing Flight Operations Manual on 10 October 2023 with an amendment to include an Airtanker Procedures section with a subsection for Minimum Drop Height.
