The Australian Transport Safety Bureau yesterday warned IFR pilots about selecting an appropriate lowest safe altitude (LSALT) after a Victoria Police helicopter had a brush with Mount Baw Baw early this year.
VicPol AW139 VH-PVO had been re-tasked from Coldstream to Orbost in March went it entered cloud near Mount Baw Baw tracking east. The aircraft's enhanced ground proximity warning system (EGPWS) prompted a left turn and climb to avoid terrain. At the time the aircraft was only 1.8 nm from and only 200 feet above ground.
The ATSB found that the pilot operated the flight on an LSALT of 5000 feet based on the Moorabbin 25-nm sector of 4700 and expected to remain VFR on top of cloud, which is an acceptable reason for going below a published grid LSALT. As the pilot expected to remain in VMC, the LSALT was not revised as had been the original plan.
At the time, the top of Mount Baw Baw at 5138 feet was covered by cloud and the pilot did not expect the aircraft would enter cloud.
“Lowest safe altitudes are published on aeronautical charts and in publications to ensure a minimum 1000-ft obstacle clearance when aircraft are operating under instrument flight rules,” ATSB Director Transport Safety Dr Stuart Godley explained.
“In this incident the helicopter was below the lowest safe altitude as, based on their estimate of height above the cloud tops, the pilot had incorrectly assessed the in-flight conditions as visual meteorological conditions after the helicopter reached 5000 ft in the vicinity of Coldstream.
“As a result, the pilot elected to remain at 5000 feet instead of recalculating the lowest safe altitude as the flight progressed.”
The ATSB investigation also found that VicPol did not have a procedure for upgrading from VFR to IFR in flight.
“Our investigation highlights the importance of lowest safe altitude calculations and to recalculate the lowest safe altitude appropriate for the area of operations,” Godley said.
“Operators should also review their operations manual to ensure they have procedures in place to adequately capture their operating procedures in order to minimise the likelihood of decision‑making errors.”
Following the incident, the Victoria Police Air Wing developed an instrument flight rules upgrade procedure for inclusion in its operations manual.
The full report is on the ATSB website.