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This week's ATSB DTS media flim flams -

Via PJ's media minions:

R44 helicopter likely overweight at high density altitude prior to take-off accident



A Robinson R44 helicopter was operating at a high-density altitude, and likely above its maximum gross weight, when it impacted rocky terrain shortly after take-off in Western Australia’s Pilbara region, an ATSB investigation has found.

On 3 November 2022, the R44 was departing a cultural heritage site in the Collier Ranges, with a pilot and three passengers, who were members of a survey team, on board.

During the take-off, travelling about 27 kt and just above treetop height, the pilot experienced a severe drop in the helicopter’s performance, and the low rotor RPM warning sounded.

“The pilot conducted the low rotor RPM recovery actions, but was unable to arrest the descent,” ATSB Director Transport Safety Dr Stuart Godley said.

The helicopter impacted rocky terrain about 150–200 m from its take-off location, and rolled onto its left side, resulting in substantial damage, serious injuries to one passenger, and minor injuries to the pilot and other two passengers.

The ATSB’s final report notes the take-off occurred at an elevation of 2,170 ft above mean sea level, with a calculated density altitude of 4,210 ft.

Compounding this, the pilot used estimated weights for the passengers, based on figures provided by one of the passengers. This resulted in the calculated helicopter gross weight below the maximum take-off weight, although the helicopter was likely being about 30 kg over the maximum take-off weight. 

“More power than the engine could provide was needed to safely conduct the take-off, given the overweight helicopter condition, confined take-off area and high-density altitude,” Dr Godley said.

“This highlights the importance of using accurate figures when calculating weight and balance, and expected performance, especially when operating at full capacity and near the maximum gross weight.”

The investigation report notes the drop in performance observed by the pilot coincided with the helicopter transitioning out-of-ground effect. (In ground effect, air drawn down through the rotor collects under the helicopter and provides a ‘cushion’ of air, meaning slightly less power is required than would otherwise be needed.)

“Regularly reviewing and being prepared to amend flight plans, such as by reducing passenger numbers to increase performance margins, is central to safe operations,” Dr Godley added. 

While not found to have contributed to the accident, the ATSB investigation also found the flight was operated under CASA’s Part 138 regulations, which are for aerial work operations.

The flight should have been operated under Part 133, for air transport operations, as it was a passenger carrying flight. Further, the operator was only approved for aerial work operations.

Read the report: Collision with terrain involving Robinson R44, VH-OCL, 8.1 km north-north-west of Kumarina Roadhouse Airport, Western Australia, on 3 November 2022

Publication Date: 21/08/2024

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Operator procedures for simulated engine failures should align with manufacturer guidance, Baron accident highlights



A Baron that yawed and rolled before impacting the ground next to the runway after the mixture instead of the throttle had been used to simulate an engine failure highlights the importance of procedures aligning with manufacturer guidance.

On 11 April 2024, an instructor and student pilot were operating the twin-engine Beechcraft E55 Baron to conduct a navigation exercise under the instrument flight rules from Cowra, New South Wales, an ATSB investigation report details

After conducting instrument approaches to Goulburn and Canberra, the aircraft returned to Cowra to fly an instrument approach with one engine inoperative.

Arriving over the airport, the instructor simulated a single engine failure by moving the left engine mixture control lever to the idle cut-off position.

“This was in accordance with the operator’s relevant procedure at the time, but differed from Beechcraft’s aircraft flight manual,” Director Transport Safety Stuart Macleod said.

The manufacturer’s procedure prescribes setting zero thrust by retarding the propeller lever to the feather detent, and the throttle lever to 12 inches of manifold pressure.

“The Beechcraft flight manual states using the throttle to simulate engine failure is to ‘avoid difficulties of restarting an engine and preserve the availability of engine power’,” Mr Macleod noted.

Civil Aviation Safety Authority guidance also recommends using the throttle, and not mixture, for one engine inoperative training.

With the aircraft operating on just the right engine, and the left engine’s propeller windmilling, the student conducted an instrument approach before visually establishing the aircraft on final approach to the runway.

During the landing flare, the instructor initiated a go-around, and the aircraft rapidly yawed and rolled to the left, impacting the ground in an almost vertical nose-down attitude, before coming to rest inverted.

Fortunately, the pilots survived with minor injuries, even though ATSB analysis found the impact deceleration likely exceeded 30 G, principally in a forward direction, with the stable collapse of the airframe structure forward of the cabin and crash-resistant fuel cells aiding their survivability.

“When attempting to set zero thrust during the downwind leg of the final circuit, it was likely the instructor unintentionally did not move the left engine’s mixture lever back to rich, to ensure it was available for instant use if needed,” Mr Macleod explained.

“As a result, the go-around was initiated below the minimum control speed, with the left engine inoperative, resulting in an asymmetric loss of control.”

Since the accident the training operator, Fly Oz, has amended its multi-engine training procedures to only simulate engine failures using throttle at any height.

“Accidents as a result of engine malfunctions in twin-engine aeroplanes are rare, but often fatal. As such, training to manage one engine inoperative flight is important but should not introduce unnecessary risks,” Mr Macleod remarked.

“In this case, the manufacturer required the throttle be used to simulate an engine failure, and CASA guidance also recommends using the throttle rather than the mixture. This ensures power can quickly be restored if needed.”

Read the report: Loss of control and collision with terrain involving Beechcraft E55, VH‑OMD, Cowra Airport, New South Wales, on 11 April 2024

Publication Date: 22/08/2024

MTF...P2