AW139 LOC-I Climbing Away from SAR Exercise (Esso Australia Leonardo AW139 VH-EXK)
On 2 October 2024 Esso Australia Leonardo AW139 VH-EXK was conducting Search and Rescue (SAR) training under Visual Flight Rules (VFR), just off the coast of Golden Beach, Victoria, when it suffered a Loss of Control – In Flight (LOC-I).
Esso Australia Leonardo AW139 VH-EXK at Longford, Victoria (Credit: Via ATSB)
The Australian Transport Safety Bureau (ATSB) issued their safety investigation report on 20 May 2025.
The Incident Flight
The helicopter departed Longford Heliport, Victoria, adjacent to the Esso Longford gas plants, at 0816 local time for a SAR exercise. The crew consisted of the Aircraft Commander (15,402 total hours, 2,603 on type), a Flight Instructor (11,129 total hours, 3,695 on type), a Check Aircrewman, and a Hoist Operator.
Esso Australia provide daytime SAR coverage in support of their Bass strait gas production. The ATSB state that on 11 June 2024, was Esso Australia issued with an CASA air operator’s certificate (AOC) and a Part 138 aerial work certificate (for SAR operations). While Esso Australia had previously operated in the private category, for at least 5 years they had operated under an AOC.
ATSB say the Aircraft Commander was initially Pilot Flying (PF) and the Instructor Pilot Monitoring (PM) and that the exercise took place c 2 km offshore and…
…involved retrieving a training aid amidst large swells, sea spray and encroaching fog from the north-west.
The instructor estimated that the fog bank was less than one kilometre from shore at the time. However, clear skies were visible to the north and north‑east…
The training aid was deployed, and the exercise commenced at about 0825.
As the training progressed, the helicopter’s proximity to the fog on the left side, where the instructor was seated, was observed to be decreasing. The flight crew noted that the skies were clear to the north and northeast of their position on the instructor’s side of the helicopter.
After conducting training for approximately 40 minutes, the instructor assumed control as PF and the check aircrewman assumed the role of hoist operator to retrieve the training aid.
This involved hovering approximately 40 ft above the sea. Their attempt was unsuccessful however. Due to “encroaching fog” the instructor elected to depart and announced they would climb to avoid fog.
At 0908, the instructor manoeuvred the helicopter onto a north-westerly heading…
…and engaged the radar height hold (RHT) system while climbing using a combination of the collective beep trim and force trim release (FTR).
Leonardo AW139 collective grips, collective FTR button and collective beep switch (Credit: Leonardo Helicopters file photos, annotated by the ATSB)
At this time, the captain, acting as the PM, was focused on marking the GPS position of the training aid.
This was to facilitate its recovery in another exercise later that day.
At about this time, the helicopter inadvertently entered instrument meteorological conditions (IMC), and the instructor announced their intention to move forward to depart.
The right cabin door was open and approximately 40 ft of the hoist cable was extended.
The check aircrewman objected via the intercom to departing with the hoist still extended, as the post‑hoist procedures requiring the aircrew to secure the hoist cable and cabin had not yet been completed.
Despite this objection, the instructor proceeded with the departure with the intention of reentering visual meteorological conditions (VMC).
The instructor accelerated and continued to climb, reaching an altitude of 185 ft and an airspeed of 72 kt before beginning a shallow descent. The instructor who was PF noticed the increasing airspeed but took no actions to arrest this trend.
As the helicopter continued accelerating, the captain [the PM] observed on the primary flight display (PFD) a nose-down attitude and airspeed increasing through 80 kt, which exceeded the operational speed for the hoist operation. The captain announced ‘80 kt’ to draw the attention of the instructor to the increasing airspeed. The airspeed continued to increase above 90 kt, which resulted in an airspeed exceedance with the RPM (NR) at 102%, despite the captain’s attempt to set the RPM switch to 100% to avoid this exceedance.
As the helicopter accelerated through 100 kt it exceeded the maximum airspeed for the right main cabin door in the open and locked position.
At 0909, the helicopter had descended to 147 ft above sea level with an airspeed of 101 kt, triggering caution and warning alerts from the [Honeywell MK XXII‑30] enhanced ground proximity warning system (EGPWS).
In the 10-second period preceding the EGPWS warning, the collective FTR was active for 5 seconds while it was engaged and disengaged 3 times.
The instructor recalled climbing and using the collective beep trim and collective FTR. However, they did not recall engaging the collective FTR after the negative vertical speed developed.
The captain later noted that the collective FTR could be activated instinctively while manipulating the collective due to the switch’s position, requiring discipline to avoid unintentional activation.
Responding to the increasing speed and ground proximity alert on the PFD, the captain reactively assumed control, reduced the helicopter’s speed, and initiated a climb by pulling back on the cyclic.
The check aircrewman suggested cutting the hoist cable for safety and indicated that the cable was trailing behind the aircraft. This was not actioned after consultation with the instructor, who stated they were satisfied that the cable did not pose a danger, and they lacked visual reference to the ground [and] they were unsure of what was underneath the helicopter at the time.
During the recovery, the captain climbed on a north‑westerly heading and reduced the helicopter’s airspeed and the instructor resumed control after a brief exchange with the captain.
They regained VMC shortly after, hoisted in the cable and returned to Longford Heliport. The helicopter landed at 0936 local time.
ATSB Safety Analysis
On the departure from the hoist training location:
Climbing immediately in the vicinity of fog may not have been necessary, as manoeuvring to the north or north‑east would have increased the distance from the fog.
However, due to the encroaching fog, the instructor elected to climb, lost visual references and reactively began to accelerate and climb the helicopter before completing the post‑hoist check [to ensure the helicopter is properly configured for departure].
ATSB note that the Aircraft Commander…
…was unaware of the instructor’s intention to depart, likely due to the expectation that the completion of the post‑hoist procedure had not been completed as a prerequisite to climb away.
ATSB examined the flight data recorder (FDR):
ATSB note that:
The recorded pitch changes during 60 seconds of flight data, showing a pitch range of up to 19°, coupled with fluctuating airspeed above limitations and unstable vertical speed, demonstrate an unstable aircraft profile during departure.
The fluctuations observed were…
…consistent with flight control inputs from the pilot flying being uncertain of the flight path, including a nose‑down attitude and airspeed increasing through 80 kt.
Therefore, without visual cues, the instructor likely became subject to the effects of spatial disorientation. This condition significantly impairs a pilot’s ability to accurately interpret attitude, altitude and airspeed.
Operating in degrading visibility creates ambiguity, stalling decision‑making as flight crew face conflicting situational cues (Orasanu, Martin, & Davidson, 2001). Continued reliance on visual cues in these scenarios can draw attention away from critical instrument readings (Summerfield & Enger, 2009).
Pilots tend to overestimate their ability to continue to control the aircraft when visual references are lost (Wiggins, Hunter, O’Hare, & Martinussen, 2012).
The ATSB say that:
Frequent engagement and disengagement of the collective force trim release (FTR) when the radar height hold (RHT) was active further destabilised the helicopter, causing altitude and airspeed fluctuations.
The FTR switch demands disciplined use, as its unintentional instinctual engagement can lead to unintended control inputs.
The Aircraft Commander was preoccupied entering GPS coordinates for the recovery of the training aid so was not monitoring the helicopter’s flight path. This meant they…
…missed the early indications of loss of spatial orientation by the PF due to the degrading visibility.
ATSB note that following the EGPWS alert the Aircraft Commander…
…took control of the helicopter without a formal handover from the instructor by reactively pulling back on the cyclic.
Before assuming control, the captain was able to identify and vocalise the increasing airspeed in an attempt to illicit corrective action from the instructor.
Due to a lack of visual cues, the captain was unsure of their altitude and reactively pulled back on the cyclic to arrest the helicopter’s forward momentum and gain altitude.
The investigators comment that the unannounced taking of control…
…had the potential to introduce further distractions, conflicting control inputs or further inappropriate control inputs in an already dynamic and demanding environment. [The] absence of a structured handover also highlights the difficulties of managing dynamic situations under pressure and balancing conflicting demands.
The investigators says that:
Despite bypassing Esso Australia handover protocols, the captain effectively recognised and responded to the EGPWS alerts and the reduced proximity to terrain.
In a matter of seconds following the initial EGPWS caution, the captain arrested the rate of descent and transitioned into a climb while reducing the forward airspeed of the helicopter. The captain’s intervention immediately reduced the risk of a collision with terrain.
…their decision to establish control of the aircraft during a critical situation was sound.
In particular:
Their decision to prioritise scanning the instruments to regain situational awareness during the event contributed to a successful recovery.
The decisive nature of their intervention further underscores the importance of training and rehearsed recovery actions to mitigate the risks of spatial disorientation in degraded visual environments.
However, concerningly the ATSB found that (our emphasis):
Esso Australia did not provide crew with structured procedures for managing inadvertent entry into IMC and EGPWS alerts during hoist operations.
Furthermore:
Although the Esso Australia exposition required a pilot response to EGPWS alerts, this did not include specific guidance for managing such alerts.
They also found that:
While training covered general EGPWS functionality, it did not include scenario‑based drills for complex situations involving degraded visibility or low-level operations.
Consequently, responses to alerts were reactive, with the crew relying on instinct rather than following a predefined recovery procedure. The absence of predefined inadvertent IMC‑specific recovery actions also exposed the crew to the cognitive effects and demands of operating in degraded visual environments.
ATSB’s Contributory Factors
- The instructor hastily departed the training area, due to encountering fog, before the hoist was secured with the door open, and while the captain as pilot monitoring was still occupied recording the training aid position.
- After inadvertently entering instrument meteorological conditions, the instructor (pilot flying) became spatially disorientated.
- The instructor’s attempt to leave IMC, while being spatially disorientated, resulted in control inputs that led to the helicopter entering an unstable state while still in IMC, triggering a terrain alert below 150 ft, and airspeed exceedances for operations with the main rotor RPM at 102%, the door open and hoist extended.
ATSB’s Other Factors that Increased Risk
- Prior to gaining situational awareness and without an appropriate control handover, the captain reactively assumed control of the helicopter after the terrain warning, increasing the risk of control conflict between the 2 crew.
- Esso Australia did not have a procedure for a helicopter recovery from inadvertent IMC during hoist operations or recovery procedures for EGPWS alerts or advisories. (ATSB Safety issue)
Similar Incidents
ATSB highlighted two previous relevant ATSB investigations, both of which Aerossurance has previously summarised:
- On the evening of 21 October 2016, Helicopter Emergency Medical Service (HEMS) Airbus BK117C2 VH-SYB operated by CHC Australia suffered a serious incident over New South Wales. ATSB explain that: Conditions were marginal and, on departure, the helicopter entered low cloud. The aircrew officer declared loss of visibility on take‑off. The pilot had poor visibility ahead yet could see well to the right. The pilot thought visibility would improve as they passed ground lighting that was reflecting in raindrops on the canopy. The visibility did not improve, and the pilot slowed the aircraft to maintain visual meteorological conditions. The low‑speed manoeuvre resulted in an undesired aircraft state and an EGPWS warning activated. The pilot conducted an inadvertent IMC drill, restabilised control, and continued the flight before landing safely. We examined this occurrence in July 2024: Night HEMS BK117 Loss of Control
- On 13 May 2018 Leonardo Helicopters AW139 VH-YHF of HEMS operator Careflight, while descending during a nighttime search, the aircraft entered a degraded visual environment, developed a high rate of descent, an autohover mode was inappropriately selected and came within 31 ft of impacting the ground. The aircraft was also then flown on for one more flight after the related 159.5% over-torque. We examined this occurrence in April 2020: SAR Helicopter Loss of Control at Night
ATSB comment (our emphasis added):
These occurrences emphasise the effects of spatial disorientation due to powerful and misleading orientation sensations during times of reduced visual cues, which can affect any pilot, no matter what their level of experience.
Esso Australia Safety Actions
Esso developed procedures and training for inadvertent IMC recovery from a SAR hoisting scenario. They also planned:
- discussing the weather phenomena and the possibility for sudden loss of visibility with crews
- updating pre-flight training brief to highlight the need to maintain a safe distance to fog or cloud
- developing training focusing on the radar height hold function of the AW139
- including upset recovery training in CRM.
Safety Resources
The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn. You may also find these Aerossurance articles of interest:
- AS365 Crewman Dragged from Boat During SAR Training
- SAR Hoist Cable Snag and Facture, Followed By Release of an Unserviceable Aircraft
- HH-60L Hoist Cable Damage Highlights Need for Cable
- Guarding Against a Hoist Cable Cut
- Fatal Fall From B429 During Helicopter Hoist Training
- TCM’s Fall from SAR AW139 Doorway While Commencing Night Hoist Training
- SAR AW139 Dropped Object: Attachment of New Hook Weight
- Military SAR H225M Caracal Double Hoist Fatality Accident
- Fatal Taiwanese Night SAR Hoist Mission (NASC AS365N3 NA-106)
- Air Ambulance Helicopter Struck Ground During Go-Around after NVIS Inadvertent IMC Entry
- A HEMS Helicopter Had a Lucky Escape During a NVIS Approach to its Home Base
- SAR Helicopter Loss of Control at Night: ATSB Report
- Night HEMS BK117 Loss of Control
- HEMS A109S Night Loss of Control Inflight (N91NM)
- Air Ambulance A109S Spatial Disorientation in Night IMC (N11NM)
- HEMS Black Hole Accident: “Organisational, Regulatory and Oversight Deficiencies”
- HEMS S-76C Night Approach LOC-I Incident
- Drift into Danger: AW109SP Night HLS Accident
- ‘Procedural Drift’: Lynx CFIT in Afghanistan
- US Fatal Night HEMS Accident: Self-Induced Pressure & Inadequate Oversight
- HEMS Black Hole Accident: “Organisational, Regulatory and Oversight Deficiencies”
- Taiwan NASC UH-60M Night Medevac Helicopter Take Off Accident
- Italian HEMS AW139 Inadvertent IMC Accident
- Dim, Negative Transfer Double Flameout
- BK117B2 Air Ambulance Flameout: Fuel Transfer Pumps OFF, Caution Lights Invisible in NVG Modified Cockpit
- HEMS Black Hole Accident: “Organisational, Regulatory and Oversight Deficiencies”
- EC135P2 Spatial Disorientation Accident
- EC135P2+ Loss of NR Control During N2 Adjustment Flight
- Austrian Police EC135P2+ Impacted Glassy Lake
- That Others May Live – Inadvertent IMC & The Value of Flight Data Monitoring
- HEMS S-76C Night Approach LOC-I Incident
- CHC Sikorsky S-92A Seat Slide Surprise(s)
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