Loss of control

What happened

On 18 April 2021, the pilot of a Cessna 172S aircraft was conducting a private flight from Jandakot Airport to White Gum aeroplane landing area (ALA), Western Australia with two passengers on board. Prior to departure, the pilot provided a safety briefing to the passengers including instructing the front seat passenger to remain clear of the aircraft flight controls.

After landing, the front seat passenger accidentally pushed the left rudder pedal causing the aircraft to veer left off the runway toward trees. The pilot attempted to steer to the right by applying right rudder, which was unsuccessful. The pilot then initiated a go-around. As power was increased, the aircraft turned further left, resulting in the left-wing colliding with a tree. The aircraft rotated through 180° before coming to rest (Figure 1). The two passengers sustained minor injuries and the aircraft was substantially damaged.

Figure 1: Accident site

Source: Aircraft operator

Safety message

This accident highlights the importance of the passenger in the front seat of a dual control aircraft remaining clear of the flight controls (Figure 2). If there is any doubt about a passenger being able to comply with briefing instructions, consideration should be given to seating them in the rear seat.

Figure 2: Cessna 172 dual controls

Source: pinterest.dk

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

What happened

On 1 October 2020, an instructor and student pilot in a Robinson R22 helicopter were conducting exercises in the helicopter training area at Jandakot Airport, Western Australia. In the pre-flight brief, the plan for the flight was to conduct some revision circuits and then cover flight control emergency recovery procedures. Having completed the circuit revision portion of the flight, the instructor demonstrated and monitored the student successfully completing the first of the practice emergency procedures.

At about 1145 Western Standard Time, the instructor assessed that the wind had increased to about 20 kt and the conditions were therefore unsuitable to continue the lesson. The instructor informed the student that they would conclude the training at that point. The student lifted the helicopter into the hover in preparation to return to the parking area.

While hovering 3 ft above the ground, there was a momentary uncommanded yaw to the right and the instructor questioned the student as to the cause. The aircraft then commenced a further uncommanded and uncontrolled right yaw and the instructor took over the controls. The yaw continued and the helicopter rapidly went through 2 to 3 rotations. The instructor assessed that the situation was unrecoverable, closed the throttle and raised the collective^[1] to cushion the helicopter onto the ground. This resulted in a heavy landing and substantial damage to the airframe, however, no injuries to the student or instructor (Figure 1).

Figure 1: The helicopter in situ after the heavy landing

Source: Airport operator

Safety action

As a result of this occurrence, the operator has advised the ATSB that a staff safety meeting was conducted following the heavy landing incident and prior to resumption of flight training activities, with the focus on mitigating future risks during hovering operations. The instructor and student also completed additional training.

Safety message

This incident is a reminder for instructors to be aware of, and respond quickly to, situations that develop during training. These may be due to the student’s limited experience, decision-making, aircraft performance limitations or changing weather conditions, which pose risks to the safe conduct of the flight.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Collective: a primary helicopter flight control that simultaneously affects the pitch of all blades of a lifting rotor. Collective input is the main control for vertical velocity.

What happened

On 14 June 2020 at approximately 1600 Central Standard Time, the pilot of a Robinson R22 helicopter was conducting mustering operations on a property near Tindal Airport, Northern Territory.

The pilot was attempting to herd a number of cattle into a yard, which was proving difficult as the cattle were not moving as required. The pilot decided to land the helicopter behind the cattle to encourage them to move forward, and selected a landing site on a graded road bordered on either side by trees. The pilot was confident that the dust would be minimal in the selected landing area and planned to use a direct-to-the-ground approach to reduce the potential of creating a dust cloud and a possible brownout condition.^[1]

As the helicopter descended below 3 ft, an excessive amount of dust was raised from the landing area and the helicopter immediately became fully enveloped by the dust cloud. The pilot elected to reject the landing and commenced a climb, but as all visual references were lost and there were obstacles close by, the pilot quickly decided to put the helicopter on the ground as soon as possible.

The pilot lowered the collective^[2] and the helicopter contacted the ground with an amount of left lateral movement resulting in a rollover. The helicopter came to rest on its side sustaining substantial damage (Figure 1). The pilot was uninjured in the accident.

Figure 1: Helicopter post-accident

Source: Operator

Pilot comments

The pilot commented that normally a request for ground personnel assistance to herd the cattle would have been made, however as one of the ground personnel was recently injured the pilot was reluctant to ask for help. The pilot also advised that the mustering job had been delayed to late in the day, and therefore self-induced time pressure to complete the task existed. On reflection, the pilot advised the ATSB that these considerations may have influenced the decisions made on the day.

Brownout condition

The brownout phenomenon can lead to accidents during helicopter take-off and landing operations in arid / desert terrain. Dust clouds created by the rotor downwash during near-ground flight can result in the pilot losing visual reference. This increases the risk of the helicopter colliding with the ground and other obstacles, as well as dynamic rollover due to sloped, uneven terrain or uncommanded aircraft movement due to spatial disorientation.

There are several factors that affect the probability and severity of brownout:

• aircraft weight / rotor disk loading
• soil composition
• wind
• approach speed and angle.

Safety message

This accident highlights the importance of selecting a suitable landing area and the best approach path and landing technique for the surrounding environment. This includes consideration of appropriate escape routes when faced with an unexpected situation such as a brownout condition. Pilots should also always maintain situational awareness of environmental factors like wind direction, obstacles and surface conditions in order to mitigate risk and avoid an unfavourable situation.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
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1. Brownout condition: is an in-flight visibility restriction due to dust or sand in the air. In a brownout, the pilot cannot see nearby objects which provide the outside visual references necessary to control the aircraft near the ground.  This can cause spatial disorientation and loss of situational awareness leading to an accident.
2. Collective: a primary helicopter flight control that simultaneously affects the pitch of all blades of a lifting rotor. Collective input is the main control for vertical velocity.

What happened

On 23 April 2020, the student pilot of a Robinson R44 helicopter was returning to Townsville Airport, Queensland, from a solo training navigation exercise.

As the pilot returned the helicopter to the parking position near the hangar and was in the process of landing from the hover, he momentarily lost directional yaw control. At this time, one of the helicopter’s skids was in contact with the ground while the collective^[1] was in a raised position. This resulted in an unstable airframe that commenced a roll about the skid.

Despite the efforts of the pilot to recover, the helicopter continued to rollover and came to rest on its side resulting in substantial damage. The pilot was uninjured in the accident.

Figure 1: Helicopter post-accident

Source: Townsville Airport

Figure 2: Helicopter’s bent tail boom and broken main rotor blade

Source: Townsville Airport

Helicopter static and dynamic rollovers

Static rollover occurs when a helicopter is pivoted about one of its landing skids or wheels and the helicopter’s centre of gravity passes outside the in-contact skid or wheel. Once in this position, removal of the original force that raised the helicopter to that angle will not stop the helicopter from rolling further. This angle is termed the ‘static rollover angle.’

A rotors-running helicopter resting with one landing skid or wheel on the ground may, without appropriate pilot input, commence rolling. Under certain circumstances, this roll cannot be controlled and the helicopter rolls over. This condition is known as ‘dynamic rollover’ and is a function of the interaction between the:

• horizontal component of the total rotor thrust (or lift) acting about the point of ground contact
• weight of the aircraft, initially acting between the helicopter’s skid landing gear or wheels. This second, counter-rolling moment decreases the greater the roll.

Recovery from dynamic rollover is by smoothly lowering the collective lever while controlling any tendency to roll in the opposite direction with cyclic^[2] to re-establish the helicopter’s weight evenly on the ground. In general, the application of smooth collective inputs is more effective in avoiding rollover issues than using the cyclic control.

Safety message

This accident highlights the importance of smooth and controlled flight control inputs in the critical phases of flight. While a helicopter is in contact with the ground and before its full weight is applied to the landing gear, it is subject to various influences such as the possibility of a rollover. A thorough understanding of the principles of, and contributing factors to, both static and dynamic rollover and the recovery methods are essential to conducting safe helicopter lift-offs and landings.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Collective: a primary helicopter flight control that simultaneously affects the pitch of all blades of a lifting rotor. Collective input is the main control for vertical velocity.
2. Cyclic: a primary helicopter flight control that is similar to an aircraft control column. Cyclic input tilts the main rotor disc, varying the attitude of the helicopter and hence the lateral direction.

What happened

On the afternoon of 30 July 2019, a local pilot and owner of a DR-107 One Design amateur-built aircraft^[1] commenced flying activities at Narromine Airport, New South Wales. At about 1415 Eastern Standard Time, while conducting aerobatics, the pilot experienced degraded rudder control. The pilot elected to land immediately on runway 22. On landing, the left rudder pedal/cable mechanism collapsed, the aircraft veered to the right of the runway and ground looped,^[2] colliding with a nearby gable marker. The pilot sustained minor injuries, and the aircraft was substantially damaged.

Post-Accident Inspection

Immediately following the accident, the aircraft owner conducted a detailed inspection of the left rudder pedal assembly, including the rudder cable, pedal and the surrounding areas for damage. The pilot discovered that the nut and bolt (with split pin) fastener, connecting the left rudder pedal to the rudder cable, had failed (Figure 1). The left rudder pedal was extended to the maximum forward position (Figure 2). The subsequent walk-around inspection identified additional external damage to the lower side of the forward fuselage, the left-wing tip and the left landing gear.

Figure 1: Left rudder pedal assembly – looking forward

Source: Aircraft owner & pilot

Figure 2: Expanded view – underneath left-hand side heel/foot rest

Source: Aircraft owner & pilot

Safety message

In this incident, the pilot recognised a potential flight control failure while inflight, and successfully recovered the aircraft to the ground as soon as he was able. Aerobatic flying can produce significant stress to flight control mechanisms. This occurrence reinforces the need to complete a diligent pre-flight inspection of all visible flight control components/attachment points, and to act promptly, yet conservatively in the event of any flight control malfunction.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Amateur-built aircraft: an aircraft, the major portion of which; has been fabricated and assembled by a person, or persons who undertook the construction project solely for their own education or recreation.
2. Ground-loop: a violent, uncontrolled horizontal rotation of an aircraft while landing, taking off, or taxiing.

What happened

On 3 May 2019, a Cirrus SR20 departed Moorabbin, Victoria (Vic.) with one pilot and two passengers on board. The pilot hired the aircraft from an operator for a private scenic flight that was planned to orbit Melbourne city before landing at Tooradin, Vic. During the initial stages of landing, the pilot observed the aircraft to be slightly high before it sank heavily onto the runway and bounced. After the second bounce, the pilot applied full power and retracted the flaps to conduct a go-around.

The aircraft yawed to the left and the pilot observed the indicated airspeed to be at 65 kt. The pilot received a stall warning annunciation and assessed that the aircraft had become airborne, and she therefore elected to pitch the nose of the aircraft down to land on the remaining runway. However, the aircraft rolled abruptly to the left and the wing struck the ground. The aircraft then collided with a drainage ditch to the left of the runway and was subsequently destroyed (Figure 1). The pilot and passengers exited without injury.

Operator’s investigation

The operator retrieved and reviewed the data from this private-hire flight and confirmed from the position of the flap transmission worm drive that, during the go-around procedure when full power was applied, the flaps were fully retracted. The pilot operating handbook recommends 50 per cent and indicates approximately 10 kt increase in stall speed from flaps 100 to zero per cent.

The data revealed that upon application of full power, a change of track of 15 degrees to the left of the runway resulting in the aircraft exiting the runway onto soft ground. The aircraft continued to diverge from the runway until it contacted the drainage ditch where it came to rest. The main landing gear tyre tracks were evident in the grass from the runway edge to the accident site, therefore confirming that contrary to the pilot’s recollection of events, the aircraft did not become airborne following execution of the go-around.

The operator advised that upon reviewing the data, it became apparent that during final approach, the pilot was pitching to control airspeed. The pilot reported that she used both power and elevator to land the aircraft.

Figure 1: Aircraft damage

Source: Operator

Safety action

As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking safety actions, including:

• teaching pilots the correct go-around technique in this aircraft type from a low airspeed situation, such as after a significant bounce or a series of bounces, which requires right rudder pressure to counteract torque roll and p-factor^[1]
• highlighting this situation to pilots during conversion training, in line with recommendations from the manufacturer.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. P-factor, also known as asymmetric blade effect and asymmetric disc effect, is an aerodynamic phenomenon experienced by a moving propeller that is responsible for the asymmetrical relocation of the propeller’s centre of thrust when an aircraft is at a high angle of attack.

What happened

On 5 January 2019 at approximately 1045 Eastern Standard Time, the pilot of an amateur built aircraft VAN’S RV-6A took off from an unsealed runway at Lakeland Downs airstrip, Queensland for a private flight with one passenger on board.

During the take-off run^[1], at approximately 250 m down the runway, the aircraft began to deviate to the right uncommanded. The pilot then conducted a rejected take-off and lost directional control resulting in the aircraft veering off the runway and colliding with a tree. The aircraft subsequently sustained substantial damage.

Pilot comments

The pilot advised that there had recently been a lot of rain in the area and the airstrip was mainly clay with overgrown grass. Upon landing at the airstrip, he had noticed that the runway had a rough surface, and during take-off he had tried to follow the same track.

After the accident, the pilot walked back along the tracks the aircraft had taken and found a large rock buried in the runway that the landing gear had struck.

Figure 1: Damage sustained to aircraft

Source: Qld Police

Safety message

This accident highlights the importance of identification and management of any risks that might be associated with an unsealed runway. Potential hazards may be hard to identify, with objects possibly obscured by vegetation. Changes in the runway surface can be hard to detect visually and without a vehicle or some means to apply a similar force to that of a landing aircraft.

Further information on being prepared when operating on remote airstrips can be found on the CASA website, Bush strips.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.

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1. Take-off run: Take-off run (ground run) is the portion of the take-off procedure during which the airplane is accelerated from a standstill to an airspeed that provides sufficient lift for it to become airborne.