The Australian Transport Safety Bureau has issued Safety Recommendations to the European Aviation Safety Agency (EASA) and aircraft manufacturer ATR seeking improved aircraft system design tolerance to inadvertent dual control inputs by pilots.

The Safety Recommendations are contained in the ATSB’s final investigation report into an inflight upset and inadvertent pitch disconnect experienced by an ATR 72 turboprop airliner on a flight from Canberra to Sydney in 2014.

During that flight, as a result of a sudden decrease in tailwind, the ATR’s pilots unintentionally applied opposing control inputs to their control columns while trying to ensure the aircraft remained below its maximum operating speed. These differential forces activated the aircraft’s pitch uncoupling mechanism. Intended for activation in the event of one of the aircraft elevators being jammed, the pitch uncoupling mechanism resulted in a pitch disconnect, where the elevators could operate independently of each other.

With the pilots applying opposing control inputs and built-up tension within the flight control system, the pitch disconnect resulted in transient asymmetric elevator deflections, generating aerodynamic loads that exceeded the strength of the horizontal stabiliser (tailplane), causing significant damage.

The aircraft landed safely and was inspected by maintenance engineers but the damage was not detected. The aircraft returned to service and operated a further 13 flights before a subsequent inspection after a suspected birdstrike found it had sustained serious structural damage to its horizontal stabiliser, which was subsequently replaced.

Discovery of that damage was the catalyst for one of the ATSB’s most complex, thorough and protracted safety investigations.

Through the release of two interim reports, the investigation has already seen the aircraft manufacturer, aircraft operator and aircraft maintenance provider address a number of safety issues identified by the ATSB.

However, as part of its final report, the ATSB has issued a Safety Recommendation to EASA, recommending taking “further action to review the current design standard (CS-25) in consideration of effect that dual control inputs may have on control of aircraft.”

In addition, the ATSB has issued two Safety Recommendations to aircraft manufacturer ATR, recommending that ATR:

• assess the operational risk associated with limited tactile feedback between left and right control columns in the context of no visual or auditory systems to indicate dual control inputs; and
• perform a detailed review of the effects of dual control inputs on the aircraft’s longitudinal handling qualities and control dynamics to determine if there are any detrimental effects that could lead to difficulty in controlling the aircraft throughout the approved flight envelope and operational range.

“What this report seeks to achieve is to influence further incremental safety improvements,” ATSB Chief Commissioner Greg Hood said.

Aircraft and aircraft systems need to be designed in anticipation of and tolerant to foreseeable inadvertent flight crew actions.

“This serious incident demonstrates aircraft and aircraft systems need to be designed in anticipation of and tolerant to foreseeable inadvertent pilot actions.

“Further, when identified, aviation safety regulators and aircraft manufacturers need to address previously unforeseen aircraft design consequences during the operational life of an aircraft type.”  

Mr Hood said the investigation also highlights the importance of a full and proper inspection to detect aircraft damage and the need for the inspection to be fit for purpose and for inspections to be coordinated and certified to avoid a single point failure.

“The ATSB looks forward to EASA’s and ATR’s responses to our Safety Recommendation from this investigation.”

Read the final report: In-flight upset, inadvertent pitch disconnect, and continued operation with serious damage involving ATR 72 aircraft, VH-FVR, 47 km west-south-west of Sydney Airport, New South Wales, on 20 February 2014

Some flying training organisations may be conducting incipient spin training in aircraft not approved for intentional spinning, an Australian Transport Safety Bureau (ATSB) investigation into a fatal training accident has found. Depending on the aircraft type, the manufacturer may not have specified whether that restriction applies to an incipient spin or only a developed spin.

A new Safety Advisory Notice issued by the ATSB advises flying training organisations using aircraft not approved for intentional spinning to clarify with aircraft manufacturers the extent to which the intentional entry into the early stages of a spin, including an incipient spin, spin is permissible.

The accident occurred on 26 September 2017, during a Recreational Pilot Licence practice flight test. The instructor and student took off from Archerfield Airport, south-west of Brisbane, Queensland, in a Diamond Aircraft DA40. Radar data showed the aircraft commenced a climb to about 4,500 ft with a reducing groundspeed, consistent with stall recovery training. The data then showed the aircraft’s flight path to be a near vertical descent with an average descent rate of about 6,000 feet per minute.

The aircraft collided with terrain, with the impact destroying the aircraft and fatally injuring the instructor and student.

The ATSB’s investigation found the instructor and the student were likely conducting advanced stall recovery training – a lesson which probably included intentionally initiating incipient spins (the early stage of a spin). The investigation also found that the instructor could not or did not prevent the aircraft from entering a developed spin from an incipient spin, for reasons that could not be established.

The aircraft manufacturer advised that the DA40’s limitation prohibiting intentional spins was intended to include incipient spins. However, the incipient spin manoeuvre was not defined and some operators considered that an incipient spin was not an intentional spin.

While the Civil Aviation Safety Authority (CASA) requires the demonstration of recovery from an incipient spin during flight tests, there is no clear and consistent definition of the point at which a manoeuvre becomes a spin – or incipient spin – for the purposes of flying training.

The investigation also identified incorrect incipient spin recovery guidance had been provided by CASA in its Flight Instructor Manual. The Authority says it will review its guidance material.

“The ATSB is calling for flying training organisations using aircraft not approved for intentional spinning to clarify with their aircraft manufacturer the extent to which the intentional entry into the early stages of a spin, including an incipient spin, is permissible and ensure that their aircraft are always operated in accordance with limitations,” ATSB Executive Director, Transport Safety Mr Nat Nagy said.

“Furthermore, operators should have procedures, and instructors should take all steps, to ensure that they maintain the necessary skills to avoid unintentional spins and recover from both incipient and developed spins.”

Read the Safety Advisory Notice AO‑2017‑096‑SAN-012: Is incipient spin training permitted in your aircraft?

Read the final report: Collision with terrain involving Diamond DA40, VH-MPM, 42 km west of Southport Aerodrome, Queensland, on 26 September 2017

For additional reading, the New Zealand Civil Aviation Authority booklet Spin Avoidance and Recovery(Opens in a new tab/window) provides valuable guidance for pilots in spin avoidance and recovery. The booklet provides the following advice for pilots regarding spin recovery:

To have a chance at recovery, the pilot must immediately recognise the spin, and its direction, know exactly what to do in the right order, and then execute the procedure correctly the first time.

A collision involving two trams operated by a tram museum highlights the importance of strong risk controls and ensuring that any changes to procedures do not reduce a risk-control’s effectiveness, a new ATSB investigation has found.

The accident occurred in Loftus in Sydney’s south when a ‘J’ class tram, operated by the Sydney Tramway Museum, was parked on a downhill gradient using its air brakes with a hardwood chock applied under its wheel. With no one on board, the tram suddenly rolled away, heading towards another of the museum’s trams – a ‘Nagasaki’ class that was travelling in the opposite direction on the same line.

Sighting the approaching ‘J’ class tram, the driver of the Nagasaki applied the emergency brake and instructed all 16 passengers to evacuate immediately. All passengers and crew had exited the Nagasaki safely before the trams collided, with both trams sustaining minor damage.

In line with the museum’s procedures, the runaway tram’s handbrake had not been applied when it was parked and when air released from its brake system, a single hardwood chock was left to restrain the tram’s movement. Previously a softwood chock, which would deform and create a tight wedge, would have been placed under the tram’s front wheel, but the tram was able to roll over the hardwood chock.

The investigation highlights the importance of ensuring that any changes to a risk-control process do not reduce that risk control’s effectiveness.  

The investigation, conducted by the Office of Transport Safety Investigation on behalf of the ATSB, found that the hardwood chock was newly adopted, and its use had not gone through a change management process.

As a result of the investigation, the museum has taken a number of proactive safety measures, including making the application of handbrakes mandatory, and taking steps to ensure that trams are parked securely on level track.

The investigation also highlights the importance of ensuring that any changes to a risk-control process do not reduce that risk-control’s effectiveness.

Read the final report: Runaway and collision between 'J' class and 'Nagasaki’ class trams, Sydney Tramway Museum, Loftus, New South Wales, on 15 May 2016

The investigation into the in-flight break-up of a Cessna 210 near Albany, Western Australia highlights the need for operators and industry associations to make information available to pilots and employees about support services for problematic substance use.

On the morning of 24 October 2017, the owner-pilot of VH-DBU was observed at Albany Airport preparing the aircraft for the flight. A witness reported seeing the aircraft with its wheels chocked and engine operating, and the pilot outside of the cockpit. No one else was observed at the controls.   

After refuelling, the aircraft took off on a private flight to Bunbury with the pilot as the sole occupant on board.

It appeared that the pilot undertook some local flying before departing the Albany area. When about 30 km to the north-west of Albany a number of witnesses reported hearing, and in some cases seeing, the aircraft fly overhead. Witnesses recalled hearing a distinctive noise described as a sharp bang, crack of a whip, gunshot, or thunder and lightning. The aircraft was then seen in a steep descent until it disappeared out of sight, with smoke appearing shortly after indicating a post-impact fire.

The wreckage of the Cessna was located later that day dispersed over a wide area in the Mount Lindesay National Park, with the pilot found to be deceased.

The investigation found, for reasons that could not be established, abnormal operation of the aircraft produced high levels of unusual aerodynamic loading that exceeded the strength of the right wing and initiated an in-flight break-up and impact with terrain.

…the risks associated with continuing to operate with problematic substance use and the benefits of accessing help and support far outweigh the risks of a self-referral…

No pre-existing aircraft structural deficiency or damage, which could have contributed to the in-flight break-up, was found during the investigation. Local weather at the time was generally calm and clear.  

A postmortem of the pilot carried out at the direction of the coroner found no evidence of significant underlying medical issues. However, an accredited forensic science laboratory toxicological examination found the presence of methylamphetamine in the pilot’s system. The ATSB found that it increased the risk of operational misjudgements or mishandling due to impairment and involuntary action or inaction due to incapacitation, but this did not necessarily contribute to the accident.          

The ATSB’s safety message from this investigation is for operators and industry associations to consider how they can make information available to pilots and employees about support services for problematic substance use.

A self-referral for problematic substance use may be perceived as a threat to a pilot’s ongoing employment in aviation. However, the risks of continuing to operate with problematic substance use and the benefits of accessing help and support far outweigh any perceived risk of a self-referral.

Information for pilots should highlight that the Civil Aviation Safety Authority’s aviation medical framework allows pilots in stable remission to return to work. Information should include the increasing availability of employer and independent peer support organisations.

Further, the ATSB encourages pilots concerned about alcohol and drug use to visit the Human Intervention Motivation Study(Opens in a new tab/window) (HIMS) website. A cornerstone of HIMS is the understanding that substance dependence is a treatable medical condition, and is modelled on well-established overseas programs that have assisted thousands of pilots return to work.

Read the final report: In-flight break-up involving Cessna 210B, VH-DBU, 30 km north-west of Albany, Western Australia, on 24 October 2017

A runway excursion involving a Boeing 737 at Darwin Airport on 6 December 2016 draws attention to the effectiveness of centreline lighting on wider than usual runways.

Landing on a wet runway at night, with visibility reduced by heavy rain, the Virgin Australia 737-800 touched down more than 20 m to the right of the runway centreline. The aircraft continued to the side of the runway, and its right landing gear ran just off the edge, destroying six runway lights along a 400 m path before returning to the runway.

There were no injuries and only minor damage to the aircraft.

The ATSB found that a relatively small increase in crosswind had occurred at a critical time a few seconds before touchdown, and the crew were not aware how far the aircraft had deviated.

The two rows of lights alongside runway 29 at Darwin are further apart than what a flight crew would normally encounter, due to the relatively wide runway. The ATSB found that, in the absence of centreline lighting, this characteristic affected the crew’s ability to detect and correct the aircraft’s deviation.

“A wide runway without centreline lighting, such as at Darwin, poses a particular challenge for aircraft making approaches in darkness and heavy rain,” said ATSB Executive Director Transport Safety Mr Nat Nagy.

“In these circumstances centreline lighting greatly helps flight crews align the aircraft with the runway.”

While studying past reports of runway side excursions in reduced visibility, ATSB investigators discovered that a disproportionate number of them occurred on wider runways.

In response to the ATSB investigation, both the aircraft operator and airport initiated a number of safety actions, including providing flight crews with information about the specific risks of approaches to Darwin Airport at night in conditions with reduced visibility.

“It is important for pilots and operators to be aware of any circumstances that are different to what they usually encounter and account for it in their planning so that they are more likely to avoid being ‘caught out’ at a critical time,” Mr Nagy said.

The International Civil Aviation Organization (ICAO) recommends, but does not mandate, the installation of centreline lighting on wider runways. Of the two runways wider than 50 m in Australia, Darwin’s runway is the only one without centerline lighting.

The ATSB previously recommended the installation of centreline lighting at Darwin Airport after a 2003 runway side excursion. Its concerns were renewed following a 2008 hard landing though no recommendation was issued.

Darwin Airport is a joint military and civilian facility – the Department of Defence owns much of the airport infrastructure, including the runways, while Darwin International Airport operates the civilian aspects of it. Both have advised the ATSB that the installation of centreline lighting will be considered during any future runway works.

While studying past reports of runway side excursions in reduced visibility, ATSB investigators discovered that a disproportionate number of them occurred on wider runways. None of the studied excursions occurred on runways that had centreline lighting.

As a result, the ATSB issued a safety recommendation to ICAO to review the runway lighting standards in light of the new evidence available. 

Read the final report: Runway excursion involving Boeing 737, VH-VUI, at Darwin Airport, Northern Territory, on 6 December 2016

An ATSB investigation into the collision with terrain involving a Bell 206 helicopter shows how rapidly emergency situations can develop.

The accident occurred 75 km north-east of Emerald Airport, Queensland, when the helicopter was conducting power line inspections. The pilot had positioned the helicopter in a hover 30 feet above the ground and 40 metres from a transmission tower so that it could be photographed by a crew member.

After a short period of hovering, the pilot heard a ‘very loud bang’ through the airframe, which was also felt through the controls. The helicopter began to shake violently and bounce vertically. The pilot also reported seeing tiny pieces of debris falling in front of the helicopter.

In response, the pilot immediately lowered the collective intending to land in a clear area below, however the helicopter did not respond to collective or cyclic control inputs. Instead, the helicopter began to pitch upward and drift backwards before yawing to the right. The yaw could not be controlled with the tail rotor pedals, so the pilot moved the throttle to the idle position.

Despite attempts to remain level during the landing, the left skid contacted the ground and the helicopter rolled over. The pilot and crewmember were uninjured.

While recognising that on this occasion the pilot had limited control authority, the safety message from this investigation is regular practice and briefings of emergency actions will increase the likelihood of a correct response during an emergency situation.

An examination of the helicopter identified that the mast, both pitch links, and the swashplate were fractured. The fractured components and trunnion bearings (connecting the pitch links to the rotor blades) were sent to Bell Helicopter’s Engineering Laboratories for detailed examination. Bell Helicopter concluded that all of the fractures, including that resulting in the mast collar separation, were a result of overstress.

There were no findings made during the inspection that identified the probable factors contributing to this occurrence.

This investigation highlights how rapidly an emergency situation can develop. While recognising that on this occasion the pilot had limited control authority, the safety message from this investigation is regular practice and briefings of emergency actions will increase the likelihood of a correct response during an emergency situation.

Read the final report: Collision with terrain involving Bell 206, VH-SDZ, 75 km north-east of Emerald Airport, Queensland, on 18 November 2017

An Australian Transport Safety Bureau (ATSB) investigation into a dual hydraulic failure involving a Boeing 757 aircraft highlights that non-mandatory service bulletins can still have an impact on an aircraft’s reliability.

Soon after departing Auckland International Airport on 5 February 2018, while passing through 6,000 ft, the aircraft’s left hydraulic system quantity warning message displayed. The crew actioned the Quick Reference Handbook (QRH) checklist and obtained clearance from air traffic control (ATC) to level out in a holding pattern north-west of the airport

Shortly after commencing the holding pattern, the crew received further warning messages regarding both the left and right hydraulic systems. Following the QRH checklists, the crew shut down both system, declared a PAN call to ATC requesting an immediate return to Auckland. The aircraft landed without incident.

The ATSB investigation identified that the dual hydraulic failure was the result of sequential failures in the hydraulic system. The initial failure was a ruptured left main landing gear flex hose, which resulted in the loss of the left hydraulic system pressure. Subsequently, the power transfer unit (PTU) pressure switch did not operate as intended, following depletion of the hydraulic fluid from the left system. This resulted in overheating and failure of the right hydraulic system.

Although some service bulletins are not deemed to be safety-critical, they can still have an impact on aircraft reliability.

The pressure switch was the subject of a 2010 non-mandatory service bulletin that, if implemented, would likely have prevented the failure of the right system.

The safety message from this investigation is that although some service bulletins are not deemed to be safety-critical, they can still have an impact on aircraft reliability. While operators are required to implement all airworthiness directives, the ATSB recommends that operators familiarise themselves with non-mandatory service bulletins and consider the potential impacts of implementation.

Following the occurrence, the operator conducted preventative maintenance on the aircraft, replacing all of the main landing gear flex hoses as well as updating the PTU pressure switch to confirm to the published service bulletin. In addition, the operator revised the aircraft maintenance plan to introduce improved inspections and a time-limited life on the flex hoses.

Boeing recommends that operators perform periodic inspection of hose assemblies, paying particular attention to the high-risk areas of the landing gear area, the engine/pylon area and the tail/empennage area.

Read the final report: Hydraulic system failure involving Boeing 757, VH-TCA, Auckland International Airport, New Zealand, on 5 February 2018

PTU pressure switch installed on VH-TCA

Recent practice of emergency procedures helped a pilot to conduct a successful forced landing of a scenic flight in remote and difficult terrain.

On 14 May 2018, a Gippsland Aeronautics GA-8 Airvan departed Bellburn Airstrip, Western Australia on a scenic charter flight with the pilot and seven passengers on board. About 12 minutes after departure, as the pilot commenced a planned climb, he felt the aircraft’s performance become a bit ‘sluggish’, with lower climb and fuel flow rates than expected.

Various checks and troubleshooting did not yield any improvement in performance, and engine power slowly started to decrease. The pilot determined that a forced landing was required, and advised the passengers, briefing them on the process for evacuating the aircraft after landing.

During the descent, at approximately 150 ft above ground level, the pilot secured the engine and turned off the aircraft’s electrical system. During the landing roll, the Airvan’s wings hit some small trees and the aircraft came to rest in a ditch, tearing off the nose landing gear. The pilot and three passengers sustained only minor injuries.

The pilot’s handling of the forced landing contributed positively to the survivability of this accident in difficult terrain.

The ATSB investigation found that the air intake pipe to engine cylinder number six had probably detached in flight, leading to the loss of engine performance. There was insufficient evidence to determine why the intake pipe detached from the engine.

The pilot advised the investigation that recent practice forced landings in the Airvan had helped him to feel more comfortable with the emergency. In particular, the recent practice gave him a good appreciation for the aircraft’s glide ratio, which helped when selecting a suitable landing site.

The ATSB’s safety message from this investigation is the value of frequent emergency procedures training. The pilot’s handling of the forced landing contributed positively to the survivability of this accident.

Although flight reviews are required every two years as a minimum, the ATSB reminds pilots and operators of the benefits of more frequent practice of emergency procedures.

Read the final report: Engine failure and forced landing involving Gippsland Aeronautics GA-8 Airvan, VH-BFL, 8.5 km north-north-west of Bellburn Airstrip, Western Australia, on 14 May 2018

On 23 October 2017, a Cessna 210 light aircraft with two pilots on board, one operating as pilot-in-command and the other as pilot-in-command-under-supervision, departed Darwin Airport for Elcho Island, 530 km to the east of Darwin.

Despite making track diversions to avoid severe thunderstorms, the aircraft entered an area of strong convective activity with rapidly developing rain cells. This resulted in the aircraft experiencing severe turbulence and possibly reduced visibility.

The aircraft entered an uncontrolled descent, with witnesses reporting seeing the aircraft descending rapidly in a relatively flat attitude with a section of each wing missing. A combination of airspeed, turbulence and control inputs probably led to excessive loading on the aircraft’s wings, which separated from the fuselage in-flight.

The aircraft subsequently collided with terrain, fatally injuring both pilots.

In many cases, deviations of 10 nautical miles may not be enough for an aircraft to remain safely clear of the turbulent and powerful forces associated with storms.

“There are several safety messages from this investigation including the recognition and avoidance of tropical weather conditions that present significant hazards to flight,” ATSB Executive Director Transport Safety Nat Nagy said.

“Particularly challenging is identifying an appropriate distance to keep from thunderstorms, which comes through experience in operating in the tropics. In many cases, deviations of 10 nautical miles may not be enough for an aircraft to remain safely clear of the turbulent and powerful forces associated with storms.”

The ATSB’s investigation found that the operator’s risk mitigation of pairing a supervisory pilot with a trainee did not adequately address the weather-related risks because neither pilot had experience flying in the build-up to the wet season.

“Smaller operators employing pilots with limited exposure to local conditions can better manage related risks by pairing new pilots with ones who are experienced in flying in the Top End,” Mr Nagy said.

“The ATSB also encourages pilots to use all available resources to avoid adverse weather, including forecasts and requesting air traffic control assistance. Awareness of the weather avoidance actions of other pilots in the area can also be useful.”

Further, there is considerable value in ongoing education and guidance for all pilots in recognising and responding to deteriorating weather conditions during flight.

Read the final report: In-flight breakup involving Cessna 210, VH-HWY, 22 km east of Darwin Airport, Northern Territory, on 23 October 2017