Anomalies in the magnetic particle inspection procedures likely led to the crack not being detected.
As a legacy of there being no inspection specific to an in-flight pitch disconnect, there is potential for other ATR aircraft to have sustained an in-flight pitch disconnect in the past and be operating with undetected horizontal stabiliser damage.
The aircraft manufacturer, ATR, did not provide a maintenance inspection to specifically assess the effect of an in-flight pitch disconnect on the structural integrity of the horizontal stabilisers. As a result, if an in-flight pitch disconnect occurred, the aircraft may not be inspected at a level commensurate with the criticality of the event.
Although the design standard for the aircraft (JAR-25) required the control system to be of sufficient strength to withstand dual control inputs, it did not require consideration of the effect that dual control inputs may have on control of the aircraft. Similarly, the current design standard (CS-25) does not address this issue.
Response from EASA
In September 2018, EASA advised the ATSB that:
The design standard for large transport aircraft, Joint Aviation Requirements - Part 25 (JAR-25), did not require that the demonstrated potential for flexibility in the control system to develop transient dynamic loads, be considered during certification. Similarly, the current certification standard for Large Aeroplanes (CS-25) does not address this issue.
Flexibility in the ATR 72’s pitch control system between the control columns results in a change in the aircraft’s longitudinal handling qualities and control dynamics when dual control inputs are made. This could result in an aircraft-pilot coupling event where flight crew may find it difficult to control the aircraft.
The design of the ATR 72 pitch control system resulted in limited tactile feedback between the left and right control columns, reducing the ability of one pilot to detect that the other pilot is making control inputs. In addition, there were no visual or auditory systems to indicate dual control inputs.
Errors remained within the ALCAM database due to the type of equipment used to measure road and rail bearings during ALCAM surveys in 2009.
V/Line’s level crossing assessment processes did not result in deployment of available risk controls at many passively protected acute-angle level crossings.
More than 100 level crossings in the V/Line regional rail network (including 35 at the intersection of passenger lines and public roads) were non-compliant with the left-side viewing angle requirements of AS 1742.7:2016. These crossings had an acute road-to-rail angle that affected the ability of drivers to sight trains approaching from their left.
The interaction between V/Line and the Colac Otway Shire Council was ineffective at addressing identified sighting issues at the Phalps Road level crossing.
Available risk controls to manage the risk posed by known sighting deficiencies at the Phalps Road level crossing were not deployed by V/Line or the Colac Otway Shire Council.
STM did not require the application of all available and reasonably practicable risk controls when parking trams with respect to their location and handbrake application.
STM did not comply with its risk control in ensuring that trams were attended when parked.
STM did not follow its change management process for adopting the new hardwood chock type. Subsequently, the hardwood chock could not be applied reliably under the ‘J’ class wheel and could not restrict its movement.
The En Route Supplement Australia (ERSA) did not have formal guidance for flight crews regarding the limited visual cues for maintaining alignment to runway 11/29 at Darwin during night landings in reduced visibility.
Virgin Australia did not have formal guidance for flight crews regarding the limited visual cues for maintaining alignment to runway 11/29 at Darwin during night landings in reduced visibility.
The absence of centreline lighting and the 60 m width of runway 11/29 at Darwin result in very limited visual cues for maintaining runway alignment during night landings in reduced visibility.
Category I runways that are wider than 50 m and without centreline lighting are over-represented in veer-off occurrences involving transport category aircraft landing in low visibility conditions. The installation of centreline lighting on wider category I runways is recommended but not mandated by the International Civil Aviation Organization Annex 14.
A NAV ADR DISAGREE alert can be triggered by either an airspeed discrepancy, or angle of attack discrepancy. The alert does not indicate which, and the associated procedure may lead flight crews to incorrectly diagnosing the source of the alert when the airspeed is erroneous for a short period and no airspeed discrepancy is present when the procedure is carried out.
