Evidence of causation required to get negligence claim off the ground

15 August 2016

The critical question at first instance and on appeal to the High Court was whether the maintenance manual for a helicopter provided an adequate inspection procedure for the detection of the defect which caused the crash and whether a manual which prescribed a more detailed inspection would have prevented the crash.

The plaintiff alleged that Robinson was liable in negligence or under the Trade Practices Act 1974 (Cth) for failing to provide a manual which contain adequate instructions to identify the defect.

The plaintiff was injured in a helicopter crash which was caused by the failure of the helicopter’s forward flex plate.  The flex plate acted as a coupling between the engine and the rotor and was secured by 4 bolts tightened to a specified degree.

Failure of the flex plate

The flex plate failed because, contrary to instructions in the manual, one of the four bolts securing the flex plate was incorrectly assembled and not tightened to the requisite degree.  Robinson did not cause the defect and it was not known who did.  The flex plate and associated parts had been removed and reassembled on 17 February 2004.  The crash occurred on 30 May 2004.

The flex plate had been subject to two inspections on 27 March 2004 and 12 May 2004.  After reassembly, but before the crash, the helicopter had also been subject to a number of routine pre-flight checks by pilots who flew the helicopter during that period.

The manual

To guard against the possibility of bolts not being properly tightened, the maintenance manual required that each of the bolts and nuts be fitted with a secondary fastener called a palnut.  A bolt fitted with the palnut could not become loose without the palnut becoming loose.  Any observable movement in a palnut, or the absence of a palnut, served as an indicator of possible bolt rotation.

Robinson’s manual provided for the use of a torque wrench to allow the bolts to be tightened to the required degree of tightness.

The manual also provided that torque seal (paint) should be applied to all critical fasteners after how much installation in a stripe across both nuts and exposed bolt threads to show the bolt location and allow any subsequent rotation of the nut or bolt to be detected visually.

The plaintiff alleged that the manual was defective because it did not contain a specific direction to check the bolts with a torque wrench rather than simply conducting a visual inspection of the torque seal.

The aircraft mechanics’ evidence

The two aircraft mechanics (Mr Fisher and Mr Brady) who conducted the 100 hourly inspections did not have a specific recollection of the inspections which they conducted prior to the crash.

Each mechanic gave evidence that they were familiar with the manual and followed it.  However, they both conceded that they did so without necessarily looking at the manual and one of them conceded that he did not make use of the checklist.

Importantly, neither of them said that they would have been more likely to follow a recommendation that they check the bolts with a torque wrench than they were likely to conduct an examination of the torque stripes for indications of possible bolt rotation.

No breach of duty of care

The High Court concluded that it was open to the trial judge to find that either no torque stripe had been applied to the bolt when it was incorrectly assembled on 17 February 2004 or if there were a torque stripe applied to the bolt that it would have been misaligned at the time of each of the two 100 hourly inspections prior to the crash.  Consequently, it was probable that if Mr Fisher or Mr Brady had properly inspected the bolts in accordance with Robinson’s manual, they would have detected the absence of a torque stripe or seen the stripe in such condition that it would have alerted them to the need for further examination which would have revealed the defect with the flex plate.

The Court held that the contents of the manual were not shown to have been inadequate to alert the mechanics to the fact that the bolts required attention.  Consequently, the plaintiff had not demonstrated that the contents of the manual fell short of what was required to discharge the defendant’s duty of care.


The High Court noted that proof of causation still requires proof on the balance of probabilities that the alleged breach of duty was the cause of the damage suffered.

The available evidence pointed against the likelihood that the aircraft mechanics would have been any more diligent in following a recommendation in the manual that they check the torque of the bolts with a torque wrench than they were in examining the torque stripes in accordance with the manual.

In short, even if there had been a specific instruction to check the bolts with a torque wrench, it was not certain on the balance of probabilities that the mechanics would have followed that instruction.  Consequently, the plaintiff failed to demonstrate that the absence of such an instruction had caused his loss.

The decision clearly illustrates that, even if there has been a breach of a defendant’s duty of care (which was not the case in this matter), a plaintiff must go on to demonstrate that the breach was causative of their loss – mere deficiency in instructions without evidence that alternative instructions would have brought about a different outcome and prevented the loss is insufficient to establish liability in negligence against a defendant.

This article was written by James McIntyre, Special Counsel and David Muir, Partner.

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