3-Jun-2011 Source: CHC
When operating his AS332L Super Puma, a CHC pilot noticed something out of the ordinary. Upon selecting the landing gear down, his cockpit indicator said otherwise.
Despite feeling and hearing the landing gear move into place, the indicators still showed one of the gears in the â€˜upâ€™ position.Â This was not the first time such an indication problem had disrupted operations, causing delayed departures and rejected or delayed approaches.
As part of the company reporting process, CHC regularly monitors all operations for trends or common themes on a monthly basis.
Using SQID, the trends are looked for within a variety of areas: by base; by Business Unit; by aircraft type.Â It was this trending which identified the higher than normal occurrence level of irregular gear indications.
Such indicators are covered in the Emergency Checklist and the crews were usually able to resolve the problem, however, as the indication issues were invariably associated with times when the aircraft was departing or making its approach to land, distractions such as these are unhelpful from a safety perspective.
â€œCrews are always prepared for the unexpected but we strive to reduce to a minimum the number of changes they receive against â€˜the Planâ€™, â€œsaid Duncan Trapp, vice president of Safety & Quality, CHC Helicopter Services. â€œIn addition, from a commercial and customer service perspective, these departures were often terminated to allow the engineering team to assess the fault; these Returns to Base disrupt the flying programme and cause frustration for the travelling customer.â€
Having identified a trend, Mike Davies, senior aviation advisor for CHC Helicopter Services, worked together with Super Puma tech type engineer Xavier Bourdouleix, Gary Dickson, S&Q manager for Canadian AOC, and other technical specialists in Australia (Don King) and Norway (where the L/L1s were also operated) to build a database of events and to identify the follow-up actions taken on each occasion.
It was known that on practically every event the â€˜problemâ€™ was a false alarm but on many occasions the sensors and micro-switches had to be changed or at least re-adjusted to clear the fault; this introduced additional unnecessary engineering activity.
In working with the aircraft manufacturer and providing the analysed data from the safety reports, Xavier was able to confirm that most of the issues were related to incorrect adjustments of the position sensors or water ingress/corrosion issues on the landing gear systems.Â With that, it was possible to develop a refined procedure which gave more focussed attention to the cleaning and alignment of the micro-switches and sensors which were causing these spurious and unhelpful indications.
â€œAs a result of this reporting, analysis and intervention, the frequency of the indicator problem in this fleet dropped dramatically and the rejected departures, disrupted arrivals declined significantly,â€ said Duncan.Â â€œUnnecessary engineering activity dropped away and the overall flying programs were less impacted.â€