I bring you a weekly bite-sized chunk of the science behind helicopter human factors and CRM in practice, simplifying the complex and distilling a helicopter related study into a summary of less than 500 words.
TITLE:
Factors affecting safety during night visual approach segments for offshore helicopters.
WHAT?
Interview-based qualitative study eliciting where helicopter pilots identify the risks of night offshore operations.
WHEN?
Published 2012 in the Aeronautical Journal.
WHERE?
Aberdeen, UK.
WHY?
Night-time flights pose considerable challenges to offshore operators, and it has been shown that the phase of greatest concern is the visual segment of the approach. This study aimed to determine the major factors affecting safety during night visual segments of instrument approaches offshore, as perceived by pilots, and discover how these interact to breach safety barriers.
HOW?
Interviews with 33 offshore pilots discussing the final visual approach segment of night approaches to helidecks were coded into categories and analysed for common themes in their perception of risk factors and the challenges to safety presented by offshore night approaches.
FINDINGS:
- The principal handling and perceptual difficulty experienced by pilots when switching from instrument to visual flight is closing speed. This can provoke further difficulties with height perception and control as pitching up to decelerate gives an illusion of height which can induce the pilot to lower the collective erroneously.
- Efficient CRM procedures including an effective and standardised talk down by monitoring pilots could contribute to reducing spatial disorientation. Effective talk-down in practice is usually acquired while line flying rather than through formal instruction and training. This generates a period of exposure until novices become experienced.
- Unless intervention procedures are well understood and well drilled, they can introduce further risk of loss of control at a critical stage on approach.
- Improving the visual environment of helidecks and ship lighting can reduce the challenge of switching from instrument to visual scans in the critical phase.
SO WHAT?
- Numerous studies support findings that transitions between IFR and VFR are a significant factor for spatial disorientation in helicopter pilots, with night approaches being particularly prone to the misjudgement of closure rate.
- In presence of featureless terrain/sea environments, the only visual cues available are those provided by the retinal image of the destination. In such circumstances pilots consistently underestimate distance.
- Accident rates for night sorties, by helicopters operating offshore, are estimated to be five times higher than for daytime.(10 year average night-time accident rate is as high as 8·4 per 100,000 flight hours).
- Other significant research on 400 fixed wing accidents/incidents found night time mishap rates at least 3x as high as daylight operations.
- A major area of concern for offshore helicopter flying relates to the approach and landing phases, especially at night and in degraded visual conditions.
- Evidence suggests that training currency requirements should be made more stringent for night operations, and further studies into optimal (from a crew readiness point of view) training periodicity should be carried out.
REFERENCE:
Nascimento FAC, Majumdar A, Jarvis S. Factors affecting safety during night visual approach segments for offshore helicopters. The Aeronautical Journal. 2012;116(1177):303-322. doi:10.1017/S0001924000006850
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