Drawing on an accident resulting in four fatalities, Mario Pierobon highlights the lethal impact of unclear Standard Operating Procedures and suggests how an operator can ensure no such confusion exists within their own flight department…
In August 2013, an AS332 L2 Super Puma helicopter carrying 18 people crashed in the sea during an approach to land at Sumburgh airport, Scotland. There were four fatalities. The helicopter had departed a platform in the North Sea and was en route to Sumburgh for refuelling before continuing to Aberdeen airport.
According to the report of the UK Air Accident Investigation Branch (AAIB) the weather conditions required the final approach to Runway 09 at Sumburgh be flown in cloud. The approach was conducted with the autopilot in 3-axes and vertical speed mode. This required the commander to operate the collective pitch control manually to manage airspeed.
“The co-pilot was responsible for monitoring the helicopter’s vertical flightpath against the published approach vertical profile and for seeking the external visual references necessary to continue with the approach and landing,” the AAIB report states. “The procedures permitted the helicopter to descend to a height of 300ft, the minimum descent altitude (MDA) for the approach, at which point a level-off was required if visual references had not yet been acquired.”
Although the approach vertical profile was maintained initially, insufficient collective pitch control input was applied by the commander to maintain the approach profile and the target approach airspeed of 80 kts - thus the helicopter’s airspeed reduced continuously during the final approach due to insufficient engine power.
“Control of the flightpath was lost and the helicopter continued to descend below the MDA. During the latter stages of the approach the helicopter’s airspeed had decreased below 35 kts and a high rate of descent had developed,” the AAIB report elaborates. “The decreasing airspeed went unnoticed by the pilots until a very late stage, when the helicopter was in a critically low energy state. The commander’s attempt to recover the situation was unsuccessful and the helicopter struck the surface of the sea approximately 1.7nm west of Sumburgh airport.”
According to the AAIB the operator’s Standard Operating Procedure (SOP) for this type of approach was not clearly defined and the pilots had not developed a clear, shared understanding of how the approach was to be flown. In addition, the operator’s SOPs at the time did not optimize the use of the helicopter’s automated systems during a non-precision approach.
Clearly defined, unambiguous SOPs should be a core responsibility (if not the main one) of an air service provider.
When it comes to aircraft operations there exist two broad categories of SOPs; namely the common ones documented in Operations Manual Section A (OM-A), and the type-specific ones, documented in Section B (OM-B).
It’s the common procedures that require a higher degree of scrutiny, since these need to be directly developed by the air operator. The type-specific procedures normally come directly from the OEM, and air operators have generally less autonomy to develop and/or adapt these procedures.
As previously discussed in this monthly safety column, it’s all too common that Flight Department Operations Manuals tend to replicate the content of applicable regulatory requirements without providing any useful guidance to the flight crew – thus, too many SOPs remain ambiguous at best, offering no clear guidance on specific situations to those crew members using them.
SOP implementation should consist of four very precise steps.
Development: A procedure must first be developed (i.e. a standard must be defined). Ideally a series of tasks should be defined as precisely as possible, each task outlining what needs to be performed; how it must be achieved (which tools, under which conditions); who should perform it; and which task must follow it. SOPs should also include contingency planning.
Documentation: A procedure must then be documented in the OM. Font size and print colours should be adequate for clarity on a printout or tablet screen, and account for different lighting conditions. As part of SOP documentation an operator may wish to develop checklists or task cards to be used during line operations.
Training: The documented content of the SOPs should then be integrated into initial and recurrent training courses.
Implementation Monitoring: Monitoring represents the most dynamic task to be performed as part of SOP implementation, and should be an on-going exercise designed to ensure that line operators’ behaviour is standardized as expected. A calendar of random inspections should be defined by compliance monitoring departments, and inspections carried out regularly and consistently.
Adequate implementation of clear, unambiguous SOPs, and ongoing monitoring should provide the opportunity for flight department management to continuously improve the safety of their operations. Standard Operating Procedures that are well-structured and communicated to all relevant parties leave far less margin for confusion or misunderstanding, thereby drastically reducing the chance of an accident occurring.
Furthermore, if non-compliances are found to be recurrent within the flight department, a deeper understanding will be gained as to why this is the case (e.g., time pressure or improper standard definition), which can then be addressed and corrected.