Apropos the discussion about the cost of operating a 'modern designed' helicopter, at least one Major Oil Company is at present attempting to design a mathematical model to cost the effect on safety of the certification state of the aircraft. This model examines accident/incident records and attempts to predict which ones might have been prevented if a helicopter had been certificate to each of the latest standards.
Such models are, by definition, difficult to apply as the Heinrich Pyramid indicates for every one major accident there are:
- three to five less significant accidents
- seven to 10 incidents; and
- several hundred unreported occurrences
- and the Heinrich taxonomy does not take into account abnormal behaviour (precursors to incidents which might be picked up by HOMP).
Each accident is also a sum of its constituent parts - some of which have been in play even before the aircraft takes off. Breaking the cause-and-effect chain at any link will of course prevent an accident - except in the case of a catastrophic failure (which might be seen as as (a predictable) failure of the certification system; interestingly, Vibration Health Monitoring is perceived as the device to prevent such catastrophic failures - even by some of the major manufacturers.)
It is clear that the examination of incidents/accidents also has to take account the perceived benefit of:
- the regulatory regime (regulatory oversight, qualification of the pilots, compliance with ICAO SARPs, performance requirements, SOPs etc);
- application of Safety Management Systems;
- quality based maintenance systems;
- Helicopter Operational Monitoring Procedures (HOMP)
- the addition of Vibration (VHM) and Usage (UMS) monitoring systems;
- the number of engines;
- the number of pilots;
- additional operational equipment such as ACAS, EGPWS etc.
and when all of this fails
- crashworthiness above the certification standard; and
- survival equipment
- all of which have to be included in the model, to be applied individually or in combinations (or in particular operational circumstances) to mitigate perceived hazards.
What is the bottom line for this exercise? When the unacceptable cost of a fatal accident rises above the cost of the application of some or all of the mitigating factors - the investment is worthwhile. (Which has been pointed out by others might be conditioned by society in the operational theatre.)
However, it is clear that the operational requirement is the first test for the customer - for it is that which will produce the short list of qualifying aircraft. In the case of the Southern North Sea, the AB139 might just be slightly too large and the competition could be narrowed to the S76 and the EC155. If that is the case it would be a pity as the certification basis and the installed power of the AB139 would have put it into a different class (but perhaps the sums will work out).