The Performance Classes should not be confused with Categories A & B which denote the build/certification standard of the aircraft out of which a performance capability is derived (see also 14 CFR/JAR 27/29). In general, the majority of present generation helicopters are not designed to full Category A and unlimited Performance Class 1 standards. Therefore, for operations in a hostile environment, Performance Class 2 helicopters are accepted by OGP although preference will be given to Performance Class 1, if available. In some operating environments it may be possible to operate Performance Class 2 helicopters to Performance Class 1 standards with minimal impact on payload. Such an approach is strongly encouraged. Where Performance Class 2 helicopters are taken on contract, the operation should be able to demonstrate, either separately, or as part of its Safety Case that the probability of power unit failure during the exposure time at take off and landing from elevated helidecks is no greater than 5x10-8 per take-off or landing.
5.3 Fuel planning
While parameters covering all circumstances cannot be clearly laid down, the following should be used as guidance for fuel planning unless otherwise stated in relevant regulations or Operating Manuals.
5.3.1 IFR flight plan
Fuel should be sufficient for the leg to destination plus the leg to an alternate plus 10% trip fuel plus 30 minutes. An allowance should also be made for start-up and taxi.
Note: Fuel computations for the leg to the alternate should be calculated at the low altitude cruise fuel consumption if this is likely to be the case.
5.3.2 VFR flight plan
Fuel should be sufficient for the proposed route plus 30 minutes at the cruising speed consumption. An allowance should also be made for start-up and taxi.
Note: The above requirements are in addition to unusable fuel as listed in the aircraft Flight Manual.
5.4 Use of offshore alternates
The reliance on offshore installations as alternates should be avoided wherever possible and is only acceptable in certain circumstances when the onshore alternative is equally unacceptable. Advice should be sought from the OGP Member’s Aviation Advisor, especially for long-term requirements. As a minimum, the following conditions need to be met:
. An offshore alternate shall be used only after a Point of No Return (PNR). Prior to PNR, onshore alternates shall be used.
. One engine inoperative landing capability shall be attainable at the alternate.
. Deck availability shall be guaranteed. The dimensions, configuration and obstacle clearance of individual helidecks or other sites shall be assessed in order to establish operational suitability for use as an alternate by each helicopter type proposed to be used.
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