Performance based navigation (PBN) has a greater navigational/positional accuracy and containment that allows helicopters to operate in instrument meteorological conditions. The use of space-based augmentation system (SBAS) in suitably equipped helicopters requires less airspace.
On the one hand the available technology and the equipment installed on commercial helicopters, in particular those of the latest generations, are making it easier to transition to PBN. On the other hand, however, the pace of implementation of PBN procedures by helicopter operators has been so far relatively slow. Some critical mass has developed, as the industry in general supports the PBN concept.
There have been some research and development programmes in Europe, including the PBN Rotorcraft Operations under Demonstration (PROuD) project with the objective of demonstrating that helicopter Point in Space (PinS) procedures implementation can allow access to heliports in difficult environments when there is reduced visibility. This project has demonstrated in live trial environments how the adoption of PBN flight procedures improves the safety and reliability of search and rescue (SAR) operations and landing site accessibility in challenging environments, such as in adverse weather conditions and mountainous areas.
The helicopter community has identified the need for a PBN navigation specification that is specific to helicopter operations: required navigation performance (RNP) 0.3.
From this particular specification, instrument flight rules (IFR) operations can enjoy various benefits, including:
- reduced protected areas, potentially enabling separation from fixed wing traffic to allow simultaneous non-interfering operations in dense terminal airspace;
- low level routes in obstacle rich environments reducing exposure to icing environments;
- seamless transition from en route to terminal route;
- more efficient terminal routing in an obstacle rich or noise sensitive terminal environment, specifically in consideration of helicopter emergency medical services (HEMS) IFR operations between hospitals; and
- transitions to helicopter Point in Space (PinS) approaches and for helicopter departures.
RNP 0.3 is used during operations at low level flight, which means that it can be used during air ambulance operations. The number “0.3” refers to the capability of the helicopter remaining 95% of the time within 0.3 NM to the right or left of the centreline. RNP 0.3 can support helicopter operations at low level in mountainous remote areas and for airspace capacity reasons in high density airspace RNP.
The applicability of RNP 0.3 is to departure, en-route, arrival (including the initial and intermediate approach segments), and to the final phase of the missed approach. This navigation specification addresses continental, remote continental and offshore operations. Route length restrictions may be applicable for en-route operations meeting RNP 0.3.
Global navigation satellite system (GNSS) plays an important role with regard to NAVAID infrastructure considerations as the RNP 0.3 specification relies on GNSS. Areas of known navigation signal (GNSS) interference are an exception; in these areas RNP 0.3 must not be used.