features Performance-based Navigation

Performance-based navigation (PBN) has been around for several years now and promises to allow cleaner, more efficient, safer use of existing airspace by both fixed-wing and rotary-wing aircraft.
Avatar for Mario Pierobon By Mario Pierobon | November 18, 2021

Estimated reading time 10 minutes, 3 seconds.

Performance-based navigation (PBN) has been around for several years now and promises to allow cleaner, more efficient, safer use of existing airspace by both fixed-wing and rotary-wing aircraft. As helicopter operations fall within the scope of PBN as an air navigation concept, it is increasing opportunities for helicopter operations to be conducted even in the face of demanding weather and environmental conditions. This includes the development of helicopter specific PBN procedures.

As PBN is based on area navigation, and not specific to ground-based navigation aid (NAVAID) infrastructures, they can be implemented at almost any site where a need is identified. Patrick Cardinal Photo

Chris Baur, president of Hughes Aerospace Corporation, said helicopter PBN is a “green technology” in that it mitigates the environmental impact of helicopter operations and provides safer, more efficient day/night and all-weather access. 

“Since PBN leverages trajectory-based operations, flight paths can be tailored to reduce track-miles flown, avoid noise sensitive areas, and provide dispatch dependable minima that reduce diversions and holding, avoid icing while also reducing pilot-controller workload,” Baur told Valor.

In Canada, most of the published procedures would fall under the “required navigation performance” approach (RNP APCH) navigation specification detailed in Transport Canada Advisory Circular 700-023, which is applicable to both fixed-wing and helicopter operations. 

“These flight procedures mainly support medevac operations to hospitals as well as passenger services to various harbors in and around the Vancouver/Victoria areas and some operations to oil rigs off the east coast,” said Jeff Dawson, assistant vice president of operational support at Nav Canada.

In Canada, most of the published procedures would fall under the “required navigation performance” approach (RNP APCH) navigation specification AC 700-023. Heath Moffatt Photo

PBN point-in-space (PinS) helicopter approach procedures under visual flight rules (VFR) conditions using Global Navigation Satellite System (GNSS) have essentially replaced conventional helicopter approach procedures in Canada, according to Transport Canada. As PBN is based on area navigation, and not specific ground-based navigation aid (NAVAID) infrastructures, they can be implemented at almost any site where a need is identified. “Helicopter PBN departure procedures also exist in Canada although they are a newer tool in the toolbox,” according to a Transport Canada spokesperson.

In general, not all helicopter PinS instrument approaches need to be “proceed VFR,” according to Baur. “Localizer performance with vertical guidance (LPV) procedures can be ‘Proceed Visually’ with required weather minima less than what is required for a ‘Proceed VFR’ visual segment,” Baur said. “Depending on the design, the procedure can be both ‘proceed visually’ and ‘proceed VFR,’” he says. “Helicopter instrument departure procedures have been around for more than 10 years. Criteria for helicopter departures are constantly improving and support both ‘proceed visually’ and ‘proceed VFR.’”

“The ability to fly RNP approaches to LPV minima represents a significant improvement in operational capabilities, safety, and efficiency,” according to Paul Bolt, manager of rotor-wing flight training standards at Ornge. “However, the improved capability has not had as significant an impact on our ability to deliver services in an instrument flight rules [IFR] environment as with our fixed-wing fleet. As the proportion of IFR flights performed by Ornge continues to increase, our flights are predominantly conducted in [VFR] conditions. This is influenced by the fact that most helicopters are not certified for flight in icing conditions, limiting the capacity to operate in instrument meteorological conditions [IMC] during colder months. Additionally, the availability of RNP approaches to LPV minima remains limited in the area of operations.”

PBN implementation

In Canada, PBN helicopter PinS approach procedures (proceed VFR) have been around for several years, according to TC. 

“In more recent years, the capability to develop helicopter PBN departure procedures has been introduced and implementation of more of these is expected as time progresses,” Transport Canada said in a statement. “Like fixed-wing aircraft that operate in IFR conditions, helicopters have access to the Canadian PBN airspace for IFR operations. Currently, no Canadian heliport is certified to an instrument standard, so helicopter approach and departure procedures are only available using the PinS technique.”

Nav Canada’s Dawson said the U.S. Federal Aviation Administration (FAA) has begun to implement some helicopter PBN procedures under a new helicopter-specific navigation specification called RNP 0.3. 

“The strict containment requirements under this specification employ tighter obstacle protection areas and allow helicopter operations within dense metropolitan, obstacle rich environments. Benefits of RNP 0.3 include low-level routes to avoid exposure to icing and more efficient terminal area routings to avoid noise-sensitive areas while enabling separation from fixed-wing traffic,” Dawson said.

Currently, there are more than 1,000 helicopter instrument flight procedures in the United States, with more in production, according to Baur. These include Copter RNP APCH, LPV/LP as well as LNAV. 

“We are also producing Copter RNP 0.3 low-level airways, and elements of Copter A-RNP using radius-to-fix segments,” Dawson said. “We worked with the FAA to develop helicopter RNP 0.3 low-altitude airways, to keep helicopters in lower, warmer air, reducing encounters with icing conditions. We developed the first helicopter RNP 0.3 routes for the FAA in the Maryland State Police Project. We have now implemented these routes along the mountainous West Coast.”

PBN procedures and training

Canadian air operators wishing to implement PBN operations are required to meet the elements specified in Transport Canada Civil Aviation Specific Approvals (SAs) for the type of operation being requested. These relevant SAs are listed in Volume III of Transport Canada’s Air Operator Certification Manual. The Transport Canada Civil Aviation Advisory Circulars are published to assist operators in the approval process of acquiring an SA for PBN related operations.

With PBN, helicopter EMS operations and the entire aviation industry could see benefits through reduced cost and green house gas emissions as a result of a more direct routing. Skip Robinson Photo

“Rotorcraft operators wishing to implement PBN can find both aircraft certification and system requirements as well as pilot knowledge and training requirements detailed within the applicable Transport Canada advisory circular — at this time — AC 700-023,” Dawson said.

The advisory circulars provide a detailed framework for flight crewmembers, operational control personnel, and maintenance personnel in order for operators to comply with operational procedures and training requirements, according to Transport Canada. As RNP 0.3 — which is helicopter specific — has not yet been implemented in Canada, a sample of the expected requirements can be reviewed under the FAA’s AC 90-105A, Appendix D.

The document provides guidance on the performance and functional requirements for rotorcraft systems used to conduct RNP 0.3 for en-route and terminal operations, as well as guidance for rotorcraft RNP 0.3 en-route and terminal operations servicing offshore rigs and where accuracy may be needed to support low level mountainous operations and also in high density airspace. 

Commercial operations must include normal and contingency RNP 0.3 operational procedures for their particular equipment installation. Commercial operators must receive approval to fly RNP 0.3 rotorcraft operations via helicopter specification. Part 91 operators are not required to have operational approval for RNP 0.3 operations. The operator must have a configuration list, and if necessary, a minimum equipment list (MEL) detailing the required aircraft equipment for RNP 0.3 operations.

The training program required by the FAA should provide sufficient training (e.g., simulator, training device, or rotorcraft) to the extent that pilots are familiar with a variety of training items — as applicable to the rotorcraft RNP system — and which include: the meaning and proper use of rotorcraft navigation suffixes, procedure characteristics as determined from chart depiction and textual description, depiction of waypoint types (flyover and flyby) and any other types used by the operator as well as associated aircraft flightpaths, required navigation equipment and MEL for operation on RNP 0.3 air traffic services (ATS) routes, RNP 0.3 system-specific information, RNP equipment operating procedures, operator-recommended levels of automation for phase of flight and workload, receiver/transmitter phraseology for RNP applications, and contingency procedures for RNP failures.

The future of helicopter PBN

The future of PBN for rotorcraft in Canada is highly dependent upon the demand from operators, according to Dawson. 

“Three key elements that need to be addressed at the regulatory level are the implementation of IFR heliport standards, required navigation specifications and flight procedure design criteria,” Dawson said.

PBN is useful for terminal operations servicing offshore rigs and where accuracy may be needed to support low level mountainous operations and also in high density airspace. Heath Moffatt Photo

Baur highlighted the need for more trajectory-based procedures and further implementation of elements of A-RNP that are suitable for helicopters.  

“We are working on improvements to Copter departure procedures for lower minimums. Particularly as operators invest in new aircraft with contemporary avionics, including A-RNP capabilities such as radius-to-fix and missed approach segments, they will want to derive the value-add of that investment,” Baur said. 

Hughes has begun a campaign to provision its customers with a Heliport Weather Camera System that interfaces with the Hughes App and its digital geo-referenced charts, providing pilots with a much higher level of situational awareness.

As PBN facilitates airspace redesign and improvements in lateral and vertical navigation capability, the entire aviation industry will see benefits through reduced cost and greenhouse gas emissions as a result of more direct routing, increased airspace capacity, better noise control and, most importantly, safer operations, according to Bolt. “The impact on helicopter operations may not be as significant as for airplane operations, but we will continue to be positively impacted,” Bolt said.  

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