PBN and Helicopters: How They Fit
PBN promises smaller separation intervals, more direct flight paths and more flexible landing/takeoff routing and other advantages. But is it going to work for helicopter operations?
By James Careless
Performance-based navigation (PBN) is a new form of aerial navigation currently being deployed by the FAA, ICAO and other aviation regulators worldwide. The reason is PBN supports smaller separation intervals, more direct flight paths and more flexible landing/takeoff routing for fixed-wing and rotary-wing aircraft alike. It does this using GPS and WAAS (wide area augmentation system) satellite signals, and advanced onboard navigation systems like the Garmin GNS-530W or Universal UNS-1FW.
For helicopter pilots and operators, PBN offers many potential advantages. These include being able to develop helicopter-specific flight paths that avoid fixed-wing traffic; reducing time and fuel spent flying circuitous IFR-based patterns, and being able to fly more of the unique vertical approaches and departures that helicopters are suited for. This said, not everyone is convinced that PBN goes far enough in supporting optimal helicopter navigation.
PBN Defined
"At its simplest level, performance-based navigation gets down to the concept that the navigation system installed on each aircraft has its own standard of possible performance," explains Chad Cundiff, Honeywell's vice president of crew interface products. "PBN is designed to take advantage of these capabilities, by coming up with navigation rules that reflect this fact on a case-by-case basis."
For instance, a pilot flying an AgustaWestland AW139 equipped with a Honeywell Primus Epic GPS/inertial system can fly within relatively tight flight and obstacle avoidance paths. But a pilot flying a helicopter with a less precise GPS-only system backed up by ground-based navigation beacons will have to leave more separation space.
"In theory, an advanced PBN system would let you fly safely down a skyscraper canyon, by keeping you nicely positioned between the buildings on either side," Cundiff notes.
Why PBN?
Helicopters have the ability to take off vertically, level off at an appropriate altitude (i.e., avoiding cool moist air where icing can be a danger), and land vertically as they please.
In a perfect world, helicopter pilots would be able to use this ability to its fullest. However, in reality the rules of aerial navigation have been dictated by the needs of fixed-wing aircraft. If helicopters are powerboats, fixed-wing aircraft are lumbering oil tankers. They need lots of space to takeoff, fly and land without hitting each other. This is why the world's air corridors are so tightly monitored and why the growing amount of fixed-wing traffic within these corridors has regulators so concerned. It is this concern that has pushed the FAA and other regulators into implementing PBN.
With PBN technology, aircraft fly closer together and employ more creative, three-dimensional takeoff and landing approaches.
PBN's capabilities are good news for the FAA, which is grappling with the relentless growth of air travel. "In 2005, passenger demand grew rapidly, with enplanements up 7 percent from the previous year to 738.6 million and revenue passenger miles increasing 8 percent to 775.3 billion," says the 2006 version of the FAA's Roadmap for Performance-Based Navigation. "Passenger demand for air transportation is projected to increase an average of 3.4 percent each year between 2005 and 2017. By 2017, U.S. commercial air carriers are predicted to transport a total of about one billion passengers, flying over 1.25 trillion passenger miles."
The FAA is currently deploying advanced PBN systems at the country's airports, and establishing PBN air corridors to serve busy air routes. The goal is to convert U.S. general aviation to PBN operation by 2025. Other countries are following suit.
"We want to extend PBN to helicopters, such that helicopters get their own air corridors where possible; have less interaction with air traffic control simply because they spend less time in fixed-wing airspace; and have easy access to heliports and other designated landing areas," says Mike Webb, of the FAA's AFS-420 Flight Procedure Standards Branch. He is currently developing PBN-compliant helicopter instrument procedures. "With the help of highly accurate GPS/WAAS satellite signals and onboard navigation systems, helicopter pilots will be able to use much more of their aircraft's maneuverability in obstacle-rich urban environments."
"Our goal is to move helicopter navigation away from its fixed-wing roots," adds Erwin Lassooji, ICAO's PBN program manager. "We are currently developing helicopter-specific PBN standards for all phases of flight, not just approach and takeoff. We anticipate updating these standards officially by March 2011."
Performance-based navigation will allow helicopter pilots to use their aircraft's avionics capabilities more, especially when approaching airports. It will allow pilots to come up with new and more relevant approaches that better meet their company's needs. This can translate into less fuel burn and savings. Honeywell
PBN Helo Advantages
Performance-based navigation will allow helicopter pilots to use their aircraft's avionics capabilities more, especially when approaching airports. Like their fixed-wing cousins, such helicopters will be allowed to fly tighter, closer and more varied approaches, using curves and even spirals where such approaches make sense.
This flexibility translates into less fuel burned and less time aloft, thus increasing the number of flights a helicopter can make before being grounded for regular maintenance. But PBN does more than just save money. It allows pilots to come up with new and more relevant approaches that better meet company needs.
"With PBN, you can work out fuel-efficient approaches to heliports, hospitals and other regular landing sites that stay clear of fixed-wing traffic," Cundiff says. "This means that you can count on being cleared by local air traffic control, even when fixed-wing traffic is heavy in your area."
PBN also offers improved, more precise IFR flight for helicopters. For some pilots, this will change the point at which to decide to go from VFR to IFR; simply because going to instruments won't necessarily mean submitting to air traffic control and its delays, holding patterns and circuitous routes.
Compared to the old radio beacons that it replaces, PBN is a real advance for helicopter aviation. But Stephen Hickok does not think PBN goes far enough. In fact, he believes that the FAA doesn't really understand rotary-wing flight, and that its 'NextGen' air traffic strategy is far too tied to traditional fixed-wing thinking. "The FAA's PBN strategy is built upon a 'one-size-fits-all' approach that does not truly recognize the unique capabilities and needs of helicopters," Hickok tells Rotor & Wing. "It is designed for aircraft that rely on runways, and helicopters don't need runways. If anything, our runway is the sky."
Hickok has the credentials to stand as a credible critic. He is president of Hickok & Associates of Orange Beach, Ala., a company that designs airspace and instrument approach procedures. According to his website (), Hickok managed the FAA's helicopter GPS flight testing, "which led to the origination of the very policies and criteria used for the development of today's IFR procedures." Hickok has served as an ICAO advisor, and has been both chairman of HAI's Flight Operations Committee, and chairman of the Vertical Flight Working Group to FAA's Performance-Based Aviation Rulemaking Committee.
If that's not enough credibility, consider this: On April 1, 2009, the FAA approved the first helicopter WAAS Localizer Performance with Vertical Guidance (LPV) Instrument Flight Procedures (IFPs). Hickok's company developed this first IFP - actually three IFPs - for California Shock/Trauma Air Rescue (CALSTAR).
When it comes to PBN, Hickok's concern about the FAA is that "they are still in a fixed-wing mindset." As such, the FAA's PBN rules do not allow pilots "to use our helicopters and their avionics to their fullest advantage," he says.
From Hickok's perspective, the FAA's PBN rules group high-capability helicopters together with their lower-performing counterparts, with the limits on missed approaches and other elements being set to the lowest common denominator. "We need to do better than just reverse-engineering fixed-wing criteria," Hickok observes. "We need helicopter-specific PBN, that matches a range of helicopter capabilities."
Sagem's analysis ground station software allows for the recreation of flight trajectories. These trajectories can then be examined and PBN approaches, departures and flight planning can be developed. Map overlay image courtesy of Sagem
Bell's PBN Research
Despite his criticism, Hickok is aiding the FAA in adapting PBN for helicopters, specifically by helping Bell Helicopter with its PBN research. Specifically, the FAA has contracted Bell to collect PBN-related measurements using a Bell 429 equipped with WAAS-enabled Garmin GNS 430W and GNS 530W avionics units (one each).
"Steve Hickok developed the profiles that we are using to collect PBN approach data," says David Downey, Bell's vice president of flight operations/safety and certification. "Our goal is to create a series of operating procedures ranging from point-in-space to landing and departure."
The Bell 429 is a single-pilot IFR helicopter, making it an ideal testbed for EMS-focused PBN procedures. "70 percent of all EMS flight are hospital-to-hospital," says Downey. "Imagine that you could go to work by getting in your car, pushing a button, and having your car execute the necessary turns and speeds. An EMS-based PBN solution could do that for hospital-to-hospital transfers.
Not only would this make flights safe in all weather conditions, but air traffic control would always know where the EMS helicopters were, simply because they would be following this predefined flight profile. That's the kind of things we are working on for the FAA."
Preparing for PBN
For helicopter pilots and operators, trying to decide where PBN fits into your operation can be confusing.
The best place to start is by looking over your avionics equipment to see just what capabilities it does and does not support. Such evaluations are a key part of the PBN approach: The FAA recognizes that not every aircraft is PBN-capable, let alone compliant.
Should you find your current avionics lacking, then now is the time "to start imaging the fuel/maintenance savings and enhanced safety you could achieve by upgrading your avionics suite," Honeywell's Cundiff says. For instance, his company's Primus Epic couples GPS/WAAS with an onboard inertial guidance system; providing key redundancy if something (i.e., strong solar flares) should knock out GPS/WAAS satellite signals. It makes your helicopter truly PBN-capable.
Sagem Avionics also supports helicopter/PBN deployments. "To enable performance-based navigation, operators must collect data and perform routine analysis of this data to design [their] PBN," explains company spokesperson Emmy Ansinelli. "Sagem's AGS (Analysis Ground Station) software allows for the recreation of trajectories. These trajectories are then examined and PBN approaches, departures and flight planning can be developed for each aircraft type within the operator's organization."
"The aim of performance-based navigation is primarily to reduce risks and costs [i.e., fuel burn] to the operator," Ansinelli adds. "To make sure that PBN implementation is successful, Sagem's AGS can be used to continuously perform post flight routine analysis. As the flight data is analyzed, the operators can measure the PBN's efficacy; for example, is the aircraft burning less fuel?"
Final Verdicts
Performance-based navigation is undeniably the way of the future. In the years to come, helicopter pilots will be able to fly more precise, shorter and tighter approaches to their targets, with the added benefit of spending more time outside of air traffic controlled airspace.
Will this aid speciality operators, such as EMS single pilots flying IFR approaches? "I don't really think anybody knows," replies Hickok. "PBN is primarily concerned with the space around airports, which is not where EMS pilots make most of their approaches."
Dave Downey is more optimistic. "We believe that, by contracting Bell to do PBN research, the FAA is saying, 'we probably didn't pay as much attention as we should have to rotary-wing when we came up with PBN initially, and now we want to fix that,'" he says. "Frankly, I think we have a tremendous opportunity to prove how well helicopter-based PBN can complement what's being put in place for fixed-wing." Wherever they stand, all helicopter pilots and operators would be well-advised to learn more about PBN through the FAA () and ICAO (). Love it or not, PBN is coming!