Page 9 - Volume12 Number 5

Illustration of the RNP approach procedure design in Queenstown, New Zealand.
APPROACH
PBN instrument approach procedures have been deployed extensively to runways across the NAS. The current inventory of RNAV (GPS) and RNAV (RNP) approaches in the U.S. NAS is over 14,400. This current inventory of PBN IAPs is less than the existing conventional instrument approach procedure counts by a few thousand, but it is significant to note that there are many airports that are only served by PBN instrument approach procedures. In addition, there are over 1600 PBN precision approaches to airports that are not equipped with an ILS. The U.S. General Aviation population has benefitted greatly from the U.S. WAAS program through the implementation of LPV approaches. These procedures have focused on the challenge of providing ILS-type guidance from the final approach fix to the runway. The benefit of Required Navigation Performance (RNP) approaches has been almost completely unavailable to this population of aircraft and is waiting for this capability to be provided by the avionics manufacturers. The benefits of this technology to address the more complex challenges of the complete set of approach, missed approach and departure operations has been widely recognized and implemented by air transport operators with Boeing and Airbus aircraft. A highly regarded example of this is the RNP operations in Queenstown, New Zealand as depicted in the graphic above, and as viewed from the cockpit in a YouTube video: www.youtube.com/ watch?v=7mxmFCw-Dig .
The development and implementation of RNP is an outcome of navigation and guidance performance of our modern airplanes that far exceeds the assumed performance used in Terminal Instrument Procedures (TERPS) design criteria.
Trajectory Based Operations and the Future
All of these activities are preparing for a much larger vision than the benefits provided by the individual elements by themselves. The primary goal of NextGen is to transition to Trajectory Based Operations (TBO) and remain the same as first envisioned by the JPDO in 2007. TBO is the air traffic concept to operate the National Airspace System based on the aircraft’s ability to fly precise paths in time and space and the Air Traffic Management’s ability to strategically manage and optimize trajectories throughout the operation. Another way to describe this is to say that we are moving from a system based on knowing where an aircraft is (radar and ADS-B) to a system based on knowing where an aircraft is going to be at any given time.
With this in mind, it will be increasingly important for each aircraft to have a sophisticated flight management function to build a precise 4-D (time and space) plan. This onboard plan will be shared via DataComm with the ground systems to support the strategic management of airspace.
All of this seems quite far away now, but it is helpful to keep the bigger picture in mind as the individual components are being developed and brought together through many separate initiatives. KA
Steve Fulton has a broad aviation background in avionics development, instrument flight procedure design and flight test. He is an Air Transport Pilot and FAA Designated Engineering Representative Flight Test Pilot with over 15,000 flight hours. He is the president of Fulton Aviation and was previously VP Sales & Marketing for Sandel Avionics, Technical Fellow for GE Aviation and co-founder of Naverus, Inc. He is a member of
the NextGen Advisory Committee subcommittee, and co-chaired the Time, Speed Spacing Task Group with a representative from FedEx, and is currently co-chair of the Performance Based Navigation – Time Based Flow Management NIWG with a representative from American Airlines.
MAY 2018
KING AIR MAGAZINE • 7