China leapfrogged its international peers in late April with what is arguably the world’s most advanced display of a precision navigation capability—satellite-guided curved approaches with multiple glideslopes that seamlessly terminated in automatic landings.
The one-day demonstration on April 29 took place at Shanghai’s Pudong International Airport using a China Eastern Airlines Airbus A321 and a Shangdong Airlines Boeing 737-800 with senior officials from China’s Civil Aviation Administration (CAAC) and air traffic management bureau onboard. Anchoring the capability is a Honeywell SmartPath ground-based augmentation system (GBAS) that has been operating at the airport since January.
The approaches at Pudong demonstrated key benefits of a digital GBAS landing system (GLS), including the ability to merge the GLS with satellite-based required navigation performance (RNP) procedures for a customized 3-D path to the runway. RNP provides the aircraft with narrow horizontal and vertical paths into the vicinity of an airport, where GLS provides the precision guidance to landing. The SmartPath system, the first certified GBAS landing system to be installed in China, uplinks digitized approach paths and correction factors to GPS signals to allow an aircraft equipped with a multi-mode receiver capturing GPS signals from space and the GLS information from the ground station to fly as many as 26 approaches to multiple runways. A GLS can replace or augment traditional instrument-approach architectures that use analog horizontal and vertical guidance transmitters placed at each runway end to transmit a straight-in path to the runway, typically at a 3-deg. glideslope. Those systems are costly to maintain and require flight inspections on at least a semi-annual basis.

A GLS approach into the Pudong Airport as seen on the primary flight display of an aircraft participating in a late-April demonstration of satellite-guided curved approaches. Credit: Hughes Aerospace

Navigation procedure developer Hughes Aerospace drafted eight approaches for Pudong in partnership with Honeywell. Included are GLS procedures for Runway 35L that offer a traditional straight-in approach with 3-deg. glidepath, a curved approach that mates with an RNP arrival and intersects a straight-in GLS final, a straight-in approach with 2.8-deg. glidepath and a straight-in approach with a 3.2-deg. glidepath and a 3,517-ft. displaced threshold. RNP approaches with curved paths can be used to join with a GLS approach closer to the airport, saving track miles and fuel compared to legacy approaches, or to avoid noise-sensitive areas.

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Chris Baur, president and chief executive of Hughes Aerospace, says choices for glidepath angle potentially could allow airports to increase runway throughput by mitigating wake turbulence concerns. For example, the arrival rate could be increased by having a heavy aircraft fly an approach with a lower glidepath while a lighter aircraft uses the steeper glidepath approach with displaced threshold.
SmartPath, to date the only FAA-certified GLS on the market, is installed at several airports worldwide, including Newark (New Jersey), Houston, Frankfurt and Sydney, where a growing number of aircraft equipped with multi-mode receivers (MMR) can access the capability. The systems are currently approved for Category 1 instrument approach minimums (aircraft must be in visual conditions at 200 ft. above the runway to continue the approach), but the FAA and others are working toward Cat. 2 (100-ft. minimums) and Cat. 3 capability (50-ft. minimums or less, including autoland) in the next several years. The FAA says Cat. 3 operations could be available in the U.S. in 2018.
A handful of airlines globally are beginning to use GLS as an alternative to a straight-in legacy instrument landing system (ILS) with a 3-deg. glideslope, particularly as newer aircraft are available from the factory with the option. Boeing says it has more than 1,000 GPS-equipped in-service aircraft, with the number growing by 25 per month. The airframer says one-third of all new 737s are being delivered with the MMRs, which are standard equipment on the 747-8 and 787.
Delta Air Lines conducted its inaugural GBAS landing with a Boeing 737 at Newark Liberty International Airport on Feb. 18, joining United Airlines and British Airways, which were already flying the approaches there. The FAA says United is averaging 65-70 GBAS landing system (GLS) approaches at Newark and Houston’s George Bush Intercontinental Airport each month with a portion of its 737 and 787 fleets. United has 95 737s and 14 787s with MMR avionics, and is selecting the option for all new 737s.
Delta is using the approaches in Houston as well as in Newark, and has a fleet of 42 GLS-equipped 737s. The carrier is investigating GLS for its Airbus fleet. In total, the airline plans to have 177 aircraft equipped for the approaches by 2019, according to the FAA. A growing number of international airlines also are using the capability at Newark and Houston. Emirates conducted its first GLS landing in Houston in December with an Airbus A380, one of 57 GLS-equipped A380s at the time. The carrier also uses the approaches at Frankfurt, Sydney and Zurich. Lufthansa made its first GLS landing in Houston in December with one of 12 equipped A380s that also use the approaches at Sydney and Frankfurt. Cathay Pacific made its first GLS landing in Houston, with a 747-8, at the end of January. The FAA says Virgin Atlantic is also planning to seek operational specification approval for the approaches into Newark. Other carriers purchasing GLS-equipped aircraft include Air Berlin, Qantas, Swiss, TUIfly and various Russian airlines.
Next steps for Pudong include CAAC certification of the GLS at the airport, an inaugural process that may allow for quicker installations at other airports in the country.