ATM Modernization, Commercial, Embedded Avionics

Airline GPS Receiver Issues Being Resolved Through Equip 2020

By Woodrow Bellamy III  | April 7, 2015
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[Avionics Today 04-07-2015] While most of the aviation industry’s focus regarding the FAA’s approaching 2020 mandate has been on equipping General Aviation (GA) aircraft with Automatic Dependent Surveillance-Broadcast (ADS-B) avionics, airlines are also facing NextGen equipage issues. Through the FAA’s recent formation of the Equip 2020 working group, however, those issues are being addressed through face-to-face meetings between avionics manufacturers, pilots, airlines, Air Traffic Controllers (ATCs), regulators and all facets of the aviation community impacted by the mandate. 
An ACSS engineer installs a DO-260B transponder on a JetBlue airliner. Photo: ACSS
One of the main issues airlines are facing right now is the GPS receivers aspect of the overall ADS-B solution. The equipment required for the ADS-B Out mandate includes a DO-260B compliant transponder, a means of providing accurate position data from GPS, annunicators and an interfacing mechanism. There are three generations of GPS equipment available for all categories of aircraft, including air transport; this includes a first, second and third generation. 
The ADS-B standard is fixed at the second generation GPS equipment, and has committed to not making any changes to it. However, airlines are trying to determine whether their current first-generation GPS equipment meets the performance requirements of the 2020 rule with the appropriate availability for their operations, or if, alternatively, there is a path to upgrade to a later generation GPS, such as SA Aware, Wide Area Augmentation System (WAAS)-enabled, or multi-constellation Global Navigation Satellite System (GNSS) equipment. 
To resolve this issue, in February, FAA Deputy Administrator Michael Whitaker said in the latest NextGen Advisory Committee (NAC) report that the Equip 2020 team reached an agreement allowing air carriers with first and second generation receivers (SA Aware) to continue using these until 2025. This issue had been unresolved over the last three years, and was decided through the Equip 2020 working group, which provided data from avionics suppliers about what equipment they’re offering and the air carriers indicating what they’re buying and when.
ACSS, an L-3 Communications and Thales joint venture, is currently involved in ongoing ADS-B Out upgrade programs with JetBlue, American Airlines and UPS, and is providing solutions that feature both SA=On and SA=AWARE positions sources, Arnold Oldach, director of product marketing at ACSS told Avionics Magazine. 
“These programs are DO-260B ADS-B Out transponder STC projects,” said Oldach. “Operators have typically performed these modifications during scheduled maintenance visits. Many airlines are using a two-step approach: first is to lay in the wiring and make all the connections from the [Multimode Receiver] MMR to the transponder; the second step is to activate the DO-260B Service Bulletin or replace the transponder. Touch-labor required for ADS-B Out modification is from 20 to 40 hours. US Airways is currently using our SafeRoute ADS-B In solutions, which provides, among other things, display of traffic in the cockpit.”
Whitaker’s announcement of the new 2025 agreement with airlines resolves one of the main issues with the considerations around what GPS receivers operators should equip with. However, Oldach noted that there are still other requirements of which operators should be aware. 
“The current FAA position is that they will allow the use of SA=ON and SA=AWARE position sources (MMR/GPS) for a yet-to-be-determined time period after the 2020 mandate,” said Oldach. “Operators will, however, be required to use the FAA ADS-B Service Availability Prediction Tool (SAPT) for pre-flight dispatch RAIM prediction. ACSS has certified ADS-B transponders with both SA=ON and SA=AWARE position sources. SBAS/WASS GNSS will meet availability requirements without the SAPT tool.”
Esterline CMC Electronics is another supplier that has a precision GPS source ready to help airliners meet the ADS-B Out mandate, with its IntegriFlight CMA-5024 landing system sensor. CMA-5024 also features an optional CMA-5025 control panel, so that the unit can act as a completely independent precision approach system for the system’s built-in RNP 0.1 performance and LPV approach capability with a path for growth to GBAS Cat I/II/II, according to Rex Hygate, business development manager for Esterline CMC Electronics. 
“We supply our CMA 5024 GPS for ADS-B equipage,” said Hygate, who is well aware of the ongoing discussions around GPS equipage for Part 25 aircraft. 

“Its very complex, there’s three classes of GPS: old, medium and new, you might call them,” said Hygate. “The old is the TSO-C129, which is on most legacy airliners. The medium is the SA Aware TSO-C196, which has started being fielded in airliners from about the past five years on. The new is the WAAS, which is on very few airliners. So, with the 2020 mandate, the old receivers probably almost certainly won’t work for normal operations. For the medium ones, it should work as long as the satellite constellation is healthy. With the new ones it will work always, guaranteed. It’s very difficult for an airline to make its decision on what GPS to get and how much they need to update. This is the issue that is being worked on.” 

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