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Monday, March 1, 2010

Situation: Airport Surface

FAA and industry teams work to accelerate development of standard for airport surface detection, alerting using ADS-B

Bill Carey

FAA and industry are developing a standard for displaying airport surface traffic in the cockpit, coupled with alerting of potential runway conflicts, using Automatic Dependent Surveillance-Broadcast (ADS-B) position reports.

Two industry teams in recent months completed evaluations of surface detection and alerting systems under FAA’s Surface Indications and Alerts (SURF IA) program, funded in 2008 with a congressional “plus-up” of $9.3 million. The intent of the evaluations, each of which culminated in an operational demonstration, is to validate requirements and accelerate a standard for the ADS-B “In” surface application.

Results of the SURF IA program will be run through the RTCA committee process to produce industry consensus Minimum Operational Performance Standards (MOPS) for the application. The technical guidance of the MOPS will serve as the basis of a FAA Technical Standard Order (TSO), expected by 2011. Manufacturers can build equipment to the TSO requirements.

The development of an indicating/alerting application using ADS-B In is happening outside the ADS-B rulemaking by FAA, which was on track for release in April. The rule will mandate that aircraft be capable of ADS-B Out, the broadcast of their GPS-derived position to other equipped aircraft and air-traffic controllers, by 2020. A mandate on ADS-B In, the ability to receive and display other aircraft and ground transmissions in the cockpit, was deferred.

“Surface indicating and alerting was the chosen application to accelerate the development of the standards,” said Vincent Capezzuto, FAA Air Traffic Organization director of Surveillance and Broadcast Services. “We’re using the acquisition process to coincide, in parallel, with the RTCA process. … We’re trying to put a little bit more confidence in the material that represents this application. Essentially, we’re buying down the risk, trying to make it easier for the manufacturers to mass produce.”

Applications exist for surface situational awareness based on ADS-B In. One, called Final Approach and Runway Occupancy Awareness (FAROA), provides pilots with information on runway occupancy on approach, and requires a moving map display and either ADS-B In or Traffic Information Service-Broadcast (TIS-B) capability. TIS-B, an advisory-only service, broadcasts air traffic information derived from secondary surveillance radar (SSR) returns from the ground to airborne systems. Non-ADS-B aircraft must be equipped with a conventional Mode S transponder to be visible to the TIS-B system and by extension to ADS-B equipped aircraft.

Another ADS-B In application, Airport Surface Situational Awareness (ASSA), displays aircraft position and the positions of other aircraft and ground vehicles in reference to an airport map.

ASSA equates to the “front end” of the application tested under the SURF IA program, Capezzuto said. The addition of an alerting function with aural and visual cues beyond providing just situational awareness requires a higher level of software design assurance and amplifies questions over where the cockpit display should be located, whether in the forward field of view or a side-mounted electronic flight bag (EFB).

“When you get into indications and alerting, the assurance level has to be higher because you’re now giving (the pilot) an alert,” he said. “On the approach, if they get a warning, the ramifications of using it are going to be ‘you do the go-around’ as opposed to challenging and questioning” the system.

Michael Grove, marketing director for safety and information management-surveillance systems with Honeywell Aerospace, one of the SURF IA contractors, said a TSO for airport surface detection and alerting is “a possibility” by 2011.

Timing Issue

“This is surface alerting. You have to draw a distinction between that and surface awareness,” Grove said. “Of course, being able to have the system have visibility of all the other aircraft requires that those aircraft either retransmit on TIS-B or be ADS-B transmitters themselves. That’s not going to be comprehensive for some time to come, depending on FAA rulemaking.” He added, “We believe it’s inevitable that this application and other ADS-B applications are going to happen. It’s just a matter of timing and how quickly regulation moves and how quickly equipage happens.”

FAA in October 2008 awarded two contracts to demonstrate surface conflict detection and alerting using ADS-B. The partnership of avionics manufacturer ACSS and US Airways was awarded $6.3 million to conduct a demonstration at Philadelphia International Airport (PHL) and to equip 20 Airbus A330s for ADS-B capability. Honeywell was awarded $3 million to demonstrate surface detection and alerting at Seattle-Tacoma and Paine Field airports in Washington state. The company was assisted by Alaska Airlines and JetBlue line pilots, who advised on the concept development and evaluated display symbology in a simulator.

Capezzuto said the proposal by ACSS, the joint venture of L-3 Communications and Thales, to outfit US Airways A330s with ADS-B hardware appealed to FAA.

“This was of great interest to us, that we would be maturing a sub-fleet with this capability,” he said. “This was a very attractive proposal to us, and they got selected.”

Cyro Stone, ACSS director of ADS-B products, described a two-part effort involving three test runs at Philadelphia airport in November and December and the ongoing equipping of A330s.

Three aircraft two A330s and one ACSS Beechcraft King Air were equipped for the demonstrations, which took place mainly at night when the airliners were out of service. One A330 was used for taxiing maneuvers; the other was equipped on a standby basis. The King Air served for airborne testing.

The purpose, according to ACSS, was to perform flight maneuvers against RTCA-developed Safety and Performance Requirements (SPR) and to validate MOPS requirements, with a limited human factors evaluation.

Nine conflict alerting scenarios were tested: four under normal operating conditions and five under alerting conditions. Examples of the latter conditions include: “own-ship departs and conflict traffic enters the runway ahead of own-ship” and “own-ship is on approach to a runway with conflict traffic on that runway so that a go-around is required.”

The demonstration aircraft were outfitted with an ACSS Mode S transponder for ADS-B Out functionality and an ADS-B In receiver, located in the company’s TCAS 3000SP surveillance processor, supporting both airborne traffic alert and collision avoidance (TCAS) and ADS-B. The surveillance processor hosts ACSS’s SafeRoute suite of ADS-B applications, a platform-independent software certified to DO-178B Level C design assurance against “major” failure.

The first release of SafeRoute’s surface situational awareness application provided own-ship position and other traffic on a moving map display. For the alerting function, ACSS developed an algorithm based on the NASA Runway Incursion Prevention System (RIPS) and incorporating an algorithm developed by MITRE Corp. It also incorporates TIS-B transmissions for non ADS-B equipped aircraft.

ADS-B data is displayed on a side-mounted Goodrich Class 3 EFB and a Gables Engineering ADS-B Guidance Display (AGD) in the primary field of view. The EFB runs Cockpit Display of Traffic Information (CDTI) software developed by ACSS in partnership with Astronautics Corp. of America the same software run in the Boeing/Astronautics EFB installed on UPS aircraft using SafeRoute applications (Avionics, June 2007, page 32).

Results from the demonstrations were to be correlated with the airport’s surface radar-based Airport Movement Area Safety System (AMASS), multi-source Airport Surface Detection Equipment, Model X (ASDE-X) system and ADS-B ground station. Stone said no false alerts were experienced during the test runs.

“There was one scenario that may not have given an alert when we expected it,” he said. “Other than that, there were no false alerts.”

The aircraft indicating/alerting system “met the expectations,” Stone said. “There were comments from the observers that this is really good technology.”

Under the program, US Airways A330s will be equipped for ADS-B In/Out, including the Gables display, EFB and CDTI software, during regular maintenance through 2011.

Honeywell’s contract was three-phased, calling for development of an operational safety assessment; an operational performance assessment; and a concept for alerting and displaying targets on and around an airport, said Bob Champion, SURF IA program manager.

The company developed software hosted in its TPA-100 TCAS unit, which receives ADS-B signals and serves as a traffic computer. The TCAS unit was installed in a Cessna Citation Sovereign business jet equipped with Honeywell’s Primus Epic integrated avionics suite, and in a Beech C90 King Air with federated avionics.

The airport surface map on the Sovereign was provided by the Integrated Navigation (INAV) display of the Primus Epic suite; on the King Air, a dedicated airport surface display was installed in the co-pilot’s seat.

The software was demonstrated to RTCA Special Committee 186, which is developing ADS-B performance standards, in December, and was to be demonstrated to FAA in late January.

Champion said the majority of alerting scenarios were conducted at Paine Field in Everett, Wash., which has converging runways as opposed to the three parallel runways at Sea-Tac. The presence of a TIS-B transmitter at Sea-Tac provided for both ADS-B and TIS-B reception.

Champion was asked about the challenges faced in developing airport surface alerting.

“Certainly the ability to put moving maps within the system that accurately depict the airport, the hold short lines, the infrastructure, to provide adequate surface situational awareness was a challenge,” he said. “The alerting algorithms themselves, just to have the proper width around the runways to ensure ourselves that we’re not giving false or nuisance or misleading cautions or alerts has been a challenge.

“We’ve done very well in eliminating those,” he added. “I’m very happy with the system that we’re going to demonstrate and I think the government will be happy with it also.”

For more on airport surface management, tune in to Avionics Magazine's March 18 Webinar, "Airport Surface Management: Enhancing Safety, Situational Awareness on Runways and Taxiways." Click here for more information or to register.

Surface Data-Sharing

The airport surface is one of the several operational “domains” identified for improvement by the RTCA NextGen Mid-Term Implementation Task Force.

Runway Access, with enhanced surveillance methods, is another.

Last September, after seven months of intensive meetings, the industry-government task force produced a set of recommendations for achieving NextGen operational efficiencies by the “midterm” of 2015 to 2018. FAA responded in January with a document listing action items for each of the domains.

The Task Force called for improved surface traffic management to reduce delays and enhance safety, efficiency and situational awareness, involving “capture and dissemination of surface operations data to pilots, controllers, ramp towers and user operations centers.” It recommended “one consolidated point of responsibility, authority and accountability” within FAA to manage the data.

In its response, FAA says it will create a more efficient airport surface environment “by sharing authoritative aircraft movement source data to foster common situational awareness among the FAA, flight operations centers and the airport. … Further collaboration is required on some issues, such as who will be responsible for surveillance in non-movement areas. We will need to address the ownership and protection of spectrum supporting this recommendation.”

FAA agrees with the Task Force on the need to establish a single point of responsibility for data-sharing, “a goal the agency intends to achieve during 2010.”

Among specific action items, FAA says it will install data distribution units at airports equipped with the Airport Surface Detection Equipment, Model X (ASDE-X) airport surface management system, as well as ASDE-3/multilateration locations between 2010 and 2013. –Bill Carey

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