Ground alert

Washington DC
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The US Federal Aviation Administration's funding of new automatic dependent surveillance - broadcast tests in the autumn moves management of aircraft in the airport surface environment beyond simple visual awareness to actual alerts of potential runway conflicts. This could create a step change in the approach pilots take to managing airport surface conflict detection.

Heralded as a major cornerstone of next generation air traffic management, ADS-B uses transponders and GPS navigation to broadcast it own position and velocity to ground stations and similarly equipped aircraft.

Using a $9.3 million grant from the FAA surveillance and broadcast services office, avionics manufacturers Honeywell and the L-3 Communications-Thales joint venture ACSS are testing the visual and audio alerts of potential traffic conflicts through various surface area trials beginning in the fourth quarter of this year and continuing into early 2010. These trials move airport ground surface area detection surveillance beyond aircraft positioning awareness to an actual alert issued to flightcrews of a potential incursion or traffic conflict.

saferoute 
 © ACSS
SafeRoute will give pilots aural and visual wrnings about potential runway conflicts

ACSS chief operating officer Cole Hedden admits a lot of debate has already taken place concerning optimal ways to develop the alerts, but "eventually industry will get there".

Hedden believes the FAA is moving quickly to establish standards for the alerting, and ACSS has already delivered one of two major documents to the agency outlining specifications for the alert certification.

Honeywell marketing director of safety and information management Mike Grove says in some ways "this demonstration will point us to when and how to do alerting", but he stresses the challenges in developing an alerting system including the accuracy and integrity of the aircraft position reported through ADS-B.

Improvements in the information transmitted through ADS-B could be advanced by the adoption of the DO-260B compliance upgrade for the Mode S transponders relaying the aircraft positioning information. The -260B requirement "takes ADS-B to the next level", says Grove, who says suppliers could begin offering the upgrade by next year.

ACSS has won approval to upgrade its Mode S transponder relaying ADS-B information for single-aisle Airbus A320s and the airframer's widebody A340/A330 family to the DO-260A standard. Hedden says only a software upgrade its necessary to achieve DO-260B compliance.

But the likelihood of the upgrade being available before each company starts testing is slim. Honeywell is conducting its trials at Paine Field and Seattle Tacoma International airport in October and January, while ACSS is partnering US Airways for trials in Philadelphia starting in the fourth quarter using the surface detection feature of its SafeRoute ADS-B applications in the carrier's A330s. In January ACSS received $6 million from the FAA to equip the A330s with SafeRoute capabilities.

Trials by ACSS in Philadelphia with Safe­Route software advance surface area indication and management beyond the airport map with ownship and other traffic to visual and aural alerts to pilots of potential ground conflicts.

Parcels carrier UPS and ACSS in 2008 launched SafeRoute operations at UPS's Louisville hub to support merging and spacing, continuous descent arrivals and visual situational awareness cues with speed cues displayed in the cockpit through electronic flight bags.

Cockpit architecture for the surface area warning trials by US Airways in Philadelphia includes electronic flight bags on each side of the cockpit with the moving map displays.

Hedden says the use of traffic information surveillance broadcast (TIS-B) is possible in the trials. This allows for the uplink of surveillance data for non-ADS-B-equipped aircraft to determine situational awareness.

Honeywell is opting to use its own Beechcraft King Air and Cessna Citation Sovereign aircraft for its ADS-B traffic conflict alerting trials. For the Sovereign tests, Honeywell is using its Epic avionics platform that incorporates runway information from the enhanced ground proximity warning database. In the King Air, pilots will view runway information displayed through a PC, with alerts originating through the traffic collision avoidance system (TCAS).

Some of the demonstration scenarios Honeywell could employ in the alert testing include an ownship taxiing towards a runway with high-speed converging conflict traffic, an ownship starting a take-off roll with conflicting traffic entering the runway or an ownship encountering conflict traffic on approach to the runway, resulting in a go-around.

RUNWAY CONFLICTS

Rounding out the trials are potential tests with the ownship landing on a runway with conflict traffic entering that runway ahead of the aircraft, ownship taxiing on a runway with conflict traffic approaching from behind and ownship departing from a runway when conflict traffic violates a land and hold short operation restriction on an intersecting runway.

Honeywell's final architecture for evolving moving map technology should depend largely on the aircraft, says Grove. Honeywell is working with Airbus to supply cockpit display of traffic information and in-trail procedures (ITP) that is scheduled for certification by year-end, and is also examining what Grove identifies as a phase two surface awareness tool displayed through an electronic fight bag.

Grove predicts widespread use of surface area moving maps, and believes Airbus is aiming to feature that technology on its aircraft within two years. But he says an "alerting solution is a little more challenging", and predicts those will not be available before 2013-14.

ACSS is thinking beyond the current tests to an examination of evolving SafeRoute capabilities. Hedden envisages a digital taxi path visible through the multipurpose control display unit.

Today controllers define and give clearance for a taxi route verbally. But Hedden believes SafeRoute could support a digital clearance to further enhance situational awareness and supply a warning if pilots enter the incorrect runway to possibly prevent accidents similar to the August 2006 Comair Bombardier CRJ200 crash in Lexington, Kentucky, when pilots ventured on to the wrong runway.

ACSS is also examining software enhancements to strengthen management of airborne traffic in the terminal area through the addition symbology showing an aircraft's position in 2D. Hedden says developing that has triggered debates over the structure and specific information depicted within the cockpit. He says a proper cut-off for altitude monitoring is necessary as aircraft operating above certain thresholds have little impact on ground operations.

The first phase of the ACSS-US Airways ADS-B trials in Philadelphia is focused on surface conflict detection and warnings. UPS has tested the SafeRoute merging and spacing function in Louisville, and demonstrated significant reductions in fuel burn.

But widespread implementation of merging and spacing is a challenge. Honeywell's Grove says all aircraft need the ADS-B equipage to maximise the gains offered through knowing an aircraft's exact position on approach. The complexity stems from cross-operator co-ordination of squitting position and intent.

Since ITP ADS-B procedures are far less complex than merging and spacing, the FAA is likely to press forward with approval of IPT procedures first. Through the use of ADS-B ITP, operators can climb and descend through altitudes where current non-ADS-B standards would not allow those changes.

United Airlines is to begin testing ADS-B ITP next year with 12 Boeing 747s, initially on flights from San Francisco to Australia. Grove cites estimates of about $200,000 annually in fuel savings per aircraft in the South Pacific using ADS-B to support modified ITPs. That type of savings "buys its way" on to a widebody quickly, he says.

Meanwhile, ACSS plans to achieve certification for ADS-B in/out capability supporting advanced ITP procedures featured in its T3CAS platform by the end of the year. In T3CAS, traffic alert and avoidance terrain awareness warning (TAWS) and a Mode S transponder are integrated into a single unit.

ACSS is also having preliminary talks with NASA, the FAA and an airline about leveraging ADS-B merging and spacing applications in wake vortex management. Hedden says sensors on the aircraft transmitting velocity and position to the ground could instantaneously uplink to an aircraft behind. That instant transmission would allow the trailing aircraft to calculate if increased separation is necessary.

Development of a new wake vortex management capability would also require participation from companies with capabilities to supply ADS-B ground station infrastructure. "We're just starting to hypothesise what could be done," says Hedden. Evolving ADS-B into wake vortex management is part of SafeRoute's transition to broader NextGen capabilities. Hedden believes ACSS is "only scratching the surface" of feasible applications.