American Airlines has flight-tested a planned update to advanced cockpit display functionality that will provide pilots with a lead aircraft’s vertical path and plans to equip its entire Airbus A321 fleet with the capability, pending FAA approval.
The update, Vertical Path Indicator (VPI), expands American’s ongoing Automatic Dependent Surveillance-Broadcast In (ADS-B In) trials in conjunction with the FAA. Previous work demonstrated the ability to use satellite guidance to manage spacing between a lead aircraft and a properly equipped trailing one. The most recent test provides the in-trail pilots with the lead aircraft’s vertical path via an ADS-B Guidance Display (AGD)—a key factor in helping avoid wake turbulence.American has outfitted its A321 fleet with not only mandatory ADS-B Out functionality that broadcasts an aircraft’s position, but also ADS-B In, which receives traffic and other information and displays it to pilots.
The retrofits add an AGD built by avionics manufacturer ACSS, a 4-in. by 4-in screen, which takes the digital distance and radio magnetic indicator’s place and eliminates the need for flight deck display modifications. The AGD is paired with an ADS-B In-capable traffic collision and avoidance system (TCAS) computer.
Working with the FAA and other stakeholders, American has trialed programs that provide precise spacing between two aircraft in the en-route and terminal area airspace. VPI adds a key safety benefit.
“This is the first time that any carrier has been able to show this type of information to pilots,” said David Surridge, American’s director of air traffic management and an Airbus pilot. “I’m proud that American is continuing its innovative partnership with ACSS and the Federal Aviation Administration to bring this incredible technology that will enhance safety on our fleet of Airbus A321 aircraft.”
The VPI trial took place overnight in late May and required 18 months of planning. An ADS-B In-equipped A321 granted FAA “experimental” status followed an American Boeing 737 during a series of planned maneuvers. The two aircraft flew for about three hours between Phoenix and Albuquerque.
American said the flight tests, which followed a series of ground tests, validated VPI’s functionality. The carrier plans to upgrade all of its A321s with the functionality pending FAA approval.
Sources with knowledge of the process tell Aviation Week that the FAA is in its final stages of green-lighting the upgrades.
The software updates also will improve other aspects of America’s ADS-B In system. Feedback from the Allied Pilots Association, which represents American’s pilots, led to changes in multipurpose control and display unit functions that pilots use to access the ADS-B In functions, the airline said.
American’s work is part of a multi-year set of trials managed by the FAA. The agency plans to use data and lessons learned to help determine what, if any, of the technologies merit wider adoption and more investment.
VPI adds to an ADS-B In suite of capabilities demonstrated by American in the FAA-led trials. The airline also uses Interval Management (IM) and Cockpit Display of Traffic Information Assisted Separation (CAS-A).
With IM, an en-route controller provides a participating aircraft with an assigned spacing goal using either time or distance relative to a lead aircraft. Examples include crossing a waypoint at a specific elapsed time after the target aircraft. Pilots then follow automatically generated speed guidance to meet the requested spacing until the IM operation is complete.
CAS-A uses ADS-B In to help a tracon maintain visual approach throughput, which requires the least separation between aircraft, during some instrument-landing weather conditions such as haze or broken clouds near the airport.
In a CAS-A approach, a controller designates a “lead” aircraft for the ADS-B In-equipped aircraft to follow and provides other instructions, such as an initial speed. The equipped aircraft’s crew selects the lead aircraft on a flight deck display that provides details such as each aircraft’s distance and ground speed. The in-trail crew uses this information to maintain visual separation standards even if the pilots cannot see the lead aircraft.
IM’s trials are ongoing in the Albuquerque Air Route Traffic Control Center for flights headed to Phoenix Sky Harbor International Airport or passing through the en route center. CAS-A is being trialed at the Dallas-Fort Worth Tracon.
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