Little did Honeywell know in the late 1970s when it introduced the idea of a performance management system for the Boeing 757 and 767 that slightly more than three decades later, the device, now universally known as the flight management system, would become the heart and soul of the next generation air traffic system (NextGen) cockpit.

With the coming of four-dimensional navigation concepts, where the altitude, longitude, altitude and waypoint arrival times will be closely co-ordinated between the air and ground to boost capacity, the FMS is taking on an expanded role in how an aircraft will be operated. As such, FMS providers are expanding not only the capabilities of the equipment, but the traditional boundaries of their product lines.

AAI shadow, ©AAI

At one extreme is work that FMS-provider GE Aviation Systems is doing with the US Federal Aviation Administration and others at its William J Hughes technical centre in Atlantic City.

Ongoing tests, part of a broader effort to help seamlessly integrate unmanned aircraft into civilian airspace, feature a GE-built Boeing 737 FMS modified with flight and engine characteristics of the AAI Shadow 200 unmanned aircraft to allow controllers in a ground station to handle the aircraft the way they would any FMS-equipped commercial aircraft. Trials include lateral and vertical path commanding as well as required time of arrival (RTA) at waypoints.

The work is seen as a precursor to "reduced crew" operations, where ground control systems could perform automatic real-time trajectory negotiations with an aircraft FMS over a datalink, with the pilot confirming the final decision on the path, thereby reducing workload.

More imminent however are 4D air transport operations that take advantage of the FMS equipment already available on thousands of aircraft. "From a needs standpoint for the 2015-18 timeframe, there's not a tremendous amount that needs to be or could be changed on the flightdeck," says Keith Wichman, director of technology for the advanced flight operations group at GE.

"All the raw materials and capabilities to enable these air-ground operations are there. The bulk of the work needs to happen on the ground," he adds.

GE in late June won a $66 million contract from the FAA that will be used in part for demonstrating the digital exchange of 4D FMS information between Alaska Airlines aircraft and Lockheed Martin's en route automation modernisation air traffic management system, in part to allow for more direct approaches.

Along with an FMS capable of flying the 4D trajectories, GE has also acquired the assets to build the "roads" for trajectory-based operations in late 2009, purchasing performance-based navigation provider Naverus. "Having those efficient and predictable paths adds to the robustness of our FMS system," says Wichman.

Honeywell nextgen FMS, ©Honeywell
Honeywell's nextgen FMS: performance predictions, secondary and pending modified flight plan. Picture: Honeywell 

The five-year project also calls for improving GE's FMS trajectory algorithms using weather data from AirDat, whose Tamdar real-time weather sensors are flying on more than 400 regional airline aircraft in the continental USA and Alaska since late 2004, measuring temperature, pressure winds aloft and other data.

"Winds and temperature are first order effects on trajectory accuracy," says Wichman. "The ones we have today may be nearly good enough, but part of the research is to find out how good is 'good enough'."

"Good enough" is likely to mean weather data that enables aircraft to have an RTA accuracy of 6s, a number the industry is "trending to", says Adam Evanschwartz, principal marketing manager for Rockwell Collins, a provider of FMS systems to the regional airline and business aviation sectors.

The company's Pro Line Fusion integrated avionics suite for the forthcoming Bombardier CSeries and Mitsubishi MRJ regional jet single-aisle aircraft will have an RTA function built in. "The industry is in a formative stage on RTA," adds Evanschwartz. "There's some activity looking at arrival RTAs and departure RTAs. We're architecting our system to support either."

Research and development at Rockwell Collins is also under way for path optimisation and expanded wind models, work that is likely to benefit from the company's acquisition of Air Routing International, an global routing and weather provider.

Wichman says GE's Boeing 737 FMS is also capable of a 6s RTA "anywhere in the profile except after the flaps and landing gear start coming out". Data continues to come in from Sweden, where Scandinavian Airlines continues to perform continuous descent approaches at Stockholm Arlanda. Wichman says RTAs, starting from take-off and ending at the landing runway, are typically accurate to "below 14s".

To get that kind of accuracy, the operation is largely hands-off, with trajectories transmitted between pilots and controllers over the ACARS datalink and the FMS doing the rest. "When the FMS is coupled [to the autopilot], the RTA algorithm closes the loop on time," he says. "If you're not using the autopilot, the pilot flies a lateral path but there's not good guidance on displays on how he would deliver an RTA."

The caveat hints at a larger question in that the role of pilots in NextGen 4D systems has not yet been established, a topic that could become controversial as the FAA and others attempt to grapple with an issue of eroding pilot skills in an increasingly comprehensive FMS.

FMS-provider Honeywell says its not yet clear either where the responsibility for trajectories will be managed. If done in the cockpit, that could keep pilots involved in at least a portion of the tactical operation. Chad Cundiff, Honeywell crew interface systems' vice-president, envisages pilots being able to use the company's graphical interface and automatic dependent surveillance - broadcast "in" to handle a variety of operations, including routeing around weather or traffic.

Using merging and spacing algorithms and displays now in development, Cundiff says air traffic control, for example, could ask pilots to select a certain target on the cockpit display of traffic to follow, which they would then click on using the graphical interface. "You could roll the cursor over the ADS-B traffic and say, 'follow'," he says - a boost in efficiency over today's method of air traffic control providing headings, altitudes or airspeeds to all aircraft diverting.

GE's Wichman says ADS-B will not have the bandwidth to perform the negotiations of trajectories between aircraft and the ground, but the system will be critical as a conformance monitoring tool to verify that an aircraft is actually flying the agreed upon trajectory.

Ahead of a datalink decision, Wichman says the industry is working through RTCA special committee-214, standards for air traffic data communications, to define the message sets that will enable trajectory-based operations, a task that should be complete by 2017 .

Given the industry's need to save money sooner than later, the process could be accelerated. "This is the biggest thing we could do to make the industry green and more profitable," says Honeywell's Cundiff of 4D FMS capabilities. "There's a huge amount of savings that is out there for some relatively straightforward technologies we've already invested in."

Honeywell decided to make the investment in developing a clean-sheet next-generation FMS several years ago, he says, not just in terms of developing new equipment on the aircraft, but for creating new concepts for how to get best value for the operator. "You could see a couple billion dollars in savings per year in the industry," he says.

Source: Flight International