Turbine Pilot

Behind every good pilot stands a flight management system

Settle into the flight deck of almost any recently minted corporate jet or airliner and you'll find the aircraft's flight management system, or FMS, conspicuously located within comfortable arm's reach. The FMS control panel, a small television screen with an alphanumeric keypad for pilot inputs, is usually located on the center instrument console, singly or in pairs. The FMS is provided such prime panel real estate simply because it does so much. Its main purpose is to monitor aircraft position and issue control instructions to the autopilot and autothrottles (if so equipped), in order to carry out precisely a desired flight plan. It does this by tapping into a wide array of digital data sources, acting as a sort of centralized information clearinghouse.

The heart and soul of any FMS is its software, which is customized to the particular aircraft and engines that it manages. Not quite as omniscient as Hal of 2001: A Space Odyssey fame, the typical FMS nevertheless closely tracks the pulse of the aircraft. Its sensory inputs include engine parameters and controls, fuel supply, and all navigation systems and databases — as well as the current configuration of flight control surfaces. It also receives information from the central air data computer, or CADC. This is a device which converts pitot static system pressure inputs into electrical signals that are then used by a variety of aircraft instruments and subsystems. (Some of these are obvious, like electric airspeed and vertical speed indicators; others are not so obvious, like TCAS [terminal collision avoidance system], GPWS [ground proximity warning system], yaw dampers, and flight control artificial feel systems, to name just a few.)

The FMS software is programmed with the operating limitations and performance capabilities of the particular aircraft so that, for example, it won't accept a flight plan when there is insufficient fuel on board to complete the flight, nor will it allow the aircraft to exceed a flap limitation speed. It can also perform such sleight of handas creating an electronic glidepath to a runway that otherwise doesn't have one or commanding the aircraft to enter and fly a published holding pattern at the push of a button.

Its ability to manage a fire-hose stream of digital information is the reason that some pilots consider an FMS indispensable. Yet learning to operate one is not a simple matter. In fact, mastering an FMS necessitates something of a mindshift for anyone who has never used one before. Other than for takeoff and landing, a pilot doesn't usually hand-fly an FMS-equipped aircraft or even directly give inputs to the otherwise dumb-as-a-rock autopilot, either. Instead, the pilot instructs the FMS as to how he or she wishes the airplane to be flown, and it carries out the command. The instructions, such as a complete flight plan, are either prestored in FMS memory or carried out as manual data entries that the pilot types into the keypad on the FMS control panel.

This subtle but important distinction can be a tough mental hurdle for an FMS novitiate, who may find that good flying skills are not enough without computer savvy to match. Like it or not, the FMS represents another thought process layer that a pilot must work through to accomplish a given task.

Suppose, for instance, that a flight is cleared to go direct to a VOR and descend so as to cross it at 15,000 feet. Without an FMS, the pilot would simply navigate to the VOR and mentally plan to begin the descent at the appropriate time so as to satisfy the altitude restriction. Using an FMS, he would instead enter the clearance into the FMS control panel. The FMS would then command the autopilot to fly to the VOR and would initiate the descent at what it computed to be the optimum descent point. The FMS might even switch VOR frequencies automatically, as some systems are capable of doing. This is analogous to balancing a checkbook by using a money management program instead of a pen. They both reach the same result, but the old-fashioned way requires one to work actively through the math, whereas the program requires only that one enter data.

Thinking becomes optional — but is highly recommended, of course, if one hopes to avoid unintended financial embarrassment.

One of the sharpest criticisms leveled against flight management systems is that they work too well. Use them long enough, detractors say, and there is a real danger that basic flying skills will become uncomfortably rust encrusted. There is a risk, they argue, that automation engenders crew complacency, removing the pilots too far from the flight management loop. This, in turn, leads to decreased crew situational awareness, which is a perennial active ingredient in aircraft accidents. There is some evidence to suggest that the crash of a Boeing 757 late last year in mountainous terrain near Cali, Colombia, may have resulted, in part at least, from just such a situational awareness breakdown. Moments before the crash, the crew programmed the FMS to fly directly to a VOR which they apparently didn't know was already behind them. The FMS dutifully complied, commanding the aircraft to reverse course. The accident occurred while the crew was descending and attempting to return to an on-course heading following this course reversal.

The flip side of this dilemma, FMS disciples point out, is that used properly, an FMS enhances situational awareness by supplying all kinds of helpful information to a crew. The twofold challenge for pilots is to choose carefully the proper level of automation for the task at hand and to stay actively involved in monitoring the job the FMS is doing. Blind trust in automation for automation's sake is risky business in anyone's book.

Interestingly, among pilots who fly FMS-equipped aircraft for a living, the jury is still out as to whether extensive automation helps or hinders their flying. Dr. Earl Weiner, an academic who has conducted years of pioneering research on airline experiences with pilots flying in highly automated cockpits, reports that there is an almost equal split of opinion on this subject. Nearly as many pilots say that it makes their job easier as there are those who decry it for creating undue complications. According to Weiner, this Hatfield-and-McCoy-like dissension holds true within pilot groups the world over.

One thing on which everyone seems to agree is that using an FMS requires pilots to pay careful attention to just what the black box is up to at all times. Weiner has concluded that the best way for pilots to do this is to conduct detailed takeoff and landing briefings, with emphasis on what to expect of the automation during critical phases of flight; brush up on their cockpit resource management (CRM) skills; and constantly work at being as standardized as possible. In other words, to make sure it is they, and not some silicon chip, who are minding the store.

UNS-1 FMS Training Simulator

PC-based training for new FMS users

Airline and corporate flight departments have always depended upon formal ground school sessions to teach FMS basics, with real-world line experience expected to provide a polished finishing touch. In recent years they have turned to personal computer-based training systems that accurately depict FMS operation.

Universal's UNS-1 FMS, the flight management system currently in use on more than 2,000 corporate and airline jet aircraft, makes up a significant chunk of the total FMS user market. Aviation Computer Based Instruction's program, already in use at FlightSafety International and a host of other international training organizations and flight departments, directly targets this large user group.

The program has several main components. First is the UNS-1 FMS software itself, which replicates every function of the actual system. It is mouse controlled through a realistic FMS control panel depicted on screen. Next is a navigation program that runs in the background, matched to the flight characteristics of a Cessna Citation. The entire Jeppesen Worldwide Database is included, which allows one to simulate real-time flight plans anywhere an actual Citation might be flown. The program is not to be confused with a flight simulator, since the only flight instrument shown on screen is an electronic horizontal situation indicator (EHSI). This is used to help maintain a student's positional awareness as each flight progresses.

Users start by learning how to initialize the FMS during preflight, and then they progress to "flying" flight plans using the Citation flight profile simulation. Any real-world FMS capability can be practiced, such as preflight planning of multiple versions of a flight plan to determine the best routing, speed, and altitude for a given set of weather variables, or creating pilot-defined waypoints and approaches.

According to a spokesman for FlightSafety, new users generally become comfortable with the program after just a few hours of classroom instruction and hands-on practice. Afterwards, however, pilots commonly report a steep learning curve during their first hundred hours or so of real-world FMS operation.

The software requires relatively little computer brawn by today's standards — just a 386 or faster processor, DOS 4.1 or higher, 640K RAM, VGA or SVGA color graphics, and 4 megabytes of free hard disk space. This same kind of specialized training software is available to anyone for $199.95 from ACBI.

While software like this is a superb way to learn all about using an FMS, pilots need to remember that technical mastery in itself is not enough. There will forever be a need for old-fashioned brain cells to back up the black box magic. For more information, contact Aviation Computer Based Instruction, 13000 East Control Tower Road, Englewood, California 80112; 303/792- 5507; fax 303/792-0032. — VC