Air Transport: How Delta Adds Safety Using the FMS

By David Jensen | July 1, 2001
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SINCE 1997, DELTA AIR LINE’S primary expansion strategy has been to strengthen its presence in Latin America, beyond its existing routes to Mexico City. It’s a strategy that brings financial rewards but operational challenges.

The strategy’s phase one was to establish non-stop routes from Hartsfield Atlanta International Airport, Delta’s main hub, to all of Latin America’s major business centers. That goal was achieved April 1, when Delta added Buenos Aires, Argentina, to its list of 18 destinations in 10 countries.

Phase two of Delta’s expansion strategy, according to public relations director Christine Frais, is to increase frequency to existing routes, plus add routes to secondary markets (Rio de Janerio, Brazil, being one example) and eventually non-stop service to Latin America from John F. Kennedy International Airport in New York City.

In total, the Latin American service development has been an ambitious effort, not only given its accelerated schedule and the fact that many bilateral agreements must be made to establish new routes, but also because of Latin’s America’s challenging environment in which to fly.

First, the navigational coverage in that part of the world is incomplete and often antiquated. Navigation by automatic direction finder (ADF) still ranks supreme; at some Latin American airports dual ADF is used for departure, as well as approach. Add to this the fact that much of South America is mountainous. The Andes extends from one end of the continent to the other, with peaks reaching almost 24,000 feet elevation.

So what happens if, at night or in inclement weather, an aircraft with 200+ passengers on-board suddenly loses cabin pressure at 35,000 feet? How do you "avoid the rocks" as you rapidly descend to the breathable air at 10,000 feet?

Here, Delta has turned to the flight management system (FMS) on-board its Latin America bound aircraft. It has expanded the system’s capabilities to automatically provide guidance to keep the aircraft from harm’s way. The airline has made the FMS an alternative to having pilots fumble with paper maps. The flight management system was designed to help crews compute efficient routes, however, Delta has broadened its usefulness to include computing safe diversionary routes, as well.

Flight management systems provide a "treasure trove" of information, says Capt. Edward Hanson, a Delta line check pilot and author of an article in the January 2001 issue ofAvionics Magazine. It is a "virtual book…and each chapter has lots of pages." What Delta has done for the FMS-equipped aircraft flying into Latin America is write more pages for the book. And each page reveals safe emergency procedures that can be performed with a minimum of pilot workload.

A First-Hand Look

The workload is easy because of the preparation, which begins at Delta’s training and simulation center in Atlanta. There, Avionics Magazine was briefed of Delta’s policy and use of FMS when flying over critical terrain. We observed firsthand the center’s achievements, initially in a Boeing 767-300 simulator and then from the jump seat of a Boeing 757 bound for Mexico City, which is surrounded by mountains.

Delta’s best-equipped aircraft fly to Latin America’s most challenging destinations. It employs MD-11s and B767ERs, as well as B757s, four of which fly exclusively on routes linking Atlanta with Bogota, Colombia, and Lima, Peru. Operations to and from both capital cities involve flying over the most rugged part of the Andes. The four B757s are fitted with dual ADF, for approaches and departures, and to provide raw data for pilots to cross check with the data in the FMS. Also installed are enhanced ground proximity warning systems (EGPWS) and the enhanced lateral and vertical navigation (LNAV and VNAV) that Delta designed in the FMS.

Eventually, according to Capt. Lawrence "Bud" Sittig, Delta’s general manager-flight operations, all of the airline’s 594 aircraft (as of early 2001) will be outfitted with EGPWS. And, he adds, the four B757s will be "prioritized" to be the first in Delta’s fleet to have Global Positioning System (GPS) receivers installed.

Delta’s decision to take extra safety measures over critical terrain by exercising the FMS began in 1997, when the airline launched its expansion into Latin America. But it was a route that the airline introduced between Frankfurt, Germany, and Bombay, India, that prompted the procedure’s development. Delta officials wanted to establish a more fuel efficient, direct route between Germany and India, as well as safe emergency procedures, especially when flying over the Zagros Mountains in Iran. They were not satisfied with conventional emergency procedures employed by other carriers. Fumbling through paper charts while attempting to descend to 10,000 feet in 12 minutes within a rugged mountainous area presents significant pilot workload and safety issues. It simply wouldn’t do.

"So, I turned to our FMS people to see what we could about this situation," says Robert Brown, B757/767 flight instructor, who pioneered Delta’s new procedures. Brown worked with two of Delta’s performance engineers, Natalie Martin and Clyde Taylor, and with James Carman, program manager-operation efficiency, flight management systems.

Their work began in Delta’s performance engineering department, where Brown took Jeppesen’s air traffic control (ATC) charts and laid them over Tactical Pilotage Charts (TPCs). The TPCs, provided by the U.S. National Imagery and Mapping Agency (NIMA) show terrain elevations, and thus, are used to determine the vertical navigation for the FMS.

With all terrain and route information in hand, Brown then calculates what Delta pilots call "Route 2 diversion legs," which are area navigation- (RNAV-) developed diversions from the primary route, or "Route 1." They also are planned for rapid decompression emergency descents to breathable air. Brown’s team factors in aircraft’s performance characteristics, its existing emergency procedures, and the fact that large airliners normally require a 20-nm turning radius. The team plots the available ground navaids, which in Latin America are largely non-directional beacons (NDBs). These calculations, in turn, furnish the FMS with altitude, navigational and airspeed data. They will assure that throughout an emergency descent, the aircraft will automatically clear the terrain by at least 2,000 feet.

"It’s largely a pencil-and-ruler process," Brown says of his cartographic calculations. And practice improves process; the Latin American emergency routing "took about a week to calculate," he says, "while the Frankfurt-to-Bombay procedures took me all summer."

During our visit, Brown, Martin and Taylor were calculating the emergency RNAV routing for Delta’s Bogota-bound aircraft. Here their charge was to determine safe Route 2s, diverting to Panama City, which was selected in part because the city is a relatively close, on-line, out-of-the-mountains airport. They established waypoints for the Route 2s to Panama’s capital. They also determined the cross-over waypoints along the primary route, to indicate when the pilot should select another standby diversion route in the FMS. This selection, incidentally, requires little keystroking; the pilot simply activates the "Route 2" on the FMS, and the standard terminal arrival routes (STARs) will immediately appear on the control display unit (CDU).

Brown’s calculations then go to Carman, who converts them into computerized, critical terrain routes (Route 2s), complying with ARINC 424-15. He uses a computer program designed to work within Federal Aviation Administration parameters as outlined in the Terminal Instrument Procedures (TERPS) manual. Carman also has the Route 2s printed for inclusion in the aircraft operations manual.

Carman’s procedure development not only will have the FMS automatically prompt the autopilot to enter into an emergency diversion, it also will present the route information on the pilot’s navigational display. In safe, normal flight, the Delta pilot can view the emergency route in blue, next to the magenta line showing the primary route. But when the pilot selects the emergency route, it automatically appears on the display as a magenta line. Thus, in normal flight or in an emergency, the crew’s navigational guide is always the magenta line.

Carman’s coding takes about a day to complete and involves a communications link with the FMS vendor–which for the B757 is Honeywell. "I get the latest [FMS] data base as an Excel spreadsheet from Honeywell, and I’ll revise that data by building routes–putting in waypoints, coordinates, airspeeds, etc.," he explains. "Then I send the revised data base back, and Honeywell will look at it on their computers, which are vendor coded, and thus, compatible with the FMS.

"We then bench check [the data base] to make sure it will work in our simulators," Carman adds, "and there we check out the procedures with our instructor pilots and line check pilots." With an all-clear, the data base finally is set for use in the aircraft’s FMS.

In a B767-300 simulator available for a demonstration, Capts. Sittig and Hanson climb into the left and right seats, respectively, while Brown occupies the instructor seat. The simulated mission is a night flight to Bogota, to demonstrate emergency procedures and the new data base.

Simulator training is critical at Delta to assure effective use of the flight management system. "We teach decompression procedures so that the pilots can do them blindfolded," says Hanson. "Decompression is an extreme situation, and the cockpit can get totally fogged up. You go immediately IFR [instrument flight rules]."

For some time, Sittig and Hanson "fly" the B767 simulator. Then Brown initiates a sudden, simulated decompression–a luggage compartment door flies off. The cockpit shutters. Sittig and Hanson immediately don oxygen masks. On Sittig’s command, Hanson turns to the FMS and activates the "Route" button, bringing the appropriate Route 2 diversion legs on display. Hanson then pushes the "Execute" button, giving the LNAV the new, emergency course to follow. Both pilots check the mode control panel to make sure both LNAV and VNAV are activated.

The critical work is done. We feel the cab pitch forward and roll as it begins its automatic descent and turn toward Panama City. Hanson reaches for the airborne communications addressing and reporting system (ACARS) to digitally inform Delta dispatch of the situation. Sittig wants to talk to dispatch directly, however, so he switches to the satcom. In minutes, the simulator cab levels off, stops shuttering and enters a level cruise. The altimeter shows 10,000 feet above sea level.

Down Mexico Way

From Delta’s training and simulation center, we join Capts. Hanson and Steve Stong at Hartsfield Atlanta. Seated in the cockpit of a B757 headed for Mexico City, Stong (in the left seat) and Hanson conduct their preflight. Hanson is acting as line check pilot here; Flight 519 is Stong’s initial flight to Mexico City as captain. They begin by initializing the FMS, providing the aircraft’s position at the Hartsfield Atlanta gate to the avionics. They then enter the flight plan into the FMS.

En route, weather conditions are CAVU (ceiling and visibility unlimited) all the way, and this allows Hanson and Stong plenty of dead time to enter the Route 2s in the FMS. Hanson points out that, for planning purposes, these Route 2 diversion legs can be used to program approaches to either end of the concrete (runway) at Mexico City International. This is important because Mexican air traffic control frequently swaps the runways around, and a planned approach to runway 5 can end up in an actual approach to runway 23. Using the Route 2 procedure to preplan the opposite runway reveals the Delta system’s versatility.

In cloudless skies, the approach to Mexico City appears fairly effortless. Simply bank left after spotting the city’s large soccer stadium, then level off for the approach, says Hanson. But clear skies also reveal the rugged mountains surrounding Mexico City, some spouting a volcanic cloud. Inclement weather, which is not unusual over Mexico’s capital, could create a perilous situation, especially in case of an aircraft emergency. The value of a well-programmed flight management system became readily apparent.

Also witnessed during the Mexico City flight was added situational awareness made possible by the EGPWS. The hazardous terrain surrounding our approach showed red (terrain above aircraft altitude) on the navigational displays. The magenta, active route threaded through the mountains and to the airport, while a blue Route 2 showed the approach to the opposite end of the runway. This is high level automation supporting the pilot operations.

Not to dismiss the old way of doing things, it should be noted that both en-route and low-level area charts and maps also were used during the Flight 519. In fact, both pilots highlighted the diversion route from Mexico City to Acapulca on their charts.

"The time to think through a divert is before you have do one," states Hanson. It would appear that Delta has thought through the safety requirements of its Latin American flying. 

Special thanks for this article goes to Delta Air Line’s Capt. Lawrence "Bud" Sittig.

Combating Noise with FMS

James Carman is a problem solver. The Delta Air Line program manager-operation efficiency, flight management systems, is able to construct with his highly capable computer RNAV routes for flight management systems to resolve a host of issues. And he sometimes does so, coordinating with his counterparts from other airlines, for example, with Mike Tragarz of America West.

Hartsfield Atlanta International Airport, Delta’s main hub, has enjoyed the benefits of FMS departures and arrivals that Carman developed. These were primarily designed to abate noise around the airport, but they also deliver greater efficiency and safety. Carman began his work by studying the aircraft movements made at Hartsfield Atlanta. He found that while aircraft departing, say, runway 27R essentially performed the same maneuver, they did not follow the same exact flight path. The aircraft all flew to the middle marker, then turned right to the 250 heading. But because of winds or the pilot not turning at an exact, consistent point, the flight paths varied. Therefore, when charted on a map of the airport area, the various departures created a fan-like splaying pattern. And this, in turn, spread the pattern of noise impacting people below.

A somewhat different situation existed at Cincinnati/Northern Kentucky (CVG) International Airport, Delta’s number two hub. CVG experiences continuous noise issues and heavy flight traffic around the north end of the Buckeye military operating area (MOA), where civilian aircraft are not allowed to penetrate. Through coordination with the military, a corridor was established, allowing only FMS-equipped aircraft a way to bypass the congested area and thus reducing departure delays.

Carman developed RNAV departures to further reduce noise. As in Atlanta, Carman began by studying the aircraft movements, and again he found that aircraft perform the same maneuver and don’t follow the exact fligh path.

Carman’s mission in both Atlanta and CVG was to establish arrivals and departures that assured each FMS-equipped aircraft fly the exact predetermined flight track. He assured this conformity by building an RNAV route with fly-over and fly-by waypoints. "The pilots will have a positive track guidance," says Carman. "The flight director course bar [vertical bar] will direct the pilot/autopilot to the next waypoint."

The result of this flight path conformity is a reduction in width of the noise corridor, which means aircraft noise will impact fewer people below. More than noise abatement, however, the continuity of the FMS arrival and departure means less intervention and workload for the flight crew and air traffic controller, according to Carman. "If the controller needs to intervene, he does so by exception," he explains, "and that means better use of the VHF voice spectrum. There’s a reduction in radio transmissions," Carman adds, "because of a reduction in vectoring. The FMS guarantees the flight track both laterally and vertically." This exactness in departures and arrivals also reduces the amount of airspace used, while still maintaining the same traffic flow. And the conformity of the movements increases safety as well.

Carman’s FMS procedures have been in effect at Hartsfield Atlanta for several years, and they have gained FAA recognition, as is evident in the increased funding Administrator Jane Garvey has been able to gain for National Airspace Redesign Committee. Established to relieve air congestion, the committee seeks ways to increase safety while increasing airspace capacity and also reducing pilot and controller workload. Carman’s work to reduce noise contributes to all of these goals.

More Oxygen

According to Federal Aviation Regulation (FAR) Part 23, air transport aircraft must have sufficient oxygen supply on board to allow passengers continued breathing for 12 minutes, in case of emergency. The agency believes that, given a sudden cabin decompression at cruise altitude, 12 minutes is enough time to descend to the breathable air at 10,000 feet above sea level (ASL).

However, after observing the ruggedness and remoteness of parts of Latin America, Delta Air Line officials decided that 12 minutes’ supply simply is not enough for its aircraft flying to and from Bogota and Lima. So the Atlanta, Ga.-based airline outfitted the four Boeing 757s it flies to those destinations with 22 minutes supply of oxygen.

Delta’s Robert Brown explains how 22 minutes was calculated. "I got together with our performance engineers, and we came up with a scenario in which, at our max cruise speed, we have a 150-nm radius from the point of decompression [for descending] down to 10,000 feet," he explains. "That’s the worst-case scenario, flying to Bogota, and we figured that, with the 12-minute [oxygen] bottle, we would only get to about 90 nm. Whenever you operate into a high-altitude airport with lots of rocks around, you can not do it [rapidly descend] within 12 minutes."

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