Timely Departures

Regulators are putting more pressure, sometimes with draconic penalties, on airlines to eliminate lengthy delays on the tarmac. These demands will require much tighter collaboration between airlines and airports to satisfy.

The first task is to minimize avoidable delays, caused by mistakes by—or miscommunication among—airlines, airports and service providers. For unavoidable delays, for example due to weather, aircraft must be kept at gates if possible, not in long, fuel-wasting queues on the tarmac.

Several airports have begun doing all this with new tools and processes. The results are encouraging and likely to spread.            

In 2003 Zurich Airport had the worst record for late departures in Europe. Andrea Werner Baroni, head of airport operation, says poor communication was partly to blame. When things went wrong, massive personal communication was necessary to discover root causes.

Moreover, good performance news promptly reached the CEOs of the 10 service providers involved in each departure, including fuel handlers, caterers and passenger-service firms. Bad news didn’t reach them.

Providers therefore kept too little reserve capacity to allow for surprises. They had service-level agreements with airlines, but not with the airport, which was blamed if things went wrong. There were so many possible causes for delay that airport managers usually did not understand them. Further, operations data were discarded each month because they were too expensive to store. New plans made without this data were naïve.

The overall result was lots of late take-offs and queues of 12 to 15 aircraft on the tarmac at a time.

Zurich first reduced avoidable delays with Collaborative Decision Making (CDM) and new software. It then cut tarmac lines with better departure control software.

Collaboration is ensured by a series of committees, most prominently a steering committee comprising the CEOs of all stakeholders. Personal communication has been cut by 60% and addresses only exceptions. Everystakeholder automatically sees deviations from plan. “Now we can spot degradation as soon as it happens,” Baroni said.

Visibility is enabled by ZEUS, an application from Neuropie Solutions, which is fed by the Airport Operational Database (AODB) and departure control. ZEUS constantly monitors performance and sends messages and alerts. “The airport uses ZEUS to orchestrate and understand who is out of synch and address problems as they come up,” Jürgen Weder, Neuropie CEO, said. “At the end of the day it can analyze problems and spot reasons for delay, so it is both real time and retrospective.”

With ZEUS, all stakeholders see all the information they need for collaboration, but confidential information is protected. Weder estimates that ZEUS has saved Zurich $20 million in operating costs and avoided $30 million in lost hub traffic over the last five years.

ZEUS is used in more limited ways at London Heathrow and Johannesburg. Neuropie is working with SITA to make it available from the cloud. Weder says no airport has built all the capabilities that ZEUS has. Unfortunately, ZEUS requires more operational data than some AODBs contain.

Baroni’s next step was keeping planes at gates when delays were inevitable. Zurich began using the Delair Arrival & Departure Management System (DARTS) to hold aircraft at gates until only three or four planes are in line, so each spends a maximum of 12 minutes on the tarmac.

DARTS takes flight plans and updates from air-traffic control and interfaces with airport, airline and service-provider systems. Zurich’s new AODB simplifies the latter interfaces, Martin Wiesner, marketing director at Delair, said.

DARTS then calculates an optimal sequence of departures based on aircraft type, direction of takeoff, wake vortex and minimum departure interval. It can do this for one or several runways.

Finally, DARTS deducts time from gate to takeoff to calculate Target Start Approval Time. Wiesner says target off-block time is becoming standard in Europe and will spread globally. If a parking position is needed for an arriving aircraft, DARTS’ target time can be overruled manually. Finalized target times are shown to airline staff and passengers at gates.

DARTS plans are updated for the latest information from ATC and other stakeholders. One worst case is a missing passenger, which may require a two-minute delay or a half-hour to unload baggage. DARTS takes the flight out of sequence and puts it in stand-by.

In bad weather, DARTS automatically reduces departures to reflect increased separation. DARTS accommodates arrivals as determined by ATC. Delair is researching how departures and arrivals might be jointly optimized.

DARTS has cut queue lengths by 75% at Zurich. Punctuality in bad weather was 10% under the old system. With CDM, ZEUS and DARTS in place, it is 75-80%.

Zurich has been winning performance awards regularly in recent years. The improvement was essential because the airport now has five peaks per day and connecting traffic has grown three times faster than local business.

Baroni says he could not have handled this growth using the old methods. Using DARTS, small airports like Zurich can move two to three times more aircraft through at peak. Without room to switch aircraft in queues, these small airports must maintain intervals based on same-direction takeoffs. But DARTS’ optimum sequencing exploits different takeoff orientations to minimize intervals and thus maximize throughput. Large airports with ample taxiways are less dependent on this feature.

A new version of DARTS to be used in Berlin next June will allow airlines toswitch the places of their own or allianceaircraft in the optimal departure sequence.

Wiesner says trials have been done in other airports and many are interested. “Europe is moving in this direction. But pushback from gates is different in the United States. Airlines have their own terminals and push their own aircraft. Then ATC takes over.”

Metering At JFK and Beyond? 

“Europe has done more,” acknowledges Tom Bock, GM of airspace and operational enhancements at the Port Authority of New York & New Jersey. “It is difficult to change mindsets in the US.”

Nevertheless, a metering approach has been used by many airports for deicing, implemented for departure control at JFK during a four-month runway shutdown in 2010 and has now been continued for regular operation at the airport. It is voluntary, but virtually all airlines have accepted the rules.

Bock compares metering to control of Los Angeles freeway ramps, where entrance is not allowed until traffic permits. “We have airline schedules, they tell us when they are ready, we assign them to buckets of time and they can swap aircraft or give priority to planes based on connections and passenger counts.”

Bucket assignments are done manually, but Bock wants to automate it. Queues that sometimes reached 30 aircraft are now limited to 10. 

PASSUR Aerospace provides both software and staff for metering in mornings and evenings. “The goal is to push back when they have an unimpeded path, but to maximize throughput of the airport,” PASSUR senior VP Ron Dunsky said. In most cases, passengers can wait in lounges when aircraft are in virtual queues.

PASSUR gets flight plans and their revisions from FAA, including the first waypoint for each flight. PASSUR staff allocates flights into 15-min. buckets by schedule. If ATC imposes a slower schedule for any reason, all airlines get proportional cuts. Carriers can switch their own aircraft within these allocations.

Dunsky sees lots of interest in the approach. “This will be the new paradigm, airlines and airports managing collaboratively, not as individuals.” PASSUR has partnered with MOSAIC, which has done surface management for governments and airports. “We will market them commercially and integrate that into our software,” he said.

Voluntary metering has earned acceptance at JFK. “It’s a transparent program, they can all see whose aircraft are out there,” Bock said. “If someone cheats, they get caught fast.”

Metering has improved performance in bad weather, but “we are still not perfect,” Bock acknowledged. Aircraft still arrive in bad weather so departures may be held up. “We had one hour of bad weather with 50 scheduled departures and could only let four out,” he said. JFK holds aircraft at gates as long as possible, but pushes them off when gates are needed.

Metering helps ensure airlines meet the US DOT’s three- and four-hour tarmac delay rules. “That really means two or three hours,” Bock said. An MIT study estimated that metering reduces taxi-out time by 14,800 hours, fuel use by 5 million gallons and carbon dioxide by 48,000 metric tons a year at JFK. These gains were apparently achieved without any clear losses, such as increased taxi-in times or reduced throughput.

Airports have been controlling ramp queues in some fashion for years, notes the study’s co-author Tom Reynolds of the MIT Partnership for Air Transportation Noise and Emissions Reduction. JFK and others are just moving to more formal and precise approaches.

So better tools help, but the approach must be customized to each airport. One difference is whether the pushback time is decided by the airline or the airport. The latter is the rule in Europe, while the former is more common in the US. Airlines determine pushback at JFK, so the program was voluntary. Boston Logan controls most pushback, so tactics were different in 2011 metering trials there.

Gate ownership also counts in handling delayed arrivals. Common-use gates can be used more flexibly, while an airline may have to push back aircraft early if it needs one of its limited gates to disembark passengers. Up to half of some airlines’ flights had to be held off gate at JFK, which
fortunately has plenty of space.

MIT estimates the net benefits of metering for the top 40 US airports out to 2035. Reynolds says these benefits vary not by airport size but by the ratio of demand to capacity. He expects to report results between January and May 2012.