Closing half the runways at one of the busiest West Coast airports for four months could be a recipe for chaos, but San Francisco International Airport is hoping that a new traffic-flow system will prevent taxiway bottlenecks and keep flight delays to a minimum.
 
Two of the airport's four runways will be closed from May 17 through September so major construction work can be carried out to meet FAA runway safety mandates. Saab Sensis has been contracted to deploy a departure manager (DMAN) system during this period to coordinate the increased load on the other two runways.
 
The DMAN system, part of an advanced version of Saab's Aerobahn product, was introduced at New York John F. Kennedy International Airport during a similar runway closure in 2010. It proved to be so successful in streamlining airline operations that it was retained and is still in use.
 
The runways being closed at San Francisco are the parallel 1L and 1R, which will have an engineered material arresting system (EMAS) installed at the runway ends. Parallel runways 28L and 28R had their thresholds extended last year, although they were closed only intermittently and mainly on weekends. Extending 1L and 1R was not an option, but airports can install EMAS to meet the new FAA requirements.
 
Runways 1L and 1R handle the majority of departing flights at the airport, with the exception of some widebody flights that need a longer takeoff roll.
 
The capacity with all runways open is about 100 arrivals and departures per hour, a San Francisco International spokesman says. During the runway closure, capacity will be down about 15% to 85 flights per hour. Airlines have agreed to help by curtailing planned growth in their summer schedules. Although there still will be a “modest increase” in operations, additional flights will be scheduled during off-peak hours.
 
The introduction of the Saab system promises to be the most effective measure during the closure. The $2 million contract with Saab includes the on-site staff who will help run the system, the airport's spokesman says. There are no plans to retain the departure manager when the runways reopen.
 
Deployment of Aerobahn at San Francisco has already begun, says Dan London, Saab Sensis's director for airline and airport automation. A 10-day operational test of the system is scheduled to begin in April. Airlines are also being trained in the system's use, as it involves collaborative decision-making.
 
Aerobahn will assist the airport, airlines and controllers in sequencing movements more precisely. The system will generate recommended gate departure times, shifting some delays from the taxiway to the gate and ramp to optimize airport flows.
 
This will reduce queues at runway thresholds to desired levels. Shorter taxi queues mean reduced fuel burn and, for passengers, less time sitting in the aircraft waiting to take off. Retaining a small queue is important to maintain pressure on the runway and ensure no takeoff opportunities are missed, says London.
 
The system considers wake vortex separation requirements as it sequences flights to minimize time intervals between aircraft without compromising safety levels. During peak times, 1-2 extra departures an hour can be achieved, in addition to the benefits from reduced taxiing, Saab says.
 
Airport personnel have estimated the runway closures will increase operator costs by more than $15 million—$8 million of this caused by longer taxiing distances and $7 million from increased queuing. Saab predicts Aerobahn will reduce this cost by $3.5 million.
 
At JFK, Saab says, Aerobahn is enabling significant taxi-time reductions and dramatic cost savings. Independent analysis by the Massachusetts Institute of Technology's Lincoln Laboratory confirmed that airlines collectively are saving an average of $15.6 million a year in fuel costs due to Aerobahn, with a reduction of 32,000 tons of CO2 emissions.
 
Of the 26 airports that use Aerobahn, 20 are in the U.S. The version that includes the departure manager has so far only been introduced in New York and San Francisco.
 
Another relatively new program at San Francisco will help relieve congestion at the airport during the runway closure. In fall 2013, the FAA introduced the closely spaced parallel runways (CSPR) initiative. This has improved arrival rates during low visibility, which can be a problem in San Francisco due to low cloud and fog. CSPR has boosted the airport's arrival rate, from about 30 per hr. in such conditions to 33-34.
 
San Francisco also will be the initial site for a surveillance system being deployed by Saab under the FAA's airport surface surveillance capability (ASSC) program. Saab is contracted to deploy ASSC at eight more airports in the U.S.