Analysis is now underway of data collected in the 26-30 October OpEval 2 operational trial of automatic dependent surveillance broadcast (ADS-B) technology, but a senior Federal Aviation Administration official says the trial clearly demonstrated that ADS-B has considerable potential for airport surface safety and in-flight applications alike.
Speaking after the United Parcel Service-hosted trial at Louisville, Kentucky's Standiford Field ended, the head of the FAA's Safe Flight 21 programme, Jim McDaniels, said: "Overall it proves that the potential for this technology is excellent."
McDaniels adds: "We're getting some really insightful comments and data from pilots and controllers on what's working and what's a problem."
FAA official Paul Fontaine says OpEval 2's test of how pilots fared using ADS-B-derived airport surface moving maps in the cockpit showing each aircraft's exact position on the airport provided particularly interesting results.
"We collected data on the pilots' ability to use the surface moving map technology on a deliberately hard-to-follow route," explains Fontaine. The test - conducted at night - involved one group of aircraft fitted with the airport surface moving map displays showing ADS-B-derived aircraft location and another group of aircraft that did not have the displays.
For the test the pilots were also given deliberately hasty, complicated and sometimes ambiguous instructions by controllers, to simulate what the pilots often are forced to deal with in real life.
"On a couple of occasions the folks who didn't [have ADS-B-fed maps] got lost," says Fontaine. "Those who did were pretty much able to execute the test dead-on."
Testing of another ADS-B application during OpEval 2, the departure spacing application, involved some degree of air traffic control procedural complexity to ensure that at no time controllers gave pilots conditional take-off clearances and that all operational responsibility for each clearance remained with the controllers.
Conducted to determine whether in future it might be feasible to use ADS-B-determined departure spacing by time or distance to tighten up elapsed time between departures and thus increase the efficiency of runway use, the OpEval 2 departure spacing test involved a procedural compromise on the controllers' part.
To make sure that no air traffic control handbook procedures were breached by giving conditional clearances, controllers only cleared each aircraft to take-off when the aircraft preceding it on the runway had already attained what in the controller's view was a safe separation from the following aircraft.
Despite this compromise, says UPS executive Dorsey DeMaster, the participants in OpEval 2 found that the ADS-B departure spacing tool did indeed offer a runway use efficiency improvement.
What happened in effect was that controllers were able to issue pilots with take-off clearances from the taxiway/runway hold line, say DeMaster and FAA executives. This meant that they were able to dispense with the usual "Taxi into position [on the runway] and hold" instruction".
Removal of the need and time taken to issue this instruction - and the time the aircraft would otherwise wait on the runway for the actual take-off clearance - did improve efficiency of usage of Louisville Standiford Field during the trial.
This is very promising for the future, says the president of the Cargo Airline Association, Steve Alterman. The association is coordinating the combined effort of the US cargo carriers to develop and adopt ADS-B technology, once mooted as an alternative means of satisfying the FAA's requirement that commercial aircraft be fitted with TCAS.
Although the FAA has now ruled against this, the cargo airlines still see safety value and economic benefits in adopting various ADS-B applications as soon as possible.
"If we can only get down to the current minimums, we'll be ahead of the game," says Alterman, noting that departure runway efficiencies today do not even approach current spacing minima.
DeMaster confirms that results from OpEval 2 were indeed sufficiently encouraging to hold out this promise.
"In our morning launch [of a large number of outbound flights] UPS now achieves [a] 1.16min" average between departures, she says. As a result of what the OpEval 2 trial has shown, we're pretty comfortable with the idea of a departure every 45s, knocking off 20s" to 25s from the time between departures.
"If we can achieve that, our last departure [in the flight bank] will be 26min earlier than today," says DeMaster, adding that this would represent an enormous saving in time and money to UPS.
She says that although it is too early yet to provide the exact results of the OpEval 2 departure spacing test, the feedback obtained from participating pilots and controllers allows several important general conclusions immediately to be made.
The ADS-B departure spacing tool "reduces radio transmissions", says DeMaster, but nevertheless "there are still concerns for defined responsibilities" between controllers and pilots regarding maintenance of aircraft separation. Most importantly, however, the trial indicated that "the procedure can optimise spacing between departures".
A third new ADS-B application tested in OpEval 2 was an approach spacing tool. United Parcel Services' Capt Bob Hilb says the initial report analyzing the data from the Louisville testing will be available on 15 December, but immediately the trial participants feel able to say that the feedback was very encouraging.
"We received very positive comments" from pilots and controllers about the approach spacing tool," says Hilb. "All [participants] felt that approach spacing will have great benefits and is very do-able."
However, he cautions that much more work needs to be done to make sure the tool is reliable and effective. Four areas of further study are particularly needed, the first being to pay attention to cockpit resource management to make sure that there is "the right distribution of workload between the flying pilot and the non-flying pilot in terms of head-up/head-down time".
Second is further improvement of the prototype tools to make them reliably accurate. Third is providing pilots with airport surface moving maps so they can make out what they are seeing through the windscreens of their aircraft while on approach, particularly it night.
"It's surprising," says Hilb, "but pilots could see targets on the airport, but they didn’t know where they were."
A fourth area that needs a lot more work is the need to develop procedures for voice communication between pilots and controllers to minimize confusion. Particularly important, says Hilb, will be to improve the use of and standardize call signs to avoid confusion and make sure that controllers can identify correctly just which aircraft they are talking to at any given time.
Past runway incursion accidents such as the collision between a landing USAir Boeing 737 and a holding Beech 1900 at Los Angeles in the early 1990s have involved controllers mistakenly issuing instructions to the wrong aircraft because they believed they were talking to other aircraft.
Once the data collected during OpEval 2 has been analyzed and digested by the trial's participants, they will prepare for OpEval 3. The FAA's McDaniels reveals that the next set of trials will be held in Memphis - and thus will be hosted by Federal Express - in May 2001 and will represent the first attempt to integrate all the technologies involved in the FAA's Runway Incursion Reduction Programme into the ADS-B operating environment.