Changes Would Save Time, Fuel

The Air Transport Association, the lobbying group for the major United States Part 121 airlines (passenger and cargo), has long been the authoritative voice of the airline industry. In the ATA's latest briefing on the contentious fuel issue, the organization mentions several potential ATC changes that might lead to time and fuel savings.

The slide begins by praising the 2005 introduction of RVSM as an example of the sort of procedural improvement that can save gas and increase system capacity while maintaining an equivalent level of safety. RVSM, Reduced Vertical Separation Minimums reduces mandatory vertical separation between flight levels 290-410 (inclusive) from 2,000 feet to 1,000 feet, providing a theoretical doubling of traffic throughout.

Are there more potential gains to be found in the system? The ATA thinks so.

Here's ATA's list -- with a little of ATA's expanding text, and our comments. Due to the amount of information involved, we've split this into two parts. Today, we look at ATA's wish for the FAA to expand the deployment of RNAV at major airports... as well as for the agency to reconsider the current 250-knot "speed limit" below 10,000 feet MSL.

On Thursday, we'll look at some of the ways ATA proposes to reduce delays and holding times, and we'll offer our summary of the situation.

The Wish List

• Accelerate RNAV deployment at hub airports; delegate development of procedures. RNAV (Area Navigation) provides more lateral freedom, so that airplanes use the whole sky instead of the narrow, constricted pipelines of airways and jetways.

ANN Take: Presumably they're talking about a terminal version of Free Flight, or at least a greater number of arrival/departure corridors for transport aircraft; with development of the procedures offloaded to the individual lines or their contractors. (Already, at present, an operator can develop a Required Navigation Performance procedure of his own and staff it through FAA). Real RNAV capability is a lot more widespread in GA than in the airline fleet at present, but ATC seems to be slow on the uptake. What's been holding it back, of course, is the airlines' reluctance to embrace this technology. Flying from beacon to beacon like Slim Lindbergh on the mail run in 1925 needs to die. But having aircraft traveling at arbitrary altitudes and speeds, in arbitrary directions, is going to tax controllers -- and their computers.

And then, there's the effect on reliever airports -- which in turn reflects back on the air carrier fields. Given that many reliever airports are in close proximity to air carrier airports, and separation of approach and departure paths to reliever airports depend on the air carrier airplanes flying through distinct arrival gates, the possibility exists that this proposal would increase throughput at air carrier facilities at the expense of IFR capacity at nearby reliever airports. This in turn is one of the few scenarios where the hoped-for explosion of VLJ traffic in and out of relievers would have a noticeable impact on air carrier operations in the terminal environment. Imagine an Atlanta metro area where traffic into KATL does not adhere to current routings, but overflies the very busy reliever airports at low altitude.

No question that GPS can make for routings and fuel savings for air carrier airplanes, but there would likely still need to be some level of SID/STAR routings to deconflict with GA traffic at outlying airports. At least with GPS there could be many more transport corridors than a ground-based navigation system provides.

• Reconsider rule limiting speeds below 10,000 feet to 250 knots; some aircraft may operate more efficiently at higher speeds (especially on climb-out) but are prevented from doing so (note: also allows controllers greater flexibility to manage air traffic)

ANN Take: One reason for this reg (FAR 91.117(a)) is that, at higher speeds, see-and-avoid isn't practical, as a couple of well-known accidents where military aircraft centerpunched loitering GA machines have illustrated. ATA tends to assume that their birds are the only ones in the sky; it ain't necessarily so. The basic problem is one of deconfliction with aircraft that are not in the system; deconfliction with IFR aircraft appears to pose no problems.

If that hurdle could be overcome, lifting this limit would be a benefit to airline and to business jet operators (especially as newer, faster jets come online in the next two decades). It would drive Boeing and Airbus wild with frustration because their latest planes are designed with this limit in mind, and might have been more efficient without it.

From the GA point of view this remains an alarming proposal without a way for participating aircraft to see and avoid nonparticipating aircraft. We're keenly aware that in a GA-airline midair, the finger of blame points to GA even when the airliner's CVR reveals the crew yukking it up about having lost sight of the Cessna they're about to hit. (Not that there isn't usually enough blame to go around in any of these crashes). The inability of the military to completely prevent even F-16s and Tornados, whose onboard radar detects even non-transponder aircraft, from the occasional midair is not encouraging about a future filled with airliners traveling at 300+ knots without such equipment.

See-and-avoid is the basis of aircraft separation even for IFR airplanes when in Visual Meteorological Conditions. See-and-avoid permits a much greater airport capacity for air carrier aircraft when conditions are VMC -- picking on ATL again, think about airline flight delays any time it's even marginal VFR at the airport. Depending on IFR separation requirements at all times to permit higher speeds would condemn air carrier airports to their low-capacity modes all of the time, not just when weather is poor.

Finally, birds (birds in the literal sense) never file IFR and don't carry transponders, and civil aircraft windshields are not certified for bird strikes at high speeds (or multiple-bird strikes for that matter). While birdstrike safety certification standards have resisted worldwide harmonization, US standards are relatively close to those of other authorities. FAA tests to 250-280 knots, the Air Force to 550 knots. The speed limit rule was imposed in North America for the principal purpose of bird-strike safety, and a thorough 2005 study in Canada presented data supporting the retention of the limit.

"[A] 20 percent increase in aircraft speed from 250 to 300 KIAS results in a 44 percent increase in impact energy during a bird strike," the authors summarized. "Clearly the speed of the aircraft and engine rotation speed are more important in a collision than the size of the bird and more controllable than the size of the bird." (.pdf here). The study notes that a previous FAA experimental study of higher speeds in Texas in 1998 was cut short as unsafe. That document contains some chilling stories of bird strike damage, casualties and near-casualties.

As proposed here, then, the ability to operate at unrestricted speed benefits the airlines by increasing on-time performance for late-launched flights, and may provide some fuel savings. Until a near-foolproof system for avoiding bird strikes is incorporated, however, those changes may come at the expense of a probable increase in aircraft lost through bird strikes and midairs.

We think that if you asked the passengers on those doomed aircraft, they'd pay a few dollars more in order not to die.

FMI: www.airlines.org