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					     AIRCRAFT AND AIR TRANSPORTATION SYSTEMS


                                Aircraft operations                                   Mode-S data link and an existing modified TCAS
                                                                                      unit in the aircraft. The audible alert is generated
                                                                                      by the Airport Surface Detection Equipment
                                One of the most pressing issues in aviation is the    Model X (ASDE-X) Safety Logic and is provided
                                inability of the National Airspace System (NAS)       to pilots at the same time that ASDE-X transmits
                                to meet predicted traffic growth, forecast at two     the information to air traffic controllers.
                                to three times its present volume by 2025. The
                                Next Generation Air Transportation System              Continuous descent approach operations
                                (NextGen) is the FAA’s plan to modernize the          In efforts to increase traffic flow and reduce
                                NAS, which must accommodate the increased             congestion, field trials studying the benefits and
                                traffic, new aircraft types, unmanned aircraft        feasibility of conducting low-power continuous
                                systems (UAS), and changed business models.           descent approach (CDA) operations using state-
                                      The evolution of NextGen will significantly     of-the-art technology and procedures have been
                                affect aircraft operations. Flight crews will take    very promising. In 2004, CDA trials using UPS
                                greater responsibility for self-separating in se-     aircraft had very successful results: 30% lower
                                lected airspace. Many of today’s manual tasks         noise, 34% less NOx emissions below 3,000 ft,
                                will be automated. Airspace sector geometries         and 250-465 lb less fuel burn per flight. The
                                will be dynamic to accommodate changing traf-         operations center provided the flight crew with
                                fic densities and weather conditions. Precision       initial speeds, aircraft to follow, and time inter-
                                navigation, digital data link, and precision sur-     val. The crew then followed on-board speed ad-
                                veillance will enable aircraft to fly closer to-      visories, from en route through CDA to landing,
                                gether safely with greater airport throughput         for consistent interarrival spacing.
                                rates. Among this year’s highlights in aircraft             Flight Deck Merging and Spacing is an Au-
                                operations are several very promising technolo-       tomatic Dependant Surveillance-Broadcast
                                gies undergoing testing and evaluation with           (ADS-B) application designed to improve run-
                                NextGen in mind.                                      way capacity. A command display unit being
                                                                                      used at NASA Langley, for example, shows
                                              Runway incursions                       which plane is assigned as the lead aircraft and
                                 The Runway Status Light System (RWSL) is de-         the desired interval to achieve when it crosses
                                 signed to prevent runway accidents and reduce        the runway threshold. The device also shows
                                                      the frequency and severity      the current spacing, distance, and ground
                                                      of runway incursions by         speed of the lead aircraft.
                                                      directly indicating to pilots         Field trials of oceanic tailored arrivals
                                                      when it is unsafe to cross      (OTA) involved sending comprehensive trajec-
                                                      or enter a runway or inter-     tory-based clearances over data link to United
                                                      section, and to take off or     Airlines Boeing 777 aircraft en route from Hon-
                                                      land. RWSL is undergoing        olulu to San Francisco. Trials were conducted
                                                      extended operational eval-      under light traffic conditions using aircraft
                                                      uations of the runway en-       equipped with Future Air Navigation System
                                                      trance lights (RELs) and        avionics that integrate communication, naviga-
                                                      takeoff hold lights (THLs)      tion, and surveillance functions. OTA clearances
                                                      at the Dallas Fort Worth        were initiated approximately 900 n.mi. from
                                                      (DFW) airport, and of RELs      landing in oceanic airspace. In addition to the
Runway entrance lights, part of                       at the San Diego (SAN) air-     basic trajectory clearance, descent speed advi-
the Runway Status Light System,  port. RWSL was recently approved for contin-         sories computed by NASA’s enroute descent ad-
are undergoing extended opera-   ued development toward installation. Next            visor (EDA) were delivered to aircraft to dynam-
tional evaluations in efforts to
prevent runway incursions.
                                 steps include RELs turning on earlier for arrivals   ically manage the vertical profile. EDA would
                                 at SAN; advanced final approach runway occu-         support CDA operations under congested traffic
                                 pancy signal operational evaluation at DFW;          conditions where capacity and separation con-
                                 and runway intersection lights with RELs and         straints must be taken into account.
                                 THLs at O’Hare.                                            Once received by the flight deck, all OTA
                                      Honeywell International and Sensis, in co-      clearances were loaded into the aircraft’s flight
                                 ordination with the FAA, have demonstrated           management computer for automatic guidance
                                 technology that can detect potential runway in-      and control to the runway, with little further pi-
                                 cursions and communicate them directly to an         lot input required. Initial results show potential
by Margaret Klemm and the aircraft cockpit. The cockpit advisory technol-             fuel savings of up to 3,000 lb per flight in heavy
AIAA Aircraft Operations         ogy sends potential ground, arrival, or departure    congestion, where CDA operations are most in-
Technical Committee              conflicts to pilots as an audible alert using a      hibited, with a corresponding reduction in

30   AEROSPACE AMERICA/DECEMBER 2007
greenhouse gas emissions of up to 10,000 lb
per flight. Plans call for initiating routine OTA
operations into San Francisco later this year
during noncongested periods. The trials were a
collaborative effort by NASA Ames, Boeing,
United Airlines, the FAA Oakland Center and
Northern California TRACON, and San Fran-
cisco International Airport.
                                                                                                          A command display unit used at
      NASA Ames has investigated how CDA                                                                  NASA Langley shows the selected
might be conducted at various ground-based                                                                lead aircraft and spacing
and airborne equipage levels. Air traffic con-                                                            interval.
trollers and airline pilots conducted a realistic
simulation of an arrival management concept          using an FAA King Air and a Convair 580 as the
termed TOOWiLD (trajectory-oriented opera-           intruding aircraft. Several climbing, descend-
tions with limited delegation) at NASA Ames’         ing, and level geometries were flown and suc-
Airspace Operations Laboratory and Flight            cessfully resolved without the safety pilot inter-
Deck Display Research Laboratory. An auto-           vening. The see and avoid flight demonstration
mated arrival management system generated a          flew 20 hr of testing involving 23 profiles with
runway schedule, appropriate speeds for the          74 encounters. Flights were against a static ob-
aircraft, and (in some conditions) airborne          ject (weather balloon), a single intruder, and
spacing information.                                 two intruders (Cessna 180 and Piper Warrior).
      That information was uplinked to partici-           Although the false alarm rates for both
pating aircraft 300 n.mi. from the airport. Con-     demonstrations were high, both systems gath-
trollers and pilots were able to routinely con-      ered much valuable data. The next hurdle for
duct CDAs for participating aircraft at peak         each is to fly the test aircraft unmanned.
traffic levels with the need for low-altitude vec-
toring nearly eliminated. Additional scheduling         NASA separation assurance research
tools on the controller workstation improved         NASA is conducting research to determine tra-
handling of nonparticipating aircraft.               jectory-based automation technology and oper-
      With flight crews providing their own          ations that could support a substantial increase
spacing, NASA is working on a wake vortex ad-        in airspace capacity with safety. Automatic con-
visory system. WakeVAS can safely reduce             flict resolution algorithms have been developed,
wake vortex minimum distances by integrating         modeled in software, and tested in fast-time
several existing technology systems. The system      simulation using Cleveland Center traffic to
is ground-based, because capacity gains are cur-     three times traffic density, albeit with near-zero
rently achieved by providing reduced spacing         trajectory prediction uncertainty.
criteria to air traffic control.                           Results show a shallow rise in resolution
                                                     trajectory delay with traffic density, suggesting
          Unmanned aircraft systems                  that capacity is not limited by airspace volume
Although assimilation of UAS into the NAS is         to 3x traffic. Researchers also conducted real-
some years in the future, progress is being made     time laboratory simulations with Fort Worth
both operationally and technologically. NASA         Center traffic assuming reliable conflict detec-
Dryden became the first non-DOD operator in          tion combined with automated but manually
the NAS when its Ikhana/Predator B flew its          driven conflict resolutions, and trajectory un-
unique thermal-infrared fire sensors in the          certainty comparable to that attainable using
Western States Fire Mission. Real-time images        state-of-the-art trajectory modelers processing
were supplied to fire commanders in several          Center Host track and flight plan data.
states during a series of 10-24-hr missions.               Results suggest that a five- to tenfold in-
     The first two flight tests of “end-to-end”      crease in controller efficiency and reduced de-
automated collision avoidance systems took           lays can be achieved while maintaining aggre-
place in December 2006. End-to-end means a           gate aircraft minimum separation characteristics
sense and avoid system consisting of a sensor        comparable to today’s. Tactical (0-3-min) tra-
feeding to a tracker that determines collision       jectory modeling and conflict detection meth-
potential, hands off high-threat tracks to an        ods, considered a critical safety net for higher
avoidance algorithm, and then issues a maneu-        levels of automation, have shown substantial
ver command to the aircraft autopilot—all with-      improvement in missed alert performance with
out a pilot’s intervention. The sense and avoid      false alert performance comparable to today’s
flight test flew 79 encounters during 21 flights,    conflict alert function.

                                                                                               AEROSPACE AMERICA/DECEMBER 2007       31

				
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