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Capstone is an accelerated Federal Aviation Administration (FAA) effort to improve aviation safety in Alaska. The program includes the installation of ground infrastructure, global positioning satellite (GPS)-based avionics, and data link communications in commercial aircraft serving the Yukon-Kuskokwim Delta/Bethel area. No state relies as heavily upon aviation as Alaska does to provide many of the bare essentials of life. Few environments are as spectacular, or as unforgiving, as Alaska. In fact, it ranks at or near the bottom in U.S. aviation safety because of its terrain, climate, and lack of such infrastructure as weather observation stations, communications, and radar coverage below 10,000 feet, where most general aviation and commercial carrier aircraft fly. Plans call for up to 200 aircraft to be voluntarily equipped with Capstone avionics.

The Yukon-Kuskokwim Delta/Bethel
Region of Alaska

As of December 2001, more than 140 aircraft had been so equipped by the FAA and they have logged 127,000 hours of flight time. Furthermore, about 100,000 square miles of western Alaska airspace is now service by the Capstone ground infrastructure.

CAASD's Role in Capstone

The MITRE Corporation's Center for Advanced Aviation System Development (CAASD) has been involved in several key elements of the Capstone Program:

  • Providing systems engineering and architecture.
  • Planning tests and evaluation strategies.
  • Building prototypes and operational models.
  • Helping evaluate Capstone's radar-like services and system safety.

As the FAA's federally funded research and development center, CAASD has worked closely with the Alaskan aviation industry, the FAA, manufacturers, controllers, pilots, contractors, and others in deploying the initial system, in developing Capstone software and infrastructure, and in conducting tests leading to Capstone's radar-like services. Furthermore, CAASD is working on and coordinating standards development for many of the other technologies being tested in Capstone.

CAASD's involvement with Capstone has been ongoing for several years, beginning as a planning and coordination effort under the Flight 2000 and Safe Flight 21 programs. Over the past year, CAASD's direct participation has grown. Since early 2000, CAASD has had a staff engineer in Anchorage as a member of the Capstone Program Office, and a number of staff devoting their energies to Capstone in CAASD's headquarters in McLean, VA. A large contingent of CAASD Capstone staff were in Alaska in August 2000 to support a major demonstration of Capstone capabilities, and throughout 2001, CAASD has continued to support Capstone from Anchorage and McLean. In January 2001, FAA Capstone Program Manager John Hallinan visited CAASD to present an award to CAASD Capstone staff for their exceptional commitment to the program.

FAA Capstone Team
FAA Capstone Program Manager John Hallinan, front row, far right, presented CAASD Director Jim Chadwick (front row, center) with a plaque commemorating CAASD's strong support of Capstone. An accompanying letter noted "The Capstone Program is technically complex and it deeply involves many of [the FAA's] lines of business. . . Consistently, over the past three years, CAASD personnel performed in an outstanding manner. Their support was invaluable as we progressed on our voyage of discovery."


The FAA's Safe Flight 21 program, of which Capstone is a part, evolved from recommendations in a 1998 report looking at Free Flight operational enhancements prepared by RTCA, Inc.–an industry-wide aviation advisory group. The first phase of Capstone is to equip small commercial aircraft in the southwest region of Alaska. The next phase will target aircraft in the Juneau region. Linking several FAA safety initiatives, Capstone is focused on enhancing safety in several areas, including situational awareness, midair collisions, and controlled flight into terrain. The program is testing and evaluating the capabilities of several technologies, including Automatic Dependent Surveillance-Broadcast (ADS-B), Traffic Information Service-Broadcast (TIS-B), and Flight Information Service-Broadcast (FIS-B).

Supporting the airborne avionics, a network of data link ground stations is being installed in up to 10 existing FAA and joint-use facilities in the test area, and connected via existing satellite-based communications systems to FAA air traffic control facilities. To facilitate the implementation of the ground network, a common ground station design is being used for both Capstone and another ADS-B-related project in which CAASD also has played a significant role--the Ohio River Valley operational evaluations. A ground broadcast server (the Capstone Communication and Control Server, or CCCS) and a gateway processor have been installed at the Anchorage Air Route Traffic Control Center (ARTCC) to receive data from each remote site and to interface with the existing Micro En route Automated Radar Tracking System (Micro-EARTS). The Micro-EARTS is programmed to depict ADS-B targets along with radar targets on air traffic controller displays. Radar data will eventually be uplinked to equipped aircraft (TIS-B) and will enable the pilot to see both ADS-B and radar targets on the multifunction display (MFD) in the cockpit. Weather information is also being uplinked to the cockpits of equipped aircraft. In the future, other non-control information, such as special use airspace status, Notices to Airmen, and Pilot Reports will be made available. ADS-B aircraft position reports also will be available to operators for flight-following purposes.

The Capstone evaluation period, which began in early 2000, initially concentrated on weather and other information in the cockpit, affordable means to reduce CFIT, and enhanced capability to see and avoid adjacent traffic operational enhancements. Part of the Capstone initiative through 2002 is to evaluate further enhancements. As part of the program, pilots, operators, safety inspectors, air traffic control specialists, and technicians will be trained to ensure gaining the greatest benefits from evaluation activities.

Although not part of Safe Flight 21, GPS non-precision instrument approach procedures are being prepared and published for one or more runways at each of 10 remote village airports in the Capstone evaluation area. Within budgetary limitations, automated weather observation systems will be installed at many of these airports to enable air carriers the use of the new non-precision GPs instrument approach procedures.

Enabling Technologies

cockpit of a Casa-212
The cockpit of a Casa-212 with the
Multifunction Display illuminated in the
center of the panel.

ADS-B technology is providing the means for air and ground vehicles to broadcast and receive ADS-B messages via a digital link. Unlike radar, ADS-B relies on the satellite-based global positioning system to determine an aircraft's precise location in space. The system then converts the position into a digital code, which is combined with information such as the type of aircraft, its speed, its flight number, and whether it's turning or climbing or descending. The digital code is updated once per second and broadcast from the aircraft on a discrete frequency called a data link. On board the aircraft, ADS-B information from other aircraft is displayed on a moving map display on the MFD, which can also display terrain and weather information, and a variety of navigation maps. This ADS-B information also provides air traffic controllers with a more complete picture of the airspace and can support flight-following by operator dispatch offices. TIS-B is the uplink of the position of non-equipped aircraft as seen by surveillance radar—this can be used as the enabling technology allowing traffic and other data available on the ground to be transmitted to the cockpit.

A Terrain Database, coupled with GPS-derived position data, provides the means to reduce or even avoid often-deadly CFIT accidents. A graphical presentation of the terrain relative to the aircraft is presented on a moving-map display to alert the pilot of potential conflicts and give the pilot sufficient time to react to the situation. Weather information uplink from the ground (FIS-B), along with the TIS-B data described above, can also be presented on the same display, providing a cost-effective, integrated approach to weather, traffic, and terrain avoidance for general aviation and commercial aircraft. In short, enhancements demonstrated in Capstone have the potential to significantly increase flight safety, system capacity, and the overall efficiency of flight operations.

Avionics and Infrastructure

The goal of the Capstone program was to design an avionics suite that is compact, multi-functional, and affordable. Part of that challenge was creating a package that would fit in smaller aircraft and at the same time would not require major modifications for installation, since the participating aircraft were almost all small single or twin engine commercial aircraft.

The Capstone avionics suite is designed to:

  • Increase the situational awareness of pilots and help prevent mid-air collisions.
  • Dramatically improve air traffic control services in non-radar space by sending ADS-B position information to the Air Route Traffic Control Center (ARTCC).
  • Reduce CFIT via a cockpit display and terrain database.
  • Increase weather awareness by obtaining real-time weather information via a cockpit display.

MFD: Multifunction Display

Universal Access Transceiver Digital Data Link
Multi-Function Display

The Capstone team is exploring one of the major advances in cockpit technology: the MFD. A digitally powered glass display on the instrument panel, the MFD gives the pilot a wealth of information in one place and has several different capabilities depending on how it is configured. Navigation maps, terrain information, weather information, and aircraft targets are all presented on the moving map-equipped MFD.

The Universal Access Transceiver Digital Data Link

The Universal Access Transceiver, or UAT, is the two-way digital data link employed in the Capstone system. It is a high-bandwidth, multi-purpose, low cost data link. UAT was initially developed by CAASD. CAASD has worked with data link technology for several years, and its work in related areas of aviation research is part of Capstone's legacy. Developed under internal research and development funds at MITRE beginning in 1995, the UAT was originally conceived as a simple, multifunction broadcast data link alternative for small aircraft. Following the successful flight demonstrations of ADS-B, FIS-B and TIS-B as part of CAASD efforts, United Parcel Services (UPS) Aviation Technologies developed a commercial version of UAT. Subsequently, UAT was included in the winning proposal by UPS Aviation Technologies for Capstone avionics and ground stations. RTCA has begun developing UAT standards, with CAASD again poised to play a key role.

Schematic Diagram of Capstone Avionics
Schematic Diagram of Capstone Avionics

Capstone Communication and Control Server

The airborne avionics are complemented by a ground-based system providing complex communications and processing for weather, maintenance monitoring and control, and surveillance. CAASD engineers developed the heart of the ground infrastructure, the Capstone Communication and Control Server, which provides the following services:

  • Multisource/multicast distribution services.
  • Multiplexing of all traffic on a single circuit to each remote site.
  • Processing for the FIS-B and TIS-B uplink services.
  • Host control services for the remote site transceivers.
  • Remote maintenance and monitoring.
  • Graphical interface of current services.

    Capstone Avionics Architecture

Results: Phase I (Making History)

FAA Capstone personnel
FAA Capstone personnel with one of Yute
Air's CASA-212 on the apron at Anchorage,
December 31, 2000.

Phase I activities (January 2000-December 2000) sought to have a positive impact on safety while creating an infrastructure to permit initial procedures development, familiarize flight crews, controllers, and avionics installers with modern equipment and future NAS concepts, and to address certification issues and procedures. Among the major accomplishments in Phase 1 were:

  • Radar-like air traffic surveillance services using ASD-B down link.
  • Initial weather uplink and weather cockpit display.
  • Cockpit display with moving map navigation.
  • Terrain avoidance information in the cockpit.
  • An operational ground site at Bethel.
  • More than 90 aircraft equipped with Capstone avionics.

On the last day of December 2000, Capstone made its way into the history books. At 3:18 p.m. on the 31st, two aircraft–a Yute Air Casa-212 and a Northern Air Cargo DC-6–departed Anchorage International Airport for Bethel. Using ADS-B as an FAA-certified and operationally approved surveillance source for radar-like ATC services while under visual flight rules and instrument flight rules, the aircraft appeared on the screen at the Anchorage air traffic control center. Both were vectored for an instrument approach to Bethel Airport. En route, the aircraft were tracked by the Anchorage ARTCC using ADS-B's radar-like capabilities. About two and a half hours later, with a ceiling of about 800 feet and visibility of 1 mile, they landed on the Bethel runway, becoming the first aircraft in history to be given such clearance to Bethel.

This first flight using ADS-B for continuous radar-like services in normal revenue service was a major event for Capstone and the FAA. In a December 29, 2000, FAA press release, FAA Administrator Jane F. Garvey said of this new technology, "[it] has the potential of filling in huge gaps in radar coverage including vast areas in South America and Africa, as well as the United States."

The initial results of Phase I have cut a clear path of transition activities by identifying and addressing National Airspace System implementation issues. Capstone's system integration approach is validating the overall safety and efficiency benefits expected from modernization. Since its initial deployment in 2000, pilots using Capstone's blend of communications, navigation, and surveillance equipment did not experience a single controlled flight into terrain accident.

A Look Ahead

For Fiscal Year 2002 (FY2002), the Capstone Program will continue its partnerships with air carriers, avionics industries, and the traveling public. Work on elements supporting technologies chosen for Phase I need to be completed so that each element is hardened, validated, and ready for further deployment throughout Alaska and potentially the National Airspace System. For example, the process to accept the CCCS as a NAS baselined and maintained system will be completed for the initial CCCS deployment.

FY2002 activities will also focus on completion of Phase I Capstone area requirements in and around Bethel. Non-precision approach procedures developed and already published will be supplemented with additional procedures at adjacent village airports within the Phase I area. To ensure constant and consistent data collection during the validation period and to provide further safety benefits to the flying community, avionics installations will continue for the remaining 60 aircraft. A new CCCS interface will be developed for the distribution of ADS-B data to commercial companies so they can provide flight following capabilities to the Alaskan operators. Remote monitoring and maintenance capabilities will also be developed in the CCCS and GBTs to reduce the labor and cost intensive maintenance procedures for remote installations.

Also in 2002, the Juneau activities will get underway. New, more capable, avionics are already being procured and will be installed on a limited basis. The installation of a ground infrastructure similar to the Bethel region will also begin.

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