Business & GA, Military

CAAS: Past, Present and Future

By David Jensen | October 1, 2006
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Major steps to modernize the U.S. Army’s aviation assets were made this past summer, which in turn, mark progress for the Common Avionics Architecture System (CAAS) developed by Rockwell Collins. On June 15, 2006, the first production CH-47F Chinook rolled out of Boeing’s helicopter manufacturing plant in Philadelphia. Then Bell Helicopter Textron successfully completed the first two flights of the Army’s new ARH-70A armed scout helicopter at the company’s XworX facility in Arlington, Texas, on July 20. Ten days later Sikorsky Aircraft in Stratford, Conn., delivered the first production UH-60M Black Hawk. Production of the CH-47F is scheduled to reach a maximum rate of two aircraft per month by the end of this year; UH-60Ms are in low-rate initial production (LRIP); and the ARH-70A, a modified commercial off-the-shelf (COTS) platform, has just transitioned into flight test phase. All three aircraft will be CAAS-equipped, although the UH-60M will not transition to the new architecture immediately.

CAAS Benefits
Meanwhile, in Cedar Rapids, Iowa, Rockwell Collins continues to expand the capabilities of CAAS, which it initially developed for the Army’s 160th Special Operations Aviation Regiment (Airborne), or SOAR(A), in 2000. Comprising a common core of assets and with open systems architecture, CAAS certainly is expandable. Using internal funding, Collins is working to enhance pilot situational awareness with CAAS by adding synthetic vision among other possible visual aids.

Enhanced situational awareness is one in a list of benefits the Army intends to gain from CAAS. Others include:

  • Reducing pilot workload,
  • Enhancing mission capability,
  • Reducing the logistics base and maintenance requirements,
  • Providing cross-platform commonality (hardware, software and training),
  • Moving from single proprietary components and using standards where appropriate,
  • Allowing rapid adoption of upgrades, including from third-party providers,
  • Leveraging other platform developments, both commercial and in the Department of Defense (DoD), and
  • Reducing ownership costs, as well as systems acquisition and sustainment costs. 

Collins’ ongoing applications development for CAAS represents a policy of "common open architecture" within the company. Technology is reused across the different markets the company serves. For example, CAAS descends from Government Systems’ Flight 2 architecture that is available for military systems, ranging from fixed-wing aircraft to ground vehicles, but it also leverages technology developed for the air transport market and for Pro Line 21, the avionics suite for the business and regional aircraft markets.

CAAS derives from the Air Force’s KC-135 GATM (Global Air Traffic Management) program launched in 1997. This technology also leverages the commercial Boeing 767, corporate Challenger 300 and the Navy’s P-3 CNS/ATM (communication, navigation, surveillance/air traffic management) programs, among others.

In turn, Collins plans to have advancements for CAAS enter the next generation of systems being developed, including for the Army Aviation Applied Technology Directorate’s MCAP III (manned/unmanned common architecture program, Phase 3), the E-6B and Army’s FCS ICS future programs. (ICS, or integrated computer system, is a common processing environment for 17 Army platforms in the FCS, or Future Combat System program.)

The Army will acquire CAAS to modernize its utility and lift fleets and, consequently, transform the CH-47, which was once relegated to being an "intermediate" platform, unable to fully contribute to today’s network centric warfare environment. "The Army made the decision to keep the CH-47 for at least 30 years as part of the future force," says Jeff Langhout, chief of the technical management division at Army’s Cargo Helicopter Project Office. "That means [satisfying] interoperability requirements and the ability to exchange information on the battlefield." CAAS also gives the Chinook fleet its first "glass" cockpit. The service’s decision to upgrade its CH-47s was made easy by adopting the CAAS system already developed for SOAR Chinooks.

The Army plans for Boeing to build 452 CH-47Fs; most will be remanufactured 47D/Es, while about 20 Chinooks will be new, replacement aircraft. In addition to CAAS, the CH-47F will be fully digitized with a new BAE Systems flight control system, aircraft survivability equipment, L-3 cockpit voice and flight data recorders, a Telephonics intercom, and a new maintenance panel, according to Langhout. Army pilots were to begin training for their new 47F models in September, and the service plans operational testing of the aircraft in the January/February timeframe, says Langhout.

Black Hawks
The Army has contracted Sikorsky to build two prototype UH-60Ms equipped with CAAS. First flight of the aircraft is slated for December 2007. The service plans to acquire 1,227 -60M Black Hawks, but all won’t have CAAS. Sikorsky will "cut in" with CAAS equipage, starting with the 123rd full-rate production aircraft, according to an Army official. As yet, the service has no plans to retrofit the initial 122 aircraft with CAAS.

Perhaps the Army’s most aggressive program is the ARH-70A, in which CAAS is an integrated system. The aircraft’s first flight followed a development contract for a militarized version of the model 407 by only 11 months. Bell expects an LRIP contract as soon as 2007. Flight testing of the avionics systems was initiated in just 12 months after the contract agreement.

CAAS will be installed in all helicopters in the Army’s modernization strategy, except the Boeing AH-64 Longbow Apache, which already has a glass cockpit and unique mission requirements not easily integrated into CAAS, and the new light utility helicopter (LUH), which will be produced with a COTS cockpit. The Army awarded Boeing a contract for Block 3 Apache upgrades, which includes implementing open systems architecture, in mid July.

Collins is working with Boeing to ensure compatibility among the Army’s helicopter upgrade programs, according to Richard Flesner, director of Army systems marketing at Collins. "For example, we’re collaborating on the integration of JTRS [joint tactical radio system] and SOSCOE [system of systems common operating environment], the software to run all Future Combat System vehicles," he adds.

In addition to the Army’s requirement for about 2,300 CAAS-equipped helicopters, the Coast Guard plans to install versions of the Collins system in 42 of its HH-60Ts. The U.S. Marine Corps, too, intends to fit a CAAS variant in 70 of its CH-53Es, the eight VH-60Ns in its presidential support unit and all of its CH-53Ks. The -53K, now under development, will replace all -53Es. The CAAS-equipped HH-60T and VN-60N are under development, and first flights are set for December 2006 and March 2007, respectively. The CH-53E with CAAS is in preliminary development, and an initial flight has yet to be scheduled.

To leverage common upgrades to CAAS, the program managers for each platform meet quarterly. Officers from the Army, Coast Guard and Marine Corps attempt to identify common approaches to upgrades in order to reduce development and acquisition costs, says Flesner.

Meanwhile, the 160th Special Ops regiment-for which CAAS was originally developed, following a contract award in April 2001-is having the new avionics installed in its MH-47Gs and MH-60s, 137 helicopters in all, by 2010. A CAAS variant for the A/MH-6 Little Birds is under consideration. CAAS installation work not performed by the respective airframe manufacturers is taken on at the Blue Grass Army Depot in Lexington, Ky.

To train SOAR pilots on the common avionics system, CAE USA has supplied desktop trainers and reconfigurable part-task trainers. The Tampa, Fla.-based company plans to deliver a MH-47G simulator in late 2006 and an MH-60L DAP (Direct Action Penetration, describing a heavily armed Black Hawk) in the second half of 2007. Both include CAAS. Last year CAE delivered the world’s first Little Bird combat mission simulator to the 160th’s base in Fort Campbell, Ky.

To explain CAAS’ flexibility, both Army and Rockwell Collins officials compare the system to an office environment in which all computers are linked by an intranet, yet each computer can be exchanged or upgraded without impacting the others. CAAS operating software is partitioned, allowing multiple applications on the same processing resources, with no chance of interference. Applications are comparable in all platforms, allowing "up to 90 percent reuse of the software code," says Flesner.

The source code for CAAS-a combination of ADA, C, C++ and Java-is nonproprietary. DoD can use the code freely and share it with third parties that are working on U.S. military programs. Flesner says Collins will deliver a tool kit that allows DoD to modify and further develop the code.

A 100 base T Ethernet local area network (LAN) distributes data among all onboard processors. This free flow of information gives CAAS extensive mission management capability, including:

  • Flight management to take care of all tactical flight planning;
  • Performance management, automatically accounting for fuel load, weight and balance, flight conditions, etc.;
  • Integrated navigation management of Doppler, GPS/inertial nav, VOR/ILS, ADF, TACAN and radio altimeter;
  • Integrated communications and identification management;
  • Sensor management of terrain-following/terrain avoidance radar, forward looking infrared (FLIR), weather radar, Stormscope and aircraft survivability equipment;
  • Avionics systems management, showing status and including built-in test equipment, data recording, alerts and aircraft configuration; and
  • On the Army’s two armed, CAAS-equipped helicopters, the MH-60L DAP and ARH-70A, weapons management of such systems as the Hellfire air-to-ground missile, Stinger air-to-air missile, rockets and guns, and accommodation for a monocle head-up display (monoHUD).

The flight management system includes a flight director function with altitude hold. A ground-speed select function helps synchronize arrivals to waypoints or destinations, and an automatic approach to hover mode determines the aircraft descent rate during adverse conditions, such as brownouts in the desert.

CAAS comprises four subsystems: 6-by-8-inch, portrait-oriented, color, multifunction displays (MFDs); control display units (CDUs); general-purpose processing units (GPPUs); and data concentrator units (DCUs). Rockwell Collins provides most, but not all, of CAAS. "It wasn’t just one big competition for CAAS that we won," says Flesner. "We were awarded the system development and software development contracts [but] there were also four separate hardware competitions." Collins won all but the DCU contract, which was awarded to Sanmina-SCI Corp., San Jose, Calif. Collins will have to compete for all additional upgrades DoD seeks for CAAS, as well.

The system incorporates the LynuxWorks’ LynxOS-178 real-time operating system. Harris Corp. licenses its digital map generator and database, which is hosted in the GPPU. Flesner cites the integration of Harris software as evidence of CAAS’ ability to accommodate third-party applications.

Each night vision-compatible MFD incorporates two independent PowerPC 500-MHz processors; one is an expandable, commercial 3D graphics card with open graphics language, and the other is a general-purpose processor. Software-controlled, bezel-mounted, push-button keys border the liquid crystal displays (LCDs), providing display format control and non-alphanumeric crew management. The top and bottom keys control the display modes, while the keys along the side control the "submodes," or the information present on the display, according to Dan Toy, marketing manager for Army programs at Collins. The pilot also can make adjustments by moving a cursor that is governed by a "coolie hat" on the helicopter’s cyclic control.

The MFDs can provide split-screen imagery, for example, a forward looking infrared (FLIR) image above or below a hover-guidance display. The pilot can call up any imagery desired on the MFDs; however, while in flight, the system assures that he maintains a view of the vertical situation display on one of the two screens in front of him. "That’s the only safety requirement we impose on the pilot," says Tom Billig, Collins’ lead technical engineer for the SOAR program.

The MH-60, MH-47G and CH-47F cockpits all feature five MFDs. The UH-60M will have four displays, to fit in a smaller cockpit panel that allows pilots a greater outside view, and the smaller ARH-70A will have two MFDs, as would the Little Bird helicopters. The systems architecture will accommodate any of the display configurations. Goodrich makes the electronic standby instruments.

The CDU, with a single general-purpose processor and 3U cPCI cards, includes a color alphanumeric LCD and a keyboard for entering flight, navigation, mission and systems information. The two CDUs on board the aircraft also operate as the primary and backup bus controllers for the dual-redundant Mil-Std-1553 data buses.

The GPPU comprises two modules: a processor switch module for the Ethernet LAN and a video processing module. The latter module accepts digital video inputs and multiplexes the signals to six independent digital video outputs. Both modules include a common processor, graphics engine and digital video output.

The DCU’s task is to take in analog inputs from the engines, transmissions, fuel system, etc., and output the data via a digital Mil-Std-1553 bus to the control display unit, where it is distributed throughout the system on the Ethernet LAN. Also run on a 3U cPCI card, the DCU has interfaces for ARINC 429 and RS-422, as well as 1553, for commercial standard connectivity and integration.

Startup and Operation
For Army pilots, particularly in the 160th, preparedness and quickness to execute a mission are paramount. Before taking off in a CAAS-equipped helicopter, the pilot and mission planning team inputs data on PCMCIA cards, which are pertinent to the mission. When the pilot enters the aircraft, instead of "fat fingering" a keyboard to input data, he simply inserts the cards.

"Within a minute and a half at most, he will load all the radio presets, all the navigation presets, all of the waypoints, all of his flight plan, all the weapons information, his "friendlies" or other assets, such as a UAV [unmanned air vehicle], reconnaissance aircraft or ground system-all he needs to get the mission done," Billig explains. "And he can start his check list while all of this is loading." SOAR helicopters have aerial refueling capability, and rendezvous with tanker aircraft also is preprogrammed.

The pilot can review the inputted data by scrolling through pages on his CDU, or he can view an entire page on the MFD. He can customize the pages, using either the CDU keyboard or cursor control. Because CAAS can provide many pages of data, Collins created six configurable mission pages, broken down to present the most critical information for the flight.

With critical data reviewed, the pilot enters the startup procedure and monitors progress on the instrumentation display and, perhaps, the warning cautionary grid on another screen. He can call up synoptic displays that show oil pressure and temperature and that include representations of the engine, input modules of the engine to the gearboxes, the main gearbox, transitional gearbox and tail rotor gearbox.

CAAS is performance-based, so it "knows the aircraft, the fuel on board and the weight," says Billig. "It evaluates the data and will tell the pilot what he can and cannot do in terms of aircraft performance." If, for example, the pilot has an insufficient fuel supply, CAAS software will automatically issue an alert on the MFD. Multiple cautions are presented in a prioritized list.

The Harris map engine, hosted in each MFD’s general-purpose processor, can draw from digital chart data, digital terrain elevation data or satellite imagery data, all stored in a mass memory file. The pilot selects the type of imagery. He also can overlay a satellite image on the digital map and, with navigation inputs, overlay a symbol to indicate ownship position, according to Jim Perkins, with Army marketing for Collins Government Systems Division. Likewise, the pilot can overlay primary flight display information on top of FLIR imagery, a common practice during the SOAR’s frequent night flights.

The Future
Taking a next step with CAAS, Collins is proposing the extended use of the terrain database to produce synthetic vision imagery, a technology the company is making available for the corporate aircraft market. Perkins says the regular Army is interested in this technology because it enhances situational awareness without adding weight. "They do not plan to have additional sensors on board," he states. The 160th, however, may consider additional sensors that, for example, detect wires, a deadly threat to rotorcraft. "They still are in a stage of determining what makes sense for them," Perkins adds.

Collins engineers working on synthetic vision have come up with several options. For instance, the lab has developed a synthetic vision system that presents both an egocentric view (out the cockpit windscreen) and exocentric view (from behind and slightly to one side of the aircraft), also called the "wingman’s view." The lab also has come up with the option of integrating the FLIR imagery in a window within synthetic vision. By correlating, or blending, the terrain data with the real-time FLIR imagery, pilots can feel more assured of a safe flight heading. "The blended solution would not run on a single-circuit processor board," Perkins admits. "You would have to have additional processing on board."

A visit to Collins’ Advanced Technology Center reveals technology taken from fixed-wing applications that could be transferred to the Army rotary-wing community. Some of the technology has been flight tested on NASA and FAA aircraft. Specifically, engineers are studying applications of the egocentric and exocentric views, different ways to render synthetic imagery of terrain, and highway-in-the-sky symbology for flight path guidance.

Perhaps most important to Army helicopter pilots, Collins is working with the University of Iowa to see how synthetic vision might best serve pilots during brownout conditions, when rotors kick up desert sand. "Our conjecture is that the exocentric view works well for aircraft in a hover or when coming in to land," says Tim Etherington, technical director-information systems at Collins. With the latter, "you can see the helicopter in relation to the landing spot." However, when the helicopter enters the brownout condition, the pilot might prefer the egocentric view, which gives a constant, eyeball’s view of a horizon. "But the study hasn’t been completed yet," he hastens to add. "We’re about at the study’s midpoint."

In a simulator with 180-degree visual system, Etherington demonstrates different ways of presenting terrain data. He shows, for example, a "wire frame" format in which thin lines produce distinct outlines of the terrain’s contours. Collins and Iowa University engineers also determined that a checkerboard pattern is an effective way to depict terrain texture. In many instances it would even surpass photo realistic imagery, Etherington maintains, because it presents less visual clutter.

The Collins lab is examining different highway-in-the-sky presentation, too. Instead of the box-like frames to cue the pilot on a flight path, the lab is looking at just a single line that gives some motion cues. Collins engineers believe this simpler approach provides sufficient situational awareness and flight guidance that, for the helicopter pilots flying close to the ground, entails less up-and-down maneuvering.

"We’re studying a whole host of things in the brownout study. For instance, we’re testing some acceleration and 2D symbology hover cues," Etherington concludes. "We’re refining what we will present to the Army."

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