Avionics manufacturers are responding to the U.S. military’s need for technologies and systems to protect pilots indegraded visual environments (DVE), such as brownouts and whiteouts.
The U.S. Department of Defense (DoD) is particularly anxious to acquire avionics systems that will assist military pilots in navigating through DVEs. Brownouts, whiteouts and other DVE events can causes spatial disorientation and loss of situational awareness, which could bring the aircraft down.
According to the Army, 98 Class A and B DVE and controlled flight into terrain (CFIT) accidents accounted for 104 fatalities and a loss of $930 million between fiscal year 2002 through fiscal year 2010. (Class A accidents are those that result in a destroyed aircraft, more than $1 million in damage, fatality or permanent disability. Class B accidents involve damage of $200,000 or more, but less than $1 million.)
DVEs caused by brownouts and whiteouts account for almost half of the U.S. Air Force rotorcraft airframe losses and are the leading cause of airframe losses for the Army, according to DoD’s Aviation Safety Technologies Report, which covered crash data from 1985 through 2005.
The need for the technology is there, but so far, avionics system developers have yet to find a price and size point for a specific system for helicopters.
Two possible reasons could exist as to why the U.S. military has yet to acquire specific avionics technology to reduce brownouts. One factor could be the ongoing disagreement between DoD and the U.S. Army regarding the major cause of non-combat related accidents. The Pentagon says Control Flight Into Terrain (CFIT) is the principal cause of these accidents, while the Army maintains that brownouts and other DVE elements is the culprit.
The Army is putting the final touches on a “clarifying study” for Army operations that will say, in effect, flying in degraded visual environments is the leading cause of non-combat related accidents, said Layne Merritt, assistant program executive officer for engineering and technology at the U.S. Army’s Program Executive Office.
The other factor: technology offered so far is limited. “We’re not talking simply about brownouts during landings or takeoffs,” Merritt said. “We’re talking about operating in any DVE where the pilot’s visual acuity is degraded.”
Consequently, “we wouldn’t want to invest, say $2 million per aircraft, for something that only solves 30 percent of your problem,” Merritt said. “I don’t think it is very feasible to expect that it will be implemented as is, on any of our platforms.”
Nevertheless, the Army, which operates approximately 3,800 rotorcraft, appears ready to move from the research and development and testing phases to putting together “an acquisition strategy to acquire these systems that will include a multi-sensor solution,” Merritt said, adding that the Army plans to seek a materiel development decision this fiscal year.
The Navy and Air Force are considering commercial-off-the-shelf (COTS) technology to deal with DVE events, a DoD official said.
The Defense Advanced Research Projects Agency (DARPA), the DoD research arm, has been studying the development of advanced see-through, see-and-remember and combination technologies for safe landings in DVEs. DARPA’s Sandblaster program, which ran from 2007 to 2009, included Sikorsky Aircraft, Honeywell and Sierra Nevada Corp., involved a series of tests and demonstrations to develop a helicopter pilot performance enhancement systems for landing in DVEs ( Avionics, April 2010, pg. 20). In Sandblaster, Sikorsky integrated its own point-in-space flight control software with a Honeywell SLEEK (Sensor-driven Localized External Evidence Knowledge) terrain database and Sierra Nevada radar. The fixed-azimuth radar could spot obstacles from 1,000 feet slant range to touch-down. The SLEEK processor overlaid return symbology on Digital Terrain Elevation Data from the National Geospatial-Intelligence Agency.
While research on specific DVE coping technology continues, and some related technology being fielded is helping reduce DVE events, aircraft continue to crash “in conditions of degraded visibility due to the pilots inability to discern obstacles, cables or other aircraft during flight or while landing,” according to the Program Overview of DARPA’s second research study on the matter published April 22, 2011. The message is clear: researchers must continue to find ways to enhance the “survivability of rotorcraft” through a multi-sensor solution. They also need to find ways to reduce the size, weight and cost of the sensors and overall system, particularly now with the budget cutting frenzy upon us.
"The military has been dealing with problems of brownout since the first Gulf War in 1991 and Somalia in 1993. Several promising sensor technologies are being developed that could help mitigate brownout accidents, but still nothing has been fielded," said Michael J. Hirschberg, executive director of the American Helicopter Society International. "DoD needs to make this a priority and fund this critical gap appropriately. The cost in lost aircraft alone, not to mention lost lives, would have paid for it many times over."
Sandblaster 2.0
DARPA is beginning the second phase of the Sandblaster research project, called Multifunction RF program, to find ways to reduce DVE-caused accidents. A flight test demonstration program will be conducted in Albuquerque, N.M., at the conclusion of the 18-month program, then full-scale development of the technology. Flight tests are planned for fiscal year 2012, according to the DoD. The goal of the DARPA Multifunction RF Program (MF RF) is to demonstrate a multifunction onboard sensor to perform a variety of tasks that enhance the survivability of rotorcraft and also provide lethality improvements for combat missions. According to the DoD 2012 budget request, the MFRF will look to develop lighter DVE systems and high-frequency multifunction radar systems, and develop and test subsystem technologies for multifunction RF waveforms and arrays.
In this follow-on program, DARPA and partners will try and develop a multifunction sensor able to satisfy numerous tasks to enhance the survivability of rotorcraft. Survivability enhancements should include landing in brownout/whiteout conditions, cable and obstacle avoidance, collision avoidance, terrain following, weather avoidance and ground mapping.
In recent years, DARPA has developed new component technology which may be applied to solving this problem. Silicon technologies have been developed which are operating at frequencies of more than 100 GHz and performing beam forming functions. According to DARPA, this program goes beyond sensor development by requiring “a broad technical approach to demonstrating a multifunctional, software-adaptable system architecture which will also provide for capability expansion in the future without the addition of new hardware.”
Honeywell, for its part, is looking at its role in the original Sandblaster program and refining and adding capabilities to its baseline system separate from the MFRF program.
During the original Sandblaster program, Honeywell performed millimeter wave sensor data integration within a synthetic vision environment to “reduce pilot workload and restore situational awareness lost in a brownout,” said Howard Wiebold, advanced technology sales manager for Honeywell Aerospace.
In some circumstances the sensors would be linked to a low-light TV camera, or millimeter wave radar, which transmits in the 94-gigahertz range. The overall plan is to use several sensors placed strategically on the rotorcraft. The so-called “sensor agnostic” system takes data from all sensors and fuses it to Honeywell’s synthetic vision system (SVS) that was developed initially for business aircraft.
Following Sandblaster, improvements included integration of high-resolution terrain data in the synthetic vision depiction in all phases of flight as well as the ability to depict terrain, including wires. Honeywell said it has invested heavily in advancing DVE technology, including simulated and actual DVE tests at the Army’s Yuma Arizona proving grounds.
“It is likely that any future system will include multiple sensors to provide the pilot with an integrated ‘vision’ of the threat environment, whether that be sand, dust, snow, sleet rain, fog or physical obstacles,” Weibold said.
Additionally, Honeywell is developing an advanced lightweight compact sensor, which is part of a Cable Warning, Obstacle Avoidance System. Data from the DARPA programs is part of Honeywell’s “product road mapping process.” A product for military application could be available within “two to four years,” Wiebold said.
Other companies are also developing technologies for DVE applications. BAE Systems’s Brownout Landing Aid System Technology (BLAST) uses “off-the-shelf” technology to help helicopter pilots see through obscurant conditions. BAE said it tested the system during a two-week campaign in April 2011 at the Yuma Proving Grounds in Arizona. Fitted on a Bell UH-1 “Huey” test-bed helicopter, the system demonstrated real-time 3-D visual landing zone representation with overlaid flight symbology information to a pilot in DVE conditions.
The system, which consists of a forward-looking 94 GHz sensor, an embedded computer with proprietary monopulse radar processing algorithm and synthetic terrain morphing display engine, multi-function displays, landing zone designation switch and tracked helmet mounted display for each pilot, can provide increased situational awareness for the pilot before takeoff, enroute, on approach and during hover and landing, the company said. “The system combines proven millimeter wave technology with advanced situational awareness capabilities, and provides safe-flight capabilities for front-line helicopter crews in diminished visibility conditions such as brownouts, whiteouts, darkness and adverse weather, helping the pilot achieve mission success,” said Paul Cooke, business development director of defense avionics for BAE Systems.
Rockwell Collins is fielding a brownout approach and hover symbology in its Common Avionics Architecture System (CASS)-equipped cockpits and other cockpits, which feature its displays. Those Rockwell Collins-equipped rotorcraft include the Army’s MH-47G Special Operations aircraft, CH-47F Chinook, UH-60M Blackhawk and the U.S. Coast Guard’s MH-60T. This technology grew out of the Brownout Situational Awareness Upgrade Program in the early 2000s that Rockwell Collins performed for the U.S. Army. However, the technology was never fielded. But, shortly thereafter, Rockwell Collins developed CASS. Among the features in CASS is an approach and hover symbology that came out of the brownout upgrade program.
“A combination of CASS cockpits and the automatic flight control system on the CH-47F has saved lives in brownout conditions,” Doug Schoen, manager of cargo utility and attack sales for Rockwell Collins Airborne Solutions said, referring to statements made by customers and Army Aviation officials. While the technology does not deal directly with brownouts, it has been helpful in reducing the number of brownout-related accidents, officials said.
In a related development, Rockwell Collins is transferring its synthetic vision technology developed for fixed wing aircraft to military rotorcraft for use in a tactical environment to improve situational awareness. The company is also working with sensor manufacturers to fuse sensor imagery with synthetic vision, similar in scope to what Honeywell did with DARPA.
Thales’ TopOwl Helmet Mounted Sight & Display system (HMSD) is not a brownout system specifically, but can provide pilots with capabilities to help them in DVE conditions. Its performance provides “level 5,” the visibility equivalent of a cloudy night with no moon, no peripheral light source and no starlight. TopOwl is capable of switching from intensified image projection to high-resolution infrared projection, through a simple click.
Another Approach to Flying in DVE Conditions
The National Research Council Canada Institute for Aerospace Research (NRC Aerospace) has developed a unique automated control system for fly-by-wire (FBW) rotorcraft that could help pilots flying in degraded visual environment (DVE) conditions.
Higher levels of stability augmentation are needed in DVE conditions. NRC Aerospace’s control system reduces the pilot’s workload by automatically balancing the stability of the aircraft with the pilot’s demands for agility and counter balancing the controls that stabilize the aircraft. The system also reduces the pilot’s tendency to “over- maneuver” the aircraft. In bad visibility, the pilot’s inputs are naturally more tentative and the aircraft responses are more stable and deliberate. In good conditions, by moving the controls more aggressively, the pilot gets a lower level of stability augmentation and can operate the aircraft more aggressively.
In effect, the control system acts as an independent controller of multiple input modes. NRC’s system blends rotorcraft control response types so that the frequency of the pilot’s input determines the control response type applied. Such an approach allows the pilot to operate the aircraft more safely in any weather.
In scientific parlance, the optimum scenario for a rotorcraft in a degraded environment is where “the speed is one integration away from the attitude, which is one integration away from the angular rate,” said Stewart Baillie, director of the NRC Aerospace Flight Research Laboratory.
In good conditions, the pilot is able to predict the outcome of the three integrations and keep the aircraft position stable. In poor visibility, this is much more difficult, “so we stabilize by raising his input from rate control to attitude or velocity control, thus reducing the number of integrations the pilot must estimate to stabilize the aircraft,” Baillie said.
The initial research that led to the eventual development of the automatic control system occurred in the 1980s when NRC Aerospace worked with the U.S. Army on helicopter design requirements. The research took on more importance in the 1990s because of incidents and accidents of military rotorcraft that involved pilots wearing night vision goggles during operations in degraded environments.
Baillie said NRC Aerospace is seeking application partners for its control system with various OEMs. NRC Aerospace has held “preliminary discussions” with OEMs, but “nothing firm on how to exploit this new technology,” he said.
Until that occurs, NRC Aerospace will continue to demonstrate the capabilities of this new unique control technology for FBW rotorcraft manufacturers and operators using its Bell 412 research aircraft equipped with an experimental FBW system.
The Bell Boeing V-22 tilt-rotor, Sikorsky S-92 and the NHIndustries NH-90 are FBW rotorcraft in production that could benefit from the NRC Aerospace control system. But rotorcraft manufacturers and civil and military operators might be reluctant to invest in new technology that, for now, could have limited applications. Fuel savings and safety benefits from FBW could outweigh those concerns over time, Baillie said. Robert Moorman
militaryPhoto courtesy HoneywellPhoto courtesy National Research Council Canada Institute for Aerospace ResearchThe fly-by-wire system was tested at the NRC Flight Research Lab in Ottawa, Ontario, using the institute’s Bell 412 Advanced Systems Research Aircraft.