Raytheon has successfully completed a demonstration of its advanced distributed aperture system (ADAS) and is looking forward to further development of what it believes to be highly promising technology, as it stitches together images from several sensors to provide spherical coverage around the aircraft.

The ADAS is generating solid interest from the U.S. military that could lead to a formal request for information from Special Operations Command early next year. Along with other industrial players, Raytheon is also taking part in a major NATO study that is tackling the subject of helicopter operations in degraded visual environments.

Raytheon’s ADAS is being focused on the rotary-wing world, where this technology offers great benefits in terms of flight safety. The ADAS provides helicopter crews with a significant tool to avoid collisions with terrain or obstacles in degraded visual conditions. The system can be integrated with other technologies, such as terrain matching and radar imaging, to enhance safety further, and in itself offers additional functionality.

The ADAS comprises six sensor groups distributed around the airframe, each with a 93- by 93-degree field of view to give spherical coverage and large (2048 by 2048) focal plane arrays. Sensors comprise cooled high-resolution mid-wave and near-infrared units that are matched pixel-by-pixel. Operators can choose either MWIR or NIR imagery, or a fused image that enhances the image by drawing on the benefits of both systems. MWIR is particularly good in very dark conditions in which traditional night-vision systems typically struggle, whereas near-IR is good in conditions when manmade light is prevalent. Local area processing provides significant image enhancement.

Imagery from the ADAS is presented on a helmet-mounted display with fully overlapped binocular 30- by 40-degree field of view. Raytheon is using a BAE Systems helmet similar to the Striker developed for the Typhoon fighter, which has highly accurate head-tracking capability. Using the Striker, the ADAS has demonstrated visual latency of less than 50 milliseconds: any greater delay can result in some disorientation for pilots. Raytheon has also incorporated active noise reduction ear-cups into the helmets, as well as 3-D audio, for greater comfort and enhanced directional awareness.

During demonstrations held earlier this year Raytheon used a U.S. Army UH-60 Black Hawk fitted with the ADAS system, supporting three helmet-mounted displays. The combination of helmet and the ADAS allows crewmembers to see everything around the helicopter, effectively allowing them to see through the aircraft’s skin in any direction. Each crewmember can use the system independently. For pilots, the system has obvious benefits in terms of navigation and low-level flight safety, but it also enhances the ability of other crewmembers to perform obstacle-clearance observation and aid them in gun firing.

With space and weight at a premium in many helicopters, the ability of systems to multi-task is appreciated. The ADAS offers a number of other functionalities, including hostile fire indication (HFI) and infrared search and track (IRST). For HFI the system uses the MWIR to detect, classify and locate hostile small arms fire, anti-aircraft artillery and rocket-propelled grenade launches. Warning of man-portable surface-to-air missile launches is also provided. Alerts can be provided in the helmet display and through directional audio, with cues to the threat position and time-to-impact predictions. These, in turn, allow appropriate countermeasures to be employed or fire to be returned. In the IRST function the system can passively track up to 128 aerial targets.

Tackling DVE

The ADAS is one of several technologies that can be fused together to enhance safety in degraded visual environment (DVE) conditions, which include not only the well-known “brown-out” conditions of dust kicked up in rotor downwash, but also “white-out” (blown snow), fog and low light. Symbology of known terrain and obstacles (derived from digital terrain elevation data) can be superimposed on the ADAS imagery to provide enhanced situational awareness in DVE. The system allows aircrew to designate a landing zone prior to takeoff or in flight, the helmet display showing symbology that allows them to fly safely through DVE to the landing point.

Following the successful demonstration this year Raytheon is working on a hardened military specification system. Further flight trials are to be undertaken in October in the “sandbox” at the Yuma Proving Grounds in Arizona as part of the U.S. Army’s Deep (degraded environment enhanced pilotage) program. Work also continues on reducing Swap (size, weight, aperture, power) requirements, and the design of A-kit equipment for UH-60 and CH-47 helicopters.