Saab 2000 AEW&C prepares for duty

 - July 3, 2008, 4:57 AM

On April 30, Saab achieved a significant milestone with the first flight of the Saab 2000 Erieye airborne early warning and control (AEW&C) aircraft, developed under Project Horizon for the Pakistan air force. The two-hour flight from Linköping, Sweden, was used to check out general handling and aircraft systems, and encountered no problems. The maiden flight came a month after the aircraft was officially rolled out in front of Pakistani commanders.

Pakistan first contemplated the acquisition of an AEW system in the early 1980s, when Soviet and Afghan air force aircraft regularly intruded into Pakistani airspace. Other priorities, and the later U.S. arms embargo, meant that the requirement went unfulfilled. However, events in the wake of the 9/11 terrorist attacks–plus ongoing tensions with India–placed renewed emphasis on the AEW requirement.

Pakistan selected the Erieye in 2005 and later revised the initial requirement for six platforms to five as a cost-reduction measure. It is buying a complete surveillance package, including ground-based systems, logistics support and mission training systems.

The Saab 2000 AEW&C is the latest iteration of the Saab Microwave Systems Erieye concept. The five-operator system has increased command and control capabilities, including the Swedish Link-E system.

The radar itself, which consists of 192 transmit/receive modules, has been improved with an extended early warning mode and the ability to spot hovering helicopters. Coverage has been increased to two 150-degree sectors (from 120-degrees, still with a 1-degree beamwidth), with range out to the horizon (typically 199 to 217 miles). The radar offers a fully fused air/sea capability, and can spot maritime targets as small as jet-skis.

Virtually all of the radar components have been replaced since the Erieye was first fielded in 1996, and all of the computer systems are COTS-based for cost-effective and rapid upgrade. Power output is around 20 percent greater than it was previously, although power requirements, and thus cooling, for the mission system have decreased by 30 percent. The effects of improvement can also be seen in a 53-percent reduction in system weight and 78-percent reduction in floor space. At the same time, computing power has increased a hundredfold.

Backing up the radar is a sophisticated Saab Avitronics HES-21 ESM/protection suite that uses interferometer antennas and digital receivers for highly accurate tracking and ranging of emitters. HES-21 data is fused with that from the radar to provide detailed tracking, and it can generate its own tracks at ranges greater than that possible with the radar. The system also includes a comprehensive self-protection function, automatically controlling the launch of chaff and flares.

Commuter on Patrol
The choice of basing Erieye on a regional airliner has obvious benefits in terms of high reliability, cost-efficiency and low maintenance requirements, but also offers significant mission benefits. The type’s hot-and-high performance is critical in the Pakistani operational environment. The aircraft has a balanced field length of 4,593 feet, allowing it to use many small airports, and it can reach 25,000 feet in 16 minutes.

Mission endurance is nine to 10 hours thanks to extra tanks in the cabin, and it can operate at up to 30,000 feet. At cruise power, the aircraft flies at about 340 knots, impressive for a turboprop. Using a 60-degree bank, the aircraft can complete a 180-degree turn at the end of a racetrack pattern in less than 30 seconds, with little interruption in track coverage.

Crew comfort is a consideration for long-endurance patrols, and through its active noise cancellation system, the Saab 2000 offers very low cabin noise levels. A 7,500-foot cabin pressure can be maintained at operational altitude. The Pakistani aircraft have a galley and rest area, with a mission display in the latter so that resting crew can stay informed of emerging situations. The flight deck is a very modern airliner-style working environment, with a six-tube Collins ProLine 4 electronic flight information system.

Erieye Conversions
Saab Aerotech performs conversions in its facilities at Linköping. For the first aircraft, the work took less than a year to complete. The conversion comprises several airframe structural modifications, including strengthening the upper rear fuselage to mount the Erieye radar.

The sensor is mounted higher than on the Saab 340 so it can “see” over the longer wings of the Saab 2000. The vertical fin is enlarged and strengthened to offset the aerodynamic effects of the radar and its support struts, while the wingtips are rebuilt and reinforced to carry antennas and chaff dispensers. The belly fairing is reworked and enlarged to mount elements of the self-protection system.

Although the aircraft are pre-owned, structural life is not a factor. The airliner was designed with an initial structural life of 75,000 hours, and on average, the fleet has used less than 20 percent. Based on typical use rates, the remaining life of the AEW&C is more than 35 years, with options for further re-lifing. Modification work on the second aircraft was already under way at the time of the rollout.