Northrop Grumman describes the architecture of its F-5 avionics upgrade as a pyramid, the broad base of which is formed by a 1553B databus. Layer after layer of modular modernisation can then be built on this digital foundation, depending on the mission requirements and money available.
The first and second stages of the upgrade incorporate several major building blocks: a Westinghouse APG-66 radar; a Honeywell inertial-navigation system, display processor and multi-function display (MFD); GEC Marconi head-up-display (HUD); and an AlliedSignal Controls and Accessories standard air-data computer. An airborne video tape recorder made by TEAC America and a Teledyne Systems airborne video camera will accompany the HUD. Navcom Defense Electronics is also supplying a radar altimeter.
Level three builds in Mason Electrice hands-on-throttle-and-stick controls and an AlliedSignal mission computer. Attack capability is enhanced with an advanced weapon-delivery system, based on a Base 10 Systems stores-management system and an armament-control unit built by Moog Esprit Technology. Level four adds a Rockwell-Collins digital tactical air-navigation UHF system, a Fairchild Defense data-transfer system, and a new instrument panel. A Honeywell liquid-crystal-display MFD will replace a standard cathode-ray-tube-based display in early 1996.
Rising towards the peak of the pyramid, the focus is on advanced radar-warning capability, electronic countermeasures, global-positioning-system navigation, secure communications, forward-looking infrared (FLIR) and a laser target-designator system.
The complex software integration task has been handled, by a specially developed laboratory, at Northrop Grumman's El Segundo plant, near Los Angeles International Airport. "We're using the actual hardware that will fly on the aircraft, to make sure the software is totally integrated," says F-5/T-38 avionics project engineer Aziz Soltani. "We're in the process of refining the flight test software load now and more testing of the systems will follow when the flying begins," he adds.
Structural changes were also required to package the new avionics in the F-5's needle nose. To improve the multi-mode performance of the radar, a bulkhead was moved back by 500mm and the radome extended aft, says Tom Cooke, of F-5 project engineering. The large antenna made possible by the enlarged radome area, improves the range of the APG-66 to more than 65km (35nm).
The enhanced avionics and the space constraints of the F-5's small front fuselage mean that the right-hand M39A2 20mm cannon has had to be removed. For flight testing, the space normally taken up by the left-hand gun is used to house flight-test recorders. Soltani explains: "We'll have a three-deck TEAC recording system in its place which will be recording the performance of the MFD and the HUD. A separate HUD camera will be standard." Cooke adds that another tape will record the activity of the 1553 bus for post-flight analysis.
The US Navy F-5 has been gutted to accommodate the upgrade, which will also include a Litton Systems on-board oxygen-generating system and a Martin-Baker Mk 10 lightweight ejection seat. "The aircraft will be reverted to US Navy service after the CRDA, so it has been very carefully dismantled," says project engineer Bob Spatz. Pre-flight checks will be completed by early March, with a first flight due in April at Los Angeles International Airport, he says.
The F-5 will be flown to Edwards AFB in California, its base for the USAF-managed flight tests. Both USAF and USN pilots will fly the aircraft in mock-combat missions against opponents, as well as performing discrete system tests. Trials are expected to last about a year, but could last longer if more tests are added, says Murphy. "We're proposing additional tests with different FLIRs and air-to-air and air-to-ground missiles. For example, the Matra Mica [missile] will make a good match with the Westinghouse radar. We may also test a Thomson [-CSF] laser pod."
As with many current defence strategies, the F-5 CRDA is undoubtedly aimed at making the most out of existing resources. The Northrop F-5 remains one of the classic examples of this and, a full 40 years on from when Northrop originally started the design, yet another chapter in the history of this versatile veteran is about to begin.
Source: Flight International
