Graham Warwick/FORT WORTH and Guy Norris/EDWARDS AFB

FIGHTER PILOTS use "check six" as slang for a look back to ensure that the enemy is not approaching from behind. It is also the motto of the Lockheed Martin F-16A/B mid-life update (MLU) programme - signifying a look back to ensure the aircraft is not being overtaken by the threat.

The MLU is the first major upgrade of the original F-16A/B Fighting Falcon since it entered service in 1979-80 with the air forces of the USA and four European countries. Of 617 F-16A/Bs delivered to Belgium, Denmark, the Netherlands and Norway, about half will be upgraded - 48 Belgian, 61 Danish, 136 Dutch and 56 Norwegian aircraft - to maintain their operational effectiveness to 2020

For Lockheed Martin, the MLU is a vital piece of its plan to keep the F-16 in production into the next century. Elements of the MLU have been selected for new F-16A/Bs being built for Taiwan, and for advanced "Block 60" F-16C/Ds being offered to the United Arab Emirates. The US Air Force is evaluating computer and display technology developed for the MLU for use in new and upgraded F-16s.

For Europe, the MLU gives the F-16A/B beyond-visual-range air-to-air capability; paves the way for the introduction of new sensors and smart weapons; makes the aircraft inter-operable with the USAF's latest Block 50 F-16C/Ds; and extends the successful industrial co-operation begun when the aircraft were originally purchased. Offset work totalling 80% of the $1 billion MLU programme value will be placed in the four countries.


Pan-European upgrading

The initial phase of operational testing has been completed at Leeuwarden AB in the Netherlands. This involved five upgraded F-16s - three trial-verification installation (TVI) and two lead-the-fleet (LTF) aircraft. Lockheed Martin modified five TVI F-16s to prove the kit installation. The US and Danish aircraft were flown to Edwards AFB, California, in mid-1995 for development testing, while the Belgian, Dutch and Norwegian TVI F-16s were flown to Leeuwarden earlier this year, to be joined by four LTF aircraft - one upgraded at each of the European F-16 depots, using kits supplied by Lockheed Martin.

Between them, the TVI and LTF aircraft cover the F-16 configurations which the depots will encounter during installation of the 305 production kits. The four European air forces operate a mix of Block 10A/B and 15A/B single- and two-seaters, and there are national differences between the aircraft - such as the unique electronic-warfare system on Belgian F-16s.

LTF aircraft upgraded at Denmark's Aalborg depot and at Fokker in the Netherlands have already been flown, and aircraft modified by SABCA in Belgium and Norway's Kjeller depot are ready to be flown.


Radar performance

Operational testing in Europe is scheduled to resume early in 1997 with seven aircraft. Initial testing at Leeuwarden focused on evaluating radar performance in the European environment. The upgraded Northrop Grumman (formerly Westinghouse) APG-66(V2) radar underwent development testing in the USA, and the air forces needed to know to what degree radar performance would degrade in Europe's more cluttered environment. The degradation was less than expected, says Lockheed Martin.

"The European air forces were pleased - surprised - that degradation of the radar in clutter was not as much as expected, or was experienced with the [original] APG-66," says MLU programme director Dave Wesolka. Testing primarily focused on air-to-air modes, and on low-altitude look-up and high-altitude look-down performance over terrain of varying clutter. Northrop Grumman says that detection ranges, false-alarm rates, automatic-acquisition and tracking performance "significantly exceeded specified levels".

When testing resumes at Leeuwarden, it will concentrate on developing operational tactics, using the upgraded radar and avionics. Development testing, meanwhile, is continuing in the USA. MLU capabilities are being developed and tested in phases corresponding with the release of software updates, or tapes. Initial European testing was conducted using Tape 2, which provides interim functionality, while testing of Tape 3, which provides the full MLU capability, is about to begin at Edwards.

According to Charlie Clark, USAF project engineer at Edwards, the initial software release, Tape 1, allowed testing of the radar and Texas Instruments modular mission-computer (MMC) to get under way. Tape 2 added weapons-delivery capability and integrated the Rockwell MAGR global-positioning-system receiver into the navigation system. Tape 2 development testing, completed in August, was an important phase because it involved integration of the radar and MMC with the AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM) - "the biggest challenge", says Greg Bice, Lockheed Martin programme manager at Edwards.

"There's new hardware and software for the MMC and radar, and the AMRAAM is now an integral part of the system, so it's been a challenge to get that all working together," he says. The first bombs were dropped from MLU F-16s in May. "It could have been a problem, but it was a good result," says Clark. Live AMRAAM firings are to begin around May 1997.

Tape 3 introduces the balance of MLU capabilities - Honeywell colour multi-function displays; intra-flight datalink using the Symmetrics improved data-modem (IDM); British Aerospace digital-terrain-system (DTS) software; Hazeltine APX-113 advanced identification friend-or-foe (AIFF); and provisions for a reconnaissance pod, forward-looking infra-red (FLIR) navigation pod and, for Norwegian F-16s, Penguin anti-ship missiles.

Tape 3 was released to Edwards ahead of schedule, says Wesolka. The two TVI aircraft there have been equipped with colour displays and the latest version of the MMC - development of which is running behind that of other MLU systems. The mission computer is being developed in stages, called passes, corresponding to increasingly advanced hardware. The Edwards F-16s now have the definitive Pass 3 hardware, which should be installed in the Leeuwarden-based operational-test aircraft by February 1997.


Growing pains

"We've gone through some growing pains with development of the MMC, but the latest hardware we've been flying with has proved far more reliable," Clark says. "So far as software and hardware are concerned, we've taken great strides in reliability. Considering we're dealing with a new radar and other hardware, we're pursuing an aggressive schedule."

LTF aircraft are being delivered with Pass 2 hardware and Tape 2 software, but, early in 1997, they will be upgraded to Pass 3/Tape 3 enabling the full MLU configuration to be evaluated operationally. A Tape 4 "clean-up" update, scheduled for April 1997, will take the software to the final production standard.

Lockheed Martin delivered the first five production MLU kits on 29 October. Norway's Kjeller depot has already inducted the first aircraft to be upgraded in the production phase, and the other three European nations will follow suit in January, says Wesolka.

Modification is expected to take five months per aircraft. Delivery of production kits will be completed by mid-1999, except for those to Belgium, which will stretch into the year 2000.

Pilots flying the upgraded F-16A/B will notice a marked difference in the cockpit, which is modelled on that of the current production-standard Block 50 F-16C/D, but which goes a step further with the introduction of colour displays. "The difference [between Block 15 and 50] is like night and day," says Clark. "It's like going from a 1950s' Chevy to a current Cadillac with all the bells and whistles. Stores management is also night and day. It's menu-driven-so it's much more friendly."

Cockpit changes include installing the GEC-Marconi wide-angle head-up display (HUD), with up-front control panel, and Lear Astronics sidestick controller from the Block 50 F-16. The HUD can project imagery from a FLIR pod, which can be mounted on intake hardpoints installed a part of the MLU. The Block 50 sidestick and throttle allow hands-on management of displays, sensors and electronic countermeasures.

The biggest change is the installation of two 100mm-square colour multi-function displays - the first use of liquid-crystal displays in any US fighter. They promise to be more reliable than the monochrome, head-down displays in the Block 50 F-16, and use of colour on the right-hand horizontal-situation display will improve pilot situational-awareness, Lockheed Martin says. While radar information on the left-hand display will be monochrome initially, the APG-66(V)2 has colour capability.

Cockpit displays, instruments, controls and lighting are compatible with night-vision goggles for the first time in the F-16A/B. Provision is made for a helmet-mounted display, and a Honeywell/GEC prototype is under test, but it is not included in the baseline MLU. Other cockpit changes include installation of the electronic-warfare management system developed for the F-16 by Denmark's Terma Elektronik.


Room for growth

The most significant avionics upgrades are to the mission computer and radar. The MMC replaces three systems, the fire-control and stores-management computers and HUD-electronics unit, using technology under development for the Lockheed Martin/Boeing F-22 - line-replaceable modules which plug into the MMC cabinet. Only half the MMC's throughput and memory are being used, says Lockheed Martin, allowing for growth.

Upgrading the radar involves modification of four line-replaceable units and installation of a new signal data processor, and improves detection and tracking range by 25%, reduces false alarms and adds new modes. Air-to-air modes include track-while-scan of up to ten targets, and simultaneous engagement of up to six with fire-and-forget AMRAAMs. Air-to-ground modes include Doppler-beam-sharpened ground imaging.

The radar is performing well, says Lockheed Martin. "We've tested tracking, accuracy performance and target detection. We've also tested it for air-to-air and air-to-ground and it's much improved over the older -66 models, particularly in track-while-scan mode," says Clark. Testing of the terrain-following mode will be performed in Europe, "...where they'll look closely at the false-alarm rate because of the more severe electromagnetic-interference effects there", he says.

Completing the MLU avionics changes are the AIFF combined interrogator/transponder, already installed on Greek F-16C/Ds; the global-positioning system, which improves navigation accuracy to within 100m; the IDM, enabling a flight of up to four aircraft to exchange and display target data; and the DTS, which provides terrain-referenced navigation, ground collision-avoidance, database terrain-following, passive ranging and obstacle warning.

Testing of the MLU F-16s at Edwards is integrated with that of F-16A/Bs for Taiwan and F-16C/Ds for the USAF - tasks performed on one programme read across to the others. The Europeans are also part of the combined test team. "It's been a big help to have European test pilots here. They see problems differently and it's been a real benefit to have a different perspective," says Clark.

Source: Flight International