INTERNATIONAL INTEREST in the US Joint Direct Attack Munition (JDAM) is growing as flight testing continues to demonstrate an accuracy better than the 13m (40ft) requirement. McDonnell Douglas (MDC) has already proposed the JDAM to at least one foreign country.
JDAMs have been dropped from the Lockheed Martin F-16, MDC F-18 and Northrop Grumman B-2, and accuracy achieved is averaging just over 10m. The weapon uses a global-positioning/inertial-navigation (GPS/INS) guidance tailkit fitted to conventional 450kg and 900kg bombs. Later versions of the JDAM could have a terminal seeker providing 3m accuracy.
Flight-testing started at Eglin AFB, Florida, in October 1996, and has included an early operational assessment of the weapon by the US Air Force. The integrated system experiment (ISE) earlier this year involved the release of 22 weapons on six missions by an operational F-16 unit based at Nellis AFB, Nevada, says Charlie Dillow, MDC's JDAM programme manager.
Tailkits were delivered to the unit, to be built up, tested, loaded on to the F-16s and dropped on targets on the US Navy's China Lake, California, weapons range. The accuracy achieved was "about 10m", says Dillow.
EARLY EXPERIENCE
Oscar Soler, USAFJDAM programme director, says that the ISE provided "-an early look at how the weapon behaves". Normal operational testing comes later in the programme, when a large number of weapons will be dropped and by which time it will be costly to make design changes. The ISE provided an opportunity to make changes, if required, earlier in the programme, and more cheaply, he says.
The ISE was timed to support an April decision on low-rate initial production (LRIP) - which comes much earlier in the programme than usual because of the compressed JDAM-development schedule. The LRIP decision precedes operational testing by several months, so the ISE was conducted to provide "-an operational flavour to go into LRIP", Dillow says.
The Nellis trial was designed to show that operational units could build up the weapon, test it and load it within the times set by the requirement. By the time of the ISE, only eight drops had been accomplished in risk-reduction flight-testing at Eglin, but the "extremely good" hardware and software reliability demonstrated had built confidence in the weapon, says Dillow.
Soler says that the emphasis on demonstrating producibility, within the JDAM engineering- and manufacturing-development effort, resulted in "-a better confidence level than in a normal programme".
The final two missions at Nellis involved live JDAMs, demonstrating an "end-to-end" capability from weapon build-up to target destruction, says Dillow. One mission provided an unplanned opportunity to test the JDAM's all-weather capability, when cloud cover at 600-800ft, snow on the ground, and rain totally obscured the targets. The weapons were released from 25,000ft "-and flew right to the targets", he says, describing the mission as a "spectacular success."
Target co-ordinates are programmed into the JDAM before take-off, and can be changed during flight. The pilot can choose between 10degree and 30 degree impact angles and air or ground fuzing during mission planning. The flightpath to the target can also be programmed in, says Dillow, enabling the weapon to fly round to attack a building from the side, for example. In flight, a continuously computed launch-acceptability region is displayed in to the pilot. This indicates the envelope within which the weapon must be released to hit its pre-programmed target.
The majority of releases to date has been from the F-16, but tests began on the F-18 in February and on the B-2 in March. Soler says that an average of about 70 drops will be conducted from each aircraft type during development and operational testing. Initial testing is focused on the baseline 900kg weapon, with both Mk84 blast-fragmentation and BLU-109 target-penetrator warheads.
Development of the 450kg JDAM is scheduled to begin in mid-1997, and will trail that of the 900kg weapon by about a year. An LRIP decision is scheduled for April 1998, says Soler. The 450kg weapon will use the same GPS/INS-guidance system, repackaged into a smaller tailkit, says Dillow. The only aircraft planned to use the 450kg JDAM is the Lockheed Martin/ Boeing F-22, which requires a smaller bomb to Ìt inside its internal weapons-bays. The F-16 will be used as an F-22 "surrogate" for development testing, with operational testing on the F-22 to begin around the year 2000.
PRODUCTION BUILD-UP
Current plans call for production of 87,500 JDAMs over ten years for the US Air Force and Navy, at an average cost per tailkit of $18,000,says Dillow. Some 650 units are being produced during the development phase, with the rate reaching just over 30 a month. "We are now certain that we will meet the cost targets established," he says. LRIP covers an additional 937 units, with production building up to 100 a month. Full-rate production will see tailkit output rise above 250 units a month, he says.
Funding for a product-improvement programme to increase JDAM accuracy to 3m was eliminated in 1996 by the Air Force, but the operational requirement has been postponed, not removed, says Soler. A decision on the improved JDAM has been delayed from 1999 to 2002, while the team studies the scope and cost of a programme to increase the weapon's accuracy. "We will have to look at what's needed," he says, adding: "The most promising possibility is a seeker, but what kind, and whether to go ahead, will be decided in 2002."
Source: Flight International
