EDWARDS AIR FORCE BASE, Calif -- About 0930L, a call came in to Edwards Air Force Base: Pilots flying combat missions over Iraq in Block 30 F-16s had a problem adversely affecting their ability to drop GBU-31 Joint Direct Attack Munitions (JDAMs). Source of the problem was a glitch in a new software load (SCU-5E1), which the Center’s 416th Flight Test Squadron (416 FLTS) had been testing for some time. The Ogden Air Logistics Center quickly identified a solution to the software problem and sent the software to the 416th electronically by 1230L. The new software was installed in a test aircraft (s/n 1120); the aircraft then conducted a successful test mission at the China Lake Naval Weapons Station—including two, single JDAM releases. The next day, 22 March, an aircraft from the Air National Guard (ANG), Air Force Reserve Test Center in Tucson, AZ, paired up with the 416 FLTS aircraft to conduct a combined developmental and operational test with the JDAMs on the Edwards PIRA, PB-10. All JDAM releases were good. With the software again working correctly, it was released back to the warfighter.
The Joint Direct Attack Munition (JDAM) GBU-31 is a tailkit under development to meet both USAF and Navy needs, with the Air Force as the lead service. The program will produce a weapon with high accuracy, all-weather, autonomous, conventional bombing capability. JDAM will upgrade the existing inventory of general purpose and penetrator unitary bombs, and a product improvement may add a terminal seeker to improve accuracy. JDAM can be launched from approximately 15 miles from the target and each is independently targeted. JDAM is not intended to replace any existing weapon system; rather, it is to provide accurate delivery of general purpose bombs in adverse weather conditions. The JDAM will upgrade the existing inventory of Mk-83 1,000- and Mk-84 2,000-pound general purpose unitary bombs and the 2,000-pound hard target penetrator bomb by integrating a guidance kit consisting of an inertial navigation system/global positioning system guidance kit. The 1,000-pound variant of JDAM is designated the GBU-32, and the 2,000-pound version of the JDAM is designated the GBU-31. JDAM variants for the Mk-80 250-pound and Mk-81 500-pound bombs are designated GBU-29 and GBU-30, respectively. Hard Target penetrators being changed into low-cost JDAMs included the 2,000 pound BLU-109 and 1,000 pound BLU-110.
Mission plans are loaded to the host aircraft prior to take off and include release envelope, target coordinates and weapon terminal parameters. The weapon automatically begins its initialization process during captive carry when power is applied by the aircraft. The weapon performs bit, and aligns its INS with the host aircraft's system. Targeting data is automatically down loaded to the weapon from the host aircraft. When the host aircraft reaches the release point within the Launch Acceptable Region (LAR), the weapon is released. Weapon maneuverability and range are enhanced by fixed aerodynamic surfaces (mid-body strakes) attached to the bomb body. Once released, the bomb's INS/GPS will take over and guide the bomb to its target regardless of weather. Guidance is accomplished via the tight coupling of an accurate Global Positioning System (GPS) with a 3-axis Inertial Navigation System (INS). The Guidance Control Unit (GCU) provides accurate guidance in both GPS-aided INS modes of operation (13 meter (m) Circular Error Probable (CEP)) and INS-only modes of operation (30 m CEP). INS only is defined as GPS quality hand-off from the aircraft with GPS unavailable to the weapon (e.g. GPS jammed). In the event JDAM is unable to receive GPS signals after launch for any reason, jamming or otherwise, the INS will provide rate and acceleration measurements which the weapon software will develop into a navigation solution. The Guidance Control Unit provides accurate guidance in both GPS-aided INS modes of operation and INS-only modes of operation. This inherent JDAM capability will counter the threat from near-term technological advances in GPS jamming.