Guided Bomb Unit-24 (GBU-24)
Paveway III

The Guided Bomb Unit-24 (GBU-24) Low Level Laser Guided Bomb [LLLGB] consists of either a 2,000-pound MK-84 general purpose or BLU-109 penetrator bomb modified with a Paveway III low-level laser-guided bomb kit to add the proportional guidance in place of the bang-bang type used in the Paveway II. The GBU-24/B was originally designed to be installed on the MK-84 General Purpose Bomb. In 1985 with the availability of the BLU-109/B Penetrator bomb the Paveway III was made to adapt it and thus was re-designated GBU-24A/B.

The GBU-24B/B (PAVEWAY III) is a converted BLU-109A/B 2000 pound class bomb designated as a hard target penetrator (HTP). The associated components required for conversion are fuze, airfoil group, FZU generator, adapter group, and guidance control unit. The heavy walled case of the bomb provides the penetration capability of 4 to 6 feet of reinforced concrete. The GBU-24B/B has a thermal protective coating applied to the surface to extend the cook-off time. The GBU-24B/B must not be missing more than 20 square inches of thermal coating in a single area or more than 40 square inches total.

The LLLGB was developed in response to sophisticated enemy air defenses, poor visibility, and to counter limitations in low ceilings. The weapon is designed for low altitude delivery and with a capability for improved standoff ranges to reduce exposure. The GBU-24 LLLGB/Paveway III has low-level, standoff capability of more than 10 nautical miles. Performance envelopes for all modes of delivery are improved because the larger wings of the GBU-24 increases maneuverability. Paveway III also has increased seeker sensitivity and a larger field of regard.

The operator illuminates a target with a laser designator and then the munition guides to a spot of laser energy reflected from the target. One way to deliver LGBs from low altitude is a loft attack. In this maneuver, the aircraft pulls up sharply at a predetermined point some miles from the target and the LGB is lofted upward and toward the target. However, if the LGB guidance system detects reflected laser energy from the target designator too soon after release, it tends to pull the LGW down below its required trajectory and the bomb will impact well short of the target.

This bomb is not nearly as delivery parameter sensitive as is the Paveway II LGB, nor is it affected by early laser designation. After a proper low altitude delivery, the LLLGB will maintain level flight while looking for reflected laser energy. If it does not detect reflected laser energy, it will maintain level flight to continue beyond the designated target, overflying friendly positions, to impact long, rather than short of the target.

Although the Paveway II kits slightly increased the cone-shaped volume or "basket" over the target into which an LGB had to be dropped by the releasing aircraft for the bomb to "see" the laser illumination, the Paveway III low-level laser-guided bomb (LLLGB) expanded release baskets many-fold by adding an autopilot that would enable the bomb to fly itself into the basket.

Unlike the Paveway II LGB, the LLLGB can correct for relatively large deviations from planned release parameters in the primary delivery mode (low-altitude level delivery). It also has a larger delivery envelope for the dive, glide and loft modes than does the earlier LGB. The wide field of view and midcourse guidance modes programmed in the LLLGB allow for a "Point Shoot" delivery capability. This capability allows the pilot to attack the target by pointing the aircraft at the target and releasing the weapon after obtaining appropriate sight indications. The primary advantage of this capability is that accurate dive/tracking is not required to solve wind drift problems.

In the Gulf War all of the 1,181 GBU-24s were released by F-111Fs.

In 1996 the Navy conducted tests of the F-14A Tomcat with the GBU-24B/B Hard Target Penetrator Laser-Guided Bomb at Naval Air Station Patuxent River, Md., as part of an air-to-ground development program to support clearance for use of the weapon in the fleet by F-14 Tomcats.

Key accomplishments in 1996 included demonstration of controlled weapon penetration and detonation depth using the Hard-Target Smart Fuse [HTSF] and successful integration of the GBU- 24/ HTSF with F-15E and F/A- 18 aircraft. The Hard-Target Smart Fuse, developed at the Wright lab, features an accelerometer that can be programmed to detonate the bomb at a precisely specified depth significantly enhancing munition lethality. The Defense Special Weapons Agency (DSWA) Counterproliferation Initiative (CPI) requires development, integration and certification of HTSF with GBU-24 B/B (Navy BLU-109) and GBU-24 D/B (Navy BLU-116) under this effort. Under a separate effort, CPI will integrate the GBU-24 B/B and GBU-24 D/B configuration HTSFs into the CPI modified Conventional Air Launched Cruise Missile (CALCM) and Tactical Land Attack Missile (TLAM) weapons.

The Multi-Segment Hard Target Penetrator (MSHTP) concept has been designed to use the penetration capability of a BLU-113 or BLU-109 linked to the void counting hard target smart fuse. This weapon detonates a copper cutter charge upon entering the target and cuts the rear portion of the bomb off, which then detonates. The rest of the weapon continues down to the next level.

GBU-24E/B, an Enhanced Paveway Laser Guided Bomb, is a precision-guided hardened target penetrator used to destroy hardened aircraft hangers and underground bunkers. It integrates a Global Positioning System and a ring laser gyro inertial measuring unit (IMU) to the already fielded GBU-24B/B "Paveway III" with the existing laser guidance. A new guidance and control unit has been modified to incorporate GPS electronics, GPS antenna, IMU and software for precision GPS/INS guidance. Testing of this system began in late 1999.

References

• HARD TARGET SMART FUZE - DRAFT STATEMENT OF OBJECTIVES - 30 April 1998
• HARD TARGET SMART FUZE - PLANNING INTEGRATED MASTER PLAN - 30 April 1998
• Initial test flights of GBU-24E/B prove successful at Point Mugu 14 October 1999 -- GBU-24E/B, an Enhanced Paveway Laser Guided Bomb, was tested in late September at NAWCWD Point Mugu to verify the ability of the aircraft to provide uninterrupted power and GPS signals to the bomb.