MGWS stands for Modular Guided Weapons System. The Boeing GBU-15 started life in 1974 as a solution to the requirement for stand-off precision guided bomb. It had been carried on the F-15E during Phase test and evaluation in March 1988. Depending on specific mission requirements the GBU-15 MGWS can be used with either electro-optical ( EO) or infrared ( IR) guidance systems, and with either blast-fragmentation or penetrating warheads. It combines either an Electro Optical, DSU-27A/B, seeker head, or one of two IR seeker heads - the WGU-33/B, which offers correlation tracking; and the WGU-10/B which is limited to centroid tracking only. All three can be mated to a BLU-109 or Mk-84 bomb body.

Several basic variations are used; the GBU-15S has a short chord wing and is designated GBU-15(V)31/B when attached to an IR seeker, or GBU-15(V)32/B with the EO head. The GBU-15L features a long chord wing and comprises the GBU-15(V)1/B, 1A/B and 1B/B when fitted with the EO seeker head; or GBU-15(V)2/B, 2A/B and 2B/B when fitted with either IR seeker.

The F-15E can carry up to two GBU-15s on weapons stations STA-2 and STA-8. If the aircraft is loaded with the weapon, an AN/AXQ-14 Data Link Pod is attached to the centreline pylon (station STA-5) to allow communication between bomb and aircraft. The sheer size of the GBU-15 prevents the carriage of the AIM-120 AMRAAM on the rail launchers of the same under-wing pylon, however, the AIM-9 Sidewinder air-to-air missile can still be carried.

Modes of Operation

A 'Direct' mode allows the bomb to be locked on to the target prior to launch. Once released it guides autonomously to the target. 'Indirect' mode makes use of either an AN/AXQ-14 DL pod or ZSW-1 Improved DL Pod ( IDLP) with which to steer the weapon to target post-launch. A training round, known as the CATM-130, is carried minus wings for training.

Launching the GBU-15 is simple, as ASL steering cues and range indications are provided in the Head-up Display (HUD) and the GBU-15 Video MPD page. The bomb can be cued from the Radar, HUD or TP, and is released in either a climbing profile or a level profile. In Indirect mode the weapon's seeker can be slewed via the DL to acquire the target as the bomb flies within visual range - the WSO slews the seeker to the target and then commits the bomb to attacking it - a process that causes the bomb's control fins to bring the bomb line of fall in line with the seeker LOS. To help the WSO, the GBU-15 offers a Ground Stabilisation option.

As the bomb flies out to the target area in Indirect mode, the WSO is initially limited to steering the weapon in azimuth only - this prevents him from inadvertently depleting the weapon's kinetic energy through unnecessary pitch transitions. During this time the weapon completes a 'terminal manouver' intended to bring it with striking range of the target. The WSO can at any time take control of pitch steering by switching the bomb from 'transition mode' to 'terminal mode'.

In the mid-1990s the USAF commenced Phase I tests at Eglin AFB, FL of the EGBU-15; an Enhanced GBU-15 that featured GPS midcourse guidance to give the bomb an all-weather capability. The EGBU-15 drives itself to the pre-entered target coordinates taking steering commands from an onboard GPS receiver; once in the target area, the WSO takes control via the Data Link Pod as normal. The EGBU-15 entered service with the 48th Fighter Wing at the end of 1999. 1,300 GBU-15 units are scheduled to receive the GPS upgrade.

Components

Each GBU-15 Guided Bomb Unit consists of five components: guidance section, warhead adapter section, control section, airfoil group, and a data link unit. The forward guidance section contains the EO or IR guidance system. An external electrical conduit carries electrical signals from the guidance section to the control section aft of the warhead. The conduit also connects the forward and aft part of the warhead adapter section and attaches the guidance section and the control section to the warhead. An umbilical receptacle passes control and guidance data between the fire control system of the aircraft and the weapon prior to release.

The weapon's control section is located aft of the warhead and contains an internal autopilot which controls the movement of the control surfaces of the airfoil group by collecting signals from the guidance system and data link system. The airfoil group consists of four rectangular shaped wings with trailing edge flap control surfaces. The wings have an X-like arrangement and line up with four strakes on the forward warhead adapter section, which add stability during flight.

Technical Data

Sources

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