THE US AIR FORCE Rockwell B-1B bomber is on schedule for clearance to carry cluster weapons from mid-1996 onwards, as the 419th flight-test squadron moves to complete Phase 1 of the three-part conventional mission upgrade programme.

Two dedicated B-1Bs are operated from Edwards AFB, California, as part of the conventional-weapons testing effort. More than 600h and 150 sorties have been flown so far in the programme, which also involves upgrades to the offensive and defensive systems.

Modifiable real-beam mapping modes have been added to the Westinghouse APQ-164 terrain-following radar which allow the crew to change settings in-flight and add new weapons without having to make major alterations to the weapons-systems avionics software.

Defensive-system enhancements on the aircraft have concentrated on software improvements to the AIL Systems ALQ-161 electronic-countermeasures system, and particularly the tail-mounted pulse-Doppler warning unit.

Test results of the improved ALQ-161, which was once notorious for jamming the B-1B's own terrain-following radar, are classified, but "...the early problems have been overcome", says the USAF.

The bomber has undergone most tests of the Mk82 225kg low- drag bomb, about 420 of which were recently dropped during a one-month test phase. Work on clearing the CBU-87/89 cluster munitions and the CBU-97 sensor- fuzed weapon is coming to a close, with the aim of a 40 millisecond interval for the final release.

The test team had hoped to reduce this even further, but restricted it to 40 milliseconds after test drops showed that weapons collided at higher drop-rates.

Four test sorties have also been flown to drop laser-guided GBU-10/27 weapons using both ground and "buddy" off-board designators. Limited clearance for GBU-carriage is expected in 1996, with full clearance due in around August 1997, although there are no plans yet to give the B-1B its own laser designator.

Source: Flight International