The U.S. Army has temporarily suspended delivery of Raytheon's GPS-guided, 155mm Excalibur artillery rounds due to problems with its Inertial Measurement Unit (IMU), service officials said.
The Army, which has taken delivery of tens of thousands of XM982s, says none of the rounds used in combat have had problems. (U.S. Army)
"The XM982 [Excalibur] round is required to operate in an environment that exceeds 15,000 times the force of gravity. There was an inherent lack of design robustness in the qualified IMU configuration which resulted in a failure rate of approximately five percent. We have not been able to conclusively trace the exact cause to a design or process issue," an Army spokesman said in a written statement.
The spokesman said the IMUs, which were made by Minneapolis, Minn.-based Honeywell, "experienced high bias accelerometer shifts during gun launch," meaning that the accelerometer did not correctly measure the movement of the shells after firing.
The Army, which has taken delivery of tens of thousands of XM982s, first fired the rounds in combat in 2006 in Iraq. The spokesman said the munitions have exceeded expectations.
None of the rounds in theater have had a problem, the spokesman said. "Problems were identified before shipment to theater and have been held at the production facility," the spokesmen said.
Raytheon will replace the IMUs on 1,075 shells, the spokesman said. The Army will pay $16.3 million for the replacement, he said.
New production will resume next month, the spokesman said.
Raytheon spokeswoman Jacklyn Guttman said, "After careful evaluation, an alternative Inertial Measurement Unit design has proven to meet system requirements while providing an opportunity for increased overall system reliability. The effort to qualify this alternative IMU is in progress, and is expected to be successful." Using the new supplier has corrected the problem, another company official said.
U.S. Suspends Delivery on GPS-Guided 155mm Shells - Defense News