US Air Force Tests B-52H Stratofortress Unguided Bomb Capability

The US Air Force Test Center has trialed the B-52H Stratofortress’ capability to deploy a GBU-38 unguided free-fall bomb with new load configurations.

The evaluation was led by experts from the 96th Test Wing Air Force SEEK EAGLE Office (AFSEO) and the Arnold Air Force Base Engineering Development Store Separation Section.

“The B-52 is a versatile aircraft with many combat roles, including close air support (CAS),”  AFSEO Store Separation Engineer Don Atkins said.

“The ability to employ a range of effects on demand is a valuable commodity over the battlefield.”

“Global Strike Command’s efforts to expand the CAS capability of the B-52 include expansion of the store types that can be carried at the same time and employed in response to dynamically changing combat demands.”

The GBU-38 is a 500-pound BLU-111/MK 82 bomb with a joint direct attack munition guidance tail kit. It was previously tested with the B-52H Stratofortress without a mixed load configuration.

In the recent trial, GBU-38 was integrated with multiple heavy stores adapter beams (HSAB), including the GBU-31 precision-guided munition, CBU-87 dispenser, and MK 64 ER air-launched mine.

Simulating Stratofortress GBU-38 Deployment

Arnold Air Force Sase’s 16-foot (5-meter) transonic wind tunnel was used for separation testing to simulate flight conditions including speed, temperature, and altitude.

“The wind tunnel test entry was designed to acquire both data supporting certification, or fielding, of expanded GBU-38 configuration capabilities and data defining configuration effects that can be applied to a range of other stores,” Atkins said.

“Such cost-effective approaches leverage discrete data with the established body of knowledge to extend test results and maximize operational application.”

scale model of a GBU-38 mounted on a sting is positioned above a scale model of a B-52 Stratofortress
A scale model of a GBU-38 mounted on a sting is positioned above a scale model of a B-52 Stratofortress in the 16-foot transonic wind tunnel at Arnold Air Force Base. Photo: Jill Pickett/US Air Force

During the store separation testing, forces and related factors acting on the GBU-38 were measured using balanced strain gauges while positioning the store in pseudo-freestream, grid, and trajectory.

“The test used pseudo-freestream positioning where the store was placed far away from the parent aircraft and then data at a large range of pitch,” Aerodynamics Test Branch Manager Austin Stewart explained.

“Grid data was taken at increments along a line stepping away from the release point of the store on the HSAB,” Stewart said. “This allowed the interference of the B-52H on the store to be characterized.”

The trajectory of B-52H’s GBU-38 deployment was analyzed using a closed-loop system computer software that predicts movement depending on force, gravity, and simulated ejector.

“The computer positioned the store at that location and repeated the process, effectively showing a predicted path or trajectory of the store if it was released during an actual flight,” Stewart said.

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