WASHINGTON — The U.S. Air Force's F-35A, in its current iteration, can't hit a moving target — at least without a human manually directing the bomb to its destination.

The service plans to change that over the next year by adding a new weapon, Raytheon's Enhanced Paveway II (GBU-49), which it hopes to integrate into the F-35's arsenal in time for full combat capability.

The GBU-49 wasn't originally included in the Block 3F weapons loadout, which, along with new software, will make the joint strike fighter fully mission-capable. The service decided to incorporate it within the last six to nine months, said Brig. Gen. Scott Pleus, director of the Air Force's F-35 integration office.

"The ability to hit a moving target is a key capability that we need in current close-air support fight, and the GBU-49 is a great solution for the F-35 and, frankly, for all of our legacy platforms to hit these moving targets," he said during a February interview.

According to the F-35 Joint Program Office, a Block 3F F-35 is supposed to be able "to search, detect, track, ID and engage multiple stationary and moving surface targets in clear and adverse weather." At the time the services formed the F-35's requirements, they believed they could use a cluster munition to meet the moving target objective, but those weapons were banned under an international treaty, said F-35 JPO head Lt. Gen. Christopher Bogdan.

"The U.S., by treaty, is not allowed to use those weapons anymore," he told reporters in February. "So when that weapon left the inventory, we were left without a weapon that could hit moving targets." 

Instead of relying on weapons like the GBU-49 with a built-in ability to prosecute moving targets, many combat aircraft employ electro-optical targeting systems, or EOTS, with "lead-laser guidance" — which calculates how far a weapon should travel beyond the target’s current location in order to hit it. However, the F-35 EOTS was designed when that tech was still in its its infancy, so while the system can find a moving target, lock onto it and track it, an F-35 pilot still has to predict where a target will move and aim there, Pleus said.

The GBU-49, however, has lead-laser capability built into its front end, so it doesn’t need to rely on the EOTS system for that data, Pleus said. "All it requires is a laser spot on the moving target and the bomb itself will produce the lead necessary to hit the moving target."

The JPO hopes to finish GBU-49 integration work by the end of calendar year 2017, Bogdan wrote in testimony submitted to Congress in February.

It already has a head start because the weapon’s flight characteristics, outer mold line and aircraft interfaces are very similar to the GBU-12 currently used by the F-35A, which also reduces integration cost. In answers to emailed questions from Defense News, the JPO noted that the GBU-49 integration and lab testing has already been completed and verified.

And because it can leverage GBU-12 flight test data, the program office is not required to conduct flight tests of the GBU-49 to validate its handling and separation characteristics — although the JPO stated it could conduct some F-35A flights with GBU-49 "on a not-to interfere basis with the completion of the development program."

The F-35’s EOTS shortcomings are neither a new problem nor a surprise. The Air Force has long been aware of the issue, as has the Pentagon’s independent tester, who dinged the system in its most recent report. Michael Gilmore, then the Pentagon’s director of operational test and evaluation, advised the Pentagon to integrate GBU-49 in time for Block 3F as a stopgap measure.

"Otherwise, the program plans to develop and field lead-laser guidance in Block 4.2" during the F-35’s follow on modernization program, "which would be delivered in [calendar year 2022], at the earliest," he warned.

The Air Force has also signaled interest in other weapons that could give the F-35A moving-target capability in time for 3F capability, slated for May 2018. On Feb. 10, it released a sources-sought notification for a non-developmental, 500-pound precision-guided munition. According to the notice, the service plans to award a contract early this summer for an initial 400 weapons, with the first deliveries occurring six months from the award. From there, the service could issue follow-on contracts "to procure and sustain a total inventory of approximately 1,200 weapons."

Presumably, Raytheon would respond to the sources-sought notification with information about the GBU-49.

Lockheed Martin also intends to provide information about its Paragon dual-mode guidance kit, Alan Jackson, the company’s vice president of strike systems, told Defense News earlier this month. Paragon — formerly known as "dual mode plus" — converts 500-, 1,000- and 2,000-pound dumb bombs to precision-guided weapons.

Lockheed has said Paragon could begin production in 2017, but it is yet to be seen whether it will fit the Air Force’s tight integration timeline. The kit is undergoing flight tests with the Navy on the F/A-18 Hornet, with tests aboard an Air Force F-16 planned for this summer. But that isn’t slated to wrap up until the end of the year.

Valerie Insinna is Defense News' air warfare reporter. She previously worked the Navy/congressional beats for Defense Daily, which followed almost three years as a staff writer for National Defense Magazine. Prior to that, she worked as an editorial assistant for the Tokyo Shimbun’s Washington bureau.

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