WASHINGTON — Pentagon officials have deferred a decision on whether to buy long-lead parts for four RQ-4 Global Hawk unmanned aerial vehicles (UAVs) after one aircraft performed poorly in tests with a “non-production representative” intelligence processing system, industry sources said.

The Defense Acquisition Board (DAB) chose that path June 24 at a meeting to discuss the high-altitude spy drone that is slated to one day replace the half-century-old U-2.

A decision on the parts, which are to equip two Block 30 and two Block 40 Global Hawks in the 10th production lot, will likely be made in October or November, one source said. That will allow Northrop Grumman to test all aspects of the UAV using the standard Distributed Common Ground System in July and again in the fall, the source said.

The board did approve the production of two Block 30 and two Block 40 UAVs in Lot 9, a production block that also includes five Airborne Signals Intelligence Payload packages, two Enhanced Integrated Sensor Suites and two Multi Platform-Radar Technology Insertion Program (MP-RTIP) sensors.

The Lot 10 batch includes similar equipment, according to one source.

Northrop Grumman is “encouraged by the recommendations the DAB has provided,” company spokesman Randy Belote said in a June 25 e-mail. “We look forward to working with the Air Force to continue Global Hawk’s proven and invaluable global intelligence, surveillance and reconnaissance service.”

In June, David Van Buren, the U.S. Air Force’s top acquisition official, told reporters that he was unhappy about the program’s cost hikes and testing delays.

Today’s Block 10 Global Hawks carry an integrated sensor suite of electro-optical/infrared sensors and synthetic aperture radar.  Block 20 jets are getting Battlefield Airborne Communications Nodes, Block 30 jets will carry the Raytheon-built Enhanced Integrated Sensor Suite, and Block 40 UAVs will get the powerful MP-RTIP moving-target ground surveillance radar.