U.S. Air Force upgrades test gear that checks F-16 radar

A micro-crack, trapped moisture or a coat of paint that’s too thick in an F-16’s nose cone “will act like a dirty lens” on the fighter’s radar, and only one shop in the U.S. Air Force tests for that: a radio frequency shop at Hill Air Force Base, Utah.

The 523rd Electronic Maintenance Squadron tests about 70 radomes and 160 fire control radar antennas a year for the F-16 fleet, according to an Air Force release. Kelly Sellers, chief of the squadron’s Avionics Flight, said its two test systems make the unit “the sole source for F-16 radar antenna repair and radome tuning.”

“The radome is not just a fiberglass cover; it is a highly engineered electromagnetic window,” Sellers said. “Even tiny, invisible physical flaws (such as moisture intrusion, micro-cracks, composite delamination, or improper paint thickness) will act like a dirty lens, refracting or absorbing radar waves.”

The radar antenna sits right behind the radome and transmits and receives through it. When either part is out of tolerance, Sellers said, detection and tracking range can drop and false returns can show up on the pilot’s display. A target can also “register in a slightly different location than it actually is,” the release said.

That error carries through the whole engagement. A pilot working with a degraded picture has a harder time holding a track, getting a lock-on and putting radar-guided weapons on target, according to the squadron.

“Because the fire control radar antenna is located directly behind (inside) the nose radome, the two systems must function in perfect electromagnetic harmony,” Sellers said.

The squadron checks each half of that pair on a separate machine. The Nose Radome Electrical Test System, or NRETS, measures how well radar energy passes through a radome and flags distortion or attenuation, which is the loss of signal strength through the material. The Fire Control Radar Antenna Test System, known as FCRATS, checks the antenna’s radiation pattern and beam-pointing accuracy, along with its sidelobe levels and transmit and receive performance.

A radome doesn’t go straight onto the test stand. It first goes through depot preparation that can include robotic coating removal and structural repair, then resurfacing and precision painting. Only then is it tuned and measured on NRETS. Antennas follow their own path: technicians diagnose and repair each one, verify it on a separate test station, and then run final FCRATS testing before it ships back to a unit.

The release didn’t say which F-16 radars the antennas come from. It also didn’t give a cost for the test system upgrades, when they were installed or how much they raised output.

That question matters because the fleet is changing radars. Most U.S. Air Force F-16s were built with Northrop Grumman’s mechanically scanned APG-68, which uses a planar antenna that physically moves behind the radome. The service has been fitting Northrop’s APG-83 Scalable Agile Beam Radar, an active electronically scanned array, to Air National Guard jets and other F-16s, and the company says it has delivered its 1,000th SABR radar for the F-16 across U.S. and international customers. An AESA steers its beam electronically, but it still radiates through the same kind of composite nose cone, so radome quality matters regardless of which radar sits behind it.

Hill has a long tie to the jet. The base’s 388th Tactical Fighter Wing received the first operational F-16A in January 1979, and the 523rd now sits within the 309th Maintenance Wing at the Ogden Air Logistics Complex, which handles depot work on the type.

The release says keeping the fleet flying “more than four decades after the F-16 entered Air Force service” depends on test equipment as much as on the parts themselves. Sellers said recent NRETS and FCRATS upgrades “replaced obsolete test equipment and increased shop throughput and capacity,” which lets the squadron respond to workload surges and urgent requests from the field.

Dan Marcom, the 523rd’s director, credited the technicians. “Keeping the F-16 combat-ready really rests on their shoulders and specialized expertise,” he said.

“By pairing unmatched craftsmanship with modernized test systems, our technicians ensure that every radome and antenna returning to the flightline delivers the clear, uncompromising radar picture our warfighters depend on,” Marcom added.