Raytheon Begins SPY-6(V)4 Testing as US Navy Readies 47-Ship Radar Backfit

SPY-6(V)4 Testing Begins as the US Navy Prepares a 47-Ship Backfit

Raytheon has delivered and installed a fixed-face SPY-6(V)4 array at the US Navy's Surface Combat Systems Center in Wallops Island, Virginia, bringing the service a step closer to replacing the ageing SPY-1 radar on a large share of its destroyer fleet. The unit will now undergo testing of its power and combat-system interfaces at the land-based facility, a phase scheduled to conclude in mid-2028.

The milestone is part of a program to backfit — retrofit — the new radar across all 47 Arleigh Burke-class (DDG 51) Flight IIA destroyers, beginning with USS Pinckney (DDG 91). Barbara Borgonovi, president of naval power at Raytheon, said the radar will be integrated with its dedicated power system before shipboard installation, which means "less time in the shipyard" for each hull.

The significance of the upgrade lies in how the two radars work. The SPY-1D is a passive electronically scanned array (PESA): it can broadcast a single radar beam at one frequency at any given microsecond, limiting how many threats an operator can handle at once. The SPY-6(V)4 is an active electronically scanned array (AESA) built from hundreds or thousands of independent solid-state transmit/receive modules, each generating its own radio frequency and giving operators far more flexibility to detect, track and classify multiple targets in a congested environment.

Not every destroyer will get the new radar. Scott Spence, Raytheon's vice president of naval systems and sustainment, said SPY-1 is out of production but will remain in the fleet for years on older hulls. Flights I and II lack the electrical and cooling capacity — and the Navy lacks the budget priority — to support SPY-6's power demands. Early DDG 51s carry three Rolls-Royce AG9130RF generators rated at 2,500 kW each, while Flight III ships use three AG9160RF units rated at 4,000 kW each. The practical result is a two-tier destroyer fleet for the foreseeable future.

Power Limits, GaN Gains and the Two-Tier Fleet Behind SPY-6

Power, Not Politics, Decides Which Hulls Get SPY-6

The split between destroyers that receive SPY-6 and those that do not is fundamentally an electrical engineering question. Three AG9160RF generators on Flight III hulls produce 4,000 kilowatts each; the three AG9130RF units on early DDG 51s produce 2,500 kW each. That is a difference of 4,500 kW across the ship — enough to power an AESA array with thousands of transmit/receive modules, or to rule it out.

Spence named the real constraints: cost, prioritisation and "severe electrical and cooling limitations." The consequence is a deliberate two-tier fleet, with the newest hulls gaining AESA flexibility while Flights I and II continue operating a radar that radiates one beam at a time. That trade-off is a useful precedent for any navy weighing a radar backfit.

AESA Is the Trend; GaN Is the Second Upgrade

The PESA-to-AESA transition is not unique to the US Navy. The article notes the Italian Air Force is upgrading its legacy ARABEL radar with an experimental AESA array, KRONOS, on SAMP/T air defence systems in Estonia. What separates programs is affordability: hardware integration, cooling requirements and microchip supply chains decide who can make the move.

Within AESA, materials matter as much as architecture. SPY-6's modules use gallium nitride rather than gallium arsenide, yielding higher power density, thermal efficiency and bandwidth. Raytheon is applying the same shift across its radar line — the 13th AN/TPY-2 delivered to the US military in May 2026 was the first with a GaN array. The company says GaN extends range, improves surveillance and enables defense against hypersonic threats; those remain company claims until operational testing verifies them.

The Threat Picture Behind the 47-Ship Program

The program's urgency is framed by recent conflict trends: low-altitude uncrewed aerial systems and electronic attack in congested maritime environments, with Red Sea and Persian Gulf incidents showing how one-way attack UAS can disrupt shipping, and the Ukraine-Russia war illustrating the contest for control of the electromagnetic spectrum. SPY-6's capacity to handle many targets at once — and software-defined apertures that let operators re-task sub-arrays through software rather than hardware replacement — is the operational answer to those pressures.

What the Backfit Means for RTX, Suppliers and Allied Navies

• For RTX and its suppliers: the mid-2028 completion date for SPY-6(V)4 interface testing at Wallops Island is the next hard milestone. A slip there delays the USS Pinckney (DDG 91) backfit and cascades across the remaining 46 Flight IIA hulls.
• For defense supply chains: the GaN content of SPY-6 arrays and the May 2026 GaN-equipped AN/TPY-2 delivery make gallium-nitride module production and shipboard power and cooling hardware the critical nodes in the program's timeline.
• For allied navies planning AESA upgrades: the US Navy's decision to leave SPY-1 on Flights I and II shows that generator capacity and cooling margins, not radar price alone, determine whether a legacy hull can be backfitted — assess those before committing.
• For naval force planners: expect a two-tier fleet through the late 2020s. Only SPY-6-equipped hulls (Flight III and backfitted Flight IIA ships) will offer the multi-target, software-definable arrays the UAS and electronic-warfare threats cited in the Red Sea, Persian Gulf and Ukraine conflicts call for.