United States Naval Air Propulsion Center (NAPC)

This place holds a special meaning for me. I’ve visited several times, determined to explore every corner and uncover its secrets. But no matter how hard I tried, I never quite managed to see it all.

The main front building, the one closest to the road? Never got inside. The massive cooling building in the back with its giant fans and smaller outbuildings? Missed that, too. And then there was the tank farm—a cluster of 22 rusty tanks tucked away in the upper right corner of the property. For some reason, no one ever took pictures of those tanks, even though they sat quietly in the shadows. I only noticed them recently, flipping through my old research notes. That’s when it hit me: I’d never taken the path that led there, too hesitant to get close to the Trenton-Mercer Airport’s fence line. I wasn’t here to get in trouble. I was here for the peaceful, empty buildings, not to risk getting caught wandering near airport grounds.

Still, being there felt like stepping back in time. Walking those halls, I could almost feel the presence of the people who once worked here, pushing the boundaries of jet propulsion and mechanical engineering. It was humbling to imagine the innovation that had happened within those walls.

The only other “locals” I encountered were deer. They’d dart away at the slightest sound, disappearing into the trees as I wandered the grounds. Their nervous energy contrasted with the stillness of the place, a site now quietly holding onto its past.

The blue cooling system building. Just beyond this building were the huge cooling fans, but I was thwarted by heavy brush and vines with a quickening of dying sunlight.

When the station closed on September 30, 1998, a range of facilities on the property were transferred or repurposed. These included five administration and office buildings spanning about 59,000 square feet, alongside five laboratory spaces offering an impressive 141,967 square feet for research. Eight additional structures provided around 40,450 square feet of covered storage.

The site’s centerpiece was its thirteen testing facilities, covering a massive 317,514 square feet—the largest portion of the property. Two off-site structures supported operations: a meter house on Scotch Road with a capacity of 100 kV and a 0.8-mile easement and a Delaware River non-potable water pumping station connected by a 2.2-mile easement.

Fuel storage was another key feature, with 22 tanks, each holding about 25,000 gallons, linked by 0.4 miles of underground pipeline. A steam plant, once capable of producing 120,000 pounds of steam per hour, also existed but may have been demolished after the property’s closure—the exact timing remains unclear.

In total, the property included 463 acres of permanent easement rights to support aircraft ascent and landing at Mercer County Airport, reflecting the scale and complexity of the station’s operations during its peak.

During World War II, the demand for cutting-edge aviation technology led to the establishment of the Eastern Aircraft Division of General Motors in Trenton, New Jersey. Beginning operations on January 2, 1942, this division played a crucial role in producing the TBF Avenger, a torpedo aircraft essential for wartime efforts. The pace was remarkable—the first aircraft was delivered by November of that year, and within just 13 months, the division had built an impressive 1,000 aircraft.

Even before the war ended, the need for more advanced testing facilities for turbine engines became apparent. In 1942, the Bureau of Aeronautics' Power Plant Design Division began studying the limitations of existing setups for testing large internal combustion turbines under simulated altitude conditions. By 1944, it was clear that a new, specialized facility was necessary. Trenton, already home to a government-owned site, was chosen as the location for what would become the Naval Air Turbine Test Station (NATTS).

NATTS officially began operations in July 1951, with full-scale engine testing starting in 1956. Over the next two decades, the facility expanded its capabilities and infrastructure, emerging as a leader in jet engine testing. It introduced groundbreaking technologies, including advanced data systems and chambers designed to simulate extreme environmental conditions, pushing the boundaries of aviation innovation.

By the 1970s, the mission at the Naval Air Turbine Test Station (NATTS) evolved to meet the growing needs of both military and civilian aviation. The facility expanded its focus, taking on testing for turboprop engines and eventually exploring unmanned aerial vehicles (UAVs). During this period, NATTS consolidated operations with the Aeronautical Engine Lab (AEL) in Philadelphia, greatly enhancing its capabilities and influence in the aerospace field.

I loved the various piping on this upper floor. A real eye-pleaser.

The 1980s brought further advancements with the addition of new test cells and cutting-edge digital control rooms. These upgrades made NATTS a state-of-the-art facility capable of handling the demands of newer, more advanced engines and systems. This period solidified its reputation as a key player in the development of naval aviation technology.

The story of NATTS, later known as the Naval Air Propulsion Center (NAPC), came to an end in 1998 following decisions made under the Base Realignment and Closure (BRAC) process. The closure led to 700 workers losing their jobs, with most relocated to facilities in Maryland and Tennessee. You will see the closure dated to 1997 in some accounts, including summaries of the Naval Air Warfare Center Trenton — that is the year the last of the testing work was transferred out. The station itself was formally closed on September 30, 1998, the end of that fiscal year, and the people who had worked there marked it with a closing party at the West Trenton firehouse.

While its doors may have closed, the legacy of NATTS/NAPC lives on. Its pioneering work in jet and turboprop engine testing shaped the future of both military and commercial aviation, leaving an indelible mark on the industry after nearly five decades of groundbreaking innovation.

And then the testing chamber building. Everyone came here specifically for this room, unlike any other on the property.

This section had so much potential for some fire portraits. Alas, I was running solo dolo.

It's one of my favorite shots from here. If only I had lined up the shot properly for the upper half.

The pipeworks remind me of the lower portion of the Fusion Paperboard plant.

These large pipes were definitely a scrapper's wet dream.

So many large cast pipes were running through this building that I never went upstairs to check out the rest of this section.

Post Update

🚧 NAPC Update — The Site Is Coming Down

Demolition of the former Naval Air Propulsion Center began in April 2024, after roughly a quarter-century of inactivity. The KRE Group joined Ewing Township officials to kick off the work, which clears the deteriorating complex for the second and final phase of the township's Parkway Avenue Redevelopment Plan, first adopted in 2013.

Four new structures are planned across about 26.28 acres: a single-story warehouse of 285,152 square feet and three flex-space buildings of 20,000 square feet each, along with stormwater infrastructure, a new NJ Transit bus stop, surface parking, a landscaped walking trail, improvements to Parkway Avenue, and a new traffic circle.

The testing chamber, the pipework, the blue cooling building — the rooms in these photographs are gone or going. Every frame above is now the record rather than the place.

Reader Callout

⚙️ Did You Work at NATTS or the Naval Air Propulsion Center?

Were you one of the engineers, technicians, or machinists at the Naval Air Turbine Test Station or the Naval Air Propulsion Center in Ewing between 1951 and 1998 — or one of the 700 people whose jobs moved to Maryland and Tennessee at the end? Do you have photographs of the test cells in operation, technical diagrams, or memories of what it sounded like when an engine lit off in the altitude chamber? With the buildings now demolished, firsthand accounts are the only way this place gets remembered accurately.

📩 Share Your Memory → or drop a comment below — full credit given to every contributor.

Keep Reading

⚙️ Related Industrial & Infrastructure Explorations

Test stands, power houses, foundries and plants — the engineered places that ran the Northeast and then went quiet.

Former Fusion Paperboard Plant (Part 1) Hydrapulpers and industrial wastewater systems — the pipeworks that these NAPC runs reminded me of. → Holo-Krome Factory (West Hartford, CT) A demolished precision manufacturer that produced socket screws for nearly a century. → Kingsbridge Substation No. 3 (Bronx, NY) NYC electrical infrastructure tied to rail electrification and early urban power distribution. → Glenwood Power Plant (Yonkers, NY) A cathedral-like power station on the Hudson, built to electrify the New York Central. → Exeter Energy Tire Incinerator Plant A purpose-built industrial plant whose only job was burning tires for power. → Aerosol Techniques Factory (Milford, CT) A sprawling abandoned industrial complex, documented room by room. →

⚙️ Thirteen test facilities, 317,514 square feet of them, and twenty-two fuel tanks — from the TBF Avenger line of 1942 to unmanned aircraft in the 1970s, this was where naval jet engines were proven.

Sources:

1. Naval Air Propulsion Center (NAPC) — Trenton, NJ. Cold War History.
2. Former Naval Air Warfare Center Trenton. U.S. Navy BRAC Program Management Office.
3. KRE Group joins Ewing Township officials to begin long-awaited redevelopment of former Naval Air Propulsion Center. (2024, April 23). Ewing Township.
4. Demolition of Naval Air Propulsion base in Ewing underway. (2024, April 23). The Trentonian.
5. KRE Group begins redevelopment effort at naval air site in Ewing. (2024, April). Jersey Digs.
6. Perry, J. (2024, May 1). Ewing's former naval facility comes down as redevelopment gets underway. NJBIZ.
7. Naval Air Warfare Center Trenton. Wikipedia.