The Tracker’s single most important contribution was to combine the anti-submarine hunter and killer in one aircraft. In the late 1940s the detection gear and the weapons could not both fit in a single carrier aircraft, so the US Navy operated them in pairs: a “hunter” such as the radar-equipped Grumman AF-2W Guardian to find the submarine, and a separate “killer” AF-2S carrying the weapons, the two coordinating an attack together.

This was inefficient and demanding — two aircraft, two crews, and the constant problem of keeping them working together. As sensors and weapons shrank and improved, Grumman was able to design the Tracker around carrying all of it in one airframe. The S-2 could detect, localise and attack a submarine on its own, and that made it the first true single-airframe carrier hunter-killer — a genuine step change in how navies hunted submarines from the air.

The Tracker was powered by two Wright R-1820 Cyclone radial engines, a nine-cylinder design from one of the most successful and long-lived engine families in aviation history — the same basic engine that had powered the B-17 Flying Fortress. For an anti-submarine aircraft the choice made perfect sense: the Cyclone was rugged, well understood, and economical enough to give the endurance a patrol aircraft needs.

Two engines also gave a vital safety margin for hours of flying far out over the open ocean, where an engine failure in a single-engine aircraft could be fatal. The Tracker could patrol for many hours, throttled back for economy, and still had the power for a carrier takeoff when heavily loaded with fuel, sensors and weapons.

Finding a submarine in the ocean is one of the hardest tasks in warfare, and the Tracker carried a whole toolkit to do it. A search radar in a retractable radome under the rear fuselage detected submarines and ships on the surface. A magnetic anomaly detector (MAD) on a long boom, extended from the tail in flight, sensed the faint distortion a submerged steel submarine makes in the Earth’s magnetic field.

Sonobuoys — expendable listening devices — were carried in the rear of the engine nacelles and dropped into the sea to detect submerged boats by sound. And a powerful searchlight under the starboard wing could illuminate a surfaced target at night for attack. Together these sensors let one Tracker carry out the full search-to-strike sequence that had previously needed two aircraft.

The Tracker was a true carrier aircraft, and everything about it was shaped by the demands of the flight deck. Its high wings folded upwards and back to shrink the aircraft for stowage in the crowded hangar below deck, and it carried the sturdy undercarriage and arrester hook needed for carrier landings. Its high-wing layout gave the sensor operators a good downward view and kept the propellers well clear of the deck.

Good low-speed handling made the Tracker manageable in the demanding business of landing on a moving carrier, and its twin engines and long endurance suited the long, patient patrols of anti-submarine work. It operated from the US Navy’s dedicated anti-submarine carriers and, in foreign service, from the flight decks of Argentine, Australian, Brazilian, Canadian and Dutch carriers.

The Tracker’s roomy, reliable airframe was quickly adapted to other jobs. The first offshoot was the C-1 Trader (originally the TF-1), a carrier-onboard-delivery aircraft — essentially a small transport version with the sensors and weapons replaced by a cabin for passengers and cargo. Its job was the unglamorous but essential one of ferrying people, mail and urgent spare parts out to aircraft carriers at sea.

The C-1 could carry a useful load out to a carrier hundreds of miles from land and, crucially, land back aboard, keeping the ship supplied without it having to return to port. Around ninety were built, and they served for many years; a specialised electronic version, the EC-1A, was also produced. The Trader kept the carriers connected to the shore long before the role passed to later aircraft.

The most important Tracker offshoot was the E-1 Tracer, an airborne-early-warning aircraft. A fleet at sea is blind to low-flying threats beyond its ships’ radar horizon, so the Navy fitted a large radar into a fixed dome mounted above a modified Tracker airframe — a distinctive shape that earned it the nicknames “Willy Fudd” (from its original designation WF) and “Stoof with a Roof.”

Entering service in the late 1950s, the E-1 Tracer was the US Navy’s first purpose-built carrier-borne early-warning aircraft, orbiting ahead of the fleet to detect threats far beyond the range of the ships’ own radars. It was the direct predecessor of the Grumman E-2 Hawkeye, the carrier early-warning aircraft that replaced it and still flies from American carriers today — making the humble Tracker the ancestor of a capability the US Navy considers essential.

The Tracker was important enough to Canada that it was built there under licence. De Havilland Canada produced around a hundred aircraft as the CS2F for the Royal Canadian Navy, which flew them in the anti-submarine role, including from the carrier HMCS Bonaventure. The Canadian Trackers were closely based on the American design but built to Canadian requirements.

Canada’s licence production is a measure of how well the Tracker fitted the needs of a serious maritime nation, and the Canadian aircraft served for many years. Some were later converted for other duties, and the CS2F is an important part of the Tracker’s wider story — one of several ways the basic Grumman design spread well beyond the US Navy.

For its first decade the Tracker was known by the US Navy’s old designation system as the S2F — the second anti-submarine (S2) type from Grumman (F). Sailors pronounced “S2F” as “Stoof,” and the nickname stuck to the aircraft for the rest of its career.

In 1962 the United States adopted a single, unified aircraft designation system across all its armed forces, and the Tracker’s labels changed accordingly: the S2F-1 became the S-2A, the S2F-3 became the S-2D, and so on, while the TF-1 Trader became the C-1 and the WF-2 Tracer became the E-1. The aircraft themselves did not change — only the labels — which is why the same machine appears in sources as both the S2F and the S-2 depending on the date.

By the early 1970s the US Navy wanted a faster, more modern carrier anti-submarine aircraft, with jet performance and a more advanced digital sensor and processing suite to keep pace with quieter, faster Soviet submarines. The answer was the Lockheed S-3 Viking, a jet-powered aircraft that began replacing the Tracker in US Navy squadrons from the mid-1970s.

The Viking was a generation ahead of the piston-engined Tracker and served for decades. But the Tracker was not simply scrapped: many foreign navies kept flying it for years afterwards, and the type found its remarkable second career fighting fires. The replacement marked the end of the Tracker’s front-line US Navy service, not the end of the aircraft — which in some forms is still flying today.

The Tracker was one of the most widely exported carrier and maritime-patrol aircraft of its era. Beyond the US Navy and the Canadian licence-built fleet, it was flown by Argentina, Australia, Brazil, Italy, Japan, the Netherlands, South Korea, Taiwan, Turkey and Uruguay, among others — well over a dozen operators in all. Several of them flew Trackers from their own aircraft carriers, including Argentina, Australia, Brazil and the Netherlands.

The reasons were straightforward: the Tracker was capable, rugged, affordable and available, and every maritime nation of the period needed to hunt submarines. Many operators kept their Trackers flying long after the US Navy retired its own, and Taiwan in particular operated modernised, turbine-converted Trackers into the twenty-first century. This breadth of service is a measure of how well the aircraft filled a role that so many navies needed filled.

As with most Cold War military aircraft, there is no single reliable, transparent public figure for the Tracker’s unit cost, cost per flight hour or total programme cost. It was procured over many years, in many variants, for many customers, through government contracts and military-assistance programmes rather than at a transparent list price, and consistent lifetime figures are not available. Any single figure quoted for it should be treated with caution.

What can be said is that the whole point of the Tracker was efficiency: putting the complete anti-submarine mission into one relatively simple, twin-piston-engined airframe was far cheaper than operating pairs of hunter and killer aircraft, and cheaper than the fleets of ships that would otherwise be needed to cover the same ocean areas. Rather than invent numbers, we list the cost fields here as “not reliably recorded.”

The Tracker family collected a set of affectionate nicknames that tell its story. The original S2F designation, pronounced as a word, gave the anti-submarine Tracker its enduring nickname, the “Stoof.” It was a plain, workmanlike aircraft, and the name fitted its unglamorous, dependable character.

The airborne-early-warning E-1 Tracer, with its big fixed radar dome perched above the fuselage, naturally became the “Stoof with a Roof,” and also “Willy Fudd” from its original WF designation. These nicknames, still used fondly by those who flew and maintained the aircraft, capture the affection the Tracker earned across a long career — a rugged, honest aircraft that always got the job done.

The Tracker’s most remarkable achievement may be that it is still flying. When the aircraft was retired from military service, its strong airframe, good low-speed handling and useful load-carrying ability made it an excellent candidate for conversion into an aerial firefighting air tanker. Many were converted to drop fire retardant, and a number were re-engined with modern turboprop engines as the S-2T, transforming their performance.

These turbine Trackers are the backbone of the aerial firefighting fleet operated by CAL FIRE, the California Department of Forestry and Fire Protection, and they still fly today, attacking wildfires across the state. For an aircraft that first flew in 1952, remaining in front-line, dangerous, essential service into the 2020s is an extraordinary tribute to the soundness of Grumman’s original design — and a fitting final chapter for one of the great workhorses of naval aviation.