v1.0.1 / 01 jan 02 / greg goebel / public domain
* The Grumman S2F "Tracker" was one of the more prominent tools of Western naval power in the 1960s. This compact carrier-based aircraft provided a capable platform for ocean patrol and sub-hunting, and also served as the basis for the "Trader" transport and "Tracer" early-warning aircraft. This document provides a short history of the Tracker, Trader, & Tracer.
* Grumman got into the antisubmarine warfare (ASW) field late in World War II, when the company developed variants of the popular Grumman TBM Avenger torpedo bomber for that role. After the war, the company followed up by developing the purpose-built AF-2W and AF-2S "Guardian" carrier-based ASW aircraft.
The Guardian was implemented as a pair of similar aircraft, the AF-2W "Hunter" and the AF-2S "Killer", since it proved difficult at the time to fit both functions in a single aircraft. The Guardian was a clumsy and unsatisfactory solution, and on 30 June 1950, even before the Guardian entered operational service in October 1950, the US Navy awarded Grumman a contract to develop a twin-engine carrier-based aircraft that could perform all the functions of the Guardian duo.
The contracted specified development of two prototypes of the Grumman "Model 89", with the initial military designation of "XS2F-1 Sentinel". The XS2F-1 was to carry a full complement of ASW sensors and weapons, and fly with good cruising speed over a range of up to 1,600 kilometers (1,000 miles).
The first XS2F-1 flew on 4 December 1952. It was a high-wing monoplane with a rounded, roomy fuselage, powered by twin Wright R-1820-82WA Cyclone nine-cylinder radial engines with 1,500 each, mounted in long nacelles on the wings. The XS2F-1's long wings and powerful engines allowed it to operate from small carriers and short airfields.
The wings folded up hydraulically over the top of the aircraft. The XS2F-1 had tricycle landing gear, with twin-wheel nose gear, and main gear retracting backwards into the engine nacelles. The aircraft was fitted with a stinger-type arresting hook, preceded by a small tailwheel to act as a bumper on carrier landings.
The XS2F-1's ASW fit included sonobuoy ejector tubes, with eight built into the rear of each of the engine nacelles and firing straight out the back; a 70-million-candlepower searchlight mounted on the right wing; an APS-38 search radar in a retractable ventral "dustbin" radome, behind the weapons bay; an APA-69 electronics countermeasures (ECM) antenna in a pod above the cockpit; and a retractable ASQ-10 magnetic anomaly detector (MAD) boom in the tail.
The XS2F-1 carried a crew of four, with the pilot on the left, co-pilot / navigator on the right, and two systems operators in the rear. The XS2F-1 had an internal fuel capacity of 1,970 liters (520 gallons). Total weapons load was up to 2,180 kilograms (4,800 pounds), including a single homing torpedo in the weapons bay, plus depth charges, rockets, bombs, or other stores fitted to six underwing hardpoints.
* The production "S2F-1" entered US Navy service in February 1954, with Squadron VS-26. The S2F-1 was much like the XS2F-1 prototypes, but had uprated Cyclones with 1,525 horsepower each. By this time, the aircraft had been officially renamed "Tracker", though flight crews generally referred to it as the "Stoof", a corruption of the "S-Two-F" designation.
A total of 755 S2F-1s were built by Grumman, with de Havilland of Canada
building an additional 43 "CS2F-1"s, with minor differences in equipment
fit.
GRUMMAN S2F-1 TRACKER:
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spec metric english
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wingspan 21.23 meters 69 feet 8 inches
length 12.88 meters 42 feet 3 inches
height 4.95 meters 16 feet 3 inches
empty weight 8,310 kilograms 18,315 pounds
max loaded weight 11,900 kilograms 26,300 pounds
maximum speed 462 KPH 287 MPH / 250 KT
service ceiling 6,710 meters 22,000 feet
range 1,350 kilometers 840 MI / 730 NMI
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The next production model, the "S2F-2", featured an offset and protruding weapons bay to accommodate an oversized nuclear depth charge, plus an enlarged tailplane to compensate for the resulting aerodynamic changes. The swollen weapons bay gave the S2F-2 a slightly pregnant look. A total of 77 S2F-2s were built by Grumman, with an additional 57 similar "CS2F-2"s built by de Havilland Canada.
The "S2F-3" first flew on 21 May 1959, and featured a fuselage stretch of 46 centimeters (1 foot six inches), a still larger tailplane, and an increase in wingspan of 89 centimeters (2 feet 11 inches). The S2F-3 was bigger overall to provide more crew space, fuel capacity, and equipment load.
As smaller nuclear depth charges had been developed, the weapons bay was
brought back to its original size. The ECM antenna on top of the cockpit
was removed, replaced by an improved ECM system using antennas fitted into
the wingtips, and most of the other electronics systems were modernized as
well. Stores pylons were strengthened, and the sonobuoy compartments at the
end of the nacelles were noticeably enlarged to increase sonobuoy capacity
from 8 to 16 in each nacelle. 100 S2F-3s were built in all.
GRUMMAN S2F-3 TRACKER:
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spec metric english
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wingspan 22.12 meters 72 feet 7 inches
length 13.26 meters 43 feet 6 inches
height 5.05 meters 16 feet 7 inches
empty weight 8,500 kilograms 18,750 pounds
max loaded weight 13,220 kilograms 29,150 pounds
maximum speed 426 KPH 265 MPH / 230 KT
service ceiling 6,400 meters 21,000 feet
range 2,090 kilometers 1,300 MI / 1,130 NMI
endurance 9 hours
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A number of S2F-3S Trackers were later fitted with AQA-7 sonobuoy processing gear and redesignated "S-2F", and apparently a large number of S2F-1S aircraft were updated to the same or similar specification and given the same S-2F designation.
There was also a minor upgrade of the S2F-3S with the designation "S-2G" to allow it to carry a pair of AGM-12 "Bullpup" radio-guided air-to-surface missiles. The copilot guided them using a joystick and watching a flare on the tail of the missile.
* A total of 20 US Navy squadrons were ultimately equipped with the Tracker. The type also did very well on the international market, with help from the US Military Assistance Program, being supplied to Argentina, Australia, Brazil, France, Italy, Japan, the Netherlands, Taiwan, Thailand, Turkey, and Uruguay.
* With such a large number of Trackers built, it wasn't surprising that many airframes were modified for other purposes:
When the US military consolidated its aircraft designation schemes in 1962,
the different Tracker variants were redesignated as follows:
S2F-1: S-2A
S2F-1T: TS-2A
S2F-1S: S-2B
S2F-2: S-2C
S2F-2P: RS-2C
S2F-2U: US-2C
S2F-3: S-2D
S2F-3U: US-2D
S2F-3S: S-2E
* The Tracker served with the US Navy with quiet distinction during the 1960s. Along with its primary role to protect the fleet from Soviet submarines, it was used for maritime patrol during the Vietnam War, assisting in rescues of aircrew downed at sea and occasionally engaging North Vietnamese patrol boats using unguided rockets, fired from underwing pods. One Tracker was lost to enemy action. Its non-combat losses were also low, and in fact the Tracker had an enviable safety record.
* The Tracker was replaced by the Lockheed S-3 Viking in first-line operation in the 1977s, and the last operational Tracker, an ES-2D, was phased out in the mid-1980s.
The type remained in use with a number of international air arms for much longer. Although it was obsolete in the ASW role by the time it ended production, it was still an effective aircraft for maritime patrol to monitor surface shipping. Thailand, Taiwan, and Argentina still operate small numbers of Trackers for this purpose.
It also remains in use as a popular "water bomber" to fight forest fires, with Trackers modified to carry 3,032 liters (800 US gallons) of fire retardant. One of the primary users is the California Department of Forestry (CDF), but other Tracker water bomber conversions have been performed for Canada and Turkey. Although the Tracker is a capable and rugged aircraft, its stubby fuselage does make it difficult to handle in turbulence, particularly after retardant release, and at least ten CDF pilots have lost their lives in crashes.
* Maintaining the old Wright Cyclones is becoming increasingly difficult, and so "Turbo Tracker" conversions are becoming popular. The engines of choice are the Garrett TPE331 or the Pratt & Whitney Canada (PWC) PT6A turboprop, both typically rated at 1,645 horsepower, and conversions have been performed by a number of companies:
The first Marsh water-bomber conversion flew in 1986 and was certified in 1990. A number have been supplied to the CDF. The first maritime patrol conversion flew in 1991, was carrier-qualified in 1992, and several have been sold. The maritime patrol conversions also include electronic system updates and other refinements.
Although most Trackers are far from the end of their airframe lives, a tribute to the traditional ruggedness of Grumman designs, military Turbo Tracker conversions have not been as popular as expected. Older versions of the P-3 Orion are now available on the international used-aircraft market, and buyers prefer the more capacious and longer-legged Orion over the Tracker.
* In 1955, Grumman flew the prototype of the "TF-1 Trader" "carrier onboard delivery" (COD) derivative of the Tracker. The Trader featured a modified fuselage, but was otherwise parts-compatible with the Tracker. The Trader could be fitted with easily-removed seats for nine passengers, and included front and back sliding bulkheads mounted on rails along with removeable posts to secure cargo for carrier landings. Life rafts were fitted into the rear of the engine nacelles.
First flight of the Trader was in January 1955, with initial service delivery in 1957. A total of 87 were built, including four fitted for the ECM role and given the designation "TF-1Q". In 1962, the TF-1 was given the new designation of "C-1A", and the TF-1Q was redesignated "EC-1A". The Trader served with three US Navy logistics support and transport squadrons, but was strictly an interim type, being replaced by the Grumman C-2 Greyhound.
* The Trader led in turn to another Tracker derivative, the "WF-1 Tracer" airborne early-warning (AEW) variant, which first flew in March 1957. The production version, the "WF-2", went into operational service in February 1958, serving with Squadrons VAW-11 and VAW-12. It was know as "Willie Fudd" by crews, in reference to its designation code, and sometimes as "Stoof With A Roof".
The Tracer featured a large fiberglass honeycomb dorsal "saucer" radome with dimensions of 6.1 by 9.14 meters (20 by 30 feet) to accommodate the antenna for its Hazeltine APS-82 search radar, and a new tail unit with three fins to compensate for the wake interference of the radome. As the radome blocked the wings from folding upward, they were redesigned to fold backward along the fuselage in classic Grumman fashion.
The Tracer had a crew of four, including pilot, copilot, and two radar
operators. A total of 89 Tracers were built.
GRUMMAN WF-2 TRACER:
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spec metric english
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wingspan 22.12 meters 72 feet 7 inches
length 13.82 meters 45 feet 4 inches
height 5.13 meters 16 feet 10 inches
empty weight 9,535 kilograms 21,025 pounds
max loaded weight 12,230 kilograms 26,970 pounds
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* I got into the Tracker by a backdoor route. I was doing a survey of AEW aircraft and got curious about the WF-2. I didn't end up finding out much about the WF-2, which appears to have had a very short and undistinguished service life, but I did find out a good deal about the Tracker. I suppose this will eventually lead to a survey of sub-hunting aircraft, but that will take a little more time.
* Sources include:
The "S-2F Tracker" website in the Netherlands was a significant source of information as well, and some minor details were obtained from the 1960 edition of JANE'S ALL THE WORLD AIRCRAFT.
* Revision history:
v1.0 / 01 mar 01 / gvg
v1.0.1 / 01 jan 02 / gvg / Minor cosmetic update.