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The Grumman Tracker, Trader, & Tracer

v1.0.2 / 01 jan 04 / 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.


[1] ORIGINS
[2] TRACKERS IN SERVICE
[3] TRACKER MODIFICATIONS
[4] SURVIVING TRACKERS
[5] TRADER COD AIRCRAFT
[6] TRACER AEW AIRCRAFT
[7] COMMENTS, SOURCES, & REVISION HISTORY

[1] ORIGINS

* 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 1,120 kW (1,500 HP) 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 AN/APS-38 search radar in a retractable ventral "dustbin" radome, behind the weapons bay; an AN/APA-69 electronics countermeasures (ECM) antenna in a pod above the cockpit; and a retractable AN/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 US 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.

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[2] TRACKERS IN SERVICE

* 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 1,138 kW (1,525 HP) each. After service introduction the type was later renamed "Tracker". Although aircraft nicknames are something of a treacherous subject, sometimes being fabrications well after the fact, it does appear that the Tracker eventually became known 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:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   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
   _____________________   _________________   _______________________

* The US Navy relied heavily on the Tracker for fleet defense, and took measures to keep the type up to date. Many USN Trackers were retrofitted with the AN/AQA-3 "Jezebel" acoustic search (passive sonar) and "Julie" echo-ranging (active sonar) gear, and redesignated "S2F-1S". The Julie system involved fitting ejector tubes for echo-sounding explosive charges in the bottom of the rear fuselage.

The next production model, the "S2F-2", featured a protruding and offset 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 shrunk 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:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                22.12 meters        72 feet 7 inches
   wing area               46.08 sq_meters     496.0 sq_feet
   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
   _____________________   _________________   _______________________

The final production variant of the Tracker was the "S2F-3S", essentially an S2F-3 with Julie-Jezebel gear and a TACAN radio beacon system. The last of 252 S2F-3s was delivered in 1968, and were the last of a total of 1,284 Trackers built in the US and Canada.

A number of S2F-3S Trackers were later fitted with AN/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.

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[3] TRACKER MODIFICATIONS

* 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
Canadian Trackers were given a service-life update in the mid-1960s, with substantial system updates, and given the new designation of "CP-121" when the Canadian Armed Forces were created by service consolidation in early 1968.

* 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.

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[4] SURVIVING TRACKERS

* 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 1,227 kW (1,645 SHP), and conversions have been performed by a number of companies:

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.

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[5] TRADER COD AIRCRAFT

* 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 rear sliding bulkheads mounted on rails, plus 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.

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[6] TRACER AEW AIRCRAFT

* 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 apparently known as "Willie Fudd" by crews, in reference to its designation code, and sometimes as "Stoof With A Roof".

The Tracer featured a large dorsal "saucer" radome made of honeycomb fiberglass, with dimensions of 6.1 by 9.14 meters (20 by 30 feet), to accommodate the antenna for its Hazeltine AN/APS-82 search radar, and a new tail unit with three tailfins 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 was built.

   GRUMMAN WF-2 TRACER:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                22.12 meters        72 feet 7 inches
   wing area               46.08 sq_meters     496.0 sq_feet
   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
   _____________________   _________________   _______________________

The WF-2 was redesignated "E-1B" in 1962. Like the Trader, the Tracer was an interim type, being replaced by the Grumman E-2 Hawkeye in the mid-1960s.

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[7] COMMENTS, SOURCES, & REVISION HISTORY

* 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. The information on Brazilian Trackers was provided by Captain Marcio Jansen Calvacanti of the Brazilian Navy.

* Revision history:

   v1.0   / 01 mar 01 / gvg
   v1.0.1 / 01 jan 02 / gvg / Minor cosmetic update.
   v1.0.2 / 01 jan 04 / gvg / Minor cosmetic update.
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