v1.0.4 / 01 dec 07 / 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 history and description of the Tracker, Trader, and Tracer.
* The Grumman company got into the antisubmarine warfare (ASW) field late in World War II, when the firm developed variants of the popular Grumman TBM Avenger torpedo bomber for that role. After the war, Grumman 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 air-cooled radial engines providing 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, with the wing fold "skewed" so the two wings would overlap each other when folded. The XS2F-1 had tricycle landing gear, with twin-wheel nose gear, and single-wheel 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 teardrop fairing 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 pylons.
* Following trials of 15 "YS2F-1" service evaluation machines, 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 providing 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, occasionally 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 740 S2F-1s was built by Grumman, not counting the YS2F-1
evaluation machines, with de Havilland of Canada (DHC) building an additional
43 "CS2F-1"s, with minor differences in equipment fit. The S2F-1 / CS2F-1
was built in larger quantities than all successive variants and derivatives
of the type combined.
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 was built by Grumman, with an additional 57 similar "CS2F-2"s built by DHC.
* The "G-121 / 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. The S2F-3 entered fleet service in May 1961.
Since smaller nuclear depth charges had been developed, the weapons bay was
shrunk back to its original size. The ECM antenna fairing 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 navigation beacon receiver
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 many S2F-1S aircraft were updated to the same or similar specification and given the same S-2F designation. There was also an upgrade of 50 S2F-3S machines 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
________________
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.
* 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, and at last notice was still being operated in declining numbers in this role by various countries.
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 have become 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:
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.
The Brazilian Trackers were then retired, one being donated to the Brazilian Air Force (FAB) museum in Rio de Janiero, and the others were mothballed. Incidentally, although the Trackers were operated off the Brazilian Navy carrier MINAS GERAIS (named after a Brazilian state), they were flown and maintained by FAB crews. However, the Brazilian Navy has considered pulling them out of storage and converting them to an AEW configuration, using a compact radar like the Brazilian Searchwater 2000 that could fit into the original Tracker belly radome.
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 "G-96 / 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. Maximum cargo capacity was 3,855 kilograms (8,500 pounds). 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 was built from 1955 into 1958, 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 it was strictly an interim type, being replaced by the Grumman C-2 Greyhound.
* The Trader led in turn to another Tracker derivative, the "G-117 / 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. Since 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 from 1958 into 1961.
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.
* The following table gives Tracker / Trader / Tracer variants and
production quantities:
variant built mod notes
____________________________________________________________________
XS2F-1 2 Initial prototypes.
YS2F-1 15 Service evaluation machines.
S2F-1 (S-2A) 740 Initial & main production variant.
CS2F-1 43 DHC-built S2F-1.
S2F-1S (S-2B) - ? S2F-1 with improved ASW kit.
S2F-2 (S-2C) 77 Bulged bombbay for nuke depth charges.
CS2F-2 57 DHC-built S2F-2.
S2F-3 (S-2D) 100 "Stretched" Tracker.
S2F-3S (S-2E) 255 S2F-3 with improved ASW kit.
S-2F - ? S2F-1 & S2F-3S with new avionics.
S2F-1T (TS-2A) - 200 S2F-1 multi-engine trainer.
US-2A - 51 S2F-1 transport / target tug.
US-2B - 75 S2F-1 utility aircraft.
S2F-2P (RS-2C) - 1 S2F-2 photo-reconnaissance conversion.
S2F-2U (US-2C) - ? S2F-2 transport conversions.
S2F-3U (US-2D) - 54 S2F-3 transport conversions.
ES-2D - 7 S2F-3 range control conversions.
S-2G - 50 S2F-3S with Bullpup ASM capability.
CP-121 - ? Canadian Tracker updates.
____________________________________________________________________
sum 1,289
____________________________________________________________________
TF-1 (C-1A) 83 Trader COD aircraft.
TF-1Q (EC-1A) 4 Trader EW aircraft.
____________________________________________________________________
sum 87
____________________________________________________________________
WF-1 1 Tracer AEW prototype.
WF-2 (E-1B) 88 Production Tracer.
____________________________________________________________________
sum 89
____________________________________________________________________
TOTAL 1,465
____________________________________________________________________
As usual, there may be minor discrepancies in this count, but it can be
regarded as well in the ballpark.
* 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.
v1.0.3 / 01 jan 06 / gvg / Minor cosmetic update.
v1.0.4 / 01 dec 07 / gvg / Minor cosmetic update.
BACK_TO_TOP
