The Grumman AF Guardian was an anti-submarine warfare aircraft that was originally designed as a replacement for the Grumman Avenger and which served in small numbers in the Korean War.
In 1943 work began on an aircraft to replace the successful TBF/ TBM Avenger torpedo bomber.
Grumman’s first proposal was the Grumman TB2F. This was to be a twin engined design, powered by two Pratt & Whitney R-2800-22 radial engines, and able to carry an 8,000lb payload over 2,280 miles. However this would have been a very heavy aircraft, with an estimated gross weight of 45,000lb, and was felt to be too heavy for carrier operations.
Next was the Grumman TSF, a modified version of the twin engined F7F Tigercat. However this project was cancelled by the start of 1945.
By then Grumman had also started work on the Grumman G-70, which after a prolonged design process and several changes of designation would enter service as the AF Guardian. This design was produced in response to a Navy requirement of 1944 for a high speed torpedo bomber with composite power – a piston engine in the nose for range and a jet engine for short bursts of speed, armed with 20mm cannon.
The initial design was for a mid-wing monoplane with a crew of two sitting side by side, capable of carrying a 4,000lb payload of bombs, depth charges or torpedoes in an internal weapons bay and armed with two 20mm cannon. It was to have a mix of power plants, with a radial engine in the nose for normal flight and a turbojet in the rear fuselage to give it the speed to escape from any pursuers.
On 9 October 1944 the Grumman design was accepted by the Navy and three prototypes were ordered, two as the XTB3F-1 and one as the XTB3F-2. The XTB3F-1 was to be powered by a 2,300hp Pratt & Whitney R-2800-34W radial engine in the nose and 1,600lb thrust Westinghouse 19XB-2B in the rear. The XTB3F-2 was to use a Wright R-3350 in the nose and Westinghouse 24C-4B in the rear. The crew of two would side almost side by side in the cockpit, with observer a little behind the pilot. Ground tests revealed problems with the jet air intake, so when the first aircraft made its maiden flight on 19 December 1946 the jet intake was covered. The jet engine would never be used in flight, and on 24 December, only five days after the initial maiden flight work on the TB3F was cancelled.
Although the Navy no longer needed the TB3F as a torpedo bomber, it did now need new anti-submarine warfare aircraft. With the jet engine removed the Grumman aircraft would have plenty of space for anti-submarine equipment, so the project was revived. The second and third prototypes were to be completed, one as a submarine killer and the other as a submarine hunter. On 29 January 1947 the Navy ordered work to resume on the two remaining prototypes, this time as a part of anti-submarine warfare aircraft.
The third prototype became the hunter, as the XTB3F-1S. The jet engine was removed, and the space released by that used to carry electronic equipment and space for a radio operator. The original observer’s seat was also moved back into the rear fuselage. The bomb bay was used to carry the AN/ APS-20 search radar with a large ventral radome below it. This aircraft made its maiden flight in November 1948. In March 1948 it became the AF-1S, in May 1949 the AF-1W and in July 1949 the AF-2W, which would be its service designation.
The second prototype became the killer, as the XTB3F-2S. This kept its bomb bay and would be used to attack the aircraft found by the hunter. The hunter could carry six 5in HVAR rockets or four 500lb bombs or four Mk 54 depth charges under the wings and a homing torpedo in the original torpedo bay. This aircraft made its maiden flight on 12 January 1949. In March 1948 it became the AF-2S, in May 1949 the AF-1S and in July 1949 the AF-2S.
The idea was for the two variants to operate in pairs, with the hunter detecting the submarine and the killer attacking it. The concept was considered successful enough for a production order to be placed, with the hunter designated as the AF-2W and the killer as the AF-2S.
The two prototypes took part in Service Acceptance and Production Trials at NAS Patuxent River, Maryland, on2-3 February 1949. Some changes to the controls were required, along with better brakes and an improved tail wheel. The second prototype was lost in a crash on 4 October 1949. The third was used for carrier suitability trials from 27 September-16 December 1949, which revealed problems with the long propeller in use. This was replaced with the same 12ft 2in propeller used on the Grumman F8F-2. A series of changes were recommended after these trials,
The aircraft had already been ordered into production, and the first production AF-2S made its maiden flight on 17 November 1949. Between May 1950 and November 1951 five of each type were used for trials with Air Development Squadron 1 (VC-1) at Key West. Carrier qualification took place on USS Wright in November 1950, USS Palau in December 1950 and USS Monterey in September 1951. The aircraft entered service with VS-25 and NAS North Island on 18 October 1950, and remained in front line service for five years. It was a sign of the speed of aircraft development that work on its replacement, the Grumman S2F Tracker, actually began on 30 June 1950, before the AF-2 had actually entered service, but that aircraft didn’t replace the last AF-2s, this time with VS-37 at NAS North Island, until 31 August 1955.
The AF-2 began to enter fleet service in September 1950 when VS-24 received its aircraft at Norfolk. At this point it still had some problems with the controls, especially at low speeds. It was used by squadrons operating from Commencement Bay escort carriers, the smallest carriers then in service, and from the Independence class light carriers, so suffered from a higher than normal accident rate. The first carrier landings took place on USS Wright (CVL-49) on 26-27 November 1950. VS-24 then carried out its carrier qualification trials on USS Palau (CVE-122) on 18-20 December.
Three more squadrons received the AF in 1951. The standard issue was nine AF-2Ss, nine AF-2Ws and one Beech SNB for use as a squadron hack. When the AF-3S entered service in 1943 it joined the attack aircraft, and the total number of aircraft was increased to twenty. At first the entire complement of aircraft would go onto the escort carriers, but later they were joined by helicopters from early HS helicopter squadrons, which reduced the available space. After this seven attack and seven hunter aircraft would be onboard. This changed again when Essex class carriers converted into CVS anti-submarine carriers began to enter service in 1953, and the full squadrons could go onboard. However in 1954 the squadrons began to convert to the Grumman S2F-1 Tracker and the last fleet aircraft, from VS-37, went to the reserves on 31 August 1955.
In service the AF-2 was seen as a significant improvement over the TBM Avengers it was replacing. It was larger and more comfortable and could be operated for longer periods without triggering pilot fatigue. The searcher carried far more effective detection equipment and the hunter a larger payload of weapons.
The AF-2 saw a limited amount of combat during the Korean War, although there was never more than one squadron in the theatre at the same time.
The first squadron to serve off Korea was VS-25, which served on USS Bairoko (CVE-115) from December 1951 to January 1952, then on the Bataan from February-April 1952 and the Bairoko again from May-June 1952.
Next was VS-20, which served on the Badoeng Strait (CVE-116) from August-October 1952. During this deployment the squadron took part in a large scale feint off Kojo on the east coast of Korea.
The last squadron to use the AF-2 off Korea was VS-21, once again on the Bairoko, from February to April 1953.
VS-931 began to convert to the AF-2 at NAS Los Alamitos on 30 September 1951. It became VS-20 on 4 February 1953 and converted to the S2F-1 Tracker from October-December 1954.
In the first few months of 1952 the squadron operated from USS Bataan (CVL-29), USS Rendova (CVE-114), USS Bon Homme Richard (CV-31) and USS Sicily (CVE-118) for training and carrier qualification. It then travelled to Japan on USS Sicily. It saw active service off Korea on the Badoeng Strait (CVE-116) from August-October 1952 then returned to the US on the Sicily.
From December 1953-June 1954 she was based on USS Rendova (CVE-114), taking part in anti-submarine warfare exercises.
VS-1 converted to the AF-2 in December 1950, when it became to receive the AF-2W. However the fisrt AF-2S didn’t arrive until May 1952 and it wasn’t fully equipped until September 1952. It began to convert to the S2F-1 Tracker in June 1955.
The squadron carried out carrier conversion and training on the Kearsarge (CV-33), Rendova (CVE-114), Valley Forge (CV-45), Philippine Sea (CV-47) and Bataan (CVL-29) from July-October 1952. It the travelled across the Pacific on the Cape Esperance (CVE-88) and was based on Guam from November 1952 to May 1953. From February to early April seventeen of its aircraft operated from the Bairoko (CVE-115) off Korea. It then returned to the US on the Bataan in May 1953.
From April-November 1954 the squadron served on USS Point Cruz (CVE-119) in the western Pacific.
VS-22 began to convert to the AF-2 on 27 June 1951 and to the S2F Tracker in June 1954.
Carrier qualification and training took place on the Siboney (CVE-112) and Mindoro (CVE-120) in the first half of 1952. From August-October the squadron deployed to the North Sea on the Mindoro to take part in Exercise Mainbrace, NATO’s first anti-submarine exercise, the Exercise Emigrant.
In 1953 the squadron operated from the Salerno Bay (CVE-110), Gilbert Islands (CVE-107) and Block Island (CVE-106), and served in the Mediterranean from October- November on the Block Island. In 1954 the squadron operated from the Sibonet (CVE-112).
VS-24 began to convert to the AF-2 in September 1950 and used it for carrier suitability trials on the Palau (CVE-122) from December 1950 to March 1951. It began to convert to the S2F Tracker in November 1954.
The squadron operated on USS Cabot (CVL-28) in the North Atlantic in August-October 1951, then the Saipan (CVL-48) from October-November. In 1952 she was on the Cabot from January-March then the Wright (CVL-49) from April-July. In 1953 she was on the Gilbert Islands (CVE-107) then the Wright.
In January –February 1954 she took part in the Leyte (CVS-32)’s shakedown cruise in her new configuration. She was back on the Leyte in March and April, serving alongside VS-36 in April, the only occasion two VS squadrons used the AF-2 on the same carrier. In June she was on the Valley Forge (CVS-45) and in August the Antietam (CVS-36).
VS-25 began to convert to the AF-2 on 17 October 1950 and was fully equipped by March 1951. It converted to the S2F in June-July 1954.
The squadron carried out exercises and carrier qualifications on the Essex (CV-9), Badoeng Strait (CVE-116) and Bairoko (CVE-115) in 1951.
In December 1951 she deployed to the Western Pacific on the Bairoko, operating on her until 21 January 1952 during the carrier’s first period off Korea. She then served on the Bataan (CVL-29) from February-April 1952, when that carrier was serving in the Yellow Sea, blockading the west coast of North Korea. She then returned to the Bairoko in May-June 1952, for another spell of active duty. She then returned to San Diego.
In July 1953 the squadron moved to Guam on the Sicily (CVE-118) and operated from Guam until it returned to the Sicily to move to Japan. It returned to San Diego early in 1954.
VS-27 converted to the AF-2 in January 1952 and to the S2F Tracker from November 1954 to January 1955.
In March-June 1952 the squadron operated from the Palau (CVE-122) in the Mediterranean, then from the same carrier in the Norfolk area in August-September and the on the Salerno Bay (CVE-110) in October.
From February-April 1953 the squadron operated on the Wright (CVL-49) in the Mediterranean. Later in the year the squadron was split, with one hunter-killer team serving on the Antietam (CVS-36) from July-September, while the rest of the squadron was deployed to Guantanamo Bay from August-October. In November the squadron was on the Kula Gulf (CVE-108).
1954 saw the squadron operate on the Kula Gulf, Antietam, Mindoro and Leyte.
VS-801 began to convert to the AF-2 in February 1952. It became VS-30 on 1 April 1953 and converted to the S2F from September-December 1954.
In 1952 the squadron trained on the Block Island (CVE-106), Palau (CVE-122) and Kula Gulf (CVE-108) then deployed to the Caribbean on the Wright (CVL-49)
In 1953 she took part in Operation Springboard in the Caribbean on the Block Island , then served on the same carrier for ASW exercises in the North Sea and Mediterranean. In October she was used for carrier qualification flights on the Mindoro (CVE-120). During 1954 she deployed four times on the Mindoro, again visiting the Caribbean and Mediterranean.
VS-31 began to convert to the AF-2 in April 1951 and converted to the S2F from Mrch 1955.
In 1951 the squadron carried out carrier qualification on the Palau (CVE-122), took part in low wing landing tests on the Monterey (CVL-27), and LANTFLEX 51 in the Caribbean on the Wright (CVL-49).
In 1952 the squadron took part in training on the Mindoro (CVE-120) before splitting up to provide contingents to the Saipan (CVL-48) and Wright for CONVEX III in the Caribbean. It then deployed to the Mediterranean on the Palau, and underwent training on the Block Island.
In 1953 it served on the Gilbert Islands (CVE-107), then the Siboney (CVE-112) in the Mediterranean.
In 1954 it took part in the shakedown cruise of the Valley Forge (CVS-45), then on the Kula Gulf (CVE-108).
VS-831 began to convert to the AF in September 1952. It became VS-36 in February 1953 and began to convert to the S2F in September 1954.
In 1953 the squadron trained on the Saipan (CVL-48) and Siboney (CVE-112) then visited South America on the Saipan before ending the year on the Gilbert Islands (CVE-107).
In 1954 the squadron served in the Mediterranean, then on USS Leyte.
VS-971 began to convert to the AF on 30 April 1953. It became VS-37 in July 1953 and converted to the S2F in June 1955.
The squadron spent 1953 training, with spells on the Bataan (CVL-29) and Rendova (CVE-114)
In 1954 is served on the Badoeng Strait from April-June, then on the Princeton (CVS-37). From November 1954-April 1955 it served in the Western Pacific on the Princeton.
VS-912 began to convert to the AF-2 in December 1951 but wasn’t fully equipped until September 1952. In February 1953 it became VS-39 and it converted to the S2F between April and June 1955.
During 1953 the squadron served on the Salerno Bay (CVE-110), Siboney (CVE-112) and Gilbert Islands (CVE-108).
In 1954 it served on the Antietam (CVS-36), including time spent operating with the Royal Navy off the coast of Northern Ireland.
In 1955 it served on the Siboney in the Caribbean.
The AF-2S was the first version of the killer part of the partnership, and a total of 193 were built. It was a conventional looking piston engine aircraft with a mid-mounted wing and high mounted horizontal tail surfaces. Early examples had rounded fin and rudder tips similar to those on the F8F Bearcat but most production aircraft had squared off wing and rudder tips more similar to the F4F and F6F. The control surfaces were fabric covered. Most were conventional, but it used hydraulically powered flaperons (spoiler ailerons), which combined the functions of flaps and ailerons in a single devise. The rudder was also hydraulically boosted. It was powered by a 2,400hp Pratt & Whitney R-2800-48W engine which was pointed 3 degress to the right to counter the high torque of the large propeller.
The AF-2S could carry up to 4,000lb of armaments in its bomb bay. It also had six underwing pylons for HVAR rockets or 250lb depth charges and carried sonobuoys under the wings. It wasn’t entirely without radar and carried a AN/ APS-31 radar set under the starboard wing. It also had a AN/ AVQW-2 high intensity searchlight under the port wing. It carried a crew of two.
Another 40 aircraft were delivered between February 1952 and November 1953 as the AF-3S. These carried more ASW equipment, including a Magnetic Anomaly Detector Boom on the starboard side of the fuselage.
A total of 153 of the hunter part of the partnership were built. These carried a crew of four and an extensive array of electronic equipment. They could easily be identified by the large radome for the AN/ APS-20 radar below the fuselage. They were entirely unarmed.
Engine: Pratt & Whitney R-2800-48W
Crew: 2 (-2S) or 4 (-2W)
Span: 60ft 9in
Length: 43ft 4in
Height: 16ft 2in
Empty weight: 14,580lb
Gross weight: 25,500lb
Max speed: 317mph at 16,000ft
Climb Rate: 1,850ft/ min
Service ceiling: 32,500ft
Range: 1,500 miles
Armament (-2S only): One 2,000lb torpedo or two 2,000lb bombs or two 1,600lb depth charges