Bell's model 47 was a development of the Model 30. Five Model 30 aircraft were built in 1943 , and the third of these provided the basis of the Model 47. Eleven prototype and evaluation aircraft were built. The first prototype to fly was on December 8 1945. The aircraft featured an open side by side cockpit, quadricycle undercarriage, and a 175hp Franklin O335-1 engine. Type certification was achieved on March 8, 1946 - the first civil helicopter certification. Stereotyped today as the 'MASH' helicopter, the aircraft proved popular in civil and military use.
The USAAF were the first air force to acquire the helicopter. Twenty-eight 175hp Franklin O-335-1 powered model 47A aircraft were received in 1947, with fifteen evaluated as the YR-13, three as winterised YR-13a, and 10 passed to the USN for evaluation as the HTL-1. Both services ordered further aircraft. The 175hp Franklin 6ALV-335 powered model 47B led to the initial US Army military version (65 aircraft ordered in 1948). This was powered by the 200hp Franklin O335-3 and designated the H-13B and named the Sioux. Parallel civil development lead to the model 47B-3 aimed at the agricultural and utility role. Military development started with the H-13C conversion of 15 aircraft which included the removal of the tail covering, a change to skid undercarriage, and provision to carry external stretchers in panniers. The civil model 47D was similar, but introduced the plexiglass 'goldfish bowl' style canopy in place of the previous 'car' type windscreen. The 1949 model 47D-1 was a three seater powered by the 200hp Franklin O335-5 and had an openwork tailboom like the H-13C. The H-13D (87 ordered) had two seats with single controls and featured the uprated O-335-5 engine. The H-13E was a dual control 3-seater, featuring a new main transmission and 490 were ordered.
The definitive civil version was the model 47G and was produced in 10 variants, primarily distinguished by engine installation. The three seater was initially powered by the 200hp Franklin 6V4-200-C32AB, added extra fuel capacity, and introduced new stability features including a small elevator on the tail. The military designation was the H-13G and 260 were delivered. The model 47G-2 was uprated with the 200hp Lycoming VO-435 engine, while the model 47G-2A (similar to the H-13H) had a 250hp Lycoming VO-435. Other models (like the 47G-2A-1) incorporated increased fuel and improvements to the rotor blades. The model 47G-3A was a 225hp supercharged Franklin 6VS-335A powered version, while the 47G-3B had a turbocharged 260hp Lycoming VO-435-25. The 47G-3B also featured a tail extension of 0.36 m (1'2ft) and had the rotor diameter increased by 0.61m (2ft). 265 were delivered as the OH-13S. Similar to the 47G-3B-1 with its increased cabin width, and featuring extra avionics, the TH-13T was a two seat instrument trainer. Two H-13H were converted to H-13K by installing the Franklin 6VS-335 engine and increasing the rotor diameter. The H-13H was also used by the USAF, as was the 3 seat 240hp Lycoming VO-435 powered H-13 J used as a Presidential transport. The model 47J Ranger was produced as a 4 seat civil version of the H-13J which ran to 6 variants.
Post 1962 the various military designations were changed in line with the new tri-service nomenclature. Most were designated as OH-13 or TH-13 of various marks, with the USAF, USN and Coast Guard having a number of versions in service. A number of non-US military operators have utilised the Bell 47. Some military operators purchased civil models. Augusta, Kawasaki , and Westland produced the aircraft under license (1,200, 239, and 216 repectively). Bell ceased production after more than 4000 units in 1973, and Augusta produced the last model 47 in 1976. Third party conversions have primarily been agricultural, or engine related (such as the Soloy turboshaft conversion).
The first model 47 to visit New Zealand came with a US Coast Guard Icebreaker in December 1955. The first model 47 on the New Zealand civil register was ZK-HAC, a model 47G imported by James Aviation. This began work in the upper South Island in May 1956. It was later used for hydro-electric survey work. The aircraft was damaged in a landing accident in a remote area along the Motu river on May 7, 1957. Although some instruments had been salvaged, the remainder of the airframe was swept away in a flash flood on May 19th. ZK-HAC was the second helicopter on the register, following ZK-HAB, a Hiller UH-12B which had first flown at Hamilton on January 11, 1955 and also belonged to James Aviation. (Helicopter registrations until fairly recently have started ZK-H). For the first ten years of helicopter operations, registrations were fairly evenly split between these two types. ZK-HAA was also a Model 47. The registration had been reserved for Helicopters (NZ) Ltd in 1955, but the model 47D-1 it was applied to did not commence work until September 1956. In the years that followed, about 60 model 47 variants have been registered in New Zealand. The aircraft has filled many roles - passenger, freight, medivac, ag-spraying, pilot and customs onboard delivery, deer culling and recovery, fish spotting, and more. In recent years the active numbers of this venerable helicopter have steadily shrunk. The last model 47 on the active register was withdrawn on March 24, 1999 having been exported to Australia (where it became VH-AHL). This was ZK-HSO (c/n 7632), a model 47G-4A operated by B A & J C Emeny Ltd. It was preceded by two model 47G-5A's; ZK-HAK (c/n 25160) which was withdrawn in February, 1998, and ZK-HUN (c/n 25052) which was also exported to Australia in November. It's hard to say thats the end of the road however, as a variety of airframes are still to be found in hangars around the country.
The RNZAF ordered its first helicopters in April 1965. The order was for 6 Bell 47G-3B1, 5 UH-1D Iroquois, and 2 Westland Wasp HAS.1 aircraft. The Model 47 aircraft arrived on December 17, 1965 and were subsequently the first helicopters to go into New Zealand military service. The aircraft were allocated to 3 (Battlefield Support) Squadron, a tri-service unit based at Hobsonville. The RNZAF have been responisible for Army and Naval pilot training, and the maintenance of their aircraft. A further order was placed in June 1968 for another 7 Model 47G-3B2 aircraft (along with more Iroquois and some A-4K Skyhawks) which arrived in 1970. These were also assigned to 3 Squadron (which had lost the 'Battlefield Support' designation in 1969), although three helicopters were assigned to the Pilot Training Squadron at Wigram later that year. Although the aircraft were built as civil versions, they correspond to the OH-13S and have been known as Sioux throughout their service. The role of the Sioux has been reconnaisance, battlefield liason, utility work, and as a basic trainer. As well as New Zealand operations (Primarily from Hobsonville and Waiouru), the aircraft have operated in Australia, Fiji, and Malaysia. As a result of the training role, and low level flying in support of the other roles, the Sioux have had the highest attrition rate of any post-war RNZAF aircraft. This is despite a number of rebuilds.
The machines lost in service were:
All surviving airframes had been converted to Model 47G-3B2 standard by 1979. In 1988, as a result of reduced airframe numbers, the aircraft was restricted to the basic training role. Training of Army pilots was discontinued. (Interestingly, the first two Army pilots had been trained in late 1963 by John Reid of Helicopters (NZ) Ltd in model 47G-2 ZK-HAQ. Captain R.Pearce and Lieutenant W.Steward were then posted to a British helicopter unit in Malaya for two years). Pilot training was moved from Wigram back to Hobsonville in 1994 (due to the impending closure of the base). Although a replacement has been considered, this has been deferred a number of times. Five aircraft remain in service as of May 1, 2000 (with three operational and two in reserve). The listing below shows the current RNZAF aircraft.
The remaining machines are:
Last Text Update:- 20 May, 2000
Last Picture Update:- 14 May, 2003
Data is for the Model 47G-3B-2
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