Bell H-12

H-12 (Model 48)

YH-12B
Role	five/eight seat utility helicopter
Manufacturer	Bell Helicopter
First flight	1946
Status	pre-series
Primary user	United States Air Force
Number built	13^[1]
Unit cost	(YR-12) $175,000^[1]

The Bell R-12 (Model 48), re-designated as the Bell H-12, was an American 1940s military utility helicopter built by Bell Helicopter company.^[2]

Design and development

During 1946, Bell Helicopter began development of a new utility helicopter, the Model 42, much larger than the Model 47, utilized a scaled-up version of the Model 47's rotor system. Three prototypes were built but serious rotor problems and complexity of mechanical systems precluded production. The initial Model 42 variant was civilian, but the United States Air Force ordered the development of its military variant, the Model 48, of which, two prototypes were ordered as the XR-12, powered by a single 540 horsepower (403 kW) Pratt & Whitney R-1340-AN-1 radial engine and featuring seating for five. Of very similar construction to the Model 42 the Model 48 had a shorter rotor mast. A production batch of 34 helicopters was ordered, under the designation R-12A, but cancelled in 1947.^[1]

Another enlarged prototype (the XR-12B, Model 48A) with seats for eight plus two pilots and a more powerful 600 horsepower (447 kW) Pratt & Whitney R-1340-55 engine was also ordered, followed by 10 pre-series YR-12B helicopters, with a glazed nose, instead of the car-like nose of the Model 42 and XR-12. While under flight test the helicopter was re-designated the H-12, but the results were not satisfactory, there were major problems with the main rotor due to blade weaving and poor rotor governor performance.^[1]

Operational history

No production H-12 aircraft were built but the prototypes and pre-production aircraft were used for various test and development programs.^[1]

Variants

Model 42: Bell's initial foray into the civilian luxury helicopter market, seating five. Three prototypes were built but serious problems precluded production.
Model 48: Company designation for the military version of the Model 42, given the designation R-12. Two built as XR-12s and a production contract for 34 was cancelled in 1947.
Model 48A: The more powerful derivative of the Model 48 with a 600 hp engine and 10 seats. One XR-12B/XH-12B prototype was produced and a pre-production batch of 10 were also built as YR-12B/YH-12Bs
XR-12: Prototype, redesignated XH-12, two built.
R-12A: Production version, 34 on order canceled.
XR-12B: Prototype with more powerful engine and increased seating, re-designated XH-12B, one built.
YR-12B: As XR-12B but with R-1340-55 engines, re-designated YH-12B, 10 built.
XH-12: XR-12 re-designated in 1947.
XH-12B: XR-12B re-designated in 1947.
YH-12B: YR-12B re-designated in 1947.^[1]

Operators

United States

United States Air Force^[3]

Specifications (XR-12B)

Data from Bell Aircraft since 1935^[1]

General characteristics

Crew: 1
Capacity: 9
Length: 56 ft 9 in (17.30 m)
Height: 11 ft 3.25 in (3.4354 m)
Gross weight: 6,286 lb (2,851 kg)
Powerplant: 1 × Pratt & Whitney R-1340-55 Wasp 9-cyl. air-cooled radial piston engine, 600 hp (450 kW)
Main rotor diameter: 47 ft 6 in (14.48 m)
Main rotor area: 1,772 sq ft (164.6 m²)

Performance

Maximum speed: 105 mph (169 km/h; 91 kn)
Cruise speed: 90 mph (78 kn; 145 km/h)
Range: 300 mi (261 nmi; 483 km)
Service ceiling: 12,800 ft (3,901 m) service ceiling
- Absolute ceiling: 15,000 ft (4,572 m)
- Hover ceiling: 4,350 ft (1,326 m)

References

Notes

1 2 3 4 5 6 7 Pelletier 1992, p. 92.
↑ Pelletier 1992, p. 91.
↑ "Bell Model 48". aer.ita.br. Retrieved 18 October 2014.

Bibliography

Andrade, John M. U.S.Military Aircraft Designation and Serials since 1909. Leicester, UK: Midland Counties Publications, 1979. ISBN 0-904597-22-9.
The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). London, Orbis Publishing, 1985.
Pelletier, A.J. Bell Aircraft since 1935. London: Putnam & Company Ltd., 1992. ISBN 1-55750-056-8.

External links

Wikimedia Commons has media related to Bell 48.

"Copter Ferry Hops To The Front.", Popular Science, December 1950, large and detailed article with rare photos

Aircraft produced by Bell Aircraft and Bell Helicopter

Manufacturer designations	1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 32 33 34 35 36 38 39 40 41 42 43 44 45 47 48 49 50 52 54 58 59 60 61 65 66 67 68 200 201 204 205 206 207 208 210 211 209 212 214/214ST 222 230 249 301 309 400 407 409 412 417 427 429 430 440 445 449 505 525 533 D-188 D-255 D-292

Fighter aircraft	YFM-1 Airacuda P-39 Airacobra XFL Airabonita P-59 Airacomet P-63 Kingcobra XP-77 XP-83

Target drones	PQM-56

Attack helicopters	207 AH-1 (singles) AH-1 (twins) 309 YAH-63

Observation and utility helicopters	H-13 Sioux UH-1 Iroquois UH-1N UH-1Y TH-57 OH-58 Kiowa TH-67 Creek ARH-70 Arapaho

Commercial helicopters	47 204 205 206 210 212 214 214ST 222 230 407 412 427 429 430 505 525

Tiltrotors	V-22 Osprey V-247 V-280 BA609 TR918 QTR

UAVs	MQ-8C

Non-production helicopters	400 417 440

Experimental aircraft	ATV 201 533 D-188 D-255 D-292 L-39 LLRV/LLTV X-1 X-2 X-5 X-14 X-22 XF-109 XP-52 XV-3 XV-15

United States helicopter designations, Army/Air Force and Tri-Service systems

Numerical sequence used by USAAC/USAAF/USAF 1941–present; US Army 1948–1956 and 1962–present; US Navy 1962–present

Main sequence
(1941–1962)

Prefix R-, 1941–1948	R-1 R-2 R-3 R-4 R-5 R-6 R-7 R-8 R-9 R-10 R-11 R-12 R-13 R-14 R-15 R-16

Prefix H-, 1948–1962	H-5 H-6 H-9 H-10 H-11 H-12 H-13/J H-15 H-16 H-17 H-18 H-19 H-20 H-21 H-22 H-23 H-24 H-25 H-26 H-27 H-28 H-29 H-30 H-31 H-32 H-33 H-34 H-35 H-36¹ H-37 H-38¹ H-39 H-40 H-41 H-42 H-43 H-44¹ H-45¹

Main joint sequence
(1962–present)

1962 redesignations	OH-13/UH-13J UH-19 CH-21 OH-23 UH-25 CH-34 CH-37 HH-43

New designations	CH-46/HH-46/UH-46 CH-47 UH-48 XH-49 QH-50 XH-51 HH-52 CH-53/HH-53/MH-53/CH-53E/CH-53K CH-54 TH-55 AH-56 TH-57 OH-58 XH-59 UH-60/SH-60/HH-60/HH-60J YUH-61 XCH-62 YAH-63 AH-64 HH-65 RAH-66 TH-67 MH-68 H-69¹ ARH-70 VH-71 UH-72 H-73 to H-89¹ MH-90 H-91¹ VH-92

1962 redesignations
reusing old numbers

¹ Not assigned

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