Volvo RM8

RM8
	An RM8 on display at the Swedish Air Force Museum
Type	Turbofan
National origin	United States/Sweden
Manufacturer	Volvo Flygmotor/Pratt & Whitney
First run	1964
Major applications	Saab 37 Viggen
Developed from	Pratt & Whitney JT8D

An RM8 on display at the Swedish Air Force Museum

The Volvo RM8 is a low-bypass afterburning turbofan jet engine developed for the Saab 37 Viggen fighter. In 1962, the Pratt & Whitney JT8D-1 engine was chosen to power the Viggen in absence of a suitable and available engine designed for military use. Basically a licensed-built version of the JT8D, heavily modified for supersonic speeds, with a Swedish-designed afterburner, the RM8 was produced by Svenska Flygmotor (later known as Volvo Aero).^[1]

Variants and applications[]

RM8A - AJ 37 Viggen

Since the original engine was constructed for subsonic speeds, most parts of the engine had to be redimensioned for the higher Mach-speeds in a military aircraft. Fans and turbine were altered, a new combustion-chamber designed and a totally new fuel-control system for both engine and afterburner.^[2]

RM8B - JA 37 Viggen

The flight envelope for the fighter-version demanded both more power and better compressor stall margins. This led to a new fan-stage (the so-called "0-stage") was introduced, making the engine longer. This led to a total redesign of the fans, the low-pressure compressor and the combustion-chambers.^[3]

Specifications (RM8B)[]

Data from Flight International.^[4]

General characteristics

Type: Afterburning turbofan
Length: 6.23 m (20.44 ft)
Diameter: 1.03 m (40.55 in)
Dry weight: 2,350 kg (5,180 lb)

Components

Compressor: Axial flow, 3-stage fan, 3-stage LP, 7-stage HP
Combustors: 9 chambers in can-annular arrangement, four injectors per chamber

Performance

Maximum thrust: 72.2 kN (16,200 lbf) dry, 125 kN (28,100 lbf) wet
Overall pressure ratio: 16.5:1
Bypass ratio: 0.97:1
Turbine inlet temperature: 1,120°C (RM8A)
Specific fuel consumption: 65 kg/(kN h) (0.64 lb/(lbf h)) dry, 257 kg/(kN h) (2,52 lb/(lbf h)) wet
Thrust-to-weight ratio: 5.4

References[]

Notes

^ Gunston, p. 236
^ JAS 39 Gripen, p.32, Gunnar Lindqvist / Bo Widfeldt, Air Historic Research AB, 2003, ISBN 91-973892-5-0
^ JAS 39 Gripen, p.32&35, Gunnar Lindqvist / Bo Widfeldt, Air Historic Research AB, 2003, ISBN 91-973892-5-0
^ Flight International 14 Dec 1972

Bibliography

Gunston, Bill (1999). The Development of Piston Aero Engines, 2nd Edition. Sparkford, Somerset, England, UK: Patrick Stephens, Haynes Publishing. ISBN 0-7509-4478-1.

External links[]

Saab Viggen engine trivia
RM8 history in Swedish

[1] Gunston, p. 236

[2] JAS 39 Gripen, p.32, Gunnar Lindqvist / Bo Widfeldt, Air Historic Research AB, 2003, ISBN 91-973892-5-0

[3] JAS 39 Gripen, p.32&35, Gunnar Lindqvist / Bo Widfeldt, Air Historic Research AB, 2003, ISBN 91-973892-5-0

[4] Flight International 14 Dec 1972

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v t Pratt & Whitney aircraft engines
Radial engines	R-985 R-1340 R-1535 R-1690 R-1830 R-1860 R-2000 R-2060 R-2180-A R-2180-E R-2800 R-4360 Double Wasp Hornet (A) Hornet B Twin Hornet Twin Wasp (R-1830) Twin Wasp (R-2000) Twin Wasp E Twin Wasp Junior Wasp series Wasp Wasp Junior Wasp Major Yellow Jacket
H piston engines	X-1800/XH-2600 XH-3130 (XH-3730)
Free-piston gas turbines	PT1
Turbojets	JT3C JT4A JT6 JT7 JT8A JT11 JT12 J42 J48 J52 J57 J58 J60 J75
Turbofans	GP7000† JT3D JT4D JT8D JT9D JTF10A JT10D JTF22 PW1000G PW1120 PW2000 PW4000 PW5000 PW6000 RTF-180† SuperFan† V2500† F100 F105 F117 F119 F135 F401 TF30 TF33 XA101 RM8
Turboprops/Turboshafts	APW34† JFTD12 PT2 PT5 T34 XT57 T73 T800-APW† T900†
Propfans	578-DX†
Rocket engines	RL10
Aeroderivative gas turbine engines	GG4/FT4
Subsidiaries	Pratt & Whitney Canada Pratt & Whitney Rocketdyne
Key people	Leonard S. Hobbs George J. Mead Frederick Rentschler Richard "Dick" Soderberg
† Joint development aeroengines See also: Pratt & Whitney Canada aeroengines

v t Svenska Flygmotor/Volvo Flygmotor/Volvo Aero aero engines
Reciprocating engines
Turbojets	RM1 RM2 RM4 RM5 RM6
Turbofans	RM8 RM12