Thrust-specific fuel consumption

Template:Short description Thrust-specific fuel consumption (TSFC) is the fuel efficiency of an engine design with respect to thrust output. TSFC may also be thought of as fuel consumption (grams/second) per unit of thrust (newtons, or N), hence thrust-specific. This figure is inversely proportional to specific impulse, which is the amount of thrust produced per unit fuel consumed.

TSFC or SFC for thrust engines (e.g. turbojets, turbofans, ramjets, rockets, etc.) is the mass of fuel needed to provide the net thrust for a given period e.g. lb/(h·lbf) (pounds of fuel per hour-pound of thrust) or g/(s·kN) (grams of fuel per second-kilonewton). Mass of fuel is used, rather than volume (gallons or litres) for the fuel measure, since it is independent of temperature.

Specific fuel consumption of air-breathing jet engines at their maximum efficiency is more or less proportional to exhaust speed. The fuel consumption per mile or per kilometre is a more appropriate comparison for aircraft that travel at very different speeds.Template:Not in body Power-specific fuel consumption, the thrust-specific fuel consumption divided by speed, can have units of pounds per hour per horsepower.

Significance of SFC

SFC is dependent on engine design, but differences in the SFC between different engines using the same underlying technology tend to be quite small. Increasing overall pressure ratio on jet engines tends to decrease SFC.

In practical applications, other factors are usually highly significant in determining the fuel efficiency of a particular engine design in that particular application. For instance, in aircraft, turbine (jet and turboprop) engines are typically much smaller and lighter than equivalently powerful piston engine designs, both properties reducing the levels of drag on the plane and reducing the amount of power needed to move the aircraft. Therefore, turbines are more efficient for aircraft propulsion than might be indicated by a simplistic look at the table below.

SFC varies with throttle setting, altitude, climate. For jet engines, air flight speed is an important factor too. Air flight speed counteracts the jet's exhaust speed. (In an artificial and extreme case with the aircraft flying exactly at the exhaust speed, one can easily imagine why the jet's net thrust should be near zero.) Moreover, since work is force (i.e., thrust) times distance, mechanical power is force times speed. Thus, although the nominal SFC is a useful measure of fuel efficiency, it should be divided by speed when comparing engines at different speeds.

For example, Concorde cruised at 1354 mph, or 7.15 million feet per hour, with its engines giving an SFC of 1.195 lb/(lbf·h) (see below); this means the engines transferred 5.98 million foot pounds per pound of fuel (17.9 MJ/kg), equivalent, for a subsonic aircraft flying at 570 mph, to an SFC of 0.50 lb/(lbf·h), better than subsonic engines of the time. The Olympus 593 used in the Concorde was the world's most efficient jet engine. However, Concorde ultimately has a heavier airframe and, due to being supersonic, is less aerodynamically efficient, i.e., the lift to drag ratio is far lower. In general, the total fuel burn of a complete aircraft is of far more importance to the customer.

Units

	Specific impulse (by weight)	Specific impulse (by mass)	Effective exhaust velocity	Specific fuel consumption
SI	=X seconds	=9.8066 X N·s/kg	=9.8066 X m/s	=101,972 (1/X) g/(kN·s) / {g/(kN·s)=s/m}
Imperial units	=X seconds	=X lbf·s/lb	=32.16 X ft/s	=3,600 (1/X) lb/(lbf·h)

Typical values of SFC for thrust engines

Rocket engines in vacuum
Model	Type	First run	Application	TSFC		Isp (by weight)	Isp (by mass)
				lb/lbf·h	g/kN·s	s	m/s
Avio P80	solid fuel	2006	Vega stage 1			280
Avio Zefiro 23	solid fuel	2006	Vega stage 2			287.5
Avio Zefiro 9A	solid fuel	2008	Vega stage 3			295.2
Merlin 1D	liquid fuel	2013	Falcon 9			310
RD-843	liquid fuel	2012	Vega upper stage			315.5
Kuznetsov NK-33	liquid fuel	1970s	N-1F, Soyuz-2-1v stage 1			331
NPO Energomash RD-171M	liquid fuel	1985	Zenit-2M, -3SL, -3SLB, -3F stage 1			337
LE-7A	cryogenic	2001	H-IIA, H-IIB stage 1			438
Snecma HM-7B	cryogenic	1979	Ariane 2, 3, 4, 5 ECA upper stage			444.6
LE-5B-2	cryogenic	2009	H-IIA, H-IIB upper stage			447
Aerojet Rocketdyne RS-25	cryogenic	1981	Space Shuttle, SLS stage 1			453
Aerojet Rocketdyne RL-10B-2	cryogenic	1998	Delta III, Delta IV, SLS upper stage			465.5
NERVA NRX A6	nuclear	1967				869

Jet engines with Reheat, static, sea level
Model	Type	First run	Application	TSFC		Isp (by weight)	Isp (by mass)
				lb/lbf·h	g/kN·s	s	m/s
Turbo-Union RB.199	turbofan		Tornado	2.5
GE F101-GE-102	turbofan	1970s	B-1B	2.46
Tumansky R-25-300	turbojet		MIG-21bis	2.206
GE J85-GE-21	turbojet		F-5E/F	2.13
GE F110-GE-132	turbofan		F-16E/F	2.09
Honeywell/ITEC F125	turbofan		F-CK-1	2.06
Snecma M53-P2	turbofan		Mirage 2000C/D/N	2.05
Snecma Atar 09C	turbojet		Mirage III	2.03	57.5
Snecma Atar 09K-50	turbojet		Mirage IV, 50, F1	1.991
GE J79-GE-15	turbojet		F-4E/EJ/F/G, RF-4E	1.965	55.7
Saturn AL-31F	turbofan		Su-27/P/K	1.96
GE F110-GE-129	turbofan		F-16C/D, F-15EX	1.9
Soloviev D-30F6	turbofan		MiG-31, S-37/Su-47	1.863
Lyulka AL-21F-3	turbojet		Su-17, Su-22	1.86
Klimov RD-33	turbofan	1974	MiG-29	1.85
Saturn AL-41F-1S	turbofan		Su-35S/T-10BM	1.819
Volvo RM12	turbofan	1978	Gripen A/B/C/D	1.78
GE F404-GE-402	turbofan		F/A-18C/D	1.74	49
Kuznetsov NK-32	turbofan	1980	Tu-144LL, Tu-160	1.7
Snecma M88-2	turbofan	1989	Rafale	1.663	47.11
Eurojet EJ200	turbofan	1991	Eurofighter	1.66–1.73	47–49

Dry jet engines, static, sea level
Model	Type	First run	Application	TSFC		Isp (by weight)	Isp (by mass)
				lb/lbf·h	g/kN·s	s	m/s
GE J85-GE-21	turbojet		F-5E/F	1.24
Snecma Atar 09C	turbojet		Mirage III	1.01
Snecma Atar 09K-50	turbojet		Mirage IV, 50, F1	0.981
Snecma Atar 08K-50	turbojet		Super Étendard	0.971
Tumansky R-25-300	turbojet		MIG-21bis	0.961
Lyulka AL-21F-3	turbojet		Su-17, Su-22	0.86
GE J79-GE-15	turbojet		F-4E/EJ/F/G, RF-4E	0.85
Snecma M53-P2	turbofan		Mirage 2000C/D/N	0.85
Volvo RM12	turbofan	1978	Gripen A/B/C/D	0.824
RR Turbomeca Adour	turbofan	1999	Jaguar retrofit	0.81	23
Honeywell/ITEC F124	turbofan	1979	L-159, X-45	0.81
Honeywell/ITEC F125	turbofan		F-CK-1	0.8
PW J52-P-408	turbojet		A-4M/N, TA-4KU, EA-6B	0.79
Saturn AL-41F-1S	turbofan		Su-35S/T-10BM	0.79
Snecma M88-2	turbofan	1989	Rafale	0.782	22.14
Klimov RD-33	turbofan	1974	MiG-29	0.77
RR Pegasus 11-61	turbofan		AV-8B+	0.76
Eurojet EJ200	turbofan	1991	Eurofighter	0.74–0.81	21–23
GE F414-GE-400	turbofan	1993	F/A-18E/F	0.724
Kuznetsov NK-32	turbofan	1980	Tu-144LL, Tu-160	0.72-0.73
Soloviev D-30F6	turbofan		MiG-31, S-37/Su-47	0.716
Snecma Larzac	turbofan	1972	Alpha Jet	0.716
IHI F3	turbofan	1981	Kawasaki T-4	0.7
Saturn AL-31F	turbofan		Su-27 /P/K	0.666-0.78
RR Spey RB.168	turbofan		AMX	0.66
GE F110-GE-129	turbofan		F-16C/D, F-15	0.64
GE F110-GE-132	turbofan		F-16E/F	0.64
Turbo-Union RB.199	turbofan		Tornado ECR	0.637
PW F119-PW-100	turbofan	1992	F-22	0.61
Turbo-Union RB.199	turbofan		Tornado	0.598
GE F101-GE-102	turbofan	1970s	B-1B	0.562
PW TF33-P-3	turbofan		B-52H, NB-52H	0.52
RR AE 3007H	turbofan		RQ-4, MQ-4C	0.39
GE F118-GE-100	turbofan	1980s	B-2	0.375
GE F118-GE-101	turbofan	1980s	U-2S	0.375
General Electric CF6-50C2	turbofan		A300, DC-10-30	0.371
GE TF34-GE-100	turbofan		A-10	0.37
CFM CFM56-2B1	turbofan		C-135, RC-135	0.36
Progress D-18T	turbofan	1980	An-124, An-225	0.345
PW F117-PW-100	turbofan		C-17	0.34
PW PW2040	turbofan		Boeing 757	0.33
CFM CFM56-3C1	turbofan		737 Classic	0.33
GE CF6-80C2	turbofan		744, 767, MD-11, A300/310, C-5M	0.307-0.344
EA GP7270	turbofan		A380-861	0.299
GE GE90-85B	turbofan		777-200/200ER/300	0.298
GE GE90-94B	turbofan		777-200/200ER/300	0.2974
RR Trent 970-84	turbofan	2003	A380-841	0.295
GE GEnx-1B70	turbofan		787-8	0.2845
RR Trent 1000C	turbofan	2006	787-9	0.273

Jet engines, cruise
Model	Type	First run	Application	TSFC		Isp (by weight)	Isp (by mass)
				lb/lbf·h	g/kN·s	s	m/s
	Ramjet		Mach 1	4.5
J-58	turbojet	1958	SR-71 at Mach 3.2 (Reheat)	1.9
RR/Snecma Olympus	turbojet	1966	Concorde at Mach 2	1.195
PW JT8D-9	turbofan		737 Original	0.8
Honeywell ALF502R-5	GTF		BAe 146	0.72
Soloviev D-30KP-2	turbofan		Il-76, Il-78	0.715
Soloviev D-30KU-154	turbofan		Tu-154M	0.705
RR Tay RB.183	turbofan	1984	Fokker 70, Fokker 100	0.69
GE CF34-3	turbofan	1982	Challenger, CRJ100/200	0.69
GE CF34-8E	turbofan		E170/175	0.68
Honeywell TFE731-60	GTF		Falcon 900	0.679
CFM CFM56-2C1	turbofan		DC-8 Super 70	0.671
GE CF34-8C	turbofan		CRJ700/900/1000	0.67-0.68
CFM CFM56-3C1	turbofan		737 Classic	0.667
CFM CFM56-2A2	turbofan	1974	E-3, E-6	0.66
RR BR725	turbofan	2008	G650/ER	0.657
CFM CFM56-2B1	turbofan		C-135, RC-135	0.65
GE CF34-10A	turbofan		ARJ21	0.65
CFE CFE738-1-1B	turbofan	1990	Falcon 2000	0.645
RR BR710	turbofan	1995	G. V/G550, Global Express	0.64
GE CF34-10E	turbofan		E190/195	0.64
General Electric CF6-50C2	turbofan		A300B2/B4/C4/F4, DC-10-30	0.63
PowerJet SaM146	turbofan		Superjet LR	0.629
CFM CFM56-7B24	turbofan		737 NG	0.627
RR BR715	turbofan	1997	717	0.62
GE CF6-80C2-B1F	turbofan		747-400	0.605
CFM CFM56-5A1	turbofan		A320	0.596
Aviadvigatel PS-90A1	turbofan		Il-96-400	0.595
PW PW2040	turbofan		757-200	0.582
PW PW4098	turbofan		777-300	0.581
GE CF6-80C2-B2	turbofan		767	0.576
IAE V2525-D5	turbofan		MD-90	0.574
IAE V2533-A5	turbofan		A321-231	0.574
RR Trent 700	turbofan	1992	A330	0.562
RR Trent 800	turbofan	1993	777-200/200ER/300	0.560
Progress D-18T	turbofan	1980	An-124, An-225	0.546
CFM CFM56-5B4	turbofan		A320-214	0.545
CFM CFM56-5C2	turbofan		A340-211	0.545
RR Trent 500	turbofan	1999	A340-500/600	0.542
CFM LEAP-1B	turbofan	2014	737 MAX	0.53-0.56
Aviadvigatel PD-14	turbofan	2014	MC-21-310	0.526
RR Trent 900	turbofan	2003	A380	0.522
GE GE90-85B	turbofan		777-200/200ER	0.52
GE GEnx-1B76	turbofan	2006	787-10	0.512
PW PW1400G	GTF		MC-21	0.51
CFM LEAP-1C	turbofan	2013	C919	0.51
CFM LEAP-1A	turbofan	2013	A320neo family	0.51
RR Trent 7000	turbofan	2015	A330neo	0.506Template:Efn
RR Trent 1000	turbofan	2006	787	0.506Template:Efn
RR Trent XWB-97	turbofan	2014	A350-1000	0.478Template:Efn
PW 1127G	GTF	2012	A320neo	0.463

Civil engines
Model	SL thrust	BPR	OPR	SL SFC	cruise SFC	Weight	Layout	cost ($M)	Introduction
GE GE90	Template:Cvt	8.4	39.3		Template:Cvt	Template:Cvt	1+3LP 10HP 2HP 6LP	11	1995
RR Trent	Template:Cvt	4.89-5.74	36.84-42.7		Template:Cvt	Template:Cvt	1LP 8IP 6HP 1HP 1IP 4/5LP	11-11.7	1995
PW4000	Template:Cvt	4.85-6.41	27.5-34.2	Template:Cvt		Template:Cvt	1+4-6LP 11HP 2HP 4-7LP	6.15-9.44	1986-1994
RB211	Template:Cvt	4.30	25.8-33		Template:Cvt	Template:Cvt	1LP 6/7IP 6HP 1HP 1IP 3LP	5.3-6.8	1984-1989
GE CF6	Template:Cvt	4.66-5.31	27.1-32.4	Template:Cvt	Template:Cvt	Template:Cvt	1+3/4LP 14HP 2HP 4/5LP	5.9-7	1981-1987
D-18	Template:Cvt	5.60	25.0		Template:Cvt	Template:Cvt	1LP 7IP 7HP 1HP 1IP 4LP		1982
PW2000	Template:Cvt	6	31.8	Template:Cvt	Template:Cvt	Template:Cvt	1+4LP 11HP 2HP 5LP	4	1983
PS-90	Template:Cvt	4.60	35.5		Template:Cvt	Template:Cvt	1+2LP 13HP 2 HP 4LP		1992
IAE V2500	Template:Cvt	4.60-5.40	24.9-33.40	Template:Cvt	Template:Cvt	Template:Cvt	1+4LP 10HP 2HP 5LP		1989-1994
CFM56	Template:Cvt	4.80-6.40	25.70-31.50	Template:Cvt	Template:Cvt	Template:Cvt	1+3/4LP 9HP 1HP 4/5LP	3.20-4.55	1986-1997
D-30	Template:Cvt	2.42			Template:Cvt	Template:Cvt	1+3LP 11HP 2HP 4LP		1982
JT8D	Template:Cvt	1.77	19.2	Template:Cvt	Template:Cvt	Template:Cvt	1+6LP 7HP 1HP 3LP	2.99	1986
BR700	Template:Cvt	4.00-4.70	25.7-32.1	Template:Cvt	Template:Cvt	Template:Cvt	1+1/2LP 10HP 2HP 2/3LP		1996
D-436	Template:Cvt	4.95	25.2		Template:Cvt	Template:Cvt	1+1L 6I 7HP 1HP 1IP 3LP		1996
RR Tay	Template:Cvt	3.04-3.07	15.8-16.6	Template:Cvt	Template:Cvt	Template:Cvt	1+3LP 12HP 2HP 3LP	2.6	1988-1992
RR Spey	Template:Cvt	0.64-0.71	15.5-18.4	Template:Cvt	Template:Cvt	Template:Cvt	4/5LP 12HP 2HP 2LP		1968-1969
GE CF34	Template:Cvt		21	Template:Cvt		Template:Cvt	1F 14HP 2HP 4LP		1996
AE3007	Template:Cvt		24.0	Template:Cvt		Template:Cvt
ALF502/LF507	Template:Cvt	5.60-5.70	12.2-13.8	Template:Cvt	Template:Cvt	Template:Cvt	1+2L 7+1HP 2HP 2LP	1.66	1982-1991
CFE738	Template:Cvt	5.30	23.0	Template:Cvt	Template:Cvt	Template:Cvt	1+5LP+1CF 2HP 3LP		1992
PW300	Template:Cvt	4.50	23.0	Template:Cvt	Template:Cvt	Template:Cvt	1+4LP+1HP 2HP 3LP		1990
JT15D	Template:Cvt	3.30	13.1	Template:Cvt	Template:Cvt	Template:Cvt	1+1LP+1CF 1HP 2LP		1983
WI FJ44-4A	Template:Cvt	3.28	12.80	Template:Cvt	Template:Cvt	Template:Cvt	1+1L 1C 1H 1HP 2LP		1992
WI FJ33-5A	Template:Cvt			Template:Cvt		Template:Cvt			2016

The following table gives the efficiency for several engines when running at 80% throttle, which is approximately what is used in cruising, giving a minimum SFC. The efficiency is the amount of power propelling the plane divided by the rate of energy consumption. Since the power equals thrust times speed, the efficiency is given by

$\eta =V/(SFC\times h)$

where V is speed and h is the energy content per unit mass of fuel (the higher heating value is used here, and at higher speeds the kinetic energy of the fuel or propellant becomes substantial and must be included).

typical subsonic cruise, 80% throttle, min SFC

Turbofan	efficiency
GE90	36.1%
PW4000	34.8%
PW2037	35.1% (M.87 40K)
PW2037	33.5% (M.80 35K)
CFM56-2	30.5%
TFE731-2	23.4%

See also

• Template:Annotated link
• Template:Annotated link
• Template:Annotated link
• Template:Annotated link

External links

• GE CF6 website Template:Webarchive
• NASA Cruise SFC vs. Year
• SFC by Engine/Mfg Template:Webarchive