Turbofans consume less vs turbojets.
Specific fuel consumption:
SNECMA Atar 9C
103 kg/(kN·h) 28.6g/(kN⋅s) (1.01 lb/(lbf·h)) military power
207 kg/(kN·h) 57.5 g/(kN⋅s) (2.03 lb/(lbf·h)) with afterburner
Rolls-Royce Spey Mk 202
0.63 lb/(lbf·h) at military thrust
1.95 lb/(lbf·h) with afterburner
Total SFC for single turbojet engine of Mirage
Military Power: 1.01 lb/(lbf·h)
With Afterburner: 2.03 lb/(lbf·h)
Total SFC for two turbofan engines of JH-7
Military Power: 2 x 0.63 lb/(lbf·h) = 1.26 lb/(lbf·h)
With Afterburner: 2 x 1.95 lb/(lbf·h) = 3.9 lb/(lbf·h)
The above data clearly shows that
overall specific fuel consumption is higher for JH-7 (25% higher at mil and 109% higher with afterburner).
plus jh7 carries more fuel.
General characteristics
JH-7
Length: 22.32 m (73 ft 3 in); Length excl probe: 21.00 m (68 ft 10.75 in)
Wingspan: 12.8 m (42 ft 0 in)
Height: 6.22 m (20 ft 5 in)
Wing area: 42.2 m^2 (454 sq ft)
Empty weight: 14,500 kg (31,967 lb)
Max takeoff weight: 28,475 kg (62,777 lb)
Engine Thrust:
2 x (54.29 kN (12,200 lbf) thrust each dry, 91.26 kN (20,520 lbf) with afterburner
)
Mirage V
Length: 15.55 m (51 ft 0 in)
Wingspan: 8.22 m (27 ft 0 in)
Height: 4.5 m (14 ft 9 in)
Wing area: 35 m^2 (380 sq ft)
Empty weight: 7,150 kg (15,763 lb)
Max takeoff weight: 13,700 kg (30,203 lb)
Engine Thrust: 41.97 kN (9,440 lbf) thrust dry, 60.8 kN (13,700 lbf) with afterburner
SNECMA Atar 9C
Length: 5,900 mm (232 in)
Diameter: 1,000 mm (39 in)
Rolls-Royce Spey Mk 202
Length: 204.9 in (5204.4 mm)
Diameter: 43.0 in (1092.2 mm)
Total fuel capacity estimation:
Although JH-7 fuselage length is about 6 m more than Mirage fuselage, but it has tandem cockpit.
However, since JH-7 houses two engines, it will be wider than Mirage fuselage (approximately 1.5:1 ratio).
Considering both factors, we can safely assume that fuel capacity of JH-7 fuselage is 50% more than Mirage fuselage.
Moreover, wing area of JH-7 is about 7 m^2 more than the wing area of Mirage. Hence, fuel capacity of JH-7 wing is approximately 20% more than Mirage wing.
Fuel capacity of JH-7 is 50-60% higher than Mirage.
Aerodynamics and weight are other two important factors which increase the fuel consumption. JH-7 is lacking in both of these factors.
Summing up the above conclusions, though JH-7 can carry 9000 kg payload, but its combat range is less, hence not suitable for deep strike missions.
PLAAF inducted JH-7 for CAS role only as they knew that it lacks air to air proficiency.
However, China is aggressively pursuing export of this aircraft (JH-7E) to other countries.
Furthermore, recent past trend and scrutiny of various statements of senior staff officers reveal that PAF is interested in inducting multi-role fighters. After light multi-role aircraft (JF-17), PAF will seek for medium weight multi-role aircraft either in the form of "Project Azm" or twin engine derivative of JF-17.
