Defense Issues

Military and general security

Gripen C upgrade proposal

Posted by Picard578 on December 20, 2014

Introduction

Similar to the F-16 upgrade proposal, this proposal will take an existing aircraft – Gripen C – and adress its greatest shortcomings with minimal redesign.

 

Modification

 

Gripen C data

Length: 14,1 m

Wing span: 8,4 m

Height: 4,5 m

Wing area: 30 m2

Turn rates:

30 deg/s instanteneous (possibly more ?)

20 deg/s sustained

>250 deg/s roll (90*/s @ 89* AoA)

Climb rates:

>200 m/s in air policing configuration

Wing loading:

293 kg/m2 with 50% fuel, 4 AMRAAM and 2 Sidewinder

333 kg/m2 with 100% fuel, 4 AMRAAM and 2 Sidewinder

Thrust-to-Weight ratio: (80,51 kN – 18 100 lbf (8 210 kgf) – thrust)

0,94 with 50% fuel, 4 AMRAAM and 2 Sidewinder

0,82 with 100% fuel, 2 Sidewinder, 4 AMRAAM

Fuel fraction:

0,26 (6 800 kg empty, 2 400 kg fuel)

Weight:

6 800 kg empty

8 779 kg with 50% fuel, 4 AMRAAM and 2 Sidewinder

9 979 kg with 100% fuel, 2 Sidewinder, 4 AMRAAM

14 000 kg max takeoff

Maximum AoA: 100 – 110 *; 50 * operational

Speed:

Mach 2,0 dash

Mach 1,15 cruise

G factor

9 G operational

12 G override

13,5 structural

min. takeoff distance: 650 m

min. landing distance: 550 m

 

Modifications

  • a Skyward IRST will be added to allow the completely passive search, track and targeting. Weigth gain: 30 kg sensor head, 25 kg processing unit = 55 kg
  • Volvo RM12 will be replaced with the F414EPE. Weight gain: 0 kg. Thrust: 26.400 lbf (120 kN, 11.975 kgf) in afterburner.

 

Gripen C2 data

Length: 14,1 m

Wing span: 8,4 m

Height: 4,5 m

Wing area: 30 m2

Weight:

6.855 kg empty

8.834 kg with 50% fuel, 4 AMRAAM and 2 Sidewinder

10.034 kg with 100% fuel, 2 Sidewinder, 4 AMRAAM

Fuel fraction:

0,26 (6 855 kg empty, 2 400 kg fuel)

Wing loading:

294 kg/m2 with 50% fuel, 4 AMRAAM and 2 Sidewinder

334 kg/m2 with 100% fuel, 4 AMRAAM and 2 Sidewinder

Thrust-to-Weight ratio: (11.975 kgf thrust)

1,36 with 50% fuel, 4 AMRAAM and 2 Sidewinder

1,19 with 100% fuel, 2 Sidewinder, 4 AMRAAM

Maximum AoA: 100 – 110 *; 50 * operational

Speed:

Mach 2,0 dash

Mach 1,3 cruise

G factor

9 G operational

12 G override

13,5 structural

min. takeoff distance: 390 m

min. landing distance: 550 m

 

Notes

Dry TWR at combat weight is 0,63 for Gripen C and est. 0,80 for Gripen C2. Rafale C has a dry TWR of 0,79 at combat weight and cruise speed of Mach 1,4. 90 kN M88, which would give a dry TWR of 0,97, would increase it to Mach 1,65 (both speeds are with 6 missiles). 4 missiles add speed penalty of 0,1 M, it means that 23% increase in dry TWR increases cruise speed by 18%. Thus increase should be 22% between Gripen C and Gripen C2. As Gripen C has a cruise speed of Mach 1,05 (Mach 1,15 clean), Gripen C2 would have a cruise speed of Mach 1,4 when clean or Mach 1,3 with 6 missiles.

Takeoff distance is 650 meters for Gripen C and 600 meters for Gripen E. Wet TWR is 0,82 for C and 0,89 for E. This means that 9% increase in TWR means 8% decrease in the takeoff distance.

 

Comparision with the FLX

Compared to the FLX, Gripen C2 has 27% higher empty weight and 5% higher combat weight. This means that it will have only slightly more inertia at combat weight. Higher wing loading (294 vs 259 kg/m2) leads to reduced turn rate and increased drag in both turn and level flight, and as cruise speed difference shows, Gripen C2 still has inferior thrust-to-drag ratio. Gripen’s thrust-to-weight ratio of 1,36 is superior to the FLXs 1,25. Span loading of 1.052 kg/m is higher than the FLXs 989 kg/m and increases the drag difference. Overall, Gripen C2 will have inferior instantaneous turn rate, sustained turn rate and cruise speed, while acceleration and climb are likely to be comparable, or even to Gripen’s favor.

At the same fuel fraction of 0,15 Gripen C2 has 1.210 kg of fuel and the FLX has 956 kg of fuel. This leads to combat weight of 8.844 kg for the Gripen and 7.284 kg for the FLX (a 21% difference). Gripen C2 would have a wing loading of 294,8 kg/m2, thrust-to-weight ratio of 1,35 and span loading of 1.053 kg/m. FLX would have a wing loading of 225 kg/m2, thrust-to-weight ratio of 1,44 and span loading of 856,9 m2, giving it superiority in instantaneous turn rate, sustained turn rate, acceleration and climb.

Both FLX and the Gripen C2 have good road basing capability due to wing spans of 8,5 and 8,4 meters, respectively. Transient maneuverability should be better for the FLX due to superior design of air intake area (wing, LERX, air intakes and canards).

While both aircraft would have same or similar passive sensors suite, Gripen suffers from lacking rearward visibility. It does have similar visual and IR signature as well as nearly identical operating costs.

 

Conclusion

This proposal would enjoy a significant superiority in air-to-air combat against any existing fighter aircraft as well as against the F-16NG proposal, and due to low acquisition and operating cost and easy maintenance would be an excellent choice for any air force. It would still be inferior to the FLX proposal, as latter is a grounds-up design.

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17 Responses to “Gripen C upgrade proposal”

  1. Chris said

    What will be interesting to see is how this will compare to the real world Gripen NG. Either it or a future Rafale will probably be as close to a good dedicated air superiority fighter as we are going to see.

    The other might be the possibility of deleting the radar. That would require a partial redesign to re-distribute the mass and for reasons of stability.

    I wonder if there could be a way to redesign the canopy and frame to improve rearward visibility. Against a supercruising opponent, there’s the very real danger of being bounced. There are a few fighters already that can cruise faster than 1.3, if only for short periods of time due to their limited fuel fraction. An FLX would have a pretty big advantage though – to the point where the aircraft would be very vulnerable due to good cruise speed and fuel fraction.

    • picard578 said

      “I wonder if there could be a way to redesign the canopy and frame to improve rearward visibility.”

      Removing the APU(?) unit blocking the visibility. But that would likely mean a complete redesign of the aircraft.

      “An FLX would have a pretty big advantage though – to the point where the aircraft would be very vulnerable due to good cruise speed and fuel fraction.”

      Any fighter aircraft in the world would be vulnerable to the FLX, even the F-22 since it has too low fuel fraction.

  2. Kjell said

    Are your given values for the start and landing distances for Gripen C correct, as for instance the swedish air force state them as start distance 400 meters and landing distance 500 meters

    http://www.forsvarsmakten.se/sv/information-och-fakta/materiel-och-teknik/luft/jas-39-gripen-cd/

    Then you may have to change the improved values for the C2 also.

  3. Chris said

    It’s interesting to note that the Gripen and Rafale need relatively few changes – largely because the designers had a better clue of what they were doing.

    The Gripen I think in particular shows that even a smaller nation can undertake a fighter project, although Sweden is quite wealthy for a smaller sized nation.

  4. Jorgen said

    As I understand it, Both suggestions are included in the Gripen NG, unclear which engine version though.
    From the Gripen official blog: “The Gripen NG is designed for the current mature version of the GE 414 but is capable of accommodating a GE414 growth version in the future. Which version of the 414 (EPE or other) will be determined depending on customer requirements”

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