Is LCA worth the cost?

Anup wrote:This site mentions the range as 2000 kms which means 1000 on turn around
http://www.aviationfans.com/node/17

Surprisingly ADA and HAL website is silent on the range of the LCA

For a small aircraft like LCA, its not possible. Even the bigger Mirage 2000 doesn't have that long a range. So I doubt, LCA would have that long a range.

2000km seems possible . Mirage 2000 is credited with having better range than MiG-29 , the Mirage's unrefuelled range is around 1900km IIRC . With the F-404 , lower weight and drag , the LCA should be able to match this . How much internal fuel does Tejas carry ?

Ricci wrote:How much internal fuel does Tejas carry ?

Tejas carries 2300 Kgs of internal fuel. BUT 2 external tanks would be standard on all long range missions, even then the range figure seems overblown.

Wiki says SFC for GE404 (vanilla version) is 82.6 Kg/KN-H and Tejas carries 3000 liters (2300 Kgs) of internal fuel. This gives a flying time of ~47 minutes (assuming 70% RPM as cruise power) on internal fuel and hence a ferry range of 800 Kms on internal fuel. Now as per wiki Tejas can carry 5 X 800 liters of fuel in external fuel tanks, which makes the total fuel available to about ~5300 Kgs. Now calculating again on the assumptions mentioned above, the flying time comes to about 1 hour 50 minutes. Assuming cruise speed of .7 mach in such loaded condition, the ferry range comes out to 1500 Kgs.

Cheers....

Thats some info neeraj.

And given the limited range, one has to keep in mind that 2 hard points of how many 5?

neerajb wrote:

Ricci wrote:How much internal fuel does Tejas carry ?

Tejas carries 2300 Kgs of internal fuel. BUT 2 external tanks would be standard on all long range missions, even then the range figure seems overblown.

Wiki says SFC for GE404 (vanilla version) is 82.6 Kg/KN-H and Tejas carries 3000 liters (2300 Kgs) of internal fuel. This gives a flying time of ~47 minutes (assuming 70% RPM as cruise power) on internal fuel and hence a ferry range of 800 Kms on internal fuel. Now as per wiki Tejas can carry 5 X 800 liters of fuel in external fuel tanks, which makes the total fuel available to about ~5300 Kgs. Now calculating again on the assumptions mentioned above, the flying time comes to about 1 hour 50 minutes. Assuming cruise speed of .7 mach in such loaded condition, the ferry range comes out to 1500 Kgs.

Cheers....

At what thrust level are you calculating the range ? Max dry thrust , right ? What isn't published is the SFC at different RPM levels . 47 minutes seems more like the total running time at 100% throttle , not accounting for taxiing at idle or so and the afterburner usage during take-off roll . For twin engine fighters , you can estimate the range to be approx 1/3rd the amount on internal fuel . The Su-27 does 4000km on ~13000 litrers of gas .The MiG-29 carries ~4500 liters of fuel internally , does 1500km on that much with 2 thirsty engines . The LCA has just one and it's less powerful than the RD-33 . I'd say the range on internal fuel and clean should 1500km at least , even accounting for the F-404 not being so frugal , and closer to 1800km . 800km on internal fuel seems useless , even MiG-21s are reportedly 900km and those weren't known for fuel efficiency. The weight and drag of drop tanks would notably alter the range calculations , but I'd stick my neck out for at least 1500km in internal fuel .

Hi Ricci,

SFC doesn't indicate the fuel consumption of an aircraft but more accurately the efficiency of engine at any throttle setting. You are right in saying that SFC changes with throttle setting but marginally since the efficiency of an engine doesn't vary over a wide range. Since afterburner wastes lots of fuel, generally you'll see the manufacturer publishing SFC for military thrust and reheat only. For example in case of Mig-21's engine you can see that the SFC at idle and max military thrust is almost the same.

Specifications (R-25-300)

[edit] References
General characteristics

* Type: Afterburning turbojet
* Length: 4,615 mm (181.7 in)
* Diameter: 1,191 mm (46.9 in)
* Dry weight: 1,212 kg (2,670 lb)

Components

* Compressor: Two-spool axial compressor

Performance

* Thrust:
o 55 kN (12,370 lb)[1] military power
o 68.5 kN (15,400 lbf) with afterburner
o 96.8 kN for 3 minutes with boosted afterburner (CSR mode, altitude < 4000 meters)
* Overall pressure ratio: 9.5:1
* Turbine inlet temperature: 1,040 °C (1,904 °F)
* Specific fuel consumption:
o 93 kg/(h·kN) (0.91 lb/(h·lbf)) at idle
o 98 kg/(h·kN) (0.96 lb/(h·lbf)) at maximum military powero 229 kg/(h·kN) (2.25 lb/(h·lbf)) with afterburner
* Thrust-to-weight ratio: 56.5 N/kg (5.8:1), 79.9 N/kg (8.1:1) with boosted afterburner
--------------

http://www.aviastar.org/air/russia/mig-21.php

I have mentioned 70% RPM or 70% of max military thrust as cruise setting for my calculations which is an approximation/assumption for my calculations and not 100% dry thrust. Again for simplicity I have omitted the afterburner use/taxi fuel etc from the calculations.

Cheers....

The reason as I see for Mig-21 and Tejas to have comparable ranges is the Mig-21s weaker engine thus utilizing even lesser fuel to dish out 28KN cruise power (despite having a more fuel inefficient engine than tejas) and Mig-21s aerodynamics which were designed to achieve Mach 2 despite the weak engine.

Cheers....