zebra7
BANNED
- Joined
- Sep 18, 2015
- Messages
- 2,135
- Reaction score
- 10
- Country
- Location
In earlier post A preliminary performance review of the Indian Light Combat Aircraft
The Author talked about the general flight performance of the Indian LCA “Tejas” as evaluated from ADA data. In an extension to that article, we now talk about the relative performance characteristics of the LCA versus the Lockheed-Martin F-16A/B aircraft operated as the premier frontline fighter by the Pakistani Air Force.
This analysis is based on computationally evaluated performance characteristics models developed by the author. The aerodynamics and flight data for the two aircraft are obtained from the published sources listed in the references of this article. The LCA aerodynamics data is obtained from the Aeronautical Development Agency (ADA) publications and the F-16A/B data is extrapolated from public-domain NASA publications on the aerodynamics of the YF-16 prototype.
The aerodynamic force-coefficient matrix is plugged with a first-order propulsion module to simulate engine performance as a function of local atmospherics and altitude. The data generated by these routines are combined with the known mass properties of the aircraft to generate range and payload data which is then presented below for analysis.
Assumptions that went into the analysis include the empty weight of the LCA as being 6,500 Kg and that of the F-16A/B as ~8,500 kg. The LCA engine used was General Electric F404-GE-IN20 with a rated output of 54 kN and a rated TSFC of 0.77 lbm/lbf-Hr. Similarly, the engine assumed for the F-16A/B is the F110-GE-100 with a rated output 76 kN and TSFC of 0.763 lbm/lbf-hr. The internal fuel capacity of the LCA is assumed to be 3,034 Liters and the aircraft is assumed to be capable of carrying a centerline external drop tank of 725 Liters as well as one 1,200 Liter drop tanks on pylon stations 1 and 2, respectively. The cruise speed of both aircraft are evaluated for maximum range for each condition.
Whilst the LCA is now available in the air-force single-seat fighter (LCA), two-seat trainer (LCA-T) and navy (LCA-N) versions, the following analysis restricts itself to the single-seat air-force version only citing the lack of available information on the other two variants. However, performance for the other variants can be extrapolated from the single-seat air-force version, on which they are all based.
Aerodynamic comparisons and validations
The aerodynamic force coefficient comparison can be summarized in the form of lift-over-drag ratio (L/D) plotted versus lift coefficients (CL) for both the aircraft. The F-16A/B is generally seen to have a slightly higher peak L/D ratio (~11.0) compared with that of the LCA (~9.0) and the peak is attained at a slightly higher CL value of 0.40. The LCA attains this peak at a lower CL value of 0.20. The F-16A/B is generally a heavier aircraft than the LCA and larger in size, which explains why its design is tuned to attain the highest L/D ratio for a higher CL value compared to the much lighter and nimble LCA. The F-16A/B sustained-turn-rate (STR) data is corroborated with the NASA YF-16 flight test data as well. The author generated a series of maximum STR rates for the extrapolated NASA aerodynamic data and has plotted it against the available F-16A/B data for the same Mach number ranges. The comparison is significantly in line with each other, suggesting that the extrapolation models for the YF-16 data to that of the F-16A/B is acceptable for this analysis.
Performance comparisons
The performance of the LCA at 20,000 ft altitude is extracted from the earlier article on its performance. The plot is modified, however, to show the F-16A/B data. The latter aircraft is evaluated for the same equivalent fuel mass as that carried by the LCA when it is armed with a centerline drop-tank and two large pylon drop tanks for a maximum of 6,159 L of fuel. The range attained by the two aircraft are summarized in the form of payload and range plots. The payload is evaluated from 0 to 10,000 kg and is assumed to include the pilot weight and all auxiliary equipment excluding fuel. The vertical axis of the plots is range, measured in kilometers. The combat-radius of the aircraft is considered to be ~40% of the range. For example, a range of 1,000 km corresponds to a combat radius of ~400 km. Plots are provided for the LCA in three conditions: clean (internal fuel only), combat (internal + centerline drop tank) and ferry (internal + centerline drop tank + 2 x wing drop tanks).
The F-16A/B has a generally higher performance engine than that used in the LCA with regard to fuel efficiency. As a result, it attains a higher range (1,930 km at 0 kg payload) versus the LCA (1,553 km at 0 kg payload) under similar conditions. As payload increases the LCA and the F-16A/B maintain this slight difference in range performance at high altitude.
In the horizontal plane STR, the LCA outperforms the F-16A/B at high Mach numbers and the F-16C/D under all Mach number regimes. The nimble LCA can out-turn an F-16A/B at higher Mach numbers and an F-16C/D by a significant margin at lower Mach numbers, which are encountered in a turning fight within visual range. As Mach number increases, the turn rates lower for the F-16 models at a faster rate than that for the LCA with a crossover point at Mach 0.65. At all higher Mach numbers, the difference in turn rates increases substantially once more. The LCA can also pull higher “gee” forces at high Mach numbers than the F-16A/B in the horizontal plane. At high Mach numbers, the F-16 pilot remains at a significant disadvantage in the horizontal plane. Newer “Block” F-16 models only worsen this gap in performance between themselves and the LCA. They are heavier and even less nimble than the early “block” models currently operated by the Pakistani Air Force.
Conclusions
The F-16 pilots are advised to stay away from the LCA in the horizontal plane at high Mach numbers. At lower Mach numbers, they can fight the LCA on an equal footing. If they get into a turning fight with an LCA at high Mach numbers, the LCA will win.
Part-II of this analysis will focus on the maneuvers in the vertical plane.
References
1. Jebakumar, S. K., “Aircraft Performance Improvements: A Practical Approach”, Center for Military Airworthiness and Certification (CEMILAC), March 2009, Bengaluru, India
Dr. Vivek Ahuja
The Author talked about the general flight performance of the Indian LCA “Tejas” as evaluated from ADA data. In an extension to that article, we now talk about the relative performance characteristics of the LCA versus the Lockheed-Martin F-16A/B aircraft operated as the premier frontline fighter by the Pakistani Air Force.
This analysis is based on computationally evaluated performance characteristics models developed by the author. The aerodynamics and flight data for the two aircraft are obtained from the published sources listed in the references of this article. The LCA aerodynamics data is obtained from the Aeronautical Development Agency (ADA) publications and the F-16A/B data is extrapolated from public-domain NASA publications on the aerodynamics of the YF-16 prototype.
The aerodynamic force-coefficient matrix is plugged with a first-order propulsion module to simulate engine performance as a function of local atmospherics and altitude. The data generated by these routines are combined with the known mass properties of the aircraft to generate range and payload data which is then presented below for analysis.
Assumptions that went into the analysis include the empty weight of the LCA as being 6,500 Kg and that of the F-16A/B as ~8,500 kg. The LCA engine used was General Electric F404-GE-IN20 with a rated output of 54 kN and a rated TSFC of 0.77 lbm/lbf-Hr. Similarly, the engine assumed for the F-16A/B is the F110-GE-100 with a rated output 76 kN and TSFC of 0.763 lbm/lbf-hr. The internal fuel capacity of the LCA is assumed to be 3,034 Liters and the aircraft is assumed to be capable of carrying a centerline external drop tank of 725 Liters as well as one 1,200 Liter drop tanks on pylon stations 1 and 2, respectively. The cruise speed of both aircraft are evaluated for maximum range for each condition.
Whilst the LCA is now available in the air-force single-seat fighter (LCA), two-seat trainer (LCA-T) and navy (LCA-N) versions, the following analysis restricts itself to the single-seat air-force version only citing the lack of available information on the other two variants. However, performance for the other variants can be extrapolated from the single-seat air-force version, on which they are all based.
Aerodynamic comparisons and validations
The aerodynamic force coefficient comparison can be summarized in the form of lift-over-drag ratio (L/D) plotted versus lift coefficients (CL) for both the aircraft. The F-16A/B is generally seen to have a slightly higher peak L/D ratio (~11.0) compared with that of the LCA (~9.0) and the peak is attained at a slightly higher CL value of 0.40. The LCA attains this peak at a lower CL value of 0.20. The F-16A/B is generally a heavier aircraft than the LCA and larger in size, which explains why its design is tuned to attain the highest L/D ratio for a higher CL value compared to the much lighter and nimble LCA. The F-16A/B sustained-turn-rate (STR) data is corroborated with the NASA YF-16 flight test data as well. The author generated a series of maximum STR rates for the extrapolated NASA aerodynamic data and has plotted it against the available F-16A/B data for the same Mach number ranges. The comparison is significantly in line with each other, suggesting that the extrapolation models for the YF-16 data to that of the F-16A/B is acceptable for this analysis.
Performance comparisons
The performance of the LCA at 20,000 ft altitude is extracted from the earlier article on its performance. The plot is modified, however, to show the F-16A/B data. The latter aircraft is evaluated for the same equivalent fuel mass as that carried by the LCA when it is armed with a centerline drop-tank and two large pylon drop tanks for a maximum of 6,159 L of fuel. The range attained by the two aircraft are summarized in the form of payload and range plots. The payload is evaluated from 0 to 10,000 kg and is assumed to include the pilot weight and all auxiliary equipment excluding fuel. The vertical axis of the plots is range, measured in kilometers. The combat-radius of the aircraft is considered to be ~40% of the range. For example, a range of 1,000 km corresponds to a combat radius of ~400 km. Plots are provided for the LCA in three conditions: clean (internal fuel only), combat (internal + centerline drop tank) and ferry (internal + centerline drop tank + 2 x wing drop tanks).
The F-16A/B has a generally higher performance engine than that used in the LCA with regard to fuel efficiency. As a result, it attains a higher range (1,930 km at 0 kg payload) versus the LCA (1,553 km at 0 kg payload) under similar conditions. As payload increases the LCA and the F-16A/B maintain this slight difference in range performance at high altitude.
In the horizontal plane STR, the LCA outperforms the F-16A/B at high Mach numbers and the F-16C/D under all Mach number regimes. The nimble LCA can out-turn an F-16A/B at higher Mach numbers and an F-16C/D by a significant margin at lower Mach numbers, which are encountered in a turning fight within visual range. As Mach number increases, the turn rates lower for the F-16 models at a faster rate than that for the LCA with a crossover point at Mach 0.65. At all higher Mach numbers, the difference in turn rates increases substantially once more. The LCA can also pull higher “gee” forces at high Mach numbers than the F-16A/B in the horizontal plane. At high Mach numbers, the F-16 pilot remains at a significant disadvantage in the horizontal plane. Newer “Block” F-16 models only worsen this gap in performance between themselves and the LCA. They are heavier and even less nimble than the early “block” models currently operated by the Pakistani Air Force.
Conclusions
The F-16 pilots are advised to stay away from the LCA in the horizontal plane at high Mach numbers. At lower Mach numbers, they can fight the LCA on an equal footing. If they get into a turning fight with an LCA at high Mach numbers, the LCA will win.
Part-II of this analysis will focus on the maneuvers in the vertical plane.
References
1. Jebakumar, S. K., “Aircraft Performance Improvements: A Practical Approach”, Center for Military Airworthiness and Certification (CEMILAC), March 2009, Bengaluru, India
Dr. Vivek Ahuja
