Calculating The Range of tejas


 Note: I am taking a very simplistic view of aircraft range here for academic purposes. In reality, calculating the range is a complex problem because of the large number of variables involved. An aircraft's flight is not conducted at a single ground speed but varies from zero at take-off, to cruise conditions, and back to zero at landing. Extra fuel is expended in climbing to altitude and in maneuvering the aircraft. The weight is constantly changing as fuel is burned, so the lift, drag, and thrust and fuel consumption rate are also continually changing. On real aircraft, just like with our cars, there is usually a fuel reserve and the pilot makes sure to land the plane with fuel still on board, however we are going to neglect all of these effects for keeping our calculations simple


R (Aircraft Range) = V (cruise speed) × T (Maximum time in air)

[ Generally military aircraft cruise at a height of 30k feet with a speed of 0.8 to 0.85 mach, given that the speed of sound at 30k feet is near near 305m/s, V would be near 260m/s ]

T = M/(SFC × F)

[ M = Fuel Load (the amount of fuel an aircraft is carrying in Kg), in our case M = 2486kg ]
[ SFC = amount of fuel needed to be burned in 1 sec to produce 1kN of thrust, in our case SFC = 23g/(kN.s) ]
[ F = Thrust needed to keep the aircraft cruising at the given parameters ]

[ Note : At cruise speed an aircrafts Lift (L) = aircrafts Weight (W) and Thrust Required (F) = Drag (D) or in other words L/D ratio (lift to drag ratio) = W/F ]

So now F = W ÷ (L/D ratio)

in other words an aircrafts Range R = {V × M} ÷ {SFC × F}

So our Tejas will have a range of {260 × 2486} ÷ {23 × F}

Given that we don't know the required F for keeping the Tejas crusing we would have to look for another aircraft of similar profile and extract the data from there using the above equations.
Gripen C/D seems to be the closest fighter to Tejas with similar empty weight (6800kg), fuel capacity (2340 kg) and same GE 404 engine, so now using the Gripen's data we can calculate the required F

F = {260 × 2340} ÷ {23 × 1600km (Conservative Range)}
F = 16.5 kN

Assuming that Tejas will need similar (or even greater) thrust for crusing we can now calculate the range of Tejas

Range of Tejas = {260 × 2486} ÷ {23 × 17} = 1653km.

This range however is highly conservative as we don't know the actual L/D ratio or the thrust required for crusing and thus have taken the most conservative values of all the variables, (Eg. Range of Gripen C/D, Fuel Capacity of Tejas etc).


sources https://www.grc.nasa.gov/www/k-12/BGP/sumran.html

https://en.wikipedia.org/wiki/Saab_JAS_39_Gripen#Specifications

https://en.wikipedia.org/wiki/General_Electric_F404#Specifications_(F404-GE-402)

https://en.wikipedia.org/wiki/HAL_Tejas#Specifications_(Tejas_Mark_1)

Comments

Post a Comment

Popular posts from this blog

Setting the record straight on Tejas

Image
Understanding the Tejas Program: Debunking Misconceptions and Explaining Shortcomings The Tejas program has often faced unfair criticism and unwarranted labeling as a failure without proper understanding of the project and the aircraft itself. While it is true that the Tejas program encountered challenges and has some shortcomings, it should not be considered a failure by any means. In this article, I aim to debunk some of the perceived problems and provide explanations for its genuine shortcomings.     Section 1: Long Development Cycle of the Tejas Program. One thing people often forget while discussing the Tejas program is that it was not solely focused on developing a fighter jet, it was much more than that and aimed at establishing a comprehensive aerospace ecosystem in India. The program oversaw the creation of the Aeronautical Development Agency (ADA) and the development of many critical subsystems such as the Multi-Mode Radar, Kaveri Engine, airframe alloys, flight con
Read more

Is India really capable of building a 5th gen fighter

Image
India has been working on its own 5th generation fighter for quite some time now, but it seems far-fetched that India would be able to develop a fifth generation fighter, particularly since the country has primarily been a license manufacturer and has only one indigenously designed and developed fighter aircraft, the 4th generation LCA Tejas, which itself was plagued with delays and numerous other shortcomings. However, some exciting developments have been taking place in the country that can change this situation in favor of India. So let's take a closer look. Is India really capable of developing a fifth-generation fighter aircraft? Before going any further let's first define what a 5th generation fighter really is, Although there is no universally accepted definition of what constitutes as a fifth generation fighter, we can make an informed guess by examining currently operational fifth generation fighters, such as the F22, F35, and J20. Typical fifth generation characterist
Read more