Designing a light fighter
Designing a Fighter Jet
Using the YSFlight system, it is possible to create a fighter model by estimating the performance of an fighter jet based on existing data. The landing speed parameter is important in determining the turn rates at all speeds. The wing loading, if it is used in the YSFlight model, will also determine turn rates. Climb is determined largely by the thrust of the engine, the weight of the aircraft. With the Mirage 2000, for example, correcting the thrust values for the engine resulted in a better climb rate.
First Step: The Engine
The engine of the Mig-21 will be used in its entirety, with its specifications, thrust and fuel consumption. Fighters using engines produced by certain countries are subject to import restrictions depending on the regime in power at that time, so using an engine from these countries may result in program delays or even cancellation,
The values of the Mig-21 engine are produced here for reference:
AFTBURNR TRUE #HAVE AFTERBURNER?
THRAFTBN 5.0t #THRUST WITH AFTERBURNER
THRMILIT 3.0t #THRUST AT MILITARY POWER
WEIGHCLN 4.0t #WEIGHT CLEAN
WEIGFUEL 3.0t #WEIGHT OF FUEL
WEIGLOAD 6.0t #WEIGHT OF PAYLOAD
FUELABRN 6.5kg #FUEL CONSUMPTION WHEN USING AFTERBURNER
FUELMILI 0.45kg #FUEL CONSUMPTION AT MILITARY POWER
The Wing
At this stage the wing plan form and area is determined. The delta wing offers simplicity and good transonic performance, and with relaxed stability and fly-by-wire will have adequate turn capability especially with low wing loading. The area of the wing has to be determined given the wing loading targeted.
Wing loadings of various aircraft are given below. This is wing loading when in combat mode, with half internal fuel, that is, 1500 kg of internal fuel.
The target wing loading then is 200 kg/sq m, which leaves us with the
The preliminary sketch shows a delta wing design with a single vertical tail, and a single engine. Wing area is 35 sq m and weight is estimated to be 7,000 kg the same as an early Mirage III. With an engine thrust of 7,000 kg with afterburner, the aircraft will have combat thrust to weight ration of 0.8 In order to obtain a better thrust to weight ratio, air frame weight will have to be reduced to 5000 kg empty. The next step is to consider the thrust to weight ratio.
Basics of air combat are revealed in this article on Here Are The Basic Fighter Maneuvers Fundamentals You Need To Understand Dogfights, Explained By A Fighter Pilot (The Aviationist)
Preliminary design sketch.
Shoulder mounted wing with under-fuselage intake.
Similar delta winged designs have been proposed in the past, notably the Atlas Carver design and the F-16U, a little know concept for an F-16 customer.
Preliminary 3D design
Refinement and wings added to design, aerodynamically rough model
Comparison with original concept
Range Considerations
One of the most important factors of an aircraft is the range, in addition to the climb and turn rates. The Mig-21, for example, has a range of about 300 nm with drop tanks and two missiles at 30,000 ft. This may have been acceptable for an air defense fighter in Vietnam or in the USSR, however it might be less effective as a ground attack aircraft, given the distance required to travel to drop bombs and return.
Range constraints affect the maneuverability of the aircraft, some times it is necessary to choose between maneuverability and range with the latter winning out. The role of an interceptor must be then clearly defined in the environment that is required, for example the requirement to fly to the borders of the terror for interception, or the stationing of an air base close to the required interceptions.
In YSFLight, the longest distance on the map is the Hawaii map, which gives a distance of roughly 200 nm and is good for testing. The next point is to create a mission profile that will define the requirement.
One approach is to take off with a reduced fuel load, for example, 10 % and extrapolate the distance that could be flown using this load, after air combat. The other possibility is to use the air interception mission and then fly until the tanks run dry. In any case the interception mission must be carefully specified, using the Hawaii map, Navigation using the VOR must be also figured out beforehand.
https://etd.lib.metu.edu.tr/upload/12624213/index.pdf