f-22 vs su-57 vs j-20
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How fast can a fighter aircraft fly without a boost?


The F-15C will reach a speed of about 1,170 km/h at an altitude of 6,500 meters with no external reserves and 1500 kg of internal fuel. The Su-27 in the same installation is slightly faster at 1180 km/h, the MiG-29 is much faster at 1230 km/h.

F-15
F-15

The higher stated maximum speed of the F-15 when adjusted for combat operations is due to the more aerodynamic design of external pylons, lighter weight and more streamlined hull OF AIM-120 than R-27 missiles, as well as fewer missiles.

The speed of sound varies depending on the temperature; it is 1,225 km/h at sea level and 1,091 km/h at an altitude of 9,000 metres, as the sound spreads faster at higher temperatures. Thus, technically, most of all supersonic fighters can go to supersonic without a boost – but not with combat load and not without serious deterioration of engine durability.

При скорости звука скорость воздуха, обтекающего корпус летательного аппарата, является сверхзвуковой. Но перекрывающиеся звуковые волны вызывают отрыв потока пограничного слоя вблизи задней части корпуса самолета, заставляя его возвращаться к дозвуковой скорости.
At the speed of sound, the speed of the air that fairs the body of the aircraft is supersonic. But overlapping sound waves cause the boundary layer to break off near the back of the plane’s hull, causing it to return to subsonic speed.

The frontal resistance peaks when the aircraft approaches the sound barrier, and when overcoming 1 Mach the aircraft will experience a sharp resumption of the speed increase, especially noticeable without a boost, because the frontal resistance factor decreases when accelerating from Mach 1. The speed will continue to increase until the frontal resistance is equal to the size of the thrust and the plane reaches the maximum speed.

This explains the sharp increase in resistance. Frontal resistance factor chart at 0-6 Mach
This explains the sharp increase in resistance. Frontal resistance factor chart at 0-6 Mach

The non-forward supersonic is not only a reflection of the increased performance of the engine, but also a decrease in the frontal resistance provided by overcoming the sound barrier. This gives a disproportionate advantage in speed and range compared to aircraft that cannot fly at supersonic speeds.

MiG-25
MiG-25

All supersonic aircraft have ways to reduce the air intake speed to about 0.5 Mach, so that the supersonic resistance on the compressor blades does not impair efficiency. This applies to even the fastest aircraft, including the MiG-25 and SR-71.

SR-71 blackbird
SR-71 blackbird
Двигатель J-58 SR-71 представляет собой турбореактивный двигатель, который становится прямоточным на высокой скорости, проблема с включением этого решения для истребителей заключается в весе неработающего турбореактивного двигателя в дополнение к прямоточному двигателю
The J-58 SR-71 engine is a turbojet engine that becomes direct at high speed, the problem with the inclusion of this solution for fighters is the weight of a non-working turbojet engine in addition to the direct engine

Super-cruise technology:

There are three main variables that determine the strength of the traction: exhaust temperature, exhaust speed and exhaust volume. Where the engines capable of supersonic cruising speed differ is the maximum temperature at the entrance to the turbine and the maximum frequency of rotation of the turbines.

An increase in the temperature of the exhaust itself will increase the traction. And higher turbine revs provide a higher exhaust speed. This allows the super-cruising engine to maintain a higher dry thrust at altitude.

As for the third variable, increasing exhaust volume is not a key component of super-cruise technology. There is no significant increase in the mass of air passing through the engine. The turbine blades can rotate at much higher revs, but the gearbox controls the frequency of the compressor’s rotation. And since Mach’s speed in the cold engine compartment is lower, the compressor’s revs should not exceed it, taking into account efficiency.

The Pratt and Whitney F-119 of the F-22 has a maximum turbine rotation rate of more than 15,000 rpm, which is much faster than the F-100 at 10,500 rpm.

F-22 overcomes the speed of sound.
F-22 plane overcomes the speed of sound.

However, the entrance of the turbine, of course, is cooled by the flow of low bypass before passing through the exhaust nozzle. A stronger thrust would otherwise be possible if the engine were converted into a turbocharger without a bypass. Information about the engine’s thrust is classified, although there are a number of unverified figures indicating a maximum dry thrust of 9,980 kgs and 15,875 cons with Fast and Furious.

The development of the AL-41F1C, called “Product 117C”which powers the prototypes su-35 and T-50, has a maximum turbine entry temperature of 1662 degrees Celsius compared to al-31F at 1412 degrees C. Maximum dry thrust is 8800 kgs and 14,500 kgs with a force camera.

Less information is available publicly about the “Product 129” engine, which will be installed on the Su-57. The maximum dry thrust is 11,000 kgs and 18,000 kgs with a booster camera, which is the highest engine power.

The Eurofighter-2000 has a maximum temperature at the turbine entrance of 1530 degrees Celsius and 1580 degrees Celsius for the Snecma M88. The Snecma M58 Mirage 2000 engine on which it was based had an input temperature of 1326 degrees Celsius.

The speed that fighter jets can reach with cruising supersonic speed is dynamic depending on the load, payload weight, and altitude. Below are unverified statements:

  • JAS-39 Gripen NG can reach 1.2 Mach
  • Typhoon pilots say Mach 1.3 is achievable in combat configuration with external reserves
  • The M88-3 engine should give Rafale a super-cruising speed of 1.4 Mach with 6 rockets, while the current M88-2 allows it to crash at a speed of 1.2 Mach with two missiles
  • Su-35 is capable of making a non-forssive flight at a speed of 1.5 Mach with external power reserves
  • F-22A is said to be on a 1.7 Mach super-cruise

Russian Su57 maximum cruising speed classified, but a number of unverified reports claim that the T-50 prototype, powered by a 117C engine, can reach 1.6 Mach or 1975 km/h, which is illogical because the Su-35, which carries the weapon from the outside and has a higher frontal resistance ratio, can reach 1.5 Mach or 1852 km/h, only 125 km/h slower than the T-50, despite the same thrust.

su-57
su-57

The actual non-force supersonic speed of the T-50 is likely to be similar to the 1.7 Mach F-22A; it has 12% less dry traction, but a slightly smaller frontal resistance ratio was mainly provided by smaller vertical stabilizers. As for the Su-57, equipped with the engines of the project-129, it has 10% more dry thrust than the F-119, and probably has a maximum cruising speed of about 2 Mach.

However Chinese latest fighter J-20 cant performance supercruise with AL-31 engine. But recently China start using WS-15 engine, Which is made in china so according many export with this new engine J-20 may be able to hit supersonic.


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