Russian Su-57 Jet’s Stealth Capability to Increase with Flat Nozzle Engine

  • Our Bureau
  • 03:59 PM, December 15, 2021
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Russian Su-57 Jet’s Stealth Capability to Increase with Flat Nozzle Engine
Video grab from Tvzvezda showing a flat nozzzle test bench

Russian Su-57 stealth fighter jet’s second stage engine will be equipped with a flat nozzle to significantly reduce its radar signature.

The unique flat nozzle technology has been incorporated in the  S-70 ‘Okhotnik’ (‘Hunter’) heavy strike drone which was rolled out today by its manufacturer, Sukhoi. Russia’s Defense Ministry uploaded a video of the roll-out on its official media channel However the rear of the drone was not shown in the video so one cannot make out the size and shape of the nozzle.

However another  TV report posted on shows a test bench where exhaust gases are being ejected in a flat manner.

The unique nozzle will most likely be installed on the next modifications of the Su-57 fifth-generation fighter TASS reported quoting, Russian Air Force merited pilot Major-General Vladimir Popov on Tuesday.

"Similar measures will most likely be taken for the Su-57 but this will be, perhaps, the second stage of its development. A new engine will be mounted on it," the military pilot said, commenting on the roll-out of the first flight prototype of the latest Okhotnik heavy strike drone at the Novosibirsk Aviation Enterprise on December 14.

A modified engine will most likely feature a flat nozzle, he said. "However, considering that the fighter employs afterburner acceleration modes, this nozzle must have the option of altering its configuration. Mounted on the fighter, it must both expand and narrow its throughput capacity," the pilot said.

Russian Su-57 Jet’s Stealth Capability to Increase with Flat Nozzle Engine
Okhotnik heavy strike drone with flat nozzle roll-out

Flat nozzle description

"A flat nozzle is designed to cut infrared radiation of the engine’s exhaust gas flow. The flow’s infrared radiation enables air defense capabilities with thermal radiation homing warheads to take aim at the drone," Popov said.

"The incoming airflow kind of compresses and blurs the gases coming out of the nozzle. There is no big [nozzle] torch and thus the flow of gases escaping from the engine is invisible. It is the torch that basically ‘attracts’ thermal homing missiles, be it air-to-air or surface-to-air weapons," the pilot said.

"The aircraft’s radar signature is also reduced after the flat nozzle is installed. The cross section that reflects radio beams is also narrowed because the airplane now has no rough features in its design and it almost becomes flat," he said.

Referring to the Okhotnik’s launch today, he said that the drone’s fuselage now  looks like one wing, "If we recall the first version (current) of the Okhotnik, the engine clearly protruded out from the fuselage and now this is not the case. Now all the leading edges are smooth as a result the cross section has been cut and the radar beam deflection has magnified," the pilot said.

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