Combat aircraft

Russian engine but also of the use of the

Chinese WS-10. A few observers were

even con dent that a mysterious WS-15

prototype had been installed.

Adding to the overall confusion, the

engines spotted on the J-20 over the

years have featured di erent types of

‘stealthy’ nozzle, like the one tested in

April 2014 on board ‘2011’. This featured a

silver color or perhaps a ceramic coating

with saw-tooth edges between the

fuselage and engine to reduce RCS and

infra-red emissions. In the end it was not

adopted. Equally unhelpful were several

CCTV reports in parallel with the 2016

Zhuhai Airshow that claimed the J-20 was

already using a Chinese engine.

Regardless of speculation and the

variations of the exhaust, it is believed

that the demonstrators were powered

by the original AL-31FN, whereas the

prototypes from ‘2011’ onwards used

the AL-31FN Series 3, as used by the

J-10B and J-10C that were produced in

parallel. Given the known thrust of the

AL-31FN Series 3, the  ghter is likely

underpowered and is expected to lack

a true supercruise capability until the

planned WS-15 turbofan enters service.

On the other hand, based on reports

from the Chinese media, the PLAAF is

more than satis ed with its latest  ghter.

When the  rst LRIP J-20 appeared in

December 2015, still in yellow primer,

the engine nozzles had reverted to those

typical of the AL-31FN.

In early October 2016 an interesting

online report was posted claiming that

the J-20 uses a specially tailored version of

the Salut AL-31 based on the AL-31FM2.

This normally reliable source reported,

‘the WS-15 has just  nished ground

testing, and it is ready to pass the test on

the IL-76LL platform. The current J-20A

uses the AL-31FM2, a special customized

version of the AL-31, based on a secret

joint development between China and

Salut’. This would be consistent with the

approach for the original AL-31FN: a  rst

development contract between Salut

and CAC concerning the AL-31FN was

signed on March 31, 1992. The J-10 made

its maiden  ight nearly six years later, on

March 23, 1998, and the J-10A has long

been in operational service with an engine

that is clearly an AL-31 derivative. Both

sides decided to keep the true nature of

this engine secret for as long as possible.

In terms of more regular AL-31F/FN

developments, both the 117 and the later

Above:

A J-20A carries

out trials of a

four-drop tank

con guration.

Though assigned

to the CFTE at

Xi’an-Yanliang,

J-20s make

detachments

to Dingxin for

weapons testing.

Left: The seventh

aircraft — ‘2016’

— was  rst seen

on September

11, 2015 and

 ew a week later.

It has undergone

several minor

modi cations,

perhaps

related to the

installation of a

more powerful

AL-31FN engine.

Below: J-20A

‘2021’, an LRIP

aircraft, still in its

yellow primer.

This aircraft

marked the

introduction

of the Chinese

WS-10B

engine — an

important step

to ending the

PLAAF’s reliance

on a foreign

powerplant

supplier.

FIGHTER FOCUS | J20

http://www.combataircraft.net January 2018

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