What's A Stealth Fighter?

If I were to explain stealth to a layperson, I'd ask them to think of the game chupan-chupai (hide and seek) we played as children, explains Air Commodore Nitin Sathe (retd).

Recent reports suggest that China has pledged its fifth-generation stealth fighter -- the J-31 or J-35 -- to Pakistan.

This development has spurred India to accelerate its stealth fighter programme.

As nations race to outdo each other in stealth technologies, the field remains locked in a high-stakes game of 'spy vs spy', where every advancement is met with a counter even before the former becomes operational.

Imagine going into battle without being seen.

That would offer an overwhelming advantage -- giving you the edge to strike first and greatly improving your chances of survival.

The less visible you are to the enemy, the lower the chances of being targeted. And that, in essence, is what stealth is all about.

So, what does it take to be stealthy? Or rather, how can one reduce their visibility to others?

To understand stealth in a aircraft, we first need to grasp the broader concept -- stealth means minimising the signatures that make an object detectable.

Every object, animate or inanimate, has a signature that defines it -- its colour, shape, size, material composition, and whether it emits sound, heat, light, or electromagnetic radiation.

These characteristics make the object identifiable from its background.

If I were to explain stealth to a layperson, I'd ask them to think of the game chupan-chupai (hide and seek) we played as children.

Remember how we crouched behind bushes, held our breath, and stayed completely still to avoid being seen?

That, in simple terms, is the principle of stealth -- employing whatever means possible to stay undetected.

Now consider a modern combat aircraft.

It's made of metal, composites, and polymers; has a specific shape; generates heat and noise from its engine; and radiates various forms of electromagnetic energy.

These all contribute to its signature -- the collection of clues that could make it detectable by the enemy.

A stealth aircraft aims to reduce each of these signatures as much as possible.

Of course, doing so might involve trade-offs in performance, so designers strive to strike a fine balance between lethality and invisibility.

Let's examine the different types of aircraft signatures and how modern technology is helping reduce each:

Visual signature-shape size and colour

Besides making components compact, minimising profile of the aircraft and shrinking complex systems that lie within an aircraft to make its size smaller, camouflage paint schemes help to blend the aircraft with the terrain or the sky and reduces the shine and glare.

Paint work on an aircraft is region specific -- the scheme for deserts, forests, maritime use being different.

A further advancement today is to use thermochromic or electrochromic materials in paints that change colour or temperature signature in real time.

Often paints also have radar absorbent material (RAM) which deflect or absorb electromagnetic energy.

This helps in reducing the radar signature of the aircraft.

With the latest technology available, aircraft have 'adaptive camouflage' which make it blend with its surroundings by 'optical cloaking' (reduces the light bounce of its surface and uses materials that bend the light around the object).

We also have real time imaging systems that project the surrounding imagery onto the aircraft surface -- something called the smart skin system developed by British Aerospace Systems.

Aircraft today can fly very low, even by night using AI assisted high end technology, assisting the pilot to mask themselves with the terrain.

To further reduce the visual signature, protrusions like sensor antennae and weapon loads are made retractable and plush with the aircraft.

India's Advanced Medium Combat Aircraft (AMCA) programme is expected to feature nano-coated RAM with high temperature resistance and multi-band absorption.

In the recent conflict with Pakistan. India is known to have used small banshee drones that mimicked high-end fighter aircraft.

Further, small drones can be deployed in large numbers in coordination with fighter movements to fool the enemy.

The radar signature.

Radio detection and ranging as it means (RADAR), electromagnetic waves are sent out in all directions into space that get reflected from the metal surface of the aircraft, thus giving its position in time and space to the enemy.

The aircraft is recognised by what is called its RCS or the radar cross section or simply put, its radar signature.

This RCS is a function of how much metal the aircraft has, its size, shape, etc.

Besides radar absorbing paint and the shapes that do not reflect this energy, the replacement of many metal parts with composite materials has helped in reducing the radar signature of the modern fighter.

This is also achieved by giving it sharp edges and geometric shapes.

Some modern fighters like the F-22 and the F-35 have internal weapon carriage bays that largely reduce the radar signature.

Infra-red Suppression (Heat)

Engines emit heat which makes them vulnerable to heat guided weapons.

The airframe of the aircraft gets heated due to friction with air and some electronic components also produce heat which can be detected by an infrared device.

Thus, there is a need to reduce the infra-red emissions of the aircraft so that its thermal signature is reduced.

Hidden engine nozzles and exhausts, materials that do not allow heat to be dissipated and using the cold outside air to suppress the infra-red signature are in use in many of the latest fighter aircraft.

The F-35 Lightning II uses a combination of hidden engine nozzles, cooling ducts and heat absorbing materials to reduce its IR signature.

Besides the above measures, modern aircraft can fire flares which are decoy sources of heat to ward off a homing missile.

Some aircraft have the infra-red suppressors or jammers which emit heat energy away from the mother aircraft for a similar outcome.

Electronic and Electromagnetic Emissions

To remain stealthy, the aircraft needs to remain as silent as possible as far as transmission of electronic emissions are concerned.

Whilst engines can be made silent to reduce their noise emission by use of active noise cancellation systems and compressor blade design changes, the aircraft emits several frequencies in the electromagnetic spectrum which make up its electronic signature.

With encrypted close loop radio communication, no outside party can log in to conversations between aircraft.

Further, the modern-day fighter can reduce its own emissions by using active cancellation systems akin to what we use on our ear pods and headphones.

This is done by emitting inverse signals to nullify the incoming radar waves.

Other than the above, modern day fighter tactics involve 'no emission' or 'silent' missions which are pre-briefed on the ground; the pilots are only permitted to open up their systems for target designation and kill, besides for emergency purposes.

Conclusion

Stealth technology has evolved from a niche capability to a cornerstone of modern air warfare strategy.

As nations invest in sixth-generation fighters, unmanned stealth drones, and multi-domain integration, the future of stealth lies not only in passive reduction of signatures but also in adaptive, intelligent, and multi-spectral counter-detection systems.

The synergy of airframe shaping, advanced RAM, IR suppression, electromagnetic management, and AI-driven systems continues to define the cutting edge of aerial stealth.

As adversaries improve sensor technologies, stealth must evolve not just to evade detection -- but to outthink it.

Feature Presentation: Ashish Narsale/Rediff