Just a general stealth question

[d0ppler]

When a stealth airplane turns on its radar, wouldn't all the stealth features be useless? Or is it possible to remain "hidden" even though the radar is on?

 

I'm just picturing an "invisible" person going into a dark room and turns on his flashlight...

[rocaf2003]

lpi aesa radar to keep rf stealth.Althrough the best stealth is radar off

[QuiGon]

On 1/22/2025 at 3:56 AM, d0ppler said:

When a stealth airplane turns on its radar, wouldn't all the stealth features be useless? Or is it possible to remain "hidden" even though the radar is on?

That would make the aircraft appear on the RWR of any targeted aircraft and thus revealing its presence. But that still doesn't mean that those other aircraft can target the stealth plane with their radars, even though they know it's there.
 

On 1/22/2025 at 3:56 AM, d0ppler said:

I'm just picturing an "invisible" person going into a dark room and turns on his flashlight...

Then others know that there is a person with a flashlight, but if they are blinded by the light they still don't see the person itself

Edited January 23 by QuiGon

[TotenDead]

20 минут назад, QuiGon сказал:

That would make the aircraft appear on the RWR of targeted aircraft of course and thus revealing its presence. But that still doesn't mean that those other aircraft can target the stealth plane with their radars, even though they know it's there.
 

Then others know that there is a person with a flashlight, but if they are blinded by the light they still don't see the person itself

It will defenitely help to detect a stealth plane by revealing where exactly to look for it. 

 

Then, There's that FSS radome thing. It needs to be transparent so that radio waves of the radar could go through it. I suppose that once a stealth fighter starts scanning its RCS should increase on around 0.5m2 because that makes its radar dish visible for other X-band radars

[DD_Fenrir]

On 1/22/2025 at 2:56 AM, d0ppler said:

When a stealth airplane turns on its radar, wouldn't all the stealth features be useless? Or is it possible to remain "hidden" even though the radar is on?

 

I'm just picturing an "invisible" person going into a dark room and turns on his flashlight...

From what I understand LPI radars essentially broadcast static but in that white noise certain select and very tight frequencies are encoded and somehow patterned in a way that only the broadcasting  emitter can decipher when the signal returns.

Edited January 23 by DD_Fenrir

[Dragon1-1]

They still do broadcast, though. You can fool some older ESM systems, particularly automated filters and the like (common on RWRs, which need to avoid adding too much pilot workload), but in the end, a dedicated EW platform like found in large SAM sites or on a surface ship will be able to look at raw emissions spectrum and see that white noise is stronger from a given direction, even if only slightly. The moment you start radiating anything, you risk giving yourself away. Of course, that alone doesn't necessarily mean you'll be engaged, but it does mean the enemy might think to point some more powerful radar at the area where the unusually strong white noise is coming from. LPI doesn't mean undetectable, it just tries to trick automatic filters into filtering it out.

[bfr]

On 1/22/2025 at 2:56 AM, d0ppler said:

When a stealth airplane turns on its radar, wouldn't all the stealth features be useless? Or is it possible to remain "hidden" even though the radar is on?

 

I'm just picturing an "invisible" person going into a dark room and turns on his flashlight...

Not useless, but certainly compromised. I suppose its a similar situation to when a submarine uses active sonar or surface radar.  If you want to remain as hidden  as possible then you're stuck with using passive sensors.

[Rick50]

On 1/21/2025 at 7:56 PM, d0ppler said:

When a stealth airplane turns on its radar, wouldn't all the stealth features be useless? Or is it possible to remain "hidden" even though the radar is on?

 

I'm just picturing an "invisible" person going into a dark room and turns on his flashlight...

 

Seems that way to me... however, just like a flashlight, you CAN shine it momentarily and then turn it off. Or put in on very low... my daily flashlight I carry for work on a lanyard, is normally set to 65 lumens, but I can turn it down to 1 lumen for various reasons (making sure no glare), and can "Turbo mode" to 500 Lumens. (I'm talking Nitecore Tini 2.)

 

So I imagine that in some situations, the stealth pilot might request a "Give me a ping, Vasili. One ping only, please." of his radar... and turn the active part of the radar off. This, much like with submarines, might give a location for the enemy to fixate on, while now dodging and planning to attack from another direction. When there is a lot of signals, the one super short stealth radar signal might get lost in the shuffle. Meaning, not relying purely on "not being seen", but rather, using deception and distraction. Remember also, subs have to fully  prioritise stealth most of ht time to survive, partly due to their slow speeds, while jets can relocate quite quickly.

 

Keep in mind these aircraft have datalinks, so maybe the Raptor that's 100nm away is actively tracking an enemy jet, while an F-35 that's just 30nm from that enemy now fires an AMRAAM completely stealthily, but using the data and radar reflection from the Raptor. The Raptor is safe due to distance, the F-35 is safe because his radar is not emitting, but still sees the big picture from the data link. The Amraam gets the coordinates, goes there, then goes mad dog and downs the enemy. 30 minutes later, the F-35 and Raptor might change roles due to an enemy near the Raptor who's now silent.

 

So I picture the radio emissions as being something that changes many times in one flight, due to differing requirements from minute to minute. 

Edited January 28 by Rick50

[Rick50]

 

It's also worth looking at Police SWAT tactics with flashlights... they will sometimes use them as a distraction and blinding tool to momentarily incapacitate the two-legged monster, giving precious moments to "solve" the problem in some way. It may be that EW and modern radars can cooperate to do the same on an enemy fighter pilot... and considering how America was fielding many EW pods during the Vietnam war, and have not stopped dev since,  have computing chips and storage on a scale unimaginable back in the 1960's now allowing for software defining processing changes on the  fly, and absolutely massive libraries of vehicle and systems identifications, and probably 70 years of ELINT signatures collected, well, someone's gonna have a bad day... shoulda pizza'd instead of french fries!  

[Kalasnkova74]

On 1/21/2025 at 8:56 PM, d0ppler said:

When a stealth airplane turns on its radar, wouldn't all the stealth features be useless? Or is it possible to remain "hidden" even though the radar is on?

 

I'm just picturing an "invisible" person going into a dark room and turns on his flashlight...

Your question contains one assumption- that a stealth aircraft would need to use its radar to find targets in the first place. 
 

Even in Southeast Asia, radar was not the only - or even the best - tool in the USAF’s box to sniff out enemy aircraft. 

[Aapje]

I assume that stealth airplanes mostly operate using passive radar. A passive radar doesn't generate it's own electromagnetic waves, but benefits from radio waves generated by other sources, like radio/tv transmissions, cell phone transmissions, GPS transmissions, etc. These then get reflected off the enemy plane, which you can detect. There are some very smart people who work on this and I bet that the passive radar of the most modern planes is way better than active radar systems of older planes. It may be one of the reasons why the US is trying to keep China from getting the best chip manufacturing processes, because these radars need a lot of compute to process all these signals.

Note that early radars were often passive, because the radar antenna could not be switched from transmit to receive. So you needed two antennas back then to generate an active signal.