Radar vs chopper

Hi guys.

I thought DCS implemented restrictions on the radar for chopper flying slower than a certain speed.

However I am still getting locked when I am stationary, hovering at 3 m high, on the ground or on a building.

Is it intended ?

I really struggle to hide myself from Fighters

Yup best thing to do is power down and sit and wait for all clear.

If memory serves me correctly if your rotor blade is spinning you are a large radar target in DCS

On all aspect ? I would assume you need to be on top of it or in a small cone no ?

If you fly slower than 87knots then only Su27 in MED mod can see you. Ground Radars wiil always detect you. I haven't checked yet M2000C BFR mod.

Moreover, all aircrafts in Vertical Scan mod will lock you even in hover.

A helicopter's rotor is propably one of the best radar reflectors you can get. It moves at a high range of speeds (slow close to the center, to very fast on the end of the blades) and works in all directions.

Yes, the fuselag radar cross section is nothing compared to the cross section of the rotor disk.

It is rotating at very large surface, all directions and at all speed from very low to near 900km/h.

The problem with the helicopters is that you are visible to radar, but radars needs a special mode to be able lock on to you, as to them you are like a huge jammer that doesn't reveal your distance, heading or altitude.

But even just a wind turbine is causing serious problems for long range radars by blocking the radar capability see behind them for long distances.

So what fighters only need, is to detect your direction and then they can just eye ball you and attack with cannons or use IR missiles to hit at you.

Some fighters newer radar systems let them to target you as well.

This was as well one of the problems with the Comanche program, that while fuselag was possible to be minimized against radars, you couldn't do that for the rotor disk as you just need aerodynamic shaping for the blades totally different manner than for fighters.

AI will lock/see you all the time. Flying slow will help being detected from human players. Its been awhile since I have tested but below 60 knots should be slow enough.

Landing and shutting down against AI with ground radar (F16)will do nothing but maybe buy you some time. They will find you and strafe you.

I'll add that getting radar locked even at low speed is pretty realistic. Don't forget that these days weather radar can track the patterns of raindrops falling to track storms and predict severe weather before it even happens. Military radar tracking abilities are [classified] but I imagine that if channel 7 in Podunk can track a raindrop, the military can tell if you haven't changed your underwear lately.

In the Sim, I think it is reduced to unclassified levels, so we get a break compared to R/L. But throw in a spinning rotor disk, and someone could probably rig up a homemade radar with parts from an old microwave and a used satelite TV dish to spot you.

As has already been stated, what's giving you away is your rotor disc. Your fuselage might be stationary but your rotor disc is moving at high speed.

Realistically, helicopters would never be sent into a situation where you didn't already have air superiority. Because they're extremely vulnerable to enemy fighters and SAM's.

In game, your best bet is to use terrain masking or hiding behind buildings to avoid detection. But in general, if there's enemy fighters about, your chances of survival are pretty slim.

I'll try to help you out with some details:

In game:

1) You have an effective notch, meaning that against a pulse-doppler radar, your radar return will be rejected if flying below some 100m/s when >10km, and you have to be below 50m/s when <= 10km. This may also depend on PRF setting of the radar. The point is, you need to be slow and you WILL be invisible to the radar unless you are at a higher altitude than the radar emitter.

2) Once you are spotted on radar from afar, even though you might try to evade, you can't really go anywhere very quickly. As a result a fighter can enter the area where you were last seen and search visually or with IRST if so equipped. Finally, AWACS can things unpleasant for you.

3) AI have god-like situational awareness ... once they acquire you, you're in trouble.

In reality:

1) Although your rotor blades generate an overall smaller radar reflection than the fuselage, their return generates a high doppler shift compared to the ground return, and your fuselage - so a doppler radar will process this and show you on the screen regardless of what speed you're travelling at, or what altitude you are at. In a well known incident, a LANDED helicopter was tracked in A2A mode by an f-15E from 50nm away. They fed this to the targeting pod to guide a bomb onto that heli. In other words, if you were facing an F-15 that is realistically modeled, you wouldn't be able to hide, and with modern versions of missiles even counting on ground clutter to increase miss distance might not be useful. Older doppler radars though, like the ones modeled for the flanker and mig (and typically Viggen, F-5, MiG-21) should probably show your rotors as a jamming strobe instead because of the spread of doppler shifts :)

In conclusion for the game, you need some of the following tools:

1) Situational Awareness, so that you know where the fighters are. Get this info from AWACS, your buddies, your own sensors, whoever and wherever you can get it from.

2) Terrain mask and plan your route if possible in such a way that you will be able to terrain mask. Stick a mountain/hill between yourself and the bandit, preferably before they ever see you.

3) Learn to fly in the notch. Even though you can slow down enough to always be in the notch, learn to fly in it given information from other sources. Put the bandit on your 3/9 and move away from where you were at best speed.

4) Be aware that notching multiple bandits coming from different directions could be difficult or impossible, given that this requires a specific geometry.

You can search the forums for 'notching, doppler notch, radar notch' to read about it and understand how it works.

Hi guys.

 

I thought DCS implemented restrictions on the radar for chopper flying slower than a certain speed.

 

However I am still getting locked when I am stationary, hovering at 3 m high, on the ground or on a building.

 

Is it intended ?

 

I really struggle to hide myself from Fighters

It has nothing to do with classified/unclassified.

It's just old code that hasn't been revised, and you are just being given a break. Helicopters are being given a huge break all in the name of MP :)

In the Sim, I think it is reduced to unclassified levels, so we get a break compared to R/L. But throw in a spinning rotor disk, and someone could probably rig up a homemade radar with parts from an old microwave and a used satelite TV dish to spot you.

thanks for the explaination

Is this implemented for all aircrafts or only russians ?

For those interested - This report describes millimeter wave Doppler signature measurements made on a hovering Mi-24 Hind-D helicopter.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a351581.pdf

Helicopters DO really struggle to hide from fighters.

If you find yourself in a mission, flying a chopper in a heavy AA environment, your mission has been designed/planned by either an idiot or a psychopath.

Helicopters and fighter jets are like tanks and logistics trucks. They have a TOTALLY different role and ought to NEVER be in direct contact with each other, and if they were, itd mean a huge human failure has taken place somewhere.

If you get shot down by a fast jet in your Ka-50, its because nobody made plan to remove the threat before your mission took place (whether this means a strong CAP presence or neutralising enemy air strategically). No ifs, ands or buts. And DEFINITELY no talk of doppler radar.

If you get shot down by a fast jet in your Ka-50, its because nobody

(aka you, the heli pilot)

made plan to remove the threat before your mission took place (whether this means a strong CAP presence or neutralising enemy air strategically). No ifs, ands or buts. And DEFINITELY no talk of doppler radar.

For those interested - This report describes millimeter wave Doppler signature measurements made on a hovering Mi-24 Hind-D helicopter.

 

https://apps.dtic.mil/dtic/tr/fulltext/u2/a351581.pdf

Nice find.

Interesting points in the conclusion:

The returns from the hub fell below the clutter filter @ 200 KHz.

(Only) the front edge of the main rotor was visible with a doppler frequency consistent with its diameter

Both the positive and negative doppler frequencies of the tail rotor were visible only at several aspect angles.

- but also worth noting that the radar used was @ 95GHz (as you said, mm wavelength - guessing ~ 3mm ?), while the AN/APG-65 radar family (F-18 / F-15E) run at 8 - 12 GHz (2.5 cm -3.75 cm ) so the results might not be directly applicable...

*

They are reasonably applicable. As frequency decreases, apparent RCS tends to increase (this is part of the basis of the argument for low frequency radars vs stealth - the other part is structural element sizes wrt wavelength).

There are also radar traces clearly showing helicopter blades vs fuselage for 'good old' surveillance radars - unfortunately those will be a pain to find again.

Long story short, if the rotor's spinning and there's LOS to a reasonably modern radar, you're not hiding.

They are reasonably applicable. As frequency decreases, apparent RCS tends to increase (this is part of the basis of the argument for low frequency radars vs stealth - the other part is structural element sizes wrt wavelength).

 

There are also radar traces clearly showing helicopter blades vs fuselage for 'good old' surveillance radars - unfortunately those will be a pain to find again.

 

Long story short, if the rotor's spinning and there's LOS to a reasonably modern radar, you're not hiding.

Even a reasonably old radar like an ASR-910 would have no problems detecting a hovering or cruising helo. At least ours had no problem...^^

Helicopters DO really struggle to hide from fighters.

 

"your mission has been designed/planned by either an idiot or a psychopath"

 

"itd mean a huge human failure has taken place somewhere"

1. Well I fly online mostly, so....

2. Did I mention point 1?

J/K (hope everyone has a sense of humor here)

But I'd say the larger issue is that for most online play are a very real lack of planning utilities. Which largely prevents good coordination on the player side. Then again I've seen it both ways, on blueflag, the helos don't go in until pretty much everything is cleared out (brave KA50's exempted).

Personally, I find most of the helo centric offline content to be pretty reasonable.

Can t really fly choppers on public servers for all the reasons mentioned before although I wouldn t call the mission designer an idiot or psyco; he is just a simple fixed wing pilot who have no idea about rw ops and adds choppers in his mission as an afterthough. Missions flown in MP have to be designed by chopper pilots for chopper pilots. It s possible to integrate a fw dimension in some cases but more as support for choppers operations.

As has already been stated, what's giving you away is your rotor disc. Your fuselage might be stationary but your rotor disc is moving at high speed.

 

Realistically, helicopters would never be sent into a situation where you didn't already have air superiority. Because they're extremely vulnerable to enemy fighters and SAM's.

 

In game, your best bet is to use terrain masking or hiding behind buildings to avoid detection. But in general, if there's enemy fighters about, your chances of survival are pretty slim.

You're right, but how about the mission conducted by the US using a good bunch of 8 AH-64s in low level flight formation sent to attack and destroy an Iraqi capable radar station? The reason why they were undetected by the radar they were sent to destroy is either due to flying well below the radar coverage cone (the further away, the lower you are below the detection cone) or due to the fact that the radar simply couldn't identify or even see them.

Terrain is one easy answer.

The helis were part of a massive effort to dismantle the IADS, and made their way in while these guys were looking at the mass of aircraft coming their way.

You're right, but how about the mission conducted by the US using a good bunch of 8 AH-64s in low level flight formation sent to attack and destroy an Iraqi capable radar station? The reason why they were undetected by the radar they were sent to destroy is either due to flying well below the radar coverage cone (the further away, the lower you are below the detection cone) or due to the fact that the radar simply couldn't identify or even see them.

Plus weren't those sights long range EWR? Such radars may be potentially quite limited in low altitude detection.

Helicopters and fighter jets are like tanks and logistics trucks. They have a TOTALLY different role and ought to NEVER be in direct contact with each other, and if they were, itd mean a huge human failure has taken place somewhere.

Not necessarily. U.S. Air Force was very worried about Soviet helicopters in a Fulga Gap scenario.

https://en.wikipedia.org/wiki/J-CATCH

To the surprise of many involved in the program, the helicopters proved extremely dangerous to the fighters when they were properly employed, racking up a 5-to-1 kill ratio over the fighters when fighting at close ranges with guns. The lesson was that fixed-wing aircraft should not attack helicopters except at long range and/or high altitudes with long range missiles.

Regarding the Desert Storm use of Apaches, those helicopters went in over flat, empty terrain at low altitudes before the fixed-wing aircraft specifically to clear a path for them. They were chosen because there was no fixed-wing aircraft that could do that mission as well as Apaches.

The idea that helicopters have to be relegated to the rear of the chain running secondary missions has never been true.