What is "notching" ?

[scottysonfire]

In air to air combat, Ironhand refers to "notching"

 

(http://flankertraining.com/ironhand/news.html)

 

Ive tried to run the track for his missile evasion tutorial, but it doesnt run properly, so Im just listening to his audio tracks and trying to visualise whats going on.

 

He mentions notching and I have no idea what it means.

 

any help would be appreciated

[RvEYoda]

Notching refers to going into your opponents doppler notch.

 

Essentially, radar uses multiple techniques to separate ground

clutter from true returns from the target, the primary method

being doppler shift separation.

 

By knowing what wavelength or frequency of the radar waves you

send out, you will be able to tell certain things.

 

Example if you send a "ping" of wavelength A on a target, the ping will return

a wavelength shorter than A if the target is moving towards you, while

the the ground returns a different wavelength.

 

So you could see the ground clutter is present as "blue color", while

the true target returns are "red". If the target moves closer and closer

to the same closure speed as the ground (that is perpendicular to the

radar beam direction) then the Red becomes more and more "blue",

and when he reaches close enough to the beam (also called the notch when

in look-down) the FCR is unable to tell the difference, and he notches you.

Edited October 9, 2008 by =RvE=Yoda

[scottysonfire]

Would notching be similar to beaming?

 

You have talked about the ground in your example - so Im assuming the notching technique youve described only works when you are lower than your oponent so he is looking down at you and the ground appears behind you?

 

So would I be correct in saying you try and keep him at your 3 or 9 o'clock position like in beaming but you are heading towards the ground or at a a lower altitude than him?

 

Do you "notch" before he launches a missile? Or do you notch after a missile is launched?

[RvEYoda]

Notching would be the same as beaming something, as long as

you are intentionally also attacking his radar notch - the

closure "band" where cannot separate ground returns from

true returns easily. (Yeah, in lockon this is just look-down)

 

Against Semiactives you can usually notch fairly easily even after

he launches. Against active missiles you should try to notch before the missile goes active.

[GGTharos]

Notching is not the same as beaming. You beam to enter the notch, which is why people may confuse one for the other, but the notch specifically refers to the range of speeds around the ground-clutter closure that will cause a radar to drop your contact in a look-down situation (for example, your ground speed +/- 50kts).

 

Beam obviously refers to placing your bandit on your 3-9. They may look the same at first, but they aren't (a slow enough plane can notch without beaming).

 

You should notch whenever you feel it will do something for you - notching before the missile is launched is certainly valid, as is notching after a missile is launched. It all depends on the situation. In the case of LOMAC, notching before a missile is launched can work to confuse a human opponent, and to delay an AI opponent's launch (but AI are omniscient and will always shoot at you the moment you exit the notch ;) )

[scottysonfire]

Yikes

 

It all sounds quite technical!

 

But surely if you go that slow (50kts) you will stall your aircraft? And even if you dont stall, you wont have much energy left for evasive or offensive flying if you survive his attack?

 

Another silly question: On the HUD in teh F-15, the numebrs on the left side of the HUD indicate airspeed? What are they set to? Miles per hour? Kilometers per Hour? Knots?

 

I find if I fly the F-15 below the number 200, it pretty much falls out th sky if you excecute high G turns

 

Is notching a high G manouvre?

 

sorry for the array of questions, I hope they all get answered

[RvEYoda]

50 kts closure more(or less) than the ground clutter could be what you need.

Not just 50 kts speed ;)

[scottysonfire]

keh?

[S77th-konkussion]

Radar will dismiss/ drop/ filter out a contact that does not maintain a certain amount of measureable motion.

 

If a contact is closing on you at less than say.. the 50 knots in his example- it will often be dropped as a valid contact.

[GGTharos]

Yikes

 

It all sounds quite technical!

 

But surely if you go that slow (50kts) you will stall your aircraft? And even if you dont stall, you wont have much energy left for evasive or offensive flying if you survive his attack?

 

You could still fly at 150 and just turn away a little, but you're correct in general.

 

Another silly question: On the HUD in teh F-15, the numebrs on the left side of the HUD indicate airspeed? What are they set to? Miles per hour? Kilometers per Hour? Knots?

 

KCAS (Knots, Calibrated Air Speed)

 

I find if I fly the F-15 below the number 200, it pretty much falls out th sky if you excecute high G turns

 

You can't execute high-g turns at anything resembling 200kts or less. Therefore, what shouldn't you do? ;)

 

The F-15's preferred energy range in LO is between 350-475.

 

Is notching a high G manouvre?

 

No. Notching has nothing to do with maneuvering, it is simply a range of velocities (specifically around closure of the ground clutter) that cause anything at those closures to not be displayed on your radar scope in a look-down situation.

 

You could use a high-g maneuver to get INTO the notch quickly (you want to get perpendicular to the radar beam ... ie beam the threat)

[ScEBlack1]

When you have performed the notch and the bandit is on your 3 or 9 position and you have dropped below his altitude and decreased your speed a bit and seen him disappear from your RWR , how long should you perform the notch before pushing back into him and firing, this is before he has fired on you. Say you have performed the Notch 20 miles out and after closing head on, what would be the next best move, considering of course there are no other bandits around and situational awareness is on the 1 bandit. How long roughly does he not pick you up on his RWR while performing the notch?, im interested in all ideas on this and i feel it is good for others to learn more about this, thanks.

[scottysonfire]

Wow!

 

thanks for all the informative answers guys...

 

this all makes a lot of sense... when I fly the F-15 quickfly mission from the startup page, I can never see the enemy helicopter on my radar. Im usually at a higher altitude than him and his airspeed is obviously very low cause hes a helicopter...

 

would this be an example of notching? Even though it might not be intentional as a tactic, rather its just due to the native slow speed of the heli?

[RedTiger]

Try this experiment:

 

Create a mission in the mission editor. Put your plane of choice at 20,000 feet. I'd suggest a Russian one. I think the SPO radar warning receiver does a better job of helping you visualize what is going on if you are new to the concept. Now put an enemy plane about 30 miles away at the same altitude. No missiles for him, he doesn't need them to demonstrate notching.

 

Now fly directly at him until he locks you up. Once you hear that lock tone, first place him on your beam, directly to your 3 or 9 oclock. Use the RWR to help you do this. Once you've done this, make a sharp dive to a lower altitude, keeping the bandit on the beam, your 3 or 9 oclock.

 

Level off at 10,000 feet. You should find that the bandit no longer has you locked. You are now officially "notching" the bandit. You have him on your beam and you are forcing his radar to look down to find you. Now, turn back towards him. You'll notice that very quickly as you turn back towards him he'll lock you up. Now swing back around and put him at your 3 or 9 oclock again. You should notice that he has lost his lock again. You've just notched for a second time.

 

You don't really have to be below the bandit to notch, but it does help.

 

There's a bit more to it when it comes to using this defensively or offensively, but this should at least give you an idea of what to look for. :)

Edited October 9, 2008 by RedTiger

[GGTharos]

Yes, however in this case the helicopter should be a big bright blip on your radar because the rotor blades are moving at speeds WELL outside the notch ;)

It is an omission in the simulation - but yes, ignoring that little piece of information, it is an example of notching.

 

Wow!

 

thanks for all the informative answers guys...

 

this all makes a lot of sense... when I fly the F-15 quickfly mission from the startup page, I can never see the enemy helicopter on my radar. Im usually at a higher altitude than him and his airspeed is obviously very low cause hes a helicopter...

 

would this be an example of notching? Even though it might not be intentional as a tactic, rather its just due to the native slow speed of the heli?

[scottysonfire]

Thanks guys!

 

A big thanks to Red Tiger for his well described practical example, I'll give that a try, except I cant fly the Russian planes to save my life (I cant understand a thing in the cockpit - I just find the American cockpit a lot easier), I'll have to try your tutorial in the F-15.

 

thanks again

[GGTharos]

Yes, you do ;) If you are above his altitude the lock will not drop - or it will due to OTHER doppler effects at longer ranges :)

 

 

You don't really have to be below the bandit to notch, but it does help.

 

[RedTiger]

Yes, you do ;) If you are above his altitude the lock will not drop - or it will due to OTHER doppler effects at longer ranges :)

 

Well, yes, obviously you can't be above them. I should have been more specific. What about co-altitude? As unlikely as it is to be EXACTLY at that same altitude, conceptually, wouldn't that work?

 

EDIT for the benefit of scottysonfire: don't try to be at the same altitude. If you want to notch, go below them. :)

Edited October 9, 2008 by RedTiger

[RedTiger]

Thanks guys!

 

A big thanks to Red Tiger for his well described practical example, I'll give that a try, except I cant fly the Russian planes to save my life (I cant understand a thing in the cockpit - I just find the American cockpit a lot easier), I'll have to try your tutorial in the F-15.

 

thanks again

 

No worries, you can do the exact same thing in the F-15 with no problems. The Russian RWR capability in LOMAC isn't realistic, but for some reason I found the little picture of the airplane in the center with the lights around it to be more intuitive at first. :D

[GGTharos]

Well, to be specific:

 

Reality: Look down is defined as having a target in ground clutter. Co-alt with mountain behind the target qualifies. LOTS of chaff in the air (more than your fighter can carry) also qualifies.

Also the ratio of distance to target and distance to ground counts (if the target's close enough, you get a strong enough return to prevent filtering, but that doesn't mean you can bypass the filter anyway).

Following this you have hardware limitation - what can the radar do, how can it do it, how DOES it do things, etc etc etc.

 

LOMAC: 1' below attacker altitude = look-down. Might be a bit of exaggeration here, but basically ...

 

Well, yes, obviously you can't be above them. I should have been more specific. What about co-altitude? As unlikely as it is to be EXACTLY at that same altitude, conceptually, wouldn't that work?

 

EDIT for the benefit of scottysonfire: don't try to be at the same altitude. If you want to notch, go below them. :)

[RedTiger]

Well, to be specific:

 

Reality: Look down is defined as having a target in ground clutter. Co-alt with mountain behind the target qualifies. LOTS of chaff in the air (more than your fighter can carry) also qualifies.

Also the ratio of distance to target and distance to ground counts (if the target's close enough, you get a strong enough return to prevent filtering, but that doesn't mean you can bypass the filter anyway).

Following this you have hardware limitation - what can the radar do, how can it do it, how DOES it do things, etc etc etc.

 

LOMAC: 1' below attacker altitude = look-down. Might be a bit of exaggeration here, but basically ...

 

I didn't think about it this way. I guess to notch you *have* to be "blending in" with something. Like the ground, a mountain, or chaff. If an object was hovering completely motionless high up in clear sky, I guess there wouldn't be anything you would have to filter? You would be able to detect it just fine.

[GGTharos]

Exactly :) I don't know however, how specific radars deal with their doppler filters. It is thus possible that some radars might be notchable in a low noise situation.

[patricio_z]

Isnt notching specially usefull against F-15´s radar, because its a doppler radar? or every radar (e.g.: the ones on the russian birds) have this capability/disadvantage also??

[Ironhand]

Isnt notching specially usefull against F-15´s radar, because its a doppler radar? or every radar (e.g.: the ones on the russian birds) have this capability/disadvantage also??

All the A2A birds we fly in this sim have pulse doppler radars. So, yes, all can be "notched". I'm at work and don't have time to read the complete thread but, if it hasn't been mentioned, the pilot can control the doppler gate (the range of closure speeds where the contact will not be displayed--ie, the contact is dropped)--there are discrete values that are selectable. This, however, isn't modelled in the sim.

 

Rich

[aaron886]

If it hasn't been mentioned...

 

"Notching" is interchangeable with the term "Beaming." "The Beam" is the imaginary line extending from your 3 and 9 o'clock positions.

[Frostie]

I have the understanding that a 'notch' is to disappear off Radar where as to 'beam' was to fly between 70-120 deg off the bandit.