How to offset laterally doing intercepts?

[Mule]

I couldn't think of a simple title sorry.

 

I've been watching

and in one of the episodes they are doing intercepts.

 

So typically during the cold war era the setup would be head on against a Tu-95 Bear and the idea is to sneak up on the six. They talk about hitting benchmarks during the approach which make perfectly good logical sense.

 

The first of these benchmarks is 40 miles out 8 miles to left of the target. The 40 mile bit is easy. How do I know I am 8 miles left of the target. Is there an easier way than having to do maths?

 

They show a math equation that you have to do on the fly in your own head. That isn't gonna happen with my brain. I struggle to count my own fingers.

 

If I do have to do the maths I am going to need Target Aspect figure. Where on the radar does it show that?

 

Many thanks.

Edited October 19, 2018 by Mule

[catt42]

Basically if you are 40nm out and let's say your target's aspect is 15°, you'll have 40*15*100=60,000 feet of lateral separation, or 10 nm. Distance and target aspect can be obtained from the radar, most of the time.

There's a CNATRA publication available online that gives more detailed information on the subject, all-weather intercept.

 

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[Mule]

Thanks Catt. Where do I get the target aspect figure from in the radar?

[catt42]

It varies from aircraft to aircraft. In the mirage it's the little number right underneath the locked contact in tws ans stt mode. I don't know about other aircrafts.

Of course it's impossible to tell if you're flying a mig-21 or an f-5.

 

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[mahuja]

If you want the less math-y version, you're on a direct intercept when the bearing to target does not change. When flying straight, the target does not slide left or right on your radar b-scope.

 

If you want to come from behind, you need to be doing a lag pursuit.

 

Point your nose directly at the target, and look at which direction they drift. That alone will say a whole lot about their aspect, in particular if they are headed left or right of you. If you then maintain a course a little to the side they drift away from (relative to the intercept course), you'll eventually be behind them.

[Frederf]

Pilots trained in intercepts get very comfy on the trigonometry and also do a lot of pre-planning so they can follow some simple rules on the day. Fighter pilots are PhD-level experts in their field.

 

 

 

Your example of 40nm SR, 8nm LS is a small cone of 11.5°. That should be read simply as aspect off the radar display. At any range >40nm if you find yourself outside this cone you would drive as efficiently as possible toward his course line until you established this angle.

 

 

E.g. if you're 45° off his right nose then if you just approached him collision course he'd maintain that angle at your desired 40nm. Instead you'd turn right so as to put him on the left edge of your radar (or perpendicular to his track but you'll lose radar contact). By cranking ahead of collision you'll be narrowing your position angle closer to being directly ahead of him.

 

 

So you monitor that angle reduction until it approaches your desired 11.5°. Then you turn to collision course (radar should provide a collision steering cue) which will ride that same angle all the way in to your 40nm SR.

 

 

Alternatively you are inside that 11.5° and you want to get out of his way which just means cranking the other way until the angle grows. In either case once you're on angle and at range then you turn to his reciprocal to maintain that 8nm lateral.

 

 

That JetStream show was giving it's 40nm, 10nm as distances along bandit track instead of slant range. It makes little difference at 40nm but I don't know if I should trust the TV's diagram which side of the triangle they label 10nm. Slant range is what is prominent in displays.

 

 

Anyway, you're anti-parallel with the target 8nm lateral, 40nm ahead and he's drifting from that 12 degree spot on the radar to bigger numbers. You're looking for a new angle and a range which should happen at the same time. Taking the show's diagram at face value you're 10x8nm offset which is 38.6° off your nose, about half of the radar's width. Then I guess the procedure is pure pursuit and some other steps after that.

 

 

It seems complex but the process is pretty simple:

1. Am I on, inside, or outside of his 12° angle?

2. Crank away (toward) if you're inside (outside) that angle.

3. When on angle fly collision intercept which maintains angle.

 

4. When 40nm SR turn to put target 12° off nose to be his reciprocal

5. Wait for 10nm and/or half scope drift.

6. Point at him and do the rest of it.

 

 

Reading P-825 CNATRA it pretty much mirrors that I pulled out of my butt by common sense thinking. There are options though. You don't have to drive to some 12 degree angle only to fly reciprocal and wait for the target to drift to 40 degrees. If you start at 40 degrees off his nose just fly collision all the way down to 10nm and do the turn, skipping the 40nm checkpoint. In other words this 12 degree "don't get run over" angle is a minimum for turning room. If you're outside it you can skip it to close on a 40 degree aspect line. The only danger is you're worried the bomber might maneuver to spoil your intercept so you want to be darn sure you get essentially ahead of it before doing anything else. This will take more time but is harder to be ditched.

[Mule]

Brilliant. Thanks for all the info. Lots to take in which is great.

 

Does the Hornet radar in it's EA state give aspect? or do we need TWS for that?

[Frederf]

When STT there's a vector drawn from the contact and on HUD the circle (weapon dependent?) will have an arrow. From these you can judge TAA to the nearest 5°.

 

 

Just RWS scanning just has contacts as blobs so no real info.