Andy's Angle Off vs. Aspect Angle

[Syzygyone]

AS a newbiue sick a emptiing lead into thin air, I have deicided to study as much as possible on line.  Luckily I found this great place and then SimHQ and Andy's great missives.  Thank all you guys so much for taking the time to put this info out there.  I hope my ignorance doesn't pester you guy but I have a question.

ON Sim HQ, Andy writes as follows:

"Angle off.  This refers to the relative headings of the fighter and its target.  Angle off is simply the difference in the direction the two aircraft are pointing.  If they are pointing in the same direction, the angle off is zero…if they are approaching head on, then the angle off is 180 degrees.  Angle off is a measurement of heading.

Aspect angle. This term is a measurement of position.  The heading of the attacker relative to the target is irrelevant.  Aspect angle refers to the attacker and is measured using the target as the reference.  This measurement originates at the target’s six o’clock.  This is the zero aspect position.  The twelve o’clock position off the target’s nose is the 180 degree aspect position.  From the six o’clock position to the twelve o’clock, aspect angles are referred to as either ‘right’ or ‘left.’  This is in reference to what side of the target you as the attacker are looking at.  If you are looking at the target from its 3 o’clock position, you have a 90 Right aspect.  And if you are looking at the target from its 7:30 position, you have a 45 Left aspect.  Remember, your heading is not included in this term.  Aspect angle is only a way of defining your position relative to the target."

Then, he shows an Image, (No. 8 in the SimHQ lesson guns1.html) with an aircraft attacker positioned at the target 9 O'clock position.  The image says that this represents an aspect angle of Left 135.  I get the Left part, but it seems that it should be Left 90 aspect angle because you are measuring from the target's tail position 90 degrees.

I don not mean to suggest for a second that the image is wrong, only that I don't understand something.  Can anyone help me out with this?

 

[Lephturn]

I think this other article on simhq might shed some light....
 http://www.simhq.com/simhq3/sims/air_combat/f3manual/bfm1.shtml

 

Here's the image your referring to for comparison:
 http://www.simhq.com/simhq3/sims/air_combat/guns1/fig8.jpg

The trick is that 0 degrees is behind, and 180 degrees is nose on.  So if you are looking at his nose, that's 180.  If you were looking at his side exactly, that's 90 right.  Since you are 45 degrees to the right of his nose... that's 135 right.  Now the two articles seem to disagree on how it's measured.. from you to your target, or the other way... so one says right, one left.  I like Skater's explanation.. since I am seeing the right side of the target's plane, I'd call that 135 right.

Course... I'm betting Andy is about to stop by any time and sort us out.   He's good like that.  

[Andy Bush]

Ahhh...the dreaded aspect angle question.

The figure in my article is correct, but I think I could draw it a lot better next time to remove the confusion. Here it is again with a red overlay to explain the 135 Left measurement.

 

In the other drawing, the aspect is 45 Right. Aspect is always measured from the tail of the target around to the position of the attacker. Attacker heading is irrelevant. So in this drawing, the angle from the target tail is only 45 degrees.

Another way to think of it....if you are ahead of the target's wingline (3/9 line), your aspect is greater than 90 degrees...behind his wingline, less than 90 degrees.

[Zapata]

FWIW, the Navy measures aspect from the bandit's nose, while the Air Force does it as described above.  You can imagine the results when a Navy ground controller assumes he's vectoring Naval aircraft to the bad guys, when in reality he's giving info to increasingly confused Air Force aircrews who don't know why their ground controller is 180 degrees off on all his calls.  Not that it's ever happened, mind you.  

Zap

[Lephturn]

Ahhh, I see Andy, I didn't pay attention to your labels... I was thinking of the bottom guy as the target.

Yeah, that overlay helped.  Thanks Andy.  

[Syzygyone]

Ahhhhhhhhh.  I feel much better now.  And Andy, your new graphic is much easier to understand that you measure from the tail.  


Now, if only I could figure out how to make my brain compute everything real fast I might only die 8 our of 10 hops as opposed to 9.5 times out of.  One thing is for certain though, when I got the impression that I was headed for a smoking hole in naval aviation, I WAS RIGHT!  I can fly real good but this ACM stuff just has me bollxed up big time!

You guys are really great to spend the time to share all this info.  Can't thank you enough.

       

[Andy Bush]

I'm glad we got that fixed...but I admit this is not one of the biggies in air combat. The question is further complicated by the existence of differing definitions...the USAF and USN do define certain things differently...ACM means one thing in the Navy, and something quite different in the USAF.

Another way to visualize aspect is to think of the angle as being the way you see the bandit irrespective of where your aircraft is pointed. The aspect angle will be your eyeball line of sight to the target...this is what the second diagram above is trying to show.

For example, if you look straight back and see a target at your exact 6 o'clock, the aspect angle will depend on your line of sight angle to his flight path. If he is pointing straight at you, the aspect is 180...if he is tail on and going away, your aspect is 0, and if he is crossing your flight path at exactly 90 degrees, then your aspect is either 90 Right or Left.

Aside from knowing the academic definition, in a sim like AH, aspect angle is not that big of a deal!

Andy

[Syzygyone]

Sorry, I don't mean to belabor minutia.  
It was just that I thought I had lost it compeltely.

Frankly, I like the idea of measuring from the pilot's point of view.  

Anyway, thanks so much for your time.