Convergence Settings

[MK-84]

Just a few planes that I often fly.

Temp/typh: 400
Fm2:          250
F4U:          300
10920mm:   200/centerline 250 pods
P47:          400

This unless i plan on strafing or attacking bombers almost exclusivley, in which case I often set at 400 regardless of the plane.

[Ramon]

In the P-51D I set convergence at D400.  That way I am good out to about 800 on small aircraft due to the pattern closing at 400 the opening up after that. (at D800 the bullets are back the width of their starting point) On bombers I can start ripping them apart consistently starting at D1000, that is of course with a high rate of closure and aiming high.  I have really good luck taking them down that way.  Another favorite convergence is on the IL-2.  After getting the advice on the forums I set them to D200.  This combined with a high angle on the tank works like magic.  Come down from high and start firing at D400 to D300 and stop at D200...pull up immediately.  Tanks just cannot withstand this type of attack.  I think everyone has to get used to their convergence setting decision.  I have flown the simulator skies for quite a spell and practice with your settings is really what you need.

[doright]

If I understood what he was saying correctly then I'll use an example that will hopefully make it clear.  Picture a blank wall, on the wall mark a point with a pencil at roughly eye level.  Get a lazer pointer, hold it at waist height and stand back 10 paces and make a note of how much an angle you have to hold the lazer pointer to put a dot on the sight.  Now step forward so that you're only a couple feet from the wall and point the lazer pointer at the dot.  In order to hit the convergence spot (the wall) you have to hold the pointer a higher elevation/angle the closer you are.  

Dang almost sucked me in with that one. Had to think about it and do some research.



In the image your laser line is the 'Line of Departure'. Notice the 'sight height' this is the same as the difference between your eye level and waist height your holding the level at; it is also equivalent to the height difference between the cockpit sight and gun mount location.  The convergence setting is 'Zero' on the illustration. Assume a 6' sight height and 300yd range and the sight depression angle is a miniscule 0.4deg. Most importantly notice that the bullet trajectory is downward shortly after 'Mid-Range Height'.

Think about setting the Zero point out to 400 yds. The line of departure would have to be raised to compensate for additional bullet drop in order to intercept the level line at 400 yds. The mid-range height would now be at 200yds. Meaning that you are lofting your shells higher with a longer convergance setting.

Back to way your example is so seductive. Move the Zero point in along the sight line. The line of departure would have to be lowered the closer you got, up to the point that the trajectory is tangent to the sight line. After that (like in your example) the line of departure would have to be raised as Zero got closer because the bullet is still on a rising trajectory. The range to that tangent point depends on Sight height, depression angle, and bullet trajectory all of which vary with the various airframes, but I'm willing to bet is closer then we usually engage at.

I'd be intersted to find out about the actual mechanics of setting convergence and sight depression on our a/c. I'm think'n its a lot easier to level the plane (usually a somewhat abriturary but consistant reference like seat/canopy rails, engine rails, marked rivet heads on fuselauge...) set the target out at the convergence distance then adjust the guns to hit it and adjust sight depression to match. Notice in this method the zero point (target) moves along the level line. And the bullets would never hit on a upward trajectory.

[Dichotomy]

well I did a little hands on research tonight and found that I hit more successfully with my convergence set at 200.  I was getting good and consistent hits at 400 to 0 which, thus far, is much better than I was doing with it set to 300.  Of course I only flew the Spit VIII and the Pony but it was working for me.  I'll try a couple of different airframes tomorrow.  Thanks gents.

[321BAR]

on the A6Ms i set the Type99s to somewhere between 300-450 yards depending on what i am fighting and the type of fight i'm in. the mgs i keep set to 500 because they are set in the fuselage and theres no need to set the convergence of them.

[morfiend]

 Doright,

 your chart shows a real life trajector with rounds converging at 200,but if you notice the trajectory also crosses the line of sight at what looks like 43 yards and according to some LW balistic graphs it show about that same thing only the convergence was at 400 IIRC for the LW graph.

 However Hitech has stated that they modeled the convergence to rise to the center of the pipper at convergence range.

 Now if this is the case the lazer annology would be correct. However I'm not 100% sure if this is the case or not and it's been a personal quest to find the correct answer.

  You can test this yourself,using center mounted guns,like on a P38 move convergence in as close as you can and use the dot target command and usual auto pilot to stablize the A/C. Then set target to 100 and move it out at 50 yard intervals and see if in fact the rounds dont strike abit high as you move the target away.

  Now there will come a point at which they should start to drop again,as they have a balistic curve.

 So I might be wrong with this and would like to hear one way or another what others think and maybe Hitech can correct any misimformation that I have stated.

   

[doright]

Doright,

 your chart shows a real life trajector with rounds converging at 200,but if you notice the trajectory also crosses the line of sight at what looks like 43 yards and according to some LW balistic graphs it show about that same thing only the convergence was at 400 IIRC for the LW graph.

 However Hitech has stated that they modeled the convergence to rise to the center of the pipper at convergence range.

 Now if this is the case the lazer annology would be correct. However I'm not 100% sure if this is the case or not and it's been a personal quest to find the correct answer.

  You can test this yourself,using center mounted guns,like on a P38 move convergence in as close as you can and use the dot target command and usual auto pilot to stablize the A/C. Then set target to 100 and move it out at 50 yard intervals and see if in fact the rounds dont strike abit high as you move the target away.

  Now there will come a point at which they should start to drop again,as they have a balistic curve.

 So I might be wrong with this and would like to hear one way or another what others think and maybe Hitech can correct any misimformation that I have stated.

   

... but I'm willing to bet is closer then we usually engage at.

Well glad I didn't place that bet.
I did what you suggested using the B25 because of its significant sight height but still close to inline. With the convergence set at 150 the bullets kept rising above the piper after 150yds then falling below again much further away. With a convergence of 600 the bullets where arcing back down before they got to the piper at 600yds. The in between land of a convergence of 300 the trajectory became pretty flat and the rise/fall of the bullets relative to the piper was less then the dispersion. So for the 50cal the convergence setting doesn't make much vertical difference in the mid-range. Other weapons probably differ significantly.

Moral of the story, the illustration I posted is correct (disregarding the range values). The important question is for a certain weapon and airframe at what convergence (zero) is the trajectory curve tangent to the sight line. At convergence settings shorter then that mystery range the rounds will continue upward for awhile after passing through the piper. For longer convergence settings the rounds will be coming back down to the piper. You might even think of it as for a certain departure angle (gun mount elevation) there may be 2 convergence ranges. 1 if your set right on the tangent range. (0 if the armourer depressed the gun).

Suggestion to see what happens to lesser rounds then the .50cal?

[Greebo]

I use a 450 yard convergance on the F6F. Reducing the range does not doesn't help as much on close shots as keeping it long helps on the longer shots. I particularly enjoy picking off bnzers from below as they try and rope me. The F6F's excellent low speed control lets me keep adjusting aim at very low prop hanging speeds. As the roper is also slow I don't need to lead them much and can hit him at longer ranges. The long convergance lets me do more damage, its pretty easy to saw the wing off a Spit at 600-700 yards.

[Ghosth]

Soulyss your original theory was correct, and I've used that very successfully with larger cannons for years. 20mm's 25 - 50 farther than MG's. 30 and 37mm will take a bit more 50 - 100 longer.

Morfiend the problem is thus. Hitech stated that the vertical convergence is there, and is set for a plane at Zero airspeed and altitude.

Once you move the speed up to 300 + that changes things. In fact the faster you are the less Vert convergience you'll see.  Which is why esp in the lower powered German cannons at faster speeds (190d9, 109k4, etc) doesn't seem to have any vertical convergence.

Here is a shot of a 109k4 firing only 30mm. Convergience set to 650, Target at 150, and shot at fairly slow speed to get as much rise as possible.

[jolly22]

-1C i have all at 325, but might extend them to 350-375 if i'm going to be shooting at grounds targets

psshhh vulcher :/

[doright]

...Hitech stated that the vertical convergence is there, and is set for a plane at Zero airspeed and altitude.
...
Once you move the speed up to 300 + that changes things. In fact the faster you are the less Vert convergience you'll see.  Which is why esp in the lower powered German cannons at faster speeds (190d9, 109k4, etc) doesn't seem to have any vertical convergence.
...

I think you're throwing the angle of attack needlessly into the picture. The .Target target is centered on the aircraft's altitude and always due N of the plane. As you slow down you increase the angle of attack, so the piper rises against the target. The plane and target are still at the same altitude just sight line and departure line has changed. The departure line of the bullet is raised by the same amount as the angle of attack. But since the departure line and piper both move the same amount the impact at a range relative to the piper stays the same. So speed doesn't really affect convergence. Don't believe it throw out some flaps and maintain alt and speed. Your angle of attack goes down to keep in level flight, so the piper drops on the target. The speed is the same, and the bullets will hit at the same distance from the piper just lower on the target. So speed has no effect on convergence.

[Ghosth]

Question, how am I adding angle of attack into the picture?

Yes as you slow the pipper rises, but your bullet stream rises with it.

What I'm saying as you SPEED UP, your bullets are dealing with a 300 + mph headwind.
That changes their trajectory.

[doright]

Question, how am I adding angle of attack into the picture?

Yes as you slow the pipper rises, but your bullet stream rises with it.

What I'm saying as you SPEED UP, your bullets are dealing with a 300 + mph headwind.
That changes their trajectory.

So try it. Keep your 650 convergence and 150 target, just change your speed. Your picture will only change in the location of target rings, the bullet strikes relative to the piper stay the same. (edited from here on) The target set at 150yds doesn't really show the effect you where going for.

Using a 650 convergence and 650 target. The cannon rounds do have increased drop as the speed increased. At 250mph it was noticeable that the rounds where falling below rather then at the piper, at 325mph it was quit a bit below. Very interesting.

The lowest shot grouping is at 325mph, significantly below the piper. At slow speeds the shots hit the piper higher on the target.

[nimble]

.50s, everything except FM2 400, FM2 250
20mm, 225 except N1K, split 250/300
30mm, 200

[whipster22]

The IJN Hade the niki convergence at 600