P-38 Nose guns are affected by convergence

[Dobs]

Last night I realized I had a shotgun effect on the 4 50s on the P-38.  My first thought was dispersion was too high, but upon further examination it appears they are affected by convergence.

The guns on a 38 are so close together there was not a need to set a horizontal convergence on them....the furthest two guns horizontally, the bottom 50s, were 19.5" apart (center of barrel to center of barrel), and the vertical distance was only 6.5" from top 50 to 20mm.








Anyway we can get a "boresight" of the guns on the 38 vs shooting a needle at 650 yards and then having it shotgun past that?

[bustr]

You will probably get this around the same time he disables elevation adjustments for motor cannons and locks them inline with the crank shaft.

[Randy1]

One of the best P-38 cockpit pictures I have seen Dobs.

I do not think the choice of convergence is as important as leaving them set in one place.

[FLS]

If you ignore dispersion the "shotgun" effect should be about 20 inches at 1300 yards if you set convergence at 650. Same as parallel. More than that is dispersion.

If you set convergence closer you'll see a bigger spread at max range.

[Dobs]

I fly with it at max....but last night I was sniping a Pony at 1k....and I zoomed in tight (don't normally do that) and that is when I noticed it. 

I'll take bore sighted guns on a parallel for a $100 please:)

[Dawger]

I fly with it at max....but last night I was sniping a Pony at 1k....and I zoomed in tight (don't normally do that) and that is when I noticed it. 

I'll take bore sighted guns on a parallel for a $100 please:)

As Dobs points out with graphics, the real world procedure was parallel to the sight line.

We get beat over the head with "Show the proof and HTC will fix it." Time for a little demonstration of that.

[FLS]

Setting convergence is a game feature common to all the aircraft.

Dobs noticed dispersion and blamed it on convergence. That's a perception issue.

What's the actual problem with the P-38 that makes it worth development time to 'fix'?

[bustr]

As Dobs points out with graphics, the real world procedure was parallel to the sight line.

We get beat over the head with "Show the proof and HTC will fix it." Time for a little demonstration of that.

Lets see, I've been at Hitech for almost 15 years over motor cannon and why he allows elevating the barrel up through the reducer gear and engine in this game.


Bf109, DB605 pass through tube and bolted in MG151\20.











ShVAK locked into a VK105 from Yak3.

[Dobs]

See rule #4

[hitech]

How much do you think the convergence effects dispersion at 1000 yards if set at 350 vs 600?

I have the luxury of being able to disable dispersion.

So here is the p38l at 100,500 and 1000 yards with convergence at 650 with no dispersion.
100

500

1000


So your asking me to do an a fair amount of work to have vertical convergence only on some guns for a mater of inches at 1000 yards. 


HiTech

[bustr]

If I remember my testing of the MK108 in the K4 set to 650, the vertical elevation at 325 was about +10 ft above the center line of the engine\cannon bore. I know (sorry 29Mil for 10ft at 325yds was too large)-->10.2Mil high of the center line at 325 isn't much if you are clueless to it. And so forth for the assortment of 20-37mm motor cannon in the game. Then as you can see from the photos above, any motor cannon shot above the center line is a physical impossibility due to the physical mounting of the cannons to shoot through the reducer gear. I have all of my motor cannon pulled in to 150 and that is still 5Mil above the center line at a very short range when the round should be hitting below the engine center line. At least gravity takes over and keeps it to 5Mil. 

[bustr]

Get a copy of AAF Manual 200-1 1945.

At 2000ft .50cal dispersion is 4Mil, and for AAF purposes ganged .50cal in wings and P38 nose are still 4Mil. Roughly a 10ft cone of dispersion at 2000ft (666yd). In real life from a moving bouncing P38 it would be wider. If you test conv650 at 650yds offline with the target, your core dispersion is about 10ft with outliers making a secondary dispersion to 20ft. Within the AAF guidelines.

[Dawger]

Setting convergence is a game feature common to all the aircraft.

Dobs noticed dispersion and blamed it on convergence. That's a perception issue.

What's the actual problem with the P-38 that makes it worth development time to 'fix'?

Apparently there is absolutely nothing worth the development time to fix when it comes to certain aircraft types.

Convergence is now suddenly dispersion.

8 degrees is half flaps.

The guns fire at an upward angle greater than AOA crit and thats okay.

Rudder authority is obviously weak. I think that was due to the slipstream canceling out due to counter rotating props yet the same counter rotating prop aircraft exhibits torque rolling with the flaps down at stall speed.

The real world level acceleration prize winner can't get out of its own way in game.

It compresses about .04 Mach too slow and nothing else in the game compresses at all.

The P-38 is pretty far off base in many areas. It would be easier to just say no one at HTC is ever going to address the issues instead of the constant stream of embarrassing counter arguments.

[FLS]

Apparently there is absolutely nothing worth the development time to fix when it comes to certain aircraft types.

Convergence is now suddenly dispersion.

8 degrees is half flaps.

The guns fire at an upward angle greater than AOA crit and thats okay.

Rudder authority is obviously weak. I think that was due to the slipstream canceling out due to counter rotating props yet the same counter rotating prop aircraft exhibits torque rolling with the flaps down at stall speed.

The real world level acceleration prize winner can't get out of its own way in game.

It compresses about .04 Mach too slow and nothing else in the game compresses at all.

The P-38 is pretty far off base in many areas. It would be easier to just say no one at HTC is ever going to address the issues instead of the constant stream of embarrassing counter arguments.

All opinions are welcome but opinions are not facts and don't make good arguments.

[bustr]

Ran the same offline target test with the P38 and conv set to default for first time install. 50's at 250 and cannon 275 I think.

The dispersion pattern on the target at 650 was identical to setting the convergence to 650 with slightly more outliers. The IP point at 650 was lower. The only place during bore sighting that the rounds will punch a circle inside of a pie plate is when the plane is locked on a stand and the live shooting target is at 500ft. In the game at 166yds using the offline target the P38 guns shoot like a laser. Past that the dispersion cone happens and Hitech modeled that faithfully including the 29ft dispersion cone for the MK108 30mm at 400m(437yds). I even think he modeled the 20inch spin drift at 400m. The patterning tends to favor the left side of the target.

The P38 dispersion cone by setting your conv 400-650 will be within AAF described limits. And on out to 1000, the dispersion creating the 4Mil cone at 2000ft is still in effect. Yes years before you and Dobs got here quite a few of us went at it with Hitech over ballistics and we literally whizzing matched this out with documents and manuals from the AAF and Luft. I had to dig up a Rheinmetall-Borsig testing document for the ballistic characteristics of the MK108 Geschoß round which had a spin drift(parabolischer rechstdrall) table.

The P38 and the Me262 have the same factor in common for their armament. All are mounted parallel and by 400yds dispersion has created a shotgun effect which was the benefit of that kind of mounting. A dispersion cone of rounds had a better chance of hits than a laser beam of rounds. Air to air gunnery is very uncertain because of all the random elements in play. Dispersion patterns were used to counter some of the random nature of flight phenomenons during air combat. And then they came up with the GGS and K14 gunsights.

So how far down this rat hole do you want to keep whizzing??