Gunnery Wish for La5 and La7

[bustr]

Some may not know that the ShVAK 20mm and UB 20mm both fired the same round with the same ballistics.

The UB was lighter than the ShVAK which resulted in three eventually being mounted in some late La7. The majority of La7 had 2 ShVAK 20mm mounted while La5 only had 2 ShVAK.  Because the 20mm round shot so flat, -.01m drop at 200m, the cannons pretty much were mounted flat with the datum line shooting parallel out over the top of the engine. The gun mounts had some adjustment to insure parallel alignment and a common pattern at 200m. As with the Yak family, the PBP gunsight line of sight was to the 20mm IP at 200m.

As with the motor cannon wish, my wish is that our La5 and La7 reflect this ballistics\gunsight relationship. Unlike our game, there was no large azimuth elevation adjustment possible. Russian pilots did that with the azimuth dial on their PBP1 gunsights.

ShVAK and UB 20mm ballistics. PBP-1 Azimuth adjustment.

Why 200m? Ballistics chart for the ShVAK 20mm round.



PBP-1 illustration for La5.



How the cannons were mounted.

Pictures of ShVAK mounted in La. Note the cramped compartment with almost no positive azimuth elevation space to lower the receiver for.



Note the recoil spring buffer mounts each side of the barrel to the mounting yoke just in front of the receiver.





Illustrations of the cannon mounting platforms from early up to a three UB tubular mount for the late La7. Very little adjustment for dropping the rear of the cannon receiver to do more than equalize the shot pattern at 200m.



Only picture I could find showing the ShVAK rear mount. Late war as the compartment was made from metal. Earlier tubeing frames had a threaded flange.









La5



La7

[BnZs]

Essentially you are trying to stop people from using extreme convergence distances on some nose-mounted guns, probably to stop them from getting extra loft that makes high-deflection shooting easier. Which is reasonable from a realism standpoint, I just thought someone ought to come out and say it. 

[bustr]

No BnZ, it didn't happen with the real aircraft.

We are not WT.

Our wing mounted fighters where azimuth adjustments are concerned fall within the 3.5 or so degree allowance of their mounting cradles. Usually -1.5\0\+2.5 or some variation. I suspect it was the expediency of simplicity in 1999 to paint every fighter with the same broad brush for the sake of coding simplicity. And who would notice anyway? Just the same as when Baumer noticed the FoV perspective for gunsights was not the same across all cockpits back in 2010. And now I build gunsights to 1Mil = 2pixel because Hitech then corrected it.

The B-25H is a departure from AH's cannons historically locked to the datum line zero coded as azimuth adjustable, and the AH sky didn't fall in. Pretty much no one even noticed, and adapted to the real world modeled relationship between the 75mm to gunsight bore alignment. So the rest of the planes that follow in that vein can be adjusted accordingly. I doubt new code was written to allow the B-25H to have it's cannon gunsight relationship. And I've followed the rules of showing the real world data.

Usually the asker of a question such as yours is the one really worried about the outcome.

[Vudu15]

I like it and would think this to be a cool addition.

[TheCrazyOrange]

Not that I disagree, or wish for it to stay (provided gunsight-facilitated convergence adjustment is added simultaneously), but you sound pedantic as hell.

[Fish42]

pedantic

I guess you have not been on these forums too long. I remember a 44 page thread concerning the amount of ammo taken in the Ju-87 for its 37mms.

[bustr]

Not that I disagree, or wish for it to stay (provided gunsight-facilitated convergence adjustment is added simultaneously), but you sound pedantic as hell.

One kindergarten class lets out, another starts up.

Guess Skuzzy never gets a break, just a lunch break during the shift change. Nature abhors a vacuum Fish.

Still I wonder if Mr. Crazy here is a shade for one of the recent Skuzzy PNG'd. 

[Xavier]

Because the 20mm round shot so flat, -.01m drop at 200m, the cannons pretty much were mounted flat with the datum line shooting parallel out over the top of the engine.

Some years ago I met a soviet La-7/9 pilot in Barcelona, in a conference.  He had only praise for the ShVAK cannons, he said that they had a nice rate of fire and were more reliable than other aircraft armament then in use in the soviet air force. When mounted in their La-7s, they checked the convergence at 400m shooting at a blanket and then checking the holes (with the aircraft on the ground, of course). He claimed that dispersion at that range was just about 40-50cm, with a similar drop. My guess is that they tested the drop at 400m to adjust their sight accordingly, since the cannon's relative position could hardly be modified.

He also mentioned Il-2 pilots being ordered to spend all their ammunition before returning to base, so they would fly circles over the german lines, strafing until their ammo was expended or they were shot down. A lot of aircraft were shot down that way, and they had no ammo to defend themselves in the trip back to base.

Two years ago some guys I know located a Komet pilot living in the spanish coast, near Valencia. We'll ask him if he'd meet with other aviation enthusiasts in Barcelona for a similar event, all expenses paid.

[bustr]

Xavier,

Thank you. That's a 9 inch drop at 437 yards, less than an inch at 218 yards. Basically a flat shot to 400m. That's less than a Mil at 400m even if it's a Soviet Mil at 1\6000.

The materials and interviews I've read, the tactical doctrine was 200m practical shooting fighter to fighter. So the factory aimpoint was 200m while the inner ring on the PBP1 reticle was the average wingspan of Luft fighters at 150m. The PBP1 gunsight had an azimuth dial, so the pilot really could choose any aimpoint. Just like US fighter groups in the combat zone would change the factory harmonization of their fighters based on combat experience in some cases.

The pilot you spoke to, what kind of missions did he fly?

[Xavier]

As long as I remember he flew base defense missions early in the war, when they used to sleep in the cockpit until the call arrived and the pilots scrambled. Later in the conflict he flew escort missions providing air cover to ground forces and Shturmoviks, I'm sure he mentioned having one or two kills. He mentioned ramming attacks being quite usual early in the war, as soviet fighters carried little armament and a lot of german bombers could take a lot of punishment. The usual method was colliding with the bomber's tail and parachuting, or belly-landing in the snow.

He was a pilot in the soviet air force until the early 50s, so he got to fly some of the last russian prop fighters.

[bustr]

I had to look around for more ShVAK InitV for different rounds.

Many of the HE\AP composite rounds from WW2 were  750m\sec, 770m\sec or 790m\sec as practical usage. The 800m\sec from the chart I introduced may well have been for a 1930's MP or TP mount rather than an aircraft SP(synchronized) mount. Higher velocity meant a higher cycle rate and lower lifetime on the parts and barrel.

770-790 with a 96g round would be the 40cm-50cm drop at 400m or about 1Mil. 200m is still flat at that InitV. The Hispano 20mm U.S. version 2700ft\sec(822.96m\sec) drops 122cm by 400 yds(366m). British versions 840-880m\sec.

[BnZs]

Hey Bustr, your logic in your posts is sound. You are without doubt factually correct on this. I have no problem with the proposed changes. (I can hardly hit anything outside of 200 with an LA cannon anyway) I just think there's an element of "Darn those Muppets for dodging my pass with their aerobatic contortions and tatering me at 400 yards" mixed in it.  

[bustr]

At least the muppets have always had the moxy to say what was really on their mind in plain English and take getting ban hammered like men.

[TheCrazyOrange]

Hey Bustr, your logic in your posts is sound. You are without doubt factually correct on this. I have no problem with the proposed changes. (I can hardly hit anything outside of 200 with an LA cannon anyway) I just think there's an element of "Darn those Muppets for dodging my pass with their aerobatic contortions and tatering me at 400 yards" mixed in it.  

Lol, he might just be ocd about it. I am with my books; all of them nice and nearly alphabetized.

[bustr]

So Crazy which recent PNG are a shade account for?