109 nose cannon

[bustr]

You can go into the hanger and pull the motorkanone back to 150 yards along with the MG. The MG lines go straight out from their barrels. The Motorkanone line goes up to meet them. It should go out angeling down slightly at 137.16(150yds) meters. The MG131 should also angle down to make a pattern at about 250 meters with the 30mm and about a 12 inch separation roughly parallel to 400 meters..This convergence line patterning is repeated on all nose cannon planes in the game. Visible angle up to visual level line at 150yds.

Then spawn on the runway with the K4 convergence set to 150yards. Set the target to say 400 yards. Auto level the K4 till your pipper stops level on the center of the target. I beleive the center of the target is a fixed line to the level line view of your pipper when the aircraft settels in on auto level. Your 30mm rounds should hit 32.4 meters below the center of the target(pipper center line). Does anyone know what the width of the rings on the target are supposed to be?

If the MK108 is being elevated based on a line of sight line from the gunsight then at 250 yards the 30mm at autolevel should impact about 60cm high of target center. Another way to test this is to take a FW190A-8. Pick the small gun package. 2-MG and 2- wing root cannon. Set the MG151/20 to 550 yards. Setup the offline target at 400 yards, auto level, then fire the MG151/20. They should impact about 80cm above the target center at 400 yards with the convergence at 550 yards. Thats if the gunnery model is keyed off the level line of sight to infinity like a lazer line from the center of the gunsight pipper.

By the way here are some photos of the Yaks VK-105PF with the autocannon locked in. You will see a 4 bolt saddel clamped down on the barrel just in front of the receiver. : http://en.valka.cz/viewtopic.php/t/54646

Notice even with the P39 Oldsmobile T9 37mm it is mounted parallel to the drive shaft: http://engineeringjohnson.blogspot.com/2008_08_01_archive.html

[Stoney]

I believe the target rings are 10 mils

[bustr]

Stoney you gave me a better idea.

I'm the first here to apologise to everyone for what I thought was the center of the target to aircraft zero line. Half a crow with sand please raw and no water.

I parked all of the aircraft I questioned on the runway and set the target to 3 yards. Went to F3 and zoomed and looked at the profile.

The center of the target is the 0-datum line of the engine if you raise the tail to level.

I will assume in flight whatever distance you set the target to, the target center is fixed to the engine 0-datum line at auto level.

If all MG or cannon firing fixed forward to a convergence point are calculated ballisticaly along that 0-datum line from the engine to strike the target center to match your chosen convergence distance point. The motorkanone rounds are being arched along that line to drop them into the center of the target. There sould be no setting to change the ballistic arch of a fixed MK108 or MG151/20 or Hub Cannon fireing level out of the spinner. The 30mm round at 400 yards should hit the target 30 meters below center. The MG151/20 1 meter below target center at 400 yards. I don't know the ballistic information for the P39 or Yaks.

Based on the engine 0-datum line alined with the center of the target at any distance at auto level. The FW190A/D MG151/20 set to 550 yards should hit at auto level on the target set for 200 yards about 115cm above target center. In the FWA7-A8 manual though, the FW 0-line for armament was the Revi center sight line to infinity about 80cm above the 0-datum line. With the 109's it was by raising the graticule center by tilting the reflector plate on some versions or titling an internal mirror on others to enable looking down to the the 100m sight line point below 0-datum then using the cross hair stadia marks to compensate for distances to 400 meters. To hit an aircraft past about 200 out to 400 yards you would have to raise the nose and aim off the stadia marks below the graticule center.

Maybe HiTech is tilting our reflector plates mathmaticly and virtualy on the fly as a consideration  to center the pipper at whatever range we set (.target xxxx) to or covergence to.

I'm probably full of it and HiTech is letting me make a fool of myself......

[bustr]

For those who are worried how what I'm arguing about would affect you in the game and your field of view through the gunsight, perform this experiment offline.

Set your K4 convergence to 150 and gunsight to a Revi gunsight with the tick marks on the cross hairs. Spawn and fly north at 1k auto level, reduce rpm until ATA is at 2. Wait for the aircraft to settel in and set (.target 600) and go to full zoom. Now lift the cross hairs to about between the 1st and 2nd or at the 2nd tick mark down and hold that on the center of the offline target. Fire only the cannon to produce a pattern.

Because convergence at 150 lofts the 30mm up to drop center of the target at 150 yards. I've chosen 600 yards to be an equivalent+- of the round having left the muzzel of the cannon level to the ground to hit the target set to 400 yards. You will notice the rounds hit about 30-35 meters low of center on the target with you aiming high by 2/3+- down the lower half of your graticule ring. About 45mil+- low of center on the graticule. This is a good approximation of what your gunnery would be like if the MK108 motorkanone in a 109 fired level from the 0-datum line of the engine as they were installed.

As you notice you would have no problem seeing and aiming at a 400 yard target. HiTech has coaded the line of view(visierlinie in the manual) angle down the line of the cowling specified by the data. Other wise you would not have been able to lift the gunsight high enough to hit the 600 yard target on center while watching the rounds impact through your available feild of view.

This can be extended to all aircraft in the game with a nose cannon bolted into the engine airscrew 0-line. The tragectory of the round 20mm, 30mm or 37mm would be compensated by the tick/stadia/hash(ladder) marks on historical gunsights out to about 400 meters. Or the abundent genius of gunsight designers in the player community.

[bustr]

If our game gunsight visual angle measurment is in "Angular Mil" based on 1-mil=1/6400, the amount of elevation for 400 yard shots with the MK108 is not as great as in my offline test trying to account for the introduced elevation at 150 convergence.

Using the figures from the BF109G5/G6 & Bf109G-6/4U manuals and the formula:

Distance in Meters = (Size\100) divided by Mils * 1000

Target Distance(m) = 400 meters

Revi center to MK108/MG151 barrel center = 74.5cm

MK108 barrel center line above IP@400m = 340cm
MG151 barrel center line above IP@400m = 200cm

MK108 - Size(cm) at 400m is 74.5cm + 340cm = 414.5cm
MG151/20 - 274.5cm

400 = (414.5\100)divided by Mils * 1000
400 = (274.5\100)divided by Mils * 1000

MK108 - Mils = 10.25+-
MG151/20 - Mils = 6.75+-

If the MK108 motorkanon was locked into the motor firing parallel with the engine datum line the aircrafts nose would only have to be lifted to about the first Revi stadia mark below center to hit the target center at 400 meters(437yrds).

Based on the ballistics for the MG151/20 motorkanone at 400 meters the Mils = 6.75+-. The Revi aimpoint for 400m would be just above the first stadia mark below center. Based on the armerors schematics for the 109 series the twin fuslage MG and gondola guns are angled to fire in downward archs to pattern ballistcaly with the primary wheapon the motorkanone. With the twin Rumpf MG thier ballistic IP is with the motorkanon at 400m.

Locking the Yak9T/U engine mounted autocannon and P39 T9 cannon in this manner would result in gunsight Mil elevations in the same neigborhoods based on our Mil based gunsights.

If you need I can repost the links to the german manuals and pictures of the Klimov M105PF with autocannon mounted and P39 T9 mouning again.

[bustr]

Testing offline with a K4 based on a 512x512 pixel bitmap (256 in the .mil file) and 1 mil=2 pixels. ReviC/12b graticule with stadia marks at 13mil/26pixel steps from 256x256 pixels as center.

By using the offline target and auto level while zoomed in, and the ballistics data for any of the Aces High motor mounted cannon firing through the spinner locked to the engine block. You should see a priedictable impact pattern starting at 50yards, 100yards then out in 100 yard steps to 800 yards that never crosses the 0-datum line after leaving the barrel.

From the Bf109G6/4U armerors chart the expected MK108 ballistics pattern below the 0-datum with the MK108 bolted parallel to the DB605 block and airscrew line should be aproximently:

Page 29. http://deutscheluftwaffe.de/archiv/Dokumente/ABC/m/Messerschmitt/Me%20109/Bf%20109%20G-6%20U4%20Wa%20Beiheft%201%20MK%20108.pdf

Distance below DB605 datum Center Line At:
50M - 2 1/3in
100m - 7 1/2in
250m - 47in
400m - 11ft
500m - 18ft

Offline in a K4 fireing only the MK108 motorkanone. Convergence 150yd. Using the Mil elevations on the ReviC/12b graticule to describe impact points below graticule center as the target is set to 50yds, 100yds, 150yds then 100 yard steps to 800 yards.

Distance below ReviC/12b graticule center, convergence zeroed(0.00mil)@150yds:

 50yds - 9.75mil below 0
100yds - 1.62mil below 0
150yds - 0.00-mil
200yds - 1.62mil below 0
300yds - 3.25mil below 0
400yds - 4.87mil below 0
500yds - 9.75mil below 0
600yds - 14.62mil below 0
700yds - 22.75mil below 0
800yds - 32.50mil below 0

I could be wrong but, it looks like the MK108 is tilted up inside of the DB650 engine block. It looks a bit closer the the ballistics for the nose mounted adjustable dual MK108 in the Me110-G2/R3 handbook Pg 18.

http://deutscheluftwaffe.de/archiv/Dokumente/ABC/m/Messerschmitt/Me%20110/Bf%20110%20G-2%20R3%20Schusswaffenanlage%202%20MK%20108.pdf