IMPORTANT: Huge undefended "empty" zone in AA coverage!

[Apollo11]

Hi all,

ORIGINAL: castor troy

The worst thing about all this damn AA thing is that it´s now spoken about at the forum! [:@]. I didn´t know that, as two of my PBEM opponents didn´t know that too. Since it is discussed at the forum those two are bombing every Japanese target at 6000 feet with their bombers. Before that, they came in at 15.000 - 25000 feet too avoid flak (but in fact lost more planes than attacking at 6000). This sucks!!!!!!!!!!![:(]

I am sorry but this simply had to be told...


Leo "Apollo11"

[Speedysteve]

You should ask them NOT to bomb at that altitude. To do so all the time to exploit a 'quirk' is not right IMO. Or at least vary it - 6000 feet now and then. 12,000 feet others, 15,000 feet etc.

[castor troy]

ORIGINAL: Apollo11

Hi all,

ORIGINAL: castor troy

The worst thing about all this damn AA thing is that it´s now spoken about at the forum! [:@]. I didn´t know that, as two of my PBEM opponents didn´t know that too. Since it is discussed at the forum those two are bombing every Japanese target at 6000 feet with their bombers. Before that, they came in at 15.000 - 25000 feet too avoid flak (but in fact lost more planes than attacking at 6000). This sucks!!!!!!!!!!![:(]

I am sorry but this simply had to be told...


Leo "Apollo11"

yes Apollo, it has to be told! But every time people know a new exploit they may use it. And you can´t have a house rule for everything in that game

[SurrenderMonkey]

I feel the pain of all other Japanese players re:AA, whether the in-game effect is correct or not.

My buddy and I have been playing one day turns, one per day, since last September, and our game has evolved into a wonderful struggle over New Caledonia in Julyof 1942. He holds Noumea in the south, and I hold Koumac in the north, and we have been viciously fighting over it for a good three months. He only has one carrier, but he has plenty of 4E bombers, so it's LBA vs LBA. I keep rotating Zero and Oscar squadrons through Koumac as I strive to build up the base, while he flies a hundred heavy bombers at a time in raids. It's been epic. I went to the trouble of shipping both heavy and light AA units from all over the Pacific into Koumac in an effort to deter him, but it's been in vain. I have a whole infantry division and two tank regiments dug in, but they get mercilessly hammered 2 out of every 3 days. My AA is almost completely ineffective. From what I can ascertain from historical accounts, this reflects history well.

IMHO.

[Apollo11]

Hi all,

I just had an idea!!!

Using simple high-school mathematics/physics we can ourselves calculate the MIN altitude ceiling of AA gun!

What we need is:

- shell exit velocity (i.e. speed shell has when exiting barrel of AA gun)
- shell weight
- MIN timing of shell fuse


Does anyone knows if such data is available in books (we as community have huge amount of books!) or Internet?

If data for Japanese AA weapons is unavailable is there any similar data for British/German/USA AA guns of similar caliber (75mm, 88mm, 90mm, 105mm)?


Leo "Apollo11"

[rtrapasso]

- MIN timing of shell fuse

I am sure some wag will say MIN timing = 0. Not that i would ever say it, but i am sure someone would...[:D]

Of course, this MIN timing might have some adverse effects on the AA gun crews!!

[Apollo11]

Hi all,

ORIGINAL: rtrapasso

- MIN timing of shell fuse

I am sure some wag will say MIN timing = 0. Not that i would ever say it, but i am sure someone would...[:D]

Of course, this MIN timing might have some adverse effects on the AA gun crews!!

[8D]

BTW, I think I remember that I once read that famous German FLAK 88mm had MIN time fusing 2 or 3 seconds for anti-aircraft shell but I am not 100% sure of that and I can't find where I read it right now (the exit velocity of that gun was around 900 m/s)...


Leo "Apollo11"

[tabpub]

ORIGINAL: Apollo11

Hi all,

ORIGINAL: rtrapasso

- MIN timing of shell fuse

I am sure some wag will say MIN timing = 0. Not that i would ever say it, but i am sure someone would...[:D]

Of course, this MIN timing might have some adverse effects on the AA gun crews!!

[8D]

BTW, I think I remember that I once read that famous German FLAK 88mm had MIN time fusing 2 or 3 seconds for anti-aircraft shell but I am not 100% sure of that and I can't find where I read it right now (the exit velocity of that gun was around 900 m/s)...


Leo "Apollo11"

3 second fusing would be right about where the current system has it at; 2 seconds still has the min height at 5500 feet or so based on these numbers.

[jwilkerson]

I'm still hunting for minimum fusing as well !!!

Looking for anything remotely in the ball park including US M.T. M43A5 fuse which was used on 3in, 90mm and 105mm AA rounds ... the max fuse setting was 30 seconds but no minimum yet ... I found a web site with old US government military pubs .. and they had manuals on some fuzes .. but alas .. not the M43A5 [&:] so ... still lookin'

[Apollo11]

Hi all,

ORIGINAL: tabpub

3 second fusing would be right about where the current system has it at; 2 seconds still has the min height at 5500 feet or so based on these numbers.

Not exactly... speed loss due to gravity pull and air friction would slow shell down from initial high speed...


Leo "Apollo11"

[rtrapasso]

Not exactly... speed loss due to gravity pull and air friction would slow shell down from initial high speed...

He may have factored that in already. 900 m/sec x 2 = 1.8 km = 1.125 miles = 5940 feet, so he knocked some off for these factors. Friction is going to be the big factor, since gravity only knocks off 9.8 meters/sec.

EDIT - for grins, i calculated the altitude of the 88 based on 900 m/sec fired straight up with NO friction. You theoretically could shoot straight up at 900 m/sec, with the velocity decreasing at 9.8 m/sec, which means that the shell would come to a halt after 91.8367+ seconds. Plugging this into s = 1/2 a t^2, solving for s, gives an altitude of 41323+ meters (41.323 km, or 25.8+ miles)!!

[ChezDaJez]

You may have already seen this sight but it does have some interesting development information. Nothing about minimum fuzing though.

http://www.smecc.org/radio_proximity_fuzes.htm

Chez

[jwilkerson]

ORIGINAL: ChezDaJez

You may have already seen this sight but it does have some interesting development information. Nothing about minimum fuzing though.

http://www.smecc.org/radio_proximity_fuzes.htm

Chez

Thanks hadn't seen this one - but I certainly have found gragantuan amounts of "interesting information" ( about flak and fuses ) ... but just like my quest for data regarding WWII TDC multi-targeting capability - no where I have looked answers the question exactly - too tactical - but then - hey tactics rule ! Unfortunately not sure historians know that !!!

Oh and btw this one is pretty much strictly about proximity fuze whereas we are looking for data on earlier "mechanical timed fuses" ... which were made obsolete by VT but not to be had by Germans ( nor my guess by Japanese ) in WWII ... fuse settings is not an issue once you get VT ( proximity ) fuses ... only on the M.T. types ...

[spence]

Actually I found a site discussing setting VT fuze time less than minumum time for field artillery firing indirectly over friendlies.
For AAA VT fuzes a small propeller on the rear (I think) of the shell would turn once the shell reached approx 100 mph (strange figure to find in a site concerned with ballistics) which armed the fuze after some number of turns/interval of time (which have been elusive exact figures). There was apparently a minimum effective distance.
The VT fuze allowed the heavy flak to engage rapidly closing a/c. As an example, the US dive bombers at Midway came approached the KB at 16000 ft. Once they tipped over into their dives (which was just about the time they were sighted) all the heavy flak in the KB was firing mostly to feel good because the fuze setters in the mounts couldn't change the settings fast enough to account for the constantly decreasing range. The planes were in a dive for say 45 secs figuring roughly 200 kt dive speed. That amount of time would have allowed a 5"/38 with a decent gun crew to crank out 12-15 VT rounds that automatically exploded at whatever range the target was at. A quantum jump in the amount of lead between the would be bombers and their targets.

[jwilkerson]

No question that proximity fuses were quantum leap ... and there is a whole lot more data about them out there than for the older M.T. fuses ... thing is we would like to have data on M.T. fuses to really nail our issue ... your speculation ( which is certainly plausible ) is that VT minimum might be the same as M.T. minimum or at least close ... but I'm still gonna keep looking for direct data on M.T. since I know germans only had M.T. during the war ... they never got VT .. and I presume that Japanese also never got VT though I don't have definitive data on that ( yet ) either.

BTW at least some M.T fuses may have worked on a different principle than the propeller system you describe.

The US M.T. M43A5 fuse which was used on the US Army AA rounds for 3in, 90mm and 105mm had an activation system described as:

"The mechanical time fuze, M43A5 used in this shell is driven by a pair of weights which are acted upon by the centrifugal force set up by the rotation of the shell in flight. The time ring is graduated for 30 seconds maximum setting" source: US Army Catalog of Standard Ordnance, 1944 as reproduced in Greenhill Books Edition, 2001 introduction by Ian V. Hogg

Further in this same reference, there is mention of an advanced mount ( M2 ) for the 90mm AA gun which also had an automated rammer-fuze setter ... described as follows:

"The purpose of the combination fuze setter rammer, which is operated automatically and is controlled by a director through remote control, is to shorten and hold constant the time interval between setting a time fuze and firing the round ... "

Note that even in the Army I was in ( late 70s ) .. field artillery fire procedure had FDC ( Fire Direction Center ) send deflection, elevation and round, charge and fuze setting over radio telephone ... which then had to be repeated by radio telephone operator and then executed by gun crew ... all this taking best case a number of seconds 10-20 depending on the order ... an early WWII AA system could not have been much different and AA directors in most services did control mutliple guns which were too far apart to hear orders from a single person ... hence this automated rammer-fuze setter would have been a big step forward ( Germans had something similar on their 105mm flak weapon ). The "gap" between the director determining the fuse setting and the elevation and the deflection for each gun ... and the rounds being fired ... might have been as short as 5 seconds depending on how the data was relayed and which functions could be performed in parallel ... but this gap could not have been zero ... and whatever it was .. it would have to be factored into the director data as the target would be in a different place after these seconds had passed by ... so the problem was not only estimating where the target would be during the flight time of the round .. but also during the time between when the direcctor data was calculated and when the round was fired.

The auto-mated rammer fuse setter briefly made this problem simpler by reducing the time ( and hence the error ) and making the time more consistent ) not done by humans ... of course the VT fuze put all the arcarne stuff out of business .. and after the war ... everyone converted over to VT .. and that is where we are today ( for the most part ! )

But despite all this interesting stuff ... I still don't have direct data on minimum effective range of heavy AA and that is really the question I'm trying to address ...

[jwilkerson]

Ok - I foudn some useful data on fuses ... the German 88 used a series of fuses called Zeitzunder ... which are abbreviated

Zi Z S/30 ( with about 20 variations like Zt Z S/30 K ... or Zt Z S/30 Z ... etc. )

The short version is that the maximum fuze settings are 30 seconds ( is that what the 30 means ? ) whereas the minimum settings vary from version to version ... from 1 second to 2 seconds ... hence going back to Apollo11's blrub above where he says 88 minimum fusing was 2-3 seconds .. well he was pretty close ... this data pegs it at 1-2 seconds depending on exactly which flavor of fuse was in use by that battery on the day in question ! All of these fuses were centrifugal weight driven.

Oh and this fuse data is on pages 278-279 of Hogg, Ian V. "German Artillery of World War II", Greenhill Books, London, 1997

Now this being said - does this enable us to "calculate" the exact minimum effective altitude of ( at least 88mm ) heavy flak ?

Well maybe.

The more I've thought about this, the more I think it might be more complex than we think. The minimum fuse setting does certainly put a lower bound on things. However, the process of calculating the director data ( gun deflection, elevation, fuze setting ) and transmitting this data to the gun and having the gun crew execute ( which includes traversing the weapon to the ordered deflection and elevation, setting the fuse, loading the round ) and fire the round and the round fly to the spot where the fuse sets it off ... all this takes X seconds ... in the mean time the target aircraft .. moved to position "P" ... the problem for the director was to estimate where position "P" would be at the time the projectile got there .. based on how long all that other stuff was expected to take to happen.

Because for the most part ( in most services ) this process was not completely automated ( i.e. humans were involved in executing some of the process ) .. the longer it took ... the more likely errors were introduced .. and the more likely the target plane would not be exactly at the position predicted ( and hence the greater likelihood a miss would result ! )

Hence due to the greater apparent different in deflection and elevation for low flying targets ( they - on average - move farther across the "aiming canvass" than targets at 20,000 feet in the same number of seconds ) the minimum effective range may be as much as matter of doctrine specifying at what altitudes we will fire under what conditions. In conjunction with of course the hard parameters like minimum fuse setting.

Thus my "hypothesis" is that even above the minimum fuze setting altitude .. that heavy AA battery's would have had a lower frequency of hits until the altitude was high enough to reduce the "tracking problem" to one which could be dealt with by the predicting technology.

So I've now shifted my search into "doctrine - and I do have a new source on that ... book by Westermann "FLAK - German Anti-Aircraft Defenses, 1914-1945, University Press of Kansas, 2001" ... so I'll take a look at that and speak up if it helps. Oh and "doctrine" will also address the willingness and pros and cons of firing "barage" fire ( or unaimed fire ) as this certainly could be done - but has the downside of expended large quantities of ammunition. So under what conditions was this used and to what effect ?

[Apollo11]

Hi all,

ORIGINAL: jwilkerson

Ok - I foudn some useful data on fuses ... the German 88 used a series of fuses called Zeitzunder ... which are abbreviated

Zi Z S/30 ( with about 20 variations like Zt Z S/30 K ... or Zt Z S/30 Z ... etc. )

The short version is that the maximum fuze settings are 30 seconds ( is that what the 30 means ? ) whereas the minimum settings vary from version to version ... from 1 second to 2 seconds ... hence going back to Apollo11's blrub above where he says 88 minimum fusing was 2-3 seconds .. well he was pretty close ... this data pegs it at 1-2 seconds depending on exactly which flavor of fuse was in use by that battery on the day in question ! All of these fuses were centrifugal weight driven.

Oh and this fuse data is on pages 278-279 of Hogg, Ian V. "German Artillery of World War II", Greenhill Books, London, 1997

Now this being said - does this enable us to "calculate" the exact minimum effective altitude of ( at least 88mm ) heavy flak ?

Well maybe.

The more I've thought about this, the more I think it might be more complex than we think. The minimum fuse setting does certainly put a lower bound on things. However, the process of calculating the director data ( gun deflection, elevation, fuze setting ) and transmitting this data to the gun and having the gun crew execute ( which includes traversing the weapon to the ordered deflection and elevation, setting the fuse, loading the round ) and fire the round and the round fly to the spot where the fuse sets it off ... all this takes X seconds ... in the mean time the target aircraft .. moved to position "P" ... the problem for the director was to estimate where position "P" would be at the time the projectile got there .. based on how long all that other stuff was expected to take to happen.

Because for the most part ( in most services ) this process was not completely automated ( i.e. humans were involved in executing some of the process ) .. the longer it took ... the more likely errors were introduced .. and the more likely the target plane would not be exactly at the position predicted ( and hence the greater likelihood a miss would result ! )

Hence due to the greater apparent different in deflection and elevation for low flying targets ( they - on average - move farther across the "aiming canvass" than targets at 20,000 feet in the same number of seconds ) the minimum effective range may be as much as matter of doctrine specifying at what altitudes we will fire under what conditions. In conjunction with of course the hard parameters like minimum fuse setting.

Thus my "hypothesis" is that even above the minimum fuze setting altitude .. that heavy AA battery's would have had a lower frequency of hits until the altitude was high enough to reduce the "tracking problem" to one which could be dealt with by the predicting technology.

So I've now shifted my search into "doctrine - and I do have a new source on that ... book by Westermann "FLAK - German Anti-Aircraft Defenses, 1914-1945, University Press of Kansas, 2001" ... so I'll take a look at that and speak up if it helps. Oh and "doctrine" will also address the willingness and pros and cons of firing "barage" fire ( or unaimed fire ) as this certainly could be done - but has the downside of expended large quantities of ammunition. So under what conditions was this used and to what effect ?

Nice find - thanks!

BTW, please note that only few heavy AA batteries (German that is) were trained and equipped to track and shoot individual (or groups) targets. Those were usually "Wurzburg" radar coupled batteries.

Other batteries used good old reliable system of placing as many shells as fast as possible in selected space of sky whilst incoming enemy bombers would just fly into this "barrage" or "curtain"...

So tracking was not an issue for most units!

BTW, I think Japanese had to rely on this technique only.


Leo "Apollo11"

[Apollo11]

Hi all,

ORIGINAL: rtrapasso

EDIT - for grins, i calculated the altitude of the 88 based on 900 m/sec fired straight up with NO friction. You theoretically could shoot straight up at 900 m/sec, with the velocity decreasing at 9.8 m/sec, which means that the shell would come to a halt after 91.8367+ seconds. Plugging this into s = 1/2 a t^2, solving for s, gives an altitude of 41323+ meters (41.323 km, or 25.8+ miles)!!

[:D]

BTW, the actual MAX altitude was around 10000m (10km)

Mass of shell (also known factor) is needed in much more complex calculation when air resistance is used...


Here is data I found for German naval 88mm FLAK (thanks to "Tiornu"):

shell weight 9 kg
muzzle velocity 790 meters per second (lower than 900 we assumed)


Leo "Apollo11"

[Apollo11]

Hi all,

Here is interesting link with applet that can calculate "projectile rajectory":

http://www.phy.davidson.edu/StuHome/joc ... ntrol.html


Leo "Apollo11"

[Apollo11]

Hi all,

Another very very interesting applet to calculate projectile trajectory and all other aspects (it even includes air drag and shell weight!):

http://galileo.phys.virginia.edu/classe ... pplet.html


Unfortunately the graph is small... darn... [:(]


Leo "Apollo11"