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Under the Hood: AA ratings for guns

 
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Under the Hood: AA ratings for guns - 6/6/2019 6:26:15 AM   
cathar1244

 

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Among the values assigned to TOAW equipment, I've always found the AA ratings a bit mysterious.

For the guns (for missiles I have no idea what criteria was used), I have found what appears to be the method by which the AA rating was derived.

The AA rating for guns is the cube root of the weight of fire (in kilograms) for the weapon in 30 seconds, rounded down.

(Weight of fire in this case is the total weight of projectiles fired in 30 seconds, rate of fire considered as cyclic.)

This calculation works for weapons with single barrels. For weapons with more than one barrel, add one to the result for each additional barrel ... but add no more than two to the result, no matter how many barrels the weapon has. Thus, in TOAW, a "generic 20mm AA gun" has an AA rating of 3, a twin-barreled 20mm AA gun has an AA rating of 4, and both the triple 20mm and quad-20mm AA gun have an AA rating of 5.

There are items of equipment that do not follow this rule, the 40mm AA gun being a prominent "violator". Not sure why that is the case, perhaps simply they are errors. If anyone knows why the 40mm Bofors should be rated at double that of a 37mm AA gun, please advise. Using the above rule, the 40mm AA gun should have an AA rating of 3, not 6 as it is in the database today.

Cheers



< Message edited by cathar1244 -- 6/6/2019 6:27:13 AM >
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RE: Under the Hood: AA ratings for guns - 6/6/2019 10:19:12 PM   
larryfulkerson

 

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quote:

If anyone knows why the 40mm Bofors should be rated at double that of a 37mm AA gun, please advise.

I'd like to know the answer to that myself. I used to work on the 40mm Bofors AA gun and I know that the slowest part of the gun is the guy that drops the clip of four into the hopper on the top of the gun ( me ) and there were lots of times that the gun got ahead of me and it ran out of bullets and the pilot complained ( again ) on the intercom that the gun stopped and would someone take a look at it. And I would press the button on my mike and tell the flight engineer to tell the pilot to try it now...and he would and of course the gun miraculously worked once more now that I've had time to stuff it with bullets. It looked like I performed my miracle fix of the gun in mear seconds and of course the flight deck crew was suitably impressed. We never told them what was really going on. They didn't have a need to know.

< Message edited by larryfulkerson -- 6/6/2019 10:23:09 PM >


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RE: Under the Hood: AA ratings for guns - 6/6/2019 11:28:40 PM   
rhinobones

 

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Maybe its because the 40mm was one of the first to use a proximity fuse, or maybe because the 40mm had a slightly larger kill radius. Send your question to Norm.

Enjoyed Larry’s live action report, but that was from an air to stationary ground target. Maybe ground to moving air target is a different story. Thanks Larry.

Regards, RhinoBones


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RE: Under the Hood: AA ratings for guns - 6/7/2019 3:58:16 AM   
cathar1244

 

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RhinoBones, I assume other AA guns have used proximity-fuzed ordnance, yet, in the TOAW equipment database, their AA rating fits into the method I describe above. But the Bofors does not.

On edit. Do you have a source for the 40mm Bofors gun (L/60) using proximity-fuzed projectiles? The data I'm seeing for its projectiles show them employing point-detonation fuzes (for the USA in World War II, the fuzes were the M71 and Mk. 27.) Best I can tell, proximity fuzes for 40mm Bofors guns were not produced until the mid-Cold War period, and that was for the L/70 version of the Bofors.

Not 100% certain, but I think the 40mm AA rating in TOAW is just a mistake in the data.

Cheers

< Message edited by cathar1244 -- 6/7/2019 4:58:49 AM >

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RE: Under the Hood: AA ratings for guns - 6/7/2019 4:57:00 AM   
cathar1244

 

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Larry,

Great story! What was your impression of the weapon's reliability (did it jam often and how difficult was it to clear?)

Cheers

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RE: Under the Hood: AA ratings for guns - 6/7/2019 5:03:19 AM   
larryfulkerson

 

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quote:

Great story! What was your impression of the weapon's reliability (did it jam often and how difficult was it to clear?)

I never had a gun have a problem of any kind. Of course we maintained the guns ourselves while we did our real jobs.

I only had to "clear" one gun in all my tour and I asked the flight engineer to ask the pilot for me if I could "clear the gun" pretty please and he did and the pilot said "sure". So I reached down and tugged on the trigger rod which pulled the trigger and the round went off immediately. And almost at the same time the round went off the pilot was on the horn asking what happened and was anybody hurt. I told the flight engineer that "nobody was hurt, I just cleared the gun. We're ready to RTB back here." He didn't say anything else to me for the rest of the flight.

And for those of you that are wondering what happened next: the flight engineer told the pilot that the guys in the back successfully cleared the gun and it's safe again. The pilot said "yeah but where did the round hit. [ We were in the middle of Laos at 02:30 and anything down there was probably a "free fire" target. I suppose it's possible that one of our LRRP teams was down there somewhere but I doubt that it was a near miss. ]

Nobody answered the pilot's question and he decided: "it's probably okay".
And the pilot blew it off but the flight engineer felt used and abused because gunners firing the guns by hand is frowned upon and asking permission would be a waste of time but if it happens nobody ever gets in trouble for some reason. We probably had a MasterSGT Gunner Section Head that was watching our back. What's probably happening is that the Squadron Commander ( full bird colonel ) probably complained to the Gunner's Section Head that "the gunners are shooting the guns again." And the MasterSgt would say something very much like" "I'll take care of it sir." and we would get a 1/2 hour lecture about the rules reguarding the guns. How the gunners aren't supposed to on-purpose cause any of the guns to fire. It's understood that sometimes a gun misfires and that one of the options to fix the problem quickly is to fire the round by hand and it's suggested by the SOP that we do that but only in the case of a mis-fire and I happen to know that we have never had a mis-fire. It's you guys shooting the guns again. Now I don't want to get anybody in trouble so let's make a deal. You guys don't shoot any more guns for the rest of my tour, three months, and then once I'm gone I couldn't give a f_ck what you guys do....


< Message edited by larryfulkerson -- 6/7/2019 5:32:41 AM >


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RE: Under the Hood: AA ratings for guns - 6/7/2019 8:54:58 AM   
cathar1244

 

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Larry, ... sounds like the military. I knew a fellow who had been a pioneer platoon leader in the Korean War. Among the platoon's duties was the detonation of unexploded ordnance. So he got told there was a "mortar shell" on top a nearby rise and that it should be blown up to remove the hazard. When the troops got there, it turned out to be an air force BOMB. Troops shrugged, wired it for detonation, and blew it up. Needless to say, the explosion was impressive, to include raining down large chunks of shrapnel on the cook's tent while the cook was there (he escaped injury). The platoon leader duly got a chewing out, but there was a war on, and life went on.

Cheers

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RE: Under the Hood: AA ratings for guns - 6/8/2019 9:48:16 AM   
cathar1244

 

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The anti-air values in TOAW IV are among the most "ancient" ratings in the equipment database, meaning they are largely unchanged from TOAW I. I was thumbing through the TOAW I manual today and the AA value for the 40mm AA gun caught my eye: 4, not 6 as it is today. It "achieved" the rating of 6 by TOAW II. Curious.

Cheers

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RE: Under the Hood: AA ratings for guns - 6/9/2019 11:10:50 AM   
cathar1244

 

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Noted today another AA gun got "jumped up" from TOAW I to TOAW II. The 90mm AA gun doubled its AA rating, from 3 to 6. An increase for this (generic) system could be supported if one assumes the weapon is the U.S. 90mm M2 AA gun. Even at the lowest quoted rate of fire, 15 rounds per minute, the calc shows the AA rating should be 4 vice the 3 given in TOAW 1. The higher quote of 25 rounds per minute, gives an AA rating of 5. Wikipedia claims the maximum rate of fire for the M2 was 37 rounds per minute ... which, if accurate, means those heavy 90mm rounds were being loaded and fired at a rate better than one every 2 seconds ... hmm. But even that rate calcs to an AA rating of 5 when rounded down.

Cheers

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RE: Under the Hood: AA ratings for guns - 6/9/2019 11:41:12 AM   
cathar1244

 

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Using this calc also indicates why the Vulcan 20mm AA rotary cannon rates as 4 in TOAW.

The (low) cyclic rate of fire for the Vulcan is 1000 rounds per minute. At 30 seconds, that is 500 rounds per minute (real performance differs because of spin-up time).

But the calc works on the basis of single barrels. A Vulcan has six barrels, so the 30 second rate of fire for a single barrel is about 83.33 . Multiply this by 0.101, the weight in kilograms for the 20mm projectile fired by Vulcan. This product equals 8.416. Taking the cube root of that and rounding down equals 2.

Since this is a multi-barrelled weapon with more than two barrels, add 2 for an AA rating of 4 ... as indicated by TOAW since TOAW II.

Cheers

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RE: Under the Hood: AA ratings for guns - 6/9/2019 3:38:48 PM   
josant

 

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A very interesting reading

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RE: Under the Hood: AA ratings for guns - 6/9/2019 7:19:26 PM   
cathar1244

 

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quote:

ORIGINAL: josant

A very interesting reading


I wish I could figure out the SAM AA rating. It appears to have a basis in either warhead or missile weight, but there are apparently adjustments to produce the final rating.

Cheers

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RE: Under the Hood: AA ratings for guns - 6/10/2019 12:52:41 PM   
cathar1244

 

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quote:

ORIGINAL: cathar1244

The anti-air values in TOAW IV are among the most "ancient" ratings in the equipment database, meaning they are largely unchanged from TOAW I. I was thumbing through the TOAW I manual today and the AA value for the 40mm AA gun caught my eye: 4, not 6 as it is today. It "achieved" the rating of 6 by TOAW II. Curious.

Cheers


Worth noting the 40mm AA gun existed in two forms. The first (L/60 barrel) falls into the TOAW I years of 1939-1955 (and beyond); the second (L/70 barrel) dates from the early 1950s and falls into the TOAW II years.

The 40mm L/70, at 240 rounds per minute, can calc'd as a "4" for AA value.
Likewise, the 90mm AA gun can be calc'd as "4" for AA value if one uses the lower rate of fire of 15 rounds per minute.

But in TOAW II, they are both rated as "6". Makes me wonder/suspect the rating boost may reflect the use of radar systems for fire control.

Cheers

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