Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: bustr on June 06, 2014, 08:19:15 PM
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I was reading about the 506th FG at Iwo Jima. Eventually the historian got to the subject of gunsights and the P-51D.
I can never resolve if the K14 gyroscopic lead compensation series was very common in the late P-51D PTO or, a very, very, late introduction. It seems P-51D were more likely to have the N-9 fixed ring optical gunsight mounted in the PTO. In research of other P-51D groups in the PTO, switching from the 101Mil fixed ring N-9 to the K14 had serious ACM gunnery problems. K14 were not very reliable early on in the PTO due to humidity issues resulting in the pilots having to use the 70Mil fixed ring backup sight. The smaller ring diameter caused pilots to miss on deflections shots.
From late 1944 all K14 production went to the ETO for P-51D. P47's didn't start receiving K14 until 1945 replacing the Mk8 or British MKII fitted in staging stations in England. It was SOP for AAF fighters upon reaching England for their N-3 gunsights with 70Mil rings to be replaced with British MKII with 100Mil rings in the staging stations. You couldn't easily calculate lead against fast 109 and 190 using a 70Mil ring.
A plane 1000ft in front of you at 100mph, moving 90 degrees to your line of travel. While viewed through a 100Mil ring, travels 50Mil in 1\3 of a second. A 50cal or 20mm Hisso round travels 1000ft in 1\3 of a second. Add 50Mil for every additional 100mph in your lead or deflection allowence. Or why the Allies called 100Mil and 101Mil rings 100mph rings. The 70Mil N-3 ring was a 65mph ring.
Interesting excerpt about gunsights and a fight against Ki-84. Gunnery before the K14 was a product of the pilot's skill just like in our game today.
http://506thfightergroup.org/mustangsofiwo.asp
In July, the last full month before the Japanese agreed to unconditional surrender, the Iwo Jima fighter groups received some P-51D-25s as replacement aircraft. Many of these had the lead-computing K-14 gyro gunsight in place of the old N-9 which required a good deal of skill and "Kentucky Windage" in making deflection shots. The K-14 required a smooth touch on the controls to be truly effective, but was deadly accurate in nearly any tactical situation. It could only be defeated if the target aircraft rapidly reversed its turn in a curving combat, momentarily tumbling the gyros when the P-51 attempted to follow.
One 21st group pilot familiar with the K-14 was shot down and captured by the Japanese. Under standing authority from intelligence officers, captured airmen were allowed to divulge almost any information which would ease their situation, and the 21st pilot explained about the K-14.
The Japanese took this information as a lesson learned, but the tale has an ironic and—to the Mustang pilots—a humorous end. In one of the last large dogfights the Mustangs fought over Japan, at least eight Franks were shot down because their pilots assumed all P-51s now had the K-14 when actually only a relatively few replacement aircraft had the lead-computing sight. When the Franks reversed their turns to topple the K-14 gyros they presented their pursuers with a brief no-deflection shot for which the N-9 was ideally suited! Had the Franks kept turning in their original direction they would have stood a good chance of outmaneuvering the 51s.
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Dude likes gunsights.
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I'll worry about your obsession with me when you start showing a hit% of 50 every month wearing a blindfold. Other wise, even if you don't put anything in that tiny clear window in the game. Your brain still uses fixed visual reference points to calculate lead in a repeatable predictable manner. If gunsights were not as important as your life in fighters, they would never have been included in the cockpit, or constantly improved upon during all of the history of aerial combat.
During the war it became painfully and costly evident that most pilots couldn't hit anything using a gunsight inside of a fighter's cockpit. So gyroscopic lead compensating gunsights were created to augment that weakness in the majority of pilots. Even in our kiddy game, the physics is reproduced to a level of fidelity that our players experience similar issues in the same population proportions as pilots in the real war.
So Floob, sorry, I'm not interested in your personal overtures towards me. That's a kind of creepy obsession on your part and I'm married.
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This stuff is always interesting Bustr. Keep posting.
In our game people have the opportunity for more and better shooting practice (shooting in actual dogfights) than anyone had in real life, thus most people eventually become adequate with the fixed sight. I think a lot of people who read your stuff aren't factoring this in and thus don't realize why this information was important in the real world.
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I always find your post interesting as well. I try to use your information to use the historically correct gun-sight in each AH plane I use.
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Bustr, have you made 100mph gun sights for anything besides the. 50/hispano? If not, could you please do so?
Particularly, gunsights for the mg151, mk108, and Ho 5 would be appreciated.
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In the gunsight.mil file you can change the size control number. If you have my latest pack, each mil file has info in it with suggested numbers. This will work for the slower 20mm initialy but, the sweet spot is really leading with the windscreen uprights as the con starts passing into the uprights. The MK108 considerably farther out. Trigger pressing time translates into travel distance for your con.
In the spits with 20mm, I shoot as the con touches the outside of the uprights getting nose to tail hits. Between 50yd to 300yd, you can hold essentially the same spot with the same results on a con "traveling across" your front quarters. I had to read that section of the 1944 AAF Fixed Gunnery training manual a few times to believe it enough to try it in game. Hitech's physics is very realistic. If you are in a "chasing mode pulling to a con" and he is traveling across your front quarter, your G load will make all of this inapplicable. And discussions about the differences defining these two modes confuse the heck out of many players. And why "Bag the Hun" and "Horrido" are deceptive unless you have already gone through basic fixed gunnery training as a fighter pilot. Both assume your attacks are blind siding the enemy fighters and that you are closing in on some curve of pursuit that won't cause you to exceed 2G in your banking turn. The emphasis in "Bag the Hun" on a 30 degree angle off to your line of travel as the maximum angle you shoot from.
See, it just got confusing..........
Here are screen shots with the 100mph calculated lead for 300mph.
MK108
(http://i1231.photobucket.com/albums/ee508/KDavis6030/Mk108SwSp.jpg)
MG151/20
(http://i1231.photobucket.com/albums/ee508/KDavis6030/MG151SwSp.jpg)
AN\M2 and Hisso 20mm. Red lines are the MG151/20 and MK108 for comparison.
(http://i1231.photobucket.com/albums/ee508/KDavis6030/SpitSwSp.jpg)
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Why not paint marks on the props? Or did they actually do such a thing? Would be useful in lead computation.
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I've never heard of that being done. The lead or deflection sweet spot was a "Kentucky Windage" skill. Most pilots did well replicating gunnery school. Thankfully most fighter vs fighter combat was not much different when it came time to shoot.
The Russians placed a 200m centering mark on the back of some props for the pilot to center the gunsight before missions. I've been informed at least one fighter group centered for 400m. With the ShVAK 20mm, the drop at 200 and 400 was very close. The AAF standardized a ww2 field technique by 10\45 of placing a gunsight zeroing mark and a camera zeroing mark on the inside of a prop blade for the P51D\K. For the most part each air force had pretty standardized harmonizing procedures since only a very tiny number of pilots could consistently hit anything. Standardization of procedures and protocols is the secret to helping average people become slightly more visa training.
All of our popular WW2 historical information for pilots is for the handful who were the exception to the rules. And as Freud observed, men dream of themselves as supermen, not as ordinary men. Good thing our game has unlimited lives, aint it.......