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Post by edrotondaro on Jun 10, 2016 18:09:20 GMT -6
Hi:
I've been reading a bit about various WWII fighters and I wonder if the use of nose mounted weapons compromised the design to a degree. I will break this topic down into a few sections:
1. Did the use of nose mounted guns limit the size of the engine that could be mounted? Considering how designers were trying to coax every ounce of performance out of their engines, the use of nose mounted guns could affect the engine chosen for the aircraft. I was particularly impressed with how the Corsair's air frame was closely sculpted to follow the lines of the massive Pratt and Whitney R-2800-8 engine which itself was tweaked to go from 2000hp up to 2380hp with water methanol injection. The same can be said of the Nakajima Ki-84 Hayate better known to the US as "Frank". It too had fine lines to maximize its already excellent maneuverability.
2. Did mounting guns in the nose limit the amount of ammo that could be carried? There isn't exactly a lot of room in the nose of a small fighter. I was curious based on what I have been reading about the Ki-84 which featured 12.7mm MGs and stored the ammo beneath the guns in the fuselage (it managed 350 rounds per gun which is about what the US managed for the outer wing guns on its six gun fighters.
3. Did firing through the propeller arc using synchronization cause a lower rate of fire compared to wing mounted guns? Obviously cannon firing through the propeller hub didn't face this challenge.
4. The use of nose mounted armament obviously made for easier shooting since you merely pointed the nose at the target and fired. Wing mounted armament had to be set up for a convergence point out from the fighter. Could this cause accuracy problems at point blank ranges?
5. Many wing mounted guns experienced failures and jams due to the stress of g forces at speed during tight turns. Also certain cannons needed to be pre-cocked by the ground crew because of g forces in combat. Late model Spitfires suffered from this.
Now obviously there are many fine fighter designs that featured nose mounted guns and in some models, this was the only place the weapons were mounted. What did pilots think of this? Hopefully this will start an interesting thread.
Respectfully, Ed Rotondaro
P.S. Who guessed that I just finished Osprey Duel #73, Corsair vs Frank?
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Post by oldpop2000 on Jun 11, 2016 8:04:13 GMT -6
Hi Ed: It's an interesting question. In most cases, the nose mounted guns did not appreciably reduce the size of an engine. If you wanted to increase the power and torque on an engine then you would increase the bore and stroke plus possibly adding another stage to the turbo or super charger. On the Zero, the Sakai engine did add another stage making the engine longer and heavier but did not change the diameter of the motor very much. For the in-line engines, you didn't add more cylinders you again, increase the bore and stroke to gain the power, which meant increasing the size of the water jacket to provide more cooling plus add possibly more super charging or turbo charging. It is a design issue and you would have to examine the room in front, check the available engine sizes and fit the proper engine or design it as a replacement. The gun breeches would be sitting on the engine mounts with a radial engine, on an inline the engines were smaller so you had room to mount the guns on gun cradles on top of the engine. As to ammunition, the larger the caliber obviously the less rounds that could be carried due to weight transfer forward by the heavier gun and ammunition. However, no matter where you put the guns, you were limited in ammunition capacity. It was better to add more guns, with a selector switch to fire only a certain number of guns at a time. So, yes, engine mounts would limit the number of rounds that you could carry as did the caliber. Yes, when you fire through the arc of the propeller, you would lower the rate of fire compared to a wing gun mounted outside the propeller arc. The harmonization of wing guns was usually pilot specific. You would standardize on a range of 800 yards, however many pilots preferred a much closer range. The plan was to set two guns to converge dead ahead, two a little farther out and the rest the max. You then created a kill zone from about 400 yards to say about 800 to 1200 yards. The P-47 had two convergence settings; 250 yards for one set of four and 350 yards for the other set. If you were planning a ground attack, you would increase the range considerably. It really depended on how good a shot you were and your experience. You would have to change your pipper setting to match the harmonization settings. en.wikipedia.org/wiki/Gun_harmonisationAll guns experience failures and jams, it didn’t matter where you mounted them. On the engines the vibration was not good for the engine or the guns, on the wings it caused mounting and aerodynamic problems. Aircraft, like ships, are a compromise of design issues.
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Post by edrotondaro on Jun 11, 2016 8:57:43 GMT -6
Hi Dennis:
Thanks for the link and the info on bore and stroke. I remember some of the older guys in high school back in the early '70s who were muscle car dudes talk about that. I did read that the FW-190's in board wing mounted cannons had a lower rate of fire compared to the out guns outside the propeller arc.
It was interesting to read the comments about the Corsair pilots regarding the Frank. It rarely burned or exploded like earlier Japanese aircraft. Indeed most of the surviving JAAF and IJNAF aces ended the war flying Franks and Georges which at least gave them a chance to bail out, something you generally could not do in a Zero. The book also mentioned that the 20mm Ho-5 cannon that armed the Frank was among the best of its type. One wonders what the air war would have been like if the Japanese had more reliable radial engines?
Ed Rotondaro
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Post by Deleted on Jun 11, 2016 9:53:19 GMT -6
interesting but prolly often mentioned topic, come to think of it all ww2 single engine fighters' armament solutions could be seen as compromise... the wing mounts suffer convergence and deformation problems, nose mounts suffer from limited space and synchronization, while a combination of the two have issues from both --> problem is not completely solved until jets.
particular subject to me is the armament on the bf109 emil series and prolly the same on the Zero. The wing MGFF cannons and its japan derivative are fairly light weight but has mediocre Rof and range, so you need machine guns to fill in which is nose mounted. the ballistics and position of the 2 are hugely different to harmonize or shoot with as if it's a pair of accurate pea shooters plus 2 unweldly hammers. The all nose mounts of the 109F series is a lot better. But they then mounted the 30mm MK108 with pathetic muzzle velocity on some G and K when the luftwaffe shifted to bomber defense which makes it less ideal for small nimble fighter targets.
Otoh the UK/US(AF) seem to tend to under-gun their fighters, the 8 .303 MGs have insufficient hitting power against the medium bombers of the Luftwaffe in BoB, the six .50cal M3s even though already nose mounted, and having almost double the Rof of the ww2 M2, with a radar ranging gunsight to boot, lacked hitting power against the Mig-15s in mig alley. -- Even today the standard cannon caliber is 20mm while most others are on 30mmm or higher!! -- I think i read also in a Osprey book that a Sabre lead and his wingman shot out both of their entire ammo loads at a single Mig, and it was still flying... They then had to 'fake' attack the mig and tricked it into an aggressive maneuver which broke off the damaged wing. The USN at the time had no swept wing fighters, but their quad 20mm mount was miles better. The mig-15 had armament probs of itself namely insufficient fire volume and ammo load as it's more suited for bomber defense. Its Lavochkin rival La-15 had a better fighter armament of 3x23mm.
PS and so it could also be a design doctrine or culture thing between US/UK and GE/JP/RU, if the intention is using 6/8 MGs of same caliber surely it's best to group them together on wings to simplify firing and maintenance. If intention is using cannons and sum total of guns is not that many, some nose mounts is preferred. the butcher bird 190 is a bit different but initial designs were 2 nose MGs, 2 inner MG151/20 and 2 outer MG/FF but the outer cannons are optional and quite often removed, until later variants (A6/7?) it was standardized to be 4 x 151/20, personally i always think ww2 germany weapons are on side of over engineering, it is much easier if they just went with 4x20mm of the same type, delete the nose machine guns and be done with it..
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Post by oldpop2000 on Jun 11, 2016 10:26:06 GMT -6
Hi Ed: No problem, I will do more research today on this subject.... I love this. Granddaughter is with us on the weekends, so I have more time.
One of the reasons many of the Japanese planes burned so easily or had wings blow off was simple. As you should know, a wing consists of the main spar running down the center of the wing. Spars are usually tapered I beams. There were two smaller spars; the front and rear. These were the three support structures attached to the fuselage. Running from the front spar to the rear were ribs, more supporting structures. On the Zero and many other Japanese aircraft there was a false spar for aileron and flap attachments. Between the front spar and main spar, inboard against the wing/fuselage tie down point was located a fuel tank. They were not self-sealing and they were seated up against the number one and two ribs, main and front spar. By seating where they did, they gained extra fuel capacity but left themselves open for some damage issues. I will explain.
Here is a scenario; you are being fired at by an enemy aircraft using one of three incendiary bullets. In other words every third or fourth bullet is an incendiary. If one pierces the fuel tank from the rear, a hydrostatic pressure wave will emanate from the point of entry. This pressure wave can push fuel up against the sides of the tanks, snapping them violently. When that occurs, they will snap the spars and ribs because of their proximity to the support structures, also igniting the fuel tanks. Now, you will see a flame start from the back of the wing inboard, the forward velocity of the aircraft will begin to tear the wing off, like tearing a piece of paper down the middle. Find some gun camera videos online, and you will see this occur on Zero's, Aichi dive bombers, Kate torpedo bombers and their Betty's and Nell's. US, German and British aircraft had expansion room between the outside tank walls and the wing supports. The rarely had wings blown off unless a large cannon shell hit the spar connections to the fuselage. Our tanks were self-sealing at least beginning in 1942. At Pearl Harbor, not all our Naval aircraft had those self sealing tanks.
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Post by oldpop2000 on Jun 11, 2016 10:35:22 GMT -6
interesting but prolly often mentioned topic, come to think of it all ww2 single engine fighters' armament solutions could be seen as compromise... the wing mounts suffer convergence and deformation problems, nose mounts suffer from limited space and synchronization, while a combination of the two have issues from both --> problem is not completely solved until jets. particular subject to me is the armament on the bf109 emil series and prolly the same on the Zero. The wing MGFF cannons and its japan derivative are fairly light weight but has mediocre Rof and range, so you need machine guns to fill in which is nose mounted. the ballistics and position of the 2 are hugely different to harmonize or shoot with as if it's a pair of accurate pea shooters plus 2 unweldly hammers. The all nose mounts of the 109F series is a lot better. But they then mounted the 30mm MK108 with pathetic muzzle velocity on some G and K when the luftwaffe shifted to bomber defense which makes it less ideal for small nimble fighter targets. Otoh the UK/US(AF) seem to tend to under-gun their fighters, the 8 .303 MGs have insufficient hitting power against the medium bombers of the Luftwaffe in BoB, the six .50cal M3s even though already nose mounted, and having almost double the Rof of the ww2 M2, with a radar ranging gunsight to boot, lacked hitting power against the Mig-15s in mig alley. -- Even today the standard cannon caliber is 20mm while most others are on 30mmm or higher!! -- I think i read also in a Osprey book that a Sabre lead and his wingman shot out both of their entire ammo loads at a single Mig, and it was still flying... They then had to 'fake' attack the mig and tricked it into an aggressive maneuver which broke off the damaged wing. The USN at the time had no swept wing fighters, but their quad 20mm mount was miles better. The mig-15 had armament probs of itself namely insufficient fire volume and ammo load as it's more suited for bomber defense. Its Lavochkin rival La-15 had a better fighter armament of 3x23mm. The Zero's cannons were French designs with a low muzzle velocity and only about 60 rnds per gun. Generally, you started shooting with the 7.7 caliber guns to get the range, then fired a simple, short burst with the 20mm. The type 32 and 52 Zero's improved the 20 mm and increased the caliber on the engine mounted guns. The Sabre's six 12.7's were always a bone of contention as they were hold over's from WWII. Eventually 20 mm were introduced but far too late for Korea. By the end of Korea, work had progressed on the sidewinder missiles so the thought was that a gun wasn't necessary. The F-8 was a borderline aircraft in that era. It had 20 mm cannons on the fuselage but also sidewinders. The MIG's were armored as we found out when a pilot defected with one.
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Post by Deleted on Jun 11, 2016 11:20:26 GMT -6
actually i've never found out if the mig-15 had self sealing or even armored fuel tanks or not, there are generic sources that state one or the other, which is confusing to say least. i got a copy of the mig-15 flight manual but it is ofc in Cyrillic. doesn't help that the mig has 2 fuel tanks so it could well be one is self sealed while the other not. i only know definitively that the cockpit is armored with 10mm steel/64mm glass. be that as it may personally i attribute jet's better resistance to gunfire in 3 areas, one is volume as jets are basically larger than ww2 prop planes so more structures to destroy before catastrophic failures, two is sturdiness as jets are built for higher air speeds and at least all metal, three that jet fuel is more resistant to fire compared to piston avgas - in this specific case worsened by the .50cal API ammo having trouble igniting its magnesium warhead at oxygen deprived high altitude. the disagreements on the net could be are 6 .50cals better than 3 large caliber cannons or the other way around, while imho neither is satisfactory and were later improved as jets themselves matured. Armament on the zero... iirc both the MG/FF and the type 99 are descendants of an Oerlikon gun so the properties are similar. I could be mistaken tho. edit: en.wikipedia.org/wiki/Oerlikon_FFen.wikipedia.org/wiki/Type_99_cannonen.wikipedia.org/wiki/MG_FF_cannonalso i think the zero mostly stayed with the same nose MGs, while the 109 nose guns went from 7.7mm MG17 to 13mm MG131 but it's always a cluster #### with 109/190 sub-variants.
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Post by Deleted on Jun 11, 2016 12:08:22 GMT -6
If one pierces the fuel tank from the rear, a hydrostatic pressure wave will emanate from the point of entry. This pressure wave can push fuel up against the sides of the tanks, snapping them violently. When that occurs, they will snap the spars and ribs because of their proximity to the support structures, also igniting the fuel tanks. Now, you will see a flame start from the back of the wing inboard, the forward velocity of the aircraft will begin to tear the wing off, like tearing a piece of paper down the middle. Find some gun camera videos online, and you will see this occur on Zero's, Aichi dive bombers, Kate torpedo bombers and their Betty's and Nell's. US, German and British aircraft had expansion room between the outside tank walls and the wing supports. The rarely had wings blown off unless a large cannon shell hit the spar connections to the fuselage. Our tanks were self-sealing at least beginning in 1942. At Pearl Harbor, not all our Naval aircraft had those self sealing tanks. eh very interesting to see that a strategical element of lacking oversea support bases effecting down to the cascading result of a hit wing tank!.. One wonders what the air war would have been like if the Japanese had more reliable radial engines? i always consider the lack of high performance engines a technological disadvantage of ww2 axis powers. Even with germany, high altitude performance was never been good enough. And when they finally came up with good designs strategical resources were so lacking that fuel quality severely degraded. Otherwise i imagine the ki-84 and N1K1s were surely to outperform allied fighters in some aspects.
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Post by oldpop2000 on Jun 11, 2016 12:29:41 GMT -6
If one pierces the fuel tank from the rear, a hydrostatic pressure wave will emanate from the point of entry. This pressure wave can push fuel up against the sides of the tanks, snapping them violently. When that occurs, they will snap the spars and ribs because of their proximity to the support structures, also igniting the fuel tanks. Now, you will see a flame start from the back of the wing inboard, the forward velocity of the aircraft will begin to tear the wing off, like tearing a piece of paper down the middle. Find some gun camera videos online, and you will see this occur on Zero's, Aichi dive bombers, Kate torpedo bombers and their Betty's and Nell's. US, German and British aircraft had expansion room between the outside tank walls and the wing supports. The rarely had wings blown off unless a large cannon shell hit the spar connections to the fuselage. Our tanks were self-sealing at least beginning in 1942. At Pearl Harbor, not all our Naval aircraft had those self sealing tanks. eh very interesting to see that a strategical element of lacking oversea support bases effecting down to the cascading result of a hit wing tank!.. One wonders what the air war would have been like if the Japanese had more reliable radial engines? i always consider the lack of high performance engines a technological disadvantage of ww2 axis powers. Even with germany, high altitude performance was never been good enough. And when they finally came up with good designs strategical resources were so lacking that fuel quality severely degraded. Otherwise i imagine the ki-84 and N1K1s were surely to outperform allied fighters in some aspects. The A6M5c dropped the fuselage mounted guns and added 12.7 mm guns outboard of the 20mm cannons in the wings. It also had clipped wings to improve its roll rate and forward speed, with bigger exhaust for the Sakai 16 engines which was larger and more powerful. The M8 dropped all fuselage guns and featured a larger Kinsai 62 engines. It was the Model 64, which was never in production. Production-wise, the Model 52 was the best and most survival of the 21, 32, and 52 models. Of course, IJN aircraft radios were worthless, and removed at Rabaul to decrease weight and gain range which was lost with the Model 32 and larger engine.
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Post by oldpop2000 on Jun 11, 2016 12:43:56 GMT -6
actually i've never found out if the mig-15 had self sealing or even armored fuel tanks or not, there are generic sources that state one or the other, which is confusing to say least. i got a copy of the mig-15 flight manual but it is ofc in Cyrillic. doesn't help that the mig has 2 fuel tanks so it could well be one is self sealed while the other not. i only know definitively that the cockpit is armored with 10mm steel/64mm glass. The MIG-15 had self-sealing tanks and armored glass and an armored cockpit.
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Post by Deleted on Jun 11, 2016 13:00:52 GMT -6
^it just seems to me that everything went downhill after model 21 for the zero that sacrificed maneuverability for the sake of straight line performance which goes against its initial design emphasis. comparing to bf109 and spitfires that were early ww2 designs that kept evolving through the war, the limiting factor of the sakae's engine power is apparent... i'd say troubles for the 109 started with the G series that it just got too heavy. trouble with the spits started with the griffon engine variants that worsened handling. the zero model 32 may be a trade off but by 52 it looks to be just coping -> i do echo the sentiment that they really needed a better engine.
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Post by Deleted on Jun 11, 2016 13:01:16 GMT -6
actually i've never found out if the mig-15 had self sealing or even armored fuel tanks or not, there are generic sources that state one or the other, which is confusing to say least. i got a copy of the mig-15 flight manual but it is ofc in Cyrillic. doesn't help that the mig has 2 fuel tanks so it could well be one is self sealed while the other not. i only know definitively that the cockpit is armored with 10mm steel/64mm glass. The MIG-15 had self-sealing tanks oldpop: source plz! I have been making a flight-sim korean air war mod so it is somewhat of importance there!
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Post by oldpop2000 on Jun 11, 2016 13:13:03 GMT -6
The MIG-15 had self-sealing tanks oldpop: source plz! I have been making a flight-sim korean air war mod so it is somewhat of importance there! Here is one: www.airvectors.net/avmig15_1.htmlAlso I've seen them at three museums including the USAF Museum, and the 8th AF museum in Savannah Georgia.
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Post by Deleted on Jun 11, 2016 13:18:34 GMT -6
ah yep seen that one but doesn't seem to mention fuel tank protection.
....fundamentally, if it is not a US/UK aircraft, information on the internet decreases drastically at least those written in english. detailed/authoritative info on the mig-15 for example, quite rare.
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Post by oldpop2000 on Jun 11, 2016 13:28:26 GMT -6
ah yep seen that one but doesn't seem to mention fuel tank protection. ....fundamentally, if it is not a US/UK aircraft, information on the internet decreases drastically at least those written in english. detailed/authoritative info on the mig-15 for example, quite rare. Here is another. weaponsandwarfare.com/2016/02/06/migs-part-i/ "The MiG had made its appearance two years earlier during the 1948 Tushino Air Show. Designed to counter a high-altitude threat posed by American bombers, the MiG was tough, simple, and easy to maintain. Self-sealing fuel tanks and cockpit armor were good inclusions; however, there were problems with nearly everything else"
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