Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Hazard69 on June 14, 2012, 10:38:06 AM
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Was just wondering why is it that the P38s nose mounted 50cals fire one at a time as opposed to simultaneously or more likely alternately (i.e. 1 & 3 fire and then 2 & 4 fire, like a pony's do).
I'm sure HTC's mimicking reality, but I'm curious as to why the manufacturer would limit the aircraft lethality that way? I mean it'd sure be way more lethal if it was spouting out twice as much lead in the same time. Heating/ventilation issues? Stability problems? What?
Also, I am not sure but I seem to recall some variant had 6 or 8 50 cals installed instead of the 20mm. Is that accurate, and was it a common enough configuration? Might have avoided any need for different convergences if all the guns were of the same variety.
And finally, also why are all 4 the 50cals of varying lengths? Just so they could all be accommodated in the nose cone or some other aerodynamic reason?
Enquiring cadets would like to know! :lol
:salute Hazardus
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This is just a hypothesis, but the guns may have been arrayed in such a fashion due to their close proximity with one another.
(http://www.fiddlersgreen.net/aircraft/Lockheed-P38/IMAGES/P-38-Lightning-cutaway.jpg)
The receiver sections, firing mechanisms, and ammunition feeds are much bulkier than the protruding barrels let on. So, perhaps they were staggered internally for space/serviceability considerations?
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They were staggered for space and feed belts. They each have to be fed and have their corresponding belt box.
There were some other setups including a 23mm and even a 30mm canon. There was also a mix of 50s and 30s. Those were tested and some used but the main setup in action was 4 50s and a 20mm.
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This is just a hypothesis, but the guns may have been arrayed in such a fashion due to their close proximity with one another.
(http://www.fiddlersgreen.net/aircraft/Lockheed-P38/IMAGES/P-38-Lightning-cutaway.jpg)
The receiver sections, firing mechanisms, and ammunition feeds are much bulkier than the protruding barrels let on. So, perhaps they were staggered internally for space/serviceability considerations?
That's a nice cutaway. I can see why they'd have to stagger them to accommodate the ammo belts. :aok
Now, any ideas as to why they had to stagger the firing sequence too? :headscratch:
:salute Hazardus
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I don't recall the firing sequence but I assume you're looking at the tracers and only every 5th round is a tracer in each gun. It makes sense to stagger the tracer rounds instead of sending them out in groups.
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I don't recall the firing sequence but I assume you're looking at the tracers and only every 5th round is a tracer in each gun. It makes sense to stagger the tracer rounds instead of sending them out in groups.
No not the tracers, Im looking at the muzzle flashes. In a pony as u fire the quad guns, u can see them firing two at a time, whereas in a P38, u can see the flashes on one gun after another.
:salute Hazardus
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might be an attempt to create a more constant stream of lead with less spacing between bullets? or maybe all 4 .50s firing at the same time created a harmonic vibration that would escalate and eventually cause damage to the plane.
just my semi-educated guesses
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No not the tracers, Im looking at the muzzle flashes. In a pony as u fire the quad guns, u can see them firing two at a time, whereas in a P38, u can see the flashes on one gun after another.
:salute Hazardus
Well, check the ammo.... and time firing (just the .50 cals) all the way down.
They should fire @ 850 RPM..... that will give you the true indicator of firing sequence...
Now, assuming this is historically accurate (and that is in no way meant to insinuate that it is anything but), if the guns are firing in sequence it may be due to the inherent inaccuracy of the average pilot of the day... to allow the greatest chance for SOME hits...
My other hypothesis would be as tmetal said... though maybe not harmonic vibration so much as the 4x force of simultaneous discharge being too much for the air frame and/or avionics to handle.
Some other food for thought... here is a pic of a P-38 firing:
(http://ww2db.com/images/air_lightning10.jpg)
In that pic, all guns fire at once (and it appears that they are all tracers).
Now, the other tidbit to keep in mind is that there is a difference between delaying the guns firing, and the guns firing sequential but each at the cyclic (or whatever was the standard) rate.
If all 4 guns empty in 35 seconds (or thereabouts) - and assuming that a total of 2,000 .50 BMG rounds are thrown downrange, then it is good to go.
If it take appreciably longer, then there is some delay being introduced into the firing sequence that does not jive with what I have read about the P-38 (however I have nothing that proves to me whether or not what I have read is legitimate)
But I love talking about the P-38 hehe
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Keep in mind that pictures are deceptive because of the length of time the shutter is open.
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Well, check the ammo.... and time firing (just the .50 cals) all the way down.
Heheh, funny you should say that. I tried something like that just yesterday. Offline, I emptied the P38s 50cals with the 200rpg loadout. It took 46 seconds by my count. Then took out a P51 and fired off the secondaries with 267rpg and they emptied in about 47seconds. (Will recheck today once I get back home). That makes it seem as though the pony is firing almost 270 rounds more in almost the same duration. :huh
Weird? :noid
Yes Im leaning towards the instability/fatigue/vibration issue as a reason too, since the only real difference seems to be that the pony's guns are wing mounted as opposed to the 38s being nose mounted.
Keep in mind that pictures are deceptive because of the length of time the shutter is open.
Yes, I doubt they had a secret 38 variant with lasers installed. :lol Or do tracers actually extend so far out? :headscratch:
Judging from the smoke, seems like a stationary aircraft, probably testing convergence? Looks like its hitting a target off in the distance?
:salute Hazardus
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Given the fact that the cyclic rate of an M2 Browning 50 caliber heavy machine gun cannot be that closely controlled, you could see pretty much any firing rhythm in those weapons on a P-38, or any aircraft that was not firing them through a propeller with interrupter gear. The actual rate of fire in rounds per minute will vary such that even if they start out firing in sequence, they will only continue to do so for a relatively short period of time. The manufacturing tolerances of both the weapons and the ammunition is too wide for that level of control. Especially considering that dispersion is built in to machine gun ammunition.
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Given the fact that the cyclic rate of an M2 Browning 50 caliber heavy machine gun cannot be that closely controlled, you could see pretty much any firing rhythm in those weapons on a P-38, or any aircraft that was not firing them through a propeller with interrupter gear. The actual rate of fire in rounds per minute will vary such that even if they start out firing in sequence, they will only continue to do so for a relatively short period of time. The manufacturing tolerances of both the weapons and the ammunition is too wide for that level of control. Especially considering that dispersion is built in to machine gun ammunition.
I remember reading a story a P-38 pilot wrote about one of his missions. No, I don't remember where, it was a long time ago.
He said that when he pulled the trigger, all the guns fired at once, then settled into a rhythm. I don't know how accurate the story, or my memory, is.
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They were staggered for space and feed belts. They each have to be fed and have their corresponding belt box.
There were some other setups including a 23mm and even a 30mm canon. There was also a mix of 50s and 30s. Those were tested and some used but the main setup in action was 4 50s and a 20mm.
Too bad they didn't go with the 2 20mm/4 .50 cal set up. :D
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No, a better version would have been four 20MM cannons with 200-225 rounds each. A C hog, with no convergence to deal with.
The parts were available to create an incredible performer out of the P-38, even better than the best version built. The G series V-1710 Allison was a "bolt in" swap. Combined with the "K" model (Hamilton Standard high activity paddle props) conversion that Lockheed did about 9 months before the G series engines were built, it would have produced a true monster. A P-38 with as much as 4500HP driving two Hamilton Standard 13 foot diameter 4 blade props would have been a real climber. Throw in the four 20MM cannons and you'd have a serious ride. You'd just have to be damned careful about not getting into compression, because it could have been easily done in level flight. Imagine this P-38 http://www.456fis.org/P-38K.htm (http://www.456fis.org/P-38K.htm) taken to the next level, the G series engines with 2250HP http://www.thunderboats.org/history/history0323.html (http://www.thunderboats.org/history/history0323.html) (almost 400HP each more than the F-15 Allisons in the P-38K) with 4 blade Hamilton Standard props. A seriously sexy beast for a P-38 fan.
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But they would have had to import 20mm guns from the UK as the home-made Hispano copies were really bad (unreliable, jamming).
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But they would have had to import 20mm guns from the UK as the home-made Hispano copies were really bad (unreliable, jamming).
*sigh*
ack-ack
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Were the M2 american rounds greased to aleviate the jamming in the P38 like those used by the NAVY?
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Was just wondering why is it that the P38s nose mounted 50cals fire one at a time as opposed to simultaneously or more likely alternately (i.e. 1 & 3 fire and then 2 & 4 fire, like a pony's do).
I'm sure HTC's mimicking reality, but I'm curious as to why the manufacturer would limit the aircraft lethality that way? I mean it'd sure be way more lethal if it was spouting out twice as much lead in the same time. Heating/ventilation issues? Stability problems? What?
Also, I am not sure but I seem to recall some variant had 6 or 8 50 cals installed instead of the 20mm. Is that accurate, and was it a common enough configuration? Might have avoided any need for different convergences if all the guns were of the same variety.
And finally, also why are all 4 the 50cals of varying lengths? Just so they could all be accommodated in the nose cone or some other aerodynamic reason?
Enquiring cadets would like to know! :lol
:salute Hazardus
They are that way so you get a consistent flow of fire from the guns. This increases the likely hood of hitting a target in a deflection shot.
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No, a better version would have been four 20MM cannons with 200-225 rounds each. A C hog, with no convergence to deal with.
The parts were available to create an incredible performer out of the P-38, even better than the best version built. The G series V-1710 Allison was a "bolt in" swap. Combined with the "K" model (Hamilton Standard high activity paddle props) conversion that Lockheed did about 9 months before the G series engines were built, it would have produced a true monster. A P-38 with as much as 4500HP driving two Hamilton Standard 13 foot diameter 4 blade props would have been a real climber. Throw in the four 20MM cannons and you'd have a serious ride. You'd just have to be damned careful about not getting into compression, because it could have been easily done in level flight. Imagine this P-38 http://www.456fis.org/P-38K.htm (http://www.456fis.org/P-38K.htm) taken to the next level, the G series engines with 2250HP http://www.thunderboats.org/history/history0323.html (http://www.thunderboats.org/history/history0323.html) (almost 400HP each more than the F-15 Allisons in the P-38K) with 4 blade Hamilton Standard props. A seriously sexy beast for a P-38 fan.
Wow. :eek:
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now there is a perk plane!
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In April 1942 a copy of the British Mk.II was sent to the U.S. for comparison, the British version used a slightly shorter chamber and did not have the same problems as the U.S. version of the cannon.[9] The U.S. declined to modify the chamber of their version, but nonetheless made other modifications to create the unreliable M2. By late 1942 the USAAC had 40 million rounds of ammunition stored but the guns remained unsuitable. The U.S. Navy had been trying to go all-cannon throughout the war but the conversion never occurred. As late as December 1945 the Army's Chief of Ordnance was still attempting to complete additional changes to the design to allow it to enter service.[9] Some variations of the 20 mm guns used on the Lockheed P-38 Lightning aircraft were produced by International Harvester.[10]
Wow that sucks, would of been nice to see 20mm cannons on the navy birds, but I understand A) gun was unreliable and B) wasn't entirely needed at the time.
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The plane, now designated the P-38K-1-LO was flown to Elgin Field for evaluation by the USAAF. Flown against the P-51B and the P-47D, this Lightning proved to be vastly superior to both in every category of measured performance. What astounded the evaluation team was the incredible rate of climb demonstrated by the P-38K. From a standing start on the runway, the aircraft could take off and climb to 20,000 feet in 5 minutes flat! The "K", fully loaded, had an initial rate of climb of 4,800 fpm in Military Power. In War Emergency Power, over 5,000 fpm was predicted.
In light of this incredible level of performance, you would certainly expect that the Government would be falling all over themselves to quickly get the P-38K into production. Yet, this was not the case. The War Production Board was unwilling to allow a short production suspension in order to get new tooling on line for the required change to the engine cowling. Even when Lockheed promised that the stoppage would only be for 2 or 3 weeks, their request was turned down.
The true consequences of this pig-headed thinking will never be known. What would have been the impact of such a high performance fighter arriving in force to the forward combat areas in mid 1943? How many lost fighter pilots would have survived thanks to the awe inspiring performance of the P-38K? Again, we can never know these things. What we do know, is that due to bureaucratic myopia, neither the P-38K nor a Merlin powered Lightning ever really had a chance to make an impact upon the air war. For all those pilots who died at the controls of lesser aircraft, the War Production Board bears a measure of responsibility for their fate.
damn I want the P-38K now :(
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Now imagine development continuing from April 1943 on based not on the J model, but rather on the K model. Four blade propellers would have become standard (owing to standardization of production), again improving performance.
For the most part, development of the P-38 really halted in 1943, other than detail work. Serious attempts to improve the airframe and the engines almost completely ceased. Time and resources were wasted on various "related" projects instead.
Of course, the biggest reason Lockheed couldn't halt production long enough to introduce the K model was that 1/2 the Burbank plant was building B-17 bombers, as much to replace losses due to unescorted bombing missions as any other reason. While Consolidated Vultee of Nashville TN struggled for 2-3 years to produce a paltry 113 P-38 fighters. Probably because Boeing was not happy with the idea of allowing Consolidated to build a Boeing aircraft.
If you read this : http://www.ausairpower.net/P-38-Analysis.html (http://www.ausairpower.net/P-38-Analysis.html) you'll see that other detail improvements were not made for much the same reasons.
Those two articles were written by Widewing, and Dr Carlos Kopp, with help from two P-38 pilots, Captain Stan Richardson Jr., and Captain Arthur Heiden, both of whom I swapped hundreds of emails with. Of particular interest in Dr. Kopp's article is a statement about climb rate and combat radius with regard to combat effectiveness by Art Heiden. Now consider again the P-38K in that regard. Consider also the effect of the power and propeller efficiency on acceleration and the ability to retain speed and energy.
To steal a line from Rod Steiger, imagine if you will, the P-38L based not on the P-38J, but rather on the P-38K, as it should have been. And then consider what it would have meant if Lockheed Burbank were using both halves of the plant capacity to produce the P-38, instead of half the plant producing the B-17, which, in late 43 and all of 44 was as much bait for the fighters over Europe as it was anything else. What you'd end up with would be around 10K P-38L fighters with a top speed of around 450MPH at 26K feet, around 4K fpm sustained rate of climb, and a 20% combat radius cushion.
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The plane, now designated the P-38K-1-LO was flown to Elgin Field for evaluation by the USAAF. Flown against the P-51B and the P-47D, this Lightning proved to be vastly superior to both in every category of measured performance. What astounded the evaluation team was the incredible rate of climb demonstrated by the P-38K. From a standing start on the runway, the aircraft could take off and climb to 20,000 feet in 5 minutes flat! The "K", fully loaded, had an initial rate of climb of 4,800 fpm in Military Power. In War Emergency Power, over 5,000 fpm was predicted.
In light of this incredible level of performance, you would certainly expect that the Government would be falling all over themselves to quickly get the P-38K into production. Yet, this was not the case. The War Production Board was unwilling to allow a short production suspension in order to get new tooling on line for the required change to the engine cowling. Even when Lockheed promised that the stoppage would only be for 2 or 3 weeks, their request was turned down.
The true consequences of this pig-headed thinking will never be known. What would have been the impact of such a high performance fighter arriving in force to the forward combat areas in mid 1943? How many lost fighter pilots would have survived thanks to the awe inspiring performance of the P-38K? Again, we can never know these things. What we do know, is that due to bureaucratic myopia, neither the P-38K nor a Merlin powered Lightning ever really had a chance to make an impact upon the air war. For all those pilots who died at the controls of lesser aircraft, the War Production Board bears a measure of responsibility for their fate.
damn I want the P-38K now :(
Hey, I remember when I wrote that piece in the late 90s.... Based upon documents provided by Warren Bodie....
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Hey, I remember when I wrote that piece in the late 90s.... Based upon documents provided by Warren Bodie....
Damned shame what they did to your website, too. What a waste.
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Hey, I remember when I wrote that piece in the late 90s.... Based upon documents provided by Warren Bodie....
Wonderful job you did, man I wish I could know 10% of what you know, i'd feel better :)
Recommend any books? :D
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To steal a line from Rod Steiger, imagine if you will,
Wrong Rod. Think that was Rod Serling. Not to be confused with "submitted for your perusal", another Rod Serling.
Now Rod Steiger might have said something like--"ye Savvy" or "I'm talkin about workin for a living! I'm talkin about Sharking!"
;)
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Wrong Rod. Think that was Rod Serling. Not to be confused with "submitted for your perusal", another Rod Serling.
Now Rod Steiger might have said something like--"ye Savvy" or "I'm talkin about workin for a living! I'm talkin about Sharking!"
;)
Damn, you're right. :bhead
Steiger's best line has to be his line from "The Longest Day".
Hey! Who let Drano in SAPP? There goes the neighborhood.
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Damn, you're right. :bhead
Steiger's best line has to be his line from "The Longest Day".
Hey! Who let Drano in SAPP? There goes the neighborhood.
:rofl
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i forgot where i read it but. i read about a merlin XX powered lightning 5,000+ climb rate and 460 straight n level flight at alt. out climbed out ran and out ranged any american fighter. 2 were built 1 compressed the other was scrapped when they were told NO you cant make it.
I dont know how true that was tho
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i forgot where i read it but. i read about a merlin XX powered lightning 5,000+ climb rate and 460 straight n level flight at alt. out climbed out ran and out ranged any american fighter. 2 were built 1 compressed the other was scrapped when they were told NO you cant make it.
I dont know how true that was tho
Total unmitigated B.S. The Merlin will not fit the P-38 without a complete rework of the airframe. It adds over 1500 pounds, the climb rate and combat radius are both reduced. Lockheed did a complete engineering study, and the conversion never left the paper it was written and drawn on.
The Allison is a lighter engine, slightly more compact in most dimensions as well. Not only that, it is a stronger engine. The only thing that made the Merlin more powerful was a two speed supercharger compared to the single speed supercharger on the Allison.
Most people do not know that no Packard or Rolls Royce Merlin engine was competitive and finished the unlimited races at Reno until one engine builder figured out how to modify the Merlin oiling system and put the connecting rods from an Allison V-1710 in it. Merlins pushed hard enough to run up front simply blew up before the race was over.
The G series Allison V-1710 is far superior to the Merlin. It would have fit in the P-38 and eliminated the need for the turbocharger (it was later used in the P-82 Twin Mustang), but if the turbocharger was retained, it could have maintained sea level horsepower to over 35,000 feet.