Hi Davparlr,
>>>>>3) Production line incorporated the 50 cal, implementing the 20 mm would interrupt the line.
...
>I don't think there was enough data available in the late 30s, when the F4F was developed, indicating the lack of effectively of the 50 cal.
Look at your original point: You claimed that the 20 mm could only be introduced by interrupting the 12.7 mm production line.
Obviously, if the decision to introduce cannon had been made early enough, this would not have created any gap in aircraft armement supply.
Why this decision was not made in time is a different question - all other major powers made the decision, and most even made it in time. All of them made it in time for the Battle of Midway.
>Again, these problems would still need to be fixed.
You don't need to argue that the lead time was insufficient - for any lead time, there is a time at which a decision for cannon could have been made that would have introduced them just in time. That's the decision at which the US failed.
>You're saying that the US, United Kingdom, Canada, all other countries that used aircraft with 50 cals, got away with failure for four years?
Since I try not to oversimplify things, here is what the data I already posted tells you:
8x ,50 Browning M2 - 425 rpg, 33 s duration - 694 kg - 2,3 MW firepower - 74,2 MJ total energy
2x Hispano II - 350 rpg, 35 s duration - 272 kg - 2,1 MW firepower - firepower per weight: 7,8 kW/kg - 74,3 MJ total energy
The weight saving consists of 422 kg, or 930 lbs. Even for a 13800 lbs gross weight fighter like the P-47D, this is a massive difference.
The conclusions of the US experts on the P-47:
"b. The rate of climb is not as good as desired, which fact limits its suitability as a medium altitude fighter and as an interceptor.
c. All weight in the structure and accessories not vital to operational use should be eliminated."
So, the USAAF's failure to have cannon ready for the P-47 incurred a weight penalty of 930 lbs in the P-47, limiting the types' suitability as a fighter and reducing overall performance, manoeuvrability, range and payload.
This deterioration of technical and tactical parameters is something that every aircraft equipped with 12.7 mm Browning Machine guns suffered from, and it could have been avoided by the adoption of superior armement.
>In reality, 20mm would probably not add much to the combat performance of the F4F. It would still be, as Nimitz stated, an inferior weapon.
What Nimitz demanded was an improvement in performance without sacrificing the strengths of the F4F.
6x ,50 Browning M2 - 240 rpg, 18 s duration - 332 kg - 1,7 MW firepower
2x Hispano II - 180 rpg, 18 s duration - 189 kg - 2,1 MW firepower
According to my calculations, this would have improved the performance of the F4F-4 by:
- 2 km/h in top speed
- 2:30 min reduction in climb time to 8 km
- A 5 % increase in turn rate at sea level, and an 8 % increase at 8 km.
Operationally, the reduction in time to altitude probably is the most important improvement.
As pointed out in my previous posts, increasing the ammunition load would also have been possible, adressing the complaint Admiral King made - and this was a specific complaint about a weakness of the F4F's armament.
>By 1939, the US had pretty well settled on the 50 cals as being the primary fighter armament.
Again the lead time question ...
>And I suspect there were no statistics that supported the increased kill effectively of the 20 mm over the expected target, which you have never addressed.
Historical statistics: In 1939, there were obviously none. However, as I pointed out above, all other major powers had even before decided to go for cannon, obviously considering the material available at the time to be sufficient.
Modern statistics: There is enough data in this thread that I consider the topic extremely well-addressed. Any specific question you might have, just ask.
>What fighters were the British flying that used the 50 cals, other than limited number of F4Fs, and P-40s with only one 50 cal.?)
Hm, looks like a misunderstanding of my regrettably ambiguous sentence: "As the British switched to 20 mm cannon after careful consideration of all the options available to them, skipping the 12.7 mm machine gun rather quickly, and had already collected quite a bit of combat experience with them, the US military could simply have learned from the British example."
My clarification: The British had considered and rejected the 12.7 mm machine gun in favour of the cannon as primary fighter armament, and collected combat experience *with the 20 mm cannon*, which is what the US could have learned something from.
>Interesting, there was no comment about the ineffectively of the four 50s, no recommendation to use 20mms, no effort to modify the Mark III with 20mm, even though the Mark IAs did come with 20mm, so installation must not have been a problem. I guess the British thought the 20mm update was not worth the effort for their 30-35 squadrons of Mark IIIs or the Mark IVs.
The pressure towards standardization in fact grew during the war and probably would have made it impossible for the British in 1944 to get it their way. If only one standard version of the P-51D/K was going to be produced, it would obviously be armed to American standards. The situation for the Mark IA had been different, and the wing actually had been re-designed between the Mark IA and the P-51D.
>Interesting, there was no comment about the ineffectively of the four 50s
The quote:
"The fire-power consists of four .5 Browning's in the wings. This is very little compared with the Spitfire."
I read this as "very little fire-power compared with the Spitfire", and little firepower equates poor effectiveness.
What do you read this as?
>Certainly, the 20 mm was more effective than 50s against the bombers they were fighting, no so much against fighters.
Hm, correct me if I'm wrong, but this looks like a completely unsupported claim to me. In fact, the Luftwaffe data I quoted indicates the opposite - explosive shells are even more effective against fighters than against bombers.
>I am only saying that the decision to maintain 50s as the mainstream US fighter weapon was not a "failure" but rather a decision based on effectiveness, logistics and productivity.
It was a decision that resulted in inferior firepower, performance, range and maneovurability of tens of thousands of US-built fighters, directly contributing to the fate of the thousands of Allied pilots that were killed flying these fighters.
>I think your interpretation of Admiral Kings telegram.
Hm ...
>I don't think he was implying that the Battle of Midway was almost lost because of the performance of the F4F.
What I wrote:
"Admiral King's telegram shows intense concern about the quality of the entire weapons system. King's specific demands were:
- Reduce the weight of the F4F-4.
- Increase the ammunition supply.
The Hispano II example battery addresses both issues King raises with the F4F-4 and its armament by increasing the ammunition supply by 40% and saving about 324 lbs of weight at the same time. It also increases firepower."
>As noted in Nimitz's message, he did not want to change the armament and felt it was a big contributor to what success the F4F had.
Nimitz did not say he did not want to change the armament, but that he did not want to sacrifice the "the overall superiority", only "part at least rest in the armor, armament, and leakproof tanks". He was wise enough not to try to micro-manage the improvement, but only pointed out that performance should not be improved by stripping the aircraft of components that had proved their worth in combat. A cannon-armed Wildcat with improved firepower at improved performance would have met his demand nicely.
>Probability of strikes would be reduced and sortie per kill is unknown (I don't know how much the gun would help). Probability comparisons of kill, given strike, is poorly known. Calculations have many variables, aspect, maneuver, etc.
The problem is not half as complex as you seem to think. The firepower, measured in MW, is an excellent indicator of the effectiveness of the weapon, judging by the various historical accounts presented here and elsewhere, British and Soviet data both show that the vast majority of kills were scored at very short ranges where the influence of other factors is minimal, contemporary doctrine (confirmed by Soviet data) shows that the rear aspect was the most effective shooting position, the German Schießfibel points out that a large pattern is not helpful in air combat and does not compensate for errors in lead estimation, and the "probability of strikes" is completely secondary to the "probability of kill" - which is improved by switching to cannon.
>I believe, and probably the war planners of the time believed, that, if the 20mms were adopted, there would have been a significant production delay and logistic trail at a time when quantity was vital.
You're passing this judgement from a implicit assumption on when the decision to adopt cannon would have had to be made, and this assumption obviously is "too late". Assume "in time" for a change, and your conclusion will be different.
>If the 50 cal was a failure or mistake, it has to be the most successful failure in the history of warfare.
Hm, I have pointed out the substantial shortcomings of the 12.7 mm Browning in fine detail, so it's really not necessary to gloss them over with a broad generalization. I think we could be making quicker progress without such statements ... your factual points are appreciated, but I feel there is occasionally a bit of unnecessary "ballast" in your posts
Regards,
Henning (HoHun)
) As far as I know, the only step taken to save weight in the aircraft models was to install a much lighter barrel that relied on the few-hundred MPH airstream to cool it.
