The problem diving a Spitfire was the dive acceleration. The MkXIV was an improvement on earlier Spits as both power (thrust) and weight were increased, along with wing loading. The 'bolt actually had a somewhat larger wing, but it had much less area proportionate to its weight and power. In a dive, the Lightning had much higher acceleration that either of the others. In level flight, it could easily out accelerate a 'bolt, or any Spit before the MkXIV. Low wing loading carries penalties as well as advantages. Also the '38s commonly got to 540mph TAS (at 30-35K) doing the tests on the dive recovery flaps. That would be about 0.8M. To get to 640 TAS in a Spit (limit 0.89 M) would have to be at or below an altitude with M at least 720mph. That would mean not much above 10K, I'd guess. Don't have a chart of Mach speeds handy, but sea level is around 760 and it drops pretty fast up to about 12K. Pulling out of that dive would be pretty chancy starting that low. Might explain why Spits occasionally suffered wing failure. As to the prop, if the tips are already in mach shock at, say, 450 and low altitude (airshow dive), in a serious high altitude dive, that effect will be creeping towards the hub pretty fast, and every inch is lost thrust and increased blade buffet.

There are at least two problems with this analysis; First; is that you have used, at least according to my flight manual, fast cruise, IE 220MPH instead of eccono cruise at 193MPH and the rate of fule conbsumption should be 28 GPH instead of 25GPH. However, I find this to be a minor differance that would make only a minimal impact on the over all missioin. Second; At the time, the SOP, Thats Standard Opperating Procedures, required that the plane fly at maximum cruise while in the combat zone to prevent unneccessary losses. Third; That the slow outbound leg of your hypothetical mission would make it much harder to intercept the enimy, than if that leg were flown at faster speeds! Since the historical rate of successfull interception, defined as actualy sighting the enimy, wether or not they were shot down, was LESS than 50%, how do you think your slower mission profile would help that? Forthly; Abet a minor one, since this rule was widely violated even though it resulted in the loss of more than a few planes, is that your mission failed to leave the required fule reserves. While this seams like a minor problem, the reserve is there because the possability of trafic, weather or field damage could force a diversion and without that reserve, could and did cause the loss of more than a few planes. So that if your opperational mission losses were prorated in porportion to that reduction in reserve, it would you would incure 45/29ths more of the 50% losses that were not combat related! Lastly; you have failed to leave some fule to land and taxi to the hard stand for service. I can't remember what that is off the top of my head, but I would guese that 10-12 minutes would do at the minimum rate of 22 gallons per hour, or 4.5 gallons. That brings the total underestimation of fule required to 8.5 Gallons. If your mission was recomputed to meet the SOPs at the time, it would look like this: (I have put the correct figures in parenthisis into your own post!) CORRECTED Summary of the Above; 85 gallons to start with. OK, but it is easier to start with the landing and work toward the start. 10 gallons used in warm up and taxi, 75 gallons remaining 11 gallons used in climb to 20,000 feet, 64 gallons remaining 12.5 (25.8Gal.@310MPH!) gallons used in cruise to 100 miles,(OR 12.5 Gallons to go 48.4 Miles @ 310MPH!) 51.5 gallons remaining (OR 38.2 Gallons left! Take your pick!) 27 gallons used in combat, 24.5 gallons remaining (7.3 Gallons for 5 minutes at 100% leaves 30.9 Gallons, OR 11.2 Gallons if you want to go 100 miles) 12.5 gallons used in return cruise, 12 gallons remaining(? If there is only 11.2 Gallons left you have to land someplace short of your home base, if you still want to go 100 Miles. OR if you restrict combat to five minutes at 100%, but only 48 miles from base AND return to base at eccono cruise, thus increasing your chance to be shot down, there is now 19.9 Gallons left of which 4.5 is required to land and taxi and thus VIOLATES the 45 minute reserve required by THREE MINUTES! As you can see once ALL of the required fule expenditures such as landing and reserve is met, your mission is impossable! The more realistic radius of intercept is thereforer LESS than 48 miles. 12 gallons is a 29 minute reserve at economical cruising speed. Greater endurance could be achieved by throttling back to maximum endurance settings, probably greater than 45 minutes. ( The actual reserve at 22 GPH would be 32.7 minutes, OR far short of the required 45 MINUTES!) I actually have a number of spitfire manuals and they agree with everything above. (Except for your failure to allow for combat cruise as required by the SOPs, landing, taxi and reallistic reserves, your math is impecable!!!) (RIGHT!)

The 50% interception rate for BoB sories came from me. I got it from DUEL OF EAGLES by Peter Townsend. Thank you Larry! You have made some very astute posts on this thread!

The rest of this post is to flawed to respond to. I just started with this because it was so agregious! >>what tosh, the p40 was vastly inferior above 9000ft << Please define "VASTLY infirior" As the various manuals dispute this! Most of the differance is minor about 10-15MPH! >>its performance at altitude was poor,<< It was however supirior to the hurricane! >> whilst it could reach the required height it could not compete at that altitude << I guess it was not up to the task in North Africa, where the P-40 downed more planes than the Spit or hurry! >> and bare in mind that the figures you quote are for a version with out armour or seal sealing tanks << This is only partialy true! It had more armor than the early Spit/Hurry. Also note that early Spits did not have self sealing tanks either! >>The limitations in GCI may have made it impossible for a squadron to make another attempt at intercept.<< Only because the Spit had such short range! A longer ranged plane would have been much more successfull. >>It may be better to get the planes back on the ground so they can be serviced and the pilots can get some rest. Don't get me wrong, extra range wouldn't have hurt, just so long as it didn't come at the cost of other more vital areas of performance. << This is your entire problem, you do not know what arias of performance are important or how important they are. Range is the single most important aspect of performance. Because ALL of the other aircraft performance criteria ARE MUTABLE! That the reallitive performance of any interceptor is supirior to any escort or bomber. That is you can traid range for speed or climb or maneuver or whatever. The weapon system exists to transport the weapon(s) and ammo to a possition where they could be brought to bear on the target with sufficiant effect. The primary component of the equasion is range. A weapon with twice the range, will be 41% more effective than one with less range. It will make 41% more intercepts, RTB 41% more offen and thus reduce the Non combat, "Opperational" losses and in general do a better job than a weapon system with less range. If you had some classes in Game theory, you would know these things. As it is you continue to argue about intangebles that change as the mission progresses or are patently not plausable as they relate to the mission! What good is 10% more speed, certainly more than the maximum differance here, If you can't reach the target 50% of the time? By your own example the differance between the P-40 and Spit is over 200 MILES in radius! Finaly the Spit and P-40 were disigned and flown at the same time. They are contemporaries in every sence of the word. That the British Government chose to build them before we chose to build the P-38/39/40 does not change the realitive time frasim of their inception. That the production figures you site come from cost not time, is also deceptive in that English labor was paid a great deal less than the equivilant US worker. The fact is that the Brits would have been better off with either the Hurricane or P-40 than the Spitfire based on the number that COULD have been made in that time fraim, had they made the same desigion on the other plane. That the Hurry was certyainly adequate to the task is beyond dought! The after all did shoot down twice as many Germans as the Spit did. If the number of Hurries that could have been built in leu of the more complex Spitfires would have made a significant differance to the BoB!

>>A merlin powered P-40 would have been able to take the place of the Hurricane, it would have required different tactics though. However, it still would have had inferior performance compared to the spit, which is what this is really all about. << Why do you think it would have had infirior performance to the Spit? Given that the P-40 was either not that far behind OR was supirior in some respects, why would you assume that it would not retain that advantage when re-engined? This is a false argument based on the ASSUMETION that the minor discrepancy in performance would change the out come significantly. This is clearly not the case as the combats in N. Africa had proven! What exactly is the differance in performance as a PERCENTAGE and would it have made a significant differance to the bombers or the Me-109 that can't use it's full throttle because of it's lack of range.

>>The fastests verified dive in a spit was a bit over 600 MPH, then there was the post war one which apparently reached 690 MPH.<< Given that for every Spit that successfully made a dive to over 500MPH TAS, there were seven or eight that disintigrated or CFIT due to the failure to recover from the dive, your espousing of this charicteristic is questionable at best. Given that Germans of the time could significantly out dive the Spit and Hurry, this would appier to be a performance criteria that you should not tout?

>>Instead of building a Merlin hawk, you could simply put a pair of fuel tanks in the wing of spit, albeit small tanks and a rear fuselage tank to increase range and endurance. You then retain the handle qualities and performance qualities of the spit while gaining the range of the P-40. << You are clearly dilusional! The fixes you want to make are not possable with the early spit! The PR types had to remove the guns and ammo to increase range due to less weight "INDUCING" less drag. That you seem to be ignorant that drag has two components, first by the form and skin friction and secondly as a condition of making lift. It is called "INDUCED DRAG" because it is that portion of the total drag that is because of weight. That the Spit's wing was totaly unsuited to adding fule is also ignored in your post. The CG of the guns and ammo were located exactly where the fule tanks would have to go! Where would you put the guns and how much ammo would you remove to make room and weight available for fule? RIGHT!!!

>>no, the wing on the spitfire was very much thinner. << NO! This is a common misconception! The Spits wing is acualy thicker than the Wing of the P-38 or 39! What we are talking about is the "REALITIVE" thickness as expressed as a percentage, but because the wing was of lower aspect ratio, it was much broader than the other types and was subsequently dimentionaly thicker. It's weakness was related to the fact it only had one spar not it's "Thickness". In addition it had the thickest part of the profile very far forward. The last 70% of the wing was tapered very sharply and was subsequently very thin dimentionaly. It is this shape or profile that caused most of the spit's problems. Because of this shape it could tollerate very little in the way of GC shift! Remember that the aft tank in the 'stang carried as much gas as the early spit-85 gallons!!!! When the 'stamg pilot had some adverse handeling with 85 gallons on board, he did not have as much of a hard time as the later Spit pilot with 30 gallons back! It is part of your problem in that you state all of these items as if they were ABSOLUTE not REALITIVE! Please state all future assessments in performance in terms of PERCENT from now on as you continualy state the P-40 was infirior at +20,000' but fail to state that that differance was less than 2% most of the time and that some aspects of performance were vastly supirior, such as rate of roll! From now on please use percentages and referance where you got them, that we could check your typing, since we all know that you would never intentionaly mislead us.

>>Testing at Boscome Down gave: Spitfire: Mach Limit in tests 0.89, advised maximum in operational use 0.85. Mustang (which had a thicker wing) was 0.8. It gave a good warning as it tended to porpoise when getting close to the limit. P-47 was 0.75 from recollection (might have been a little lower than this). << Thanks Dude! What I am curious about is how long the various planes needed to reach those speeds at what altitudes. I would also like to see the figures for the early models of Spitfire as my flight manual lists numbers far short of this. IE lower speeds at lower altitudes, for the Mk-V and Mk-1-3 were lower yet!

The rear chain wasn't done until after the BoB. They knew they needed to track a/c (friendly as well as hostile) over their own territory, so had the observer system. The need to provide held with identification is why RAF ftrs of the period had that odd, half-black, half-white paint job on the underside. The accuracy of info available to GCI for a second intercept attempt should have been just about as good as for the first try.