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Subject: How to fix the design defects of the Spitfire airplane of WW-II.
Shooter    5/26/2005 5:12:16 PM
Given 20-20 hind sight, It is easy to see where R.M. went wrong with the Spitfire! The following list of items is my idea of how they should have done it, IF THEY HAD READ ANY OF THE COMMON TEXTS instead of designing a newer SPAD for the last war! 1. Start with the late Seafire or even better the Martin Baker MB-5! they have contra props and wide track gear. The MB-5 also has a much higher LOS out of the pit forward. This is also one of the Spits larger problems. 2. Change the shape/planform of the wing and eppinage from eliptical to trapiziodal. The eliptical surfaces caused the construction time and cost of the Spitfire to be more than double that of the Mustang and almost as much as the P-38. 3. Reduce the wing cord and thus area by 35-40%! This reduction in surface aria will increase the cruising speed substantialy! This is probably the single biggest defect in the design. The change in aspect ratio will also help fuel ecconomy! 4. To compensate for the increased landing and take off speeds install triple slotted fowler flaps with a long hinge extension. This gives a huge increase in wing area and changes the camber for supirior "DOG FIGHT" ability, should you ever need it! ( because the pilot really screwed up!) At full extension and deflection, they would reduce the landing speed by 11~13MPH? (Slip Stick calcs!) 5. Remove the wing mounted radiators and install a body duct like the P-51 or MB-5! This one change would add ~35MPH to the plane? 6. use the single stage griphon engine and install a "Turbo-charger" like the P-38 and Most American Bombers had. This would increase power and save weight, both significant contributers to performance. 7. Remove the guns from the wings! This would lower the polar moment of rotation and give the plane snappier rates of roll! It also makes room for "wet wings" with much more fuel. A chronic Spit problem. It also fixes the Spit's gunnery problem of designed in dispersion! 8. Install the Gun(s) in the nose! Either fireing threw the prop boss/hub or on either side 180 degrees either side of the prop CL. This fixes the afore mentioned dispersion problem. One bigger gun between the cilinder banks or upto four 20MMs beside the engine or both, depending on what your mission needs were! 9. Make a new gun based on the American 28MM or 1.1" Naval AA ammo! This shell was particuarly destructive, had a very high MV and BC and was all ready in service. A re-engineered copy of the existing gun to reduce weight and increase RoF is a faily simple task. Pay the Americans for it if British spring technology is not up to the task! it also frees up much needed production capasity for other things. 10. Design a new drawn steel "Mine" shell for the above gun! Spend the money to load it with RDX instead of the TNT used for the first 4/5s of the war. 11. Pay North American or Lockheed to design it for you, since the Supermarine staff was to tied up fixing the origional spitfire design to get it done any time soon. Did I miss anything?
 
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MustangFlyer    RE:Spit XIV vs George - Roll Rates   5/6/2006 2:51:13 AM
Actually Larry, if you go back to AE's earlier post (with the NACA roll rate charts) The P47 was inferior to the normal wing spit up to 280 mph and inferior to the clipped wing Spit at all speeds. The P38J was inferior at all speeds and the P38L inferior up to 280mph as well. The p47 was superior to the P38J at all speeds and superior to the L up to 280 mph. The king of the rollers was the FW190, with the clipped wing Spit the next closest (amazing the difference a few feet off the wings made, which explains why the majority of TAF Spits had clipped wings). The Mustang was equal to the jug to 240mph, after which it was superior, the 38L was inferior up to 340mph and the 38J inferior at all speeds. Note a very important fact, these are indicated speeds. At 30,000 feet 280mph indicated is actually 448mph true air speed. Only close to the deck and flat out would a 47 outroll a normal wing Spit, but since the spit could out accelerate it, outrun it (Jugs were not fast low down), outturn it (vertically and horizontally) and out climb it, and with no altitude for the Jug to dive ... well. Bit like a destroyer running rings around an aircraft carrier.
 
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MustangFlyer    RE:Spit XIV vs George - Roll Rates   5/6/2006 3:34:33 AM
AE, digging through Morgan's "Spitfire The History". The late model MkIXs had 2 x 18 gals in the wings, plus 33 or 41 gals rear tanks. Some rough calculations on power loadings: Spit IX: 7,500 lbs (max permissible w/o overload tanks), 1650hp =4.54lbs/hp P-47D: 13,000lbs (used in test), 2300 hp = 5.65 lbs/hp P-38L: 17,000 lbs (used in test), 2 x 1,530 hp = 5.56 lbs/hp. P-51D: 9,700 lbs (fully fueled, no overload tanks), 1650 hp = 5.88 lbs/hp (the P-51B was a bit lighter and actually faster). Basically the Spit would outclimb and out accelerate any of them. The superior aerodynamic drag of the Mustang gave it its incredible speed (at all altitudes) as well as its excellent dive characteristics. The Mustang had the next highest mach limit next to the Spit (Spits combat limit was 0.85 mach, the Mustang 0.8, P-47 mid 0.7s and the P38 low 0.7s, in fact the late P-38Ls mach limit was virtualy their max speed at 30,000ft). Most other planes (Me-109, Mosquito, Tempest) were all about the 0.8 limit, with the Me109 probably being the lowest (due to yaw tearing off the wings and the ailerons freezing up). No idea what the Fw-190s limit was, should be pretty high though.
 
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larryjcr    RE:Spit XIV vs George   5/6/2006 3:42:17 AM
Not so on ailerons. Those have a maximum deflection. Once that is reached, additional force has no effect. The Spitfire's control surfaces would reach max. deflection with the application of less force than most other a/c, so higher force application would favor other a/c types over the Spit. The chart in question gives results for similar force applications, not similar control surface deflections. We've argued that chart before. Actual experience by pilots at the time indicated that the best roll rates were from the P47, FW190 and Corsair out of the standard WW2 types. The J and L P38s had better acceleration than the earlier F. As the MkIX continued in service until the end of the war, and the P38F was long replaced by later Lightnings, the comparison to the J/L is valid. Also, note that your quote specifies that is the case 'when both a/c were flying at slow speeds', not as a general rule. You make much of the power improvement at the high boost rate, but I never see those numbers quoted in sources. Could it be that this was something on the same level with methane boosting? Something that would give you extra power in an emergency, at risk of damage to the engine?? One of those reports on the P38 found on the Spitfire site mentioned a few dozen posts ago was on the subject of increased engine power from increased boost levels and use of hight octain fuel. When experimental data doesn't agree with real world experience, there's a reason of some kind. Quite often it's misinterpretation of the data.
 
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larryjcr    RE:Spit XIV vs George - Roll Rates   5/6/2006 3:46:43 AM
To MF: ref roll. I just covered this one. the chart doesn't give practical roll rate, only the rate at a particular control pressure which artifically favors a/c with light controls. The USAAF considered the control forces of the Mustang to be undesirably light as it interferred with accurate gunnery.
 
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larryjcr    RE:Interesting thing on Spit VIII range   5/6/2006 3:51:40 AM
You comment that the Spit VIII carried 80% of the internal fuel of the early Mustang (before installation of the fuselage tank). Quite right, but the P51B-1 had less range than the mid series P47D on internal fuel only.
 
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MustangFlyer    RE:Spit XIV vs George Boost   5/6/2006 3:58:05 AM
25lbs boost was introduced in early 44 with 150 octane for use against the V1s (for Spits, Tempests, Mustangs and Mosquitos). Later 150 octane became available to basically everyone (9th, TAF, etc). All engines could be boosted higher with the higher octane. Boost limits were raised as the fuel became more available and the R2800 and Allison all raised their boost levels in late 44. The Allison tended to spit bottom ends so its boost was more limited. There is a whole section on 150 octane in the Spitfire performance website. Water/methanol injection was first used by the Germans, then for the R2800. Basically it permits higher boost by cooling the cylinders and preventing pre-detonation. This is particularly important for an air cooled engine. The methanol is just an anti-freeze. Most German engines max boost was only allowed with water injection, run out of water and you have to back off. The British never used it and only the (incredible) P-51H used water injection for (at least) 28lbs boost.
 
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MustangFlyer    RE:Spit XIV vs George Roll Rates   5/6/2006 4:12:27 AM
I'm pretty sure that 50lbs was chosen as the max because it was pretty much what a pilot could sustain for a period of time in combat. Think about it, fill a 20 litre jerry can (roughly the same weight), lift up and down 50 times, swing it around as well ;). You could not get max deflection at high speed in virtually any plane in WW2 (P-38L possibly excepted). The loading quickly built up and with manual systems ... I think (from memory) that you could just get about 1/8th deflecton in spit at 400mph, no matter how strong you were. This also applied to rudder and elevator, Clostermann (in his book) talked about having to use his elevator trim tab to get out of a dive (chasing a Me 109 from 40,000ft) because everything froze up. Things got very interesting close to a plane's mach limit. P-47 pilots used to get huge bruises on their legs from the stick whacking from side to side in dives. I know I had to use all my strength (both hands) to hold a P51D in a 400mph dive.
 
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AussieEngineer    RE:Spit XIV vs George   5/6/2006 5:05:08 AM
The quote actually said the Spitfire IX was faster accelerating at all heights, particularly at slow speeds. So in other words it accelerates faster at all speeds, but the difference is most marked at slow speeds(dogfight speeds). The spit in the test was also a Mk IX powered by a Merlin 61, which had a 100 hp less than the Merlin 66 and 500 HP less than the 25lb boosted spits. I take the different view on the NACA tests, I take scientific tests over pilots impressions. As pilot impressions vary wildly.
 
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larryjcr    RE:Spit XIV vs George   5/6/2006 10:39:45 AM
As MF admitted in just prior post, the use of 150 octain fuel and higher boost could be used to improve the performance of ALL a/c, not just the Spitfire, so citing it as an advantage for the MkIX Spit only doesn't 'fly'. Also, I see you're refer to slow speeds as 'dogfight' speeds. That is, you retrun to the claim that a dogfight is just a horizontal turning contest. Open style combat, as usually practiced by the USAAF, and with '47s and '38s in particular, focused on keeping combat speed high! The question of acceleration came up when I stated that the Spitfire was not well suited for use in open 'hit and run' style combat. If the Spitfire pilot gets into a turning contest with a George, his acceleration isn't going to matter -- nor will anything else, for very long!
 
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larryjcr    RE:Spit XIV vs George Roll Rates   5/6/2006 10:47:17 AM
Clostermann is the fellow who claimed that the RAFs kill standards were higher than the USAAFs, when, in fact, they were the same. And, you're talking about his 'impressions' which by your own suggestion, may be 'wildly inaccurate'. Certainly true enough that pull outs from near compressibility made for heavy controls, especially if you lacked recovery flaps. Again, I point out that on the same chart is data for a Bf109 for 66 lbs pressure, so obviously, and increase of at least 1/3 over the 50 lbs used for the rest of the a/c is entirely practical. I continue to believe that you're applying the data in a way that isn't supported by the actual information available. And, by the way, when two pilots, in different a/c are in a rolling contest, and one gets around twice while the other guy hasn't gotten around once yet, that isn't an 'impression', that is an observation.
 
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