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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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Yimmy    RE:I wander   4/7/2006 7:18:09 PM
...what the implications would have been concerning long range air combat in the war had in-flight refueling been developed. Doubtless there would be issues, such as the big twirly thing at the front of the aircraft cutting the hose, but I am sure such issues could have been worked around. If only I could photoshop, I would create a picture of a Lancaster with a couple of hoses refueling a pair of Mossies....
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larryjcr    RE:Long Range Spit   4/8/2006 11:37:19 AM
To AE. My understanding is that the fuel capacity of the wing was limited by the lack of free space due to internal structure. They would have increased the wing tanks in the MkVIII if they could have. By then the RAF was well aware of how badly the Spitfire's lack of range was handicapping it. The tanks in the MkVIII (17 gal./wing) were only made possible in the redesign of the wing, and results were limited. In the Mk XVIII the wing tanks were increased to 26.5 gal./wing, but that required replacing Mitchell's telescoping wing spar with a newer, stronger unit, manufactured by a newly developed extrusion process. That was not used on later models as the increase of 18 gal.(total) wasn't enough to justify the increased cost of the new type spar. The problem wasn't weight, but the fact that building an elliptical pattern wing on a single spar required very extensive internal structure. That was why the Spitfire was so much more expensive to build than the Mustang, which used a simpler, two spar wing structure, and planform shape. The internal structure was a problem in other ways as well. Besides preventing the consturctuon of a hard point for inward folding landing grear, it interferred with the placement of armament. Even after redesign to allow for cannon, the 20mms couldn't be harmonized for a range as short as the RAF would have liked, because there wasn't enough space in the cannon bays to point them 'in' that far.
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larryjcr    RE:Long Range Spit   4/8/2006 6:56:48 PM
ToMustangFlyer: Yes, the Spits went into Normandy first, but it was out of need, not choice. Spitfires were tasked with CAPing the beach-head against Luft. Fighter-bombers. Due to the Spit's limited range, the time they could spend over the beach-head flying from England was very limited. The only way to deal with the problem was to base them closer as soon as possible, in spite of the added logistical burden on the invasion. Note that the US beaches were CAPed by P38s, which had farther to go, but could stay much longer, and had no need to add to the supply problems. The Spitfire's comparatively low landing speed saved it from a lot of problems, but the landing gear still resulted in a high incidence of opperational losses. That's also the reason that the SeaFire was unpopular with RN pilots. On flight decks the problems were much worse. With the later (and heavier) Spitfires, like the MkXIV, the problem extended to take off. With the high torque of the Griffin, the take off run was greatly extended by the need to open the throttle VERY slowly. The alternative to the extended take off run was either losing control of the a/c, or a vicious ground loop. The problem was that with the narrow landing gear, the pilot had very little 'leverage' to control the torque effect. The Mk XII was by far the worst. Due to the hurry to get them into service, no one seems to have thought about changing the 'bend' in the forward airframe, even though the Griffin turned opposite to the Merlin, so that the torque effect was actually increased by the engine thrust line offset instead of being reduced. The MkXIV was not that bad. It used airframes built for the Griffin, rather than standard MkV and MkVIIIs, but it was still pretty bad. Just recently, I believe, a MkXIV was wrecked -- I think in New Zealand -- because of that problem.
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larryjcr    RE:Long Range Spit   4/8/2006 7:00:30 PM
To MustangFlyer. The rear tank in the Spitfire was much farther from the Cl than the one in the Mustang. While you could do combat maneuvers in a Mustang with the tank half full, the one in the Spit had to be totally empty, or the Cg was too far out. That meant that the tank had to be empty BEFORE the a/c entered airspace where it might encounter the enemy. With the capacity of the main tanks and the leading edge tanks so limited, the rear fuselage tank added little or nothing to what could be done with drop tanks on a combat mission. That's why the RAF never considered it worth while to make it self-sealing -- it was only used for ferry flights.
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MustangFlyer    RE:Long Range Spit   4/8/2006 9:26:20 PM
From Jeffrey Quill's "Spitfire - a test pilot's story' Pasted from (to save me typing it): "This from Jeffrey Quill?s ?Spitfire , a test pilot?s story? Long range escort was the role in which the Merlin Mustang was particularly excellent because of the large load of fuel it was able to carry. True, the Spitfire Mk VIII, in service in 1943, was carrying additional fuel in its wing roots and also in jettosonabale tanks under the fuselage, but it was serving overseas and the problem of accommodating larger loads of fuel in the Spitfire at home was acute. The only available space was in the fuselage behind the pilot, but a tank of significant size there would have a major effect on the centre of gravity. However, it seemed to both Joe Smith and myself that, for the purpose of escorting bomber formations in daylight, a degree of longitudinal stability in the early stages of a sortie would be acceptable. Therefore the fuel in the rear fuel tank could be used for take off and climb and during the early stages of the sortie, the main tanks and wing tanks remaining full. In this case the centre of gravity would be moving forward to an acceptable position by the time the aircraft reached hostile airspace. It was decided therefore to embody a rear fuselage tank in a derivative of the MkXIV shortly due to come into production, the Mk XVIII. In the meantime a 75-gallon tank was fitted in the fuselage of a Mk IX behind the pilot and we also fitted a bob-weight in the elevator circuit, so what with this and the large horn-balance on the elevator we hoped for the best. However the best and most expedient way to test this aeroplane was to fly it a good long way and see how everything worked. So I took off from High Post on Salisbury Plain with all tanks full, carrying a 45-gallon drop tank in addition, and set off at economical cruising boost and RPM in the general direction of Scotland. The weather was unsettled, so I decided to fly at low altitude which was not, of course, a favourable height for optimum air miles per gallon: but I thought that if I could fly a distance equivalent to John o?Groats and back non-stop at that rather unfavourable height, keeping to the east of the Pennines and the Grampians, it would be a useful demonstration. The aeroplane was unstable to start with, but as soon as I had used up the rear fuselage fuel the handling was back to normal and I settled down to a long and enjoyable flight over a great variety of countryside from Salisbury Plan to the Moray Firth and back again, all below 1,000ft. In distance, and not taking into account the various diversions for weather and terrain, it was the equivalent to flying from East Anglia to Berlin and back. It took five hours. This flight demonstrated, if nothing else, that there was no fundamental reason why the Spitfire should not be turned into a long-range escort fighter provided that certain problems could be solved." I agree about the wing, which is why I've said the MkVII could have hit the 400 mile radius, but earlier mks would have been more limited (though still useful). Note that the Mustang also had severe stability problems with a full tank. So much so the Mustang IIIs (the British version of the P51 B/C) had them removed! However good operational practice reduced or elimitated the problem. Operational Procedurew: (1) Take off on main tank (for safety). (2) Switch to rear tank for climb and approach. For the Mustang this meant burning off about one third to one half of the tank to restore stability. (3) Switch to drop tanks and stay on them as long as possible. This weas helped by a layer defense. Shorter range fighters (Spits & P47s) protecting the bombers over France and entry into Germany, saving the Mustangs from having to drop their tanks too soon. (4) Drop tanks and burn off remaining rear tank. (5) Remaining rear/main tanks for combat and return. The reason you couldn't get a Spit up to Mustang range (500 miles) was the need to burn off more of the rear tank (half to 2 thirds), plus less fuel in the main tanks and slightly poorer drag (not a lot at crusing speed, but even a few % adds up). But adding it all up gives a Mk VIII about a 400 mile range, similar to a later P47s, with Mk V/IX about 300 miles, similar to earlier P47s. Again I wouldn't go to far on the U/C issue. Good operational practice helped the swing issue, plus some aerodynamic changes (e.g. larger tails). Sure the later Giffen Spits were a handfull, but they were no worse that Jugs (or probably worst of all the Typhoon). Pilots soon learned to deal with it. Similarly, better operational practice greatly reduced the landing issue for Seafires. Similar to landing/takeoff. In TAF, Spits were usually loaded up with bombs, they managed. Not to say that it was perfect and that there weren't better planes for this, it took good skill
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larryjcr    RE:Long Range Spit   4/9/2006 1:56:37 AM
To MustangFlyer. The problem remained that combat radius of any a/c cannot exceed about 80% of its range on the fuel it can carry into combat (95 gal. in main tanks and 34 in the wing tanks, total of under 130) for a MkVIII (by far the best of the Spits for range, this was 480 miles (maximum even in theory) The only point in the fuselage tank would be if the drop tanks couldn't get you that far. The late model P47D-25RE could fly escort to within sight of Berlin, and did. Even the early 'jugs' could manage a 450 mile combat radius with drop tanks for the trip out (170 gal. for the pre -25s, additional 83 gal.thereafter). Yes, the R-2800 drank more than a Merlin, but that was still nearly twice the usable internal fuel load. For a MkIX, 80% on range on internal fuel that could be carried into combat (95 gal.) was under 350 miles. The Mustang could fight with all internal fuel except about 40 gal. that had to be burned off of the fuselage tank(184 gal. in wing tanks and about 40 more left in fuselage tank for total of @225). One other matter, the RAF pilots who converted to Mustangs from Spitfires all loved the larger pit. It was still very small, compared to a 'bolt, or Lightning, but much larger than that of a Spit. The Spit was cramped enough to seriously reduce pilot effectiveness on a three hour flight. Mustangs, 'bolts and Lightnings regularly exceeded six hours on long escort flights, and occassionally approached 10 to 12. I believe the quote I saw, from an RAF Flt Lt. was that after three hours in a Spit, "one's lower half was well and truly 'seized up.'"
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AussieEngineer    RE:Long Range Spit   4/9/2006 2:43:39 AM
I think you might be underestimating how much drop tanks were used. Most of the time escort fighters had at least half, usually more, of their fuel in drop tanks or apparently combat unusable fuel. G and H P-38s only had 300 gal of internal fuel. On that they only had a range of less than 800 miles, not much better than the range of the MkVIII spit 740 miles. On the long range missions they carried 600 gal of external fuel, 2 300 gallon tanks. P-51s did the same, they carried 75 or 110 gallon tanks plus the 85 gal in the rear tank. I think they also carried 150 gallon tanks in some cases as well. As you can see the MkVIIIs already had a very respectable range, hence their use in the med, middle and far east. With a 30 gal rear fuselage tank they are easily within the range envelope of early P-38s and P-47s. If they had really wanted to they could have removed the 4 .303s(for weight reasons, the guns and cannon were entirely behind the main spar, except for the barrels) and had a fairly sizeable integral tank in the wing leading edge like the PR spits had. Spit VIII data sheet P-38 and P-51 ferry ranges P-38L FOIC
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MustangFlyer    RE:Long Range Spit   4/9/2006 4:38:07 AM
Plus a 75-80 gal (imperial measure) rear tank. Takes the Mk VIII right into later P47/P38 class.
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larryjcr    RE:Long Range Spit   4/9/2006 11:00:07 AM
To AE. It appears that our sources differ. Mine indicate range on internal fuel for the MkVIII as 660 miles (by far the best range of any Mk of Spitfire). Range listings for the P38 differ depending on flight altitude. Best range on internal fuel listed for a P38F is 900 miles at 10K. My source does not list altitude of operation for the given range on Spits, so I assume it is best cruising height (about 10K for most period a/c). While both the P38s (especially earlier models) and the P47s could carry much more fuel externally than internally that didn't help the combat radius, as long as external fuel was enough to get you to the combat area. C/R depended on how much fuel you could actually carry into a fight. For a MkVIII that was what I listed in my earlier post. That was what you had to fight, and fly home afterwards. What you threw away when you jetison partly emptied drop tanks couldn't get you home.
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larryjcr    Spitfire Undercarrige   4/9/2006 3:56:16 PM
I would argue that the worst offender was the Spitfire XII. As bad as any Typhoon, certainly much worse than any of the Thunderbolt. As the MkXII was a crash program for a low level counter to the FW190 harrassment raids. They just shovelled a Griffin into a re-enforced MkV (later ones used MkVIII) airframe with only a slightly enlarged fin and rudder. Trouble was than nobody seems to have thought to change the 'bend'. (the Spit, like nearly all single engine high performance prop a/c has a built in 'bend' that moves the thrust line of the engine one to one and a half or so degrees off the center line of the airframe to help compensate for torque effect on take off) Since the Griffin had a lot more torque, and turned the opposite way compared to the Merlin, the torque effect was amplified instead of compensated for. The RAF built 100 MkXIIs to keep two squadrons operational for a few months. The MkXIV changed the 'bend' and further increased the fin and rudder cord, but it still needed a much longer take off run as the throttle had to be opened VERY slowly. A New Zealander, Sir Tim Wallis, wrecked a MkXIV not long ago, just that way. Appearantly forgot for a moment that he wasn't flying his other Spit (MkXVI, Packard Merlin engine) when he opened the throttle. Charged off the strip out of control into a perimeter fence. Both a/c and pilot seriously injured. The Typhoon's problem was that the rudder had no authority below about 100 mph. to control the torque. If it had a Spit style U/C none of them would ever have gotten off the ground. Thunderbolt had plenty of torque, but nice wide gear, and effective rudder and plenty of weight, and was not a problem to anyone who paid any attention at all. As to the suggestion of dropping the .303s for wing fuel space -- well into 1943 the MkVs were having serious trouble with the 20mms in the tropics due to freezing up. A lot of Japanese a/c escaped with a bunch of rifle caliber holes in them, than should have been kills.
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