Interesting, well first of all, the 12+ lbs boost is effective only up to around 10,000 feet (approx 3300m) and actually im fairly sure Kwiatek ur using Spitfireperformance.com data. The absolute top speed of the Spitfire with DeHavilland constant speed with all up weight including IFF and armour protection, standard mirror and standard cutout on the canopy, for hitting with the small crowbar on the door (increasing drag) was 353 mph at approx 20,000 feet (approx 6,000 m). The performance was rather OVER rated for the mark I once u take into account average performance in the field.
Spitfire Mark I (production)
Horsepower Max Engine Speed Fuel Octane Max Boost Pressure Propeller type Weight
1,030 HP 3,000 rpm at 1,680 m 87 octane fuel + 6 lb boost de Havilland/Rotol 2,600 kg
Spitfire Mark IA (fully modified)
Horsepower Max Engine Speed Fuel Octane Max Boost Pressure Propeller type Weight
1,310 HP 3,000 rpm at 2,700 m 100 octane fuel +12 lb boost de Havilland/Rotol 2,900 kg
Now having dug up some interesting information for you all to dabble.
Note that even Dowding wrote in his reports:
Battle of Britain in the Words of Air Chief Marshal Hugh Dowding
Part 3 - Aircraft and Tactics
By Air Chief Marshal Sir Hugh C. T. Dowding, G.C.B., G.C.V.O., C.M.G., A.D.Cs,
Air Officer Commanding-in-Chief, Fighter Command, Royal Air Force
Despatch submitted to the Secretary of State for Air on August 20th, 1941
I must now give a brief account of the characteristics of the aircraft commonly employed on both sides. As regards the fighter types available in the Command, the bulk of the force consisted of Hurricanes and Spitfires; the former were beginning to be outmoded by their German counterparts. They were comparatively slow and their performance and manoeuvrability were somewhat inadequate at altitudes above 20,000 ft. The Spitfires were equal or superior to anything which the Germans possessed at the beginning of the Battle.
In the a forementioned publication entitled The Battle of Britain, issued by the Air Ministry, the speed of the Hurricane is seriously over-rated at 335 m.p.h. I carried out a series of trials to obtain the absolute and comparative speeds of Hurricanes and Spitfires at optimum heights. Naturally the speeds of individual aircraft varied slightly, but the average speed of six Hurricanes came out at about 305 m.p.h.
The Hurricanes and Spitfires had bullet-proof windscreens and front armour between the top of the engine and the windscreen. They also had rear armour directly behind the pilot, which was previously prepared and fitted as soon as we began to meet the German fighters. The early adoption of armour gave us an initial advantage over the Germans, but they were quick to imitate our methods. While German aircraft remained unarmoured, I think it is now generally agreed that the single-seater multi-gun fighter with fixed guns was the most efficient type which could have been produced for day fighting.
Note that if the Hurricanes performance was detiorating so quickly with use, the Spitfires and 109's would too, but this seems to be more of an issue with the RAF and 336 mph - 305 = 31 mph difference in top speed, such a difference, it can be estimated that at least half of that is from the exterior, but surely some of that is coming from engine wear too i imagine. Either way even the figure of 353 mph top speed seems to be a VERY ROUGH and OPTIMISTIC top speed for the Spitfire of an average aircraft.
“4. Flight Test figures, by themselves, should be treated with considerable reserve, since they may be obtained under non-standard conditions, and the aircraft flown may differ from production machine.”
- Air Ministry document from 29thOctober 1943 details the protocol to use in arriving at performance figures for aircraft
"What did I think of the Spitfire? Every single one was different, with her own characteristics and foibles; if your own was unserviceable and you took somebody else's, you could feel the difference at once. During the war I never wanted to operate in any other type of aircraft; the Spitfire was a darling little aeroplane."
- Flight Lieutenant Raymond Baxter, No 602 Squadron RAF Spitfire pilot
What you also need to know is the German engineering companies including Daimler Benz and Messerschmitt were monitored thoroughly and were the most accurate in performance estimation and trial in the WORLD. They had the largest wind tunnels, capable of reaching speeds in excess of mach 4 during mid / late war and the most advanced technology development of any country for the period. The Finnish report this several times, recognising that of all the variants of aircraft given, only the Messerschmitt Bf 109 and one other American fighter (i believe the Buffalo) actually reached its "official" performance data.
Consider this. And the next quote is from James Holland who released the book "battle of britain" recently:
Since the end of the Battle of Britain, there has been almost endless discussion about the various merits of the fighters involved. Most conclude, however, that, on balance, there was not much in it between the Spitfire Mk I and the Me 109E series.
On paper, the maximum speeds of the two were about the same, while the Spitfire could out-turn an Me 109E, something that has always been viewed as a key attribute in dog-fighting. ‘But who gives a bugger about turning?’ says Tom Neil, a former pilot in 249 Squadron and veteran of the Battle. ‘You don’t need to turn. All you need to do is go like a bat out of hell, catch the other fellow, fire your guns, and disappear. These things the Me 109 did very, very well. It could catch us and it could run away from us, almost at will.’
Tom is quite right. When compared with the either the Spitfire or Hurricane Mk Is, the Me 109E had a superior rate of climb and speed of dive, and most definitely vastly superior firepower. These were the key ingredients to successfully shooting down lots of the enemy in the summer of 1940.
The reason for its superb acceleration was a combination of its supercharger, fuel-injection and electric variable pitch propeller, all of which also contributed to its swift rate of climb. During the first half of the summer of 1940, Me109Es had a far more sophisticated propeller than either Spitfires or Hurricanes, something that was revealed by extensive tests at Farnborough in May and June 1940 on two intact Me109s captured intact in France. Up to this time, British fighters, on the other hand, had two-speed propellers, that is, the angle of their propellers could be varied between just two settings, coarse and fine. Coarse pitch meant its blades were angled so that as it rotated, it would ‘bite’ the air more effectively. At fine pitch, the propeller was at a flatter angle, which allowed the engine revs to be greater, but did not provide as much ‘bite.’ But getting the best from a plane meant striking a balance between performance and fuel consumption in a range of different flying altitudes, speeds and other scenarios such as, for example, diving or climbing. Thus having just two pitch options was somewhat limiting, especially when compared to a variable pitch propeller, which enabled a pilot to maintain a far more varied and subtle use of the interchange between thrust, engine revs and power.
On the back of the Farnborough tests, however, first Spitfires and then Hurricanes were hurriedly converted to De Havilland variable pitch propellers. In an astonishing feat of British production, over a thousand existing, repaired and new-build Spitfires and Hurricanes had been converted by 15 August, which did much to improve their performance during the crucial weeks of the Battle.
This put them on an equal footing with the 109E in only one regard, however. The Me 109’s ability to dive away from any mêlée quickly was largely due to the DB601’s fuel injection, which Spitfires and Hurricanes did not have, nor would not acquire throughout the Battle. Rather, the Merlin engine which powered the British fighters relied on a carburettor. Any sudden dive downwards created negative gravity, or negative-g, which not only pushed the pilot up against his straps, but also forced all the fuel to the top of the float chamber. If the negative-g was maintained, this would cause the carburettor to become flooded with fuel because the float was no longer controlling the fuel flow into the carburettor. This in turn then caused the engine to cut out (called a rich-cut), producing a large puff of black smoke as it did so. This only lasted as long as the duration of the negative-g, and might only take a few seconds, but it was in that moment that an enemy could make good his escape.
This was not an issue for the Me 109 because with its pioneering Bosch fuel injection fuel was pumped into the engine consistently even when under negative-g. It was this feature of the Me 109 that saved Siegfried Bethke’s life on 2 September. A pilot in 2/JG 2, Siegfried had been around 12,000 feet above the eastern edge of London, and escorting bombers, when they were, as expected, attacked by British fighters. In a confused tussle, Siegfried was performing a very steep left turn, and glancing up in his mirror his blood suddenly chilled. Just behind him was a Hurricane with all of its eight machine guns spitting bolts of lightning at him. He knew that the 109 could out-dive the British fighters and that therefore his only chance of escape was by quickly diving away. The Hurricane followed after him, but could not catch up, having lost precious seconds.
The Me 109 also suffered little sideslip when banking, unlike the Spitfire and Hurricane. Sideslip occurred because of the change of airflow caused by the turn, which meant it would literally slide, or drop a bit of altitude. But by keeping this to a minimum, an attacker could keep an enemy aircraft in his sights with greater ease.
It is true that in the Daimler-Benz 601 the Me 109 had a beast of a powerplant, but in addition to its supercharger and airscrew, it was the thrust from this engine combined with superb airframe design and high wing loading that gave the Me 109E such high speed and aggressive handling. Wing loading refers to the weight of the aircraft divided by the area of the wing, and on the Me109E was 32 lb per square foot, while that of the Spitfire Mk I was 25 lb per square foot – in other words, it was much higher on the Me109 than on the Spitfire. This was because the Me 109E had comparatively small wings; the Spitfire had very thin wings, but their elliptical shape gave them quite a large surface area. The advantage of small wings is that speed is created by forward thrust countering drag; thus, the smaller the wings, the less the drag, and this contributed to greater speed.
There is, however, a pay-off for having high wing loading, namely that the aircraft will stall at higher speeds. A stall occurs when the airflow over the wing reaches a stage where it no longer provides lift, at which point the aircraft starts to drop out of the sky. This is not necessarily a problem when operating at height, but it can be when taking off and landing, when the aircraft would be necessarily travelling at low speeds. Inexperienced Me 109 pilots could find taking off particularly difficult because the propeller would be rotating one way, creating enormous torque. This meant that lift was being caused over one of the wings and prop-wash – airflow over the wing caused by the propeller – over the other. This needed to be corrected by use of the rudder and aileron, but if a pilot was not careful, he could over-correct, the aircraft would roll, and he would crash into the ground.
When coming in to land, the high stalling speed was lowered by slats at the front of the wing, which automatically extended from the leading edge of the wings at around 110 mph, and flaps at the back, thus giving the wings greater surface area and preventing the aircraft from stalling. Me109 pilots, however, could use this capability in combat to help them achieve a tighter turn. The theoretically minimum turning circle of the Me 109E was 885 feet, while that of a Spitfire was 696 feet. Any aircraft will lose speed when turning, which is one of the reasons not to turn in the first place when in the middle of a dogfight. However, by pulling back on the stick, and allowing the slats to open an Me 109 could, in fact, out-turn a Spitfire.
In any case, as was revealed by the Farnborough tests, Spitfire and Hurricane pilots were often reluctant to push their aircraft in as tight a turn as possible because they were worried about stalling. A pilot could feel the aircraft nearing the stall as the control column would start to shake; it was what was called ‘pre-stall buffeting’. It was easy to recover an Me 109E from a stall, but this was not always the case with the Hurricane, which, despite being a very forgiving aircraft, could flip over and go into a spin. ‘The Hurricane would always drop a wing,’ says Pete Brothers, a pilot with 32 and 257 Squadrons. ‘It was notorious for it.’ The Spitfire, despite its thoroughbred, silky handling, could also prove a handful if ever pushed to stalling point. Pilots were warned of this in the accompanying Pilot’s Notes. ‘Never attempt a “tail-chase” with an enemy aeroplane having a smaller turning circle than the Spitfire,’ it noted. ‘If stalling incidence is reached, the aeroplane usually does a violent shudder, with a loud “clattering” noise, and comes out of the turn with a violent flick. This would be a serious loss of advantage in a combat.’
Certainly, during the Farnborough tests, the pilots, despite being highly experienced combat and test pilots, were nervous about stalling both the Spitfire and the Hurricane. ‘In a surprisingly large number of cases, however,’ noted the report, ‘the Me 109 succeeded in keeping on the tail of the Spitfire or Hurricane during these turning tests, merely because our pilots would not tighten up the turn sufficiently from fear of stalling and spinning.’ It is interesting that those writing the report felt it necessary to underline this key part of their findings. In other words, what was comparable on paper did not really represent what was happening in the air. The Me 109E, on the other hand, was less likely to flip and spin in a stall, and its high stalling speed could be used by skilled pilots to good effect in combat, because a stall enabled it to lose sudden height very quickly, a useful trick when being pursued.
-As from Dowding in the book the Narrow Margin, the definitive book on the subject
The attitude towards the Me 109 was different. This type was very effective and accounted for most of the losses suffered by Fighter Command during the battle. It was as fast as the Spitfire, considerably faster than the Hurricane and it would out-dive and out-climb either. Its armament was formidable. Half a dozen explosive shells from its cannon could do far more damage than the equivalent length of burst of Browning rounds. On the other hand, the firing rate of the Brownings was much higher, which gave the British pilots a better chance of scoring with a short burst.
At the beginning of the battle the German fighters used their speed to advantage which, coupled with their more recently evolved tactics, played havoc with the antiquated practices of Fighter Command.
British tactics were completely wrong when the Battle began, but steadily improved. Fighter Command squadrons at the outset flew in tidy tight formation, so close that only the leader could see where he was going and what was going on. The other members of the formation concentrated on keeping station.
This was a handover from peacetime. It looked good at an air display but in combat this formation of aircraft is easier to see. The result was that many unsuspecting pilots were ‘bounced’.
Since the battle the importance of the Hurricane to victory has been slowly undermined. The Spitfire tends to hold pride of place to the extent that a fallacy runs the risk of becoming accepted as a historical fact.
There were more Hurricanes in the Battle of Britain than Spitfires. The Hurricane Mk.1, with a constant speed propeller, was a fine fighting aircraft, an excellent gun platform and it was magnificently manoeuvrable up to 20,000 feet. It was extremely strong and could take an extraordinary amount of punishment.
In the winter of 1940 Luftwaffe daylight activity was limited to sneak raids and to fighter sweeps at high altitude, the latter proving very difficult to combat. Squadron leader (now Group Captain retired) H.J. Wilson O.C. Aerodynamics Flight, Experimental Section, Royal Aircraft Establishment (RAE), was put on temporary attachment with No 74 Squadron, Biggin Hill, to study fighter requirements.
In his report Squadron Leader Wilson called for improved cannon armament and more powerful engines etc, particularly for the Spitfire. He concluded with remarks which summarise the whole position as it existed in the Battle of Britain:
“It can hardly be said that the RAF Spitfire squadrons have superior fighting material to the enemy, and it is my considered opinion that the only reason why we are just managing to maintain the balance of fighter power is due entirely to the outstanding flying and leadership of the pilots.”
-Adolf Galland on Bf 109 and Bf 110 versus RAF
“The destroyer (Bf 110) aircraft was born from an accurately recognised shortcoming of the Bf 109 – its restricted range. The modern Vickers Supermarine Spitfires were slower than our planes by about 10 to 15 mph but could perform tighter and steeper turns. The older Hawker Hurricane... compared badly with our Bf 109 as regards speed, and rate of climb. Our armament and ammunition were also undoubtedly better. Another advantage was that our engines had fuel injection pumps instead of carburettors used by the British, and therefore did not conk out through lack of acceleration in critical moments during combat.
The short range of the Bf 109 became more and more of a disadvantage. During a single sortie my group lost 12 fighter planes, not by enemy action but simply because after two hours flying time, the bombers we were escorting had not reached the mainland on their return journey.”[/size]
Luftwaffe comparison flight between Bf 109 E, Bf 110 C, Spitfire, Hurricane and Curtiss (supporting Adolf Gallands claim on inferior top speed of Spitfire)
“In the following the performance- and air combat comparison that has been performed at the E-Stelle Rechlin between Bf 109 E and Bf 110 C and the captured enemy fighters Spitfire, Hurricane and Curtiss shall be brought to acknowledgement. The results of the comparison are to be announced immediately to all Jagd and Zerstörer units under command, to guarantee the appropriate air combat behaviour in the engagements on the basis of technical conditions.
The Bf 109 E type clearly outperforms all foreign planes: Speed: the Spitfire is at 0 m by ca. 20 km/h, at 4 km by ca. 10 km/h, Hurricane and
Curtiss at 0 and 4 km altitude by ca. 60 km/h. A similar superiority of the Bf 109 E exists in the climb performance as well. Climb times to 4 km:
Bf 109 E 4.4 min, Spitfire 5 min, Hurricane 5.6 min, Curtiss 5.2 min.
The plane Bf 110 C is speed-wise inferior to the Spitfire, superior to the Curtiss and Hurricane. Regarding the climb performance is the Curtiss equal at ground level, up to 4 km superior then inferior. Hurricane is inferior up to altitude 2 km, then superior up to 6.5 km. Spitfire is equal at ground level, otherwise superior.
The best climb for Bf 109 E and Bf 110 C is achieved with shallow climb angle and higher speeds than at the enemy fighters. It is wrong to climb away steep or climb behind an enemy fighter with the same angle.
Before turning fights with the Bf 109 E type, it must be noted in every case, that all three foreign planes have significantly smaller turning circles and turning times. An attack on the opponent as well as disengagement can only be accomplished on the basis of existing superiority in performance.
For this the following suggestions are given:
The Spitfire and partly the Hurricane have two-pitch propellers. Climbing away with the Bf 109 and Bf 110 must be done with the best climbing speed or even higher speeds of about 280 – 300 km/h. On aircraft with two-pitch propellers with low blade angle the engine will experience a very high over-revolution, and on the other hand with high blade angle high boost pressure – therefore in other words, performance loss.
-William Green, RAF Sergeant, Hurricane Mk I pilot, 1940 & author of Warplanes of the Second World War (1971)
“By the summer of 1940, five years after its combat debut, it was still superior to any fighter extant, with the possible exception of its principle opponent, the Spitfire, and even this formidable British fighter was at a disadvantage in climbing, diving and in level speeds below 6,000 m. The Bf 109 possessed its share of shortcomings, as indeed, has every warplane ever designed, the advanced features that it presaged demanding certain penalties; penalties widely publicised and greatly exaggerated by the Allies for wartime propaganda purposes.”
- Charlie Brown, RAF Flying Instructor, test flight of restored Me 109 E-4 WN 3579 (Note this is rarely quoted compared to Boscombe Down trial ( i believe this was farnborough trial by RAF)
"I was amazed at how docile the aircraft was and how difficult it was to depart, particularly from manoeuvre - in a level turn there was lots of warning from a wide buffet margin and the aircraft would not depart unless it was out of balance. Once departed the aircraft was recovered easily by centralising the controls. I established a recommended minimum looping speed of 450 km/h and found that the gearing of the propeller control was just right for looping with a little practice it was easy to keep the RPM at 2300 throughout looping manoeuvres. I would not however describe looping as easy. The ailerons were light and extremely effective. The rate of roll is at least 50 % faster than a Mk V Spitfire with full span wingtips. During the VNE dive I achieved an IAS of 660 km/h. The original limit was 750 km/h. I was only limited by the height available, not by any feature of the aircraft which was extremely smooth and stable at 660 km/h."
I took a performance climb at 1.15 ATA and 2300 RPM (30 minute limit). A climb speed of 250 km/h gave an average rate of climb of 2145 ft/min. Bearing in mind the maximum boost limit of 1.35 ATA the "all out" climb must be impressive."[/size]
AS FOR WHY RAE/RAF CANNOT BE TRUSTED (because the engineer responsible had only done a BACHELORS OF SCIENCE (BSc) in damn aeronautics as i found out:
“Such diagrams have been constructed for the Spitfire and Me 109, and are given in Fig. 17, together with an explanation of their use. The turning performance of the Hurricane is probably little different from that of the Spitfire, these aircraft being roughly similar in wing loading and level performance. The “stall boundary" depends on an estimate of CL max, at full throttle. In the case of the Spitfire this has been measured in flight, while the Me 109 figures were based on the Spitfire results; tables of the assumed values of CL max are given in Fig. 17. CL falls off as g is increased, because the stalling speed increases as g gets larger, thus lessening the slipstream effect.”
- RAF Royal Aircraft Establishment (RAE) Farnborough handling trials, Bf.109E Wn: 1304. M.B. Morgan and R. Smelt of the RAE, 1944.
(At Hucknall the propeller was also replaced, a British oxygen system fitted and the rebuilt fighter sprayed in RAF camouflage markings and yellow undersides, receiving the RAF serial DG200. Also delivered to Hucknall on this date were two DB601 engines, the original 64760 and 65134.)
“The parts required for restoration were acquired from Farnborough. Mr Birch had interviewed one man tasked with finding replacement parts who went to Farnborough - and got locked up in the guardroom because nobody told them that a man from Rolls-Royce was coming. When released he obtained two wings, each from a different aircraft, and a tail. Three serviceable propeller blades were secured from various enemy aircraft dumps. Mr Birch collected recollections of other people who worked on the aircraft - its unusual smell and the cannon shell hole up through the base of the pilot's seat (not recorded in official damage report).”
- Letter by David Birch (Aviation News 27 November - 10 December 1987 p.653) giving interesting details of DG200’s time at Hucknall
And as for the elliptical wing of the Spitfire:
“The elliptical planform has a very small theoretical advantage, but only theoretical and only if the planform is truly elliptical. The Spitfire's planform is only approximating elliptical, and what is left has been sold out by the aerodynamic twist its wing has. It has an effect on just one of several factors of wing efficiency, causing a whopping 0.05 improvement in comparison to a trapezoidal planform used in the Bf 109, that is, If the Spitfire’s wing were truly elliptical... (which it is not).
You also have to take into account the fact that the profile thickness ratio of Spitfire’s wing is VERY thin, both in maximum and in average. This in turn leads to the small coefficient of lift. This pretty much takes away the advantage of the large wing area.
By the way, ever wondered where did all the elliptical wings go?
If they are so magically efficient, why is it nobody uses them anymore?
The answer is simple, later aerodynamic research has proven that most of the benefits of elliptical wing were a fallacy created by insufficient or faulty research methods. They simply were not worth the trouble.
Even the developments of Spitfire, Spiteful and Seafang gave up on the elliptic planform and went to normal trapezoid form. Wonder why?
The only thing special in it is the elliptic planform that dropped in favour just after it, when it was found out that the theoretical benefits of elliptic planform were actually only theoretical, and practical applications did not yield benefits that would justify the almost astronomical manufacturing difficulties and costs.
In the Spitfire's case the benefits of elliptic planform (even lift distribution along the span) are nullified by the 2 degree twist (washout) that was needed for at least partially taming the nasty and violent stall behaviour of such a wing. In short, the wing twist negated the effect of the elliptical wing. Although the wing was physically elliptical, its lift was not.
Besides, wing aspect ratio has larger effect on the lift/drag characteristics than the Oswald efficiency factor (where the theoretical difference between Spitfire's and Bf 109's wing is only of magnitude of 0.05), and the Bf 109's wing has a higher aspect ratio than the Spitfire's...
The Spitfire's wing uses the exact same NACA 2300 root profile as the Bf 109's wing, but with only 13 % thickness ratio, while the Bf 109 has 14.2 % thickness ratio. Lower thickness ratio translates to lower Cl max. The Bf 109 uses the same NACA 2300 with thickness ratio of 11%, but the Spitfire's wing profile gradually changes along the span to NACA 2200 (more symmetric profile with smaller Cl max) with thickness ratio of only 9 %.
All the above leaves the lower wing loading as the only even theoretical advantage for Spit's wing, but even that is somewhat negated by wing profile that has less Cl max and Cl in general. “
- Myths of the Elliptical wing’s theoretical advantages as explained by Pentti Kurkinen
