FW-190 - How Good Was It, Really?

[GregP]

When they needed more guns than available in the cowling, the Germans went to in-wing or under-wing guns. When they didn't, they seemed to me to prefer fuselage-mounted guns first. The reality could be different, and I am aware that the Fw 190 had wing armament, but putting a wide-chord, 4-blade prop on the Fw 190 would seriously detract from the fuselage gun rate of fire.

 

[Shortround6]

It might. I don't KNOW one way or the other. However the Germans used electric synchronization. Electric currant feed through the bolt ignited an electric primer in the cartridge.
I think the theory was that it allowed tighter control of when the cartridge fired vs mechanical or hydraulic synchronization (which operated a sear that released the firing pin to hit the primer. more "dead time"? or variation?
In any case a DB engine turning 2700rpm and using a 0.53 reduction gear had a prop turing 23.85 rpm per sec while a MG 131 machine gun fired at 15 rounds per second. Or on shot every 1.59 revolutions of the propeller. This seems a bit odd and perhaps the gun fired every 1.66 revs ( between the 5-6 propblade to pass by?) Gun firing speed can vary due to spring tension and temperature so things get screwed up even more which is why positive control of the instant of firing is so important.
With a 20mm cannon the prop might make two full turns for each time the gun fires.

Granted 4 blade props give less "opportunity" but I don't really know if they fired the guns when ever the gun was loaded and space came up between blades or if the gun just fired an a certain spot in the crankshaft rotation. I don't know how the Germans did it but the Allison used synchroniser drives off the camshafts.

 

[pbehn]

It might. I don't KNOW one way or the other. However the Germans used electric synchronization. Electric currant feed through the bolt ignited an electric primer in the cartridge.
I think the theory was that it allowed tighter control of when the cartridge fired vs mechanical or hydraulic synchronization (which operated a sear that released the firing pin to hit the primer. more "dead time"? or variation?
In any case a DB engine turning 2700rpm and using a 0.53 reduction gear had a prop turing 23.85 rpm per sec while a MG 131 machine gun fired at 15 rounds per second. Or on shot every 1.59 revolutions of the propeller. This seems a bit odd and perhaps the gun fired every 1.66 revs ( between the 5-6 propblade to pass by?) Gun firing speed can vary due to spring tension and temperature so things get screwed up even more which is why positive control of the instant of firing is so important.
With a 20mm cannon the prop might make two full turns for each time the gun fires.

Granted 4 blade props give less "opportunity" but I don't really know if they fired the guns when ever the gun was loaded and space came up between blades or if the gun just fired an a certain spot in the crankshaft rotation. I don't know how the Germans did it but the Allison used synchroniser drives off the camshafts.

Why don't they put all the prop blades together to leave more space to shoot through?

 

[nuuumannn]

One thing that everyone here has overlooked with regards to the Fw 190 was how advanced technologically it was. Most of its systems were electrically actuated, which was a major step forward and had been attempted before only in bomber designs (such as the Avro Manchester), by pushing a button. Not to forget the 'Kommandgerat' incorporated into the engine management system, which electrically governed the power output, boost and fuel flow automatically, thus requiring only one lever on the throttle console and negating the need for a separate fuel mixture lever. Propeller pitch was also done electrically by a button on the side of the power lever. This tech was in advance of every other front line fighter in service when the Fw 190A first flew.

It was also maintenance friendly; easy to work on and good access to internal spaces. This is very helpful in the front line, of course.

 

[nuuumannn]

Here is some text from an article I wrote for an aviation magazine some years ago and was published. The article was called 'The RAF's Bogeyman, the Fw 190 Butcher Bird Goes To War'. I won't quote the whole thing, just snippets. Being a general thing, it's not overly long nor detailed, so don't expect too much, but it outlines a little of the Fw 190's early history.

"An Unexpected Arrival

At 8:35 pm on 23 June 1942, Oberleutnant Arnim Faber, Gruppen-Adjutant of III/Jagdgeschwader 2 'Richthofen' inadvertently landed his Fw 190A-3 single-seat fighter at at RAF Pembry in Wales. Having mistaken the Bristol Channel for the English Channel, he followed a reciprocal heading and ended up in enemy hands. The implications of his error immediately dawned on him once Pembry's duty pilot for the day, Sgt Jeffries leaped on the wing of his taxying fighter and waved a Very signal pistol in his face; Faber had just delivered an intact example of the much vaunted Focke Wulf Fw 190 to the British.

This sudden and unexpected arrival was a stroke of good fortune for the RAF, whose fighter squadrons were suffering at the hands of this new Luftwaffe fighter. Since its first combat with Spitfires in September 1941 it was ominously apparent that the German machine was more than a match for the RAF's premier front line fighter; the Fw 190 was superior to the Spitfire Mark V in every respect except turning circle. As one exasperated pilot exclaimed when this quality of the Spitfire was pointed out to him; "turning doesn't win battles!"

Tank's Masterpiece

Conceived by Dipl-Ingenieur Kurt Waldemar Tank in 1937, the Fw 190 was to the Luftwaffe "ein zweites eisen im feuer" – a second iron in the fire to Willi Messerschmitt's famed Bf 109. Widely regarded as one of history's greatest combat aircraft, the Fw 190 saw use in every theatre the Luftwaffe found itself fighting in. A masterful example of the designer's art, it combined pleasing aesthetics with functional simplicity and technical excellence; it was at the time of its development the most advanced fighter in the world. Its principal systems were electrically actuated with the push of an array of button switches, which caused British test pilot Eric 'Winkle' Brown to muse over the fact that the aircraft's designers; "...never had to think in terms of those massive leather flying gauntlets issued as standard to British pilots and guaranteed to convert their hands into bunches of bananas..." At the heart of its engine management system was a device called the Kommandgerät, which combined the functions of altering fuel mixture, boost and RPM into one simple lever, with propeller pitch actuated by a push-button on the side of its handle.

An outstanding trait of the best combat aircraft of the World War Two era was versatility of purpose and the Würger or "Butcher Bird", as Tank named his fighter after a species of shrike, was no exception to this. Tank's intent was to produce a versatile fighter that was easy to build and maintain;

"The Fw 190 was designed to be built by a great number of small sub-assemblers. We designed it with ease of maintenance in mind, plus quick replacement of entire sections. It was a sturdy machine and extremely versatile. Although conceived as a fighter, it did double duty as an attack bomber and, in fact, throughout most of the war, was the only reliable light attack bomber we possessed in numbers."

The decision to power the Fw 190 with a radial engine set it apart from its contemporaries and Tank initially had difficulty convincing technical staff in the Reichsluftfahrtministerium (RLM; German Air Ministry) of the wisdom of his decision;

"When we designed the Focke Wulf 190 in the summer of 1937, there were many in the RLM who believed our fighter had little chance against the concepts then coming from Messerschmitt. But because we chose a radial engine that would not conflict with the short supply of the liquid cooled powerplants earmarked for aircraft then in production, yet one that promised a great deal more horsepower than available at the time, several of our friends in procurement persuaded the technical bureau to give us a chance."

Initially however, the fighter's manufacturers had much difficulty with cooling its tightly cowled 14 cylinder radial engine. On the prototype's first flight on 1 June 1939, Focke Wulf's Chief Test Pilot Flugkapitän Hans Sander described his experience as "...like sitting with both feet in the fireplace", having experienced temperatures as high as 55 degrees Celsius. Both airframe and engine manufacturer blamed the other for the over-heating engines and the decision by the Bayerische Motoren Werk to discontinue production of the under-performing BMW 139 engine almost brought about the promising little fighter's premature demise.

Fortunately for Tank and his team, after a demonstration in front of senior RLM staff, including Reichsmarschall Herman Göring, an order for pre-production airframes was placed in early 1940. Despite the installation of the new 1,660 hp BMW 801 engine, the over-heating issue persisted, even once a cooling fan had been fitted ahead of the engine. Pilots test flying the Fw 190A-0 pre-production aircraft from Rechlin rarely strayed from within eyesight of the airfield and as one witness to the activities of the Erpobungsstaffel (Operational Test Squadron) 190 put it, the fighters flew back and forth, "...smoking and stinking like bees with their backsides on fire." Nevertheless, those that had flown the Fw 190 were convinced of its future by its exceptional performance and pleasant handling characteristics.

The RAF's Bogeyman

With their BMW 801 engines still overheating, the first Fw 190A-1 production models equipped II/JG 26 at Le Bourget, Paris in August 1941. Although impressed with their new fighter's superb control harmony and excellent performance, the former Bf 109 drivers still regarded them with some caution, particularly their tendency to catch fire. Less than a month after re-equipping however, JG 26's Butcher Birds were in action against RAF Spitfires.

The new fighter's ascendency over its enemy began almost immediately, with Luftwaffe units equipping with Fw 190s devising tactics to take full advantage of their superior performance over the Spitfire V. Since the Spitfire's tight turning circle was well known, engaging the British fighter in the horizontal plane was dangerous and to be avoided. With superior dive and climb speed to the Spitfire, the Fw 190 was best flown in the vertical plane, diving upon enemy aircraft from altitude in high speed slashing attacks, followed by zoom climbs back to altitude. Best of all was the Fw 190's ability to out run its opponent, which gave its pilots the advantage of breaking off from combat at will.

With the RAF's first encounter with Fw 190s in September 1941, which were tentatively misidentified in combat reports as a "Curtiss Hawk", Fighter Command's fortunes reached a low ebb; the previous six months of cross-channel operations had seen losses soar to as many as 416 fighters during 20,495 sorties flown. Some 700 enemy aircraft were claimed in that period, but actual Luftwaffe losses were as low as 103 fighters.

Occupying the job of Fighter Command C-in-C since Air Chief Marshal Sir Hugh 'Stuffy' Dowding was ousted after the Battle of Britain, Air Marshal William Sholto Douglas had initiated his squadrons' offensive charges into enemy territory, carrying out 'Circusses' and 'Rhubarbs', quaint code names for luring enemy aircraft into combat by attacking random targets of opportunity on the ground. Despite favourable reports however, losses suffered during these dangerous missions were taking their toll and the RAF was forced into the disagreeable situation of maintaining a more defensive stance by curtailing cross-channel ops. Once the Fw 190 arrived on the scene, the Air Staff issued a Directive on 13 November 1941 halting all RAF operations over northern Europe.

Aircrew morale within Fighter Command plummeted. News of successful enemy action, such as the "Channel Dash" of 12 February 1942, where the Kriegsmarine battleships Scharnhorst and Gneisenau and their destroyer escort steamed brazenly through the English Channel in broad daylight gave them even more reason to fret.

Operation Cerberus-Donnerkeil was the first combined operation the Fw 190 was engaged in. Organisation of air cover was the responsibility of celebrated German fighter leader Oberst Adolf 'Dolfo' Galland, who had relinquished command of JG 26, the first Luftwaffe unit to convert to the new fighter, to become Inspecteur der Jagdflieger (Fighter Pilot Inspector). Paltry attacks by Royal Navy Fairey Swordfish torpedo bombers, gallantly led by Lt Cdr Eugene Esmonde were violently opposed by JG 26's Butcher Birds, whose pilots found themselves frantically pushing buttons to lower flaps and undercarriage to slow their fighters to attack the antiquated biplanes. Sadly, all of Esmonde's charges were shot down and not a single torpedo struck home. Esmonde was posthumously awarded the Victoria Cross for his unfailing courage during the hopeless attack.

"What would be the result if a Merlin 60 was installed in a Spitfire?"

Throughout the first half of 1941, the Spitfire Mk.V fitted with a 1,230 hp single-stage supercharged Rolls Royce Merlin 45 proved a tractable fighter that was believed to be able to counter the new Messerschmitt Bf 109F adequately, despite the latter's superior altitude performance. It was minuted by the Air Staff that, "The aircraft has a superior initial climb and dive to that of the Spitfire, but it is considered that the Spitfire could easily out-turn the Me 109F, especially at high speed.". In practise however, the 'F model Messerschmitt was proving a headache and was largely responsible for the high losses of fighters in the first six months of 1941. The appearance of the Butcher Bird changed attitudes toward Fighter Command's failing cross-channel campaign, however.

Three weeks after the Fw 190 entered service, on 27 September 1941 Spitfire Mk.III N3297 took to the air powered by a new variant of the Merlin engine. The Merlin 60 was originally intended for the Vickers Wellington Mk.VI, a high altitude version of the famous bomber fitted with a pressurised cabin. With two modified single stage blowers coupled together, fitted with an intercooler and mounted on a basic Merlin 45, the new 60 Series offered greater power at height compared to the earlier engine. It was Lord Hives of Rolls-Royce who asked the pertinent question as to whether one could be fitted to a Spitfire.

Following successful trials with N3297, enthusiasm for a production 60 Series Merlin Spitfire was high within the Air Staff, which prompted the Air Ministry's Director of Technical Development Air Cdre Reynell Verney to minute on 6 November 1941;

"I want to recommend to the Air Staff for adopting a new version of the Spitfire engined with the Merlin 61. The airframe is essentially the Spitfire Mk.III. It is essential that the immediate aim would be to transfer all Spitfire production by Supermarine from the Spitfire Mk.V to the new aircraft and production deliveries could begin by mid-1942."

Three new Spitfire variants were immediately investigated by the Boffins at Vickers-Supermarine's. These were the high altitude HF.VII, fitted with extended wing tips and a pressurised cockpit, and the aircraft intended as the next standard production variant, the Spitfire Mk.VIII; essentially a Mk.VII without a pressurised cockpit. The third was the machine prompted by Verney in his minutes to the Air Staff; a stop-gap specifically to counter the Fw 190 by fitting a 1,280 hp Merlin 61 to Mk.V airframes currently occupying Spitfire production lines. This was the Spitfire Mk.IX, which, although intended as an interim until the Mk.VIII entered service, was built in greater numbers than any other Spitfire variant and according to its pilots, was the nicest of all Spitfires to fly."

 

[Ivan1GFP]

They also needed to fire a couple of heavy machine guns through the propeller disc. Using wider three blade propellers to absorb the increasing engine power, rather than increasing the number of blades may have made the armament more effective, and the interrupter system simpler or more reliable.

Gentlemen,
I believe there is a serious misconception about how guns are fired through a propeller arc.
First of all, there is a difference between an "interrupter" and a "synchronizer" mechanism.
The interrupter may have been used in the early days of he Great War, but in general not much later.
It works by "interrupting" the firing cycle of the gun which would be firing free between the propeller blades.
The synchronizer is much different. It triggers the gun to fire. If the gun is ready to fire and if the trigger is pulled, the gun fires.
A typical synchronizer would trigger the gun once in each gap between blades.
For some typical (and simple) numbers, figure that an engine might be turning 2500 RPM with a reduction ratio of 0.500:1 to the propeller.
For a 3 blade propeller that would be 1250 x 3 = 3750 times per minute that the synchronizer would attempt to fire the gun.
We know of course that a typical MG / Cannon cyclic rate is much lower than that, so many times when the synchronizer connects, the gun is not ready to fire.
The reduction in firing rate happens because sometimes the gun IS ready to fire but the synchronizer has not reached the proper position yet.

There are plenty of aeroplanes with synchronized guns and 4 blade propellers, especially in Japanese service. Think N1K1-J and Ki 84.

Part of the reason for picking a propeller with fewer blades might be the belief in the theory that a propeller with more blades is less efficient. As for why the FW 190D had such wide chord propeller blades, one must keep in mind that the JuMo 213 was a fairly high powered engine and turned a relatively small diameter propeller and thus its Propeller Power Coefficient was much higher than most comparable aircraft of the time. In other words, it needed a "high activity factor" propeller to absorb all that torque.

Another factor that I do not believe I have seen mentioned in this discussion thus far is the that often Wing Area and Wing Loading are not telling the entire story. The real factor to consider is Lift Loading: The maximum Coefficient of Lift and shape of the CL graph are quite important and are dependent on the Airfoil selected. (I am sure some of you already know what I will be attempting to describe.)
The Spitfire used a NACA 2200 series airfoil which meant that it had decent lift and gentle stall characteristics but unfortunately also generated more drag than most.
The Yakovlev fighters typically used a Clark-Y with pretty similar characteristics to Spitfire.
The Mustang used a NACA Laminar Flow section (I forget the exact designation) that was excellent for drag but a little lacking in maximum Coefficient of Lift relative to the others.
The FW 190, Hellcat, Corsair and many other WW2 Fighters used a NACA 23000 series airfoil. CL was very good, Drag was fairly low, but the stall was fairly harsh and the center of pressure would tend to move with changes in Angle of Attack
Some of the unfavourable stall charateristics were addressed by using washout to cause the root sections of the wing to stall first so that buffeting would warn the pilot while the wing tips and ailerons still had not stalled.
Some other aircraft took an entirely different approach by using a different airfoil at the root than the one at the tip.
Although the AoA was the same for the entire wing, the airfoil at the root would stall first. The P-38 used such a system.
This description because of its brevity (and my lack of in depth knowledge) is a bit simplified but hopefully gives an idea of other factors besides just wing loading.

- ivan.

 

[GregP]

We all know about CL. Yet the WWII designers were all trying to optimize their pet fighter, and the CLs were often very close. So, wing loading is a good indication of general maneuverability. Doesn't tell the whole story, to be sure, but can serve as a good indicator. If CL didn't matter, then maneuvering flaps and-or slats would not have been effective. But they were.

As for synchronizing guns though a 4-blade prop, the Germans had a VERY wide blade at the cowl arc. A 4-blade would cover a significant portion of the prop arc. Had they employed a more conventional-looking prop (more narrow at the hub), then maybe sure. Even a 5-blade, as in the late Spitfires (with narrow hubs).

Let's look at the MG 151 (15x96). The cyclic rate of fire is 700 rpm, or one every 85.7 msec. The blades pass by, as you said, every 16 msec, so you'd shoot once every 5.36 blades, or between the 5th and 6th blade pass. Unfortunately, the wide-chord hub might seriously interfere with that, causing you to miss that window and have to wait another blade. That's one shot about every 96 msec or so, plus the time to move to empty space. Call it one shot every 100 msec. That's about 10 shots per second in an ideal world and doesn't SEEM like it would affect the cyclic rate much (700 down to 600). The reality was that real gun synchronization rates made it MUCH slower, due to mechanical constraints and spring return rates.

The guns may have been electrically fired, but they weren't computer operated. Solid state components were decades away. It was done with cams and springs that have mechanical constraints. They got really slow with wide chord and more than 3 blades. Since the fuselage guns were the German pilot's primary weapons, that was not acceptable to the pilots or the Luftwaffe. At least, I have heard that.

In the end, I don't care how many blades it had. The Fw 190D was a good fighter. I doubt going to 4 blade would have changed that, but I wasn't making the aircraft buying decisions at the time, either. The real reasons for the decisions at the time are probably lost to time and the death of the people who really knew. All I know for sure is that production Fw 190s had 3-blade props, with experimental models using a 4-blade that was never adopted en masse. I believe the 4-bladers mostly went on the turbocharged units that were not selected for production. There are pics.

Fw 190 V32/U2:

Fw 190c:

The last one doesn't look so wide-chord to me.

 

[alejandro_]

Part of the reason for picking a propeller with fewer blades might be the belief in the theory that a propeller with more blades is less efficient.

I discussed this many years ago in another forum. More blades give an more even distribution of the power, but apparently they perform less well when it comes to compresibility in the blade tips. I never researched the subject more, maybe someone can provide more information.

 

[tomo pauk]

...
The Spitfire used a NACA 2200 series airfoil which meant that it had decent lift and gentle stall characteristics but unfortunately also generated more drag than most.
The Yakovlev fighters typically used a Clark-Y with pretty similar characteristics to Spitfire.

Spitfire used the wing that was 13% thick at the root, it's wing was as of low drag as realistically possible on military aircraft designed in late 1930s. There was several posts and thread here where Spitfire was measured with highest dive speeds for non-jet aircraft.
Things that were slowing down Spitfire were items like external BP glass, not covered U/C, bad carburetor, bad layout of exhust stacks, presence of rear wiev mirror, sometimes sloppy fit and finish. As time went on, those things were rectified. The radiator system was to wait until the advent of Spiteful.
Yakovlev's fighters were small, this is where from the reasonable performance came from. Does not equate with low-drag wing.

 

[pbehn]

Spitfire used the wing that was 13% thick at the root, it's wing was as of low drag as realistically possible on military aircraft designed in late 1930s. There was several posts and thread here where Spitfire was measured with highest dive speeds for non-jet aircraft.
Things that were slowing down Spitfire were items like external BP glass, not covered U/C, bad carburetor, bad layout of exhust stacks, presence of rear wiev mirror, sometimes sloppy fit and finish. As time went on, those things were rectified. The radiator system was to wait until the advent of Spiteful.
Yakovlev's fighters were small, this is where from the reasonable performance came from. Does not equate with low-drag wing.

Great post Tomo but it should be borne in mind that some of these were choices. The original prototype Spitfire had covered wheels, they reverted to covered wheels with the Mk 22. The prototype also didn't have an armoured windscreen, whereas the angle of the windscreen is known to be poor from a drag point of view we must remember you also have to see through it. The mirror was introduced and then removed. The finish of aircraft improved as things progressed but there is a financial and time cost associated, for example flush rivets are better but cost more and take more time. The fit up of panels became increasingly important but this is frequently part of the basic design and system of manufacture.

 

[swampyankee]

I discussed this many years ago in another forum. More blades give an more even distribution of the power, but apparently they perform less well when it comes to compresibility in the blade tips. I never researched the subject more, maybe someone can provide more information.

I used to do prop aero for a division of UTC once called Hamilton Standard. The choice of number of blades has a number of considerations:

• Diameter is set by external factors, like the aircraft's geometry.
• Total blade area -- prop designers use activity factor, which ignores the inner 15% of the blade, and is the integral of (chord divided by diameter) times (r divided by tip rqdius) cuved with respect to r -- is set by thrust. Again, prop designers use a thrust coefficient, which is a dimensionless number.
• Constant speed props operate with large areas stalled during takeoff. This causes high vibratory loads, which dictates blade root dimensions, and minimum blade chord
• Since the induced drag per blade is proportional to the lift squared on that blade, increasing the number of blades reduces the propeller's total induced drag, e.g., going from three to four blades reduces induced drag by 25%.
• Compressibility effects are difficult to quantify as the flow near the blade tips is very three-dimensional. Tip sweep, airfoil thickness, and thickness distribution all affect it. At the time NACA's 66-xxx series airfoils probably had the best behavior at high subsonic Mach numbers
• A prop with more blades will be more expensive, as each blade needs a pitch change bearing, and the general pitch change mechanism will be more complex and costlly
• Narrower chord blades will tend to have poorer damage tolerance

Generally, more blades is aerodynamically better but more expensive, possibly lighter as the individual blades may be lighter, but the parts count is greater and some parts are more complex and more difficult to manufacture, and the prop is less tolerant of FOD and has tighter repair limits.

 

[Ivan1GFP]

Hello GregP,

We all know about CL. Yet the WWII designers were all trying to optimize their pet fighter, and the CLs were often very close. So, wing loading is a good indication of general maneuverability. Doesn't tell the whole story, to be sure, but can serve as a good indicator. If CL didn't matter, then maneuvering flaps and-or slats would not have been effective. But they were.

Many times the CL was close because the majority of designs used the NACA 23000 series airfoils. Of course there will be differences depending on the actual planform and other interference issues.
As an example though, sometimes maximum CL makes a difference: The P-51 Mustang's maximum CL is around 1.45 from the documentation I have seen. As a contrast, the maximum CL for the FW 190 is 1.58 and that difference is not trivial. The maximum CL of the wing on the Me 109 is even higher IIRC.

As for synchronizing guns though a 4-blade prop, the Germans had a VERY wide blade at the cowl arc. A 4-blade would cover a significant portion of the prop arc. Had they employed a more conventional-looking prop (more narrow at the hub), then maybe sure. Even a 5-blade, as in the late Spitfires (with narrow hubs).

Let's look at the MG 151 (15x96). The cyclic rate of fire is 700 rpm, or one every 85.7 msec. The blades pass by, as you said, every 16 msec, so you'd shoot once every 5.36 blades, or between the 5th and 6th blade pass. Unfortunately, the wide-chord hub might seriously interfere with that, causing you to miss that window and have to wait another blade. That's one shot about every 96 msec or so, plus the time to move to empty space. Call it one shot every 100 msec. That's about 10 shots per second in an ideal world and doesn't SEEM like it would affect the cyclic rate much (700 down to 600). The reality was that real gun synchronization rates made it MUCH slower, due to mechanical constraints and spring return rates.

The guns may have been electrically fired, but they weren't computer operated. Solid state components were decades away. It was done with cams and springs that have mechanical constraints. They got really slow with wide chord and more than 3 blades. Since the fuselage guns were the German pilot's primary weapons, that was not acceptable to the pilots or the Luftwaffe. At least, I have heard that..

By my understanding, wide chord or narrow chord blades really does not matter as long as there is enough time between blades so that the gun has time to fire before the next blade arrives. It will only fire ONE shot anyway. If lock time is known to be slow then the adjustment is made to trigger the gun earlier relative to the propeller blade.
The mechanical delays and electrical switching delays, spring rates and other mechanical constraints are what the timing is all about in a manner pretty similar to engine ignition timing.
The only problem is that often the cyclic rate of the gun is not constant. Guns have a tendency to cycle slower for their first shots than for following shots because the first cycle is driven by spring pressure alone while each shot after the first is driven by springs AND by the rebound action of the preceding shot.
With the numbers you are using, 100 milliseconds give 600 rounds per minute and 96 milliseconds gives 625 rounds per minute which sounds about right.
There is of course the slight lag between when the pilot pulls the trigger and when the gun actually fires.
First there is the lock time as I mentioned but there is also the random position of he propeller when the trigger is pulled. It will be somewhere between 0 milliseconds to 16 milliseconds before the propeller is in line to fire for an average delay of 8 milliseconds, but note that this delay only happens once per burst of fire.
Perhaps that is what you were describing?

- Ivan.

 

[Ivan1GFP]

Spitfire used the wing that was 13% thick at the root, it's wing was as of low drag as realistically possible on military aircraft designed in late 1930s. There was several posts and thread here where Spitfire was measured with highest dive speeds for non-jet aircraft.
Things that were slowing down Spitfire were items like external BP glass, not covered U/C, bad carburetor, bad layout of exhust stacks, presence of rear wiev mirror, sometimes sloppy fit and finish. As time went on, those things were rectified. The radiator system was to wait until the advent of Spiteful.
Yakovlev's fighters were small, this is where from the reasonable performance came from. Does not equate with low-drag wing.

Hello Tomo Pauk,
Most of the other fighters of the period used a 15% thickness at the wing root which is not that different. A for low drag, the NACA 2200 series airfoil is not. A high dive speed / critical Mach number does not necessarily mean the wing is low drag.
The Spiteful / Seafang used a laminar flow airfoil and gave up on the wonderful elliptical wing which shows what they thought of the value of the airfoil and wing planform on the Spitfire.
The Clark-Y airfoil used on the Yakovlev fighters is not a low drag airfoil either. It is a fairly high lift airfoil with very benign characteristics.

If you really want to see what can be done with a little (or a lot) of aerodynamic clean up, compare the Lavochkin La-5FN and the La-7.
The two are nearly identical in size weight and have identical engines and yet the La-7 is about 20 MPH faster.

- Ivan.

 

[tomo pauk]

Hello Tomo Pauk,
Most of the other fighters of the period used a 15% thickness at the wing root which is not that different. A for low drag, the NACA 2200 series airfoil is not. A high dive speed / critical Mach number does not necessarily mean the wing is low drag.
The Spiteful / Seafang used a laminar flow airfoil and gave up on the wonderful elliptical wing which shows what they thought of the value of the airfoil and wing planform on the Spitfire.
The Clark-Y airfoil used on the Yakovlev fighters is not a low drag airfoil either. It is a fairly high lift airfoil with very benign characteristics.

If you really want to see what can be done with a little (or a lot) of aerodynamic clean up, compare the Lavochkin La-5FN and the La-7.
The two are nearly identical in size weight and have identical engines and yet the La-7 is about 20 MPH faster.

- Ivan.

The La-5FN, once the wartime emergency passed and fit & finish improved, was clocked at 680 km/h, or same as the La-7.
I never said that NACA 2200 series were low drag airfoils, but that thickness chosen was an excellent move. BTW - the XP-40Q was clocked at 420+ mph, or about as same as the much smaller and lighter Bf 109K-4, so the 2200 was not that draggy either. Granted, new profiles will improve streamlining.
Difference when going from 13% to 15% represents increase of thickness by 15%. The Fw 190 was with a 15.6% thick wing at root - it's thickness to chord ratio was 20% bigger than with Spitfire.
Yakovlev fighters used the Clark YH profile.

 

[DarrenW]

Does anyone have any raw data concerning the FW-190's "military achievements", such as number of sorties flown, aerial victories, losses to both enemy aircraft and ground fire, etc.?

I would be interested in seeing them.....

 

[pbehn]

Does anyone have any raw data concerning the FW-190's "military achievements", such as number of sorties flown, aerial victories, losses to both enemy aircraft and ground fire, etc.?

I would be interested in seeing them.....

There was a report summing up the service of the FW190, it was very brief.

20,000 produced, in service from 1941 to 45, not as good as the F6F.

 

[Greyman]

For what it's worth, another Eric Brown quote - his summation of the Fw 190 from Wings of the Luftwaffe:

"I was to fly the Fw 190 many times and in several varieties ... and each time I was to experience that sense of exhilaration that came from flying an aircraft that one instinctively knew to be a top-notcher, yet, at the same time, demanded handling skill if its high qualities were to be exploited. Just as the Spitfire Mk. IX was probably the most outstanding British fighter to give service in World War II, its Teutonic counterpart is undoubtedly deserving of the same recognition for Germany."

Another from an Air Fighting Development Unit pilot who took part in the trials on Faber's 190:

"With some disappointment, I found that the 190 had already had its black crosses and swastikas replaced by British roundels and a hastily applied coat of RAF camouflage. In the few places that had been missed the beautiful smooth original finish could be felt. The 190 was a perfect example of precise German design and workmanship. Unlike our Spitfires, the panels were so well fitted that they looked like one piece. Ingeniously designed finger-operated locks opened the panels to reveal an engine that had been designed for easy maintenance. To reduce drag, the space between the spinner and the outer cowling was reduced and the turbine impeller on the same axis as the prop, rotating three times as fast, sucked air in to facilitate cooling. It had a wide sturdy undercarriage and cockpit that was a fighter pilot's dream. All engine, undercarriage and flap controls were neatly arranged for fingertip control beside the throttle leaving the right hand free to manoeuvre the airplane and fire the guns. The one-piece perspex top came down half-way to the elbows on either side and gave almost perfect visibility to the sides and the rear."

 

[DerAdlerIstGelandet]

There was a report summing up the service of the FW190, it was very brief.

20,000 produced, in service from 1941 to 45, not as good as the F6F. Inferior to anything with roundel with a star in it.

Fixed for preconceived notional accuracy...

 

[pbehn]

Fixed for preconceived notional accuracy...

I think you misunderstood my point Adler. This whole thread was created to conclude that the FW 190 was inferior to the F6F, purely because of one comparative test quoted on another thread.

 

[DerAdlerIstGelandet]

I think you misunderstood my point Adler. This whole thread was created to conclude that the FW 190 was inferior to the F6F, purely because of one comparative test quoted on another thread.

No I understood your post. I was just adding to it.