The Zero's Maneuverability

[Reluctant Poster]

The 61 series Merlins were not much different from the 66 series except for the supercharger gearing, it was found the FW190's best performance was right around the low/high gear change so it was changed for the definitive LF version of the MkIX. The carburetor issue was addressed with the Merlin 45 but solved with the pressure carb in 1943.

Actually it was a much improved supercharger. As i posted previously:

The origins of the Merlin 66 and 65 are discussed in "Rolls Royce and the Mustang" by David Birch. These versions of the Merlin were developed at the same time, the 65 for the Mustang and the 66 for the Spitfire. The main difference between them was the propeller reduction ratio (.477 for the 66, .42 for the 65).

Birch quotes a letter of June 24, 1942 from Lovsey to Bulman which discusses the subject of the improved supercharger being developed for the 2 stage Merlin and the plan to lower the supercharger gear ratios concurrently with the introduction of the new supercharger. Since the meeting it references took place on June 10 and since the first FW 190 to be tested by the allies was captured on June 23, the testing story can be discounted. The following quotes are from that letter:

"With reference to your telephone inquiry this morning , in conjunction with the revised supercharger ratios for the improved performance Merlin 61 blower the following points were discussed with DTD during his visit to Derby on June 10th​.

Modifications to the Merlin 61 blower by increasing the diameter of the first stage rotor and changes in the in the rotating guide vane and diffuser have resulted in increasing the full throttle height by approximately 2,000 ft., at the expense of a small reduction of the h. p. at the present all-out boost pressure of 15 lb./sq. in. This blower improvement could, therefore, be used for increasing aircraft performance above the full throttle heights, or by adjustment of the supercharger gear ratios could be used for obtaining a substantial improvement in performance below the full throttle heights, while maintaining the present standard Merlin 61 performance power at full throttle."

This clearly shows that Rolls Royce was thinking about reducing the gear ratios from the beginning. Note that the Spitfire IX with Merlin 61 first went into service around this time

At the time this was going on Rolls Royce was putting Merlins into Mustangs. They proposed using the improved supercharger and the same lower gear ratios for the Mustang.

The following are extracts from a letter to Ellor in Detroit dated, July 1942:

"Proposed Modifications to the Merlin 61 Supercharger and Bendix Carburettor

Since the Merlin 61 was put into production supercharger development has led to several modifications which have resulted in an improved performance.

It seems possible that these modifications might be standardised from the start in America and full details are therefore attached for vour information. Briefly the modifications consist of the adoption of thin vane diffusers in place of the existing wedge vane type, modified circular arc rotating guide vanes and an increase in the first stage rotor diameter from 11.5 ins. to 12.0 ins."

"As a further development of the improved supercharger a set of revised supercharger gears are now being made up (5.78 :1 and 7.06:1 instead of 6.39 and 8.03)."

"The intention is to improve the low altitude performance as much as possible."

 

[Engineman]

The 61 series Merlins were not much different from the 66 series except for the supercharger gearing, it was found the FW190's best performance was right around the low/high gear change so it was changed for the definitive LF version of the MkIX. The carburetor issue was addressed with the Merlin 45 but solved with the pressure carb in 1943.

You are ignoring the timelines and defaulting to later performance. The reality is that there is a lot of development difference between a Merlin 61 and a Merlin 66. Also, until 1944 there was only performance rated on 100/130 fuel which limited the Boost pressure. Apart from this, the Merlin 66 introduced the double 5.5 inch throttles Bendix carb, the previous 60 series versions were limited by the old RR/SU AVT 40 with only double 5.0 inch throttles, some with the RAE restrictor and later with the RAE anti-G modifications.
The limitations to boost on the 100/130 fuel were; M61 15lb, M63 63A 66 18lb. With 100/150 fuel as cleared 1944; M61 M63 M63A 21lb, M66 25lb.
The float carburettor negative G cutting-out was not simply "addressed with the Merlin 45" but was a long and complicated problem. RAE restrictor modification began in early 1941 on all Merlins from the Mk III in service. Modified RAE Anti G carbs were introduced in 1942, and that continued on many Merlin types until after the War. The RR/Bendix pressure carb introduced on the Merlin 66 did not need Anti G modifications.

Eng

 

[PAT303]

You are ignoring the timelines and defaulting to later performance. The reality is that there is a lot of development difference between a Merlin 61 and a Merlin 66. Also, until 1944 there was only performance rated on 100/130 fuel which limited the Boost pressure. Apart from this, the Merlin 66 introduced the double 5.5 inch throttles Bendix carb, the previous 60 series versions were limited by the old RR/SU AVT 40 with only double 5.0 inch throttles, some with the RAE restrictor and later with the RAE anti-G modifications.
The limitations to boost on the 100/130 fuel were; M61 15lb, M63 63A 66 18lb. With 100/150 fuel as cleared 1944; M61 M63 M63A 21lb, M66 25lb.
The float carburettor negative G cutting-out was not simply "addressed with the Merlin 45" but was a long and complicated problem. RAE restrictor modification began in early 1941 on all Merlins from the Mk III in service. Modified RAE Anti G carbs were introduced in 1942, and that continued on many Merlin types until after the War. The RR/Bendix pressure carb introduced on the Merlin 66 did not need Anti G modifications.

Eng

Your arguing about nothing, the FW190 problem was addressed with the MkIX, it wasn't perfect but it gave RAF pilots confidence in dealing with it as well making 190 pilots warry because it is very difficult to tell the difference between the MkV and MkIX from a distance. The Merlin evolved at a fantastic pace during the war, so fast the 61 series was outdated almost as soon as it was put into service.

 

[SaparotRob]

I can't tell the difference between the MkV and a MkIX from a distance of some eighty years.

 

[Greg Boeser]

I can't tell the difference between the MkV and a MkIX from a distance of some eighty years.

It's easy, the MkIX is IV marks better than the MkV.

 

[Thumpalumpacus]

It's easy, the MkIX is IV marks better than the MkV.

Those goddamned Romans and their letters. They should be beaten VI ways to Sunday. And if the jailers don't know what VI is, just let 'em go until we're happy. Goddamned Romans.

 

[GrauGeist]

Those goddamned Romans and their letters. They should be beaten VI ways to Sunday. And if the jailers don't know what VI is, just let 'em go until we're happy. Goddamned Romans.

Just be glad it was Roman and not ancient Greek.

And don't get me started on ancient Sumerian numerals, FFS

 

[Ivan1GFP]

His Fokker Dr.I is basically to the last nut and bolt an exact copy, and it's powered by an original 110 hp Le Rhone so it's as close as it gets.

I suppose his replica also uses the rather poor quality fabric that the originals used?

 

[GrauGeist]

Fokker's fabric was not poor quality and was the same on the DR.I as it was on the D.VII, which was one of the best fighters of WWI.

 

[tyrodtom]

Fokker's fabric was not poor quality and was the same on the DR.I as it was on the D.VII, which was one of the best fighters of WWI.

It was the glue bonds on the wooden wings that Fokker had problems with, especially with the Dr.I.

 

[Engineman]

Your arguing about nothing, the FW190 problem was addressed with the MkIX, it wasn't perfect but it gave RAF pilots confidence in dealing with it as well making 190 pilots warry because it is very difficult to tell the difference between the MkV and MkIX from a distance. The Merlin evolved at a fantastic pace during the war, so fast the 61 series was outdated almost as soon as it was put into service.

No argument, you are comparing Spitfire Mk IX with Merlin 66 25lb boost 1944 performance against the 1941 Fw 190. Further to that, the July 1942 AFDU trial against the captured Fw 190 showed that the 1941 Fw 190 had the edge over the new Spit Mk IX, below 20,000 feet, which was also badly placed with the float carb weaknesses.

Eng

 

[Holtzauge]

I suppose his replica also uses the rather poor quality fabric that the originals used?

Fokker's fabric was not poor quality and was the same on the DR.I as it was on the D.VII, which was one of the best fighters of WWI.

Not sure about the actual quality of the covering, but the lozenge camouflaged pre-printed linen cloth was knowns as "Flugzeugstoff" which literally translates to "aircraft cloth" as I understand it. However, it was not only used by Fokker, but also Albatros and Pfalz used it, and while some say Fokker was in the habit of cutting corners when it came to quality, Pfalz was known for good workmanship. But maybe there were different vendors for Flugzeugstoff? I don't know.

But neither the Germans in WW1, nor Mikael on his scouts, use anything else but clear dope on the Flugzeugstoff, so Mikael does everything in his power to limit the time his planes are exposed outside since every hour in the sun is harsh on the fabric. But in WW1, enemy action or obsolescence probably ended most wings service life long before the sun did. And using this method instead of the Entente's more elaborate paint jobs not only made the Flugzeugstoff-covering cheaper to do, but it also that it weighed less. But for sure, the Fokker Dr.I was not covered in Flugzeugstoff, but natural linen and painted. But the blue and olive streaked factory camo it got was very thin and probably did not do much in terms of UV-protection either.

It was the glue bonds on the wooden wings that Fokker had problems with, especially with the Dr.I.

Yes, it was partly glue bonds, but it was initially also poor workmanship, failure to moisture proof, and that some parts really were too weak in the early production Dr.I's. But after the wing structure was strengthened as mandated by Idflieg (after Gontermann's and Pasteur's crashes), and the quality in Fokker's production line increased, then things did get better. But the problems did not end completely even so due to aerodynamic issues, and wing failures continued to occur, albeit now at a lower rate and not with fatal consequences (e.g. Lothar von Richtofen's Dr.I crash). But all of this is certainly is an interesting story, and I actually dedicate almost a whole chapter about it in my book WW1 Aircraft Performance.

 

[GrauGeist]

The two issues that plagued the DR.I (aside from the engine), was quality control which led to wing failure as well as the upper wing having a higher lift ratio to the lower wings, which in turn amplied the first problem.

 

[Holtzauge]

The two issues that plagued the DR.I (aside from the engine), was quality control which led to wing failure as well as the upper wing having a higher lift ratio to the lower wings, which in turn amplied the first problem.

Yes, the higher lift on the upper wing was what I alluded to as "aerodynamic issues" above. And what they did not understand at the time was that there is something we today call leading edge suction (LES) and the leading edge vortex (LEV). And both these effects come into play at a sudden increases in the angle of attack, such as in a rapid pull-out or sharp turn. And on both the Fokker Dr.I and the Nieuport 28 for example, there were instances where the ribs forward off the spar on the upper wing was torn off forwards and upwards and then carried back over the wing, thus stripping off the upper covering. Also happened on the Fokker D.VII as the lower picture shows. However, on the early Dr.I's, the combination of poor workmanship, moisture effects and too weak structure stripped off everything on the upper wing, only leaving the box spar on the upper wing as can be seen on Gontermann's Dr.I below.

But what they did understand at the time, was that the upper wing did carry a disproportional amount of load. And both British and German structural testing instructions mandated that a higher load be applied to the top wing during structural testing. For example, the British assumed that for a triplane wing equal wing areas on each wing, 40% of the load was carried by the upper wing, 26% by the middle, and 34% by the lower wing. If one on top of this considers that the upper wing on the Fokker Dr.I was larger, then they did actually sand load it decently even at the time. However, what they failed to do at the time, was to take into account LES/LEV effects, and which is why there are pictures showing aircraft with the fabric stripped only on the upper wing even on sturdier aircraft like the Fokker D.VII shown below.

 

[Ivan1GFP]

Fokker's fabric was not poor quality and was the same on the DR.I as it was on the D.VII, which was one of the best fighters of WWI.

The British thought it was quite poor in quality when they examined a captured Eindecker and stated so in their evaluation.

 

[wrathofatlantis]

Three or four quotes out of more than 50,000 combat reports and you come to a conclusion that Spitfire wasn't a good dogfighter? One can find very many more that say the exact opposite,

Cool. Let's hear those anecdotes. I have been looking for 30 straight years, and found nothing but the contrary in actual first hand accounts. And basically zero circle fighting. Brief turns yes, but even one full circle is rare, and by the time you get to two circles it usually ends badly for the Spit.

Yes there are those Russian Mk V and Mk IX turn times in the 18 second range, I'll admit, but altitude loss is stated in those tests, while the speed is not.

The only real world minimum radiuses I have ever seen for Spitfires were the Mark I: 1025 feet, Me-109E: 880 feet, Hurricane: 800 feet (all RAE tests) : Note how this tallies perfectly with the John Weir general statement concerning all 3.

The only other Spitfire radius I have ever seen were just 180s radiuses for the Mk XIV at 400 mph TAS: 1875 feet. P-51D 180 degrees at 400 mph: 1350 feet: Vastly superior (probably with flaps: They could stay down at small angles even at these speeds)...

It could be that this is one case where everyone is wrong, especially since most of the "four quotes" I posted are general statements, in Clostermann's case after completing the RAF's mission record (425 if memory serves) and studying thousands of gun camera films, and giving wartime conferences to fellow pilots on Luftwaffe aircrafts (which I know of no other WWII pilots doing).

When the doctor takes your blood, does he take all your blood?

Another example is even more illustrative: Up even to the 90s the ratings of a TV show are measured with a special "metering panel" attached to fewer than one thousand households for a country of 30 million. That was over a 10 000 to one ratio, with completely credible results for random tv watching behaviour... In the US today statistical sampling is at around 20 000 sets for 121 million homes. That's a 6050 to one ratio. All staticians will tell you the Nielsen ratings are quite accurate (figures range up to 97%), even with a one in 6000 sample.

I have easily read over 500 if not more Spitfire combat encounters. None of them demonstrate the Spitfire can sustain multiple circles against FW-190s or Me-109s. I have seen nothing but vague general statements the Spitfire turns better (which was absolutely true at high altitudes, high speeds, and in the "stalling" snapshot trick I described), including a Johnny Johnson early war statement among them. Then after the War, in a 1946 article, he describes the FW-190A easily out-turning him in multiple circles... Multiple circles is the key here, and what do you think happened between his early War statement and the 1946 article?

Statistically, especially with the lack of counter-examples, this is pretty much like taking a whole liter of blood...

and the Spitfire is renowned as an EXCELLENT dogfighter the world over. If you allowed your airspeed to get down to 200 mph unintentionally, you weren't going to last long in combat, no matter which side you were on. The Bf 109 was excellent below 200 mph and the stall speed was quite low. But, that wasn't the speed you were supposed to use for air combat.

Except that it was even lower than that. Karhila, a 32 kill Finn ace, recommended 160 mph as "optimal" for the Me-109G-6 with gondolas:

virtualpilots.fi: WW2History-KyostiKarhilaEnglish.html

" When the enemy decreased power, I used to throttle back even more. In a high speed the turning radius is wider, using less speed I was able to out-turn him having a shorter turning radius. Then you got the deflection, unless the adversary did not spot me in time and for example banked below me. 250kmh seemed to be the optimal speed."
- Kyösti Karhila, Finnish fighter ace. 32 victories.

To say 200 mph was not the appropriate circle fighting speed speed you have to ignore basically all WWII circle fighting accounts. Turn fighting that went into circle fighting always ended there (or lower).

If you were down low at 200 mph, the gunners on the ground had an easy target. If you were in combat against airplanes, then everyone, even bombers, could disengage and avoid contact with you.

You have to understand circle fighting: Circle fighting not only broke overtaking attacks to the point a single Oscar could survive passes by 16 P-38s for thirty minutes, it also "trapped" your target.

Here's a little engraved baseplate I did to illustrate the point:

"Never reverse your turn."

-Maj. Robert Elder, 24 March 1945 (P-51D): "With this top cover to encourage me, I managed
to out-turn another FW-190, and, just as I was about 30 degrees angle off, this Jerry reversed
his turn (they are stupid that way) and I latched on to his tail at about 100 yards range. I got
strikes all over the plane and he caught fire in the air and crashed."

-Capt. Glendon V. Davis, March 8 1944 (P-51B): "I turned into him and he (lone FW-190A)
swung around, almost getting on the tail of Lt. Smith, following me. I called to him to put down
flaps and turn with him, as I had 20 degrees myself. We went around five or six times with the
issue very much in doubt. I could not quite get enough deflection to nail him, though I was
firing short bursts trying to get him to roll out, which he was too smart to do."

Osprey "VIII Fighter Command at War, -Long Reach-", P. 31 (On the tactical significance
of using the roll rate in combat, Lt. Col. H. C. Craig):
"Once a turn is started in an engagement, it is of the most importance, and safety, to remember
to NEVER reverse your turn. It has been my observation that a great majority of the
victories of my unit were made good when the Hun reversed the turn."


Now you know why they can't "disengage and avoid contact with you"... And yes, turning at 190 mph is basically all the P-47 did in Europe, at least the Razorback...

Again, the term "circle fight isn't used. The term is dogfighting. Everyone in here knows what you mean, but "circle fighting" tags you as likely a rookie in talking about air combat. Just FYI and no more mention of it.

On the contrary I decided to use this term after reading the engagement below (just a one in 6000 "Nielsen rating sample" of how the Zero turned but rarely, if ever, circle fought), because it appropriately distinguishes low speed turning from high speed turning, which most pilots fail to distinguish: The "circling" part is absolutely critical for clarity:



"On October 21, 1943, the Group launched eight aircraft along with four Mustangs from the 530th on a big Japanese supply dump at Kamaing in Burma. The 530th squadron's P-51As met numerous Mitsubishi Zeros when they accompanied B-24s and B-25s on bombing missions. On the way down, I came up behind Lt. Geoffrey Neal, who was chasing a Zero [Mitsubishi A6M] down to the deck! I latched on to their formation and watched as he drove the enemy fighter right into the ground. The pilot of the Zero had tried everything to get rid of Lt. Neal except to circle fight. At this point, Lt. Arasmith had two confirmed kills, but the fight wasn't over…"-311th Fighter Group Unit history

Don't get me wrong. The Fw 190 was a very good airplane with excellent roll authority. It wasn't going to out-turn a Spitfire if both pilots understood they were in a fight. If they were ambushed, like a large percent of aerial victories in the war were, then comparative performance wasn't an issue.

Cheers.

Never found a single instance of a Spitfire gaining on a FW-190A during multiple circles. Johnnie Johnson, Pierre Clostermann (30 FW-190 kills combined between them), John Weir, all disagree with you. I have been looking for 30 years, so I can't wait for the one counter-example...

 

[GregP]

Quote: "Cool. Let's hear those anecdotes."

You might start with:

• Spitfire Pilot: An Extraordinary True Story of Combat in the Battle of Britain, Roger Hall - Amazon
• Spitfire – A Very British Love Story – Jihn Nichol
• Spitfire – Flying the Icon – Jarrod Cotter
• Spitfire Pilot, Davis Cook

Oh wait, I know, try Google! Search for "books about the Supermarine Spitfire." You'll probably find a bunch of books on the Spitfire, too, like I did. I own about 6 - 8 of them.

You are the only person in the last 60 years I ever heard say the Zero and Spitfire can't dogfight. Wing loading alone would make me curious. I'm curious how is it possible you can find obscure quotes to bring forth your contentions above and yet miss the rest of the folklore depicting these two iconic aircraft as premier fighters of their time, especially in the dogfight area. Let's just say there is a lot of opinion out there that runs runs contrary to your contentions and let it go at that.

The guys I know who fly Spitfires today have a universal high regards for it's power-to-weight ratio and it's maneuverability. The Griffon units are very nose-heavy on the ground and take care with ground operations to not nose over with brakes.

There are any number of threads in here about the Spitfire.

Cheers.

 

[GrauGeist]

I have never heard of the term "circle fighting" used before - is that a War Thunder thing?

 

[Holtzauge]

People just don't realize how good Volkswagens are at cornering. Never found a single instance of a F1 Ferrari overtaking a Beetle during multiple laps on an F1 circuit. And I have been looking for 30 years, so I can't wait for the one counter-example...

 

[GrauGeist]

People just don't realize how good Volkswagens are at cornering. Never found a single instance of a F1 Ferrari overtaking a Beetle during multiple laps on an F1 circuit. And I have been looking for 30 years, so I can't wait for the one counter-example...

Depends on what year of VW Bug/Beetle - the early Bugs had a swing-axle rear end with a beam front end and would roll quite easy, the later Beetle (Super Beetle) had a decent suspension, though nothing quite like a BMW 320i did.