Design and properties of the Spitfire Mk. 21+ wing

Shortround6 · May 17, 2024

Fighter or dogfighter?

Ki-43 was one of the absolute best dog fighters up until the end of the war, Problem was the Allies weren't dogfighting anymore, at least in low speed, tight turn way. The Ki-43 could not force the 1944-45 Allied fighters to fight it. They could leave/ignore it and come back later.

The 190 was better able to force the fight. But maybe not by 'dogfighting'.

yulzari · May 18, 2024

Shortround6 said:
You can only adjust so much before things start breaking, and then you need more planes and pilots.
P-40 long nose wing weighed about 150lbs more than a P-36 wing. P-36s and French Hawk 75s were breaking/bending wings at higher than expected rates when landing.

It is a delicate balance.

Happy to be corrected but my memory is that the wing weakness was skin buckling in the air rather than landing issues. The RAF used them operationally for two years in Burma with the last being just into 1944 so they must have been robust enough for them. Perhaps the later Mohawk wings were beefed up?

PAT303 · May 18, 2024

Shortround6 said:
Fighter or dogfighter?

Ki-43 was one of the absolute best dog fighters up until the end of the war, Problem was the Allies weren't dogfighting anymore, at least in low speed, tight turn way. The Ki-43 could not force the 1944-45 Allied fighters to fight it. They could leave/ignore it and come back later.

The 190 was better able to force the fight. But maybe not by 'dogfighting'

The Ki-43 wasn't a great dogfighter because as you have mentioned almost every other fighter could dictate the fight, no pilot flying a 400+mph fighter is going to slow down to 180mph and get into a turning fight with it, the Anton on the other hand could absolutely take on any Allied fighter up to 20,000ft all being equal. The fact that Supermarine developed the MkIX LF and RR the Merlin 66 to counter it proves how potent it was.

spicmart · May 18, 2024

Afaiu the Spitfire was the best dogfighter among the late-war props combined with high speed and best climb rate which make it the best point-defense interceptor as well.
The new wing gave it superb agility at high speed to boot which the previous models were lacking. It had the highest service ceiling even without lengthened wings.
Only the Ta 152H could keep up with it albeit with that (imo awkwardly) long wingspan. Also as a recon plane it was unmatched.
Only its top speed, though sufficient, was somewhat less than other superprops.
I would try and install the Spiteful flat radiator config if this had been possible.

tomo pauk · May 18, 2024

dedalos said:
Still the Fw190 was very very heavy for its size. That wàs Fw s responsibility.

Fw 190 was so heavy because it used a very heavy engine. Engines were not Fw's responsibility.

dedalos said:
If you don't have enough power, then you adjust in order to obtain the desired performance

What do you suggest to be put on the weight reduction? What is the end goal - 100 kg less, 300 kg less, 500 kg less?
What is a desired performance for the Fw 190 in your opinion, and for what time frame?

spicmart · May 18, 2024

Taking Wikipedia as a fast source.

Fw 190D-9:

Empty weight: 3,490 kg (7,694 lb)
Gross weight: 4,270 kg (9,414 lb)
Jumo 213E, dry weight: 1040 kg (2,072 lb)
Jumo 213A, dry weight: 940 kg
Armament: 2 x 42.7 kg + 2 x 16.6 kg = 118.6 kg; Ammo: 90 kg + 38 kg = 128 kg

Spitfire Mk. XIV:

Empty weight: 6,578 lb (2,984 kg)
Gross weight: 7,923 lb (3,594 kg)
Griffon 65: 1,980 lb (898 kg)
Armament: 2 x 49 kg + 2 x 28 kg = 154 kg, Ammo: 43.2 kg + 20 kg = 63.2 kg

With overall dimensions similar the D-9 is a whopping 506 kg heavier in empty weight and 676 kg heavier in gross weight. That's a difference of 170 kg.
The Jumo 213A is 42 kg heavier than the Griffon 65. The armament of the Spitfire 35.4 kg heavier but ammo load 64.8 kg less (I just took the figures from the German weapons weight table to calculate).
So where are the about 100 kg rest difference in gross weight missing? MW50 installation? Fuel tank difference?

The U/C and tailwheels are heavier for the D-9 because of worse TO/landing surfaces and higher loads. Are there any figures for them?

So the empty structure of the D-9 is a LOT heavier despite less bulk of wing than the Spit XIV's and the similar Fiat G.56.

Tank wanted a cavalry horse which turned out to be a pretty good one-on-one fighter nonetheless.

The Ta 152H had enough wing to be a decent dogfighter, the C, though, must have handled/turned like a truck by all foresight.

dedalos · May 19, 2024

tomo pauk said:
Fw 190 was so heavy because it used a very heavy engine. Engines were not Fw's responsibility.

The engine was the main reason. But there were 3 more 1) ease of construction prevented the use of weight saving technics 2) lack of advanced construction alloys 3) the requirement to carry heavy bomb loads resulted in heavy construction and landing gear

tomo pauk said:
What do you suggest to be put on the weight reduction? What is the end goal - 100 kg less, 300 kg less, 500 kg less?reventef

I believe they should create two separate branches of the aircraft 1) the historical multipurpose A/F/G-8 2) a dedicated air superiority branch ,based on Fw190A4, with advanced engines as soon as they become available. This branch should have lighter structure , and any weight saving measure possible.
I would target a normal take off weight of 3500 kgr . In combination with 1.65 ata engine boost and wide corded propeller, in low and middle altitude would be excellent
In high altitudes there s no hope without 2 stage supercharger. External intakes should have been used, to help a little ,but once again production reasons cancelled them.
From such an aircraft I would expect 600km/h at 0m and 680+ km/h at optimum altitude.
With the use of the jumo 213a , I would expect 620km/h at 0m and 700-715 km/h at altitude.

tomo pauk said:
What is a desired performance for the Fw 190 in your opinion, and for what time frame?

The A4 had a top speed of 670 km/h. The following versions had worse performance.
I believe that the dedicated fighter units should have a fw with at least that level of performance and agility. And improve on it with the increased boost pressure after mid 1943.
The A/F/G-8 versions should be used by the cos units, and former zerstorcher units for bomber interception
The historical Fw190A8 was good at many roles, but great at none

tomo pauk · May 20, 2024

dedalos said:
The engine was the main reason. But there were 3 more 1) ease of construction prevented the use of weight saving technics 2) lack of advanced construction alloys 3) the requirement to carry heavy bomb loads resulted in heavy construction and landing gear

At the end, it seems like there is no reason to point out to Fw as the one 'guilty' that the 190 picked up the weight during it's career.
SInce MTT have had the similar, if not same constraint of resources and the Bf 109 ended up as a light aircraft, the construction alloys were as good as any (bar the Japanese 'super aluminium').
As per 1) - what weight saving tecnhiques you have in mind?
As per 3) - when was the requirement to carry heavy bomb loads - was it before Fw 190 materialized, or after the 1st flights?

dedalos said:
I believe they should create two separate branches of the aircraft 1) the historical multipurpose A/F/G-8 2) a dedicated air superiority branch ,based on Fw190A4, with advanced engines as soon as they become available. This branch should have lighter structure , and any weight saving measure possible.
I would target a normal take off weight of 3500 kgr . In combination with 1.65 ata engine boost and wide corded propeller, in low and middle altitude would be excellent

I'm afraid that one should specify the weight savings measures, as well as what should be lightened.
3500 kg is a pretty tall order for the 4000 kg Fw 190A4 to attain, unless we start removing cannons & ammo, as well as protection. Especially with 'advanced engines' wanted.
With the Fw 190, and per what it should be doing in this thread that features the late Griffon Spitfires, lacking the high altitude abilities will not cut it.

dedalos said:
In high altitudes there s no hope without 2 stage supercharger. External intakes should have been used, to help a little ,but once again production reasons cancelled them.
From such an aircraft I would expect 600km/h at 0m and 680+ km/h at optimum altitude.
With the use of the jumo 213a , I would expect 620km/h at 0m and 700-715 km/h at altitude.

Agreed pretty much wrt. the necessity of the engine with the 2-stage S/C. The turboed BMW 801, as on some Ju 388s, would've also been interested.
Optimum altitude for the Spitfire 21 was 5000-7000 ft higher than what will BMW 801 or Jumo 213A provide. Above 25000 ft, there is no advantage for the 190 to be had, even with the tweaks suggested.

dedalos said:
The A4 had a top speed of 670 km/h. The following versions had worse performance.
I believe that the dedicated fighter units should have a fw with at least that level of performance and agility. And improve on it with the increased boost pressure after mid 1943.

Fw lists the earlier 190A3 as having the top speed of 660 km/h. Perhaps 670 km/h was attainable with a pair of cannons removed?
Trick with increased boost of the BMW 801 is that the effects are long gone once above ~6.5 km of altitude. B-17s are flying at 8 km, so are the escorts (when available), and the escorts are far better at these altitudes.

Fw 190 for mid 1943 to mid 44 would've fared far better if the BMW 801E was introduced in mass production, but that was not the case.

Jabberwocky · May 21, 2024

spicmart said:
The Spitfire Mk. 21 introduced a new wing which much improved the fighter's handling and agility at high speeds. Potential aileron reversal would occur at over 1300 km/h.

This would erase the Spitfire's one weakness in a dogfight.

Does that make it the best dogfighting/interceptor plane together with the F8F Bearcat?

Not really. The Mk 21 seems to have been a rather poor dogfighter.

The new wing cured some of the Spitfire's issues with lateral control, but it also brought in other problems with directional stability.

This was most noticeable in the yawing plane, with the aircraft being over sensitive to changes in rudder trim, with a pronounced tendency to slideslip or fly 'crabwise' through the air. This tendency increased with both altitude and speed.

The Mk 21 was also very pitch sensitive. Changes in speed or power resulted in the nose having a tendency to wander about. Changing longitudinal trim started the aircraft yawing. Correcting the yaw out the aircraft back out of longitudinal trim. The nose would also 'corkscrew' as speed built up, particularly above 25,000 ft and in a dive.

When flown against the Mk XIV by the AFDU, the early Spitfire 21s were considered to be a decidedly worse as a dogfighter. According to Peter Caygill, the tests showed the Mk 21 was inferior to the Mk XIV when turning at all speeds and could be "out turned at will". This was because the aircraft became more unstable the harder it turned, which meant the pilots lacked confidence in the aircraft. Test pilots also reported aileron buffeting as the aircraft approached stall speeds, which were already higher than the Mk XIVs.

The Mk 21 was also considered a generally poor gunnery platform, being both unstable and very sensitive to speed and throttle changes.

A partial cure was found in revised control and rudder balance arrangements and changes to the tailplane, although the rudder was still considered overly sensitive at high speed. Even in April 1945 with the revised tail, Geoffrey Quill was reporting that directional stability at high speed wasn't acceptable.

A full fix had to wait for the arrival of the Spiteful type tail and contra-rotating props in the Mk 22 and 24.

spicmart · May 21, 2024

Jabberwocky said:
Not really. The Mk 21 seems to have been a rather poor dogfighter.

The new wing cured some of the Spitfire's issues with lateral control, but it also brought in other problems with directional stability.

This was most noticeable in the yawing plane, with the aircraft being over sensitive to changes in rudder trim, with a pronounced tendency to slideslip or fly 'crabwise' through the air. This tendency increased with both altitude and speed.

The Mk 21 was also very pitch sensitive. Changes in speed or power resulted in the nose having a tendency to wander about. Changing longitudinal trim started the aircraft yawing. Correcting the yaw out the aircraft back out of longitudinal trim. The nose would also 'corkscrew' as speed built up, particularly above 25,000 ft and in a dive.

When flown against the Mk XIV by the AFDU, the early Spitfire 21s were considered to be a decidedly worse as a dogfighter. According to Peter Caygill, the tests showed the Mk 21 was inferior to the Mk XIV when turning at all speeds and could be "out turned at will". This was because the aircraft became more unstable the harder it turned, which meant the pilots lacked confidence in the aircraft. Test pilots also reported aileron buffeting as the aircraft approached stall speeds, which were already higher than the Mk XIVs.

The Mk 21 was also considered a generally poor gunnery platform, being both unstable and very sensitive to speed and throttle changes.

A partial cure was found in revised control and rudder balance arrangements and changes to the tailplane, although the rudder was still considered overly sensitive at high speed. Even in April 1945 with the revised tail, Geoffrey Quill was reporting that directional stability at high speed wasn't acceptable.

A full fix had to wait for the arrival of the Spiteful type tail and contra-rotating props in the Mk 22 and 24.

I included the later marks in the thread title.

PAT303 · May 21, 2024

The later marks were never as nicer handling as the earlier models but 455-460mph with 4 hispano's is fast.

spicmart · May 21, 2024

Jabberwocky said:
Not really. The Mk 21 seems to have been a rather poor dogfighter.

The new wing cured some of the Spitfire's issues with lateral control, but it also brought in other problems with directional stability.

This was most noticeable in the yawing plane, with the aircraft being over sensitive to changes in rudder trim, with a pronounced tendency to slideslip or fly 'crabwise' through the air. This tendency increased with both altitude and speed.

The Mk 21 was also very pitch sensitive. Changes in speed or power resulted in the nose having a tendency to wander about. Changing longitudinal trim started the aircraft yawing. Correcting the yaw out the aircraft back out of longitudinal trim. The nose would also 'corkscrew' as speed built up, particularly above 25,000 ft and in a dive.

When flown against the Mk XIV by the AFDU, the early Spitfire 21s were considered to be a decidedly worse as a dogfighter. According to Peter Caygill, the tests showed the Mk 21 was inferior to the Mk XIV when turning at all speeds and could be "out turned at will". This was because the aircraft became more unstable the harder it turned, which meant the pilots lacked confidence in the aircraft. Test pilots also reported aileron buffeting as the aircraft approached stall speeds, which were already higher than the Mk XIVs.

The Mk 21 was also considered a generally poor gunnery platform, being both unstable and very sensitive to speed and throttle changes.

A partial cure was found in revised control and rudder balance arrangements and changes to the tailplane, although the rudder was still considered overly sensitive at high speed. Even in April 1945 with the revised tail, Geoffrey Quill was reporting that directional stability at high speed wasn't acceptable.

A full fix had to wait for the arrival of the Spiteful type tail and contra-rotating props in the Mk 22 and 24.

They still had the lowest wing-loading of all super-props so they should be able to out-turn them.

And with more than comparably stiffer wings they should/could roll with the best.

The faster the fighters became the less important turning ability got.

PAT303 · May 21, 2024

Jabberwocky said:
A full fix had to wait for the arrival of the Spiteful type tail and contra-rotating props in the Mk 22 and 24.

Not really, a change in the way the controls were set up made the plane easy to fly, from what I understand the controls were over sensitive which caused pilots to over correct inputs and the plane was twitchy.

Shortround6 · May 21, 2024

PAT303 said:
Not really, a change in the way the controls were set up made the plane easy to fly, from what I understand the controls were over sensitive which caused pilots to over correct inputs and the plane was twitchy.

Kind of sounds like a repeat of the Early MK I Spitfires. Those were very twitchy in elevator control.
When you are flyng 75-100mph faster with 75% or more power (torque) and a lot more slipstream from the Prop things can really change.

PAT303 · May 21, 2024

Shortround6 said:
Kind of sounds like a repeat of the Early MK I Spitfires. Those were very twitchy in elevator control.
When you are flyng 75-100mph faster with 75% or more power (torque) and a lot more slipstream from the Prop things can really change.

Going from fabric to metal made a big difference but the problem returned once again in the MkV and MkIX, bob weights and gearing were adjusted but the ultimate fix was reprofiling the elevators, I think it was Jeffery Quill who went into detail about it.

GregP · May 21, 2024

Jabberwocky said:
Not really. The Mk 21 seems to have been a rather poor dogfighter.

The new wing cured some of the Spitfire's issues with lateral control, but it also brought in other problems with directional stability.

This was most noticeable in the yawing plane, with the aircraft being over sensitive to changes in rudder trim, with a pronounced tendency to slideslip or fly 'crabwise' through the air. This tendency increased with both altitude and speed.

The Mk 21 was also very pitch sensitive. Changes in speed or power resulted in the nose having a tendency to wander about. Changing longitudinal trim started the aircraft yawing. Correcting the yaw out the aircraft back out of longitudinal trim. The nose would also 'corkscrew' as speed built up, particularly above 25,000 ft and in a dive.

When flown against the Mk XIV by the AFDU, the early Spitfire 21s were considered to be a decidedly worse as a dogfighter. According to Peter Caygill, the tests showed the Mk 21 was inferior to the Mk XIV when turning at all speeds and could be "out turned at will". This was because the aircraft became more unstable the harder it turned, which meant the pilots lacked confidence in the aircraft. Test pilots also reported aileron buffeting as the aircraft approached stall speeds, which were already higher than the Mk XIVs.

The Mk 21 was also considered a generally poor gunnery platform, being both unstable and very sensitive to speed and throttle changes.

A partial cure was found in revised control and rudder balance arrangements and changes to the tailplane, although the rudder was still considered overly sensitive at high speed. Even in April 1945 with the revised tail, Geoffrey Quill was reporting that directional stability at high speed wasn't acceptable.

A full fix had to wait for the arrival of the Spiteful type tail and contra-rotating props in the Mk 22 and 24.

Never have heard ANY Spitfire described as a "poor gun platform" before. You might have to cite some references for that one to get any traction.

Jabberwocky · May 21, 2024

GregP said:
Never have heard ANY Spitfire described as a "poor gun platform" before. You might have to cite some references for that one to get any traction.

From Ultimate Spitfires by Peter Caygill

p 54

"In simulated air combat the significant improvement made with aileron control on the Spitfire F.21 was nullified by its instability in yaw as it proved difficult to hold the gunsight on target, especially if the other aircraft carried out rapid changes of direction. It was also felt that the aircraft's instability would lead to its deterioration as a sighting platform when it was fitted with a gyro gunsight. Although simulated ground attack could be flown successfully under trial conditions with experienced pilots, it was considered that the F.21's tendency to wander directionally would have been beyond the skills of an average pilot and, as a result, it was unsuitable for the ground attack role."

PAT303 · May 22, 2024

Jabberwocky said:
From Ultimate Spitfires by Peter Caygill

p 54

"In simulated air combat the significant improvement made with aileron control on the Spitfire F.21 was nullified by its instability in yaw as it proved difficult to hold the gunsight on target, especially if the other aircraft carried out rapid changes of direction. It was also felt that the aircraft's instability would lead to its deterioration as a sighting platform when it was fitted with a gyro gunsight. Although simulated ground attack could be flown successfully under trial conditions with experienced pilots, it was considered that the F.21's tendency to wander directionally would have been beyond the skills of an average pilot and, as a result, it was unsuitable for the ground attack role."

Read my above post, once the control linkage leverage/gearing was adjusted to lower their sensitivity the instability went away.

PAT303 · May 22, 2024

The elevators were larger on the 20 series Spitfires which would have added to the handling problem, but like most things it just needed time to be sorted out.

spicmart · May 22, 2024

Talking about very late marks.
They went from the classical supercharger air intake located just a bit behind under the engine to a Mustang-style inlet just right behind under the spinner with the Mk 24, 47 and late Spiteful/Seafang.
How much was the speed gain achieved with this alteration?

Aesthetically it's a guppification/uglification imho.

Design and properties of the Spitfire Mk. 21+ wing

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