Spitfire as a diver

[Gaston]

Do not underestimate the vertical performance of the Spitfire because of the carburator issues which robbed some slight power on negative G even on later models: Except for brief high G turns, it was used mainly as a superior boom and zoom vertical maneuvering fighter and avoided studiously low speed prolonged turning contests... After reading hundreds of combat accounts, I hardly found any accounts where the later Spitfire Mk V and especially the Mk IX was used as a prolonged low-speed turn fighter, and in every instance this happened it was completely at a loss versus the FW-190A (roughly even with the 109F or better than the Me-109G):

-Squadron Leader Alan Deere, (Osprey Spit MkV aces 1941-45, Ch. 3, p. 2: "Never had I seen the Hun stay and fight it out as these Focke-Wulf pilots were doing... In Me-109s the Hun tactic had always followed the same pattern- a quick pass and away, sound tactics against Spitfires and their SUPERIOR TURNING CIRCLE. Not so these 190 pilots: They were full of confidence... We lost 8 to their one that day..."


Vertical fighting was the bread and butter of most Spifire combats, to a more extreme extent than I have encoutered in any other fighter type, especially compared to the horizontal turn obsessed P-47D (which the Germans conceded in captured tests easily ou-turned their Me-109Gs, and this with a needle tip prop...: Source "KG 200: On Special Missions")...

Turn performance was the same by the way between the Mk V and the Mk IX, as tested by the RAE, so the edge they described for the Mk IX was entirely related to using climb, dive and zoom maneuvers, which they did in spades...

The Russains tried to use their Spitfire Mk Vs in turning combat against German aircrafts, and their usual slow turn tactics failed utterly with the Spitfire, so much so they tried to remove the outer 7.7 mm machine guns to improve its maneuverability performance, to no avail.

They then adapted their fighting technique to the Spitfire by using the dive and climb, and immediately met with success after early failures at turn-fighting: Translation: "The Spitfire is particularly adapted to vertical fighting."

"Fana de l'Aviation", no. 496, p.40:

Première citation : " Dans la journée du 29 avril, le régiment effectua 28 sorties pour escorter des bombardiers et des avions d'attaque au sol et 23 en protection de troupes, avec quatre combats aériens. Les premiers jours furent marqués par des échecs dus à une tactique de combat périmée dans le plan horizontal (l'I-16 était remarquablement agile en virage N.D.L.R), alors que le Spitfire était particulièrement adapté au combat dans le plan vertical. Selon A.L. Ivanov qui fit la guerre au sein du 57° Régiment, il était supérieur aux Yak-1 ou La-5."

Deuxième citation : " A basse et moyenne altitude, la version VB était surclassé par les chasseurs allemands et soviétiques de son époque. Pour tenter d'améliorer la maniabilité et la vitesse, les Soviétiques l'allégèrent en retirant les quatre mitrailleuses ainsi que leurs munitions, ne laissant que les canons. Cette variante fut évalué par le centre d'essais des VVS au cours de l'été de 1943. Apparemment ce ne fut pas concluant, car il n'y eu pas d'instructions pour généraliser la modification."

The idea that the Spitfire could not dive equal or better than the Me-109G is just wrong, especially at high altitudes where the Mach limit happened a lot sooner to the Me-109G, and especially so for the later Spitfire models who had very minor carburator negative G power loss issues... It would initially fall slightly behind and then catch up.

For the later Spitfire models, diving/climbing was the main way of fighting...

As for the roll rate, it was about equal on the Mk V to the Me-109G, at 70-80°/sec, but steadily decreased to 60°/sec on one Mk XII wartime chart (probably similar here to the Mk IX), and barely 40-50° on the Mk XIV, regardless of what these Warbirds seem to do today (the aileron problem seems to have been definitely fixed post-war, but the Mk XII chart at 60°/sec seems more indicative of wartime performance, and pilot comments, to me)... Note the NACA 868 roll rate chart is dated 1947, and the Spitfire Mark there is not stated: It could be wartime Spits did a lot better rolling at high altitudes, as has been observed on other types, but NACA 868 specifies 10 000 ft., so it unlikely to be a wartime Spit...

Gaston

 

[Jabberwocky]

As for the roll rate, it was about equal on the Mk V to the Me-109G, at 70-80°/sec, but steadily decreased to 60°/sec on one Mk XII wartime chart (probably similar here to the Mk IX), and barely 40-50° on the Mk XIV, regardless of what these Warbirds seem to do today (the aileron problem seems to have been definitely fixed post-war, but the Mk XII chart at 60°/sec seems more indicative of wartime performance, and pilot comments, to me).

Gaston,

I'll ignore your usual copypasta rubbish as I dont have that much time, but I'll pull you up on this point. The Mk XII roll rate that you keep spouting on about, and have been doing so for years (and equally been corrected on for years), is not a steady state roll rate but TIME TO BANK...

As can clearly be seen here: http://www.spitfireperformance.com/mk12roll.gif

The graph shows the time to transition from 30 degree left bank to 30 degree right bank, and vica versa. At no point does it show a "60°/sec" roll rate. The HIGHEST roll rate is shows is about 50°/sec - for an anti-clockwise roll at 300 mph ASI. The SLOWEST roll rate it shows is about 14.5°/sec, for a clock-wise roll at just under 375 mph ASI.

There is a delay between roll initiation and roll acceleration. An aircraft does not instantly begin rolling at its steady state roll rate...

Secondly, as the graph does not show roll rates below 300 mph ASI, a full picture is not given of the Mk XII's rate of roll at lower speeds and thus your reading of the chart is fundamentally flawed.

NACA 868 shows a Spitfire roll rate peaking at 200 mph, at 150°/sec for a clipped wing version and 105°/sec for full wing version. It lines up exactly with the 1943 RAE test, comparing the roll rates of the Spitfire V with clipped and unclipped wings against the Typhoon, Mustang and FW 190.

You can see the graph here, at an old ubi forums thread: Roll rates | Forums - Page 3

Strange coincidence, huh...

From the same thread, there is this information from Joseph Smith's lectures on the development of the Spitfire, with these data points:

Spitfire V / fabric covered frise ailerons:
90 deg/sec @ 170 mph (lowest speed graphed)
75 deg/sec @ 200 mph
55 deg/sec @ 250 mph
40 deg/sec @ 300 mph
27 deg/sec @ 350 mph
20 deg/sec @ 380 mph (end of graphed values)

Spitfire Mk V / metal covered frise ailerons
85 deg/sec @ 150 mph
105 deg/sec @ 200 mph <----- WOW look at that, it matches the data points too!
90 deg/sec @ 250 mph
75 deg/sec @ 300 mph
60 deg/sec @ 350 mph
40 deg/sec @ 400 mph

Spitfire Mk V / plain ailerons with tabs
65 deg/sec @ 180 mph
75 deg/sec @ 200 mph
95 deg/sec @ 250 mph
118 deg/sec @ 300 mph
90 deg/sec @ 350 mph
70 deg/sec @ 400 mph

" Careful analysis over a long period of time on various marks of Spitfire had revealed fairly wide variations in aileron section and in the position of the ailerons relative to the wings. These differences resulted in inconsistent aileron characteristics, and it was felt that ailerons of a type which would be simple to manufacture and which would be less sensitive to manufacturing tolerances were necessary.

Quantitative data obtained from flight trials on a Spitfire Mark V with plain ailerons fitted with a balance tab had previously indicated that aileron properties comparable with those of a metal-covered Frise type could be achieved, with a reduction in drag due to the elimination of the gap. Ailerons of this type with area increased to 6 per cent of the total wing area, as against 5 per cent on earlier marks, were fitted to the stiffer Mark 21 wing and gave a high rate of roll with reasonable stick forces at high speeds. "

As for the rate of roll diminishing through the marks:

RAE testing of Mk XIV vs P-51

Rate of Roll
36. The advantage tends to be with the Spitfire XIV.


Mk XII vs Mk IX

Manoeuvrability
10........... The manoeuvrability of the Spitifre XII is considered to be excellent. It was compared with the Spitfire IX (R.M. 10 SM engine), also designed as a high performance low-altitude fighter, over which it has an advantage in speed but not in climb, and found to be much better in rate of roll. Above 20,000 feet however, the Spitfire IX with standard wing tips has a better all-round performance and was able to out-manoeurvre the XII. It was unfortunate that in the trials the Spitfire IX was only an average aircraft on controls and was inferior to both of the Mk. XIIs flown. It is considered that when used below 20,000 feet it will be able to out-pace, out-turn and roll as well as the FW.190. The general manoeuvrability for dog-fighting is slightly limited by the fact that the engine cuts under negative acceleration forces.

Mk IX vs 109G

Rate of Roll
21.........Here again the Spitfire has a marked advantage at all speeds.

Mk VIII vs IX

Manoeuvrability

5......... There was nothing to choose between either aircraft as regards turning circles at any height; whether on offensive or defensive manoeuvres neither could make any impression on the other. In rate of roll, however, the Spitfire IX was considerably better especially at low altitude. A number of full rolls through 360 degrees were timed by the same pilot flying each aircraft in turn and although quanitative tests are difficult to produce, it appeared that there was often more than 1.5 seconds superiority for the Mark IX over the Mark VIII. The Mark VIII feels fairly light on the ailerons but at high speeds it becomes very heavy, and so this new combination of extended wing and small aileron cannot be considered satisfactory.

Strangely enough, the Mk VIII reverted to normal ailerons and normal span wings after testing....

Spitfire XIX vs Tempest V

Rate of Roll
36. The Spitfire XIV rolls faster at speeds below 300 mph, but definitely more slowly at speeds greater than 350.00 mph.

 

[Edgar Brooks]

2 The Spitfire is regarded as a single spar aircraft. .

By whom? Certainly not by Supermarine and the RAF (via the newish Haynes Manual,) who both show a "rear spar" in various drawings.

Stringers and a smaller spar to the rear of this D box carried little of the load and served mainly to hang of control surfaces and to finish of the wing. A two spar design would have two large spars with a box formed by the upper and lower skins.

There were no "stringers." The wing had ribs, throughout its entire span, which were attached to both spars, then covered by the top and bottom skins. You have a main spar, with a rigid "D" box attached to its front, ribs attached to its rear, to which is attached a rear spar, all covered with aluminium skins, which were made still thicker, as the war progressed; now, please, find some other hobbyhorse.
An excerpt from a report on a wing twisting test of 1940:-

And this is one of your "stringers," or , as Supermarine titled it RIB 14:-

If you look carefully you'll also find references to "spars" and "rear spar."

 

[tomo pauk]

Thanks for the input, the entries by Edgar Jabberwocky are most helpful.

 

[stona]

Edgar will be familiar with this.

"Each wing comprises a leading edge D spar,a REAR AUXILIARY SPAR and 21 ribs attached to both the D spar and the auxiliary spar.
The front spar,comprising the upper and lower booms and the spar web,together with the thick skin of the wing leading edge,combine to form a D shaped box......

Each wing is attached to the fuselage by seven large bolts.These go through the upper and lower spar booms,joining it to the carry-through stub spars on Frame 5 of the fuselage.
An additional large bolt secures THE REAR SPAR."

Cheers
Steve

 

[fastmongrel]

It says single spar on wikipedia so it must be true I mean when has wikipedia ever got anything completely wrong

 

[Tante Ju]

By whom? Certainly not by Supermarine and the RAF (via the newish Haynes Manual,) who both show a "rear spar" in various drawings.

By this definition every aircraft is a two spar design - you have to hang aileron, flap etc. to somewhere...

 

[tomo pauk]

Not really, IIRC P-40 was having 5 spars, P-47 from 3 to 5 (depending what wing section we talk about).

 

[Siegfried]

It says single spar on wikipedia so it must be true I mean when has wikipedia ever got anything completely wrong

wing | main spar | construction note | 1940 | 0363 | Flight Archive twin spar

This article clearly explains the difference between a single spar and a two spar design. It classifies the Spitifre as a single spar design. The main spar of the Spitfire carries the lifting forces while the D-box of the leading edge carries torsional loads. Anything aft of this is structurally not significant and that includes the so calle rear spar. From a structural point of view the rear spar does not carry any load in normal flight.

 

[Edgar Brooks]

A friend of mine was called a "bastard," by our Production Manager, but I happen to know that his parents were married, when he was born. What something/someone is called isn't necessarily the whole story (or even true.)
If Supermarine (who built the thing, not "Flight" magazine) say that the wing contains two spars, then what gives others the right, 70 years on, to argue?

 

[stona]

I'll stick with Supermarine too. It was the Supermarine Spitfire,not the Flight Magazine Spitfire after all.
Steve

 

[Juha]

I'm with Siegfried in this, the Spit and Bf 109 wings are generally known as single spar wings in spite of the auxiliary spar, the latter was called aux. just because of it wasn't a proper spar and wasn't the rear of a strenght box.

Juha

 

[cimmex]

The Spanish Me109 Buchon had two wing spars to carry the heavy Hispano cannon.
Regards
Cimmex
pics here but you must be registered to see.
http://www.warbirdforum.de/forum/thread.php?threadid=27176&sid=47e659aed64c9597e5fb55f0185c0cb6

 

[riacrato]

I'm with Siegfried in this, the Spit and Bf 109 wings are generally known as single spar wings in spite of the auxiliary spar, the latter was called aux. just because of it wasn't a proper spar and wasn't the rear of a strenght box.

Juha

Exactly. The context is important here.

 

[Edgar Brooks]

I'm with Siegfried in this, the Spit and Bf 109 wings are generally known as single spar wings in spite of the auxiliary spar, the latter was called aux. just because of it wasn't a proper spar and wasn't the rear of a strenght box.

R.J. Mitchell (the designer) called it a rear spar, not an auxiliary; not once, on any of his drawings, will you find the words "auxiliary spar," but, always "rear spar."
According to all of you, we have ribs bolted to a main spar, then bolted to a non-spar (which is rigidly bolted, by three, not a single, bolts to a fuselage former,) all covered by sheets of metal rivetted in place, and it imparts no extra strength to the overall structure. Truly we have myopia taken to a new level.

Exactly. The context is important here.

I'm delighted that you agree.

 

[Gaston]

Gaston,

I'll ignore your usual copypasta rubbish as I dont have that much time, but I'll pull you up on this point. The Mk XII roll rate that you keep spouting on about, and have been doing so for years (and equally been corrected on for years), is not a steady state roll rate but TIME TO BANK...

As can clearly be seen here: http://www.spitfireperformance.com/mk12roll.gif

The graph shows the time to transition from 30 degree left bank to 30 degree right bank, and vica versa. At no point does it show a "60°/sec" roll rate. The HIGHEST roll rate is shows is about 50°/sec - for an anti-clockwise roll at 300 mph ASI. The SLOWEST roll rate it shows is about 14.5°/sec, for a clock-wise roll at just under 375 mph ASI.

There is a delay between roll initiation and roll acceleration. An aircraft does not instantly begin rolling at its steady state roll rate....

Which shows you know little about how they roll: The distinction you are making is actually pretty small on most single engine types unless it was a roll reversal, which it is not...

Secondly, as the graph does not show roll rates below 300 mph ASI, a full picture is not given of the Mk XII's rate of roll at lower speeds and thus your reading of the chart is fundamentally flawed.....

True, but we still can easily extrapolate the rest which points to a non-spectacular result of around 60°/sec, which is exactly what I suggested... And it was still basically a Mk V with a Gryphon engine, for which Mk V we DO have lower speed data, however desperately you want to avoid it...:

NACA on Mk V`s roll rate :

"Measurements of the flying qualities of a Supermarine Sptitife VA airplane." NACA Advanced Confidental Report, by William H. Phillips and Joseph R. Vensel.

The tests were conducted at Langley field, Va., during the period from December 30, 1941 to January 29, 1942. Sixteen flights and apprx. 18 hours flying time were required to complete the tests.

[...]

Desription of the the Supermarine Spitfire airplane

Name and Type : Supermarine Spitfire VA (Air Mininstry No. W3119).
Engine : R-R Merlin XLV
Weight, empty : 4960 lbs
Normal gross weight : 6237 lbs
Weight as flown for tests : 6184 lbs

Ailerons (metal-covered)
Lenght (each) : 6 feet, 10 1/2 inches
Area (total area, each) : 9.45 sq. feet
Balance area (each) : 2.45 square feet



Lateral Stability and Control

Aileron-control characteristics : The effectiveness of the ailerons of the Supermarine Spitfire airplane was determined by recording the rolling velocity produced by abrubtly deflecting the ailerons at various speeds. The aileron angles and stick forces were measured. It should be noted that the airplane tested was equipeed with metal covered ailerons.

[...]

The ailerons were sufficiently effective at low speeds, and were relatively light at small deflections in high speed flight. The forces required to obtain high rolling velocities in high-speed flight were considered excessive.
With a stick force of 30 lbs, full deflection of the ailerons could be obtained at speeds lower than 110 miles per hour. A value of pb/2V of 0.09 radian in left rolls and 0.08 radian in right rolls were obtained with full deflection.

Rolling velocity (at 6000 ft altitude) of about 59 degrees per second could be obtained with 30 lbs stick force at 230 miles per hour indicated speed.

The ailerons were relatively light for small deflections, but the slope of the curve of stick force against deflection increased progressively with deflection, so that about five times as much force was required to fully deflect the ailerons as was needed to reach one-half of the maximum travel. The effectiveness of the ailerons increased almost linearly with deflection all the way up to maximum position. The value of pb/2V obtained for a given ailerons deflection was nearly the same in speeds and conditions tested. It may be concluded, therefore, that there was very little reduction in aileron effectiveness either by separation of flow near minimum speeds or by wing twist at high speed.

Fig 27 shows the aileron deflection, stick force, and helix angle obtained in a series of roll at various speeds intended to represent the maximum rolling velocity that could be readily obtained.

The pilot was able to exert a maximum of about 40 lbs on the stick. With this force, full deflection could be attained only up to about 130 miles per hour. Beyond this speed, the rapid increase in stick force near maximum deflection prevented full motion of the control stick. Only one-half of the available deflection was reached with a 40 lbs stick force at 300 miles per hour, with the result that the pb/2V obtainable at this speed was reduced to 0.04 radian, or one-half that reached at low speeds.

Another method of presenting the results of the aileron-roll measurements is that given in figure 28, where the force for different rolling velocities is plotted as a function of speed. The relatively light forces required to reach small rolling velocities are readily seen from this figure. The excessive forces required to reach high rolling velocities and the impossibility of obtaining maximum aileron deflection much above 140 miles per hour are also illustrated.


From :

STABILITY AND CONTROL SUB-COMMITEE. AERONAUTICAL RESEARCH COMMITEE
Comparision of aileron control charactheristics as determined in Flight Tests of P-36, P-40, 'Spitfire' and 'Hurricane' Pursuit airplanes.

By William H. Philps. N.A.C.A. Confidental Bulletin. 16th November, 1942

[..]

The aileron effectiveness of the various airplanes is compared in the following table on the basis of the response obtained with stick forces of 30 and 5 pounds. A force of 30 lbs is somewhat less than the greatest stick force exerted by the pilot. Repeated flight measurements have shown, however, that this forcer is a reasonable upper limit for manouvering at high speeds. A comparision at a stick force of 5 lbs are also included to bring out a rather interesting fact regarding the order of merit of aileron effectiveness for the various airplanes when very light forces are used :

Rolling velocities obtained with 30 lbs stick force at 230 mph indicated airspeed at 10 000 ft. (deg/sec)

P-36 : 43
P-40 : 90
Hurricane : 64
Spitfire : 63

Rolling velocities obtained with 5 lbs stick force at 230 mph indicated airspeed at 10 000 ft (deg/sec)

P-36 : 9
P-40 : 8
Hurricane : 19
Spitfire : 15



This from Jeff Ethell:

"The elevator is very light, while the rudder is stiff and the ailerons even more so. Every Spitfire I have flown take more muscle to roll than most other fighters. As speed increases, both rudder and ailerons get heavier, creating a curious mismatch at high speeds... on has to handle the almost oversensitive elevators with a light fingertip touch while arm-wrestling the stiff ailerons."

And this if from Alex Heshaw, the Chief pilot of the Castle Bromwhich Spitfire plant. He basically flew hundreds of Spitfires after they left the factory and were tested for airworthyness.

"I loved the Spit, every Marks of it. But I must admit, that altough later Marks were much faster, they were also progressively inferior to previous Marks in manouveribility. When we checked how a Spit behaves during roll, we counted how many complete rolls we could do under a given time. With the Mark II and V, we did 2 1/2 rolls, but the Mark IX was heavier, and only capable of 1 1/2 rolls. The later, more heavier versions could do even less. Designing an aircraft is about finding balance. It`s hardly possible to improve performance without degrading other properties of the aircraft. "

This last quote is particularly noteworthy, because it points to scale of comparison between the Mk V and the various later, heavier marks.

What I think is a true representative value of the Spitfire's roll rate is the RAAF's roll rate chart which pegs the Mk V at a peak of 78°/sec against a fair selection of other aircrafts: The peak was similarly at a very low, below 200 mph, speed, just like many other charts...

If you take the Australian 78° value and substract over one third, as advised by Alex Heshaw, you get the roughly the same 50-55° degree value as in the Spit XII chart... What a coincidence!


Most Me-109 pilots peg the Spitfire as close in roll rate to the Me-109, but the Me-109 got better with speed while the Spitfire got decidedly worse, as the M XII chart show... And no Spitfire pilot ever said it matched closely or even remotely the FW-190A... So that gives an indication of the real roll value range...

It is true today's warbirds show faster roll rates than 80° sec, but maybe the Spitfire ailerons were more affected by actual ammunition load and the weight of the real guns?

Also, as I pointed out earlier, at high altitudes it could be the Spitfire's roll rates got much better in thinner air: This pattern has been shown on other roll rate charts such as that of the P-59 Airacomet...

One Spitfire pilot quote I read long ago did say: "It took more effort to roll it than other aircraft types, and this had to be kept in mind when going up agaisnt the FW-190..."

They did go through considerable testing with the wing tips clipped: Did it bridge the gap with the FW-190A?: One pilot's curt answer: "Hardly."

Ah, the British understatement...

But if you want to indulge in the fantasy of Spitfires closely matching the FW-190A in roll rate, hey, nobody's holding you back! Me, I'm quite taken by Eric Brown-inspired fantasies of vertical fighting against the Spitfire in my FW-190A!

Don't do it while awake though...

Gaston

 

[riacrato]

R.J. Mitchell (the designer) called it a rear spar, not an auxiliary; not once, on any of his drawings, will you find the words "auxiliary spar," but, always "rear spar."
According to all of you, we have ribs bolted to a main spar, then bolted to a non-spar (which is rigidly bolted, by three, not a single, bolts to a fuselage former,) all covered by sheets of metal rivetted in place, and it imparts no extra strength to the overall structure. Truly we have myopia taken to a new level.

I'm delighted that you agree.

You will agree that it is not as simple as what is bolted to what. The question is wheter it is designed structurally to form a torsion box. And afaik it is true that the forward spar and the leading edge form the stress carrying portion of the wing in the case of the Spitfire. Even the excerpt you posted mentions that. Hence it is considered a single spar design from a structural point of view.

But if you find a source saying the Spitfire has a strength box between the first and second spar, I'd be "delighted" to see that.

 

[Jabberwocky]

Gaston, I have all those test documents, you're telling me nothing I didn't already know.

RAE tests of Spitfire rolling velocity were done with 50 lbs of stick force or maximum aileron deflection.

NACA Mk V tests give 59 degrees a second, but on an war weary example that they could only get 40 lbs of stick force out of the aircraft. The roll tests were done at just 30 lbs stick force.

RAAF Mk VB tests during the A6M evaulation were also at 30 lbs of stick force, yet they show 78 deg/second at a speed of just over 150 mph ASI at 10,000 ft. The later Boomerang rolling trials test have exactly the same measurements (see this thread: http://www.ww2aircraft.net/forum/aviation/fighter-best-roll-rate-23223.html for the 'Boomerang' graph)

NACA P-36, P-40, Hurricane, Spitfire tests were done with just 30 lbs of stick force on a Spitfire Mk I with fabric covered ailerons - and still they got 64 degrees a second, a better rate of roll than the Mk VA with metal ailerons...

Nothing you've linked to shows Spitfire roll rates at the same conditions as the RAE tested them. Nothing you've added disproves the RAE's tests that show the Spitfire's lateral control improving thoroughout the war. Nothing you've added disproves the AFDU Tactical trials, which have the Spitfire IX and XIV at roughly approximate roll rates and both better than the P-51 and the 109G.


PS: Its intellectually dishonest to take old (2003 old) posts from ubi.com Il-2 discussion boards and just copy/paste them trying to pass them off as your own. At least have the courtesy and honesty to add a link to the older discussions:


http://forums.ubi.com/showthread.php/14137-Spitfire-roll-rate

Its like deja-vu all over again, only Gaston, you're not half the expert that Barbi/Kurfurst/Isegrim was. At least he actually went out and researched these things.

 

[Siegfried]

You will agree that it is not as simple as what is bolted to what. The question is wheter it is designed structurally to form a torsion box. And afaik it is true that the forward spar and the leading edge form the stress carrying portion of the wing in the case of the Spitfire. Even the excerpt you posted mentions that. Hence it is considered a single spar design from a structural point of view.

But if you find a source saying the Spitfire has a strength box between the first and second spar, I'd be "delighted" to see that.

Immagine a situation in which a Spitifre suffers an impact on the wing leading edge by a 30mm canon shell destroying everything up to but not including the spar.

We can say that the Spitfire wing has lost most of its torsional strength and the pilot would need to be very carefull to avoid high G manouvers.

If the same shell hit the leading edge of a two spar design the overall strenght and torsional rigididy would hardly be effected at all as the leading edge skinning is an insignificant component in terms of structure. I could be covered in cardboard reinforced plastic as it acts as a wind shield only.

 

[Edgar Brooks]

You will agree that it is not as simple as what is bolted to what. .

No, I won't; we're dealing with pure semantics, here. To recap, somebody said that he thinks that he read, somewhere, that the Spitfire might have suffered aileron reversal, but didn't provide any evidence. Another contributor said that this was possible, because the Spitfire had a single spar, thereby implying that the wing, aft of that, was free to twist, which would have reversed the action of the aileron. We know that the Spitfire had a second spar (whether you call it auxiliary [which it wasn't] or rear [which it was] is academic, since it was there.) The rear spar was fixed to the fuselage, which means that it was not free to flap up and down as the wing (allegedly) flexed. If the skin (which was rigidly rivetted or screwed to the underlying ribs [not stringers] ) and spars (both of them) wrinkled by as much as 1/16" (1.5mm) the wing had to be checked, and the attachment bolts checked for bending, which must make the idea (that the wing could flex enough to reverse the aileron direction) questionable, if not completely ludicrous.

The question is wheter it is designed structurally to form a torsion box.

No, it isn't; the question is whether the wing was free to flap up and down enough to negate the action of the ailerons

And afaik it is true that the forward spar and the leading edge form the stress carrying portion of the wing in the case of the Spitfire. Even the excerpt you posted mentions that. Hence it is considered a single spar design from a structural point of view.

How it is considered is immaterial; it's how it was actually built which matters.

But if you find a source saying the Spitfire has a strength box between the first and second spar, I'd be "delighted" to see that

Since Mitchell had a loathing of technical expressions ("It's all balls" was his response,) you'll find only simple words, like "front spar" and "rear spar," which brings us, not-so-neatly, back to square one.