Spitfire as a diver

[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/thr...fb55f0185c0cb6

[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/avi...ate-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...fire-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.

[Edgar Brooks]

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.

Or, lets say that the 30mm shell missed, leaving the Spitfire pilot free to turn his aircraft, using his non-reversing ailerons, and shoot his attacker down.

[riacrato]

Yes Edgar, it is purely academic. If you choose to ignore the fact that the torsion box of the Spitfire wing was formed by the leading edge and the main spar because to you a torsion box is just semantics instead of being basics in wing design and layout, fine. Ignoring proven technical / scientific concepts seems to be the thing these days.

BTW: I never claimed the Spitfire suffered from aileron reversal excessively.

[Tante Ju]

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.

I don't think Spitfire had capacity for actual aileron reversal. However report shown show the aircraft had a very low aileron reversal speed compared to other two spar and even single spar aircraft, in order of 5-600 mph, depending on report. This suggest clear that the wing was more prone to flexing under aileron load, making the question of if it was single spar or two spar design a bit academic. Because of known twisting tendency, it was either a single spar design with load bearing more towards leading edge and so not well situated position to carry twist load (force generated far, at trail edge) - which is I believe is true - or it was an extreme poor executed two spar design which had a rear spar designed into it, but was just not working at all (since it could do little to carry twist loads). Every above suggest the 'rear spar' had no real load bearing capacity, it was what is called an auxilary spar, good to hang things on it, but cannot carry real load.

I believe Mk 21 was considerable imporved for reversal speeds, suggest new wing was better designed.

[stona]

Here's a picture.



That bit labelled 61. We can argue semantics and call it what we like. I'll call it what Supermarine called it...Rear Spar.

Cheers
Steve

[Shortround6]

There are aircraft with two spar wings that do not form a torsion box and there are aircraft with two spar wings that do use a torsion box construction and loading.

It is in the designers intention and construction. The Buffalo used a torsion box. it also used heavier than normal metal skinning between the spars to help form the torsion box. The Potez 230 used a torsion box which interested the Germans in 1940 enough to have them ship the plane back to Germany for further study.

The Hurricane had a two spar wing, I doubt it was a torsion box when fabric covered. Did it become a torsion box in the metal covered version ( there were other changes besides just replacing fabric with metal) ?

If you build a two spar wing and make it a torsion box things like landing gear bays and gun bays have to outside the "box" or have considerable reinforcement around them to carry the loads.

Just like the Spitfire had to be careful about what could be done with the leading edge.

Semantics does count but we also have to KNOW the designers intent and not GUESS from first impressions.