BoB after: how would you like to see Spitfire further developed?

wuzak · Feb 16, 2012

Siegfried said:
1: Install a 'Germanic" style annular radiator (used on a tempest prototype) or the Lancaster/Beafighter style power egg installation.

This does three things
a/ it allows Rolls Royce to deliver complete engine/radiator units thus sinplifying installation.
b/ it removes the plumbing though the fueselage and wings and thus allows much more room for fuel in the wings as well as reducing weight.
c/ reduces the length of plumbing and hence battle vulnerabillity.

The Meredith effect on the Spitfire was not a particulary effective implementation.
The effect, which was widely known and understood well before
Meredith published a 'laymens paper'. Hugo Junkers, a Mechanical engineer and a thermodynaics
specialist had a patent on this dating from the 20's.
The Me 109F had a particularly elegant system complete with
boundary layer bypass ducts. The Tempest and Typhoon did not
havw wing radiators and did well without them. AFAIKT
the Ta 152 and FW 190D-9) recovered engine
cooling system waste heat via the radiator: note the cowling flaps
which would allow ejection of the heated air at optimal velocity.

2: Cleanup the underside smoothness of the wings. Its a bloody disgrace down there.

Two problems with the annular radiator. One, they were usually fitted to aircraft that were or could be powered by radials and, two, it would require modifications to the Merlin reduction gear and housing to make space for the radiator on the nose. This would lengthen the forward fusealge noticeably.

The Tempest was designed, from the outset, to take the Centaurus. In the annular radiator installation the Sabre was not very closely cowled.

Not sure that the Merlin XX power egg would have improved performance. It would have been convenient for production.

wuzak · Feb 16, 2012

tomo pauk said:
We could take a look at Hawker - from Typhoon, it took them 2 years to developed a completely new wing for Tempest.

Supermarines weren't Hawkers. And the Typhoon wasn't being made in the same numbers as the Spitfire.

wuzak · Feb 16, 2012

And we know that Supermarines were working on two new wings during the war - to appear in prototype form in late 1944/early 1945.

tomo pauk · Feb 16, 2012

That direct us at the fact that people at Supermarine were convinced that Spitfire could be improved with a better wing. A new wing would inevitably made hiccups in the production, be it in 1943, '44 or '45. With one factory changed after another, starting in winter 1942/43, the new wing would hopefully appear in all Spitfires by the end of 1943.

wuzak · Feb 16, 2012

tomo pauk said:
That direct us at the fact that people at Supermarine were convinced that Spitfire could be improved with a better wing. A new wing would inevitably made hiccups in the production, be it in 1943, '44 or '45. With one factory changed after another, starting in winter 1942/43, the new wing would hopefully appear in all Spitfires by the end of 1943.

Why do you think Supermarines could have got the wing into production a couple of years before they were able to historically?

Not sure they were after a better wing so much as a stronger wing. The Laminar flow wing was, arguably, not as good as the original Spitfire wing.

tomo pauk · Feb 16, 2012

It depends about the timing of the impetus. Even the Spitfire III was featuring a wing different of that of Spit I II. So with design work starting in Autumn of 1940, my take is that service usage by 1943 is no problem.

If you could point me to the good source that would confirm that Spit's original wing was better than a laminar flow wing, that would be cool.

wuzak · Feb 16, 2012

tomo pauk said:
It depends about the timing of the impetus. Even the Spitfire III was featuring a wing different of that of Spit I II. So with design work starting in Autumn of 1940, my take is that service usage by 1943 is no problem.

If you could point me to the good source that would confirm that Spit's original wing was better than a laminar flow wing, that would be cool.

Not necessarily better than "a" laminar flow wing, but certainly regarded better than the Supermarine laminar flow wing.

No doubt the Spiteful was fast, but I don't believe it handled as well as the Spitfire.

Shortround6 · Feb 16, 2012

tomo pauk said:
It depends about the timing of the impetus. Even the Spitfire III was featuring a wing different of that of Spit I II. So with design work starting in Autumn of 1940, my take is that service usage by 1943 is no problem.

If you could point me to the good source that would confirm that Spit's original wing was better than a laminar flow wing, that would be cool.

I believe the Spit III wing was just clipped but I could be wrong. As far as the "Spit's original wing was better than a laminar flow wing", it might depend on what you are measuring. as it turned out the original wing did have a rather high mach number limit. A gentile, predictable stall helps pilots (especially lower time pilots) fly closer to the limits and reduces landing accidents. Getting laminar flow wings to actually work turned out to be a lot harder than they thought, even the thickness of the paint used to apply the national insignia disrupted the laminar flow. The difference between the wings may actually be due to the airfoil profiles used rather than actual laminar flow.

Edgar Brooks · Feb 17, 2012

tomo pauk said:
That direct us at the fact that people at Supermarine were convinced that Spitfire could be improved with a better wing./QUOTE]
Stronger, yes, but better? The shape remained elliptical, with just a wider centre section/ tracking, and shortened wingtips. There seems to be a collective memory fade, regarding the 21; it had a new wing, both in its construction, and load-carrying/aerodynamic capabilities

A new wing would inevitably made hiccups in the production, be it in 1943, '44 or '45. With one factory changed after another, starting in winter 1942/43, the new wing would hopefully appear in all Spitfires by the end of 1943

Click to expand...

It did; the prototype flew in January 1944. As it was to be exclusive to Griffon engines, production was planned for Eastleigh (Spitfire 21, 22 24,) and Westland (Seafire 45, 46 47.) Castle Bromwich remained a Merlin unit, concentrating on the IX XVI.
"New wing" does not inevitably = laminar flow; the Spiteful Seafang were viewed as new aircraft, not just extensions of the Spitfire. The Spiteful was not just a Spitfire XIV + laminar-flow wing; check on the cockpit layout, to view the differences.
The Spitfire III wing was not a new wing, either; it was the same shape, with the same two spars, same leading-edge "D-box," same washout, and same aerofoil section. All that happened was some rejigging of the internal structures, to (theoretically) enable various combinations of 8 guns to be carried. This is why it was called the "universal wing," but it was exactly the same as the earlier wing, in all but a few minutiae.

tomo pauk · Feb 17, 2012

Hi, wuzak,
Thanks for clearing your point re. laminar wing Spitfire.
The Spiteful did featured also a considerably smaller wing area, so it's not a surprise if it's handling was worse than Griffon Spitfires, let alone Merlin Spitfires.

Hi, SR6,

Yes, the figures about dive speed limits (kindly provided by Glider in another thread) clearly put Spitfire in a league above Bf-109, P-47 P-38. The pilots of RAF were pretty experienced by 1943, so I guess they would not have any more issues than the ones flying Mustangs (that was also a heavier plane).

Hi, Edgar,

No memory fade about the wing of Spit 21; the only thing that is 'bad' with that wing was timing. Of course, I do not see Spiteful as just another Spitfire.

Gixxerman · Feb 17, 2012

My answer is of course range.
It was all the Spit lacked really.....and as has been said given the UK's priorities it is completely understandable that the UK chose to concentrate on bombers straight after the BoB.

Siegfried · Feb 17, 2012

tomo pauk said:
Yes, the figures about dive speed limits (kindly provided by Glider in another thread) clearly put Spitfire in a league above Bf-109, P-47 P-38. The pilots of RAF were pretty experienced by 1943, so I guess they would not have any more issues than the ones flying Mustangs (that was also a heavier plane).
.

It's questionable to me as to how significant this was in combat: intitial dive acceleration of the Spitifre was slower than the Me 109/FW 190 though it would speed up latter on in the dive. Me 109 dive performance improved considerably with the replacement of the horn balanced rudder with a tall tail and a balance tab: the earlier Me 109 was Mach limited by rudder overbalancing, not Mach tuck. The improvement was to the point that P-51D pilots reported being outdived by Me 109's; the P-51's dive speed being a very high dive speed indeed. The famous Mach 0.9 dives of the Spitifre were test dives with special propellors and resulted in airframe damage. Note also possibillity of other problems of the Pre mk 20 series Spitifires: aileron reversal a high speed. I wouldn't say that the Spitfire was in a league of its own at all when all factors considered.

Milosh · Feb 17, 2012

Flying Limitations of the Spitfire IX (from Pilot's Notes)
Maximum speeds in m.p.h I.A.S.
Diving (without external stores), corresponding to a Mach No. of - .85:

Between S.L. and 20,000 ft. - 450
20,000 and 25,000 ft. - 430
25,000 and 30,000 ft. - 390
30,000 and 35,000 ft. - 340
Above ..................35,000 ft. - 310

The maximum permissible indicated airspeeds in the different heights are not being observed and are widely exceeded. On the basis of evidence which is now available the speed limitations ordered by teleprint message GL/6 No. 2428/41 of 10.6.41 are cancelled and replaced by the following data:

Up to 3 km (9,842 ft.) 750 km/h. (466 m.p.h.)
At 5 km (16,404 ft) 700 km/h. (435 m.p.h.)
At 7 km (22,965 ft) 575 km/h. (357 m.p.h.)
At 9 km (29,527 ft) 450 km/h. (280 m.p.h.)
At 11 km (36,089 ft) 400 km/h. (248 m.p.h.)

Except below 10,000' I don't see the Bf109 being faster in a dive.

Spitfire Mk IX versus Me 109 G - Flight Testing

Afiak, the Bf109K-4 had the same limitations.

Siegfried · Feb 17, 2012

Supermarine did experiment with reprofiled, laminar flow ellipitical wings, prior to the Spitefull wings. They were not a success.

The Spitifre used NACA 4 digit airfoils which had been developed by Eastman Jacobs of the NACA. These profiles had a fairly blunt stall curve ie a plot of Cl versus angle of attack would show a smooth curve.

The NACA 4 digit series were latter replaced in many aircraft with the NACA 5 digit series, also designed by Jacobs, in which systematic variation of the leading edges of the 4 digit series priduced higher lift coefficients. (FW 190, Corsair and Hellcat used these, with the latter having good stall characteristics) however the 4 digit series did however produced a slightly more progressive stall.

The NACA laminar flow profile series were also designed by Eastman Jacobs; the idea being to let the pressure build up progressively at a carefully designed rate over a wing leading edge
whose peak thickness was around 50% of chord instead of 20%; this kept the flow laminar. The trailing edge had a fish tail look and was intended to recover pressure.

A side effect of the profiles was
1 Much larger internal volume for strong wing spars and fuel.
2 the sharper angled leading edge leads to a higher critical Mach, which also reduces high speed drag. This latter effect was much more significant than the 'laminar flow' effect (actually didn't work)

The Spitifre achieved a relatively high mach limit by having a slim thickness/chord ratio in part by a slim wing though this left little room in the wing for fuel.

The best stalling characteristics actually come from ordinary rectangular planform wings in which the stall develops at the wing roots. Tapered wings (eg Me 109, P-40, FW 190) stall at the win tips first, which could lead to a spin and so these wings need either slats or "washout" (ie a wing twist to reduced angle of attack at the tips) of about 2 degrees. A elliptical planform wing stalls evenly along the whole wing (better than tapered planform but worse than square) however even though the the Spitifre elliptical wing needed LESS washout than a tapered planform wing it actually had about the same 2 degree washout as other aircraft.

As soon as one drops the elliptical planform for a tapered planform one needs MORE washout; which I doubt was added.

The gentle stalling characteristics of the Spitifre are probably ratherexaggeragted relative to other aircraft. The Me 109's stall was mild due to the slats and unlike the spitifre didn't tend to flip inverted after the stall. The US fighters also had annuciated stalls, with tail bueet providing warning. In fact the only European fighter with a harsh stall was the FW 190 and it had good handling up to the stall. It's stall at low G was very mild however under high G the wing could twist. I suspect the Ta 152 handled completely differently due to the new structure and materials. Spitifre's low wing loading gave it a tight turning radious; the weight of the wings being compensated by the power 100/130 fuel could provide.

Juha · Feb 17, 2012

Never heard that RAE High Speed Unit used special propeller in their Spit PR XI in their high speed dive tests, the main point was that it was without protruding cannon barrels and it had 60 series Merlin, so it could made very long dives. Aside tail problem 109 had also aileron problem in high speed dives, that's why in Rechlin dive tests the movement of ailerons in the test 109 was reduced by 50%. 109 was a good diver but P-51B and Spitfire had higher critical Mach number, fighter Spit and P-51B were about equal. The critical Mach number of P-51D was a bit lower than that of P-51B, IIRC mainly because of the bubble canopy, (.84 vs .82, IIRC). Max Mach number achieved in German 109 tests (with the new high tail) was .805, but maybe the hunted was sometimes ready to take higher risks than the hunter.

Juha

Gixxerman · Feb 17, 2012

Siegfried said:
This latter effect was much more significant than the 'laminar flow' effect (actually didn't work)

I remember reading some time back that even the Mustang's wing wasn't a true laminar flow wing.
Anyone know if this is a myth or is it the case?

Obviously the Mustang benefitted from some effect but the level of that is actually fairly low, from what I've seen somewhere (wish I could recall where).

Edgar Brooks · Feb 18, 2012

Siegfried said:
The gentle stalling characteristics of the Spitifre are probably (You have evidence of this?) ratherexaggeragted relative to other aircraft. The Me 109's stall was mild due to the slats and unlike the spitifre didn't tend to flip inverted after the stall. .

You've been reading fairy stories again; at the stall, the Spitfire never showed any tendency to go into an inverted spin. Trials of K9788 showed a tendency for "aileron snatch," which could be easily held by operation of the control column. Test reports, from K5054 onward, all state that behaviour at the stall is mild, with no wing drop, and with no terndency, at all, for a spin.

Siegfried · Feb 18, 2012

Gixxerman said:
I remember reading some time back that even the Mustang's wing wasn't a true laminar flow wing.
Anyone know if this is a myth or is it the case?

Obviously the Mustang benefitted from some effect but the level of that is actually fairly low, from what I've seen somewhere (wish I could recall where).

The Mustang wing was unable to sustain laminarity over any significant portion of its wing.

In theory however it was a laminar profile wing as good as any modern wing

It was a larger portion of laminarity but not significant nor sustainable in real opperations; metal wings: painted or painted simply have too much surface roughness. Laminarity has been achieved only in modern designs made of Glass Fibre Reinforced Plastics or similar composits. To make this realistic such designs exude cleaning detergents out of small holes drilled into the leading edges.

Had the P-51's wing been made of GFRP it would have been genuinely laminar. (so long as an insect strike didn't ruin the surface)

One particular German sailplane has a rail beneath the wing which provides for wiper arm to clean the leading edge during flight. There was considerable German work in and before WW2 on using boundary layer suction to achieve laminarity: this was achieved on some experimental designs but was only usefull for increasing lift and handling as the size of the suction slots meant too much power was required. The development of prous wing surfaces (made of sintered materials) based on the work of Tolman and Schictling did not achieve a conclusion by wars end but became part of the intellectual war booty the allies reaped. (Even private patents were not recognised). Prandtl flew a AVA AF-1 with borundary layer suction.

The background of the NACA lamair profile is interesting: Eastman Jacobs (of the NACA) met the British aerodynamacist Melville Jones at Musolini's Volta conference. Jones had theorsised that a positive pressure gradient would secure laiminarity and tested such on a Hawker Hart. Jacobs went back to the USA where he used his bitter work enememies (theodore theorresen's) complex number comformal mapping techniques in reverse to engineer a wing with the required pressure gradients that eventually became the Mustang wing.

However the side effect was that the wing was 30% thicker but still had a higher critical Mach. The Laminar profiule wings had outstanding Mach characteristics, the series being used for the A-26 invader through to bell X-1.

Interestingly at Mussolinis Volta conference all these same people missed Adolf Bussmann's talk on wing sweep.

Siegfried · Feb 18, 2012

Edgar Brooks said:
You've been reading fairy stories again; at the stall, the Spitfire never showed any tendency to go into an inverted spin. Trials of K9788 showed a tendency for "aileron snatch," which could be easily held by operation of the control column. Test reports, from K5054 onward, all state that behaviour at the stall is mild, with no wing drop, and with no terndency, at all, for a spin.

This would be the stalling characteristics at 1G or the landing configuration. A Spitfire stall at high g showed a pronounced tendancy to flip inverted. Don't get me wrong, the aircraft handled well. Me 109's simply mushed into a stall and remained controllable due to the slats and long tail momment arm.

DVH · Feb 19, 2012

I agree with switch to the p51. The last gasp spitfire designs ( seafire, spiteful) started to look like mustangs' it was a better design. Those eliptical wings had a shelf life, the p51 laminar angular shape was the way to go.

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