Spitfire Combat Radius (range) evolution, limitations?

[tomo pauk]

The Spit wing combined with low W/L was a superior maneuver aircraft to the P-51, but the wing of the 51 was a marvel

It is really impressive how much of the stuff NAA packed in the wing of the P-51, no doubt due to the wing airfoil contributing there, especially with it's relatively thick (for the era) profile. Loads of fuel, armament of up to 4 cannons and sizable ammo count, and obviously the landing gear. Granted, part of the fuel load was, geometrycally, in the wing-fuselage intersection, bu still.
Compare to the later wing on the P-63, that carried 70% of fuel of the P-51, while being unable to install a single HMG in the wing proper. And still the P-63A was not able to out-pace the P-51A, despite the former having a 2-stage engine with water injection.

The underwing radiator for the Spit (or Bf 109) was never entirely successful, but the Bf 109G (and maybe F but my memory fails me) and later were a better design for reducing drag.

Bf 109F indeed received the redesigned radiators, them being wider, thus allowing for greater percentage of the radiators to be buried in the wing. Experiment with boundary layer tunnel was discontiued with the 109G, where the tunnel was 'deleted' so the bigger radiators were installed.
Spiteful's radiators were similar to the Bf 109G/K, granted these sported oil, coolant and intercooler radiators. Spitfires with 2-stage engines were probably 'dirtiest' wrt. radiator setup.

 

[drgondog]

It is really impressive how much of the stuff NAA packed in the wing of the P-51, no doubt due to the wing airfoil contributing there, especially with it's relatively thick (for the era) profile. Loads of fuel, armament of up to 4 cannons and sizable ammo count, and obviously the landing gear. Granted, part of the fuel load was, geometrycally, in the wing-fuselage intersection, bu still.
Compare to the later wing on the P-63, that carried 70% of fuel of the P-51, while being unable to install a single HMG in the wing proper. And still the P-63A was not able to out-pace the P-51A, despite the former having a 2-stage engine with water injection.

Tomo - the High Speed/Low drag airfoil enabled the same drag rise characteristics of the thinner Spit wing, but at sustained lower pressure drag at speeds lower than .6M. Additionally the Moment induced pitch down was less severe due to the aft location of max T/C and CP. The aft T/C also enabled complete housing of belt fed armament as well as the large wing fuel cells.

Curiously, neither P-38, P-39, P-40, P-47, F4U, F6F had any washout. All had negative angle of incidence (constant) ranging from 1 degree (P-40 and P-47), 2 degree (P-38, P-39 and F4U) to 3 degree (F6F). The P-51 and Spitfire had nearly the same washout near 2 degree.

The P-47 S-3 airfoil was actually slightly 'thinner' than Spitfire with 11% max T/C at 30%, then Spit 13%, then P-38/39/40 and F6F 15%, then P-51 16.3% and F4U at 18%.

Bf 109F indeed received the redesigned radiators, them being wider, thus allowing for greater percentage of the radiators to be buried in the wing. Experiment with boundary layer tunnel was discontiued with the 109G, where the tunnel was 'deleted' so the bigger radiators were installed.
Spiteful's radiators were similar to the Bf 109G/K, granted these sported oil, coolant and intercooler radiators. Spitfires with 2-stage engines were probably 'dirtiest' wrt. radiator setup.

Thanks for the 'refresher..

 

[tomo pauk]

Tomo - the High Speed/Low drag airfoil enabled the same drag rise characteristics of the thinner Spit wing, but at sustained lower pressure drag at speeds lower than .6M. Additionally the Moment induced pitch down was less severe due to the aft location of max T/C and CP. The aft T/C also enabled complete housing of belt fed armament as well as the large wing fuel cells.

Curiously, neither P-38, P-39, P-40, P-47, F4U, F6F had any washout. All had negative angle of incidence (constant) ranging from 1 degree (P-40 and P-47), 2 degree (P-38, P-39 and F4U) to 3 degree (F6F). The P-51 and Spitfire had nearly the same washout near 2 degree.

Thank you.

The P-47 S-3 airfoil was actually slightly 'thinner' than Spitfire with 11% max T/C at 30%, then Spit 13%, then P-38/39/40 and F6F 15%, then P-51 16.3% and F4U at 18%.

Seems like the P-47 max t-t-c was 14% per this table.
I'd be grateful for the US data wrt. the % t-t-c on the P-47's S-3 airfoil.

 

[pbehn]

Curiously, neither P-38, P-39, P-40, P-47, F4U, F6F had any washout. All had negative angle of incidence (constant) ranging from 1 degree (P-40 and P-47), 2 degree (P-38, P-39 and F4U) to 3 degree (F6F). The P-51 and Spitfire had nearly the same washout near 2 degree.

Were/ are there any ways to get the same effect without washout?

 

[drgondog]

Thank you.



Seems like the P-47 max t-t-c was 14% per this table.
I'd be grateful for the US data wrt. the % t-t-c on the P-47's S-3 airfoil.

try his - REPUBLIC S-3 AIRFOIL (s3-il)

 

[drgondog]

Were/ are there any ways to get the same effect without washout?

Slats.

 

[tomo pauk]

try his - REPUBLIC S-3 AIRFOIL (s3-il)

Thank you. Under 'US data', I've meant something sourced by Republic or NACA.
Unfortunately, the discrepancy between 14% and 11% is too great to just accept the 11% figure and discard the 14% figure.

 

[drgondog]

Thank you. Under 'US data', I've meant something sourced by Republic or NACA.
Unfortunately, the discrepancy between 14% and 11% is too great to just accept the 11% figure and discard the 14% figure.

Not arguing, but Lednicer is a VERY respectable source. As to NACA, the S-3 was a homegrown airfoil. On the other hand the RAF tables has no cited source, nor is there guarantee that it is not a typo, or the result of physical measurement in error. That said I seem to recall another source in the 14% range.

 

[tomo pauk]

Not arguing, but Lednicer is a VERY respectable source. As to NACA, the S-3 was a homegrown airfoil. On the other hand the RAF tables has no cited source, nor is there guarantee that it is not a typo, or the result of physical measurement in error. That said I seem to recall another source in the 14% range.

Unfortunately, the NACA data about the S-3 is very, very 'thin', while the Republic archives ended up in a landfill when they were bough by Fairchild. Damn.

 

[tomo pauk]

Seems like the max t-t-c of 14.6% for the root of the wing of P-47 per this excerpt. The 11% t-t-c figure is for the wing section 2 feet outboard from the flap.

 

[drgondog]

Seems like the max t-t-c of 14.6% for the root of the wing of P-47 per this excerpt. The 11% t-t-c figure is for the wing section 2 feet outboard from the flap.

I don't have a problem with 14.6 as 11% just seems too low for 1941 aerodynamics. FYI - The XP-47F Laminar Flow wing is cited 15.6 with max T/C at 45%. (Freeman Drawing pg 139).

What is the source for the excerpt?

 

[tomo pauk]

What is the source for the excerpt?

Don't know.
I've asked the person that posted it at another forum to post the name of the source of the excerpt.

 

[GregP]

Thank you.



Seems like the P-47 max t-t-c was 14% per this table.
I'd be grateful for the US data wrt. the % t-t-c on the P-47's S-3 airfoil.

Hi Tomo. Where did you find that table? Not questioning it ... just curious so I can see it when I magnify it.

 

[tomo pauk]

Hi Tomo. Where did you find that table? Not questioning it ... just curious so I can see it when I magnify it.

Here.

 

[Jugman]

I don't have a problem with 14.6 as 11% just seems too low for 1941 aerodynamics. FYI - The XP-47F Laminar Flow wing is cited 15.6 with max T/C at 45%. (Freeman Drawing pg 139).

What is the source for the excerpt?

I think that excrept is from a NACA report that can be found on the NTRS. It seems awfully familiar to me. 11% is to thin to allow the wheels to fit in the wings without bulges.

 

[Jugman]

Found IT! It's on Page six of "Flight Investigation of Boundary-layer and Profile-drag Characteristics of Smooth Wing Sections of a P-47D Airplane".

 

[drgondog]

Found IT! It's on Page six of "Flight Investigation of Boundary-layer and Profile-drag Characteristics of Smooth Wing Sections of a P-47D Airplane".

Interesting. Couple of comments:
The S3 wing was 11.7 T/C Max at semi span 63%, 14.7% T/C Max at 25%. Extrapolating to Root chord puts it in the 16% T/C Max range - about the same as P-51.

The Cd profile drag (pure shape, no friction) a low CL (High Speed) in the RN=19 x 10^6 range is 0.0062 for that puttied, primed and sanded smooth wing.

The P-51D wing CD profile drag is 0.0070 at RN=2x10^6, at RN=19x10^6, the P-51D wing CD profile drag =~0.0040.

 

[Wild_Bill_Kelso]

That may be true but a lot of the other fighters (especially in 1939-43) weren't really all that good at a varity of roles. P-40s didn't do well at intercepting anything flying at 20,000ft or above for example, let alone trying to escort B-17s or B-24s unless they were flying low and close to home.

Well, I agree with that with some qualifiers. P-40s appear to have worked much better for the defense of Darwin than the Spit Mk Vs did, (and these were the early ones with the critical altitude around 12k ft) and the difference seems to be largely down to range / endurance. They could form up, climb laboriously up to altitude, and fly out to intercept the incoming aircraft and still have enough fuel to make multiple attacks and still make it back to base.

P-40s were notoriously bad at escorting heavy bombers, and they were tried for this task a few times, mainly with B-24s, both in the Pacific and the Med, with poor results.

Merlin powered P-40s were used in the Med with considerable success to escort medium bombers, in fact one of the FG there was assigned to the main B-26 bomber group, and they did really well. P-40N and M were used in the pacific and CBI to escort bombers and transports (notably over 'the hump') again in spite of having to fly at relatively high altitudes.

Generally speaking, I think you wouldn't want this plane to escort any heavy bombers.

A Spitfire V was shorter in range than a P-40 but it took rougly 2/3s of the time to get to 20,000ft and when flying above 20,000ft it had around double the rate of climb.

Depends on the types, but generally Spit V had an excellent climb rate. Early "Kittyhawk" P-40s as I previously mentioned, had a critical altitude down around 12,000 ft, Tomahawks were a little better, at about 15k. Merlin (F and L) types had a critical altitude at just under 20,000 ft so were good up to about 2,5000 or so. N and M (Allison) model had around 16-17k and were ok up to about 20k.

Now for all the "early long range Spitfire" fans see.

http://www.spitfireperformance.com/ab320climb.jpg

for times with and without a 90 gallon tank. Granted the tank has drag but we can pretty quickly figure out that the Spitfire V could loose around 200 fpm of climb even with a 45 gallon extra fuel load. and since at 26,000ft the climb rate was only about 1400fpm to begin with losing 10% or more due to to even 45 imp gallons extra fuel might not have been popular.

Now a MK IX Spit could climb (proving ground) at a bit under 2400fpm while carrying at 30 gallon tank at "Normal" (12lbs boost) rating.

Now in late 1942 which Spifire do you want to try escort for American B-17s in the mid 20,000ft area of the sky? Even if only over Holland
The Idea of an escort fighter is to actually provide an escort to the bombers, not provide alternative targets for the enemy to shoot down.
Simply flying along with or over the bombers isn't enough, the escort fighters need to be able to fight the enemy intercepters with at least some degree of success even if not shooting them down a 1:1 ratio.

I really wasnt' ever thinking of using Spitfires to escort B-17s or B-24s, at least not as the main escort, though if you had say, Spit VIII range plus a little extra from streamlining etc., it could be quite helpful in covering the return leg of a bombing raid. They did use Spits for this role, but if you had double the range that could really help.

However, I really think Spits would have been more effective both as interceptors, (especially with Radar / integrated defense system) and as tactical fighters, fighting over the various battlefields, if they had say 50-100% more range, and I think that was probably technically feasible. Whether it was feasible in industrial terms is unclear to me.

 

[Wild_Bill_Kelso]

That's an easy question. I pick Spitfire IX to escort B-17s at any altitude they might be, range/radius of Spits permitting. We know that Mk.IX was at least equal to the Fw 190s performance-wise.

Longer ranged Spit VIII also pretty good match for a FW 190 too.

 

[Wild_Bill_Kelso]

What happened in Darwin?


While I know that ADC/TAC and part of SAC became ACC in the United States in 1992, I didn't know there was an ACC entity in either the USAAF/RAF during WWII. Regardless, I gotta say that the decision made was quite foolish, but not an uncommon rationale: "They're making us look bad, so we're edging them out the way so we can get all the glory".

Spitfire Wing was sent in, under veteran leadership, to defend Darwin after the US 49th FG was rotated out (and soon after, north up to New Guinea). The Spitfire unit had a lot of problems. They took heavy losses to enemy aircraft, accidents, and fuel starvation over the water. Part of this was due to some unique maintenance issues, part was routine teething trouble of deploying these planes at the end of a very long supply line (and in part, relying on Aussie manufacturing which wasn't quite up to speed yet). But arguably the biggest single problem was fuel. Spitfires were used in the Pacific, and they were needed, but short range / endurance largely kept them out of the fight.

Getting back to the main subject of the OP, looking at Geoffrey Sinclair's post with all the Spitfire drag improvements here Spitfire Combat Radius (range) evolution, limitations?

... it seems like with some effort they could have made an improved 'lower drag' Spitfire which was at least 30-40mph faster, and some of this will also translate into better endurance / range... then combine that with the extra fuel carried by the Mk VIII, and I think you have possibly an aircraft with an additional improved range over that of the Mk VIII.

I do know that the MK VIII had a few of these drag improvements built in, which is part of why it was faster, but there was still room for many more.

Conceivably, you could fit even more fuel in, given that the range of the PR Spits was so good. There has to be some room between 'no guns' and 'six guns' where you could fit some more petrol instead.

I don't necessarily see this as a primary Strategic escort fighter, but I think it would still be a bit of a game changer just by significantly leveraging the advantages of the Spitfire in the various battlefield zones around the world - Med / Malta / Italy, Pacific, and later on in France etc. I think the Russians might have found more use for it as well.