An Allison V-1710 with a two-speed supercharger in 1942 (6 Viewers)

[MiTasol]

To reiterate my introduction, the RAF deliberately and necessarily, prioritised the fighter defence of Britain itself which meant that they prized the rôle of their fighters as interceptors above all. Whether they chose well or carried it out well is another matter. They wanted interceptors above all.

Exactly. Interceptors not long range escort fighters because intercepting and destroying the German aircraft was number one, number two and number three priorities. If Britain fell nothing else mattered..

American fighters had a different context. The sheer size of the United States and the likely use of its forces as an expeditionary force required that they had a far greater range.

Yet despite that the USAAC/F refused to allow drop tanks when Curtiss and Lockheed proposed fitting them to extend the range of their aircraft.

Different answers to different questions. The respective operational requirements that resulted in the aeroplanes were both quite specific in this matter.

Yes.

 

[PAT303]

The Mustang I had the same engine power as the Spit V but far more range. The Mustang I was not comparable to the Spit V as a point interceptor, but was quickly adaptable to the same engine integrated into the Mark IX. The resultant Mark X/Mustang III Still faster than the Spit IX at all altitudes, would have been comparable to the Spit V as a point interceptor, but vastly more range.

The reason (rational) that RAF declined to add more fuel to extend tactical radius, was that there were other aircraft (available) that were better suited for roles that may have overlapped the Spit IX/XIV 'super' with more fuel and bomb racks.

The weight comparison between the Spit IX and the P-51B resulted in favoring the Spit IX by 1,480 pounds (5,559 vs 7,039) sans armament but all fixed equipment, for Empty Weight. Before an ounce of fuel was added but the significant differences were the wing group (255lbs), the Landing Gear (322lbs), Fuel tanks (214lbs), prop (156lbs), Cooling system (184lbs), Oil supply system (207lbs).

Part of the reason was the difference in design limit load of 7.5G AoA loads vs 8G for Mustang. When you are forced to account for greater weight in the wings due to vast difference in fuel supply the weight penalty to account for was beyond the weight of fuel/oil for longer range.

By contrast the XP-51F compared to Spit IX was 91lbs (2,258lbs vs 2,167lbs) for Wing, fuselage, empennage, main gear, engine mount. The Bare Weight difference before Fixed Equipment was 174lbs (5,203lbs vs 5,029lbs). That said the P-51F fully loaded internally (180-gal fuel, 12-gal oil, 1000 rnd 50 cal) for a long range escort mission, sans drop tanks but 180-gal fuel, was 8,117lbs. ROC with the 1650-9 engine (same as P-51H and equivalent to Merlin 100) was 6,550fpm at SL, 4,720fpm at 20,000ft, 2,640fpm at 30,000ft.

The combat radius with 2x75-gal tanks and 180-gal internal fuel was 790 miles with 20 minutes combat, average cruise speed of 344mph and dropping external fuel tanks with 7-gal in each tank. The latter to reserve 30 minutes loiter at the end of the mission.

But it could NOT add a fuselage tank and still fly due to impossible aft CG issue, worse than the P-51B/D.

The point (finally) is that 'simply adding more fuel', ain't simple and far beyond finding a location for the addition.

The P-47D-25 had to be re-designed from firewall to pilot's seat to add 65-gal to main fuel tank. A P-47D-4 was tested with 75-gal aft of the seat and deemed dangerously unstable. All in it took six months for a prototype demonstration in November 1943. It took NAA and Lockheed two weeks to add and test the 90-gal steel fuselage tanks in the P-51B and add the two 55-gal LE tanks for the P-38J in July 1943.

The P-47N had a 13" plug inserted outboard of landing gear to add the 2 extra 93-gal wing tanks.

So, you be the designer - tell me how you add 80-gal to the Spit IX to match the XP-51F, or 170-gal to match the P-51B? And remember, it still needs to retain superb handling qualities as well as pull out of a dive with both wings attached?

This is a point that is constantly pushed and it's false, the Spitfire wasn't going to match the range of the P51 and it didn't have to, all it had to do was have operational flexibility by having the ability to carry more fuel, flexibility in increased range, increased cruising speed or loiter time and it could have had all that 12 months before the P51. As has been discussed instead of having factories making obsolete or rubbish aircraft or like MB make a 1943 aircraft in 1946 they could have been making or modifying Spitfires for specific roles, the Mk V could have had extra tanks and fit and finish adjustments afterwards so the production lines weren't effected, once the 60 series Merlins arrived MkIX's likewise could have had the same treatment which would have allowed escort missions to the Ruhr from late 1942, there was huge numbers of military complexes in the Ruhr that were well within the range of modified Spitfires that could have been pounded late '42 and right throughout 1943 which would have caused a major shift in Luftwaffe strategy which did happen in 1944 when they were pushed out of the low countries and forced back to Germany. We are not making a Mk 51 Spitang, what we are doing is best utilizing the extra power and performance offered by the newer engines as they are developed along with available factories to perform airframe improvements and then putting it all together to update tactics as the environment or mission required. Forget the rubbish constantly spewed about poor handling and the Spitfires inability to carry fuel, the fact is they did and all the fighters that came later all had the same COG issues, the same flight restrictions and required the same hands on control until the extra fuel as burnt off.

 

[PAT303]

Is there any reason why they couldn't have added the fuel capacity of the Spit VIII to the V or IX?

Air vice Marshal Portal.

 

[PAT303]

question is if they fit in-between two ribs or if the noses of one or more ribs have to be cutaway or modified?
One excuse was they didn't want to retool the factories than were making the wings. I cannot make a judgement on that one way or another. How much production disruption could be tolerated? Obviously, it could be done and was done but only in a few factories.

If you look at the Spitfires leading edge the tanks could have easily been extended inwards to rib 2, there's more than enough room to fit 25G per side with 42/33G rear aux and a 90G dropper, you then have enough range to cover right up the the German border once enough 60 series Merlin's are produced.

 

[PAT303]

The 'fuel pump' carb was tested on the Spit V and found to add 8-10 mph and 1500 to the celing.
link
I don't know whether the Spit Vs were actually retrofitted with the better carbs in 1943-44.

Better panel fit and paint finish, individual ejector nozzles, retractable tail wheel, stream lined blusters the list goes on all added up and all could have been done at Blackburn, instead they made Botha's, and Martin Baker made the MB 5, in 1946

 

[wuzak]

Better panel fit and paint finish, individual ejector nozzles, retractable tail wheel, stream lined blusters the list goes on all added up and all could have been done at Blackburn, instead they made Botha's, and Martin Baker made the MB 5, in 1946

1946?

Only 1 prototype was built, and it first flew in May 1944.

Also, Martin-Baker didn't make production aircraft in WW2. Instead they manufactured components, and did re-engineering on soem products.

 

[MiTasol]

Better panel fit and paint finish,

Yep, take the aircraft out of service for a couple of weeks when it is needed. That will really help the war effort.

individual ejector nozzles

Can be done during routine servicing but the people who actually knew what was possible at the time said no. Possibly because they did not have enough exhausts or the ability to manufacture them due to material or manpower availability.

retractable tail wheel

That is a total replacement of the stern frame so first you have to build the stern frames and related tail wheel and retraction system components. Then it is just higher level servicing but involves moving over the tailplanes and flight controls as a minimum. Those parts may have needed mods or repairs as well. Again the people who actually knew what was possible at the time said no. Possibly because the units just did not have the manpower. Equally possible that this required materials and facilities that were not available to make the parts. Yes I agree the Botha was a waste of manpower and material but those who had the whole picture in front of them said it was needed. That they were wrong on some things in hindsight is another matter.

stream lined blusters

I presume you mean blisters. Another item that can be changed during routine servicing so long as there are no changes to primary structure and again the people who actually knew what was possible at the time said no. Possibly because the squadrons just did not have the manpower. Equally possible that this required materials and facilities that were not available to make the parts. They would also have looked at new mini factories just to make these sorts of parts. Obviously they decided they were not ESSENTIAL.

and Martin Baker made the MB 5, in 1946

Check your history, not some AI "expert".

 

[Shortround6]

And at the stage the Spitfire was designed Merlin was one of, if not the, most powerful V12 engines in production.

yes and no. Being a bit pedactic here.
The following comments are in general and not in reply to MiTasol.
By the time the Spitfire entered production (mid 1938) the Merlin was the most powerful V-12 engine in production at Altitude (anywhere near 15-16,000ft).
Other engines may have beaten it a low altitude. RR could change supercharger gears and become the most powerful low altitude engine.
British then shot their fighters in both feet with the prop selection.
Fixed pitch prop was like a car locked in high gear. It could go fast but accelerating or climbing hills really sucked.
Two Pitch prop was like a car with a 6 speed box with 2,3,4 and 5th gears blocked off. Car can do either 25mph or 150mph. Can accelerate will well up to 25mph but then shifting and trying to get up to 150 takes a long time. And trying to climb a hill at 50mph is really hard.
CS prop is a variable speed drive between the lower and upper limits.

We are discussing the suitability as interceptors and as longer range aircraft and in these 1938-39 aircraft even with constant speed props around 440-450lbs could add over a minute to 20,000ft and 4-5 minutes climbing to 30,000ft. The Merlin III was supposed to use 2600rpm when climbing, not the later 2850rpm.
The planes gained 400-600lbs from prototype to early production with more equipment.
The early planes could not carry an extra 30-40 gal of fuel and fight well, mostly climb and turn, with poor excess power it doesn't matter so much about turn radius, what is important is being able to turn and not loose too much altitude.
Things changed with 12lb override and the Spitfire IIs could get to 25,000/30,000ft several minutes quicker than a Spitfire I could when not using boost override.
Radar also was giving advanced warning.
Things were looking much better for adding fuel to fighters in late 1940 than it did in 1938. Now was when some of the air ministers may have made mistakes, but in 1938 they probably made the right choices or they could have saddled the RAF with "British P-40s". Fast but heavy and can't climb for crap.
Be careful what you ask for, you just might get it
Internal fuel that can't dropped needs heavier structure for maneuver if bounced early. Also needs heavier structure and landing gear to land safely if engine craps out right after take-off. While taking off it is crash regardless of weight.
Once the shooting starts some of the safety rules tend to fade a bit. Crashing a higher than "normal" rate of aircraft in take-off and landing accidents is not a good thing and crash rate was pretty high as it was compared to even 1960s standards.

Only some fighters got more fuel as they got newer models. And sometimes it took considerable modification to add internal fuel.

 

[Engineman]

yes and no. Being a bit pedactic here.
The following comments are in general and not in reply to MiTasol.
By the time the Spitfire entered production (mid 1938) the Merlin was the most powerful V-12 engine in production at Altitude (anywhere near 15-16,000ft).
Other engines may have beaten it a low altitude. RR could change supercharger gears and become the most powerful low altitude engine.
British then shot their fighters in both feet with the prop selection.
Fixed pitch prop was like a car locked in high gear. It could go fast but accelerating or climbing hills really sucked.
Two Pitch prop was like a car with a 6 speed box with 2,3,4 and 5th gears blocked off. Car can do either 25mph or 150mph. Can accelerate will well up to 25mph but then shifting and trying to get up to 150 takes a long time. And trying to climb a hill at 50mph is really hard.
CS prop is a variable speed drive between the lower and upper limits.

The Merlin superiority at Altitude largely rested on the efficiency of the Superchargers. The original supercharger design from 1933 was, at 65% efficiency, very efficient for its time and this efficiency was reflected in less heating of the air charge into the combustion chambers. Coupled with the charge-cooling effect of the fuel, the Merlin was able to use relatively high Boost pressures. Development saw increases in the mechanical ability of the engine to survive longer hours and greater Boost pressures, coupled with better fuels. The later refinement of the supercharger designs, led by Sir Stanley Hooker, saw the efficiency of the superchargers in engines including and after the Merlin XX and 45 raised to around 75%. This improvement in efficiency could further reduce the power required for compression and reduce the charge heating. In fact, this increase in efficiency was required to make the 2-Stage supercharger a viable device, due to the compounding of losses suffered in multiple stage supercharging.
The analogy of car gears for propeller pitch-changing effect is basic, but useful for understanding. However, there are pitfalls in calling the Constant Speed Propeller a "variable speed drive" when it is actually, a Constant Speed Drive, that allows the engine and propeller to operate at, Constant Speeds (rpm).
Lastly, it is worth noting that the subject of efficient Supercharging was not the sole domain of RR. The Germans in particular had considerable achievement and wide ranging technical abilities. The Americans succeeded well with some of their superchargers and their Turbocharging was a mature product by WW2.

Eng

 

[MiTasol]

CS prop is a variable speed power drive between the lower and upper limits except when power diving.

In the simplest terms, the constant speed prop maintains engine rpm regardless of how much power the engine is developing so that as power drops off with altitude the engine maintains rpm. Maximum power at any altitude is obtained at, or close to, max rpm so keeping the revs up by reducing pitch as the power drops is the most efficient way to maintain power. The CS prop also prevents the engine over-speeding except in a power dive.

 

[PAT303]

And at the stage the Spitfire was designed Merlin was one of, if not the, most powerful V12 engines in production. And fighter tactics did move with the experience gained. In the opinion of those at the coal face experts there at the time fuel tank protection, heavier armour and heavier weapons were needed more than range to support the evolving tactics because the Germans had fitted heavier armour that protected the crew and had heavier weapons that could puncture the existing armour.

Using your perfect hindsight expertise how do you think they could have done better.

I clearly stated that the extra performance gained from engine development should have been used to carry bigger guns or more fuel allowing tactics to evolve from point interception engagements such as what happened in the BoB to then being able to cruise at higher speeds during the Leaning on France fighter sweeps which was beneficial if bounced .

 

[PAT303]

Exactly. Interceptors not long range escort fighters because intercepting and destroying the German aircraft was number one, number two and number three priorities. If Britain fell nothing else mattered..

What about after 1940?, from 1941 onwards the air war didn't need point interceptors.

 

[PAT303]

Yep, take the aircraft out of service for a couple of weeks when it is needed. That will really help the war effort.

Can be done during routine servicing but the people who actually knew what was possible at the time said no. Possibly because they did not have enough exhausts or the ability to manufacture them due to material or manpower availability.


That is a total replacement of the stern frame so first you have to build the stern frames and related tail wheel and retraction system components. Then it is just higher level servicing but involves moving over the tailplanes and flight controls as a minimum. Those parts may have needed mods or repairs as well. Again the people who actually knew what was possible at the time said no. Possibly because the units just did not have the manpower. Equally possible that this required materials and facilities that were not available to make the parts. Yes I agree the Botha was a waste of manpower and material but those who had the whole picture in front of them said it was needed. That they were wrong on some things in hindsight is another matter.


I presume you mean blisters. Another item that can be changed during routine servicing so long as there are no changes to primary structure and again the people who actually knew what was possible at the time said no. Possibly because the squadrons just did not have the manpower. Equally possible that this required materials and facilities that were not available to make the parts. They would also have looked at new mini factories just to make these sorts of parts. Obviously they decided they were not ESSENTIAL.


Check your history, not some AI "expert".

You should actually read what I wrote, the ''people'' who apparently knew what was possible didn't have to invent anything, do structural changes or anything else simply because what I suggested was done on production Spitfires.

 

[Shortround6]

The analogy of car gears for propeller pitch-changing effect is basic, but useful for understanding. However, there are pitfalls in calling the Constant Speed Propeller a "variable speed drive" when it is actually, a Constant Speed Drive, that allows the engine and propeller to operate at, Constant Speeds (rpm).

In the simplest terms, the constant speed prop maintains engine rpm regardless of how much power the engine is developing so that as power drops off with altitude the engine maintains rpm. Maximum power at any altitude is obtained at, or close to, max rpm so keeping the revs up by reducing pitch as the power drops is the most efficient way to maintain power. The CS prop also prevents the engine over-speeding except in a power dive.

Thank you, gentlemen. I over simplified and confused things.
with the CS prop the power to the prop could stay constant and the rpm of the propeller stayed constant while the aircraft speed changed considerably. Assuming the same altitude/air density.
With the 2 pitch props the pilot often changed to high pitch (top gear analogy) soon after take-off and at around 140-160mph. Engine revs dropped to a little over 2000rpm for a Merlin and power dropped though the not only the floor but the basement floor. Propeller efficiency also dropped a huge amount. The book 880hp at 3000rpm for take-off of a Merlin III disappeared really quick. Engine was giving around 70% power (?) and using a prop that was way under 80% efficient at climbing speed.

Constant speed prop allowed for 2600rpm or 2850 rpm or 3000rpm at 160mph and 1-2000ft. Prop will adjust the blade pitch to balance the load and power as much as possible.
Prop can operate at a more efficient pitch and allow for more power to be transmitted until either altitude or forward speed (or both) allows propeller to reach full pitch.

 

[drgondog]

This is a point that is constantly pushed and it's false, the Spitfire wasn't going to match the range of the P51 and it didn't have to, all it had to do was have operational flexibility by having the ability to carry more fuel, flexibility in increased range, increased cruising speed or loiter time and it could have had all that 12 months before the P51. As has been discussed instead of having factories making obsolete or rubbish aircraft or like MB make a 1943 aircraft in 1946 they could have been making or modifying Spitfires for specific roles, the Mk V could have had extra tanks and fit and finish adjustments afterwards so the production lines weren't effected, once the 60 series Merlins arrived MkIX's likewise could have had the same treatment which would have allowed escort missions to the Ruhr from late 1942, there was huge numbers of military complexes in the Ruhr that were well within the range of modified Spitfires that could have been pounded late '42 and right throughout 1943 which would have caused a major shift in Luftwaffe strategy which did happen in 1944 when they were pushed out of the low countries and forced back to Germany. We are not making a Mk 51 Spitang, what we are doing is best utilizing the extra power and performance offered by the newer engines as they are developed along with available factories to perform airframe improvements and then putting it all together to update tactics as the environment or mission required. Forget the rubbish constantly spewed about poor handling and the Spitfires inability to carry fuel, the fact is they did and all the fighters that came later all had the same COG issues, the same flight restrictions and required the same hands on control until the extra fuel as burnt off.

Which RAF critical tactical requirement dictated investing in adding additional fuel to the Spit V or Spit IX? At the cost of actual deliveries of the actual fuel configuration? Given that performance in range, acceleration, climb and turn are reduced until the extra internal fuel is burned away.

Escort to the Ruhr wasn't a factor. The RAF neither cared about, nor was equipped, for daylight strikes to the Ruhr. Escort at night was off the table.

Oh, and for what is worth the P-51H, P-82 had no maneuverability restrictions due to cg issues. Ditto the P-51B/D if 40 gallons were burned from the fuse tank on climb to altitude. Presumably the same for Spitfire but the role of the Spitfire dictated zero additions to weight at the expense of climb and turn for interceptor role.

So what is the mission that no other fighter in RAF inventory could achieve better than a Spitfire with extra internal fuel?

 

[yulzari]

What about after 1940?, from 1941 onwards the air war didn't need point interceptors.

Er, it was in 1941 that my home city received its worst bombing raids. Even when Germany was daft enough to attack the Soviet Union there was a very real perception that, at best, an invasion of Britain was merely delayed. Whilst the Barbarossa assault continued forward and reached the gates of Leningrad and Moscow that perception was still current. It was only in 1942 that the halt of the Germans and some reverses for them changed the perception. Until then the home islands were, not unreasonably in the light of the time, under a genuine threat. The priority pure interceptor rôle was thus current until well into 1942. The last raid on my home city was in May 1944. The last cruise missile raid on London was on the 29th of March 1945. Dealing with V1 raids was very much an interceptor rôle, within a whole defence system.

We saw this again in the 1950s and 1960s when the emphasis of British fighters was to get fighters up and away to meet Soviet bombers as fast as possible in all weathers. Hence the English Electric Lightning with the climb rate of an angel leaving work on a Friday and the fuel storage of a human bladder with prostate difficulties.

 

[Shortround6]

Spitfire IIA with 40 gal tank.

Tested at Boscombe Down in Sept 1941 (?) .
Some were flown by Sqadron Nos 66, 118, and 154.
I don't know if any squadron was fully equipped or not.
This was the 2nd attempt at fitting the wing tank. It had been tried on a MK I.
Somewhere there was a report on the MK I. The Report on the MK IIA gives speeds and climbs.
The MK IIB had metal alerions and handling was a marked improvement over the MK I and the plane was considered satisfactory as a fighter.
Granted this tank has a fair amount of drag and cost a bit over 20mph in speed. It also cost about 700fpm in climb under 20,000ft.
How much was drag and how much was weight can be argued. Fitting the fuel tanks inside would get rid of the drag (except for a few mph) but the weight is still a problem.
Engaging the enemy over the French/Belgian coast is problematic. Near the end of the misson/sweep (longer than a normal Spitfire) there isn't going be much difference.
At the start or entry into enemy airspace the planes carrying the extra fuel are going to have much degraded climb.
Early MK Vs (eight gun) show a bit better climb using standard 2850rpm and 9lbs climb compared to the MK IIs with Merlin XII engines. Above 20,000ft the MK Vs show more advantage.
MK Vs seem to show rather different performance from each other.
A MK Vb with standard tanks was within 15lbs of the MK IIA with the fuel tank. Extend range Vb might have had similar performance to a standard IIa? Or IIb? Is that good enough in late 1941?

 

[Shortround6]

Ditto the P-51B/D if 40 gallons were burned from the fuse tank on climb to altitude

Post war manual for the P-51D wanted the pilots to keep some fuel in the rear tank. 25-35 gallons ?
This fuel was only to be used when the wing tanks went dry.
I have no idea what the post War P-51Ds were using for radios, oxygen equipment or other equipment that could have required keeping that amount of fuel in the rear tank to keep the CG where they wanted it.
Something was going on. Going from dangerous to fly with more than 50 gal in the rear tank to dangerous to fly with less than 35 gallons in the rear tank?????
Could very well be dangerous for different reasons.
We are also arguing about US standards vs British standards for flight/cg location/control response.

 

[Steamed_Banana]

yes and no. Being a bit pedactic here.
The following comments are in general and not in reply to MiTasol.
By the time the Spitfire entered production (mid 1938) the Merlin was the most powerful V-12 engine in production at Altitude (anywhere near 15-16,000ft).
Other engines may have beaten it a low altitude. RR could change supercharger gears and become the most powerful low altitude engine.
British then shot their fighters in both feet with the prop selection.
Fixed pitch prop was like a car locked in high gear. It could go fast but accelerating or climbing hills really sucked.
Two Pitch prop was like a car with a 6 speed box with 2,3,4 and 5th gears blocked off. Car can do either 25mph or 150mph. Can accelerate will well up to 25mph but then shifting and trying to get up to 150 takes a long time. And trying to climb a hill at 50mph is really hard.
CS prop is a variable speed drive between the lower and upper limits.

We are discussing the suitability as interceptors and as longer range aircraft and in these 1938-39 aircraft even with constant speed props around 440-450lbs could add over a minute to 20,000ft and 4-5 minutes climbing to 30,000ft. The Merlin III was supposed to use 2600rpm when climbing, not the later 2850rpm.
The planes gained 400-600lbs from prototype to early production with more equipment.
The early planes could not carry an extra 30-40 gal of fuel and fight well, mostly climb and turn, with poor excess power it doesn't matter so much about turn radius, what is important is being able to turn and not loose too much altitude.
Things changed with 12lb override and the Spitfire IIs could get to 25,000/30,000ft several minutes quicker than a Spitfire I could when not using boost override.
Radar also was giving advanced warning.
Things were looking much better for adding fuel to fighters in late 1940 than it did in 1938. Now was when some of the air ministers may have made mistakes, but in 1938 they probably made the right choices or they could have saddled the RAF with "British P-40s". Fast but heavy and can't climb for crap.
Be careful what you ask for, you just might get it
Internal fuel that can't dropped needs heavier structure for maneuver if bounced early. Also needs heavier structure and landing gear to land safely if engine craps out right after take-off. While taking off it is crash regardless of weight.
Once the shooting starts some of the safety rules tend to fade a bit. Crashing a higher than "normal" rate of aircraft in take-off and landing accidents is not a good thing and crash rate was pretty high as it was compared to even 1960s standards.

Only some fighters got more fuel as they got newer models. And sometimes it took considerable modification to add internal fuel.

The thing is, we're talking mainly about Spit V here I think. Spit V was being manufactured for a long time. And it changed a lot during that time. As did fuel and boost settings.

At one point, probably starting in later 1943, they actually had more Spit Vs than they knew what to do with, partly because due to their limited range, they had limited application outside of the Home Islands.

Spit V with higher boost settings and / or a theoretical / imaginary Spit VXX with two speed supercharger can overcome some extra weight for that initial climb-up.

Extra fuel tanks do not need to be kept full, and empty fuel tanks don't add nearly as much weight. You are often pointing out that P-40s were often used without their fuselage tank filled, which is true. It depended on the mission profile, it was pretty common to fly with 120 gal vs 160 gal, or 200-230 gal with an external tank. Sometimes for interception / point defense missions almost all fighter types were used with half fuel for better climb rate.

It would also be theoretically possible to make different types of Spit Vs, just as they in fact did make the LF and HF versions, clipped and not clipped and so on. You could also have had a Spit V "OS" - overseas service, for longer (i.e. medium) range.


By the way, in all this talk about armor, it is worth noting that Spitfires up to I'm not sure which mark, or maybe all of them, had that big fuel tank in front of the cockpit which was not armored, or rather was 'armored' with aluminum alloy only which is more or less the same thing. Just one other little factor to consider.

I'd also like to consider in the discussion of Spits the external tank. It seems like they struggled to make a good well streamlined and jettisonable external tank. The slippers had a lot of drag and the 'cigar' type seemed to be worse. The Navy had similar problems for (to me) inexplicable reasons with the Wildcat for a long time. Meanwhile the 52 and 75 gallon tanks used on the P-40 seemed to mostly be pretty good by comparison, and were used with many other types of aircraft.

 

[Engineman]

Spitfire IIA with 40 gal tank.
View attachment 879720
Tested at Boscombe Down in Sept 1941 (?) .
Some were flown by Sqadron Nos 66, 118, and 154.
I don't know if any squadron was fully equipped or not.
This was the 2nd attempt at fitting the wing tank. It had been tried on a MK I.
Somewhere there was a report on the MK I. The Report on the MK IIA gives speeds and climbs.
The MK IIB had metal alerions and handling was a marked improvement over the MK I and the plane was considered satisfactory as a fighter.
Granted this tank has a fair amount of drag and cost a bit over 20mph in speed. It also cost about 700fpm in climb under 20,000ft.
How much was drag and how much was weight can be argued. Fitting the fuel tanks inside would get rid of the drag (except for a few mph) but the weight is still a problem.
Engaging the enemy over the French/Belgian coast is problematic. Near the end of the misson/sweep (longer than a normal Spitfire) there isn't going be much difference.
At the start or entry into enemy airspace the planes carrying the extra fuel are going to have much degraded climb.
Early MK Vs (eight gun) show a bit better climb using standard 2850rpm and 9lbs climb compared to the MK IIs with Merlin XII engines. Above 20,000ft the MK Vs show more advantage.
MK Vs seem to show rather different performance from each other.
A MK Vb with standard tanks was within 15lbs of the MK IIA with the fuel tank. Extend range Vb might have had similar performance to a standard IIa? Or IIb? Is that good enough in late 1941?

That is awful. The Bf109 had a good 300l centreline droptank by 1941, it cost 19mph off the top speed and 6mph for the carrier, so, -25mph for the tank when fitted, that could be dropped at any time, although the carrier remained.

Eng