Escort Fighter Performance Comparison

[Shortround6]

Have you noticed your Spitfires tend to turn up later, thirstier, more fragile, harder to fly and modify than the ones the British built?

Some of the modifications don't seem that difficult.
But the whole rear tank set up seems a bit dodgy compared to the Mustang.
Mustangs in US service were allowed to keep using their rear tanks for years after the war (I don't know if the shifted anything else. like radios or got ballast or????)
High back Spitfires were allowed to fill the rear tanks with special permission, otherwise wired shut.
Low back Spitfires were prohibited from using the rear tanks under any circumstances.
The test of the Spitfire in Jan 1945 used metal covered elevators. A relatively simple change but not done on service aircraft even post war?
This is the plane with evaluation of burning down the fuel by 30 gals leaving 43 in the tank/s.
What was the recommendation for fabric covered elevators?
Post war Manual says 30 gallons remaining was dividing line between what you could do and what you couldn't.
Extra insurance in peacetime or different elevator required a different limit or both.

Low back Spits (at least MK XVIs ) might have benefited from a broader tail/rudder like the Griffon powered XIV. when trying to fly with a rearward CG?

As far as thirstier goes, I don't go with best estimates for the Mustang either. The Manual for the P-51B was all estimates and provisional and said so, twice. It does not line up with the charts for the P-51D.

US radius charts were done at 25,000ft. The advocates of the Spit want to use 20,000ft. How do you want to cover the difference?
The US also figured the exit speed at 215 IAS. I am not saying they were right but we do need to use a common speed to compare planes.

 

[33k in the air]

It would be interesting trying to control 100's of miles of bomber stream made up of 1000's of individual bombers transiting in and out of the UK at the same time, it would certainly overwhelm the day defences not to mention saving a lot of black paint.

It would require a lot of retraining of Bomber Command crews. Its aircraft flew to and aimed at the target individually in nighttime bombing, a sharp contrast to the USAAF approach of large, tight formations and the aiming done by lead crews. (The retraining matter was something which the USAAF cited as one of the reasons to not switch to nighttime bombing.)

As it was historically, when Bomber Command did do daytime bombing in 1944, it had to come up with its own tactics since its crews were not trained in tight formation flying. The target marking methods used at night also didn't work as well in daylight and required modification.

 

[drgondog]

It would require a lot of retraining of Bomber Command crews. Its aircraft flew to and aimed at the target individually in nighttime bombing, a sharp contrast to the USAAF approach of large, tight formations and the aiming done by lead crews. (The retraining matter was something which the USAAF cited as one of the reasons to not switch to nighttime bombing.)

100% correct. The ENTIRE US Heavy Bomber crew training pipeline was dedicated to learning the B-24 and B-17 systems, charateristics, daylight (primary) navigation and bomb aiming. It would have deeply impacted expectations for POINTBLANK objectives to be achieved before D-Day. In October, then the brief experience of setting up RAF linked operational training for night operations during November 1943 made it abundantly clear there was no turning away from daylight ops.

As it was historically, when Bomber Command did do daytime bombing in 1944, it had to come up with its own tactics since its crews were not trained in tight formation flying. The target marking methods used at night also didn't work as well in daylight and required modification.

The AAF problem in reverse.

Additionally, no one or unit devoted any significant time understanding the consequences of hearing many airborne collisions over Britain...as two enormous Air Forces competed for airspace at night.

 

[nuuumannn]

I yield to your more thorough knowledge.

I do wonder though what Harris would have made of going back to daylight bombing in late 1942/early 1943.

Aww shucks, I don't do this to prove my superiority, but because of the reading I've done I know the RAF and Supermarine discussed the idea. The issues that were raised, in reality and here on this thread were/are not insurmountable and if the desire to do it had been there, it would have been done. The work that was done proves that it could have been if there was a need to do it. After all, they turned the Spitfire into a naval fighter, which required a huge amount of structural modification, probably more than what would have been required to turn it into a long range escort fighter.

Harris might have grumbled and groaned, but he wasn't beyond reason. On his watch was the introduction of sophisticated nav aids, which he expressed dismay about, the panacea targets he despised were targeted and so forth. One of his underlying beliefs was that his bomber boys should have the best equipment and ability to do their jobs. If he could have been convinced that having escort fighters along for the ride on daylight ops would have prevented bomber and crew losses, he would have supported the idea. Who knows, he could have thrown his weight behind their development - that might have yielded results. Harris could be very persuasive when he wanted to be.

100% correct.

Yup, agree. When the 8th AF first arrived in Britain, their operational training was done there, including gunnery training, as power turrets were still very new on US bombers even into mid-1942. It wasn't until some bright spark realised the US has acres of uninterrupted sky so training should take place there.

US 8th units did embark on night operations with Bomber Command and to all intents and purposes they were successful, so the Americans could have done night bombing, but the joint chiefs of the 8th and BC came to the conclusion that round-the-clock bombing was a better way of bringing the Reich to its knees.

 

[33k in the air]

US 8th units did embark on night operations with Bomber Command and to all intents and purposes they were successful, so the Americans could have done night bombing, but the joint chiefs of the 8th and BC came to the conclusion that round-the-clock bombing was a better way of bringing the Reich to its knees.

Quoting from Roger Freeman's Mighty Eighth War Manual (p.93-94):

In July [1943] it was planned to equip and train six B-17 groups, three in each Division initially, the 92nd, 94th, 96th, 305th, 306th and 385th, to join in raids by RAF Bomber Command. Thirty aircraft in each were to be modified for the task, receiving resin lights, engine exhaust flame dampers and blackout curtains for the navigator's compartment. Gun barrels would need flash eliminators to prevent gunners from being temporarily blinded when firing. Additionally, night adaption goggles had to be supplied for the crews. It was also desirable that the B-17s involved had Gee and Standard Beam Approach equipment, while it was essential that only those with long-range wing tanks were selected.

On 20 July the 422nd Bomb Squadron of 305th Group was selected to act as a trials squadron to co-operate in RAF night bombing attacks. An RAF Bomber Command liaison officer was later attached to the unit at Chelveston where night flying training began on 2 August 1943 . . . This squadron attacked coastal defences near Boulogne on 8 September for its first night bombing mission and during the following four weeks flew seven more to targets with RAF Bomber Command . . . No more than five aircraft were despatched on any one night and the total effective sorties for the eight raids was 32 . . .

Throughout September the six groups assigned to night bombing preparations had been carrying out modifications and training and by October several crews were considered ready to participate in operations. However, all night training was stopped when, following a conference at VIII BC, the decision was made to not proceed with the plans for night bombing. Factors influencing this move were: despite heavy losses the day bombing brought positive destruction of industrial targets while there was no immediate hope of any such accuracy in the night attacks; 422nd's performance had shown that losses would not be substantially reduced by operating in darkness; if night bombing was continued the assigned groups would have to practise this exclusively thus weakening the daylight effort; the anticipated availability of long-range fighters for escort should reduce day bomber losses.

 

[Howard Gibson]

I yield to your more thorough knowledge.

I do wonder though what Harris would have made of going back to daylight bombing in late 1942/early 1943.

The American heavy bombers had turbochargers. The British heavy bombers did not. American bombers flew high enough that to attack them, the Germans had to climb up above 30,000ft, which suited the escorting P-47s, also turbocharged, perfectly. At 30,000ft, P-47s had a huge speed advantage over the Germans, something like 50mph. In combat, this is not manageable. Escorting Lancasters in daylight would have placed Spitfires at altitudes that suited Fw-190s. The Spitfires could escort American bombers, and they would be faster at 30,000ft, but not as much faster as the P-47s.

 

[PAT303]

The British heavy bombers did not

They had superchargers instead.

 

[Milosh]

They had superchargers instead.

2 speed superchargers that had the engine producing it max HP at 6000ft.

 

[PAT303]

2 speed superchargers that had the engine producing it max HP at 6000ft.

The Merlin XX had just under 1300hp @ 10,000ft and just under 1200 @ 17,500. If the need arose to fly higher there's no reason high altitude merlins couldn't be fitted.

 

[EwenS]

The Merlin XX had just under 1300hp @ 10,000ft and just under 1200 @ 17,500. If the need arose to fly higher there's no reason high altitude merlins couldn't be fitted.

The RAF did experiment with two stage Merlin engined Lancasters.

Rolls Royce converted 9 Lancaster III into Mk.VI with two speed, two stage Merlin 85/87 in annular cowlings. 7 were used by 4 of the 8 Group Pathfinder squadrons often as Master Bomber aircraft and the other pair for trials. Withdrawn from operational use in Nov 1944. The engines proved difficult for ground crews to maintain however. Probably nothing that could not have been overcome, especially in light of the engines fitted to the Lincoln.

313mph at 18,200ft at take off weight of 65,000lbs. Service ceiling 28,500 ft at same weight.

AIRCRAFT OF THE ROYAL AIR FORCE, 1939-1945: AVRO 683 LANCASTER.

Lancaster B Mark VI, JB675 at Hucknall, Nottinghamshire, after conversion from a B Mark III by Rolls-Royce Ltd, who installed 1,635 hp Merlin 85 engines and four-bladed propellers.

www.iwm.org.uk

Merlin 85 & 68A were used on the Lincoln I & II respectively (originally designated Lancaster IV & V) which reached the first squadrons in Sept 1945.

 

[Geoffrey Sinclair]

Some of the modifications don't seem that difficult.

Which ones? As so far it comes across as all too hard

But the whole rear tank set up seems a bit dodgy compared to the Mustang.

If you changed that to had more problems you would join everyone else.

Mustangs in US service were allowed to keep using their rear tanks for years after the war (I don't know if the shifted anything else. like radios or got ballast or????) High back Spitfires were allowed to fill the rear tanks with special permission, otherwise wired shut. Low back Spitfires were prohibited from using the rear tanks under any circumstances.

As has been reported many times, add the RAF was wary about operating wartime Mustangs using the rear tank. The post war pilot's notes for the Mustang say carrying under wing loads made the handling better and caution about the effects of dropping the loads with the rear tank still full. So putting a 90 gallon external tank on the Spitfire should to the same sort of thing. As the cut down fuselages on the P-47 and P-51 caused handling issues, requiring a dorsal fin extension, you would expect the same for the Spitfire.

The test of the Spitfire in Jan 1945 used metal covered elevators. A relatively simple change but not done on service aircraft even post war? This is the plane with evaluation of burning down the fuel by 30 gals leaving 43 in the tank/s.

Actually wrong, the early 1945 tests used a standard Spitfire that was also given hand made metal covered elevators for *some* of the tests, they made handling better. There were July 1944 tests on a mark VIII with a 75 gallon rear fuselage tank. The 30 odd gallons level had been worked out some time previously. Not sure if the 1945 tests made it official or not. The post war Spitfire IX and XVI notes state all XVI and some late model IX had the rear fuselage tanks, the effective start of XVI production was September 1944.

Post war Manual says 30 gallons remaining was dividing line between what you could do and what you couldn't. Extra insurance in peacetime or different elevator required a different limit or both.

Whatever. It is clear you consider the rear tank in a Spitfire a bad idea, you are just having trouble finding a good reason why, trialing various thoughts like reaching back to 1942. The US mark IX modification was adding 43 gallons in the rear fuselage, plus 16.5 gallons in each wing and plumbing the wings to allow a pair of 62.5 gallon drop tanks, similar to the Mustang. The Spitfire VIII pilot's notes have a 26 gallon rear fuselage tank

Low back Spits (at least MK XVIs ) might have benefited from a broader tail/rudder like the Griffon powered XIV. when trying to fly with a rearward CG?

As a first problem that adds weight aft, which makes the CoG issues worse. A post war trial with a 58% bigger tail on the mark IX had a mixture of handling advantages and disadvantages.

US radius charts were done at 25,000ft. The advocates of the Spit want to use 20,000ft. How do you want to cover the difference?

The one data point we have for calculating the Spitfire is at 20,000 feet and "advocates" is an interesting adjective, does that make you a detractor, anti advocate? As for the altitude correction the post war Mustang notes on fuel consumption with altitude have the datum point as 10,000 feet, and say consumption increases over datum by 4.5% at 20,000 feet and 5.5% at 25,000 feet.

The US also figured the exit speed at 215 IAS. I am not saying they were right but we do need to use a common speed to compare planes.

So the P-38 and P-47 combat radius figures require them to use the same speed as the Mustang? Remembering that being slower than the Mustang they would have the same reserve power issues you brought up about the Spitfire.

We have no idea how the 8th Air Force calculated combat radius, how much allowance for formation flying, for the inevitable difference between aircraft and pilots, whether it was a fast climb to operational height or a steady one, the climb fuel allowance, if economic cruise was employed between base and a given distance from hostile airspace or further and probably other factors. Until that is clarified no one can apply similar adjustments to the Spitfire.

According to Roger Freeman adding an 84 gallon external tank gave the P-47 a combat radius of 280 miles, 108 gallons external increased the radius to 325 miles, so around 90 more miles at a mile a gallon. Upping the external load to 165 gallons increased radius to 375 miles, so 190 more miles from 81 gallons, over 2 miles per gallon. The different external loads 165-108 = 57 gallons for 100 more miles. At 2 miles per gallon going out and back to 280 miles requires 280 gallons, leaving 305-280+84 = 109 for combat and reserves for the earlier P-47D, going out to 325 miles leaves 108-20 = 88 for combat and reserves, to 375 miles leaves 165-70 = 95 gallons for combat and reserves.

According to Francis Dean the yardstick range for a P-47 with 305 gallons was pushing 1,000 miles, so over 3 miles per gallon but adding another 65 gallons internal does not raise the range by around 200 miles. His combat radius with 370 gallons internal is 225 miles, adding 300 gallons of external fuel pushes that to 670 miles, so over 3 miles per gallon. Mission profile is 5 minutes warm up and take off climb to 25,000 feet covering no horizontal distance, cruise (but not at what setting), drop tanks 5 minutes combat and 15 minutes military power for combat, 30 minutes reserves at economic cruise.

Essentially keeping the Spitfire VIII range comparable to the P-47D was possible for much of 1943 as built and required around 33 gallons of rear fuselage fuel to remain so in early 1944, and the engineering issues for the additional tank were historically largely solved in 1942/43 given things like the rear fuselage ferry tank for the mark V and we know that the issues were not major for that fuel load.

Arthur Harris turned down an offer from James Doolittle to mount a combined day mission to Berlin in 1944 citing the lack of fighters available. Eaker had the 1943 problem of a lack of fighter range but also a lack of fighters compared with his bomber strength, it meant running unescorted raids or an underemployed bomber force.

 

[PAT303]

I've posted this before but simply increasing the size of the leading edge tanks is also a viable option, for reasons unknown the tanks were only between ribs 7 and 5, the PR spits had the tanks from rib 2 outwards, making the MkVIII tanks from rib 2 to 7 doubles their capacity to 50G combined with the added bonus of keeping it on the COG.

 

[drgondog]

I've posted this before but simply increasing the size of the leading edge tanks is also a viable option, for reasons unknown the tanks were only between ribs 7 and 5, the PR spits had the tanks from rib 2 outwards, making the MkVIII tanks from rib 2 to 7 doubles their capacity to 50G combined with the added bonus of keeping it on the COG. View attachment 680836

Something about flying an unarmed Spit, maybe. Additionally, complicated to fill multiple tanks, as well as complicating plumbing outboard of the guns as well as screwing up oll inertia as you move outboard. The Mustang was delivered with two auxilary tanks (total 26 gal) in each wing gun and ammo bays. RAF had choice of Very long range (for that time) Recon with only the two fuseage cowl guns. A similar approach leaves a Spitfire defenseless.

 

[Shortround6]

Most of the swo stage PR Spits got enlarged oil tanks.

Many of the PR Spits were allowed to fly (or take-off) hundreds of pounds heavier than the combat versions.
Some of the PR Spits had no BP glass.

Most of the PR Spit pilots were instructed to get the pictures back, not muck about with German fighters, even if they had a few guns.

going back to the P-51 for moment.

Two different tails and two different rear fuselages for 3 different combinations.
A Pilots manual may have to cover all three.

The British may have been able to build a longer range Spitfire.
But what version shouldn't' they have built and what do you need to t do ( I am assuming it could have been done, eventually) to get the Performance you want.

Performance includes climb, turn, roll rate, etc.
Perhaps they set the Performance standard too high (weren't willing to accept the loss in handling/flying qualities) ?
Perhaps they didn't have the engineering staff to handle too many changes at once and other projects (Stuffing Griffons in the airframe) took priority.

 

[NevadaK]

Well, a different take would be that a longer range Spitfire would have hurt the daylight bomber offensive.

My understanding (albeit a little under informed) is that bomber escort was conducted in zones, or waves. The first zone, or wave, was conducted by Spitfires and P-47 ranging our about 250 miles (rough memory here), after that a second zone with P-47's and P-51's out to about 400 miles, and after that P-51's. The planning was for each escort fighter group to be at optimal fighting weight in its area of coverage, not carrying too much fuel to be a liability. On return, bomber groups would be picked up by different escort groups at optimal ranges.

The Spitfire was being used in its best range and performance. Trying to extend the range, duplicates the capabilities of an already excellent aircraft (Mustang) and creates a void in the shorter coverage area.

 

[drgondog]

Most of the swo stage PR Spits got enlarged oil tanks.

Many of the PR Spits were allowed to fly (or take-off) hundreds of pounds heavier than the combat versions.
Some of the PR Spits had no BP glass.

Most of the PR Spit pilots were instructed to get the pictures back, not muck about with German fighters, even if they had a few guns.

going back to the P-51 for moment.
View attachment 680932
Two different tails and two different rear fuselages for 3 different combinations.
A Pilots manual may have to cover all three.

The British may have been able to build a longer range Spitfire.
But what version shouldn't' they have built and what do you need to t do ( I am assuming it could have been done, eventually) to get the Performance you want.

Performance includes climb, turn, roll rate, etc.
Perhaps they set the Performance standard too high (weren't willing to accept the loss in handling/flying qualities) ?
Perhaps they didn't have the engineering staff to handle too many changes at once and other projects (Stuffing Griffons in the airframe) took priority.

Better comparison perhaps is same basic wing/fuselage/empennage for all three 'combinations' - different afterdeck and cockpit enclosure - requiring slightly different DF. Same fuel capacity. Same basic engine, but different supercharger stage variation for different performance envelope. The Dorsal Fin and reverse rudder boost kits added to B/C/D/K until they became production articles. Most of the fuselage and wing from firewall aft, save cooling scoop and radiators to handle heavier load than NA-73 through NA-99 (P-51A).

The only significant changes were related to visibility (cockpit enclosure) and Reduced manueverability through additions of DF and RRB to both B and D.

The handling qualities reduced with each successive model from A to H, where B and D were less 'pilot natural'than A, until the redesign of the H restored 'handling quality' - the only exception is that B/D rolled better with +/- 15 degree and H matched with +/ 10 but larger ailerons.

The growth of the Spitfire variations from Spit V through Spit XIV are analogous to P-51A through P-51D with diffrent and heavier engines, more weight/torque and design compensations of new rudder and GW without dramatic changes to fuselage/wing. For my, I like to think of the Mark XIV/XVI (and 109K) were top of the line muscle cars similar to P-51D, when compared to Mark V (and Bf 109F) and P-51A as the Gran Prix 'nimble and fun' types.

 

[PAT303]

Something about flying an unarmed Spit, maybe

Huh?.

 

[PAT303]

A similar approach leaves a Spitfire defenseless.

Why would making the tank from rib 2 to rib 7 leave the Spit defenceless?, your not taking the guns out.

 

[PAT303]

The Spitfire was being used in its best range and performance. Trying to extend the range, duplicates the capabilities of an already excellent aircraft (Mustang) and creates a void in the shorter coverage area.

We are not trying to make the Spit a Mustang, we are trying to extend the range of the Spit before the Mustang comes into service.

 

[PAT303]

The British may have been able to build a longer range Spitfire.
But what version shouldn't' they have built and what do you need to t do ( I am assuming it could have been done, eventually) to get the Performance you want.

Which version should they have built, the one with more than 175 mile radius, why don't we start with that. Seriously we are going around in circles.