1000-1200 HP: long range fighter vs. interceptor?

[tomo pauk]

The thing was raised several times in the forum: long range fighter will be at disadvantage vs. an interceptor, provided they were powered by same generation of engines.
Wonder if someone can come up with a viable escort fighter on 1000-1200 HP (at 20000-15000 ft of altitude; historical engines only)? How would it stack vs. historical fighters with same power? What weaponry to choose (historically available for the country, of course). How good an escort range?
What about historical long range fighters with modest power on board?
Would a long-range fighter force offer enough tactical or strategic advantages vs. the force comprised of short range interceptor?
Obviously, the time of interest would be the 1st years of the war (only for hypothetical fighters).

 

[Messy1]

Would it be similar to comparing a Mustang to a Spitfire or FW-190?
Or Spitfire vs. BF109?

 

[DonL]

@ Tomo

this is also the subject, which we are discussing with the FW 187.
To my opinion you are in need of a two engine a/c as an escort fighter to have a chance against an interceptor at the 1000-1200PS class.

We have discussed this on several issues,
we had a discussion, if a P51A with a merlin XX could do long range fighting 1941/42. I have said not a single chance against a Bf 109 F4 or FW 190 as interceptors, other members have other opinions. The FW 187 as two engined fighter, has to my opinion a real chance against a Spitfire at the 1000-1200PS class, but not any single engined long range fighter, because the P51A was the best on the market ever, as a single engined long range fighter, but with 1000-1200PS she would be a lame duck in the air, especially at any accelaration.

 

[OldSkeptic]

The issue is if the LR Escort (LRE for Short) arrives at the point of battle with a similar weight load (or easily jettisonable extra weight) as the possible interceptor, given similar power levels.

So the issue for the LRE is whether it can carry enough non performance affecting fuel for a period of combat and return.
If that extra weight needed is not that great that the performance hit is not significant (say within 5%) then you can have a good performing LRE.

Of course aerodynamic tricks, such as better wing loadings and/or overall drag/etc can help close the gap, of those are significant the they can even provide a better performance for the LRE. Such as the Mustang vs the much lighter 109, which on comparable power was significantly faster.

You can do engine tricks too, optimising the power for the altitude band required for escorting. And so on.

Taking the MK VIII Spit as an example. 96 (UK) gals in the front tanks (bit more than the V or IX) and 26 (28 capacity, 26 usable probably) in the wings. Now for a Berlin mission, 500 miles, and 15 min combat allowance.
We assume it uses the entire rear tank of 66 gals taking off, climb and initial cruise. Then switches to the 90 drop tank for rest of trip, rendezvous and escort until combat, where it drops whatever is remaining.
It now has 122 gals. 15 mins combat leaves 87 gals. Most econ cruise return uses 72 gals, leaving 15 reserve.

Now it needs those 26 gals in the wings, weight approx 320 pounds say for the fuel and the bags. At an all up weight of 7,800 lbs that's only about 4%. That is not going to have any significant affect on performance. Most of the performance tests on the VIII were at that, or close to, weight anyway.

So it really depends on the extra fuel required fraction. If that is not too significant then it is not an issue. Sure if that was 20% of the weight then you'd take a real performance hit.

 

[Shortround6]

A problem with the late 30s designed fighters is that you not only have to worry about the extra weight of the fuel affecting speed, climb and turn ( and speed is the least of the worries) but about field performance. Most countries were building aircraft to use exiting airfields. Not building/extending airfields to suit higher take-off and landing speed aircraft. The British even had a specified maximum air pressure for the tires of ALL aircraft to avoid putting ruts in the grass fields. Add 3-400 lbs of fuel and you may need a bigger wing, not just to hold the fuel but to keep the take-off and landing speed down. The bigger wing adds both weight and drag. You may need bigger tires to hold the weight at the same ground pressure, maybe only a few more pounds each but it all adds up. If you are designing to an 8 "G" service and 12 "G" ultimate load for a 7000lb fighter and you add 300lbs fuel you now have a 7.67 G service loading and 11.5 ultimate which means beefing up the structure to meet the requirement.

What governments allowed BEFORE the shooting started and what they allowed AFTER were not the same thing.

It is this 'creep' that meant that a long range fighter was so hard to design with a 1000-1200hp engine. The long range fighter not only had to try to equal the interceptor in speed and climb, it had to do it carrying near equal armament, carry more fuel, AND take-off in the same distance, land at the same speed, be built to the same stress (G) levels and in some cases , exert the the same ground pressure (pounds per sq in) through the tires.

Early Spitfire and and Hurricane were around 24-26lb per sq ft of wing area, adding 320lbs of fuel calls for another 12-13 sq ft of wing area. the bigger wing weighs another 40-50lbs which call for another 2 sq ft of wing. beefing up the structure requires ?? pounds. Changing tire size calls for ??

If you can get the Army, Air Force or Navy involved to waive one or more 'standard' requirements you have a better chance.

 

[OldSkeptic]

A problem with the late 30s designed fighters is that you not only have to worry about the extra weight of the fuel affecting speed, climb and turn ( and speed is the least of the worries) but about field performance. Most countries were building aircraft to use exiting airfields. Not building/extending airfields to suit higher take-off and landing speed aircraft. The British even had a specified maximum air pressure for the tires of ALL aircraft to avoid putting ruts in the grass fields. Add 3-400 lbs of fuel and you may need a bigger wing, not just to hold the fuel but to keep the take-off and landing speed down. The bigger wing adds both weight and drag. You may need bigger tires to hold the weight at the same ground pressure, maybe only a few more pounds each but it all adds up. If you are designing to an 8 "G" service and 12 "G" ultimate load for a 7000lb fighter and you add 300lbs fuel you now have a 7.67 G service loading and 11.5 ultimate which means beefing up the structure to meet the requirement.

What governments allowed BEFORE the shooting started and what they allowed AFTER were not the same thing.

It is this 'creep' that meant that a long range fighter was so hard to design with a 1000-1200hp engine. The long range fighter not only had to try to equal the interceptor in speed and climb, it had to do it carrying near equal armament, carry more fuel, AND take-off in the same distance, land at the same speed, be built to the same stress (G) levels and in some cases , exert the the same ground pressure (pounds per sq in) through the tires.

Early Spitfire and and Hurricane were around 24-26lb per sq ft of wing area, adding 320lbs of fuel calls for another 12-13 sq ft of wing area. the bigger wing weighs another 40-50lbs which call for another 2 sq ft of wing. beefing up the structure requires ?? pounds. Changing tire size calls for ??

If you can get the Army, Air Force or Navy involved to waive one or more 'standard' requirements you have a better chance.

Well yes and no. I mean longer takeoff were not an issue, just a longer field, so what. Landing about the same.
They had all those issues adding bombs and drop tanks, just did them, maybe pumped up the tyres a bit.......

No need to beef up the structure for that small diff. After all they didn't for the Mustang, even though the D's G limit was well under the A's.

And the Spits wing didn't change from the Mk V with the universal wing until the Mk XVIII, so didn't seem to be a issue.

You can add the P-47 too, look at its weight gain with more internal fuel, external tanks, bombs, rockets...again big deal.

There was a bigger diff in landing between a (say) Mustang than between a Spit I and a Spit XIV....

It is not that big a deal. realistically no pilot is going to note the diff of 5% in weight unless it affects CoG markedly. They weren't that delicate those things.

 

[Shortround6]

It depends on when you begin work.

Tomo wanted it for the first year of the war.

BY August 1940 many of the "rules" had been done away with.

In August 1938 they had not, in August 1939 some had been.

How many planes do you want and when do you want them?
In the Summer of 1939 Spitfires were still being fitted with fixed pitch props, take off to clear a 50ft screen (trees?) was 790yds. Fitting the two pitch prop cut that to 390yds and fitting the constant speed prop cut it to 270yds. Obviously even with 880hp for take-off a Spitfire with a constant speed prop can get more fuel off the ground than the fixed pitch on can. However going to the Merlin XII in Aug/Sept 1940 gives 1175 hp for take-off which makes things much better.

The 'rules' in peacetime meant that your design/modification could be rejected out of hand for not meeting requirements. There was some arguing back and forth over the tire pressure issue with the Westland Whirlwind and in the end the Whirlwind was allowed to pump up the tires which saved redesigning the rear of the nacelles.

Curtiss was advertising the Hawk 75 as stressed for 12 "G"s with the Wright 9 cylinder engine. When fitted with the P&W R-1830 it was rated at 11.5 G, with the note that 12 "G"s was available at a slight increase in weight and cost. XP-40 and early P-40s had to be stressed for the 12 "G" ultimate load clean at 'normal' gross weight. P-36 and early P-40s did have an internal fuel tank that was called an overload tank that was NOT filled when making these calculations. But you needed a fuselage big enough to hold a 58 gallon fuel tank.

Modifying an exiting design and getting into service once the shooting starts is one thing. Having several hundred "escort" fighters available when the shooting starts is quite another.

A bit like the Navy specifying the plane that replaced the TBD had to land at 70mph while carrying a torpedo. This lead to the Avenger but there were 13 paper designs submitted. If one proposal had said " this is a great design but it lands at 77mph (10% faster than requirement) just beef-up your flight decks and arresting gear to handle it" where do think that proposal would have wound up in the stack?

edit, changed distance for constant speed prop.

 

[tomo pauk]

Thanks for posting out the numbers, SR6.
I do have some remarks, however (as always ). 1st is that a Spitfire with Merlin X would be taking off with 1070 HP, instead with 880 HP, a 22% increase. The engine was available from 1939 in more than token numbers. Of course, the Merlin X was never installed in a fighter (other than for test purposes?) historically.
Second, Germany did have both constant speed props available, along with engines providing a decent power for take off. 1100 PS for the DB-601A, 1200 for the Jumo 211B. At 5000 m (16130 ft) they were good for 960 and 930 PS, respectively. The engine ratings being 'Erhohte Dauerleistung' ('Increased Continous power' - duration 30 min) and 'Kampf und Steigleistung' ('Combat and climb power' - duration 30 min) for the 601A and 211B, respectively.
Power was ~1045 PS for the 'pre-Hooker' Merlins (III, VIII, X, XII). V-1710-33 (C series) was good for ~1000 PS at 16000 ft; both engines operating at max RPM boost for that altitude (5 min limit?). The Allison was providing 1055 PS for take off, but, when it became available, the UK and German engines moved on.

From 1939 until BoB, Germany was in position to have a fighter fitted with a drop tank, that would be capable to take off from same airfield the Spitfire I would take off clean? Or, the Spit with Merlin X would take off with a drop tank as fast as the Spit I clean?

 

[Shortround6]

Yes, the British were a bit behind in the propeller area.

The other thing to remember is that all the prewar aircraft were having protection (armor) and self sealing tanks fitted. Many US fighters had good range with internal fuel before fitting the protected tanks. The P-40 went from a high of 180 US gallons in the P-40 no letter to 135 gallons in the P-40C. Fuel system (tanks, pipes and pumps) went from 171lbs to 420lbs while 93 lbs of armor and bullet proof glass were added. P-39 went from 200 gallons in the XP-39 to 170 gallons in the YP-39/P-39C to 120 gallons in the P-39D and later. P-39 added 245-265lbs of armor and glass. P-38 dropped from 400 gallons to 300 gallons with self sealing tanks. The F4F didn't drop as bad but went from 160 gallons to 144-147 gallons and added around 160lbs of armor and glass.

Performance chart for a 109E showing take off to 20 meters (66ft instead of 50):

http://www.wwiiaircraftperformance.org/me109/me109e-handbookcurve.jpg

It doesn't look like the 109 is going to get out off the same sized airfield with a drop tank as the Spitfire will without one once the Spitfire gets even a 2 pitch prop.

A P-40E (overloaded with it's six .50cal mgs) clean (no drop tank) needs 975 yds to clear a 50 ft screen from a sod runway on a 59-60degree F day. adding 600lbs to the take-off weight adds over 200yds to the distance.

Earlier P-40s that were lighter would do better.

Once the shooting started it was a lot easier to take over land, cut down trees and knock down building bordering airfields.

 

[tomo pauk]

Fine points.

...

Performance chart for a 109E showing take off to 20 meters (66ft instead of 50):

http://www.wwiiaircraftperformance.org/me109/me109e-handbookcurve.jpg

It doesn't look like the 109 is going to get out off the same sized airfield with a drop tank as the Spitfire will without one once the Spitfire gets even a 2 pitch prop.

The Bf-109 have had it's limitations, re. short field performance. That should be tied to the small wing - result being a high wing loading. IIRC the LW pilots claimed that British fighter were 'childishly easy to take off and land', no doubt because of their low wing loading.
BTW, the Bf-109E-7 was outfitted with drop tanks, so we can safely conclude that LW did not considered that combination as a problematic one.

 

[tomo pauk]

We might try to consider some real-world long range fighters, and see how they stack vs. short range competition.
But 1st, let's discount for a moment the P-51 (as too advanced for early war) and Zero (as too fragile). The good contenders might be the D.520 (1540 miles of range*, no drop tanks), Ki-61 (600-650 liters, or 158-172 US gals internally, in protected tanks, according to the 'Bunrin Do' book about it, plus 2 x 200 L drop tanks - 106 US gals; non-protected tanks found in some examples were good for 380+170+200= 750 L, almost 200 gals). I know that Mustang actually predates the Ki-61, but aerodynamics applied to the Ki-61 were less advanced than ones at Mustang.
Then we have Italian fighters. Re.2001 (DB-601Aa license engine) was carrying 540 liters, or 143 US gals, or one imp gal less than Spit VIII. The Re.2002 (Piaggio radial engine) was carrying 600 liters. Both Reaggianes were capable to take off with a 650 kg (1430 lbs) torpedo. The Re.2000 - 640L; the 'G.A.' version (Grande autonomia) was carrying 980 L of internal fuel, capable to take off from 210 m runaway (230 yds, not sure that is with obstacle or without), vs. 170 m for the regular Re.2000. The G.A. model was 10 km/h slower, the climb was hurt more (7 min 45 sec to 6000m, vs. 6 min 10 sec for 'regular' 2000). The MC.202 was carrying 87 imp gals, ie. not that a long range bird - on par with BoB trio.

Neither of the listed, longer ranged fighters was regarded as a easy meat IIRC.

*edited

 

[OldSkeptic]

Amazing what happening pre-Portal and Dowding was still around eh?

Here's your long range 1,000bhp fighter:

 

[tomo pauk]

Thanks for that.

Anybody wants to estimate what kind of performance one might get from Mustang with V-1650-1 on board?

 

[stona]

Amazing what happening pre-Portal and Dowding was still around eh?

Here's your long range 1,000bhp fighter:

Which was being mooted in June 1940 at about the same time as the RAF was desperately trying to develop cannon armament for its fighters as the machine guns were starting to prove inadequate.
I don't find it at all surprising that as the RAF faced a defensive battle following the fall of France they opted not to develop a tankage system that was incompatible with cannon armament. It is a matter of priorities and in June 1940 longer range Spitfires were not the priority.
In fact probably the most important criteria for intercepting fighters during the BoB was rate of climb, given the limited warning times. This would certainly been adversely affected by a system like that.
Cheers
Steve

 

[Shortround6]

In General, when something seems too good to be true it probably isn't.

The good contenders might be the D.520 (1540 miles of radius, no drop tanks)

Figures I have seen are 1540 kilomters of range. and 620 miles miles 'normal' range and 777 miles max range.

And rem wiki; take as you will: "A self-sealing fuel tank with a capacity of 396 litres (87 imp gallons) was mounted between the engine and cockpit, along with two wing tanks which, combined, carried another 240 litres (53 imp gallons), for a total of 636 litres (131 imp gallons);[14] this was considerably more than the contemporary Bf 109E, Spitfire I and early Italian fighters, each with about 400 litres (88 imp gallons) fuel capacity. The ferry range was from 1,300 km (810 mi) to 1,500 km (930 mi) at 450 km/h (280 mph) which, from June 1940, allowed D.520s to escape to North Africa when France fell.[15] The handling changed according to the amount of fuel carried; using the fuselage tank alone, fuel consumption had no appreciable effect on handling because the tank was at the centre of gravity, but with full wing tanks, directional control was compromised, especially in a dive."

The wing tanks were in the leading edge or at least forward of the spar outboard of the wing guns. The speed given as as a 'ferry' speed seems a little suspect too. The P-40E with about the same amount of fuel total but using only 100 imp gallons for the cruise (23 imp being used for warm-up, take-off and climb) could cover 700 miles at 235mph at 15,000ft. speeding up to 280mph at 15,000 dropped the range to 565 miles. Granted it is a bigger, heavier airplane but NOBODY was using 280mph as a ferry cruise speed.

Empty and gross weights don't add up either.
Empty weight: 2,123 kg (4,680 lb)
Loaded weight: 2,677 kg (5,902 lb) useful load 1228lbs
Max. takeoff weight: 2,785 kg (6,140 lb) useful load 1460 lbs

Pilot and chute 200lbs
131 IMP gallons fuel 982lbs (at 7.5lbs per gallon)
2700 rounds 7.5 ammo 162 lbs?
60 round cannon drum 60lbs ?
oil ____?

And this is assuming the empty weight is empty equipped weight.

The Zero had several things going for it, one was it carried a fair amount of fuel to begin with, 120ip gallons in internal tanks in early models. AN engine that would run in extremely lean conditions. Flights were over water and low cruise speeds could be used. early use of external tank.

As far as far as this goes:

Here's your long range 1,000bhp fighter:

We are supposed to believe that those two tanks had less drag than the bullet proof windscreen fitted to the Spitfire? (6mph reduction in speed for the Windscreen)
And even if true (and the 90 gallon slipper tank caused a much larger reduction in speed 14-17mph depending on altitude?) speed is just one aspect of fighter performance. the 90 gallon tank on a MK V with a Merlin 45 engine caused a 18% reduction in climb rate at 1000ft, 19% at 10,000ft, 24% at 20,000ft and 30% at 30,000ft.
Climb rate is also an indication of the ability to maintain height in a turn.

 

[tomo pauk]

Indeed you're right re. D.520 range being 1540 km; 'radius' was a typo and I will correct the previous post.

 

[OldSkeptic]

Which was being mooted in June 1940 at about the same time as the RAF was desperately trying to develop cannon armament for its fighters as the machine guns were starting to prove inadequate.
I don't find it at all surprising that as the RAF faced a defensive battle following the fall of France they opted not to develop a tankage system that was incompatible with cannon armament. It is a matter of priorities and in June 1940 longer range Spitfires were not the priority.
In fact probably the most important criteria for intercepting fighters during the BoB was rate of climb, given the limited warning times. This would certainly been adversely affected by a system like that.
Cheers
Steve

True. But there was an expectation then that longer ranged missions would be required later and in the other theatres of the war, which was in fact the case ... called 'thinking ahead', Dowding had a bit of a track record of doing that.

The statement there is that the big tanks were necessary for reinforcement in the Middle East. Though the statement says 'Douglas' the desire would have come from Dowding. who was obviously thinking ahead and on a much bigger scale and this is in Jan 1940, even before the BoB started.... I rest my case.

Note that after the 'regime change', the RAF didn't send any Spitfires to North Africa until the end of '42 and Malta until March '42. Hundreds of airmen died in their obsolete Hurricanes and P-40s' in that time.
While Douglas, now head of Fighter Command and his side kick Leigh Mallory fought bitterly not to release a single Spit to the Med.. right the the very end.
Hence the Hurricanes and P-40s going up against 109Fs and even Gs... and dying in droves.

I suspect that it might just have been just a bit sooner under Dowding and Park. In fact you can speculate that the whole Malta siege might never have happened, or at least been very, very short. Worse than that for the Germans and Italians, Spits of even that range could have ensured the convoys got through.

These early tanks were interesting, basically conformal tanks with much less drag than a normal drop tank, clever thinking. A picture of the 29 gal ones would have been interesting, they would be much smaller than the 70 gals ones, but still added significant range (about a 250 mile combat radius), those with a centre 45 or 90 gal drop tank would have been quite interesting..

 

[stona]

I think you are re-fighting the war with limitless resources and aircraft available, and with the benefit of hindsight which is not entirely realistic.

As for Malta, the actual saga of the attempts to fly aircraft in for her defence makes for hair raising reading. It seems impossible that the RAF would embark aircraft along with ferry tanks that didn't fit, but they did. It seems incredible that they would fly off Hurricanes too far away and when they had no chance of meeting their pathfinders (Marylands), but they did. It seem inconceivable that they would allow a shambolic situation to develop in which aircraft were destroyed on the ground before they ever went into action, but they did.

The famous plea for Spitfires ("Malta's need is for Spitfires, Spitfires and still more Spitfires. And they must come in bulk, not in dribs and drabs.") was made by Squadron Leader Gracie on behalf of Air Vice Marshall Sir Hugh Lloyd (the new AOC Malta) in April 1942. It was bad timing, the ships were simply not available. The flight deck of HMS Argus was not long enough to fly off Spitfires with long range ferry tanks and HMS Eagle was undergoing repairs to her steering gear. The lifts on other carriers could not cope with the wingspan of the Spitfire. We know the fates of HMS Illustrious and Ark Royal.

Things in a war are always easier said than done.

Cheers

Steve

 

[tomo pauk]

Is there a reason (technical, not political) that would prevent the arrival of Spitfires at Malta in, say, second half of 1941?

 

[Shortround6]

Not really, it depends on the risks they were willing to take. How close to get the carriers flying them off to Malta or how many crated aircraft on freighters they were willing to loose. 8 crated planes on each of 6 freighters gets you 24 delivered Spitfires even if 50% of the freighters were sunk. Granted you have to assemble the aircraft rather than just refuel them in order to use them.