Prospective lightweight multi-role single seat fighter.

[BarnOwlLover]

I got this idea from some discussions I've had elsewhere and something that was brought up in a thread about making a "Spitfire into a baby Tempest". I sort of don't think that the Spitfire IX as built would be 100% suitable for what was mentioned in that thread for a "multi-role" fighter.

Here's what I'm thinking of, and I want those who know more/better than me to chime in. I was thinking of an aircraft powered by a 1700-2000+hp Rolls Royce Merlin or a 2000-2300+hp Rolls Royce Griffon. Both are intended to use two stage superchargers. The intended roles are interceptor, escort fighter and ground attack. This aircraft is intended to be the lightest for the power plants, and suitable armor, self sealing fuel tanks, and range, while being both fast climbing and highly maneuverable.

Basically, the broad specs are a top speed 440-460+mph, a range of 700+ miles on internal fuel (and up to 1500 with drop tanks), a climb rate of 4500+ ft/min., a large wing to minimize wing loading, the ability to carry 1000-2000 lbs of bombs or 8-16 RP-3 rockets or 6-8 HVARs, and the use of Fowler or Fairy-Youngman type flaps for good low speed performance and combat maneuvering.

The aircraft can be made out of wood or aluminum (or a mix of the two), has to be easy to make and maintain, be durable, and maintain performance in concert with those attributes.

Of course, I should note that this was basically what many late war IJA/IJN fighters were aiming for. So maybe use that as a reference if those designers had the Merlin of Griffon available to them.

 

[wuzak]

Supermarine Spiteful?

Data from Supermarine Spiteful - Wikipedia

Maximum speed: 483mph @ 21,000ft
Service Ceiling: 42,000ft
Rate of Climb: 4,890ft/min

Armament
Guns: 4 × 20 mm (0.787 in) Hispano Mk.V cannon with 156 rpg
Rockets: 8–12 × 3 in (76 mm) 60 lb RP-3 rocket projectiles or 4 × 300 lb (140 kg) rockets
Bombs: 2 × 1,000 lb (450 kg) bombs

 

[tomo pauk]

The P-51B/D/H with Fowler flaps? Sea Fury if the bigger wing is required?
What kind of weights should we have in mind?

 

[Shortround6]

Decide what you want, most successful "multi-role" aircraft were adopted from limited role aircraft.
Most planes designed as "multi-role" aircraft while still on the drawing boards were flops.

P-51Ds worked at ground attack but they were not Ideal. They may have been off by 10-15%? but trying to get the last 10-15% is what screwed up many designs.

Want a P-51 for ground attack?
Yank the 2 stage supercharger. Unless you are attacking ground troops in highest of the alps or Himalaya's you don't need it. Lighter engine, smaller radiator, no intercooler, and so on.
Want a high altitude interceptor, leave the hundreds of pounds of armor thy Typhoons and tempests carried at home.

Want to use wood? Sorry, add 300-500lbs to airframe weight. Which affects either weapons load or fuel load and/or wing loading for an air to air aircraft.
Large wing means more drag

and so on.

TANSTAAFL

 

[Admiral Beez]

• 1700-2000+hp Rolls Royce Merlin or a 2000-2300+hp Rolls Royce Griffon.
• top speed 440-460+mph, a range of 700+ miles on internal fuel (and up to 1500 with drop tanks)
• the ability to carry 1000-2000 lbs of bombs

Your adjective in the title is lightweight. I do not see how the above three requirements can be achieved in anything considered lightweight. What weight class are you considering as "light"?

And why is achieving a light weight your primary objective here? Once you're putting on a Griffon, enough gas for extended range and robust construction to carry 2,000 lbs of bombs, all while exceeding 450 mph.... I would think any cost savings of reducing weight would be the last of any concerns.

 

[yulzari]

If you are going to be using the P51 at low level as a strike aeroplane then swap the Merlin for the Allison.

 

[BarnOwlLover]

Weight for the Merlin powered version would be normal take off weight of 8000-8800 lbs. Griffon would be 9200-9900 lbs. And for those who are curious, armament would be preferably 4x20mm cannons. I did mention that I favored a format similar to late war IJA/IJN fighters that favored speed, climb rate and agility in fighter vs fighter combat. An example would be the Mitsubishi A7M. It was nearly as big as the F6F Hellcat, but was faster (near 400mph top speed) and was designed to mimic the agility of the A6M Zero. Of course, that meant a large wing and low wing loading, given its size. the Kawanshi J3K/J6K aimed to do much the same (Top speed of 425+ mph, and be very maneuverable).

Granted, I do believe that some of you would argue (and one poster already kind of suggested it) that my prospective fighter got built with the later Griffon-powered Spitfires, the Spiteful or the lightweight Mustangs.

Also, I'm not a big fan of annular radiators, and I'm not sold on the Meredith radiators from a survivablity standpoint. So I'd favor either leading edge radiators or a boundary layer control version of the Spitfire radiators that can make better use of the Meredith effect.

Of course, power and size does favor the Griffon, but the deal with the Merlin option was that, one, the Spiteful was initally looked at to use the Merlin if there were problems with the two stage Griffons (which didn't happen), and the DH Hornet was powered by two 2000+bhp Merlins, as was the F-82 Twin Mustang (XP-82 and P-82B initial production variant), both having phenomenal speed and climb abilities. And both the Hornet and Twin Mustang weighted nearly twice as much as single seaters powered by similar engines.

 

[tomo pauk]

I did mention that I favored a format similar to late war IJA/IJN fighters that favored speed, climb rate and agility in fighter vs fighter combat. An example would be the Mitsubishi A7M. It was nearly as big as the F6F Hellcat, but was faster (near 400mph top speed) and was designed to mimic the agility of the A6M Zero. Of course, that meant a large wing and low wing loading, given its size.

If the late-war Japanese fighters favored speed, they were bad in expressing that, especially the A7M. 400 mph is a good turn of speed in 1942, by 1944 it is well behind the curve. Hellcat was also near 400 mph top speed when water injection was used.

Also, I'm not a big fan of annular radiators, and I'm not sold on the Meredith radiators from a survivablity standpoint. So I'd favor either leading edge radiators or a boundary layer control version of the Spitfire radiators that can make better use of the Meredith effect.

FWIW, the people at RAF were against the leading edge radiators on the Tempest due to the greater vulnerable area they represent to the enemy fire. Annular radiator provides a far smaller target, and can be easily armored. Merredith radiators do come in various forms, some were better than the other, ditto for the size and number of radiators per aircraft and size as a target.

 

[BarnOwlLover]

For a ventral Meredith radiator, would something like the Hawker P1027 (Tempest fitted with a Rolls Royce Eagle engine) or a refined version of the Curtiss XP-46 maybe be good to use?

 

[Shortround6]

A few points.

Meredith radiators. They need good execution.
The goal is to have the heat from the radiator increase the temperature/pressure of the air flowing through the radiator duct to point that the speed of the exiting air equals or exceeds the drag of the cooling air going through the duct form beginning to end AND exceeds the drag of the air going through the radiator matrix. AND it has to do it a various inlet temperatures and air densities.
If you put a long gentle flowing duct under a plane (with gentle changes in cross section and changes in direction of airflow) but put in a small radiator matrix that causes a sharp pressure change in the air flow it means you have too much drag and you won't get you desired drag reduction. If you go the other way and use a large matrix you have more frontal area and you may need steeper changes in direction or changes in cross sectional area (turbulence) even though the airflow through matrix has a lower pressure drop.
The Mustang designed the Meredith effect in. They did not add it later. And they changed things as they changed engines. Look at the P-51B vs an Allison engine Mustang they were constantly tweaking the design and the P-51B needed a lot more cooling air flowing through the radiator than the Allison did.

I would also note that the super Merlins and Griffons were not truck engines. They were sprint engines. The high power levels were done with 150 fuel at high boost for around 5 minutes and needed extra attention from the ground crews.

Most later Merlins, even if rated at at 25lbs for max power were rated 12lbs for take off until you get to the 80 Series engines. Then take-off power goes to 18lbs .
Climb power was 2850rpm at 12lbs (30 minute rating) even for a Merlin 130.
This is one reason the Shackletons got Griffons. You would have burned out Merlins trying to use them for trying fly large heavy bombers at high power settings for long periods of time. Merlins had max rich cruise of 2650rpm and 7lbs boost for most of them, the later ones got 2650rpm and 9lbs

 

[nuuumannn]

I was thinking of an aircraft powered by a 1700-2000+hp Rolls Royce Merlin or a 2000-2300+hp Rolls Royce Griffon. Both are intended to use two stage superchargers. The intended roles are interceptor, escort fighter and ground attack. This aircraft is intended to be the lightest for the power plants, and suitable armor, self sealing fuel tanks, and range, while being both fast climbing and highly maneuverable.

Basically, the broad specs are a top speed 440-460+mph, a range of 700+ miles on internal fuel (and up to 1500 with drop tanks), a climb rate of 4500+ ft/min., a large wing to minimize wing loading, the ability to carry 1000-2000 lbs of bombs or 8-16 RP-3 rockets or 6-8 HVARs, and the use of Fowler or Fairy-Youngman type flaps for good low speed performance and combat maneuvering.

The issue with all this is when do you want it? You have two options, either modify an existing design or design something new. If it's something new, this kind of performance is suited to an aeroplane first entering service in mid/late 1944 - early 1945 from design being undertaken in 1943 at the earliest based on engine availability, by which time the roles envisaged are being carried out in combat by lesser performing aircraft, but with high availability and acceptable performance compared to the status quo. Your aeroplane becomes the Hornet, late Marque Spitfires/Spiteful, RAF Fury, Martin Baker MB.5 etc which is at the tail end of piston-engined development and the subsequent introduction of jets. What does it bring to the table that existing last-swing-of-the-bat piston-engined fighters already bring?

I'd say this would have made a good aircraft to fulfil that role, although differing in specification from the OP; the Fury.

Sea Typhoon descendant

 

[Shortround6]

Now the Sea Fury meets just about all of your goals except the weight, It went around 12,000lbs clean which sort of shows what Hawker at least, thought was needed to do the job.
Or look at the F8F-2, or a late model Corsair (F4F-4)

You are going to need to be very tricky indeed to get all of the performance goals into an airplane that is 3-4000lbs lighter.

P-51H was about 9500lbs and only had six .50 cal guns.

 

[BarnOwlLover]

Now, maybe to add to the discussion, or at least confusion, I dug out my DH Hornet and Sea Hornet book that I bought quite a few years ago. Notably, I decided to check the weight specs. It turns out the Hornet F1 had a normal takeoff weight of just above 14,000 lbs, and normal max take off was less than 17,000 lbs. I don't know how accurate those figures are, though that book also notes that most sources do get the Hornet's dimensions wrong, namely length (based on DH plans, the Hornet is at least a foot longer in overall length than often stated). So, I do assume that the same type of research was done on the Hornet's weights.

So it seems that I may be off in terms of weight specs even for my speculative fighter, especially for Merlin power, since I was basing that estimate on the fact that the Hornet and the F-82 Twin Mustang (powered by similar Merlin engines) weigh nearly twice as much as common single seaters. Instead, the Hornet weights more like 2 Spitfire IXs or Spitfire XIIs. And even the F-82 estimates may be off, given that normal takeoff weight for it has been stated (based on the XP-82 restoration) to be a bit more than 1.5x the weight of a P-51D/K.

Not to mention that the XP-51F/G models had weight reduced to about that of a Spitfire IX. But those made an compormise in armament (4x.50 cal MGs with max 440 rpg) to keep range up, while the Spitfire IX sacrificed range in favor of firepower, as it was initially an interceptor. Even later on, it (and other Spitfires) tended to operate close to the front lines or close to base. If you wanted to mount 6x.50s or 4x20mm cannons in a XP-51F/G, you might have to fill the tanks short if you plan on using it as an interceptor or attack aircraft, which in those roles doing so wasn't a big problem unless you were patrolling for V-1 flying bombs (though Spitfires were used to shot them down, though the Hawker Tempest was king when it came to that).

And even the ground attack versions of the FW-190 couldn't carry insanely large bomb loads. 1000-1500 lbs was usually the max. And in such missions, it's often not the size of the weapons but their accuracy that's important.

 

[nuuumannn]

Now the Sea Fury meets just about all of your goals except the weight, It went around 12,000lbs clean which sort of shows what Hawker at least, thought was needed to do the job.
Or look at the F8F-2, or a late model Corsair (F4F-4)

You are going to need to be very tricky indeed to get all of the performance goals into an airplane that is 3-4000lbs lighter.

So it seems that I may be off in terms of weight specs even for my speculative fighter, especially for Merlin power, since I was basing that estimate on the fact that the Hornet and the F-82 Twin Mustang (powered by similar Merlin engines) weigh nearly twice as much as common single seaters.

I suspect that the weight issue would scupper you here. In attempting to fulfil this requirement, with the weight figures you think are pertinent (not mentioned in the original post, I might add, which then makes the Fury quite ideal), you are essentially wanting a British designed A6M concept in 1944! Given power output and performance from given engines but at a lighter weight than its contemporaries with equal load carrying capability?

 

[BarnOwlLover]

You also have to remember that even if you don't count the Yak-3, most Russian fighters of World War II tended to be smaller and lighter than a lot of German, American or British aircraft. They seemed to be happy to give up multi-role capability (the most that most Russian fighters could carry for bombload was less than 500 lbs, and, like the British and Americans in the end, favored air to ground rockets). Even late war IJA/IJN fighters that were far more competitive with allied fighters tended to be a bit smaller.

Maybe wouldn't it be better to go down the light and heavy fighter path (be it light single seat and heavy single seat or LW twin engine fighter)? Or bite the bullet and go for a relatively lightweight fighter powered by a 2000+hp engine? Even now, there are smaller and larger fighters aimed at different primary roles.

 

[GrauGeist]

The Soviets generally did not intend to use their fighters in multi-role, so you won't see them employed much in that role.

They had the Tu-2, Pe-2, IL-2 and other types for ground attack.

It's not that Soviet fighters couldn't, it's just not what the Soviets wanted.

 

[BarnOwlLover]

Speaking of Soviet fighters, maybe a multi-role capable, "Westernized" version of this might be what I'm looking for.

Mikoyan/Gurevich I-225 - fighter

Mikoyan and Gurevich I-225

MiG Fighter Aircraft Development WWII

I-211 After operational tests of the MiG-3 powered by the M-82, produced in a small batch of five aircraft designated MiG-9 M-82, one ...

soviethammer.blogspot.com

Also, looking at it's specs, maybe a P-51D/K type with the gross weight lowered to a similar amount and a somewhat more powerful engine might foot the bill.

And the I-225 IMO is also a good case for the "aircraft improvements" thread, too.

 

[tomo pauk]

Now, maybe to add to the discussion, or at least confusion, I dug out my DH Hornet and Sea Hornet book that I bought quite a few years ago. Notably, I decided to check the weight specs. It turns out the Hornet F1 had a normal takeoff weight of just above 14,000 lbs, and normal max take off was less than 17,000 lbs. I don't know how accurate those figures are, though that book also notes that most sources do get the Hornet's dimensions wrong, namely length (based on DH plans, the Hornet is at least a foot longer in overall length than often stated). So, I do assume that the same type of research was done on the Hornet's weights.

See here for very, very accurate figures wrt. ww2 fighters (and some bombers): WWII Aircraft Performance

 

[BarnOwlLover]

Actually reading reports from a test that was done and recorded on that site, maybe the P-51H could also maybe fit?