A better FAA twin seat, single engine fighter for 1940?

[Admiral Beez]

For wargame purposes, I have spent way too much time on this particular question. The only solution I was able to find was the Super Fulmar (I called it the Fulmar FBR Mk IIIE ). The increase in wing loading was a little under 2 lb/ft2, and the stall & landing speeds only increased by ~1.5 mph.

interesting. Tell us more

 

[ThomasP]

See my post:"Could the FAA have been better prepared for WW2?"

In the campaign I used a higher power 'R' engine so I needed to use a 6-blade contra-rotating prop to absorb the full power and special racing fuel. I balanced most of the increased weight forward of CG with armour for the Observer/REO, the rest by relocation of equipment. The higher powered 'R' could handle 2350 BHP for 30 min (2850 rpm at +15 lbs) and 2450 BHP for 5 min (3000 rpm at +15 lbs). I fitted it for the removable CL bomb crutch and 45 Impgal DTs on the wing hard points. Gun armament was as for the Spitfire Mk VB (2x 20mm and 4x .303 cal) but with 180 rpg belt feed for the 20mm. Bomb crutch was for the pre-war 1500 lb AP bomb ("http://www.wwiiequipment.com/index....armour-piercing-bomb&catid=43:bombs&Itemid=60").

 

[Admiral Beez]

I used a higher power 'R' engine so I needed to use a 6-blade contra-rotating prop to absorb the full power and special racing fuel. I balanced most of the increased weight forward of CG with armour for the Observer/REO....

Goodness, this is 1938, not 1945. You’ve made a Super Firefly, not a better 1938-tech twin seater.

 

[ThomasP]

I know, but all the tech in the campaign was historically available prior to 1 July 1941, even the Rotol contra-rotating prop, except the developed 'R' engine. The rules of the campaign were that planning for the coming war would begin 1 January 1936, with anything on the table as long as the basic system (hull, airframe, engine, gun, etc) was available and that it would be feasible to modify or adapt in the succeeding time frames. We decided that turning the'R' into a usable engine would have been practical within ~4 years of serious effort, maybe not to the point of the Griffon in size and arrangement, but at least to a reliable engine at high power. Historically because of production/rearmament and financial/manpower issues it might not have been practical, but in the campaign the war that would begin 1 January 1942 was similar to the proxy wars of the Cold War period.

 

[Shortround6]

Use of special "racing fuel" for combat aircraft performance gets very tricky indeed.
It is not just cost. From Wiki for one use in the "R", fuel blend changed over time and use.

30% benzole, 60% methanol, 10% acetone, plus 4.2 cc of tetra-ethyl lead per gallon.

Aviation fuel had a freezing point of -76 degrees F and a heat value of 18,700 btu's per pound.

Benzole freezes at +42 degrees F and has a heat value of 17,300 btu's per pound.

Methanol freezes at -144 degrees F and has a heat value of 8,600 btu's per pound.

Acetone freezes at -138 degrees F and has a heat value of 12,250 btu's per pound.

Perhaps the mixture can keep from thickening up in low temperatures.

However the heat value was around 11,580 btu's per pound. Which means you need a crap load of fuel to go very far. The race mixture has about 62% of the heat value per pound as aviation fuel.

There are more problems, like Methanol's ability to absorb water out of the air.

 

[Admiral Beez]

I know, but all the tech in the campaign was historically available prior to 1 July 1941,

I know, but.... we need to design this in 1938.

Perhaps the Fulmar is the right bird, we just need to apply successive Merlin upgrades. That might be our best hope to get a twin seater over 300 mph.

 

[ThomasP]

Hey Shortround6,

Yeah, I know, tell me about it. I had to trade a significant amount of fuel oil stowage on the armoured carriers I used for RN standards of protection for the 'Special'. I had to trade 500 tons of fuel oil stowage space for 160 tons (50,000 Impgal) of 'Special' fuel stowage. So 40% of the Aviation fuel stowage was dedicated to the Super Fulmar, with the rest (75,000 Impgal) normal 130 grade for the Albacores and Hurricanes.

 

[Shortround6]

I know, but.... we need to design this in 1938.

Perhaps the Fulmar is the right bird, we just need to apply successive Merlin upgrades. That might be our best hope to get a twin seater over 300 mph.

300mph where?

You might be able to get the Fulmar to do 300mph without too much trouble ( the prototype did 284mph) but if you are doing 300mph at 16-17,000ft and the medium altitude bombers and the low altitude bombers and the torpedo bombers and the recon planes/shadower's are all flying at below 7,000ft then the ability to fly 300mph at 16,500ft is useless.

Flying 300mph at 7,000ft is a lot harder. Hurricane I with Rotol prop and using 6 1/4lbs of boost was 280.5mph at 6,500ft. Plane topped out at 316mph at 18,000ft.
A Spitfire MK II did 311mph at 6,500ft using 8.8lbs of boost. It did 354mph at 18,000ft using 8.3lbs of boost.

Now figure out when the Merlin upgrades became available and why. (Hint Hooker was only hired by RR in Jan 1938 and it took a while before he started working on superchargers)

 

[SplitRz]

Back to the OP, my money would be on a Defiant conversion. It has wide track undercarriage for starters - which would be a massive advantage for carrier operation - and the removal of the hefty turret with drag reduction would offset the retained weight of the extra crewman. It should also provide space for kit The P.94 derivative proposal with 12 .303s had a reasonably predicted top speed of circa 360mph. Lets chop a good lump off of that because of the FAAs obsession with filling airframes with equipment (with the obvious necessities like an arrestor hook, long range radio, decent dingy etc) - but a 330 mph aircraft is surely still a reasonable proposition? ... its also an aircraft in production - and the proposed P85 turreted naval variant of the Defiant may have already covered off some of the other required design mods for arrestor hook installation etc.

However, its still a Merlin engine - and regardless of rating, as others have said, its going to deliver its best performance at higher altitude, not low down as per the Fulmar spec. However, even a Defiant *with* its turret looks to have had a better climb rate than the Fulmar, so perhaps a faster climbing P.94 would have the advantage of being able to convert altitude into speed. Its mentioned in several passages I've read that Fulmars on interception often only had a chance to attack head on in a single pass or by diving onto things like JU88s if they had an altitude advantage.

And please give the poor old Nav Op a decent weapon to defend the tail. Perhaps a good fast firing gun like a VGO in a double Hampden style mounting?

 

[SplitRz]

Back to the OP, my money would be on a Defiant conversion. It has wide track undercarriage for starters - which would be a massive advantage for carrier operation - and the removal of the hefty turret with drag reduction would offset the retained weight of the extra crewman. It should also provide space for kit The P.94 derivative proposal with 12 .303s had a reasonably predicted top speed of circa 360mph. Lets chop a good lump off of that because of the FAAs obsession with filling airframes with equipment (with the obvious necessities like an arrestor hook, long range radio, decent dingy etc) - but a 330 mph aircraft is surely still a reasonable proposition? ... its also an aircraft in production - and the proposed P85 turreted naval variant of the Defiant may have already covered off some of the other required design mods for arrestor hook installation etc.

However, its still a Merlin engine - and regardless of rating, as others have said, its going to deliver its best performance at higher altitude, not low down as per the Fulmar spec. However, even a Defiant *with* its turret looks to have had a better climb rate than the Fulmar, so perhaps a faster climbing P.94 would have the advantage of being able to convert altitude into speed. Its mentioned in several passages I've read that Fulmars on interception often only had a chance to attack head on in a single pass or by diving onto things like JU88s if they had an altitude advantage.

And please give the poor old Nav Op a decent weapon to defend the tail. Perhaps a good fast firing gun like a VGO in a double Hampden style mounting?

.... it appears some dude has already done us the artwork! - WI-The Boulton Paul defiant had forward facing guns?

 

[Admiral Beez]

.... it appears some dude has already done us the artwork! - WI-The Boulton Paul defiant had forward facing guns?

View attachment 620847

I like it, but goodness how long is this thing? Will it fit down a 45ft long lift? Why not keep it simple with the below?

About Bolton Paul, perhaps it’s no difference, but I don’t think they have any history of making carrier aircraft. At least until the postwar Boulton Paul Balliol. Of note, the Balliol was probably the last Merlin powered landing on a British carrier, since by then everything else was either Griffon or Centaurus powered.

 

[Shortround6]

Go back and see about making the list of British carriers.


Defiant has wing in-between the Spitfire and Hurricane but weighed a lot more.

Take-out turret but stick Fulmar type armament out in the wings (about where the Defiant had it's fuel tanks)
Now add enough fuel for the desired 4 hour endurance.

Whatever you saved by yanking the turret just disappeared,

You have a plane with a higher wing loading than Seafire XV.

There is more to landing on a carrier than a wide track undercarriage.

1937-38 nobody knows that the Courageous and Glorious will be lost due to stupidity. Your fighter/recon plane has to operate from some of the older carriers.

 

[yulzari]

Re the Rolls Royce R. With the special fuels needed for the published power outputs it drank the stuff like a dipsomaniac elephant in a brewery. Endurance would be measured in minutes rather than hours.

 

[Shortround6]

Re the Rolls Royce R. With the special fuels needed for the published power outputs it drank the stuff like a dipsomaniac elephant in a brewery. Endurance would be measured in minutes rather than hours.

Agree.
However even at cruise speeds endurance would be reduced by a large amount, perhaps 40%.
Some of the components or indeed the complete mixture did not vaporize well at low temperatures making use (especially cruising) at higher altitudes problematic.

I think (could be wrong) that they sometimes started the race engines with shots of ether into the intake tract. Most of us older members can remember cans of "starter fluid" even for gasoline engined cars in really cold weather.
If P-38s had trouble with fuel puddling in the intake manifolds some of these racing mixtures would be a real nightmare.

 

[fastmongrel]

Some of the R engines were started on AVGAS then when warmed up the spark plugs were swapped for the race plugs and the special brew fuel was pumped into the tank while a couple of mechanics stood by with fire extinguishers.

 

[ThomasP]

re: "However even at cruise speeds endurance would be reduced by a large amount, perhaps 40%."

Hence the wing hardpoints rigged for 45 Impgal DTs (internal fuel remained 155 Impgal).

The Special Fuel I used was not as exotic as the early 1930s racing mix. It was basically the equivalent of UK 1941 130 grade with increased TEL and xylene as anti-knock additives. Effectively, I had the ~equivalent of late-war 150 grade. I would have used the Super Fuel for the Merlins fitted to the Albacores and SeaHurricanes, but since the Merlins at the end of 1941were already at their maximum mechanical power (+16 lb boost in real life) we decided that there was not any practical increase in development time available. The Merlins could be run on the Special Fuel if we really needed to but only at the normal fuel power settings, and with increased maintenance. (I do not remember exactly how much TEL, but it required changing out spark plugs about twice as often as for the normal fuel.)

The thirsty engine problem was really only apparent when it was used as an interceptor (ie at max climb) and/or at combat settings. The max sustained climb used 180 Impg/hr, Combat climb used 215 Impgal/hr, and WEP used 270 Impgal/hr.

The best economical cruise rating for the Super Fulmar went up about 100 BHP and the range decreased by about 20% in clean configuration. The 2x45 Impgal added the operational range back.

 

[SplitRz]

Go back and see about making the list of British carriers.


Defiant has wing in-between the Spitfire and Hurricane but weighed a lot more.

Take-out turret but stick Fulmar type armament out in the wings (about where the Defiant had it's fuel tanks)
Now add enough fuel for the desired 4 hour endurance.

Whatever you saved by yanking the turret just disappeared,

You have a plane with a higher wing loading than Seafire XV.
.

The turret when fully equipped weighed 950 lb (thats presumably minus crewman!). Thats quite a significant amount of weight - not to mention drag. Weight of 8x brownings plus ammo comes out at about 440lbs. So there's still 500lbs to play with before the standard turreted Defiant weight is exceeded. What's the additional endurance for each extra 100lbs of fuel for a Merlin? The standard Defiant (with drag enduing turret) managed around 1.78

Maybe a more informative comparison would be with the Roc? Interestingly, its only 350lbs lighter than the turreted Defiant - but has 110hp less (though its unclear what the rated altitude is for either the Merlin or Perseus). The Roc has 60 square ft additional wing area.

Would a wingspan increase be inconceivably difficult?

 

[Shortround6]

The turret when fully equipped weighed 950 lb (thats presumably minus crewman!). Thats quite a significant amount of weight - not to mention drag. Weight of 8x brownings plus ammo comes out at about 440lbs. So there's still 500lbs to play with before the standard turreted Defiant weight is exceeded. What's the additional endurance for each extra 100lbs of fuel for a Merlin? The standard Defiant (with drag enduing turret) managed around 1.78

Let's see. A Merlin can burn about 30 gallons an hour at 2000rpm and -4lbs boost (yes minus 4lbs). 30 gallons of fuel in about 225lbs. Weight of tanks, especially with self sealing materials? There goes just about the weight savings from yanking the turret.

Maybe a more informative comparison would be with the Roc? Interestingly, its only 350lbs lighter than the turreted Defiant - but has 110hp less (though its unclear what the rated altitude is for either the Merlin or Perseus). The Roc has 60 square ft additional wing area.

Merin III is rated at 16,250ft, regardless of aircraft type. FTH did vary with aircraft type due to differences in RAM because of speed.
Perseus XII may have been rated at 905hp at 6,500ft (the 890hp rating is for take-off)

Would a wingspan increase be inconceivably difficult?

Depends on what is meant by "inconceivably difficult" You aren't going to get much increase in wing area if you just change the tips.
You could extend the center section, with much in the way of new parts/tooling (same ribs?) But larger wings, extended span do have to be stressed to take the change in the G load. The wing doesn't "bend" quite the same. Longer wings will put a greater load on the center portion of the spar/s.
Longer, bigger area wings usually require bigger ailerons to restore roll capability.

 

[Admiral Beez]

How about we stick the Fulmar’s eight guns and Merlin onto the Skua?

 

[SaparotRob]

And change the Skua's ridiculous cockpit windscreen. I'm no aerodynamicist, but c'mon, that "forward swept" barn door windshield can't possibly help.