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

[stona]

It was Douglas who said in his minute of 28th August 1940 that 100 octane "hitherto reserved for Hurricane and Spitfire aircraft" should be made available to Blenheims.

I have had a quick look into this and I think he was mistaken. It appears to me that 100 octane fuel was being made available to all aircraft in Fighter Command and that this would include Blenheims. This might be a whole other argument though! I haven't looked at those in Bomber Command.

I would hazard a guess that this may have led Dowding to ask about "modifications".

The confusion is probably because between October and December 1939 there was much correspondence concerning the approval of the use of 100 octane fuel in Spitfires, Hurricanes and Defiants, all Merlin powered and requiring some adjustment. The Blenheim was not mentioned, maybe because its engines could easily use the higher octane fuel.

Cheers

Steve

 

[Greyman]

The need for modification makes sense, as I don't think Fighter Command had any Mk.IVf Blenheims at this time, unsure though. I think they were all the Mk.If type. At least the majority were. I think Coastal Command and the Desert ended up with most of the IVf models.

 

[tomo pauk]

"Merlin XII was aboard, not the XX. Unfortunately, if I may add."

I think you just answered your own question.

If the Merlin XII isn't good enough at 1175hp for take-off and 1140hp at 14,750ft (at 9lbs boost) in the low drag (for the time) Spitfire carrying 440lbs(200kf) of guns and ammo, then what kind of engine or airplane do you need?

Merlin XII was enough for two things - it was able to propel Spitfire II to the speeds as good as what lighter Mk.I achieved. It was only 10 HP weaker for T.O than Merlin 45, and a Spitfire with M.45 was able to take off with almost 200 imp gals (=1420 lbs) of additional fuel, plus additional engine oil, minus 3/4s of weaponry (350 lbs?).
However, Merlin XII comes short, compared to Merlin XX and 45, with the power at all altitudes - eg. what M.XII was been able to do at 15000 ft, the M.XX and 45 were able to do at 18500 ft. That was worth ~15 mph at 20000 ft, ~20 mph at 25000 ft. RoC above 15000 was also better for the M.45 engined Spit, by some 20%. The take off power is also down some 100 HP - that might prevent a Spitfire, at ferry weight, to take off from a carrier? The power between SL and 10000 FT is also smaller, provided same boost levels are used.

Having a plane that is fast isn't the answer. It has to be able to fight even if not tight dog fight in the traditional sense. The Bf 110 was faster than the Hurricane I and that didn't work out so well.

Disagreed with these two claims. A faster Spitfire was a better Spitfire, despite weight growth. Merlin XX would've enabled it also to climb better, above 15000 ft. Nobody in ww2 clamored 'give me slower aircraft', either.
The BF-110 was faster than Hurricane, but it was slower than Spitfire. The close escort tactics and low numbers of deployed aircraft didn't help either. P-38, F4U and F6F were faster than all Japanese pre-1945 aircraft, right tactics and good numbers helped too, and nobody asked their P-40s and F4Fs back instead.

The MB.2 is a dead end. The Defiant is a dead end. ANY existing fighter with under 1200hp is a dead end. And a new design has to give up what? protection? Armament?

Depends what one does with MB-2. Retract the U/C and install back-facing exhausts and it's as fast/faster than Hurricane I. Stick a Merlin on it and it's fast as Spitfire? The fuel tankage is low, however, despite ample distance between pilot and engine.
The really new fighter might start with, say, a Merlin XX, 120 imp gals of fuel, with leading-edge radiators and better choice of high-lift devices. I won't say 'Mustang with two-speed Merlin' yet.

For an escort fighter the British needed plane that could fight the 109 on near equal terms and do it about 300 miles from it's bases just to hit the Ruhr. Depending on route home (Essen to Burge=165miles, Cologne to Dunkirk is 200miles) a considerable period of time/distance is spent in enemy controlled air-space which means cruise speed must be kept high.

The Spit with M.XX was feasible in 1940; it would trump any 109E, and be equal to 109F-1/F-2.

For the Germans it is 114 miles from London to Derby (add to radius) and 178 miles from London to Liverpool, forget Northern Ireland. 258 miles from Arras to Derby. SO the Germans have the same problem. The need to be able to beat the Hurricane and come close to the Spitfire but do it at a radius 100-175 miles further than they were doing it. It is 67 miles from London to Dover.

These distances just get you out of AA range, pursuing fighters are another matter.

All fine. A tidbit: pursuing fighter need range, too, to really pursue a retreating fighter.

 

[davparlr]

In my opinion, and disregarding ancillary impacts, it would be possible technological wise to field a capable escort fighter in 1939-40 that was capable of handling enemy point defense fighters using a current 1200 hp engine. First mandatory thing is to start off with is a very aerodynamically clean aircraft. And, of course, cleanest of the clean was the P-51. I think the P-51 or a P-51-like aircraft could have been started earlier than 1940. The technology that made it so good was pretty well defined by 1939. Both the (almost) laminar wing and the Meredith effect radiator application were known. Also, detail attention to aerodynamic efficiency was also known as was demonstrated by Howard Hughes on his H-1 racer. It did take an out-of-the-box thinker, like North American seem to have, to apply them. Let's take the earlier P-51.

1. Design it to British stress levels. This should save several hundred pounds, maybe as much as 500lbs.
2. Install the latest Spitfire Merlin. This plane should always be faster than the Spitfire, and, just about any other contemporary fighter, and be more maneuverable (at the same power setting) than the P-51/A/B/D due to its lighter weight.
3. Keep the four fifties. Maybe later install two 20mm instead (preferred?).
4. Because of the lighter weight and less powerful engine (lower airspeed), less fuel would be required, maybe not even an extended range tank would be needed (maybe not as long a range as a P-51B but quite useful to penetrate well into Germany). That would save another couple of hundred pounds of weight, or accept the weight and include it.

So basically, the early P-51 could be like a several hundred pounds lighter P-51A with the latest Merlin engine instead of the Allison. It would be fast, even at altitude, with excellent range and with effective armament, especially with the twin 20s. And I think it could easily have flown a year earlier or more.

Now all the ancillary impacts as brought up by many previous posters would have, and did, prevented this from occurring, but, technologically, I think it was reasonably possible.

 

[Shortround6]

Merlin XII was enough for two things -.................. The take off power is also down some 100 HP - that might prevent a Spitfire, at ferry weight, to take off from a carrier? The power between SL and 10000 FT is also smaller, provided same boost levels are used.

Your original question was for a 1100-1200hp engine. The Merlin XX is a 1200-1300hp engine to start with and becomes a nearly 1500hp engine when 14-16lbs or boost are allowed.

Disagreed with these two claims. A faster Spitfire was a better Spitfire, despite weight growth. Merlin XX would've enabled it also to climb better, above 15000 ft. Nobody in ww2 clamored 'give me slower aircraft', either.

It is not a claim, some people have been fixed on the slight loss in speed (which might be acceptable) due to the extra weight without considering the loss of other performance. It is the loss of climb performance, and by extension, the loss of turning ability that is the real problem. The 110 was faster than the Hurricane but not only couldn't it out turn it ( more of a defensive move) but it could not out climb it, which means the Hurricane may be able to evade by climbing and turning instead of diving and turning. Once the Hurricane has a height advantage it can dive and turn the height advantage into a speed advantage.

Depends what one does with MB-2. Retract the U/C and install back-facing exhausts and it's as fast/faster than Hurricane I. Stick a Merlin on it and it's fast as Spitfire? The fuel tankage is low, however, despite ample distance between pilot and engine.

This obsession with taking obsolete and/or not too good aircraft and trying to turn them into war winners is fun but not practical.

The Martin Baker prototype was about 340lbs lighter than the Spitfire prototype. But then it didn't have about 300lbs worth of liquid cooling system either. By the time you stick a Merlin in it, fit it with armor, self sealing tanks, a constant speed prop, retracting landing gear, etc it will go faster and climb better than the prototype but it will be just as heavy as the Spitfire. It smaller wing means higher wing loading.

The really new fighter might start with, say, a Merlin XX, 120 imp gals of fuel, with leading-edge radiators and better choice of high-lift devices.

well, starting with a 1300-1400hp engine does give you advantages that an 1100-1200hp engine doesn't have

The Spit with M.XX was feasible in 1940; it would trump any 109E, and be equal to 109F-1/F-2.

It was feasible in late summer of 1940 to start production and issue. In service squadrons avaialbe in the fall of 1940 and numbers enough to really do anything in the winter?
And unless you can pry a few hundred engines out of Bomber Commands tight little fists it means NO Hurricane IIs which means your super Spits will really bear the brunt of the work.

All fine. A tidbit: pursuing fighter need range, too, to really pursue a retreating fighter.

Depends doesn't it

German fighter unit returning from Derby gets bounced by Spitfire squadron based south east of London? German unit has already dropped tanks and fought one fight 150 miles further back. Now it is facing another fight and another 100-150 miles to home.

Or flip it. MR Spits dropped tanks and fought over Dusseldorf and get bounced (engaged) by fresh German Squadron over/near Rotterdam (110-115miles) . It is another 136 miles to Harwich and the English coast.

That is the problem with escort fighters in Europe. They are not facing ONE fight but the possibility of several fights on the way back.

The short range interceptors can attack in relays too.

 

[stona]

The short range interceptors can attack in relays too.

Which, whilst slightly off topic, is precisely why Dowding/Park used the Squadron as their basic tactical unit and allowed them to be controlled at Group level rather than by Fighter Command HQ. The enemy formation could, when everything worked well, be engaged almost continually in and out with units arriving from different directions, making life very difficult for the escort.

A somewhat similar system proved very effective for the Luftwaffe later in the war, though having more time they could assemble larger formations, particularly against the deep penetration raids that proved so costly for the USAAF.

Cheers

Steve

 

[tomo pauk]

Your original question was for a 1100-1200hp engine. The Merlin XX is a 1200-1300hp engine to start with and becomes a nearly 1500hp engine when 14-16lbs or boost are allowed.

My original question was : Wonder if someone can come up with a viable escort fighter on 1000-1200 HP (at 20000-15000 ft of altitude; historical engines only)?

Merlin XX was able to make 1270 HP at 15000 ft, but only once boosts above +9 lbs were allowed; before that it was ~1100 HP. At 20000 ft it was good for 1070 HP. It's not a long stretch for it to fit in this thread. Merlin III and XII were also 1300 HP engines, but not above 15000 ft, hence they fit in this thread.

It is not a claim, some people have been fixed on the slight loss in speed (which might be acceptable) due to the extra weight without considering the loss of other performance. It is the loss of climb performance, and by extension, the loss of turning ability that is the real problem. The 110 was faster than the Hurricane but not only couldn't it out turn it ( more of a defensive move) but it could not out climb it, which means the Hurricane may be able to evade by climbing and turning instead of diving and turning. Once the Hurricane has a height advantage it can dive and turn the height advantage into a speed advantage.

Well, I'm not among those fixed on the slight loss of speed - faster is better in my eyes Or, if you are a tad slower, than you better be a good climber - so either on tries to equal Mustang, or Zero. I've already said here that it would be hard for the Defiant to really attend those claimed 360 mph as a single seater with Merlin XX.

This obsession with taking obsolete and/or not too good aircraft and trying to turn them into war winners is fun but not practical.

The Martin Baker prototype was about 340lbs lighter than the Spitfire prototype. But then it didn't have about 300lbs worth of liquid cooling system either. By the time you stick a Merlin in it, fit it with armor, self sealing tanks, a constant speed prop, retracting landing gear, etc it will go faster and climb better than the prototype but it will be just as heavy as the Spitfire. It smaller wing means higher wing loading.

All fair. I was mostly thinking about the possible fuel load at the position similar to what F4U had, but 83 imp gals is even under Bf-109 and Spit capacity.

well, starting with a 1300-1400hp engine does give you advantages that an 1100-1200hp engine doesn't have

Covered above

It was feasible in late summer of 1940 to start production and issue. In service squadrons avaialbe in the fall of 1940 and numbers enough to really do anything in the winter?
And unless you can pry a few hundred engines out of Bomber Commands tight little fists it means NO Hurricane IIs which means your super Spits will really bear the brunt of the work.

Doh, Super Spits
The Hurricanes can have Merlin XIIs and 45s once they become available.

Depends doesn't it

German fighter unit returning from Derby gets bounced by Spitfire squadron based south east of London? German unit has already dropped tanks and fought one fight 150 miles further back. Now it is facing another fight and another 100-150 miles to home.
Or flip it. MR Spits dropped tanks and fought over Dusseldorf and get bounced (engaged) by fresh German Squadron over/near Rotterdam (110-115miles) . It is another 136 miles to Harwich and the English coast.
That is the problem with escort fighters in Europe. They are not facing ONE fight but the possibility of several fights on the way back.
The short range interceptors can attack in relays too.

Again, fair points. The quirk with having MR/LR fighters is that you have more options to hit the enemy, than without such fighters. Especially once LW starts deploying it's fighter assets elsewhere. The MR Spit will be really an asset once deployed in the Med and Asia/Pacific, but that was not so well until the war was more or less decided.

added: I've found two internet sources claiming the MB.2's speed was 515 km/h - 320 mph (here and here). Anyone can confirm or refute this?

 

[wuzak]

According to Buttler, British Experimental Combat Aircraft of WWII the top speed of the M.B.2 wa 305mph (491km/h) @ 9250ft.

 

[OldSkeptic]

It would always be ideal to intercept bombers before they bombed, as Douglas conceded, but this was not practically possible. Official figures are hard to find, but reference to memoirs and individual pilot's log books would indicate that roughly 6 out of 10 sector controlled interceptions were successful.
All Douglas wanted to do was shoot down as many bombers as possible, whenever that was possible, which seems eminently sensible to me.

Park's sensible plan to engage primarily bombers and not tangle with escorts (with either Spitfires or Hurricanes) was of course at the mercy of German tactics. One of the inadvertent effects of the Luftwaffe's change in tactics around 24th August was that it became virtually impossible to avoid the escort fighters, even though they were now flying in a less advantageous state.

When the Luftwaffe moved to huge amounts of escorts for the bombers for various attacks (4:1, even 6:1 at times) he peeled them off by hitting them with Spit squadron attacks at the escorts. This broke up the escorts, caused them to use up fuel, use ammo, lose altitude and opened gaps. Then the bomber killers were sent in. So he constantly changed his tactics according to the situation. Fighter sweeps were just ignored.

So the primary t6arget was always the bombers, but how that was achieved varied on the situation at the time.

When the bombers were attacked, before they dropped their bombs, even when they got through their formations were disrupted and their accuracy dropped, often considerably as it is a bit hard to aim well when being shot up. This was important since they were hitting airfields, not such an issue as it is hard to take them out, but they were also going for the aircraft manufacturers, which were all within 109 range at that time. That was one of the nightmare scenarios facing the British.

So the idea of 'letting them though' and then hammering them on the way out was fraught with danger, which was in inevitable consequence of the 'big wing' concept. You had to start hammering them on the way in. In fact they were hit on the way in, at their targets and on the way out... so there was no rest.

This was another advantage of the 'head on' attacks he favoured. Not only devastating in terms of the crews being hit but it disrupted their formations .... damn scary when a squadron of fighters are heading right at you.
Disrupted formations also made the escorts jobs a lot hard too therefore making it a lot easier for follow on attacks later.
You have to give the Luftwaffe credit, they constantly changed tactics, trying to find new ways through. They were very innovative (particularly Kesselring), sadly for them they had met their match in Park.

 

[Aozora]

Air Publication 1530B - September 1939 (Revised October 1939)
Pilot's Notes
The Blenheim IV Aeroplane
Two Mercury XV Engines

View attachment 246699

Dowding had a lot on his plate, and I'm sure he wasn't aware of every single wheeling and dealing in the RAF/RAE/A&AEE/etc.



Do you have evidence for this?

Some great documents from wwiiaircraftperformance.org
http://www.wwiiaircraftperformance.org/hurricane/AASF-Fuel.pdf
http://www.wwiiaircraftperformance.org/hurricane/RAF-Component-15may40.pdf

Blenheim IVs of Bomber Command were using 100 Octane fuel from the start of the war, albeit using the outer wing fuel tanks:

which led to tricky engine/flight handling problems for the pilots:

From pages 130, 99-100:

However, Graham Warner was wrong to state that there was a shortage of 100 Octane fuel; Britain had its own supplies of 100 Octane fuel, plus there was a steady supply from America. Pre-war planning was based on building up 800,000 tons of 100 Octane stocks while taking into account the possibility that America would invoke the Neutrality Act and refuse to supply Britain with 100 Octane fuel. Hence the stipulation that Blenheim IVs would use only the outer tanks, with priority of supply going to Fighter Command.

As events proved, there were no problems with supply of 100 Octane and stocks built up steadily: 263,000 tons by 18 April 1940

404,000 tons by August 1940; peaking at 527,000 tons in February 1941:

versus an average monthly consumption of 12,200 tons June 1940-October:

Thus, on 7 August 1940, 100 Octane fuel was allocated to all RAF Commands:

 

[stona]

So the idea of 'letting them though' and then hammering them on the way out .....'

Who had that idea? At no point in the quotes I gave for Douglas is there any suggestion of letting the bombers through. The first was written when EVERYONE, with the possible exception of Dowding, assumed that the bomber would always get through.
Dowding had said in a speech in Coventry of all places, on 14th February 1939.

"I am not one to minimise air raid precautions, particularly in the matter of fire services, but I think the politicians have allowed the nation to get altogether the wrong idea about modern air war. I believe the fighter has sixty to four the best of the bomber."

Douglas wrote.

"Our objective is not to prevent enemy bombers reaching their objectives, though it would be nice if we could, but to cause a high casualty rate among enemy bombers, with the result that the attack will dwindle rapidly to bearable proportions."

The second quote, after the BoB when Douglas is frankly stating the obvious.

"The best, if only way of achieving air superiority is to shoot down a large proportion of enemy bombers every time they come over.........I would rather shoot down fifty of the enemy bombers after they had reached their objective than shoot down only ten before they do so."

The "Big Wing" wasn't supposed to intercept the raid on the way out either. It just took too long to assemble. The actual time was still causing acrimony in the 1970s to my certain and personal knowledge. Bader was still accusing 11 Group of ordering the Duxford Wing into the air too late. 11 Group was still accusing Leigh Mallory and 12 Group of failing to cover its airfields.

This became a bone of contention at the time. Park, as you rightly say, was keen to get to raids before they bombed and harass them in and, if possible, out.

On 17th September Leigh Mallory wrote a report to Dowding on his wing patrols. Five had taken place and they claimed 105 aircraft destroyed plus another probably destroyed and eighteen damaged. These claims are simply fantastic and many copied in to the report, including Douglas, Dowding and Park must have know it. Tellingly, on Park's copy, a note reads.

"Did these Wings engage before targets were bombed?"

Leigh Mallory, like Douglas, thought that defence of targets should be left to ground forces and a concentrated fighter attack made on the enemy formation, if necessary after it had bombed.

I have never seen any evidence, apart from one comment by Park, that Fighter Command tasked specific squadrons to specific elements of a formation. This may well have been Park's intended tactic but is entirely dependant on the local tactical situation and in no small part the reaction of the enemy. The reasons why this could rarely be done in reality I have already mentioned. A look at the types credited to the various Hurricane 'aces' would tend to confirm this. Tietzen (who was lying fourth in Signal Magazine's unofficial league table behind Galland, Molders and Wick) was not the only senior Bf 109 pilot to fall victim to a tired old puffer.

Both Dowding and Park (and others) wrote, said and emphasised that the primary target for all Fighter Command aircraft was the enemy bombers. They had to keep reiterating this point because in all the scenarios for which Fighting Area and then Fighter Command had exercised before the war the bombers were unescorted.

At a meeting of the Air Fighting Committee on 12th February 1940 Dowding said that he,

"wished to emphasise the point that the primary job of fighters was to shoot down bombers, not to fight other fighters."

It was a point reiterated by both men (Park and Dowding) throughout the summer of 1940.

Again there were some, particularly kicking their heels at 12 Group, who disagreed.

Cheers

Steve

 

[stona]

Blenheim IVs of Bomber Command were using 100 Octane fuel from the start of the war, albeit using the outer wing fuel tanks:

That doesn't surprise me!

It is clear that stocks of 100 octane fuel were adequate and substantial throughout 1940. It is also clear that most if not all squadrons within Fighter Command were operating with the fuel throughout 1940. There are dozens of extant documents in the National Archives to support this. Nonetheless, for some reason, probably based on a misinterpretation of an earlier document, this has been contentious over the years.

Given the state of reserves and supply it does not seem unreasonable that the Blenheims of Bomber Command should be operated with the fuel, assuming it was available at their operational airfields.

Why Douglas thought that the fuel was reserved for certain aircraft I have no idea. I can only conjecture that he may have been under a misapprehension or he may have considered Fighter Command at the time to be effectively "Spitfire and Hurricane aircraft."

Cheers

Steve

 

[Milosh]

But, but there was only 16 squadrons of fighters using 100 octane fuel during the BoB. That is according to some so called aviation experts.

 

[Glider]

No 2 group were also authorized to use 100 octane with fighter command so the Blenheim's would have been so equipped.

Milosh, go and wash your mouth out with soap and water

 

[Aozora]

That doesn't surprise me!

It is clear that stocks of 100 octane fuel were adequate and substantial throughout 1940. It is also clear that most if not all squadrons within Fighter Command were operating with the fuel throughout 1940. There are dozens of extant documents in the National Archives to support this. Nonetheless, for some reason, probably based on a misinterpretation of an earlier document, this has been contentious over the years.
Cheers

Steve

I know there was some extensive discussion on this a couple of years ago - I got the impression there were only one or two people who refused to believe that all Fighter Command squadrons were using 100 Octane in 1940. Evidence shows that several squadrons at the very least started using the fuel in 1939.

 

[stona]

But, but there was only 16 squadrons of fighters using 100 octane fuel during the BoB. That is according to some so called aviation experts.

I know that you're joking, but it is a view vigorously supported by some in the face of overwhelming evidence to the contrary.

I believe that the confusion arises from a meeting held on 16th March 1939 in which it was decided that INITIAL delivery of 100 octane fuel would be to sixteen fighter and two twin engine bomber squadrons.
Subsequently the word 'initial' has either been misunderstood or ignored by researchers pushing their own agenda.

It hasn't helped that a report of the meeting appears in "Spitfire the History" meaning that it is often read and misquoted.

Cheers
Steve

 

[Milosh]

Milosh, go and wash your mouth out with soap and water

Sorry Glider, couldn`t help myself.

Steve, you mean people like Crumpp and Kurfurst.

 

[stona]

Steve, you mean people like Crumpp and Kurfurst.

They are by no means the only ones

Cheers

Steve

 

[oldcrowcv63]

Tomo's post seems to be fairly limiting for considering western options:

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)."

The escort fighter doesn't have to have all the performance of the interceptors because the latter's primary mission is to take out the bombers. Also, speed is an important attribute but perhaps a bit more so for an interceptor that an escort fighter. even an interceptor's speed disadvantage can be overcome if other attributes are strong. Allied examples: RN-FAA Fulmar, FAF B-239/F2A-1, RAF and FAA Gladiator.

That being said, I think a single seat Fulmar derived design is a contender for an effective long range escort.

However, I also believe, that a fighter in the 1939-1940 time frame possessing the range, firepower and performance attributes necessary to carry out offensive missions could be derived from designs based on land-based variants of either the F2A-2/3 or the F4F-3 Wildcat which themselves possessed combat radii of between 300-500 miles (range ~800+ to 1,600 miles) without drop tanks.
I'd expect the design to be equipped with 4 x .5" or 6 to 8 x .3" guns. with an internal fuel capacity of 150 to 160 gallons of internal fuel with accommodation for a 50 gallon drop tank. I'd imagine a narrow 48" P&W 1,200 HP Wasp with a single stage, two-speed supercharger. I'd expect it would have a max speed at 15,000-20,000' of about 335 mph and a range with drop tank of something over 300 miles. The closest operational aircraft I can think of to this model would be the presumably heavier F4F-3A or a Martlet I, first appearing in late Spring of 1940.

 

[tomo pauk]

I need bacon (though I'd need Lucky 13 to explain this new feature to me)

In the meantime: West does not have that much of a disadvantage. UK can use Merlin, and match or better what Germans have had, at least from 1940 on. USA can indeed use R-1830, but I think that V-1710 will be better choice. Actually, the P-40 was there about fuel-wise, while offering a speed better than those 335 mph wanted.