[WWII] Curtiss P-40 Warhawk (USA)

[copeab]

I had originally done the P-40 in 2002. However, that was the -N model and the write-up was a bit skimpy. I decided to redo the write-up for a more important version and greatly expand the write-up.
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Curtiss P-40 Warhawk
Copyright 2009 by Brandon Cope

The P-40 was the primary US fighter early in the war and served throughout with several countries. Although considered inferior to contemporary fighters, it was available in useful numbers early in the war, when the P-51 (p.W110) and P-47 (p.W:DF112) were still years from production, Despite being surpassed by other American fighters during the war, it was produced until 1944 and served until 1945. The Warhawk was a 1938 development of the P-36 Hawk (pW.MP104), replacing the radial Pratt & Whitney with a more streamlined inline Allison engine. Originally, the radiator was located behind the wings, but the Curtiss sales department told the engineers to move it forward; the distinctive P-40 'chin' was born and the rear-mounted radiator was left for the P-51.

The P-40 first saw service with the British in North Africa in June 1941.It also saw significant service in the South Pacific and , most famously and successfully, China with the American Volunteer Group (from December 1941 to August 1942, flying -C models built to the -B standard). It was also used in most other theatres (including the Aleutian campaign), the most notable exception being Western Europe. Aside from Britain and China, numbers were also used by Russia. In addition to use as an air-superiority fighter, it was used in ground-attack and interdiction roles. Some 2,300 of the P-40E were built out of a total production run of over 13,700 planes.

The main limitation of the P-40 was it's Allison engine, which lacked a two-stage supercharger. While reliable and easy to maintain, it lacked high-altitude (over 15,000 feet) performance. It also had a poor climb rate. The P-40 has long had a poor reputation as a fighter, mainly due to combat with the Mitsubishi Zero (p.W112) in 1942. However, this reputation is not deserved. While it is true the P-40 was easily out-turned by the Zero at low speed (~250 mph), so were virtually all other allied fighters. If a P-40 pilot refused to get into a low-speed dogfight with the Zero, however, the advantage was his. The P-40 was faster in level flight (20-30 mph), much faster in a dive (120+ mph) and considerably more resistant to battle damage. One little known fact is that if the planes were at top speed. the P-40 could actually out-turn the Zero. Against German fighters, the problem was less about agility and more about the poor high-altitude performance. The preferred method of using the P-40 in combat, especially against the Japanese, was to dive on an enemy formation from high altitude and keep on diving to get away after firing.

The P-40E uses 38.5 gallons of aviation fuel per hour.

Subassemblies: Medium Fighter Body with Good streamlining +3, Heavy Fighter Wings +2, three retractable wheels +0
P&P: 858 kW aerial HP gasoline engine with 858-kW propeller, 159 gallons aviation gasoline in self-sealing fuel tanks (Body and Wings)
Occ: 1 CS Cargo: 2.5 Body

Armor
All: 3/5
Cockpit: FBU 0/+30

Weaponry
6*Long Aircraft MG/Browning M-2 [Wing:F] (233 rounds each) *
* Linked

Equipment
Body: Long range radio transmitter and receiver, bombsight, autopilot. 1,000-lb hardpoint. Wings: 500-lb hardpoint each.

Statistics
Size: 33'x37'x12'
Payload: 1.2 tons
Lwt: 4.4 tons
Volume: 200
Maint.: 39 hours
Price: $25,700

HT: 11
HP: 240 [body], 180 [each wing]

Hardpoints loaded
aSpeed: 342
aAccel: 6
aDecel: 25
aMR: 7.25
aSR: 2
Stall: 83 mph

Hardpoints empty
aSpeed: 360
aAccel: 7
aDecel: 33
aMR: 8.25
aSR: 2
Stall: 78 mph

Design Notes
Design speed was 381 mph. The historical value has been used, as well as the historical wing area (236 sf). Chassis cost, weight and HP were doubled. Loaded weight was decreased by 4%. Loaded weight includes 1,000 pounds of bombs.

Although the plane has hardpoints for 2,000 pounds of bombs, it seldom f;ew with more than 1,000 pounds.

Variants
The P-40 (1940) was armed with only one .30-cal and one .50-cal MG in nose and, optionally, one .30-cal MG in each wing. Bomb load was six 20-lb bombs ubder the wings. Top speed 347 mph. Called the 'Tomahawk' by the British, who took over a French order. Just under 350 were built, with 142 used by the British.

The P-40B/Tomahawk IIA (1941) had two .30-cal Browning M-2's in each wing (Aircraft LMGs), replaced the nose .30-cal with a .50-cal, and introduced crude self-sealing tanks and basic pilot armor (DR 15). It had no provisions for bombs or drop tanks. sSpeed 352. 131 built for the US, 110 for the British and 23 for Russia.

The P-40C/Tomahawk IIB (1941) added the underbelly hardpoint for a bomb or drop tank, and had full self-sealing tanks and better pilot armor (DR 20 F/B). aSpeed 345. Some 190 were built for the US, over 900 for Great Britain (some going to Egypt and Turkey, and nearly 200 transferred to Russia after June 1941) and 23 for Russia.

The P-40D/(1941) Kittyhawk Mk I removed the nose guns and had two .50-cal MGs in each wing and a 500-lb bomb rack was added under the fuselage and six 20-lb racks under the wings. Armor was the same as the -E. Top speed 354 mph with a more powerful engine. 22 were built.for the US and 560 for the British.

The P-40F (the first to be called Warhawk in American service) used the Rolls-Royce Merlin engine, giving it aSpeed 364. The fuselage was lengthened 18 inches during this series to correct stability problems, so there were short and long P-40Fs. Along with higher top speed, high altitude performance was improved. Only around 2,000 built, however as the P-51 Mustang was given priority for the engine.

Some 1,300 P-40K 91942) were built, similar to the -E but with a more powerful engine (aSpeed 362).192 Went tp Britain, 25 to Brazil and an unknown number to the Chinese Air Force.

The P-40M (1942) was built for Lend-Lease and was similar to the -K. Nineteen went to Brazil; the rest of the 480 built went to British and Commonwealth forces.

The P-40L was the same as the -F, except most were lightened by the removal of two wing guns and 37 gallons of wing tanks; aSpeed was only 368 mph The British referred to it as the "Gypsy Rose Lee" after a famous stripper of the era.

The P-40N/Kittyhawk Mk IV (1943) was the most numerous version, with some 5,200 built. It could reach 378 mph. Many were armed with only four MGs.

The P-40Q (1944) was a very clean design capable of 422 mph. Unfortunately, most top fighters by then were nearing 500 mph and the 'Q' model ended its days as a civilian racer after the war.

Several other improvements of the P-40 were offered by Curtis (XP-46, XP-60, etc) but none were accepted for service.

[Mr Frost]

Originally Posted by copeab

...
The P-40L was the same as the -F, except most were lightened by the removal of two wing guns ...

Most had those guns put back in in the field {withering firepower was concidered far more important by combat pilots by that period of the war than a slightly increased roll rate} .

Originally Posted by Copeab

...aSpeed was only 368 mph...

I've seen higher figures {I forget exactly where now} and it was concidered one of the fastest P-40s .

The simple nature of G.U.R.P.S. vehicle modeling runs up against this problem often with aircraft . The advantage of the Merlin over the Allison used in those birds was the supercharger {The Allison was actually a good engine , if had be designed with a supercharger from the get go , the P-40s would have been credable first tier fighters -not great , but good enough- for the first half of the war} which gave it a dramatic improvement in performance above 15,000 feet {given most serious aerial combat in Western Europe at that time and a fair chunck of it in the Pacific took place above 20,000 feet , this made it a big deal} .

Above 20,000 feet , no unsupercharged Allison engined P-40 could match it .




One day , someone needs to come up with some realistic rules for aerial movement and especially combat .

[Disclaimer : this someone is not that someone . No , really , I'm a gearhead , not a rules lawmaker Jim]

The different speeds at different altitudes alone makes a huge difference : for example an unmodifyed {they could be modifyed for higher boost and be given a coating of wax both which would increase speed} bf109E-4 {1940} is clearly faster on the deck than a Spitfire Mk V H.F. {1941-'42} despite the Mk V having an overall top speed 20-30 miles per hour greater than the E-4 . A similar case existed for late build Mk V L.F. Spits on the deck Vs Fw 190s of 1944 {a fair number of them were used for very low level C.A.P. missions to cover the landings from German C.A.S.} where the by then supposedly obsolete Mk Vs {with L.F. engines} could actually outrun/catch most other fighters and had the advantage of better agility from a lighter wingloading than the Mk IXs and other late war Allied fighters {and good roll from their clipped wings} .





I'll post a small saga about that in a bit :)

[Mr Frost]

M.R and S.R. likewise cannot hope to come close to modelling the different types of maneuvering capabilities and types of stability of different aircraft .
Good examples are :

[disclaimer , if it seems like I'm trying to argue "XYZ fighter {read , Bf109} was uber and needs special rulz becoz its the uber™" , that's only because those {that's} are the fighters {or specific information there on} I know best and/or if I go into too much detail on why what could do which and was such it will become a small book :) . The P-38 for example has a number of useful and unique tricks it could do {and one really big flaw in way of pilot workload that could have been easily fixed} that would justify special rules and/or techniques/perks a pilot could learn on it that would confer bonuses in certain situations , but you can look those up yourself]

*the difference between susstained and instantanious turn rates {The Fw 190 had an excellent instantanious turn rate at medium to high speeds but a terrible sussatained turn , the Mitsubishi A6m at those speeds had the opposite . it makes for aircraft that must be flown and fought very differently to survive and win}

*roll rate {this is a massive component in medium and high speed maneuverability to the point where the British were willing to sacrifice climb and even top speed by clipping the wings on many late model Spitfires to achieve it} Removing the outer wing MGFFM cannon in the Fw190A-4 noticably increaed the already excellent rollrate {and slightly improved turn rates too}

*the effect of wing design and wing loading on climb rate {it makes a big difference sometimes . The Italian Falco biplane fighter had a lower accelleration -drag was a problem- than the Hurricane 1a , but it could out climb it in susstained climb} .

*energy retention in turning maneuvers {the Spitfires , especially early models , were very good at keeping their energy -ie their speed/momentum- when turning hard either susstained or instantanious , the bf 109 was not . This meant that a 109 pilot could quickly find himself at a massive energy deficit Vs a Spit even should He beging with a large energy superiority should he fly carelessly to the Spitfires' strengths} . Sometimes it can differ between susstained and instantanious for rare aircraft , the Vought Corsair is one such if I remember correctly {good retention in High speed instantanious , crap in every other type of turn} .

*energy retention exiting a dive and in a climb {the Fw 190s , Mustangs and P47s all had excellent energy retention in level flight after a dive and in a zoom climb . The Late war Bf 109s will out zoom most models of these -the K-4 C3 might beat them all or atleast match even the P51 H and P-47 N- for maximum altitude but for most of the zoom will appear to be falling behind , it is the legendary susstained climb rate that gives it the extra altitude but for most real war uses of zoom climb this wont be a factor} . Sometimes this could vary for an aircraft type between retention in level flight and in a zoom such as in eliptical winged Spits where the retention exiting a dive was good {though not as good as the champions I mentioned} whist the retention in a zoom climb was merely acceptable . G.U.R.P.S. doen't model this properly even in the 3rd Edition Vehicles rules .

*dive accelleration verses maximum dive speed {the eliptical winged Spitfires could actually dive faster than the legendary dive monster P-47 Thunderbolts -it was the wing shape that made the difference- but the Thunderbolts prodigous dive accelleration meant that unless the dive was susstained to a dangerously high speed -compression is just part of the problem , negotiating with inertia and the ground is the real bitch- it would practically walk away from any Spit that tried to follow} . I don't remember G.U.R.P.S. modelling this accurately enough .

*{related to the above point} stability in a dive {the Spit not only had a lesser dive accelleration , but more important is the way it behaved iniating and during a dive -the Thunderbolt was typically described as "it's like the bottom falls out" and was rock solid in the dive whereas the Spit "acted like it didn't want to dive" and was described as "floating down" rather than diving .

*stability as a gun platform {some fighters were simply better at this than others and it wasn't neccessarily in fighters that would qualify for a higher stability rating in G.U.R.P.S. terms . The bf109G-6 and later versions were described like this by many experten -even when talking about wing mounted cannon pods- as "flying on rails" . Conversly , some fighters were less than satisfactory gun platforms} . At the ranges fighters typically shoot at each other {anything closer than 50 yards , even approaching from dead 6 , is approaching suicide or an atempt by your fighter to mate with His the rough way} even a + or - 1 {or 2} is realistic .

*weapons layout and convergence {part of the reason the Hurricane was concidered a more accurate weapons platform was that its' guns were tightly packed in each wing so when one bank was on target , typically all guns in that wing would score hits reguardless of convergance -unless each pair was converged at a different distance which was of dubious value and quickly fell out of "fashion"- whereas the Spitfire had its guns spaced unevenly and far apart which could result in even only one single gun being on target even if the pilots' aim was good . Convergence its' self is the term for adjusting each gun -or bank of guns if tightly grouped in the wing , this made particular sense with .50+ cal and 20+mm weapons where there was little in the aircraft that a single round couldn't punch clean through so spreading the hits out a little caused more actual damage- so they hit the same spot a given distance infront of the fighter -in general , anything above 200 yards was only good Vs bombers and surface targets , 100 yards for fighters was optimal and one crazy Finn ace set the .50s in His Brewster Buffalo to 50 meters because the barrels were so worn that anything further would have been ineffective by His reasoning- to maximise the effect of the guns package . The problem arises if firing on a target outside of -or inside , though unless convergence is set extreamly far out such as 400 yards or more it is less of an issue- convergence where in some cases you aim and deflection might be perfect yet not one round hits because the guns are literally pointing completely wide of him to either side . Not a small issue . In such cases , a pilot that wished to still hit an opponent would aim slightly to one side of the target however this meant

*The ability or lack there of to dump energy fast {useful to force an overshoot , though risky . It is related to energy retention and wing loading but the effect is that a fighter that can do this -Fw 190 is a "champ" at dumping energy fast , the Spitfire however is lagely the opposite- however the effect for those that do dump energy quickly is quite dramatic compared to those that can't . With the examples I gave in the right circumstance the 190 could slow down so rapidly that if the Spit is close -and moving fast- it would over shoot and the 190 be able to lay guns on Him before the Spit could maneuver out of that guns solution . It can also be used to slow down enough to successfully turn to avoid say a moutain you just glimpsed infront of you through the cloud layer} . G.U.R.P.S. doesn't model this at all . It is far more rapid and dramatic in the right aircraft than the aDcell stat measures .


Wall of Text™ shall continue after this brief message from the sponsor

[Mr Frost]

Wall of Text™ part deux

*flaps , trim and leading edge slats
Flaps {these are a huge influence of agility , and the first two are variable in almost all fixed wing aircraft from WWII onwards . Some designs only had a few set flap settings -Spitfires and I think the P-38 was the same had only one each of take off , landing and combat settings- where as others had fully manual settings -bf 109 pilots could adjust flaps to anything from 0 to 100 %- and the N1K2 had automatically adjusting flaps that would deploy to a suitable degree depending on the measured positive G force of the moment . Different designs of flaps have different effects on susstained turn , energy retention , accelleration and top speed -and the top speed before damage can occur for those flaps or even the wing its' self at that flap setting which can vary wildly by design- and whilst some might transform an otherwise ungainly turner into a dancer -P-38 with combat flaps deployed enjoys a dramatic improvement in susstained turn- others will give only slight benifit to actual turn performance -other than slowing the bird down so it can complete the turn in a shorter radius- and is really only useful for reducing stall speed and slowing down} . Trying to fight or in some cases even fly safely any real distance with flaps jammed at or near full setting would be difficult . Trying to take off or land with damaged {or sabotaged ! oohhh , drama} flaps would require a lot more runway and might be extreamly dangerous or even impossible in the case of some cargo transports when fully laiden {a heafty headwind might fix that though , got any useful spells ?} .
Trim {whilst most aircraft have it , some can get more benifit from it in maneuvering and especially in combat . Some designs are just better for trim adjustment -without throwing the aerolon and elevator trim out of harmony so each is trimmed to a different speed which would mess up the birds handling making shooting and energy retention tough to begin with- in the heat of combat and depending on cockpit layout , being crippled in a certaiin hand or arm could give a big penalty to maneuvers too much slower or faster than what the trim was set for the last time you adjusted it -in the 109 , adjusting the trim with your right hand is not only very awkward , it is down right dangerous as it is so cramped in the cockpit you would need long arms to avoid nudging the joystick you have to let go of to do it meaning if your trimmed for say 400 kmh , landing is going to be a bitch . On 109 trim , manipulating those trim wheels hard throughout a long turning dogfight without gloves should cause 1 hp of damage - it rubs your hand raw- but it is so intuitive to do , there might be some grounds for a perk that allows you a +1 to maneuver if you're willing to take that damage} .
Leading edge slats {the Bf109 series had them as does the F/A 18 Hornet of today -the Hornet almost seems like it evolved from the 109 in a darwinian way- and the certainly alter stall and turn performance which is important to model in any Vehicle Design System , however for the inertia deployed slats of WWII {and before} , they can cause serious and sometime catastrophic instability in maneuvers when they deploy assermetrically which is one reason why the 109 got a bad reputation for stability in very acrobatic maneuvers -allied pilots that got to fly captured examples weren't used to it and the badly trained late war German pilots were to poorly skilled to manage the issue well- . There should be a rule/s to model this and properly trained pilots familiar with the 109 -and other fighters with leading edge slats- should probably be able to develop a Hard Technique or such that might allow a small bonus in certain maneuvers if they're willing to risk serious misshaps on a failed roll -it could cause the plane to stall out or even enter a nasty spin which at low altitude is death .

*Engine design
Carburettors Vs fuel injection and similar concerns {asside from early war problems with some designs -Merlins being famous for conking if the pilot bunted , and it took several measures to fix it properly- , flying upside down for extended periods without the engine cutting out or even being damaged due to oil starvation was only really possible with fuel injected engines to the best of my knowledge , atleast for most of WWII} .
Staged/geared superchargers Vs barometer controled fluid coupling and close cousines {basically , the supercharger , fuel mix and prop pitch on the 109 was fully automatic and adjusted the boost etc in a smooth curve without and spikes which was intuitivly predictable and required no attention from the pilot -allowing more attention on the opponent/s- whereas staged/geared superchargers etc not only required the pilot to keep one eye one the altometer and such at most times but also run constant mental checklists of when to make adjustments or run the risk of not only being low on performance at that altitude but also damaging the engine and/or propellor/governor . The system -design philosophy really- was adopted by the British whole heartedly at the end of the war in their Hawker Fury and is now an uncontestable standard in design philosophy for combat aircraft . The smooth curve in performance Vs altitude also meant that whilst staged supercharger engined fighters would get a sudden boost in performance that could put them ahead of the 109 in performance , they also would approach a similar -though gradual- point at given altitudes where performance was less than the engine/supercharger should theoretically been capable of . Furthermore , either a staged supercharger/engine was designed to opperate below optimum at most -or close to most- altitudes or it allowed the engine to overboost to a degree that shortened engine life span and could make existing problems -like a coolant leak or oil that needs changing but suppilies havn't reached your unit yet- by nature of its' design -curved drops in power as atltitude increases then sudden increase in boost as you engage the next gear/stage- whereas the fluid coupling allowed the powerplant to ride much closer to tollerance throughout from deck to ceiling .} . This obvioulsly effects relative speed and aAcell of aircraft and would dramatically alter an engagement or situation depending on altitude and supercharger design .


The list could go on , but before you all think that that stuff all belongs in notes , try to image what a confusing mess that would look like and how clumsy it would be to work with . Some would belong there , but a more elegant solution would be required to present all the stuff needed to do the complexity that is aircraft performance {and especially combat} justice .

Whilst points some might seem unneccessary , if you research the subject , it becomes clear that the increase sophistication of rules and stats on the subject is neccessary . On the deck , a Spit V L.F. would be very superior to a P-47D and be able to catch it then dance around it too ; at 30,000 feet the P-47 would toy with that Spit !
On the Deck a P-40B would be a better dogfighter than a P-40F despite the stability issue ; at 30,000 feet that P-40B has almost no chance !
In a climbing Turn a P-38 pilot whom knows the technique can effortlessly out turn a Bf 109 F-4 that is right on His 6 and possition Himself for a likely guns solution very shortly thereafter ; if that P-38 pilot has not learned that trick , He is in deep trouble !
Currently there is no way to show this properly in G.U.R.P.S. vehicle combat rules .

[copeab]

The only problem is that most data of this kind is not commonly available for most aircraft. Things like wing loading and power/weight ratio, OTOH, are easily calculated from common data.

[Phaelen Bleux]

Glad to see this one written up. . .it has always been one of my favorite warbirds. I was rather dismayed to see that it never made into an official GURPS WWII sourcebook. It seems to me to be an iconic U.S. WWII fighter (or should I say pursuit) aircraft. Thanks!!

[copeab]

Originally Posted by Phaelen Bleux

Glad to see this one written up. . .it has always been one of my favorite warbirds. I was rather dismayed to see that it never made into an official GURPS WWII sourcebook. It seems to me to be an iconic U.S. WWII fighter (or should I say pursuit) aircraft. Thanks!!

I think the idea was to "budget" vehicles for various planned books in the WWII line. When these plans fell through, vehicles like the P-40, F6F Hellcat and B-24 Liberator never made it into print.

I believe it was originally planned for a 32- or 48-page book on the Flying Tigers (or possibly China). When that never materialized, I think it was shifted to the Japanese sourcebook, which itself has yet to appear.