Westland Whirlwind revisited

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The Hispano engine was the height of technology..................in 1931.

The French actually had very little choice unless another company came up with brand new engine. They were trapped trying build Hispano engines on existing machinery. The 170mm bore spacing goes back to the 300hp Hispano V-8 of 1918.
One of the things the Swiss did was increase the weight of the crankshaft from 50kg to 80kg. The Hispano engine's crankcase and crankshaft were not strong enough to stand up to the power that the customers were looking for.
The increase power variants always came with major changes in structure and weight. The Hispano needed a change from two valves. and it needed a bunch of other changes.

The 12Z got 4 valve heads and gained around 140kg (almost 30%) in weight.

The Russian M-105 got 3 valve heads and gained around 80-90kg in weight. also gained a two speed supercharger drive which helped boost the low altitude power.
They also reduced the bore size to strengthen the cylinders.

The Swiss Saurer YS-2 gained 190-200kg to get 4 valve heads and other improvements. Result was
1300hp for take-off at 2600rpm.
1410hp/2600rpm/15,700ft..........................................in 1946/47.

The Swiss ended with the Saurer YS-4 that used a variable speed supercharger, Bosch fuel injection, 100/130 fuel and a weight of 1555lbs/705kg (43% increase) for
1600hp/2800rpm/46.7in (8.6lbs boost) take-off
1580hp/2800rpm/ 15,300ft/4600meters Military power.

even later in timing. Swedes post war were building DB605 engines that gave 1475hp at take-off and 1575hp at 7,000ft on 91/96 fuel that weighed 725kg for perspective.

The Hispano had been passed by in 1939/40 and the only countries that kept it had lot invested in tooling.

Look up the problems the Russians had with the V-106 and V-107 engines.
 
The P-36 pilots in France had the advantage of a few weeks to get familiarized with their aircraft, which I think helped a lot. D.520 pilots were thrown into the breach with little if any training on type. Same for the Bloch 150 series though those probably had more development work needed before they would be viable.
 
MIflyer said:
I understand that in North Africa the Tomahawk I's had their nose mounted .50 cal guns replaced with .303. I assume that was due to logistics but perhaps reliability had something to do with it.
Click to expand...

That would be the first I heard of this - do you have a source?

To the contrary, several British Aces in North Africa commented on the .50 caliber guns, Clive Caldwell mentioned he liked to be able to recharge the guns manually if they did jam (electric charging didn't work in the early Kittyhawks), and Bobby Gibbes said the smell of gunpowder in the cockpit which you only got from the Tomahawk.

Most photos I've seen seem to show the bigger guns.

I'm not saying it didn't happen, but my guess is that if they did do it it was in the earliest days and they soon shifted over to the 0.5 inch.

 
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I'd say that's quite impressive - Switzerland is a very small country and probably only a tiny part of it was engaged in this (it's really like 5 different countries loosely linked together) - and for them, military production wasn't the same urgent priority it was for a country like France, at least until they were conquered. The French themselves seem to have been pretty confident they could get power in this same ballpark or a bit better within months of the first deployment of the D.520. They did not necessarily have the fuel available for the YS-4 type you mention below of course.


I think the Soviets had a lot of problems with V-106 and engines in general for a variety of special reasons somewhat unique to the Soviet Union at that time. Designing planes and engines from prison or with the threat of gulag and / or execution isn't always conducive to creativity or design genius, and when the fearless leader kills off enough of the university educated engineers you are left with people who are on let's just say a steeper learning curve, often working in very difficult conditions and relatively poor organization. There is a reason why the Soviets focused so much on very simple, very utilitarian weapons for so long.
 
Some of the Hawk pilots (not exactly P-36s) were flying them in France in March of 1939, a lot longer than a few weeks. The A-2s (the 2nd hundred) started showing up in France (not Buffalo) in May of 1939. I don't know if the French mounted the machineguns in France or of FN of Belgium shipped the guns to the US and the the knocked down crated aircraft were shipped to France with the guns.
It was the A-3s that showed up with a few weeks to spare but by this time some French pilots had over 10 months on type.
 
The Swiss may have been small but the Swiss had always had a strong defensive mind set. They had also a fair amount of industry. The US and Britain were both buying machine tools from the Swiss in the 1930s (Germany too), there were also domestic locomotive builders. Brown-Boveri had built an industrial gas turbine generator for the city of Neuchatel in 1939 (and it was located in a bomb proof building). The Swiss were not ignorant of what was going on.

The French had a lot of optimistic power estimates in 1939/40. Some of which failed to come true in 1945/46 production even with the better fuel available.

The Russians were not happy with the Hispano from day one and that was in 1933. They were paying cash money for the design and assistance and the initial contract was for 5 years.
They were not getting the engine life they wanted even at 750hp in 1933. Things got better but it was always a struggle. One of the first test engines broke at the Hispano Factory in France so ignore the stuff about conditions in the Soviet Union. The Russians had to down rate the early versions from the French promises.
 

Information are not 100 % sure, but for the best :
100 H75 A-1
100 H75 A-2
135 H75 A-3
81 H75 A-4 ordered, maybe only 6 delivered ; not used in combat before the Armistice.
It equipped at first four Groupes (squadrons) : I/4, II/4, I/5, II/5 and lately a fifth III/2 plus some miscellaneous units.

After the Armistice, 186 fled to North Africa, 45 remained in France.
36 captured by the Germans were delivered to Finland.
 

What about the 23 airframes that ended up on Martinique, alongside some ex-Belgian Brewster B339Bs?




Here are some pics of the Brewsters:





 
Greg Boeser said:
Weren't the Finns using licence built Swedish SC3-Gs?
Click to expand...
IIRC no, we got from Germany 101 - 166 war booty Twin Wasps, most of which went into Myrskys (51 built) but that meant that there were enough to change Cyclones from those Cyclone Hawks (originally 7) that were still in use to P&Ws by November 1941, and as spare engines for the rest of the Hawks. A total of 29 Hawks were obtained in 1941 and 15 more were bought in 1943, some of these were originally versions equipped with Cyclones, but I don't know if the P&Ws had already been changed into them before they arrived to Finland. The last two of these 15 arrived to Finland on 5 Jan 1944.
 
GrauGeist said:
The Finns got a mixed bag of captured Hawks from Germany, such as Norwegian and French with different sub types.

They did remarkably well against the VVS, too.
Click to expand...
Yes, IMHO Hawk 75A was not a bad fighter for 1939 - 42 if used correctly as shown by French in 1939-40, Finns in 1941-43 and RAF in Burma 42-43. In 1944 it was completely outclasses by La-5Fs in Karelia. The Finns were handicapped by the fact that they had to used 87 octane fuel with their Hawks so 1065 hp was the max power also for the newer versions P&W R-1830s.
 

Ok according to this site...

Fighter squadron-GC-II-4

Site dedicated to the French Air Force in 1939-1940. In these pages, you will discover the Airplanes, the Squadrons, the forces in presence, but also the Pilots and Crews who fought in extreme conditions: the record of the casualtys and victories is there to attest.
www.passionair1940.fr

GC I/4 got Hawk 75 April 1939
GC II/4 got Hawk 75 May 1939
GC I/5 got Hawk 75 Feb 1939
GC II/5 got Hawk 75 March 1939
GC III/2 started fighting with MS 406, switched to Hawk 75 May 1940

So SR6 was right, most of them had H75 for a year or more before the real battle started in May 1940. The first A-3 arrived in March 1940.

From the site:

".. A first contract for the purchase of 100 Curtiss H75 A1 (see "Version") was signed in May 1938. After testing by French pilots in Buffalo, the first Curtiss H75 A1, brought back to French standards, are dismantled in France December 1938. They were directly purchased routed to the plant of Bourges in charge of assembly. The situation in Europe is deteriorating after the Munich crisis, and new negotiations are being launched with the United States to acquire new aircraft. The Curtiss H81 was chosen as the curtiss P40, but the delivery delays of the Allison engines of this version led to the choice of the Curtiss H75 A2, an improved version of the H75 equipped with a motor and an armament more powerful. A new order of 100 machines has passed ..

In September 1939, the entire order was honored, and the first fighter Group were equipped as of March 1939 : GC I / 5, GC II / 5, GC I / 4,. After the declaration of War, in September 39, France again turns to the United States for a third command. The context is however more difficult with a France now in war, the United States now neutral, and a unit price of Curtiss H75 even higher ... An order is finally passed for the supply of 530 Curtiss H75 A3, and 100 new Curtiss H81 (P40) now available. The first Curtiss H75 A3 arrives in France in March 1940. Only part of the order can arrive in time on the national territory: a part sinks at sea, the rest is diverted to the West Indies to be stored, or Casablanca in Morocco. As for the H75 A4 version, less than a dozen aircraft arrive in France, too late to take part in the fighting.

At the signature of the Armistice, all the Fighter Groups equipped with Curtiss H75 take refuge in North Africa. TThere are about 186 aircraft, while 45 others stayed in metropolitan France.The GC I / 4, GC I / 5 and GC II / 5 were kept in the Vichy Air Force, based in Rabat, Casablanca and Morocco respectively. These groups had to face the allied planes during the regrettable case "Mers El Kebir", and raids of retaliation that followed. After the rallying to the French Free Forces, the Curtiss H75 aging finish their career in the schools of fighter, or in secondary missions.

The final outcome of the use of the Curtiss H75 during the Frances campaign is 275 sures victories and 96 likely for the loss of 35 pilots. Some pilots will win numerous victories aboard this aircraft, such as Edmond Marin la Meslee, the Aces of the French Aces with his 16 victories..

This aircraft was appreciated by its pilots for its ease of piloting, its large cokpit,and its general stability which made it a good platform of shooting. On the other hand, its armament was far too weak: 4 machine guns of 7.5mm, 6 for the last versions, and its engine, although reliable and robust, was not powerful enough. Its protection was perfectible, including unprotected tanks."

For D.520, it looks like GC I/3, GC II/3, and GC II/7, then GC III/3 and GC III/6 eventually g ot some. Manufacturing didn't start though until April 1940, with 437 eventually delivered before armistice, if I'm reading this right only 330 got delivered to combat units, and I'm not sure how many of those flew. 106 were destroyed in combat and accidents, quoting the site "the aircraft was delicate in piloting".
 

IIRC means "If I recall correctly" it's not a statement of irrefutable fact. I figured someone would know, and someone did give us the units, which made the rest doable.

Looks like most H75 were equipped in spring of 1939. Only one new unit in May 1940 (switched from MS.406) but the delivery schedule continued right into the war, with most of the A3s arriving from April 1940.
 
Thank you, GrauGeist, Greg, Frog and buffnut453.

I had a pretty good idea of what showed up when, and it didn't line up with what somebody else was saying. It still doesn't.
There was a lot of confusion at the time and few planes may have fallen through the cracks and I am not going to argue about a handful of planes out of around 300.
Also the difference between built, accepted by French at the factory, shipped, received, and used by actual units.

and now he has done his home work.
 
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