Advanced French Fighters vs 1942/1943 contemporaries (2 Viewers)

[Bretoal2]

Regarding the second chart, first column is of course altitude in m, 2nd column is rate of climb in m/s over the given 1000m altitude range, 3rd column is climb time to a given altitude in minutes (') and seconds ("), and finally rpm and manifold pressure.

What makes you think that there is room for extra power with better cooling? I'm curious about the factor you saw?

The 12Y-45 and 49 themselves improved performance over the 12Y-31 essentially through the supercharger which reduced losses and increased efficiency so you could increase power a little bit on similar fuel without changing the rest of the engine, while the 12Y-51 achieved that through increased rpm (enabled by the Sarrazin devices increasing crankshaft strength) and improving combustion (larger valves while the fuel now goes to 92/100 octane to prevent knock).
I would infer from this that the 12Y-31 basis that the 12Y-45/49 used was limited at this stage by mechanical durability and breathing rather than cooling, though this is partially accounted for by the larger valves and increased octane rating.

The swirl throttle supercharger meant that the power loss when going from the critical altitude to sea level was lower (the power curve is flatter below critical altitude), such that it was possible to keep a given sea level/low altitude power while increasing critical altitude (shifting the curve to the right on a power/altitude diagram), thus increasing available power at altitudes above the critical altitude. The 12Y-51 engine with the original H-S supercharger is a straight up more powerful raw engine with a worse supercharger, so low altitude power is better but not as much as it could be while the critical altitude is lower.

In theory at least, the 12Y-51 with the swirl throttle supercharger would at least enable the same curve shifting that happened with the -45/49 and thus actually exploit the more powerful base engine at high altitude; depending on the selected critical altitude, it should also generally increase low altitude power a bit to make it closer to the peak power which is achieved at critical altitude. Possibly, if mechanical durability or breathing aren't the limiting factors, it may be possible to repeat the trick of the -45/49 compared to -31 and actually achieve a little extra maximum power over the base engine with H-S supercharger, but public information on that engine/supercharger combination is basically nonexistent AFAIK.

Assuming that the maximum output couldn't exceed 1000 hp and that 1100 hp remained reserved to take-off however, we can know that the minimum low altitude power even with S-P supercharger can only be somewhere between 900 and 1000 hp (so 0 to 100 hp gain over H-S supercharger). So, compared with a hypothetical D520 with 12Y-51 with H-S supercharger, the low altitude speed could only ever be increased by what an extra 100 hp gets you.

Indeed, the early models of the Hispano-Suiza 12Y-51 were equipped with the original H-S supercharger, which was significantly inferior to the Turboméca (Planiol-Szydlowski) unit.

At low altitudes, the P/S supercharger's main advantage was its ability to significantly lower intake temperatures; this feature simultaneously reduced the risk of detonation and improved efficiency by increasing the charge density.

There remained, of course, the question of the engine's structural integrity—its ability to withstand these conditions. While Hispano's finish and manufacture quality was universally praised, its lightweight design meant it lacked the robustness needed to handle the increased stresses associated with higher performance.

It is also worth noting that, in Émile Dewoitine's view, the arrival of the D551 rendered the D520 obsolete. Had the collapse of June 1940 not occurred, the D551—which offered superior performance and, crucially, was far easier to manufacture—would likely have quickly replaced its predecessor.

 

[Elan Vital]

It is also worth noting that, in Émile Dewoitine's view, the arrival of the D551 rendered the D520 obsolete. Had the collapse of June 1940 not occurred, the D551—which offered superior performance and, crucially, was far easier to manufacture—would likely have quickly replaced its predecessor.

Indeed. There was no question of keeping both types in production concurrently aside from what was necessary to wait until D55X tooling was completed.

 

[bf109xxl]

It should be noted, however, that "Anazot' type foam does not prevent fuel leakage, although it will reduce the loss rate.

According to Russian-language sources, "Anazot" foam was used specifically as a sealing layer in a multilayer coating to protect fuel tanks from small-caliber bullets. In general, starting in 1937, several different types of multilayer protective coatings were developed in the USSR to prevent fuel leakage if the tank were damaged by a bullet.

 

[Steamed_Banana]

One thing I'm noticing reading operational histories of Japanese Army and Navy air forces in WW2, is that the importance of self-sealing tanks seems to be somewhat exaggerated in the conventional wisdom. A6Ms, Ki-43s, bombers like D3As, Ki-51s, Ki-21s and Ki-48s seem to routinely get shot up and still fly back to base, sometimes riddled with holes and with wounded crew and pilots. But they don't seem to ignite and detonate at the first spark like a car in a 1970s movie, the way I think a lot of us were taught to expect.

 

[ThomasP]

re

According to Russian-language sources, "Anazot" foam was used specifically as a sealing layer in a multilayer coating to protect fuel tanks from small-caliber bullets. In general, starting in 1937, several different types of multilayer protective coatings were developed in the USSR to prevent fuel leakage if the tank were damaged by a bullet.

You have me wondering how that worked. Maybe an additional liquid substance poured/brushed onto the Anazot that seeped in and filled up the cellular air spaces?

 

[Steamed_Banana]

Indeed. There was no question of keeping both types in production concurrently aside from what was necessary to wait until D55X tooling was completed.

Assuming D55X worked out as a design, which was always a gamble...

 

[Bretoal2]

Assuming D55X worked out as a design, which was always a gamble...

The D551 was not a new aircraft, but essentially an evolution of a well-known and proven design. The risk of failure regarding the airframe was minimal.

I believe that if there was any risk, it lay primarily in the powerplant: Hispano-Suiza was struggling to improve its 12Y-45/49 engines, which were essentially 12Y-31s "boosted" by a much more efficient supercharger. For complex reasons, the company was reluctant to equip its 12Y-51s with this revolutionary supercharger, persisting instead in offering the engine with its "maison" supercharger, which had far lower efficiency. Meanwhile, the major evolution represented by the 12Z engine remained bogged down by the issue of "differential scavenging," leading to significant development hurdles that were never truly resolved, even after the war.

Finally, it is worth recalling that plans to manufacture foreign engines (Pratt, Allison, Bristol, and especially Rolls-Royce) in France had been largely scuttled by domestic engine manufacturers...

 

[Steamed_Banana]

It would not be the first time that an otherwise promising design was derailed by problems with engine development.

After the war, the development of improved piston powered engines were rapidly diminishing in terms of national and major commercial priorities, I think.

In 1940, the pressure seemed to be very much on, and following a decade or more of counterproductive struggles, infighting and confusion, French industry seemed to suddenly be much more dialed in. It's interesting that the engine companies blocked license production of US and British designs.

 

[Bretoal2]

It would not be the first time that an otherwise promising design was derailed by problems with engine development.

After the war, the development of improved piston powered engines were rapidly diminishing in terms of national and major commercial priorities, I think.

In 1940, the pressure seemed to be very much on, and following a decade or more of counterproductive struggles, infighting and confusion, French industry seemed to suddenly be much more dialed in. It's interesting that the engine companies blocked license production of US and British designs.

1029

In the wake of the Liberation, French engine manufacturers faced the ruin of their production capabilities—a decline that had unfolded in three stages: the occupying force's rejest on any new design work; the confiscation and dismantling of a large portion of their machine tools; and, finally, the massive Allied bombings of 1943–44.

Consequently, from 1945 onwards, production focused primarily on pre-war designs: the Hispano 12Y-49 (as the company failed to make the 12Z reliable) and the Gnome-Rhône (then Snecma) 14M, 14N, and 14R—engines that also required a long time to achieve reliability. And communist Air Minister Charles Tillon viewed Snecma more as a social laboratory than an engine factory; furthermore, its production lines were cluttered with engine types inherited from other companies nationalized alongside it, such as the Renault 12S (actually the Argus 411) and the 4Lo and 6Lo (in reality, 4- and 6-cylinder Régnier engines, which were themselves improved licensed versions of de Havilland Gipsy engines).

Nevertheless, these firms recognized that the future lay in jet propulsion. Snecma quickly established a dedicated department that—once the political turmoil had subsided—produced the famous Atar engine family, while the more cautious Hispano opted to acquire licenses to manufacture Rolls-Royce jet engines.

 

[Shortround6]

Post war the French also had production facilities that could build Jumo 213 engines and facilities that could make BMW 801s (or a large part of the components that made up BMW 801's). Problem was selling them. Nobody, except the US, had money for new planes (or at least more than handfuls) and the US had captured the civilian market. Both with surplus aircraft (C-47s, C-46s and C-54s) and with new aircraft. US engine manufacturers (mostly P&W) had also captured the large airliner market. Surplus engines were available; Parts were now worldwide and P&W had engines that had demonstrated engine lives in the hundreds of hours.
Only real reasons for using French engines were balance trade and providing at least some local employment. Sales to other European soon faced the same problems in reverse. Italy was not going to give money to France for example, when Italy needed to keep as much money as possible at home and Italian workers needed jobs.

The engine market worldwide had changed in 1945-46-47. Not overnight but planes that looked modern in 1939-40 in terms of payload and range and cost per seat/mile (or ton/mile for cargo) were now well behind the existing US transports let alone what the American designers were planning for new aircraft. Even for the US the Post war years did not go smoothly.
Martin miscalculated the 202 Airliner by not pressurizing the fuselage (changed in later models) and by running into fatigue problems with new material/s that led to a fatal crash.
Airlines were now expected to make money and it was harder to subsidize them for national prestige or as a showcase for future orders.

 

[Shortround6]

Nevertheless, these firms recognized that the future lay in jet propulsion.

Yes and no.
Military was very focused on jet propulsion. Civilian aviation.........not so much, at least in the 1940s and early 50s.
The promise for civilian aviation was there. Actual delivery kept getting put off.
Jets could use cheap fuel (although some 1944-47 jets used gasoline) but they needed a lot of it. An awful lot of it so long-range flights needed refueling stops. The refueling stops killed any speed advantage the jets had over piston engine airliners. Needing thousands of gallons more cheap fuel per flight also canceled out the price advantage.
The British tried with DH Comet I with DH Ghost engines (promised (?) Avons were running late?). But a 36-44 seat 50,000kg airplane that could only fly 1500m/2400km was not very useful even before the metal fatigue problems. The Comet 2 (first flight in Aug 1953) added about 70% more range but still not enough for transatlantic flights. Comet 4 showed up in 1957-58 at about 50% more max gross weight, engines of double the thrust (and better fuel efficiency) and could hold almost twice the passengers.
Unfortunately for the British the Boeing 707 showed up in late 1957 along with the Convair 880 and the DC-8 all in the 1957-58 time-frame.
Piston engines ruled the airlines until the late 50s, First DC-7 piston engine airliner entered service in Dec 1953.
It took a lot of engineering to get better than WW II piston engines and it took as much or more to jet engines to be useful for commercial aviation.
Business jets didn't really start to sell until the 1960s although there were several attempts in mid/late 50s with 4 seat widened trainers.

 

[Bretoal2]

Yes and no.
Military was very focused on jet propulsion. Civilian aviation.........not so much, at least in the 1940s and early 50s.
The promise for civilian aviation was there. Actual delivery kept getting put off.
Jets could use cheap fuel (although some 1944-47 jets used gasoline) but they needed a lot of it. An awful lot of it so long-range flights needed refueling stops. The refueling stops killed any speed advantage the jets had over piston engine airliners. Needing thousands of gallons more cheap fuel per flight also canceled out the price advantage.
The British tried with DH Comet I with DH Ghost engines (promised (?) Avons were running late?). But a 36-44 seat 50,000kg airplane that could only fly 1500m/2400km was not very useful even before the metal fatigue problems. The Comet 2 (first flight in Aug 1953) added about 70% more range but still not enough for transatlantic flights. Comet 4 showed up in 1957-58 at about 50% more max gross weight, engines of double the thrust (and better fuel efficiency) and could hold almost twice the passengers.
Unfortunately for the British the Boeing 707 showed up in late 1957 along with the Convair 880 and the DC-8 all in the 1957-58 time-frame.
Piston engines ruled the airlines until the late 50s, First DC-7 piston engine airliner entered service in Dec 1953.
It took a lot of engineering to get better than WW II piston engines and it took as much or more to jet engines to be useful for commercial aviation.
Business jets didn't really start to sell until the 1960s although there were several attempts in mid/late 50s with 4 seat widened trainers.

That is only partly true.

As early as 1951, the French Civil Aviation Secretariat issued specifications for a medium-range airliner designed to connect European capitals while carrying 50 to 60 passengers. The document did not specify the type of propulsion...

SNCASE (later Sud-Aviation) immediately responded with a design that would become the famous Caravelle (SE 210); prototype construction began early 1953.

SNCASE's initial plan was to equip the aircraft with SNECMA ATAR engines, which had been undergoing flight testing since 1950. It can therefore be said that the emergence of the first French jet airliners closely followed the availability of the engines themselves.

However, it is entirely accurate to say that, at the time, reliability and specific fuel consumption figures were not yet fully established; consequently, the Caravelle prototype flew with well-proven Rolls-Royce Avon engines. The ATAR remained primarily a military engine, and commercial aircraft powered by piston engines remained a common sight for a long time.

The French military, too, had shown a preference for piston engines in transport aircraft; for many years, the Air Force operated the Noratlas (Nord 2501), powered by the excellent Bristol Hercules—manufactured in France under license—which was powerful, reliable, and inexpensive to maintain. Some are still flying today.

 

[Shortround6]

That is only partly true.

Caravelle (SE 210); prototype construction began early 1953.

First flight of the prototype was 27 May 1955. First service flight was April 1959.
The Caravelle was innovative and did a lot of things right.

Jets got to be very reliable in the 1950s but it took 7-10 years from 1945 to really start fulfilling the promise.
Granted with a limited design staff trying to build both good piston engines and good jets may have been impossible.
Some companies (including American ones) tried licensing engines and while that kept some companies alive for a while it rarely (never?) worked long term.