1939/40: ideal Italian fighter?

[tomo pauk]

...
That's at 2400rpm, but the engine can go up to to 2590rpm for 30". Even considering the corresponding loss in efficiency (less torque at higher rpm) that means a figure of about 990 PS at 3500m, 940PS at 4000m and 930 at 4100m.

I know the manual says that over-revving was possible in such a fashion, but the Asso was not unique. Eg. many engine tables for the V-1710 give 120-150 rpm for over-revving in dive; the B series of the R-2800 was limited up to 3050-3060 (vs. 'regular maximum' of 2700 rpm), again in dive, so I'd be very careful claiming that Asso was really capable to use the extra 190 rpm in climb or level flight.
The Issota-Fraschini has a better engine to offer, prior the 1939, namely the L.121, the engine more or less comparable with DB-601A an Merlin III.

It was only marginally faster than the C.200, but what makes it interesting is his 1200 km range (vs 600 km for the C.200) and his installed power (more than 1700PS for 4055kg at takeoff).
The single engined italian fighters couldn't really cover the convoys to north africa, or the fleet, since they hadn't the range to fly over them for long (in substitution, the CR.25 were sometimes used). The Ro.57 had the range, and was certanly a more effective fighter than the CR.25.
His scarce max speed was due to the aerodynamic hindrance of the engines, but, that means that the installation of an heavier armament would not have worsened the prestations of the aircraft further (infact, later, a "quadriarma", four weapon, version was tested, and ordered for the production).
The S.M.79 proved to be a good torpedo bomber, but it was an expensive aircraft, in terms of both material and crew. Even the DB601 engined fighters, with 1100 PS, couldn't carry a full blown 900kg torpedo (the Re.2001 can carry a 600 kg "reduced" one), the DB605 engined ones could (the 1000 kg rack was installed on the Re.2005, and a G55 "silurante" was tested with good results), but it was too late. The Ro.57 could have been a good torpedo bomber from the outbreak of the war (and a naval bomber, with a 500 kg bomb).
For these tasks, his opponents would have been Gladiator, Swordfish, Fulmar, Beaufort... nothing he could not deal with.

Form my point of view, the Ro.57 can make two 'appearances' - one would be the fast bomber, with either the Piaggio P.XI, or the Asso RC.15 with cropped compressor. Another one would be the heavy fighter fighter-bomber, a single seater with Asso RC.40, or L.121 (= a plane similar to the Ro.58, but that one was a two-seater). The Ro.58 was claimed to make 610 km/h with (second-hand?) DB-601s.

 

[Dogwalker]

I know the manual says that over-revving was possible in such a fashion, but the Asso was not unique. Eg. many engine tables for the V-1710 give 120-150 rpm for over-revving in dive; the B series of the R-2800 was limited up to 3050-3060 (vs. 'regular maximum' of 2700 rpm), again in dive,

But the manual say nothing about dive, if there was that limitation, one may think that they would have written in the manual, but it's written only as "exceptional" and allowed for no more than 30". And, also, the manual don't give time limits for revving at 2400rpm (while giving a, quite long, 180" limit for overboosting), so we can consider 2400rpm as maximum continuosus power rpm, and the 2590rpm as the so called "+100" on italian aircrafts.
On that matter, Macchi C.200 pilot Adelmo Rigoli on +100: "At the 'scramble', immediate take off, turn, and close the undercarriage, engaged the +100, it should have been used for a short time at crucial moments... but we went up too slow!"
The +100 began to be called so, because, at that time, it consisted of about further 100 rpm more than the maximum (but how many exactly they were, depended on the engine).

 

[Dogwalker]

Form my point of view, the Ro.57 can make two 'appearances' - one would be the fast bomber, with either the Piaggio P.XI, or the Asso RC.15 with cropped compressor. Another one would be the heavy fighter fighter-bomber, a single seater with Asso RC.40, or L.121 (= a plane similar to the Ro.58, but that one was a two-seater). The Ro.58 was claimed to make 610 km/h with (second-hand?) DB-601s.

An Asso engined Ro.57 would likely have had far superior prestations (The Ro.58 was marginally faster than the C.202, with second hand engines, and being a two seater with larger wingspan than the Ro.57), but:
1) it would have been more expensive.
2) In this scenario, all the Asso XI/L.121 were likely needed for the C.200.
The Fiat A74 was the least expensive of first/line engines in italian inventory, Fiat was the producer with the bigger productive capacity, and, for the naval multirole heavy/long-range fighter-bomber, the prestations of the Ro.57 were adeguate in 1940/41.

Only in 1941 when, in the production of Macchi fighters, the Ra.1000 had, in any case, replaced the IF Asso, then these could have been diverted to Ro.57 production. Moreover, at that point, if the development of the Asso would not had halted in 1939, there would probably have been available a two-speed-supercharger version of it, An Asso Rc.15/50, or 25/60, like there was for the Delta IV and the Zeta.

 

[tomo pauk]

But the manual say nothing about dive, if there was that limitation, one may think that they would have written in the manual, but it's written only as "exceptional" and allowed for no more than 30". And, also, the manual don't give time limits for revving at 2400rpm (while giving a, quite long, 180" limit for overboosting), so we can consider 2400rpm as maximum continuosus power rpm, and the 2590rpm as the so called "+100" on italian aircrafts.

Guess we disagree on this - the manual, when listing the appropriate regimes, lists 2250 rpm for 'normal' power, both at SL and critical altitude, while 2140 rpm is the limit on take off. The 'normal' power should be the equivalent of 'maximum continous' IMO. The 2400 rpm is listed as 'maximum' ('massima'), while the 2590 is listed as 'exceptional' ('eccezionale').

On that matter, Macchi C.200 pilot Adelmo Rigoli on +100: "At the 'scramble', immediate take off, turn, and close the undercarriage, engaged the +100, it should have been used for a short time at crucial moments... but we went up too slow!"
The +100 began to be called so, because, at that time, it consisted of about further 100 rpm more than the maximum (but how many exactly they were, depended on the engine).

The +100 should point us to manifold pressure - from 790 mm Hg to 890 mm Hg for the A.74? The corresponding rpm for the 890 mm Hg was 2520, and that rpm value is listed for take-off, 'maximum horizontal speed flight' and emergancy regime (later two allowed for 'few minutes'). So if we want to draw parallels, the 2520 rpm in the A.74 is 'related' to 2400 rpm in the Asso, and 2400 rpm in A.74 is 'related' to 2250 rpm in the Asso.

An Asso engined Ro.57 would likely have had far superior prestations (The Ro.58 was marginally faster than the C.202, with second hand engines, and being a two seater with larger wingspan than the Ro.57), but:
1) it would have been more expensive.
2) In this scenario, all the Asso XI/L.121 were likely needed for the C.200.
The Fiat A74 was the least expensive of first/line engines in italian inventory, Fiat was the producer with the bigger productive capacity, and, for the naval multirole heavy/long-range fighter-bomber, the prestations of the Ro.57 were adeguate in 1940/41.

Agreed that, if the IF engines are allocated for the Macchi, there Ro.57 would unlikely get any; ditto for Asso/Ro.57 being more expensive than the a historical one, we don't know how much The historical Ro.57 was good performer for MTO in 1939/40, but not so much for 1941?

Only in 1941 when, in the production of Macchi fighters, the Ra.1000 had, in any case, replaced the IF Asso, then these could have been diverted to Ro.57 production. Moreover, at that point, if the development of the Asso would not had halted in 1939, there would probably have been available a two-speed-supercharger version of it, An Asso Rc.15/50, or 25/60, like there was for the Delta IV and the Zeta.

Probably we would see the L.122 coming into fruition? Or L.121 with two-speed compressor?

 

[tomo pauk]

There were some interesting and/or useful fighter planes where the Italian engines will be good at. Eg:
-D.520, VG.33, IK-3 and Avia 135 - all powered by Hispano V-12 engines, capable for speeds between 520-560 km/h on modest power (850-900 HP). I-F engines should be able to emulate that, provided the airframe remains also modestly sized (like Macchi fighters).
-P-66, IAR-80A, FFVS J 22 - about 1000 HP at 12-14 kft, speeds claimed from 540-575 km/h; here the Piaggio XI could step in, powering, again, a modestly-sized fighter
-Fokker D.XXIII - originally with two Walter Saggita engines of 530 HP each, Italians can try something similar with I-F Delta engines.

 

[Dogwalker]

Guess we disagree on this - the manual, when listing the appropriate regimes, lists 2250 rpm for 'normal' power, both at SL and critical altitude, while 2140 rpm is the limit on take off. The 'normal' power should be the equivalent of 'maximum continous' IMO.

I do not see why. If the manual give a time limit for oveboosting, and for 2590rpm, but do non give time limits for reving at 2400rpm, it seems obvious to me that this is not an oversight of those who wrote the manual, but that 2400rpm could be held as long as the pilot want, and then it was the maximum continuous power regime, and 2590rpm the emergency, which could be held for 30". It do not seems to me that "normal" can be considered "maximum"

The +100 should point us to manifold pressure - from 790 mm Hg to 890 mm Hg for the A.74? The corresponding rpm for the 890 mm Hg was 2520, and that rpm value is listed for take-off, 'maximum horizontal speed flight' and emergancy regime (later two allowed for 'few minutes'). So if we want to draw parallels, the 2520 rpm in the A.74 is 'related' to 2400 rpm in the Asso, and 2400 rpm in A.74 is 'related' to 2250 rpm in the Asso.

Again, I do not see why. The 2520rpm "emergency" power in the A.74, that could be held for "few minutes" are the 2590 "exceptional" power of the Asso XI, that could be held for 30". It is noteworthy that, in both in the A.74 and Asso XI, what determined the time limit were higher revs, not the pressure, infact, in the A.74, there was a "few minutes" limit for reving at 2520 rpm for both 790mm Hg than 890mm Hg (in the Asso, the overboost was not possible over 2000m).

The historical Ro.57 was good performer for MTO in 1939/40, but not so much for 1941?

In his naval role, the first real opponents would be the Hurricanes that we began to see on board of the British carriers in the Med by mid-1941, but against them also, I would not give the Ro.57 for dead (and the aircrafts available on carriers were not usually many. The entire air escort embarked on the Carriers Argus and Eagle in Operation Harpoon, june '42, consisted of 16 Sea Hurricane, 6 Fulmar, and 18 Swordfish). The first Seafires are in action in Operation Torch, so, for the great part of the "battle of the convoys" the Ro.57 would be effective. Different situation on the ground, where P.40s are available in North Africa from the beginning of 1941.

Probably we would see the L.122 coming into fruition? Or L.121 with two-speed compressor?

The two speed compressor would be the "natural" evolution. I.F. did it for the engines he could sell (Delta IV and Zeta), if there had been, for the Asso XI / L.121, other use than the Cant Z.501 flying boat, they would have done for it. Other refinements were certainly possible, but it is hard to think of big changes. Those engines were already present at the Aviation Fair of Milan in 1937. Having always the same 87 octane gasoline available, and not being able to have better materials, it is not easy to increase the power. From Piaggio P.XII to P.XV it takes two years to earn less than 200 hp. The same from P.XI to P.XIX, While the A.76 was never ready.

 

[tomo pauk]

I do not see why. If the manual give a time limit for oveboosting, and for 2590rpm, but do non give time limits for reving at 2400rpm, it seems obvious to me that this is not an oversight of those who wrote the manual, but that 2400rpm could be held as long as the pilot want, and then it was the maximum continuous power regime, and 2590rpm the emergency, which could be held for 30". It do not seems to me that "normal" can be considered "maximum"

Could the 2400 rpm be mantained as long as pilot wanted? IMO - no, it could not. The manual on page 25 is clear about 2400 being 'maximum', and 2590 rpm being "exceptionally (allowed for no more than 30 sec)"; normal being 2250.

Manual can be downloaded from here

Again, I do not see why. The 2520rpm "emergency" power in the A.74, that could be held for "few minutes" are the 2590 "exceptional" power of the Asso XI, that could be held for 30".

Few minutes could be, say, 3 minutes? It is a 6-fold duration vs. 30 sec, and that is a major difference - we can note that early DB-601s have had 5-fold difference for the take-off rating and 'Kurzleistung' (1.40 ata vs. 1.30, on same rpm). The manual does not say anything about the "exceptional" power on 2590 rpm, but merely that such rpm is exceptionally allowed; contrary to that, 2520 rpm for the A.74 is clearly noted by manual.

It is noteworthy that, in both in the A.74 and Asso XI, what determined the time limit were higher revs, not the pressure, infact, in the A.74, there was a "few minutes" limit for reving at 2520 rpm for both 790mm Hg than 890mm Hg (in the Asso, the overboost was not possible over 2000m).

Could I read in the manual about the Asso not being possible to over-boost over 2000m? Would that be for all models, or just for the RC.40 ones?

In his naval role, the first real opponents would be the Hurricanes that we began to see on board of the British carriers in the Med by mid-1941, but against them also, I would not give the Ro.57 for dead (and the aircrafts available on carriers were not usually many. The entire air escort embarked on the Carriers Argus and Eagle in Operation Harpoon, june '42, consisted of 16 Sea Hurricane, 6 Fulmar, and 18 Swordfish). The first Seafires are in action in Operation Torch, so, for the great part of the "battle of the convoys" the Ro.57 would be effective. Different situation on the ground, where P.40s are available in North Africa from the beginning of 1941.

Overall agreable. What would be the "bomb load over distance" capabilities of the Ro.57/bis?

 

[Dogwalker]

Could the 2400 rpm be mantained as long as pilot wanted? IMO - no, it could not. The manual on page 25 is clear about 2400 being 'maximum', and 2590 rpm being "exceptionally (allowed for no more than 30 sec)"; normal being 2250.

Yes, and it not give limits for reving at 2400rpm, while it gives for 2590rpm (30") and for the overboost (180"). so, 2400rpm are the maximum continuous. Still, I do not think there was a limit, but they forget to write it.

Few minutes could be, say, 3 minutes? It is a 6-fold duration vs. 30 sec, and that is a major difference

Certainly is a different time, we are talking about different engines.

The manual does not say anything about the "exceptional" power on 2590 rpm, but merely that such rpm is exceptionally allowed; contrary to that, 2520 rpm for the A.74 is clearly noted by manual.

As the engine was built, it is difficult to think that, at 2590 rpm it gave the same power than at 2400.

Could I read in the manual about the Asso not being possible to over-boost over 2000m? Would that be for all models, or just for the RC.40 ones?

At p.146. Over 2000m (of course this is not an exact value) the automatic barometric control that regulates the intake valve of the compressor opens it more than the manual control can do, so the overboost lever is in neutral. As the overboost lever opens the valve for a fixed angle, the complete overboost, 900mm hg, is possible only at sea level.

 

[tomo pauk]

Yes, and it not give limits for reving at 2400rpm, while it gives for 2590rpm (30") and for the overboost (180"). so, 2400rpm are the maximum continuous.

What is the Italian term for 'maximum continuous'?

Still, I do not think there was a limit, but they forget to write it.

I'd agree about that.

Certainly is a different time, we are talking about different engines.

Sorry if it sounds like nitpicking, but then one should not draw parallels comparations to prove the point.

As the engine was built, it is difficult to think that, at 2590 rpm it gave the same power than at 2400.

Sure enough that 2590 rpm sounds like more power. Question is whether that rpm was allowed for same/greater manifold pressures than as it was possible for 2400?

At p.146. Over 2000m (of course this is not an exact value) the automatic barometric control that regulates the intake valve of the compressor opens it more than the manual control can do, so the overboost lever is in neutral. As the overboost lever opens the valve for a fixed angle, the complete overboost, 900mm hg, is possible only at sea level.

Thanks for the information.

 

[Dogwalker]

What is the Italian term for 'maximum continuous'?

Literally it's "massimo continuo", but the thechnical terms are not translated literally. Tehere is not a literal equivalent for WEP, or "military power".

Sorry if it sounds like nitpicking, but then one should not draw parallels comparations to prove the point.

Why not? Both the engines have a high rpm regime they can keep for a limited time, that do not means that, on different engines, this time limit had to be the same. It can be different even in two versions of the same engine.

Sure enough that 2590 rpm sounds like more power. Question is whether that rpm was allowed for same/greater manifold pressures than as it was possible for 2400?

It exists a lever to close the intake valve of the compressor. The manual say to use it at low regime.

 

[tomo pauk]

Literally it's "massimo continuo", but the thechnical terms are not translated literally.

Would you please be so kind to translate what engine regimes are described in the tables:

Why not? Both the engines have a high rpm regime they can keep for a limited time, that do not means that, on different engines, this time limit had to be the same. It can be different even in two versions of the same engine.

One engine has three regimes, thoroughly described in the manual, that we can classify as emergency, or over-revving, or something similar. Manual for another engine does not mention a single regime that would include maximal RPM (=2400 here), let alone the exceptionally allowed RPM (=2590 here). As for the duration of the exceptional limits, a 6-fold difference is a realy big one - the 3 minutes can and will offer the plane to either close to the prey, or maybe to run away, the 30 second regime will hardly offer anything similar.
We can also note that there was no engine with 30-60 seconds regime, apart from take-off rating in early DB-601s.

It exists a lever to close the intake valve of the compressor. The manual say to use it at low regime.

Does the manual makes the connection with the operation of the lever with engine making 2590 rpm? What would be the 'low regime'?

from the manual for the A.74:

 

[Civettone]

Wasn's the latest Asso disregarded as it was considered unreliable?

I never understood why the Caproni-Vizzola F.4 was not a real candidate. Given the fact that it would have been more aerodynamical with a similar hp than the F.5, speed must have been superior. Probably around 530 kmh? I have seen speed figures for the F.4, but I believe they are bogus. So, I assume again, that the Asso was not considered sufficiently reliable.

Also, I read that the Caproni aircraft won the competition. I assume that the author meant the Caproni-Vizzola F.5. In that nice table we can see that the speed of the F.5 was almost as good as the C.200, but that it had by far the best climb rate!

Given the mentality of the day concerning manoeuvrable aircraft, I understand that they took the CR.42 as well. But the Fiat G.50?? Two fighter aircraft from Fiat? Unbelievable!

Kris

 

[Dogwalker]

The F5 came late to the competition, as the Regia already ordered the other models and there was no more space for it. Moreover, it's wooden wings had raised some eyebrows, since the competition was for metallic aircrafts.
The Asso XI RC.15 used on the Z.506 was reliable, hovever the F.4 was stopped for the same reason the Ca.165 was never really taken into consideration. The Regia Aeronauitca didn't want that engine on a fighter.
The G.50 was choosen for the same reason the Cr.42 was (or the C.205V some years later). It was ready to be produced (infact it was already used in Spain), while all the others needed time to be put in production. A slightly inferior fighter is better than no fighter at all.

 

[pattle]

I think the Italians were pretty well stuck with what they already had in 1940. They could have built something better because they had talented enough designers, but they didn't because the country was run by people who didn't know what they were doing, a lot like Britain since the eighties.

 

[Tollmar]

The fiat g 50 was designed for a much more powerful engine by Gabrielli, but this engine had so many problems during the validation. So the designer had to give up and fall back on this A.74. If you do the calculations on the performance of the original engine, the aircraft would have been much more performances. What I think was the real loser in the choice instead of fighter for Regia Aeronautica is the REGGIANE Re.2000 which I think was the most modern, least expensive and the most performance of the aircraft in the competition for the Fighter.

 

[davebender]

So was everyone else except USA. Most American military units didn't experience combat prior to June 1944 so we had all the time in the world to develop, produce and stockpile equipment.

 

[Civettone]

REGGIANE Re.2000 which I think was the most modern, least expensive and the most performance of the aircraft in the competition for the Fighter.

Least expensive? That seems a dubious claim.


And what engine was the Fiat G.50 supposed to have? There was a Fiat G.50ter with a 1,000 hp Fiat A.76 engine and a Fiat G.52 with a Fiat A.75 R.C.53 engine.
Kris

 

[davebender]

Especially if it's competing against the dirt cheap Me-109.

 

[pattle]

So was everyone else except USA. Most American military units didn't experience combat prior to June 1944 so we had all the time in the world to develop, produce and stockpile equipment.

Most other countries had something in the pipeline that could match what their adversaries were bringing through. Britain and Germany were both able to improve their existing aircraft and develop new types while the Italians had reached a dead end through lack of a suitable engine and were left behind. Italian fighters were also generally to lightly armed. You have to remember that the Italians were not ready for war in 1940, yes they had a good sized air force but it had very few modern aircraft which is why the Italians entered the Battle of Britain from Belgian bases with CR42 biplanes.
I knew the Americans were rather late in joining the war but I didn't realise that most American units didn't experience combat until June 1944.

 

[parsifal]

Especially if it's competing against the dirt cheap Me-109.

Sorry, but this is a totally spurious claim, that ive seen many times. Facts are, its impossible to determine the full cost of any aircraft at this point because of the differing and articficial pegging of price mechanisms at that time. That applies to all nationalities, but particularly the totalitarian regimes.

However, its a telltale sign that this claim is totally bogus, by the numbers of foreign sales and orders the germans had received pre-war for the 109. By my quick reckoning, the Germans had received orders, or had provided as gifts, for around 300 Me 109s, of various marks. By comparison the foreign orders for the Spitfire was running in the thousands. Most were never delivered, but its a measure of the relative expense of each type, at least in part. And Germany was operating on a subsidised command management system, whilst Britain was operating on a free market model (more or less).admittedly countries were lining up to buy British rather than German, because Germany by 1938-39 was actibg clearly as an agressor nation and the neutrals were trying to get ready for a war that would probably see the germans as their enemies.

I think it significant also, that the Hungarians initially chose the RE 2000 as the basis for their indigenous production program over the 109. Eventually the reggiane design was exposed as inferior, and the hungarians switched to 109 production, but pre-war....up to 1940, they didnt particualalry like the 109, despite a very aggressive sales pitch by the Germans, mixed in with not a little implied threats......