1939/40: ideal Italian fighter?

[tomo pauk]

The data for the Italian engines is puzzling, to say at least.
The Manual for the engine "Fiat A 74 RC 38 S" allows for 2520 rpm in three cases: take off, 'high speed level flight (for few minutes)' (max 840 HP at 790 mm Hg at 4300m) and 'emergency (for few minutes)' (max 960 HP at 890 mm Hg at 3000m). However, that is for the engine with 'S' suffix (when that engine was being built?), the manual being dated 28th Feb 1941. Manual is available here, and seems it was in possession of the Finnish air force.

 

[Shortround6]

It is sort of understandable.
A bit like the Merlin III, 1030hp at 16,500ft but only 880hp for take-off. Once they got the 100 octane they could open the throttle more at low altitudes. The Italian engine was full at 4300 meters and at part throttle below that. The supercharger would supply more than enough air but with 87 octane fuel detonation may set in. Again the difference between 3800 meters (official?) and 4300 meters may be due to RAM in the intake (?) just as the Merlin was actually good for several thousand more feet in high speed level flight.

I wouldn't worry much about 20-30 rpm one way or another in a particular test. the only question is the emergency (for few minutes) part, at a rough guess being 800-1300 meters below the rated altitude of the engine there should be some spare supercharge capacity available. The question is how well the engine stands up to the extra power, how fast it may overheat (less of a problem in Finland or what maintenance procedures needed to be done/changed following such use.

 

[Elmas]

Here you can find some manuals of the Italian engines.
A registration is required.

AVIA - Associazione di Volontariato in Italia per l'Aviazione

 

[davebender]

Jumo 211 is an interesting idea though the Germans refused to sell any to Rumania

Italy is not Romania. They had much more diplomatic clout when dealing with WWII era Germany.

During 1939 to 1940 Germany was practically begging Italy to join the war against Britain and France. Delivery of 200 Jumo 211 engines per month could be part of the deal which gets Italy into the war.

 

[tomo pauk]

To clarify the 3800 vs. 4300m: the 'rated altitude' (Quota normale da funzionamente) was the one where engine was making the 'normal power at normal altitude' (ie. max continous, or 'Potenza normale a quota normale'), or, 3800m was the rated altitude, where 840 HP was being produced on 2400 rpm.
The regime titled as 'Volo orizontale a velocita maxima (per pochi minuti)' (~ 'Horizontal flight at maximum speed (for few minutes)') should increase the RPM to 2520 rpm, so those 840 HP could be attained at altitude 500m greater. Or at least that's how I gather it.
The data is from engine manual, not from aircraft manual - that should exclude ram? Our Italian members could chime in, my Italian if far from fluent

added: the manual for the G.50 notes that high speed for each km of altitude is to be attained with engine running at 2520 rpm, engine being "Fiat A 74 RC 38" - no suffix S at the name.

 

[GregP]

Hey Elmas,

My refernces have the AUT 18 at 300 mph! How can it be too slow? The Macchi (and Fiat for that matter) wasn't much faster and the AUT 18 could have been developed. Instead it faded away but looked pretty solid in prototype form.

 

[Denniss]

Romania got Jumo 211 engines for their upgraded SM.79 bomber (twin-engine version).

 

[davebender]

What's really strange is Junkers couldn't use Jumo 211 engines for their Ju-252 transport even though there was an obvious surplus of that engine type. Makes me wonder about the sanity of government officials managing German aircraft production.

 

[Elmas]

Hi Greg
Yes, you're right, I do not have in my hands Ing. Felice Trojani book, "La coda di Minosse", into wich he personally states a maximum speed of 489 km/h (303,4 mph). In the afternoon I will confirm.
But the Italian Air Ministry required a speed over 500 km/h, say over 310 mph, that MC 200 was able to attain.
And, while the MC 200 had an engine Fiat A.74 RC.38 840 CV (618 kW), the Aut 18 had the Fiat RC.41 18 cilinders 1000 CV (735,5 kW).
I will be more exaustive in the afternoon.
Bye

That it was solid (too much solid...) no doubt: the three different versions (only one built) of AUT 18:

From http://www.trojani.it/Historia/Felice/FeT_articoli_AUT 18.html

 

[GregP]

Bye and thank you for the reply. Seems that a little more speed could have been gotten from it with some attention to weight and streamlining ... but I have not even looked at the reality of it. Maybe not. If it missed by that little, it was within 3% of the design goal, which is pretty good, all things considered, for the time.

Should have been a player and AUT should have cleaned it up a bit to meet the spec, but it is possible they didn't even have the chance. The competition might have been a 1 time only flight ... I don't know.

Do you know why it wasn't considered or given a chance to get better? Most good planes had to go through at least 1 redesign to correct something, even if it was the paint scheme. Many times the propeller was at fault and nothing else. The AUT 18 had a 1,044 HP Fiat A.80 R.C. 41 engine. If the issue was power, it would only have needed another 108 HP to make 310 mph or the equivalent in drag reduction. That seems possible to me but I wasn't there and don't know why it was excluded.

 

[CobberKane]

Hey Greg - replied to your email via this forum, but not sure I did it right - did you get it?

Cobber

 

[tomo pauk]

The AUT 18 have had three things going against it.
One was the engine choice: the diameter of the Fiat A.80 was 1335 mm, vs. 1200 mm for the A.70. That would transpire in ~20% more profile area for the A.80. It was also heavier, 750 vs. 590 (dry weight), or some 27% heavier. The whole power plant weight, of course, goes up in such a fashion. So, much of the engine power surplus of the 18 cyl engine was used up just to overcome the increased drag and weight, compared with 'common' Italian fighter engine of the time. The empty weight was 2300+ kg, vs. the 1800-1900 for the competing fighters that had A.74 installed. The climb time to 6000 m was more than 8 minutes, compared to 6-7 vs. competition (Italian one; biplanes included, the CR.42 and Ca.165) - the AUT 18 was weighting 2975 kg loaded, vs. 2200 kg for the MC.202, or 2530 vs Re.2000.**
Another thing was the internal fuel weight: twice as much vs. the winning competitor, the MC.202 (230 kg vs. 470+ kg). Good for the range* (1000+ km on internal fuel only, or almost double than competition), bad for performance - and the Italian Air ministry wanted performance.
Third thing, at least as I see it, was the thick wing, much more reminiscent to, say, Hurricanes, than of MC.202. At the end of the day, it was some 30-40 km/h slower than Re.2000, and half of that vs. MC.202.

*makes for the good 'what if', doesn't it? Just install some better engines
**weights of competing prototypes

 

[Elmas]

Yes Greg, you're right. First it must be said that the Factory that built AUT 18 ( Aeronautica Umbra Trojani, 18 mq being the wing surface) was owned by the Macchi family, the same of MC 200.
The Designer wanted to redesign the airframe with a substantial reduction of the safety factor, that was excessive, as a private venture, but the owner of the Factory refused, probably because the factory, that was located not far from Rome, while the main Macchi Factory is not far from Milan, was heavily involved (and making a lot of money) just repairing airplanes damaged in Spain during the Civil War and producing MC 200 in quantities, by Italian standards, of course.
Even in this case, even if to a lesser extent than Breda 88, the structure was redundant, stressed skin plus metallic tubes. And also the wing profile seems very thick. I don't think that a substantial increase in power would have improved things: this aeroplane has a P47 like appearence, but P47 had a wing area of 29 square meters and AUT 18....18....

 

[tomo pauk]

This could be interesting for the members to read - the 1st generation of Italian monoplane fighters competition, with competitors' data. Can be translated.

Programma R

The table I was drawing my info from (translation by yours truly):

 

[GregP]

Looking at that chart, the MC.200, Re.2000, and Caproni-Vizzola F.5 seem to be good places, speed-wise, to start with wing loading being about a wash.

 

[Dogwalker]

Crediting the Macchi C.202 of a max speed of 596 km/h with a 1175 PS engine, a 960 PS Isotta Fraschini Asso XI engined Macchi 200, would have had a max speed of 580 km/h.
Reducing the ammo load to 250 rounds for gun (still enough for 26 sec. of fire), it can be armed with a third synchronized Breda SAFAT with only 30kg more weight, still in central position (virtually negligible in a three-ton heavy aircraft).
I think that the pilots would have liked both the increased performance and the greater volume of fire. But the plane would have been more expensive to produce.

Wanting to produce both an in-line and a radial engined fighter, in 1939 there were really no alternatives to the radials used in the "Serie 0" fighters. But, in november 1939, The Regia Aeronautica requested to Reggiane to design a DB601 engined Re.2000 prototype (of which the Alfa Romeo had just purchased the production license). It was the beginning of the development of the DB601 engined italian fighters.
Really, that of Alfa Romeo was a normal commercial transaction, and, during the war, the lack of production capacity of Alfa plants was a source of problems for the supply of their engines, especially for the Reggiane itself, since the Macchi C.202 was favoured in supplies.
In the same last weeks of 1939 however was homologated the 1500 PS Piaggio P.XII. It was larger and heavier than the P.XI, but the Reggiane 2000 fuselage was already large enough to accomodate it, the fighter had a low wingload, and the P.XII was a "cool" engine, on which were used the very enclosed, aerodynamically efficient, cowlings we see on Cant Z.1018 and Caproni Ca.169.
If the request of the air force had been different, then the Reggiane would have been able to begin first the production of Re.2000, go to a P.XII engined, and better armed, "Re.2001" as soon as possibile (probably at the end of 1940) and then to its further evolution, the 1700 PS Piaggio P.XV, around 1943. The Re.2001 was a good fighter-bomber. With a 1500 PS radial, probably it would have been better.

Speaking of twin engined fighters, Italy had a good base in the Imam Ro.57 in 1939. The late attempt to turn it into a dive bomber was unsuccessful, because in 1943 his performances were already obsolete, because of the many aerodynamic hindrances the conversion brought, and because the base was poorly suited for the purpose. But, with 1,200 km range, and more than 1700 ps of installed power (two Fiat A74), with an heavier armament, and a single ventral rack for a 500/600 kg bomb, or a torpedo, it could have been the ideal naval multirole fighter-bomber (in addition to maintaining a use for the radial engines produced by Fiat).

 

[GregP]

Hi Cobber,

Having an issue with email right now. Probably will work it out by Friday afternoon.

 

[tomo pauk]

Crediting the Macchi C.202 of a max speed of 596 km/h with a 1175 PS engine, a 960 PS Isotta Fraschini Asso XI engined Macchi 200, would have had a max speed of 580 km/h.
Reducing the ammo load to 250 rounds for gun (still enough for 26 sec. of fire), it can be armed with a third synchronized Breda SAFAT with only 30kg more weight, still in central position (virtually negligible in a three-ton heavy aircraft).
I think that the pilots would have liked both the increased performance and the greater volume of fire. But the plane would have been more expensive to produce.

Fine proposal. The production cost of the Asso-MC.200 should be probably under the cost of the MC.202?
BTW, the altitude where the Asso XI RC.40 was making just a tad more than 950 PS was 3500m, while the Alfa Romeo RA 1000 RC.41 was making 1050 PS at 4100m (or was it 1100 at 3700, like the DB-601Aa?)? At 4100m, the Asso gives 890 PS - so maybe not 580 km/h, but 550-560, ie. comparable to the Arsenal VG-33 and Avia-135?

Wanting to produce both an in-line and a radial engined fighter, in 1939 there were really no alternatives to the radials used in the "Serie 0" fighters. But, in november 1939, The Regia Aeronautica requested to Reggiane to design a DB601 engined Re.2000 prototype (of which the Alfa Romeo had just purchased the production license). It was the beginning of the development of the DB601 engined italian fighters.
Really, that of Alfa Romeo was a normal commercial transaction, and, during the war, the lack of production capacity of Alfa plants was a source of problems for the supply of their engines, especially for the Reggiane itself, since the Macchi C.202 was favoured in supplies.

The MC.202 was also 50km/h faster.

In the same last weeks of 1939 however was homologated the 1500 PS Piaggio P.XII. It was larger and heavier than the P.XI, but the Reggiane 2000 fuselage was already large enough to accomodate it, the fighter had a low wingload, and the P.XII was a "cool" engine, on which were used the very enclosed, aerodynamically efficient, cowlings we see on Cant Z.1018 and Caproni Ca.169.
If the request of the air force had been different, then the Reggiane would have been able to begin first the production of Re.2000, go to a P.XII engined, and better armed, "Re.2001" as soon as possibile (probably at the end of 1940) and then to its further evolution, the 1700 PS Piaggio P.XV, around 1943. The Re.2001 was a good fighter-bomber. With a 1500 PS radial, probably it would have been better.

+1 for the Re2000+P.XII, even if it was quite a bulky engine. 1400 PS was available at 4000m (~12900 ft).

Speaking of twin engined fighters, Italy had a good base in the Imam Ro.57 in 1939. The late attempt to turn it into a dive bomber was unsuccessful, because in 1943 his performances were already obsolete, because of the many aerodynamic hindrances the conversion brought, and because the base was poorly suited for the purpose. But, with 1,200 km range, and more than 1700 ps of installed power (two Fiat A74), with an heavier armament, and a single ventral rack for a 500/600 kg bomb, or a torpedo, it could have been the ideal naval multirole fighter-bomber (in addition to maintaining a use for the radial engines produced by Fiat).

Seems the Ro.57 was too many engines for too little speed punch?

 

[davebender]

Italy designed plenty of good airframes. The real issue is producing or purchasing 200+ world class aircraft engines per month.

 

[Dogwalker]

Fine proposal. The production cost of the Asso-MC.200 should be probably under the cost of the MC.202?

Dunno at what price the two producers sold their engines, but likely the Asso was cheaper, it was in production for more time, while the construction of the Ra 1000 required the installation of brand new tooling (as the previous Alfa Romeo in-line engines were smaller).

BTW, the altitude where the Asso XI RC.40 was making just a tad more than 950 PS was 3500m,

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.

Seems the Ro.57 was too many engines for too little speed punch?

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.