What would you say about the A.82? I have seen a proposal for the Fiat G.57, a G.55 with the Fiat A.82. Would that have been a possible engine for a fighter aircraft??
I assume the A.82 was derived from the A.80 and not the A.76?
Yes. But the G.57 remained a project that was never accepted by the Regia, that did not ordered even a prototype.
Actually I have to revise my previous statement, since the A .82 was actually used on a production aircraft (FIAT BR.20bis, only fifteen samples, but still a production aircraft). It was a powered-up A.80. However, with 1250ps, and the drag of a radial, it could not replace a DB.605 / Ra.1050 on a fighter. The FIAT CANSA Fc.20 instead would have drawn much benefit from it. Mysteries of the FIAT's choices.
That is very interesting, but you are very right. The P.XV was a 18 cyl, not a 14 cyl as I thought. But, I always thought the P.XV had an output of around 1,500 hp, equal to that of the P.XII. And wouldn't the P.XV still be too big for fighter aircraft?
Being essentially the same engine, the power advantage of the P.XV over the P.XII was not exceptional (similar to that of the P.XIX over the P.XI), but there was, and the rest was up to the two speed supercharger. The P.XV RC.25/60 was rated at 1650ps at takeoff and 1500ps at 6000m, while the P.XII RC.40 had 1500ps at takeoff and 1400ps at 4000m. The performance advantage in having 100ps more 2000m higher is evident.
The overall dimensions were the same of the the P.XII, and of the R.2600, which, for example, has been used on several single-engine aircrafts. It has never been used for a fighter, but the Australians wanted it for the Boomerang. Certainly, if you have the R.2800, and the gasoline to make it work, it is better to use it, but, if you do not have it, to make a good fighter with the P.XV is possible.
To give an idea, The P.XII and P.XV had the same diameter of a Bristol Centaurus. So, If a Sea Fury could do 740km/h with 2480hp, it could do 645km/h with a P.XV and 625km/h with a P.XII. Not bad for 1943 and 1941 respectively. This is higly unscientific, since I didn't take in account the power curve at height, nor the minor weight of the Piaggo engines, but is good for an orientation.
Your suspicion may well be justified. But I think the Germans must have been meticulous in their testing,
I think they were not. Furthermore the first few hundred Ra.1050 engines, as the first few hundred Ra.1000 engines, were made in assembling German parts in Italy. Only gradually, when the various parts of the engine entered in production, the Italian parts replaced the original ones. in February '43 even a prototype Ra.1050 could only widely be a German engine assembled in Italy, and even in the incredible case that the fighters tested had three Ra.1050 made assembling only the prototypes of pieces made in Italy:
1) the Germans had no way of knowing what their power was, as they did not test them at the bench, but on the aircrafts. As much as I value German testers, I do not think that they had the ability to know how powerful an engine is, only turning it on.
2) Even if the German testers had the ability to estimate the power of an engine just by looking at it, as you said, the measure would not make sense with engines made assembling prototype parts and, moreover, the test themselves would not have been consistent with the performances of standard production aircrafts.
However, I have read that there were some small differences. From the Italian wiki: "I DB 605C prodotti dalla FIAT avevano un rapporto di riduzione tra albero motore e elica diverso da quello di serie: 1:0,485 e non 1:0,593." If correct, why was this?
Those figures seems to indicate that the Italian engines could turn at even higher RPM than the german ones!
But really they had only to use different propellers. The Piaggio propellers had larger diameter than the VDM, so their optimum turn speed is slower.
And thanks DW, this is very interesting stuff !
Thanks to you.