Thanks Brian ... I don't seem to be able to resist those under-the-hood-gubbins
'Ragazzo di Corso' - The Fiat V-16-Powered Macchi 'C.204/A.38' ProjectBy the summer of 1939,
ing. Mario Castoldi was considering a planned Fiat V-16 engine as a potential powerplant for the Macchi C.204. In its original iteration, this Fiat A.38 engine was an upright V-16 related to the 1939 Fiat AS.8 racing engine. To produce the A.38, Fiat's
ing. Tranquillo Zerbi had simplified his AS.8 racing engine. Compared with the AS.8, the A.38 had a revised bore and stroke [1] as well as a much lower compression ratio.
The adaptation of the Macchi airframe was not a simple one due to the length of the Fiat engine. However, such an installation appeared achievable with some re-arrangement of internal equipment. Although long, the new Fiat A.38 engine was compact in height and width compared with the existing Isotta-Fraschini
Asso L.121 V-12 which was also being considered for the Macchi C.204.
The so-called 'C.204/A.38' first appeared in early May 1939 Aer.Macchi drawings. These revealed considerable deviations from the contemporary 'C.204/L.121' concept. Whereas the latter was essentially a C.202 airframe with different engine mounts and cowling for the
Asso L.121 engine, the longer Fiat V-16 required the firewall to be moved aft. This was feasible because the compact frontal area of the A.38 allowed this engine to sit atop the undercarriage wheel bays and wing structure. Castoldi believed that, with the engine set as far back as possible, manoeuvrability would be as good as - if not better than - the C.202
Folgore.
Despite the aft-positioned engine, it quickly became apparent that nose-heaviness was going to be an issue. For '
Fase di progettazione Ia' ('Design Phase Ia'), notional work was begun on redressing that nascent imbalance. An obvious start was moving the convenient but drag-inducing under-engine radiator bath aft to below the rear fuselage. A more radical possibility was to lengthen the rear fuselage itself. If necessary, it was considered reasonable to enact both changes. Some design work was also begun on armament options - since cowl-guns were not practical in the 'C.204/A.38' design.
Unfortunately, the 'C.204/A.38' never had a chance to prove its mettle. By July 1939, Fiat Motori [2] had abandoned the complex and weighty reduction gearbox for contra-rotating propellers. The A.38 R.C.42 would, instead, drive a 3-bladed variable-pitch propeller. This raised concerns as to whether the C.204 airframe's tail was large enough to deal with 'propeller torque'. That was a moot point. Before design work could be completed on the 'C.204/A.38 FdP Ia', Fiat Motori advised the Varese design office that work was being discontinued on the upright A.38 engine. In the absence of a viable Fiat rival, the 'C.204/L.121' was the model which would see production and active service with the Regia Aeronautica.
(To be continued ...)
_______________________________
[1] The AS.8 racing engine had a 'square' bore and stroke of 140 x 140mm. Bore and stroke dimensions for the A.38 fighter engine was 138 x 145 mm.
[2] In its full form, S.A. Fiat Motori d'Aviazione. Fiat Motori had facilities at Torino and Firenze.