The Hispano-Suiza 12N was one of two new V-12 engine designs first run in 1928 and was manufactured by Hispano-Suiza's French subsidiary for the Armee d'l'Air. It produced about, was the first to use gas nitride hardening and introduced wet cylinder liners into Hispano-Suiza's aircraft engine range. It powered the first non-stop flight from Europe to the United States.
Design and development
Up to 1927, Hispano-Suiza's many engine types, of various layouts and cylinder numbers, were all recognisable developments of the World War I V-8Hispano-Suiza 8. 1927-8 saw the introduction of four completely new engines, two V-12s and two with six cylindersinline. The Hispano-Suiza 12N, known by the manufacturers as the Type 61, was the larger of the V-12s, with a displacement of, the other being the 12M. Apart from capacity and power, these two engines had much in common. The 12M first ran in 1927 and the 12N a year later. Both 12M and 12N were 60° V engines with carburettors, inlets and exhausts on the outer faces. There were three carburettors per bank, each charging a pair of cylinders. Much of the new technology was in the cylinder design: these types introduced wet liners, an Hispano automobile engine innovation which brought the cooling water into direct contact with the steel cylinder barrel rather than by screwing it into an aluminium water jacket. This improved cooling, simplified assembly and allowed larger cylinder bores without increasing their separation. The cylinder barrels were open at top and bottom and threaded for screwing into the block only near the top, with valve seats ground into the aluminium cylinder head. The lower end of the barrel extended into the crankcase, simplifying both manufacture and assembly. Block and crankcase were bolted together. The 12M and 12N engines were the first to use the gas nitriding surface hardening process on the cylinder walls, which reduced both wear and oil consumption. They also used a novel, complicated but effective method of main bearing cooling, enhancing the local lubricant flow without requiring high overall oil pump speeds. Both types were designed so that Epicyclic gearing could be added or removed quickly; some earlier Hispano-Suiza engines offered gearing but as a permanent fixture on a specific sub-type. The gears added to the weight. In 1935 the 12Ner variant was fitted with an in-flight- electrically operated variable pitch propeller. The 12N series was developed into the 12Y supercharged engine, first run in 1932.
Operational history
A Hispano-Suiza 12Nb powered the Breguet XIX Point d'Interrogation on the first non-stop flight from Paris to New York in September 1930. This was the first east to west flight between Europe and the United States, rather than to the North American continent. In the early 1930s, 12N engines powered the flying boats operating the French Atlantic and African routes. The Swiss government, in the form of the KTA purchased construction licences for the 12Nb and in 1932 eighty units were built at the Saurer lorry factory.
Variants
Data from Hispano Suiza in Aeronautics. ;12Nb/650: Compression ratio 6.2, maximum power at 2,100 rpm. ;12Nbr/650: Compression ratio 6.2, maximum power at 2,100 rpm. Gearing ratio of 2:1 or 1.61:1. ;12Ns: Compression ratio 7, nominal power at 2,200 rpm. For Schneider Cup 1928. ;12Nsr: Compression ratio 10, nominal power at 2,400 rpm. For Schneider Cup 1931. Farman compressor. ;12Nc: Compression ratio 6.2, nominal power at 2,000 rpm. For Ford 14A Trimotor. ;12Ncr: ;12Ndr: Electrically controlled pitch propeller, anti-clockwise turning. ;12Ner: As 12Ndr, modified with articulated connecting rods. ;12Nfr: As Ndr, clockwise turning. ;12Ngr: As Ner, clockwise turning.
