Hispano-Suiza 12Z

The 12Z was the final evolution of the series of Hispano-Suiza V-12 aircraft engines, which had just entered production when France fell to the Germans during World War II. A small number were produced during the war but the German occupation government would not allow full-scale production to start. After the war small numbers were built to equip new designs, but the rapid introduction of the jet engine ended further development.

The 12Z differed from the earlier 12Y primarily in the use of four valves per cylinder operated by dual overhead cams. This gave the cylinders considerably better volumetric efficiency and faster operation, raising the RPM from 2,400 to 2,700. The engine was also designed to run only on 100 octane fuel (instead of 87, which was common at that point) which allowed the compression ratio to rise from the 12Y's 5.8:1 to the 12Z's 6.75:1. These changes raised the power from 1,000 to 1,300 hp (750 to 970 kW) at sea level. Unfortunately the engine continued to use a single-stage, single-speed supercharger and therefore lacked the all-altitude performance of German and British designs. But tuning the supercharger for a different critical altitude improved high-altitude performance considerably, delivering 1,500 hp (1,120 kW) at 21,000 ft (6,400 m) as opposed to 930 hp (690 kW) at 2,950 ft (900 m) for the 12Y.

Small prototype runs started in 1939, and were fitted to the French Armée de l'Air's front-line fighter aircraft, the M.S.410 and D.520, creating the M.S.450 and D.524 respectively. Production of the main model, the 12Z-17, was just starting at the time of the armistice. Production was undertaken in Hispano-Suiza's Spanish factories, but these engines had many problems and were never used in any numbers.

After the war a new version tuned to operate with 92 octane fuel, as opposed to the -17's 100/130, was built in limited numbers as the 12Z-89. Compression ratio was raised slightly to 7:1, but with the lower grade fuel the power dropped slightly to 1,280 hp (950 kW) at 2,600 rpm (1,479 hp (1,100 kW) maximum take-off). These engines apparently had the same sorts of reliability issues as the earlier -17's made in Spain, and the type never entered production.

pecifications (12Z-17)

pistonspecs

type=12-cylinder supercharged liquid-cooled 60° Vee piston engine
bore=150 mm (5.9 in)
stroke=170 mm (6.7 in)
displacement=36 L (2,197 in³)
length=
diameter=

width=
height=
weight=690 kg (1,520 lb)
valvetrain=Two intake and two sodium-cooled exhaust valves per cylinder actuated by dual overhead camshafts
supercharger=Gear-driven single-stage single-speed centrifugal type supercharger
turbocharger=
fuelsystem=
fueltype=100/130-octane rating gasoline
oilsystem=
coolingsystem=Liquid-cooled
power=
*970 kW (1,300 hp) at 2,650 rpm for takeoff
*1,120 kW (1,500 hp) at 2,700 rpm at 6,400 m (21,000 ft)
specpower=31.1 kW/L (0.68 hp/in³)
compression=6.75:1
fuelcon=
specfuelcon=0.29 kg/(kW·h) (0.48 lb/(hp·h)) at cruise
oilcon=
power/weight=1.62 kW/kg (0.99 hp/lb)

Applications

* Ikarus S-49C
* Hispano Aviacion Ha 1112

ee also

*List of aircraft engines