AIRCRAFT INVESTIGATION

performance calculations for the SPA 6A WWI aero engine

SPA 6a aero engine at display at the Gianni Caproni museum of aeronautics. The dry weight on this picture is indicated as 240 kgs.

SPA 6A liquid-cooled 6 -cylinder inline engine 220 [hp](161.8 KW)

introduction : January 1918 country : Italy importance : ***

applications : Ansaldo S.V.A.5, Ansaldo S.V.A.9

general information:

Settled in Turin in 1906 by Michele Ansaldi and Matteo Ceirano, Spa (Società Piemontese Automobili) was one of major companies producing cars, industrial vehicles and air engines. During the first world war Spa manufactured the 6A engine, designed by Matteo Ceirano, based on requirements made by the Technical Direction of Air Forces. The 6A model was mainly long-lasting in all three designed versions and was serially manufactured not only by SPA, but also by Ansaldo, Talamona and Industrie Meccaniche Ferroviarie of Arezzo. The marriage between SPA engines and Sva-Ansaldo aircrafts of series 4 (scouts), 5 (scouts), 9 (school planes) e 10 (scouts-bombers) was protagonist of several and memorable war operations: in one of the these crafts Gabriele D'Annunzio on 9th August 1918 made a demonstrative raid over Vienna.

normal rating : 220 [hp](161.8 KW) at 1600 [rpm] at 500 [m] above sea level

high compression engine : cannot run at full power at sea level,

constant power to height : 500 [m]

no reduction, direct drive, valvetrain : SOHC, two valves per cylinder

fuel system : Twin Zenith carburettors

weight engine(s) dry : 240.0 [kg] = 1.48 [kg/KW]

bore : 135.0 [mm] stroke : 170.0 [mm]

Mechanical efficiency/mean pressure correction factor : 0.583 [ ]

invloed hoogte > cm : 0.30 [ ]

compression ratio: 5.46 :1

calculated compression ratio : 5.46 : 1

high compression engine cannot run with full power/throttle at sea-level (only for short period)

published volume (displacement): 14.600 [litre]

calculated stroke volume (Vs) : 14.600 [litre]

compression volume (Vc): 3.274 [litre]

total volume (Vt): 17.874 [litre]

power / stroke volume (litervermogen Nl): 11.1 [kW/litre]

torque : 966 [Nm]

engine weight/volume : 16.4 : [kg/litre]

average piston speed (Cm): 9.1 [m/s]

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intake pressure at 500 [m] altitude Pi : 0.90 [kg/cm2]

mean engine pressure (M.E.P.) at 500 [m] altitude Pm : 6.38 [kg/cm2]

compression pressure at 500 [m] altitude Pc: 7.90 [kg/cm2]

estimated combustion pressure at 500 [m] Pe : 31.61 [kg/cm2]

exhaust pressure at 500 [m] Pu : 3.58 [kg/cm^2 ]

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compression-end temperature at 500 [m] Tc: 595 [°K] (322 [°C])

caloric combustion temperature at 500 [m] Tec: 2265 [°K] (1992 [°C])

polytroph combustion temperature at 500 [m] Te (T4): 2374 [°K] (2101 [°C])

exhaust temperature at 500 [m] Tu: 1299 [°K] (1026 [°C])

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compression pressure at sea level Pc: 8.21 [kg/cm2]

estimated combustion pressure at sea level Pe : 32.83 [kg/cm^2 ]

compression-end temperature at sea level Tc:597 [°K] (324 [°C])

mean engine pressure at sea level Pm : 6.63 [kg/cm2]

emergency/TO rating can be increased with higher [rpm}

(emergency/take off) rating at 1752 [rpm] at sea level : 250 [pk]

Thermal efficiency Nth : 0.346 [ ]

Mechanical efficiency Nm : 0.824 [ ]

Thermo-dynamic efficiency Ntd : 0.285 [ ]

design hours : 612 time between overhaul : 44

fuel consumption optimum mixture at 1600.00 [rpm] at 500 [m]: 51.69 [kg/hr]

specific fuel consumption thermo-dynamic : 222 [gr/epk] = 302 [gr/kwh]

specific fuel consumption (cruise power) at 500 [m] optimum mixture : 316 [gr/kwh]

estimated sfc (cruise power) at 2500 [m] rich mixture : 330 [gr/kwh]

specific fuel consumption at 500 [m] at 1600 [rpm] optimum mixture : 319 [gr/kwh]

estimated specific oil consumption (cruise power) : 28 [gr/kwh]

Literature :

Wikipedia

DISCLAIMER Above calculations are based on published data, they must be

regarded as indication not as facts.

Calculated performance and weight may not correspond with actual weights

and performances and are assumptions for which no responsibility can be taken.

Calculations are as accurate as possible, they can be fine-tuned when more data

is available, you are welcome to give suggestions and additional information

so we can improve our program. For copyright on drawings/photographs/

content please mail to below mail address

(c) B van der Zalm 23 November 2019 contact : info.aircraftinvestigation@gmail.com python 3.7.4