RAF 4a

AIRCRAFT INVESTIGATION

RAF 4a

RAF 4a on display at the Koninklijk Museum van het Leger en de Krijgsgeschiedenis in Brussel (c) B van der Zalm

air-cooled 12 -cylinder V-engine 163 [hp](119.9 KW)

introduction : 1916 country : United Kingdom importance : ****

applications : RAF R.E.8

normal rating : 163 [hp](119.9 KW) at 1800 [rpm] at 0 [m] above sea level

reduction : 0.5 , valvetrain :

weight engine(s) dry : 312.8 [kg] = 2.57 [kg/KW]

bore : 100.0 [mm] stroke : 140.0 [mm]

Mechanical efficiency/mean pressure correction factor : 0.591 [ ]

invloed hoogte > cm : 0.68 [ ]

compression ratio: 4.30 :1

calculated compression ratio : 4.30 : 1

published volume (displacement): 13.200 [litre]

calculated stroke volume (Vs) : 13.195 [litre]

compression volume (Vc): 3.998 [litre]

total volume (Vt): 17.193 [litre]

power / stroke volume (litervermogen Nl): 9.1 [kW/litre]

torque : 636 [Nm]

engine weight/volume : 23.3 : [kg/litre]

average piston speed (Cm): 8.4 [m/s]

***************************************************************************

intake pressure at 0 [m] altitude Pi : 0.95 [kg/cm2]

mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 5.00 [kg/cm2]

compression pressure at 0 [m] altitude Pc: 6.17 [kg/cm2]

estimated combustion pressure at 0 [m] Pe : 24.70 [kg/cm2]

exhaust pressure at 0 [m] Pu : 3.80 [kg/cm^2 ]

**************************************************************************

compression-end temperature at 0 [m] Tc: 572 [°K] (299 [°C])

caloric combustion temperature at 0 [m] Tec: 2137 [°K] (1864 [°C])

polytroph combustion temperature at 0 [m] Te (T4): 2283 [°K] (2009 [°C])

exhaust temperature at 0 [m] Tu: 1370 [°K] (1097 [°C])

*********************************************************************************

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

(emergency/take off) rating at 1971 [rpm] at sea level : 178 [pk]

See the source image

Thermal efficiency Nth : 0.306 [ ]

Mechanical efficiency Nm : 0.765 [ ]

Thermo-dynamic efficiency Ntd : 0.234 [ ]

design hours : 1436 time between overhaul : 105

fuel consumption optimum mixture at 1800.00 [rpm] at 0 [m]: 55.36 [kg/hr]

specific fuel consumption thermo-dynamic : 270 [gr/epk] = 368 [gr/kwh]

specific fuel consumption (cruise power) at 0 [m] optimum mixture : 390 [gr/kwh]

estimated sfc (cruise power) at 2058 [m] rich mixture : 421 [gr/kwh]

specific fuel consumption at 0 [m] at 1800 [rpm] optimum mixture : 462 [gr/kwh]

estimated specific oil consumption (cruise power) : 21 [gr/kwh]

Literature :

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