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performance calculations for the Pratt & Whitney R-1690 Hornet aircraft engine
Pratt & Whitney R-1690 Hornet air-cooled 9 -cylinder radial engine 525 [hp]
(391.5 KW)
German engine rating : 532.3 [PS]
introduction : June 1926 country : United States importance : ***
applications : Junkers G.31 number built : 2944
normal rating : 525 [hp] (391.5 KW) at 1900 [rpm] at 0 [m] above sea level
no reduction, direct drive, valvetrain : pushrod-actuated
fuel system : two-barrel Stromberg carburettor oil system :
starting system : electric motor
weight engine(s) dry : 362.0 [kg] = 0.92 [kg/KW]
bore : 155.6 [mm] stroke : 161.9 [mm]
valve inlet area : 37.0 [cm^2] one inlet and one exhaust valve in cylinder head
gasspeed at inlet valve : 37.1 [m/s]
throttle : 93 /100 open, mixture :13.0 :1
compression ratio: 6.00 :1
high compression engine cannot run with full power/throttle at sea-level (only for short period)
stroke volume (Vs) : 27.700 [litre]
compression volume (Vc): 5.542 [litre]
total volume (Vt): 33.242 [litre]
diam. engine : 138.2 [cm]
engine length: 129.5 [cm]
specific power : 14.1 [kW/litre]
R-1690 Hornet engine on display at the Deutsches museum in Munich
torque : 1968 [Nm]
engine weight/volume : 13.1 : [kg/litre]
average piston speed (Cm): 10.3 [m/s]
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intake pressure at 0 [m] altitude Pi : 0.89 [kg/cm2]
mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 7.38 [kg/cm2]
compression pressure at 0 [m] altitude Pc: 8.36 [kg/cm2]
estimated combustion pressure at 0 [m] Pe : 33.38 [kg/cm2]
exhaust pressure at 0 [m] Pu : 3.49 [kg/cm^2 ]
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compression-start temperature at 0 [m] Tic: 358 [°K] (85 [°C])
compression-end temperature at 0 [m] Tc: 547 [°K] (274 [°C])
average engine wall temperature at 0 [m] : 476 [K] (202 [°C])
caloric combustion temperature at 0 [m] Tec: 2221 [°K] (1948 [°C])
polytroph combustion temperature at 0 [m] Tep : 2184 [°K] (1911 [°C])
estimated combustion temperature at 0 [m] Te (T4): 2167 [°K] (1894 [°C])
polytrope expansion-end temperature at 0 [m] Tup: 1155 [°K] (881 [°C])
exhaust stroke end temperature at 0 [m] Tu: 1089 [°K] (816 [°C])
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calculations for take-off/emergency power at sea level
intake pressure at sea level Pi : 0.88 [kg/cm2]
compression-end temperature at sea level max rpm Tc:559 [°K] (286 [°C])
polytrope combustion temperature at sea level Tec: 2232 [°K] (1959 [°C])
caloric combustion temperature at sea level Tec: 2192 [°K] (1919 [°C])
emergency/take off rating at 2023 [rpm] at sea level : 553 [hp]
Thermal efficiency Nth : 0.361 [ ]
Mechanical efficiency Nm : 0.779 [ ]
Thermo-dynamic efficiency Ntd : 0.281 [ ]
design hours : 1246 [hr] time between overhaul : 35 [hr]
dispersed engine heat by cooling air : 5477.70 [Kcal/minute/m2]
required cooling surface : 20.84 [m2]
weight cooling ribs : 230.11 [kg]
fuel consumption optimum mixture at 1900.00 [rpm] at 0 [m]: 110.12 [kg/hr]
specific fuel consumption thermo-dynamic : 214 [gr/epk] = 286 [gr/kwh]
published specific fuel consumption (cruise power) at 0 [m] : 362 [gr/kwh]
estimated sfc (cruise power) at 2200 [m] rich mixture : 366 [gr/kwh]
specific fuel consumption at 0 [m] at 1900 [rpm] with mixture :13.0 :1 : 281 [gr/kwh]
estimated specific oil consumption (cruise power) : 16 [gr/kwh]
time between engine failure : 173 [hr]
Literature :
Handbook of aeronautics volume II aero-engines page 9
Pratt & Whitney R-1690 Hornet - Wikipedia
Pratt & Whitney Hornet (aviation-history.com)
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 10 May 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4