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performance calculations for the Pratt & Whitney R-1690 Hornet aircraft engine

P&W Hornet (R-1690)

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

New England Air Museum

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