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weight and performance calculations for the Northrop Alpha 2
Northrop Alpha 2
role : medium weight passenger aircraft
importance : **
first flight : operational : April 1931
country : United States of America
design : John K. Northrop
production : 17 aircraft at Burbank, California
General information :
Airfoil : Clark Y (18% at root, 12% at tip) Useful load (fuel & payload) : 868 kg
Landing speed : 96.5 km/hr climb at sea level : 427 m/min, time to 3048m : 10.5 min
Absolute ceiling : 6431m take-off ground roll : 163m landing ground roll : 145m
Fuel capacity : 116 gallon = 439 litre oil : 13 gallon = 49.2 litre
Blower ratio 10:1
users : TWA
crew : 1 passengers : 6
engine : 1 Pratt & Whitney R-1340-SC1 Wasp air-cooled 9 -cylinder radial engine 450
[hp] (335.6 KW) supercharged engine, constant power to height : 1828 [m]
dimensions :
wingspan : 12.8 [m], length : 8.7 [m], height : 2.7[m]
wing area : 27.4 [m^2]
weights :
max.take-off weight : 2045 [kg]
empty weight operational : 1177 [kg] useful load : 600 [kg]
performance :
maximum speed :285 [km/u] op 1800 [m]
cruise speed :256 [km/u] op 1800 [m]
service ceiling : 5885 [m]
range : 939 [km]
description :
low-winged monoplane with fixed landing gear with tail wheel
tapered wing
engine in the nose, fuel tanks in the wing, landing gear attached to the wing
construction : all-metal (duraluminium) airplane
airscrew :
ground adjustable 2 -bladed metal Hamilton Standard tractor propeller with max.
efficiency :0.72 [ ]
estimated diameter airscrew 2.64 [m]
power loading prop : 127.11 [KW/m]
prop efficiency ratio: 11.99 [1/s]
angle of attack prop : 19.56 [ ]
reduction : 1.00 [ ]
airscrew revs : 2150 [r.p.m.]
pitch at Max speed 2.21 [m]
blade-tip speed at Vmax and max revs. : 308 [m/s]
calculation : *1* (dimensions)
measured wing chord : 2.13 [m] at 50% wingspan
mean wing chord : 2.14 [m]
wing aspect ratio : 5.98 []
seize (span*length*height) : 301 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 6.0 [kg/hr]
fuel consumption(cruise speed) : 77.4 [kg/hr] (105.6 [litre/hr]) at 75 [%] power
distance flown for 1 kg fuel : 3.31 [km/kg] at 2942 [m] height, sfc : 307.2 [kg/kwh]
estimated total fuel capacity : 439 [litre] (322 [kg])
calculation : *3* (weight)
weight engine(s) dry : 324.0 [kg] = 0.97 [kg/KW]
weight 37.9 litre oil tank : 3.23 [kg]
oil tank filled with 2.5 litre oil : 2.3 [kg]
oil in engine 1.9 litre oil : 1.7 [kg]
fuel in engine 2.3 litre fuel : 1.68 [kg]
weight 44.9 litre gravity patrol tank(s) : 6.7 [kg]
weight gas starter : 8.2 [kg]
weight cowling (Townend ring) 13.4 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 26.4 [kg]
total weight propulsion system : 384 [kg](18.8 [%])
***************************************************************
fuselage aluminium frame : 119 [kg]
cabin layout : pitch : 87 [cm] (1+1) seating in 3.0 rows
weight 1 fire extinguisher : 3 [kg]
weight 6.0 windows : 5.40 [kg]
passenger cabin width : 1.23 [m] cabin length : 2.61 [m] cabin height : 1.80 [m]
weight cabin furbishing : 11.71 [kg]
weight cabin floor : 20.61 [kg]
fuselage covering ( 14.3 [m2] duraluminium0.70 [mm]) : 25.2 [kg]
weight radio navigation equipment : 6.0 [kg]
weight instruments. : 5.0 [kg]
weight lighting : 1.5 [kg]
weight controls : 5.0 [kg]
weight seats : 35.0 [kg]
weight air conditioning : 9 [kg]
weight engine mounts & firewalls : 17 [kg]
total weight fuselage : 250 [kg](12.2 [%])
***************************************************************
total weight aluminium ribs (49 ribs) : 73 [kg]
weight fuel tanks empty for total 394 [litre] fuel : 32 [kg]
weight wing covering (painted aluminium 0.96 [mm]) : 142 [kg]
load on front upper spar (clmax) per running metre : 1553.6 [N]
load on rear upper spar (vmax) per running metre : 484.3 [N]
total weight 4 aluminium spars : 90 [kg]
weight wings : 305 [kg]
weight wing/square meter : 11.12 [kg]
cantilever wing without bracing cables
weight rubber de-icing boots : 14.1 [kg]
weight fin & rudder (1.9 [m2]) : 21.4 [kg]
weight stabilizer & elevator (3.1 [m2]): 34.5 [kg]
total weight wing surfaces & bracing : 406 [kg] (19.9 [%])
*******************************************************************
wheel pressure : 1022.5 [kg]
weight 2 wheels (790 [mm] by 156 [mm]) : 42.3 [kg]
weight tailwheel(s) : 5.9 [kg]
weight undercarriage with axle 67.9 [kg]
total weight landing gear : 116.1 [kg] (5.7 [%]
*******************************************************************
********************************************************************
calculated empty weight : 1157 [kg](56.6 [%])
weight oil for 4.4 hours flying : 26.5 [kg]
calculated operational weight empty : 1184 [kg] (57.9 [%])
published operational weight empty : 1177 [kg] (57.6 [%])
___o___
"
weight crew : 81 [kg]
weight fuel for 2.0 hours flying : 155 [kg]
********************************************************************
operational weight empty: 1420 [kg](69.4 [%])
weight 6 passengers : 462 [kg]
weight luggage & freight : 138 [kg]
operational weight loaded: 2020 [kg](98.8 [%])
fuel reserve : 25.5 [kg] enough for 0.33 [hours] flying
operational weight fully loaded : 2045 [kg] with fuel tank filled for 56 [%]
published maximum take-off weight : 2045 [kg] (100.0 [%])
calculation : * 4 * (engine power)
power loading (Take-off) : 6.09 [kg/kW]
power loading (operational without useful load) : 4.23 [kg/kW]
total power : 335.6 [kW] at 2150 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 6.3 [g] at 1000 [m]
limit load : 3.0 [g] ultimate load : 4.5 [g] load factor : 2.4 [g]
design flight time : 2.93 [hours]
design cycles : 7374 sorties, design hours : 21595 [hours]
operational wing loading : 508 [N/m^2]
wing stress (3 g) during operation : 137 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.90 ["]
max. angle of attack (stalling angle) : 14.41 ["]
angle of attack at max. speed : 0.10 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.15 [ ]
lift coefficient at max. angle of attack : 1.29 [ ]
lift coefficient at max. speed : 0.16 [ ]
induced drag coefficient at max. speed : 0.0018 [ ]
drag coefficient at max. speed : 0.0344 [ ]
drag coefficient (zero lift) : 0.0327 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 1968 [kg]): 108 [km/u]
landing speed at sea-level: 126 [km/hr]
min. drag speed (max endurance) : 172 [km/hr] at 2942 [m](power :37 [%])
min. power speed (max range) : 172 [km/hr] at 2942 [m] (power:37 [%])
max. rate of climb speed : 162.9 [km/hr] at sea-level
cruising speed : 256 [km/hr] at 2942 [m] (power:76 [%])
design speed prop : 271 [km/hr]
maximum speed : 285 [km/hr] at 1800 [m] (power:105 [%])
climbing speed at sea-level (loaded) : 349 [m/min]
calculation : *9* (regarding various performances)
take-off speed : 131.6 [km/u]
static prop wash : 152 [km/u]
start time : 10 [s]
take-off distance at sea-level : 198 [m]
lift/drag ratio : 10.38 [ ]
climb to 1000m with max payload : 2.90 [min]
climb to 2000m with max payload : 5.83 [min]
climb to 3000m with max payload : 9.31 [min]
practical ceiling (operational weight 1420 [kg] ) : 7293 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:2006 [kg] ) : 5883 [m]
calculation *10* (action radius & endurance)
published range : 939 [km] with 1 crew and 496.9 [kg] useful load and 88.1 [%] fuel
range : 597 [km] with 1 crew and 600.0 [kg] useful load and 56.1 [%] fuel
range : 856 [km] with 6.0 passengers with each 10 [kg] luggage and 80.3 [%] fuel
Available Seat Kilometres (ASK) : 5136 [paskm]
max range theoretically with additional fuel tanks total 1064.5 [litre] fuel : 2586 [km]
useful load with range 500km : 629 [kg]
useful load with range 500km : 6 passengers
production (useful load): 161.45 [tonkm/hour]
production (passengers): 1539.00 [paskm/hour]
oil and fuel consumption per tonkm : 0.52 [kg]
fuel cost per paskm : 0.05 [eur]
crew cost per paskm : 0.09 [eur]
economic hours : 12775 [hours] is less then design hours
time between engine failure : 170 [hr]
writing off per paskm : 0.05 [eur]
insurance per paskm : 0.05 [eur]
maintenance cost per paskm : 0.22 [eur]
direct operating cost per paskm : 0.46 [eur]
direct operating cost per tonkm : 4.64 [eur]
Literature :
Piston-engined airliners page
Northrop Alpha - Holcomb's Aerodrome (airminded.net)
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/
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(c) B van der Zalm 18 September 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4