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weight and performance calculations for the Lockheed model 14 Super Electra
Lockheed model 14 Super Electra
importance : ****
first flight : 29 July 1937 piloted by Marshall Headle operational : October 1937
country : United States of America
design : Don Palmer
production : 114 aircraft built by Lockheed, 119 built under license in Japan by
Tachikawa and 121 by Kawasaki.
general information :
Scaled-up version of the Model 10, intended to compete with the Boeing 247D and
Douglas DC-2. It had lower seat-mile cost and higher cruise speed. Fuel capacity :
2440 litre. From the Model 14 the Lockheed Hudson maritime patrol aircraft was
developed, which was much used in WWII.
users : Northwest Airlines, KLM, Aer Lingus, British Airways, LOT
registrations : PH-APE “Ekster”, PH-ASL “Lepelaar”, PK-AFQ, PJ-AIT
crew : 2 passengers : 12
power plant : 2 Wright SGR-1820-F62 Cyclone air-cooled 9 -cylinder radial engine 900
[hp] (671.1 KW) normal rating, supercharged engine, low blower, constant power to
height : 2134 [m] and with 1000 [hp] (745.7 KW) available for take-off
dimensions :
wingspan : 19.96 [m], length : 13.51 [m], height : 3.48 [m]
wing area : 51.19 [m^2]
weights :
max.take-off weight : 7099 [kg]
empty weight operational : 4876 [kg] useful load : 1200 [kg]
performance :
maximum speed :400 [km/u] op 1800 [m]
cruise speed :380 [km/u] op 1800 [m]
service ceiling : 7500 [m]
range : 2027 [km]
description :
low-winged monoplane with retractable landing gear with tail wheel
tapered wing with split flap airfoil : Clark Y
engines and landing gear attached to the wings, fuel tanks in the wings
double fin tail plane
construction : all-metal stressed-skin (duraluminium) airplane
airscrew :
two Hamilton Standard constant speed 3 -bladed tractor airscrews with max. efficiency
:0.74 [ ]
estimated diameter airscrew 3.03 [m]
power loading prop : 147.66 [KW/m]
angle of attack prop at max. speed : 33.01 [ ]
reduction : 0.62 [ ]
airscrew revs : 1438 [r.p.m.]
pitch at Max speed 4.52 [m]
blade-tip speed at max.continous speed : 252 [m/s]
calculation : *1* (dimensions)
measured wing chord : 2.71 [m] at 50% wingspan
mean wing chord : 2.56 [m]
calculated average wing chord tapered wing with rounded tips: 2.49 [m]
wing aspect ratio : 7.78 []
seize (span*length*height) : 938 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 18.8 [kg/hr]
fuel consumption(cruise speed) : 295.4 [kg/hr] (403.0 [litre/hr]) at 71 [%] power
distance flown for 1 kg fuel : 1.29 [km/kg] at 3750 [m] height, sfc : 308.2 [kg/kwh]
estimated total fuel capacity : 2440 [litre] (1788 [kg])
calculation : *3* (weight)
weight engine(s) dry with reduction gear : 1060.0 [kg] = 0.79 [kg/KW]
weight 167.5 litre oil tank : 14.24 [kg]
oil tank filled with 10.1 litre oil : 9.0 [kg]
oil in engine 7.5 litre oil : 6.7 [kg]
fuel in engine 9.2 litre fuel : 6.71 [kg]
weight 171.3 litre gravity patrol tank(s) : 25.7 [kg]
weight starter (E.H.I. - Electric Hand Inertia): 16.4 [kg]
weight NACA cowling 30.1 [kg]
weight variable pitch control : 11.5 [kg]
weight airscrew(s) incl. boss & bolts : 149.8 [kg]
total weight propulsion system : 1319 [kg](18.6 [%])
***************************************************************
fuselage aluminium frame : 677 [kg]
cabin layout : pitch : 87 [cm] (1+1) seating in 6.0 rows
weight toilet : 8 [kg]
weight 2 fire extinguisher : 6 [kg]
weight 12 windows : 10.8 [kg]
weight door : 5.0 [kg]
passenger cabin width : 1.51 [m] cabin length : 6.30 [m] cabin height : 1.90 [m]
weight cabin furbishing : 37.1 [kg]
weight cabin floor : 55.7 [kg]
fuselage covering ( 51.9 [m2] duraluminium 3.22 [mm]) : 433.8 [kg]
fuselage (sound proof) isolation : 15.0 [kg]
weight radio transceiver equipment : 7.0 [kg]
weight Sperry gyro auto-pilot - course control equipment : 1.5 [kg]
weight instruments. : 6.0 [kg]
weight lighting : 3.0 [kg]
weight electricity generator : 6.5 [kg]
weight dual controls + indicators: 21.6 [kg]
weight seats : 70.0 [kg]
weight air conditioning : 18 [kg]
total weight fuselage : 1359 [kg](19.1 [%])
***************************************************************
total weight aluminium ribs (141 ribs) : 253 [kg]
weight engine mounts : 67 [kg]
weight two 1134 [litre] main fuel tanks empty : 181.5 [kg]
weight wing covering (painted aluminium 1.91 [mm]) : 527 [kg]
total weight aluminium spars (multi-cellular wing structure) : 322 [kg]
weight wings : 1103 [kg]
weight wing/square meter : 21.54 [kg]
cantilever wing without bracing cables
weight rubber de-icing boots : 22.0 [kg]
weight fin & rudder (4.6 [m2]) : 100.3 [kg]
weight stabilizer & elevator (5.8 [m2]): 155.5 [kg]
weight split flap (2.6 [m2]) : 30.6 [kg]
total weight wing surfaces & bracing : 1660 [kg] (23.4 [%])
*******************************************************************
wheel pressure : 3549.5 [kg]
weight 2 wheels (1060 [mm] by 212 [mm]) : 146.7 [kg]
weight tailwheel(s) : 5.9 [kg]
weight wheel hydraulic operated retraction system : 30.8 [kg]
weight undercarriage with axle 278.4 [kg]
total weight landing gear : 461.8 [kg] (6.5 [%]
*******************************************************************
********************************************************************
calculated empty weight : 4799 [kg](67.6 [%])
weight oil for 6.4 hours flying : 120.3 [kg]
calculated operational weight empty : 4919 [kg] (69.3 [%])
published operational weight empty : 4876 [kg] (68.7 [%])
___o___
" "
weight crew : 162 [kg]
weight fuel for 2.0 hours flying : 591 [kg]
weight catering : 22.4 [kg]
weight water : 9.0 [kg]
********************************************************************
operational weight empty: 5703 [kg](80.3 [%])
weight 12 passengers : 924 [kg]
weight luggage & freight : 276 [kg]
operational weight loaded: 6903 [kg](97.2 [%])
fuel reserve : 195.8 [kg] enough for 0.66 [hours] flying
operational weight fully loaded : 7099 [kg] with fuel tank filled for 44 [%]
published maximum take-off weight : 7099 [kg] (100.0 [%])
calculation : * 4 * (engine power)
power loading (Take-off) : 5.29 [kg/kW]
power loading (operational without useful load) : 4.25 [kg/kW]
power loading (Take-off) 1 PUF: 10.58 [kg/kW]
total power : 1342.3 [kW] at 2300 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 6.1 [g] at 1000 [m]
limit load : 3.0 [g] ultimate load : 4.5 [g] load factor : 2.5 [g]
design flight time : 3.73 [hours]
design cycles : 9660 sorties, design hours : 36070 [hours]
operational wing loading : 1093 [N/m^2]
wing stress (3 g) during operation : 152 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.76 ["]
max. angle of attack (stalling angle) : 13.73 ["]
angle of attack at max. speed : 0.26 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.15 [ ]
lift coefficient at max. speed : 0.17 [ ]
lift coefficient at max. angle of attack : 1.32 [ ]
max.lift coefficient full flaps : 1.42 [ ]
induced drag coefficient at max.speed : 0.0016 [ ]
drag coefficient at max. speed : 0.0295 [ ]
drag coefficient (zero lift) : 0.0279 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 6804 [kg]): 145 [km/u]
stalling speed at sea-level with full flaps (normal landing weight): 128 [km/u]
landing speed at sea-level (normal landing weight : 5747 [kg]): 147 [km/hr]
max. rate of climb speed : 150 [km/hr] at sea-level
max. endurance speed : 154 [km/u] min. brpu : 106 [kg/hr] at height : 610 [m]
max. range speed : 243 [km/u] min. fuel consumption : 0.597 [kg/km] at cruise height :
4267 [m]
cruising speed : 380 [km/hr] at 3750 [m] (power:82 [%])
max. continuous speed : 390.00 [km/hr]
maximum speed : 400 [km/hr] at 1800 [m] (power:110 [%])
climbing speed at sea-level (loaded) : 653 [m/min]
climbing speed at 1000 [m] with 1 engine out (PUF / MTOW) : 234 [m/min]
The PH-APE “Ekster” crashed 09 December 1938 during a training flight short after take-off from Schiphol airport, all 4 on board died
calculation : *9* (regarding various performances)
take-off speed : 177.3 [km/u]
emergency/TO power : 1000 [hp] at 2424 [rpm]
static prop wash : 152 [km/u]
take-off distance at sea-level : 421 [m]
lift/drag ratio : 12.83 [ ]
climb to 1000m with max payload : 1.63 [min]
climb to 2000m with max payload : 3.29 [min]
climb to 3000m with max payload : 5.31 [min]
practical ceiling (operational weight 5703 [kg] ) : 8500 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:6951 [kg] ) : 7400 [m]
calculation *10* (action radius & endurance)
published range : 2027 [km] with 2 crew and 442.3 [kg] useful load and 88.1 [%] fuel
range : 1052 [km] with 2 crew and 1200.0 [kg] useful load and 45.7 [%] fuel
range : 1253 [km] with 12.0 passengers with each 10 [kg] luggage and 54.5 [%] fuel
Available Seat Kilometres (ASK) : 15035 [paskm]
max range theoretically with additional fuel tanks total 2863.5 [litre] fuel : 3517 [km]
useful load with range 500km : 1710 [kg]
useful load with range 500km : 12 passengers
production (useful load): 650 [tonkm/hour]
production (passengers): 4560 [paskm/hour]
oil and fuel consumption per tonkm : 0.48 [kg]
fuel cost per paskm : 0.048 [eur]
crew cost per paskm : 0.046 [eur]
economic hours : 12775 [hours] is less then design hours
time between engine failure : 58 [hr]
can continue fly on 1 engine, low risk for emergency landing for PUF
writing off per paskm : 0.048 [eur]
insurance per paskm : 0.030 [eur]
maintenance cost per paskm : 0.126 [eur]
direct operating cost per paskm : 0.299 [eur]
direct operating cost per tonkm : 2.988 [eur]
Literature :
Lockheed Model 14 Super Electra - Wikipedia
Piston-engined airliners page 35
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 28 November 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4