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weight and performance calculations for the Lockheed model 10A Electra
Lockheed model 10A Electra
importance : ****
first flight : 23 February 1934 flown by Marshall Headle operational : August 1934
country : United States of America
design : Hall Hibbard
production : 101 aircraft
general information :
Designed to compete with the Boeing 247 and Douglas DC-2 . First all-metal Lockheed design. It could compete with the Boeing 247 and DC2 for it’s high cruise speed and low purchase price of 36.000 usd. (The Boeing 247 was sold for 65.000 usd !) while the Model 10A carried the same number of passengers its empty weight was much lower.
Wind-tunnel research was done at the University of Michigan, and Clarence “Kelly” Johnson , then a student assistant did much work, later he became famous for leading the Lockheed Skunk works , responsible for the Lockheed SR-71 Blackbird .
users : Northwest Airlines, Delta airlines , Eastern airlines, Ansett, Cubana de Aviacion,
KLM (west Indies), VARIG, LAN Chile, TASA, LOT, and many more airlines.
crew : 2 passengers : 10
engine : 2 Pratt & Whitney R-985-SB Wasp Jr air-cooled 9 -cylinder radial engine 400 [hp](298.3 KW)
supercharged engine, constant power to height : 1500 [m]
dimensions :
wingspan : 16.76 [m], length : 11.76 [m], height : 3.07 [m]
wing area : 42.58 [m^2]
weights :
max.take-off weight : 4581 [kg]
empty weight operational : 2869 [kg] useful load : 1100 [kg]
performance :
maximum speed :338 [km/u] op 1524 [m]
cruise speed :321 [km/u] op 1524 [m]
service ceiling : 6480 [m]
range : 1176 [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 variable pitch 2 -bladed tractor airscrews with max. efficiency
:0.73 [ ]
estimated diameter airscrew 2.83 [m]
power loading prop : 105.40 [KW/m]
angle of attack prop at max. speed : 21.01 [ ]
tip/speed little higher then speed of sound, need for thin metal tips
reduction : 1.00 [ ]
airscrew revs : 2200 [r.p.m.]
pitch at Max speed 2.56 [m]
blade-tip speed at Vmax and max revs. : 339 [m/s]
calculation : *1* (dimensions)
measured wing chord : 2.52 [m] at 50% wingspan
mean wing chord : 2.54 [m]
calculated average wing chord tapered wing with rounded tips: 2.53 [m]
wing aspect ratio : 6.60 []
seize (span*length*height) : 605 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 9.5 [kg/hr]
fuel consumption(cruise speed) : 129.4 [kg/hr] (176.6 [litre/hr]) at 70 [%] power
distance flown for 1 kg fuel : 2.48 [km/kg] at 3240 [m] height, sfc : 308.5 [kg/kwh]
estimated total fuel capacity : 734 [litre] (538 [kg])
calculation : *3* (weight)
weight engine(s) dry : 580.0 [kg] = 0.97 [kg/KW]
weight 61.6 litre oil tank : 5.24 [kg]
oil tank filled with 4.5 litre oil : 4.0 [kg]
oil in engine 3.3 litre oil : 3.0 [kg]
fuel in engine 4.1 litre fuel : 2.98 [kg]
weight 75.1 litre gravity patrol tank(s) : 11.3 [kg]
weight starter (E.H.I. - Electric Hand Inertia): 7.3 [kg]
weight NACA cowling 13.4 [kg]
weight variable pitch control : 7.7 [kg]
weight airscrew(s) incl. boss & bolts : 69.7 [kg]
total weight propulsion system : 692 [kg](15.1 [%])
***************************************************************
fuselage aluminium frame : 425 [kg]
cabin layout : pitch : 87 [cm] (1+1) seating in 5.0 rows
weight toilet : 8 [kg]
weight 2 fire extinguisher : 6 [kg]
weight 10 windows : 9.0 [kg]
passenger cabin width : 1.54 [m] cabin length : 4.95 [m] cabin height : 1.80 [m]
weight cabin furbishing : 30.3 [kg]
weight cabin floor : 48.8 [kg]
fuselage covering ( 45.7 [m2] duraluminium 1.23 [mm]) : 146.0 [kg]
fuselage (sound proof) isolation : 13.2 [kg]
weight radio transceiver equipment : 7.0 [kg]
weight Sperry gyro auto-pilot - course control equipment : 1.5 [kg]
Model 10E adapted for long range flights
weight instruments. : 6.0 [kg]
weight lighting : 2.5 [kg]
weight electricity generator : 4.8 [kg]
weight dual controls + indicators: 19.7 [kg]
weight seats : 60.0 [kg]
weight air conditioning : 15 [kg]
total weight fuselage : 783 [kg](17.1 [%])
***************************************************************
total weight aluminium ribs (92 ribs) : 163 [kg]
weight engine mounts : 30 [kg]
weight two 330 [litre] main fuel tanks empty : 52.7 [kg]
weight wing covering (painted aluminium 1.64 [mm]) : 377 [kg]
total weight aluminium spars (multi-cellular wing structure) : 230 [kg]
weight wings : 771 [kg]
weight wing/square meter : 18.10 [kg]
cantilever wing without bracing cables
weight fin & rudder (3.3 [m2]) : 59.5 [kg]
weight stabilizer & elevator (4.8 [m2]): 108.8 [kg]
weight split flap(2.1 [m2]) : 22.3 [kg]
total weight wing surfaces & bracing : 1044 [kg] (22.8 [%])
*******************************************************************
Can only operate from paved runways
wheel pressure : 2290.5 [kg]
weight 2 wheels (900 [mm] by 138 [mm]) : 119.8 [kg]
weight tailwheel(s) : 5.9 [kg]
weight wheel hydraulic operated retraction system : 21.7 [kg]
weight undercarriage with axle 177.4 [kg]
total weight landing gear : 324.8 [kg] (7.1 [%]
*******************************************************************
********************************************************************
calculated empty weight : 2843 [kg](62.1 [%])
weight oil for 4.4 hours flying : 41.9 [kg]
calculated operational weight empty : 2885 [kg] (63.0 [%])
published operational weight empty : 2869 [kg] (62.6 [%])
___o___
" "
weight crew : 162 [kg]
weight fuel for 2.0 hours flying : 259 [kg]
weight catering : 14.6 [kg]
weight water : 5.9 [kg]
********************************************************************
operational weight empty: 3327 [kg](72.6 [%])
weight 10 passengers : 770 [kg]
weight luggage & freight : 330 [kg]
operational weight loaded: 4427 [kg](96.6 [%])
fuel reserve : 154.4 [kg] enough for 1.19 [hours] flying
operational weight fully loaded : 4581 [kg] with fuel tank filled for 77 [%]
published maximum take-off weight : 4581 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (Take-off) : 7.68 [kg/kW]
power loading (operational without useful load) : 5.58 [kg/kW]
power loading (Take-off) 1 PUF: 15.36 [kg/kW]
total power : 596.6 [kW] at 2200 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 6.0 [g] at 1000 [m]
limit load : 3.0 [g] ultimate load : 4.5 [g] load factor : 2.8 [g]
design flight time : 2.93 [hours]
design cycles : 11940 sorties, design hours : 34983 [hours]
operational wing loading : 766 [N/m^2]
wing stress (3 g) during operation : 127 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.84 ["]
max. angle of attack (stalling angle) : 14.19 ["]
angle of attack at max. speed : 0.18 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.15 [ ]
lift coefficient at max. angle of attack : 1.30 [ ]
max.lift coefficient full flaps : 1.40 [ ]
lift coefficient at max. speed : 0.16 [ ]
induced drag coefficient at max. speed : 0.0017 [ ]
drag coefficient at max. speed : 0.0233 [ ]
drag coefficient (zero lift) : 0.0215 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 4452 [kg]): 129 [km/u]
stalling speed at sea-level with full flaps (normal landing weight): 112 [km/u]
landing speed at sea-level (normal landing weight : 3595 [kg]): 128 [km/hr]
max. endurance speed : 147 [km/u] min. brpu : 64 [kg/hr] at cruise height : 100 [m]
max. rate of climb speed : 146.6 [km/hr] at sea-level
max. range speed : 194 [km/u] min.fuel cons.: 0.378 [kg/km] at cruise height : 100 [m] (power:40 [%])
cruising speed : 321 [km/hr] at 3240 [m] (power:83 [%])
maximum speed : 338 [km/hr] at 1524 [m] (power:106 [%])
climbing speed at sea-level (loaded) : 390 [m/min]
climbing speed at 1000 [m] with 1 engine out (PUF / MTOW) : 102 [m/min]
calculation : *9* (regarding various performances)
take-off speed : 157.0 [km/u]
emergency/TO power : 450 [hp] at 2333 [rpm]
static prop wash : 179 [km/u]
high wheel pressure, can only take off from paved runways
take-off distance at sea-level : 237 [m]
lift/drag ratio : 13.43 [ ]
climb to 1000m with max payload : 2.81 [min]
climb to 2000m with max payload : 6.06 [min]
climb to 3000m with max payload : 10.54 [min]
practical ceiling (operational weight 3327 [kg] ) : 7400 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:4516 [kg] ) : 5600 [m]
calculation *10* (action radius & endurance)
published range : 1176 [km] with 2 crew and 1059.8 [kg] useful load and 88.1 [%] fuel
range : 1076 [km] with 2 crew and 1100.0 [kg] useful load and 80.6 [%] fuel
range : 1647 [km] with 10.0 passengers with each 10 [kg] luggage and 123.4 [%] fuel
Available Seat Kilometres (ASK) : 16467 [paskm]
max range theoretically with additional fuel tanks total 2203.0 [litre] fuel : 4272 [km]
useful load with range 500km : 1413 [kg]
useful load with range 500km : 10 passengers
production (useful load): 454 [tonkm/hour]
production (passengers): 3211 [paskm/hour]
oil and fuel consumption per tonkm : 0.31 [kg]
fuel cost per paskm : 0.031 [eur]
crew cost per paskm : 0.066 [eur]
economic hours : 12775 [hours] is less then design hours
time between engine failure : 115 [hr]
can continue fly on 1 engine, low risk for emergency landing for PUF
writing off per paskm : 0.041 [eur]
insurance per paskm : 0.016 [eur]
maintenance cost per paskm : 0.124 [eur]
direct operating cost per paskm : 0.278 [eur]
direct operating cost per tonkm : 2.780 [eur]
Literature :
Lockheed Model 10 Electra - Wikipedia
Praktisch handboek vliegtuigen deel 2 page 256,257
Piston-engined airliners page 35,36,37
Encyclopedie van de luchtvaart 1848-1939 page 200,201
Aircraft of the United States vol.1 blz.186
Amelia Earhart disappeared in July 1937 over the vast ocean flying a Model 10E Electra on a round the world attempt. The Model 10E was specially adapted for long range flights.
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 22 October 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4