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weight and performance calculations for the Lockheed model 18 Lodestar
Lockheed model 18 Lodestar
importance : ***
first flight : 21 September 1939 operational : April 1940
country : United States of America
design :
production : 625 aircraft
general information :
Sales of the Lockheed Model 14 Super Electra was disappointing and to make a more competitive and economic aircraft Lockheed made a stretched model. The fuselage was lengthened by 1.68 [m] giving space for two extra rows of seats. Now the seat-mile cost equalled the Douglas DC-3 while the Lodestar maintained a higher cruise speed.
But by know most major airlines were committed to the DC-3, only 31 Lodestars did go to US airlines. Foreign sales went little better, but now many were sold to the US military forces (model C-56 and C-60).
The Lockheed PV-1 Ventura (1600 built for the US Navy) and PV-2 Harpoon were developed from the Lodestar.
Fuel tanks have total maximum capacity of 2438 litres. Maximum oil capacity : 166.5
litres
users : Mid-Continent airlines, South African Airways (21), New Zealand National
Airways (13), Trans-Canada airlines (12), BOAC (9), Royal Netherlands East Indies
Army air force (KNIL) (29)
crew : 3 passengers : 16
power plant : 2 Wright R-1820-87 Cyclone air-cooled 9 -cylinder radial engine 1000 [hp]
(745.7 KW) normal rating, supercharged engine, low blower, constant power to height :
2100 [m] and with 1200 [hp] (894.8 KW) available for take-off
dimensions :
wingspan : 19.96 [m], length : 15.19 [m], height : 3.61 [m]
wing area : 51.19 [m^2]
weights :
max.take-off weight : 8400 [kg]
empty weight operational : 5670 [kg] useful load : 1600 [kg]
performance :
maximum speed :428 [km/u] op 530 [m]
cruise speed :407 [km/u] op 530 [m]
service ceiling : 9200 [m]
range : 2191 [km]
Chord at root measured at 4.20 [m] chord at midwing measured : 2.70 [m] fuselage width measured at 1.87 [m] prop.diam : 2.98 [m]
description :
low-winged monoplane with retractable landing gear with tail wheel
tapered wing with Fowler flaps interlinked with the ailerons 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
:0.75 [ ]
estimated diameter airscrew 2.98 [m]
power loading prop : 166.82 [KW/m]
angle of attack prop at max. speed : 33.56 [ ]
reduction : 0.67 [ ]
airscrew revs : 1532 [r.p.m.]
pitch at Max speed 4.54 [m]
blade-tip speed at max.continous speed : 266 [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: 2.52 [m]
wing aspect ratio : 7.78 []
seize (span*length*height) : 1095 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 17.9 [kg/hr]
fuel consumption(cruise speed) : 292.3 [kg/hr] (398.7 [litre/hr]) at 62 [%] power
distance flown for 1 kg fuel : 1.39 [km/kg] at 4600 [m] height, sfc : 315.0 [kg/kwh]
estimated total fuel capacity : 2439 [litre] (1787 [kg])
calculation : *3* (weight)
weight engine(s) dry with reduction gear : 1190.0 [kg] = 0.80 [kg/KW]
weight 166.2 litre oil tank : 14.13 [kg]
oil tank filled with 11.2 litre oil : 10.0 [kg]
oil in engine 8.3 litre oil : 7.5 [kg]
fuel in engine 10.2 litre fuel : 7.46 [kg]
weight 169.5 litre gravity patrol tank(s) : 25.4 [kg]
weight starter (E.H.I. - Electric Hand Inertia): 18.3 [kg]
weight NACA cowling 33.4 [kg]
weight variable pitch control : 11.9 [kg]
weight airscrew(s) incl. boss & bolts : 155.0 [kg]
total weight propulsion system : 1461 [kg](17.4 [%])
***************************************************************
fuselage aluminium frame : 873 [kg]
cabin layout : pitch : 87 [cm] (1+1) seating in 8.0 rows
weight toilet : 8 [kg]
weight 2 fire extinguisher : 6 [kg]
weight pantry : 12.1 [kg]
weight 16 windows : 14.4 [kg]
weight door : 5.0 [kg]
passenger cabin width : 1.70 [m] cabin length : 8.54 [m] cabin height : 1.90 [m]
weight cabin furbishing : 61.0 [kg]
weight cabin floor : 87.0 [kg]
fuselage covering ( 67.1 [m2] duraluminium 3.21 [mm]) : 558.8 [kg]
fuselage (sound proof) isolation : 19.3 [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 : 4.0 [kg]
weight electricity generator : 8.2 [kg]
weight controls : 7.6 [kg]
weight seats : 95.0 [kg]
weight air conditioning : 24 [kg]
total weight fuselage : 1769 [kg](21.1 [%])
***************************************************************
total weight aluminium ribs (167 ribs) : 300 [kg]
weight engine mounts : 75 [kg]
weight two 1135 [litre] main fuel tanks empty : 181.5 [kg]
weight wing covering (painted aluminium 2.15 [mm]) : 594 [kg]
total weight aluminium spars (multi-cellular wing structure) : 386 [kg]
weight wings : 1279 [kg]
weight wing/square meter : 24.99 [kg]
cantilever wing without bracing cables
weight rubber de-icing boots : 22.0 [kg]
weight fin & rudder (4.6 [m2]) : 116.3 [kg]
weight stabilizer & elevator (5.8 [m2]): 180.4 [kg]
weight fowler flap (4.3 [m2]) : 59.3 [kg]
total weight wing surfaces & bracing : 1913 [kg] (22.8 [%])
*******************************************************************
wheel pressure : 4200.0 [kg]
weight 2 wheels (1140 [mm] by 228 [mm]) : 184.4 [kg]
weight tailwheel(s) : 5.9 [kg]
weight wheel hydraulic operated retraction system : 35.4 [kg]
weight undercarriage with axle 305.5 [kg]
total weight landing gear : 531.2 [kg] (6.3 [%]
*******************************************************************
********************************************************************
calculated empty weight : 5642 [kg](67.2 [%])
weight oil for 6.5 hours flying : 115.7 [kg]
calculated operational weight empty : 5758 [kg] (68.5 [%])
published operational weight empty : 5670 [kg] (67.5 [%])
___o___
"
weight crew : 243 [kg]
weight fuel for 2.0 hours flying : 585 [kg]
weight catering : 30.2 [kg]
weight water : 12.1 [kg]
********************************************************************
operational weight empty: 6627 [kg](78.9 [%])
weight 16 passengers : 1232 [kg]
weight luggage & freight : 368 [kg]
operational weight loaded: 8227 [kg](97.9 [%])
fuel reserve : 172.7 [kg] enough for 0.59 [hours] flying
operational weight fully loaded : 8400 [kg] with fuel tank filled for 42 [%]
published maximum take-off weight : 8400 [kg] (100.0 [%])
calculation : * 4 * (engine power)
power loading (Take-off) : 5.63 [kg/kW]
power loading (operational without useful load) : 4.44 [kg/kW]
power loading (Take-off) 1 PUF: 11.26 [kg/kW]
total power : 1491.4 [kW] at 2300 [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 : 2.4 [g]
design flight time : 3.77 [hours]
design cycles : 9663 sorties, design hours : 36449 [hours]
operational wing loading : 1270 [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 : 0.05 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.15 [ ]
lift coefficient at max. speed : 0.15 [ ]
lift coefficient at max. angle of attack : 1.32 [ ]
max.lift coefficient full flaps : 1.57 [ ]
induced drag coefficient at max.speed : 0.0013 [ ]
drag coefficient at max. speed : 0.0239 [ ]
drag coefficient (zero lift) : 0.0226 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 8108 [kg]): 158 [km/u]
stalling speed at sea-level with full flaps (normal landing weight): 132 [km/u]
landing speed at sea-level (normal landing weight : 6762 [kg]): 152 [km/hr]
max. rate of climb speed : 173 [km/hr] at sea-level
max. endurance speed : 177 [km/u] min. brpu : 131 [kg/hr] at height : 610 [m]
max. range speed : 280 [km/u] min.fuel consumption: 0.643 [kg/km] at height : 4267 [m]
cruising speed : 407 [km/hr] at 4600 [m] (power:71 [%])
max. continuous speed : 417.30 [km/hr]
maximum speed : 428 [km/hr] at 530 [m] (power:110 [%])
climbing speed at sea-level (loaded) : 596 [m/min]
climbing speed at 1000 [m] with 1 engine out (PUF / MTOW) : 240 [m/min]
calculation : *9* (regarding various performances)
take-off speed : 192.9 [km/u]
emergency/TO power : 1200 [hp] at 2520 [rpm]
static prop wash : 166 [km/u]
take-off distance at sea-level : 522 [m]
lift/drag ratio : 14.24 [ ]
climb to 1000m with max payload : 1.77 [min]
climb to 2000m with max payload : 3.58 [min]
climb to 3000m with max payload : 5.83 [min]
practical ceiling (operational weight 6627 [kg] ) : 8300 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:8254 [kg] ) : 7100 [m]
calculation *10* (action radius & endurance)
published range : 2191 [km] with 3 crew and 824.6 [kg] useful load and 88.1 [%] fuel
range : 1112 [km] with 3 crew and 1600.0 [kg] useful load and 44.7 [%] fuel
range : 1402 [km] with 16.0 passengers with each 10 [kg] luggage and 56.4 [%] fuel
Available Seat Kilometres (ASK) : 22426 [paskm]
max range theoretically with additional fuel tanks total 3494.5 [litre] fuel : 3985 [km]
useful load with range 500km : 2202 [kg]
useful load with range 500km : 16 passengers
production (useful load): 895 [tonkm/hour]
production (passengers): 6506 [paskm/hour]
oil and fuel consumption per tonkm : 0.35 [kg]
fuel cost per paskm : 0.035 [eur]
crew cost per paskm : 0.034 [eur]
economic hours : 12775 [hours] is less then design hours
time between engine failure : 55 [hr]
can continue fly on 1 engine, low risk for emergency landing for PUF
writing off per paskm : 0.041 [eur]
insurance per paskm : 0.027 [eur]
maintenance cost per paskm : 0.101 [eur]
direct operating cost per paskm : 0.237 [eur]
direct operating cost per tonkm : 2.365 [eur]
Literature :
Amerikaanse vliegtuigbouwers page 103,104,105
prakt. handb. vliegt. deel 5 page 28,29
piston engined airliners page 35,39
Jane’s fighter aircraft WWII page 243
Lockheed Model 18 Lodestar - Wikipedia
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