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weight and performance calculations for the Fokker F.XII
Fokker F.XII
role : multi-engined passenger aircraft
importance : **
first flight : 5 December 1930 PH-AFL operational : March 1931
country : The Netherlands
design :
production : Fokker 11, 2 license built in Denmark.
general information :
Successor of the F.VIIb/3m. Streamlined wheel covering was removed by the KLM.
KLM used the F.XII on the long distance route to Batavia, Indonesia taking only 4
passengers. But it was also used on the European routes with seating for 16
passengers.
Registrations : PH-AFL “Leeuwerik”, PH-AFV “Valk”, PH-AFU “Uil”, PH-AID “Duif”, PH-AIE “Ekster”, PH-AIH “Havik”, PH-AII “Ibis”, PH-AIJ “IJsvogel”, G-AEOS, G-ADZJ, G-AEOT, SE-ACZ “Varmland” , PK-AFH (KNILM)
users : KLM, DDA, ABA, KNILM
crew : 3 passengers : 16
engine : 3 Pratt & Whitney R-1340-C1 Wasp air-cooled 9 -cylinder radial engine 420
[hp] (313.2 KW) supercharged engine
dimensions :
wingspan : 22.99 [m], length : 17.5 [m], height : 4.29[m]
wing area : 83.0 [m^2]
weights :
max.take-off weight : 7251 [kg]
empty weight operational : 4350 [kg] useful load : 1600 [kg]
performance :
maximum speed :220 [km/hr] at sea-level
cruise speed :198 [km/u] op 100 [m]
service ceiling : 4500 [m]
range : 1270 [km]
description :
high-winged with fixed landing gear and tail wheel
two spar tapered wing
2 engines attached to the wings 1 in the fuselage, landing gear attached to the wings,
useful load inside the fuselage, fuel tanks in the wings
construction : fuselage of welded steel tubes covered with canvas, wooden wing covered
with plywood.
airscrew :
ground adjustable 2 -bladed metal Hamilton Standard tractor propeller with max.
efficiency :0.72 [ ]
estimated diameter airscrew 2.68 [m]
power loading prop : 116.86 [KW/m]
prop efficiency ratio: 11.99 [1/s]
angle of attack prop : 16.19 [ ]
reduction : 1.00 [ ]
airscrew revs : 2000 [r.p.m.]
pitch at Max speed 1.83 [m]
blade-tip speed at Vmax and max revs. : 287 [m/s]
calculation : *1* (dimensions)
measured wing chord : 3.83 [m] at 50% wingspan
mean wing chord : 3.61 [m]
calculated average wing chord tapered wing with rounded tips: 3.62 [m]
wing aspect ratio : 6.37 []
seize (span*length*height) : 1726 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 15.0 [kg/hr]
fuel consumption(cruise speed) : 214.8 [kg/hr] (293.0 [litre/hr]) at 71 [%] power
distance flown for 1 kg fuel : 0.92 [km/kg] at 2250 [m] height, sfc : 323.5 [kg/kwh]
estimated total fuel capacity : 2133 [litre] (1563 [kg])
calculation : *3* (weight)
weight engine(s) dry : 1020.0 [kg] = 1.09 [kg/KW]
weight 152.4 litre oil tank : 12.95 [kg]
oil tank filled with 7.0 litre oil : 6.3 [kg]
oil in engine 5.2 litre oil : 4.7 [kg]
fuel in engine 6.4 litre fuel : 4.70 [kg]
weight 124.6 litre gravity patrol tank(s) : 18.7 [kg]
weight gas starter : 7.7 [kg]
weight cowling (Townend ring) 12.5 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 77.1 [kg]
total weight propulsion system : 1152 [kg](15.9 [%])
***************************************************************
fuselage skeleton (steel tubes) : 8.56 [cm]): 1010 [kg]
cabin layout : pitch : 87 [cm] (2+1) seating in 5 rows
weight toilet : 8 [kg]
weight 2 fire extinguisher : 6 [kg]
weight pantry : 14.4 [kg]
weight 10 windows : 9.60 [kg]
passenger cabin width : 2.02 [m] cabin length : 5.24 [m] cabin height : 1.90 [m]
weight cabin furbishing : 51.92 [kg]
weight cabin floor : 67.89 [kg]
bracing : 134.0 [kg]
fuselage covering ( 57.8 [m2] doped linen fabric) : 17.9 [kg]
weight radio navigation equipment : 7.0 [kg]
weight instruments. : 4.0 [kg]
weight lighting : 4.0 [kg]
weight controls : 8.6 [kg]
weight seats : 95.0 [kg]
weight air conditioning : 24 [kg]
weight engine mount and firewall : 16 [kg]
total weight fuselage : 1478 [kg](20.4 [%])
***************************************************************
weight 2.4 mm plywood wing covering : 127 [kg]
total weight wooden ribs (109 ribs) : 431 [kg]
weight engine mounts : 31 [kg]
weight fuel tanks empty for total 2008 [litre] fuel : 161 [kg]
load on front upper spar (clmax) per running metre : 1790.2 [N]
load on rear upper spar (vmax) per running metre : 781.5 [N]
total weight 4 wooden spars : 347 [kg]
weight wings : 905 [kg]
weight wing/square meter : 10.91 [kg]
cantilever wing without bracing cables
weight fin & rudder (6.1 [m2]) : 67.8 [kg]
weight stabilizer & elevator (9.3 [m2]): 102.5 [kg]
total weight wing surfaces & bracing : 1268 [kg] (17.5 [%])
*******************************************************************
wheel pressure : 3625.5 [kg]
weight 2 wheels (1350 [mm] by 270 [mm]) : 239.1 [kg]
weight tailwheel : 14.3 [kg]
weight undercarriage with axle 144.0 [kg]
total weight landing gear : 397.4 [kg] (5.5 [%]
*******************************************************************
********************************************************************
calculated empty weight : 4295 [kg](59.2 [%])
weight oil for 7.7 hours flying : 115.7 [kg]
calculated operational weight empty : 4410 [kg] (60.8 [%])
published operational weight empty : 4350 [kg] (60.0 [%])
***o***
"
weight crew : 243 [kg]
weight fuel for 2.0 hours flying : 430 [kg]
********************************************************************
operational weight empty: 5083 [kg](70.1 [%])
weight 16 passengers : 1232 [kg]
weight luggage & freight : 368 [kg]
operational weight loaded: 6683 [kg](92.2 [%])
fuel reserve : 568.0 [kg] enough for 2.64 [hours] flying
operational weight fully loaded : 7251 [kg] with fuel tank filled for 64 [%]
published maximum take-off weight : 7251 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (Take-off) : 7.72 [kg/kW]
power loading (operational without useful load) : 5.41 [kg/kW]
power loading (Take-off) 1 PUF: 11.58 [kg/kW]
total power : 939.6 [kW] at 2000 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 2.5 [g] at 1000 [m]
limit load : 2.5 [g] ultimate load : 3.8 [g] load factor : 1.7 [g]
design flight time : 4.49 [hours]
design cycles : 4370 sorties, design hours : 19621 [hours]
operational wing loading : 601 [N/m^2]
wing stress (3 g) during operation : 165 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -2.11 ["]
max. angle of attack (stalling angle) : 12.02 ["]
angle of attack at max. speed : 1.18 ["]
SE-ACZ “Varmland” . Used by the Swedish airline ABA until 1946. It flew the route Malmo - Amsterdam
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.17 [ ]
lift coefficient at max. angle of attack : 1.14 [ ]
lift coefficient at max. speed : 0.27 [ ]
induced drag coefficient at max. speed : 0.0047 [ ]
drag coefficient at max. speed : 0.0586 [ ]
drag coefficient (zero lift) : 0.0539 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 7036 [kg]): 124 [km/u]
landing speed at sea-level: 146 [km/hr]
min. drag speed (max endurance) : 156 [km/hr] at 2250 [m](power :53 [%])
min. power speed (max range) : 156 [km/hr] at 2250 [m] (power:53 [%])
max. rate of climb speed : 131.8 [km/hr] at sea-level
cruising speed : 198 [km/hr] op 2250 [m] (power:75 [%])
design speed prop : 209 [km/hr]
maximum speed : 220 [km/hr] op 100 [m] (power:107 [%])
climbing speed at sea-level : 433 [m/min]
calculation : *9* (regarding various performances)
take-off speed : 151.5 [km/u]
static prop wash : 152 [km/u]
take-off distance at sea-level : 380 [m]
lift/drag ratio : 8.34 [ ]
climb to 1000m with max payload : 4.78 [min]
climb to 2000m with max payload : 11.77 [min]
climb to 3000m with max payload : 22.03 [min]
practical ceiling (operational weight 5083 [kg] ) : 6048 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:7144 [kg] ) : 4033 [m]
calculation *10* (action radius & endurance)
published range : 1270 [km] with 3 crew and 1220.0 [kg] useful load and 88.1 [%] fuel
range : 920 [km] with 3 crew and 1600.0 [kg] useful load and 63.8 [%] fuel
range : 1111 [km] with 16.0 passengers with each 10 [kg] luggage and 77.1 [%] fuel
Available Seat Kilometers (ASK) : 17783 [paskm]
max range theoretically with additional fuel tanks total 3764.7 [litre] fuel : 2544 [km]
useful load with range 500km : 2217 [kg]
useful load with range 500km : 16 passengers
production (useful load): 439.01 [tonkm/hour]
production (passengers): 3168.00 [paskm/hour]
oil and fuel consumption per tonkm : 0.52 [kg]
oil and fuel consumption per paskm : 0.05 [kg]
fuel cost per paskm : 0.05 [eur]
crew cost per paskm : 0.07 [eur]
economic hours : 12775 [hours] is less then design hours
time between engine failure : 65 [hr]
writing off per paskm : 0.06 [eur]
insurance per paskm : 0.02 [eur]
maintenance cost per paskm : 0.28 [eur]
direct operating cost per paskm : 0.48 [eur]
direct operating cost per tonkm : 4.78 [eur]
Literature :
Alles over de Fokker Friendship page 59,60,130
Fokker verkeersvliegtuigen 1920-1940 page 43 – 47
Fokker – bouwer aan de wereldluchtvaart page 85
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 18 September 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4
PH-AIE “Ekster”
PH-AIJ “IJsvogel”
OY-DAJ “Kronprinsesse Ingrid” built in Denmark under license. It was in use by DDL until 1947.