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weight and performance calculations for the Fokker F.VIIb/3m
Captain George Hubert Wilkins used F.VIIa prototype c/n 4899 together with F.VII/3m “Detroiter” for his arctic expeditions in Alaska in 1926. This was the first F.VII/3m with a bigger wing, and so can be seen as the first F.VIIb/3m although this indication was only later officially introduced in 1928. It had 200 hp Wright J-4 Whirlwind engines. The “Detroiter” was taken to Alaska medio 1926 but was damaged in a ruff landing. It was taken to Seattle, repaired and became the famous “Southern Cross” flown by Charles Kingsford Smith (c/n 4954 , reg. 1985)
Fokker F.VIIb/3m
role : multi-engined passenger aircraft
importance : ****
first flight : Spring 1926 operational : July 1928
country : The Netherlands
design : Reinhold Platz
production : 63 aircraft by Fokker, about 80 license built ( Poland 30, Avro 13, Avia Prague 21, SABCA Belgium 29)
general information :
Fokker offered the F.VII/3m with a bigger wing. The wing centre section was enlarged
KLM started to use the F.VIIb/3m September 1928 on a scheduled service to
Indonesia. The FVIIb/3m was license built by Plage & Laskievicz , Lublin,Poland.
20 were used by the Polish Airforce as bomber from May 1931 (max bombload 1500
kg). During the German invasion in September 1939 they were used as military transport. About 10 F.VIIb/3m served with the LOT from May 1930 on.
6 Aircraft flew with the KNILM in Dutch east India (Indonesia).
The KLM flew the F.VIIb/3m with 230hp Gnome Rhone Tit an engines upon till 1935.
Airfoil : Root > Goettingen 386 (20%), tip > Goettingen 388 (11.3%)
users : KLM (14), Sabena (28), Swissair, LOT, Imperial Airways, CLS, CSA, Air Orient,
KNILM(6), Japan Air Transport co. (9)
KLM F.VIIb/3m pilots : G.A. Koppen , Jan Moll , E.A.J. Prillwitz , I.W.Smirnoff ,
J.J. Schott , L.Sillevis , G.M.H Frijns , J.J.E.Duimelaar , I.A.Aler , W.M.O.A.Beekman ,
Piet Soer , Evert Van Dijk , J.J.Hondong , Quirinus Tepas , Thaeke Wiersma ,
Pieter Both , W.C. van Veenendaal
crew : 2 passengers : 8 - 10
engine : 3 Wright R-975 J-6-9 Whirlwind air-cooled 9 -cylinder radial engine 300 [hp](223.7 KW)
compressor height 1000
dimensions :
wingspan : 21.7 [m], length : 14.6 [m], height : 3.89[m]
wing area : 67.6 [m^2]
weights :
max.take-off weight : 5250 [kg]
empty weight operational : 3050 [kg] useful load : 1000 [kg]
F.VIIb/3m had a bigger wingspan, this was done by extending the wing centre-section, the part with the even wing-chord. In this way the wing area was enlarged from 58.50 m2 ( F.VIIa/3m) to 67.6 m2 (F.VIIb/3m). At first the wing was not strengthened and the MTOW was limited to 4500 kg for passenger flights. Later built aircraft had stronger wings according new airworthiness regulations and could fly with weight up to 5250 kg.
Now in July 1928 with the stronger wing and indicated as F.VIIb/3m it was ready for scheduled passenger flights in Europe.
performance :
maximum speed :205 [km/hr] at sea-level
cruise speed :184 [km/u] op 100 [m]
service ceiling : 4800 [m]
range : 1120 [km]
description :
parasol wing with fixed landing gear and tail strut
two spar wing
2 engines attached to the wings 1 in the nose, landing gear attached to the wings, useful load in the fuselage
fuel tanks in the wing centre section
airscrew :
three fixed pitch 2 -bladed tractor airscrews with max. efficiency :0.67 [ ]
estimated diameter airscrew 2.68 [m]
angle of attack prop : 15.14 [ ]
reduction : 1.00 [ ]
airscrew revs : 2000 [r.p.m.]
pitch at Max speed 1.71 [m]
blade-tip speed at Vmax and max revs. : 286 [m/s]
calculation : *1* (dimensions)
measured wing chord : 3.12 [m]
mean wing chord : 3.12 [m]
calculated average wing chord tapered wing with rounded tips: 3.12 [m]
wing aspect ratio : 6.97 []
seize (span*length*height) : 1232 [m^3]
Australian WWI pilot and adventurer Charles Kingsford Smith bought the “Detroiter” from G.H.Wilkins. Kingsford Smith wanted to beat the endurance record, being at that moment 52 hours and 22 minutes. Smith had the engines replaced by 220 hp Wright J-5 Whirlwinds. The landing gear was strengthened and additional fuel tanks installed for total 5760 litre. At the end of 1927 he undertook several attempts but he reached only 50 hours and 4 minutes.
Empty weight ca. 2700 kg + weight crew : 162 kg + weight oil for 50 hrs 380 kg + 4223 kg fuel = TOW 7465 kg. With this weight it could just take off and fly not higher than 100m for the first 30 mins. flight. TO distance 536m wing loading 1083 N/m2 ! wing stress 121 N/kg wing. 5760 litre used in 50 hours is 115 litre/hour (84 kg/hr) for this it had to fly really economical close to the max.endurance speed. Normally at cruise speed it would use 140 litre/hour. With 5760 litre it could fly a distance of 6670 km.
calculation : *2* (fuel consumption)
oil consumption : 12.1 [kg/hr]
fuel consumption(cruise speed) : 153.2 [kg/hr] (209.0 [litre/hr]) at 74 [%] power
distance flown for 1 kg fuel : 1.20 [km/kg] at 2400 [m] cruise height, sfc : 307.8 [kg/kwh]
estimated total fuel capacity : 1440 [litre] (1055 [kg])
calculation : *3* (weight)
weight engine(s) dry : 918.0 [kg] = 1.37 [kg/KW]
weight 114.8 litre oil tank : 9.76 [kg]
oil tank filled with 5.0 litre oil : 4.5 [kg]
oil in engine 3.7 litre oil : 3.4 [kg]
fuel in engine 4.6 litre fuel : 3.36 [kg]
weight 88.8 litre gravity patrol tank(s) : 13.3 [kg]
weight self-starter : 5.5 [kg]
weight cowling 8.9 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 65.1 [kg]
total weight propulsion system : 1022 [kg](19.5 [%])
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fuselage skeleton (steel tubes) : 6.82 [cm]): 535 [kg]
cabin layout : pitch : 87 [cm] (1+1) seating in 5.0 rows
In 1928 Kingsford Smith set upon a new adventure. This was to try the first flight across the Pacific ocean from the USA to Australia. On 31 May 1928 he took of from San Franscisco, together with Harry Lyon , Charles Ulm and James Warner in his F.VIIb/3m witch he now had given the name “Southern Cross” , after a small village in Australia, whose people helped to raise the money to make his flights possible. After stops at Wheeler field , Honolulu 3873 km from San Francisco flown in 27 hrs 27 mins. > 141 km/hr) and Suva, Fuji (5097 km from Honolulu, in 34 hrs 33 min > 147.5 km/hr the longest over water flight till then) landed on 9 June 1928 at Brisbane (2788 km from Suva in 21 hours 35min > 129 km/hr). They continued to Sydney where they were welcomed as heroes. The flight was also special because it was done with a normal passenger aircraft, not a for the purpose designed aircraft. The publicity boosted Fokker his selling of the F.VIIb/3m.
The Southern Cross could take 4911 litre of fuel, enough for 37 hours flight. (132.7 litre/hour > economic cruise speed ca. 145 km/hr, cabin tank 3028 litre, beneath the pilot seat 1 tank 378 litre and four 378 litre tanks in the wing).
The cabin tank had an emergency valve and could be empty in 50 seconds, the fuselage was not strong enough for an (hard) emergency landing with the cabin tank full with fuel. The big cabin tank prevented that the pilots in front could get to the rest of the crew in the back. Communication was done by passing a stick with messages.
weight toilet : 5 [kg]
weight 10.0 windows : 9.00 [kg]
passenger cabin width : 1.67 [m] cabin length : 4.35 [m] cabin height : 1.90 [m]
weight cabin furbishing : 31.70 [kg]
weight cabin floor : 46.54 [kg]
bracing : 55.1 [kg]
fuselage covering ( 40.3 [m2] doped linen fabric) : 12.4 [kg]
weight radio navigation equipment : 7.0 [kg]
weight instruments. : 4.0 [kg]
weight lighting : 2.5 [kg]
weight dual controls + indicators: 27.8 [kg]
weight seats : 60.0 [kg]
weight three 450 [litre] main fuel tanks empty : 108.1 [kg]
Kingsford Smith continued to make long distance flights, by now it had Australian registration VH-USU : 8 – 9 August 1928 non-stop across Australia from Melbourne to Perth, 10 – 11 September 1928 across the Tasman-sea to New Zeeland, 25 June – 10 July 1929 from Australia to London, 24-25 June 1930 from London to New York, with Evert van Dijk as his co-pilot. From New York he continued to San Francisco and now he was the first man who had flown round the world via Australia. In 1935 Kingsford Smith disappeared over the Andaman Sea flying a Lockheed Altair in an attempt to break the speed record from London to Australia. You would say it was not wise to change his 3-engined “Old Bus” for the high speed single engine Altair. The “Southern Cross” is preserved at the Kingsford Smith memorial , Brisbane airport and is shown in above picture. This is the only F.VIIb/3m that still exists.
weight air conditioning : 15 [kg]
weight fuel lines : 5 [kg]
weight engine mount and firewall : 11 [kg]
total weight fuselage : 935 [kg](17.8 [%])
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weight plywood wing covering : 71 [kg]
total weight ribs (92 ribs) : 312 [kg]
weight engine mounts : 22 [kg]
load on front upper spar (clmax) per running metre : 1189.5 [N]
load on rear upper spar (vmax) per running metre : 636.7 [N]
total weight 4 spars : 272 [kg]
PH-AFS was sold in August 1936 to Crilly airways but when this airline went bankrupt the aircraft found there way to the Spanish National forces and were used in the Spanish civil war.
weight wings : 654 [kg]
weight wing/square meter : 9.68 [kg]
cantilever wing without bracing cables
weight fin & rudder (5.5 [m2]) : 53.7 [kg]
weight stabilizer & elevator (7.6 [m2]): 74.1 [kg]
total weight wing surfaces & bracing : 804 [kg] (15.3 [%])
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wheel pressure : 2625.0 [kg]
weight 2 wheels (1250 [mm] by 250 [mm]) : 156.7 [kg]
weight tailskid : 8.4 [kg]
weight undercarriage with axle 72.8 [kg]
total weight landing gear : 237.8 [kg] (4.5 [%]
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calculated empty weight : 2999 [kg](57.1 [%])
weight oil for 7.3 hours flying : 88.0 [kg]
calculated operational weight empty : 3087 [kg] (58.8 [%])
published operational weight empty : 3050 [kg] (58.1 [%])
***o***
"
weight crew : 162 [kg]
weight fuel for 2.0 hours flying : 306 [kg]
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operational weight empty: 3556 [kg](67.7 [%])
weight 10 passengers : 770 [kg]
weight luggage & freight : 230 [kg]
operational weight loaded: 4556 [kg](67.7 [%])
fuel reserve : 694.3 [kg] enough for 4.53 [hours] flying
operational weight fully loaded : 5250 [kg] with fuel tank filled for 95 [%]
published maximum take-off weight : 5250 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (Take-off) : 7.82 [kg/kW]
power loading (operational without useful load) : 5.30 [kg/kW]
Lt.Cdr. Richard E. Byrd bought F.VII/3m N-X4204 for his Antarctic expedition. But because this expedition was sponsored by Henry Ford he had to switch his aircraft for a Ford Trimotor . He sold N-X4204 to the wealthy American Amy Guest . She named the aircraft “Friendship” and planned to make a transatlantic crossing with it, to be the first female to do this. She could not fly herself so she hired a flying crew. Here family opposed to this flight because of the involved danger and so she passed the honour upon Amelia Earhart.
F.VIIb/3m c/n 5028 “Friendship” reg. NX-4204, was fitted with floats, so in case of an emergency during its Atlantic crossing it could land on the water. c/n 5028 was built in The Netherlands early 1928. It was used by Amelia Earhart for the first women to cross the Atlantic in an airplane. She flew as passenger while the airplane was flown by Wilmer Stulz and Louis Edward Gordon , co-pilot and mechanic. On 17 June 1928 it took of from Trepassy , New Foundland. On the last part of the flight visibility was low. They saw the coast and landed in a bay, what proved to be near Burry Port , west of Llanelly in Wales. They had flown 3380km (through air, straight distance is ca. 3535 km > slight tailwind) in 20 hr 49 mins. (average speed 162 km/hr). It had Wrigh J-5C Whirlwind radials.
It had additional fuel tanks for total 3293 litre (2415 kg) enough for 3813 km flying
Weight empty : 2625 kg + weight crew 240 kg + weight oil 220 kg (for 25 hrs) + fuel 2415 kg = TOW 5500 kg
power loading (Take-off) 1 PUF: 11.73 [kg/kW]
total power : 671.1 [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 : 1.4 [g]
design flight time : 4.25 [hours]
design cycles : 2507 sorties, design hours : 10654 [hours]
operational wing loading : 516 [N/m^2]
wing stress (3 g) during operation : 160 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -2.06 ["]
max. angle of attack (stalling angle) : 11.81 ["]
angle of attack at max. speed : 1.12 ["]
The Fokker F.VIIb/3m was built in the UK under license by Avro. It got the indication Avro 618 Ten . The first 5 aircraft were sold to Australia ( reg. VH-UMF, VH-UMG, VH-UMH, VH-UMI, VH-UNA). They were powered with 240 hp Armstrong Siddeley Lynx IVB engines
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.17 [ ]
lift coefficient at max. angle of attack : 1.15 [ ]
lift coefficient at max. speed : 0.26 [ ]
induced drag coefficient at max. speed : 0.0042 [ ]
drag coefficient at max. speed : 0.0596 [ ]
drag coefficient (zero lift) : 0.0554 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 5097 [kg]): 117 [km/u]
landing speed at sea-level: 137 [km/hr]
min. drag speed (max endurance) : 145 [km/hr] at 2400 [m] (power:52 [%])
min. power speed (max range) : 145 [km/hr] at 2400 [m] (power:52 [%])
max. rate of climb speed : 121.6 [km/hr] at sea-level
cruising speed : 184 [km/hr] op 2400 [m] (power:74 [%])
design speed prop : 195 [km/hr]
maximum speed : 205 [km/hr] op 100 [m] (power:107 [%])
climbing speed at sea-level : 426 [m/min]
calculation : *9* (regarding various performances)
take-off speed : 142.3 [km/u]
static prop wash : 153 [km/u]
take-off distance at sea-level : 255 [m]
lift/drag ratio : 8.61 [ ]
climb to 1000m with max payload : 4.61 [min]
climb to 2000m with max payload : 10.53 [min]
climb to 3000m with max payload : 18.53 [min]
I found 15 F.VIIb/3m with PH- registration, 14 flew with the KLM. PH-AEN, PH-AEO, PH-AEZ, PH-AFO, PH-AFR, PH-AFS, PH-AGB, PH-AGR were used on regular basis with the KLM and were also used for flights all the way to Indonesia. For the other registration I could not find a track that they were used by KLM, those are PH-AFT, PH-AGJ, PH-AGX, PH-AIC, PH-AIM,PH-AIN, PH-AIW which were soon sold to CIDNA in France.
practical ceiling (operational weight empty 3556 [kg]) : 6733 [m]
practical ceiling fully loaded (mtow- 30 min.fuel = 5173 [kg] ) : 4563 [m]
max. dive speed : 486.3 [km/hr] at 3563 [m] height
turning speed at CLmax : 153.5 [km/u] at 50 [m] height
turn radius at 50m: 82 [m]
time needed for 360* turn 12.1 [seconds] at 50m
load factor at max. angle turn 2.46 ["g"]
calculation *10* (action radius & endurance)
published range : 1120 [km] with 2 crew and 1070.8 [kg] useful load and 88.1 [%] fuel
range : 1205 [km] with 2 crew and 1000.0 [kg] useful load and 94.8 [%] fuel
range : 1362 [km] with 10.0 passengers with each 10 [kg] luggage and 107.1 [%] fuel
Available Seat Kilometers (ASK) : 13618 [paskm]
max range theoretically with additional fuel tanks for total 2839.8 [litre] fuel : 2507.3 [km]
useful load with range 500km : 1666 [kg]
useful load with range 500km : 10 passengers
production (useful load): 307.47 [tonkm/hour]
production (passengers): 1845.00 [paskm/hour]
oil and fuel consumption per tonkm : 0.54 [kg]
oil and fuel consumption per paskm : 0.09 [kg]
fuel cost per paskm : 0.09 [eur]
crew cost per paskm : 0.08 [eur]
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time between engine failure : 245 [hr]
low risk for emergency landing, can continue flying with 1 engine out
writing off per paskm : 0.11 [eur]
insurance per paskm : 0.0162 [eur]
maintenance cost per paskm : 0.3146 [eur]
direct operating cost per paskm : 0.61 [eur]
Serious accidents :
CH-161 c/n 5207 flew against a chimney at Essen-Mulheim, Germany in fog 30 Oct 1930, all three crew members were killed. Spf AMS > BSL
Pilot : Otto Berchtold
The Swiss F.VIIb/3m had three bladed propellors. By miracle the 3 passengers escaped unhurt.
21 March 1931 Avro 618 Ten VH-UMF , c/n 241 of ANA disappears on a flight between Sydney and Melbourne. Only 27 years later it was found in the Snowy Mountains . Two crew and 6 passengers died in the crash.
06 December 1931 KLM PH-AFO c/n 5236 “Ooievaar” crashed during take-off from Bangkok, due to open emergency hatch. Pilot Thaeke Wiersma. Of the seven on board the aircraft only 1 survived.
Most serious crash happened with Avro 618 Ten G-ABLU “Apollo” c/n 528 on 30 December 1930. Lost in fog over snow covered Belgium it hit a telegraph pole at Ruiselede and crashed, killing all 10 on board. People came to the rescue, but then the wreckage exploded wounding even more people. Pilot : J.M. Gittens
Literature :
Piston-engined airliners page 13,15
Alles over de Fokker Friendship page 122
Praktisch handboek vliegtuigen deel 2 page 200,201
Fokker verkeersvliegtuigen page 56-63
Fokker – bouwer aan de wereldluchtvaart page
Van Spin tot Fokker 100 page
Fokker verkeersvliegtuigen 1920-1940 page
Fokkers “Roaring twenties”page
De Nederlandse vliegtuigen page
Ooievaar Bangkok (aviacrash.nl)
Fokker F.VIIB/3m Archives - This Day in Aviation
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 16 March 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4