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weight and performance calculations for the Fokker D.II
Fokker D.II reg 1512/16 attached to Flieger Ersatz abteilung 10 in Boblingen
Fokker D.II
role : fighter
importance : ***
first flight : operational : June 1916
country : Germany
design : Martin Kreutzer
production : 202
general information : Problems with delivery of the inline Mercedes engines for the D.I
led Fokker to develop the D.II fitted with a rotary engine, based on the M.17 prototype. It was in use before the D.I. Dimensions were the same as for the D.I and also the performance was comparable. The aircraft still used wing-warping for control ! At the front the performance was only slightly better than the E.III, it was underpowered and it proved inferior to the new Nieuport 16 and 17 and were soon replaced by the better Albatros fighters.
D.II’s intercepted the bombers that raided Oberndorf, am-Neckar, 12 October 1916. The allied bombers aim was the Mauser arms factory.
users : Germany, Austria(20)
crew : 1
armament : 1 LMG08/15 Spandau 7.92 [mm] (0.312 in) machine-gun
engine : 1 Oberursel U.1 air-cooled 9 -cylinder atmospheric inlet-valve rotary engine
100.0 [hp] (73.6 KW)
dimensions :
wingspan : 8.75 [m], length : 6.4 [m], height : 2.55[m]
wing area : 18.0 [m^2]
weights :
max.take-off weight : 575 [kg]
empty weight operational : 384 [kg] bombload : 0 [kg]
performance :
maximum speed : 150 [km/hr] at sea-level
climbing speed : 252 [m/min]
service ceiling : 4000 [m]
endurance : 1.5 [hours]
estimated action radius : 101 [km]
description :
2-bay biplane with fixed landing gear and tail strut
two spar upper and lower wing
engines, landing gear, fuel and bombs in or attached to the fuselage
airscrew :
fixed pitch 2 -bladed tractor airscrew with max. efficiency :0.63 [ ]
estimated diameter airscrew 2.57 [m]
angle of attack prop : 18.99 [ ]
reduction : 1.00 [ ]
airscrew revs : 1200 [r.p.m.]
pitch at Max speed 2.08 [m]
blade-tip speed at Vmax and max revs. : 167 [m/s]
calculation : *1* (dimensions)
mean wing chord : 1.03 [m]
calculated wing chord (rounded tips): 1.15 [m]
wing aspect ratio : 8.51 []
estimated gap : 1.22 [m]
gap/chord : 1.19 [ ]
seize (span*length*height) : 143 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 6.3 [kg/hr]
fuel consumption(cruise speed) : 28.0 [kg/hr] (38.2 [litre/hr]) at 66 [%] power
distance flown for 1 kg fuel : 4.82 [km/kg]
estimated total fuel capacity : 65 [litre] (48 [kg])
calculation : *3* (weight)
weight engine(s) dry : 139.7 [kg] = 1.90 [kg/KW]
weight 14 litre oil tank : 1.8 [kg]
oil tank filled with 0.6 litre oil : 0.5 [kg]
oil in engine 0 litre oil : 0.4 [kg]
fuel in engine 1 litre fuel : 0.4 [kg]
weight 16 litre gravity patrol tank(s) : 1.6 [kg]
weight cowling 2.9 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 16.9 [kg]
total weight propulsion system : 162 [kg](28.2 [%])
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Fokker D.II flown by Otto Dessloch. Force landed in Switzerland on 13 October 1916
fuselage skeleton (wood gauge : 4.98 [cm]): 41 [kg]
bracing : 1.8 [kg]
fuselage covering ( 7.7 [m2] doped linen fabric) : 2.5 [kg]
weight controls + indicators: 5.4 [kg]
weight seats : 3.0 [kg]
weight other details, lighting set, etc. : 5.1 [kg]
weight 49 [litre] main fuel tank empty : 4.7 [kg]
weight engine mounts & firewalls : 4 [kg]
total weight fuselage : 67 [kg](11.6 [%])
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weight wing covering (doped linen fabric) : 12 [kg]
total weight ribs (46 ribs) : 34 [kg]
load on front upper spar (clmax) per running metre : 571.4 [N]
load on rear upper spar (vmax) per running metre : 193.6 [N]
total weight 8 spars : 25 [kg]
weight wings : 71 [kg]
weight wing/square meter : 3.93 [kg]
weight 8 interplane struts & cabane : 6.4 [kg]
weight cables (52 [m]) : 2.0 [kg] (= 39 [gram] per metre)
diameter cable : 2.5 [mm]
weight fin & rudder (0.9 [m2]) : 3.6 [kg]
weight stabilizer & elevator (2.0 [m2]): 8.1 [kg]
total weight wing surfaces & bracing : 91 [kg] (15.8 [%])
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weight machine-gun(s) : 17.0 [kg]
weight ammunition magazine(s) :2.3 [kg]
weight Fokker Stangensteuerung synchronization gear : 1.0 [kg]
weight armament : 20 [kg]
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An acrylic I did of a Fokker D-II fighter engaging a Nieuport 11 of the French air-force. This action took place during the famous Allied bombing raid on the German town of Oberndorf where the Mauser rifle factory was situated. In the first large-scale aerial daylight bombing raid in history, over 60 French and British light bombers, including Farmans, Breguet Vs and Sopwith 1&1/2 Strutters flew to Germany on October 12th 1916. Accompanying them was an escort of Nieuport 11s of the French air-force and the Lafayette Escadrille.
The raid was not a success, many of the Allied bombers had to turn back, either lost or suffering mechanical problems and several had to force or crash-land in German territory. Of those that did reach Oberndorf, they achieved only a few bomb hits in or around the factory, doing little damage.
German fighters, including Fokker D-IIs and two-seater Roland C-IIs, rose to intercept the Allied formation.
French-American ace Raoul Lufbery was in the air that day and he was credited with one of the Rolands shot down. It was his 5th confirmed victory, making him an Ace.
German pilot Otto Kissenberth, piloting a Fokker D-II, flew two sorties that day, attacking the bomber formation on both its inward and homeward legs. In what was one of his first fighter sorties, Kissenberth shot down two Farmans and a Breguet V. It would be well over a year before he had the chance to score again but he finished the war with 20 kills to his name.
Ten Allied bombers failed to return and an 11th crashed on landing. The raid, however, did teach the Allies many vital lessons on long-range bombing tactics.
wheel pressure : 287.5 [kg]
weight 2 wheels (680 [mm] by 81 [mm]) : 13.8 [kg]
weight tailskid : 1.5 [kg]
weight undercarriage with axle 16.8 [kg]
total weight landing gear : 32.0 [kg] (5.6 [%]
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calculated empty weight : 372 [kg](64.8 [%])
weight oil for 1.8 hours flying : 11.3 [kg]
weight ammunition (500 rounds) : 14.1 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
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calculated operational weight empty : 399 [kg] (69.4 [%])
published operational weight empty : 384 [kg] (66.8 [%])
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weight crew : 81 [kg]
weight fuel for 1.5 hours flying : 42 [kg]
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operational weight : 522 [kg](90.8 [%])
estimated bomb load : 25 [kg]
operational weight bombing mission : 547 [kg]
fuel reserve : 6 [kg] enough for 0.20 [hours] flying
Fokker D.II Ltn Fritz Grunzweig Jasta 16
Lt.Fritz Grünzweig, a fighter pilot also renowned as an excellent painter, cartoonist and a buffoon. His machines were adorned with elaborated mouths and eyes on the cowlings and thus belonged to the most eye-catching of all Fokker D.IIs
possible additional useful load : 22 [kg]
operational weight fully loaded : 575 [kg] with fuel tank filled for 100 [%]
published maximum take-off weight : 575 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (operational without bombload) : 7.10 [kg/kW]
total power : 73.6 [kW] at 1200 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 2.5 [g] at 1000 [m]
limit load : 4.5 [g] ultimate load : 6.8 [g] load factor : 2.2 [g]
design flight time : 1.20 [hours]
Kesta = Kampfeinsitzerstaffel
design cycles : 375 sorties, design hours : 450 [hours]
operational wing loading : 284 [N/m^2]
wing stress (3 g) during operation : 217 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.15 ["]
max. angle of attack (stalling angle) : 12.02 ["]
angle of attack at max. speed : 1.96 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.10 [ ]
lift coefficient at max. angle of attack : 1.14 [ ]
lift coefficient at max. speed : 0.27 [ ]
induced drag coefficient at max. speed : 0.0048 [ ]
drag coefficient at max. speed : 0.0580 [ ]
drag coefficient (zero lift) : 0.0531 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 73 [km/u]
landing speed at sea-level (OW without bombload): 87 [km/hr]
min. drag speed (max endurance) : 91 [km/hr] at 2000 [m](power :38 [%])
min. power speed (max range) : 104 [km/hr] at 2000 [m] (power:43 [%])
max. rate of climb speed : 90.7 [km/hr] at sea-level
cruising speed : 135 [km/hr] op 2000 [m] (power:66 [%])
design speed prop : 146 [km/hr]
maximum speed : 150 [km/hr] op 100 [m] (power:99 [%])
climbing speed at sea-level (without bombload) : 284 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 153 [m]
lift/drag ratio : 8.41 [ ]
max. practical ceiling : 4925 [m] with flying weight :479 [kg]
practical ceiling (operational weight): 4500 [m] with flying weight :522 [kg]
practical ceiling fully loaded (mtow- 1 hour fuel) : 4250 [m] with flying weight :547 [kg]
published ceiling (4000 [m]
climb to 1500m (without bombload) : 5.97 [min]
climb to 3000m (without bombload) : 15.26 [min]
max. dive speed : 318.3 [km/hr] at 3250 [m] height
load factor at max. angle turn 2.14 ["g"]
turn radius at 500m: 49 [m]
time needed for 360* turn 10.2 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 1.70 [hours] with 1 crew and 47 [kg] useful (bomb)load and 100.0 [%] fuel
published endurance : 1.50 [hours] with 1 crew and possible useful (bomb) load : 53 [kg] and 88.1 [%] fuel
action radius : 181 [km] with 1 crew and 20[kg] photo camera/radio transmitter or bombload
max range theoretically with additional fuel tanks for total 151 [litre] fuel : 532 [km]
useful load with action-radius 250km : 7 [kg]
production : 0.90 [tonkm/hour]
oil and fuel consumption per tonkm : 38.09 [kg]
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Literature :
Fokkers uit de eerste wereldoorlog page 34,35
Fighters 1914-19 page 64
Warplanes WWI page 56, 67f, 70
Jane’s fighting aircraft WWI page 148
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 23 January 2020 contact : info.aircraftinvestigation@gmail.com python 3.7.4