Aircraft investigation
weight and performance calculations for the Pfalz D.XII WWI fighter biplane
Pfalz D.XII
role : fighter
importance : ****
first flight : March 1918 operational : July 1918
country : Germany
design : Rudolph Gehringer
production : 800 aircraft
general information :
The Pfalz D. XII was an excellent
Fighter plane, but it was overshadowed by the Fokker D.VII.
The D.XII entered service along with the Fokker D.VII.
This direct confrontation gave the pilots a lack of self-confidence in the possibilities of the Pfalz fighter aircraft. The D. XII was not as good as the D. VII but
it was strong, fast and manoeuvrable and it was able to fight his allied opponents with succes. The airplane it still with tension wires reinforced, while the Fokker D.VII had cantilever wings with no outside bracing wires, giving better aerodynamics and less maintenance for the D.VII.
The D. XII had a solid construction that gave good diving capacities.
Wing design had been copied from a captured SPAD VII.
Petrol capacity : 18.75 gallons = 85 litre, endurance : 2.5 hrs
propeller : Heine No.26.206 diam. 2.78m pitch 2.0 m, made off 8 layers Mahony and
walnut wood.
users : Luftwaffe
crew : 1
armament : 2 synchronized 7.92 [mm] (0.312 in) Spandau LMG 08/15 machine-guns
engine : 1 Mercedes D.IIIa liquid-cooled 6 -cylinder inline engine 175 [hp](128.7 KW)
dimensions :
wingspan : 9.0 [m], length : 6.35 [m], height : 2.7[m]
wing area : 21.7 [m^2]
weights :
max.take-off weight : 902 [kg]
empty weight operational : 716 [kg] bombload : 0 [kg]
performance :
maximum speed : 170 [km/u] op 3000 [m]
climbing speed : 245 [m/min]
service ceiling : 5640 [m]
endurance : 1.93 [hours]
estimated action radius : 148 [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 :0.64 [ ]
diameter airscrew 2.78 [m]
angle of attack prop : 17.17 [ ]
reduction : 1.00 [ ]
airscrew revs : 1400 [r.p.m.]
pitch at Max speed 2.02 [m]
blade-tip speed at Vmax and max revs. : 209 [m/s]
calculation : *1* (dimensions)
mean wing chord : 1.21 [m]
calculated wing chord (rounded tips): 1.35 [m]
wing aspect ratio : 7.47 []
gap : 1.35 [m]
gap/chord : 1.12 [ ]
seize (span*length*height) : 154 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 3.6 [kg/hr]
fuel consumption(cruise speed) : 28.4 [kg/hr] (38.7 [litre/hr]) at 63 [%] power
distance flown for 1 kg fuel : 5.39 [km/kg]
estimated total fuel capacity : 85 [litre] (62 [kg])
calculation : *3* (weight)
weight engine(s) dry : 297.0 [kg] = 2.31 [kg/KW]
weight 13 litre oil tank : 1.1 [kg]
oil tank filled with 1.0 litre oil : 0.9 [kg]
oil in engine 7 litre oil : 6.4 [kg]
fuel in engine 1 litre fuel : 0.6 [kg]
weight 16 litre gravity patrol tank(s) : 2.5 [kg]
weight radiator : 18.4 [kg]
weight exhaust pipes & fuel lines 11.6 [kg]
weight cowling 5.1 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 19.0 [kg]
total weight propulsion system : 362 [kg](40.1 [%])
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fuselage skeleton (wood gauge : 6.20 [cm]): 62 [kg]
bracing : 2.8 [kg]
fuselage covering ( 7.6 [m2] doped linen fabric) : 2.4 [kg]
weight controls + indicators: 5.4 [kg]
weight seats : 3.0 [kg]
weight other details, lighting set, etc. : 5.1 [kg]
weight 68 [litre] main fuel tank empty : 5.5 [kg]
weight engine mounts & firewalls : 6 [kg]
total weight fuselage : 93 [kg](10.3 [%])
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weight wing covering (doped linen fabric) : 14 [kg]
total weight ribs (61 ribs) : 54 [kg]
load on front upper spar (clmax) per running metre : 862.8 [N]
load on rear upper spar (vmax) per running metre : 295.4 [N]
total weight 8 spars : 40 [kg]
weight wings : 108 [kg]
weight wing/square meter : 4.96 [kg]
weight 8 interplane struts & cabane : 10.8 [kg]
weight cables (55 [m]) : 3.5 [kg] (= 63 [gram] per metre)
diameter cable : 3.2 [mm]
weight fin & rudder (0.9 [m2]) : 4.8 [kg]
weight stabilizer & elevator (2.4 [m2]): 12.3 [kg]
total weight wing surfaces & bracing : 139 [kg] (15.4 [%])
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weight machine-gun(s) : 34.0 [kg]
weight ammunition magazine(s) :3.5 [kg]
weight Fokker Zentralsteuerung synchronization gear : 2.0 [kg]
weight armament : 40 [kg]
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wheel pressure : 451.0 [kg]
weight 2 wheels (800 [mm] by 101 [mm]) : 21.7 [kg]
weight tailskid : 2.3 [kg]
weight undercarriage with axle 19.3 [kg]
total weight landing gear : 43.2 [kg] (4.8 [%]
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According www.wingnutwings.com a D.IIIau engine was installed.
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calculated empty weight : 676 [kg](75.0 [%])
weight oil for 2.3 hours flying : 8.3 [kg]
weight cooling fluids : 27.8 [kg]
weight ammunition (1000 rounds) : 28.2 [kg]
weight signal pistol with cartridges : 3.6 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
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calculated operational weight empty : 745 [kg] (82.6 [%])
published operational weight empty : 716 [kg] (79.4 [%])
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weight crew : 81 [kg]
weight fuel for 1.5 hours flying : 43 [kg]
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operational weight : 869 [kg](96.3 [%])
estimated bomb load : 25 [kg]
operational weight bombing mission : 894 [kg]
fuel reserve : 8 [kg] enough for 0.28 [hours] flying
operational weight fully loaded : 902 [kg] with fuel tank filled for 81 [%]
published maximum take-off weight : 902 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (operational without bombload) : 6.75 [kg/kW]
total power : 128.7 [kW] at 1400 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 2.3 [g] at 1000 [m]
limit load : 4.5 [g] ultimate load : 6.8 [g] load factor : 2.2 [g]
design flight time : 1.54 [hours]
design cycles : 324 sorties, design hours : 500 [hours]
operational wing loading : 393 [N/m^2]
wing stress (3 g) during operation : 238 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -2.02 ["]
max. angle of attack (stalling angle) : 11.62 ["]
angle of attack at max. speed : 2.58 ["]
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 : 0.39 [ ]
induced drag coefficient at max. speed : 0.0114 [ ]
drag coefficient at max. speed : 0.0551 [ ]
drag coefficient (zero lift) : 0.0437 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 85 [km/u]
landing speed at sea-level (OW without bombload): 102 [km/hr]
min. drag speed (max endurance) : 121 [km/hr] at 3000 [m](power :43 [%])
min. power speed (max range) : 134 [km/hr] at 3000 [m] (power:47 [%])
max. rate of climb speed : 110.3 [km/hr] at sea-level
cruising speed : 153 [km/hr] op 3000 [m] (power:56 [%])
design speed prop : 165 [km/hr]
maximum speed : 170 [km/hr] op 3000 [m] (power:70 [%])
climbing speed at sea-level (without bombload) : 303 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 157 [m]
lift/drag ratio : 8.69 [ ]
max. practical ceiling : 5900 [m] with flying weight :808 [kg]
practical ceiling (operational weight): 5375 [m] with flying weight :869 [kg]
practical ceiling fully loaded (mtow- 1 hour fuel) : 5350 [m] with flying weight :874 [kg]
published ceiling (5640 [m]
climb to 1500m (without bombload) : 5.48 [min]
climb to 3000m (without bombload) : 13.25 [min]
max. dive speed : 415.2 [km/hr] at 4350 [m] height
load factor at max. angle turn 2.00 ["g"]
turn radius at 500m: 69 [m]
time needed for 360* turn 12.7 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 1.96 [hours] with 1 crew and 20 [kg] useful load and 89.4 [%] fuel
published endurance : 1.93 [hours] with 1 crew and possible useful (bomb) load : 21 [kg] and 88.1 [%] fuel
action radius : 150 [km] with 1 crew and 20[kg] photo camera/radio transmitter or bombload
max range theoretically with additional fuel tanks for total 148 [litre] fuel : 585 [km]
useful load with action-radius 250km : 16 [kg]
production : 2.42 [tonkm/hour]
oil and fuel consumption per tonkm : 13.20 [kg]
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literature :
Jane’s Fighting Aircraft WWI page 182,183
Praktisch handboek vliegtuigen deel 1 page 289
Air International April 90 page 203
Fighters 1914-19 page 42,120
Warplanes WWI page 156f
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 17 November 2019 contact : info.aircraftinvestigation@gmail.com python 3.7.4