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weight and performance calculations for the Gotha WD.14
Gotha WD.14
role : torpedo bomber
importance : **
first flight : operational : August 1917
country : Germany
design :
production : 69 aircraft
general information :
It was under-powered and difficult to fly loaded with a torpedo. Only high skilled pilots could carry out attacks with torpedo’s. After some unsuccessful torpedo attacks the allied counter measures made it to dangerous to carry on with this kind of raids. WD.14’s were then converted to long-range reconnaissance planes intended as substitute for the vulnerable Zeppelins. It had a jettisonable fuel tank fitted in the torpedo slings and with this fuel it had an endurance up to 10 hours. It was unable to stay airborne on one engine.
They could only operate from flat-calm sea, and many soon broke up due
to high seas.
The WD14 was tried as mine-layer but without success. Before abandoned altogether it was used as coastal convoy escort.
users : Germany
crew : 3
armament : 2 movable 7.92 [mm] (0.312 in) Parabellum MG 14 machine-guns
engine : 2 Benz Bz.IV liquid-cooled 6 -cylinder inline engine 220 [hp](164.1 KW)
dimensions :
wingspan : 25.5 [m], length : 14.45 [m], height : 5.0[m]
wing area : 132.0 [m^2]
weights :
max.take-off weight : 4642 [kg]
empty weight operational : 3150 [kg] bombload : 725 [kg]
performance :
maximum speed : 130 [km/hr] at sea-level
climbing speed : 78 [m/min]
service ceiling : unknown
endurance : 8.0 [hours]
estimated action radius : 468 [km]
description :
3-bay two float biplane no tip floats
two spar upper and lower wing
engines and floats attached to the wings, fuel and bombload in or attached to fuselage
airscrew :
two fixed pitch 2 -bladed tractor airscrews with max. efficiency :0.64 [ ]
estimated diameter airscrew 2.93 [m]
angle of attack prop : 12.64 [ ]
fine pitch
reduction : 1.00 [ ]
airscrew revs : 1400 [r.p.m.]
pitch at Max speed 1.55 [m]
blade-tip speed at Vmax and max revs. : 218 [m/s]
calculation : *1* (dimensions)
mean wing chord : 2.59 [m]
calculated wing chord (rounded tips): 2.77 [m]
wing aspect ratio : 9.85 []
estimated gap : 2.45 [m]
gap/chord : 0.95 [ ]
seize (span*length*height) : 1842 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 4.3 [kg/hr]
fuel consumption(cruise speed) : 86.3 [kg/hr] (117.7 [litre/hr]) at 80 [%] power
distance flown for 1 kg fuel : 1.36 [km/kg]
estimated total fuel capacity : 1069 [litre] (783 [kg])
calculation : *3* (weight)
weight engine(s) dry : 740.0 [kg] = 2.26 [kg/KW]
weight 54 litre oil tank : 6.8 [kg]
oil tank filled with 2.5 litre oil : 2.2 [kg]
oil in engine 18 litre oil : 16.4 [kg]
fuel in engine 2 litre fuel : 1.6 [kg]
weight 50 litre gravity patrol tank(s) : 4.9 [kg]
weight radiator : 49.2 [kg]
weight exhaust pipes & fuel lines 33.7 [kg]
weight self-starter : 8.0 [kg]
weight cowling 13.1 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 49.2 [kg]
total weight propulsion system : 918 [kg](19.8 [%])
***************************************************************
fuselage skeleton (wood gauge : 12.12 [cm]): 478 [kg]
bracing : 42.9 [kg]
fuselage covering ( 30.5 [m2] doped linen fabric) : 9.8 [kg]
weight controls + indicators: 9.2 [kg]
weight seats : 9.0 [kg]
weight other details, lighting set, etc. : 9.1 [kg]
weight bomb storage : 50.8 [kg]
weight two 509 [litre] main fuel tanks empty : 97.8 [kg]
weight interior + equipment + fuel lines: 58 [kg]
total weight fuselage : 765 [kg](16.5 [%])
***************************************************************
weight wing covering (doped linen fabric) : 84 [kg]
total weight ribs (147 ribs) : 276 [kg]
weight engine mounts : 16 [kg]
load on front upper spar (clmax) per running metre : 1054.6 [N]
load on rear upper spar (vmax) per running metre : 437.7 [N]
total weight 8 spars : 277 [kg]
weight wings : 637 [kg]
weight wing/square meter : 4.83 [kg]
weight 12 interplane struts & cabane : 141.2 [kg]
weight cables (155 [m]) : 77.8 [kg] (= 501 [gram] per metre)
diameter cable : 9.0 [mm]
weight fin & rudder (9.4 [m2]) : 46.9 [kg]
weight stabilizer & elevator (14.9 [m2]): 72.7 [kg]
total weight wing surfaces & bracing : 992 [kg] (21.4 [%])
*******************************************************************
weight machine-gun(s) : 19.0 [kg]
weight Schneider ring mounting mg :11.0 [kg]
weight armament : 30 [kg]
********************************************************************
weight floats : 381 [kg] (8.2 [%])
*******************************************************************
********************************************************************
calculated empty weight : 3086 [kg](66.5 [%])
weight oil for 9.6 hours flying : 40.9 [kg]
weight cooling fluids : 67.6 [kg]
weight 2 drums empty : 4.5 [kg]
weight ammunition (1000 rounds) : 32.7 [kg]
weight signal pistol with cartridges : 3.6 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
*******************************************************************
calculated operational weight empty : 3232 [kg] (69.6 [%])
published operational weight empty : 3150 [kg] (67.9 [%])
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weight crew : 243 [kg]
weight fuel for 2.0 hours flying : 173 [kg]
********************************************************************
operational weight : 3648 [kg](78.6 [%])
bomb load : 725 [kg]
operational weight bombing mission : 4373 [kg]
fuel reserve : 269 [kg] enough for 3.12 [hours] flying
operational weight fully loaded : 4642 [kg] with fuel tank filled for 56 [%]
published maximum take-off weight : 4642 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (operational without bombload) : 11.12 [kg/kW]
total power : 328.1 [kW] at 1400 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 1.9 [g] at 1000 [m]
limit load : 2.5 [g] ultimate load : 3.8 [g] load factor : 1.8 [g]
design flight time : 5.60 [hours]
design cycles : 375 sorties, design hours : 2100 [hours]
operational wing loading : 271 [N/m^2]
wing stress (3 g) during operation : 168 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.12 ["]
max. angle of attack (stalling angle) : 11.45 ["]
angle of attack at max. speed : 2.71 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.10 [ ]
lift coefficient at max. angle of attack : 1.13 [ ]
lift coefficient at max. speed : 0.34 [ ]
induced drag coefficient at max. speed : 0.0067 [ ]
drag coefficient at max. speed : 0.0545 [ ]
drag coefficient (zero lift) : 0.0478 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 71 [km/u]
landing speed at sea-level (OW without bombload): 86 [km/hr]
min. drag speed (max endurance) : 83 [km/hr] at 1000 [m](power :46 [%])
min. power speed (max range) : 96 [km/hr] at 1000 [m] (power:52 [%])
max. rate of climb speed : 81.4 [km/hr] at sea-level
cruising speed : 117 [km/hr] op 1000 [m] (power:73 [%])
design speed prop : 124 [km/hr]
maximum speed : 130 [km/hr] op 100 [m] (power:99 [%])
climbing speed at sea-level (without bombload) : 167 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 402 [m]
lift/drag ratio : 9.54 [ ]
max. practical ceiling : 4750 [m] with flying weight :3319 [kg]
practical ceiling (operational weight) : 4100 [m] with flying weight :3648 [kg] line 3385
practical ceiling fully loaded (mtow- 1 hour fuel) : 2450 [m] with flying weight :4556 [kg]
published ceiling (0 [m]
climb to 1500m (operational weight without bombload) : 10.15 [min]
max. dive speed : 345.0 [km/hr] at 1450 [m] height
load factor at max. angle turn 1.80 ["g"]
turn radius at 500m: 51 [m]
time needed for 360* turn 11.6 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 5.12 [hours] with 3 crew and 725 [kg] bombload and 56.4 [%] fuel
published endurance : 8.00 [hours] with 3 crew and possible useful (bomb) load : 477 [kg] and 88.1 [%] fuel
action radius : 778 [km] with 3 crew and 20[kg] photo camera or bombload
max range theoretically with additional fuel tanks for total 1864 [litre] fuel : 1853 [km]
useful load with action-radius 250km : 998 [kg]
production : 116.74 [tonkm/hour]
oil and fuel consumption per tonkm : 0.78 [kg]
_
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Literature :
Jane’s fighting aircraft WWI page 159
German aircraft of the first world war page 133
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
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(c) B van der Zalm 28 June 2020 contact : info.aircraftinvestigation@gmail.com python 3.7.4