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weight and performance calculations for the Airco D.H.9 WWI light bomber biplane
DH9 with 240 hp BHP engine
Airco D.H.9
role : light bomber
importance : ****
first flight : operational : December 1917
country : United-Kingdom
design :
production : 6295 aircraft
general information :
The D.H.9 was developed from the D.H.4. The fuel tank was now placed before the pilot so he and the gunner could now be seated closer together for better co-operation. The D.H.9 was much used but due to engine problems performance were inferior to that of the D.H.4 it replaced ! The airframe was good with pleasant handling qualities. Production of the excellent Rolls Royce Eagle were falling far short of demand. The Puma engine was intended for mass production and the DH9 was designed to take this engine. Due to engine failure the intended 300 hp output was de-
rated to 230 hp. With bombload the ceiling was limited to 3658m. At this height it could be easily intercepted by German fighters.
Puma engine was directly derived from the 230 hp BHP engine
Gap : 1.67 m chord : 1.67 m, airscrew diam : 2.90 m pitch : 2.10 m > met 240 hp BHP engine at 1525 rpm
Total area of tail (empennage) : 7.53 m2 area of elevators : 1.11 m2 area of rudder : 1.27 m2 area of fin : 0.50 m2 tank capacity : 74 gallon = 336 litre.
Bombs could be carried under the wing and under the fuselage, typical loads being two 104 kg bombs or four 51 kg bombs. There was also possibility to carry smaller bombs internally.
users : RFC
crew : 2
armament : 1 synchronized 7.70 [mm] (0.303 in) Vickers machine-gun
and 1 movable 7.70 [mm] (0.303 in) Lewis machine-gun for the observer
engine : 1 Armstrong Siddeley Puma liquid-cooled 6 -cylinder inline engine 230 [hp](169.2 KW)
dimensions :
wingspan : 12.92 [m], length : 9.29 [m], height : 3.4[m]
wing area : 40.32 [m^2]
weights :
max.take-off weight : 1662 [kg]
empty weight operational : 1014 [kg] bombload : 209 [kg]
performance :
maximum speed : 180 [km/u] op 3048 [m]
service ceiling : 4724 [m] , with full bombload 3650 [m]
endurance : 6.71 [hours]
estimated action radius : 544 [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 :0.67 [ ]
diameter airscrew 2.90 [m]
angle of attack prop : 17.41 [ ]
reduction : 1.00 [ ]
airscrew revs : 1400 [r.p.m.]
pitch at Max speed 2.14 [m]
blade-tip speed at Vmax and max revs. : 218 [m/s]
calculation : *1* (dimensions)
mean wing chord : 1.56 [m]
calculated wing chord (rounded tips): 1.71 [m]
wing aspect ratio : 8.28 []
gap : 1.67 [m]
gap/chord : 1.07 [ ]
seize (span*length*height) : 408 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 3.4 [kg/hr]
fuel consumption(cruise speed) : 31.0 [kg/hr] (42.3 [litre/hr]) at 53 [%] power
distance flown for 1 kg fuel : 5.22 [km/kg]
estimated total fuel capacity : 322 [litre] (236 [kg])
calculation : *3* (weight)
weight engine(s) dry : 308.0 [kg] = 1.82 [kg/KW]
weight 35 litre oil tank : 2.9 [kg]
oil tank filled with 1.3 litre oil : 1.1 [kg]
oil in engine 9 litre oil : 8.5 [kg]
fuel in engine 1 litre fuel : 0.8 [kg]
weight 18 litre gravity patrol tank(s) : 2.7 [kg]
weight radiator : 27.1 [kg]
weight exhaust pipes & fuel lines 21.5 [kg]
weight self-starter : 4.1 [kg]
weight cowling 6.8 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 25.4 [kg]
total weight propulsion system : 406 [kg](24.4 [%])
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fuselage skeleton (wood gauge : 7.20 [cm]): 123 [kg]
bracing : 8.1 [kg]
fuselage covering ( 16.3 [m2] doped linen fabric) : 5.2 [kg]
weight controls + indicators: 6.7 [kg]
weight seats : 6.0 [kg]
weight other details, lighting set, etc. : 5.1 [kg]
weight bomb storage : 14.6 [kg]
weight bomb sight : 1.0 [kg]
weight 304 [litre] main fuel tank empty : 24.3 [kg]
weight oxygen/compressed air flasks for high altitude : 14.6 [kg]
weight engine mounts & firewalls : 8 [kg]
total weight fuselage : 217 [kg](13.1 [%])
***************************************************************
weight wing covering (doped linen fabric) : 26 [kg]
total weight ribs (87 ribs) : 99 [kg]
load on front upper spar (clmax) per running metre : 781.7 [N]
load on rear upper spar (vmax) per running metre : 365.9 [N]
total weight 8 spars : 75 [kg]
weight wings : 199 [kg]
weight wing/square meter : 4.94 [kg]
weight 8 interplane struts & cabane : 23.2 [kg]
weight cables (74 [m]) : 8.8 [kg] (= 118 [gram] per metre)
diameter cable : 4.4 [mm]
weight fin & rudder (1.9 [m2]) : 9.9 [kg]
weight stabilizer & elevator (4.5 [m2]): 22.7 [kg]
total weight wing surfaces & bracing : 264 [kg] (15.9 [%])
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weight machine-gun(s) : 28.6 [kg]
weight Scarff ring mounting mg :6.9 [kg]
weight ammunition magazine(s) :1.8 [kg]
weight Constaninesco synchronizing system : 1.2 [kg]
weight Aldis gunsight : 0.8 [kg]
weight armament : 39 [kg]
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wheel pressure : 831.0 [kg]
weight 2 wheels (810 [mm] by 125 [mm]) : 41.7 [kg]
weight tailskid : 5.6 [kg]
weight undercarriage with axle 24.5 [kg]
total weight landing gear : 71.9 [kg] (4.3 [%]
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calculated empty weight : 998 [kg](60.1 [%])
weight oil for 8.1 hours flying : 27.2 [kg]
weight cooling fluids : 36.5 [kg]
weight 5 drums empty : 1.0 [kg]
weight ammunition (635 rounds) : 18.5 [kg]
weight Very pistol with cartridges : 3.6 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
*******************************************************************
calculated operational weight empty : 1085 [kg] (65.3 [%])
published operational weight empty : 1014 [kg] (61.0 [%])
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weight crew : 162 [kg]
weight (electrical heated) clothing for high altitude : 12.0 [kg]
weight fuel for 2.0 hours flying : 62 [kg]
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operational weight : 1321 [kg](79.5 [%])
bomb load : 209 [kg]
operational weight bombing mission : 1530 [kg]
fuel reserve : 132 [kg] enough for 4.24 [hours] flying
operational weight fully loaded : 1662 [kg] with fuel tank filled for 82 [%]
published maximum take-off weight : 1662 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (Take-off) : 9.82 [kg/kW]
total power : 169.2 [kW] at 1400 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 2.7 [g] at 1000 [m]
limit load : 3.0 [g] ultimate load : 4.5 [g] load factor : 1.6 [g]
design flight time : 4.70 [hours]
design cycles : 224 sorties, design hours : 1050 [hours]
wing loading (MTOW) : 404 [N/m^2]
wing stress (3 g) during operation : 226 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.39 ["]
DH9 in Musee de l’air, le Bourget
max. angle of attack (stalling angle) : 11.88 ["]
angle of attack at max. speed : 1.90 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.12 [ ]
lift coefficient at max. angle of attack : 1.15 [ ]
lift coefficient at max. speed : 0.28 [ ]
induced drag coefficient at max. speed : 0.0055 [ ]
drag coefficient at max. speed : 0.0290 [ ]
drag coefficient (zero lift) : 0.0235 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 77 [km/u]
landing speed at sea-level (OW without bombload): 92 [km/hr]
min. drag speed (max endurance) : 125 [km/hr] at 3048 [m](power :34 [%])
min. power speed (max range) : 132 [km/hr] at 3048 [m] (power:36 [%])
max. rate of climb speed : 118.5 [km/hr] at sea-level
cruising speed : 162 [km/hr] op 3048 [m] (power:47 [%])
design speed prop : 171 [km/hr]
maximum speed : 180 [km/hr] op 3048 [m] (power:59 [%])
climbing speed at sea-level (without bombload) : 313 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 208 [m]
lift/drag ratio : 12.48 [ ]
max. practical ceiling : 5150 [m] with flying weight :1159 [kg]
practical ceiling (operational weight): 4625 [m] with flying weight :1321 [kg]
practical ceiling fully loaded (mtow- 1 hour fuel) : 3650 [m] with flying weight :1631 [kg]
** fully loaded for bombing mission no oxygen flasks and no heated clothing needed
published ceiling (4724 [m]
climb to 1500m (without bombload) : 5.43 [min]
climb to 3000m (without bombload) : 13.83 [min]
max. dive speed : 497.1 [km/hr] at 2650 [m] height
load factor at max. angle turn 1.94 ["g"]
turn radius at 500m: 66 [m]
time needed for 360* turn 12.6 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 6.63 [hours] with 2 crew and 209 [kg] bombload and 87.0 [%] fuel
published endurance : 6.71 [hours] with 2 crew and possible useful (bomb) load : 206 [kg] and 88.1 [%] fuel
action radius : 1030 [km] with 2 crew and 20[kg] photo camera/radio transmitter or bombload
max range theoretically with additional fuel tanks for total 708 [litre] fuel : 2710 [km]
useful load with action-radius 250km : 319 [kg]
production : 51.66 [tonkm/hour]
oil and fuel consumption per tonkm : 0.67 [kg]
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Literature :
Warplanes WW1 page 132,133,134f
Praktisch handboek vliegtuigen deel 1 page 205
Bombers 1914-19 page 141,142
Jane’s FAWOI page 43dft
Armament of British aircraft 1909-1939 page 130,131
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.
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(c) B van der Zalm 15 September 2019 contact : info.aircraftinvestigation@gmail.com python 3.7.4