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weight and performance calculations for the RAF R.E.7
RAF R.E.7
role : light bomber
importance : ***
first flight : 1915 operational : January 1916
country : United-Kingdom
design :
production : 250 aircraft
general information :
The RAF had designed at the start of WO I a new 152 kg bomb and this and
it’s carrying gear was tested on a modified R.E.5 in 1915. The R.E.7 developed from the R.E.5 was specially designed to carry the new bomb. It was very similar but had an even greater wing. It was also suited for reconnaissance and escort duties. Orders were placed for 500 aircraft but only half of this would be produced. Delivery started late in 1915, and the first squadron fully equipped with the type, 21 squadron, arrived January 1916 in France. The aircraft was of no use for escort-sorties because it’s defensive gun had a very limited field of fire from the observer’s front seat and it’s lack of manoeuvrability. Only from the early summer of 1916 the aircraft was used for bombing-missions. Already in august replacement started with the R.E.12 and it was withdrawn from frontline duties. But the R.E.7 was kept in use as trainer and for target-towing till 1918.
users : RFC
crew : 2
armament : 1 movable 7.70 [mm] (0.303 in) Lewis machine-gun for the observer
engine : 1 RAF 4a air-cooled 12 -cylinder V-engine 163 [hp](119.9 KW)
dimensions :
wingspan : 17.37 [m], length : 9.72 [m], height : 3.84[m]
wing area : 50.91 [m^2]
weights :
max.take-off weight : 1564 [kg]
empty weight operational : 1036 [kg] bombload : 152 [kg]
performance :
maximum speed : 134 [km/hr] at sea-level
service ceiling : 3200 [m]
endurance : 2.0 [hours]
estimated action radius : 121 [km]
description :
2½-bay biplane with fixed landing gear with nosewheel and tail strut
upper wingtips supported by slanted struts
two spar upper and lower wing
engines, landing gear, fuel and bombs in or attached to the fuselage
airscrew :
fixed pitch 4 -bladed tractor airscrew with max. efficiency :0.60 [ ]
estimated diameter airscrew 3.10 [m]
angle of attack prop : 18.77 [ ]
reduction : 0.50 [ ]
airscrew revs : 900 [r.p.m.]
pitch at Max speed 2.48 [m]
blade-tip speed at Vmax and max revs. : 151 [m/s]
calculation : *1* (dimensions)
mean wing chord : 1.67 [m]
calculated wing chord (rounded tips): 1.82 [m]
wing aspect ratio : 10.37 []
estimated gap : 1.86 [m]
gap/chord : 1.11 [ ]
seize (span*length*height) : 648 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 2.5 [kg/hr]
fuel consumption(cruise speed) : 33.8 [kg/hr] (46.1 [litre/hr]) at 68 [%] power
distance flown for 1 kg fuel : 3.57 [km/kg]
estimated total fuel capacity : 105 [litre] (77 [kg])
calculation : *3* (weight)
weight engine(s) dry : 308.0 [kg] = 2.57 [kg/KW]
weight reduction gear : 4.8 [kg]
weight 10 litre oil tank : 1.2 [kg]
oil tank filled with 0.9 litre oil : 0.8 [kg]
oil in engine 1 litre oil : 0.6 [kg]
fuel in engine 1 litre fuel : 0.6 [kg]
weight 20 litre gravity patrol tank(s) : 1.9 [kg]
weight cowling 4.8 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 42.0 [kg]
total weight propulsion system : 368 [kg](23.5 [%])
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fuselage skeleton (wood gauge : 7.46 [cm]): 139 [kg]
bracing : 9.5 [kg]
fuselage covering ( 17.8 [m2] doped linen fabric) : 5.7 [kg]
weight controls + indicators: 7.4 [kg]
weight seats : 6.0 [kg]
weight other details, lighting set, etc. : 5.1 [kg]
weight bomb storage : 10.6 [kg]
weight 85 [litre] main fuel tank empty : 8.2 [kg]
weight engine mounts & firewalls : 6 [kg]
total weight fuselage : 197 [kg](12.6 [%])
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weight wing covering (doped linen fabric) : 33 [kg]
total weight ribs (76 ribs) : 93 [kg]
load on front upper spar (clmax) per running metre : 592.4 [N]
load on rear upper spar (vmax) per running metre : 242.7 [N]
total weight 8 spars : 102 [kg]
weight wings : 228 [kg]
weight wing/square meter : 4.48 [kg]
weight 12 interplane struts & cabane : 52.8 [kg]
weight cables (82 [m]) : 13.2 [kg] (= 161 [gram] per metre)
diameter cable : 5.1 [mm]
weight fin & rudder (3.5 [m2]) : 16.2 [kg]
weight stabilizer & elevator (5.7 [m2]): 26.0 [kg]
total weight wing surfaces & bracing : 336 [kg] (21.5 [%])
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weight machine-gun(s) : 12.7 [kg]
weight pivot mounting mg :6.0 [kg]
weight armament : 19 [kg]
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wheel pressure : 688.2 [kg]
weight 3 wheels (780 [mm] by 98 [mm]) : 40.8 [kg]
weight tailskid : 3.3 [kg]
weight undercarriage with axle 66.2 [kg]
total weight landing gear : 110.3 [kg] (7.0 [%]
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calculated empty weight : 1031 [kg](65.9 [%])
weight oil for 2.4 hours flying : 6.0 [kg]
weight 5 drums empty : 1.0 [kg]
weight ammunition (235 rounds) : 7.5 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
*******************************************************************
calculated operational weight empty : 1045 [kg] (66.8 [%])
published operational weight empty : 1036 [kg] (66.2 [%])
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weight crew : 162 [kg]
weight fuel for 2.0 hours flying : 68 [kg]
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operational weight : 1275 [kg](81.5 [%])
bomb load : 152 [kg]
operational weight bombing mission : 1427 [kg]
fuel reserve : 9 [kg] enough for 0.27 [hours] flying
possible additional useful load : 128 [kg]
operational weight fully loaded : 1564 [kg] with fuel tank filled for 100 [%]
published maximum take-off weight : 1564 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (Take-off) : 13.05 [kg/kW]
total power : 119.9 [kW] at 1800 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 1.9 [g] at 1000 [m]
limit load : 3.0 [g] ultimate load : 4.5 [g] load factor : 1.8 [g]
design flight time : 1.60 [hours]
design cycles : 500 sorties, design hours : 800 [hours]
wing loading (MTOW) : 301 [N/m^2]
wing stress (3 g) during operation : 184 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.33 ["]
max. angle of attack (stalling angle) : 11.01 ["]
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 : 1.12 [ ]
lift coefficient at max. speed : 0.29 [ ]
induced drag coefficient at max. speed : 0.0035 [ ]
drag coefficient at max. speed : 0.0441 [ ]
drag coefficient (zero lift) : 0.0406 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 68 [km/u]
landing speed at sea-level (OW without bombload): 82 [km/hr]
min. drag speed (max endurance) = minimum speed*1.1 at cruise height : 81 [km/hr] at 1600 [m] (power:37 [%])
min. power speed (max range) : 92 [km/hr] at 1600 [m] (power:42 [%])
max. rate of climb speed : 80.5 [km/hr] at sea-level
cruising speed : 121 [km/hr] op 1600 [m] (power:67 [%])
design speed prop : 127 [km/hr]
maximum speed : 134 [km/hr] op 100 [m] (power:98 [%])
climbing speed at sea-level (without bombload) : 185 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 207 [m]
lift/drag ratio : 12.26 [ ]
max. practical ceiling : 4225 [m] with flying weight :1134 [kg]
practical ceiling (operational weight) : 3750 [m] with flying weight :1275 [kg] line 3385
practical ceiling fully loaded (mtow- 1 hour fuel) : 2925 [m] with flying weight :1530 [kg]
published ceiling (3200 [m]
climb to 1500m (without bombload) : 9.32 [min]
max. dive speed : 315.0 [km/hr] at 1925 [m] height
load factor at max. angle turn 1.94 ["g"]
turn radius at 500m: 50 [m]
time needed for 360* turn 11.0 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 2.27 [hours] with 2 crew and 280 [kg] bombload and 100.0 [%] fuel
published endurance : 2.00 [hours] with 2 crew and possible useful (bomb) load : 289 [kg] and 88.1 [%] fuel
action radius : 601 [km] with 2 crew and 20[kg] photo camera or bombload
max range theoretically with additional fuel tanks for total 609 [litre] fuel : 1593 [km]
useful load with action-radius 250km (with no gunner/observer) : 306 [kg]
useful load with action-radius 250km : 217 [kg]
production : 26.12 [tonkm/hour]
oil and fuel consumption per tonkm : 1.39 [kg]
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Literature :
Praktisch handbook vliegtuigen deel 1 blz.176
Bombers 1914-19 Page 58
Bomber 1914-1939 page 23
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/
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(c) B van der Zalm 23 March 2020 contact : info.aircraftinvestigation@gmail.com python 3.7.4