AIRCRAFT INVESTIGATION

weight and performance calculations for the Vickers F.B.5 Gunbus

Vickers F.B.5 Gunbus

role : fighter

importance : ****

first flight : 17 July 1914 operational : November 1914

country : United-Kingdom

design : Archibald Lowe

production : 224 aircraft (at Crayford, London suburb)(99 in France and 6 in Denmark)

general information :

In 1912 Vickers was already developing a fighter plane that could shoot down another plane. The result, the "Destroyer" was seen at the Olympia air show in February 1913. However, it crashed on its first flight. The Gunbus was the first aircraft developed as fighter plane. The British had no solution for shooting through the propellor-disc and therefore came with a aircraft with pusher propellor. This gave the observer-gunner a clear field of fire forward and sideward and this seemed like a logical development. However, the push-screwed planes were slower than those with pull screw due to the extra amount of wires and tubes needed to carry the tail and by the weight of a 2nd crew member. The free field of fire is of little use if you can't get to the opponent. (tfs049). The F.B.5 (F.B. = Fighter Biplane) was too slow to chase an enemy plane and if it was forced into a fight it couldn't escape.

In practice, it could only escort the unarmed scouts, and in this role it proved useful to keep the enemy at bay. The question is how many planes fell prey to the Gunbus, which is indicative that only the duo pilot/observer Lionel Rees and James McKinley Hargreaves flying in an F.B.5 became aces. Initially, the intention was to install a Wolseley engine, but this one was not a success.

The Monosoupape (single valve) engines built in Britain were less reliable than the French and very inefficient with the valve system. The Gunbus was plagued by engine failures.

The first F.B.5 was delivered to the sixt squadron of the RFC in Netheravon in November 1914. On 25 December 1914, the F.B.5 first saw action when The F.B.5 s/n 664 took off from Joyce Green Airfield, at Dartford to intercept a Friedrichshafen FF29 which had just thrown off the first German bomb on British soil at Dover. However, the Lewis machine gun blocked as usual and they could only fire some shots with a carbine. The FF29 was hit but managed to escape.

In mid-January 1915, the same crew, 2nd Lt. Montagu Reaney Chidson and D.C.W. Sanders the^1th flew the fisrt F.B.5 (s/n 1621) to France, however, they were forced to land behind the German lines and the new plane fell into German hands. They probably weren't impressed and they didn't copy this configuration, as they had done before with good Allied planes like the Morane Saulnier "Parasol".

In February 1915 the first aircraft arrived on the western front. The first were delivered to No.2 SQ on February 5, 1915. Several squadrons were allocated 1 or 2 aircraft until No.11 SQ was fully equipped with the F.B.5, and became the very first squadron equipped exclusively with fighter aircraft. On July 25, 1915 it became operational from Villers-Brettonneux (East of Amiens).

The Gunbus was deployed for escort but also deployed for artillery observation, aerial photography and reconnaissance.

2nd Lt. Gilbert.S.M. Insall of 11 squadron RFC received the VC for an action on November 7, 1915 in which he destroyed a German Aviatik plane from a Gunbus. Insall flew along with first class mechanic T.H. Donald. Near Achiet-le-Grand, they attack the Aviatik 2-seater. The Aviatik was hit in the engine and then makes a rough landing on a ploughed field 4 miles south-east of Arras. The Gunbus dives to 500 ft and opens fire. The German crew fled and the British throw a incendiary bomb on the Aviatik. They fly at 2000 ft over the German trenches, and they are badly shot. They are hit in the fuel tank and managed to make an emergency landing just 500m within their own lines. They got under enemy artillery fire and 150 grenades are falling into their neighborhood. However, they stay by their plane and at night they manage to make their plane ready again and at sunrise they flew back to their base.

Lt.Insall couldn't personally receive the VC because on December 14, 1915 he and T.H. Donald was brought down by Hauptmann Martin Zander. He's injured and captured as prisoner of war.

Also 18 squadron RFC was exclusively equipped with the Gunbus.

In autumn 1915, the F.B.5 was no match for the Fokker E.I.

In december 1915, the F.B.9 entered service,

this was an improved F.B.5. It had no more skis,

the wings were rounded.

In July 1916, the F.B.5 was withdrawn from the front,

it was no longer up against the new fighter planes with

synchronized machine guns. It was still quite a time

used as training aircraft.

No original F.B.5 has been preserved, but a replica was built in the 1950s that can be seen at the RAF museum in Hendon. This was given the registration 2345 "Bombay", a machine of 18 squadron that was flown by Captain Hereward de Havilland. Minimum speed : 70 km/h

users : RFC, France, Denmark

crew : 2

armament : 1 movable 7.70 [mm] (0.303 in) Vickers machine-gun for the observer

engine : 1 Gnome B2 Monosoupape air-cooled 9 -cylinder Monosoupape rotary engine 100 [hp](73.6 KW)

dimensions :

wingspan : 11.13 [m], length : 8.28 [m], height : 3.5[m]

wing area : 35.49 [m^2]

weights :

max.take-off weight : 930 [kg]

empty weight operational : 553 [kg] bombload : 0 [kg]

performance :

maximum speed : 113 [km/u] op 1524 [m]

climbing speed : 96 [m/min]

service ceiling : 2743 [m]

endurance : 4.0 [hours]

estimated action radius : 203 [km]

description :

2-bay biplane with fixed landing gear and tail strut

two spar upper and lower wing

tail supported by two open tail booms

engines, landing gear, fuel and bombs in or attached to the fuselage

airscrew :

fixed pitch 2 -bladed pusher airscrew with max. efficiency :0.66 [ ]

estimated diameter airscrew 2.76 [m]

angle of attack prop : 14.02 [ ]

fine pitch

reduction : 1.00 [ ]

airscrew revs : 1160 [r.p.m.]

pitch at Max speed 1.62 [m]

blade-tip speed at Vmax and max revs. : 171 [m/s]

calculation : *1* (dimensions)

mean wing chord : 1.59 [m]

calculated wing chord (rounded tips): 1.78 [m]

wing aspect ratio : 6.98 []

estimated gap : 1.84 [m]

gap/chord : 1.15 [ ]

seize (span*length*height) : 323 [m^3]

calculation : *2* (fuel consumption)

oil consumption : 8.1 [kg/hr]

fuel consumption(cruise speed) : 23.0 [kg/hr] (31.4 [litre/hr]) at 72 [%] power

distance flown for 1 kg fuel : 4.42 [km/kg]

estimated total fuel capacity : 142 [litre] (104 [kg])

calculation : *3* (weight)

weight engine(s) dry : 137.0 [kg] = 1.86 [kg/KW]

weight 45 litre oil tank : 3.8 [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 13 litre gravity patrol tank(s) : 2.0 [kg]

weight cowling 2.9 [kg]

weight airscrew(s) (wood) incl. boss & bolts : 16.9 [kg]

total weight propulsion system : 160 [kg](17.2 [%])

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weight tail boom : 29 [kg]

fuselage skeleton (wood gauge : 6.40 [cm]): 87 [kg]

bracing : 5.3 [kg]

fuselage covering ( 8.4 [m2] doped linen fabric) : 2.7 [kg]

weight controls + indicators: 6.2 [kg]

weight seats : 6.0 [kg]

weight other details, lighting set, etc. : 5.1 [kg]

weight 129 [litre] main fuel tank empty : 10.3 [kg]

weight engine mounts & firewalls : 4 [kg]

total weight fuselage : 126 [kg](13.6 [%])

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weight wing covering (doped linen fabric) : 23 [kg]

total weight ribs (48 ribs) : 55 [kg]

load on front upper spar (clmax) per running metre : 779.5 [N]

load on rear upper spar (vmax) per running metre : 226.5 [N]

total weight 8 spars : 52 [kg]

weight wings : 130 [kg]

weight wing/square meter : 3.67 [kg]

weight 8 interplane struts & cabane : 28.8 [kg]

weight cables (71 [m]) : 5.9 [kg] (= 83 [gram] per metre)

diameter cable : 3.7 [mm]

weight fin & rudder (1.4 [m2]) : 5.5 [kg]

weight stabilizer & elevator (3.4 [m2]): 12.7 [kg]

total weight wing surfaces & bracing : 183 [kg] (19.7 [%])

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weight machine-gun(s) : 15.9 [kg]

weight pivot mounting mg :6.0 [kg]

weight armament : 22 [kg]

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wheel pressure : 465.0 [kg]

weight 2 wheels (710 [mm] by 79 [mm]) : 23.1 [kg]

weight tailskid : 2.5 [kg]

weight undercarriage with axle 23.0 [kg]

total weight landing gear : 48.6 [kg] (5.2 [%]

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calculated empty weight : 540 [kg](58.1 [%])

weight oil for 4.8 hours flying : 38.8 [kg]

weight 1 drums empty : 1.8 [kg]

weight ammunition (400 rounds) : 12.7 [kg]

weight automatic pistol with spare magazines : 1.2 [kg]

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calculated operational weight empty : 593 [kg] (63.7 [%])

published operational weight empty : 553 [kg] (59.5 [%])

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weight crew : 162 [kg]

weight fuel for 1.5 hours flying : 34 [kg]

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operational weight : 789 [kg](84.9 [%])

estimated bomb load : 25 [kg]

operational weight bombing mission : 814 [kg]

fuel reserve : 70 [kg] enough for 3.04 [hours] flying

possible additional useful load : 46 [kg]

operational weight fully loaded : 930 [kg] with fuel tank filled for 100 [%]

published maximum take-off weight : 930 [kg] (100.0 [%])

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calculation : * 4 * (engine power)

power loading (operational without bombload) : 10.73 [kg/kW]

total power : 73.6 [kW] at 1160 [r.p.m]

calculation : *5* (loads)

manoeuvre load : 1.8 [g] at 1000 [m]

limit load : 4.5 [g] ultimate load : 6.8 [g] load factor : 2.6 [g]

design flight time : 3.20 [hours]

design cycles : 312 sorties, design hours : 1000 [hours]

operational wing loading : 218 [N/m^2]

wing stress (3 g) during operation : 178 [N/kg] at 3g emergency manoeuvre

calculation : *6* (angles of attack)

angle of attack zero lift : -1.21 ["]

max. angle of attack (stalling angle) : 12.65 ["]

angle of attack at max. speed : 3.86 ["]

calculation : *7* (lift & drag ratios

lift coefficient at angle of attack 0° :0.10 [ ]

lift coefficient at max. angle of attack : 1.15 [ ]

lift coefficient at max. speed : 0.42 [ ]

induced drag coefficient at max. speed : 0.0143 [ ]

drag coefficient at max. speed : 0.0669 [ ]

drag coefficient (zero lift) : 0.0526 [ ]

calculation : *8* (speeds

stalling speed at sea-level (OW): 63 [km/u]

landing speed at sea-level (OW without bombload): 76 [km/hr]

min. drag speed (max endurance) : 82 [km/hr] at 1524 [m](power :51 [%])

min. power speed (max range) : 91 [km/hr] at 1524 [m] (power:56 [%])

max. rate of climb speed : 75.3 [km/hr] at sea-level

cruising speed : 102 [km/hr] op 1524 [m] (power:65 [%])

design speed prop : 110 [km/hr]

maximum speed : 113 [km/hr] op 1524 [m] (power:80 [%])

climbing speed at sea-level (without bombload) : 174 [m/min]

calculation : *9* (regarding various performances)

take-off distance at sea-level : 146 [m]

lift/drag ratio : 7.66 [ ]

max. practical ceiling : 4275 [m] with flying weight :671 [kg]

practical ceiling (operational weight): 3325 [m] with flying weight :789 [kg]

practical ceiling fully loaded (mtow- 1 hour fuel) : 2450 [m] with flying weight :907 [kg]

published ceiling (2743 [m]

climb to 1500m (without bombload) : 10.10 [min]

max. dive speed : 265.2 [km/hr] at 1450 [m] height

load factor at max. angle turn 1.69 ["g"]

turn radius at 500m: 41 [m]

time needed for 360* turn 11.0 [seconds] at 500m

calculation *10* (action radius & endurance)

operational endurance : 4.54 [hours] with 2 crew and 71 [kg] useful (bomb)load and 100.0 [%] fuel

published endurance : 4.00 [hours] with 2 crew and possible useful (bomb) load : 83 [kg] and 88.1 [%] fuel

action radius : 344 [km] with 2 crew and 20[kg] photo camera/radio transmitter or bombload

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max range theoretically with additional fuel tanks for total 369 [litre] fuel : 1196 [km]

useful load with action-radius 250km : 157 [kg]

production : 15.99 [tonkm/hour]

oil and fuel consumption per tonkm : 1.94 [kg]

Literature :

praktisch handboek vliegtuigen deel 1 page 170

jagdflugzeuge WO I page 28

tussen vleugels van linnen page 61

“Against the odds - the life of group captain Lionel Rees, VC”

Written by W.Allister Williams ISBN 1-872424-00-7

Fighters 1914-19 page 22

Jane’s fighting aircraft WOI page 90

Warplanes WWI page 37, 44, 45, 46dt,48,54,55

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 November 2019 contact : info.aircraftinvestigation@gmail.com python 3.7.4