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weight and performance calculations for the Short Type 320
Short Type 320
role : torpedo bomber
importance : ***
first flight : operational : April 1917
country : United-Kingdom
design : Horace and Oswald Short
production : 127 aircraft
Manufacturers: Short Bros (serialled N1300-1319, N1390-1409 and N1480-1504) and
Sunbeam (serialled N1360-1389, N1690-1696 and N1702-1709).
general information :
Despite the outstanding, if isolated success achieved by the torpedo-carrying Short 184s at the Dardanelles in August 1915, it was evident that in order for a single-engine aircraft to possess adequate performance while carrying a 1000 lb wet-heated torpedo. (particularly in hot climates) it was necessary to acquire an engine of more than 300 horsepower, itself weighing scarcely more than the existing 250hp engines. The new Rolls-Royce twelve-cylinder water-cooled powerplant, soon to be named the Eagle, was already approaching the 300hp rating, but production engines were being earmarked for the Handley Page O/100.
At Sunbeam, however, Louis Coatalen was developing a 300hp engine, later named the Cossack, and it was for this engine that Horace and Oswald Short designed new seaplanes, the Type 310A (torpedo-carrier) and the 310B (patrol scout) * - the former being accorded the highest priority owing to increased enemy naval activity in the Mediterranean early in 1916. It was intended to carry the new 996 lb 18-in Mk.IX torpedo.
* Confusion has existed for many years with regard to the correct designation of the Type 310, resulting from the various systems of referring to the Short seaplanes. The term Type 310 was adopted to identify aircraft powered by the 310hp Sunbeam engine, this being the initial normal power. The rating was soon raised to 320hp (maximum), and eventually came to be regarded as the 'normal' rating. Strictly speaking the aircraft with these more powerful engines should have been referred to as Type 320s, and often were. However, the designation was never sanctioned, and Short's own designation, the Type 310-A4, came to be officially adopted.
In contrast to the earlier Type 184, which carried its torpedo beneath arched float cross-members, the Type 310A incorporated torpedo crutches on the fuselage underside, thereby ensuring that the torpedo was always carried clear of the water. To provide additional float rigidity, a detachable cross-member interconnected the rear ends of the floats when a torpedo was not carried, and extra fixed raked struts gave adequate float rigidity when carrying the torpedo, while allowing the weapon unrestricted fall when released. The front float crossmember was located forward of the torpedo in any case, and therefore remained fixed.
When carrying a torpedo, the Short 310A was invariably flown as a single seater, the pilot occupying the rear cockpit so as to maintain the aircraft cg within acceptable limits. These crew dispositions were regarded as unsatisfactory as, occupying the front cockpit, the observer was so beset by interplane struts and upper wing that, without a gun
mounting, the aircraft was defenceless. To overcome this, later aircraft featured a Lewis gun with Scarff ring level with the upper wing trailing edge; to man the gun, the observer was obliged to stand on his seat with most of his body exposed to the slipstream but at least he possessed an excellent field of fire.
Two prototype Type 310As and two 310Bs had been ordered, and the first two, Nos 8317 and 8318, were first flown by Ronald Kemp in July and August 1916 respectively. (Of the two 310Bs ordered, only No 8319 was completed as such, No 8320 being converted to become an additional Type 310A during manufacture.)
Nos 8317 and 8318 were quickly despatched to RNAS Otranto in Italy for operational torpedo trials, but both aircraft broke up in the air following failures of their rear float attachment. This was rectified in production aircraft by moving the floats further apart, and an additional V-strut was added to brace the float to the lower wing on each side; these struts were disconnected and rotated downwards to allow the wings to be folded. With this modification in place, the aircraft was termed the 310-A4.
A total of 127 Type 310-A4s was built by Short Bros and the Sunbeam Motor Car Company, all carrying N-prefix serial numbers. The first 54 production machines were shipped to Otranto and Malta during the spring of 1917.
Their first operation, however, ended in failure before it even began, when six 310-A4s, having been towed on rafts to Traste Bay, were destroyed by a sudden storm which capsized all the craft moments before the aircraft were due to be disembarked for take off. Their task had been to attack with torpedoes a flotilla of enemy submarines, known to be off Cattaro (Kotor) in the Adriatic. No such target was ever again presented.
The Mediterranean-based seaplanes were employed on long-range patrols, made possible by their six-hour endurance when carrying a pair of 230 lb bombs. No submarine kill by a 310-A4 was ever confirmed, although the pilot of a Kalafrana-based aircraft claimed to have 'probably destroyed' a submarine which had attacked a French warship off Malta on 8 February 1918.
The production of torpedo-carrying seaplanes was ended by the Admiralty late in 1917 when it became evident from trials aboard HMS Furious that year that deck-landing aircraft could operate with greater flexibility a belief that persisted for the remainder of the aerial torpedo's history.
Nevertheless, no fewer than fifty Short Type 310-A4s remained in service with the RAF at the Armistice. (source : F.Manson British Bomber Since 1914 (Putnam))
users : RNAS
RNAS coastal air stations which, following the formation of the RAF, were designated No.229 Squadron (Great Yarmouth), No.240 Squadron (Calshot), No.248 Squadron (Hornsea). No.263 Squadron (Otranto), No.264 Squadron (Suda Bay), No.266 Squadron (Mudros), No.268 (Malta) and No.269 Squadron (Kalafrana).
crew : 2
armament : 1 movable 7.70 [mm] (0.303 in) Lewis machine-gun for the observer
engine : 1 Sunbeam Cossack liquid-cooled 12 -cylinder V-engine 320 [hp](235.4 KW)
dimensions :
wingspan : 22.86 [m], length : 13.95 [m], height : 5.34[m]
wing area : 75.3 [m^2]
weights :
max.take-off weight : 3188 [kg]
empty weight operational : 2242 [kg] bombload : 450 [kg]
performance :
maximum speed : 117 [km/hr] at sea-level
service ceiling : 1676 [m]
endurance : 6.0 [hours]
estimated action radius : 316 [km]
description :
2-bay two float biplane with tail float
2 (aid) tip floats
upper wingtips supported by slanted flying wires
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 [ ]
estimated diameter airscrew 3.30 [m]
angle of attack prop : 14.08 [ ]
fine pitch
reduction : 0.50 [ ]
airscrew revs : 1000 [r.p.m.]
pitch at Max speed 1.95 [m]
blade-tip speed at Vmax and max revs. : 176 [m/s]
calculation : *1* (dimensions)
mean wing chord : 1.88 [m]
calculated wing chord (rounded tips): 2.02 [m]
wing aspect ratio : 12.14 []
estimated gap : 1.85 [m]
gap/chord : 0.98 [ ]
seize (span*length*height) : 1703 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 5.9 [kg/hr]
fuel consumption(cruise speed) : 65.9 [kg/hr] (89.9 [litre/hr]) at 84 [%] power
distance flown for 1 kg fuel : 1.60 [km/kg]
estimated total fuel capacity : 612 [litre] (449 [kg])
calculation : *3* (weight)
weight engine(s) dry : 605.0 [kg] = 2.57 [kg/KW]
weight reduction gear : 11.8 [kg]
weight 53 litre oil tank : 6.7 [kg]
oil tank filled with 1.8 litre oil : 1.6 [kg]
oil in engine 13 litre oil : 11.8 [kg]
fuel in engine 2 litre fuel : 1.2 [kg]
weight 38 litre gravity patrol tank(s) : 3.7 [kg]
weight radiator : 37.7 [kg]
weight exhaust pipes & fuel lines 32.4 [kg]
weight self-starter : 5.8 [kg]
weight cowling 9.4 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 35.3 [kg]
total weight propulsion system : 756 [kg](23.7 [%])
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fuselage skeleton (wood gauge : 10.17 [cm]): 325 [kg]
bracing : 28.1 [kg]
fuselage covering ( 28.5 [m2] doped linen fabric) : 9.1 [kg]
weight controls + indicators: 8.8 [kg]
weight seats : 6.0 [kg]
weight other details, lighting set, etc. : 5.1 [kg]
weight bomb storage : 31.5 [kg]
weight 574 [litre] main fuel tank empty : 55.1 [kg]
weight 1 fire extinguisher : 3 [kg]
weight engine mounts & firewalls : 12 [kg]
total weight fuselage : 484 [kg](15.2 [%])
***************************************************************
weight wing covering (doped linen fabric) : 48 [kg]
total weight ribs (138 ribs) : 189 [kg]
load on front upper spar (clmax) per running metre : 842.5 [N]
load on rear upper spar (vmax) per running metre : 378.8 [N]
total weight 8 spars : 252 [kg]
weight wings : 490 [kg]
weight wing/square meter : 6.51 [kg]
weight 8 interplane struts & cabane : 43.6 [kg]
weight cables (86 [m]) : 34.3 [kg] (= 397 [gram] per metre)
diameter cable : 8.1 [mm]
weight fin & rudder (7.3 [m2]) : 48.5 [kg]
weight stabilizer & elevator (8.5 [m2]): 55.7 [kg]
total weight wing surfaces & bracing : 672 [kg] (21.1 [%])
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weight machine-gun(s) : 12.7 [kg]
weight Scarff ring mounting mg :6.9 [kg]
weight armament : 20 [kg]
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weight floats : 260 [kg] (8.1 [%])
*******************************************************************
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calculated empty weight : 2190 [kg](68.7 [%])
weight oil for 7.2 hours flying : 42.4 [kg]
weight cooling fluids : 48.5 [kg]
weight 5 drums empty : 1.0 [kg]
weight ammunition (235 rounds) : 7.5 [kg]
weight Very pistol with cartridges : 3.6 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
*******************************************************************
calculated operational weight empty : 2294 [kg] (71.9 [%])
published operational weight empty : 2242 [kg] (70.3 [%])
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weight crew : 162 [kg]
weight fuel for 2.0 hours flying : 132 [kg]
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operational weight : 2587 [kg](81.2 [%])
Short type 310, note the 4-bladed prop
bomb load : 450 [kg]
operational weight bombing mission : 3037 [kg]
fuel reserve : 151 [kg] enough for 2.29 [hours] flying
operational weight fully loaded : 3188 [kg] with fuel tank filled for 63 [%]
published maximum take-off weight : 3188 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (operational without bombload) : 10.99 [kg/kW]
total power : 235.4 [kW] at 2000 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 1.1 [g] at 1000 [m]
limit load : 2.5 [g] ultimate load : 3.8 [g] load factor : 1.7 [g]
design flight time : 4.20 [hours]
design cycles : 369 sorties, design hours : 1550 [hours]
operational wing loading : 337 [N/m^2]
wing stress (3 g) during operation : 155 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.29 ["]
max. angle of attack (stalling angle) : 10.25 ["]
angle of attack at max. speed : 4.36 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° :0.12 [ ]
lift coefficient at max. angle of attack : 1.07 [ ]
lift coefficient at max. speed : 0.53 [ ]
induced drag coefficient at max. speed : 0.0097 [ ]
drag coefficient at max. speed : 0.0984 [ ]
drag coefficient (zero lift) : 0.0887 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 81 [km/u]
landing speed at sea-level (OW without bombload): 98 [km/hr]
min. drag speed (max endurance) : 92 [km/hr] at 458 [m](power :56 [%])
min. power speed (max range) : 92 [km/hr] at 458 [m] (power:56 [%])
cruising speed : 105 [km/hr] op 458 [m] (power:74 [%])
design speed prop : 111 [km/hr]
maximum speed : 117 [km/hr] op 100 [m] (power:98 [%])
climbing speed at sea-level (without bombload) : 182 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 308 [m]
lift/drag ratio : 8.98 [ ]
max. practical ceiling : 3200 [m] with flying weight :2395 [kg]
practical ceiling (operational weight) : 2800 [m] with flying weight :2587 [kg] line 3385
practical ceiling fully loaded (mtow- 1 hour fuel) : 1750 [m] with flying weight :3122 [kg]
published ceiling : 1676 [m]
climb to 1500m (without bombload) : 9.93 [min]
max. dive speed : 271.4 [km/hr] at 750 [m] height
load factor at max. angle turn 1.61 ["g"]
turn radius at 500m: 70 [m]
time needed for 360* turn 14.9 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 4.29 [hours] with 2 crew and 450 [kg] bombload and 62.9 [%] fuel
published endurance : 6.00 [hours] with 2 crew and possible useful (bomb) load : 337 [kg] and 88.1 [%] fuel
action radius : 569 [km] with 2 crew and 20[kg] photo camera or bombload
max range theoretically with additional fuel tanks for total 1127 [litre] fuel : 1319 [km]
useful load with action-radius 250km : 513 [kg]
production : 53.99 [tonkm/hour]
oil and fuel consumption per tonkm : 1.33 [kg]
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Literature :
Warplanes WWI page 33
Armament of British Aircraft 1909-1939 page 310
https://flyingmachines.ru/Site2/Crafts/Craft29864.htm
Aircraft of the royal air force since 1912, Thetford
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 12 April 2020 contact : info.aircraftinvestigation@gmail.com python 3.7.4