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weight and performance calculations for the Savoia-Pomilio S.P.3
Savoia-Pomilio S.P.3
role : two-seat armed reconnaissance and artillery observation
importance : ***
first flight : operational : June 1917
country : Italy
design : Umberto Savoia and Ottorino Pomilio
production : 300 aircraft
general information :
Version with smaller wingspan and stronger engine, in attempt to improve performance.
This machine was what their Italian crew said 'siamo perduti' (S.P.) translated ' we are lost'. It was not very popular. Deliveries of the 300 Savoia-Pomilio SP 3 two-seat reconnaissance machines might have been more understandable had they been made two or even three years earlier, as it was they started in mid-1917. Clearly, by this time, not even the powerful 300hp Fiat A 12Bis fitted could give this tired old pusher-engined design sufficient impetus to extricate it from hostile fighter attack. The resultant operational loss rate was high and SP 3 crew morale low
users : Italy
crew : 2
armament : 1 movable 7.70 [mm] (0.303 in) Lewis machine-gun for the observer
engine : 1 FIAT A-12 bis liquid-cooled 6 -cylinder inline engine 280 [hp](205.9 KW)
dimensions :
wingspan : 14.7 [m], length : 10.95 [m], height : 3.55[m]
wing area : 60.0 [m^2]
weights :
max.take-off weight : 1498 [kg]
empty weight operational : 1048 [kg] bombload : 0 [kg]
performance :
maximum speed : 145 [km/hr] at sea-level
service ceiling : 5000 [m]
estimated action radius : 225 [km]
description :
3-bay biplane with fixed underwing 4 -wheel landing gear and tail strut
two spar upper and lower wing
tail supported by two open tail booms
engine, fuel and bombload in or attached to fuselage, landing gear attached to the wing
airscrew :
fixed pitch 2 -bladed pusher airscrew with max. efficiency :0.64 [ ]
estimated diameter airscrew 2.90 [m]
angle of attack prop : 12.47 [ ]
fine pitch
reduction : 1.00 [ ]
airscrew revs : 1600 [r.p.m.]
pitch at Max speed 1.51 [m]
blade-tip speed at Vmax and max revs. : 246 [m/s]
calculation : *1* (dimensions)
mean wing chord : 2.04 [m]
calculated wing chord (rounded tips): 2.25 [m]
wing aspect ratio : 7.20 []
estimated gap : 1.91 [m]
gap/chord : 0.94 [ ]
seize (span*length*height) : 571 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 4.7 [kg/hr]
fuel consumption(cruise speed) : 47.0 [kg/hr] (64.1 [litre/hr]) at 62 [%] power
distance flown for 1 kg fuel : 2.78 [km/kg]
estimated total fuel capacity : 251 [litre] (184 [kg])
calculation : *3* (weight)
weight engine(s) dry : 438.0 [kg] = 2.13 [kg/KW]
weight 27 litre oil tank : 3.4 [kg]
oil tank filled with 1.5 litre oil : 1.4 [kg]
oil in engine 11 litre oil : 10.3 [kg]
fuel in engine 1 litre fuel : 1.0 [kg]
weight 27 litre gravity patrol tank(s) : 2.7 [kg]
weight radiator : 29.5 [kg]
weight exhaust pipes & fuel lines 25.9 [kg]
weight self-starter : 5.0 [kg]
weight cowling 8.2 [kg]
weight airscrew(s) (wood) incl. boss & bolts : 30.9 [kg]
total weight propulsion system : 553 [kg](36.9 [%])
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weight tail boom : 32 [kg]
fuselage skeleton (wood gauge : 5.81 [cm]): 95 [kg]
bracing : 7.7 [kg]
fuselage covering ( 14.7 [m2] doped linen fabric) : 4.7 [kg]
weight controls + indicators: 7.4 [kg]
weight seats : 6.0 [kg]
weight other details, lighting set, etc. : 5.1 [kg]
weight 224 [litre] main fuel tank empty : 21.5 [kg]
weight oxygen/compressed air flasks for high altitude : 7.5 [kg]
weight engine mounts & firewalls : 10 [kg]
total weight fuselage : 165 [kg](11.0 [%])
***************************************************************
weight wing covering (doped linen fabric) : 38 [kg]
total weight ribs (60 ribs) : 89 [kg]
load on front upper spar (clmax) per running metre : 450.2 [N]
load on rear upper spar (vmax) per running metre : 255.6 [N]
total weight 8 spars : 46 [kg]
weight wings : 173 [kg]
weight wing/square meter : 2.89 [kg]
weight 12 interplane struts & cabane : 33.2 [kg]
weight cables (104 [m]) : 8.6 [kg] (= 83 [gram] per metre)
diameter cable : 3.7 [mm]
weight fin & rudder (2.5 [m2]) : 7.6 [kg]
weight stabilizer & elevator (5.7 [m2]): 17.0 [kg]
total weight wing surfaces & bracing : 240 [kg] (16.0 [%])
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weight machine-gun(s) : 12.7 [kg]
weight pivot mounting mg :6.0 [kg]
weight armament : 19 [kg]
********************************************************************
good soft ground capabilities
wheel pressure : 374.5 [kg]
weight 4 wheels (820 [mm] by 96 [mm]) : 45.4 [kg]
weight tailskid : 2.1 [kg]
weight undercarriage with axle 20.6 [kg]
total weight landing gear : 68.1 [kg] (4.5 [%]
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calculated empty weight : 1044 [kg](69.7 [%])
weight oil for 4.1 hours flying : 19.6 [kg]
weight cooling fluids : 42.4 [kg]
weight 5 drums empty : 1.0 [kg]
weight ammunition (235 rounds) : 7.5 [kg]
weight signal pistol with cartridges : 3.6 [kg]
weight automatic pistol with spare magazines : 1.2 [kg]
*******************************************************************
calculated operational weight empty : 1118 [kg] (74.7 [%])
published operational weight empty : 1048 [kg] (70.0 [%])
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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 : 94 [kg]
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operational weight : 1386 [kg](92.5 [%])
estimated bomb load : 50 [kg]
operational weight bombing mission : 1436 [kg]
weight camera : 20 [kg]
operational weight photo mission : 1406 [kg]
fuel reserve : 90 [kg] enough for 1.91 [hours] flying
possible additional useful load : 2 [kg]
operational weight fully loaded : 1498 [kg] with fuel tank filled for 100 [%]
published maximum take-off weight : 1498 [kg] (100.0 [%])
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calculation : * 4 * (engine power)
power loading (operational without bombload) : 6.73 [kg/kW]
total power : 205.9 [kW] at 1600 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 2.9 [g] at 1000 [m]
limit load : 3.75 [g] ultimate load : 5.6 [g] load factor : 1.3 [g]
design flight time : 2.76 [hours]
design cycles : 127 sorties, design hours : 350 [hours]
operational wing loading : 230 [N/m^2]
wing stress (3 g) during operation : 239 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.20 ["]
max. angle of attack (stalling angle) : 12.56 ["]
angle of attack at max. speed : 1.56 ["]
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 : 0.23 [ ]
induced drag coefficient at max. speed : 0.0042 [ ]
drag coefficient at max. speed : 0.0542 [ ]
drag coefficient (zero lift) : 0.0500 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW): 65 [km/u]
landing speed at sea-level (OW without bombload): 78 [km/hr]
min. drag speed (max endurance) : 88 [km/hr] at 2500 [m](power :37 [%])
min. power speed (max range) : 98 [km/hr] at 2500 [m] (power:40 [%])
max. rate of climb speed : 86.8 [km/hr] at sea-level
cruising speed : 130 [km/hr] op 2500 [m] (power:63 [%])
design speed prop : 138 [km/hr]
maximum speed : 145 [km/hr] op 100 [m] (power:99 [%])
climbing speed at sea-level (without bombload) : 313 [m/min]
calculation : *9* (regarding various performances)
take-off distance at sea-level : 61 [m]
lift/drag ratio : 7.98 [ ]
max. practical ceiling : 5600 [m] with flying weight :1211 [kg]
practical ceiling (operational weight) : 4925 [m] with flying weight :1386 [kg] line 3385
practical ceiling fully loaded (mtow- 1 hour fuel) : 4700 [m] with flying weight :1451 [kg]
published ceiling (5000 [m]
climb to 1500m (without bombload) : 5.38 [min]
climb to 3000m (without bombload) : 13.38 [min]
max. dive speed : 324.7 [km/hr] at 3700 [m] height
load factor at max. angle turn 2.22 ["g"]
turn radius at 500m: 39 [m]
time needed for 360* turn 8.9 [seconds] at 500m
calculation *10* (action radius & endurance)
operational endurance : 3.57 [hours] with 2 crew and 50 [kg] useful (bomb)load and 91.2 [%] fuel
published endurance : 3.45 [hours] with 2 crew and possible useful (bomb) load : 56 [kg] and 88.1 [%] fuel
action radius : 274 [km] with 2 crew and 20[kg] photo camera or bombload
max range theoretically with additional fuel tanks for total 442 [litre] fuel : 899 [km]
useful load with action-radius 250km : 144 [kg]
production : 18.74 [tonkm/hour]
oil and fuel consumption per tonkm : 2.76 [kg]
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Literature :
Jane’s fight aircraft WWI page 205
http://www.airwar.ru/enc/other1/sp3.html
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