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weight and performance calculations for the Armstrong Whitworth AW.15 Atalanta
Armstrong Whitworth AW.15 Atalanta
role : medium weight passenger aircraft
importance : **
first flight : 06 June 1932 flown by Alan Campbell-Orde operational : October 1932
country : United-Kingdom
design : John Lloyd
production : 8 aircraft at Coventry
general information :
Designed to operate safe and with good comfort in tropical and warm climates. The four engine design gave sufficient power, and could stay in the air on 3 engines.
It was in service for 12 years and only one was lost in a crash as proof of its safe design. It flew the route between Karachi and Singapore and also flew in South Africa.
Direct behind the flight crew was an airmail/airfreight compartment. As combi mail/pax it took 1000 kg mail and freight with 9 passengers.
Special care was taken to provide good air conditioning for the envisioned use in hot climates.
Only 8 were built, so it was a limited success.
users : Imperial Airways, RAF, Indian air force
registrations : G-ABPI “Arethusa” prototype, G-ABTH “Andromeda”, G-ABTI “Atalanta”, G-ABTG “Amalthea”, G-ABTJ “Artemis”, G-ABTK “Athena”, G-ABTL “Astraea”, G-ABTM “Aurora”
crew : 3 (pilot, co-pilot and radio-operator) passengers : 17
powerplant : 4 Armstrong Siddeley Serval III air-cooled 10 -cylinder radial engine 340
[hp] (253.5 KW) normal rating, supercharged engine, low blower, constant power to
height : 1219 [m] and with 380 [hp](283.4 KW) available for take-off
dimensions :
wingspan : 27.43 [m], length : 21.79 [m], height : 4.27 [m]
wing area : 119.4 [m^2]
weights :
max.take-off weight : 9525 [kg]
empty weight operational : 6728 [kg] useful load : 1900 [kg]
performance :
maximum speed :251 [km/u] op 910 [m]
cruise speed :238 [km/u] op 910 [m]
service ceiling : 4300 [m]
range : 1030 [km]
description :
high-winged monoplane with fixed landing gear with tail wheel
tapered wing with no flaps airfoil : RAF
engines attached to the wing, fuel in the upper wing, landing gear attached to the
fuselage
construction : fuselage and wing steel frame covered with plywood and fabric (rear of fuselage)
airscrew :
four wooden fixed pitch 2 -bladed tractor airscrews with max. efficiency :0.69 [ ]
estimated diameter airscrew 2.72 [m]
relative pitch (J) : 0.75 [ ]
power loading prop : 93.21 [KW/m]
theoretical pitch without slip : 2.42 [m]
blade angle prop (fixed) : 20.65 [ ]
tip-speed close to speed of sound (above Mach 0.85) > loose of efficiency
reduction : 1.00 [ ]
airscrew revs : 2000 [r.p.m.]
aerodynamic pitch at max. continuous speed 2.04 [m]
blade-tip speed at max.continuous speed : 293 [m/s]
propellor noise in flight : 101 [Db]
calculation : *1* (dimensions)
measured wing chord : 4.20 [m] at 50% wingspan
mean wing chord : 4.35 [m]
calculated average wing chord tapered wing with rounded tips: 4.37 [m]
wing aspect ratio : 6.3 []
seize (span*length*height) : 2552 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 15.2 [kg/hr]
fuel consumption(cruise speed) : 259.7 [kg/hr] (354.4 [litre/hr]) at 79 [%] power
distance flown for 1 kg fuel : 0.92 [km/kg] at 2150 [m] height, sfc : 325.9 [kg/kwh]
estimated total fuel capacity : 1737 [litre] (1273 [kg])
calculation : *3* (weight)
weight engine(s) dry : 1296.0 [kg] = 1.28 [kg/KW]
weight 113.2 litre oil tank : 9.62 [kg]
oil tank filled with 7.6 litre oil : 6.8 [kg]
oil in engine 5.6 litre oil : 5.1 [kg]
fuel in engine 6.9 litre fuel : 5.07 [kg]
weight 150.7 litre gravity patrol tank(s) : 22.6 [kg]
weight Burgess type silencers : 20.3 [kg]
weight Rotax starter : 6.2 [kg]
weight cowling (Townend ring) 10.1 [kg]
weight airscrew(s) incl. boss & bolts : 96.7 [kg]
total weight propulsion system : 1478 [kg](15.5 [%])
***************************************************************
fuselage skeleton (steel tubes) : 4.55 [cm]): 1445 [kg]
cabin layout : pitch : 87 [cm] (2+1) seating in 5.7 rows
pax density : 2.07 [m2/pax]
weight 1 fire extinguisher : 3 [kg]
weight pantry : 11.7 [kg]
weight 13 windows : 12.0 [kg]
weight door : 5.0 [kg]
passenger cabin max.width : 2.47 [m] cabin length : 6.05 [m] cabin height : 1.90 [m]
weight cabin furbishing : 76.7 [kg]
weight cabin floor : 86.0 [kg]
bracing : 287.5 [kg]
fuselage covering ( 131.8 [m2] plywood 5.4 [mm]) : 451.6 [kg]
weight radio transceiver equipment : 7.0 [kg]
weight instruments. : 8.0 [kg]
weight lighting : 4.2 [kg]
weight electricity generator : 4.2 [kg]
weight controls : 10.3 [kg]
weight seats : 100.0 [kg]
weight air conditioning : 26 [kg]
total weight fuselage : 2533 [kg](26.6 [%])
***************************************************************
weight 5.5 [mm] plywood wing covering : 419 [kg]
total weight steel ribs (50 ribs) : 566 [kg]
weight engine mounts : 51 [kg]
weight fuel tanks empty for total 1586 [litre] fuel : 127 [kg]
load on front upper spar (clmax) per running metre : 2165.9 [N]
load on rear upper spar (vmax) per running metre : 897.2 [N]
total weight 4 steel wing spars : 691 [kg]
weight wings : 1676 [kg]
weight wing/square meter : 14.04 [kg]
cantilever wing without bracing cables
weight fin & rudder (8.7 [m2]) : 123.9 [kg]
weight stabilizer & elevator (13.4 [m2]): 189.5 [kg]
total weight wing surfaces & bracing : 2167 [kg] (22.8 [%])
*******************************************************************
wheel pressure : 4762.5 [kg]
weight 2 Dunlop main wheels (1490 [mm] by 248 [mm]) : 274.6 [kg]
weight tailwheel(s) : 5.9 [kg]
weight Bendix wheel-brakes : 8.6 [kg]
weight Dowty shock absorbers : 11.5 [kg]
weight undercarriage with axle 204.8 [kg]
total weight landing gear : 505.4 [kg] (5.3 [%]
*******************************************************************
********************************************************************
calculated empty weight : 6685 [kg](70.2 [%])
weight oil for 5.2 hours flying : 78.9 [kg]
calculated operational weight empty : 6764 [kg] (71.0 [%])
published operational weight empty : 6728 [kg] (70.6 [%])
weight crew : 243 [kg]
weight fuel for 2.0 hours flying : 519 [kg]
weight catering : 29.4 [kg]
weight water : 11.7 [kg]
********************************************************************
operational weight empty: 7567 [kg](79.4 [%])
weight 17 passengers : 1309 [kg]
weight luggage : 207 [kg]
weight cargo : 384 [kg]
operational weight loaded: 9467 [kg](99.4 [%])
fuel reserve : 57.9 [kg] enough for 0.22 [hours] flying
operational weight fully loaded : 9525 [kg] with fuel tank filled for 45 [%]
published maximum take-off weight : 9525 [kg] (100.0 [%])
calculation : * 4 * (engine power)
power loading (Take-off) : 9.39 [kg/kW]
power loading (operational without useful load) : 7.46 [kg/kW]
power loading (Take-off) 1 PUF: 12.52 [kg/kW]
total power : 1014.2 [kW] at 2000 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 3.1 [g] at 1000 [m]
limit load : 3.0 [g] ultimate load : 4.5 [g] load factor : 1.8 [g]
design flight time : 3.46 [hours]
design cycles : 4064 sorties, design hours : 14045 [hours]
operational wing loading : 622 [N/m^2]
wing stress (3 g) during operation : 133 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.50 ["]
max. angle of attack (stalling angle) : 12.68 ["]
angle of attack at max. speed : 1.35 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.12 [ ]
lift coefficient at max. speed : 0.23 [ ]
lift coefficient at max. angle of attack : 1.14 [ ]
induced drag coefficient at max.speed : 0.0035 [ ]
drag coefficient at max. speed : 0.0328 [ ]
drag coefficient (zero lift) : 0.0293 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 9265 [kg]): 119 [km/u]
landing speed at sea-level (normal landing weight : 7958 [kg]): 127 [km/hr]
max. rate of climb speed : 155 [km/hr] at sea-level
max. endurance speed : 145 [km/u] min.fuel/hr : 189 [kg/hr] at height : 610 [m]
max. range speed : 200 [km/u] min. fuel consumption : 1.112 [kg/km] at cruise height :
3353 [m]
cruising speed : 238 [km/hr] at 2150 [m] (power:93 [%])
max. continuous speed : 244.72 [km/hr]
maximum speed : 251 [km/hr] at 910 [m] (power:112 [%])
climbing speed at sea-level (loaded) : 160 [m/min]
climbing speed at 1000 [m] with 1 engine out (PUF / MTOW) : 81 [m/min]
climbing speed at 1000 [m] with 2 engines out (2xPUF / MTOW) : 0 [m/min]
## so could not stay in the air on 2 engines !
calculation : *9* (regarding various performances)
take-off speed : 144.8 [km/u]
emergency/TO power : 380 [hp] at 2114 [rpm]
static prop wash : 160 [km/u]
take-off distance at sea-level gras field : 298 [m]
take-off distance at sea-level over 15 [m] height : 539 [m]
landing run : 200 [m]
lift/drag ratio : 11.24 [ ]
climb to 1000m with max payload : 6.40 [min]
climb to 2000m with max payload : 15.31 [min]
climb to 3000m with max payload : 32.51 [min]
practical ceiling (operational weight empty 7567 [kg] ) : 4900 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:9395 [kg] ) : 3600 [m]
calculation *10* (action radius & endurance)
published range : 1030 [km] with 3 crew and 1396.5 [kg] useful load and 88.1 [%] fuel
range : 568 [km] with 3 crew and 1900.0 [kg] useful load and 48.6 [%] fuel
range : 920 [km] with 17.0 passengers with each 12.2 [kg] luggage and 78.7 [%] fuel
Available Seat Kilometres (ASK) : 15639 [paskm]
max range theoretically with additional fuel tanks total 3656.8 [litre] fuel : 2411 [km]
useful load with range 500km : 2136 [kg]
useful load with range 500km : 17 passengers
production (theor.max load): 509 [tonkm/hour]
production (useful load): 453 [tonkm/hour]
production (passengers): 4054 [paskm/hour]
oil and fuel consumption per tonkm : 0.54 [kg]
fuel cost per paskm : 0.068 [eur]
crew cost per paskm : 0.074 [eur]
economic hours : 12775 [hours] is less then design hours
time between engine failure : 674 [hr]
can continue fly on 3 engines, low risk for emergency landing for PUF
writing off per paskm : 0.096 [eur]
insurance per paskm : 0.002 [eur]
maintenance cost per paskm : 0.347 [eur]
direct operating cost per paskm : 0.587 [eur]
direct operating cost per tonkm (max. load): 4.671 [eur]
direct operating cost per tonkm (normal useful load): 5.251 [eur]
Literature :
Praktisch handboek vliegtuigen deel 2 page 100, 101
Piston-engined airliners page 48
wikipedia
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 22 January 2022 contact : info.aircraftinvestigation@gmail.com python 3.7.4