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weight and performance calculations for the Armstrong Whitworth A.w.27 Ensign Mk.I
G-ADSR “Ensign” prototype in mid-air
Armstrong Whitworth A.w.27 Ensign Mk.I
role : commuter airliner
importance : **
first flight : 24 January 1938 G-ADSR operational : October 1938 Croydon - Paris
country : United-Kingdom
design : John Lloyd
production : 14 aircraft at Hamble
general information :
Largest airliner built in the UK before WWII. Designed for Imperial Airways as 4-engined high winged mail/passenger monoplane. Early operations were hindered by mechanical problems.
It had a hydraulic retractable landing gear of considerable length to contract in the high wing. The Dunlop wheels were the largest produced in the UK, being 1.91m tall. It had oleo shock-absorber struts and Dunlop pneumatic brakes.
At first it was powered with 800 hp supercharged A.S.Tiger IX engines driving De Havilland 3-bladed two-position adjustable pitch propellors. But with this configuration it was underpowered and had a low rate of climb. Due to problems with the wheel retraction gear and other mechanical problems Imperial Airways returned the Ensigns to the A.W. factory. There the engines were replaced with more powerful 855 hp Tiger XIC engines and constant speed propellors. After further checks and improvements the aircraft were returned to Imperial airways in June 1939. The outbreak of WWII soon ended the civil career of the Ensign. With the Tiger XIC it was still underpowered and the last 2 aircraft built were equipped with 950 hp Wright GR-1820-G102 Cyclone radials now with designation Ensign Mk.II. Later the Mk.I aircraft were upgraded with this engine and now it could also be used in hot climates although pilots still complained about the bad climbing performance. It had a petrol-driven generator (APU) for lighting and recharging of the batteries while on the ground. Marconi wireless transmitter/receiver and Radio direction finding (RDF) equipment
On the Empire routes it carried 27 passenger and on the European routes it took 40 passengers.
It had split trailing-edge flaps. Petrol capacity 650 imp.gallons (2955 litre)
Oil capacity : 40 Imp.gallons (182 litre).
7 aircraft survived through WWII but were scrapped in 1946.
crew : 3 : pilot, co-pilot and radio-operator and 2 cabin attendants.
users : Imperial Airways, BOAC
registrations : G-ADSR “Ensign” prototype, G-ADSS “Egeria”, G-ADST “Elsinore”,
G-ADSU “Euterpe”, G-ADSV “Explorer”, G-ADSX “Ettrick “, G-ADSY “Empyrean”,
G-ADSZ “Elysian”, G-ADTC “Endymion”, G-ADSW “Eddystone”, G-ADTA “Euryalus”,
G-ADTB “Echo”, Mk.II G-AFZV “Enterprise”, Mk.II G-ADTE / G-AFZU “Everest”
crew : 5 passengers : 40
powerplant : 4 Armstrong Siddeley Tiger XIC air-cooled 14 -cylinder radial engine 850 [hp](633.8 KW)
normal rating, supercharged engine, low blower, constant power to height : 2180 [m]
and with 935 [hp](697.2 KW) available for take-off
dimensions :
wingspan : 37.49 [m], length : 34.75 [m], height : 7.01 [m]
wing area : 227.6 [m^2]
weights :
max.take-off weight : 22226 [kg]
empty weight operational : 14900 [kg] useful load : 4300 [kg]
performance :
maximum speed :328 [km/u] op 2135 [m]
cruise speed :312 [km/u] op 2135 [m]
service ceiling : 5490 [m]
range : 1288 [km]
description :
high-winged monoplane with retractable landing gear with tail wheel
tapered wing with split flaps airfoil : RAF
engines and landing gear attached to the wings, fuel tanks in the wings
construction : corrugated light alloy construction. Wing built around single massive
internally braced box spar made. Aft of the box spar the wing was covered with fabric.
Tailplane and fin also covered with fabric. Otherwise fuselage was of semi-monocoque
construction with the frame covered with riveted stress-bearing skin.
airscrew :
four Hamilton-Standard constant speed full-feathering 3 -bladed tractor airscrews with
max. efficiency :0.74 [ ]
estimated diameter airscrew 3.80 [m]
relative pitch (J) : 0.96 [ ]
power loading prop : 111.20 [KW/m]
theoretical pitch without slip : 4.22 [m]
blade angle prop at max.speed : 26.25 [ ]
tip-speed close to speed of sound (above Mach 0.85) > loose of efficiency
reduction : 0.59 [ ]
airscrew revs : 1455 [r.p.m.]
aerodynamic pitch at max. continuous speed 3.66 [m]
blade-tip speed at max.continuous speed : 303 [m/s]
propellor noise in flight : 105 [Db]
calculation : *1* (dimensions)
measured wing chord : 6.09 [m] at 50% wingspan
mean wing chord : 6.07 [m]
calculated average wing chord tapered wing with rounded tips: 6.10 [m]
wing aspect ratio : 6.2 []
seize (span*length*height) : 9132 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 25.4 [kg/hr]
fuel consumption(cruise speed) : 618.5 [kg/hr] (843.8 [litre/hr]) at 83 [%] power
distance flown for 1 kg fuel : 0.50 [km/kg] at 2745 [m] height, sfc : 294.6 [kg/kwh]
estimated total fuel capacity : 3959 [litre] (2902 [kg])
calculation : *3* (weight)
weight engine(s) dry with reduction gear : 2240.0 [kg] = 0.88 [kg/KW]
weight 203.5 litre oil tank : 17.30 [kg]
oil tank filled with 19.0 litre oil : 17.1 [kg]
oil in engine 14.1 litre oil : 12.7 [kg]
fuel in engine 17.3 litre fuel : 12.68 [kg]
weight 358.7 litre gravity patrol tank(s) : 53.8 [kg]
weight Burgess type silencers : 50.7 [kg]
weight NACA-type cowling 28.4 [kg]
weight variable pitch control : 44.4 [kg]
weight airscrew(s) incl. boss & bolts : 577.7 [kg]
total weight propulsion system : 3010 [kg](13.5 [%])
***************************************************************
fuselage aluminium frame : 4014 [kg]
cabin layout : pitch : 87 [cm] (2+2) seating in 10.0 rows
pax density : 1.88 [m2/pax]
weight two toilets : 16 [kg]
weight 4 fire extinguisher : 12 [kg]
weight buffet : 34.4 [kg]
weight racks for hand luggage : 20.0 [kg]
weight 22 windows : 19.8 [kg]
weight door : 5.0 [kg]
passenger cabin max.width : 2.96 [m] cabin length : 11.47 [m] cabin height : 1.90 [m]
weight cabin furbishing : 209.6 [kg]
weight cabin floor : 205.5 [kg]
fuselage covering ( 250.0 [m2] duraluminium 1.47 [mm]) : 975.5 [kg]
fuselage (sound proof) isolation : 98.7 [kg]
weight radio transceiver equipment : 7.0 [kg]
weight radio direction finding (RDF) equipment : 5.0 [kg]
weight artificial horizon : 1.1 [kg]
weight instruments. : 13.0 [kg]
weight APU / engine starter: 31.7 [kg]
weight lighting : 10.0 [kg]
weight electricity generator : 21.1 [kg]
weight controls : 15.0 [kg]
weight seats : 225.0 [kg]
weight air conditioning : 60 [kg]
total weight fuselage : 5880 [kg](26.5 [%])
***************************************************************
total weight aluminium ribs (187 ribs) : 793 [kg]
weight engine mounts : 127 [kg]
weight fuel tanks empty for total 3600 [litre] fuel : 288 [kg]
weight wing covering (painted aluminium 0.92 [mm]) : 1130 [kg]
total weight aluminium spars (multi-cellular wing structure) : 1497 [kg]
weight wings : 3420 [kg]
weight wing/square meter : 15.02 [kg]
cantilever wing without bracing cables
weight rubber de-icing boots : 41.2 [kg]
weight fin & rudder (16.3 [m2]) : 247.6 [kg]
weight stabilizer & elevator (25.6 [m2]): 386.4 [kg]
weight split flap (11.4 [m2]) : 88.5 [kg]
total weight wing surfaces & bracing : 4598 [kg] (20.7 [%])
*******************************************************************
wheel pressure : 11113.0 [kg]
weight 2 Dunlop main wheels (1910 [mm] by 382 [mm]) : 681.6 [kg]
weight tailwheel(s) : 5.9 [kg]
weight pneumatic Dunlop wheel-brakes : 19.2 [kg]
weight oleo shock absorbers : 25.6 [kg]
weight wheel hydraulic operated retraction system : 92.4 [kg]
weight undercarriage with axle 561.3 [kg]
total weight landing gear : 1386.0 [kg] (6.2 [%]
*******************************************************************
********************************************************************
calculated empty weight : 14874 [kg](66.9 [%])
weight oil for 5.0 hours flying : 125.8 [kg]
calculated operational weight empty : 15000 [kg] (67.5 [%])
published operational weight empty : 14900 [kg] (67.0 [%])
weight crew : 405 [kg]
weight fuel for 2.0 hours flying : 1237 [kg]
weight catering : 66.1 [kg]
weight water : 26.5 [kg]
********************************************************************
operational weight empty: 16734 [kg](75.3 [%])
weight 40 passengers : 3080 [kg]
weight luggage : 488 [kg]
weight cargo : 732 [kg]
operational weight loaded: 21034 [kg](94.6 [%])
fuel reserve : 1191.6 [kg] enough for 1.93 [hours] flying
operational weight fully loaded : 22226 [kg] with fuel tank filled for 84 [%]
published maximum take-off weight : 22226 [kg] (100.0 [%])
calculation : * 4 * (engine power)
power loading (Take-off) : 8.77 [kg/kW]
power loading (operational without useful load) : 6.60 [kg/kW]
power loading (Take-off) 1 PUF: 11.69 [kg/kW]
total power : 2535.4 [kW] at 2450 [r.p.m]
calculation : *5* (loads)
manoeuvre load : 4.6 [g] at 1000 [m]
limit load : 3.0 [g] ultimate load : 4.5 [g] load factor : 1.9 [g]
design flight time : 3.31 [hours]
design cycles : 5798 sorties, design hours : 19172 [hours]
operational wing loading : 721 [N/m^2]
wing stress (3 g) during operation : 144 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.51 ["]
max. angle of attack (stalling angle) : 12.73 ["]
angle of attack at max. speed : 0.69 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.12 [ ]
lift coefficient at max. speed : 0.17 [ ]
lift coefficient at max. angle of attack : 1.13 [ ]
max.lift coefficient full flaps : 1.23 [ ]
induced drag coefficient at max.speed : 0.0021 [ ]
drag coefficient at max. speed : 0.0235 [ ]
drag coefficient (zero lift) : 0.0214 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 21607 [kg]): 132 [km/u]
stalling speed at sea-level with full flaps (normal landing weight): 113 [km/u]
landing speed at sea-level (normal landing weight : 17373 [kg]): 130 [km/hr]
max. rate of climb speed : 141 [km/hr] at sea-level
max. endurance speed : 147 [km/u] min.fuel/hr : 305 [kg/hr] at height : 610 [m]
max. range speed : 229 [km/u] at cruise height : 3962 [m]
cruising speed : 312 [km/hr] at 2745 [m] (power:96 [%])
max. continuous speed : 319.80 [km/hr]
maximum speed : 328 [km/hr] at 2135 [m] (power:113 [%])
climbing speed at sea-level (loaded) : 338 [m/min]
climbing speed at 1000 [m] with 1 engine out (PUF / MTOW) : 191 [m/min]
climbing speed at 1000 [m] with 2 engines out (2xPUF / MTOW) : 37 [m/min]
(could just stay airborne with 2 engines out at 1000m height)
calculation : *9* (regarding various performances)
take-off speed : 160.4 [km/u]
emergency/TO power : 935 [hp] at 2570 [rpm]
static prop wash : 193 [km/u]
take-off distance at sea-level gras field : 278 [m]
take-off distance at sea-level over 15 [m] height : 382 [m]
landing run : 212 [m]
lift/drag ratio : 13.00 [ ]
climb to 1000m with max payload : 3.42 [min]
climb to 2000m with max payload : 6.97 [min]
climb to 3000m with max payload : 11.70 [min]
practical ceiling (operational weight empty 16734 [kg] ) : 7000 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:21917 [kg] ) : 5400 [m]
calculation *10* (action radius & endurance)
published range : 1288 [km] with 5 crew and 4264.6 [kg] useful load and 88.1 [%] fuel
range : 1270 [km] with 5 crew and 4300.0 [kg] useful load and 86.9 [%] fuel
range : 1639 [km] with 40.0 passengers with each 12.2 [kg] luggage and 112.1 [%] fuel
Available Seat Kilometres (ASK) : 65557 [paskm]
max range theoretically with additional fuel tanks total 9747.8 [litre] fuel : 3982 [km]
useful load with range 500km : 6153 [kg]
useful load with range 500km : 40 passengers
production (theor.max load): 1917 [tonkm/hour]
production (useful load): 1340 [tonkm/hour]
production (passengers): 12464 [paskm/hour]
oil and fuel consumption per tonkm : 0.34 [kg]
fuel cost per paskm : 0.052 [eur]
crew cost per paskm : 0.024 [eur]
economic hours : 12775 [hours] is less then design hours
time between engine failure : 381 [hr]
can continue fly on 3 engines, low risk for emergency landing for PUF
writing off per paskm : 0.078 [eur]
insurance per paskm : 0.003 [eur]
maintenance cost per paskm : 0.251 [eur]
direct operating cost per paskm : 0.408 [eur]
direct operating cost per tonkm (max. load): 2.653 [eur]
direct operating cost per tonkm (normal useful load): 3.796 [eur]
Literature :
Piston-engined airliners page
Praktisch handboek vliegtuigen deel 5 page
Jane’s all the world aircraft 1938 page 17c, 18c
Jane’s fighting aircraft WWII page 103,104
Armstrong Whitworth Ensign - 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