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weight and performance calculations for the Douglas DC-7C
Douglas DC-7C “seven seas”
role : heavy prop 80
importance : ****
first flight : 20 December 1955 operational : June 1956
country : United States of America
design :
production : 121 aircraft till 1958
General information :
Further development of the DC-7. The range of the DC-7B was still not enough to cross the Atlantic Ocean with an economic payload non-stop form east to west against the prevailing winds. To extend the range addition fuel capacity was created for 5100 litre by inserting a wing-section at the wing root giving a 3 [m] bigger wing span. This also placed the engines 1.5 m further from the fuselage reducing cabin noise and vibrations.
The fuselage was strengthened to allow for higher MTOW and lengthened by 1.07 [m] to give space for 62 first class passengers (2+2 seating) or up to 105 in tourist class (3+2 seating).
A new version of the Turbo Compound engine was installed, the R-3350-18EA1 giving more cruise power and 3400 [hp] for take-off.
It had a dual cloud-collision radar in the nose. It had an improved de-icing system.
Th DC-7C was equipped with the Sperry Integrated flight system which combined several instruments making flying on instruments more easy.
The HF/RT receivers are equipped with selective-calling system ( Selcal ), so the crew only receives radio message directed to them and not all the other radio messages for other planes.
Panam starting operations with the DC-7C on 1 June 1956. It could cross the Atlantic ocean now fairly reliable. For not be passed BOAC also ordered the DC-7C and not to wait for the Bristol Britannia.
On 11 November 1956 a BOAC DC-7C flew non-stop from London to New York in 10 hours 40 minutes. The DC-7C sold better than its rival, the Lockheed L-1649A Starliner but the arrival of the Boeing 707 and DC-8 jetliners cut all further sales.
Later after the arrival of the jetliners many DC-7C’s were converted to DC-7F freighters.
KLM received on 18 April 1957 her first DC-7C’s of total 15. KLM used it for passengers flights till 1965 and after that 4 converted to freighter DC-7F till 1969.
With the DC-7C KLM could fly for the first time via the North pole to Indonesia and Tokyo. Non-stop Amsterdam – Anchorage, Alaska is 7188 km. straight distance Anchorage – Tokyo is 5360 km and Tokyo – Jakarta is 5565 km
Fuel capacity : 29617 litre. Basic price 1.15 mln USD in 1956.
Due to its cumbersome complicated engines the DC-7 was sooner replaced then its predecessor the reliable workhorse DC-6.
Primary users : PAA, KLM(15), Swissair, Japan Airlines, Martinair, Alitalia, Scanair,
Sudflug, BOAC, Airlift, Braniff, Northwest, Saturn, SAS
flight crew : 5 cabin crew : 3 passengers : 62-105
flight crew consist of pilot, co-pilot, engineer and 2 relieve crew
powerplant : 4 Wright R-3350-18EA1 Turbo Compound air-cooled 18 -cylinder radial engine 1800 [hp](1342.3 KW)
normal rating, supercharged engine, high blower, constant power to height : 7400 [m]
and with 3400 [hp](2535.4 KW) available for take-off
dimensions :
wingspan : 38.86 [m], length : 34.21 [m], height : 9.65 [m]
wing area : 152.1 [m^2]
weights :
max.take-off weight : 64864 [kg]
empty weight operational : 35780 [kg] useful load : 10592 [kg]
performance :
maximum continuous speed : 648 [km/u] op 7400 [m]
normal cruise speed : 591 [km/u] op 6600 [m] (83 [%] power)
service ceiling : 8656 [m]
range with max fuel : 10400 [km] and allowance for 1108.5 [km] diversion and 30 [min] hold
description :
low-winged monoplane with retractable landing gear with nose wheel
tapered multi-cellular wing with flush-riveted stressed skin
with Fowler flaps airfoil : root : NACA 23016 tip : NACA 23012
engines and landing gear attached to the wings, fuel tanks in the wings
construction : all-metal aluminium-alloy stressed-skin construction with pressurized
fuselage
fuselage shape : O
airscrew :
four Hamilton-Standard constant speed, reversible pitch 4 -bladed tractor airscrews
with max. efficiency :0.76 [ ]
diameter airscrew 4.27 [m]
relative pitch (J) : 2.41 [ ]
power loading prop : 157.17 [KW/m]
theoretical pitch without slip : 11.43 [m]
blade angle prop at max.speed : 49.64 [ ]
tip-speed close to speed of sound (above Mach 0.85) > loose of efficiency
reduction : 0.44 [ ]
airscrew revs : 1050 [r.p.m.]
aerodynamic pitch at max. continuous speed 10.29 [m]
blade-tip speed at max.continuous speed : 296 [m/s]
propellor noise in flight : 102 [Db]
calculation : *1* (dimensions)
measured wing chord : 3.67 [m] at 50% wingspan
mean wing chord : 3.91 [m]
calculated average wing chord tapered wing with rounded tips: 3.77 [m]
wing aspect ratio : 9.9 []
seize (span*length*height) : 12829 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 40.3 [kg/hr]
fuel consumption (econ. cruise speed) : 1085.2 [kg/hr] (1480.6 [litre/hr]) at 83 [%] power
distance flown for 1 kg fuel : 0.54 [km/kg] at 6600 [m] height, sfc : 243.0 [kg/kwh]
estimated total fuel capacity : 29571 [litre] (21676 [kg])
calculation : *3* (weight)
weight engine(s) dry with reduction gear : 6200.0 [kg] = 1.15 [kg/KW]
weight 1081.4 litre oil tank : 91.92 [kg]
oil tank filled with 40.3 litre oil : 36.1 [kg]
DC-7C flight deck, note the two weather-radar screens
oil in engine 29.9 litre oil : 26.8 [kg]
fuel in engine 36.6 litre fuel : 26.85 [kg]
weight 629.4 litre gravity patrol tank(s) : 94.4 [kg]
weight jet stacks : 134.2 [kg]
weight NACA cowling 60.1 [kg]
weight variable pitch control : 39.0 [kg]
weight airscrew(s) incl. boss & bolts : 1098.8 [kg]
total weight propulsion system : 7769 [kg](12.0 [%])
***************************************************************
fuselage aluminium frame : 7538 [kg]
typical cabin layout for 76 passengers : pitch : 81 [cm] ( 2+2 ) seating in 19.0 rows
pax density (normal seating) : 0.86 [m2/pax]
high density seating passengers : 112 at 5 -abreast seating in 22.4 rows
weight 6 toilets : 47.4 [kg]
weight 6 hand fire extinguisher : 18 [kg]
weight pantry : 187.2 [kg]
weight 40 windows : 36.0 [kg]
weight 4 emergency exits : 12.0 [kg]
weight 4 life rafts : 95.0 [kg]
weight oxygen masks & oxygen generators : 49.4 [kg]
weight emergency flare installation : 10 [kg]
weight emergency evacuation slide : 15 [kg]
weight 2 entrance/exit doors : 24.0 [kg]
weight 2 freight doors (belly) : 8.0 [kg]
extra main deck space for freight/mail/luggage etc. : 2.89 [m3]
cabin volume (usable), excluding flight deck : 136.99 [m3]
passenger cabin max.width : 2.97 [m] cabin length : 22.10 [m] cabin height : 2.36 [m]
pressure at cruise height 6100.00 [m] : 0.47 [kg/cm2] cabin pressure : 0.77 [kg/cm2]
weight rear pressure bulkhead : 180.7 [kg]
weight air pressurization system : 38.7 [kg]
fuselage covering ( 229.0 [m2] duraluminium 4.38 [mm]) : 2632.5 [kg]
weight floor beams : 119.0 [kg]
weight cabin furbishing : 465.8 [kg]
weight cabin floor : 408.3 [kg]
fuselage (sound proof) isolation : 99.9 [kg]
weight radio transceiver equipment : 7.0 [kg]
weight dual cloud-collision radar : 25.0 [kg]
weight radio direction finding (RDF) equipment : 5.0 [kg]
weight Sperry Integrated Flight System : 11.0 [kg]
weight artificial horizon : 1.1 [kg]
weight instruments. : 38.0 [kg]
weight APU / engine starter: 67.1 [kg]
weight lighting : 19.0 [kg]
weight electricity generator : 19.0 [kg]
weight controls : 15.0 [kg]
weight seats : 420.0 [kg]
weight air conditioning : 114 [kg]
total weight fuselage : 12566 [kg](19.4 [%])
***************************************************************
total weight aluminium ribs (846 ribs) : 2313 [kg]
weight titanium firewalls and engine mounts : 191 [kg]
weight fuel tanks empty for total 28942 [litre] fuel : 2315 [kg]
weight wing covering (painted aluminium 2.85 [mm]) : 2339 [kg]
total weight aluminium spars (multi-cellular wing structure) : 2754 [kg]
weight wings : 7407 [kg]
weight wing/square meter : 48.70 [kg]
cantilever wing without bracing cables
weight rubber de-icing boots : 42.7 [kg]
weight fin & rudder (17.5 [m2]) : 856.2 [kg]
weight stabilizer & elevator (17.1 [m2]): 834.4 [kg]
weight flight control hydraulic servo actuators: 57.1 [kg]
weight fowler flaps (12.7 [m2]) : 314.6 [kg]
total weight wing surfaces & bracing : 12018 [kg] (18.5 [%])
*******************************************************************
wheel pressure : 16216.0 [kg]
weight 4 Dunlop main wheels (1330 [mm] by 266 [mm]) : 799.2 [kg]
weight 2 Dunlop nose wheels : 199.8 [kg]
weight hydraulic wheel-brakes : 46.4 [kg]
weight pneumatic-hydraulic shock absorbers : 61.8 [kg]
weight wheel hydraulic operated retraction system : 176.2 [kg]
weight undercarriage struts with axle 1468.4 [kg]
total weight landing gear : 2642.9 [kg] (4.1 [%]
*******************************************************************
********************************************************************
calculated empty weight : 34996 [kg](54.0 [%])
weight oil for 21.1 hours flying : 850.3 [kg]
calculated operational weight empty : 35847 [kg] (55.3 [%])
published operational weight empty : 35780 [kg] (55.2 [%])
weight crew : 648 [kg]
weight fuel for 2.0 hours flying : 2170 [kg]
weight catering : 468.1 [kg]
weight water : 374.5 [kg]
********************************************************************
operational weight empty: 39508 [kg](60.9 [%])
weight 76 passengers : 5852 [kg]
weight luggage : 927 [kg]
weight cargo : 3813 [kg]
operational weight loaded: 50100 [kg](77.2 [%])
fuel reserve : 14764.3 [kg] enough for 13.60 [hours] flying
operational weight fully loaded : 64864 [kg] with fuel tank filled for 78 [%]
published maximum take-off weight : 64864 [kg] (100.0 [%])
calculation : * 4 * (engine power)
power loading (Take-off) : 6.40 [kg/kW]
power loading (operational without useful load) : 7.36 [kg/kW]
power loading (Take-off) 1 PUF: 8.53 [kg/kW]
max.total take-off power : 10141.5 [kW]
calculation : *5* (loads)
manoeuvre load : 4.6 [g] at 1000 [m]
limit load : 2.5 [g] ultimate load : 3.8 [g] load factor : 1.2 [g]
design flight time : 12.32 [hours]
design cycles : 3151 sorties, design hours : 38818 [hours]
operational wing loading : 3656 [N/m^2]
wing stress (3 g) during operation : 225 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.77 ["]
max. angle of attack (stalling angle, clean) : 12.59 ["]
max. angle of attack (full flaps) : 11.70 ["]
angle of attack at max. speed : 1.32 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.16 [ ]
lift coefficient at max. speed : 0.28 [ ]
lift coefficient at max. angle of attack : 1.30 [ ]
max.lift coefficient full flaps : 1.73 [ ]
induced drag coefficient at max.speed : 0.0032 [ ]
drag coefficient at max. speed : 0.0151 [ ]
drag coefficient (zero lift) : 0.0119 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 63779 [kg]): 259 [km/u]
stalling speed at sea-level with full flaps (normal landing weight): 164 [km/u]
landing speed at sea-level (normal landing weight : 48546 [kg]): 188 [km/hr]
max. rate of climb speed : 271 [km/hr] at sea-level
max. endurance speed : 290 [km/u] min.fuel/hr : 698 [kg/hr] at height : 610 [m]
max. range speed : 543 [km/u] min. fuel consumption : 2.087 [kg/km] at cruise height : 7315 [m]
cruising speed : 591 [km/hr] at 6600 [m] (power:88 [%])
max. continuous speed* : 648.00 [km/hr] at 7400 [m] (power:100 [%])
climbing speed at sea-level (loaded) : 267 [m/min]
climbing speed at 1000 [m] with 1 engine out (PUF / MTOW) : 255 [m/min]
climbing speed at 1000 [m] with 2 engines out (2xPUF / MTOW) : 60 [m/min]
calculation : *9* (regarding various performances)
take-off speed : 313.3 [km/u]
emergency/TO power : 3400 [hp] at 2800 [rpm]
static prop wash : 185 [km/u]
high wheel pressure, can only take off from paved runways
take-off distance at sea-level concrete runway : 1947 [m]
take-off distance at sea-level over 15 [m] height : 2200 [m]
landing run : 768 [m]
landing run from 15 [m] : 1515 [m]
lift/drag ratio : 22.60 [ ]
climb to 1000m with max payload : 9.21 [min]
climb to 2000m with max payload : 19.64 [min]
climb to 3000m with max payload : 31.79 [min]
climb to 5000 [m] with max payload : 71.46 [min]
practical ceiling (operational weight empty 39508 [kg] ) : 10300 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:64321 [kg] ) : 6100 [m]
calculation *10* (action radius & endurance)
published range : 10400 [km] with 8 crew and 9272.0 [kg] useful load and 88.1 [%] fuel (no reserves)
range : 9681 [km] with 8 crew and 10592.0 [kg] useful load and 82.0 [%] fuel
range : 11757 [km] with 76.0 passengers with each 12.2 [kg] luggage and 99.6 [%] fuel
Available Seat Kilometres (ASK) : 893570 [paskm]
max range theoretically with additional fuel tanks total 39476.6 [litre] fuel : 13866 [km]
useful load with range 500km : 28018 [kg]
useful load with range 500km : 76 passengers
production (theor.max load): 16559 [tonkm/hour]
production (useful load): 6260 [tonkm/hour]
production (passengers): 44916 [paskm/hour]
combi aircraft mail/freight/passengers
oil and fuel consumption per tonkm : 0.068 [kg]
fuel cost per paskm : 0.025 [eur]
crew cost per paskm : 0.023 [eur]
economic hours : 18250 [hours] is less then design hours
time between engine failure : 5194 [hr]
can continue fly on 3 engines, low risk for emergency landing for PUF
writing off per paskm : 0.036 [eur]
insurance per paskm : 0.0000 [eur]
maintenance cost per paskm : 0.169 [eur]
direct operating cost per paskm : 0.253 [eur]
direct operating cost per tonkm (max. load): 0.686 [eur]
direct operating cost per tonkm (normal useful load): 1.814 [eur]
Literature :
Douglas DC-7 Archives - This Day in Aviation
Piston-engined airliners page 59,60,61
Verkeersvliegtuigen Moussault page 117
Amerikaanse vliegtuigbouwers page 64
Praktisch handboek vliegtuigen deel 5 page 55,56,57
KLM gegevens page 10
De Nederlandse DC-7C’s page 1 - 32
http://www.airwar.ru/enc/aliner/dc7c.html
* max. continuous speed : max. level speed maintainable for minimal 30 min.
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 22 January 2022 contact : info.aircraftinvestigation@gmail.com python 3.7.4