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weight and performance calculations for the Douglas DC-7
Douglas DC-7
role : heavy prop 80
importance : ****
first flight : 18 May 1953 operational : December 1953
country : United States of America
design :
production : 120 aircraft at Santa Monica
general information :
Lockheed decided to build a new version of the existing Constellation equipped with the new Wright Turbo Compound engine. This became the L-1049 Super Constellation which had a superior flight range. It was ordered almost immediately by TWA. It was even able to bridge the American continent non-stop with a strong headwind, something that was not yet possible with the DC-6B. American and United Airlines found themselves in a disadvantageous competition position and went to Douglas for an improved version of the DC-6B equipped with the Turbo Compound engine. American Airlines paid the development costs for a large part and this quickly removed all doubts at Douglas.
For the development of the new aircraft, soon referred to as DC-7, the DC-6B was taken as the base. The fuselage was extended by 1.02 [m] and strengthened and the take-off weight was increased to a maximum of 55,429 [kg]. It received four-bladed Hamilton-Standard 34E60 air screws made of duralumin and with a diameter of 4.10 [m]. The DC-7 received motor nacelles and firewalls made of titanium. This was the first application of this new metal in an airliner. Compared to the traditional stainless steel engine nacelles, 118 [kg] of weight per nacelle was saved. The landing gear was designed in such a way that it could be used as an air brake. It could already be lowered at air speeds of up to 660 km/h at an altitude of 6100 [m]. The wheels and wheel doors then provided as much resistance as the entire fuselage and wings! It could thus decent at 1200 [m/min]. Outwardly, the DC-7 differed little from the
DC-6B. On 18 May 1953 the aircraft made its first flight. American Airlines made the first service flight with the DC-7 on the Los Angeles – New York route on December 1, 1953. The DC-7 was the first airline who could fly this route non-stop. The non-stop flight had to be made within 8 hours, for not to exceed the flight crew max. allowed flight time before relief by a new crew. For this a high cruise speed had to be maintained but this placed more strain on the high power engines, leading to frequent engine failures and low MTBO. Straight distance NY – LA is 3950 km, to fly this distance within 8 hrs a ground speed of more then 500 km/hr is needed, to take in account 30 min time for take-off and landing and 25 km/hr head-wind the
DC-7 had to cruise at 550 km/hr.
The DC-7 had a range of 7130 [km] with 20,834 liters of fuel flying at cruising speed at 4575 [m] altitude. This was too little for non-stop transatlantic flights, for which purpose Douglas began developing a long range version, which was given the designation DC-7B.
The DC-7 was an improvement over the DC-6B regarding useful load and range but it had higher operating cost and more engine noise and vibrations.
Basic price : 823000 USD in 1953
primary users : American Airlines (25), Aerovias Panama, Delta, Internord,
United Airlines, Eastern Airlines
flight crew : 4 cabin crew : 3 passengers : 74
flight crew consist of pilot, co-pilot, radio operator and engineer
powerplant : 4 Wright R-3350-18DA4 Turbo Compound air-cooled 18 -cylinder radial engine 1700 [hp](1267.7 KW)
normal rating, supercharged engine, high blower, constant power to height : 7400 [m]
and with 3250 [hp](2423.5 KW) available for take-off
dimensions :
wingspan : 35.81 [m], length : 33.19 [m], height : 8.71 [m]
wing area : 135.9 [m^2]
weights :
max.take-off weight : 55429 [kg]
empty weight operational : 30500 [kg] useful load : 9072 [kg]
performance :
maximum continuous speed : 648 [km/u] op 7400 [m]
normal cruise speed : 587 [km/u] op 6600 [m] (82 [%] power)
service ceiling : 7620 [m]
range with max fuel : 7593 [km] and allowance for 731.6 [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 : NACA
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 :0.75 [ ]
diameter airscrew 4.10 [m]
relative pitch (J) : 2.51 [ ]
power loading prop : 154.60 [KW/m]
theoretical pitch without slip : 11.43 [m]
blade angle prop at max.speed : 50.80 [ ]
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 : 288 [m/s]
propellor noise in flight : 100 [Db]
calculation : *1* (dimensions)
measured wing chord : 3.77 [m] at 50% wingspan
mean wing chord : 3.80 [m]
calculated average wing chord tapered wing with rounded tips: 3.68 [m]
wing aspect ratio : 9.4 []
seize (span*length*height) : 10352 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 40.6 [kg/hr]
fuel consumption (econ. cruise speed) : 1040.3 [kg/hr] (1419.2 [litre/hr]) at 82 [%] power
distance flown for 1 kg fuel : 0.56 [km/kg] at 6600 [m] height, sfc : 250.0 [kg/kwh]
estimated total fuel capacity : 20836 [litre] (15273 [kg])
calculation : *3* (weight)
weight engine(s) dry with reduction gear : 6000.0 [kg] = 1.18 [kg/KW]
weight 828.2 litre oil tank : 70.40 [kg]
oil tank filled with 38.0 litre oil : 34.1 [kg]
oil in engine 28.2 litre oil : 25.4 [kg]
fuel in engine 34.6 litre fuel : 25.35 [kg]
weight 603.3 litre gravity patrol tank(s) : 90.5 [kg]
weight jet stacks : 126.8 [kg]
weight NACA cowling 56.8 [kg]
weight variable pitch control : 33.5 [kg]
weight airscrew(s) incl. boss & bolts : 945.3 [kg]
total weight propulsion system : 7375 [kg](13.3 [%])
***************************************************************
fuselage aluminium frame : 6271 [kg]
typical cabin layout for 74 passengers : pitch : 81 [cm] ( 2+2 ) seating in 18.5 rows
pax density (normal seating) : 0.86 [m2/pax]
high density seating passengers : 107 at 5 -abreast seating in 21.5 rows
weight 4 toilets : 33.7 [kg]
weight 6 hand fire extinguisher : 17 [kg]
weight pantry : 134.0 [kg]
weight 39 windows : 35.1 [kg]
weight 4 emergency exits : 12.0 [kg]
weight 4 life rafts : 92.5 [kg]
weight oxygen masks & oxygen generators : 48.1 [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. : 4.44 [m3]
cabin volume (usable), excluding flight deck : 132.70 [m3]
passenger cabin max.width : 3.01 [m] cabin length : 21.19 [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 : 157.2 [kg]
weight air pressurization system : 37.3 [kg]
fuselage covering ( 221.3 [m2] duraluminium 3.77 [mm]) : 2189.0 [kg]
weight floor beams : 120.8 [kg]
weight cabin furbishing : 437.3 [kg]
weight cabin floor : 381.5 [kg]
fuselage (sound proof) isolation : 89.7 [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: 63.4 [kg]
weight lighting : 18.5 [kg]
weight electricity generator : 18.5 [kg]
weight controls : 14.4 [kg]
weight seats : 405.0 [kg]
weight air conditioning : 111 [kg]
total weight fuselage : 10657 [kg](19.2 [%])
***************************************************************
total weight aluminium ribs (746 ribs) : 1977 [kg]
weight titanium firewalls and engine mounts : 180 [kg]
weight fuel tanks empty for total 20233 [litre] fuel : 1619 [kg]
weight wing covering (painted aluminium 2.74 [mm]) : 2007 [kg]
total weight aluminium spars (multi-cellular wing structure) : 2304 [kg]
weight wings : 6287 [kg]
weight wing/square meter : 46.26 [kg]
cantilever wing without bracing cables
weight rubber de-icing boots : 39.4 [kg]
weight fin & rudder (14.9 [m2]) : 690.9 [kg]
weight stabilizer & elevator (15.3 [m2]): 708.4 [kg]
weight flight control hydraulic servo actuators: 46.1 [kg]
weight fowler flaps (11.3 [m2]) : 268.0 [kg]
total weight wing surfaces & bracing : 9839 [kg] (17.8 [%])
*******************************************************************
wheel pressure : 13857.2 [kg]
weight 4 Dunlop main wheels (1330 [mm] by 266 [mm]) : 740.1 [kg]
weight nose wheel : 92.5 [kg]
weight hydraulic wheel-brakes : 39.6 [kg]
weight pneumatic-hydraulic shock absorbers : 52.8 [kg]
weight wheel hydraulic operated retraction system : 156.7 [kg]
weight undercarriage struts with axle 1283.9 [kg]
total weight landing gear : 2351.0 [kg] (4.2 [%]
*******************************************************************
********************************************************************
calculated empty weight : 30221 [kg](54.5 [%])
weight oil for 15.5 hours flying : 629.7 [kg]
calculated operational weight empty : 30851 [kg] (55.7 [%])
published operational weight empty : 30500 [kg] (55.0 [%])
weight crew : 567 [kg]
weight fuel for 2.0 hours flying : 2081 [kg]
weight catering : 335.0 [kg]
weight water : 268.0 [kg]
********************************************************************
operational weight empty: 34101 [kg](61.5 [%])
weight 74 passengers : 5698 [kg]
weight luggage : 903 [kg]
weight cargo : 2471 [kg]
operational weight loaded: 43173 [kg](77.9 [%])
fuel reserve : 12255.7 [kg] enough for 11.78 [hours] flying
operational weight fully loaded : 55429 [kg] with fuel tank filled for 94 [%]
published maximum take-off weight : 55429 [kg] (100.0 [%])
365 mph = 587 km/hr fuel 5500 US gallon = 20790 litre range 3000 miles = 4827 km
calculation : * 4 * (engine power)
power loading (Take-off) : 5.72 [kg/kW]
power loading (operational without useful load) : 6.73 [kg/kW]
power loading (Take-off) 1 PUF: 7.62 [kg/kW]
max.total take-off power : 9694.1 [kW]
calculation : *5* (loads)
manoeuvre load : 7.0 [g] at 1000 [m]
limit load : 2.5 [g] ultimate load : 3.8 [g] load factor : 1.2 [g]
design flight time : 9.05 [hours]
design cycles : 3450 sorties, design hours : 31238 [hours]
operational wing loading : 3508 [N/m^2]
wing stress (3 g) during operation : 227 [N/kg] at 3g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.79 ["]
max. angle of attack (stalling angle, clean) : 12.84 ["]
max. angle of attack (full flaps) : 11.95 ["]
angle of attack at max. speed : 1.23 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.16 [ ]
lift coefficient at max. speed : 0.27 [ ]
lift coefficient at max. angle of attack : 1.31 [ ]
max.lift coefficient full flaps : 1.74 [ ]
induced drag coefficient at max.speed : 0.0032 [ ]
drag coefficient at max. speed : 0.0157 [ ]
drag coefficient (zero lift) : 0.0125 [ ]
calculation : *8* (speeds
stalling speed at sea-level (OW loaded : 54389 [kg]): 252 [km/u]
stalling speed at sea-level with full flaps (normal landing weight): 160 [km/u]
landing speed at sea-level (normal landing weight : 41798 [kg]): 184 [km/hr]
max. rate of climb speed : 266 [km/hr] at sea-level
max. endurance speed : 289 [km/u] min.fuel/hr : 676 [kg/hr] at height : 610 [m]
max. range speed : 514 [km/u] min. fuel consumption : 2.028 [kg/km] at cruise height :
6401 [m]
cruising speed : 587 [km/hr] at 6600 [m] (power:87 [%])
max. continuous speed* : 648.00 [km/hr] at 7400 [m] (power:100 [%])
climbing speed at sea-level (loaded) : 299 [m/min]
climbing speed at 1000 [m] with 1 engine out (PUF / MTOW) : 303 [m/min]
climbing speed at 1000 [m] with 2 engines out (2xPUF / MTOW) : 88 [m/min]
calculation : *9* (regarding various performances)
take-off speed : 305.3 [km/u]
emergency/TO power : 3250 [hp] at 2800 [rpm]
static prop wash : 177 [km/u]
high wheel pressure, can only take off from paved runways
take-off distance at sea-level concrete runway : 1739 [m]
take-off distance at sea-level over 15 [m] height : 1962 [m]
landing run : 731 [m]
landing run from 15 [m] : 1463 [m]
lift/drag ratio : 21.38 [ ]
climb to 1000m with max payload : 7.42 [min]
climb to 2000m with max payload : 15.65 [min]
climb to 3000m with max payload : 24.97 [min]
climb to 5000 [m] with max payload : 51.97 [min]
practical ceiling (operational weight empty 34101 [kg] ) : 10400 [m]
practical ceiling fully loaded (mtow- 30 min.fuel:54909 [kg] ) : 7200 [m]
calculation *10* (action radius & endurance)
published range : 7593 [km] with 7 crew and 10555.3 [kg] useful load and 88.1 [%]
fuel (no reserves)
range : 8430 [km] with 7 crew and 9072.0 [kg] useful load and 97.8 [%] fuel
range : 9824 [km] with 74.0 passengers with each 12.2 [kg] luggage and 114.0 [%]
fuel
Available Seat Kilometres (ASK) : 727012 [paskm]
max range theoretically with additional fuel tanks total 33420.6 [litre] fuel : 12077
[km]
useful load with range 500km : 23611 [kg]
useful load with range 500km : 74 passengers
production (theor.max load): 13860 [tonkm/hour]
production (useful load): 5325 [tonkm/hour]
production (passengers): 43438 [paskm/hour]
combi aircraft mail/freight/passengers
oil and fuel consumption per tonkm : 0.08 [kg]
fuel cost per paskm : 0.025 [eur]
crew cost per paskm : 0.021 [eur]
economic hours : 18250 [hours] is less then design hours
time between engine failure : 2106 [hr]
can continue fly on 3 engines, low risk for emergency landing for PUF
writing off per paskm : 0.032 [eur]
insurance per paskm : 0.000 [eur]
maintenance cost per paskm : 0.147 [eur]
direct operating cost per paskm : 0.225 [eur]
direct operating cost per tonkm (max. load): 0.705 [eur]
direct operating cost per tonkm (normal useful load): 1.835 [eur]
Literature :
Praktisch handboek vliegtuigen deel 5 page 55
Amerikaanse vliegtuigbouwers page 64
Piston-engined airliners page 60
Verkeersvliegtuigen Moussault page 116,117
* 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