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weight and performance calculations for the McDonnel Douglas DC-8-71
Delta DC-8-71 N825E c/n 45944 taking off at Fort Lauderdale, Florida, November 1987
McDonnel Douglas DC-8-71
role : long-range jet airliner
importance : **
first flight : 15 August 1981 operational : begin 1983
country : United States of America
ICAO aircraft type designator : DC87
production : 53 aircraft
general information :
At the end of the seventies, people started to think of ways to
DC-8 to be able to keep in service longer. The exorbitant noise needed to be addressed. It was decided to equip existing -61,-62 and -63's with the quiet and economical CFM56 engine, so the -71, -72 and -73 were born. The MTOW has remained the same, only the empty weight is slightly higher due to the heavier engines. The Super 70 series was only used for the transport of passengers for a short time, soon they were converted into cargo aircraft. The freight version of UPS can carry 42638 [kg] of cargo.
The Super Seventies was roughly 70% quieter than the 60 Series and, at the time of their introduction, the world's quietest four-engined airliner. As well as being quieter and more powerful, the CFM56 was up to 23% more fuel-efficient than the JT3D, which reduced operating costs and extended the range.
primary users : Delta Airlines, United Airlines
Accommodation:
flight crew : 4 cabin crew : 7
flight crew consist of pilot, co-pilot, navigator and flight engineer
passengers : seating for 200 in two class : 26 first class and 174 economy class seats
( 32 -in pitch) high density seating for max 259 passengers (equal to exit limit)
engine : 4 GE-Snecma CFM56-2C1 turbofan engines of 97.5 [KN] (21919 [lbf])
Measured tail-angle : 8°
dimensions :
wingspan : 43.41 [m], length overall: 57.12 [m], length of fuselage : 55.75 [m] height : 12.92 [m]
wing area gross : 267.9 [m^2] fuselage exterior width : 3.73 [m]
weights :
operating empty weight : 74299 [kg] max. structural payload : 27307 [kg]
Zero Fuel weight (ZFW) : 101606 [kg] max. landing weight (MLW) : 108864 [kg]
max. take-off weight : 147420 [kg] weight usable fuel : 69513 [kg] (88552 [litres])
performance :
Max. operating Mach number (Mmo) : 0.886 [Mach] (965 [km/hr]) at 9150 [m]
critical Mach speed : 0.83 [Mach]
max. cruising speed : 887 [km/hr] (Mach 0.82 ) at 9449 [m] (34 [%] power)
economic cruising speed : 850 [km/hr] (Mach 0.78 ) at 9449 [m]
service ceiling : 12000 [m]
range with max fuel and MTOW : 9800 [km] (ATA domestic fuel reserves - 370.0 [km] alternate)
description :
*Cantilever low-wing monoplane with retractable landing gear with nose wheel
*Engines attached with pylons to the wing, main landing gear attached to the wings, fuel tanks in the wings and fuselage
*Wings : two main spar fail-safe wing structure
with double slotted trailing edge flaps with leading edge slots ,with spoilers airfoil : NACA with supercritical cross-section average thickness/chord ratio : 10.0 [%], sweep angle 3/4 chord: 30.0 [°]
incidence at root : 2.00 [°], dihedral : 7.0 [°]
*Fuselage : Pressurized aluminium-alloy stressed-skin structure of elliptical 0 section
calculation : *1* (dimensions)
measured wing chord at root: 10.71 [m]
measured wing chord at tip : 2.20 [m]
taper ratio : 0.205 [ ]
United DC-8-71 N8087U c/n 45977 at Chicago O’hare airport. May 1987
mean wing chord : 6.17 [m]
wing aspect ratio : 7.03 []
Oswald factor (e): 0.689 []
seize (span*length*height) : 32036 [m^3]
calculation : *2* (fuel consumption)
oil consumption : 1.2 [kg/hr]
fuel consumption (econ. cruise speed) : 5809.9 [kg/hr] (7401.1 [litre/hr]) at 24 [%] power
distance flown for 1 kg fuel : 0.15 [km/kg] at 9449 [m] height, sfc : 61.5 [kg/KN/h]
total fuel capacity : 88552 [litre] (69513 [kg])
calculation : *3* (weight)
weight engine(s) dry : 8400.0 [kg] = 21.54 [kg/KN]
weight 26.9 litre oil tank : 2.29 [kg]
oil tank filled with 2.5 litre oil : 2.2 [kg]
oil in engine 4.8 litre oil : 4.3 [kg]
weight all fuel lines and pumps containing 91 litres fuel : 140.6 [kg]
weight engine cowling : 1014.0 [kg]
weight double thrust reversers : 663.0 [kg]
total weight propulsion system : 10226 [kg](6.9 [%])
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Accommodation cabin facilities:
Length 187ft 5in = 57.12 [m] = DC-8-71 length
typical 2-class cabin layout for 200 passengers : economy : pitch : 81.3 [cm] 32.0 [-in] ( 3+3 )
seating in 35.5 rows
first class pitch : 157.0 [cm] 61.8 [-in] at 4 -abreast
weight passenger seats (width 50.5 [cm]) : 1145.5 [kg]
weight cabin crew seats : 35.0 [kg]
weight flight crew seats : 84.0 [kg]
high density seating passengers : 259 [pax] at mainly 6 -abreast seating in 44.7 rows, pitch
81.3 [cm] 32.0 [-in]
pax density, normal seating : 0.779 [m2/pax], high density seating : 0.602 [m2/pax]
weight 6 lavatories : 173.0 [kg]
weight 4 galleys : 202.4 [kg]
weight overhead stowage for hand luggage (total : 12.4 [m3] = 257 55x35x25cm carry-on
trolleys) : 192.8 [kg]
weight 6 wardrobe closets : 131.4 [kg]
weight 3 movie screens : 26.7 [kg]
weight 73 windows (47x38cm) made of acrylic glass: 310.3 [kg]
weight 2 (1.83 x 0.88 [m]) main entry doors : 127.0 [kg]
weight 2 (1.63 x 0.85 [m]) galley service doors : 109.7 [kg]
weight 4 (main door size : 1.12 x 0.91 [m]) freight doors (belly) : 175.6 [kg]*
total usable belly baggage/cargo hold volume : 74.6 [m3]
cabin volume (usable), excluding flight deck : 286 [m3]
passenger compartment volume : 198 [m3]
Height cabin is 2.21m minus thickness of cabin 11 cm gives internal standing height of 2.10m
passenger cabin max width : 3.51 [m] cabin length : 44.38 [m] max cabin height : 2.10 [m]
floor area : 141.5 [m2]
weight cabin facilities : 2713.4 [kg]
safety facilities:
weight 4 type III over wing emergency exits (51x97 cm): 77.7 [kg]
weight 4 type I emergency exits (61x142 cm): 137.5 [kg]
evacuation time with 259 passengers : 45 [sec]
weight 5 hand fire extinguisher : 15 [kg]
weight cockpit voice recorder (CVR) and flight data recorder (FDR): 20.0 [kg]
weight oxygen masks & oxygen generators (deploy cabin alt.>4267m): 130.0 [kg]
weight emergency flare installation : 10 [kg]
weight 4 emergency evacuation slides : 169.5 [kg]
weight safety equipment & facilities : 560 [kg]
fuselage construction:
fuselage aluminium frame : 17195 [kg]
floor loading (payload/m2): 193 [kg/m2]
weight rear pressure bulkhead : 221.2 [kg]
fuselage covering ( 499.0 [m2] duraluminium 3.84 [mm]) : 5042.6 [kg]
weight paint fuselage : 104.8 [kg]
weight aluminium floor beams : 711.5 [kg]
weight cabin furbishing : 1181.5 [kg]
weight cabin floor : 2150.7 [kg]
weight (sound proof) isolation : 372.3 [kg] TO-noise level : 96.0 [EPNdB]
weight 43594 [litre] main central fuel tank empty : 871.9 [kg]
weight empty 371 [litre] potable water tanks : 32.8 [kg]
weight empty waste tank : 22.8 [kg]
weight fuselage structure : 27907.3 [kg]
Avionics:
weight VHF radio and Selcal : 9.0 [kg]
weight flight and service attendants intercom : 5.0 [kg]
BAX global DC-8-7(F) cockpit, N829BX
weight monochromatic weather X-band (3.2cm wavelength) radar system : 25.0 [kg]
weight VOR/ILS,RMI,DME,radio altimeter, ASI, time clock : 20.0 [kg]
weight dual digital Flight Management System (FMS) for navigation/auto-pilot : 20.0 [kg]
weight Cat IIIA auto-landing system : 10.0 [kg]
weight EFIS (4 Rockwell Collins CRT screens ADI/PFD+HSI/ND displays) : 20 [kg]
weight ground proximity warning system (GPWS) : 6 [kg]
weight 2 Rockwell Collins CRT screens to display EICAS information : 36 [kg]
weight reserve ADI, ASI, alti-meter, compass, engine temp. and rpm indicators : 15 [kg]
weight avionics : 153.0 [kg]
Systems:
Air-conditioning and pressurization system maintains sea level conditions up to 7100 [m]
and gives equivalent of 2000 [m] at 12200 [m]. pressure differential : 0.62 [bar] (kg/cm2)
pressurized fuselage volume : 502 [m3] cabin air refreshment time : 3.0 [min]
weight air-conditioning and pressurization system : 280 [kg]
weight APU / engine starter : 48.8 [kg]
weight lighting : 66.0 [kg]
weight 210 bar hydraulic system : 162.5 [kg]
weight engine-driven 40kVA electricity generators : 50.0 [kg]
weight ram air turbine for emergency electric power : 5.0 [kg]
weight 22Ah battery : 28.5 [kg]
weight controls : 22.3 [kg]
weight systems : 658.2 [kg]
total weight fuselage : 31992 [kg](21.7 [%])
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total weight aluminium ribs (46 ribs) : 4806 [kg]
weight engine mounts : 195 [kg]
weight 6 wing fuel tanks empty for total 45312 [litre] fuel : 680 [kg]
weight 354 [litre] vent surge tanks : 43 [kg]
weight wing covering (painted aluminium 3.77 [mm]) : 5457 [kg]
total weight aluminium spars (multi-cellular wing structure) : 5514 [kg]
weight wings : 15777 [kg]
weight wing/square meter : 58.89 [kg]
weight bleed air thermal leading-edge anti-icing : 47.8 [kg]
weight ailerons (11.0 [m2]) : 259.4 [kg]
weight fin (30.3 [m2]) : 894.1 [kg]
weight rudder (13.5 [m2]) : 381.5 [kg]
weight tailplane (horizontal stabilizer) (71.2 [m2]): 2311.2 [kg]
weight elevators (17.1 [m2]): 272.3 [kg]
weight paint wing & tail surfaces : 155.1 [kg]
weight flight control hydraulic servo actuators: 53.4 [kg]
Zambia Airways DC-8-71 9J-AFL c/n 46099 on finals, approaching at London Heathrow (LHR)
weight trailing-edge double slotted flaps (46.5 [m2]) : 1169.9 [kg]
weight leading edge slots (1.9 [m2]) : 34.2 [kg]
weight aluminium honeycomb spoilers (12.8 [m2]) : 174.6 [kg]
total weight wing construction : 22448 [kg] (30.2 [%])
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tire pressure main wheels : 13.20 [Bar] (nitrogen), ply rating : 23 PR
tire speed limit : 338 [km/hr]
total tyre footprint : 0.50 [m2]
Runway LCN at MTOW (0.76m radius of rigidity) : 76 [ ]
Aircraft Classification Number (ACN), MTOW on rigid runway and medium subgrade
strength (B) : 47 [ ]
Can only operate from unpaved runways with reduced weight and reduced tyre pressure
wheel pressure : 16216.2 [kg]
wheel track : 6.34 [m] wheelbase : 23.62 [m]
weight 8 Dunlop 44.0 x 16.0 main wheels (1118 [mm] by 406 [mm]) : 1030.0 [kg]
weight 2 nose wheels : 128.7 [kg]
weight multi-disc wheel-brakes : 119.5 [kg]
weight Hydro-air flywheel detector type anti-skid units : 9.0 [kg]
weight oleo-pneumatic shock absorbers : 135.5 [kg]
weight wheel hydraulic operated retraction system : 1517.8 [kg]
weight undercarriage struts (four-wheel bogies) with axle 4572.5 [kg]
total weight landing gear : 7513.0 [kg] (5.1 [%]
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calculated empty weight : 72179 [kg](49.0 [%])
weight oil for 13.3 hours flying : 16.8 [kg]
unusable fuel in engine and tanks 354.2 litre fuel : 278.1 [kg]
weight lifejackets : 90.0 [kg]
weight 4 life rafts : 125.0 [kg]
weight catering : 237.6 [kg]
weight water : 327.9 [kg]
weight crew : 891 [kg]
weight crew luggage, navigation chards, flight docs (NOTOC), manuals, miscellaneous items : 153 [kg]
operational weight empty : 74299 [kg] (50.4 [%])
********************************************************************
weight 200 passengers : 15400 [kg]
weight luggage : 3200 [kg]
weight cargo : 8707 [kg] (cargo + luggage/m3 belly : 137 [kg/m3])
zero fuel weight (ZFW): 101606 [kg](68.9 [%])
weight fuel for landing (1.2 hours flying) : 7258 [kg]
max. landing weight (MLW): 108864 [kg](73.8 [%])
max. fuel weight : 143812 [kg] (97.6 [%])
payload with max fuel : 39 passengers + luggage 3608 [kg]
can take only few passengers with max.fuel, more like a flying tanker
published maximum take-off weight : 147420 [kg] (100.0 [%])
calculation : * 4 * (engine power)
power loading (Take-off) : 378 [kg/KN]
power loading (Take-off) 1 PUF: 504 [kg/KN]
max. total take-off power : 390.0 [KN]
calculation : *5* (loads)
manoeuvre load : 1.3 [g] at 9000 [m]
limit load : 2.5 [g] ultimate load : 3.8 [g] load factor : 1.3 [g]
design flight time : 2.53 [hours]
design cycles : 23535 sorties, design hours : 59544 [hours]
max. wing loading (MTOW & flaps retracted) : 550 [kg/m2]
wing stress (2 g) during operation : 159 [N/kg] at 2g emergency manoeuvre
calculation : *6* (angles of attack)
angle of attack zero lift : -1.81 ["]
max. angle of attack (stalling angle, clean) : 13.47 ["]
max. angle of attack (full flaps) : 15.51 ["]
angle of attack at economic cruise speed : 2.23 ["]
calculation : *7* (lift & drag ratios
lift coefficient at angle of attack 0° : 0.15 [ ]
lift coefficient at max. speed : 0.29 [ ]
lift coefficient at max. angle of attack (clean): 1.27 [ ]
max. lift coefficient 50 [° ] flap setting : 1.71 [ ]
drag coefficient at max. speed : 0.0316 [ ]
drag coefficient at econ. cruise speed : 0.0286 [ ]
induced drag coefficient at econ. cruise speed : 0.0074 [ ]
drag coefficient (zero lift) : 0.0213 [ ]
lift/drag ratio at econ. speed : 9.04 [ ]
calculation : *8* (speeds
Risk of tailstrike when taking off with OEI (engine failure), pilot must not rotate to fast
minimum unstick speed (Vmu) at TO angle 10.0 ° : 303 [km/u] (164 [kt])
take-off decision speed (V1) : 290 [km/u] (157 [kt])
take-off rotation speed (VR) : 316 [km/u] (171 [kt])
lift-off speed (VLOF) : 333 [km/u] (180 [kt]) at pitch angle : 7.7 [°]
take-off safety speed (V2) : 336 [km/u] (181 [kt])
flap retraction speed (V3) at 500m (OW loaded : 141610 [kg]): 318 [km/u] (172 [kt])
steady initial climb speed (V4) : 362 [km/u] (195 [kt])
climb speed (to FL150 with 63 [%] power) : 579 [km/hr] (313 [kt])
max. endurance speed (Vbe): 470 [km/u] min. fuel/hr : 5079 [kg/hr] at height : 3658 [m]
max. range speed (Vbr): 855 [km/u] (0.81 [mach]) min. fuel consumption : 6.16 [kg/km] at cruise height : 11582 [m]
max. cruising speed : 887 [km/hr] (479 [kt]) at 9449 [m] (power:26 [%])
max. operational speed (Mmo) : 965 [km/hr] (Mach 0.89 ) at 9150 [m] (power:34 [%])
airflow at cruise speed per engine : 255.8 [kg/s]
speed of thrust jet : 1238 [km/hr]
initial descent speed 10000 - 7315 [m]: Mach 0.82
descent speed 7315 - 3048 [m]: 537 [km/u] (290 [kt])
approach speed 3048 - 500 [m] (clean): 463 [km/u] (250 [kt])
minimum control speed (MCS) Vmca (clean): 291 [km/u] (157 [kt])
stalling speed clean at 500 [m] height at Max.Landing Weight : 108864 [kg]): 264 [km/u]
(143 [kt])
DC-8-71 approach speed at MLW 108864 [kg] (240.000 LB) : 143 kts = 264 km/h
final approach speed (landing speed) at sea-level with 50 [°] flaps VREF (max. landing
weight): 265 [km/u] (143 [kt])
ICAO Aircraft Approach Category (APC) : D
stalling speed at sea-level with full flaps VSO (max. landing weight): 204 [km/u] (110 [kt]
rate of climb (max. continous power) at sea-level ROC (loaded, 63 % power) : 1012 [m/min]
rate of climb at sea-level ROC (loaded, 75 % power) : 1379 [m/min]
rate of climb at 1000 [m] with 1 engine out (PUF/MTOW, 63 % power on remaining engines)
: 417 [m/min]
can not stay on height 1000 [m] with 2 engines out, immediate emergency landing needed
rate of descent from FL240 to FL100 (7315m > 3048m): 914 [m/min] (2999 [ft/min])
rate of descent during approach with landing gear extended, with use of spoilers: 457
[m/min] (8 [m/s])
calculation : *9* (regarding various performances)
take-off with reduced take-off power (92 % max thrust power)
ICAO Aerodrome Reference Code : 4D
Brake kinetic energy capacity : 2449 [KW]
FAR takeoff runway length at MTOW (147420 kg / 325000 lb) , seal level, standard day : 8900 ft > 2715m. Calculated TO distance with full power : 2475m. Possible the DC-8-71 was somewhat overpowered, the efficient by-pass engines installed to give better fuel economics, allowing take-off with reduced take-off power to have longer engine life and less overhaul needed. With 92% power calculated TO distance : 2716m. Compared the data with the DC-8-61 with same take-off weight and same lift-off speed, no other explanation I could find.
ASDA with reduced power setting : 2605m, TO distance PUF after V1 : 2509m
FAR TO balanced runway length (TOFL) requirement at TOW 147420 [kg] standard day at
SL (distance to 10.7m height x 1.15): 2716 [m]
Take-off flap setting : 10 [° ]
Landing run at sea level, over 15m, dry runway at MLW 108864 [kg] (240000 LB) : 6450 ft > 1965 [m]. Not clear why the DC-8-71 has a 100 [m] longer RW length than the DC-8-62/62 with the same MLW and approach speed…maybe because of glideslope 3° !?
+++ FAA certification landing distance : +++
landing weight : 108864 [kg], TE flap setting : 50 [°]
runway condition : dry , landing over 50ft (15m) at threshold at sea-level
without use of thrust reversers, glideslope : 3.0 [°]
FAA approved landing field length at SL, dry runway : 1779 [m] (5836 [ft])
FAA approved landing field length at SL, wet runway: 2029 [m] (6657 [ft])
max. lift/drag ratio : 13.38 [ ]
climb to 5000 [m] with max payload : 4.57 [min]
climb to 10000 [m] with max payload : 14.07 [min]
descent time from 10000 [m] to 250 [m] : 24.33 [min]
max. ceiling fully loaded (mtow- 60 min.fuel): 141610 [kg] ) : 16400 [m]
ceiling limited by max. pressure differential 16225 [m]
max. theoretical ceiling (OWE + 60 min.fuel) : 19300 [m] with flying weight :80109 [kg]
calculation *10* (action radius & endurance)
range with max. payload: 6342 [km] with 27307.0 [kg] max. useful load (65.9 [%] fuel)*
range with high density pax: 6840 [km] with 259 passengers (70.5 [%] fuel)*
range with typical two-class pax: 7704 [km] with 200 passengers (78.4 [%] fuel)*
Range with max payload (27307 kg / 60200 lb) : 3300nm > 6110 km. According to Wikipedia range with max payload : 2900 nm (5400km) !
Range with max fuel : 6000 nm = 11110 km with 5000 lb (2268 kg) payload , MTOW 325000 lb = 147420 kg, max. fuel 23393 US gallon = 88552 litre, including 370 km (200nm) diversion.
Adjustment made for range with max payload > range with max. fuel used for calculations : 9800km (5300nm) to have a more correct value for Cdo.
Ferry range 6090 nm : 11281 km
range with max.fuel and MTOW : 10170 [km] with 11 crew and 39 passengers and 0 [kg] cargo*
ferry range (calculated): 10390 [km] with 4 crew and zero payload (100.0 [%] fuel)*
max range theoretically with additional fuel tanks total 94590 [litre] fuel : 10981 [km]*
* calculated ranges without fuel reserves
Available Seat Kilometres (ASK) : 1666754 [paskm]
useful load with range 1000km : 27307 [kg]
useful load with range 1000km : 259 passengers
production (theor.max load): 24221 [tonkm/hour]
production (useful load): 24221 [tonkm/hour]
production (passengers): 203213 [paskm/hour]
oil and fuel consumption per tonkm : 0.240 [kg]
calculation *11* (operating cost)
fuel cost per hour (7401 [litre]):4440 [eur] (27 [pax-km/litre fuel])
fuel cost per seat 1000km flight (229 [pax] 2-class seating): 21.85 [eur/1000PK]
oil cost per hour: 5 [eur]
crew cost per hour : 1500 [eur]
list price 2024 : 164 [mln USD]
average flying hours in 1 year : 2850 [hours] technical life : 21 [year]
real average service life : 20 [years]
depreciation : 20 [years] to 10% residual value
financing interest per flying hour : 1296 [EUR]
write off per flying hour : 2392 [EUR]
mean time between engine failure (MTBF) : 8043 [hr]
can continue fly on 3 engines, low risk for emergency landing for PUF
Kenya Airways Douglas DC-8-71 EI-BZU c/n 45994 parked at Nairobi, Kenia, May 1991
workhours per day : 10.12 [hr]
no fatalities during service life > 100%% safe
average flight hours till crash : 3.02 [mln hr] (1060 service years)
safe flight hours till fatality : 3021000 [hr] (1060.0 service years)
reservation pax liability/flying hour : 0.04 [SDR*] (0.05 [eur])
insurance cost per hour : 250 [eur] insurance rate : 1.2 [%]
engine maintenance cost per hour : 611.1 [eur]
wing maintenance cost per hour : 233.0 [eur]
fuselage maintenance cost per hour : 155.90 [eur]
tire life (time till worn out) : 86 [cycles]
maintenance cost per hour (excluding engines): 1661 [eur]
direct operating cost per hour: 12156 [eur], DOC per km : 14.30 [eur]
DOC per seat 1000km flight (229 [pax] 2-class seating): 59.82 [eur/1000PK]
DOC per seat 1000km flight (high density seating): 52.91 [eur/1000PK]
DOC per kg cargo for a 1000km flight : 0.50 [eur/kg] (= DOC/tonkm)
passenger service charge (depart at Schiphol): 11.34 [eur]
security service charge (depart at Schiphol): 10.08 [eur]
airport take-off fee / passenger : 4.21 [eur/pax]
airport landing fee / passenger : 4.21 [eur/pax]
retour ticket price 1000km trip : 197.25 [eur/pax]
price retour ticket Schiphol-Barcelona : 230.15 [eur/pax]
There have been no fatal accidents with a DC-8-71 jetliner
Notes : together with the DC-8-61 longest length (57.12m) and passenger cabin (44.38m) of all classic jetliners
Literature :
https://contentzone.eurocontrol.int/aircraftperformance/default.aspx ?
Air International feb’99 page 120
Observers Airliners page 135
https://www.boeing.com/commercial/airports/plan-manuals
confidence rating regarding source data : medium - all information is only available from news, social media or unofficial sources
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 14 April 2025 contact : info.aircraftinvestigation@gmail.com ac jetpax 2020.py python 3.7.4
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