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weight and performance calculations for the McDonnel Douglas DC-9-31

Eastern Airlines DC-9-31 N8988E c/n 47098/108 at Toronto, August 1979

McDonnel Douglas DC-9-31

role : short-range regional jet airliner

importance : ****

first flight : 1 August 1966 operational : March 1967 (Eastern Airlines, delivery 27 Feb.1967)

country : United States of America

ICAO aircraft type designator : DC93

design :

production : 220 aircraft at Long Beach, California

general information :

With 4.6m stretched version raising seating to 115. Has more powerful engines, a

bigger wingspan and higher MTOW.

A tail stair is optional. It has full span leading edge slats.

primary users : Eastern Airlines, Hughes Airwest, Allegheny, North Central Airlines,

Delta Airlines

Accommodation :

flight crew : 2 cabin crew : 3

passengers : seating for 98 in two class : 8 first class and 90 economy class seats

( 32 -in pitch) high density seating for 115 passengers

engine : 2 Pratt & Whitney JT8D-7B turbofan engines of 64.0 [KN] (14388 [lbf])

Measured geometrical tail angle : 10°, measured chord at root : 4.87m, at tip : 1.09m

dimensions :

wingspan : 28.47 [m], length overall: 36.37 [m], length of fuselage : 32.61 [m] height :

8.38 [m] wing area gross : 92.97 [m^2] fuselage exterior width : 3.34 [m]

weights :

manufacturer’s weight empty : 24011 [kg]

operating empty weight : 25331 [kg] max. structural payload : 11864 [kg]

Zero Fuel weight (ZFW) : 37195 [kg] max. landing weight (MLW) : 42365 [kg]

max. take-off weight : 44450 [kg] weight usable fuel : 10931 [kg] (13925 [litres])

performance :

Max. operating Mach number (Mmo) : 0.817 [Mach] (909 [km/hr]) at 7620 [m]

critical Mach speed : 0.77 [Mach]

max. cruising speed : 871 [km/hr] (Mach 0.800 ) at 9150 [m] (33 [%] power)

economic cruising speed : 830 [km/hr] (Mach 0.76 ) at 9150 [m]

service ceiling : 10000 [m]

range with max fuel and MTOW : 2630 [km] (ATA domestic fuel reserves - 370.0 [km]

alternate)

description :

*Cantilever low-wing monoplane with retractable landing gear with nose wheel

engines attached to the tail, landing gear attached to the wings, fuel tanks in the

wings

*Wings : aluminium alloy fail safe wing structure with double slotted trailing edge flaps

with full-span leading-edge slats ,with spoilers airfoil : NACA

average thickness/chord ratio : 11.6 [%], sweep angle 3/4 chord: 24.0 [°]

incidence at root : 1.00 [°], dihedral : 6.0 [°]

*Tail Unit: Cantilever all-metal structure with tailplane mounted at tip of fin

*Fuselage : Pressurized conventional all-metal semi-monocoque structure with double-

bubble cross section

USAir DC-9-31 N964VJ c/n 47373/522 at Newark, August 1980 .

calculation : *1* (dimensions) :

measured wing chord at root: 4.87 [m]

measured wing chord at tip : 1.09 [m]

measured geometric tail-angle : 10.5 [° ]

taper ratio : 0.224 [ ]

mean wing chord : 3.27 [m]

wing aspect ratio : 8.72 []

Oswald factor (e): 0.700 []

seize (span*length*height) : 8677 [m^3]

calculation : *2* (fuel consumption) :

oil consumption : 4.5 [kg/hr]

fuel consumption (econ. cruise speed) : 3024.3 [kg/hr] (3852.6 [litre/hr]) at 29 [%]

power

fuel burn per seat per hour (average seating) : 36.17 [litre], sfc : 80.6 [kg/KN/h]

calculation : *3* (weight) :

weight engine(s) dry : 3000.0 [kg] = 23.44 [kg/KN]

weight 24.3 litre oil tank : 2.07 [kg]

oil tank filled with 0.8 litre oil : 0.7 [kg]

oil in engine 1.6 litre oil : 1.4 [kg]

weight all fuel lines and pumps containing 60 litres fuel : 31.7 [kg]

weight engine cowling : 332.8 [kg]

weight thrust reversers : 192.0 [kg]

total weight propulsion system : 3561 [kg](8.0 [%])

***************************************************************

Accommodation cabin facilities :

typical 2-class cabin layout for 98 passengers : economy : pitch : 81.3 [cm] 32.0 [-in]

( 3+2 ) seating in 20.0 rows

first class pitch : 96.5 [cm] 38.0 [-in] at 4 -abreast

weight passenger seats (width 52.6 [cm]) : 489.5 [kg]

weight cabin crew seats : 15.0 [kg]

weight flight crew seats : 42.0 [kg]

high density seating passengers : 115 [pax] at mainly 5 -abreast seating in 23.8 rows,

pitch 73.7 [cm] 29.0 [-in]

pax density, normal seating : 0.679 [m2/pax], high density seating : 0.579 [m2/pax]

weight 2 lavatories : 67.8 [kg]

weight 2 galleys : 54.1 [kg]

Aserca Airlines DC-9-31 YV1663 c/n 48144/1039 in flight over Venezuela, December 2007. The aircraft was delivered to US Air in December 1981.

weight overhead stowage for hand luggage (total : 5.8 [m3] = 121 55x35x25cm carry-on

trolleys) : 90.5 [kg]

weight 1 wardrobe closets : 23.1 [kg]

weight 42 windows (41 x 28 cm) made of acrylic glass : 178.5 [kg]

weight 1 (1.83 x 0.86 [m]) main entry doors : 33.8 [kg]

weight 1 (1.22 x 0.69 [m]) crew/service doors : 18.1 [kg]

weight built-in airstair for the front passenger door : 83.5 [kg]

weight 2 (main door size : 1.35 x 1.27 [m]) freight doors (belly) : 79.9 [kg]*

total usable belly baggage/cargo hold volume : 25.3 [m3]

passenger compartment volume : 84 [m3]

cabin volume (usable), excluding flight deck : 123 [m3]

passenger cabin max width (trim to trim): 3.14 [m] cabin length : 21.20 [m] max cabin

height : 2.06 [m] floor area : 59.2 [m2], cabin width at floor : 2.87 [m]

10.1 [%] of cabin floor area is occupied by toilets & galleys, the same at high density

seating

weight cabin facilities : 1092.2 [kg]

safety facilities :

weight 4 type III over wing emergency exits (0.51 x 0.91 [m]): 43.2 [kg]

evacuation time with 115 passengers : 54 [sec]

weight 3 hand fire extinguisher : 8 [kg]

central aisle : 0.51 [m] wide

weight cockpit voice recorder (CVR) and flight data recorder (FDR): 20.0 [kg]

weight oxygen masks & oxygen generators (deploy cabin alt.>4267m): 63.7 [kg]

weight emergency flare installation : 10 [kg]

weight 2 emergency evacuation slides : 74.4 [kg]

weight safety equipment & facilities : 303 [kg]

fuselage construction :

fuselage aluminium frame : 4386 [kg]

floor loading (payload/m2): 200 [kg/m2]

weight rear pressure bulkhead : 167.6 [kg]

fuselage covering ( 234.7 [m2] duraluminium 3.64 [mm]) : 2232.0 [kg]

weight paint fuselage : 49.3 [kg]

weight aluminium floor beams : 218.1 [kg]

weight cabin furbishing : 441.8 [kg]

weight cabin floor : 788.9 [kg]

weight (sound proof) isolation : 230.3 [kg] TO-noise level : 116.0 [EPNdB]

weight empty 57 [litre] potable water tanks : 5.0 [kg]

weight empty waste tank : 2.9 [kg]

weight engine mounts : 64 [kg]

weight fuselage structure : 8585.7 [kg]

Avionics :

weight VHF radio and Selcal : 9.0 [kg]

weight flight and service attendants intercom : 5.0 [kg]

weight dual cloud-collision radar : 25.0 [kg]

weight VOR/ILS,RMI,DME,radio altimeter, ASI, time clock : 20.0 [kg]

Northwest Airlines DC-9-31 N8925E c/n 45840/117 cockpit. It was delivered to Eastern Airlines in May 1967. Later if flew for Midway Airlines, Northwest Airlines and Delta airlines.

weight Sperry AD-200 flight director system with Sperry SP-50A auto-pilot : 25.0 [kg]

weight Cat II minima DH 30m RVR >=350m autoland system : 20.0 [kg]

weight artificial horizons, gyro-compass, radio altimeters : 7 [kg]

weight engine monitoring gauges & control switches : 14 [kg]

weight reserve ADI, ASI, alti-meter, compass, engine temp. and rpm indicators : 15

[kg]

weight avionics : 146.0 [kg]

Systems :

Air-conditioning and pressurization system maintains sea level conditions up to 5900

[m] and gives equivalent of 2250 [m] at 10700 [m]. pressure differential : 0.54 [bar]

(kg/cm2) pressurized fuselage volume : 149 [m3] cabin air refreshment time : 2.4

[min]

weight air-conditioning and pressurization system : 105 [kg]

weight Auxiliary Power Unit (APU) : 21.2 [kg]

weight lighting : 32.3 [kg]

weight 218 [bar] hydraulic system : 15.2 [kg] for take-off and landing, pressure could be

manually reduced during cruise flight to 209 [bar]

weight engine-driven 40kVA electricity generators : 24.5 [kg]

weight 22Ah battery : 28.5 [kg]

weight controls : 14.4 [kg]

weight stick pusher anti-stall warning system : 15 [kg]

weight systems : 256.2 [kg]

total weight fuselage : 10383 [kg](23.4 [%])

***************************************************************

North Central Airlines DC-9-31 N953N c/n 47083/177 at Columbus, Ohio (CMH), September 1976 .

wing construction :

total weight aluminium ribs (105 ribs) : 1559 [kg]

weight 6 wing fuel tanks empty for total 13925 [litre] fuel : 209 [kg]

weight 56 [litre] vent surge tanks : 7 [kg]

weight wing covering (painted aluminium 3.36 [mm]) : 1689 [kg]

total weight aluminium spars : 2205 [kg]

weight wings : 5454 [kg]

weight wing/square meter : 58.66 [kg]

weight bleed air thermal leading-edge anti-icing : 31.3 [kg]

weight two boundary-layer fences (vortilons) : 30.0 [kg]

weight ailerons (3.3 [m2]) : 98.0 [kg]

weight fin (8.7 [m2]) : 332.0 [kg]

weight rudder (3.8 [m2]) : 106.2 [kg]

Air Aruba DC-9-31 P4-MDD c/n 47271/389 at Miami, January 1997

weight tailplane (horizontal stabilizer) (23.1 [m2]): 747.1 [kg]

weight elevators (5.7 [m2]): 91.0 [kg]

weight paint wing & tail surfaces : 52.4 [kg]

weight flight control hydraulic servo actuators: 14.5 [kg]

weight trailing-edge double slotted flaps (19.2 [m2]) : 484.9 [kg]

weight leading edge slats (9.3 [m2]) : 153.2 [kg]

weight spoilers (2.6 [m2]) : 44.5 [kg]

weight airbrakes (0.0 [m2]) : 0.0 [kg]

total weight wing construction : 7855 [kg] (31.0 [%])

*******************************************************************

landing gear :

tire pressure main wheels : 9.10 [Bar] (nitrogen), ply rating : 20 PR

tire speed limit : 364 [km/hr]

total tyre footprint : 0.19 [m2]

Runway LCN at MTOW (0.76m radius of rigidity) : 59 [ ]

Aircraft Classification Number (ACN), MTOW on rigid runway and medium subgrade

strength (B) : 27 [ ] Can also operate from unpaved runways subgrade B

wheel pressure : 9779.0 [kg]

wheel track 5.03 [m], wheelbase : 16.22 [m]

weight 4 Dunlop 40.0 x 14.0 main wheels (1016 [mm] by 356 [mm]) : 356.7 [kg]

weight 2 nose wheels : 89.2 [kg]

weight heavy-duty hydraulic disc brakes : 43.8 [kg]

weight Hydro-air flywheel detector type anti-skid units : 5.4 [kg]

weight oleo-pneumatic shock absorbers : 49.6 [kg]

weight wheel hydraulic operated retraction system : 552.8 [kg]

weight tailskid : 25 [kg]

weight undercarriage struts with axle 1613.9 [kg]

total weight landing gear : 2736.2 [kg] (6.2 [%]

*******************************************************************

********************************************************************

calculated empty weight : 24535 [kg](55.2 [%])

Trans Australia Airlines DC-9-31 VH-TJP “Charles Kingsford Smith” c/n 47418 at Sydney, April 1970.

aircraft equipment and service utensils :

weight oil for 3.6 hours flying : 19.4 [kg]

unusable fuel in engine and tanks 118.4 litre fuel : 92.9 [kg]

weight lifejackets : 44.1 [kg]

weight 2 life rafts : 61.2 [kg]

weight catering : 36.2 [kg]

weight water : 50.0 [kg]

weight crew : 405 [kg]

weight crew luggage, navigation chards, flight docs (NOTOC), manuals, miscellaneous

items : 87 [kg]

operational weight empty : 25331 [kg] (57.0 [%])

********************************************************************

useful load breakdown :

weight 98 passengers : 7546 [kg]

weight luggage : 1568 [kg]

weight cargo : 2750 [kg] (cargo + luggage/m3 belly : 138.7 [kg/m3])

zero fuel weight (ZFW): 37195 [kg](83.7 [%])

weight fuel for landing (1.7 hours flying) : 5170 [kg]

max. landing weight (MLW): 42365 [kg](95.3 [%])

* max. landing weight higher than max. fuel weight makes it possible to make

intermediate stops without refuelling, also no fuel dump system needed, saves weight

max. fuel weight : 36262 [kg] (81.6 [%])

payload with max fuel : 88 passengers + luggage 8188 [kg]

published maximum take-off weight : 44450 [kg] (100.0 [%])

Hughes Airwest DC-9-31

calculation : * 4 * (engine power) :

power loading (Take-off) : 347 [kg/KN]

power loading (Take-off) 1 PUF: 695 [kg/KN]

max. total take-off power : 128.0 [KN]

calculation : *5* (loads) :

manoeuvre load : 1.4 [g] at 9000 [m]

limit load : 2.5 [g] ultimate load : 3.8 [g] load factor : 2.4 [g]

design flight time : 0.92 [hours]

design cycles : 59200 sorties, design hours : 54464 [hours]

max. wing loading (MTOW & flaps retracted) : 478 [kg/m2]

wing stress (2 g) during operation : 156 [N/kg] at 2g emergency manoeuvre

calculation : *6* (angles of attack) :

angle of attack zero lift : -1.72 ["]

max. angle of attack (stalling angle, clean) : 13.87 ["]

max. angle of attack (full flaps) : 19.74 ["]

angle of attack at economic cruise speed : 2.15 ["]

calculation : *7* (lift & drag ratios) :

lift coefficient at angle of attack 0° : 0.15 [ ]

lift coefficient at max. speed : 0.26 [ ]

lift coefficient at max. angle of attack (clean): 1.36 [ ]

max. lift coefficient ( 40 [° ] flaps) : 2.24 [ ]

drag coefficient at max. speed : 0.0347 [ ]

drag coefficient at econ. cruise speed : 0.0332 [ ]

induced drag coefficient at econ. cruise speed : 0.0060 [ ]

drag coefficient (zero lift) : 0.0272 [ ]

lift/drag ratio at econ. speed : 7.55 [ ]

New York Air DC-9-31 N1308T c/n 47315/433 at Newark, June 1982

calculation : *8* (speeds) :

Risk of tailstrike when taking off with OEI (engine failure), pilot must not rotate to fast

tail protected by a tailskid

minimum control speed (Vmc): 277 [km/u] (149.6 [kt])

minimum unstick speed (Vmu) at TO angle 11.5 ° : 284 [km/u] (153 [kt])

take-off decision speed (V1) : 279 [km/u] (151 [kt])

take-off rotation speed (VR) : 291 [km/u] (157 [kt])

lift-off speed (VLOF) : 313 [km/u] (169 [kt]) at pitch angle : 9.6 [°]

take-off safety speed (V2) : 316 [km/u] (171 [kt])

flap retraction speed (V3) at 500m (OW loaded : 41426 [kg]): 288 [km/u] (155 [kt])

steady initial climb speed (V4) : 342 [km/u] (185 [kt])

climb speed (to FL150 with 67 [%] power) : 510 [km/hr] (276 [kt])

max. endurance speed (Vbe): 363 [km/u] min. fuel/hr : 2322 [kg/hr] at height : 914 [m]

max. range speed (Vbr): 819 [km/u] (0.77 [mach]) min. fuel consumption : 3.27 [kg/km]

at cruise height : 10668 [m]

max. cruising speed : 871 [km/hr] (470 [kt]) at 9150 [m] (power:34 [%])

max. operational speed (Mmo) : 909 [km/hr] (Mach 0.82 ) at 7620 [m] (power:43 [%])

airflow at cruise speed per engine : 90.5 [kg/s]

speed of thrust jet : 1729 [km/hr]

initial descent speed 10000 - 7315 [m]: Mach 0.75

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): 283 [km/u] (153 [kt])

stalling speed clean at 500 [m] height at Max.Landing Weight : 42365 [kg]): 270 [km/u]

(146 [kt])

final approach speed (landing speed) at sea-level with 40 [°] flaps VREF (max. landing

weight): 235 [km/u] (127 [kt])

ICAO Aircraft Approach Category (APC) : C

stalling speed at sea-level with 40 [°] flaps VSO (max. landing weight): 181 [km/u] (98

[kt]

stalling speed at sea-level with 40 [°] flaps VSO at 44450 [kg] AUW): 185 [km/u] (100

[kt]

rate of climb (max. continuous power) at sea-level ROC (loaded, 67 % power) : 916

[m/min]

rate of climb at sea-level ROC (loaded, 75 % power) : 1137 [m/min]

rate of climb at 1000 [m] with 1 engine out (PUF/MTOW, 67 % power on remaining

engines) : 99 [m/min]

rate of descent from FL240 to FL100 (7315m > 3048m): 701 [m/min] (2300 [ft/min])

rate of descent during approach with landing gear extended, with use of spoilers: 205

[m/min] (3.4 [m/s])

calculation : *9* (regarding various performances) :

low wheel pressure, can also take off from unpaved runways

take-off distance at sea-level gravel/packed earth field : 2125 [m]

Brake kinetic energy capacity : 1197 [KW]

FAR take-off length at MTOW 44450 kg (98000 lb) > 1600m

Jane’s all the world aircraft 1970-71 page 401 : 2075m

FAR TO runway length (TOFL) requirement at TOW 44450 [kg] standard day at SL

(= ASDA) : 2197 [m]

ICAO Aerodrome Reference Code : 3C

Take-off flap setting : 20 [° ]

+++ FAA certification landing distance : +++

landing weight : 42365 [kg], TE flap setting : 40 [°]

runway condition : dry , landing over 50ft (15m) at threshold at sea-level

without use of thrust reversers, glideslope : 3.00 [°]

FAR landing runway length at MLW 42365 kg (93400 lb) : 5050 ft > 1540m

FAR landing field length ISA at SL, dry runway : 1544 [m] (5067 [ft])

FAR landing field length ISA at SL, wet runway: 1750 [m] (5741 [ft])

max. lift/drag ratio : 13.27 [ ]

climb to 5000 [m] with max payload : 5.05 [min]

climb to 10000 [m] with max payload : 15.54 [min]

descent time from 10000 [m] to 250 [m] : 24.33 [min]

max. ceiling fully loaded (mtow- 60 min.fuel): 41426 [kg] ) : 16800 [m]

ceiling limited by max. pressure differential 12850 [m]

max. theoretical ceiling (OWE + 60 min.fuel) : 18700 [m] with flying weight :28355 [kg]

calculation *10* (action radius & endurance) :

range with max. payload: 1957 [km] with 11864.0 [kg] max. useful load (66.4 [%] fuel)*

range with high density pax: 2285 [km] with 115 passengers (77.1 [%] fuel)*

range with typical two-class pax: 2734 [km] with 98 passengers (91.5 [%] fuel)*

Range with max payload (11864 kg) : 700 nm > 1300 km

Range with max fuel (13925 liters, MTOW 44450 kg) : 1420 nm > 2630 km

Ferry range (zero payload) : 1660 nm > 3075 km

range with max.fuel and MTOW : 3000 [km] with 5 crew and 88 passengers and 0

[kg] cargo*

ferry range (calculated): 3225 [km] with 2 crew and zero payload (100.0 [%] fuel)*

max range theoretically with additional fuel tanks total 24775 [litre] fuel : 5543 [km]*

* calculated ranges without fuel reserves

Available Seat Kilometres (ASK) : 267929 [paskm]

useful load with range 1000km : 11864 [kg]

useful load with range 1000km : 115 passengers

production (theor.max load): 10334 [tonkm/hour]

production (useful load): 10334 [tonkm/hour]

production (passengers): 85275 [paskm/hour]

oil and fuel consumption per tonkm : 0.293 [kg]

calculation *11* (operating cost) :

fuel cost per hour at econ.speed (3853 [litre]):2311 [eur] (21 [pax-km/litre fuel])

fuel cost per seat 1000km flight (98 [pax] 2-class seating): 28.44 [eur/1000PK]

oil cost per hour: 19 [eur]

crew cost per hour : 600 [eur]

list price 2024 : 62 [mln USD]

average flying hours in 1 year : 2580 [hours] technical life : 21 [year]

real average service life : 22 [years]

depreciation : 22 [years] to 10% residual value

financing interest per flying hour : 542 [EUR]

write off per flying hour : 910 [EUR]

mean time between engine failure (MTBF) : 8103 [hr]

insufficient engine reliability for ETOPS flights

can continue fly on 1 engine, low risk for emergency landing for PUF

workhours per day : 12.83 [hr]

average flight hours till crash : 1.04 [mln hr] (403 service years)

safe flight hours till fatality : 24974 [hr] (9.7 service years)

reservation pax liability/flying hour : 5.16 [SDR*] (6.45 [eur])

insurance cost per hour : 278 [eur] insurance rate : 3.1 [%]

engine maintenance cost per hour : 359.1 [eur]

wing maintenance cost per hour : 222.3 [eur]

fuselage maintenance cost per hour : 554.59 [eur]

tire life (time till worn out) : 103 [cycles]

maintenance cost per hour (excluding engines): 1343 [eur]

direct operating cost per hour: 6367 [eur], DOC per km : 7.67 [eur]

DOC per seat 1000km flight (98 [pax] 2-class seating): 74.67 [eur/1000PK]

DOC per seat 1000km flight (high density seating): 63.57 [eur/1000PK]

DOC per kg cargo for a 1000km flight : 0.62 [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 : 3.06 [eur/pax]

airport landing fee / passenger : 3.06 [eur/pax]

retour ticket price 1000km trip : 224.86 [eur/pax]

price retour ticket Schiphol-Barcelona : 265.93 [eur/pax]

Wednesday 23 June 1976 Allegheny Airlines DC-9-31 N994VJ c/n 47333/481

DSP Flight AL121 from Windsor Locks (BDL) to Philadelphia (PHL) with 4 crew and 102 passengers. Instrument approach to Philadelphia apt. RW 27R in a thunderstorm. The captain initiated a go-around in heavy rain. A windshear pushed the aircraft to the ground, tail first. YOM : 1969. Airframe hrs : 21320 engines : JT8D-7A. No people died in the crash but there were 86 injured.

location : +- 100m 39°52’17”N 75°14’49”W

12 fatal accidents with a total of 500 fatalities > see the accident file

Literature :

McDonnell Douglas DC-9 - Wikipedia

Jane s all the world aircraft 1970-71 page 398,399,400

verkehrsflugzeuge page 65

The Fliers handbook page 104

Verkeersvliegtuigen Moussault page 141

Verkeersvliegtuigen B. Van der Klaauw page 38

KIJK straalverkeersvliegtuig page 68,69

https://www.boeing.com/commercial/airports/plan-manuals

rescue : https://www.boeing.com/commercial/airports/rescue-fire

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 08 May 2026 contact : info.aircraftinvestigation@gmail.com ac jetpax 2020.py python 3.7.4

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