# Calculating fuel to load, and crusie level (etc).?

Quite often we see questions here about 'How much fuel?' 'How long can an aircraft fly?'
'What earns more - self-loading cargo or loaded cargo?'.
Often, the experienced contributors (pilots) give a generalised answer, and often a lot of it boils down to 'depends' on a lot of...
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Quite often we see questions here about 'How much fuel?' 'How long can an aircraft fly?'

'What earns more - self-loading cargo or loaded cargo?'.

Often, the experienced contributors (pilots) give a generalised answer, and often a lot of it boils down to 'depends' on a lot of things.

So, my question is a challenge. I'm sure it's one pilots learn to do during training, and thereafter it is mostly (?) done by tapping the info into the computer and pressing the 'Gimme answer' button.

Scenario. (See end of question full full technical spec of the aircraft).

B737-400.

You are routing from Point A to B to C. Airfields at points A and C are at sea level. Point B is at 5000ft AMSL. Points A,B,C are in a plumb line direct line. Between point B and C - you have to get over a 10,000ft peak within 5 mins of departure. Thereafter it is 'downhill' to Point C which is at sea level.

Temperature between Point A is Ground = 20c, B is Ground = 35c, C is 20c, No winds/jetstreams.

Crew = 2 flight deck, 4 cabin.

Aicraft has just recently been through overhaul and tanks are completely empty. Last snagging list reported faulty fuel readings.

Engineers report states that 'faults rectified'

Point A to B. Distance 2200 nautical miles. Nearest alternate to Point B is 200 nautical miles.

Passengers onboard = 80

Passenger baggage = 800kg

Cargo you can load = unlimited - assume earn rate of 1 GECU per KG/unit area of cargo.

Cost of fuel at Point A = 1 GECU/litre

Point B to C. Distance 1500 mautical miles. Nearest alternate to Point C is 100 nautical miles.

Passengers onboard = 160

Passenger baggage = 2400kg

Cargo you can load = unlimited - assume earn rate of 0.5GECU per KG/unit area of cargo.

Cost of fuel at Point B = 3 GECU/litre !!!!

1 GECU = One Global Economic Currency Unit.

So, essentially, the question is, is it cheaper to load up with lots of fuel so that you do not need to buy so much expensive fuel at Point B, and a few other variables thrown in for good measure.

Your company will reward you 50% of the profit it makes on arrival in point C, after paying for fuel - and raking in whatever you've earned from cargo ops.

I hope the below is all the technical data you need, and I'm sorry if I've missed important data out, or the imaginary figues I've quoted are totally off-the-wall. I'm not a pilot.

Have fun. Best answer goes to whoever makes the best reasoned profit statement.

Series B737-400

Powerplant:

Model CFM56-3

Type C-1

Static Thrust (kN) 104.5

Static Thrust (Lb) 23,500

Bypass Ratio 4.9

EGT Margin (C) 45

Operational Items:

Accomodation:

Max certified seating 188

Hold volume (m³) 38.9

Volume per Passenger 0.22

Std Weights (kg):

Max. ramp 63049

Max. take-off 62822

Max. landing 54885

Max. zero-fuel 51256

IGW Weights:

Max. ramp 68266

Max. take-off 68039

Max. landing 56245

Max. zero-fuel 53070

Fuel capacity (ltrs) 20103

Fuel capacity (kg) 16200

Typical DOW 35100

Design payload 16530

Max payload 18260

Weight Ratios:

Ops Empty/Max T/O 0.516

Payload/Max T/O 0.243

Max Fuel/Max T/O 0.237

Fuel (litres):

Standard 20105

Optional 23829

Performance:

Loadings:

Thrust Loading (kg/kN) 325.35

Wing Loading (kg/m²) 645.15

Thrust/Weight Ratio 0.3133

Take-off (m):

ISA s.l. 2540

ISA +20ºC s.l. 2665

ISA 5,000ft 2932

ISA +20ºC 5,000ft 4005

Landing (m):

ISA s.l. 1540

Speeds (kt/Mach):

V2 F5 at MTOW 167

Vref F40 at MLW 139

Vmo/Mmo 340/0.82

CLmax (T/O @ MTOW) 2.02

CLmax (Land @ MLW) 2.76

Long range cruise:

IAS / Mach 250/0.745

TAS (kt) 430

Ceiling (ft) 37000

L.R. Fuel flow (kg/h) 2377

Range with max payload (nm) 2800

Design Parameters:

(W/S)/CLmax 2296

W/SCLtoST 2792

Seat x Range (seats.nm) 469800

'What earns more - self-loading cargo or loaded cargo?'.

Often, the experienced contributors (pilots) give a generalised answer, and often a lot of it boils down to 'depends' on a lot of things.

So, my question is a challenge. I'm sure it's one pilots learn to do during training, and thereafter it is mostly (?) done by tapping the info into the computer and pressing the 'Gimme answer' button.

Scenario. (See end of question full full technical spec of the aircraft).

B737-400.

You are routing from Point A to B to C. Airfields at points A and C are at sea level. Point B is at 5000ft AMSL. Points A,B,C are in a plumb line direct line. Between point B and C - you have to get over a 10,000ft peak within 5 mins of departure. Thereafter it is 'downhill' to Point C which is at sea level.

Temperature between Point A is Ground = 20c, B is Ground = 35c, C is 20c, No winds/jetstreams.

Crew = 2 flight deck, 4 cabin.

Aicraft has just recently been through overhaul and tanks are completely empty. Last snagging list reported faulty fuel readings.

Engineers report states that 'faults rectified'

Point A to B. Distance 2200 nautical miles. Nearest alternate to Point B is 200 nautical miles.

Passengers onboard = 80

Passenger baggage = 800kg

Cargo you can load = unlimited - assume earn rate of 1 GECU per KG/unit area of cargo.

Cost of fuel at Point A = 1 GECU/litre

Point B to C. Distance 1500 mautical miles. Nearest alternate to Point C is 100 nautical miles.

Passengers onboard = 160

Passenger baggage = 2400kg

Cargo you can load = unlimited - assume earn rate of 0.5GECU per KG/unit area of cargo.

Cost of fuel at Point B = 3 GECU/litre !!!!

1 GECU = One Global Economic Currency Unit.

So, essentially, the question is, is it cheaper to load up with lots of fuel so that you do not need to buy so much expensive fuel at Point B, and a few other variables thrown in for good measure.

Your company will reward you 50% of the profit it makes on arrival in point C, after paying for fuel - and raking in whatever you've earned from cargo ops.

I hope the below is all the technical data you need, and I'm sorry if I've missed important data out, or the imaginary figues I've quoted are totally off-the-wall. I'm not a pilot.

Have fun. Best answer goes to whoever makes the best reasoned profit statement.

Series B737-400

Powerplant:

Model CFM56-3

Type C-1

Static Thrust (kN) 104.5

Static Thrust (Lb) 23,500

Bypass Ratio 4.9

EGT Margin (C) 45

Operational Items:

Accomodation:

Max certified seating 188

Hold volume (m³) 38.9

Volume per Passenger 0.22

Std Weights (kg):

Max. ramp 63049

Max. take-off 62822

Max. landing 54885

Max. zero-fuel 51256

IGW Weights:

Max. ramp 68266

Max. take-off 68039

Max. landing 56245

Max. zero-fuel 53070

Fuel capacity (ltrs) 20103

Fuel capacity (kg) 16200

Typical DOW 35100

Design payload 16530

Max payload 18260

Weight Ratios:

Ops Empty/Max T/O 0.516

Payload/Max T/O 0.243

Max Fuel/Max T/O 0.237

Fuel (litres):

Standard 20105

Optional 23829

Performance:

Loadings:

Thrust Loading (kg/kN) 325.35

Wing Loading (kg/m²) 645.15

Thrust/Weight Ratio 0.3133

Take-off (m):

ISA s.l. 2540

ISA +20ºC s.l. 2665

ISA 5,000ft 2932

ISA +20ºC 5,000ft 4005

Landing (m):

ISA s.l. 1540

Speeds (kt/Mach):

V2 F5 at MTOW 167

Vref F40 at MLW 139

Vmo/Mmo 340/0.82

CLmax (T/O @ MTOW) 2.02

CLmax (Land @ MLW) 2.76

Long range cruise:

IAS / Mach 250/0.745

TAS (kt) 430

Ceiling (ft) 37000

L.R. Fuel flow (kg/h) 2377

Range with max payload (nm) 2800

Design Parameters:

(W/S)/CLmax 2296

W/SCLtoST 2792

Seat x Range (seats.nm) 469800

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