Propulsion Systems
Major US Airline Year 2000 Operating Costs
Cost per ASM = 9.75 ¢
Aircraft Fuel
Engine Maint. Material
& OSR
2%
Engine Ownership
Salaries
3%
40%
Airframe Ownership
10%
Airframe Maint. Material
&OSR
2%
Landing fees and other
rents
5%
Passenger service
3%
Other
13%
13%
Selling expenses
9%
"Other" includes contracted services,
asset write-downs, other non-recurring items
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
25%
30%
-15% -10% -5% 0% 5% 10% 15% 20% 25% 30% 35% 40% 45%
Relative Cash DOC per Trip
Relative Cash DOC per Seat
Airplane Operating Cost Comparison
Three Class Seating
3000 nm Trip
Se
a
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s
=
C
o
n
s
t
a
n
t
GOAL
-
1
0
%
Current State-of-Art
I
n
c
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e
a
s
i
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S
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Typical Engine-Related Airline Cost Breakdown
33%
13%
54%
Initial Cost (List)
Maintenance Cost
Fuel Cost
777-200ER/PW4090
$0.75/gal Fuel Price
Thrust Sizing Requirements
Y Limit
TOGW
T/W
W/S
X Limit
? Number of Engines
? Aircraft Max Take Off Gross Weight
? Take Off Field Length
? Time to Climb
? Cruise Altitude and Mach Number
? Lift to Drag of Wing
? Aircraft Potential Growth
Basic engine relationships
Thrust = (Velocity of exhaust - velocity of aircraft)
Mass
Overall engine efficiency = K thermal X K propulsive
Overall Engine Efficiency Includes Two Processes:
Energy Conversion and Thrust Production
Gas Generator
Available
Propulsion
Energy
Fuel Input
K overall = K thermal X K propulsive
Thermal efficiency measures the process of converting chemical
energy of the fuel into energy available for propulsion
- Function of overall pressure ratio and component efficiencies -
h
s
Current engines at 40:1
overall pressure ratio
Future engines at 60:1
overall pressure ratio
Propulsive efficiency measures the process of converting energy
available for propulsion into useful propulsive power
Gas Generator
Gas Generator
Turbofan
or
Turboprop
Gas Generator
Kpropulsive 100% as Vexhaust
Vo
Lower specific thrust is fundamental to improving fuel
economy
goodness
Fuel
economy
Drag/thrust
Engine efficiency
Weight/thrust
Specific thrust (lb /lb mass)
Increasing bypass ratio
Commercial Turbofan