1. Matching of Propulsion Systems for an Aircraft
P M V Subbarao
Professor
Mechanical Engineering Department
Matching of Flying Machine and Power Plant…..

2. Flight Missions and Constraints Analyses
There exist an optimum match point between an engine and a configuration of an aircraft.
This match point depends on ;
the available engine propulsive performance,
flight mission profile and
the constraints.
Demands an optimization process, which includes aerodynamics and flight performance module coupled with another module for engine performance prediction.

3. Typical flight mission profile for a passenger airplane
Engine capacity
Thrust
Flight Velocity
Turn
Turn
Cruise
Climb in Altitude
Descent
Takeoff
Landing

4. Cruise Flight Strategy
Cruising Speed
The objective of flight designer is, during the cruise flight the flight must use as few fuel as possible.
There are two strategies selected for this purpose.
Endurance & Range

5. Endurance Vs Range
If the flight is to stay as long in the air as possible, it should have maximum Endurance.
The endurance E is the time which flight can stay in the air with a given amount of fuel.
To maximize E the fuel consumption rate must be minimized.
If the flight is to go as far as possible, it should have maximum the Range.
The range R is the distance a flight can cover with a given amount of fuel.
So the distance ds per unit mass of fuel used dmf should be maximized.

6. Design for Maximum Range
Maximize
For cruising:
For jet engines the fuel flow varies linearly with the thrust,

7. Cruise Flight Strategy
Cruising Speed
Lift and drag coefficients CL and CD are defined as:

8. Cruising for Maximum Range
Define lift to Drag Ratio , L/D
For cruising:

9. Lift to Drag Ratio Vs Mach Number : Cruising

10. The Parameters of Concern to Reach Cruising Altitude
The parameters for reaching the cruising altitude:
field lengths at takeoff and landing,
climb rate/time,
optimum cruising speed, and
Cruising altitude.
The segments of takeoff, climb, cruise, and landing are considered as the critical phases .
These phases are assessed separately in terms of
thrust-to-weight ratio T/WTO
and wing loading W/STO referring to takeoff conditions.

11. Optimization for Match Point

12. Force Balance on a Climbing Aircraft

13. Speed Vs Rate of Climb

14. Feasible Domains for Constraints

15. Feasible Domains for Constraints

16. Typical Airplane Characteristics

17. Engine Capability
Flight Velocity

18. Convergent-Divergent Nozzle Under Take off Conditions

19. Steady Cruising Design Conditions