This document discusses the key differences between propeller-driven aircraft and jet aircraft, focusing on higher altitudes, faster speeds, larger size and heavier weight, and turbofan powerplants. It covers topics like optimal cruise altitude and speeds, transonic flight challenges, wing design features to increase maximum cruise speed like sweep, thin wings, and area rule. Challenges of swept wings like lower speeds and longer takeoffs/landings are addressed. The importance of momentum and handling the larger size and weight variation of jets is also covered.

1. Propeller to Jet
Transitioning to High Speed, High Altitude Flight in a Heavy,
Swept-Wing Transport Jet

2. First Order Differences
• Higher
• Faster
• Bigger & Heavier
• Powerplant

3. The KEY MESSAGE!

4. Higher & Faster

5. Higher
Why do transport jets all
operate in a narrow
altitude band
(FL 300 – FL400)?

6. Speed vs Height?
• How do we measure speed?
• Why do we use Mach Number at
High Altitude?
• What is Crossover Altitude?

7. Transonic Flight
What is MCRIT?

8. Mach Buffet / Shock Stall
Variation of CL with Mach number

9. Wave Drag / MCDR

10. Buffet Boundary Limit

11. Design for High Speed Flight
What are the different design features used to
increase MCRIT ?
Swept
Wing
Thin
Wing
Supercritical
Wing
Area
Rule

12. Wing Sweep

13. Disadvantages of Sweep
• Very poor lift at low speed:
• Higher take off & landing speeds
• Longer Runways
• Low CL MAX which occurs at higher alpha
• Very high drag at high alpha
• Tip Stall
• Pitch up at the stall
• Wing Flexing
• Dutch Roll
Why do Civil Jet Transport Aircraft Have
Moderate Sweep?

14. Lift Augmentation

15. Lift Augmentation

16. Swept Wing Flying Technique – Take Off
A swept wing must be
presented at a high
angle of attack to
generate sufficient lift
for take off.

17. Swept Wing Flying Technique - Approach
Speed Unstable at VAPP
Note flaps improve the situation
somewhat
Lift doesn’t increase
much for a relatively large
change in AoA
Accurate glidepath and speed control are cardinal!

18. T/C Ratio
Thin wings reduce drag and smooth out CL variations…...
…...but bring problems with strength and flexibility and give poor low speed lift

19. Area Rule

20. Supercritical Wing Section
Flat upper Surface
(reduces airflow acceleration)
Pronounced T/E
Reflex Camber
(recovers lift lost by flat upper surface)
Blunt Leading Edge
& Deep Section

21. Bigger & Heavier

22. Bigger & Heavier
1 815kg x 62 m/s
=
112 530 kg ms-1
A320
75 000kg x 227 m/s
=
17 025 000 kg ms-1
150 x A380
450 000kg x 227 m/s
=
102 150 000 kg ms-1
900 x

23. The effect of MOMENTUM

24. Weight & CG Range
• What is affected by weight
changes?
• What is affected by CG changes?
• How does this affect the design of
the aeroplane?

25. Variable Incidence Tail

26. Typical Descent Profile
• Flown at IDLE thrust
• Go Down OR Slow Down… but
Not Both!

27. Large Variation in Reference Speeds

28. Ground Manoeuvring

29. Powerplant
High-Bypass Ratio Turbofan Engines

30. Why Turbofan Engines?

31. Engine Parameters

32. Engine Handling

33. Jet Cruise Procedures
• ECON
• LRC
• MRC

34. Optimum Altitude
“90% RPM at 1.32 VIMD”
Airbus:
“The most economic FL for a
given CI, weight, weather
data…”

35. The KEY MESSAGE!