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Aero474 01 Design example
- 1. Aircraft Design Aero474 Dr. Mohammad Tawfik E-mail: Mohammad.tawfik@gmail.com Aero474 Aircraft Design
- 2. Design Example Aero474 Aircraft Design
- 3. Problem definition • A military training aircraft • Load factors +6 & -3G • Two pilots, 105 Kg each • Baggage 22.5 Kg • Takeoff distance of 1500 m • Climb to 5000 m • Cruise 15 min at a speed of no less than 87 m/s • Manoeuvre at 103 m/3 for 60 min • Return to base • Taxi and parking Aero474 Aircraft Design
- 4. Data Collection ● Data of 30 different aircraft was collected ● Some relations were plotted and regression relations were calculated Aero474 Aircraft Design
- 5. Thrust History 1.2 1 0.8 0.6 0.4 T/Tmax(25.98 KN) 0.2 0 1955 1960 1965 1970 1975 Year 1980 1985 1990 1995 Aero474 Aircraft Design
- 6. Empty to Take-off weight 0.8 0.75 0.7 0.65 0.6 Wo/We 0.55 0.5 0.45 0.4 1000 2000 3000 4000 5000 Wo (Kg) 6000 7000 8000 9000 Aero474 Aircraft Design
- 7. Wing loading vs aspect ratio 550 500 450 400 350 300 L (Kg/m^2) 250 200 150 100 4 4.5 5 5.5 AR 6 6.5 7 Aero474 Aircraft Design
- 8. JPAT Data Aero474 Aircraft Design
- 9. Preliminary Sizing ● Using the relations obtained from the data, equations could be obtained to fill in the equation ● You obtain a quadratic equation in the take-off weight which can be solved readily ● The number was 3220 Kg Aero474 Aircraft Design
- 10. Preliminary Sizing ● Similarly, the wing loading could be found to be: 290 Kg/m2 ● From which you get the wing area to be 11 m2 ● Which yields and Aspect ratio of 5 and span of 7.5 m Aero474 Aircraft Design
- 11. Geometric Considerations ● From the data collected, the taper ratio of 0.5 was used ● The distance between the tail and the is, similarly, taken to be 3 times the mean wing chord ● For the area of the stabilizers, the volume ratio was the determinant as per a reference and taken as 0.7 Aero474 Aircraft Design
- 12. First Sketch Aero474 Aircraft Design
- 13. First Sketch Aero474 Aircraft Design
- 14. Undercarriage Placement Aero474 Aircraft Design
- 15. Longitudinal Position Aero474 Aircraft Design
- 16. Lateral Position Aero474 Aircraft Design
- 17. Components Weight ● Formulae are given in different references to estimate the weight of different components ● What is really important is the weight distribution ● The distribution of the masses of the aircraft will be assumed to be regular as per the external size Aero474 Aircraft Design
- 18. Mass Distribution Table Aero474 Aircraft Design
- 19. Aerodynamic Performance Estimation Aero474 Aircraft Design
- 20. Aerodynamic Performance Estimation ● The Aerodynamic coefficients may be evaluated using different methods ● There are simple formulae to determine them ● You may use some Lattice methods to estimate the coefficients ● You may solve the full Navier Stokes equations! Aero474 Aircraft Design
- 21. For the Example ● Selection of the aerofoil was NACA4212 for the wing and NACA0009 for the tail. ● Using Prandtl lifting line theory, the wing and tail lift coefficients were calculated ● The induced drag coefficient was also evaluated using the same theory ● Finally, the maximum lift coefficient was calculated using emperical relations. Aero474 Aircraft Design
- 22. Total Coefficients ● Finally, the total lift, drag, and moment coefficients were calculated ● BUT … Flight stability literature indicated that the moment and lift coefficients were not adequate! ● First modification was to change the tail incidence angle Aero474 Aircraft Design
- 23. Total Lift 1.2 1 0.8 0.6 0.4 CL total 0.2 0 -4 -2 0 2 4 6 8 10 12 14 16 18 20 -0.2 -0.4 Alpha Aero474 Aircraft Design
- 24. Lift-Drag ratio variation with CL 12 10 8 6 CL/CD 4 2 0 0 0.2 0.4 0.6 CL 0.8 1 1.2 Aero474 Aircraft Design
- 25. CL-M curves for different altitudes 2 1.8 1.6 1.4 1.2 CL SL 1 CL 5000 CL 0.8 CL 10000 0.6 0.4 0.2 0 0 0.1 0.2 0.3 0.4 0.5 M 0.6 0.7 0.8 0.9 1 Aero474 Aircraft Design
- 26. CRITICAL!!! ● Reviewing those results, it was found that the lift coefficient at cruise conditions is so much near the maximum! ● To remedy this problem, the wing loading was reduced! ● Increasing the area of the wing, changed EVERYTHING!!! Aero474 Aircraft Design
- 27. Flight Dynamics and Stability Aero474 Aircraft Design
- 28. Flight Dynamics and Stability ● Now that we have all the aerodynamic coefficients, we may approach the problem of dynamics of the aircraft Aero474 Aircraft Design
- 29. Longitudinal Dynamics & Stability ● The Response for an impulse elevator input could be plotted using the Runge- Kutta method ● The two main modes of motion of the aircraft in longitudinal direction are: ● Phugoid ● Short period Aero474 Aircraft Design
- 30. Pitching Angle Response Aero474 Aircraft Design
- 31. The reason for instability! Aero474 Aircraft Design
- 32. Third iteration! ● Now, the aircraft need to be modified again! ● However, before doing all that effort again, let's examine the weight requirements of the fuel ● When recalculating the fuel requirements using detailed relations for each step of the mission, the weight was reduced ● That lead to the stability of the aircraft! ● Fuel weight was reduced by more than 50%!!! Aero474 Aircraft Design
- 33. Aerodynamic Refinement ● A VLM code was developed for the aerodynamic analysis of aircraft components ● The results obtained for the combined wing-tail problem gave better estimates for the aerodynamic characteristics Aero474 Aircraft Design
- 34. Performance Analysis Aero474 Aircraft Design
- 35. Engine Performance 14000 12000 10000 0 3300 8000 5000 6600 T (N) 6000 10000 13000 4000 16000 2000 0 0 0.1 0.2 0.3 0.4 0.5 M 0.6 0.7 0.8 0.9 1 Aero474 Aircraft Design
- 36. Drag-Thrust vs Mach Number Aero474 Aircraft Design
- 37. Max M vs Altitude 14000 12000 10000 8000 6000 Altitude (m) 4000 2000 0 0.65 0.67 0.69 0.71 0.73 M max 0.75 0.77 0.79 0.81 Aero474 Aircraft Design
- 38. Vertical Speed vs Mach No. Aero474 Aircraft Design
- 39. Climb Speed vs Altitude Aero474 Aircraft Design
- 40. Time to reach Altitude 500 450 400 350 300 250 200 Time (Sec) 150 100 50 0 0 2000 4000 6000 8000 Altitude 10000 12000 14000 16000 Aero474 Aircraft Design
- 41. Other Parameters ● Range ● Endurance ● Flight in a horizontal circle ● Take-off runway ● Stall speed ● Time to reach 5000 m Aero474 Aircraft Design
- 42. Wing Loads Aero474 Aircraft Design
- 43. Forces and Moments 14000 4000 12000 3500 10000 3000 2500 8000 2000 6000 My Vz 1500 4000 1000 2000 500 0 0 0 1 2 Y 3 4 5 0 1 2 Y 3 4 5 30000 25000 20000 15000 Mx 10000 5000 0 0 1 2 Y 3 4 5 Aero474 Aircraft Design
- 44. Aircraft Skeleton Aero474 Aircraft Design
- 45. Wing Section Aero474 Aircraft Design
- 46. Cost Estimates ● Engineering hours ● Tooling hours ● Manufacturing hours ● Quality control hours ● Development Support ● Flight test cost ● Material cost ● Avionics ● Engine Aero474 Aircraft Design
- 47. Homework #1 ● Form teams ● Collect data ● Create correlation graphs ● Prepare a report ● Prepare a presentation! Aero474 Aircraft Design