Aero474 Design Example
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This document provides an overview of the aircraft design process for a military training aircraft. It includes collecting reference data, preliminary sizing calculations to determine the empty weight, wing area and aspect ratio. Further iterations were needed to achieve stability. Performance analysis was conducted including drag and thrust curves. Cost estimates were also outlined. The design process involved collecting data, iterative sizing, aerodynamic analysis and stability evaluation. Students were assigned homework to present their work in a 30 minute presentation.
Aero474 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 T /T ma x(25.98 KN) 0.6 0.4 0.2 0 1955 1960 1965 1970 1975 1980 1985 1990 1995 Ye a r Aero474 Aircraft Design
- 6. Empty to Take-off weight 0.8 0.75 0.7 0.65 W o/W e 0.6 0.55 0.5 0.45 0.4 1000 2000 3000 4000 5000 6000 7000 8000 9000 W o (Kg) Aero474 Aircraft Design
- 7. Wing loading vs aspect ratio 550 500 450 400 350 L (Kg/ m^2) 300 250 200 150 100 4 4.5 5 5.5 6 6.5 7 AR 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 ● W o=W e W f W pW c ● 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 2 to be: 290 Kg/m ● 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 1.4 1.2 1 0.8 0.6 CL total 0.4 0.2 0 -0.2 -0.4 -4 -2 0 2 4 6 8 10 12 14 16 18 20 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 0.8 1 1.2 CL Aero474 Aircraft Design
- 25. CL-M curves for different altitudes 2 1.8 1.6 1.4 1.2 1 CL SL CL CL 5000 0.8 CL 10000 0.6 0.4 0.2 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 M 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 8000 0 3300 T (N) 5000 6000 6600 10000 13000 4000 16000 2000 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 M Aero474 Aircraft Design
- 36. Drag-Thrust vs Mach Number Aero474 Aircraft Design
- 37. Max M vs Altitude 14000 12000 10000 8000 Altitude (m) 6000 4000 2000 0 0.65 0.67 0.69 0.71 0.73 0.75 0.77 0.79 0.81 M max 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 Time (Sec) 250 200 150 100 50 0 0 2000 4000 6000 8000 10000 12000 14000 16000 Altitude 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 10000 3000 8000 2000 My Vz 6000 4000 1000 2000 0 0 0 1 2 3 4 5 0 1 2 3 4 5 Y Y 30000 25000 20000 15000 Mx 10000 5000 0 0 1 2 3 4 5 Y 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 #5 ● Prepare a 30 minutes presentation ● Presentation includes all your work up to this point ● History, data, project plan, etc... ● Plus preliminary weight estimations and geometric considerations Aero474 Aircraft Design