Summary of Analysis
The preliminary design process in its most fundamental form can be boiled down to four major tasks, based upon what flight training curricula often call “the four forces of flight”. First, one must estimate the weight of the airplane. Second, a wing must be designed to provide lift at least as large as the weight. Third, the drag of the airplane must be estimated. And fourth, a propulsion system must be selected or designed to provide thrust which is greater than the drag.
Additional follow-on analysis is then appropriate in order to quantify performance, stability and control, structural concepts, and cost. All of this must then be clearly presented and documented, often in the form of CAD solid models (drawings).
All of this is represented in the deliverables list in the Statement of Work, which for practical purposes described above, has been expanded into the following twenty-four item list. In summary, items 1 through 13 are finished, and items 15-18 and 21-23 are currently in progress.
Meekins amphibian design project plan, revised 7/17/2004
1. Study patent to determine key features to be preserved in the design.
2. Literature search to find data and design equations for amphibian design.
3. Initial weight estimate using equation curve fit from collected data on existing similar amphibians.
4. Initial estimate of engine HP by comparison with existing similar amphibians
5. Use existing prop design spreadsheet to design ducted prop, to verify reasonableness of prop diameter consistent with hull spacing.
6. Initial estimate of CG position using rough estimates of weights of major components. Verify that wing position on original configuration is consistent with the need to have CG near the wing aerodynamic center in order to have manageable stability and control.
7. Initial estimate of drag using Raymer’s chapter 12 equations, to verify reasonableness of initial engine HP choice.
8. Selection of stall speed consistent with typical takeoff and landing distance.
9. Selection of airfoil and flap configuration, estimate of CLmax.
10. Calculation of required wing planform area.
11. Design of wing: aspect ratio, taper ratio, sweep, twist.
12. Update prop design spreadsheet, finalize prop design.
13. Begin Catia model, concentrating initially on buoyancy of hulls and the specific hull shape and dimensions needed to provide adequate freeboard. Hull shapes also must accommodate 4 occupants. Standard stepped hull will be assumed for first iteration.
14. Incorporate preliminary structural concept into Catia model. This will include conceptual placement of wing spars, fuselage seat and hull bottom reinforcement, attachment of fuselages to wing spars, engine attachment, and tail moveable surfaces.
15. Refine weight and balance when vehicle dimensions are finalized. Finalize wing and engine placement and hull step location based on iteration of CG location.
16. Model ducted prop on PSW panel-method software to attempt to quantify rudder and elevator control surface sizes required. Also attempt to scale up similar data from SRDC UAV.
17. Finalize drag estimate using Raymer’s ch.12 equations, but also use strip theory model to get more accurate wing drag.
18. Calculate static performance using Raymer’s equations, but supplemented with other reference for water takeoff and landing distance.
19. Analyze dynamic performance on water to whatever level of detail can be found in references.
20. Estimate cost using Litecost software. Include finalized engine choice.
21. Analyze elliptical hull shape as alternate design, to whatever level of detail references can be found for. Buoyancy can definitely be done with Catia. Dynamic water-borne characteristics will be attempted but that seems like low probability at present.
22. Complete Catia models of stepped hull design and alternate elliptical hull design.
23. Compile technical report, include disk/CD with all spreadsheets and other calculation software files so that sponsor can continue to tweak the design.
24. Have Fall 2004 AE420 section continue to pursue the same design ?
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