For your team’s selected project aircraft, collaboratively create an instructional team wiki (Canvas page within your group work space – see again ARAPA Overview Page for instructions) that contains a representative drag table and associated diagram. For inputs about this module’s tasks, please review also the associated 3.3.1 – ARAPA: Resources and Inputs page. As a starter for your team’s wiki, your team can again copy the information below.
For the speeds in the first column, start with your aircraft’s stall speed, then continue in intervals of 20 or less knots (consider increasing the detail in the important portions near (L/D)max – see also this module’s tutorial videos within the 3.2 Lectures and Tutorials), and continue to at least a speed of 300kts or higher if required to allow for answering the questions and explaining all drag phenomena.
|V (KTAS)||q (psf)||CL||CDP||CDI||CD||CL / CD||DP (lb)||DI (lb)||DT (lb)|
To fill out your table and subsequently create a diagram with the total drag curve, you will need to research a variety of variables, formulas, and components. Again, the emphasis in this project task is on explaining your methodology as if you attempted to instruct someone unfamiliar with the aerodynamic details and relationships. Therefore, make sure to detail all assumptions, all formulas used, and all steps that were taken. The following will give you some starting points for your search and consideration.
- Assumptions and conditions:
- Assumed atmospheric conditions
- Calculated dynamic pressure (second column; based on the assumed atmospheric conditions and KTAS)
- Necessary aircraft information:
- Wing size and configuration (e.g., AR & efficiency factor – if you can’t find an efficiency factor for your aircraft, you can make an assumption [i.e., pick a vlaue] somewhwere between 0.75 and 0.85)
- Weight (should, of course, fall between MTOW and empty weight of your aircraft)
- Airfoil information (e.g., CLmax from last module & CDP– if you can’t find the CDP for your entire aircraft, you can utilize the minimum drag for your airfoil [see the 3.3.1 – ARAPA: Resources and Inputs page for inputs on how to read the drag polar in the airfoil database] and add a value of 0.02, which will account for the parasite drag of your aircraft’s fuselage)
- Required formula (for inputs see the formula summary on the 3.3.1 – ARAPA: Resources and Inputs page)
- Dynamic pressure
- Lift equation (two forms: one solved for stall speed and the other solved for required CL)
- Drag coefficients (CDi & CD)
- Application of coefficients to find actual forces (Dp, Di, Dt)
- Possibly wing geometry conversions (e.g., wingspan and area into AR or wingspan and average chord into AR)
- Do not forget to create the diagram.
To build your team’s table and diagram, you are encouraged to utilize appropriate computational software such as Excel® or MATLAB®. For inputs to this module’s tasks, please review the 3.3.1 – ARAPA: Resources and Inputs page, which also contains a short Excel® Tutorial and Excel® Diagram Work videos.
Once created, utilize your derived table and diagram data to answer the following associated questions:
- What are the minimum drag parameters for your aircraft?
- Minimum drag value D(min)
- Speed VD(min)at which minimum drag occurs
- Relationship between Dp and Di at D(min)
- What are the maximum lift to drag ratio CL/CDparameters for your aircraft?
- (CL/CD)max value
- Speed at which (CL/CD)max occurs
- Compare answers in A. and B. and comment on the findings.
- Explain which of your derived values will allow glide performance predictions for your aircraft and quantify best glide conditions with specific values.