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Exercise 3: Lift and AirfoilsPurpose

Evaluate the relationships between Coefficient of Lift (CL) and Angle of Attack (AOA), Airfoil Camber, and Airfoil Thickness and the variables of the Lift Equation using graphs and equations. If you are able, review the concepts using an on-line simplified simulated Wind tunnel.

Scope

(Questions 1-4) Looking at Dole and Lewis textbook Figure 4.4 and Figure 4,3, you will evaluate Lift Curve slope Parameters of a Symmetrical (NACA 0012) and Cambered Airfoil (NACA 4412) of similar thickness and evaluate the thickness effect on Coefficient of Lift and AOA for cambered airfoils of different thicknesses (NACA 4412 and NACA 4406)

1. Find the CLmax for the two airfoils in Figure 4.4.What is the relationship between Camber and CLmax ?

2. Find the AOA at Zero Lift for the two airfoils in Figure 4.4.What is relationship between Camber and zero lift (CL = 0)?.

3. Find the AOA at CLmax for the two airfoils in Figure 4.4.What is the relationship between Camber and Stall AOA?.

4. Looking at Figure 4.3, what is the relationship between airfoil thickness, CLmax and AOA?

This document was developed for online learning in ASCI 309.File name: Ex_3_Lift_Airfoils

Updated: 11June12

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(Questions 5-7) With some algebraic analysis, find the effects of Airspeed and Altitude on Lift by finding the Lift of an airplane with the following fixed parameters with various airspeeds and altitudes. Use Equation 4.1, Table 2.1, and Figure 4.4 in Dole & Lewis .

Given: NACA 4412Wing Chord (c) =5 ftWing Span (b) = 40 ftAOA= 7 degStandard Day Conditions

5. First-make a table of Airspeed (0 KTAS, 40 KTAS, 80 KTAS, 120 KTAS) vs. Lift @ Pressure Altitude of (0 ft Altitude, 10,000 ft Altitude, 40,000 ft Altitude)

LIFT (lb) Pressure Altitude (PA) ft0 10,000 40,000

0 KTAS 40 KTAS 80 KTAS 120 KTAS

6. What is the relationship between True Airspeed and Lift at a constant Pressure Altitude?

7. What is the relationship between Altitude and Lift at a constant True Airspeed?

8. If the gross weight is 1950 lbs. Estimate the true airspeed in KTAS to maintain level flight (Lift = Gross Weight) at the given Angle of Attack conditions at sea level, 10,000 ft and 40,000 ft.

This document was developed for online learning in ASCI 309.File name: Ex_3_Lift_Airfoils

Updated: 11June12

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(Questions 9-10) With some algebraic analysis, find the effects of Airspeed and AOA on Lift by finding the Lift of an airplane during a takeoff roll. Using Figure 4.4 in Dole and Lewis, assume that the Cambered airfoil (NACA 4412) is the wing airfoil with Flaps Down and the Symmetrical Airfoil (NACA 0012) is the wing airfoil with Flaps up. Takeoff configuration will be flaps Down (NACA-4412). On the ground and during rotation to takeoff assume that the AOA is 8 deg. Once airborne (L=W), assume staying at essentially at a constant sea level altitude and accelerating. The AOA must change to keep the same lift. Raise the Flaps at 80 KTAS and continue to accelerate to an airspeed of 120 KTAS, in preparation for a climb, by keeping Lift = ~1950 lb.

Given:Takeoff Weight is 1950 lbWing Chord (c) =5 ftWing Span (b) = 40 ftSea Level Standard Day Conditions:

Make a Table of Airspeed vs. Lift and AOA using Equation 4.1 and Figure 4.4

Airspeed (KTAS)

AOA (deg)

CL Lift (lb) Remarks

0 8 1.1 0 No Airspeed No Lift FLAPS DN20 40 50 60 80 (Flaps DN) 80 (Flaps UP) 100 120

9. Find the approximate Lift-Off Speed (KTAS).(i.e. the True Airspeed where Lift = Weight for the given configuration on the ground at lift-off)

10. What is the relationship between Airspeed and AOA as an airplane accelerates at a constant altitude?

This document was developed for online learning in ASCI 309.File name: Ex_3_Lift_Airfoils

Updated: 11June12

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Not required but feel free to connect on-line to NASA Glen Research Center education website to further explore aerodynamic concepts. This is an excellent this web site to use as an on-line Lab. http://www.grc.nasa.gov/WWW/K-12/airplane/foil3u.html. You may have to load the Java plugin or download the applet to enable the website to work

Similar exercise questions have been developed below to explore the relationships of Coefficient of Lift (CL) and Angle of Attack (AOA), Airfoil Camber, and Airfoil Thickness and the variables of the Lift Equation.

This document was developed for online learning in ASCI 309.File name: Ex_3_Lift_Airfoils

Updated: 11June12

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Exercise A

Compare three airfoils that have different thickness and camber to see how thickness and camber affect Coefficient of Lift (CL) vs. Angle of Attack (AOA).

Connect to FoilSim III.

SET UPInitial Conditions: Imperial Units

Input: Change Flight

Speed 100 mphAltitude 0 ft

Change to SizeChord-5.0 ftSpan 40.1 ftArea-200.5 Ft2

Change to ShapeAngle-0 degCamber-0 %Thickness- 12%

Change to AnalysisStall Model

Select PlotCl vs Angle

Data Window-Change Lift to CL

Set up your own table in Microsoft Word or Excel (AOA vs. CL) and use Shape to answer the following questions:

(AOA = -10, -5, 0, 5, 10, 14, 16, 18)Airfoil 1-(0 % Camber/12 % Thickness)Airfoil 2-(6% Camber/ 12 % Thickness)Airfoil 3-(6% Camber/ 19.8 % Thickness

Questions:

1. What is the relationship between Camber and CLmax?

2. What is relationship between Camber and zero lift (Cl =0)

3. What is the relationship between airfoil thickness and CLmax?

This document was developed for online learning in ASCI 309.File name: Ex_3_Lift_Airfoils

Updated: 11June12

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Exercise B QuestionsExamine how True Airspeed and Altitude affect Lift.Set up Angle-5 deg

Camber-6 %Thickness-12%Chord 5 ftSpan 40.1 ftData Window- Lift

Set up Table FlightAirspeed (0 mph, 40 mph, 80 mph, 120 mph) vs. Lift @ (0 ft Altitude, 10,000 ft Altitude, 40,000 ft Altitude)

Exercise B Questions4. What is the relationship between True Airspeed and Lift?

5. What is the relationship between Altitude and Lift?

6. If your gross weight is 1050 lbs. Estimate the true airspeed in M PH to maintain level flight (Lift = Weight) at the given Angle of Attack conditions at sea level, 10,000 ft and 40,000 ft.

Exercise C

This exercise will evaluate an aircraft on a takeoff roll, takeoff and accelerate to flap speed and then accelerate to climb speed. With the given conditions find when wings can support aircraft weight and takeoff can occur on a takeoff roll in (mph) and compare AOA to Lift and Airspeed (0-120 mph) while maintaining level flight accelerating at sea level.

Exercise C Conditions

Aircraft weight: 1600 lbs Wing Area: 200.5 sfWing Span: 40.1 ft Chord: 5 ftThickness: 12% CCamber 6% at speeds less than 65 mph (flaps in takeoff position).Camber 0% at speeds greater than 65 mph (flaps up).Let’s use AOA for takeoff is 10 deg. Once you get enough lift to equal weight. Keep Lift = Weight and adjust AOA, Camber, and airspeed.

Exercise C QuestionMake a table of Airspeed vs. Lift and AOA. Start at 10 deg AOA. Then when Aircraft Weight = Lift that will be takeoff. Then extend the table to greater airspeeds simulating the aircraft accelerating to 120 mph. Keep Lift at ~1600 lbs, but the AOA must change. Raise Flaps (Camber 0%) at 65 mph. Compare Airspeed to AOA in the accelerating aircraft keeping Lift @~1600 lbs.

This document was developed for online learning in ASCI 309.File name: Ex_3_Lift_Airfoils

Updated: 11June12