Flight Test Evaluation of Cherokee II Sailplane

Tony CondonAere 492

December 11, 2008

Cherokee II Sailplane

• Gottingen 549 Airfoil• 40 ft wingspan• 125 ft2 wing area• 14.4 ft2 tail area• 2.5:1 taper ratio• 600 lb weight• 6.66 G ultimate load

Objectives

• Determine Glide Polar• Determine actual performance• Compare to expected performance• Find Aerodynamic Characteristics• Find Stability Derivatives

Calibrate Instruments

• Airspeed and Altimeter–WWII Vintage

• Constructed Manometer to calibrate Airspeed

• Used test set to calibrate Altimeter

Calibrate Instruments

Calibrate Instruments

Test Flight

Calculate Polar

• Determine Altitude change on each run

• Time between start and finish• Calculate descent rate• Plot descent rate vs speed• Calculate L/D ratio at each speed

Calculate Polar

Calculate L/D

Compare

Polar Comparison

L/D Comparison

Find Aerodynamic Characteristics

2

sin12

D

WC

V S

21cos

2

L

WC

V S

2

,0L

D D

CC C

eAR

,0L L L L eC C C C

,00m m m m eC C C C

Process CL

• All variables known, find CL vs V

• Know δe vs V

• Calculate CLα and CLδ

• Take CL,0 from Lockheed code

• Find CL vs. α

21cos

2

L

WC

V S

,0L L L L eC C C C

Calculate CLα and CLδ

• Use pitch attitude and flight path angle change to find change in alpha

• Use stick position measurements to find change in elevator angle

CLδ vs Speed

CL vs α

CL vs α

Process CD

• Know everything for Weight based CD

• Use Minimum Sinking condition to find CD,0 , e

2

sin12

D

WC

V S

2

,0L

D D

CC C

eAR

,0

1

4D DC C

Process CD

CD vs α

Process Cmδ

• Cm = 0, trim condition

• Know Cm,0 and Cmα from Lockheed

code

• Know α and δe for each speed

• Find Cmδ

,00m m m m eC C C C

Cmδ vs Speed

Future Work

• Better camera setup• Digital Level• More accurate stick position• Automated processing• More glider types!

Questions?