SPEED TO FLY THEORY

WHEN TO USE IT

AND

WHEN NOT TO

Basic Glider Performance.

• Minimum Sink– The speed at which the glider’s sinking speed is

at its lowest.

• Best Glide– The ratio of forward speed to sinking speed.– As the gliders speed increases it’s sink rate

increases– This can be plotted on a polar curve.

The Polar Curve

Polar Curve

Best GlideMinimum sink

Minimum sinking speed Best glide speed

AIRSPEED / SINK RATE = BEST GLIDE ANGLE 53 / 1.2 = 40.8

Glides in a sinking airmass

Graphical representation• To represent 2kts of sink the polar can be

moved down the graph by 2kts

2kts

OR

• The 0,0 point can be moved UP 2kts

New 0,0

Note the new speed to fly

of 71 kts

• All speeds to fly for various sink conditions can be calculated and plotted onto a new graph

Mc Cready Graph

Mc Cready Ring• These values can be plotted on a ring that

fits round the vario

• When constructing a Mc Cready ring include the gliders sink rate