Chapter 5 Glider Performance Flashcards
What 4 factors affect glider performance?
Glider design, Density, Weight, Wind
How does Density Altitude affect glider performance?
High Altitude Density decreases lift and therefore increases take-off distance and decreases climb.rate.
3 types of Wind?
Headwind, Tailwind, crosswind. If headwind and tailwind are not direct, they will have crosswind components to them.
Tailwind increases?
Ground roll on take-off and landing.
Headwind increases/decreases slope of landing and take-off.
Increases. Steeper
Does headwind or tailwind increase sink rate?
Neither. Sink rate is independent of wind.
How is a glider affected by an obstacle at the beginning of a runway with a tailwind?
Tailwind will create a sink zone downstream of the obstacle. A headwind will create lift.
What is wind gradient?
Wind speed aloft is usually higher than wind close to the ground.
What speed to fly when landing into a headwind?
Landing speed plus 1/2 of the wind speed.
What speed to fly when landing into a headwind with gusts?
Landing speed + 1/2 wind speed + 1/2 of difference between wind speed and gust speed.
LS = 55 Headwind = 10 Gust = 30
55 + .5(10) + .5(30 - 10)
30 - 10 = Gust Factor
The closer to the ground, the more/less uniformity in the wind speed?
Less uniformity close to the ground.
Additional weight causes the stall speed to (increase/decrease.
Increase
How much does the stall speed increase with additional weight?
Stall speed increases as the square root of the weight increase.
150% of normal weight = Sq Rt of 1.5 = 122% of normal stall speed.
What is the relationship between bank angle, load factor , and stall speed?
Stall speed increases as the Sq Rt of the Load Factor increase.
Angle Load Factor Stall Speed
30 120% 110%
45 140% 120%
60 200% 141%
How does weight affect turn radius?
Additional weight requires higher speed. Higher speed at same bank angle means larger turn radius.
What is plotted on the X & Y axies of a Polar Graph?
X-axis = Airspeed knots
Y-axis = Sink Rate knots
Where is min sink rate found on the Polar?
The highest point of the curve. Min sink speed corresponds to the speed at this point.
Where is the best L/D speed found on the curve?
Draw a line from the origin to a tangent point on the curve. Airspeed at this point is Best L/D speed.
How does the polar curve shift with a heavier glider?
For added weight it moves the curve down and to the right. Min sink increases. Min sink speed increases. Best L/D speed increases.
Which speed is higher Min Sink or Best L/D?
Best L/D speed is always higher than Min Sink speed.
How do you adjust the Polar for a headwind?
Move the origin to the right on the X-axis by the amount of the headwind. Draw a line from the new origin to the tangent point.
How do you adjust the Polar for a tailwind?
Move the origin to the left on the x-axis by the amount of the tailwind. Draw a line to the tangent point. But do not fly lower than Min Sink speed.
How is the Polar adjusted for flying sinking air?
To find best L/D speed in sink, move the origin up on the Y-axis by the sink rate. Drawi tangent line to curve.
What is the best speed to fly in lift?
Min sink speed.
