Forced Landing without Power, Basics
Chapter 16.1
Gliding Distance
The gliding distance is the ratio between the height and the possible distance to be traveled in descending flight.
The maximum glide distance can only be reached by strictly maintaining the V BEST GLIDE airspeed given in the AFM.
Glide ratio is best lift to drag ratio of the aircraft with a given airspeed and configuration.
Gliding Distance
Calculation of gliding distance according to glide ratio
Basic training aircraft have a glide ratio of about 1:10, gliders have 1:30 to 1:60
Airplane: glide ratio 1:10
Possible distance from 1’000 ft
Glider: glide ratio 1:40
Possible distance from 1’000 ft
Speed for maximum glide ratio / V BEST GLIDE
It is at this speed that one travels the most distance from the remaining altitude. It corresponds in most cases to the climb speed Vy. It depends on the mass and the altitude. The expression «BEST GLIDE» refers to that speed.
The configuration for this speed is specified in the AFM.
Speed for minimum descent / V BEST ENDURANCE
This is the speed at which the airplane remains in the air for the longest time. It is generally not shown in the AFM of powered airplanes and is about 15% below V BEST GLIDE.
In the event of an engine failure, this speed has the following meaning:
For tactical reasons, it may be advantageous to stay longer in the air rather than cover a greater distance (Preparing for landing).
Stabilization of the Glide
It is only possible to reach the longest distance, or stay in flight for the longest time, by rapidly stabilizing the aircraft at the corresponding glide speed.
Warning:
A gliding flight must be absolutely trimmed, or the search for a suitable place to land may lead to an uncontrolled attitude.
Rate of Descent, Angular Velocities in Gliding Flight
A knowledge of the airplane’s straight or turning glide rates is essential for a systematic distribution of the glide. With the basic training airplane, you will experience these values in practice and you will learn them by heart.
Straight flight:
As a rule one can assume: with the training airplanes, the rate of a gliding descent is about twice as much as during the approach flight path with the support of the engine.
Rate of Descent, Angular Velocities in Gliding Flight
A knowledge of the plane’s straight or turning glide descent rates is essential for a systematic distribution of glide. With the basic school airplane, you will experience these values in practice And you will learn them by heart.
Turns:
In a turn, the descent rate is greater than in straight flight, varying with bank and mass. The assumption that the loss of altitude per circle increases with the bank is not true in all cases.
Rate of Descent, Angular Velocities in Gliding Flight
Note:
Turns with 45° bank have a greater rate of descent than those at 30°, but it is with them that the least height is lost.
Explanation:
60° bank: The circle is done in the shortest time, the plane rotates with a high angular speed, the rate of descent is however very large.
15° bank: Although the rate of descent is low, it takes a long time to complete each circle, which means that the airplane finds itself lower after an entire circle than after one with a bank of 45°.