Flow Separation / V stall

Chapter 10.3

Objectives

To know the influence of the flaps on the flight attitude and the angle of attack on the descent

To know the different types of STALL

To know recovery measures after a STALL

Definition of the stall speed / V stall or Vs according to CS 23

Vs: STALLING SPEED, General / Speed at which the aircraft makes an uncommanded movement due to flow separation.

Factors which affect flow separation of the lift producing parts of the aircraft

Cross section of the wing

Angle of Attack / AoA

Mass and load factor

Signs of an imminent V stall

The following signs let you know that it is approaching V stall:

Visual:

Unusual combination of attitude (horizon), power and speed

Sensitivity:

A "spongy" reaction is noticeable with control deflections. The controls feel sluggish and have to be manipulated with greater effort to be effective. The plane «floats». The aircraft is not being trimmed in this phase. BUFFETING is felt when approaching the stall. Tendency to pitch down.

Audible:

Wind sounds are weak and also those of the engine during PWR OFF Stall.

Technical Warning System: STALL
WARNING

An audible warning system is built into most light aircraft.

STALL, Flaps, Angle of Attack and Attitude

The STALL Training will be conducted in two different exercises:

Approach to STALL / IMMINENT STALL

The goal is to recognize a STALL SITUATION in time

Fully developed STALL / FULL STALL

The goal is to restore normal flight attitude

Approach to STALL / IMMINENT STALL

The purpose of this exercise is to prevent complete air flow separation.

We start the recovery process as soon as there are signs of a STALL

• Visual
  

• Sensitivity

• Audible

are felt and when the warning system is activated.

Conduct the exercises as follows:

• without power in cruise configuration / clean configuration
  

• without power / POWER IDLE in landing configuration

• with power / POWER ON, in take-off and climb configuration

Fully developed STALL / FULL STALL

The procedure starts in the same way as the IMMINENT STALL.

However, in this case, the speed will be decreased until a wing-drop occurs.

Here again, the recovery begins with a relaxation of the back pressure on the elevator control, followed by a smooth increase in engine power.

As soon as the required speed is reached and the airflow is restored, the nose can be raised.

Do not lose more than 100 ft in altitude, do not «stick» down.

Execute the exercises as follows:

• without power in cruise configuration / clean configuration
  

• without power / POWER IDLE in landing configuration

Summary: Immenent Stall V STALL, Partial Stall

POWER IDLE

Summary: Immenent Stall V STALL, Partial Stall

POWER ON

Summary: Fully developed STALL in horizontal flight / FULL STALL

POWER IDLE