EUGC Training TalkWednesday 18th October 2006

Stalling and Spinning

Chord

Span

Horizontal fuselagedatum

Attitude

Flight path

Horizontal fuselage datum

Flight pathRelative airflow

Chord line

Angle of incidence

Angle of attack

For AoA less than the critical angle lift is proportional to AoA.Beyond the critical angle lift reduces with AoA and drag increases rapidly.

CL

AoA

Stalling depends only on the angle of attack exceeding the critical angle.This can happen at any airspeed given a sufficiently high load factor.Load factor increased by turning, vertical acceleration, winch launch.Example: in a 2G turn

L1 = ½C

LV

12 L

2 = ½ C

LV

22 L

2 = 2L

1

V2 = V

1√2

So if the 1G stalling speed is 37kts, for example, the stalling speed in a 2G turn will be 52kts.

Recovery

Stall caused by too high an AoA.Therefore recovery is to reduce to AoA.Rate of acceleration/decrease of AoA depends on attitude.Therefore amount of forward movement required depends on attitude.Failure to lower nose sufficiently results inlow/no acceleration – risk of another stall.

Symptoms

Attitude – nose high

Low airspeed

Airflow noise

Buffeting

Changing effect of controls

Stick position

Elevator fails to raise the nose

Mushing Stall

Hammerhead Stall

Stall off a Launch Failure

Spinning

Glider is asymmetrically stalled

Pitching, rolling and yawing simultaneously

Low airspeed

High rate of descent

Unusual attitude

Rapid rotation

High rate of yaw

Rapid descent

Low IAS

Low and steady G

Laughter from back seat

Spin Recovery

Full opposite rudder

Centralise the ailerons

Pause (not normally necessary in gliders)

Move the stick forwards until the rotation stops

Centralise the rudder

Recover from the dive