Jenx Aviation - Flying Techniques

Stall Turns

There are three phases to the Stall Turn; the vertical, the turn and factors therein, and the recovery.

The Vertical First, we must remember that running out of speed in the vertical can result in a tailslide. During a tailslide, any control deviation from neutral can cause huge forces on the control lines and result in damage. Many aircraft cleared for advanced aerobatics are not cleared for tailslides. Never exceed the Flight Manual Limitations. It is possible to avoid tailslides easily but, if you consider there is a risk of a slide, centralise and very firmly hold the controls. To avoid the tailslide and before the speed has washed off and the controls become uneffective, you can either hammerhead (pitch forward or backward) or stall turn (yaw) to 'break the vertical and then, if the manouvre 'hangs up' you should centralise.

The Pure vertical. The best way, short of placing a gauge on the wing tip, to judge the vertical is to check the wing against the horizon. As the wing is fixed onto the aircraft at, say, 4o, the pure vertical is very hard to judge however for our purposes 86o will do fine and help prevent a tailslide. We must remember that to achieve and maitain the vertical needs a lot of 'flying' in that we need:

  • Compensate for increased slipstream effect as the airspeed decreases with appropriate rudder.
  • Compensate for changes in the thrust/drag couple as speed decreases (this gives a tendency to pitch forward at very low speed in a low wing).
  • Compensate for the change in lift direction ie we want zero lift to stay vertical or we pitch on our back (this is the most important factor and common error).
  • Ensure that the aircraft pitches straight up and stays straight.

    We can deal with the slipstream with the ball and lots of practice. The thrust/drag effects are finesse which will come later but the lift and 'straight' pull are key to the vertical:

  • To help keep the pull straight, we can tape a vertical line on the panel in front of you and use it to help keep the wings level and yaw to a minimum.
  • Once in the vertical, we must look left and right to check that the wing tips are equal distance from/or on the horizon.
  • To stay vertical we must push forward on the stick to maintain the wing 'attitude' against the horizon.

    During the first practices we should do this to about Vs and then push or pull (hammerhead) out (depending on the nearest horizon), whatever happens do not try to push out from an on-the-back attitude as this may induce an inverted spin!

    NB: If in doubt centralise and close the throttle.

    • The Turn After we have got the vertical hacked, we can perfect the turn. The factors affecting the turn are:

  • Aerodynamic effects - there are 2 aerodynamic effects:
    Roll as a secondary effect of the yaw - this is because the application of the rudder and requires opposite aileron to prevent the aircraft altering its plane of rotation.
    Yaw and roll as an effect of directional stability - the fin assists the aircraft to end nose down but can also induce some roll requiring into turn aileron to compensate.
  • Gyro & torque effects - the effect of the engine and propellor and the precession of the yaw through gyro and the 'hang up' of the turn (going right in a Lycoming).
  • Slip effects - the effect of the slipstream on the fin and rudder.

    In most aircraft with low power, it will be better to yaw in the direction of the low wing. In more powerful aircraft, the gyro and slip effects of the engine may make one direction always the best however closing the throttle will resolve this (see factors in the turn).

    Yaw/roll Training To be able to use the right amount of opposite aileron, we can do a simple training exercise to get a feel for what will be required in the stall turn. First slow to Vs + 10kts. Then using a maximum of half rudder, gently apply rudder while maintaining S&L flight. Practice this in both directions and slowly increase the amount of yaw to full rudder - beware, this is close to the stall regime and pro-spin controls - if in doubt centralise!

    The way to fly the aircraft through the turn is to:

  • Decide on the direction (based on the low wing or engine considerations).
  • Pick a point on the horizon on that wing tip.
  • At the correct speed, apply full rudder and some opposite aileron.
  • Scan from point to nose and ensure that the nose is flown through the point - this may well require a pitch input.
  • Scan from nose to the top wing-tip to fly that through the point as well.
  • As the wing-tip hits the 'vertical attitude' centralise or apply opposite rudder to check in the vertical.
    • The Recovery The recovery is straight forward:

  • Look forward to the horizon and roll to correct line.
  • Hold the vertical to correct height and monitor speed & power - that which we determined during looping as the height required to pitch out from a 90o dive.
  • Pitch out wings level to base height.

    • This page is maintained by Jenx
    Last updated on 10 Aug 2004