Ex 10/11 Loss of Control – Wake Turbulence

wake-turbulenceWake Turbulence-if you learned to fly using the 1950s Tiger Moth syllabus (still in use at many flying schools) you will probably never have practiced wake turbulence recovery or even been briefed on it!

Aerodynamic Stall isn’t the only thing that can cause loss of control in an aircraft! The consequences of hitting low level wake turbulence can be even more catastrophic than a low level aerodynamic stall, as the pilot of this Robin aircraft found out after taking off with 39 seconds separation behind an Antonov Bi Plane. He was killed along with his 3 passengers. The Robin rolled through 90 degrees, hit the ground and burst into flames.

In 1978 the Chief Flying Instructor of the Oxford Aviation (CSE) flying school at Carlisle was killed, along with his student, in a PA28 when they made an intersection departure behind a  4 engined AW Argosy freighter.He was a very experienced instructor/examiner with over 12000 hours.

Instructor & Student Killed at Carlisle

By RuthAS - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=35236585

AW Argosy photograph By Ruth AS

Pilots should remember some basic warnings concerning wake turbulence:
Do not get too close to the leading aircraft.
Do not fly below the leading aircraft’s flight path.
Be particularly wary in light wind conditions.
If in doubt-wait or increase spacing
RECOVERY (copied from Sky Library) – Note, if you are flying with me we will practice Wake Turbulence recovery on final approach along with other Loss of Control scenarios.

Immediate Actions

In the event of a Wake Vortex Encounter, pilots should immediately take the following actions:

  • Power – Whenever you are low and slow as will be the case in a WVE during approach, add the power – you’ll need it (Full Power)
  • Push – Unload the wings or “push” on the yoke until you are slightly “light in the seat”. This reduces the angle of attack of the wings which gives better roll control with the ailerons. It simultaneously reduces the drag on the aircraft for better acceleration and, if you are rolling over, slows your descent towards the ground.
  • Roll – If aircraft controlability allows a choice, roll (unloaded) to the nearest horizon. If there isn’t a nearest horizon, or if you have significant rolling momentum, continue to roll (unloaded) in that direction to the horizon.
  • Go Around – Do not try to salvage a landing after a WVE during approach. Depending upon the atmospheric conditions, there is a risk of re-entering the wake vortex from the preceeding aircraft later in the approach at a lower altitude where a recovery might not be successful.

More reading

http://www.ead.eurocontrol.int/eadbasic/pamslight-936FBED04EA6355039E50B506548775E/7FE5QZZF3FXUS/EN/AIC/P/001-2015/EG_Circ_2015_P_001_en_2015-01-22.pdf

http://www.skybrary.aero/bookshelf/books/660.pdf