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ALC-33: Inflight Icing
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Roll Upset

Most pilots have experience with recovering from aerodynamic stalls with clean wings, but the aircraft may stall very differently with ice on the wings. Aggressive actions may be needed to break an ice-induced wing stall.

Another hazard of structural icing is roll upset, an uncommanded roll phenomenon associated with severe inflight icing.  Roll upset can result from severe icing conditions, and occur without the usual symptoms of ice accumulation or aerodynamic stall.

Wing stalls typically occur following a speed reduction or premature flap retraction.

Recovery from Uncommanded Roll or Wing Stall:

  1. Immediately reduce the angle of attack, lower the nose (Be prepared for more aggressive pitch and greater loss of altitude than during training for clean wing stalls)
  2. Add power
A tailplane stall occurs when, as with the wing, the critical angle of attack is exceeded. Since the horizontal stabilizer counters the natural nose down tendency caused by the center of lift of the main wing, the airplane will react by pitching down, sometimes uncontrollably, when the tailplane is stalled. Application of flaps can aggravate or initiate the stall. The pilot should use caution when applying flaps during an approach if there is the possibility of icing on the tailplane.

Tail Stall

Another hazard of structural icing is the tailplane (empennage) stall. Sharp-edged surfaces are more susceptible to collecting ice than large blunt surfaces. For this reason, the tailplane may accumulate ice before the wings, and may accumulate ice faster.

Because you cannot readily see the tail, you may be unaware of the situation until the stall occurs. Few pilots have any experience recovering from tail stalls.

Tailplane Stall Symptoms

Tail stalls usually occur during an approach when flaps are at full extension and/or the aircraft is being flown near the upper speed limit for flap extension. There may be few or no symptoms prior to flap extension.  Symptoms include:

  • Abnormal elevator authority, vibrations, and or/effectiveness.
  • Sudden uncommanded nose down pitch
  • Autopilot performing excessive pitch trimming.

Recovery from Tail Stall

To recover from a tail stall, you must take actions that are almost completely opposite from those required to recover from a wing stall.   If flaps are extended and you experience lightening of the controls, difficulty trimming, or buffet in the control column, immediately retract the flaps and maintain or reduce thrust -- in other words, undo what you just did.

  • Pull yoke back (opposite to action for a wing stall recovery). This reduces angle of attack of the tailplane and moves it away from the critical angle.
  • Retract flaps.
  • Maintain or reduce thrust.

Related Media for this Section
View the file Course Notes - Icing.pdf
Course Notes - Icing
Course Notes - Icing.pdf (2.55 MB)