A Pilot's Guide to Inflight Icing
Module III - In an Emergency
Cues
Section: Airspeed and Flap Position
Start This SectionAirspeed & Flap Position Cues
In almost all aircraft designs, the tailplane has a sharper leading edge than the wing. The sharper leading edge makes it a more efficient ice collector. If there is ice on the wing, there may be proportionally much more ice on the tailplane. However, this does not mean that an ice-induced tail stall is more likely than an ice-induced wing stall. To distinguish between wing and tail stalls, you must rely on other cues.
Ice Shape Tracings from Wing Section Tested in the NASA Icing Research Tunnel
Ice Shape Tracings from Tail Section Tested in the NASA Icing Research Tunnel
Airspeed & Flap Position Cues
When flying in icing conditions, airspeed awareness is critical.
Wing stalls, including roll upsets, typically occur when the aircraft is flying at high angles of attack and slower speeds, e.g., after a speed reduction or premature flap retraction. Both of these changes increase the wing angle of attack.
Tail stalls typically occur during or immediately after flap extension or near the high speed limit for flap extension. Tail stalls may also occur with large inputs of nose down elevator. These changes increase the tail angle of attack.
Cues used to distinguish between wing & tail stall
Airspeed & Flap Position Cues
Tail stalls due to ice are rarely a problem in cruise flight. During this phase of flight, the tailplane is not working anywhere near its performance limits. Consequently, there may be no visual, performance, or tactile cues that ice is building until the aircraft configuration is changed.
In most cases, tailplane pitch anomalies are encountered during an approach when the flaps are at full extension. In this phase of flight, the tailplane is working near its performance limits.
Tail stalls typically occur during or after flap extension