Whether you're flying a Piper Warrior or a Boeing 757, aircraft icing is a hazard for every pilot. It's one of the top safety-related concerns of the FAA, and it's led to hundreds of aviation accidents.

There are two primary reasons why icing is so hazardous to your aircraft: it decreases lift, and it increases drag.

Icing Problem #1: You Stall At A Lower Angle-Of-Attack

Ice adversely affects your wing's lift coefficient. According to the FAA's Flight In Icing Guide, the "Maximum Coefficient of Lift (CLmax) is significantly reduced by the ice, and the Angle of Attack (AOA) at which a stall occurs (the stall angle) is much lower with ice than without ice.

You can see in the diagram below how significant the difference is between a clean airfoil and an airfoil with ice.

So what does it really mean? When you have ice on your wing, you'll stall at lower angle-of-attack, and at a higher-than-normal indicated airspeed.

Icing Problem #2: Drag Significantly Increases

Even at very low AOAs, ice has a significant impact on the drag coefficient of an airfoil.

As ice accumulates on your wing, drag steadily increases. An airfoil drag increase of 100 percent is not unusual, and for large-horn ice accretions, the increase can be 200 percent or even higher.

It's easy to see the problem here. With increased drag, your plane requires significantly more power to maintain airspeed and altitude. And with an increased stall speed from the ice, a reduction in airspeed (from the drag) can lead you to an early stall.

Effects Of Icing On Roll Control

Ice on your wings forward of the ailerons can dramatically affect roll control as well.

Why? Most wing tips are thinner than the root of the wing, making them more efficient at collecting ice. This can lead to a partial stall of the wings at the tips, which affects roll control. As airflow is separated around the wing, control surfaces lose effectiveness because they're no longer flying in undisturbed airflow.

Similarly, pitch and yaw control may be affected by significant ice buildup on the horizontal/vertical stabilizer of your aircraft.

You've Slowed Down For Final Approach...

So how exactly does all of this affect your flight? Imagine you're flying an instrument approach. As you slow from approach speed to landing speed, you increase your AOA. Ice that had little effect on your aircraft during the approach, could have a significant effect on your stalling AOA and airspeed as you approach the runway threshold.

The problem? You'll stall at a lower AOA and a higher airspeed. Even a thin layer of ice at the leading edge of a wing, especially if it is rough, can have a significant effect on stall speed as you approach the runway threshold and flare to land.

Know Your Checklist And Aircraft Procedures

If you're flying a non-icing certified aircraft, you should always stay out of ice (obviously). But if you do have an inadvertent icing encounter, know your checklists.

Every aircraft is different, but in general, most checklists recommend that you fly final approach at a faster-than-normal airspeed. And the checklist might recommend to only use partial flaps (or no flaps at all) to avoid a tailplane stall.

In addition to that, the Cessna C172S POH recommends that pilots land at a "level attitude" to avoid increasing AOA beyond the Critical AOA, and inducing an unexpected stall.