Helicopter IFR Technique: Recognizing and Escaping Icing
When flying IFR in a helicopter that is not equipped with de-ice or anti-ice capabilities, the most important thing to know about icing is that your goal is not to manage it.
Your goal is to avoid it—and if you find yourself in it, to escape it.
The first challenge is to recognize it early.
By the time ice becomes obvious through performance degradation and airframe vibrations, you’ve likely been accumulating it for some time.
Ice usually appears first on small objects protruding into the airstream.
Look at your windshield wipers, outside air temperature probe, radar radome, door handles, mirror stanchions, antennas, portions of the landing gear/skids, or any other surface you can see protruding into the airstream. These often provide the first visual clues that ice is beginning to accumulate.
Once you’ve confirmed ice in a helicopter with no de-ice or anti-ice systems your attention should immediately shift from recognition to escape.
If there was no icing behind you, the simplest solution is often the best one: turn around.
If warmer air is available below you, and terrain permits, descend.
If the cloud tops are within reach, climb into VMC above the layer.
In some unique situations, climbing into significantly colder air, where the cloud is composed primarily of ice crystals rather than supercooled liquid water, may also be an effective strategy. Unlike supercooled liquid droplets, ice crystals generally do not adhere to the airframe. As always, this strategy depends on the weather conditions you identified during your preflight planning.
Whenever you’re operating in conditions where icing is possible, establish a performance baseline at your cruise altitude and airspeed.
Note your airspeed, torque, engine temperatures, and any other aircraft-specific performance indications while the helicopter is performing normally. Then monitor those values to determine if icing is encountered.
For example, the rate of increase in required torque to maintain level flight and a consistent airspeed indicates a rate at which the ice is degrading the aerodynamic efficiency of the rotor blades while also increasing the weight of the airframe.
Having a baseline and observing the trend provides valuable insight into how quickly the ice is affecting your helicopter’s performance. After escaping the ice, the torque baseline can provide reassurance that ice is no longer accumulating, or the ice accumulated has been shed.
Remember, however, that these indications are diagnostic—not corrective.
Don’t become so focused on interpreting the aircraft’s performance that you delay the one action that matters most: leaving the icing environment.
The best icing encounter in a helicopter not equipped for flight into known icing is the one that ends quickly.
For helicopters equipped with anti-ice and de-ice systems, the baseline mentioned above is critical for determining how effectively the aircraft is shedding ice—or whether ice is accumulating too rapidly for the equipment to keep up.
If the equipment is unable to keep pace with the accumulation, the courses of action discussed above for escaping icing conditions can be implemented.