Helicopter IFR Technique: Weather Across the Vertical Spectrum
One of the biggest mindset shifts when transitioning from VFR to IFR flying is learning to think beyond the weather at the surface.
As VFR helicopter pilots, we naturally focus on questions like:
- What are the ceilings?
- What is the visibility?
- Is there enough clear air to maintain space between the helicopter and the terrain?
- Can I maintain the visibility to see and avoid obstacles?
Ceilings and visibility remain critical for instrument flights, but your planning should include additional weather considerations.
An IFR helicopter pilot must begin thinking vertically. The weather above you often becomes just as important as the weather below you.
Here are three weather considerations that deserve far more attention during IFR planning than they typically receive during VFR operations.
Icing
Many helicopter pilots spend years operating at low altitudes and in visual metrological conditions (VMC) where icing is rarely a significant concern. Flying in instrument meteorological conditions (IMC) at altitude changes that equation.
Instrument departures, enroute segments, and arrivals frequently place us in visible moisture at altitudes where temperatures are significantly colder than they were at takeoff. A flight that begins in 45°F rain can quickly become an encounter with ice just a few thousand feet higher.
Before every IFR flight, know the freezing level, where the visible moisture exists, and whether your planned altitude places those two hazards together.
Foreflight has an excellent icing tool that predicts ice on your map and on the profile view of your flight plan at different altitudes – ForeFlight’s icing tool predicts ice by combining NOAA’s Current Icing Product (CIP) and Future Icing Product (FIP) plus observed data (temperature and moisture data from a range of altitudes) to show icing probability and severity in 3D. The data is updated frequently for both current and forecast conditions.
Additionally, the National Weather Service has created an amazing free tool called Graphical Forecasts for Aviation (GFA) that depicts a plethora of weather information to include icing prediction at different altitudes for present and up to 18 hours in the future.
Other predictive tools:
- Freezing Level Charts
- Forecast Icing Potential (FIP)
- Current Icing AIRMETs/SIGMETs
- Current Icing PIREPs
- Winds and Temperatures Aloft
In a helicopter that is not equipped with anti-ice and de-ice capabilities, the best strategy is almost always to avoid ice altogether. However, if there is any potential to encounter ice, having a plan ahead of an unexpected encounter is a far less exciting event than trying to create one from scratch as ice is accumulating on your helicopter.
Cloud Tops
VFR helicopter pilots naturally focus on cloud bases to determine if there is room to fly underneath.
IFR pilots should also be interested in the tops.
A cloud layer extending from 800 to 4,000 feet presents a very different operational picture than one extending from 800 to 18,000 feet.
Knowing the tops may allow you to spend most of the flight in VMC above the layer. It can also provide valuable options if you experience a malfunction, encounter unexpected icing, or simply need to change your plan. Climbing into visual conditions may become your safest and simplest course of action.
Foreflight also provides the ability to display clouds on the map and profile views. If you know you’re your specific route of flight, the profile view is outstanding. However, for more general situational awareness, I have found that the NWS GFA and NOAA Aviation Clouds Forecast products provide me with a quick snapshot of bases and tops for the area of the country that I am currently operating in.
These are outstanding tools for VFR operations as well, particularly for helicopter response when the crew does not know exactly where they will be called to operate. However, it is worth emphasizing that both the GFA and the Aviation Clouds Forecast cloud layers (coverage and height) are shown in MSL. So, to determine the base AGL, you must compare the MSL base altitude to the MSL terrain altitude underneath.
Some of my favorite mountain rescues have involved IFR departures to get “on top” to locate and hoist survivors followed by an IFR recovery.
Here is a post: describing some of those evolutions:
Winds Aloft
Wind speeds often increase dramatically with altitude. A relatively light surface wind can become a significant headwind just a few thousand feet higher, affecting groundspeed, fuel burn, range, and the options available to you later in the flight.
Sometimes climbing higher results in a stronger tailwind that more than offsets the climb. Other times, remaining lower is the better choice. The only way to know is to include winds aloft in your planning.
Once again, the ForeFlight app allows pilots to overlay winds aloft on both the map and profile view of their EFB. The GFA provides an excellent overview at various altitudes at the present moment and in the future.
Here is a post discussing wind and other max range considerations:
As your operational world expands vertically, so should your weather considerations.
IFR flying is not simply about flying on instruments. It is about making better decisions with a more complete understanding of the environment. The more accurately you can visualize what the weather is doing from the surface to your cruising altitude and beyond, the more options you’ll have—and in aviation, options are almost always synonymous with efficiency, effectiveness, and safety.