As we enter the winter months, I’ve asked T &T contributor and safety expert Thomas Turner to provide strategies regarding cold-weather flying and icing conditions. For additional icing tips and tales, readers can also reference articles found in our November 2021 issue (available online).
We all want maximum utility from our airplanes. We don’t want to have to limit a non-ice-certified airplane to VFR-only operation in the wintertime. Even in airplanes approved for flight in ice (so-called FIKI airplanes), we need to fly within the limits of that certification. Although recent years have brought us tremendous advances in icing forecasts, there is still no Stormscope or StrikeFinder equivalent for airborne ice detection. You don’t know you’re in it until you are, and you can’t predict how heavy the ice will be until it accumulates.
FAA Advisory Circular (AC) 91-74B, “Pilot Guide: Flight in Icing Conditions,” states a “thin ice accretion on critical surfaces, developing in a matter of minutes, can sometimes have dramatic effects on stall speeds, stability and control. Wind tunnel testing indicates that if such accretions are particularly rough, they can have more adverse effects than larger accretions that are relatively smooth.” That, and the fact that ice is very unpredictable and varies rapidly, is the hazard of flight in clouds and visible moisture when the temperature is near or below freezing.
So how can we get maximum utility from an airplane
in cold-weather conditions?
In airplanes not approved for ice:
- Fly VFR and remain clear of all clouds and precipitation.
- If you elect to fly IFR, avoid flight in freezing temperatures (from about +5°C to -15°C in stratus clouds and as cold as -40°C in cumulus).
- Ask for block altitudes or request a VFR on Top clearance to remain in ice-free air, but only if you can climb and descend to those altitudes without entering clouds in the ice-likely temperature range.
- Remember that even if your airplane has the power to climb through unexpected ice, eventually, you may have to come back down into it.
- Take icing PIREPs seriously.
In airplanes with FIKI approval:
- Treat the first wisps of ice accumulation the same way you’d react if you unexpectedly heard the stall warning horn – do something NOW to eliminate the problem. Climb, descend, or turn to ice-free air… don’t try to ride it out if you can escape, even if the paperwork says you’re legal.
- Any mention of supercooled liquid droplets (“SLD”), means enough liquid moisture is suspended in the atmosphere to invalidate even “known icing” certification. SLD potential you cannot fly around, or under at temperatures well above freezing, is a no-go item.
In all aircraft:
- If you have an encounter, file icing PIREPs, so the system works for the next pilot.
- Figure icing delays or cancellations into your trip planning. If you pre-plan for flexibility you’ll be less likely to be pressured into making a bad decision.
You wouldn’t fly into a line of towering cumulus that is alive with lightning and extreme precipitation; you’d fly completely around it, delay your trip or cancel altogether. That’s a reality of flying during thunderstorm season. Icing is exactly the same – except we have no good way to actually detect ice location, type or intensity. So we have to be even more conservative to avoid encountering ice.
Many Pilot’s Operating Handbooks carry the limitation “flight into icing conditions is prohibited.” Those that list approval for flight in ice have certification limits on when that approval is valid. These limitations are not negotiable. The good news: Warmer weather is only a few months away.
So, if I’m on an approach in my FIKI approved plane and encounter a wisp of ice, I’m to do something now? Break off the approach? Don’t try to ride it out?
Mr Chavez, sarcasm has no place in a discussion of dealing with airplanes and icing. Let’s provide the whole story to readers who may never have experienced icing and those, perhaps like you, who have never had the opportunity to be really scared during an icing situation. Your “wisp” inside the FAF is not what this article is about and I think you know that. A “wisp” while being vectored 15 miles out might be a hint of what is to come depending on the surface temperature and the potential of being cleared to hold. A “wisp” at the FAF could be a warning that you better not need to go around. Have great respect for icing conditions regardless of your aircraft’s equipment or authorization.
If you are given a decent for an approach that will put you into icing request a discretionary decent. Then stay above the clouds until you can make a faster decent through the icing layer.