Story ID: 042
Knowing the Known in Icing
By: Julie Boatman
Caption: Pilots must be aware of when known icing is present and prepare
Word Count: 1643
Icing’s specter looms over a wide swath of our flying lives. During the winter, we’re particularly attuned to its presence, but those conditions that constitute “icing” can occur any time of year, no matter where we fly.
As a pilot, you’re tasked to know when icing conditions are likely to exist, and whether your airplane has the approval and equipment to enter those known icing conditions. The certainty implied by the term “known” eludes most of us, however. Still, the burden is on those operating under Part 91 to weigh the risk as well as any airframe limitations on launching a flight into these conditions. If you fly under Part 135, Part 91 Subpart K, or other approval regimes, you’ll reference your operations specifications for guidance on what makes for a “no go” in times of known icing.
However, nailing down the FAA on what constitutes “known icing” is a bit, well, slippery. David St. George, executive director of the Society of Aviation and Flight Educators and an active corporate pilot, summed it up: “If the composite information indicates to a reasonable and prudent pilot that he or she will encounter visible moisture at freezing or near-freezing temperatures and that ice will adhere to the aircraft along the proposed route and altitude of flight, then known icing conditions likely exist.”
You can expect icing when flying in visible moisture—that’s rain, snow, fog, or clouds—if the temperature of the airframe is below freezing. True, not every “cold cloud” produces ice of significance on the airplane. But to launch up into them without due regard runs you afoul of FAR 91.13, with a “careless and reckless operations” charge possible if anything happens.
Fortunately, technologies have evolved in both anti- and de-icing equipment, and they’re now available on a broad range of business aircraft, including turboprops and the single-engine Cirrus Vision Jet. For engines that produce enough hot bleed air, thermal anti- and de-icing systems are the gold standard, providing the ability in some installations to heat the accumulation to an evaporation point, preventing run-back.
Electro-thermal anti-ice systems use a graphite foil electrically heated to prevent leading-edge buildup and work when switched on before the icing encounter. Inflatable rubber “boots,” found on most turboprops and some jets, work only after accumulation has begun, cycling to remove buildup. Weeping wing systems, such as TKS, use perforated distribution foils to seep antifreeze fluid onto the leading edges in flight—and they are limited by the amount of fluid carried in the reservoir—yet they have brought flight into known icing (FIKI) to the single-engine piston fleet.
Types and Levels of Icing
Though there are light icing conditions that may lull us into thinking they are benign, any icing can degrade performance. You never know when you might need that percentage of capability in flight, on takeoff, during landing, or when going around.
Even in aircraft certificated for FIKI, it is nearly impossible—and you cannot presume—that the test aircraft encountered all types of icing in its program for certification. These unexplored realms may include: freezing rain, freezing drizzle, mixed conditions combining rime and clear ice, and any conditions termed “severe.” In these regimes, you put yourself (and your passengers) in the role of test pilot—and that’s not a comfortable place to be. You may note accumulation upon surfaces that don’t normally pick up ice, as well as the usual places.
Some rules of thumb:
	A proper preflight includes understanding the current icing levels, both reported and forecast.	Once in it, you should look at one of two ways to exit the icing:
a. Get out of the area of visible moisture laterally.
b. Get to an altitude where the temperature is above freezing. The warmer altitude is not always the one below you, particularly in the event of a temperature inversion.
3. Report icing to ATC and request a new route or altitude as needed, without hesitation.
Keep in mind the axiom: “Change altitude, change course, or continue into the clear.”
Pilot, Brief Thyself
While few of us call an actual briefer these days, the depth of the self-brief—taking advantage of the astounding visual and data-rich tools available with a briefing query via ForeFlight or another planner—has outstripped most concerns about its thoroughness. This is one area where the technology has evolved tremendously, yet it still relies upon reporting to validate complex models.
Yes, an IFR brief when icing is in the picture is only as good as the reporting. You can click on visual representations of pilot reports—as long as the pilots are already up there making them. You may not have the luxury in the midst of the fight, but if you can, give a quick update to ATC and do your fellow pilots on the ground a solid. Your position report turns into a dot on the map laid next to a course line—and that is gold. This goes for braking-action reports, too.
Check the Aviation Winter Weather Dashboard for a wide-scale assessment. Convective forecast products for areas of convection—and thus, icing—run throughout the winter months. Also, review the winter “snowbird” advisories for impact in the NAS: www.fly.faa.gov/adv/advAdvisoryForm.jsp and https://nasstatus.faa.gov for airport closures.
If you’re in a hold and ice begins to accrete beyond a touch of light rime, understand that everyone stacked up with you is probably experiencing the same—albeit at different rates at different altitudes and positions on the approach. If the accumulation gives you pause, look at diversion promptly, especially if the conga line ahead of you extends beyond an airplane or two. If there’s widespread icing potential around a major terminal area—I’m looking at you, Boston through Philly—consider delaying the flight for better conditions if you can. Unless you have a rock-solid plan B, C, and D.
And that’s the key. Corporate pilot Wayman Luy has ferried many single-engine turboprops across the North Atlantic—and he remains cautious regarding ice. He points to a recent trip he took repositioning a Daher TBM 960 from Buffalo, New York (KBUF), to Fort Lauderdale, Florida (KFLL), as an exercise in flight planning and preflight risk mitigation. “Looking at the route on ForeFlight, I stay away from forecast moderate conditions and pick a route around that ice.” Be flexible with your departure schedule to mitigate. And be ready to fly the airlines. “I sit it out,” he said. “If you need to deice, it’s the wrong decision to go” in light business aircraft.
If he finds himself in it unexpectedly, he has a couple of tips. “Keep your speed up,” he said. “And I like to warm up the propeller and windshield early on.” That reminds me of an adage I learned flying around with a former colleague from the Aircraft Owners and Pilots Association. When I asked about turning on the pitot heat on the Beech A36 Bonanza we were flying as we were about to depart into the soup—on a summer day—he answered: “Use it. All the time. It’s free.” The hazard induced by not having the pitot tube warmed up before encountering any ice outweighs any possible cost of drawing those amps or wearing out the heating element.
Airport Considerations
Another part of your preflight brief includes conditions at the departure, destination, and alternate airports. As part of the FAA’s Takeoff and Landing Performance Assessment (TALPA) initiative, airports began using the current Runway Assessment and Condition Reporting system in October 2016, which assigns values to both coverage and braking action of runway and taxiway surfaces.
The Field Conditions Notices to Air Missions (one version can be found here: https://nbaa.org/wp-content/uploads/2018/01/ficon-notam-reportable-contaminants.pdf) outlines the reported information, to help mitigate the need to call the airport directly for conditions.
A cold-soaked airplane needs careful consideration and handling, and this includes the wings, nacelles/inlets, empennage, braking and landing gear systems, and other protrusions on the exterior. Interior fittings, appliances (the lav), and avionics can also lose utility in cold weather, and the total airplane must be safely brought up to operating temperatures before passengers arrive. Remove fluids that can freeze from the cabin and water system—and also any cold-sensitive items from onboard medical kits—after you arrive to mitigate this hazard.
Also, be prepared in case of holding time or overnight snowfall that it doesn’t induce enough weight on the empennage or horizontal tail surfaces to put the aircraft on its tail.
The pilot and crew must observe icing holdover times to ensure that deicing and anti-icing procedures and fluid application have the desired effect. The FAA publishes Holdover Tables for each winter season based on what’s available. Type I and Type 4 are the most common deicing and anti-icing fluids available.
Pilot Error
Common mistakes of pilots? Not recognizing that slowing airspeed is a key indicator of ice accumulation. Not getting out quickly enough. And not removing completely any frost or ice accumulation before departure. According to the AOPA Air Safety Institute, nearly one-quarter of icing accidents were caused by failure to ensure clean surfaces before takeoff—and two-thirds of all fatal icing accidents are the result of ice buildup in flight. Ice is deadly either way.
My sense has always been that if you grow too confident in your jousts with ice, it will find a way to smack you and shellack you—on the wings, stabs, filters, and probes.