The phrases “all weather” and “single-engine airplane” belong in the same sentence only for a select few pilots whose tolerance for risk is best described as elastic. What has always been true, remains true: One mans routine trip through cold clouds is another mans (or womans) agita-inducing nightmare.
Of late, the industry has made remarkable strides in giving even the most risk-tolerant pilots better tools to detect threatening weather and deal with its
consequences. Still, even for many experienced pilots, structural icing represents an exceptional terror. Ice forecasting has improved-even in the last five years-but intensity forecasting is still uncertain at best. And many pilots worry-irrationally in our view-about the FAA-legal definition of known icing. When is it legal to depart? When is it not? Do so-called inadvertent ice protection systems really buy you any risk mitigation? (Short answer: yes.) For some pilots, worrying about these fine details leads to distracting hand wringing. It really shouldnt.
Cirrus Steps Up
Seeing an opportunity in this conundrum, Cirrus Aircraft (formerly Cirrus Design) recently developed and will soon certify and ship what is, in our view, the most sophisticated and possibly effective integrated approach to ice protection for any single-engine piston airplane weve seen. And thats saying a lot, given the excellent TKS-based known-ice package that Mooney has offered for years, not to mention inadvertent and certified systems for Beechcraft and Cessna models, including the composite Bend, Oregon-built Corvallis line. Prior to Cessna buying the then-Columbia Aircraft Company, Columbia had dabbled in electric ice protection systems, but without much success. TKS is now the market leader in new aircraft de-icing systems. By way of definition, “inadvertent” means a system is designed to provide some margin of protection without being certified for flight into known ice.
For its new generation SR22, Cirrus saw a market opportunity to upgrade its inadvertent TKS-based system to a full-up, flight-into-known-ice (FIKI) package. The intent was to both extend the airplanes safety envelope and allow pilots the expanded utility of departing into forecast icing when they otherwise wouldnt, either in an unprotected airplane or one equipped with an inadvertent system. The capability doesnt come cheap. The inadvertent system is a $19,950 option, while the approved system is $44,450. The hit against payload is 61 pounds, plus fluid weight.
Cirrus tackled the envelope expansion by working with CAV Ice Protection LTD to produce a system thats as close to a clean-sheet design as it is an upgrade of the Cirrus inadvertent system. Few of the parts are common between both systems. As with the inadvertent package, the new Cirrus FIKI system has laser-drilled titanium leading edges on the wings, the horizontal stabilizer, plus prop protection. But the certified system adds protection for the vertical fin and windshield.
The wing panels have been extended chordwise slightly toward the rear of wing to provide protection for a larger envelope of airspeeds and attack angles. In flight, the wings are noticeably covered by a thin layer of fluid.
Because of the tight tolerances between control surfaces-especially where the elevator horn nestles next to the horizontal stabilizer-Cirrus and CAV added a unique short curved panel at the front surface of the elevator to protect against ice bridging. The wing-mounted stall warning vane is electrically heated, as is the pitot tube.
For the prop, Cirrus uses a slinger on each blade, with rubber channels to flow the fluid out toward the tips. The windshield has automotive-style dual spray heads that are more streamlined than the traditional spray bars and that absolutely inundate the pilots side windshield with fluid. We tried this in the air with no ice and it appears the fluids flow pattern would open up a generous clear hole on an iced windshield.
For ice detection at night, Cirrus has installed prismatic LED lights forward of the main wing on both sides. These split illumination between the main wing and the horizontal stabilizer. As is required by FAA certification for known-ice TKS systems, redundancy is required, which Cirrus has incorporated by installing two fluid pumps: a main pump and a back-up unit. (Theres actually a third for the windshield sprayer.) As installed in the Cirrus, there are three fluid settings: Normal, High and Max. Fluid duration for each mode is 150 minutes, 75 minutes and 37.5 minutes respectively, according to Cirrus specs. (The max setting is actually controlled through a two-minute cycle, once the button is pushed.)
Mechanically, the Cirrus known-ice package is not much different functionally than Mooneys similar system, although it has some nicer touches, such as the unobtrusive windshield treatment and the elevator de-ice feature. Whats most interesting about the Cirrus system, however, is its total integration into the rest of the airframe to provide a multi-lateral approach to ice risk mitigation. Specifically, system monitoring is integrated into the Garmin Perspective EFIS suite and, for those who purchase XM Wxs top-drawer Aviator Pro Service, the Perspective will display two weather products specifically aimed at depicting potential icing areas: The Current Icing Product is a NOAA display that depicts icing potential graphically by altitude and by potential severity. The service also has another product called SLD Icing or supercooled large-droplet icing. This condition is thought to represent a hazard serious enough to overwhelm FAR Part 25 ice protection systems. In addition, XM Wx also provides current Pireps on icing. Its called the Current Icing Product and is based on a new NOAA model.
The Perspective MFD displays fluid levels in both tanks-four gallons per side in two wing-mounted tanks-flow rates, duration and even how far in miles the fluid will last. Fault annunciators include low flow, low level and clogged filters. Fluid levels are automatically balanced, but theres also a manual override accessed through the MFD.
The additional arrow in the new SR22s ice flying quiver is the airplanes turbocharging system, widely regarded as the most efficient system available in new GA aircraft. Turbocharging has been-and remains-a potent tool to avoid ice because it allows rapid climbs through icy layers to on-top conditions or colder temperatures where ice stops accreting. One addition we would like to see is electronic ice detection sensor to illuminate an annunciator on the Perspective panel. The TKS technology works best if its activated before serious accretion begins and an ice detector would help. (Cirrus considered this, but didnt find a detector it liked.)
FIKI: Is It Better?
From the risk-mitigation point of view, is a known-ice system really better than an inadvertent system? Theres little doubt it is. Having windshield and vertical fin protection is better than not having it and, other than weight and cost, theres no downside to having a second fluid pump. The redundancy makes for a more robust system.
The difficult question is whether it makes any functional difference in ice survival. Even with a known-ice system, prudent pilots will try to quickly exit any icing conditions approaching moderate accretion, which is the same strategy youd follow in an airplane with no icing protection or with only an inadvertent system.
The path to survival is the same as it has always been: a solid gold out consisting of some acceptable combination of high ceilings, a thick above-freezing-layer near the surface, low tops, flat terrain, a temperature inversion and plenty of realistic bolt holes to get into along the intended route if the icing becomes untenable.
As for the legalities of flight into icing, pilot attitudes define a spectrum. At one end are pilots who have been flying for years in airplanes with no ice protection, understand the risk and are willing to take it, accepting that being wrong will exact at high price. For them, debates about all-weather airplanes are pointless.
At the opposite end-or perhaps somewhere in between-are pilots guided strictly by the FAAs thou-shalt-not proclamations concerning flight into forecast icing. For these pilots, the new Cirrus system-or any known-ice package-represents both an attractive option and a dilemma.
With the legal restriction tidily dismissed by known-ice capability, the pilot now has to make a finer point judgment on whether the ice protection system (and the pilot) can handle the icing conditions likely to be encountered. Although the TKS system has been extensively tested-100 hours in natural icing on the Cirrus-any reasonable person knows theres ice out there (however rarely encountered) that TKS cant handle. As long as there are exit options available-as listed above-the risk of being smacked out of the sky in a TKS-equipped airplane is close to zero. But its not exactly zero.
What the Cirrus systems does-with its incrementally improved fluid distribution, ice detection lights, integrated management and monitoring and datalinked access to the latest ice forecast products-is to effectively chip away at whats left of the risk of flying in ice. Were not sure if we would call that a true all-weather airplane, but were comfortable calling it one thing: Progress.