This time of year, pilots main weather worry turns to airframe icing. The thunderstorms are (mostly) gone, replaced by layers and layers of moisture-laden clouds. Depending on where and how high you fly, there be ice in them there clouds. Or not. Much has been said recently about a legal opinion rendered by the FAAs Eastern Regional Counsel, redefining what constitutes “known icing” with the worst-case scenario of potentially grounding for the winter a bunch of airplanes not approved for flight into known icing. Regardless of whether an airplane is approved for known icing or not, its rarely a good idea to enter and remain in such conditions. On occasion, Mother Nature simply doesnt want an airplane plying her skies and will send it back toward the ground with a load of ice. This can happen to light airplanes, to heavy jet transports and everything in between. Hopefully, during your flying career you will only encounter ice in the airport bar after a safe, successful flight. On the occasions you encounter it while airborne, you should be planning and executing ways to get out of it. Youll already be descending to warmer air on approach, or have the power to carry the airplane and the ice to a higher altitude where there is too little moisture for ice to form. If that doesnt work, youll do a 180 and get the heck out of there and find an alternate route. Or youll land. What you wont do is take a normally aspirated piston single whether or not its approved for flight in known icing into the mid-teens with a load of ice, hoping to get on top and continue to your destination. Period. Heres why. Background On February 6, 2005, at about 1820 Pacific time, a Cirrus Design SR22 G2 impacted mountainous terrain after encountering icing conditions near Norden, Calif. The solo Instrument-rated Private pilot who had less than 500 hours total flight time sustained fatal injuries; the brand-new airplane was destroyed. The flight departed the Reno (Nev.)/Tahoe International Airport (RNO) at about 1750, en route to Oakland, Calif. Instrument conditions prevailed along the route and an IFR flight plan had been filed, listing 12,000 feet as the intended cruising altitude. The pilot received a standard weather briefing, which included advice that there were no Pireps along the intended route. Weather in the Reno area at the time of departure included an overcast at 5500 feet and a surface temperature of six degrees C. The freezing level in the Reno area was 6000 feet; there was no precipitation. The pilot indicated he might request 14,000 feet once he was airborne. The airplane was equipped with an ice protection system designed to distribute deicing fluid along the wing, horizontal stabilizer and propeller blades. It was not approved for flight in known icing conditions. After takeoff, recorded radar data shows the Cirrus executed the Mustang 6 departure procedure, climbing on a westerly course for about 18 minutes 30 seconds. At 1807:46, the pilot requested to continue his climb to 16,000 feet to “see if I can get above these clouds” and was cleared as requested. At 1813:40, the pilot told ATC, “Uh, I guess this isnt gonna work, Im still in the clouds, any chance of lower?” The controller responds by asking him to “stand by one.” At 1815:00, the pilot told ATC that if he could go up another 200 or 300 feet, he could get on top. The controller cleared the Cirrus to maintain a block altitude between 16,000 and 17,000 feet, which the pilot acknowledged. About two minutes later the pilot transmitted, “Uh, Im coming down …. Im icing up.” The controller asked the pilot to repeat his transmission. At 1817:42, the pilot made his last transmission, stating, “Im icing up. Im coming down.” Radar data indicated the airplane leveled off and maintained 16,100 feet msl for about 3 minutes 40 seconds. The airplane then initiated a climb and attained an altitude of 16,700 feet msl. The last 12 seconds of recorded radar data indicated the airplane was in a descent. Radar contact was lost at 18:17:29, at a Mode C reported altitude of 15,700 feet msl. Representatives from the airframe parachute manufacturer examined it and its associated components, which were recovered about 4000 feet north of the accident site. The representatives determined the parachute assembly had separated from the airplane almost immediately after deployment. Examination revealed the parachute separated from the airplane under extremely high loads. Both risers were separated from the parachute assembly. The parachute separated from the suspension lines. The ends of the suspension lines were “broomstrawed,” indicating they had been parted by extreme force. The parachute manufacturers representatives concluded the extent of damage was consistent with a high-speed deployment. The deployment was outside of the operating envelope of the system. The placarded deployment speed on the Cirrus SR22 is 133 knots indicated airspeed. Probable Cause The National Transportation Safety Board determined the probable cause of this accident to include: “The pilots in-flight loss of control following an inadvertent encounter with unforecast severe icing conditions. A factor in the accident was the inaccurate icing forecast developed by the NWS Aviation Weather Center.” Analysis of the weather conditions the Cirrus encountered revealed the likelihood that severe icing related to super-cooled large water droplets was present as the aircraft climbed to 16,000 feet and higher. Despite the preflight weather briefing conforming fully to FAA standards, including observed and forecast weather conditions, the NTSB said post-accident analysis of weather conditions showed the clear likelihood of severe icing conditions. The NTSB also said the algorithms used by the National Weather Service Aviation Weather Center to predict icing conditions showed only a low probability of icing in the area, and, in the absence of Pireps to the contrary, an icing forecast was not triggered. Even though the forecast did not include in-flight icing, a cloud layer above the freezing level should have been a clue for everyone. Once the icing was noted and it appears to have been ungodly severe it was time to start down or turn around. By delaying his descent and, in fact, trying to climb, the pilot put his airplane into a situation for which it was not designed and he was not prepared. At that point, the sad results became predictable.
