Inaccurate Icing Reports Cited As Factor In Fatal Crash

The NTSB has determined the probable cause of a February 2005 SR22 crash near Norden, CA in which the sole occupant, pilot Bill McGrath, was killed. In its preliminary report issued a couple of weeks after the accident , the NTSB said McGrath had radioed to ATC he was encountering icing conditions and was unable to maintain altitude. Although equipped with a TKS "weeping wing" ice protection system, the aircraft was not certified for flight in known icing conditions.

In its latest report, the board says the McGrath obtained a preflight weather briefing for a flight from Reno, NV to Oakland, CA. There were no valid SIGMETs or AIRMETs for icing along the route and no PIREPs were available. The briefer also told him the freezing level in the Reno area was reported at 6,000 feet with no precipitation.

McGrath filed an IFR flight plan for 12,000. After takeoff, at 18:07 he contacted Oakland Center and requested clearance to 16,000 to get above the clouds. At 18:13 he reported he was still in the clouds and asked about going lower.

At 18:15 McGrath told Center if he could climb another 200 - 300 feet he could get above the clouds. When Center asked if he wanted to go up or down, McGrath said he wanted to climb first to get airspeed. Center cleared him for a block altitude between 16,000 and 17,000.

About 2 minutes later McGrath radioed his last transmission saying he was "coming down" and that he was "icing up." A worker grooming ski runs at Sugar Bowl Ski Resort found the wreckage in the early morning hours the next day. The plane's airframe parachute system had been deployed.

The closest official weather observation station was Truckee-Tahoe Airport, Truckee, California, (TRK), which was 9.3 nautical miles northeast of the accident site at 5,900 feet MSL. TRK issued an aviation routine weather report (METAR) for 18:10 reporting winds from 240 degrees at 6 knots; visibility 10 miles; skies 3,400 feet broken, 10,000 feet overcast; temperature 37 degrees Fahrenheit; dew point 27 degrees Fahrenheit; altimeter 29.87 In/Hg.

Investigators from Ballistic Recovery Systems, the airframe parachute system manufacturer, determined the system had been deployed beyond the it's maximum deployment airspeed of 133 knots indicated.

According to the board, a post-crash analysis of the actual weather conditions suggested the likelihood McGrath encountered severe icing related to super-cooled, large water droplets (photo of ice on the wing of a Cessna Caravan above). Further, despite fully-conforming to FAA standards, the weather briefing never warned the McGrath he might encounter such conditions.

The NTSB officially lists the probable cause of this accident as the pilot's 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.

FMI: www.ntsb.gov