Trapped in Ice: The Cost of a 10-Hour-Old Briefing

A weather briefing is a snapshot. The forecast you read the night before was the best information at the time, but AIRMETs expire, new ones get issued, and icing forecasts update every hour. If you don't look again before you go, you're flying on old news.

The AOPA Air Safety Institute (ASI) re-creates this flight in its video "Accident Case Study: Trapped in Ice," which you can watch below. The summary that follows is ours and is based on the NTSB final report (CEN18FA144), which also gives the official probable cause. Watch the full case study for ASI's own analysis.

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The flight, in short

On April 19, 2018, a 65-year-old instrument-rated private pilot with about 496 hours, 245 of them in type, departed Lancaster, Pennsylvania (LNS) in a Cirrus SR22 on an IFR flight plan to South Bend, Indiana (SBN). One passenger was aboard. The airplane had no anti-icing or deicing system, so it was not equipped for flight into known icing.

The pilot got his weather briefing through an app on his mobile device about 10 hours before the flight. It showed cloud cover, snow showers and IFR conditions. The AIRMET in that briefing expired at 0500, before he departed. In the hours between, a new AIRMET was issued for moderate icing, IFR and mountain obscuration, and low-level turbulence, valid until 1100. An updated AIRMET was recorded under his flight plan identification number less than 2 hours before departure, but the NTSB could not determine whether he checked it, and found no record that he got any other weather before or during the flight.

According to the NTSB, the airplane likely entered the clouds about 500 feet above the ground on climbout and stayed in IMC and icing conditions for the rest of the flight. To get above it, the airplane would have needed to climb above 10,400 feet. Before departure, the icing forecast showed light to moderate icing near the accident site, and the current icing product showed supercooled large droplets (SLD) nearby.

About 55 minutes after takeoff, at about 5,400 feet, the pilot told Johnstown Approach the airplane was accumulating ice and asked to divert. Johnstown was reporting a 200-foot overcast and Altoona a 500-foot overcast, so he chose the ILS at Altoona. During the descent he flew through the localizer and didn't notice until the controller told him. On the turn back to intercept, the airplane began to descend, the airspeed increased, and the left turn tightened into a spiral. It struck the ground near Williamsburg, Pennsylvania, and both people aboard were killed.

The NTSB determined the probable cause to be: “The pilot’s failure to obtain an updated weather briefing before the flight and his subsequent loss of airplane control due to spatial disorientation while maneuvering in instrument meteorological conditions during a diversion to an alternate airport after encountering forecast icing conditions.”

Why the update matters

The NTSB said the pilot had enough forecast information available before departure to have known about the icing along the route, but it couldn't determine whether he saw all of it. That gap is the lesson. The night-before briefing showed IFR weather. The morning picture added moderate icing, SLD potential and tops above 10,000 feet, in an airplane with no ice protection. Those are different flights.

• Check the valid time on every advisory. An AIRMET that expires before you depart tells you nothing about your flight.
• Get a fresh look as close to departure as you can, and again before you take the runway if anything has changed.
• In an airplane without ice protection, “forecast icing along the route with tops above my ceiling” is the question, not “IFR conditions.”
• Know your outs before you need them. Here, both nearby airports were reporting low overcasts by the time the ice showed up.

The NTSB also found two impairing medications, diphenhydramine and clonazepam, in toxicology testing, and couldn't determine whether they contributed. It's a reminder to include medications in your personal checklist before any flight.