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How Freezing Rain Forms

_Night Flier_

Winter is almost here, and that means it's a good time to refresh your knowledge of icing conditions.

What Creates Freezing Rain

According to the FAA, "freezing rain forms when snowflakes fall into a warm (Temperature above 0 degrees C) layer aloft, melt into raindrops, and then falls through a subfreezing layer of air again before reaching the ground." How is this temperature inversion generated?

Warm fronts can create a reversal in the temperature profile, allowing subfreezing temperatures to be present again aloft. Also, if you're flying above mountainous terrain consider that a layer of sub-zero air could be pushed against the slope below some warmer air, creating a pseudo warm front, increasing the risk for freezing rain.

Also stated by the FAA, "Ordinarily, air temperatures rise steadily with decreasing altitude, and therefore, temperatures below the 0 degrees C level aloft will be warmer than freezing. But freezing rain requires a reversal in the temperature profile somewhere below the melting layer such that subfreezing temperatures are again present at or above ground level. This can occur in connection with a warm front when warm air overruns a subfreezing layer of air already in place."

ATC Recording: Inadvertent Icing Encounter In Freezing Rain

Now that you understand how freezing rain forms, here's a real-world scenario to apply your knowledge to.

In 2020, a tragic accident occurred on approach to Lubbock, Texas. As the weather gets colder this fall, and icing conditions become more prevalent, pay extra attention to freezing levels, PIREPs, and precipitation moving through your local area before you fly.

Before we dive into the NTSB's preliminary report, take a listen to the ATC audio and radar imagery in the video below. Think to yourself, "what could I do differently if caught in this situation?"

The NTSB Preliminary Report

The following report was published by the NTSB shortly after this accident.

On October 26, 2020, at 1558 central daylight time, a Cessna 210 airplane, N9622T, was destroyed when it was involved in an accident near Lubbock, Texas. The private pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The airplane was operated on an instrument flight rules (IFR) flight plan from Belen Regional Airport (BRG), Belen, New Mexico, to Corsicana Municipal Airport (CRS), Corsicana, Texas, but had diverted to Lubbock Preston Smith International Airport (LBB), Lubbock, Texas.

A review of the air traffic control recordings and ADS-B data revealed the airplane was in instrument meteorological conditions (IMC) during the descent toward LBB and the pilot reported that he had been in IMC "for quite a while." The pilot was instructed to set up for the RNAV (GPS) Y instrument approach to runway 35L. During the approach, the pilot was unsure of the instrument approach to expect and was not in position to intercept the final approach course, so the controller vectored him to the east to set up for the same approach with a different initial approach fix (IAF).

NTSB

When queried by the controller, the pilot reported that he was experiencing structural icing and was in "freezing rain." After the airplane crossed the intermediate fix, ZOVOC, and turned inbound, the groundspeed (gs) gradually decreased from about 80 kts to about 50 kts. After crossing the final approach fix, UFACI, about 4,700 ft mean sea level (msl) and 48 kts gs, the airplane made a left turn toward south-southeast and descended. The pilot reported to the controller that the airplane experienced an autopilot issue, so the controller provided new vectors to the pilot. The flight track showed that the airplane continued to descend, then made a sharp left turn before the data ended. The controller reported that radar contact was lost and there were no further communications from the pilot. Figure 1 shows the ADS-B flight track overlaid onto Google Earth with the approach fixes and the accident site labeled.

The responding Federal Aviation Administration (FAA) inspectors reported that the airplane impacted a residential area about 200 yards from the final recorded ADS-B point and about 6 miles south of LBB. A post-impact fire consumed most of the fuselage and the inboard sections of each wing. The inspectors found numerous chunks of ice in the wreckage near the wings, and pieces still attached to some of the airplane's leading-edge surfaces. The ice chunks were concave-shaped and featured a smooth surface on the inside of the curve (likely the shape of the wing's leading edge). The ice ranged from 1 to 2 inches thick.

NTSB

What Can You Do?

Specific to freezing rain, the warm layer aloft is a well-known phenomenon. If you know there's warmer air above you, climbing may be an option. However, that option is typically only a real option for jet with lots of excess thrust. If you don't have the performance to climb out of the conditions, turning around and flying back to non-icing weather is another option.

Freezing rain will overwhelm most anti/de-icing equipment quickly and entirely coat non-protected surfaces, and regardless of your decision to climb, turn around, or take another action, you need to exit freezing rain conditions as quickly as possible.

Have you encountered freezing rain on the ground or in the air? Tell us about your icing experiences in the comments below.

Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and an Embraer 145 First Officer for a regional airline. He graduated as an aviation major from the University of North Dakota in 2018, holds a PIC Type Rating for Cessna Citation Jets (CE-525), and is a former pilot for Mokulele Airlines. He's the author of articles, quizzes and lists on Boldmethod every week. You can reach Swayne at swayne@boldmethod.com, and follow his flying adventures on his YouTube Channel.

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