Safety Recommendation A-22-022

Aviation Investigation Report AIR-26-05 “In-Flight Loss of Control and Impact with Pack Ice Bering Air Flight 445 Textron Aviation 208B, N321BA, Near Nome, Alaska February 6, 2025” published on July 30, 2026:

2.5 Supercooled Large Droplet Forecast Products for Alaska

The NTSB’s investigation was unable to determine what weather sources or products the pilot referenced before the accident flight. However, the weather reports and forecasts that were available before the flight did not represent the severity of the icing encountered during the flight, and none contained SLD-specific information.

The AIRMET icing forecast issued about 2 hours before the pilot departed PAUN indicated occasional moderate icing between 2,000 and 8,000 ft msl, and the graphic icing product issued by the AAWU about 1.5 hours before the pilot departed PAUN indicated occasional-to-constant moderate icing within the same altitude range. Further, the AIRMET text did not accurately indicate the area of forecast icing (indicating southwest of Unalakleet rather than moving north into Norton Sound). So, if the accident pilot only saw the AIRMET text, he would have been under the impression that the worse area of forecasted icing was not along his route of flight.

The AAWU does not issue SLD-specific forecasts or products. Based on experience, the lead meteorologist responsible for forecasts at the accident time identified the combination of forecasted elements in the graphical forecast editing software (and subsequently in AIRMET Zulu) as representative of SLD conditions. However, at the time of the accident, no official product existed in which that feature could be explicitly communicated.

When asked about the tools he used to develop icing forecasts, the lead meteorologist mentioned experimental guidance produced by NCAR that he used for coverage information but rarely used its SLD probabilities because “the output that comes from that is very small, very sporadic.”

The NTSB previously identified the lack of SLD-specific forecast products for Alaska as a safety issue for aviation operations there. On August 16, 2021, the pilot of a Cessna 208B airplane, being operated as a Part 135 scheduled commuter flight from Fairbanks International Airport to Huslia Airport; Huslia, Alaska, experienced a loss of control while descending from 10,500 to 10,000 ft msl in SLD conditions. The pilot later reported that, during the accident, it felt as if the aileron controls were jammed. She regained control of the airplane, declared an emergency, and returned to the departure airport where she landed without further incident.

None of the occupants were injured, and the airplane was substantially damaged. We determined the probable cause of the accident, in part, was “the pilot’s unexpected encounter with [SLD], which resulted in a loss of control due to ice accumulation.” Footnote: The full probable cause statement was “the pilot’s unexpected encounter with [SLD], which resulted in a loss of control due to ice accumulation.

Contributing to the accident were: (1) the pilot’s failure to maintain the minimum airspeed for flight in icing conditions, (2) the pilot’s failure to disconnect the autopilot every 10 minutes to check for ice buildup, (3) the overweight airplane, (4) the lack of an SLD forecast product for the state of Alaska, and (5) the Federal Aviation Administration's failure to require weight and balance documentation for each flight in Title 14 Code of Federal Regulations Part 135 single-engine operations.” Use the CAROL Query to search for more information about this accident (case number ANC21LA073).

As a result of our investigation, we issued Safety Recommendations A 22-21 and -22 in June 2022. These recommendations asked the FAA and NWS, in collaboration with each other, to develop a graphical forecast depicting potential areas of SLD icing conditions in Alaska and to make this information available to pilots (NTSB, 2022b). Both the FAA and the NWS responded positively, in October 2023 and July 2024, respectively, and the recommendations were classified Open–Acceptable Response awaiting further action.

On March 23, 2026, the NWS issued Service Change Notice 25-80, updated on March 30, announcing the inclusion of information indicating the potential for SLD conditions over Alaska in AWC graphical icing forecasts.

The updating of AWC graphical icing forecasts to include potential SLD conditions in Alaska is responsive to Safety Recommendations A-22-21 and -22. Thus, the NTSB concludes that graphical forecasts depicting potential areas of SLD icing conditions in Alaska will help pilots avoid inadvertent encounters with these hazardous conditions. Therefore, the NTSB classifies Safety Recommendations A-22-21 and -22 CLOSED—ACCEPTABLE ACTION.

We note that you remain committed to improving your current icing product and forecast icing product in support of the FAA; however, due to a moratorium on the transition to a new supercomputer, your planned enhancements may be delayed until 2027. Pending the completion of a graphical forecast depicting potential areas of supercooled large droplet icing conditions in Alaska, the Board has classified Safety Recommendation A-22-22 OPEN-- ACCEPTABLE RESPONSE.

-From Ken Harding, Chief Operating Officer, NOAA National Weather Service: The NWS remains committed to improving the Current Icing Product (CIP) and Forecast Icing Product (FIP) in support of the FAA. However, due to a scheduled moratorium for the transition to a new supercomputer, any planned enhancements will be delayed until 2027.

From the aviation report of accident ID ANC21LA073. Accident occurred in Fairbanks, Alaska on August 16, 2021, Cessna 208, Loss of control in flight, published on April 26, 2023:

Analysis

After departure, the pilot climbed the airplane with the autopilot engaged to her assigned altitude of 10,000 ft mean sea level (msl), where she encountered instrument meteorological conditions and “light rime” icing conditions. To exit the icing conditions, she climbed the airplane to 10,500 ft msl. However, she was unable to exit the icing conditions and began a gradual descent back to 10,000 ft msl. She noted that while en route, the airplane’s deicing boots, and heated propeller were operating normally by removing ice accumulations.

While in a gradual descent from 10,500 ft msl to 10,000 ft msl, the autopilot disengaged without warning, and the airplane entered an abrupt uncommand right bank followed by a steep, nose-down, spiraling descent. The pilot stated that during the upset, it felt as if the aileron controls were jammed as she tried to regain control of the airplane. After regaining control of the airplane, she declared an emergency and made an emergency landing back at the departure airport. The airplane sustained substantial damage to the wings and the right aileron during the upset.

Postaccident examination revealed no evidence of preaccident mechanical malfunctions or anomalies with the airplane that would have precluded normal operation. Flight control continuity was confirmed from the cockpit to all control surfaces. Additionally, testing of the autopilot and deice systems did not reveal any anomalies.

Weather soundings, forecasts, and experimental weather products indicated a 30% to 60% chance of light to moderate icing in the accident region with supercooled liquid water in the clouds from 7,000 ft to 13,000 ft and favorable conditions for supercooled large droplets (SLD). It is likely the airplane encountered SLD conditions that degraded the airplane’s performance, which resulted in the upset.

Graphical aviation forecast information that showed areas of icing (trace to severe/heavy) was available in Alaska. However, that information did not depict areas with potential SLD icing. If a product that included SLD icing information for Alaska had been available, the accident may have been avoided. As a result, the National Transportation Safety Board (NTSB) issued recommendations to the Federal Aviation Administration (FAA) and the National Weather Service (NWS) to collaborate in the development of a graphical forecast showing the potential for SLD icing conditions in Alaska and to make this information available to pilots (Safety Recommendations A-22-21 and -22).

-John D. Murphy, Chief Operating Officer, NOAA National Weather Service: The NWS acknowledges receipt of this NTSB Safety Recommendation and advises we are working to determine how to best incorporate supercooled droplet information into future graphical icing products. The NWS Forensic Services Program will lead the response for the NWS recommendations with coordination and inputs from the NWS Aviation Weather Center (AWC), NWS Alaska Region Headquarters (ARH), the Alaska Aviation Weather Unit (AAWU), and partners.

The NWS point of contact, NWS Forensic Services Program Manager Lora Wilson, will be responsible for the coordination and consolidation of future responses for this recommendation. Please have your staff contact her.

The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to provide assistance to victims and their family members affected by major transportation disasters.

The attached letter from the NTSB Chair provides information about the May 24, 2022, report Provide Graphical Forecast of Potential Supercooled Large Droplet Icing Conditions in Alaska. The details of this accident investigation and the resulting safety recommendation may be found in the attached report, which can also be accessed at http://www.ntsb.gov. For more information about NTSB and our recommendation process, please see the attached one-page summary.

The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days of the date of this letter, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendation by number (for example, A-22-22). We encourage you to submit your response to ExecutiveSecretariat@ntsb.gov. If your reply exceeds 20 megabytes, including attachments, please e mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response.

All communications regarding safety recommendations will be stored by the NTSB and viewable by the public. Please do not send privileged or confidential communications in response to this recommendation. Responses marked as confidential or privileged (or similar designations) will be considered nonresponsive. If you have concerns about this protocol, please contact us at ExecutiveSecretariat@ntsb.gov.

The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters.