Safety Recommendation A-22-021

-From Bryan Bedford, Administrator: The Federal Aviation Administration (FAA) and the National Weather Service (NWS) developed the Domestic Aviation Forecast System (DAFS), a graphical forecast of supercooled large droplet icing conditions in Alaska. Implemented on March 30, 2026, DAFS v1.0 provides a consistent and comprehensive set of aviation forecasts, such as a graphical forecast depicting icing probability, icing severity, and the potential of supercooled large droplet icing conditions, for the contiguous United States and Alaskan domain.

DAFS v1.0 is a standalone system that utilizes the FAA-developed Forecast Icing Product and Graphical Turbulence Guidance products from the High-Resolution Rapid Refresh model. Additional information on the DAFS v1.0 can be found at:

https://www.weather.gov/media/notification/pdf_2026/scn25-80_Update_DAFS_aad.pdf

I believe the FAA has effectively addressed the intent of Safety Recommendation A-22-21 and consider our actions complete.

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

We note that you continue to work with the NWS to develop a graphical forecast of supercooled large droplet icing conditions in Alaska. We also note that the NWS’s Rapid Refresh Forecast System (RRFS) is scheduled to be implemented in September 2024, and will provide the in-flight icing capability that is needed to support aviation forecasts from the NWS’s Alaska Aviation Weather Unit. You reported that, initially, the NWS will provide graphical output across the contiguous United States and that the FAA will sponsor efforts to formally evaluate the Alaska output.

We continue to believe your ongoing work with the NWS to develop a graphical forecast of supercooled large droplet icing conditions in Alaska and the planned implementation of the NWS’s RRFS are responsive to this recommendation. Pending future updates and completion of the recommended action, Safety Recommendation A-22-21 remains classified OPEN-- ACEPTABLE RESPONSE.

-From Kathryn B. Thomson, Deputy Administrator: The Federal Aviation Administration (FAA) continues to work with the National Weather Service (NWS) to develop a graphical forecast of supercooled large droplet icing conditions in Alaska. Scheduled for September 2024, the implementation of the NWS’s Rapid Refresh Forecast System (RRFS) will provide the in-flight icing capability needed to support aviation forecasts from the NWS’s Alaska Aviation Weather Unit. Initially, the NWS will provide graphical output across the contiguous United States. The FAA is sponsoring efforts to formally evaluate the Alaska output.

The FAA and the NWS will determine when the output can be made available, pending favorable evaluation results.

I will keep the Board informed of the FAA’s progress on Safety Recommendation A-22-21 and anticipate providing an update by September 30, 2024.

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).

We note that you have sponsored the Icing Product Alaska (IPA), which is a graphical forecast of supercooled large droplet icing conditions in Alaska and is based on the NWS’s Current Icing Product and Forecast Icing Product. You reported that the IPA has been delayed, but that you are working with the NWS to implement a temporary solution with similar capabilities until the IPA can be implemented. You also reported that the NWS’s Rapid Refresh Forecast System—a next-generation convection-allowing, rapidly-updated ensemble prediction system—is scheduled to be implemented in 2024, and will support aviation forecasts from the NWS’s Alaska Aviation Weather Unit.

We believe your actions thus far are responsive to this recommendation. Pending future updates and completion of the recommended action, Safety Recommendation A-22-21 is classified OPEN--ACCEPTABLE RESPONSE.

-From Billy Nolen, Acting Administrator: The Federal Aviation Administration (FAA) sponsored research and development of a graphical forecast of supercooled large droplet icing conditions in Alaska, called the Icing Product Alaska (IPA). The IPA was based on the contiguous United States capabilities of the Current Icing Product (CIP) and Forecast Icing Product (FIP), which were also developed. The CIP and FIP are maintained and operated by the National Weather Service (NWS) and are available at: www.aviationweather.gov/icing.

In June 2022, the NWS informed the FAA that the IPA is delayed indefinitely, and as a result, the FAA is working with the NWS to implement an IPA-like capability. With the implementation of the NWS’s Rapid Refresh Forecast System (RRFS), the planned FIP enhancements will include the Alaska domain, and will provide the in-flight icing capability needed to support aviation forecasts from the NWS’s Alaska Aviation Weather Unit. The RRFS will be the next generation convection-allowing, rapidly-updated ensemble prediction system, and we expect implementation of the RRFS by September 2024.

I will keep the Board informed of the FAA’s progress on Safety Recommendation A-22-21, and anticipate providing an update by September 30, 2023.

The attached letter from the NTSB Chair provides information about the NTSB’s 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 recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov.

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 recommendations by number (for example, A-22-21). 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.

This letter provides information about the National Transportation Safety Board’s (NTSB) 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 recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov.

As a result of this investigation, we identified the following safety issue:

• A need to provide pilots operating in Alaska with graphical forecasts of potential supercooled large droplet icing areas to prevent flight into those areas.

Accordingly, the NTSB makes the following safety recommendation to the Federal Aviation Administration:

• In collaboration with the National Weather Service, develop a graphical forecast depicting potential areas of supercooled large droplet icing conditions in Alaska and make this information available to pilots. (A 22 21)