Safety Recommendation A-22-006

We note that you have reviewed and concur with Cirrus’s updated FHA for the fuel and power plant systems installed on Cirrus SR20/22/22T series airplanes and the supplemental systems safety assessment (SSA) that Cirrus developed for the electric auxiliary fuel pump installed on Cirrus SR22T model airplanes. We also note that, following the issuance of this recommendation, you worked with Cirrus to further evaluate the accidents discussed in our report and the updated FHA and determined that no design changes are needed.

We are aware, however, that Cirrus has included procedures in the SR22T Pilot Operating Handbook to mitigate the risk of an engine failure and, in the SR22T Aircraft Maintenance Manual (AMM), to mitigate errors related to fuel flow adjustment. In addition, we note that, during your investigation of the maximum fuel flow values, you discovered a discrepancy between the Cirrus AMM and the Continental Maintenance Manual, and that Continental was working to resolve this discrepancy by updating its maintenance manual to reference the Cirrus AMM.

During a February 8, 2024, meeting between Cirrus and National Transportation Safety Board staff, we learned that Continental completed these updates in 2023.

We believe your review of Cirrus’s updated FHA for the fuel and power plant systems installed on Cirrus SR20/22/22T series airplanes, and the supplemental SSA for the SR22T model airplane’s electric auxiliary fuel pump, satisfy the intent of Safety Recommendation A-22-6, which is classified CLOSED-- ACCEPTABLE ACTION.

-From Kathryn Thomson, Deputy Administrator: On September 30, 2022, Cirrus Aircraft provided the Federal Aviation Administration (FAA) an updated FHA for the fuel and power plant systems installed on Cirrus SR20/22/22T series airplanes. The FHA revision added the failure condition–excessively rich mixture delivered to the engine–in both the cruise and critical stages of flight. Cirrus determined the safety hazard classification to be hazardous/extremely remote during the airplane’s takeoff, ascent to cruise altitude, landing, and/or aborted landing go-around, which corresponds with the loss of engine power and failure condition in the same operating phases.

On November 3, 2022, Cirrus provided a supplemental systems safety assessment (SSA) for the SR22T airplane’s electric auxiliary fuel pump, which provided a detailed analysis of the airplane’s fuel control system, and primarily focused on the failures of the fuel system that cause uncommanded activation of the electric auxiliary fuel pump. Their analysis determined that the probability of failures causing the FHA failure condition would satisfy the top event probability requirements assigned to these conditions based on their safety hazard classifications.

Cirrus also reviewed the available data from the accident aircraft and for conditions where an excessively rich mixture can be associated with the loss of power. They believe that the SSA is consistent with the failure effects observed in the accident records. They also noted that operator error and improper maintenance actions were not part of the analysis per the guidance in Advisory Circular 23.1309-1E, System Safety Analysis and Assessment for Part 23 Airplanes. The FAA reviewed the FHA and SSA and provided its concurrence to Cirrus on January 18, 2023.

The FAA also worked extensively with Cirrus on determining the probable cause of excessive fuel flow events on the SR22T airplane. Cirrus provided an analysis of each event and determined that the probable root cause was improper maintenance actions and/or pilot error. The latest service bulletins (SB) released by Cirrus, SB2X-42-22R3, Perspective+ S/W Update v2647.N8, published on November 9, 2021, and SB2X-42-19, Perspective S/W Update v0764.38, published on May 18, 2021, were designed to mitigate both issues by preventing inadvertent selection of the boost pump with a software lockout, along with added visual cues and warnings for the pilot in the event of excessive fuel flow.

We note that, before you can begin the work described in this recommendation, Cirrus Aircraft must complete the FHA described in Safety Recommendation A-22-7. On July 8, 2022, Cirrus Aircraft informed us of plans to develop a new FHA in response to Safety Recommendation A-22-7. Pending your review of Cirrus Aircraft’s FHA and completion of the recommended actions, Safety Recommendation A-22-6 is classified OPEN-- ACCEPTABLE RESPONSE.

-From Billy Nolen, Acting Administrator: The Federal Aviation Administration (FAA) received Safety Recommendation A-22-6 and is developing an action plan to address this recommendation upon receipt of the FHA identified in Safety Recommendation A-22-7, which is assigned to Cirrus Aircraft.

I will keep the Board informed of the FAA’s progress on Safety Recommendation A-22-6, and anticipate providing an update by July 31, 2023.

The attached letter from the NTSB Chair provides information about the NTSB’s April 12, 2022, report Loss of Engine Power due to Excessive Fuel Flow in Cirrus SR22T Aircraft, NTSB/AIR-22-04.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-22-6).

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) April 12, 2022, report, NTSB/AIR-22-04. The details of the referenced accident investigations 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 these investigations, we identified the following safety issues:

• The lack of a functional hazard assessment for the Cirrus SR22T to identify all potential causes of excessive fuel flow during takeoff and climb that would result in a loss of engine power. • The need for additional mitigation actions to prevent the loss of engine power due to excessive fuel flow during takeoff and climb.

Accordingly, the NTSB makes the following safety recommendation to the FAA:

• Review the functional hazard assessment (FHA) recommended in Safety Recommendation A-22-7 and ensure it meets the objectives of Advisory Circular 23.1309-1E. Upon approval of the FHA, work with Cirrus to identify necessary mitigating actions and require their implementation through the appropriate means, such as an airworthiness directive. (A 22-6)