Safety Recommendation A-22-007

You previously informed us that you had updated the FHA for the fuel and power plant systems installed on Cirrus SR20/22/22T series airplanes and developed a supplemental SSA of electric auxiliary fuel pump functions for SR22T model airplanes, and that the Federal Aviation Administration had concurred with these documents. You also informed us that, following the issuance of this recommendation, Cirrus had performed flight tests to further evaluate the accidents that are discussed in our report and determined that no design changes are needed.

Although we considered these actions responsive to this recommendation, we had requested additional information about the flight tests that Cirrus conducted.

We have reviewed your white paper, and, on February 8, 2024, our staff met to discuss its contents. We believe the white paper includes information that supports Cirrus’s claim that selecting HIGH BOOST/PRIME will not cause a loss of combustion if the aircraft fuel system is compliant with the SR22T Aircraft Maintenance Manual (AMM). In addition, we note that the white paper references procedures that have been included in the SR22T Pilot Operating Handbook (POH) to mitigate the risk of an engine failure and, in the SR22T AMM, to mitigate errors related to fuel flow adjustment. We believe the information that you provided is responsive to our request.

We also believe the updated FHA for the fuel and power plant systems installed on Cirrus SR20/22/22T series airplanes, the supplemental SSA for the SR22T model airplane’s electric auxiliary fuel pump, and the procedures that have been included in the SR22T POH and AMM satisfy the intent of Safety Recommendation A-22-7, which is classified CLOSED-- ACCEPTABLE ACTION.

Thank you for your help to improve aviation safety.

-From Pat Waddick, President, Cirrus Aircraft: Cirrus Design Corporation sincerely appreciates the NTSB' s continuing leadership in promoting general aviation safety. We are very proud of our industry-leading safety performance and are dedicated to continuous improvement in safety. Our corporate code of ethics is that "safety is our highest priority," and we routinely implement unique safety features into our aircraft that exceed FAA certification requirements.

This recommendation is the first (and only) NTSB recommendation received by Cirrus since our first aircraft, the SR20, was certified in 1999. We have now produced more than 9,900 aircraft in a variety of models, with an estimated total flight time exceeding 15 million hours. We continue to innovate to maintain our position at the leading edge of aviation safety technology, and recently opened a dedicated Cirrus Aircraft Innovation Center to accelerate these efforts.

In our letter of January 19, 2023, Cirrus provided our completed response to A-22-07, along with the FAA Chicago Aircraft Certification Office (ACO) approval of the requested Failure Hazard Assessment (FHA) and corresponding supplemental System Safety Assessment (SSA). Cirrus has also included this SSA as part of any potential future versions of the SR22T. This submission is in response to the NTSB' s questions from our April 11,2023 meeting with your staff, and in response to your letter of June 30, 2023. Our supplemental SSA will only apply to the SR22T model, as it addresses issues unique to the turbo-charged engine on that model.

It is our desire to exceed NTSB expectations with our response to recommendation NTSB/AIR-22-04. As a consequence, Cirrus planned and accomplished an Engineering Flight Test program during 2022 validating the original SR22T certification test program data from 2009. This flight test program expanded those requirements to specifically focus on the Continental Aerospace Technology (CAT) IO-550K turbocharged-engine response to high levels of fuel flow, and the engine's response to the HIGH BOOST function of the electric fuel pump. That Flight Test Report is attached to this submission.

The new Flight Test Report provides considerable additional information that was not available to your NTSB investigators during the period (2017-2019) of the six cited incident investigations. There are now more than 2,300 SR22T aircraft in service, with an estimated total of approximately 1.8 million hours of SR22T flight time.

We note that you have developed a supplemental SSA, including an FHA, of electric auxiliary fuel pump functions for Cirrus SR22T aircraft and, on January 18, 2023, this document was approved by the Federal Aviation Administration (FAA). We also note that, following the issuance of this recommendation, Cirrus performed flight tests to further evaluate the accidents discussed in our report and determined that no design changes are needed.

On April 11, 2023, our staff met to discuss your evaluation of these accidents, the hazards that were identified, and the updated FHA and supplemental SSA. Your staff informed us that Cirrus is developing a white paper that will include flight test data to support your claim that selecting HIGH BOOST/PRIME will not cause a loss of combustion if the aircraft fuel system is compliant with the SR22T Airplane Maintenance Manual.

We look forward to reviewing the white paper once it is available. We also request additional details about the flight tests that Cirrus conducted, including flight test plan procedures and results, number of aircraft, aircraft model, type of avionics, fuel flow rates that were tested, crew alerting and expected pilot response times related to loss of engine power, and at what altitudes fuel flow rates were tested.

We note that the FHA provides evidence of mitigations for the new hazards that are identified in the SSA; however, you did not state what those mitigations are. We would like to know what mitigations have been identified for each hazard. We would also like to know which aircraft (model and type) will use the updated SSA.

Pending our receipt and review of this additional information, Safety Recommendation A-22-7 remains classified OPEN-- ACCEPTABLE RESPONSE.

-From Pat Waddick, President, Cirrus Aircraft: • Cirrus has completed the FHA and SSA in response to A-22-07 and notes that the design of the SR-22T aircraft as originally certified meets or exceeds all requirements of the SR22T Type Ce1iificate without any necessary changes. The updated FHA and Supplement SSA is attached (document EOOOO 4489).

• During the FHA and SSA process, Cirrus worked closely with the FAA's Chicago Aircraft Ce1iification Office (ACO) in compliance with recommendation A-22-06 issued to the FAA. The FAA ACO's approval of the Cirrus Supplemental SSA is attached.

• Through their approval of the SSA, the FAA has approved Cirrus work under AIR-22-07. We note that no mitigations or changes were required.

Cirrus examined the operation and interaction of the fuel, turbocharging, and induction systems of the TSIO-550-K engine to identify if other potential factors could contribute to changes in the air/fuel mixture. As noted in the FHA (SSA pg 16) "Flight testing performed on multiple aircraft representative of the type design has indicated robust engine performance even when the aircraft fi1el system is delivering high fuel flow rates. Intentionally-produced high fuel flow rates (in excess of those stated in the Airplane Maintenance Manual) were demonstrated to support continued combustion and engine operation under the test conditions."

As a result of this NTSB safety recommendation, we performed an additional, very detailed evaluation of all available data for the incidents cited in AIR-22-04. We did not identify any information requiring any design changes. We did identify a number of areas where appropriate intervention by the incident pilots would have mitigated the event. We would like to highlight the requirement for the aircraft to be maintained in accordance with approved procedures, for pilots to operate their aircraft in accordance with the Pilot's Operating Handbook (POH), and to intervene appropriately when immediate pilot action is required.

The Supplement SSA conclusion (SSA pg 27) is that "The quantitative analysis provided in Section 4.4 demonstrates that the probability of failures causing FHA #2800.01 and 2800.02 'Excessively rich mixture delivered to engine' would satisfy the top event probability requirements assigned to these conditions based on their hazard classifications." This FHA and Supplement SSA have reinforced the validity of the SR22T's design as originally certified.

-From Chris Glaeser, Director, Air Safety, Cirrus Aircraft: October 31, 2022, update: There was considerable engineering analysis required to appropriately address the FHA and SSA for this issue, and that work has been completed very recently. That Cirrus engineering analysis is undergoing final internal review and approval, and we anticipate that it will be forwarded to the FAA ACO within 2-3 weeks. We are working closely with the FAA Chicago’s ACO office in addressing these NTSB recommendations, and the FAA is also highly motivated in addressing recommendation A-22-6. We will continue to work with the FAA to ensure the FHA and SSA from recommendation A-22-7 is approved.

Once that FAA approval has been received, and any additional actions from A-22-6 have been identified, we will submit our formal response on A-22-7. November 7, 2022, update: Cirrus delivered the FHA and SSA discussed in A-22-7 was delivered to the FAA ACO on Thursday, Nov 3rd. This would also indicate their work relative to recommendation A-22-6 (approval of the FHA/SSA) has begun. I’ll keep you posted on progress and we will submit a formal closure to A-22-7 when approved by the FAA.

We note that you are working with the Federal Aviation Administration to develop a new FHA. We also note that you have concerns with some of the factual information in our aviation investigation report.

We are in the process of setting up a meeting to discuss your concerns. In the meantime, we believe your plan to develop a new FHA for the SR22T is responsive to this recommendation. Pending our review of the completed FHA and updated system safety assessment, Safety Recommendation A-22-7 is classified OPEN-- ACCEPTABLE RESPONSE.

-From Brandon Pavlish, Vice President: We have received your letter dated April 12, 2022 (AIR-22-04) with safety recommendations A-22-6 (FAA) and A-22-7 (Cirrus). While we are continuing to research the issues associated with the events highlighted by the NTSB and coordinating with the FAA in the process, we believe that it is important to highlight several facts and factual errors identified in AIR-22-04.

• From the time of the certification of the SR22T in 2010 until 2017, there were no incidents involving higher than expected fuel flow to our knowledge, indicating that the design and certification of the SR22T met all Part 23 requirements and that the design is sound; • In certification testing and in subsequent post-2017 testing, Cirrus has demonstrated that the application of HIGH BOOST/PRIME will not cause a loss of combustion in an aircraft with fuel system in compliance with the SR22T Aircraft Maintenance Manual (AMM). Accordingly, Cirrus disagrees that the selection of HIGH BOOST/PRIME was the cause of any accident;

• The incidents identified in AIR-22-04 demonstrate significantly different and varied engine parameters and settings, and it is not clear that they all are related events. We believe it is likely more accurate to characterize them as high air/fuel mixture events than high fuel flow events.

Cirrus Aircraft is dedicated to delivering an aviation experience that is the pinnacle of innovation, quality, and safety to our customers, and we routinely upgrade the design of our aircraft to integrate safety and operational improvements that exceed regulatory requirements. Safety commitment and safety innovation has been a critical part of our company mission since day one. We have worked closely with our FAA Aircraft Certification Office throughout the design and certification process of the SR22T, and in supporting continuing airworthiness of this aircraft thereafter.

We note that none of the accidents cited by the NTSB identified any specific compliance issues with the original aircraft certification, nor has the NTSB identified any specific aircraft design issues.

Cirrus is actively engaged in examining the operation and interaction of the fuel, turbocharging, and induction systems of the TSIO-550-K engine to identify if other potential factors could contribute to changes in the air/fuel mixture. We will report to the FAA and the NTSB any findings and evidence in this regard, which was not considered in the NTSB investigations of any of the identified accidents and incidents.

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 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 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-22-7). 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.