U.S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Flight Hazard Analysis Date: 08/05/2021 Initiated By: AST-1 AC No: 450.109-1
This Advisory Circular (AC) provides guidance for conducting a flight hazard analysis to identify and control public safety hazards and risks associated with flight, and phases of flight, for a launch or reentry vehicle (hereafter referred to as system) in accordance with § 450.109 of Title 14 of the Code of Federal Regulations (14 CFR). Section 450.109 requires an operator using a flight hazard analysis as a hazard control strategy for one or more phases of flight to identify, describe, and analyze all reasonably foreseeable hazards to public safety resulting from the flight of a launch or reentry vehicle. In accordance with § 450.109(b)(3) through (5), operators must mitigate hazards, as appropriate, and validate and verify the hazard mitigations.
The FAA considers this AC an accepted means of compliance for satisfying the regulatory requirements of § 450.109 It presents one, but not the only, acceptable means of compliance with the associated regulatory requirements. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way. The document is intended only to provide clarity to the public regarding existing requirements under the law or agency policies.
If you have suggestions for improving this AC, you may use the Advisory Circular Feedback form at the end of this AC.
Contents Paragraph Page ii
1 Purpose4
2 Applicability4
3 Applicable Regulations and Related Documents5
4 Definition of Terms6
5 Acronyms6
6 Overview7
6.1 Objective of Flight Hazard Analysis7
6.2 A Flight Hazard Analysis differs from Flight Safety Analysis7
6.3 Flight Hazard Analysis Methodology7
6.4 Aspects of a Flight Hazard Analysis7
6.5 Formal Traceability of System Safety Hazards8
6.6 System Safety Hazards and Software Safety8
7 Performing a Flight Hazard Analysis9
7.1 Identify Hazards9
7.1.1 Hazard Traceability9
7.1.2 Data from the Functional Hazard Analysis9
7.1.3 Data beyond the Functional Hazard Analysis9
7.2 Assessing Likelihood and Severity of Each Hazard10
7.2.1 Resources for System Safety Risk Assessments10
7.2.2 Utilizing a Systematic Assessment Process10
7.2.3 Risk Assessment Traceability10
7.3 Mitigate Risk to Acceptable Levels11
7.3.1 Proper Risk Mitigation Process11
7.3.2 Developing Risk Acceptance Criteria11
7.3.3 Baseline of Risk Acceptability11
7.4 Identifying and Describing Risk Mitigation Measures12
7.4.1 Risk Mitigation Traceability12
7.4.2 System Safety Design Order of Precedence12
7.4.3 Potential Risk Mitigation Methods12
7.5 Validation and Verification14
Contents (continued) Paragraph Page iii
7.5.1 Validation of Risk Mitigations and Verification Methods14
7.5.2 Verifying Risk Mitigations14
7.5.3 Iterative Approach of Validation and Verification15
7.6 Identifying New Hazards and Updating the Flight Hazard Analysis16
7.6.1 Updates from Lifecycle Data16
7.6.2 Accuracy via the System Safety Program16
7.6.3 Completeness Prior to Flight16
7.7 Application Requirements16
Appendix A. System Safety Template for § 450.109 Flight Hazard AnalysisA-1
4 1 PURPOSE.
1.1 This advisory circular (AC) provides guidance for an operator to apply a systematic and logical hazard analysis to identify, analyze, and control public safety hazards and risks associated with flight, and phases of flight, for a launch or reentry vehicle (hereafter referred to as system) in accordance with § 450.109.
1.2 Scope.
Section 450.109(b) requires a flight hazard analysis to identify, describe, and analyze reasonably foreseeable hazards to public safety resulting from the flight of a launch or reentry vehicle. The flight hazard analysis must identify all reasonably foreseeable hazards associated with the launch or reentry system relevant to public safety, in accordance with § 450.109(b)(1); assess each hazard’s likelihood and severity, in accordance with § 450.109(b)(2); and document the risk mitigation, with associated verifications, of each one, in accordance with § 450.109(b)(5). Section 450.107(c) states that an operator must conduct a flight hazard analysis, in accordance with § 450.109 for the flight, or phase of flight, of a launch or reentry vehicle if the public safety hazards cannot be mitigated adequately to meet the public risk criteria of § 450.101(a), (b), and
(c) using physical containment, wind weighting, or flight abort.
1.3 Level of Imperatives.
This AC presents one, but not the only, acceptable means of compliance with the associated regulatory requirements. The FAA will consider other means of compliance that an applicant may elect to present. In addition, an operator may tailor the provisions of this AC to meet its unique needs, provided the changes are accepted as a means of compliance by FAA. Throughout this document, the word “must” characterizes statements that directly follow from regulatory text and therefore reflect regulatory mandates. The word “should” describes a requirement if electing to use this means of compliance; variation from these requirements is possible, but must be justified and accepted by the FAA as an alternative means of compliance. The word “may” describes variations or alternatives allowed within the accepted means of compliance set forth in this AC. In general, these alternative approaches can be used only under certain situations that do not compromise safety.
2 APPLICABILITY.
2.1 The guidance in this AC is for launch and reentry vehicle applicants and operators required to comply with 14 CFR part 450. The guidance in this AC is for those seeking a launch or reentry vehicle operator license, and a licensed operator seeking to renew or modify an existing vehicle operator license.
2.2 The material in this AC is advisory in nature and does not constitute a regulation. This guidance is not legally binding in its own right and will not be relied upon by the FAA as a separate basis for affirmative enforcement action or other administrative penalty.
Conformity with this guidance document (as distinct from existing statutes and
5 regulations) is voluntary only, and nonconformity will not affect rights and obligations under existing statutes and regulations. It describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. The FAA will consider other means of compliance that an applicant may elect to present.
2.3 The material in this AC does not change or create any additional regulatory requirements, nor does it authorize changes to, or deviations from, existing regulatory requirements.
3 APPLICABLE REGULATIONS AND RELATED DOCUMENTS.
3.1 Related U.S.C. Statute.
51 U.S.C. Subtitle V, Chapter 509.
3.2 Related FAA Commercial Space Transportation Regulations.
The following 14 CFR regulations must be accounted for when showing compliance with 14 CFR 450.109 Flight Hazard Analysis. The full text of these regulations can be downloaded from the U.S. Government Printing Office e-CFR. A paper copy can be ordered from the Government Printing Office, Superintendent of Documents, Attn: New Orders, PO Box 371954, Pittsburgh, PA, 15250-7954.
Section 450.101, Safety criteria.
Section 450.103, System safety program.
Section 450.107, Hazard control strategies.
Section 450.141, Computing Systems.
3.3 Related FAA Advisory Circulars.
FAA Advisory Circulars are available through the FAA website, http://www.faa.gov.
AC 450.103-1, System Safety Program, when published.
AC 450.107-1, Hazard Control Strategy Determination, dated June 15, 2021.
AC 450.141-1, Computing Systems Safety, dated October 15, 2020.
3.4 Related Industry Documents.
MIL-STD-882E, Department of Defense Standard Practice, System Safety, dated May 11, 2012, https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36027.
Note: The industry documents referenced in this section refer to the current revisions or regulatory authorities’ accepted revisions.
6 4 DEFINITION OF TERMS.
For this AC, the terms and definitions from § 401.7 apply.
5 ACRONYMS.
AC – Advisory Circular CFR – Code of Federal Regulations ESD – Electro-Static Discharge FAA – Federal Aviation Administration FOD – Foreign Object Debris FHA – Flight Hazard Analysis FMEA – Failure Modes and Effects Analysis FSS – Flight Safety System FTA – Fault Tree Analysis NOTMARs – Notices to Mariners OMB – Office of Management and Budget TBD – To Be Determined V&V – Validation and Verification
7 6 OVERVIEW.
6.1 Objective of Flight Hazard Analysis.
A flight hazard analysis identifies key system design and operation data, documents the overall system safety risk to the public, and determines the necessary hazard controls (mitigations) to ensure the residual risk meets acceptable criteria. System safety risk documented in the flight hazard analysis is typically expressed in qualitative terminology; however, there may be sufficient operational history and subsystem analysis to express risk in quantitative terms.
6.2 A Flight Hazard Analysis differs from Flight Safety Analysis.
6.2.1 Risk as stated in the flight hazard analysis is different than as stated in the flight safety analysis requirements of § 450.113. Flight hazard analysis and flight safety analysis are somewhat interrelated but intentionally independent analyses that are both integral to the overall hazard control strategy. It is important to note that compliance with § 450.101 risk criteria does not relieve the operator from completing the flight hazard analysis.
6.2.2 A flight hazard analysis will identify all reasonably foreseeable hazards to public safety from the operation. Most of those hazards can be eliminated or mitigated with validation and verification. But there will always be residual risk from the operation. A flight hazard analysis must ensure that the likelihood of any hazardous condition that may cause death or serious injury to the public is extremely remote in accordance with § 450.109(b)(3).
6.2.3 The objective of the flight safety analysis is to characterize the overall risk to the public caused by the operation as a whole in consistent quantitative terms. A flight safety analysis is used to derive necessary operational controls and demonstrate compliance with public safety criteria in accordance with § 450.101.
6.3 Flight Hazard Analysis Methodology.
The flight hazard analysis methodology must be defined per § 450.103(b)(1). Per the guidance of AC 450.103-1, System Safety Program, this should be accomplished by the documented system safety program. Application of mitigation measures identified by the flight hazard analysis are intended to help reduce the system safety risk to the public to the acceptable levels determined by the system safety program and in accordance with § 450.109(b)(3). Additionally, the data documented in the flight hazard analysis is utilized to ensure public safety as defined by the documented system safety program.
6.4 Aspects of a Flight Hazard Analysis.
Flight hazard analysis may be utilized as a hazard control strategy but is also mandated by § 450.107(c) for a flight, or phase of flight, if the public safety hazards cannot be mitigated adequately to meet the public risk criteria of § 450.101(a), (b), and (c) using physical containment, wind weighting, or flight abort. This use of a flight hazard analysis to derive hazard controls provides flexibility that does not currently exist under the prescriptive requirements of Part 417 but is broadly consistent with Part 431 and
8 Part 435. In accordance with § 450.109(b), a flight hazard analysis must identify, describe, and analyze all reasonably foreseeable hazards to public safety resulting from the flight of a launch or reentry vehicle. The flight hazard analysis should be performed early in system development and operation conceptualization to define the system safety risk to the public in order to positively influence design and operation decisions.
Flight hazard analysis products must be submitted to the FAA as part of an application, per § 450.109(f)(1) and continued to be maintained throughout the lifecycle of the launch or reentry system, in accordance with § 450.109(c) through (e). A flight hazard analysis must:
1. Identify all reasonably foreseeable hazards, and the corresponding failure mode for each hazard, associated with the launch or reentry system relevant to public safety (§ 450.109(b)(1));
2. Assess the likelihood and severity of each system safety hazard to the public (§ 450.109(b)(3);
3. Ensure that the system safety risk associated with each system safety hazard to the public meets defined acceptance criteria (§ 450.109(b)(3));
4. Identify and describe the risk elimination and mitigation measures required to satisfy the acceptance criteria (§ 450.109(b)(4)); and
5. Document that the risk elimination and mitigation measures achieve the acceptable levels through validation and verification (§ 450.109(b)(5)).
6.5 Formal Traceability of System Safety Hazards.
Formal tracking methods should be established to show direct connections between all aspects of system safety hazards to the public. Hazard tracking systems may contain all the necessary data but do not typically show these direct connections. Table A-1 shows the types of information that an applicant should provide to demonstrate traceability.
6.6 System Safety Hazards and Software Safety.
6.6.1 In accordance with § 450.141(a), if the flight hazard analysis identifies software or data utilized in a subsystem or the integrated system as potential hazard sources or hazard controls, then the applicant should perform a software hazard analysis to identify computing system safety items and assess their level of criticality.
6.6.2 Per the guidance of AC 450.141-1, software hazard analyses identify potential software faults and their effects on the computing system and the system as a whole, as well as mitigation measures that can be used to reduce the risk. The analytical method and level of detail in the analysis should correspond to the complexity of the software and computing system, intricacy of the operations, and scope of the program. Also, software hazard analyses should consider a range of potential error conditions.
9 7 PERFORMING A FLIGHT HAZARD ANALYSIS.
7.1 Identify Hazards.
The hazards referred to in a flight hazard analysis are the system safety hazards to the public that occur from a system failure. The starting point for identifying system safety hazards to the public is the functional hazard analysis as required by § 450.107(b) that decomposes the system functions and assesses the end effect of their possible failures on system operation. In accordance with § 450.109(b)(1), a flight hazard analysis must identify all reasonably foreseeable hazards associated with a launch or reentry system relevant to public safety.
7.1.1 Hazard Traceability.
Traceability ensures proper identification of system safety hazards to the public for § 450.109(b)(1) and should be demonstrated from:
1. Subsystem and component functional failures to their causes; and
2. Subsystem and component functional failures to respective system safety hazards to the public at the system and mission level.
7.1.2 Data from the Functional Hazard Analysis.
System failures leading to system safety hazards to the public should include all applicable failures identified in the functional hazard analysis. Other possible failures not in the functional hazard analysis should be included if new ones are uncovered when considering public safety. To ensure proper identification of system safety hazards to the public for § 450.109(b)(1), an operator should use decomposition of systems beyond what is in the functional hazard analysis to identify the causes of system failures. This identification is an essential precursor to applying mitigations that reduce or eliminate the system safety hazards to the public. There will likely be multiple potential causes for each system failure. To ensure proper identification and mitigation of system safety hazards to the public for § 450.109(b)(1) and (4), each potential cause of a failure should be specified to a level of detail (down to a subsystem or component level) in accordance with § 450.109(b)(1)(ii) where it is possible to apply a mitigation.
7.1.3 Data beyond the Functional Hazard Analysis.
Beyond the functional hazard analysis, supplemental data routinely utilized to identify system failures and their causes include:
Fault Tree Analysis (FTA) – A reliability engineering analysis that uses a logic diagram to identify and map causes of top-level events. Additionally, a FTA allows for quantification of system failure probability, determination of fault tolerance, identification of common causes and single point failures, etc.
Failure Modes and Effects Analysis (FMEA) – A reliability engineering analysis used to identify low-level component failures and their causes and assess their effects on higher-level systems.
7.2 Assessing Likelihood and Severity of Each Hazard.
The likelihood and severity of each system safety hazard to the public must be assessed, in accordance with § 450.109(b)(2), in order to determine the associated system safety risk. The characterization of each system safety risk allows for determining the necessity, and proper application, of any additional mitigation actions.
7.2.1 Resources for System Safety Risk Assessments.
To satisfy § 450.109(b)(2), suitable assessment severity categories and likelihood levels criteria should be determined for each specific program. The risk assessment with respect to system safety hazards to the public generally utilizes qualitative statements;
however, there may be sufficient data to utilize quantitative terms. AC 450.103-1, System Safety Program, provides guidance on assessing and documenting system safety risk, including severity categories and likelihood levels.
7.2.2 Utilizing a Systematic Assessment Process.
7.2.2.1 The FAA encourages, but does not require, the utilization of a systematic development process that allows for a baseline assessment of premitigation risk for each hazard. It is a common system safety practice to assess risk prior to implementing a mitigation in order to deliberately design a mitigation strategy for each hazard. The FAA recognizes that some applicants will not utilize a pre-mitigation risk assessment as is common in rapid development and experimental programs. The FAA recommends that applicants who choose not to utilize a pre-mitigation risk assessment strategy discuss the appropriateness of their development process and any risk assessment assumptions during pre-application consultation. This strategy may not be acceptable with all programs.
Irrespective of the applicant’s development process, post-mitigation risk assessment should be performed to determine the residual system safety risk to the public.
7.2.2.2 Additionally, to ensure proper mitigation of system safety hazards to the public for § 450.109(b)(4), risk assessment should be performed at the appropriate levels, primarily the: (1) subsystem and component level and
(2) system and mission level. Risk assessment at these levels allows for greater insight into the effectiveness of mitigations and verifications specific to each cause of each functional failure resulting in a system safety hazard to the public and appropriate application of component, subsystem, system and mission mitigations and verifications.
7.2.3 Risk Assessment Traceability.
Traceability ensures proper assessment for § 450.109(b)(3) and should be demonstrated from subsystem and component level risk assessment to system and mission level risk assessment.
7.3 Mitigate Risk to Acceptable Levels.
Risk elimination or mitigation measures must be implemented to reduce risks to the acceptable level of § 450.109(b)(3).
7.3.1 Proper Risk Mitigation Process.
Mitigating risk does not change severity of the hazard, only the likelihood. If there is a change in severity, it should be documented as a new risk. For example, a main fuel valve mechanical failure may cause unterminated thrust and a departure of the vehicle from the operating area. The hazard risk was determined to have a consequence of “Catastrophic” and a likelihood of “Remote.” That valve was replaced with a more reliable valve as a mitigation. The mitigation is determined to change the likelihood to “Extremely Remote,” but the new valve cannot impact the consequence of the failure, which remains “Catastrophic.”
7.3.2 Developing Risk Acceptance Criteria.
Risk acceptance is determined by comparison of final assessed system safety risk against established acceptance criteria. Suitable risk acceptance criteria must be determined for each specific program and documented in the system safety program compliant with § 450.103 and utilizing the guidance of AC 450.103-1, System Safety Program. To ensure proper acceptance of risks associated with system safety hazards to the public for § 450.109(b)(3), the associated residual risk should meet the established acceptance criteria and the rationale for acceptance should be documented.
7.3.3 Baseline of Risk Acceptability.
In accordance with § 450.109(b)(3), the baseline standard for risk acceptability of system safety hazards to the public is to ensure the likelihood of any hazardous condition that may cause death or serious injury to the public is extremely remote as defined in AC 450.103-1.
As documented in AC 450.103-1, System Safety Program, extremely remote should be considered “so unlikely, it can be assumed occurrence may not be experienced, with a likelihood of occurrence less than 10-6 in any one mission.”
Note: The standards for risk acceptability are intentionally strict to ensure protection of the public. Sufficient mitigation to control the hazard should be demonstrated.
7.4 Identifying and Describing Risk Mitigation Measures.
Risk elimination and mitigation measures must be identified and described for system safety risks to the public that are initially deemed unacceptable in accordance with § 450.109(b)(4). In accordance with § 450.109(b)(5), the risk elimination and mitigation measures must document reduction to the acceptable qualitative level of § 450.109(b)(3). Consideration should be given as to whether proposed risk mitigation measures introduce new hazards. To allow flexibility, the FAA has not mandated any particular mitigation approach. Selection of a risk elimination or mitigation measure is usually based on a number of factors, such as the type of operation, feasibility of implementation, effectiveness, and impact on system performance. Where possible, the FAA expects the utilization of existing industry standards for mitigations.
7.4.1 Risk Mitigation Traceability.
Traceability ensures proper application of mitigations for § 450.109(b)(4) and should be demonstrated from:
1. Subsystem and component functional failures to their causes to respective mitigations;
2. Subsystem and component functional failures to respective system safety hazards to the public at the system and mission level;
3. Subsystem and component level risk assessment to system and mission level risk assessment; and
4. System safety hazards to the public at the system and mission level to their respective mitigations.
7.4.2 System Safety Design Order of Precedence.
MIL-STD-882E identifies the following mitigation approaches in order of decreasing effectiveness:
a. Eliminate hazards through design selection;
b. Reduce risk through design alteration;
c. Incorporate engineered features or devices;
d. Provide warning devices; and
e. Incorporate signage, procedures, training, and personal protective equipment (PPE).
7.4.3 Potential Risk Mitigation Methods.
7.4.3.1 Design or Operate for Minimum Risk.
The first priority should be to eliminate system safety hazards to the public through appropriate design selections or operational decisions.
Unacceptable system safety risk to the public that cannot be eliminated must be reduced to acceptable levels. An example of designing out risk to the public would be eliminating the use of toxic substances.