1. Safety Assessments & Certification
SAREL Consult GmbH offers system safety analyses throughout the entire development process for various industries. Our services cover the complete safety process according to SAE ARP4761 CS 25.1306 AMC.

Functional Hazard Assessment (FHA)
The Functional Hazard Assessment (FHA) is the starting point of the safety process. The aim of the FHA is to assess the repercussions of malfunctions and functional failures on the safety of the aircraft and its occupants; this contains the definition of safety requirements and failure conditions according to FAR/CS 25.1309. The depth of analysis of the following system safety assessments according to 25.1306 AMC is based on the results of the FHA.

Preliminary System Safety Assessment (PSSA)
Within the scope of the PSSA alternative design concepts are assessed and different system architectures are compared from a safety perspective. The system architecture and the degree of redundancy are determined by the safety requirements. The PSSA defines the system architecture so that compliance with the failure condition can be efficiently demonstrated.

System Safety Assessment (SSA)
The System Safety assessment (SSA) is the continuation of the PSSA. Qualitative and quantitative safety assessments are performed for all significant failure conditions, which were identified in the FHA, to demonstrate compliance according to FAR/CS 25.1309. The quantitative safety assessment is based on fault trees analysis or reliability block diagrams and it is an essential certification document.

Common Cause Analysis (CCA)
The results of the safety assessment are based on the assumption that failures of redundant components are independent events. This assumption has to be verified within the scope of the Common Cause Analysis (CCA). According to AMC 25.1309 it has to be demonstrated that a single event will not result in the loss of multiple redundant components causing catastrophic effects. The Common Mode Analysis (CMA) shall mitigate risk of common cause failure due to environmental factors, development errors and specification errors to ensure that redundant components are independent. Within the scope of Particular Risk Analysis common cause hazards due to external events are considered, e.g.: uncontained engine rotor failure, wheel & tire failure, lightning, bird strike, and appropriate protection means are defined. Common cause hazards that result from the interference of system components located closed to each other are considered within the scope of the Zonal Safety Analysis.

Failure Mode Effect Analysis (FMEA)
The Failure Mode and Effect Analysis (FMEA) identifies potential failure causes on piece part level and their consequences on component and system level. The summary of the FMEA, the Failure Mode and Effect Summary (FMES) provides essential input data for further safety and reliability analyses.

Intrinsic Hazard Analysis (IHA)
The Intrinsic Hazard Analysis (IHA) considers hazards coming from inside the equipment associated with the technology used for the item of equipment. The consequences in the event of failure are assessed and appropriate mitigations means are defined. The IHA is based on application of a generic check list of intrinsic hazard types.

Aeronautical Certification Support
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Special Methods

Assessment of Degraded System Configurations
Loss of single components in redundant system architectures generally does not lead to total loss of function, but results in a degraded system performance. On component level the contribution to total system performance can be quantified. SAREL Consult GmbH has developed methods that allows for calculating the occurrence probability of degraded system configurations. The analysis is performed with the Software ToolSyRelAn based on the Reliability Block Diagram for “total loss of function” with the definition of the performance contribution of certain components. SyRelAn compiles the performance distribution function of large systems within seconds.

Importance Analyses
An analysis of potential weak spots through importance analyses identifies how components contribute to system reliability and system safety. This allows efficient optimization of complete systems. The software tool SyRelAn contains five importance measures; marginal importance, reduced structural importance, competitive importance, diagnostic importance and minimal cut set importance. Reduced-structural importance is a proprietary development, which allows assessing contribution of components to the system reliability based on the architecture. This method enables analyzing weak spots in the system during the concept phase when component failure rates are not available.

Structural Reliability Methods
The resistance of the material and the applied load are considered as stochastic variables described by probability distributions to allow calculation of the failure probability. The rupture of mechanical components and the integrity are now quantifiable, based on operating parameters and the associated safety margins.

2. Functional Safety - Safety Case

Hazard Analysis and Risk Assessment
Identification of possible risks in case of malfunction of the systems according to applicable standards (ISO26262, EIC61508) and definition of Safety Integrity Level (SIL) or Automotive Safety Integrity Level (ASIL), respectively.

Design Concept Analysis
An assessment of new design solutions from a safety and reliability point of view is essential, particularly in the early design phase. The market success and customer acceptance of technical innovations requires a detailed safety and reliability assessment. We carry out design concept analyses under safety, reliability and economic aspects. SAREL Consult GmbH offers innovative methods and customized software solutions, based on the software tool SyRelAn ( System Reliability Analysis). Particular emphasis is placed on economical optimization through comparison of different system architectures. We support you in the selection and the assessment of new technologies, considering the complete life cycle and various operating scenarios.

Functional Safety Concept
Using the results of the hazard analysis, the functional safety concept is elaborated further. Technical means and operational measures are defined to ensure safe operation; on this basis the system concept is established. The Safety Integrity Level (SIL) or Automotive Safety Integrity Level (ASIL), respectively, will be allocated on subsystem- and component level.

Technical Safety Concept
The functional requirements provide the basis for the evaluation of technical safety requirements for the hardware and the software. Qualitative and quantitative assessment based on Reliability Block Diagram or Fault Tree Analysis will be performed. Technical, probabilistic and interface requirements are defined as well as the test program.

Functional Safety Assessment - Safety Case
SAREL Consult GmbH compiles proof of functional safety according to the generic standard EIC 61508 or related standards for specific industries (e.g. ISO2626, ISO 25119, EN 50126 etc.). The Safety Case demonstrates that the system complies with the requirements regarding functional safety. The results of related analyses, e.g. hazard analysis, functional safety concept, technical safety concept, FMEA, FTA are summarized in the Safety Case.

Failure Mode Effect Analysis (FMEA)
The Failure Mode and Effect Analysis (FMEA) identifies potential failure causes on piece part level and their consequences on component and system level. The summary of the FMEA, the Failure Mode and Effect Summary (FMES) provides essential input data for further safety and reliability analyses.

3. Operational Reliability & Availability
System down time can result in severe economic damage. In asset intensive industries in particular, the reliability of capital assets is essential to the company’s financial success. Company’s reputation and competitiveness suffer if reliability and availability of theirs products to not meet customer expectations. SAREL Consult GmbH offers wide range of services to analyse and improve the reliability and availability of your products.

In-Service Reliability Analysis
Using field data of your products SAREL Consult GmbH estimate the reliability, failure rate, MTBF and if relevant also the Weibull parameter of the components. We develop specific strategies to improve the reliability taking various factors like stress, environment, system design, manufacturing process and quality management into account.

Reliability Prediction
Within the scope of the reliability prediction component failure rates are determined to provide the basis for further quantitative assessments on system level. The following standards mainly distributed by the Reliability Information Analysis Center (RIAC) provide the basis for the reliability prediction:

• MIL 217 Plus
  
• NPRD-2011
  
• FMD-2013
  
• MechRel Handbook of Reliability Prediction Procedures for Mechanical Equipment - NAVSEA
  
• SN 29500 (Siemens Norm)
  

Availability Assessment
We perform an assessment of the availability of your system taking system architecture, failure probabilities and inspection patterns into account. The Markov model is used for the quantitative assessment of repairable systems. We develop concepts to improve life cycle cost (LCC) and economic benefit for your customers.

4. Systems Engineering
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