Civil Aircraft Electrical Power System Safety Assessment

Issues and Practices

Peng Wang

• Publisher: Butterworth-Heinemann
• Year: 2017
• ISBN:
  9780081007327
• Topic: Technology & Engineering
• Subtopic: Aeronautic & Astronautic Engineering
• Index: Technology & Engineering

Civil Aircraft Electrical Power System Safety Assessment: Issues and Practices provides guidelines and methods for conducting a safety assessment process on civil airborne systems and equipment. As civil aircraft electrical systems become more complicated, electrical wiring failures have become a huge concern in industry and government—especially on aging platforms. There have been several accidents (most recently battery problems on the Boeing 777) with some of these having a relationship to wiring and power generation.

Featuring a case study on the continuous safety assessment process of the civil airborne electrical power system, this book addresses problems, issues and troubleshooting techniques such as single event effects (SEE), the failure effects of electrical wiring interconnection systems (EWIS), formal theories and safety analysis methods in civil aircrafts.

• Introduces how to conduct assignment of development assurance levels for the electrical power system
• Includes safety assessments of aging platforms and their respective Electrical Wiring Interconnection System (EWIS)
• Features material on failure mechanisms for wiring systems and discussion of Failure Modes and Effects Analysis (FMEA) sustainment

Chapter 1

Airworthiness Regulations and Safety Requirements

Abstract

In this chapter, we introduce the documents of airworthiness standards and requirements, as well as safety-related terminologies and definitions for transport category airplanes. This chapter focuses on the revision history, contents, and compliance means of §25.1309, and outlines the evolution history and compliance means for the civil aircraft system safety.

Keywords

Safety; §25.1309; compliance means

Contents

1.1 Airworthiness Standards of Transport Category Airplanes 1

1.1.1 Airworthiness 1

1.1.2 Airworthiness Standards 2

1.2 Terms and Definitions 4

1.2.1 Risk 4

1.2.2 Safety 4

1.2.3 Failure Condition Classifications and Probability Terms 4

1.3 Evolution History of the Aircraft Safety Assessment Process 6

1.4 Revision History of §25.1309 10

1.4.1 The Content of §25.1309 10

1.4.2 The Origin of Safety Objectives 13

1.4.3 Revision History of §25.1309 15

1.5 Compliance With §25.1309 16

1.5.1 AC25.1309-1B (Arsenal) 18

1.5.2 Industry Standards Related to §25.1309 20

References 26

1.1 Airworthiness Standards of Transport Category Airplanes

1.1.1 Airworthiness

The definition of “Airworthy” in the Oxford Dictionary is “(of aircraft) safe to fly.” “Airworthiness” is the noun form of “Airworthy.”

The definition of the word “Airworthy” was never included in the Code of Federal Regulations until the Federal Aviation Regulations (FAR) Part 3, General Requirements, was established. The definition was included in the guidance materials, such as Advisory Circulars (ACs) and Orders, but never in the Rule. In Part 3, the definition of Airworthy is defined that the aircraft conforms to its type design and is in a condition of safe flight.

In Canadian Aviation Regulations, CAR 101.01, Subpart 1—Interpretation, “airworthy”, with respect to an aeronautical product, means a fit and safe state for flight and in conformity with its type design.

Airworthiness is the measure of an aircraft’s suitability for safe flight. The application of airworthiness defines the condition of an aircraft and acts as the basis for judging its fitness to fly in that it has been designed with engineering rigor, that it has been properly constructed and maintained, and that it is expected to be operated according to approved standards and limitations, by competent and approved individuals, who are acting as members of a certification organization.

1.1.2 Airworthiness Standards

Airworthiness standards are special technical standards and minimum safety standards established to ensure the implementation of civil aircraft airworthiness. Unlike other standards, civil aircraft airworthiness standards are part of national regulations and require strict enforcement.

The establishment of an airworthiness standard has involved continuous revision by accumulating long-term experience, drawing lessons from flight accidents, conducting necessary demonstration or argumentation, and soliciting opinions from the public. Thus far, FAR of Federal Aviation Administration (FAA) and Certification Specification (CS) of European Aviation Safety Agency (EASA) dominate the worldwide airworthiness standards. Taking the international characteristics of civil aviation airworthiness standards into account, many countries have established their airworthiness standards by recognizing FAR and CS with consideration of their own national situations. For instance, certification authorities from China, Canada, and Russia all have established their own airworthiness standards based on FAR and CS.

FAA airworthiness standards are as follows:

• Part-23 Airworthiness Standards: Normal, Utility, Acrobatic, and Commuter Category Airplanes.

• Part-25 Airworthiness Standards: Transport Category Airplanes.

• Part-26 Continued Airworthiness and Safety Improvements for Transport Category Airplanes. (Note: EASA also contains CS-26, but its name is Additional airworthiness specifications for operations, its initial release was on December 5, 2015.)

• Part-27 Airworthiness Standards: Normal Category Rotorcraft.

• Part-29 Airworthiness Standards: Transport Category Rotorcraft.

• Part-31 Airworthiness Standards: Manned Free Balloons.

• Part-33 Airworthiness Standards: Aircraft Engines.

• Part-34 Fuel Venting and Exhaust Emission Requirements for Turbine Engine Powered Airplanes.

• Part-35 Airworthiness Standards: Propellers.

• Part-36 Noise Standards: Aircraft Type and Airworthiness Certification.

• Part-39 Airworthiness Directives.

The above airworthiness standards are all appropriate for civil products. For materials, parts, and appliances used on civil products, they are referred to as TSO authorization according to the Technical Standard Order (TSO) standard. A TSO is a minimum performance standard issued by the certification authority for specified materials, parts, processes, and appliances used on civil products.

As of May 2016, there are 162 current effective FAA TSOs and 144 current effective EASA European Technical Standard Order (ETSOs). In recent years, despite of some slight differences in marking and data requirements, the contents of TSOs issued by the FAA and ETSOs have been basically identical in technical aspects (except the ETSO 2C series). FAA and EASA introduce mature technical standards in industry as the key technical requirements for TSO.

Airworthiness Directives (ADs) are legally enforceable rules that are applied to the following products: aircrafts, aircraft engines, propellers, and appliances. In FAA, each AD is a part of Part-39, but they are not codified in the annual edition. The authority issues an AD addressing a product when it finds that: (1) an unsafe condition exists in the product; and (2) the condition is likely to exist or develop in other products with the same type of design. Anyone who operates a product that does not meet the requirements of an applicable AD is in violation of Part-39.

AC is a recommended and interpretative material of the compliance means with the applicable regulations. Though it is stated in almost all ACs that the means it introduces are not mandatory or are not the only means, and that the applicants can adopt other methods to demonstrate their compliance with the regulation. In general, if the type certificate applicants do not propose more appropriate means, priority should be given to using the means introduced in the AC to demonstrate their compliance with applicable regulations.

1.2 Terms and Definitions

1.2.1 Risk

The IEC61508 Standard defines risk as the combination of the possibility and severity of hazards. It is common to use the following formulation to describe the above definition:

$R=S\times P$

R is the risk, S is the severity resulted from the hazard, and P is the possibility of the result.

The definition of “Risk” in Society of Automotive Engineers (SAE) Aerospace Recommended Practice (ARP) 4761 is the frequency (probability) of occurrence and the associated level of hazard [1].

1.2.2 Safety

The definition of “Safety” in the Oxford Dictionary is the state of being safe and protected from danger or harm.

The definition of “Safety” in International Civil Aviation Organization (ICAO) Annex 19 is the state in which risks associated with aviation activities, and related to, or in direct support of the operation of aircraft, are reduced to and controlled at an acceptable level.

Safety risk: The predicted probability and severity of the consequences or outcomes of a hazard.

1.2.3 Failure Condition Classifications and Probability Terms

Failure Condition: A condition having an effect on the airplane and/or its occupants, either a direct or a consequential, which is caused or contributed to by one or more failures or errors, consideration flight phase and relevant adverse operational or environmental conditions or external events [2].

1. Classifications
Failure Conditions may be classified according to the severity of their effects as follows [2]:

a. No Safety Effect: Failure Conditions that would have no effect on safety; e.g., Failure Conditions that would not affect the operational capability of the airplane or increase the crew workload.

b. Minor: Failure Conditions that would not significantly reduce the airplane safety and that involve crew actions that are well within their capabilities. Minor Failure Conditions may include, e.g., a slight reduction in safety margins or functional capabilities and a slight increase in crew workload, such as routine flight plan changes, or some physical discomfort to passengers or the cabin crew.

c. Major: Failure Conditions that would reduce the capability of the airplane or the ability of the crew to cope with adverse operating conditions to the extent that there would be, e.g., a significant reduction in safety margins or functional capabilities, a significant increase in crew workload or decrease of crew efficiency, discomfort to the flight crew, or physical distress to passengers or cabin crew, possibly including injuries.

d. Hazardous: Failure Conditions that would reduce the capability of the airplane or the ability of the crew to cope with adverse operations and conditions to the extent that there would be:

i. a large reduction in safety margins or functional capabilities;

ii. physical distress or excessive wo...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• About the Author
• Foreword
• Preface
• Acknowledgments
• Abbreviations and Acronyms
• Chapter 1. Airworthiness Regulations and Safety Requirements
• Chapter 2. Safety Management
• Chapter 3. Aircraft Functional Hazard Assessment
• Chapter 4. System Functional Hazard Assessment
• Chapter 5. Preliminary System Safety Assessment
• Chapter 6. Common Cause Analysis
• Chapter 7. Failure Modes and Effects Analysis with Summary
• Chapter 8. System Safety Assessment
• Chapter 9. Single Event Effects in Avionics
• Chapter 10. Formal Model Based Safety Analysis Methods and the Application
• Index