MODELING OF HUMAN AND TECHNICAL FACTORS INTER-

RELATIONSHIP IN MAINTAINING CIVILIAN AIRCRAFT SAFETY

ZENTY RAZILANATY BINTI SAHARI

This project is submitted in partial fulfillment of the requirements for the

Degree of Bachelor of Engineering with Honors

(Mechanical and Manufacturing System)

Faculty of Engineering

UNIVERSITY MALAYSIA SARAWAK

2006

To My Incredible Parents, Brothers and Sisters,

Lecturers and Friends;

i

ACKNOWLEDGEMENT

This project was made possible through the support of many individuals

directly or indirectly. Most and foremost, I would like to take this opportunity to

express my deepest gratitude and respect to Ir. Dr. Andrew R. H Rigit for his

generosity, kindness and guidance upon completion of this project. My deep

appreciation also goes out to all staff and lecturers of Faculty of Engineering for their

assistances and supports.

I would like to offer my sincere thanks to my friends for their excellent

suggestions, criticisms and encouragement throughout the project. Last but not least

to my incredible family, who has been wonderfully patient and understanding

throughout my journey of education.

11

ABSTRAK

Selaras dengan peningkatan teknologi, penggunaan sistem komunikasi,

navigasi, peninjauan, dan teknologi paparan juga semakin meluas dalam arena

penerbangan. Pada masa yang sama, pengendalian sistem penerbangan moden amat

memerlukan kaedah atau penyelesaian yang melibatkan faktor kemanusiaan, teknikal

dan persekitaran memandangkan kadar kemalangan udara yang melibatkan kapal

terbang komersial telah meningkat selaras dengan penambahan kapasiti kapal

terbang. Projek ini dijalankan bagi mengkaji sistem kapal terbang yang kompleks

bagi mengelak kejadian yang boleh menyebabkan kemalangan nyawa daripada

berlaku. Kajian menunjukkan penyumbang utama kemalangan kapal terbang adalah

disebabkan kesilapan manusia yang terlibat dalam operasi penerbangan dan

selalunya kemalangan ini berlaku kerana rentetan beberapa peristiwa. Oleh yang

demikian, kaedah yang efektif untuk meramal risiko mengalami kemalangan amatlah

diperlukan bagi mengelak kejadian yang tidak di ingini sebelum ia berlaku. `Pilot's

Decision-making Programming Model' menunjukkan tindakan yang bakal di

lakukan oleh juruterbang sekiranya mereka berhadapan dengan masalah ketika

melakukan penerbangan. Selain itu, penggunaan teknologi `Artificial Intelligence' di

nilai dalam projek ini memandangkan teknik tersebut mempunyai potensi yang tinggi

bagi meningkatkan keselamatan dalam sistem penerbangan yang melibatkan nyawa

ramai manusia.

111

ABSTRACT

Aviation has always been a technology driver, therefore, the introduction of

new communication, navigation, surveillance, and display technology is moving

forward at a rapid pace. At the same time, modem aviation operational environment

crucially needs to find a new way of evaluating human, technical, and external (i. e.

environmental) factors, in order to maintain the civilian aircraft safety. The rate of air

disaster involving the civilian aircraft is increasing due to the growing capacity of the

aircraft. In this project, the large civilian aircraft system will be investigated in order

to avoid the errors that contribute to air disaster. The accident investigation

concluded that the main cause of accidents was largely human error and the accidents

occur as a result of a chain of events. Therefore, an effective way to predict risk is

needed to prevent accidents in complex large-scale systems before they occurred. A

Pilot's Decision-making Programming Model was developed to demonstrate the

decision-making process by the pilots when they are confronting with problems

during flight operation. In addition, the effectiveness of artificial technology is

evaluated in which the Artificial Intelligence techniques have a great potential to

improve aviation safety.

iv

LIST OF CONTENTS

CONTENTS

DEDICATION

ACKNOWLEDGEMENTS

ABSTRAK

ABSTRACT

LIST OF TABLE

LIST OF FIGURES

LIST OF ABBREVIATIONS

CHAPTER 1

INTRODUCTION

1.1 Overview

1.2 Socio-Technical System

1.3 The Aircraft System

1.4 The Piloting Environment

1.5 Objectives

1.6 Project Overview

CHAPTER 2

PAGE

1

Ü

iii

iv

ix

I

%11

1

4

6

7

8

9

LITERATURE REVIEW

2.1 Introduction to Air Safety 11

2.2 Factors Causing Fatal Accidents 12

2.2.1 Social or human factors 13

2.2.1.1 Fatigue 16

2.2.1.1.1 Factors responsible of pilot fatigue 17

2.2.1.2 Age, Experience, Gender and Personality Traits 20

2.2.1.3 Attitude 21

2.2.2 Technical or Aircraft Factors 23

2.2.2.1 Aerodynamics (Stalling) 24

2.2.2.2 Communication System 29

2.2.2.3 Structural Mechanics 31

2.2.3 Environmental Factors 33

2.2.3.1 Runway Obstructions 34

2.2.3.2 Turbulence 37

2.2.3.3 Bird Strike 40

2.3 Flight Control System 41

2.3.1 Types of flight control system

2.3.1.1 Mechanical Flight Control System

2.3.1.2 Hydraulically Flight Control System

2.3.1.3 Primary Flight Control System

2.3.1.4 Longitudinal Control System

2.3.1.5 Lateral Control System

2.3.1.6 Directional Control System

2.3.2 Mechanism of Flight Control System

42

42

44

45

45

48

52

54

vi

2.3.2.1 Mechanical Control System

2.3.2.2 Hydraulic Control System

2.3.2.3 Fly-By-Wire Control System

CHAPTER 3

METHODOLOGY

3.1 Data Collection

3.1.1 Design of study

3.1.2 Data Collection Procedure

3.2 Methodology for Assessing Aircraft Safety

3.2.1 C++ Software

3.2.2 Artificial Intelligence Software

3.2.2.1 Expert System

3.2.2.2 Fuzzy Logic

3.2.2.3 Neural Network

CHAPTER 4

ANALYSIS AND DISCUSSION

4.1 General

4.2 Applications of Artificial Intelligence

4.2.1 Cockpit Applications

4.2.2 Maintenance and Test Equipment

4.2.3 Autopilot

55

56

56

60

60

60

61

61

62

63

65

67

69

69

70

71

72

vii

4.2.4 Discussion on Al-based Avionics 73

4.3 Flowchart for Pilot's Decision Making Programming Model 75

4.4 Analysis 79

4.4.1 Wind 79

4.4.2 Turbulence 82

4.4.3 Poor Visibility

4.4.4 Wildlife Appearance

4.4.5 Engine Failure

4.4.6 Stalling

4.4.7 Poor Communication

84

87

89

91

93

4.5 Aircraft Accidents or incidents as a chain of events 95

CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 Conclusion 97

5.2 Recommendations and Further Workl02

REFERENCES 104

APPENDIX I 107

viii

LIST OF TABLE

TABLE TITLE PAGE

1.1 Air accident from 1945 through 2004 3

1.2 Relevant parameters in maintaining air safety 7

2.1 Multifaceted human error taxonomy 15

2.2 Estimated annual turbulence injuries for part 121 carriers 39

2.3 Turbulence Injury Rate Summary 40

ix

LIST OF FIGURE

FIGURE TITLE PAGE

1.1 A Socio-technical system 5

1.2 The Socio-technical system of an aircraft 6

1.3 A simple relationship of man-machine interface 6

1.4 Behavioral factors cited in consecutive sample

of 22,228FAA-ASRS reports 8

2.1 Example of leading-edge stall 26

2.2 Example of trailing-edge stall 27

2.3 Lift-coefficient curves for three airfoils with different

aerodynamic behavior: trailing-edge stall

(NACA 4421 airfoil), leading-edge stall (NACA 4412 airfoil)

thin airfoil stall (flat plate) 27

2.4 Example of thin airfoil stall 28

2.5 High-Frequency Radio Control Panel 29

2.6 VHF Radio Control Panel 30

2.7 Turbulence in the tip vortex from an airplane wing 38

2.8 Mechanical (unboosted) flight control system 43

2.9 Hydraulically powered elevator control system 44

2.10 Elevator forward bobweight and damper assembly 46

2.11 Stabilizer Control System 47

2.12 Aileron Power Mechanism 50

X

2.13 The Flaperon Control System 51

2.14 The Rudder Control System 53

3.1 C++ Programming 62

4.1 Pilot's Decision-Making Programming Model 79

4.2 Tail wind conditions 80

4.3 Example of decision making by pilots for tail wind condition 80

4.4 Wind shear conditions 81

4.5 Example of decision making by pilots for

wind shear condition Si

4.6 Turbulence conditions 82

4.7 Example of decision making by pilots for

turbulence condition 83

4.8 Poor visibility conditions 85

4.9 Example of decision making by pilots for

poor communication condition 85

4.10 Wildlife appearance conditions 87

4.11 Example of decision making by pilots for wildlife condition 88

4.12 Engine failure conditions 89

4.13 Example of decision making by pilots for

engine failure condition 89

4.14 Stalling conditions 91

4.15 Example of decision making by pilots for stalling condition 92

4.16 Poor communication conditions 93

4.17 Example of decision making by pilots for

poor communication condition 93

X1

LIST OF ABBREVIATIONS

Al - Artificial Intelligence

ASDA - Accelerate/Stop Distance Required

ASDR - Accelerate/Stop Distance Required

ATC - Air Traffic Control

ATE - Automated Test Equipment

BIT Build-In Test

CASSY - The Cockpit Assistant System

CFIT - Controlled Flight into Terrain

CPLDC - Controller to Pilot Datalink

DWI - Driving-While-Intoxicated

ES - Expert Systems

FAA - Federal Aviation Administration

FINDER - Flight-Plan Interactive Negotiation and Decision-Aiding

System for Enroute Rerouting

HF - High Frequency Radio

HRA - Human Reliability Assessment

ICAO - International Civil Aviation Organization

IEEE - The Institute of Electrical and Electronics Engineers

INS - Inertial Navigation System

ILS - Instrument Landing System

IRAS - Incident Reports Analysing System

LDA - Landing Distance Available

LDR - Landing Distance Required

X11

LRU - Line Replaceable Units

NASA - National Aeronautics and Space Administration

NN - Neural Network

NTSB - National Transportation Safety Board

RTO - Reject Take-Off

UUT - Unit Under Test

VHF - Visual High Frequency Radio

X111

CHAPTER 1

INTRODUCTION

1.1 Overview

Since the beginning of modem aviation history, aircraft have crashed with

serious consequences due to several factors in term of human errors, technical

malfunctions and/or environmental factors. According to a recent world airliner

fatality report from Planecrashinfo. com database, there were 2,147 aircrafts accident

from 1950 through 2004 and killed more than 70,000 civilians. In Malaysia, two

major air accidents involving the aircrafts of the national carrier, Malaysian Airlines

had been reported. In December 1977, a Boeing B737-200 experienced mid-air

explosion, and a Fokker F-50, which crashed upon landing at Tawau Airport in

September 1995. The former case was considered to be due to an unlawful

interference, terrorism act, and the later case was blamed on human error.

Historically, as the rapid growth in air transport, it has often followed by a

series of accidents. It was reported by the International Civil Aviation Organization

(ICAO) that the fatality rate for international and domestic schedule aviation

operations has been consistently decreasing over time. The fatality rate decreased

from 0.18 to 0.04 fatalities per 100 million passenger kilometers between 1970 and

1993 with particularly marked reductions recorded. This trend was relatively stable

during the period of 1984 to 1993. The analysis indicates that the number of fatal

1

accidents varied between 16 and 31 accidents per year during this 23 years period.

The average number of accident per annum was 25 and the average annual number

of passenger fatalities was 741 per annum. At the same time, the output of the sector

rise from 1971 to 389 billion passenger-kilometers which are over a 500 percent

increase (International Civil Aviation Organization, 1992 and 1994). However,

further improvements in safety are becoming exhausted implying that if the accidents

rate remains the same, while air transport increases, so, the number of accidents will

certainly rise.

The research and development are still carried out to improved aviation

technology and reduced air accidents. The improvement that had been done to the

technology of materials, propulsion system, aerodynamic science, navigation and

communication system, and also the study of human ergonomic for pilots, had helps

enhancing the air safety. As an example, Boeing has launched their Electronic flight

Bags (EFB) where the EFB system stores digitally all the documentation and forms

pilots typically carry onto airplanes. It also has an on-board performance tool that

instantly calculates an airplane's ideal speed and engine setting, in any weather, and

runway, with any payload. The EFB also provides a view from cabin surveillance

systems which helped meet current and anticipated regulatory requirements. Overall,

United States have experienced the safest period in aviation history because of the

standards set by the Federal Aviation Administration (FAA) and the realization of

focusing on safety by the United States Airlines.

Air disasters still happen even though the improvement in science and

technology growth from time to time. It is widely accepted that human error is a

major contributing factor in aircraft accident which shows by the statistic table

2

summarized in Table 1. The table shows worldwide accident rate causes by category

in percent; for data taken from the year 1950s to 2004, showed that 37 percent

accident cause by total pilot error from the total of 2,147 fatal accidents. "Pilot error

(weather related)" represents accident in which pilot error was involved but brought

about by weather related phenomena. While, "pilot error (mechanical related)"

represents accidents in which pilot error was involved but brought about by

mechanical failure. "Other human error" includes air traffic controller error,

improper loading of aircraft, fuel contamination, improper maintenance etc.

"Sabotage" includes explosive devices, shoot downs and hijackings. "Total pilot

error" is the total for all types of pilot error.

Table 1.1: Air accident from 1945 through 2004 (PlaneCrashlnfo. com, 2005)

Fatal Accident Causes Cat o Percent Cause 1950s 1%Os 1970s 1980s 1990s+ Total

Pilot Error 27 24 17 19 21 22

Pilot Error weather related) 5 13 10 11 15 11 Pilot Error (mechanical related) 5 3 3 3 4 4

Total Pilot Error 37 40 31 33 40 37 Other Human Error 2 5 6 4 5 4 Weather 9 7 8 10 6 7

Mechanical Failure 12 13 14 13 14 13 Sabotage 3 3 6 7 6 5

Other Cause 0 2 2 1 0 1 Undetermined or missing 37 30 34 32 29 33

The fatal accident involving an Airbus A320 near Strasbourg in France in

1992 was due to poor weather and pilot confused with the `vertical speed' and the

`flight path angle' modes of descent. The crew intended to descend at 3.3 degrees

and made the aircraft descended far too steeply and crashed. Therefore, aircraft

system needs to be monitored both technical aspects and human aspects. Reason

(1990) define human errors as "all the occasions in which a planned sequence of

3

mental or physical activities fails to achieve its intended outcome, and when these

failures can not be attributed to the invention of some change agency".

There are two major systems to describe an aircraft, which can be categorized

into technical systems (i. e. aircraft physical system) and human aspects (i. e. pilots).

Socio-technical system is the interactions between technical and human systems.

However, the large civilian aircraft is formed by many sub-systems and become a

complex socio-technical system.

1.2 Socio-Technical System

The social system is a system of social relations that refer to human

intelligent and their activities, their habitual attitudes, values, behavioral styles and

relationship. On the other hand, in a general engineering application, the technical

systems refer to the machinery, processes, procedures, instructions and a physical

arrangement such as factory or manufacturing plant. Figure 2 shows the overall

system performance relies on how good the social and technical systems integrate

and assist one another. This "living" system is a system where the machine aspects

can continuously updating the information and run the analysis program; and the

human can use their past experience and cognitive ability to make a judgment. Thus,

through this interconnection, many human errors can be corrected by the computer

calculation, control and feedback.

4

Figure 1.1: A Socio-technical system (R. H Andrew, 2005)

Safe flight operation can be regarded as a socio-technical system which

consists of human factors and technical efficiency, as well as the external factor, i. e.

environmental factors. The function below shows the inter-relationship of the socio-

technical system of an aircraft.

The percentage (%) of flight safety

=f Sum of human factors x Sum of technical efficiency)

where;

Sum of Human Factors = f( Demographic, Health, Experience, Knowledge,

Proficiency)

Sum of Technical Efficiency =f (Mechanical control, Aircraft System, Structural

Fatigue, etc)

For an example;

Percentage (%) of flight safety = (pilot) (aircraft)

If pilot = 100%, aircraft = 100%, then flight safety is 100%

If pilot = 100%, aircraft = 50%, then flight safety is 50%

5

1.3 The Aircraft System

From the above Figure 2, an aircraft socio-technical can be achieved, which

consists of a pilot (i. e. social factor) and an aircraft (i. e. technical factor) system, as

shown in Figure 3. As very often, deteriorating weather conditions (i. e. environment)

are hazardous to aviation, thus, the environmental factor is also crucial in the overall

aircraft system.

Figure 1.2: The Socio-technical system of an aircraft (R. H Andrew, 2005)

Figure 4 below shows a simple relationship of man-machine interface to

avoid a control flight from flying into a terrain. Altimeter reading is based on the

available air pressure and corrected to mean sea level. The flying altitude is

determined by the differences in the ambient pressure around the aircraft and the

pressure at the mean sea level. A mistake in the pressure setting can result in a

control flight flying into a terrain.

I Air Pre»ure º Altimeter ~--- 00 Pilot

YY!

machine human

7ePfä111

Clearance

Figure 1.3: A simple relationship of man-machine interface (R. H Andrew, 2005)

6

Safe flight operation are critically depends on parameters such as flight

management control system, measurement system (e. g. altitude, air speed, pressure,

temperature), fuel distribution system, landing gear system, electrical and electronic

systems. Table 2 summarizes the relevant parameters from social (i. e. human),

technical (i. e. aircraft) and environmental factors that can affect air safety.

Table 1.2: Relevant parameters in maintaining air safety (Stephen et al, 2003)

Social/Human Factors Technical/Aircraft Factors Environmental Factors Fatigue Mechanical control system Visibility Visual/Blind Spot Electronic control system Cloud ceiling Ergonomic design Structural mechanics Wind gust Emotional Aerodynamic Jet stream Moral Communication system Ambience air properties Behavior Navigation system Turbulence

Culture Cockpit display system Air pocket Age Bird strike Experience Airport facilities Attitude Runway obstruction

1.4 The Piloting Environment

The piloting environment for a flight is a classification of the social/human

factors. This consists of the cockpit environment, flight deck design, display systems

and pilot psychology. Advances in future aircraft cockpits are being made possible

by the rapid progress in display media, graphics displays, computer technologies, and

human factor methodologies and are found as factors in the piloting environment.

The behavioral factors mentioned in a consecutive sample of 22,228 FAA-ASRS

reports were quantified as summarized by the pie chart in Figure 5.

7

D tract on

2 3' C.

Incapac tation, Physical Problem

I9C.

Workload FatiguC-

U

2 5°0

Fi? S OlI I-C t?

I 1til ration 2. ̀ 'a

Figure 1.4: Behavioral factors cited in consecutive sample of 22,228FAA-ASRS reports (R. H Andrew, 2005)

The perfect coordination between the air traffic controller and the pilot will

defined whether the flight journey from one point to another point is successful or

failure. The failure occurred sometimes because of the coordination could be `slips'

or `mistakes' and may cause fatal accidents. Hollnagel (1993) defined `slips' as skill-

based errors that happen when action is incorrectly performed, frequently during

familiar work requiring little attention. On the other hand, `mistakes' are either rule-

based or knowledge-based errors and associated with problem solving.

1.5 Objectives

The objectives of this study are:

i) To investigate the inter-relationship between the sub-systems (i. e. social,

technical and environmental) in order to avoid the `slips' and the

`mistakes';

Sensory Interference

5 c.

EV per ence 8 F: naýý ledcýe

Deficiencies

8

ii) To evaluate the effectiveness of artificial intelligence technology (i. e.

expert system, fuzzy logic and neural network) as a way of maintaining

aircraft safety;

iii) To study the nature of flight control system;

To build a programming model on the procedure of pilot's action or

decision making by the cockpit crews whenever encounter with different

situations during flight operations;

1.6 Project Overview

This project will focus on the investigation of the human and technical

factors inter-relationship in maintaining aircraft safety. Other than that, a

programming model is build to show the decision making by the pilots when

confront with different situation during flight operation.

In this report, the content of the study is arranged and divided into few

chapters.

Chapter 1 as the introduction of the project will provide the necessary

background or context of this study. Besides, the objectives that need to be

achieved are revealing in this chapter.

Chapter 2 introduces the definition of civilian aircraft safety and

explains the factors that contribute to the accident or incident in aviation

arena. This includes the human/social, technical/aircraft and environmental

9

factors. Other than that, the advancement of flight control systems is

discussed in the end of this chapter.

The methodology used in this study is covered in Chapter 3. This

section includes the plan to tackle project problem and the activities

necessary for the completion of the need of this study and the software used

for the modeling purpose.

Chapter 4 concentrates on the analysis of the investigation and from

the programming model that, then, it is followed by some discussion.

Finally, Chapter 5 includes the conclusion of this study, the

difficulties and encounter during completion of this report and some

recommendation for the future work relates to the aviation safety area.

10