MODULE 9

HUMAN FACTORS

9.1 Human Factors General

Issue No.: 01 Date: 09 January 2022 FOR TRAINING PURPOSES ONLY

Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

TABLE OF CONTENTS
 Objective

 Assessment Methods

 Objectives & Examination Levels

 0. Introduction

 1. The need to take human factors into account

 1.1 What is “Human Factors”?

 1.2 The SHEL Model

 2. Incidents and Accidents Attributable To Human Factors / Human Error

 2.1 CASE STUDY: ALOHA AIRLINES FLIGHT 243

 2.2 CASE STUDY: BRITISH AIRWAYS BAC-111; WINDSCREEN BLOWOUT

 3. Murphy’s Law

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 2
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

OBJECTIVE

After study of this Module, the student will be able to:

Define the terms ‘Human Factors’

Relate at least two (2) separate examples of incidents attributable to human factors/errors in a maintenance environment

Explain the need to take human factors into account when carrying aircraft maintenance work

Explain the adage ‘Murphy’s’ law’

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 3
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

ASSESSMENT METHODS
No. of 50 min
Module Theory Practical Exam (min.)* Sub-Total % Practical
Periods
25 (MCQ) +
9 50 hrs 0 hrs 60 0% 62
20 (Essay)

* 20 MCQ + 1 ESSAY
(Slides + Textbook)

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 4
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

OBJECTIVES & EXAMINATION LEVELS

Type of Assessment No of Questions Time Allowed

20 MCQ 25 Minutes
Module 09 Knowledge Examination
1 Essay 20 Minutes

Formal Practical Assessment Not required

Obj Description MCQ Guide

1 Human Factors General 2
2 Human Performance Limitations 2
3 Social Psychology 2
4 Factors Affecting Performance 3
5 Physical Environment 2
6 Tasks 2
7 Communication & Information Transfer 3
8 Human Error 2
9 Hazards in the Workplace 2

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 5
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

0. INTRODUCTION

Would you like to

Do humans make
Are you human? reduce the possibility
mistakes?
of mistakes?
• Yes • Yes • Yes
• No • No • No

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 6
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1. THE NEED TO TAKE HUMAN FACTORS INTO ACCOUNT

 Aviation safety relies heavily on maintenance

 When it is not done correctly, it contributes to a significant proportion of accidents and
incidents
 Some examples of maintenance errors may include;
• parts installed incorrectly,
• missing parts, or
• necessary checks not being performed

 In comparison to many other threats to aviation safety, the mistakes of an Aviation

Engineers can be more difficult to detect.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 7
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1. THE NEED TO TAKE HUMAN FACTORS INTO ACCOUNT

 Often, Aviation Engineers are working in

• the evening or early morning hours
• in confined spaces
• on platforms that are up high, or
• in a variety of adverse temperature/humidity conditions

 The work can be physically tireless, yet also requiring a high degree of
• attention to detail.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 8
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1. THE NEED TO TAKE HUMAN FACTORS INTO ACCOUNT

 Because of the nature of maintenance tasks, AMTs commonly spend more time
preparing for a task than actually carrying it out
 Proper documentation of all maintenance work is a key element
 Human factors and how they affect people are very important to aviation
maintenance
 Such awareness can lead to
• improved quality,
• an environment that ensures continuing worker and aircraft safety, and
• a more involved and responsible work force.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 9
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1. THE NEED TO TAKE HUMAN FACTORS INTO ACCOUNT

 The evolution in aviation safety thinking can be divided into four consecutive eras

• The technical era: this lasted from the

beginning of public air transportation
until the late 1960s

• Safety occurrences were initially related to

technical and technological failures, therefore
safety events focused in improving those areas.
Efforts were successful since by the 1950s the
frequency of accidents had gradually declined.

Fig. 1 - Worldwide Commercial Accident Rate and Safety Thinking

Evolution

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 10
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1. THE NEED TO TAKE HUMAN FACTORS INTO ACCOUNT

 The evolution in aviation safety thinking can be divided into four consecutive eras

• The human factors era: this was developed

from the early 1970s until the mid-1990s.
Although in those days the frequency of
aviation accidents was significantly reduced,
and aviation became a safer mode of
transportation due to the

• Investments in technology improvements

• But several unimaginable accidents switched

investigators’ interest to human Fig. 1 - Worldwide Commercial Accident Rate and Safety Thinking
Evolution
performance.
Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 11
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1. THE NEED TO TAKE HUMAN FACTORS INTO ACCOUNT

 The evolution in aviation safety thinking can be divided into four consecutive eras

• The organizational era: the organizational era

began in the mid-1990s. In fact, safety thinking
encompassed also the organizational factors that
might potentially jeopardize safety, in addition to
the already human and technical factors on
board.

Fig. 1 - Worldwide Commercial Accident Rate and Safety Thinking

Evolution

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 12
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1. THE NEED TO TAKE HUMAN FACTORS INTO ACCOUNT

 The evolution in aviation safety thinking can be divided into four consecutive eras

• The total system era: this was introduced from the

beginning of the century

• Nowadays, both safety agencies and organizations, on

either a mandatory or voluntary basis, are following a
holistic approach in safety. In that event, they
implement a safety management system (SMS), which
starts from the management and is driven by the:

o Routine collection and analysis of safety data

o It includes the identification of the various hazards

Fig. 1 - Worldwide Commercial Accident Rate and Safety Thinking
and safety risks, in an effort to mitigate and if Evolution
possible, restrict them from occurring.
Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 13
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1.1 WHAT IS “HUMAN FACTORS”?

 The term “human factors” is used in many ways in the

aviation industry

 Aircraft accidents such as that to the Aloha aircraft in the USA in

1988 and the BAC 1-11 windscreen accident in the UK in Fig. 2 - Aloha aircraft in the USA in 1988

June 1990 brought the need to address human factors issues

in this environment into sharp focus

 This does not imply that human factors issues were not present
before these dates, nor that human error did not contribute
to other incidents; merely that it took an accident to draw
attention to human factors problems and potential
solutions.
Fig. 3 - BAC 1-11 windscreen accident in the UK in June 1990

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 14
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1.1 WHAT IS “HUMAN FACTORS”?

 Before discussing how these accidents were

related to human factors, a definition of
human factors is required

 There are many definitions available. Some

authors refer to the subject as ‘human factors’
and some as ‘ergonomics’

 A good definition in the context of aviation Fig. 4 - Aviation maintenance technicians (AMTs) are confronted
with many human factors due to their work environments
maintenance would be:

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 15
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1.1 WHAT IS “HUMAN FACTORS”?

 "Human factors" refers to the study of human capabilities and

limitations in the workplace

 Human factors researchers study system performance

 That is, they study the:

• interaction of maintenance personnel,

• the equipment they use,

• the written and verbal procedures and rules they follow, and

• the environmental conditions of any system

 The aim of human factors is to optimize the relationship between

maintenance personnel and systems with a view to improving
Fig. 5 - A list of human factors that affect AMTs.
safety, efficiency and well-being”.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 16
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1.1 WHAT IS “HUMAN FACTORS”?

 This is what the Authority has to say about it :

 http://www.youtube.com/watch?v=4VIYlxTowq8

 This is another way of looking at human factors:

 http://www.youtube.com/watch?v=1KEse_x1Sko&list=PLMJTnKO9Amcxx5jph5Cban-CZ-
WLeCGW2&index=13

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 17
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1.2 THE SHEL MODEL

 It can be helpful to use a model to aid in the understanding of human factors, or as a

framework around which human factors issues can be structured. A model which is
often used is the SHEL model, a name derived from the initial letters of its components: H
• Software (e.g., maintenance procedures, maintenance manuals, checklist layout,

S L E
etc.);

• Hardware (e.g., tools, test equipment, the physical structure of aircraft, design of
flight decks, positioning and operating sense of controls and instruments, etc.);

L
• Environment (e.g., physical environment such as conditions in the hangar, conditions
on the line, etc. and work environment such as work patterns, management
structures, public perception of the industry, etc.);

• Liveware (i.e., the person or people at the centre of the model, including
Fig. 6 - SHEL Model
maintenance engineers, supervisors, planners, managers, etc.).

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 18
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

1.2 THE SHEL MODEL

 Human factors concentrates on the interfaces between the

human (the ‘L’ in the centre box) and the other elements of the
SHEL model, and - from a safety viewpoint - where these
elements can be deficient

 Since Liveware is at the centre of the model, all other

aspects (Software, Hardware and Environment) must be
designed or adapted to assist his performance and respect his
limitations

 If these two aspects are ignored, the human - in this case the
maintenance engineer - will not perform to the best of his
Fig. 7 - Example of SHEL Model
abilities, may make errors, and may jeopardise safety.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 19
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

2. INCIDENTS AND ACCIDENTS ATTRIBUTABLE TO HUMAN FACTORS / HUMAN ERROR

 In 1940, it was calculated that approximately 70% of all aircraft accidents were attributable to man’s performance, that is to say human
error.

 A study was carried out in 1986, in the USA by Sears, looking at significant accident causes in 93 aircraft accidents. These were as follows:
% of accidents in
Causes/ major contributory factors
which this was a factor
Pilot deviated from basic operational procedures 33 OTHER
Inadequate cross-check by second crew member 26 CAUSES
Design faults 13 25%

Maintenance and inspection deficiencies 12 HUMAN FAILURE

Flight Crew, ATC,
Absence of approach guidance 10
Maintenance,
Captain ignored crew inputs 10 Aircraft
Air traffic control failures or errors 9 Design, etc.
75%
Improper crew response during abnormal conditions 9
Insufficient or incorrect weather information 8
Runways hazards 7
Air traffic control/crew communication deficiencies 6
Fig. 8 - The dominant role played by human
Improper decision to land 6 performance in civil aircraft accidents

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 20
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

2. INCIDENTS AND ACCIDENTS ATTRIBUTABLE TO HUMAN FACTORS / HUMAN ERROR

Fig. 8 - Aviation Accidents

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 21
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

2.1 CASE STUDY: ALOHA AIRLINES FLIGHT 243

 Aloha Airlines Flight 243 (AQ 243, AAH 243) was a scheduled
Aloha Airlines flight between Hilo and Honolulu in Hawaii

 On April 28, 1988, a Boeing 737-297 serving the flight suffered

extensive damage after an explosive decompression in
flight but was able to land safely at Kahului Airport on Fig. 9 - Aloha Airlines Flight 243
Video - https://www.youtube.com/watch?v=YYa7Fq5Ec6c
Maui
 There was one fatality, a member of the flight crew who was swept overboard from the airplane

 Another 65 passengers and crew were injured. The safe landing of the aircraft despite the substantial damage
inflicted by the decompression established Aloha Airlines Flight 243 as a significant event in the history of
aviation, with far reaching effects on aviation safety policies and procedures.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 22
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

2.2 CASE STUDY: BRITISH AIRWAYS BAC-111; WINDSCREEN BLOWOUT

 The aircraft, captained by 42-year-old, who had logged 11 050

flight hours, and copiloted by 39-year-old, who had logged
7500 flight hours, was a BAC One Eleven Series

 The aircraft took off at 7:20am local time, with 81 passengers, four
cabin crew and two flight crew

 The plane had climbed to 17,300 feet (5,270 m) over Didcot, Fig. 10 - Incorrect windscreen retention bolts;
(too small) led to the windshield blowout.
Oxfordshire. Suddenly, there was a loud bang, and the fuselage Video - https://www.youtube.com/watch?v=6SI2V_DbCTw

quickly filled with condensation

 The left windscreen, on the captain's side of the cockpit, had separated from the forward fuselage

 The Captain was jerked out of his seat by the rushing air and forced head first out of the cockpit, his knees snagging
onto the flight controls.
Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 23
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

2. INCIDENTS AND ACCIDENTS ATTRIBUTABLE TO HUMAN FACTORS / HUMAN ERROR

 In all of these incidents, the engineers involved were considered by their companies to be well
qualified, competent and reliable employees. All of the incidents were characterised by the
following:
• There were staff shortages;
• Time pressures existed;
• All the errors occurred at night;
• Shift or task handovers were involved;
• They all involved supervisors doing long hands-on tasks;
• There was an element of a “can-do” attitude;
• Interruptions occurred;
• There was some failure to use approved data or company procedures;
• Manuals were confusing;
• There was inadequate pre-planning, equipment or spares.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 24
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

2. INCIDENTS AND ACCIDENTS ATTRIBUTABLE TO HUMAN FACTORS / HUMAN ERROR

 In all of the examples, the accident or incident was preventable and could have been avoided if
any one of a number of things had been done differently

 As with many incidents and accidents, all the

examples involved a series of human factors
problems which formed an error chain

 If any one of the links in this ‘chain’ had been broken

by building in measures which may have
prevented a problem at one or more of these
stages, these incidents may have been prevented. Fig. 11 - The Error Chain

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 25
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

3. MURPHY’S LAW

 There is a tendency among human beings towards complacency

 The belief that an accident will never happen to “me” or to “my Company” can be a major problem when
attempting to convince individuals or organisations of the need to look at human factors issues, recognise risks
and to implement improvements

“Murphy’s Law” can be regarded as the notion:

“If something can go wrong, it will.”
 If everyone could acknowledge Murphy’s Law, this might help overcome the “it will never happen to me” belief that
many people hold

 It is not true that accidents only happen to people who are irresponsible or ‘sloppy’. The incidents and accidents
described show that errors can be made by experienced, well-respected individuals and accidents can occur in
organisations previously thought to be “safe”.

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 26
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 27
Revision No.: 00 Status: Draft
 MODULE 9 - HUMAN FACTORS
9.1 Human Factors General

LIST OF REFERENCES

 https://nbaa.org/aircraft-operations/safety/human-factors/
 https://www.aerotime.aero/18542-history-hour-aloha-airlines-flight-243-incident
 https://admiralcloudberg.medium.com/the-near-crash-of-british-airways-flight-
5390-89a4370c92bb
 http://avionics-system-design.blogspot.com/2013/12/ergonomics-of-aircraft-
cockpit.html
 https://slideplayer.com/slide/9938661/
 http://www.dviaviation.com/engine-failures.html

Issue No.:
Original Author: JTS 01 Date: 09 January 2021 FOR TRAINING PURPOSES ONLY Slide No. 28
Revision No.: 00 Status: Draft