Human Performance and Limitations

1. The Knowledge Requirement

Part 2 of the Air Regulations book is designed to meet the ICAO requirements of human factor knowledge for the flight crew. The relevant portions of the information are also useful to other key aviation personnel:

• Cabin Crew
• Air Traffic Controllers (ATCs)
• Maintenance personnel

Why the Human Element Matters

The human element is the most flexible, adaptable and valuable part of the aviation system — but it is also the most vulnerable to influences which can adversely affect its performance.

Human errors are now considered as being inherent to the cognitive function of humans and are generally inescapable. A sound understanding of Human Performance and Limitations will help enhance performance and safety.

2. Disciplines Frequently Involved in Human Factors Activities

Human Factors are multidisciplinary in nature. Information is drawn from many fields:

• Psychology — to understand how people process information and make decisions.
• Psychology & Physiology — sensory processes for detecting and transmitting information.
• Anthropometry & Bio-mechanics — body measures & movement for optimizing flight deck and cabin design.
• Biology & Chronobiology — body rhythms and sleep, effects in night flying and time-zone changes.
• Statistics — proper analysis or presentation of data from surveys/studies.

Scope of Disciplines

Human Factors disciplines are inclusive of, but not limited to:

• Psychology
• Engineering
• Physiology
• Sociology
• Anthropometry

Other disciplines with active representatives in Human Factors activities include:

• Education
• Physics
• Biochemistry
• Mathematics
• Biology
• Industrial design
• Operations research

2.1 Disciplines Table (Authoritative)

2.2 Visualising the Multidisciplinary Web

flowchart TD
    HF([HUMAN FACTORS
Problem-Oriented])
    HF --> PSY[Psychology
mind & behavior]
    HF --> ENG[Engineering
design & systems]
    HF --> PHY[Physiology
body function]
    HF --> MED[Medicine
health & injury]
    HF --> SOC[Sociology
teams & groups]
    HF --> ANT[Anthropometry
body size & reach]
    HF --> OTH[Other fields:
Education, Physics,
Biochemistry, Maths,
Biology, Industrial Design,
Operations Research]

    style HF fill:#2c5aa0,stroke:#1a3a6c,stroke-width:3px,color:#fff
    style PSY fill:#e8f1fb,stroke:#2c5aa0
    style ENG fill:#e8f1fb,stroke:#2c5aa0
    style PHY fill:#e8f1fb,stroke:#2c5aa0
    style MED fill:#e8f1fb,stroke:#2c5aa0
    style SOC fill:#e8f1fb,stroke:#2c5aa0
    style ANT fill:#e8f1fb,stroke:#2c5aa0
    style OTH fill:#fff8e1,stroke:#f57c00

3. Qualities of a Professional Pilot

The source lists the following qualities of a professional pilot:

1. Situation awareness
2. Flexibility
3. Task management
4. Effective communications
5. Threat and error management
6. High sense of responsibility
7. Aircraft handling skills
8. Sound knowledge of flying theory
9. Motivation
10. Physical fitness
11. Reliability
12. Balanced personality
13. Teamwork
14. Stress management
15. Quick reflexes
16. Risk assessment capabilities
17. Decision making
18. Crew resource management

3.1 Grouping for Easier Recall

4. Causes of Aircraft Accidents

4.1 Accident Rate

4.2 Human Performance as Root Cause

Most aircraft accidents are linked to deficiencies in human performance. These deficiencies may involve a variety of factors. The factors include:

• Poor lookout
• Situation awareness (SA)
• Decision-making
• Task organization
• Communication
• Failure to recognize threats to safety
• The commission of errors

4.3 Most Common Form of Air Accident

CFIT occurs when an airworthy aircraft, under the control of a qualified pilot, is flown unintentionally into terrain, water, or an obstacle — usually with no prior awareness by the crew. Because the aircraft is functioning normally, CFIT is overwhelmingly a human factors accident category (loss of situation awareness, poor decision-making, communication breakdown, navigation errors).

flowchart LR
    A[Accident Trigger] --> B{Aircraft
Airworthy?}
    B -- No --> X[Technical Failure
Mechanical Accident]
    B -- Yes --> C{Crew Aware
of Threat?}
    C -- Yes --> D[Recoverable
or Avoidable]
    C -- No --> E[CFIT
Controlled Flight
Into Terrain]
    E --> F[Human Factors
Dominant Cause]

    style E fill:#fdecea,stroke:#c0392b,stroke-width:3px
    style F fill:#fdecea,stroke:#c0392b,stroke-width:2px
    style X fill:#fff8e1,stroke:#f57c00
    style D fill:#e8f5e9,stroke:#2e7d32

5. Human Factors — Physiological Demands & Adaptation

5.1 Environmental Changes of Greatest Physiological Significance

In aviation, the demands upon the compensatory mechanisms of the body are numerous and of considerable magnitude. The environmental changes of greatest physiological significance involved in flight are:

a) marked changes in barometric pressure,
b) considerable variation in temperature, and
c) movement at high speed in three dimensions.

The limiting factors in adjustment of the human body to flight must be appreciated.

5.2 The Body's Remarkable Adaptive Capacity

Human beings have the remarkable ability to adapt to their environment. The human body:

• Makes adjustments for changes in external temperature.
• Acclimates to barometric pressure variations from one habitat to another.
• Compensates for motion in space and postural changes in relation to gravity.
• Performs all these adjustments while meeting changing energy requirements for varying amounts of physical and mental activity.

5.3 Compensating for Reduced Oxygen Supply

The human body can adjust to acute and chronic reductions in its oxygen supply by:

1. Increasing respiratory rate
2. Chemical changes in the blood
3. Increasing the production of red blood cells

flowchart TB
    A[Reduced Oxygen Supply
Acute or Chronic] --> B[Body Compensation]
    B --> C[1. Increased
Respiratory Rate]
    B --> D[2. Chemical Changes
in Blood]
    B --> E[3. Increased
Red Blood Cell Production]
    C --> F([Restored O₂ Delivery])
    D --> F
    E --> F
    F -. Failure / Total Absence .-> G[Death in
5–8 minutes]

    style A fill:#fff8e1,stroke:#f57c00
    style B fill:#e8f1fb,stroke:#2c5aa0
    style F fill:#e8f5e9,stroke:#2e7d32
    style G fill:#fdecea,stroke:#c0392b,stroke-width:3px

5.4 Why HPL Training is Mandatory

If the accident rate is to be decreased, Human Factors issues in aviation must be:

• Better understood, and
• Human Factors knowledge more broadly and proactively applied.

6. Accident Distribution by Phase of Flight

6.1 The Headline Insight — Risk vs. Time

6.2 Phase-by-Phase Accident Percentages (DGCA chart, recreated)

6.3 Numerical Breakdown