# Human Factors in Aviation

> Core models and definitions of human factors in aviation.

- **Subject:** 040 — Human Performance Limitations
- **Section:** 040-01 — Human Factors: Basic Concepts
- **Topic code:** 040-01-01
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/human-performance-limitations/human-factors-basic-concepts/human-factors-in-aviation/

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## Definition

![NTSB discusses human factor issues in general aviation](https://upload.wikimedia.org/wikipedia/commons/5/58/NTSB_discusses_human_factor_issues_in_general_aviation_%2814797380573%29.jpg)

Human Factors is the discipline that studies the capabilities and limitations of the human being and applies this knowledge to the design of tools, machines, systems, tasks, jobs, and environments for safe, comfortable, and effective human use.

## The SHELL Model
Proposed by Edwards (1972) and modified by Hawkins (1975), it illustrates the interaction between the human and other components.
*   **L (Liveware)**: The human operator (Center of the model). The most critical and flexible component, but also the most error-prone.
*   **S (Software)**: Procedures, checklists, manuals, symbology, computer programs.
*   **H (Hardware)**: The aircraft, equipment, tools, physical controls.
*   **E (Environment)**: The context in which the system operates (cockpit environment, weather, social pressure, economic climate).
*   **L (Liveware - Peripheral)**: Other humans (crew, ATC, maintenance, passengers).

**Interfaces**: Mismatches at the interfaces (e.g., L-H, L-S) are common sources of error.
*   **L-H**: Designing a seat that fits the pilot, controls that are reachable.
*   **L-S**: Writing checklists that are easy to read and unambiguous.
*   **L-L**: Crew Resource Management (CRM), communication.

## The "Dirty Dozen"
Dupont defined 12 factors that degrade human performance:
1.  Lack of communication
2.  Complacency
3.  Lack of knowledge
4.  Distraction
5.  Lack of teamwork
6.  Fatigue
7.  Lack of resources
8.  Pressure
9.  Lack of assertiveness
10. Stress
11. Lack of awareness
12. Norms

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