Line Pilot Perspectives on Complexity of Terminal Instrument Flight Procedures [2016]

Chandra, Divya C; Markunas, Rebecca · 2016 · ROSA P / John A. Volpe National Transportation Systems Center (U.S.)

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Summary

This study investigates the subjective complexity of Performance Based Navigation (PBN) Instrument Flight Procedures (IFPs) from the perspective of line pilots. As the United States transforms its airspace to improve safety and efficiency, new IFPs are being implemented, yet operational integration often encounters difficulties. While previous research focused on objective design parameters or visual chart complexity, this work aims to understand what makes IFPs difficult for pilots in practice, defining subjective complexity as any factor requiring extra mental or physical steps. The researchers conducted qualitative interviews with 45 professional instrument-rated pilots from major airlines, regional carriers, and corporate operators. Participants were grouped by operator and aircraft type and met in small groups to review, brief, and discuss six specific IFPs (including SIDs, STARs, and IAPs) using Jeppesen charts in an office setting. The study observed pilot briefing techniques and gathered feedback on what makes procedures and charts difficult to use. Data were analyzed using a rubric to categorize responses into operational factors, IFP design issues, and chart design issues. The findings identified three primary drivers of complexity. First, operational complexity factors outside designer control—such as Air Traffic Control interventions, aircraft equipment limitations, weather, and crew fatigue—significantly impact workload. Second, IFP design parameters were the main source of subjective complexity; specific issues included excessive speed and altitude constraints, multiple flight path transitions, ambiguous waypoint names, and non-smooth energy profiles. Third, chart design issues arose when IFP parameters forced novel visual depictions, such as non-contiguous paths using insets or inconsistent placement of notes. The study also highlighted cross-cutting issues like visual density and inconsistencies in how data (e.g., altitudes) are depicted across different procedure types. The authors propose a subjective complexity framework linking IFP design, chart design, and operational factors. They recommend that IFP designers minimize path constraints and transitions, ensure smooth energy profiles, and use pronounceable waypoint names. Chart designers should prioritize notes based on action versus awareness and clarify guidance for splitting complex procedures. Additionally, designers should account for operational variability and aircraft equipment differences rather than assuming ideal conditions. These insights aim to improve the human factors alignment of PBN implementation, reducing pilot workload and confusion during terminal operations.

Key finding

IFP design parameters, particularly the number of transitions and flight path constraints, are the primary drivers of subjective complexity for line pilots.

Methodology

lab_experiment

Sample size: 45

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• mental demand