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TWG debates measurement approach for gap/oceanic departures; leans toward noise monitoring below 3,000 ft
Summary
Panelists discussed whether to score carriers on altitude gates (e.g., meeting 3,000-foot minimums) or by ground-level noise during the first climb. The group favored starting with noise measurements below 3,000 feet and using exceedance/stack-rank analysis to identify outliers for airline engagement.
The working group spent substantial time on how to evaluate Transpacific "gap" departures, including whether to use altitude gate compliance or direct noise monitoring as the performance metric. One technical participant reported having pulled a single-day sample showing "87 flights" on the gap departure, demonstrating there is enough sample size to analyze airline behavior.
Multiple members recommended measuring noise during the first phase of climb (below 3,000 feet) and using exceedance-percentile analysis (for example the top decile of noise events) to identify operators that deviate from expected behavior. As Moderator framed it: "We're gonna look at the noise level for the 1st 3,000." Speakers suggested stack-ranking carriers at the same monitor for comparable aircraft types and then using outlier analysis to direct targeted airline engagement.
Operational implications: the group discussed practical monitoring (five to six monitors in the gap), how to control for aircraft type, and whether to use proxy metrics (fastest to 2,800 ft) as a simple surrogate. Staff and technical members recommended beginning with noise monitoring, then layering altitude gates and aircraft-type adjustments as needed.
