The Effect of Altitude Upon Jet Transport Emissions of Nitrogen Oxides: A Flight and Empirical Data Study
Bibliographic record
Abstract
Consideration of aviation’s climatological impact encompasses both CO2 and non-CO2 emissions, notably contrails and nitrogen oxides (NOx). To quantify altitude-dependent NOx emissions, empirical adjustments are typically applied to sea-level (SL) engine test-cell emission indices (EINOx) to represent conditions encountered in upper troposphere–lower stratosphere (UTLS) operations. However, cruising flights involve extended durations, making altitude corrections derived from ground-based test-cell data highly extrapolative. This NRC study evaluates NOx emissions during aircraft takeoff, climb, and cruise phases (Mach 0.5 and 0.75) using corrected predictions derived from ground-based test cell measurements, applying two empirical models: the Boeing Fuel Flow Method 2 (FFM2) and the Aviation Environmental Design Tool (AEDT). Both methods predict a decreasing trend in EINOx from takeoff to climb and then cruise at Mach 0.5. However, as the cruise speed increases to Mach 0.75, the EINOx in AEDT exceed those observed during the climb phase, whereas in FFM2 they remain below climb-phase values. Comparisons between FFM2 and AEDT reveal differences of approximately 10–40%, primarily due to differing thermodynamic modeling capabilities not fully captured by FFM2. Additionally, detailed total reactive nitrogen content (NOy) emission measurements from Jet A-1, on an experimental contrail flight project conducted on 20th November 2017 were compared against AEDT and FFM2 predictions. Significant discrepancies in magnitude and trends between measured emissions and model predictions underscore the limitations inherent in current sea-level extrapolation techniques. These results emphasize the necessity for refined altitude-correction methods and targeted flight tests specifically designed to accurately measure NOx emissions across typical jet transport flight profiles, explicitly accounting for chemical transformations of NOx into reservoir species (NOy). Furthermore, the nonlinear partitioning of NOx across altitude underscores the need to explicitly account for altitude-dependent chemical transformations in future atmospheric assessments and modeling refinements.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".