Aircraft Calibration

How HyPlan’s aircraft performance models are derived from in-situ field-campaign data.

What “calibrated” means

For each calibrated platform, the following parameters in hyplan/aircraft/_models.py come from per-altitude-bin medians of real flight data rather than manufacturer brochures:

• climb_profile and descent_profile (VerticalProfile) — active-VS bin medians (5-kft bins, n≥30/bin) from sustained- climb and sustained-descent fixes. “Active” means vertical_rate * sign ≥ ACTIVE_VS_THR_FPM, where the threshold is per-aircraft (1500 fpm for jets and most turboprops, 1000 fpm for the B-200, 500 fpm for the Twin Otter).

• climb_schedule / cruise_schedule / descent_schedule (TasSchedule) — per-phase TAS-vs-altitude medians at the same 5-kft binning, anchored at the typical rotation TAS at SL and picked at aircraft-specific target altitudes.

• turn_model.max_bank_deg — usually max(AFM normal-ops 30°, data p90) of |roll_deg| over fixes with |roll| > 5°.

• approach_speed — median TAS in the last ~500 ft AGL with vertical_rate < -200 fpm.

• service_ceiling — operational p99 of per-sortie peak altitudes (not the certified service ceiling at MTOW).

• sources (SourceRecord) — campaign / archive citation + number of sorties + confidence.

We don’t enforce monotonicity on climb_profile / descent_profile. Jets and turboprops typically peak ROC near FL050-FL100 (limited below by 250-KCAS ATC procedures); descent VS typically peaks around FL150-FL200 (descent at VMO in CAS) and then declines in the upper levels (Mach-limited descent at constant M). Clamping these to monotone shapes pushes bins outside their IQRs and obscures the real envelope, so the calibration step ships the raw bin medians and lets reviewers see the shape directly.

Calibration status

Each aircraft class exposes its provenance via the Aircraft.calibration_status attribute, with values "calibrated", "inferred", or "uncalibrated" corresponding to the Status column below.

Aircraft class	Status	Source	Sorties	Notebook
NASA_ER2	calibrated	NASA AFRC IWG1	cache-dependent	NASA_ER2/calibration.ipynb
NASA_GIII	calibrated	NASA ASP archive IWG1	~152	NASA_GIII/calibration.ipynb
NASA_GV	calibrated	NASA ASP archive IWG1	~84	NASA_GV/calibration.ipynb
NASA_WB57	calibrated	NASA ASP archive IWG1	~100	NASA_WB57/calibration.ipynb
NASA_C130	calibrated	NASA ASP archive IWG1 (ACT-America)	~91	NASA_C130/calibration.ipynb
NASA_P3	calibrated	NASA ASP archive IWG1	~252	NASA_P3/calibration.ipynb
NOAA_WP3D	calibrated	NOAA CSL ICARTT (ARCPAC 2008, CalNex 2010, SENEX 2013, SONGNEX 2015)	~18	NOAA_WP3D/calibrate.py
KingAirB200	calibrated	NASA ICARTT (ACTAMERICA, DISCOVER-AQ, KORUS-AQ, LMOS)	250	KingAirB200/calibration.ipynb
NOAA_TwinOtter	calibrated	NOAA FIREX-AQ + NOAA CSL ICARTT (TopDown 2014, UWFPS 2017, CalFiDE 2022, AEROMMA 2023, AMMBEC 2024, USOS 2024)	~164	NOAA_TwinOtter/calibrate.py
NCAR_GV	calibrated	NSF/NCAR HIAPER ICARTT NAV (DC3 2012, LaRC ASD); TAS reconstructed via wind triangle	~22	NCAR_GV/calibrate.py
FAAM_BAe146	calibrated	FAAM Core Data Product 1 Hz, CEDA archive 2017-2024 (27 ASMM-tagged campaigns: DCMEX, ACSIS/ARNA, MPHASE, CCREST, CLARIFY, ACRUISE, ICE-D, WESCON, …)	125	FAAM_BAe146/calibrate.py
SAFIRE_ATR42	calibrated	CEDA EUFAR (TAS reconstructed via wind triangle; 7 transnational-access projects) + AERIS EUREC4A 2020 (native TAS)	44	SAFIRE_ATR42/calibrate.py
DLR_HALO	calibrated	DLR HALO BAHAMAS (HALO-AC3 2022, Arctic, single campaign — confidence 0.7)	18	DLR_HALO/calibrate.py
BAS_TwinOtter	calibrated	BAS MASIN core nav, CEDA: OFCAP 2010-2011 (23) + ACCACIA 2013 (34) + ORCHESTRA 2017-18 (22) + IGP 2018 (14) + ArcticCyclones 2022 (15)	105	BAS_TwinOtter/calibrate.py
NERC_DO228	calibrated	NERC ARSF D-CALM CEDA: ACTIVE 2005-2006 NetCDFs + Eyjafjallajökull 2010 ARSF CSV (TAS reconstructed via wind triangle)	34	NERC_DO228/calibrate.py
NASA_C20A	inferred	Mirrored from NASA_GIII (same type certificate)	—	(deferred — see below)
NASA_GIV	uncalibrated	Manufacturer brochure	—	—
NASA_B777	uncalibrated	Manufacturer brochure	—	—
KingAirA90	calibrated	airplanes.live ADS-B (30-day archive, skydive-filtered)	428	KingAirA90/calibrate.py
KingAir350	calibrated	airplanes.live ADS-B (UWKA-2 single-tail, science-campaign sample)	22	KingAir350/calibrate.py

Sortie counts may shift as data deliveries refresh. See each notebook’s §1 summary table for the current count.

Data sources

HyPlan’s calibrated performance models draw on a handful of public archives. The table below groups aircraft by source archive, auto-generated from the live class definitions by python -m docs._gen_fleet_tables.

Archive / source	Aircraft	Citation	Notes
NASA AFRC IWG1	NASA_ER2	link	Armstrong Flight Research Center IWG1 / nav telemetry. Used for ER-2.
NASA Airborne Science Program archive	NASA_GIII, NASA_GV, NASA_P3, NASA_WB57, NASA_C130	link	Public asp-archive.arc.nasa.gov IWG1 archive. Used for G-III, G-V, WB-57, P-3, C-130.
NASA ICARTT campaign archive	KingAirB200	link	Multi-campaign NASA ICARTT data (ACT-America, DISCOVER-AQ, KORUS-AQ, LMOS). Used for KingAirB200.
NOAA CSL ICARTT	NOAA_WP3D, NOAA_TwinOtter	link	ICARTT archive of NOAA Chemical Sciences Laboratory chemistry missions. Used for NOAA_TwinOtter (6 campaigns) and NOAA_WP3D (4 campaigns).
NASA FIREX-AQ	NOAA_TwinOtter	link	Firefighter EXperiment for Air Quality 2019. Used for the original NOAA_TwinOtter calibration.
NSF/NCAR HIAPER	NCAR_GV	link	NSF/NCAR HIAPER (N677F) DC3 ICARTT NAV files via LaRC ASD. TAS reconstructed via wind triangle. Used for NCAR_GV.
CEDA FAAM	FAAM_BAe146	doi:10.5285/86433ad261a64a82a3b7b56ed29e4717	FAAM Core Data Product 1 Hz NetCDFs from CEDA, 2017-2024 ASMM-tagged campaigns. Used for FAAM_BAe146.
CEDA EUFAR	SAFIRE_ATR42	link	European Facility for Airborne Research transnational-access archive. Used for SAFIRE_ATR42 (7 EUFAR projects).
AERIS EUREC4A	SAFIRE_ATR42	doi:10.25326/162	French AERIS portal — EUREC4A 2020 SAFIRE ATR-42 L2 1 Hz NetCDFs.
CEDA BAS MASIN	BAS_TwinOtter	doi:10.5285/8be3dd7cdf44090d89aeb8f105421506	British Antarctic Survey MASIN core nav across 5 campaign archives (OFCAP, ACCACIA, ORCHESTRA, IGP, ArcticCyclones).
DLR HALO BAHAMAS	DLR_HALO	doi:10.1594/PANGAEA.967719	DLR HALO native sensor system. Used for DLR_HALO (HALO-AC3).
CEDA NERC ARSF	NERC_DO228	doi:10.5285/d2c5c36981824b71a98a2906394d61f3	NERC Airborne Research and Survey Facility D-CALM Dornier 228 (ACTIVE 2005-2006 + Eyjafjallajökull 2010). TAS reconstructed via wind triangle.
AWI PANGAEA Polar 5/6	AWI_BaslerBT67	doi:10.1594/PANGAEA.902849	Alfred Wegener Institute Basler BT-67 nav/met. Used for AWI_BaslerBT67.

Adding a new aircraft from one of these archives is mostly a matter of writing a per-source loader; the shared recipe in notebooks/calibration/_common.py handles filtering, phase labeling, and binning. Adding a new source archive means writing a fetcher (auth and idempotent download) plus a loader that returns a DataFrame with the canonical columns (timestamp, altitude, vertical_rate, tas_kt, optionally roll_deg, pitch_deg, heading_deg, groundspeed).

Methodology

Each calibration.ipynb notebook follows the same recipe (the ER-2 notebook predates this builder pattern but the structure is the same):

1. Load every IWG1 / ICARTT file from the campaign directory, trim ground taxi (or fall back to altitude-only airborne detection when groundspeed is missing).

2. Filter sorties on duration (60–600/900 min, per-aircraft) and peak altitude (per-aircraft floor and ceiling), drop sorties with no valid altitude or vertical rate.

3. Phase-label each fix as climb / cruise / descent from vertical_rate against ±300 fpm gates.

4. Bin climb / descent fixes by 5-kft altitude bin and compute median, p25, p75 of vertical rate.

5. Bin TAS the same way for each phase.

6. Pick breakpoints at aircraft-specific target altitudes; anchor SL at typical rotation / approach TAS so the SL point isn’t contaminated by takeoff-roll or pattern fixes.

7. Validate by overlaying the proposed VerticalProfile on the per-bin IQR + median plot.

8. Emit a paste-ready cell with the calibrated constants, SourceRecord, and labeled service_ceiling / approach_speed so it’s clear which numbers are operational vs aircraft- intrinsic.

Shared helpers live in notebooks/calibration/_common.py: label_phases, apply_sortie_filters, per_bin, tas_per_bin, schedule_pts, evaluate_profile, summary_table. The aircraft-specific knobs (active-VS threshold, target altitudes, rotation TAS, hold bands for the ER-2) stay in the per-aircraft builder.

Operational vs aircraft-intrinsic numbers

Several reported metrics describe operational behavior across the sortie set rather than aircraft-intrinsic performance:

• Wall-clock time-to-cruise (TOC) includes pre-cruise level-offs, ATC routing, and weight-management step climbs. Reviewers should not read TOC variance as a performance bound; the planner’s modeled TOC comes from integrating the calibrated climb_profile, which excludes those operational delays.

• service_ceiling as shipped is the operational p99 of per-sortie peak altitudes for the mission mix. This is below the airframe service ceiling under MTOW (e.g., B-200 ships 30000 ft vs 35000 ft brochure; Twin Otter ships 17500 ft vs 25000 ft brochure). Each calibration notebook explicitly labels this in its paste-ready cell.

• approach_speed is the median final-approach TAS for the mission mix. The Twin Otter notebook’s 105 kt is on the high side of the DHC-6’s 80–90 kt typical AFM approach, reflecting the NOAA mission profile.

Performance envelope cross-check

Each calibrated aircraft was cross-checked against manufacturer brochures and published specifications. This section summarizes the comparison so users can judge confidence in HyPlan’s planning output and so reviewers can see exactly which numbers come from data, which from brochures, and where the two diverge.

Most discrepancies trace to the operational context discussed above: HyPlan’s service_ceiling is op-p99 of the actual mission mix (typically below the certificated AFM ceiling at MTOW); cruise schedules reflect the research-mission profile (often slow-cruise dwell over plumes); the approach-speed measure is final-descent TAS at light-fuel landing weight, which can sit above the certificated Vref for some types and below for others.

Calibrated platforms — consistent with brochure

Class	Ceiling	Cruise	Approach
NASA_ER2	70k ft ✓	401 kt @ FL650 (M0.65) ✓	130 kt ✓
NASA_GIII	45k ft ✓	472 kt @ FL300 (M0.80) ✓	139 kt ✓
NASA_GV	51k ft ✓	M0.80 cruise ✓	126 kt — below 130-140 Vref; light science fuel state
NASA_P3	27k ft (op-p99 vs 28k brochure) ✓	333 kt @ FL200 ✓	132 kt ✓
NASA_WB57	63k ft (op-p99) ✓	382 kt @ FL550 (M0.65) ✓	117 kt — below 130 Vref; light science fuel state
NASA_C130	28k ft (op-p99 vs 30k brochure) ✓	305 kt @ FL200 ✓	126 kt ✓
KingAirB200	30k ft (op-p99 vs 35k brochure) ✓	239 kt @ FL250 ✓	112 kt — above 100 brochure; mission profile
NCAR_GV	51k ft ✓	M0.80 ✓	141 kt ✓
NOAA_WP3D	27.6k ft (op-p99 vs 28k) ✓	343 kt plateau @ FL200+ ✓	132 kt ✓
NOAA_TwinOtter	17.5k ft (op-p99 vs 25k brochure) ✓	142 kt @ FL100 ✓	105 kt — above 75-80 brochure Vref; NOAA mission
BAS_TwinOtter	14.6k ft (polar BL ops) ✓	141 kt @ FL100 ✓	95 kt — above 75-80 Vref
FAAM_BAe146	34.5k ft vs 35k brochure ✓	369 kt @ FL300 (M0.62) — slow vs brochure M0.70; FAAM science profile	121 kt ✓
SAFIRE_ATR42	24.7k ft vs 25k brochure ✓	227 kt @ FL150 — slow vs 265 brochure max cruise; EUFAR survey	117 kt ✓
AWI_BaslerBT67	25k ft ✓	186 kt @ FL100 ✓	90 kt ✓
KingAirA90	25k ft (op-p99 vs 26.4k POH) ✓	222 kt @ FL160 ✓ vs 226 kt @ FL150 brochure	149 kt — TAS in last 500 ft AGL during descent; AFM Vref 95-100 KIAS
KingAir350	35k ft ✓	318 kt @ FL330 ✓ (vs brochure 312 @ FL280; UWKA-2 has Blackhawk XP-67A upgrade)	110 kt (brochure retained — single-tail descent sample artifacts above FL200)

Calibrated platforms — known artifacts

These aircraft have published values that trace to identifiable sample-size or selection artifacts. None block release; flagged here so reviewers and users planning around these envelopes know where the calibration is on thinner ice.

• NOAA_GIV — service_ceiling=47500 ft exceeds the certificated G-IV-SP brochure ceiling of 45000 ft. Op-p99 over the 93-sortie hurricane-surveillance sample where the airframe was light enough to overshoot AFM in practice. Realistic for the NOAA mission mix but worth noting.

• NERC_DO228 — cruise schedule decreases above FL100 (176 kt → 146 kt by FL200), which is unphysical for a turboprop. Small-sample artifact at the upper bins (n=34 sorties across two CEDA campaigns; the FL150-FL200 cruise bins are populated by fewer than 200 fixes). Approach speed 110 kt is also above the 80-90 kt brochure Vref. Queued for v1.6.1 (truncate cruise schedule at FL100 or add caveat).

• DLR_HALO — cruise schedule is implausibly flat at 457 kt through FL200-FL300; the brochure long-range cruise band starts above FL400 and a G550 climbing through these levels should see ~360 kt @ FL200 and ~430 kt @ FL300. 18-sortie HALO-AC3 sample is heavily biased toward high-altitude transit, and sub-FL300 bins are populated by descent fixes mislabeled as cruise. The class already ships with confidence=0.7 reflecting the single-campaign sample size. Queued for v1.6.1 (truncate cruise schedule below FL300).

Uncalibrated brochure values — reasonableness

Class	Source	Notes
NASA_GIV	G-IV-SP brochure	Coherent: 45k ceiling, M0.80 cruise, 5130 nm range
NASA_C20A	Mirrors NASA_GIII	Coherent (same airframe + type certificate)
NASA_B777	777 brochure	Generic; suitable for transit-style planning

Deferred calibrations

One aircraft class remains on inferred values because its public data source is auth-walled:

• NASA_C20A (NASA 502, AFRC G-III variant) — currently inferred from NASA_GIII (same airframe + type certificate). No public ICARTT/IWG1 nav data; AFRC mission ops contact required for NASDAT housekeeping logs.

Order of effort if access becomes available: C-20A (only meaningful if AFRC ops shares data) → A-90 (wind-derivation last resort). NCAR_GV (HIAPER) was deferred in earlier releases but is now calibrated against 22 NSF-GV ICARTT NAV sorties from DC3 2012 (LaRC ASD); see the row above.

Conventions

• Active-VS thresholds (per-aircraft):

  • Jets and most turboprops: 1500 fpm

  • King Air B-200: 1000 fpm (climb rates drop below 1500 fpm above FL150; the lower threshold extends bin coverage to FL250-FL280)

  • Twin Otter: 500 fpm (slow climber; 1500 fpm loses everything above FL050, 800 fpm cuts off above FL100)

• 5-kft bin width is universal; smaller bins thin the per-bin sample below the n=30 floor at high altitude.

• n≥30/bin floor for VS bins; n≥50–200/bin for TAS bins (per-aircraft, set in the builder).

• n≥30/bin for active-VS keeps every bin that survives contamination filtering above autopilot precision.

• The ER-2 notebook excludes weight-management hold bands (FL220–FL260, FL240–FL280, FL336–FL376) when computing active-climb medians so sortie-specific level-offs and holds do not depress the aircraft-intrinsic climb profile.

• Default confidence=0.85 for data-fit calibrations, confidence=0.7 for inferred-from-sibling values.

• max_bank_deg ships as max(AFM normal-ops 30°, data p90) so the planner uses a bank that the aircraft is willing to fly, not the typical-mix median or a steep-turn / emergency value.