Every source behind the digital twin

The model is only worth what its inputs are worth, so this is the complete list — 39 sources across regulation, standards, programme documents, property data and journal literature. Each entry says what we actually took from it. Where we cannot publish a document, it is still listed, with its marking, so that a figure resting on it can be challenged rather than quietly trusted.

9hosted here

17third party

8purchase

5not published

On the restricted sources. The Bristol Airport ACT programme documents were provided for use inside the HyFlux project team only. We do not host them, link them, or quote them at length. They appear here because a reader is entitled to know which numbers depend on material they cannot see — and because the Bristol Airport ACT programme, not HyFlux, decides when that changes.

Regulatory and safety framework

The CAA Hydrogen Challenge set is the spine of the safety case. CAP 3284A defines the standard hazard HC.LH2 1.3 (SP) and the single top event our bowtie work aligns to.

CAP3284A open Read →

CAP 3284A — Bowtie Analysis: Aircraft Refuelling

UK Civil Aviation Authority · July 2026 · 22 pp · OFFICIAL-Public

Used for — Hazard framework; standard hazard HC.LH2 1.3 (SP); barrier taxonomy

CAP3284E open Read →

CAP 3284E — Regulations Relevant at Aerodromes Utilising Hydrogen

HSE for the UK CAA (lead author H. Brocklehurst) · July 2026 · 60 pp · OFFICIAL-Public

Used for — COMAH 2015, DSEAR 2002, PSSR 2000, PESR, CDM applicability

CAP3284F open Read →

CAP 3284F — Regulations Infographic

UK Civil Aviation Authority · July 2026 · one page · OFFICIAL-Public

Used for — Regulatory map, orientation

CAP3284D open Read →

CAP 3284D — supporting material

UK Civil Aviation Authority · July 2026 · web format

Used for — Supporting detail to the Hydrogen Challenge set

CAP3284 not published Held under project NDA

CAP 3284 — Hydrogen Sandbox Summary Report

CAA / Baringa · July 2026 · 25 pp · 13 sandbox projects

Marking: client-confidential

Used for — Trial precedent (Heathrow P601, Exeter Zero Carbon Turn, Qdot); the Exeter data-yield lesson behind our metering ask

COMAH2015 third party Publisher →

Control of Major Accident Hazards Regulations 2015

UK Government · 2015

Used for — Inventory tiering — 5 t lower, 50 t upper, 2 t controlled quantity

Bristol Airport ACT programme documents

Provided by Bristol Airport on 25 September 2026 for use inside the HyFlux project team only. Four of the five carry restrictions and are NOT published here. They are listed so that every figure drawn from them can be traced, challenged and, if necessary, withdrawn.

JAC not published Held under project NDA

BRS Hydrogen Report

Jacobs · 2025 · 171 pp · Final Draft

Marking: Final Draft — publication status unconfirmed

Used for — Demand forecasts to 2060; tube trailer 1,016 kg; liquefier scale ladder 15 kWh/kg at 5 TPD and 11 at 15–30 TPD; bowser refill 16.7 kg/min; the 9-minute fixed refuelling steps; turnaround scenarios 32/42–48/53–60 min; NFPA separation set; COMAH milestones 2027 and 2047

ARC not published Held under project NDA

ARC-019-139-R001 Safety Review of Concept of Operations

Abbott Risk Consulting for Jacobs UK · November 2025 · 70 pp · issued as Issue 0 draft for workshop reading

Marking: draft — pre-workshop

Used for — Bowtie scope and top-event choice; DDT confinement risk between refueller and aircraft; LOX-on-tarmac; the finding that industrial hydrogen good practice does not transfer to the apron; the open passenger/crew question

EQF not published Held under project NDA

EQ-R-0037 Application of Eq.flight, Nuclear-derived SAF and Hydrogen Technology

Equilibrion Limited · 8 March 2026 · 56 pp

Marking: COMMERCIAL IN CONFIDENCE — written permission required before disclosure to any third party

Used for — Context only. Contains no liquefaction, cryogenic or boil-off content. Its energy figures are not used.

UF not published Held under project NDA

Liquid hydrogen refuelling feasibility study — technical report

Ultima Forma · September 2025 · 24 pp

Marking: publication status to confirm

Used for — Small-system boil-off 3 %/day; reliquefier 10.8 kWh/kg; 112 mm vacuum-insulated line; release rates 0.7 and 1.7 kg/s — the only release rates in any source

ACN open Read →

Project Acorn Summary Report — the UK's first airside hydrogen refuelling trial

Project Acorn consortium (easyJet, Cranfield, Connected Places Catapult, Jacobs, IAAPS, DHL, CAA) · July 2024 · 15 pp · public summary

Used for — Real trial precedent — 60 kg stored, 175 bar, 6 m in-use safety zone

Aviation hydrogen programmes

FLYZERO third party Publisher →

FZO-CST-POS-0035 — Airports, Airlines and Airspace Operations and Hydrogen Infrastructure

FlyZero / Aerospace Technology Institute · 2022

Used for — Fill-rate cases (Table 12, two 6″ hoses at 5 m/s); safety zones 20 m connect and 8 m flow; the 2-day buffer stock rule

NAPKIN open Read →

Project NAPKIN — Final Report

NAPKIN consortium (Rolls-Royce, GKN, Cranfield Aerospace, Heathrow, London City) · 2022 · 122 pp

Used for — UK domestic ZE route economics; demand and airline behaviour

NAPKIN_PAGES open Read →

Project NAPKIN — figure set

NAPKIN consortium · 2022

Used for — Presentation-format companion

Standards — fuelling interface and safety

AIR8466 / ER-034 is the only PUBLISHED aviation hydrogen fuelling baseline. The high-flow work that our fast-turnaround cases depend on is still unpublished, which is why the model gates those cases rather than claiming them.

AIR8466 purchase Publisher →

SAE AIR8466 / EUROCAE ER-034 — Hydrogen Fuelling Stations for Airports, Gaseous and Liquid

SAE International / EUROCAE · PUBLISHED

Used for — The reference fuelling envelope our rate gate tests against

AIR8999 purchase Publisher →

SAE AIR8999 — high-flow LH₂ couplings

SAE International · IN DEVELOPMENT

Used for — The missing enabler. Our 5 and 10 kg/s cases sit above the published envelope and depend on this.

AIR8547 purchase Publisher →

SAE AIR8547 — LH₂ aircraft ground-handling procedures

SAE International · IN DEVELOPMENT

Used for — Ground-handling sequence

AIR8833 purchase Publisher →

SAE AIR8833 — airport LH₂ infrastructure interface

SAE International · IN DEVELOPMENT

Used for — Infrastructure interface

AIR7765 purchase Publisher →

SAE AIR7765 — hydrogen refuelling envelope

SAE International · IN DEVELOPMENT

Used for — Baseline single-hose fill rate (0.8 kg/s)

ISO17268 purchase Publisher →

ISO 17268-1:2025 — gaseous hydrogen land vehicle refuelling connection devices

ISO

Used for — GH₂ transfer rate 120 g/s (with SAE J2601)

ISO14687 purchase Publisher →

ISO 14687 / SAE J2719 — hydrogen fuel quality

ISO / SAE International

Used for — 99.97 % purity requirement for PEM fuel cells

NFPA2 purchase Publisher →

NFPA 2 — Hydrogen Technologies Code

National Fire Protection Association · 2023

Used for — Separation distances. Note its bulk LH₂ guidance stops at 283.9 m³ (~20.1 t); Bristol exceeds that in 2034, beyond which no published basis exists.

Thermophysical property data

This is the only layer of the model that is VERIFIED against an external authority. CoolProp is cross-checked against NIST REFPROP with deviation ≤0.0002 %.

REFPROP third party Publisher →

NIST REFPROP — Reference Fluid Thermodynamic and Transport Properties Database

National Institute of Standards and Technology

Used for — Para-hydrogen property cross-check; the validation evidence pack

LEACHMAN third party Publisher →

Leachman, Jacobsen, Penoncello & Lemmon (2009) — Fundamental equations of state for parahydrogen, normal hydrogen and orthohydrogen

J. Phys. Chem. Ref. Data 38(3) · 2009

Used for — The equation of state behind every LH₂ property in the model

COOLPROP third party Publisher →

CoolProp — open-source thermophysical property library

Bell, Wronski, Quoilin & Lemort

Used for — Runtime property evaluation

Journal literature

BAE2021 open Read →

Bae et al. (2021) — Multi-objective optimisation of hydrogen liquefaction integrated with LNG

Energy Conversion & Management 231:113835 · 2021

Used for — Liquefaction cycle efficiency and figure-of-merit context

ALVAREZ2012 open Read →

Alvarez et al. (2012) — Greater focus needed on methane leakage (supporting information)

PNAS 109(17) · 2012

Used for — Indirect GHG accounting for leakage; blue-pathway upstream treatment

Emission factors and accounting standards

DEFRA third party Publisher →

UK Government GHG Conversion Factors for Company Reporting

DEFRA / DESNZ · 2025

Used for — Jet A1 baseline, grid intensity, road freight factors

GHGP third party Publisher →

GHG Protocol Corporate Value Chain (Scope 3) Standard

WRI / WBCSD

Used for — Category 3 (fuel- and energy-related) and Category 11 (use of sold products)

Sources cited within the ACT documents

We have not read these directly. They are recorded because figures we use rest on them, and a reader challenging a number should know where the chain actually ends.

DECKER2019 third party

Decker (2019) — LH₂ road trailer transfer rates