Ticket 095: SORA Air Risk Class and SAIL Determination¶

Status¶

Implemented and hardened for the SORA 2.5-only mission.v7 contract. The command rejects incomplete footprint/airspace evidence, unsupported ARC-a and above-FL600 shortcuts, and every applied ground-risk mitigation until the necessary evidence evaluators exist.

Goal¶

Complete the SORA pre-assessment by computing the Air Risk Class (ARC) for the operational volume and combining it with the Ground Risk Class (Ticket 094) to determine the SAIL (Specific Assurance and Integrity Level) — the single output that tells a BVLOS operator how much rigour their operation must demonstrate. Produce a SORA summary report aligned with the EASA submission structure.

Why This Is High Impact¶

The SAIL is the keystone of a SORA submission. It determines which Operational Safety Objectives (OSOs) apply and at what robustness level. An operator preparing a BVLOS authorisation needs to know their SAIL before they write a single line of their operations manual.

Ticket 094 gives the Ground Risk Class. This ticket adds the Air Risk Class and the GRC × ARC → SAIL determination, turning bvlos-sim into a tool that produces the headline number of a SORA application. Together, 094 and 095 are the features most likely to make a professional operator choose this tool.

Background: ARC and SAIL¶

Air Risk Class (ARC-a … ARC-d): the likelihood of encountering manned aircraft in the operational volume, driven by airspace class, altitude band, proximity to aerodromes, and whether the volume is atypical/segregated.
SAIL (I … VI): a lookup combining the final GRC (rows) and the residual ARC (columns). Higher GRC or ARC raises the SAIL.

Scope¶

Air Risk Class inputs¶

ARC is derived from airspace context. The mission gains an optional operational airspace descriptor:

airspace:
  class: "G"                       # ICAO airspace class at operational altitude
  max_altitude_agl_m: 120.0        # worst-case whole-volume ceiling above ground
  operational_and_contingency_volume_assessment_reference: "AS-014 rev 2"
  worst_case_arc_declared: true
  aerodrome_environment: false     # explicit SORA Annex I whole-volume assessment
  atypical_or_segregated: false    # true unsupported pending authority evidence
  over_urban_area: false           # required for low uncontrolled airspace
  transponder_mandatory_zone: false # Mode-C veil or TMZ
  entirely_above_flight_level_600: false # true unsupported pending pressure-altitude evidence

The initial ARC is assigned by a deterministic rule set based on worst-case conditions across the whole operational and contingency volume. A non-blank assessment reference and explicit worst-case declaration are mandatory. ARC-a from an atypical/segregated boolean and the above-FL600 shortcut are rejected until authority and pressure-altitude evidence workflows exist.

Strategic and tactical mitigation boundary¶

Residual ARC currently equals initial ARC. A boolean strategic_mitigation claim is rejected because a reduction requires local encounter-rate evidence. Tactical mitigations satisfy the TMPR derived from residual ARC and do not lower that ARC; a bare tactical-credit declaration is likewise rejected.

SAIL determination¶

Read the final GRC from the ground-risk computation (Ticket 094).
Read the residual ARC from the airspace rule set.
Look up SAIL via the SORA GRC × ARC matrix.
Emit all 17 Table 14 OSO rows for the selected SAIL, including NR rows, an explicit required flag, note references, and operator/training-organisation/ designer dependencies with criterion references.

New `sora` command¶

Rather than overloading estimate, add a dedicated command that runs the full SORA pre-assessment and renders the report:

bvlos-sim sora mission.yaml vehicle.yaml --format markdown
bvlos-sim sora mission.yaml vehicle.yaml --format json

The command reuses the estimator (for the route + ground risk) and adds the air-risk and SAIL layers. --format markdown renders a SORA-style summary:

# SORA Pre-Assessment: alpine_demo_001

Intrinsic Ground Risk Class (iGRC): 4
Final Ground Risk Class (GRC):      4   (no mitigations applied)
Air Risk Class (ARC):               b
SAIL:                               III

Table 14 OSOs at SAIL III: OSO#01 (M, required), OSO#04 (NR), ...

New schema, enum, and module additions¶

File	Change
`schemas/mission.py`	Add optional `airspace` descriptor block
`schemas/sora.py`	SORA requirements output schema (now `sora-assessment.v3`)
`estimator/execution/air_risk.py`	ARC rule set
`estimator/execution/sail.py`	GRC × ARC → SAIL + OSO table
`adapters/commands/sora.py`	New `sora` command
`adapters/sora_markdown.py`	SORA report renderer
`adapters/sora_envelope.py`	`sora-assessment.v3` in `sora-envelope.v3` JSON
`adapters/cli.py`	Register `sora` command
`tests/test_air_risk.py`	ARC rule-set tests
`tests/test_sail.py`	SAIL matrix tests
`tests/test_sora_cli.py`	End-to-end command tests
`docs/USAGE.md`	New `## SORA Pre-Assessment` section

Dependencies¶

Requires Ticket 094 (Ground Risk Class) — the SAIL needs the GRC.
Composes with Ticket 093 (time-varying geofences) and Ticket 058 (NOTAM) for a richer airspace picture, but does not require them.

Non-goals¶

This is a pre-assessment aid, not a certified SORA determination. The output must carry a prominent disclaimer (consistent with the existing README disclaimer) that it does not replace a competent authority review.
Mitigation robustness evidence (the actual OSO compliance) is out of scope; the report lists which OSOs apply, not whether they are met.
Quantitative/PRA SORA (the numerical path) is out of scope; this ticket implements the standard qualitative table-driven SORA.

Acceptance criteria¶

bvlos-sim sora mission.yaml vehicle.yaml with complete population coverage, characteristic dimension, maximum speed, airspace descriptor, and explicit SORA 2.5 ground-risk footprint produces a SAIL value.
A class-G, low-altitude, no-aerodrome operation yields a low ARC; a near-aerodrome operation yields a higher ARC, matching the SORA airspace categorisation.
The GRC × ARC → SAIL lookup is unit-tested at every matrix cell.
A mission missing the airspace descriptor or assessed ground-risk footprint is rejected as invalid rather than producing a partial operational SAIL.
The --format markdown report lists the applicable OSOs for the determined SAIL.
The report carries the non-certification disclaimer.