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Ticket 062 — Wind-Corrected Divert and Landing-Zone Energy

Status: Implemented

Problem

Historically, both the landing-zone reachability check (estimator/execution/landing_zone.py) and the divert route estimate (estimator/execution/divert.py) computed energy cost as cruise_power_w × (distance_m / tas_mps) without wind correction. In a 10 m/s headwind the actual ground speed can be half the TAS, doubling the flight time and energy. This silently under-estimates the divert energy, which can produce an is_feasible=true result for a divert that would actually fail in a real headwind scenario.

Both functions carry docstring notes ("without wind correction") but there is no warning emitted and no machine-readable flag in the output.

Acceptance Criteria

  1. compute_divert_estimate accepts the current wind vector at the action point and applies a wind-triangle correction to compute ground speed and energy.
  2. Landing-zone reachability integrates the divert path through the active wind provider and includes terminal vertical energy to the landing surface.
  3. Direct scenario divert routing preserves its explicit TAS-only compatibility path and warning when wind correction is not requested.
  4. The divert energy field in DivertRouteEstimate is correctly higher in a headwind scenario and correctly lower in a tailwind scenario.
  5. At least 4 new tests verify headwind, tailwind, crosswind, and no-wind cases.
  6. The assumption text in the envelope ("TAS-based transit time without wind correction") is updated or removed for the affected code paths.

Scope

  • estimator/execution/divert.py — wind-corrected energy calculation
  • estimator/execution/landing_zone.py — wind-corrected energy
  • estimator/core/scenario.py — DivertRouteEstimate may need wind_speed_mps field for provenance
  • tests/test_divert_routing.py — new wind-aware tests

Notes

  • The wind at the divert action point is available from the EstimationContext.wind_provider. The scenario runner needs to pass this through.
  • Backwards compatibility: headwind cases will now show lower feasibility rates than before. Golden fixtures that involve divert scenario assertions may need regeneration.

Completion

Scenario divert routing (compute_divert_estimate) and landing-zone reachability both apply the wind-triangle correction: reachability delegates to estimate_emergency_path in energy.py, which integrates the active wind provider per segment (ground speed, not TAS) and adds terminal vertical energy to the landing surface. Tests cover headwind, tailwind, crosswind, and no-wind for both paths. The envelope assumption for landing-zone reachability, which had still described the energy as TAS-only, now describes the wind-corrected behaviour; the affected golden fixtures were regenerated. DivertRouteEstimate records wind provenance negatively, through the presence of DIVERT_ENERGY_TAS_ONLY when no wind was applied; a positive wind_speed_mps field remains an optional future addition, deferred to avoid a scenario-report.v3 contract change for a value the warning already implies.