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

Status: Implemented (divert estimate; landing-zone energy remains TAS-only)

Problem

Both the landing-zone reachability check (estimator/execution/landing_zone.py) and the divert route estimate (estimator/execution/divert.py) compute 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. _divert_energy_wh in landing_zone.py applies the same correction.
  3. When no wind provider is available the behaviour is unchanged (TAS-only, no regression).
  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.