Feature #1908 — FTDT Rest Rules Implementation Overview

Updated: 2026-08-08 07:02 ET · Audited: 2026-06-26 · Prepared: 2026-03-03 · Platform: .NET 10, MAUI, C# · Approach: TDD

Point-in-time planning record — do not read as current status. This captures the implementation status as of 2026-03-03 and is kept for the scoping rationale and estimates, not as a status board. Every ❌ row below has since shipped: the USA §117.25 rules (Rule_117_25_a.cs–Rule_117_25_e.cs, Rule_117_25_g.cs), the CARs rules (Rule_700_40.cs–Rule_700_43.cs), the RestRulesCalculationEngine, the rest-period UI (RestRulesInputs.razor), and the PreFDPRest_USA data model.

For live documentation of what the engine enforces today, see Calculator (USA, Part 117) and Calculator (Canadian, CARs).

Executive Summary

Feature #1908 implements rest period validation for two regulatory frameworks:

Total scope: 23 unique regulatory categories across 2 jurisdictions · 92 rest-specific test cases · 31 regulatory categories

Current Implementation Status

AreaStatus
USA FDP Limits (Table B/C)✅ Implemented (with known issues in docs)
USA §117.25 Rest Requirements❌ Entirely missing — 0% implemented
CARs FDP Limits (§700.28)✅ Implemented (basic)
CARs Rest (§§700.40–700.43)⚠️ Partial — §700.40(2) and §700.43 exceeded cases only; §700.40(1) baseline, §700.41, §700.42 missing
CARs Reserve REST (§700.70)❌ Not implemented — RAP/RDP durations exist but rest period calculations missing
Data Model: Rest properties❌ Missing from both DutyPeriod_USA and DutyPeriod_CAN
UI: Rest period controls❌ None
Results class: Rest output❌ No rest period result fields

Regulatory Coverage — USA Part 117 §117.25 (10 categories)

  1. §117.25(a) — No assignment during required rest period
  2. §117.25(b) — Weekly rest (30 consecutive hours free from duty in past 168 hours)
  3. §117.25(c) — Theater acclimation credit (36-hour rest = acclimated + weekly rest satisfied)
  4. §117.25(d) — Trans-theater home base rest (56 hours + 3 physiological nights after >60° longitude travel, >168h away)
  5. §117.25(e) — Pre-FDP rest (10-hour minimum + 8-hour sleep opportunity)
  6. §117.25(f) — Crew member self-declaration (insufficient sleep opportunity)
  7. §117.25(g) — Deadhead overage rest (rest ≥ deadhead duration, minimum 10 hours)
  8. §117.3 — Physiological night definition (0100–0700 at home base or acclimated location)
  9. §117.3 — Home base tracking (for trans-theater rest calculations)
  10. §117.3 — Deadhead transportation (duty time, not rest; not counted as flight segment)

Regulatory Coverage — CARs Division III Rest Requirements (12 categories)

  1. §700.40(1) — Baseline rest periods (12h at home base, 10h away from home OR 10h with suitable accommodation)
  2. §700.40(2) — Exceeded FDP rest minimum (FDP exceeded by ≥1 hour)
  3. §700.41 — Disruptive schedule local night's rest (late duty → early duty without 9-hour local night)
  4. §700.42 — Time zone difference rest (additional rest based on TZ change)
  5. §700.43 — Positioning rest (rest equal to positioning time)
  6. §700.50 — Split duty credit formula (FDP extension based on break duration)
  7. §700.51 — Consecutive WOCL FDP limits (restrictions on back-to-back overnight operations)
  8. §700.60(7) — Post-augmented extended FDP rest
  9. §700.61 — Long-range augmented WOCL restrictions
  10. §700.62 — Ultra long-range crew requirements
  11. §700.63(3) — Post-UOC extension rest (already partially implemented)
  12. §700.70 — Reserve operations rest (12h or 32h advance notice for WOCL assignments, 10h between RAPs)

Cross-border: USA/Canada validator interaction — ensures proper regulatory framework selection for cross-border operations.

Implementation Estimates

Option A — Manual (Traditional Development)

PhaseHoursNotes
Phase 0 — USA §117.25 (7 subsections)48Highest regulatory density; no existing code
Phase 1 — CARs §§700.40–700.43, §700.7056Complex time-zone logic; most test cases
Phase 2 — Data Model (foundation)24Must complete first
Phase 3 — FTDTRestValidator classes40TDD core; two validator classes
Phase 4 — UI + ViewModel integration32MAUI controls; multi-platform testing
Phase 5 — Calculator wiring24Wire validators into existing calculators
Phase 6 — SQLite migrations16Schema changes; relatively low risk
Phase 7 — E2E + Legal review48Includes regulatory expert review coordination
TOTAL288~7.2 weeks / 2 developers · 14–16 weeks total elapsed
PhaseHoursSavings
Phase 0 — USA §117.2522−54%
Phase 1 — CARs rest28−50%
Phase 2 — Data Model10−58%
Phase 3 — Validation Logic18−55%
Phase 4 — UI Integration20−38%
Phase 5 — Calculator wiring12−50%
Phase 6 — Database migrations8−50%
Phase 7 — E2E + Legal review34−29%
TOTAL152−47% (136 hours saved)
Recommendation: Use Option B (AI-Assisted) — 47% time savings, 6–8 weeks faster delivery, same test coverage and quality standards (TDD approach: AI must pass human-written tests). Timeline: 3 sprints (6 weeks) + 2 weeks legal review = 8 weeks to production.

AI Agent Strategy

Where AI Excels (50–58% time reduction)

Where AI Helps Less (29–38% time reduction)

Test Coverage

PhaseTest Cases
Phase 0 — USA §117.25 Rest Requirements (10 regulatory categories)28
Phase 1 — CARs Rest Requirements (12 regulatory categories)49
Phase 2 — Data Model20
Phase 3 — Validator logic20
Phase 4 — UI/ViewModel10
Phase 5 — Calculator integration10
Phase 6 — Database migrations8
Phase 7 — E2E regulatory compliance15
TOTAL160

Critical Path

Phase 2 (Data Model) — Foundation, must complete first
    ↓
Phase 3 (Validation Logic) ←→ Phase 0 (USA §117.25 specs, in parallel)
                           ←→ Phase 1 (CARs specs, in parallel)
    ↓
Phase 5 (Calculator Integration)
    ↓
Phase 6 (Database Schema)
    ↓
Phase 4 (UI Integration)
    ↓
Phase 7 (Testing + Legal Review) — 2–4 weeks elapsed time

Risk Factors

RiskSeverityMitigation
Airport coordinates data availabilityMedium (+4 hrs)Use OpenFlights dataset or free ICAO DB as embedded resource
DST-aware datetime arithmetic bugsHigh (+6 hrs)Use TimeZoneInfo.ConvertTime consistently — no manual offset math
CARs §700.42 time zone interpretation ambiguityHigh (+8 hrs)Early Transport Canada clarification; document in legal package
Legal review cycle timeMedium (+2–4 weeks elapsed)Prepare legal packages during Sprint 3 (Option B), run review in parallel with final dev
AI agent hallucinationsLow (TDD catches errors)Tests written first; human code review before merge

References