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IFR LOFT Scenario

LOFT: Santo Domingo to St. Thomas

Route: MDSD → TIST

Caribbean overwater IFR with tropical convection, limited alternates, and terrain-constrained island approach.

View FAA WINGS activity on FAASafety.gov →

Scenario Overview

Caribbean island IFR flight from Santo Domingo to St. Thomas through tropical weather with limited diversion options. The pilot manages overwater fuel planning, tropical convective weather deviations, and a terrain-limited island approach with short final. This scenario highlights the unique challenges of Caribbean IFR operations. Available on the Cirrus SF50 AATD simulator with Perspective Touch+ avionics at Grand Central, or the G1000 NXi AATD with King Air B200 turboprop configuration.

FAA WINGS Credit
Master 99556 cr

Complete this LOFT with one of our CFIIs to earn WINGS credit toward your pilot proficiency. Learn more at FAASafety.gov

ILSRNAVOverwaterFuel PlanningTropical WeatherTerrain

Route & Flight Plan

MDSD IDOKO UB455 DIRAN TIST
AltitudeFL310
Distance345 nm
ETE1:18

Airport Information

Departure
MDSD
Las Américas International Airport
Santo Domingo, Dominican Republic
Elevation: 59 ft MSL
Runways
RWYLengthSurface
17/3511,002 ftasphalt
Frequencies
ATIS126.4
CLR121.7
GND121.9
TWR118.3
APP119.1
DEP119.1
Approaches
ILS RWY 35, VOR RWY 35, VOR RWY 17, RNAV (GPS) RWY 35
Destination
TIST
Cyril E. King Airport
Charlotte Amalie, US Virgin Islands
Elevation: 23 ft MSL
Runways
RWYLengthSurface
10/287,000 ftasphalt
Frequencies
ATIS128.275
GND121.9
TWR118.1
APP119.35
DEP119.35
Approaches
ILS RWY 10, RNAV (GPS) RWY 10, RNAV (GPS) RWY 28, VOR-A

Weather Scenario

The Intertropical Convergence Zone drives daily convective cycles across the Caribbean. Morning heating produces towering cumulus that build into embedded thunderstorms by midday. The route crosses open water between Hispaniola and the US Virgin Islands — a 200nm stretch with no diversion airports. St. Thomas sits in the ITCZ convective belt, with the TAF showing thunderstorms during the 1300-1500Z arrival window. The trade winds are pushing the cells westward, which could clear the approach corridor — or not. The decision to continue past the halfway point versus return to Santo Domingo must be made with current fuel state and TIST conditions.

Departure 09:00L (1300Z)MDSDVFR
MDSD 141300Z 08012KT 8SM SCT025 BKN050 TCU NW 28/22 A2990 RMK CB DSNT NW
Warm tropical morning, scattered clouds, towering cumulus and distant cumulonimbus to northwest
Arrival 10:30L (1430Z)TISTMVFR
TIST 141430Z 10015G22KT 5SM TSRA SCT020 BKN040CB OVC070 27/23 A2986 RMK FRQ LTGICCC TS MOV W
Thunderstorms with rain, visibility 5 miles, frequent lightning, gusty trade winds

Terminal Aerodrome Forecasts

DepartureMDSD
TAF MDSD 140530Z 1406/1506 08010KT 9999 SCT025 BKN050 FM141000 09012KT 8000 SCT020 BKN040 FM141300 10014KT 6000 -SHRA SCT018 BKN035 TEMPO 1313/1318 4000 TSRA BKN020CB FM141800 08010KT 9999 SCT025 BKN050 FM150000 06008KT 9999 SCT030
En Route (Punta Cana)MDPC
TAF MDPC 140530Z 1406/1506 10012KT 9999 SCT030 BKN060 FM141000 10014KT 8000 SCT025 BKN050 FM141300 10016KT 6000 SHRA SCT020 BKN040 TEMPO 1313/1318 3000 TSRA BKN015CB FM141800 10012KT 8000 SCT025 BKN050 FM150000 08010KT 9999 SCT030
ArrivalTIST
TAF TIST 140530Z 1406/1506 10012KT 9999 SCT025 BKN050 FM141000 10014KT 8000 SCT020 BKN045 FM141300 10016G24KT 5000 TSRA SCT018 BKN035CB OVC070 TEMPO 1313/1500 3000 +TSRA BKN015CB FM141800 10014KT 6000 -SHRA SCT020 BKN045 FM150000 10010KT 9999 SCT025 BKN050

Lesson Profile

Scenario timeline with phases, altitudes, and key events
PhaseTimeAltitudeEvents
Briefing & Setup0:00-0:20GroundFuel planning: calculate point of no return and equal-time point. Brief overwater requirements, TIST approach with terrain constraints, and alternate options (TJSJ San Juan, TISX St. Croix). Review tropical convective patterns and deviation authority.
Departure0:20-0:3559-FL310Depart MDSD RWY 35. Climb over the Caribbean. Contact Santo Domingo Control. Avoid towering cumulus building to the northwest.
Overwater Cruise0:35-1:00FL310Overwater cruise southeast toward the Virgin Islands. Monitor onboard weather radar/XM for convective cells. At the halfway point (approx. 170nm), make the continue/return decision based on fuel state and TIST conditions. ATC may offer routing around weather cells.
Descent & Approach1:00-1:25FL310-23Descend toward St. Thomas. Navigate around convective cells near the island chain. ILS RWY 10 at TIST — terrain on both sides of final (St. Thomas hills to the north, Water Island to the south). Gusty trade wind crosswind. Short runway (7,000 feet) at sea level.
Landing & Debrief1:25-2:00GroundLand at TIST. Debrief: fuel planning accuracy, overwater decision-making (continue vs. return), convective weather deviation technique, terrain awareness on island approach. Discuss how Caribbean operations differ from domestic IFR.

Post-LOFT Approach Practice

After the LOFT scenario concludes, practice 2 additional approaches for a total of 3 per session. Session is planned for up to 6 approaches — ask your CFII for additional practice.

Approach 2
TIST
RNAV (GPS) RWY 28
Opposite direction approach; practice terrain avoidance on the westbound arrival with Water Island obstacle
Approach 3
TIST
VOR-A
Non-precision circling approach — circle-to-land practice at a terrain-constrained island airport

Training Objectives

Proficiency

  • Plan and execute overwater IFR with limited alternate options
  • Navigate around tropical convection using onboard weather tools
  • Fly the ILS RWY 10 at TIST with terrain on both sides of final

Progress

  • Calculate fuel requirements for Caribbean operations with mandatory reserves
  • Interpret tropical weather patterns and make deviation decisions
  • Apply island approach procedures with terrain and obstacle awareness

Single-Pilot CRM

  • Make diversion decisions with limited options over water
  • Manage workload during weather deviations
  • Brief approach at a terrain-constrained island airport

Prepare for Your Session

What is the "point of no return" and "equal-time point" for overwater IFR?
The point of no return (PNR) is the farthest point from which you can return to departure with required fuel reserves. The equal-time point (ETP) is where continuing forward takes the same time as returning. For the MDSD-TIST route (~345nm), the ETP is approximately 170nm out. Beyond the ETP, your best option if TIST goes below minimums is to continue to the alternate (San Juan), not return to Santo Domingo.
What makes the ILS RWY 10 approach at TIST particularly challenging?
St. Thomas terrain rises to 1,500+ feet just north of the airport. The ILS RWY 10 final approach course has hills on both sides — St. Thomas to the north and Water Island to the south. The runway is 7,000 feet at sea level, which is adequate but leaves no room for a long float in gusty trade winds. The missed approach requires an immediate climbing right turn to stay clear of terrain.
How do Caribbean convective weather patterns differ from continental US?
Caribbean convection is trade-wind driven and follows daily cycles: morning buildup, midday to afternoon storms, evening clearing. Unlike US frontal weather that moves and clears, Caribbean convection regenerates in the same areas daily. Storms are typically fast-moving and narrow, but they can be intense with heavy rain reducing visibility to near zero. The key difference: in the continental US you can often wait out a storm or divert 50nm. Over water with limited alternates, you must plan around the cycle.
What alternate airports should you consider for TIST and what drives the choice?
Primary alternate: TJSJ (San Juan, Puerto Rico) — 75nm west, larger airport with multiple approaches, typically better weather. Secondary: TISX (Henry E. Rohlsen, St. Croix) — 40nm south, closer but also island weather. The choice depends on which direction the convection is moving. If storms are moving west (typical trade wind pattern), San Juan may have the same weather in 30 minutes. If storms are localized to the northern Leeward Islands, St. Croix may be clear.
Instructor Notes
This scenario is about decision-making with limited options. The overwater segment removes the "I can always divert" safety net that domestic pilots take for granted. The key teaching moment is the halfway decision point: make the student verbalize their fuel state, destination conditions, and alternate plan before crossing the equal-time point. If they cannot articulate a clear plan, they should not continue. The TIST approach is the secondary challenge — gusty crosswind plus terrain on both sides tests scan and awareness. Use the convective weather display to force at least one deviation request en route.