Section 04 / Nav Log
Enter your route, winds aloft, and altitude. The calculator solves the full heading chain (TC → WCA → TH → MH → CH), ground speed, ETE, and fuel per leg — with cruise TAS and GPH drawn from C172S POH Section 5 tables and step-by-step math shown for every value.
TC True Course — from chart, degrees true
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Var + = West (add), − = East (subtract)
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WCA + = crab right, − = crab left
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FB winds are always true direction
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Full glossary
Departure, arrival, field elevations, and frequencies
Frequencies, TPA, and field elevation come from the Chart Supplement / ForeFlight — verify against current official sources. Field elevations feed the climb & descent calculations below.
Aircraft, fuel and reserve, climb/cruise/descent defaults
C172S POH cruise, climb, descent, and winds aloft — fills TAS, GPH, and wind per leg
Pressure altitude corrects your indicated altitude to the standard datum (29.92 inHg):
PA = Indicated Alt + (29.92 − Altimeter) × 1000
Each 0.01 inHg below 29.92 raises PA by ~10 ft. With the altimeter set to 29.92, PA equals indicated altitude.
Density altitude is pressure altitude corrected for non-standard temperature — the altitude the airplane "feels":
DA = PA + 120 × (OAT − ISA_temp), where ISA_temp = 15 − 2 × (PA ÷ 1000) °C
High DA means thinner air: less power, less lift, longer takeoff/climb. See PHAK Ch. 16 (cross-country planning) and the density-altitude page in Learn.
The cruise table (Figure 5-8) is 3-axis: pressure altitude × RPM × temperature deviation from ISA standard. Each cell has three temperature columns: −20°C from ISA, ISA standard, and +20°C from ISA.
temp_dev = OAT − ISA_std(table_alt). Linearly interpolate across temperature columns to get {BHP%, KTAS, GPH}.Worked example: PA 4500 ft, OAT 16°C, RPM 2400
Note: above 75% BHP use full rich mixture (POH §5-14). The 2 kt speed-fairings deduction is already applied to the result shown above.
Unlike climb, the C172S POH does not publish a descent performance table. This estimate uses:
For a more precise number, use your planned descent power setting from POH §4 and look up that fuel flow in the cruise table (Fig. 5-8). Always add a margin — real descents vary with ATC, terrain, and traffic.
FT 3000 6000… header line).KDAB or DAB — not city names).
Attempts to fetch directly from aviationweather.gov. Most browsers block this due to CORS policy on AWC's server — if you get a network error, use the paste method above instead.
Two formats are supported:
FT 3000 6000…. Stations are 3-letter AWC IDs; the leading K is stripped automatically (KDAB → DAB).268° 17kts. Waypoint names come directly from your ForeFlight route, so they match your Fix entries naturally (e.g. KDAB).Data currency: Winds aloft are a forecast, not observed data. Not a substitute for an official preflight weather briefing.
Educational use only · Not for flight planning · Always consult official FAA/NWS sources and obtain a full preflight weather briefing.
Add waypoints — heading chain, ground speed, ETE, and fuel compute as you type
KIAS indicated
→ calibration →
KCAS calibrated
→ altitude & temp →
KTAS true
→ wind triangle →
GS ground speed
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The POH climb table gives speed in KIAS; cruise gives KTAS. This tool turns TAS + wind into GS via the wind triangle — the same chain an E6B walks.
| Waypoint | Winds / Airspeed (input) | Heading Chain (computed ←→ input) | Route | Speed & Time (computed) | In-Flight (actual) | Fuel | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TC ° | WD ° | WS kt | TAS kt | WCA ° | TH ° | Var ° | MH ° | Dev ° | CH ° | Alt ft | NAV Freq | NAV ID | Dist NM | Rem NM | GS kt | ETE | ETA UTC | GS act | ATE min | ATA UTC | GPH | Leg gal | Rem gal | Rem hh:mm | ||
| TOTALS | — | — | — | — | — | — | ||||||||||||||||||||
§91.151 reserve, minimum fuel needed, and endurance at a glance
Trip fuel includes a 1.4 gal start, taxi, and takeoff allowance (C172S POH Section 5, Figure 5-7, Note 1) — it appears as the START/TAXI row when you insert the POH climb. Headline trip fuel is rounded down to the whole gallon; per-leg and running totals stay to a tenth so the §91.151 reserve check is exact.
14 CFR §91.151 requires fuel to fly to the first intended landing plus 30 min (day VFR) or 45 min (night VFR) at normal cruise consumption.
These figures assume all fuel on board is usable. Always consult your aircraft's POH for unusable fuel quantity.
Fill these in the air, not while planning — void times, sunset, and a quick divert solver
Tail number, ETD, and fuel on board are set in the Flight Profile. The two Operator Time Limit fields are blank on purpose — label them with whatever time limits your operation uses.
Diversion ETE = Distance ÷ GS. ETA = Time + ETE. FOB carries your fuel remaining from the planned route — in the air, use your actual gauge reading. PHAK Ch. 16.
| N-NUMBER / TYPE | — | ETD (UTC) | — | FUEL ON BOARD | — gal |
| TOTAL DISTANCE | — | TOTAL ETE | — | TRIP FUEL | — |
| VOID TIME | — | SUNSET | — | NOTES |
Why the numbers work
Heading conversion chain
Every heading starts as a True Course from your chart and gets transformed through four corrections before you read it on the compass. The mnemonic: "Tall Virgins Make Dull Companions" (or any phrase you like).
The core formulas
WCA = asin( WS/TAS × sin(WD − TC) )
TH = TC + WCA
MH = TH + Var (+W, −E)
CH = MH + Dev
GS = √(TAS² + WS² − 2·TAS·WS·cos(TH − WD))
ETE = Dist / GS × 60 (minutes)
Fuel = ETE(hrs) × GPH
All angles in degrees; converted to radians internally for trig. Headings normalized to 0–359°. WCA exceeding ±30° usually means your wind speed is unrealistically high relative to TAS.
Most common student mistakes
| Sign flip | Adding east variation instead of subtracting — check "East is least." |
| True wind | FB winds aloft are TRUE. Don't convert before entering WD here. |
| Course vs heading | TC is what you measure from the chart. TH is what you fly into the wind. |
| Climb fuel | Climb burns more fuel — your first leg GPH should reflect the higher climb burn or add a margin. C172S POH §5 includes a 1.4 gal start/taxi/T.O. allowance in the climb tables (Figure 5-7). Also increase time/fuel/distance by 10% per 10°C above standard temperature. |
| Reserve math | The 30/45 min reserve is computed at cruise GPH, not at endurance speed. |
| GS check | With a headwind GS < TAS; tailwind GS > TAS. If GS is way off, check WD. |
Rounding conventions
Common cross-country planning practice, applied so your numbers stay conservative:
| Temperature | Nearest whole degree. |
| Fuel flow (GPH) | Up to the nearest tenth — never under-state burn. |
| True airspeed | Down to the nearest whole knot — conservative ground speed. |
| Time | Each leg's ETE rounds up to the whole minute. |
| Fuel quantity | Read fuel you have conservatively (round down). Per-leg burns are shown to a tenth so the running total stays accurate; the headline figures are what you'd log. |
Checkride connection
The Private Pilot ACS (FAA-S-ACS-6C) expects you to "prepare, present, and explain a cross-country flight plan … including calculations of headings, fuel requirements, and ETE/ETA." EFB or paper — either is accepted under the 2023 ACS update.
Examiners want to hear you reason through the numbers, not just read them. When they ask about your heading, explain the WCA correction. When they ask about fuel, mention the reserve requirement and climb allowance. This tool's "show work" feature (≡ button in each row) models exactly that chain of reasoning.
| TC | True Course — Direction of travel measured from chart vs. true north. Read with your plotter from the sectional. |
| WD | Wind Direction — Direction the wind blows FROM, in degrees true (as reported in FB forecasts). |
| WS | Wind Speed — Forecast wind velocity from winds-aloft report (FA/FB), in knots. |
| TAS | True Airspeed — Your calibrated airspeed corrected for altitude and temperature. Look up in POH Section 5 cruise table. |
| WCA | Wind Correction Angle — The crab angle you apply to stay on course despite crosswind. Positive = crab right, negative = crab left. |
| TH | True Heading — TC ± WCA. Your aircraft's nose direction relative to true north. |
| Var | Magnetic Variation — Angular difference between true and magnetic north, read from isogonic lines on your sectional. Positive = West (add to TH), Negative = East (subtract from TH). |
| MH | Magnetic Heading — TH corrected for variation. This is what your DI (directional gyro) shows when set. |
| Dev | Compass Deviation — Local error in your aircraft's magnetic compass, from the compass correction card in the cockpit. |
| CH | Compass Heading — The number you actually fly on the wet compass: MH ± Dev. |
| GS | Ground Speed — Actual speed over the ground: TAS adjusted for the wind vector. |
| ETE | Estimated Time En Route — Time to fly this leg: (Dist ÷ GS) × 60. |
| ETA | Estimated Time of Arrival — Your ETD plus the running total of ETE legs, in UTC. |
| GPH | Gallons Per Hour — Fuel burn rate at cruise from POH Section 5. |
| ETD | Estimated Time of Departure — Your planned takeoff time, in UTC. |
| FB | Winds Aloft Forecast — The FAA product (formerly "FD winds") giving wind direction/speed and temperature at standard altitudes. |
| ATE | Actual Time En Route — The real elapsed time for a leg, read from your timer in flight (minutes). Compare against ETE to refine your remaining estimates. |
| ATA | Actual Time of Arrival — The clock time (UTC) you actually crossed a checkpoint. |
| NAVAID | Navigational Aid — A VOR/VORTAC/NDB you can tune for the leg. Enter its frequency and identifier as a backup to pilotage/GPS. |
| PA | Pressure Altitude — Indicated altitude corrected to 29.92 inHg: IndAlt + (29.92 − altimeter) × 1000. |
| DA | Density Altitude — Pressure altitude corrected for temperature: PA + 120 × (OAT − ISA). The altitude the airplane performs at. |