Correcting track and ETA

Correcting Track and ETA

When you find yourself off-track or your ETA wrong, you must systematically correct — this lesson explains the procedures.

Track correction

Tool: the 1-in-60 rule (see separate lesson).

Step 1: Measure off-track distance

Visually or by GPS: how far off the planned track are you? Example: 3 NM right.

Step 2: Estimate distance flown since waypoint

Example: 40 NM since last waypoint.

Step 3: Compute track-error angle

TE = (off-track × 60) / flown = (3 × 60) / 40 = 4.5°.

Step 4: Compute closing angle

Remaining distance to next waypoint: 20 NM. CA = (off-track × 60) / remaining = (3 × 60) / 20 = 9°.

Step 5: Adjust heading

Total correction = TE + CA = 4.5° + 9° = 13.5° left (opposite the off-track direction).

Step 6: Fly the new heading, recheck position when reaching next waypoint

If the new position is exactly at the waypoint → correction was right. Otherwise: residual correction.

ETA correction

ETA (estimated time of arrival) is the estimated arrival time at the next waypoint or destination.

New ETA calculation

1. Determine current position (fix).
2. Measure remaining distance to destination on the chart or GPS.
3. Determine current GS (from last two fix times).
4. Remaining time = remaining distance / GS.
5. ETA = current time + remaining time.

Example

• Off-block 0900Z. Current fix: over Erding (1000Z). Plan: ETA Augsburg 1030Z (i.e. 30 min from Erding).
• Actual GS = 100 kt. Remaining distance Erding → Augsburg = 60 NM.
• New remaining time = 60 / 100 = 0.6 h = 36 min.
• New ETA = 1000Z + 0
  = 1036Z, i.e. 6 min later than planned.

If ETA differs greatly (>15 min)

• Weather / wind changing: check whether TAF still applies.
• Re-think fuel plan: is the reserve still sufficient? If not, consider intermediate stop.
• Filed flight plan: if a VFR flight plan is mandatory, you may need to inform ATC/FIS that ETA has shifted.
• Receivers at destination (family, maintenance) informed if needed.

When the correction doesn't work

Combination of factors: stronger wind, inaccurate position, compass error, variation mishandled.

Robust procedure:

1. Fly to a near distinctive point and refix — no 1-in-60 without a clear position.
2. Check chart against reality — perhaps you are somewhere completely different.
3. Radio bearing (VOR cross cut) as additional verification.
4. GPS as backup (should be a secondary check, not primary navigation for PPL exercises).
5. If in doubt: contact ATC, ask for position confirmation.

Consequences for the rest of the route

• Shift subsequent waypoints: adjust all later ETAs.
• Recompute fuel: longer flight time = more burn.
• Daylight remaining (on later flights) check — sunset must not be exceeded without night-VFR qualification.