Paraparaumu to Nelson: 11 nm off track over Cook Strait
You are flying NZPP–NZNS in a PA-28-161 (TAS 115 kt, fuel burn 36 L/hr). Planned track is 265°M, distance 72 nm, planned GS 105 kt. After 40 min and 66 nm flown, a GPS fix shows you 11 nm right of track. The remaining distance along track to Nelson is 34 nm. The Nelson CTR boundary is 5 nm ahead and you are still outside it. The latest wind is 290/25, stronger than forecast. Your heading has been 265°M. Fuel remaining is 54 L, of which 12 L is final reserve. The VNC shows a 2,500 ft minimum safe altitude and the sea below; you are at 4,500 ft. ATC has not yet identified you on secondary surveillance radar. There is a parachute area 8 nm to your right.
1. Calculate the track error, closing angle and new heading using the 1-in-60 rule.
Read the worked answer
Use distance flown for track error and distance to go for closing angle.
Track error = 60 x off-track distance / distance flown = 60 x 11 / 66 = 10°. Closing angle = 60 x off-track distance / distance to go = 60 x 11 / 34 = 19.4°, say 19°. Total correction = 10 + 19 = 29° left.
You are right of track, so turn left. New heading = 265 - 29 = 236°M.
Check the geometry: remaining track distance is 34 nm and off-track is 11 nm, so the direct distance to Nelson is sqrt(34² + 11²) = 35.7 nm. A 29° left turn is large but justified because the remaining leg is short and the cross-track error is significant. Do not chase the GPS needle with continuous small turns; establish 236°M, allow the aircraft to settle, then reassess in 5 min. If the wind is 290/25, the new heading also compensates for drift, but the 1-in-60 correction is the priority.
2. Recalculate ETA and fuel, and decide whether the remaining fuel is adequate.
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At 105 kt GS, time remaining = 35.7/105 = 0.34 hr = 20.4 min. ETA is about 60 min after departure. Fuel used in 20.4 min at 36 L/hr = 0.34 x 36 = 12.2 L. Fuel remaining after landing = 54 - 12.2 = 41.8 L. Reserve is 12 L, so the margin is 29.8 L, which is comfortable.
If the stronger wind reduces GS to 95 kt, time = 35.7/95 = 0.376 hr = 22.6 min; fuel = 13.5 L; remaining = 40.5 L; margin above reserve = 28.5 L. Even at 85 kt GS the fuel is adequate. The limiting factor is not fuel but controlled-airspace entry and the parachute area. The fuel check does, however, confirm that a go-around or a short hold at Nelson is feasible without eating into reserve.
3. What ATC call and tracking action would you take before the control zone boundary?
Read the worked answer
Turn left to 236°M first, then call before the boundary: 'Palmerston North Approach, [callsign], PA-28, 12 nm east, 4,500 ft, VFR to Nelson, request clearance into the control zone, estimating boundary in 6 minutes.' Give position, altitude and request. If clearance is not received, remain outside controlled airspace: turn parallel to the boundary or orbit east of it at 4,500 ft. Do not turn west toward the high terrain to avoid the zone. Keep clear of the parachute area 8 nm right of track; after turning left it should be behind you, but confirm on the VNC. If ATC issues a squawk, set it and confirm identification. If the zone cannot be entered, hold east of the boundary and revise the plan rather than pressing in.