CAA NZ Instrument Rating Navigation cheat sheet

1 NM = 1.852 km = 1.15078 statute miles; 1 kt = 1 NM/h, so time (min) = distance (NM) ÷ groundspeed (kt) × 60.

Track is the intended path over the ground; heading is where the nose points. Drift angle = track − heading (positive right). Wind correction angle is applied opposite the drift.

Wind triangle: GS and drift come from the wind vector plus TAS. Headwind/tailwind component = wind speed × cos(angle between wind direction and track); crosswind component = wind speed × sin(angle).

1-in-60 rule: a 1 NM off-track error at 60 NM equals 1°. Closing angle to regain track = (distance off track ÷ distance remaining) × 60; total heading change = track error + closing angle.

ISA: sea-level temperature 15 °C, pressure 1013.25 hPa, lapse rate 1.98 °C per 1000 ft. Pressure altitude = elevation + 30 ft per hPa below 1013 (subtract 30 ft per hPa above).

True altitude from indicated altitude: add 30 ft per hPa when QNH is above 1013, subtract when below; add about 120 ft per 1 °C that mean temperature exceeds ISA.

Density altitude ≈ pressure altitude + 120 × (OAT − ISA temperature at that level). High density altitude raises TAS for a given IAS and lengthens take-off/landing distances.

TAS from IAS: TAS ≈ IAS × (1 + 0.02 × altitude in thousands of ft) as a rough rule; at 10 000 ft TAS is roughly 20% higher than IAS in still air.

Mach number = TAS ÷ local speed of sound; speed of sound ≈ 38.97 × √(temperature in kelvin) kt, about 661 kt at sea-level ISA.

NZ uses the NZTM2000 grid on topographical charts and WGS84 for GNSS; positions must be quoted in the datum of the chart in use.

WAC charts are 1:1 000 000; NZ topographical maps are commonly 1:50 000 (NZTM) and 1:250 000. Scale 1:250 000 means 1 cm = 2.5 km on the ground.

Magnetic variation in NZ is easterly and increasing westward; convert true to magnetic by adding easterly variation (variation east, magnetic least).

GNSS RAIM availability must be checked before an approach; a RAIM prediction uses the published approach and the planned time of arrival.

RNAV/GNSS approaches in NZ are designated RNP APCH; LNAV minima are non-precision, LNAV/VNAV and LPV use vertical guidance.

IFR alternate minima and take-off minima are published in the NZ AIP; a GNSS approach without baro-VNAV may not be used as an alternate unless the plate permits it.

Minimum safe altitude (MSA) sectors on NZ approach plates are usually based on 25 NM from the navigation aid or waypoint, with a 1000 ft (or published) obstacle clearance.

Dead reckoning leg time = leg distance ÷ groundspeed; fuel required = (leg time + reserve) × hourly burn, with NZ reserves typically 30 min holding plus approach and missed approach fuel.

Point of no return (equal-time point) = (total fuel available × GS out) ÷ (GS out + GS home), measured from the departure point along track.

Critical point (equal fuel to either destination) uses the same formula with total fuel usable to the decision point rather than total endurance.

Radius of action = (endurance × GS out × GS home) ÷ (GS out + GS home); the outbound leg is limited by the return groundspeed.

To intercept a track after a known off-track distance, use the 1-in-60 rule: closing angle = (off-track distance ÷ distance to go) × 60, then add the original track error.

Drift and groundspeed from two fixes: compare actual time and position with the DR position; apply the correction to the remaining legs, not the leg just flown.

Descent planning: required rate of descent (ft/min) = groundspeed (kt) × gradient (ft/NM) ÷ 60; a 3° path is about 318 ft/NM.

Top of descent distance (NM) ≈ altitude to lose (ft) ÷ 300 for a 3° path; adjust for wind by using groundspeed in the rate calculation.

When ATC clears a direct-to waypoint, verify the new track against the charted MSA and terrain before turning, because the direct track may leave the protected area.