CAA NZ ATPL Theory - Flight Planning common mistakes
CAA NZ ATPL Theory - Flight Planning · Understand the traps and how to avoid them.
Treating the MTOW, MLW and MZFW as interchangeable limits, then checking only one of them against the planned take-off mass.
Candidates memorise the three abbreviations but never build the habit of comparing the actual mass against each limit in sequence, so a load that is legal against MTOW but illegal against MZFW slips through.
What to do instead
For every loading question, write the three limits in a column and put the computed mass beside each one, stating pass or fail. If any fails, reduce payload or fuel and recompute before answering.
Using the zero-fuel mass as the take-off mass when computing take-off and landing performance, or forgetting to add trip fuel and taxi fuel to the operating mass.
The question gives several masses and candidates grab the first plausible number rather than building the mass chain from BEM through DOM, ZFM, TOM to LM.
What to do instead
Always rebuild the chain explicitly: BEM plus crew and equipment gives DOM; add payload gives ZFM; add take-off fuel gives TOM; subtract trip fuel gives LM. Show each line before touching the performance chart.
Reading take-off distance charts at the wrong reference point, for example using the 50 ft screen height distance when the question asks for ground roll, or vice versa.
Charts present several distance definitions close together and candidates do not re-read the question wording after locating the chart entry.
What to do instead
Before opening the chart, underline the exact distance the question asks for (ground roll, take-off distance to 50 ft, accelerate-stop distance). Enter and leave the chart only for that quantity and note the definition beside the answer.
Failing to apply the wind and slope corrections in the correct order, or applying a percentage correction to the wrong base value.
Performance charts apply corrections multiplicatively or additively depending on the chart, and candidates apply them in whatever order they read them.
What to do instead
Follow the chart's own sequence exactly as printed, and write each intermediate value down. When a correction is given as a percentage, state clearly what it is a percentage of before calculating.
Computing fuel required as trip fuel only, omitting contingency, alternate, final reserve and taxi fuel.
Candidates focus on the headline trip fuel figure and forget the regulatory fuel components that must be carried in addition.
What to do instead
Use a fixed fuel ladder: taxi, trip, contingency, alternate, final reserve, then any extra. Total each line and compare the sum against usable fuel. Show the ladder even when the answer seems obvious.
Mixing units, converting litres to kilograms with the wrong density, or using the wrong specific gravity for the fuel type stated.
Questions deliberately mix volume and mass, and candidates apply a remembered density instead of the one given or implied.
What to do instead
Write the density being used and its units next to every conversion. If the question does not state a density, use the standard value the syllabus specifies and state that assumption in the working.
Plotting or reading a track on a chart using the wrong north reference, confusing true, magnetic and grid, and then applying variation in the wrong direction.
Candidates measure a true track from the chart then apply variation with the sign reversed, or forget to convert at all before comparing with a magnetic heading.
What to do instead
Label every angle as true or magnetic as soon as it is written. Convert with the mnemonic that variation east is magnetic least, and check the answer by converting back to true.
Computing wind triangle values with the drift and groundspeed swapped, or solving for heading when the question asks for track.
The triangle has several outputs and candidates stop as soon as they get a plausible number rather than identifying which output the question wants.
What to do instead
State the required output before starting the triangle (heading, track, drift, groundspeed, wind). After solving, read the question again and confirm the number produced matches that output and its units.
Ignoring the effect of temperature and pressure on performance, using ISA values when the question gives an actual temperature or QNH.
Candidates default to standard atmosphere figures and do not notice the non-standard conditions embedded in the question.
What to do instead
Highlight every non-standard value in the question (temperature, pressure altitude, QNH, wind, slope). Enter the chart with pressure altitude, then apply temperature correction as the chart directs, and note each correction applied.
Filing or checking an ATS flight plan with inconsistent fields, such as a route that does not connect to the stated destination, or an EET that does not match the route and speed.
Candidates treat the flight plan as a form to fill rather than a cross-checked document, so internal inconsistencies survive.
What to do instead
After completing the plan, run a consistency pass: departure and destination aerodromes match the route, each route point connects to the next, total EET matches the sum of legs at the stated TAS, and alternate and endurance figures agree with the fuel ladder.