GCAA Ghana ATPL Theory common mistakes
GCAA Ghana ATPL Theory · Understand the traps and how to avoid them.
When computing a crosswind component, candidates use the full wind speed or the headwind component instead of multiplying wind speed by sin of the wind angle, or they swap sine and cosine when the wind is reported relative to the runway rather than magnetic north.
The wind angle given in METAR or ATIS is relative to magnetic north, but the candidate has to convert it to an angle relative to the runway heading first. Under time pressure, many candidates grab the headwind formula (cos) for the crosswind, or forget to subtract the runway heading from the wind direction before entering the table.
What to do instead
Always compute the angle between wind direction and runway heading first (theta = wind direction minus runway heading, taken as the smaller angle). Then crosswind = wind speed x sin(theta) and headwind = wind speed x cos(theta). Practise with three or four angles (30, 45, 60 degrees) until the sine values are automatic, and sanity-check the answer: at 90 degrees the crosswind equals the full wind speed, at 0 degrees it is zero.
Candidates compute take-off or landing distance from the chart using the pressure altitude and temperature at the departure aerodrome, then forget to apply the subsequent corrections for wind, runway slope, runway surface, and any clearway or stopway credit.
The performance chart is usually presented in two stages: first a base distance from pressure altitude and temperature, then percentage corrections applied in sequence. Candidates who are rushing stop after the first stage because the number looks plausible, or they add corrections in the wrong order or apply a headwind correction as an increase.
What to do instead
Work through the chart in the exact order printed on the chart and write each intermediate figure down before moving to the next correction. Memorise the sign convention: headwind and downhill slope reduce distance, tailwind and uphill slope increase it, and a clearway reduces the required runway length but not the ground roll. Cross-check the final figure against the runway length available and state whether the take-off is legal.
In mass and balance questions, candidates use the wrong datum or arm for the empty aircraft, or they add fuel and payload moments without converting units (kg to lb, inches to metres, or litres to kg using the correct density).
The loading schedule gives arms in one unit system and the question stem may give masses in another, or the candidate confuses the empty mass and empty mass moment with the zero-fuel mass. Fuel density of 0.72 kg/litre for AVGAS and 0.8 kg/litre for Jet A-1 is often assumed incorrectly.
What to do instead
Before calculating, write down the datum, the unit system, and the fuel density stated in the question. Build a standard table with columns for item, mass, arm, and moment, and fill it row by row. Compute CG as total moment divided by total mass and compare with the forward and aft limits at the actual mass, not at maximum mass. If any unit is unclear, convert everything to SI first.
Candidates answer air law questions from memory of national rules or from a different ICAO annex, rather than from the specific annex or Ghana CAA regulation being tested, and they confuse definitions such as 'aerodrome traffic zone', 'control area', 'terminal control area', and 'advisory route'.
Air law is the domain with the most definitions and the most cross-references between Annex 2 (Rules of the Air), Annex 11 (Air Traffic Services), and the Ghana Civil Aviation (Air Navigation) Regulations. Candidates skim the definitions because they seem obvious, then misapply them in scenario questions.
What to do instead
Build a one-page glossary of the key definitions from Annex 2 and Annex 11 with the exact wording, and for each one note the annex and chapter. For every practice question, identify which document the answer comes from before choosing an option. Pay particular attention to the differences between controlled and uncontrolled airspace, VMC and IMC minima, and the classes of airspace A to G.
In meteorology, candidates read the METAR or TAF cloud base as height above mean sea level rather than above aerodrome elevation, or they interpret the trend group and the QNH incorrectly, and they confuse the meanings of CAVOK, NSC, and NCD.
METAR cloud heights are reported above aerodrome elevation, but the candidate's mental model is often height above sea level from previous study. Trend groups such as BECMG and TEMPO are frequently misread as a forecast for the whole period rather than a temporary or gradual change.
What to do instead
Adopt the rule 'cloud base in METAR is above aerodrome elevation, cloud base in a significant weather chart is above MSL'. Learn the exact definitions of CAVOK (visibility 10 km or more, no cloud below 5000 ft or MSA, no CB or TCU, no significant weather) and NSC/NCD. Practise decoding ten real METARs and TAFs and write out each group in plain language.
In general navigation, candidates plot a course on a Mercator chart and measure the track with a protractor relative to the chart grid rather than relative to true north at the point of departure, or they mix up true, magnetic, and compass headings and apply variation in the wrong direction.
Mercator charts show meridians as parallel vertical lines, so the angle measured on the chart is the rhumb line track, not the great circle track. Variation is east or west and must be added or subtracted according to the mnemonic, but candidates often apply it backwards under exam pressure.
What to do instead
Always convert in one direction using a written ladder: true track, apply variation (east subtract, west add) to get magnetic, apply deviation to get compass. For Mercator plotting, remember that a straight line on the chart is a rhumb line and that a great circle appears curved except at the equator. Practise converting ten headings in each direction until the sign convention is automatic.
In radio navigation, candidates confuse the indications of VOR, DME, ILS, and GPS, for example treating the VOR CDI as showing the aircraft's heading rather than the bearing to or from the station, or misreading a DME slant range as ground distance.
These systems are taught as separate chapters but share a common display language, so under exam conditions the candidate applies the wrong mental model. The difference between 'radial' and 'bearing', and between 'course' and 'heading', is often the deciding factor in the question.
What to do instead
For each aid, write a one-line rule: VOR CDI shows the selected radial relative to the aircraft, not the aircraft heading; DME shows slant range, which overstates ground distance at high altitude and close range; ILS localiser shows deviation from the runway centreline, glidepath shows deviation from the nominal 3 degree path. Draw the geometry for each aid once and refer to it when practising questions.
In principles of flight, candidates apply the lift formula qualitatively but get the relationship between angle of attack, speed, and stall wrong, for example assuming that a heavier aircraft stalls at a higher angle of attack, or that lowering flaps increases the stall angle rather than the stall speed.
The stall is defined by the critical angle of attack, which is fixed for a given wing regardless of weight, speed, or bank angle. Candidates conflate the stall speed with the stall angle and then answer questions about load factor and bank angle incorrectly.
What to do instead
Memorise the single sentence 'an aircraft stalls at the critical angle of attack, whatever its weight, speed, or configuration'. Then reason from lift = 0.5 rho V squared S CL: increased weight or load factor raises the stall speed, flaps raise CL max and lower the stall speed, and a forward CG raises the stall speed slightly. Work through a bank-angle stall speed example (stall speed increases by the square root of the load factor).
In human performance, candidates answer questions about hypoxia, hyperventilation, and spatial disorientation from everyday assumptions rather than from the specific symptoms and time of useful consciousness figures, and they confuse the effects of alcohol, fatigue, and carbon monoxide.
The symptoms of hypoxia and hyperventilation overlap (dizziness, tingling, euphoria), and candidates rely on general knowledge. Time of useful consciousness at various altitudes is a memorised table that is often recalled imprecisely.
What to do instead
Build a comparison table for hypoxia versus hyperventilation, listing the distinguishing signs and the correct response (100 percent oxygen and descent for hypoxia; controlled breathing and reassurance for hyperventilation). Memorise the time of useful consciousness at 18000, 25000, 30000, and 40000 ft, and the fact that carbon monoxide produces a cherry-red complexion and is not detected by the symptoms alone.
In instrumentation, candidates confuse the sources and failure indications of the pitot-static system and the gyroscopic instruments, for example assuming that a blocked pitot tube affects the altimeter, or that a suction failure affects the attitude indicator and the turn coordinator in the same way.
The pitot-static system feeds the ASI, altimeter, and VSI, but each instrument uses a different combination of pressures, and the failure modes differ. Gyroscopic instruments are powered either by engine-driven vacuum or by electricity, and the candidate often forgets which is which.
What to do instead
Draw the pitot-static plumbing once: pitot pressure to ASI only, static pressure to ASI, altimeter, and VSI. Then learn the failure signatures: blocked pitot gives a frozen ASI that behaves like an altimeter in climb and descent; blocked static gives all three instruments wrong, with the ASI over-reading in climb and under-reading in descent. For gyros, list which instruments are vacuum-driven and which are electric, and what the failure indications are.