Instrumentation: 6 Latest ATPL Exam Questions Explained
In this walkthrough we break down the latest EASA ATPL exam questions from the Instruments topic — focusing on Air Data Measurements. If you’re preparing for your ATPL Instruments exam, this session will help you understand key concepts behind airspeed, pressure systems, and altitude instruments — and how to avoid common exam traps.
Prefer to watch instead of read? You can also follow along with the video version of this walkthrough for a more interactive experience.
Subscribe to the AirheadATPL YouTube channel and hit the notification bell for weekly ATPL revision videos. Each video helps you tackle the latest challenging questions from all 13 ATPL subjects, straight from recent EASA ATPL exams.
Let’s get started.
In this review, you’ll learn:
What happens to IAS and TAS when flying through a cold front with decreasing OAT;
How the airspeed indicator works and what’s inside its capsule;
What a barometric VSI with a non-linear scale means in practice;
Which speed to use when ATC asks for an expedited climb after departure;
Which systems make use of Air Data Computer outputs;
When EAS equals CAS and why it matters.
1. IAS and TAS When Flying Through a Cold Front
Question ID AIR-239730 – You are cruising at Mach 0.70 at FL390 when suddenly you fly through a cold front, and outside air temperature OAT decreases by a couple of degrees. IAS...
and TAS decrease
and TAS increase
decreases and TAS increases
increases and TAS decreases
Correct Answer: IAS increases and TAS decreases.
Explanation: Mach number is the ratio between the true airspeed (TAS) and the local speed of sound. The speed of sound depends on air temperature (approximately 39 × √T). When temperature drops, the speed of sound decreases. To maintain the same Mach number, TAS must decrease. Meanwhile, colder air is denser, which causes indicated airspeed (IAS) — derived from dynamic pressure — to increase slightly.
Notes: IAS = 1/2ρ V2 (aka Q). If the air is colder, it is denser, so the 1/2ρ has gone up, so IAS also goes up.
M = TAS/LSS. We know that LSS is affected only by temperature. Temp down, LSS down, so TAS goes down to keep the Mach number constant.
2. How Airspeed Indicator Works
Question ID AIR-239981 – An airspeed indicator includes a capsule; inside this capsule is:
total pressure and outside is static pressure
a very low residual pressure, and outside is the static pressure
dynamic pressure and outside is static pressure
static pressure and outside is dynamic pressure.
Correct Answer: total pressure and outside is static pressure.
Explanation: The ASI is fed pitot (static + dynamic) and static pressure. Pitot is fed to a capsule and static to the sealed case surrounding the capsule. The two static pressures cancel each other out, and the instrument responds to dynamic pressure due to movement of the aircraft through the air.
The airspeed indicator calculates dynamic pressure = total pressure – static pressure.
If the pitot tube is blocked: IAS underreads in descent (remember “PAT” — Pitot blocked: Airspeed underreads in descent).
If the static port is blocked: IAS overreads in descent (“SOD” — Static blocked: Overreads in descent).
Exam Tip: Remember the mnemonic: “PUD – Pitot blocked → Underreads in descent; SOD – Static blocked → Overreads in descent.”
3. ‘Nonlinear’ or ‘Logarithmic’ Scale
Question ID AIR-240364 – Consider a barometric VSI with a non-linear scale. What does this mean?
The ROD scale is more accurate than the ROC scale.
The ROC scale is more accurate than the ROD scale
The increments between zero and the maximum value are equally spaced.
A small ROC or ROD is displayed more accurately than a larger one.
Correct Answer: A small ROC or ROD is displayed more accurately than a larger one.
Explanation: Most Vertical Speed Indicators are designed with a logarithmic scale to provide better sensitivity near level flight, where precision matters most. At higher climb or descent rates, the instrument’s response becomes less sensitive.
Also note: the VSI has a lag error, since it measures the rate of change in static pressure with a delay.
Non-linear displays offer advantages as they extend readings relevant for the initial 1,000 feet of ascent or descent. This boosts readability and facilitates greater accuracy in level flight for pilots, with deviations being detected promptly.
Exam Tip: VSI lag and logarithmic scaling are frequently tested — remember: accurate at low rates, delayed response, zero reading if static source blocked.
4. Expedited Climb After Departure
Question ID AIR-240451 – ATC asks you to expedite your climb after departure. Which speed should you use, and how is it indicated?
Best rate of climb speed. Blue Line
Best angle of climb speed. Blue Line
Best rate of climb speed. Green arc.
Best angle of climb speed. White arc.
Correct Answer: Best rate of climb speed. Blue Line.
Explanation: Use Vy – best rate of climb speed, indicated by the blue line on the airspeed indicator (for multi-engine aircraft).
Vx = best angle of climb (most altitude over shortest distance)
Vy = best rate of climb (most altitude in least time)
When ATC asks for an expedited climb, they want altitude as fast as possible, so you use Vy. The blue line represents the best single-engine rate of climb for multi-engine aircraft.
Exam Tip: “Expedite climb → Vy (blue line).” Don’t confuse the green arc (normal operating range) with climb speeds.
5. Air Data Computer Outputs
Question ID AIR-239051 – Which of the following systems can make use of Air Data Computer output data?
The transponder
The DG
The CVR
The direct reading magnetic compass
Correct Answer: The transponder.
Explanation: The air data computer processes inputs like total and static pressure, temperature, and angle of attack to calculate airspeed, Mach, and altitude.
The Mode C/S transponder uses the pressure altitude data to report your vertical position to ATC radar.
Exam Tip: ADC → feeds systems like FADEC, GPWS, and transponder. Remember: Mode C/S = altitude reporting.
6. EAS
Question ID AIR-240363 – Equivalent Airspeed (EAS) is equal to what?
TAS corrected for compressibility and density.
TAS corrected for compressibility.
CAS corrected for density.
CAS corrected for compressibility.
Correct Answer: Calibrated Airspeed (CAS) corrected for compressibility error.
Explanation: There are four main airspeeds to know:
IAS – Indicated Airspeed (instrument reading)
CAS – IAS corrected for instrument and position error
EAS – CAS corrected for compressibility
TAS – EAS corrected for air density
Exam Tip: EAS questions are straightforward memory checks — make sure you know the correction sequence by heart. Use mnemonic Ice-T(ea) Is Pretty Cold Drink
ATPL Instrumentation Exam Overview
For those studying Human Performance or planning to take the exam soon, we’ve added the ATPL Instrumentation Overview at the end of this walkthrough. It’s a perfect summary of what to expect on the test, including:
Questions: 60
Duration: 1 hour 30 mins
Difficulty: Easy to medium
This subject covers all the essential on-board systems and instruments (speed, navigation, and system monitoring). It's one of the most manageable ATPL exams — just focus on learning the core material and practising the question bank to ensure you're ready!
Explore key subtopics & core concepts of the Instrumentation Syllabus.
Prepare smarter for your ATPL exams with the Airhead Question Bank — the most up-to-date source of real ATPL exam questions across all EASA subjects. Study offline anytime and boost your confidence for exam day.
Practise Instrumentation questions with Airhead ATPL Question Bank.
