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100+ Free PNG CASA Basic Gas Turbine Practice Questions

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Sample PNG CASA Basic Gas Turbine Practice Questions

Try these sample questions to test your PNG CASA Basic Gas Turbine exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What primary thermodynamic cycle models the working process of a standard open-cycle gas turbine engine?
A.The constant-pressure Brayton cycle
B.The constant-volume Otto cycle
C.The constant-temperature Carnot cycle
D.The dual-combustion Diesel cycle
Explanation: The gas turbine operates on the constant-pressure Brayton cycle (also known as the Joule cycle), where combustion occurs at approximately constant pressure while volume increases. In contrast, piston engines operate on constant-volume (Otto) or Diesel cycles.
2A gas turbine engine has an overall compressor pressure ratio (r_p) of 16:1. Assuming a ratio of specific heats (gamma) of 1.4 for air, what is the ideal thermal efficiency of this Brayton cycle?
A.54.7%
B.37.5%
C.68.2%
D.42.1%
Explanation: Ideal Brayton cycle thermal efficiency is given by eta = 1 - (1 / (r_p)^((gamma - 1) / gamma)). Here, (gamma - 1) / gamma = 0.4 / 1.4 = 0.2857. Calculating (16)^0.2857 yields 2.2084. Thus, eta = 1 - (1 / 2.2084) = 1 - 0.4528 = 0.5472 or 54.7%.
3According to Charles's Law, if air entering a combustor at 500 K (227 °C) is heated at constant pressure to 1,500 K (1,227 °C), by what factor does its specific volume increase?
A.3.0
B.2.45
C.5.41
D.1.5
Explanation: Charles's Law states that at constant pressure, volume is directly proportional to absolute temperature (V1/T1 = V2/T2). The ratio V2/V1 = T2/T1 = 1500 K / 500 K = 3.0. Temperatures must be evaluated in absolute Kelvin.
4How does reaction propulsion in a gas turbine engine demonstrate Newton's Third Law of Motion?
A.The forward thrust produced is equal and opposite to the backward momentum rate imparted to the gas mass flow
B.The acceleration of the aircraft is inversely proportional to the mass of air entering the inlet diffuser
C.Pressure energy created in the compressor directly converts to mechanical shaft power at constant volume
D.The total energy of the airstream decreases across each turbine stage to balance ambient pressure drag
Explanation: Newton's Third Law states that for every action there is an equal and opposite reaction. In a gas turbine engine, accelerating a high mass flow of air rearward creates a forward reaction force (thrust) equal in magnitude to the rate of change of momentum of the exhaust gases.
5What is the key functional difference between the working cycle of a four-stroke piston engine and a gas turbine engine?
A.A gas turbine performs intake, compression, combustion, and exhaust continuously and simultaneously in separate components
B.A gas turbine completes all four cycles in a single cylinder during one rotation of the main shaft
C.A piston engine operates at constant pressure during combustion whereas a gas turbine operates at constant volume
D.A gas turbine does not require an ignition source because combustion occurs spontaneously via static compression heat
Explanation: In a gas turbine, the four processes (intake, compression, combustion, exhaust) occur continuously and simultaneously in dedicated sections of the engine. In a four-stroke piston engine, these processes take place intermittently and sequentially in the same cylinder.
6In a convergent inlet duct operating at subsonic speeds, how do air velocity and static pressure change prior to reaching the compressor inlet?
A.Velocity increases and static pressure decreases
B.Velocity decreases and static pressure increases
C.Velocity increases and static pressure increases
D.Velocity decreases and static pressure decreases
Explanation: According to Bernoulli's principle for subsonic airflow, a convergent duct accelerates the airflow (velocity increases) while its static pressure decreases.
7What happens to the total pressure of a gas stream passing through a frictionless, non-work-producing diffuser duct under subsonic flow conditions?
A.Total pressure remains constant while static pressure increases
B.Total pressure increases proportional to the square of velocity reduction
C.Total pressure drops to equal ambient atmospheric pressure
D.Total pressure fluctuates in direct ratio to absolute temperature changes
Explanation: In an ideal frictionless subsonic diffuser where no mechanical work or heat transfer occurs, total pressure (dynamic plus static pressure) remains constant. Kinetic energy (dynamic pressure) is converted into static pressure.
8A high-bypass turbofan engine has a fan mass airflow of 400 kg/s and a core mass airflow of 50 kg/s. What is its bypass ratio?
A.8:1
B.0.125:1
C.9:1
D.7:1
Explanation: Bypass ratio is defined as the mass airflow passing through the fan duct divided by the mass airflow passing through the core engine. Bypass Ratio = Fan Airflow / Core Airflow = 400 kg/s / 50 kg/s = 8:1.
9What is the primary operational advantage of a high-bypass turbofan engine compared to a pure turbojet for commercial transport aircraft?
A.Higher propulsive efficiency and lower specific fuel consumption at subsonic cruise speeds
B.Superior supersonic thrust acceleration and lower frontal aerodynamic drag
C.Elimination of the need for multi-stage turbine assemblies and reduction gearboxes
D.Higher exhaust gas velocity resulting in greater specific thrust per unit engine frontal area
Explanation: High-bypass turbofans accelerate a larger mass of air to a lower velocity, which significantly increases propulsive efficiency (eta_p = 2V_a / (V_j + V_a)) and reduces specific fuel consumption (SFC) during subsonic flight compared to turbojets.
10In a free-turbine turboprop design, how is the propeller reduction gearbox mechanically connected to the gas generator section?
A.There is no direct mechanical shaft connection; the power turbine is driven solely by exhaust gas energy from the gas generator
B.The propeller reduction gearbox is connected directly to the high-pressure compressor shaft via a centrifugal clutch
C.A flexible drive shaft connects the propeller gearbox directly to the starter-generator drive gear
D.The power turbine and high-pressure compressor share a single rigid spool with an automatic sprag clutch
Explanation: In a free-turbine turboprop (such as the PT6A), the power turbine driving the propeller gearbox is mechanically independent of the gas generator spool (compressor and compressor turbine). It is driven purely aerodynamically by the expansion of hot exhaust gases.

About the PNG CASA Basic Gas Turbine Exam

The PNG CASA Basic Gas Turbine examination is a mandatory requirement under PNG CAR 61.73(3) for pilots seeking a turbine-powered aircraft class rating. The theory syllabus is set out in CASA PNG Advisory Circular AC61-3 Appendix II (adapted from NZ CASO 12) and covers gas turbine thermodynamic cycles (Brayton cycle), compressor and turbine design, combustion, fuel systems, lubrication, instrumentation, performance, anti-icing/fire protection, and starting malfunction theory.

Assessment

Approved written theory examination delivered as a computer-based Aspeq e-Exam, plus an approved practical simulator phase for starting malfunction recognition.

Time Limit

Not published by CASA PNG

Passing Score

75% of the total examination marks (CAR 61.17(b))

Exam Fee

Aspeq exam fee per the published Aspeq fee schedule (quoted in NZD), plus a K110 (GST incl.) CASA PNG sitting fee payable before results are released (Civil Aviation Safety Authority of Papua New Guinea (CASA PNG), delivered by Aspeq Assessment Specialists)

PNG CASA Basic Gas Turbine Exam Content Outline

Not published

Basic Principles and Thermodynamic Cycles

Newton's third law and jet propulsion, Boyle's and Charles' Laws, pressure-volume and pressure-temperature cycles, Brayton cycle vs Otto cycle, and thermal efficiency.

Not published

Engine Types and Architectural Layouts

Turbojet, turbofan (high vs low bypass), turboprop, turboshaft, free turbine vs fixed shaft, and gas generator arrangements.

Not published

Compressors, Diffusers, and Airflow Control

Centrifugal and axial flow compressors, rotor/stator blades, diffusers, compressor stage pressure ratios, bleed valves, and compressor stall/surge phenomena.

Not published

Combustion Chambers and Air Distribution

Can/multiple, turbo-annular (can-annular), and annular combustion chambers, flame stabilization, primary air for combustion, and secondary/tertiary air for liner cooling.

Not published

Turbines, Nozzle Guide Vanes, and Cooling

Multi-stage turbines, impulse and reaction blading, nozzle guide vane choked flow, blade root attachment, active clearance control, and internal blade cooling.

Not published

Exhaust Systems, Noise Suppression, and Thrust Reversal

Convergent and divergent exhaust passages, propelling nozzles, noise suppression mixers/hush kits, cascade and target thrust reversers, and interlock safety.

Not published

Fuel Systems, Metering, and Fuel Types

Hydromechanical and FADEC controls, simplex/duplex nozzles, pressurising and dump valves, fuel specific gravity, Jet A/A-1 specifications, and water/methanol injection.

Not published

Engine Lubrication Systems

Turboprop vs turbojet/turbofan oil requirements, synthetic oils, dry-sump circuits, pressure and scavenge pumps, oil heat exchangers, chip detectors, and seals.

Not published

Ignition and Starting Systems

High-energy ignition units, joule energy ratings, igniter plugs, automatic/continuous ignition modes, electric/air starter cycles, and in-flight re-light envelopes.

Not published

Air Cooling, Sealing, and Internal Airflow

Internal air sealing, turbine disc and blade cooling paths, labyrinth and carbon ring seals, compressor bleed air uses, and buffer air pressure control.

Not published

Engine Instrumentation and Parameter Monitoring

Engine Pressure Ratio (EPR, Pt7/Pt2), TIT, JPT, EGT/TGT, fuel flow meters, N1/N2 RPM tachometers, torque meters, shaft horsepower, and oil temperature/pressure.

Not published

Thrust Augmentation

Afterburner/reheat operating principles, duct burning, and water-methanol mass flow injection for hot-and-high takeoff thrust restoration.

Not published

Engine Performance, Environmental Effects, and SFC

Ram effect and forward speed, altitude and air density effects, ambient temperature and humidity impact on net thrust, and Specific Fuel Consumption (SFC).

Not published

Ice and Fire Protection Systems

Engine inlet thermal and electrical anti-icing, continuous-loop and thermocouple fire detection, and Halon fire extinguishing system operation.

Not published

Starting Malfunctions and Simulator Recognition

Theoretical causes, instrument indications, and immediate corrective actions for hung start, hot start, wet start, no-start/false start, and tailpipe fire.

How to Pass the PNG CASA Basic Gas Turbine Exam

What You Need to Know

  • Passing score: 75% of the total examination marks (CAR 61.17(b))
  • Assessment: Approved written theory examination delivered as a computer-based Aspeq e-Exam, plus an approved practical simulator phase for starting malfunction recognition.
  • Time limit: Not published by CASA PNG
  • Exam fee: Aspeq exam fee per the published Aspeq fee schedule (quoted in NZD), plus a K110 (GST incl.) CASA PNG sitting fee payable before results are released

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

Frequently Asked Questions

What is the pass mark for the PNG CASA Basic Gas Turbine examination?

Under PNG Civil Aviation Rule 61.17(b), candidates must achieve at least 75% of the total examination marks to pass.

Why is the Basic Gas Turbine rating required in Papua New Guinea?

PNG Civil Aviation Rule 61.73(3) requires that, for a turbine powered aircraft, an applicant for an aircraft class rating must "have passed an approved basic turbine knowledge examination". Advisory Circular AC61-3 describes the same requirement as holding a Basic Gas Turbine rating and states that attaining the syllabus in its Appendix II would meet it.

Does this examination include a practical component?

Yes. Rule 61.73(3) itself requires a passed examination, and the acceptable means of compliance in AC61-3 Appendix II is a two-part syllabus: a theory phase, examined by CASA PNG through the Aspeq e-Exam system, plus "a practical simulation phase that demonstrates student recognition of starting malfunctions and corrective actions conducted in a simulator approved for this purpose".

What fees are associated with the PNG CASA e-Exams?

Candidates pay the Aspeq sitting fee per the published schedule (in NZD) plus a CASA PNG sitting fee of K110 (GST incl.) payable prior to result release.

Are foreign basic turbine examination credits accepted in PNG?

According to AC61-3 paragraph (b), foreign basic turbine examination credits are not normally recognized in Papua New Guinea unless the applicant has already obtained a turbine aircraft class rating in that foreign country.