Aircraft General Knowledge (CSYA / CSYH)

Carburettor Icing & Carburettor Heat

Venturi and vaporisation cooling, ice accretion at the throat and butterfly, and the correct use of carburettor heat.

• CASR Part 61 MOS Schedule 3 (BAK) 2.2.4 (p.390) — Cockpit indications of engine (carburettor) ice and its clearanceVerified“Describe the cockpit indications in an aeroplane fitted with a variable pitch propeller which could signify: (a) the presence of engine ice; and (b) when engine ice has been cleared after application of carburettor heat.”
• CASR Part 61 MOS Schedule 3 (BAK) 2.2.5 (p.390) — Effect of using carburettor heatVerified“Explain the effect of using carburettor heat on aeroplanes fitted with a CSU.”
• CASR Part 61 MOS Schedule 3 (BAK) — carburettor vs fuel-injection comparison not separately clause-numbered — Simple carburettor versus direct injectionNeeds review

• Applying carb heat causes an INITIAL FURTHER RPM DROP before recovery.
• Carburettor icing is possible at outside air temperatures above 30°C in humid air.
• Use FULL hot, not partial — partial heat can warm ice-free air into the icing range.
• Carb heat is hot UNFILTERED air; avoid on the ground where dust can be ingested.

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Four-Stroke Cycle

Induction, compression, power and exhaust strokes, valve timing and ignition in a naturally aspirated piston engine.

• CASR Part 61 MOS Schedule 3 (BAK) — four-stroke cycle not a titled clause in the current corpus — Piston engine operating cycleNeeds review

• Only ONE of the four strokes produces power; the other three are driven by inertia.
• Ignition occurs BEFORE top dead centre, not at it — combustion takes time to develop.
• The crankshaft turns twice for one complete four-stroke cycle.

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Naturally Aspirated, Supercharged & Turbocharged Induction

How manifold pressure varies with altitude for each induction system, and what critical altitude means.

• CASR Part 61 MOS Schedule 3 (BAK) 2.1.3 (p.385) — Supercharging — purpose, supercharger types, and turbocharger componentsVerified“Supercharging (a) state the purpose of supercharging; (b) list the types of superchargers for the following: (i) geared (mechanically driven); (ii) turbo (exhaust driven); (c) state the purpose and function of the following components: (i) geared superchargers; (ii) impeller; diffuser; (iii) turbo-chargers: compressor; waste gate (fixed, manual and automatic).”
• CASR Part 61 MOS Schedule 3 (BAK) 2.1.1 (p.392) — Turbocharger system function and malfunction indicationsVerified“For each of the following systems, explain its function and that of the major components listed below the system and state the indications that a pilot would observe if the system or one of the components malfunctioned: (a) exhaust driven supercharger systems (turbochargers): (i) compressors; (ii) turbines; (iii) waste gates.”

• A supercharger is driven by the CRANKSHAFT, so it always costs engine power.
• A turbocharger is driven by EXHAUST GAS, so it recovers otherwise wasted energy.
• Critical altitude is the highest altitude at which rated manifold pressure can still be maintained.
• A naturally aspirated engine loses manifold pressure continuously with altitude — it has no critical altitude.

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Gas Turbine — Suck, Squeeze, Burn, Blow

Compressor, combustion chamber, turbine and nozzle, and how the pressure and velocity of the gas stream produce thrust.

• CASR Part 61 MOS Schedule 3 (BAK) — no gas-turbine clause in the current corpus — Gas turbine engine — working cycleNeeds review

• The turbine drives the compressor — it does not itself produce the thrust.
• Pressure PEAKS at the compressor outlet, not in the combustion chamber.
• The combustion chamber burns at roughly constant pressure while velocity and temperature rise.
• Thrust comes from the momentum change of the gas stream, not from the burning itself.

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Aircraft Electrical Systems & Load Shedding

Alternator generation vs battery storage, ammeter indications, low-voltage warnings, and in-flight load shedding.

• CASR Part 61 MOS Schedule 3 (BAK) 2.2.3 (p.386) — Electrical system components, alternator failure precautions and circuit breakersVerified“Describe or state the function of the following typical components mentioned in pilot operating handbooks, including considering the possibility of overpowering the system and the associated precautions pilots should take when operating these systems.”

• Alternator failure immediately shows as a DISCHARGE (-) on the ammeter and a LOW VOLTS warning.
• A battery with full electrical load will typically be exhausted in 15 to 20 minutes.
• Load shedding extends battery endurance to over 45 minutes by shedding non-essential bus loads.
• Alternator voltage (28.4V) is intentionally higher than battery voltage (24V) to allow charging.

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Retreating Blade Stall & Rotary Aerodynamic Limits

The high-forward-speed limit of a helicopter: dissymmetry of lift, the stalling retreating blade, and the flight-condition factors (high weight, high density altitude, turbulence) that bring it on early.

• CASR Part 61 MOS Schedule 3 (AD) 2.4.1 (p.400) — Forward-flight terms — dissymmetry of lift, flapback, retreating blade stallVerified“Explain the meaning of each of the following terms: (a) dissymmetry of lift; (b) flapback; (c) cyclic limits; (d) airflow reversal; (e) retreating blade stall.”
• CASR Part 61 MOS Schedule 3 (AD) 1.1.2 (p.402) — Rotor terms — dissymmetry of lift, blade flapping, retreating blade stallVerified“Explain the meaning of the following terms: (a) rotor force; ... (f) dissymmetry of lift; (h) blade coning; (i) blade flapping/overteetering; (j) retreating blade stall; (k) translational lift.”

• It is the retreating blade that stalls first — it meets the lowest relative airflow, needs the highest pitch to balance lift across the disc, and reaches the stalling angle first.
• Onset is at high forward airspeed, not low — the opposite of aeroplane stall intuition.
• High weight, high density altitude, low rotor RPM, turbulence and high G all reduce the airspeed at which it bites (effective VNE comes down).
• First cues are vibration, a nose-up pitch and a roll; recover by lowering collective, reducing airspeed and easing G — not by adding power.