A Cessna 172 training aircraft is powered by a Lycoming O-360 engine. What type of engine is this, and how does it produce power?

A turboprop engine — a gas turbine drives the propeller via a reduction gearbox A turbojet engine — all thrust comes from a high-velocity exhaust jet A piston (reciprocating) engine — combustion pressure drives a piston that rotates a crankshaft A turbofan engine — a large front fan provides most of the thrust

The ATR 72 regional airliner cruises at about 510 km/h and uses turboprop engines. Why is the turboprop better suited to this role than a pure turbojet?

Turboprops produce more thrust at high altitude than turbojets Turboprops are more fuel-efficient than turbojets at speeds below about 600 km/h Turboprops are cheaper because they have no compressor or turbine stages Turboprops can be throttled by changing the number of active cylinders

In a turbojet engine, air passes through intake → compressor → combustion chamber → turbine → nozzle. What is the sole function of the turbine in this engine?

The turbine burns additional fuel to increase exhaust temperature The turbine compresses the incoming air before combustion The turbine extracts just enough energy from the hot exhaust to drive the compressor The turbine slows the exhaust to increase pressure in the nozzle

A CFM56 turbofan engine has a bypass ratio of approximately 6:1. What does this mean?

The engine produces six times as much thrust as its predecessor Six times as much air bypasses the hot core as flows through the combustion section The fan diameter is six times the core diameter The engine burns six times less fuel than a piston engine of equivalent power

Why are high-bypass turbofan engines used on all modern airliners instead of turbojets?

Turbojets produce excessive thrust for commercial aircraft and must be replaced High-bypass turbofans are significantly quieter and more fuel-efficient at subsonic cruise speeds High-bypass turbofans can operate at higher altitudes than turbojets High-bypass turbofans are simpler to manufacture because they have no combustion chamber

A military fighter jet uses a low-bypass turbofan with a bypass ratio of 0.4:1. Why is low bypass preferred over high bypass for this application?

Low-bypass turbofans are quieter, reducing the aircraft's acoustic signature Low-bypass turbofans have a higher thrust-to-weight ratio, which is more important for combat than fuel efficiency Low-bypass turbofans can burn any type of fuel, including diesel Low-bypass turbofans do not require a compressor, making them lighter

What is specific fuel consumption (SFC), and what does a lower value indicate?

SFC is the ratio of thrust to engine weight; a lower value means the engine is heavier SFC is the maximum speed achievable; a lower value means the aircraft is slower SFC is the mass of fuel burned per unit of thrust per unit of time; a lower value means the engine is more fuel-efficient SFC is the ratio of exhaust speed to intake speed; a lower value means more bypass air

A fighter pilot engages the afterburner during a combat manoeuvre. What happens inside the engine, and what is the trade-off?

The compressor spins faster, increasing airflow and thrust with no fuel penalty Fuel is injected into the hot exhaust and burned again, increasing thrust by up to 50% but consuming fuel at a very high rate Water is injected into the intake, cooling the air and increasing its density for more thrust Bypass ratio is temporarily increased, forcing more air around the core

A cargo aircraft has a total thrust of 800 kN and a maximum takeoff weight of 3,600 kN. What is its thrust-to-weight ratio, and what does this tell you?

T/W ≈ 4.5; the aircraft can climb steeply and needs only a short runway T/W ≈ 0.22; the aircraft cannot accelerate vertically and needs a long runway for takeoff T/W ≈ 1.0; the aircraft can hover and takeoff vertically T/W ≈ 2.2; the aircraft can climb vertically but not sustain supersonic flight

A variable-pitch propeller automatically adjusts blade angle. What is the primary benefit of this design?

It reduces the structural loads on the propeller blades during takeoff It prevents the propeller from rotating during engine shutdown It maintains efficient propeller operation across a wide range of airspeeds and power settings It allows the propeller to reverse direction for braking after landing

An eVTOL air taxi uses electric motors instead of gas turbines. What is the current main technical limitation of battery-electric aircraft?

Electric motors produce too much noise for urban operations Electric motors cannot produce enough torque to spin large rotors Battery energy density is much lower than aviation fuel, severely limiting range and payload Electric motors require special atmospheric conditions and cannot fly above 1,000 m

At high forward speed, ram drag reduces the net thrust of a jet engine. What causes ram drag?

High-speed airflow heats the intake, reducing air density and mass flow The momentum of air being swallowed by the intake must be subtracted from the momentum of the exhaust jet when calculating net thrust The fan blades stall at high forward speed, reducing compression efficiency Ram pressure forces extra air into the combustor, causing rich-mixture flameout