Engine Performance and Matching Questions and Answers

Answer: C

Worn seals, eroded blades and growing tip clearances all force the engine to run hotter for the same output. Tracking that trend allows a shop visit to be planned rather than forced by an eventual exceedance in service.

Answer: D

Correct answer: The working line rising towards surge

Slamming the throttle open adds fuel faster than the rotor can accelerate, so temperature and pressure ratio rise while flow lags, and the working line climbs into the surge line. The acceleration schedule limits the fuel flow to what the engine can absorb at its current speed, keeping the transient excursion inside the margin at the cost of a slightly slower response.

Answer: A

Dividing by the appropriate functions of inlet temperature and pressure removes the dependence on ambient conditions. That collapse is exactly what makes a single map a usable design and diagnostic tool across the whole envelope.

Answer: B

Each component's deterioration produces a distinct pattern across the measured parameters. An unchanged turbine flow capacity alongside a compressor efficiency loss points clearly to the front of the engine rather than the back.

Answer: C

Air taken after compression has absorbed work and then leaves without doing any in the turbine. The engine must work harder to produce the same thrust, which is why performance figures always state the offtakes assumed.

Answer: D

It is placed by the matching conditions rather than by any preference of the designer. Its distance from the surge line is the surge margin, which must remain adequate through transients and through the engine's whole service life.

Answer: A

The relation follows from the way blade Mach numbers depend on temperature. Cold air gives a higher corrected speed at unchanged shaft rpm, which is why an engine behaves differently on a cold day even at the same physical speed.

Answer: B

Once sonic conditions exist in the throat, nothing downstream alters the flow passing through it. That fixed capacity ties the compressor's operating point directly to the turbine's geometry, which is why nozzle area is such an effective lever.

Answer: C

Cutting fuel faster than the shaft slows leaves the mixture below the limit that sustains a flame. The fuel control schedules it for the same reason it schedules acceleration, protecting the engine at both ends of the throttle range.

Answer: D

Each component's deterioration produces a distinct pattern across the measurements rather than moving one reading alone. Recognising that pattern narrows the diagnosis considerably before the engine is opened for inspection.