Engine Performance and Matching Questions and Answers

Answer: A

Correct answer: Both Statement I and Statement II are correct

Both are true and the second explains the first. Air bled off after compression never reaches the turbine, so the turbine sees less flow than the compressor delivered and the matching is disturbed - the working line rises and the surge margin falls. This is why bleed extraction changes where the engine runs, not just how much thrust is left over.

Answer: B

The first is correct and the second reverses the basis of the technique. Each fault produces a distinct pattern across the measurements, and recognising that pattern is precisely what narrows the diagnosis before any inspection.

Answer: C

The three conditions must hold simultaneously, and the operating point is wherever they are all satisfied at once. It is rarely where any single component would perform best, which is exactly what makes matching a compromise.

Answer: D

Area is the lever because the choked nozzle fixes the flow the compressor must deliver. A few per cent of change moves the line a long way, which makes it a far more effective remedy than any aerodynamic redesign of the blading.

Answer: A

Correct answer: 1, 2, 3, 4, 5

Fuel flow responds first, since it is what the throttle commands. The extra heat raises turbine entry temperature and the pressure ratio before the rotor inertia has allowed the speed to change, so the working line moves up towards surge. Only then does the shaft accelerate and the flow rise to match, and once the new speed is established the working line settles back to its steady position.

Answer: B

Correct answer: 1, 2, 3, 4

Exhaust gas temperature at fixed thrust rises monotonically through the engine’s life as clearances open and seals wear, so the order of increasing temperature is simply the order of increasing age: new from the factory, after several thousand cycles, approaching the limit, and finally removed with the margin exhausted. That monotonic behaviour is what makes the margin usable as a life indicator.

Answer: C

It is the pattern rather than any single reading that identifies the component. A compressor efficiency loss and a turbine flow capacity change both raise the exhaust temperature, but they differ in what else moves alongside it.

Answer: D

Correct answer: Only three

The first three are correct: continuity means the flow leaving one component enters the next, work balance means the turbine produces what the compressor demands, and speed compatibility means components on a shaft turn together. The fourth repeats the work balance statement under the heading of continuity, so it is the mismatched pair.

Answer: A

Correct answer: Only three

The first three are the standard corrections: speed divided by the square root of the temperature ratio, flow multiplied by root temperature and divided by pressure ratio, and thrust divided by pressure ratio. The fourth is wrong - speed corrects on temperature alone, because it is blade Mach number that must be preserved, and Mach number depends on the speed of sound and hence on temperature.

Answer: B

Correct answer: Only three

Opening either nozzle lowers the working line and improves the margin, and rapid acceleration raises it transiently. The fourth entry contradicts the first, claiming that opening the turbine nozzle area raises the working line. It does the opposite: a larger throat passes more corrected flow at a given pressure ratio, so the compressor is asked for more flow and less pressure.