How do you recognize an engine compressor stall?

How do you recognize an engine compressor stall?

• A. A slight tremor in the airframe with no TGT change
• B. Engine oil pressure drop only
• C. A loud banging or popping accompanied by rapid increase in TGT and fluctuations in NG, Q, and NP
• D. A sudden decrease in RPM

Answer: (C)

A compressor stall (surge) is an unstable flow condition in the engine’s compressor that suddenly disrupts air through the spooling stages. The hallmark sign is a loud banging or popping sound from the engine, driven by pressure oscillations as the flow separates and reattaches. This surge also causes a rapid rise in turbine gas temperature because the unstable flow leads to less efficient combustion and heat buildup. At the same time, the engine speeds and torque become erratic, so you’ll see fluctuations in NG (gas generator speed), NP (power section speed), and Q (torque). That combination—audible banging or popping plus a rapid TGT increase and unstable engine speeds—is the clearest indication of a compressor stall. Other signs like a slight airframe tremor with no TGT change point to something milder, oil pressure changes indicate lubrication issues, and a simple RPM drop can happen for various reasons but doesn’t capture the surge and temperature spike that define a stall.

A compressor stall (surge) is an unstable flow condition in the engine’s compressor that suddenly disrupts air through the spooling stages. The hallmark sign is a loud banging or popping sound from the engine, driven by pressure oscillations as the flow separates and reattaches. This surge also causes a rapid rise in turbine gas temperature because the unstable flow leads to less efficient combustion and heat buildup. At the same time, the engine speeds and torque become erratic, so you’ll see fluctuations in NG (gas generator speed), NP (power section speed), and Q (torque).

That combination—audible banging or popping plus a rapid TGT increase and unstable engine speeds—is the clearest indication of a compressor stall. Other signs like a slight airframe tremor with no TGT change point to something milder, oil pressure changes indicate lubrication issues, and a simple RPM drop can happen for various reasons but doesn’t capture the surge and temperature spike that define a stall.