Compressor Stall: What It Is, How to Recover + Prevention
As your jet plane turns onto the runway you eagerly anticipate the takeoff. Suddenly, you are startled by a loud bang and flash of fire from one of the engines. What's going on? Is everything alright?
In this article, we'll delve into the world of compressor stalls—what they are, how to handle them, and how to avoid them altogether.
As your jet turns onto the runway, you eagerly anticipate takeoff. Suddenly, you’re startled by a loud bang and a flash of fire from one of the engines. What’s going on? Is everything alright?
If you don’t have experience with gas turbine engines, you may not be familiar with compressor stalls. But if you ever encounter one, it’s an experience you won’t soon forget.
In this article, we’ll break down compressor stalls—what they are, what causes them, how to recover, and how to reduce the chances of one happening in the first place.
What is a Compressor Stall?
Compressor stall is common in gas turbine engines when airflow through the compressor becomes unstable or disrupted. That disruption can reduce thrust, trigger loud bangs, and even produce visible flames.
A more severe event is compressor surge, where airflow can reverse or collapse—potentially causing significant engine damage. Both require immediate attention and proper procedures.
What Causes a Compressor Stall?
A compressor stall occurs when smooth airflow over compressor blades is disturbed, causing unstable compression and a momentary power drop. This can happen during high-demand phases like takeoff, climb, or rapid power changes.
In normal operation, air enters the engine, is compressed in stages, mixes with fuel in the combustor, and expands through turbines to generate thrust. During a stall, airflow becomes unstable and disrupts that process.
If not managed correctly, a stall can develop into a surge—where airflow can momentarily stop or reverse—creating a more serious risk to engine health.
Key Causes of a Compressor Stall or Surge
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Foreign object damage (FOD): debris, sand, or dirt can damage blades and reduce stall margin.
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Compressor contamination or wear: buildup and erosion can degrade airflow and raise the operating line.
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Bird strikes: can cause an abrupt airflow disruption and rapid loss of surge margin.
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Runway/flight deck debris: can be ingested and damage compressor stages.
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Operating outside the envelope: unusual profiles or improper procedures can increase stall risk.
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Inlet distortion: turbulent, hot, or uneven inlet airflow (including re-ingestion) can destabilize compressor flow.
How to Recover from a Compressor Stall
If a compressor stall occurs, pilots should always follow the published procedures for their specific aircraft and engine. In general, recovery focuses on stabilizing airflow and protecting engine limits.
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Throttle Response
Reduce thrust on the affected engine as appropriate. Smooth, controlled power reduction can help stabilize airflow and prevent escalation. Monitor engine indications closely—especially temperature, vibration, and spool speeds.
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Adjust Flight Profile (As Appropriate)
In some scenarios, leveling off or reducing angle of attack can help restore more stable inlet airflow and reduce stress on the compressor.
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Engine Restart
If the stall persists or the engine shuts down, a restart may be required—strictly in accordance with the aircraft checklist and manufacturer guidance.
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Maintenance and Inspection After Landing
After any suspected stall/surge event, maintenance should inspect the engine for damage, FOD, and compressor blade condition before the aircraft returns to service.
These actions can help mitigate a stall, but the correct response depends heavily on the aircraft type, engine model, and operating conditions.
How to Prevent Compressor Stalls
Preventing compressor stalls in turbine engines comes down to maintaining stable airflow and avoiding situations that reduce stall margin.
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Angle of Attack: Avoid aggressive pitch/energy states that can increase inlet distortion. Stable flying helps maintain consistent airflow into the engine.
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Air Pressure Management: Modern turbine engines use systems like bleed air, variable inlet guide vanes, and variable stator vanes to protect the compressor across different RPM ranges.
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Throttle Technique: Avoid abrupt throttle movements. Rapid power changes can create mismatches between airflow and compressor demand.
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Minimize Inlet Distortion: Uneven airflow into the engine can reduce stall margin and trigger local stalls—especially in turbulence, crosswinds, or re-ingestion conditions.
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Regular Maintenance: Routine inspections and cleaning help preserve compressor performance and reduce stall/surge susceptibility.
Real Examples of a Compressor Stall
The best way to recognize a compressor stall is to see and hear one. These videos show what it can look and sound like from the cabin and cockpit perspective.
This video provides an in-depth look at a compressor stall that occurred shortly after takeoff on an Aer Lingus Airbus.
This passenger video clearly captures the sound of a compressor stall and the decision to return and have the engine inspected.
Frequently Asked Questions
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What does a compressor stall sound like?
It can sound like a loud bang or series of pops. Some events also come with vibration, yaw, or a noticeable change in thrust.
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Can a compressor stall cause flames to shoot out of the engine?
Yes. A stall can disrupt combustion and airflow, which may create visible flashes or flames—especially at night.
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What’s the difference between compressor stall and compressor surge?
A stall is unstable airflow over compressor blades. A surge is more severe and can involve airflow reversal or a major breakdown in compressor flow.
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Is a compressor stall an emergency?
It can be. Some stalls are momentary and recover quickly, but others can escalate into surge or engine damage. Pilots should follow the aircraft checklist and treat abnormal engine indications seriously.
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What is the most common cause of compressor stalls?
Causes vary, but inlet airflow disturbances, rapid power changes, and compressor contamination/FOD are common contributors.
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How can pilots reduce the risk of compressor stalls?
Use smooth throttle technique, avoid operating outside limitations, maintain stable airflow conditions, and ensure proper maintenance and inspections.
Takeaway
Compressor stalls are rare—but they can be dramatic and require immediate attention. Safe operations come down to recognizing the signs, following aircraft-specific procedures, and reducing the risk through good technique and maintenance.
As always, rely on your aircraft’s POH/AFM and official training sources for procedures and limitations.
Fly safe!
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