Last evening I was out in my driveway and as far as I could tell there was a c172 flying about 2,000 feet overhead. Just as I was watching it, there was a loud "pop" from the engine then no sound as I watched it sail behind other houses. My question is if during training the instructor will stall the engine as a test for the trainee? If so, wouldn't that be too low for that test? I did hop in my truck to try and follow it and where I thought it would go down if indeed needed. Found nothing, haven't heard anything.

Sounds like a misfiring engine. It happens sometimes and when I was working towards my PPL, experienced a few pops myself. To your question, no, the instructor will not cutoff the engine purposely. In a simulated engine failure, the instructor throttles back the engine to idle.

Most likely practicing emergency procedures and the instructor simulating an engine failure by retarding the throttle to idle. The pop was from the throttle being closed too quickly, resulting in unburned fuel detonating in the exhaust.

In aviation we avoid using the word "stall" is reserved for the aerodynamic phenomenon, it's not used in any relation to the power plant to avoid confusion. But to answer your question, the engine is never shut down on purpose for training, engine failures are simulated by retarding the power to idle.

Yeah, I should have used a different term. Thanks guys! I pry wasn't close enough hear it throttle back up.

Conniston wrote:

Most likely practicing emergency procedures and the instructor simulating an engine failure by retarding the throttle to idle. The pop was from the throttle being closed too quickly, resulting in unburned fuel detonating in the exhaust.

In aviation we avoid using the word "stall" is reserved for the aerodynamic phenomenon, it's not used in any relation to the power plant to avoid confusion. But to answer your question, the engine is never shut down on purpose for training, engine failures are simulated by retarding the power to idle.

The term "engine stall" is used in jet engines to describe a flow disruption.

Conniston wrote:

In aviation we avoid using the word "stall" is reserved for the aerodynamic phenomenon, it's not used in any relation to the power plant to avoid confusion.

Ummm, compressor stall in a jet engine?

Starlionblue wrote:

Conniston wrote:

Most likely practicing emergency procedures and the instructor simulating an engine failure by retarding the throttle to idle. The pop was from the throttle being closed too quickly, resulting in unburned fuel detonating in the exhaust.

In aviation we avoid using the word "stall" is reserved for the aerodynamic phenomenon, it's not used in any relation to the power plant to avoid confusion. But to answer your question, the engine is never shut down on purpose for training, engine failures are simulated by retarding the power to idle.

The term "engine stall" is used in jet engines to describe a flow disruption.

No it isn’t. Compressor fan blades experience stalls; engines do not.

fr8mech wrote:

Conniston wrote:

In aviation we avoid using the word "stall" is reserved for the aerodynamic phenomenon, it's not used in any relation to the power plant to avoid confusion.

Ummm, compressor stall in a jet engine?

Not related to the operation of the engine. Again, the fan blade is stalling, in exactly the same way a wing stalls: airflow disruption. It’s purely aerodynamic.

Not related to the engine? Of course it is. When the fan or compressor stalls, or surges, you most certainly affect the operation of the engine, to include the very real possibility of a flameout.

So, yes, there word stall is used when we describe power plant faults on aircraft.

fr8mech wrote:

Not related to the engine? Of course it is. When the fan or compressor stalls, or surges, you most certainly affect the operation of the engine, to include the very real possibility of a flameout.

So, yes, there word stall is used when we describe power plant faults on aircraft.

That’s entirely misleading and inaccurate. The term “stall” is used to describe airflow disruptions that can have *effects* on turbine engines. You are describing the *symptoms* of a compressor stall; its effects (which are related, obviously). The actual *stall* is a disruption of airflow, in this case over a fan blade or blades, and the stall itself can happen regardless of the overall health of the engine. Therefore, the compressor stall and its root cause have nothing to do with the engine itself, and one would never refer to an engine fault that did not involve disrupted airflow as a “stall,” as that word is purely used to describe aerodynamics, not mechanical parts. Do you see what I’m saying here?

N766UA wrote:

That’s entirely misleading and inaccurate. The term “stall” is used to describe airflow disruptions that can have *effects* on turbine engines. You are describing the *symptoms* of a compressor stall; its effects (which are related, obviously). The actual *stall* is a disruption of airflow, in this case over a fan blade or blades, and the stall itself can happen regardless of the overall health of the engine. Therefore, the compressor stall and its root cause have nothing to do with the engine itself, and one would never refer to an engine fault that did not involve disrupted airflow as a “stall,” as that word is purely used to describe aerodynamics, not mechanical parts. Do you see what I’m saying here?

I see what you’re saying, and don’t really dispute the airflow bit, but, and you know there is a but, the overall health of the engine can cause a stall (of the airflow). Bleed valve (chapter 75) faults, variable stator vane faults, fuel control faults, the various linkages and controls that link all together can be worn. All those are part of the engine and the engine’s overall health can be affected by the components’ health.

Reciprocating engines do stall in the classic sense. And, I’ve never heard another term used to describe a recip that has unexpectedly shutdown, other than stall. If the engine stalls, then it’s an engine stall, if the aircraft stalls, then the aircraft has stalled. The word “stall” is used correctly in both case.

The op used the proper term with proper usage when he said “the instructor will stall the engine”.

fr8mech wrote:

N766UA wrote:

That’s entirely misleading and inaccurate. The term “stall” is used to describe airflow disruptions that can have *effects* on turbine engines. You are describing the *symptoms* of a compressor stall; its effects (which are related, obviously). The actual *stall* is a disruption of airflow, in this case over a fan blade or blades, and the stall itself can happen regardless of the overall health of the engine. Therefore, the compressor stall and its root cause have nothing to do with the engine itself, and one would never refer to an engine fault that did not involve disrupted airflow as a “stall,” as that word is purely used to describe aerodynamics, not mechanical parts. Do you see what I’m saying here?

I see what you’re saying, and don’t really dispute the airflow bit, but, and you know there is a but, the overall health of the engine can cause a stall (of the airflow). Bleed valve (chapter 75) faults, variable stator vane faults, fuel control faults, the various linkages and controls that link all together can be worn. All those are part of the engine and the engine’s overall health can be affected by the components’ health.

Reciprocating engines do stall in the classic sense. And, I’ve never heard another term used to describe a recip that has unexpectedly shutdown, other than stall. If the engine stalls, then it’s an engine stall, if the aircraft stalls, then the aircraft has stalled. The word “stall” is used correctly in both case.

The op used the proper term with proper usage when he said “the instructor will stall the engine”.

That's not correct. In aviation, the term "stall" is not used for describing an engine shutdown, regardless of whether is a piston or a turbine, to avoid confusion with the term stall used in aerodynamics.

I could have worded my earlier post better, as the blades on a jet engine compressor can indeed stall under certain conditions, and as such the word stall can be "related" to a jet engine (still in the aerodynamic sense, completely unrelated to the term stall used to signify engine stoppage)

However for the purpose of the OP's question, the main point is that the term engine stall as commonly used in automobiles is not applicable for aircraft, it has a completely different meaning.

The term "Engine Stall" is used multiple times in the Airbus 330 FCOM I'm looking at right now. This includes an abnormal procedure for "ENG 1(2) STALL". "This alert triggers when an engine stall is detected."

If it's good enough for Airbus and Rolls-Royce....

Misfiring like an older muscle car would, common in the 177, and in older 172s

The instructor retarded the throttle to idle. In a piston engine, there is afterfiring and backfiring. What you heard was an possibly afterfire. (backfire through the induction or intake, afterfire through the exhaust).

Then again, it could have been an actual problem.

When rapid throttle movement creates a bang or pop, it's usually an indication of rough handling, and it's never beneficial for the engine.