Definition
A descriptive phrase used in engine operating limitations and troubleshooting references to indicate that a measured parameter — such as cylinder head temperature, oil temperature, oil pressure, manifold pressure, or RPM — has reached a value above which continued operation will cause mechanical harm to the engine. The threshold is defined by the engine manufacturer and is reflected in the red-line markings and operating limits published in the Pilot's Operating Handbook or engine manual.
Plain English
The reading on a gauge has gone past the safe limit set by the engine maker, and if the engine keeps running at that level, parts will start to break or wear out.
Context Anchor
Seen in engine operation, engine troubleshooting, and maintenance descriptions of overheating, improper starting, excessive pressure, or over-speed conditions.
Why Pilots Care
Continuing to operate past this point can cause immediate engine failure or hidden damage that leads to failure later in flight.
Analogy
It is like running a household machine past the point it was built to handle. A brief strain may be tolerated, but too much heat or force can permanently damage the machine.
Grounding Statement
The phrase points to a condition that is no longer just abnormal; it has reached a level where the engine itself may be harmed.
Intuition Check
Do not read this as simply meaning 'higher than normal.' Here it means high enough to exceed a safe limit and possibly cause actual engine damage.
Example Sentence 1
When the cylinder head temperature climbed high enough to damage the engine, the pilot reduced power and enriched the mixture to bring it back into the green arc.
Example Sentence 2
After the propeller strike the engine was still high enough to damage the engine if run at full throttle.