Definition
A malfunction of the turbocharger system in which the unit can no longer compress induction air to the level required for normal engine performance. Failures generally fall into two categories: those affecting the turbocharger itself (such as bearing failure, turbine or compressor wheel damage, or oil supply loss) and those affecting the system that controls it (such as a stuck or failed wastegate or controller). The result is either a loss of manifold pressure and engine power, or an uncontrolled overboost in which manifold pressure exceeds limits and can damage the engine.
Plain English
When the turbocharger or the system that regulates it stops working properly, the engine either loses the extra power the turbocharger was providing, or it gets too much boost and risks internal damage.
Context Anchor
Encountered in abnormal and emergency procedures for turbocharged piston airplanes, especially during climb or high-altitude cruise.
Derivation
Turbo comes from a Latin word meaning a spinning top or whirling motion, which fits the spinning turbine inside the unit. Charger means something that forces in or loads up, so a turbocharger is a spinning device that forces more air into the engine.
Why Pilots Care
The sudden power loss can prevent the airplane from maintaining altitude or clearing terrain, requiring immediate descent and a revised flight plan to reach a safe landing.
Grounding Statement
At high altitude the air is thin, so if the turbocharger stops adding air pressure, the engine can lose a large amount of usable power.
Intuition Check
Do not assume turbocharger failure always means the engine has quit. It usually means the engine has lost its boost and may keep running with much less power.
Example Sentence 1
After a sudden drop in manifold pressure during cruise at 16,000 feet, the pilot suspected a turbocharger failure and began a descent to a lower altitude.
Example Sentence 2
With the turbocharger failure confirmed, the crew elected to divert to a lower airport rather than continue across the mountains.