A pilot notices blue exhaust smoke and unusually high oil consumption on a turbocharged airplane, along with normal manifold pressure indications. Which turbocharger-related failure is the most likely cause of these symptoms?
- AOverboost (pop-off) valve stuck in the closed position
- BFailed turbocharger center bearing/oil seals allowing engine oil to enter the induction and exhaust system
- CFailed absolute pressure controller reference line
- DWastegate stuck in the fully closed position
Show answer & explanationAnswer & explanation
Correct answer: B. Failed turbocharger center bearing/oil seals allowing engine oil to enter the induction and exhaust system
Blue exhaust smoke with high oil consumption but normal manifold pressure points to a turbocharger bearing/seal failure, which allows engine oil to leak past the seals into the exhaust and induction airstream where it is burned. A stuck wastegate, pop-off valve, or failed density controller would instead cause abnormal manifold pressure readings (overboost or underboost), not oil-related smoke.
Why the other options are wrong
- A. A stuck-closed pop-off valve would allow dangerous overboost, not oil consumption symptoms.
- C. A failed density controller reference line typically causes abnormal manifold pressure control, not oil smoke.
- D. A wastegate stuck closed would cause overboost (excess manifold pressure), not oil smoke.
Turbocharger Bearing/Seal Failure
Wear or failure of the turbocharger's center bearing and oil seals allows engine oil to leak into the exhaust and induction system, producing blue smoke and high oil consumption despite normal manifold pressure.
- Symptom: blue smoke plus high oil consumption
- Manifold pressure often remains normal
- Different from wastegate/pop-off failures, which cause pressure anomalies
Memory trick: Blue smoke with normal MP means oil is sneaking past worn turbo seals.