A pilot operating a turbocharged reciprocating engine notices that manifold pressure is not automatically controlled and instead relies entirely on pilot throttle input, with the wastegate fixed in one position. What type of turbocharger control system does this aircraft most likely have?
- AA ground-boosted system that provides turbocharging only below a critical altitude
- BA density controller system that automatically compensates for changes in altitude and temperature
- CA fixed wastegate system requiring careful pilot throttle management to avoid overboosting
- DAn automatic wastegate system using a controller to modulate exhaust bypass continuously
Show answer & explanationAnswer & explanation
Correct answer: C. A fixed wastegate system requiring careful pilot throttle management to avoid overboosting
Some early or simpler turbocharger installations use a fixed (or manually adjusted, non-automatic) wastegate position, meaning the pilot must carefully manage throttle input, especially during climbs and descents, to avoid exceeding maximum manifold pressure limits (overboosting), since there is no automatic controller continuously modulating exhaust flow to the turbine.
Why the other options are wrong
- A. Ground boosting refers to turbocharger sizing/limitations at altitude, not to fixed vs automatic wastegate control.
- B. A density controller automatically adjusts wastegate position, which contradicts the fixed wastegate description.
- D. This describes a fully automatic system, which is not what's being described since the wastegate is fixed.
Fixed Wastegate Turbocharger
A turbocharging system in which the wastegate position is fixed or manually set rather than automatically controlled, requiring the pilot to closely monitor and manage manifold pressure to prevent overboost.
- No automatic controller adjusts exhaust bypass
- Pilot must manage throttle carefully during power changes
- Risk of overboost if throttle advanced too quickly at low altitude
Memory trick: Fixed wastegate = pilot is the 'human governor'