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Office of Aviation Safety

PC-12 Fuel System

Airworthiness presentation

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Right Fuel Tank

Left Fuel Tank

To Engine

Fuel System Delivery Fuel Pump

Delivery Fuel Pump

To Engine

R

L

Fuel System

Check Valve

Check Valve

To Engine

R

L

Fuel System

Fuel Filter

Bypass Valve

To Engine

R

L

Fuel System

Engine-Driven Fuel Pump

To Engine

R

L

Fuel System

Fuel Supply

Fuel Return

To Engine

Fuel System

Fuel Boost Pumps

Check Valves

To Engine

Fuel Low Pressure

To Engine

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Fuel Low Pressure

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Fuel Low Pressure

Fuel Quantity Imbalance

To Engine

Fuel Quantity Imbalance

To Engine

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Accident Scenario• Low fuel pressure 1 hour 13 minutes

into flight• Corrected through fuel boost pump

operation• No fuel pressure cautions• Annunciations first indications of

anomaly

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Accident Scenario

• Lack of FSII• Ice accumulation• Ice/water might have been found if

pilot performed preflight inspection

• Low pressure state• Described in checklist• Occurred on previous flights

Flight Time - 1 Hour 13 Minutes

To Engine

Flight Time – 1 Hour 18 Minutes

To Engine

Flight Time - 1 Hour 21 Minutes

To Engine

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Accident Scenario• Performance of fuel system

degraded over time, resulting in significant fuel imbalance

• If pilot had added FSII, low pressure state and subsequent imbalance would not have developed

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Accident Scenario• By 1 hour 52 minutes, imbalance

about 25% of one tank’s capacity• Pilot likely recognized fuel

imbalance before this point• Pilot attempted to manually balance

fuel through activation of left boost pump

• Similar actions observed later in flight

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Flight Time - 2 Hours 17 Minutes

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Safety Issues• Fuel filler placards not required to

advise necessity for FSII• FAA guidance on fuel system icing

prevention does not include information on need for FSIIs

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