MD10 first officer reported a fuel system malfunction that led to a diversion.

Attributes
ACN	1539149
Time
Date	201804
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	DC-10 Undifferentiated or Other Model
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Fuel Storage System
Person 1
Function	First Officer
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Fuel Issue

Narrative:

During cruise we received a tnk 3 tip trapped level 1 alert and tnk 3 fuel qty lo level 1 alert. The message said that 5;800 lbs of fuel in tank 3 was unusable. There was no QRH for tnk 3 tip trapped so the captain ran the tnk 3 fuel qty lo QRH while I flew the plane. The QRH took fuel from tank 2 into tank 3; so we stopped the QRH because it was compounding the problem of unusable fuel in tank 3. We determined that continuing to [destination] would possibly cause us to run out of fuel in the number 3 engine so as we were passing ZZZ we decided the safest course of action was to land in ZZZ and fix the problem.

Original NASA ASRS Text

Title: MD10 First Officer reported a fuel system malfunction that led to a diversion.

Narrative: During cruise we received a TNK 3 TIP TRAPPED Level 1 Alert and TNK 3 FUEL QTY LO Level 1 Alert. The message said that 5;800 Lbs of fuel in tank 3 was unusable. There was no QRH for TNK 3 TIP TRAPPED so the Captain ran the TNK 3 FUEL QTY LO QRH while I flew the plane. The QRH took fuel from Tank 2 into Tank 3; so we stopped the QRH because it was compounding the problem of unusable fuel in tank 3. We determined that continuing to [destination] would possibly cause us to run out of fuel in the Number 3 engine so as we were passing ZZZ we decided the safest course of action was to land in ZZZ and fix the problem.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.