Educational familiarization only. This TechOpsBase resource is an original learning transformation grounded in a privately supplied B737 MAX ATA 28 source. It does not reproduce manufacturer task steps, limits, figures or controlled maintenance instructions. Current approved data and aircraft effectivity control real work.
What this resource teaches
Connect servicing/quantity functions with bonding, controlled configuration and ignition-prevention reasoning.
Refuel and defuel are controlled flow paths
The chapter contains pressure-refuel and defuel functions, which means servicing has its own valves, indications and safety logic rather than simply reversing the engine-feed path.
Quantity is an information system
Fuel quantity indications depend on sensing, processing and display. A displayed quantity should be separated mentally from the physical presence of fuel and from pump feed performance.
Bonding and configuration control matter
The source contains stringent electrical-bonding checks and airworthiness-limitation/CDCCL context. Those controls exist because fuel vapor ignition risk can be influenced by electrical/static energy and by maintenance configuration.
Safety is part of architecture
Fuel-system learning is incomplete if it only draws pumps and valves. Ignition prevention, bonding, contamination control, tank-entry controls and approved configuration are part of the system design intent.
Do not convert study into procedure
TechOpsBase does not provide tank-entry, bonding-limit, refuel/defuel or component-installation instructions. Those tasks require current approved data and authorization.
Put this topic into the wider system
Fuel safety is functional architecture
Bonding, ignition-source control, venting, configuration control and inerting are not administrative extras. They preserve the assumptions under which the tank was shown to be safe. Maintenance that disturbs those assumptions can affect airworthiness even if the fuel-feed function appears normal.
Cross-system dependencies
ATA 28 depends on ATA 24 electrical power for pumps/control, interfaces with ATA 49 for APU feed, and shares the center-tank safety objective with ATA 47. Treat these interfaces as part of the system map when symptoms appear in more than one chapter.
Deeper system reasoning
Treat storage, pressure and routing as separate layers
The fuel system becomes easier to reason about when tank quantity, pump pressure and routing are kept separate. Main and center tanks store fuel; boost pumps create feed pressure; crossfeed and shutoff/spar valves determine connectivity; engines and the APU are consumers. A pump running does not prove useful fuel reaches a consumer, and an open routing valve does not create pressure. Mapping those layers prevents one indication from being treated as a complete diagnosis.
Technician evidence matrix
Record tank quantity, expected pump/source, valve/manifold connectivity, affected consumer, crossfeed configuration and whether the symptom follows the source or remains with the path/consumer.
Before using a maintenance message as a conclusion, note what independent evidence agrees with it and what evidence does not. If an alternate source, channel or display changes the symptom, record that explicitly because it can separate a common path from a source-specific path. Preserve configuration and event conditions in the handover so the next technician does not have to rebuild the diagnostic context from memory.
Evidence-first study method
For any system complaint, separate source/input, control logic, physical response, sensing/indication and consumer/result. When two layers disagree, that disagreement is useful evidence. Do not turn that evidence into a maintenance action until the applicable approved fault-isolation or maintenance data is open.
Approved-data boundary
Educational system explanation only. Do not use this page to perform maintenance, operate aircraft systems, isolate components or determine dispatch status. Current approved maintenance data, aircraft effectivity and operator procedures control real aircraft work.
