King Air PT6A-60A Fuel Metering & Diagnostic Testing
Explore the named components, make a prediction, then connect the supplied result to the system. This workshop adds coached practice alongside the course handbook and assessed lab.
King Air PT6A-60A fuel metering: routes, signals and residual fuel
Trace the liquid-fuel route from heater to nozzles through the fuel control unit (FCU), then compare it with the mechanical and pneumatic paths that influence metering. Open each component to see its purpose and the evidence it requires. For each fictional comparison, make a prediction before revealing the changed record, then interpret only what that record establishes.
Liquid fuel, mechanical Ng feedback and governing air follow different paths
Recorded state: before the supplied change
Green outlines identify components named in the selected exercise record; they do not indicate a healthy component.
Named connections and what each arrow means
- Oil-to-fuel heater → Gear pump and fuel filtersPhysical relationship: Conditioned liquid-fuel supply
- Gear pump and fuel filters → FCU metering, bypass and cutoffPhysical relationship: P1 pump-delivery fuel
- FCU metering, bypass and cutoff → Gear pump and fuel filtersPhysical relationship: Po excess-fuel return passages
- Gear pump and fuel filters → Selected Ng and mechanical feedbackPhysical relationship: Coupling carries actual Ng rotation
- Selected Ng and mechanical feedback → FCU metering, bypass and cutoffPhysical relationship: Selected demand and opposing Ng feedback
- P3 source, tubes and filter → FCU metering, bypass and cutoffInformation / signal: P3 compressor-response air signal
- Nf governor and Py air route → FCU metering, bypass and cutoffInformation / signal: Py governing-air communication
- FCU metering, bypass and cutoff → Flow divider and purge interfacePhysical relationship: Metered delivery after shutoff
- Flow divider and purge interface → Manifolds and simplex nozzlesPhysical relationship: Primary and secondary fuel paths
- P3 source, tubes and filter → B300 purge air tank and checksPhysical relationship: P3 charges a separate purge branch
- B300 purge air tank and checks → Flow divider and purge interfacePhysical relationship: Stored purge air at shutdown
- P3 source, tubes and filter → Separate gas-generator fuel drainsPhysical relationship: P3 closing influence on separate case drains
Oil-to-fuel heater
Uses engine-oil heat to warm fuel before the engine-driven pump.
Supplied record: Connected supply path; thermal performance unmeasured
How it works with the rest
Fuel and oil travel in separate heat-exchanger circuits. The thermal element senses fuel temperature and moves an oil bypass sleeve: cold fuel calls for oil through the core; warmer fuel progressively diverts oil around it. This heater oil bypass is separate from the pump filter bypass and the FCU regulating bypass.
What the evidence must show
Identify the sensed fuel temperature and the oil route. Available fuel flow alone does not establish heat transfer or correct thermal selection.
Selected: Oil-to-fuel heater
Follow the change through the system.
Fictional PT6A-60A route comparison: the inlet screen is supplied intact, the discharge-filter medium is initially clear and its bypass is closed. The connected pump-to-FCU route and other pump interfaces are supplied available. Reveal changes only the discharge medium to blocked and its serviceable bypass to open. No flow rate, contamination amount, operating pressure or nozzle result is supplied.
Before the recorded change
Clear-medium record: fuel has a route through the discharge filter toward the FCU. The inlet screen is intact. Metering, local spray and actual flow quantities remain unmeasured.
Next observation
Choose your prediction before revealing the supplied result.
Reference: P&WC 3034342 Rev 43: 73-10-02 pp. 1-2; 73-20-00 p. 1; 73-00-00 Figure 2, p. 3/4 (Nov 5/1999).
Course applicability and study references
B300/B300C with PT6A-60A, using the supplied historical P&WC 3034342 Revision 43 (October 7, 2013) and the identified B300/B300C air-tank purge interface in Textron 130-590031-11 (April 1, 2018). Supplier dump/purge and P3-filter-drain service-bulletin branches stay explicit. Arrows summarize physical routes or control influences; they are not an installation drawing. These qualitative comparisons supply no engine performance, maintenance acceptance threshold, operating sequence or aircraft release.
- Historical engine architecture and metering
P&WC PT6A-60A/-60AG/-61 Maintenance Manual P/N 3034342, supplied Revision 43, October 7, 2013; this workshop addresses PT6A-60A. Read 73-00-00 pp. 1, 3/4 Figure 2, 5-6 and 73-20-00 pp. 1, 7-9/10 (Nov 5/1999). These explain selected demand, mechanical Ng feedback, P1/P2/Po fuel and separate P3/Py air influences. The supplied edition is historical; current applicable approved instructions and installed configuration govern maintenance.
- Heater, pump filtration and distribution
3034342: 73-10-01 pp. 1-2, 73-10-02 pp. 1-2 and 73-10-05 pp. 1-2 (Nov 5/1999); 73-10-04 p. 1 (Aug 19/2005). The heater senses fuel temperature while routing oil. Distinct inlet/discharge bypasses preserve routes without restoring their media. The described nozzle installation is seven primary plus seven secondary simplex adapters. Divider transition and dump/purge arrangement depend on the specified configuration.
- Pneumatic transfer and leak-location boundaries
3034342: 73-10-07 p. 1/2 and 73-10-08 p. 1/2 (Nov 5/1999); 73-10-07 pp. 211-212 (Jan 27/2012). Read the actual delivered signal separately from source pressure or tube appearance. Named FCU/governor bleed holes and the limited post-SB13175 P3-filter-drain exception do not authorize tube-connection leakage. This workshop supplies observations and gives no test-air connection or running procedure.
- Installed B300 purge and separate case drainage
Textron B300/B300C Maintenance Manual 130-590031-11, 28-00-00 p. 4 (Apr 1/2018), establishes P3 filter/check charging, the air tank and shutdown purge into the chamber. 72-00-00 p. 1 (Apr 1/2018) refers detailed PT6A-60A subjects to P&WC 3034342. P&WC 73-10-04 p. 1 distinguishes pre-SB13074 dump and post-SB13074 purge; 73-10-06 p. 1/2 identifies the separate P3-closed, spring-open gas-generator drains. No universal supplier configuration, residual quantity or speed transient is inferred.
Original learning diagrams and supplied training records explain the stated relationships. Current aircraft-effective instructions and authorization govern actual maintenance.