Which component provides fuel for initial engine start and serves as a backup to the engine driven low-pressure fuel pump?

The electrical boost pump plays a crucial role in the T-6B aircraft's fuel system by supplying fuel for the engine during initial start-up. When the engine starts, it requires a reliable fuel supply, particularly at low RPMs, where the engine-driven low-pressure fuel pump may not provide adequate fuel flow. The electrical boost pump ensures that there is enough fuel to start the engine efficiently.

Additionally, the electrical boost pump acts as a backup to the engine-driven low-pressure fuel pump during normal operation. If for some reason the engine-driven pump fails or provides insufficient pressure, the boost pump can continue to supply fuel to the engine, ensuring that it operates safely and effectively. This redundancy is critical for maintaining engine performance and safety throughout various phases of flight.

Other options represent different components of the fuel system, but they do not serve the same dual purpose of initiating fuel flow during engine start and providing backup support. The engine-driven high-pressure fuel pump, for instance, is primarily responsible for delivering fuel at high pressures once the engine is running, but it does not assist with starting the engine or act as a backup for the initial start process.