FAA Powerplant Written Practice Test

In what scenario might a start stop button be necessary in a starter-generator system?

1. Cold start

2. Hung start

3. Hot start

4. Normal operation

The correct answer is: Hung start

A start stop button in a starter-generator system is particularly necessary during a hung start scenario. A hung start occurs when the engine does not achieve the required RPM to become self-sustaining after the ignition has been initiated. This situation can lead to excessive fuel flow, increased temperature, and potential engine damage if not addressed promptly. In a hung start, the start stop button allows the operator to interrupt the starting sequence safely, protecting the engine from conditions that could result in damage or failure. The ability to stop the starter and thereby halt the flow of fuel or air can mitigate risks associated with overheating and potential engine fire due to the prolonged cranking situation. During scenarios such as a cold start or hot start, while a start stop button can be useful, they don’t necessitate its immediate use in the same critical manner because these conditions are generally part of normal engine operations. In normal operation, the starter-generator functions efficiently without the need for intervention unless problematic conditions arise.