Answer the following questions.

1. Describe the term "feathering" as it pertains to propeller function and why it's essential to be aware of this dynamic during an accident investigation such as the Zonk Air accident.
2. What is meant by the general investigative expression, "Turbine parts may have a memory?" (Note: the word "memory" does not refer to a human factors issue.)
3. What is meant by "critical flows" needed by a turbine engine to operate properly, and is there a cause-and-effect relationship in regards to these flows and an accident involving turbine power plants?
4. Support your opinions with at least one valid reference. .