FAA Turbine engine FCU regulations Does the FAA have any regulations governing the design of a turbine engine FCU? I'm being questioned about an older Beechcraft PT6A FCU - in particular, how can I guarantee that when the power condition lever is at the shutoff/cutoff position, no fuel is moving to the combustor...? Any help would be appreciated... Thanks!

Edit - for those needing clarification:

Does the FAA have any regulations governing the design of a turbine engine FCU?

Simply as stated, does the FAA regulate how a turbine engine FCU can be designed - pressure allowances, flow volumes, etc. 

I'm being questioned about an older Beechcraft PT6A FCU - in particular, how can I guarantee that when the power condition lever is at the shutoff/cutoff position, no fuel is moving to the combustor...?

As stated, I'm being asked to prove that when the power condition lever in the cockpit is moved to the shutoff/cutoff (pick one term) position, fuel will not flow into the combustor. Tying into my first question, does the FAA regulate that a turbine FCU MUST absolutely cut off all fuel moving to the combustor, or is that just left to the designer to ensure...? 

Hope that clarifies everything. Not sure how much more detailed I can get without specific and possibly pointed questions.
Subpart E (Powerplant) of Part 23 (AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES) has quite a few regulations regarding fuel system operation. In particular, section 23.995, "Fuel Flow".

However, I could not see in there a regulation requiring no fuel to flow in the off position, but given the safety implications of that not occurring, I would fully expect that is a requirement that needs to be demonstrated. 

It appears to exist in Part 33 (AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES), subpart E (Design and Construction; Turbine Aircraft Engines) section 33.75 "Safety Analysis". This states:


  The applicant must analyze the engine, including the control system, to assess the likely consequences of all failures that can reasonably be expected to occur.... The safety analysis must also include, but not be limited to, investigation of the following: (vii) complete inability to shutdown the engine.


I don't expect there are any regulations defining how it needs to be designed to do this - but rather regulations saying what it needs to do, and the way of achieving it is left up to the designer.