As of May 2019, the links in this post to John Deakin’s Pelican Perch articles in AvWeb don’t work.  I contacted AvWeb and they are changing servers and conducting some web site maintenance and told me that they expect the links to be back up soon.

The recent change to the commercial Airmen Certification Standards (ACS) eliminated the requirement for a complex airplane on the practical (check ride).  This is also true for the single-engine CFI.  A brand new commercial pilot can take the check ride in a Cessna 172 and walk across the ramp the very same day with their brand new Commercial temporary pilot certificate and climb in a Cessna Skylane or DA40 with a constant speed prop and take off.  So using a non-complex plane for the check ride does not relieve the applicant of the requirement to know about constant speed props and manifold pressure.  I like to ask questions during the oral about constant speed props, how the work, and manifold pressure.  I don’t expect an applicant to build the airplane but they should have a working knowledge of the systems as a commercial pilot.  A CFI applicant should be able to explain and instruct these systems.

One area of confusion is the difference between a constant speed prop on a single-engine piston airplane and a multi-engine airplane.  A multi-engine airplane prop feathers (or should!) to reduce drag.  A single-engine airplane (at least small piston airplanes) does not feather when the engine fails.  It would be nice if the propeller did feather but adding that feature to a small single would add weight and complexity that is just not necessary.  So a  single-engine prop fails to the low pitch setting.  When you walk up to a piston multi-engine on the ramp (e.g., PA-44), you’ll see the prop at flat pitch, not in the feather position.  But walk up to a turbine like a King Air, and you’ll notice the prop is feathered.  This is because turbines (at least most) are “free turbines” and the prop is not connected to a crankshaft like a piston.  The AvWeb website is home to John Deakin’s Pelican Perch series of articles.  Mr. Deakin does a great job of explaining airplane “stuff,” and his Pelican Perch #16 does a great job explaining props.  While you are there check out #15 on manifold pressure.