The relatively new Airmen Certification Standards, which replaces the Practical Test Standards for private pilot and instrument students, reflects a change in how CFIs should teach slow flight, as well as what candidates on their check ride are expected to demonstrate.
An FAA SAFO (Safety Alert for Operators), released Aug. 30, provides some clear guidance for the aviation community and students.
The revised evaluation standard expects students to establish and maintain an airspeed approximately 5 to 10 knots above the 1G stall speed, without activating a stall warning. No more flying with the stall-warning horn (and indicator light) blaring.
Loss of control in flight in general aviation is on the National Transportation Safety Board’s “Most Wanted List of Safety Improvements” for 2016. Hence, the FAA revised the slow-flight evaluation to align with the NTSB’s findings and concerns.
You can download the PDF of the SAFO, which contains detailed guidance, here: http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2016/SAFO16010.pdf