of the airfoil. This can also be referred to as stall margin  awareness. More simply explained, it is the margin that exists  between the current AOA that the airfoil is operating at, and  the AOA at which the airfoil will stall (critical AOA).  Angle of attack is taught to student pilots as theory in ground  training. When beginning flight training, students typically  rely solely on airspeed and the published 1G stall speed to  avoid stalls. This creates problems since this speed is only  valid when the following conditions are met:  Speed by itself is not a reliable parameter to avoid a stall.  An airplane can stall at any speed. Angle of attack is a better  parameter to use to avoid a stall. For a given configuration,  the airplane always stalls at the same AOA, referred to as  the critical AOA. This critical AOA does not change with:  state of an airplane is the balance between airspeed, altitude,  drag, and thrust and represents how efficiently the airfoil is  operating. The more efficiently the airfoil operates; the larger  stall margin that is present. With this increased situational  awareness pertaining to the energy condition of the airplane,  pilots will have information that they need to aid in preventing  a LOC scenario resulting from a stall/spin. Additionally, the  less energy that is utilized to maintain flight means greater  overall efficiency of the airplane, which is typically realized in  fuel savings. This equates to a lower operating cost to the pilot.  Just as training is required for any system on an aircraft,  AOA indicators have training considerations also. A more  comprehensive understanding of AOA in general should be  the goal of this training along with the specific operating  characteristics and limitations of the installed AOA indicator.  Ground and flight instructors should make every attempt  to receive training from an instructor knowledgeable about  AOA indicators prior to giving instruction pertaining to or in  airplanes equipped with AOA indicators. Pilot schools should  incorporate training on AOA indicators in their syllabi,  whether their training aircraft are equipped with them or not.  An AOA indicator can have several benefits when installed  in general aviation aircraft, not the least of which is increased  situational awareness. Without an AOA indicator, the AOA  is “invisible” to pilots. These devices measure several  parameters simultaneously and determine the current AOA  providing a visual image to the pilot of the current AOA along  with representations of the proximity to the critical AOA.  [Figure 5-42]  These devices can give a visual representation  of the energy management state of the airplane. The energy  Installation of AOA indicators not required by type  certification in general aviation airplanes has recently been  streamlined by the FAA. The FAA established policy in  February 2014 pertaining to non-required AOA systems and  how they may be installed as a minor alteration, depending  upon their installation requirements and operational  utilization, and the procedures to take for certification of  these installations. For updated information, reference the  FAA website at www.faa.gov.  While AOA indicators provide a simple visual representation  of the current AOA and its proximity to the critical AOA, they  are not without their limitations. These limitations should  be understood by operators of general aviation airplanes  •  Weight  •  Bank angle  •  Temperature  •  Density altitude  •  Center of gravity  •  Unaccelerated flight (a 1G load factor)  •  Coordinated flight (inclinometer centered)  •  At one weight (typically maximum gross weight)  Figure 5-41.  A variety of AOA indicators.  5-27 