Airworthiness Directive (AD) . A regulatory notice sent  out by the FAA to the registered owner of an aircraft  informing the owner of a condition that prevents the aircraft  from continuing to meet its conditions for airworthiness.  Compliance with AD notes must be within the required time  limit, and the fact of compliance, the date of compliance, and  the method of compliance must be recorded in the aircraft’s  maintenance records. Aircraft categories. (1) As used with respect to the  certification, ratings, privileges, and limitations of airmen,  means a broad classification of aircraft. Examples include:  powered parachute, airplane, rotorcraft, glider, lighter-than- air, and weight-shift control. (2) As used with respect to the  certification of aircraft, means a grouping of aircraft based  upon intended use or operating limitations. Examples include:  transport, normal, utility, acrobatic, limited, restricted, and  provisional. Aircraft flight manual (AFM).  Also called the Pilot’s  Operating Handbook (POH), a document developed by the  aircraft manufacturer and approved by the FAA. It is specific  to a particular make and model aircraft by a serial number,  and contains operating procedures and limitations. Altimeter.  A flight instrument that indicates altitude by  sensing pressure changes. AME.  See Aviation Medical Examiner. Ammeter.  An instrument installed in series with an electrical  load used to measure the amount of current flowing through  the load. Aircraft operating instructions (AOI).  An alternative to  the approved term, Pilot's Operating Handbook. Airfoil.  Any surface, such as a wing or propeller, which  provides aerodynamic force when it interacts with a moving  stream of air.  Angle of attack (AOA).  The acute angle between the chord  line of the airfoil and the direction of the relative wind. Angle of incidence.  The angle formed by the chord line  of the wing at the keel of a WSC and a line parallel to the  longitudinal axis of the WSC carriage. The angle of incidence  changes in the WSC controlled by the pilot. Airmanship.  A sound acquaintance with the principles of  flight, the ability to operate an airplane with competence and  precision both on the ground and in the air, and the exercise  of sound judgment that results in optimal operational safety  and efficiency. Airmanship skills.  The skills of coordination, timing, control  touch, and speed sense in addition to the motor skills required  to fly an aircraft. Anhedral.  A downward slant from root to tip of an aircraft’s  wing opposite from dihedral. Annual inspection.  A complete inspection of an aircraft and  engine, required by the Code of Federal Regulations, to be  accomplished every 12 calendar months on all certificated  aircraft. Only an A&P technician holding an Inspection  Authorization can conduct an annual inspection. AOA.  See angle of attack. AOI.  See aircraft operating instructions.  Arm.  The horizontal distance in inches from the reference  datum line to the center of gravity of an item. Used in weight  and loading calculations. Airport/facility directory (A/FD).  A publication of the  Federal Aviation Administration containing information  on all airports, seaplane bases, and heliports open to the  public. The A/FD contains communication data, navigational  facilities, and certain special notices and procedures. Airport.  An area of land or water that is used or intended to  be used for the landing and takeoff of aircraft, including its  buildings and facilities, if any. Airspace.  The space above a certain geographical area. Airworthiness . A state in which an aircraft or component  meets the conditions of its type design and is in a condition  for safe operation. AROW.  Certificates and documents required to be onboard  an aircraft to determine airworthiness: Airworthiness  certificate, Registration certificate, Operating limitations,  Weight and balance data. ASOS.  See Automated Surface Observing System. Aspect ratio.  Span of a wing divided by its average chord. Airworthiness Certificate . A certificate issued by the  FAA to aircraft that have been proven to meet the minimum  standards set down by the Code of Federal Regulations.  G-2