Note: Helicopter pilots may use the Category A line of  minimums provided the helicopter is operated at Category  A airspeeds.  An airplane is certified in only one approach category, and  although a faster approach may require higher category  minimums to be used, an airplane cannot be flown to the  minimums of a slower approach category. The certified  approach category is permanent and independent of the  changing conditions of day-to-day operations. From a  TERPS viewpoint, the importance of a pilot not operating  an aircraft at a category line of minimums lower than the  aircraft is certified for is primarily the margin of protection  provided for containment of the aircraft within the  procedure design for a slower aircraft. This includes height  loss at the decision altitude, missed approach climb surface,  and turn containment in the missed approach at the higher  category speeds.  Pilots are responsible for determining if a higher approach  category applies. If a faster approach speed is used that  places the aircraft in a higher approach category, the  minimums for the appropriate higher category must be  used. Emergency returns at weights in excess of maximum  certificated landing weight, approaches made with  inoperative flaps, and approaches made in icing conditions  for some airplanes are examples of situations that can  necessitate the use of higher approach category minima.  Circling approaches are one of the most challenging  flight maneuvers conducted in the NAS, especially for  pilots of CAT C and CAT D turbine-powered, transport  category airplanes. These maneuvers are conducted at  low altitude, day and night, and often with precipitation  present affecting visibility, depth perception, and the ability  to adequately assess the descent profile to the landing  runway. Most often, circling approaches are conducted to  runways without the benefit of electronic navigation aids to  support the descent from the Circling Minimums Decision  Altitude (CMDA) to the runway.  Circling approaches conducted at faster-than-normal,  straight-in approach speeds also require a pilot to  consider the larger circling approach area, since published  circling minimums provide obstacle clearance only  within the appropriate area of protection and is based  on the approach category speed. [Figure 4-2] The circling  approach area is the obstacle clearance area for aircraft  maneuvering to land on a runway that does not meet the  criteria for a straight- in approach. The size of the circling  area varies with the approach category of the aircraft, as  shown in Figure 4-2.  Many airplanes have more than one allowable flap  configuration for normal landing. Often, a reduced flap  setting for landing allows the airplane to operate at a higher  landing weight into a field that has restrictive obstacles in  the missed approach or rejected landing climb path. On  these occasions, the full-flap landing speed may not allow  the airplane enough energy to successfully complete a  go-around and avoid any high terrain and/or obstacles  that might exist on the climb out. Therefore, all-engine  and engine-out missed approaches, as well as rejected  landings, must be taken into consideration in compliance  with the regulations.  Aircraft approach category means a grouping of aircraft  based on a reference landing speed (V$_{REF}$), if specified, or  if V$_{REF }$ is not specified, 1.3 V$_{SO }$ at the maximum certified  landing weight. V$_{REF}$, V$_{SO}$, and the maximum certified  landing weight are those values as established for the  aircraft by the certification authority of the country of  registry. A pilot must use the minima corresponding to  the category determined during certification or higher.  Helicopters may use Category A minima. If it is necessary  to operate at a speed in excess of the upper limit of the  speed range for an aircraft’s category, the minimums for  the higher category must be used. For example, an airplane  that fits into Category B, but is circling to land at a speed of  145 knots, must use the approach Category D minimums.  As an additional example, a Category A aircraft that is  operating at 130 knots on a straight-in approach must use  the approach Category C minimums. See the following  category limits noting that the airspeeds depicted are  indicated airspeeds (IAS):  4-8  • Category E: Speed 166 knots or more.  • Category D: Speed 141 knots or more but less than  166 knots.  • Category C: Speed 121 knots or more but less than  141 knots.  • Category B: Speed 91 knots or more but less than  121 knots.  • Category A: Speed less than 91 knots.  • Land within the distance required by the regulations.  • Climb from the missed approach point (MAP) and  maintain a specified climb gradient with one engine  inoperative.  • Perform a go-around from the final stage of landing  and maintain a specified climb gradient with all  engines operating and the aircraft in the landing  configuration.  Aircraft Approach Categories 