APPROACH SPEED AND CATEGORY

Two other critical performance factors that should be considered during the planning phase of an instrument approach are aircraft approach category and planned approach speed. According to the December 26, 2002 amendment of Part 97.3 (b), aircraft approach category means a grouping of aircraft based on reference landing speed (VREF), if specified, or if VREF is not specified, 1.3 VS0 (the stalling speed or minimum steady flight speed in the landing configuration) at the maximum certificated landing weight. VREF refers to the speed used in establishing the approved landing distance under the airworthiness regulations constituting the type certification basis of the airplane, regardless of whether that speed for a particular airplane is 1.3 VSO, 1.23 VSR, or some higher speed required for airplane controllability such as when operating with a failed engine. The categories are as follows:

• Category A: Speed less than 91 knots.
• Category B: Speed 91 knots or more but less than 121 knots.
• Category C: Speed 121 knots or more but less than 141 knots.
• Category D: Speed 141 knots or more but less than 166 knots.
• Category E:Speed 166 knots or more.

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 airplane at a category line of minimums lower than the airplane is certified for is primarily the margin of protection provided for containment of the airplane within the procedure design for a slower airplane. 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 a higher approach category minima.

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 5-3] The circling approach area is the obstacle clearance area for airplanes 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 airplane, as shown in Figure 5-3. A minimum of 300 feet of obstacle clearance is provided in the circling segment. Pilots should remain at or above the circling altitude until the airplane is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent and using normal maneuvers. Since an approach category can make a difference in the approach and weather minimums and, in some cases, prohibit flight crews from initiating an approach, the approach speed should be calculated and the effects on the approach determined and briefed in the preflight planning phase, as well as reviewed prior to commencing an approach.

Figure 5-3. Construction of Circling Approach Area

OPERATIONAL CONSIDERATIONS

Most commercial operators dictate standard procedures for conducting instrument approaches in their FAA approved manuals. These standards designate company callouts, flight profiles, configurations, and other specific duties for each cockpit crewmember during the conduct of an instrument approach.

APPROACH CHART FORMATS

Beginning in February 2000, NACO began issuing the current format for IAPs. This chart was developed by the Department of Transportation, Volpe National Transportation Systems Center and is commonly referred to as the Pilot Briefing Information format. The NACO chart format is presented in a logical order, facilitating pilot briefing of the procedures. [Figure 5-4]