Mercury
Well-known member
- Joined
- May 24, 2003
- Posts
- 233
Explanation form the AIM:
5-4-7. Instrument Approach Procedures
a. Aircraft approach category means a grouping of aircraft based on a speed of VREF, if specified, or if VREF not specified, 1.3 VSO at the maximum certificated landing weight. VREF, VSO, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry. Helicopters are Category A aircraft. An aircraft must fit in only one category. Pilots are responsible for determining and briefing which category minimums will be used for each instrument approach. If a higher approach speed is used on final that places the aircraft in a higher approach category, the minimums for the higher category must be used. Approaches made with inoperative flaps, circling approaches at higher-than normal straight-in approach speeds, and approaches made in icing conditions for some types of airplanes are all examples of situations that can necessitate the use of a higher approach category. See the following category limits:
1. Category A: Speed less than 91 knots.
2. Category B: Speed 91 knots or more but less than 121 knots.
3. Category C: Speed 121 knots or more but less than 141 knots.
4. Category D: Speed 141 knots or more but less than 166 knots.
5. Category E: Speed 166 knots or more.
And FWIW, I was taught to set "blue2" 12 knots above the Vref bug and target Blue2 during the circling procedure. The circling mins are based on the max KIAS and the tangential (sp) arcs for obstacle clearance that are specified in the AIM. Basically a larger radius of turn.
More from the AIM:
5-4-7. Instrument Approach Procedures
a. Aircraft approach category means a grouping of aircraft based on a speed of VREF, if specified, or if VREF not specified, 1.3 VSO at the maximum certificated landing weight. VREF, VSO, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry. Helicopters are Category A aircraft. An aircraft must fit in only one category. Pilots are responsible for determining and briefing which category minimums will be used for each instrument approach. If a higher approach speed is used on final that places the aircraft in a higher approach category, the minimums for the higher category must be used. Approaches made with inoperative flaps, circling approaches at higher-than normal straight-in approach speeds, and approaches made in icing conditions for some types of airplanes are all examples of situations that can necessitate the use of a higher approach category. See the following category limits:
1. Category A: Speed less than 91 knots.
2. Category B: Speed 91 knots or more but less than 121 knots.
3. Category C: Speed 121 knots or more but less than 141 knots.
4. Category D: Speed 141 knots or more but less than 166 knots.
5. Category E: Speed 166 knots or more.
And FWIW, I was taught to set "blue2" 12 knots above the Vref bug and target Blue2 during the circling procedure. The circling mins are based on the max KIAS and the tangential (sp) arcs for obstacle clearance that are specified in the AIM. Basically a larger radius of turn.
More from the AIM:
b. Obstacle Clearance. Final approach obstacle clearance is provided from the start of the final segment to the runway or missed approach point, whichever occurs last. Side-step obstacle protection is provided by increasing the width of the final approach obstacle clearance area.
1. Circling approach protected areas are defined by the tangential connection of arcs drawn from each runway end. The arc radii distance differs by aircraft approach category. Because of obstacles near the airport, a portion of the circling area may be restricted by a procedural note: e.g., "Circling NA E of RWY 17-35." Obstacle clearance is provided at the published minimums for the pilot that makes a straight-in approach, side-steps, circles, or executes the missed approach. Missed approach obstacle clearance requirements may dictate the published minimums for the approach. (See FIG 5-4-23.)
1. Circling approach protected areas are defined by the tangential connection of arcs drawn from each runway end. The arc radii distance differs by aircraft approach category. Because of obstacles near the airport, a portion of the circling area may be restricted by a procedural note: e.g., "Circling NA E of RWY 17-35." Obstacle clearance is provided at the published minimums for the pilot that makes a straight-in approach, side-steps, circles, or executes the missed approach. Missed approach obstacle clearance requirements may dictate the published minimums for the approach. (See FIG 5-4-23.)
[SIZE=-2]FIG 5-4-23 [/SIZE]
Final Approach Obstacle Clearance
Final Approach Obstacle Clearance
