# IFR Approach procedure - Final approach segment^{[PDF]}

## Contents

## Introduction

## Straight in and circling approach

- Straight-in
- Circling

In case of non-precision approach, a straight-in approach is considered acceptable if the angle between the final approach track and the runway centre line is __30° or less__.

A circling approach is specified in those cases where a straight-in approach is not possible. The criteria can be:

- Terrain or other constraints cause the final approach track alignment is not possible with the runway centre line inside the 30° tolerance.
- Descent gradient is not compatible with landing using straight-in approach

## Types of final approach

- Non precision approach (NPA) with final approach fix (FAF)
- Non precision approach (NPA) without final approach fix (FAF)
- Approach with vertical guidance (APV)
- Precision approach (PA)

### Categories of precision approaches

Category of Operation | Decision Height (DH) | Runway Visual Range (RVR) |
---|---|---|

CAT I | DH ≥ 200 ft (60m) | RVR ≥ 550 m or VIS ≥ 800m
RVR ≥ 1750 ft or VIS ≥ 2400 ft |

CAT II | 100 ft ≤ DH < 200 ft | RVR ≥ 300 m |

CAT IIIA | No DH or DH < 100 ft | RVR ≥ 175 m |

CAT IIIB | No DH or DH < 50ft | 50 m ≤ RVR < 175 m |

CAT IIIC | No DH | No RVR limitation |

### Non precision approach with FAF

The FAF is sited on the final approach altitude to the appropriate MDA/H either for a straight-in approach or for a visual circling. The distance for locating the FAF relative to the runway threshold is:

- 9.3km (5NM) as optimum distance
- 5.6km (3NM) as minimum distance
- 19km (10NM) as maximum recommended distance

The optimum final descent gradient for a non-precision approach shall be 5.2% (3°), providing a rate of descent of 52m per kilometre (318ft per NM). This value is published on charts.

The maximum standard descent gradient for non-precision procedures with FAF is:

- 6.5% for category A and B aircraft
- 6.1% for category C, D and E aircraft
- 10% for category H, helicopter

__Non-standard procedures__published with a final approach descent gradient greater than these values can exist and it requires a special approval by the national competent authority.

__The descent is normally initiated prior to the FAF in order to achieve the prescribed descent gradient/angle.__

- A higher value is applicable to the primary procedure until the step-down fix.
- A lower value is applicable only if the step-down is positively identified during the approach.

### Non precision approach without FAF

A procedure may be designed where the facility is both IAF and the MAPt.

These procedures indicate:

- A minimum altitude/height for a reversal procedure or racetrack
- An OCA/H for final approach

### Vertical path control on non-precision approach procedures

They __typically employ one of 3 techniques for vertical path control__ on non-precision approaches:

- Continuous descent final approach (CDFA)
- Constant angle descent
- Step-down descent

__Continuous descent final approach (CDFA) is a continuous descent__, flown either with VNAV guidance calculated by on-board equipment or based on manual calculation of the required rate of descent without level-offs.

__The rate of descent is selected and adjusted to achieve a continuous descent__ to a point approximately 15m (50ft) above the landing runway threshold or the point where the flare manoeuvre should begin.

__The constant angle descent is a unbroken angle__of descent from the final approach fix (FAF) or optimum point on procedures without a FAF

__to a reference datum above the runway threshold__(e.g. 15m (50ft)).

__The step-down descent involves an expeditious descent and is described as descent immediately__to not below the minimum step-down fix altitude or MDA/H. This technique is acceptable as long as the descent gradient remains less than 15% and the missed approach is initiated at or before the MAPt.

### Precision approach

__A precision approach (PA) procedure__is an instrument approach procedure based on navigation systems (ILS, MLS, GLS and SBAS CAT I) designed for 3D instrument approach operations Type A or B.

Lateral and vertical guidance refers to the guidance provided either by:

- Ground based navigation aid
- Computer-generated navigation data

The intermediate approach altitude generally intercepts the glide path at heights from 300m (1000ft) to 900m (3000ft) above runway elevation.

The final approach area contains a fix or a facility that permits verification of the glide path versus altimeter relationship. The outer marker or equivalent DME fix is normally used for this purpose. After the final approach point, descent may be made on the glide path to the altitude of the published fix crossing.

Minimum requirement to make a __standard precision approach with an ILS__:

- ILS Category I must be flown with pressure altimeter
- ILS Category II must be flown with pressure altimeter, radio altimeter and flight director
- Missed approach climb gradient is 2.5%
- Glide path angle is
- Optimum = 3°
- Minimum = 2.5°
- Maximum = 3.5°

The protection area of a precision ILS approach assume that the pilot does not __normally deviate from the centre line more than half-scale deflection__ after being established on track.

### Approach procedure with vertical guidance (APV)

__An approach procedure with vertical guidance (APV)__is a performance-based navigation (PBN) instrument approach procedure designed for 3D instrument approach operations Type A.

Lateral and vertical guidance refers to the guidance provided either by:

- Ground based navigation aid
- Computer-generated navigation data

This APV approach benefits over advisory VNAV guidance being overlaid on a non-precision approach, as they are based on specific procedure design criteria:

- Height loss after initiating a missed approach allowing the use of a DA instead of an MDA, thereby standardizing flight techniques for vertically guided approach operations
- Obstacle clearance throughout the approach and landing phase taking into account temperature constraints down to the DA, therefore resulting in better obstacle protection compared to a non-precision approach procedure.

## See also

- IFR arrival and approach procedure, IFR Approach procedure - Intermediate approach segment, IFR Approach procedure - Missed approach segment

## Reference

- ICAO Documentation 8168 - Aircraft Operations - Volume I - Flight Procedures - 6th Edition 2010 - Section 4 - Chapter 5

## Author

- VID 150259 - Creation
- VID 531824 - Wiki Integration

## DATE OF SUBMISSION

- 01:02, 14 May 2021

## COPYRIGHT

- This documentation is copyrighted as part of the intellectual property of the International Virtual Aviation Organisation.

## DISCLAIMER

- The content of this documentation is intended for aviation simulation only and must not be used for real aviation operations.