Operations Performance Training Section
Central Training Establishment
Hyderabad

AOM TRAINING NOTES
CHAPTER -1
AERODROME OPERATING MINIMA (AOM)

Definition:
1.1. Aerodrome Operating Minima comprise the limits of usability of an aerodrome for either take-off or landing, usually expressed in terms of visibility or Runway Visual Range (RVR), and Decision Altitude/Decision Height (DA/DH) or Minimum Descent Altitude/Minimum Descent Height (MDA/MDH).  
1.2 Decision Altitude (DA) / Decision Height (DH) -A specified altitude or height in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. Decision Altitude (DA) is referenced to mean sea level (MSL) and Decision Height (DH) is referenced to the Rwy threshold elevation.
1.3 The required visual reference means that section of the visual aids or of the approach area, which should have been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position, in relation to the desired flight path.
1.4 Minimum Descent Altitude (MDA) /Minimum Descent Height (MDH):
MDA/MDH is a specified Altitude in a non-precision approach or circling approach, below which descent may not be made without the required visual reference.
1.5 Obstacle Clearance Altitude (OCA)/Obstacle Clearance Height (OCH) is the lowest Altitude (OCA), or alternatively the lowest height above the elevation of the relevant runway threshold or above the 
Pg-1/28 aerodrome elevation as applicable (OCH), used in establishing compliance with the appropriate obstacle clearance criteria.

i)  Minimum obstacle clearance for Non-precision Approach with Final Approach Fix (FAF) is 246 ft. and without FAF is 295 ft.
ii)  Minimum Obstacle Clearance for Precision Approach is not specified.
iii)  Minimum Obstacle Clearance for visual circling for Category A and B aircraft is 295 ft. and for Category C is 394 ft.
iv)  The Minimum Obstacle Clearance Height (OCH) for visual circling for Category A aircraft is 394 ft, Category B aircraft is 492 ft. and Category C aircraft is 591 ft.
DA/DH or MDA/MDH depend upon the OCA/OCH specified in the Instrument Approach Procedure (Precision / Non-Precision Approach).
The value of Visibility (RVR) minima depends upon Decision Height /Minimum Descent Height and Approach Lighting System (Basic, Intermediate or full facilities).  Higher the DH/MDH, higher will be the corresponding visibility / RVR minima.
2. While establishing the operating minima, following points to be considered in details:
i) The type, performance and handling characteristics of the aeroplane. (Specified under Approach Category table-1 below)  ii) The composition of flight crew, their competence and experience. iii) The dimensions and characteristics of the runways, which may be selected for use.  
　
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