IFR Altitudes

DA/H - Decision Altitude/Height

• The altitude (MSL) or height (above runway threshold) on an instrument approach where a pilot must decide to continue or go around

MAA - Maximum Authorized Altitude

• The highest altitude allowed on an IFR route

MCA - Minimum Crossing Altitude

• The minimum altitude a pilot must cross a fix

MDA/H - Minimum Descent Altitude/Height

• The lowest altitude (MSL) or height (above runway threshold) on a non-precision approach before the pilot must have visual references to land

MEA - Minimum En Route Altitude

• The lowest published altitude between fixes ensuring acceptable navigation signal coverage and obstacle clearance

MOCA - Minimum Obstruction Clearance Altitude

• Provides obstacle clearance and navigation coverage only within 22 NM of a VOR

What if both a MOCA and MEA are prescribed?

• A pilot may fly below MEA but not below MOCA provided the applicable navigation signals are available

MORA - Minimum Off Route Altitude

• Route MORA: Obstruction clearance within 10NM of airway centerlines

• Grid MORA: Obstruction clearance within a latitude/longitude grid

MRA - Minimum Reception Altitude

• The lowest altitude at which an aircraft can receive adequate navigation signals

MTA - Minimum Turning Altitude

• Ensures vertical and lateral obstacle clearance in turns over specific fixes

MVA - Minimum Vectoring Altitude

• The lowest altitude an IFR aircraft will be vectored by ATC, potentially lower than MEA or MOCA

OROCA - Off Route Obstruction Clearance Altitude

• Provides 1,000 ft clearance in non-mountainous areas and 2,000 ft in mountainous areas but may not ensure navigation coverage

When is an aircraft allowed to operate under IFR below the minimum IFR altitudes?

• Only during takeoff or landing, or if otherwise authorized by the FAA

What is the minimum IFR altitude for a flown segment?

• The minimum altitude prescribed for the flown segment

What is the minimum IFR altitude in mountainous areas?

• 2,000 feet above the highest obstacle within a horizontal distance of 4 NM from the centerline

What is the minimum IFR altitude in non-mountainous areas?

• 1,000 feet above the highest obstacle within a horizontal distance of 4 NM from the centerline