A pilot is flying an IFR flight and notices an area on an en route low-altitude chart depicted with a large blue number, such as '12,500', within a grid quadrangle. There is no route or airway associated with this altitude. What does this altitude represent?
- AMinimum Vectoring Altitude (MVA).
- BOff-Route Obstruction Clearance Altitude (OROCA).
- CMinimum Obstruction Clearance Altitude (MOCA).
- DMinimum En Route Altitude (MEA).
Show answer & explanationAnswer & explanation
Correct answer: B. Off-Route Obstruction Clearance Altitude (OROCA).
The Off-Route Obstruction Clearance Altitude (OROCA) is a published altitude on IFR en route charts that provides obstruction clearance of 1,000 feet in non-mountainous areas and 2,000 feet in mountainous areas within a designated grid quadrangle. It does not guarantee navigation signal reception or communication coverage, unlike MEA or MOCA.
Why the other options are wrong
- A. MVA is an ATC-assigned altitude for radar vectoring and is not charted on en route charts in this manner.
- C. MOCA is associated with airways and guarantees obstacle clearance and navigation signal reception within 22 NM of a VOR.
- D. MEA is associated with airways and guarantees both obstacle clearance and navigation signal reception.
Off-Route Obstruction Clearance Altitude (OROCA)
OROCA is a charted altitude on IFR en route charts that provides obstruction clearance within a specified grid quadrangle. It ensures 1,000 feet of clearance in non-mountainous terrain and 2,000 feet in mountainous terrain but does not guarantee navigation signal reception or communication coverage.
- Provides obstruction clearance (1000' non-mtn, 2000' mtn).
- Depicted in blue numbers on en route charts within grid quadrangles.
- Does NOT guarantee navigation signal reception.
- Does NOT guarantee communication coverage.
Memory trick: OROCA: On Route, Obstacle Clearance, No Nav or Comms Assured!