En Route - En route Limitations

Question 1

List and Define IFR altitudes.

Answer 1

• MEA Minimum Enroute Altitude: lowest publish altitude between fixes ensuring navigation clearance and obstacle clearance
  
  • MOCA Minimum Obstruction Clearance Altitude: lowest published altitude between fixes that meets obstacle clearance and navigation within 25 SM or 22 NM
  • MCA Minimum Crossing Altitude: Lowest altitude at certain fixes aircraft must cross when proceeding in direction of higher MEA
  • MRA Minimum Reception Altitude: lowest altitude at which an intersection can be determined
  • MAA Maximum Authorized Altitude: Maximum usable altitude for an airspace or route segment that ensures adequate navigation reception
  • OROCA Off-Route Obstruction Clearance Altitude: provides 1,000’ clearance in non mountainous areas and 2,000’ clearance in mountainous terrain. May not provide navigation or comm signal

Question 2

If no applicable minimum altitude is prescribed (no MEA, or MOCA), what minimum altitudes apply for IFR operations?

Answer 2

91.1777/part 95
Mountainous terrain: 2,000’ above highest obstacle within 4 NM
Other than mountainous terrain: 1,000’ above highest obstacle within 4 NM

Question 3

What cruising altitudes shall be maintained while operating under IFR in controlled airspace (Class A/B/C/D/E)? In uncontrolled airspace (Class G)?

Answer 3

91.179
In controlled airspace pilot should fly ATC assigned altitude.
In uncontrolled airspace pilot should fly based on magnetic course:
0° to 179° odd thousand or odd flight levels
180° to 359° even thousand or even flight levels

Question 4

What procedures are applicable concerning course to be flown when operating IFR/

Answer 4

91.181
Unless authorized by ATC no person may operate IFR except on air traffic services (ATS) route, or on route direct between navigational aids

Question 5

On a direct flight not flown on radials or courses of established airways or routes, what points serve as compulsory reporting points?

Answer 5

Must report over each reporting point used to define the route of flight

Question 6

What are “unpublished” RNAV routes?

Answer 6

Direct routes based on RNAV capability, ATC radar monitoring is required (except GNSS equipped aircraft)