AIM Text
- Operators not authorized for RNP 10 or RNP 4 may still file for any route and altitude within the Gulf of America CTAs. However, clearance on the operator's preferred route and/or altitude will be provided as traffic allows for 90 or 100 NM lateral separation between the non-RNP 10 aircraft and any others. Priority will be given to RNP 10 or RNP 4 aircraft.
- Operators of aircraft not authorized RNP 10 or RNP 4 must include the annotation “RMK/NONRNP10” in Item 18 of their ATC flight plan.
- Pilots of non-RNP 10 aircraft are to remind ATC of their RNP status; i.e., report “negative RNP 10” upon initial contact with ATC in each Gulf CTA/FIR.
- Operators will likely benefit from the effort they invest to obtain RNP 10 or RNP 4 authorization, provided they are flying aircraft equipped to meet RNP 10 or RNP 4 standards.
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-7-2.
Research Notes
AIM 4-7-2 covers Emergency Frequency Procedures — operating on 121.5 MHz (the international emergency frequency).
121.5 MHz monitoring: When equipped with a second comm radio, monitor 121.5 in addition to the working frequency. ATC, military, and search-and-rescue facilities monitor 121.5 continuously. Emergency calls (Mayday, Pan-Pan) heard on the frequency get immediate attention.
When to use 121.5:
- Distress ("Mayday"): immediate threat to life requiring immediate assistance
- Urgency ("Pan-Pan"): situation requiring assistance but not immediately life-threatening
- Lost comms recovery: try 121.5 to reach a controller when primary frequency fails
- Interceptor contact: report interception per AIM 4-6
The Mayday call format: "Mayday, Mayday, Mayday, [aircraft], [position], [altitude], [problem], [intentions]." Example: "Mayday, Mayday, Mayday, Cessna Two-Three-Uniform, ten miles south of [airport], 4,000 feet, engine out, descending, requesting vector to nearest airport."
Reference: AIM 4-7-2; AIM 6-3 (Distress and Urgency Procedures).