AIM Text
- For U.S. operators, AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace, provides the aircraft and operator qualification criteria for RNP 10 or RNP 4 authorizations. FAA personnel at flight standards district offices (FSDO) and certificate management offices (CMO) will use the guidance contained in AC 90-105 to evaluate an operator's application for RNP 10 or RNP 4 authorization. Authorization to conduct RNP operations in oceanic airspace is provided to all U.S. operators through issuance of Operations Specification (OpSpec), Management Specification (MSpec), or Letter of Authorization (LOA) B036, as applicable to the nature of the operation; for example, part 121, part 91, etc. Operators may wish to review FAA Order 8900.1, Flight Standards Information Management System, volume 3, chapter 18, section 4, to understand the specific criteria for issuing OpSpec, MSpec, and/or LOA B036.
- The operator's RNP 10 or RNP 4 authorization should include any equipment requirements and RNP 10 time limits (if operating solely inertial-based navigation systems), which must be observed when conducting RNP operations. RNP 4 requires tighter navigation and track maintenance accuracy than RNP 10.
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-7-3.
Research Notes
AIM 4-7-3 covers ELT — Emergency Locator Transmitter operations and ELT inadvertent activations.
ELT background: Required by § 91.207 on most U.S.-registered civil aircraft. Transmits on 121.5 (legacy ELTs) or 406 MHz (modern ELTs). Activates automatically on impact (G-switch) or manually via a switch.
Inadvertent activation: Common causes include hard landings, vibration during maintenance, or accidental switch activation. The 121.5 signal alerts ATC, search-and-rescue, and aircraft monitoring 121.5 in the area.
If you hear an ELT signal:
- Note your position and time
- Continue listening — does the signal strengthen or weaken (indicates direction)?
- Report to FSS, ATC, or by phone: "Heard ELT signal at [time] at [position], [direction] direction"
If your ELT activates: Immediately verify (most have a panel indicator showing transmit), shut it off if false, and notify ATC or FSS that the activation was inadvertent.
ELT inspection: Per § 91.207, ELT must be inspected within 12 calendar months for proper installation, battery condition, and transmitter operation. Batteries must be replaced after 1 hour of cumulative use OR when 50% of useful life expires.
Reference: § 91.207 (ELT); AIM 4-7-3; AC 91-44A (ELT performance).