Definition
A chart note indicating that the procedure may not be flown using DME/DME-only RNAV equipment that requires an RNP value of 0.3 nautical miles. The procedure's design does not provide adequate DME ground-station coverage to support an RNAV system relying solely on two or more DME stations to achieve and hold lateral accuracy within 0.3 NM, so that navigation source is prohibited for this approach. Aircraft using GPS or other approved RNAV sources may still be authorized.
Plain English
On this approach, you are not allowed to navigate using a system that figures out your position by measuring distances from two ground-based DME stations alone. There aren't enough DME stations in the right places to keep you accurate enough, so that method is off-limits here.
Context Anchor
Seen in the notes area of an instrument approach chart, including approach procedures used when arriving at an airport without an operating control tower.
Why Pilots Care
The pilot must select a different authorized navigation source to complete the approach legally and safely.
Grounding Statement
The note is a limitation on what kind of navigation equipment may be used for that approach.
Intuition Check
Do not read NA as meaning “not applicable.” On FAA charts here, NA means “not authorized.” Also, “performance” here means navigation accuracy, not engine performance.
Example Sentence 1
The approach plate shows DME/DME RNP-0.3 NA, so we'll need to use the GPS as our navigation source rather than the DME/DME RNAV mode.
Example Sentence 2
Before descending, the crew confirmed DME/DME RNP-0.3 NA applied and verified an alternate navigation method was available.