Appendix C to Part 91 - Operations in the North
Atlantic (NAT) Minimum Navigation Performance Specifications (MNPS)
NAT MNPS airspace is that volume of airspace between FL 285 and FL 420
extending between latitude 27 degrees north and the North Pole, bounded in
the east by the eastern boundaries of control areas Santa Maria Oceanic,
Shanwick Oceanic, and Reykjavik Oceanic and in the west by the western
boundary of Reykjavik Oceanic Control Area, the western boundary of Gander
Oceanic Control Area, and the western boundary of New York Oceanic Control
Area, excluding the areas west of 60 degrees west and south of 38 degrees
30 minutes north.
The navigation performance capability required for aircraft to be
operated in the airspace defined in section 1 of this appendix is as
(a) The standard deviation of lateral track errors shall be less than
6.3 NM (11.7 Km). Standard deviation is a statistical measure of data
about a mean value. The mean is zero nautical miles. The overall form of
data is such that the plus and minus 1 standard deviation about the mean
encompasses approximately 68 percent of the data and plus or minus 2
deviations encompasses approximately 95 percent.
(b) The proportion of the total flight time spent by aircraft 30 NM
(55.6 Km) or more off the cleared track shall be less than 5.3×10−4
(less than 1 hour in 1,887 flight hours).
(c) The proportion of the total flight time spent by aircraft between
50 NM and 70 NM (92.6 Km and 129.6 Km) off the cleared track shall be less
than 13 × 10−5 (less than 1 hour in 7,693 flight hours.)
Air traffic control (ATC) may authorize an aircraft operator to deviate
from the requirements of §91.705 for a specific flight if, at the time of
flight plan filing for that flight, ATC determines that the aircraft may
be provided appropriate separation and that the flight will not interfere
with, or impose a burden upon, the operations of other aircraft which meet
the requirements of §91.705.
[Doc. No. 18334, 54 FR 34327, Aug. 18, 1989, as amended by Amdt.
91-254, 62 FR 17487, Apr. 9, 1997]