Garmin GTN 6XX/7XX and GNS 400W/500W series units operating in a QFE environment are affected. Includes GTN 625, GTN 635, GTN 650, GTN 725, GTN 750, GPS 400W, GNC 420W, GNS 430W, GPS 500W, and GNS 530W.
Most locations utilize the QNH altitude that provides altitude above mean sea level. However QFE altitude may be used in some locations (e.g. Russian Federation and the People's Republic of China). In many locations that normally utilize QFE, the flight crew may request the QNH altimeter setting.
QFE operations are not supported. Sequencing of altitude based navigation legs requires use of QNH altitudes.
Use only a QNH altimeter setting when using GPS navigation with altitude based navigation legs.