The AA Enhanced Hover Hold (EHH) STC adds a GPS-based velocity sensor and second radar altimeter to provide the AFCS with additional modes and improved hover hold performance. With EHH STC installed, the 412EPI/EPX provides mark-on-target (MOT), automated approach and return to hover, hover hold with commanded velocity, and automated climb and departure from hover. The velocity sensor supports hover cues on the PFD and on FLIR® video overlays. The Enhanced Hover Hold Kit contains: Second Radar Altimeter Ground Velocity Sensor Flight Director Mode Select (FDMS) Panels 5-position cyclic beep switch Radar Altimeter Annunciators Router/Filter with Configuration Plug Installation Prerequisites The following prerequisites are required before installing the Enhanced Hover Hold STC Kit: 4-axis AFCS w/ GTN-750 configuration (412EP w/ BHTI STC SR09600RC 412-510-005 or 412EP SN 37002 thru 37999 412-705-042). GTN-750 main software version 6.11 (P/N 006-B1026-43) or later approved version. ADIU 412-074-011-107 (ADIU OFP software P/N 412-770-013-107 version 3.0 or later approved version) and 412-374-007-105 (DU CPU software P/N 0666-0278, version 3.0 or later approved version). GTN 7XX enablement card 010-00878-03 (installer provided). Compliance with BHTI ASB 412-15-169 for LCR 100 Attitude Heading Reference Unit (AHRU).