Stadia Neptune radar altimeter

While the original Stadia LIDAR model ($645) excels over land but struggles over water because of infrared absorption, the Neptune uses radar to provide reliable altitude measurements over aquatic environments. Priced at $1,220, this compact, portable altimeter can be a valuable tool for floatplane pilots, although its setup presents some challenges.

The Stadia Neptune mounts on a floatplane’s wing strut or tiedown ring, and is available in three models: Model A for struts between 1-5/32 inches and 1-3/4 inches (common for Cub-style aircraft), Model B for struts between 1-3/4 inches and 2-3/8 inches (suited for Cessna-style aircraft), and Model L for aircraft with tiedown rings or other attachment points. The device connects via Bluetooth to an iOS or Android app, which displays real-time altitude data and provides aural alerts. With a battery life of up to 10 hours and a maximum altitude range of 300 feet, the Neptune is tailored for low-altitude operations critical during landings. Its accuracy of plus or minus 8 inches is less precise than the LIDAR-based Stadia’s plus or minus 2 inches but outperforms commercial jet radar altimeters.

Mounting the device as far outboard as possible on the wing strut helps avoid interference from the float. The app delivers both visual and audible altitude cues, with altitude callouts as altitude decreases, allowing pilots to focus on flying rather than constantly checking the screen. The altitude is transmitted via Bluetooth to the phone and then to the aircraft’s audio panel. Altitude callouts are like traditional radar altimeters: 50, 40, 30, 20, 10, 5….

Initial pairing and calibration through the app require careful attention, and while instructional videos simplify the process, it may feel cumbersome for less tech-savvy pilots. Once configured, however, the app automatically reconnects. Concerns arise with the multiple dependencies involved: a smartphone, Bluetooth connectivity, and battery life introduce potential points of failure. Not to mention that you need to make sure the unit is turned on, accomplished by a switch on the side of the transmitter, a task that I neglected—twice! The 10-hour battery is sufficient for most flights, but standby mode can extend life to 12 to 13 hours.

Introduced in 2024, the Stadia Neptune was designed in response to feedback from floatplane pilots, particularly in regions like Alaska where glassy water landings are common. Its portability allows for easy transfer between aircraft. In the coming months, Stadia expects to release an inspection panel mounted unit that can be plugged into an audio panel input.

The Stadia Neptune Radar Altimeter offers precise altitude measurements over water where traditional altimeters and vertical speed indicators fall short. While the setup process and reliance on multiple components raise minor concerns, the device’s performance and ease of use after initial configuration make it a worthwhile investment.

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