Use Case: US-D1 Pro Radar Altimeter for Low-Altitude Awareness in UAM and AAM Air Taxi Operations
Overview
As urban and advanced air mobility platforms move from concept to certified service, OEMs developing piloted and optionally piloted air taxis face a demanding sensor environment. These aircraft must operate safely at very low altitudes, often in dense and visually degraded urban settings, while meeting stringent certification and airworthiness requirements.
For UAM and AAM platforms such as eVTOLs and light air taxis, accurate altitude awareness is a core safety function. However, conventional altitude sources—including GNSS, barometric sensors and vision-based systems—were not designed to deliver the required combination of low-altitude accuracy, robustness and certification readiness. The US-D1 Pro radar altimeter addresses this gap by providing true height above ground (AGL) data with performance and design assurance suitable for manned, certified aircraft.
The Low-Altitude Challenge
The highest operational risk for air taxis occurs close to the ground: during take-off, hover, transition, approach and landing. At these heights, even small altitude errors can affect safety, passenger comfort and flight control performance.
Traditional sensing methods each have limitations. Barometric altimeters measure pressure altitude rather than true AGL and are affected by weather changes, urban pressure gradients and calibration drift. GNSS altitude can degrade near buildings and infrastructure due to multipath and signal blockage. Vision-based systems can struggle in low light, rain, fog, dust or snow, and over uniform surfaces such as rooftops, water or pavement—conditions common in urban operations.
For piloted and optionally piloted AAM aircraft operating from vertiports, rooftops and confined spaces, these limitations introduce unacceptable risk without a robust, independent sensing solution.
Direct AGL Measurement for Air Taxi Operations
The US-D1 Pro radar altimeter provides direct, true AGL measurement independent of lighting, weather or surface texture. Operating at 24 GHz, it delivers consistent, high-integrity altitude data over a wide range of surfaces, including concrete, asphalt, vegetation, water, snow and unprepared terrain.
This capability supports safer and more predictable operation during:
- Vertical take-off and landing at vertiports and rooftop pads
- Precision hover control for passenger boarding and disembarkation
- Transition between vertical and forward flight
- Approach and landing in confined or obstacle-rich environments
- Operations in degraded visual conditions
Reliable low-altitude AGL data makes the US-D1 Pro a key input for flight control laws, pilot cueing, envelope protection and alerting functions.
Supporting Certified Avionics Architectures
In addition to performance, UAM and AAM OEMs must demonstrate a credible certification path for all onboard sensors. The US-D1 Pro was designed with this requirement from the outset.
With low latency and a 30 Hz update rate, it supports real-time flight control, hover stabilisation and warning systems without introducing delay or architectural complexity. Alignment with DO-160, DO-178 and DO-254 allows integration into safety-critical avionics without reliance on non-certifiable commercial sensors.
This reduces programme risk by enabling:
- Redundant altitude sensing architectures
- Clear allocation of safety requirements and assurance levels
- Streamlined certification and airworthiness approval
- Scalable designs for piloted, optionally piloted and autonomous variants
Why Radar Altimetry Matters for Certified Air Taxis
While radar altimetry is well established in aviation, many existing solutions are not optimised for the size, weight, power and certification needs of modern air taxis. The US-D1 Pro is designed specifically for these platforms, offering:
- High-precision altitude measurement from 0.5 m to 120 m AGL
- All-weather operation in rain, fog, dust and low visibility
- Low latency and high update rate for control and pilot-assist systems
- Compact, low-power design suited to SWaP-constrained eVTOL aircraft
Designed for Certification and Airworthiness
Unlike many commercial off-the-shelf radar sensors, the US-D1 Pro is explicitly aligned with aerospace certification expectations. It is designed to support compliance with:
- DO-160 environmental qualification
- DO-178 software assurance considerations
- DO-254 complex electronic hardware considerations
- IP69K ingress protection for harsh operating environments
This makes it well-suited to UAM and AAM aircraft pursuing type certification, special class certification or supplemental type certification.
Enabling Safer Advanced Air Mobility
By delivering reliable, certifiable AGL data, the US-D1 Pro supports critical safety and automation functions, including:
- Pilot height-above-ground displays and cues
- Automated landing and flare logic
- Hover height stabilisation
- Terrain awareness and warning functions
- Redundant altitude sensing strategies
For OEMs and integrators, this results in improved safety margins, reduced integration risk and a clearer path from prototype to certified operation.
Built for the Next Generation of Air Mobility
As regulators place increasing emphasis on low-altitude safety, autonomy and sensor reliability, UAM and AAM developers must select components designed for certification from the start. The US-D1 Pro combines modern radar altimetry performance with the rigour required for certified, piloted advanced air mobility platforms.
To discuss integrating the US-D1 Pro into your next air taxi or UAM programme, contact the Sundance team at sales@sundance.com
to request technical information.