Sky-Watch Examines Tactical Benefits of Deep Stall Landing for Fixed-Wing UAS

Sky-Watch has incorporated deep stall landing capability into its RQ-35 Heidrun unmanned aerial system, providing an alternative to vertical take-off and landing (VTOL) for situations where infrastructure is minimal and global navigation satellite system (GNSS) access may be unreliable or unavailable.

The method has been tested extensively in operational environments, including active conflict zones.

A deep stall landing is a controlled maneuver in which the aircraft enters a high-angle stall, typically between 65 and 80 degrees, to descend steeply while remaining stable. Just before touchdown, the aircraft briefly levels to ensure a safe landing. The technique requires very little ground space and does not depend on additional landing infrastructure, making it suitable for deployment in confined or uneven terrain.

Operational Advantages in Specific Conditions

Small landing footprint: Compared with belly landing or parachute recovery, deep stall enables the RQ-35 Heidrun to land in restricted areas such as forest clearings or improvised sites close to the point of operation, while maintaining landing precision.

Recovery in contested areas: A steep descent reduces time spent descending through threat zones, which can help improve the likelihood of retrieval in hostile environments.

Adaptability to varied terrain: The RQ-35 Heidrun can land on uneven ground without nets, cables, or prepared pads. It is also designed to operate in winds up to 16 m/s, allowing continued use in conditions that could limit other types of recovery.

Energy-conscious operation: With a single drivetrain and endurance-focused batteries, the aircraft avoids the higher power requirements of VTOL launch and recovery, preserving more energy for flight and range.

Simplified field deployment: The absence of nets, arrestor gear, or GNSS-dependent landing aids can reduce the complexity and cost of operating in remote areas.

Service Record in Ukraine

Multiple RQ-35 Heidrun units have carried out more than 500 missions in Ukraine using deep stall landings. These missions have included recoveries in areas with limited landing options, as well as operations where GNSS signals were jammed or unavailable. In one instance, the system completed a reconnaissance mission in a hostile urban area and landed on the roof of an abandoned building, allowing retrieval with minimal exposure to threats.

By offering a landing method suited to restricted spaces and contested environments, deep stall capability supports operational flexibility for fixed-wing UAS. While not a universal replacement for other recovery methods, it provides an option tailored to missions where ground conditions, available space, or GNSS access are constrained.

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