09/29/2026
Online Aviation Library
Curtiss-Wright X-100 Experimental VTOL
Aircraft
Technical Documentation & Engineering Synthesis Report
1. Archival & Historical Record
The primary technical documentation, engineering drawings, and historical flight test data for the Curtiss-Wright
X-100 experimental vertical take-off and landing (VTOL) aircraft are officially preserved within the
Curtiss-Wright Corporation Records Collection at the Smithsonian Institution's National Air and Space Museum
(NASM) Archives. This extensive document repository provides the historical foundation for the engineering
synthesis presented below.
2. Aerodynamic & Core Propulsion Concepts
• The Radial Force Principle: The X-100 was built specifically to evaluate the proprietary 'radial force'
concept developed by chief aerodynamicist Henry Borst. The theory demonstrated that specially contoured,
highly pitched propellers could generate significant aerodynamic lift force perpendicular to the airflow as the
angle of attack increased, drastically minimizing the aircraft's reliance on traditional wing surfaces during
horizontal transitions.
• Propeller Configuration: The lifting and propulsive architecture featured two 10-foot-diameter tilting
fiberglass propellers. These units were mounted on short, rigid 16-foot wings. In contrast to standard
helicopter rotors, these blades utilized collective pitch changes exclusively, omitting cyclic control while
keeping a pronounced structural blade twist.
3. Powerplant & Control Interfacing
• Primary Engine: Propulsion was driven by a single fuselage-mounted Lycoming YT53-L-1 turboshaft
engine, delivering approximately 825 to 860 shaft horsepower (shp). Mechanical cross-shafting delivered
power outward to the pivoting wingtip nacelles.
• The 'Jetivator' Control System: Because the wingtip propellers lacked cyclic control, attitude control during
hover relied completely on engine exhaust ducted through a rear-mounted, swiveling nozzle arrangement
designated the 'Jetivator'. Differential collective propeller pitch provided roll control, while pitch and yaw
were dictated by the Jetivator's deflection.
4. Handling, Stability, and Flight Dynamics
Historical flight evaluations spanning from 1959 to 1961 exposed several severe flight-stability anomalies:
• Transition Pitch-Up: Accelerating forward during the critical transition phase from vertical hover to
horizontal flight induced an aggressive, inherent nose-up pitching moment due to the complex
aerodynamics of the highly loaded tilt-propellers.
• Hover Control Insufficiency: Low exhaust gas velocities from the YT53 engine at hover power severely
restricted the mechanical control authority of the Jetivator nozzle system, leaving the pilot with sluggish
response cycles.
• Ground Effect Turbulence: Entering ground effect caused high-velocity downwash turbulence. Combined
with the slow spool-up and spool-down response of early turboshaft controls, this produced severe pitching
instability near the ground. Engineers installed auxiliary forward wheel extensions to protect against
tail-strikes.
• Critical Power-Off Limitations: Aerodynamic analyses concluded that safe autorotation was
mathematically impossible. The high disk-loading and small diameter of the propellers prevented power-off
rotor descents, and the abbreviated wingspan could not support an acceptable glide ratio.
5. Performance Data & Operational Specifications
Parameter Specification / Metric
Empty Weight 3,265 lb (1,481 kg)
Maximum Gross Weight 3,729 lb (1,691 kg)
Propeller Diameter 10 ft (3.05 m) x 2 units
Wingspan 16 ft (4.88 m)
Powerplant 1x Lycoming YT53-L-1 Turboshaft (825-860 shp)
First Free Hover September 1959
First Full Transition April 1960
NASA Test Cessation October 1961 (Following landing accident)
