Bell XV-3

Bell XV-3
Country	USA
Type	Experimental VTOL aircraft
First flight	1955
Built	2

Fotogalleri af en Bell XV-3, The Klokke XV-3 (Bell 200) var et tiltrotorfly udviklet af Bell Helicopter til et fælles forskningsprogram mellem United States Air Force og United States Army for at udforske convertiplane-teknologier. XV-3 havde en motor monteret i skroget med drivaksler, der overførte kraft til tobladede rotorsamlinger monteret på vingespidserne. Vingespidsrotorsamlingerne blev monteret til at vippe 90 grader fra lodret til vandret, hvilket var designet til at gøre det muligt for XV-3 at starte og lande som en helikopter, men flyve med hurtigere lufthastigheder, svarende til et konventionelt fastvinget fly.

Kilde: Klokke XV-3

Klokke XV-3
Fotografer	Unknow
Lokalisering	Unknow
Billeder	45

Bell XV-3 01

Bell XV-3 02

Bell XV-3 03

Bell XV-3 04

Bell XV-3 05

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Bell XV-3 09

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Bell Helikopter Textron XV-3 Gå rundt
Fotografer	Vladimir Yakubov
Lokalisering	National Air & Space Museum, Washington DC
Billeder	69

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The Missing Link Between Helicopter and Plane

Den Klokke XV-3 was a pioneering experimental aircraft that proved the concept of the tiltrotor. Developed in the 1950s for a joint Army and Air Force program, it sought to combine the vertical takeoff capability of a helicopter with the high-speed cruise of a fixed-wing airplane. While it never entered mass production, it successfully completed the world’s first full-scale conversion from vertical to horizontal flight in 1958. Every modern tiltrotor, including the V-22 Osprey og V-280 Valor, owes its existence to the data gathered by this fragile-looking machine.

Attribute	Technical Specification (XV-3)
Rolle	Experimental V/STOL Tiltrotor
Besætning	1 (Pilot)
Motor	1 × Pratt & Whitney R-985-AN-1 Wasp Junior radial (450 hp)
Maximum Speed	291 km/h (181 mph)
Service Ceiling	4,570 m (15,000 ft)
Rotor Diameter	7.01 meters (23 ft) each
Vingefang	9.54 meters (31 ft 3 in)
Status	Experimental / Research

Design Engineering: Tilting the Paradigm

The Tilting Mast: Unlike the V-22 Osprey, which tilts its entire engine nacelle, the XV-3 featured an engine buried in the fuselage. A complex series of driveshafts and gearboxes transmitted power to the wingtips, where only the rotor masts tilted from 0 to 90 degrees.
The Radial Heart: Surprisingly, this futuristic concept was powered by a classic World War II-era 450-hp radial engine. The engine was mounted in the fuselage behind the pilot, which helped maintain a stable center of gravity during the transition between flight modes.
Evolution of Rotors: The XV-3 originally used three-bladed rotors, but they were found to be highly unstable due to “aeroelastic” vibrations (flutter). Engineers replaced them with two-bladed “semirigid” rotors, which allowed the aircraft to successfully complete its conversion tests.
High Disk Loading: Because the rotors had to act as propellers in forward flight, they were smaller than typical helicopter rotors. This meant the XV-3 required much more power to hover and had a very “sinky” feel during vertical landings.

Operational History: Proving the Impossible

The First Conversion: On December 18, 1958, pilot Bill Quinlan successfully moved the masts from the vertical to the horizontal position for the first time in history. This proved that a tiltrotor could actually transition between flight modes without falling out of the sky.
NASA Wind Tunnel Tests: After its flight test program ended in 1962, the XV-3 spent years being tested in the massive wind tunnels at NASA Ames. This research identified “proprotor whirl flutter,” a dangerous vibration that engineers had to solve before the next generation of tiltrotors (the XV-15) could be built.
A Brush with Disaster: During a 1965 wind tunnel test, a rotor failed and ripped off the wing, nearly destroying the aircraft and the tunnel. This failure provided the critical data needed to design the much stronger wings found on modern tiltrotors.
Where it is Today: The original XV-3 was painstakingly restored and now resides at the National Museum of the United States Air Force in Dayton, Ohio.