An Undergraduate Research Paper Submitted to the Extended Campus in Partial Fulfillment of the Requirements of ASCI 310: Aircraft Performance and the Degree of Bachelor of Professional Aeronautics
Embry-Riddle Aeronautical University
Oakland Resident Center
Title:Tilt Rotors, Best of Both Worlds?
Institution:Embry-Riddle Aeronautical University
Tilt rotors have been in prototype aircrafts since 1947. Have these aircrafts ever been successful? Is there future development for these double edged swords? Or are these types of aircraft doomed to be a part of the infamous airplane boneyard? These questions will be brought to light along with any other facts and tidbits that people should know about tilt rotor applications and the projects they have become. TABLE OF CONTENTS
IWHAT IS A TILT ROTOR1
IIHISTORY OF TILT ROTORS2Research Design6
IIIFAMOUS TILT ROTOR AIRCRAFT4
Bell-Boeing V-22 Osprey7
IVADVANTAGES AND DISADVANTAGES 9
WHAT IS A TILT ROTOR
A tilt rotor is a pair of powered rotors, sometimes called proprotors, which are mounted on rotating shafts at the end of a fixed wing. According to Chambers (2000), the tilt rotor is used for both lift and propulsion and it combines the vertical lift capability of a helicopter with the speed and range of a conventional fixed-winged aircraft. When the aircraft takes vertical flight, the rotors are angled so that the plane of rotation is horizontal, lifting it like a helicopter. When the aircraft starts to gain forward momentum, the rotors progressively tilt forward until the plane of rotation is completely vertical. The tilt rotor aircraft now acts like a fixed-wing where the wing is used for lift and the propellers are used for power. These rotors are also configured to be more efficient for propulsion, much like a C-130, instead of a typical helicopter blade. Since the blades are more of a propeller design or root-to-tip twist design, it avoids retreating blade stall, which is when the aircraft will start to shudder, pitch the nose up and, if uncorrected, will result in a roll in the direction of the retreating blade. This means that the tilt rotor will achieve faster airspeeds than the fastest helicopter.
HISTORY OF TILT ROTORS
By the time we evolved flying into a safe, reliable mode of transportation, people have been intrigued to create an aircraft with the capability to vertically take off and land (VTOL). The first design that resembles a tilt rotor dates back to May 1930 where George Lehberger patented the idea. Further development did not start until mid-1942 by Germans in World War II but no prototype ever took flight. Inspired by the German prototype called the Focke-Achgelis FA-269, Americans decided to make a one seated Transcendental Model 1-G and a two seated Transcendental Model 2, both powered by a single engine. It took almost ten years for the Model 1-G to take flight. After a devastating crash a year later in the Chesapeake Bay, engineers started to design the Model 2. At this time, the United States Air Force were looking for a more stable design capable of carrying out military missions like observation, reconnaissance, and medical evacuation. They then put their funding into an upcoming project by Bell called the XV-3. In 1972 NASA launched a competition for $0.5 million research and development contracts. Boeing built a design Model, 222 which included the fixed engine pods and a small rotating pod for the rotor. Bell, who won the competition, designed Model 301 that included the whole engine and rotor assembly in one rotating pod. This aircraft,...