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30-596: Gyrodyne purchased the assets of Bendix Helicopters in 1949, including the Model 2C coaxial helicopter which provided the technology for the XRON-1. In 1951 the Model 2C was demonstrated to the Navy with shortcomings noted in autorotation control. The XRON-1 was demonstrated under a new Navy contract NOas 55-388-c for a lightweight single man helicopter. Gyrodyne 's design was an open-framework helicopter with coaxial rotors, which

60-554: A jet engine or other turbine engine due to the extinguishment of the flame in its combustor . The loss of flame can have a variety of causes, such as fuel starvation , excessive altitude, compressor stall , foreign object damage deriving from birds , hail , or volcanic ash , severe precipitation , mechanical failure, or very low ambient temperatures. Early jet engines were prone to flameout following disturbances of inlet airflow, or sudden or inappropriate thrust lever movements, which resulted in incorrect air-fuel ratios in

90-407: A type certificate . The longest helicopter autorotation in history was performed by Jean Boulet in 1972 when he reached a record altitude of 12,440 m (40,814 ft) in an Aérospatiale SA 315B Lama . Because of a −63 °C (−81.4 °F) temperature at that altitude, as soon as he reduced power, the engine flamed out and could not be restarted. By using autorotation he was able to land

120-437: A continual acceleration force. This inclination supplies thrust, which tends to accelerate the rotation of the blade. Driving region size varies with blade pitch setting, rate of descent, and rotor rotational speed. The inner 25 percent of the rotor blade is referred to as the stall region and operates above its maximum angle of attack (stall angle) causing drag, which slows rotation of the blade. A constant rotor rotational speed

150-407: A continuous ignition function. Ignitors are normally used only at engine start, until the flame in the combustion chamber becomes self-sustaining. With continuous ignition, instead, the ignitors are continually sparked every second or less, so that if a flameout occurs, combustion can immediately be restored. Following a flameout, jet engines can normally be restarted in flight, provided the aircraft

180-821: A radio-controlled drone version of the Rotorcycle, to be used as an Anti-Submarine Warfare platform. Using the dynamic components of the RON, this was eventually developed as the Gyrodyne QH-50 . The Rotorcycle went on to win the prize for most maneuverable helicopter at the Paris Air Show in 1961, and was selected for a 1964 trade fair in Morocco by the United States Department of Commerce . A two-place enclosed "gyrocycle" commercial variant

210-425: Is achieved by adjusting the collective pitch so blade acceleration forces from the driving region are balanced with the deceleration forces from the driven and stall regions. By controlling the size of the driving region, the pilot can adjust autorotative rotational speed. For example, if the collective pitch is raised, the pitch angle increases in all regions. This causes the point of equilibrium to move inboard along

240-400: Is achieved from a slight decrease in normal airspeed. Following this general procedure of fitting airspeed to existing conditions, the pilot can achieve approximately the same glide angle in any set of circumstances and estimate the touchdown point. This optimum glide angle is usually 17–20 degrees. During vertical autorotation, the rotor disc is divided into three regions—the driven region,

270-463: Is flying within the portion of its flight envelope defined as the engine relight envelope . Depending on where in the relight envelope the restart is attempted (that is depending on the aircraft's airspeed and altitude), the procedure may simply rely on the airflow ( windmill restart ) or require the use of the starter ( starter-assisted restart ) in order for the compressor to achieve sufficient rotational speed for successful ignition. For example,

300-564: Is virtually no torque produced in an autorotation. If altitude permits, autorotations may also be used to recover from a vortex ring state , also known as settling with power . In all cases, a successful landing depends on the helicopter's height and velocity at the commencement of autorotation (see height-velocity diagram ). At the instant of engine failure, the main rotor blades are producing lift and thrust from their angle of attack and velocity . By immediately lowering collective pitch , which must be done in case of an engine failure,

330-426: The action of air moving up through the rotor, as with an autogyro , rather than engine power driving the rotor. The term autorotation dates to a period of early helicopter development between 1915 and 1920, and refers to the rotors turning without the engine. It is analogous to the gliding flight of a fixed-wing aircraft. Some trees (for example maple trees) have seeds that have wing-like structures that enable

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360-502: The aircraft are used to decrease the rate of descent and make a soft landing. A greater amount of rotor energy is required to stop a helicopter with a high rate of descent than is required to stop a helicopter that is descending more slowly. Therefore, autorotative descents at very low or very high airspeeds are more critical than those performed at the minimum rate of descent airspeed. An optimum landing manoeuvre stops all of vertical movement, horizontal movement and rotational movement within

390-404: The aircraft safely. Autorotation is the normal operating mode of autogyros ; the distance record is 1653 km. For helicopter, "autorotation" refers to the descending maneuver in which the engine is disengaged from the main rotor system and the rotor blades are driven solely by the upward flow of air through the rotor. The freewheeling unit is a special clutch mechanism that disengages any time

420-478: The award, as stated in Army Regulation 672-74, are, "An aircrew member must, through outstanding airmanship, minimize or prevent aircraft damage or injury to personnel during an emergency situation. The aircrew member must have shown extraordinary skill while recovering an aircraft from an in-flight emergency situation." Flameout In aviation, a flameout (or flame-out ) is the run-down of

450-422: The blade's span, thereby increasing the size of the driven region. The stall region also becomes larger while the driving region becomes smaller. Reducing the size of the driving region causes the acceleration force of the driving region and rotational speed to decrease. The Broken Wing Award is a United States Army award for successful execution of an autorotation under emergency conditions. The requirements for

480-503: The combustion chamber. Modern engines are much more robust in this respect, and are often digitally controlled , which allows for significantly more effective control of all engine parameters to prevent flameouts and even initiate an automatic restart if a flameout occurs. Flameouts occur most frequently at intermediate or low power settings such as in cruise and descent. To prevent a flameout when atmospheric or operational conditions are conducive to it, engine control systems usually provide

510-424: The craft to a perfect standstill. In practice a perfect landing is rarely achievable. Each type of helicopter has a specific airspeed at which a power-off glide is most efficient. The best airspeed is the one that combines the greatest glide range with the slowest rate of descent. The specific airspeed is different for each type of helicopter, yet certain factors (density altitude, wind) affect all configurations in

540-417: The driving region, and the stall region. The sizes of these regions vary with the blade pitch, rate of descent, and rotor rotational speed. When changing autorotative rotational speed, blade pitch, or rate of descent, the sizes of the regions change in relation to each other. The driven region, also called the propeller region, is the region at the end of the blades. Normally, it consists of about 30 percent of

570-439: The engine rotational speed is less than the rotor rotational speed. If the engine fails, the freewheeling unit automatically disengages the engine from the main rotor, allowing the main rotor to rotate freely. The most common reason for autorotation is an engine malfunction or failure, but autorotation can also be performed in the event of a complete tail rotor failure, or following loss of tail-rotor effectiveness , since there

600-403: The factors previously mentioned. As the airspeed increases beyond the speed that gives minimum rate of descent, the rate of descent increases again. Even at zero airspeed, the rotor is quite effective, as it has nearly the drag coefficient of a parachute despite consisting of blades. When landing from an autorotation, the kinetic energy stored in the rotating blades and the forward movement of

630-426: The pilot reduces lift and drag and the helicopter begins an immediate descent, producing an upward flow of air through the rotor system. This upward flow of air through the rotor provides sufficient thrust to maintain rotor rotational speed throughout the descent. Since the tail rotor is driven by the main rotor transmission during autorotation, heading control is maintained as in normal flight. Several factors affect

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660-413: The program for testing. The Marine Corps also tested one XRON-1, and three YRON-1 prototypes. The Marine Corps eventually concluded that both the RON, and the competing Hiller ROE were too heavy and too difficult to fly and abandoned the project. The United States Navy , however, had noticed the compact size and high load-carrying capacity of the RON, and in 1960 awarded a contract to Gyrodyne to produce

690-421: The radius. It is the driven region that produces the most drag. The overall result is a deceleration in the rotation of the blade. The driving region, or autorotative region, normally lies between 25 and 70 percent of the blade radius, which produces the forces needed to turn the blades during autorotation. Total aerodynamic force in the driving region is inclined slightly forward of the axis of rotation, producing

720-427: The rate of descent in autorotation: density altitude , gross weight , rotor rotational speed, and forward airspeed . The pilot's primary control of the rate of descent is airspeed. Higher or lower airspeeds are obtained with the cyclic pitch control just as in normal flight. Rate of descent is high at zero airspeed and decreases to a minimum at approximately 50 to 90 knots, depending upon the particular helicopter and

750-471: The rotor system from below as the helicopter descends. Autorotation is permitted mechanically because of both a freewheeling unit , which allows the main rotor to continue turning even if the engine is not running, as well as aerodynamic forces of relative wind maintaining rotor speed. It is the means by which a helicopter can land safely in the event of complete engine failure. Consequently, all single-engine helicopters must demonstrate this capability to obtain

780-494: The rotors. Gyrodyne patented the control on 24 October 1954 Patent No. 2,835,331. There is a small inverted V-tail for control at forward speeds. The rotors are laminated wood construction. The mast is pressure lubricated and becomes a cooling surface for oil inflight. The landing gear consists of three small wheels. The first flight was in November 1955. The two-cycle engine was prone to overheating and other engines were added to

810-403: The same manner. The specific airspeed for autorotations is established for each type of helicopter on the basis of average weather and wind conditions and normal loading. A helicopter operated with heavy loads in high density altitude or gusty wind conditions can achieve best performance from a slightly increased airspeed in the descent. At low density altitude and light loading, best performance

840-485: The seed to spin to the ground in autorotation, which helps the seeds to disseminate over a wider area. The most common use of autorotation in helicopters is to safely land the aircraft in the event of an engine failure or tail-rotor failure. It is a common emergency procedure taught to helicopter pilots as part of their training. In normal powered helicopter flight, air is drawn into the main rotor system from above and forced downward, but during autorotation, air moves into

870-424: Was evaluated with three different power plants (two reciprocating, one turbine). The XRON-1 used a manually started 40 hp two-cycle engine with a gross weight capability of 500 lb. The fuselage is a simple box-beam construction. The rotor uses co-axial blades which alleviate the need for an anti-torque tail rotor. Yaw control is provided by rotor tip mounted "tip brakes" providing differential torque between

900-402: Was proposed after initial tests. Data from Jane's All The World's Aircraft 1961–62 General characteristics Performance Related development Aircraft of comparable role, configuration, and era Related lists Autorotation (helicopter) Autorotation is a state of flight in which the main rotor system of a helicopter or other rotary-wing aircraft turns by

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