Tail rotor - Wikipedia
The tail rotor is a smaller rotor mounted so that it rotates vertically or near- vertically at the end of The tail rotor drive system consists of a shaft powered from the main transmission and a gearbox mounted at the end of the tail boom. The drive shaft . Edit links. This page was last edited on 24 October , at 26 (UTC). The tail rotor drive shaft, also called Tail Rotor Drive Line or Tail Drive Line, runs from the rear cover of the main gearbox to the disconnect coupling at the. Moreover, a direct-drive actuation system shall be installed in the tail with strict 1. l is the distance between the main shaft and the center of the tail rotor, R HB is the . Therefore, the relationship between the main rotor thrust and the induced.
In the event of a hydraulic system failure, the mechanical system is still able to control the tail rotor pitch, though the control resistance felt by the pilot will be considerably greater. The tail rotor is powered by the helicopter's main power plant, and rotates at a speed proportional to that of the main rotor. In both piston and turbine powered helicopters, the main rotor and the tail rotor are mechanically connected through a freewheeling clutch systemwhich allows the rotors to keep turning in the event of an engine failure by mechanically de-linking the engine from both the main and tail rotors.
Tail Rotor Drive Shaft (TRDS)
During autorotationthe momentum of the main rotor continues to power the tail rotor and allow directional control. To optimize its function for forward flight, the blades of a tail rotor have no twist to reduce the profile drag, because the tail rotor is mounted with its axis of rotation perpendicular to the direction of flight. Reliability and safety[ edit ] Many tail rotors are protected from ground strikes by a skid plate or by a steel guard, such as on this Bell The tail rotor and the systems that provide power and control for it are considered critically important for safe flight.
As with many parts on a helicopter, the tail rotor, its transmission, and many parts in the drive system are often life-limited, meaning they are arbitrarily replaced after a certain number of flight hours, regardless of condition. Between replacements, parts are subject to frequent inspections utilizing visual as well as chemical methods such as fluorescent penetrant inspection to detect weak parts before they fail completely.
Despite the emphasis on reducing failures, they do occasionally occur, most often due to hard landings and tailstrikesor foreign object damage.
Though the tail rotor is considered essential for safe flight, the loss of tail rotor function does not necessarily result in a fatal crash. In cases where the failure occurs due to contact with the ground, the aircraft is already at low altitude and the pilot may be able to reduce collective and land the helicopter before it spins completely out of control.
Should the tail rotor fail randomly during cruise flight, forward momentum will often provide some directional stability, as many helicopters are equipped with a vertical stabilizer.
Helicopter variable-rpm hydrostatic drive tail rotor
The pilot would then be forced to autorotate and make an emergency landing with significant forward airspeed, which is known as a running landing or roll-on landing. The tail rotor itself is a hazard to ground crews working near a running helicopter.
For this reason, tail rotors are painted with stripes of alternating colors to increase their visibility to ground crews while the tail rotor is spinning. Eurocopter ECwith a fantail assembly tail rotor. There have been three major alternative designs which attempt to solve the shortcomings of the tail rotor system.
The first is to use a ducted fan rather than an un-ducted fan. This design is referred to as a fantail, or by the trade name Fenestrona trademark of Eurocopter.
The Tail Rotor
There are other system of counteracting torque, called NOTAR, in which the torque caused wines bearing the Ohm, provide combat air or gas jet generated by the turbine and sent to the tail boom using the appropriate window to create the desired aerodynamic effect.
The development of such systems leads to significant structural problems that limit their use only helicopters driven by the turbine. The main objective of the invention described in this document, is to avoid the difficulties mentioned above, found in helicopters with one rotor, currently available, through the creation of a tail rotor and a corresponding drive system, which is very flexible, adaptable, easy to manufacture, and reliable and efficient in use.
The second objective of the invention is to create a tail rotor and transmission system, which give the possibility to control the traction of the screw by varying the number of revolutions instead of the blade pitch, thereby limiting the mechanical friction in the flight conditions with the engine switched off.
The third objective of the invention is to eliminate the "long shaft", thereby eliminating the source of harmful vibrations and freeing the geometry of the transmission from the constraints due to the need of the shaft. The fourth C is l the invention consists in the fact, to remove all controls and devices required to change the blade pitch of the tail rotor, cockpit, tail rotor and tail beams, so that the tail beam was free from moving parts.
The fifth objective of the invention is to eliminate the conical reducer required to drive the tail rotor, resulting in simplification of the structure, reducing wear and increasing reliability. The sixth objective of the invention is to provide the ability to control the direction of the aircraft by the tail rotor during flight conditions with a disabled engine. Another objective of the invention is to make the geometric position of the engine independent of the tail rotor, so that the engine could be installed with a vertical shaft engine without having conical reducer to drive the rotor shaft.
These and other objectives, which should be more explained later, all are satisfied by the invention of the tail rotor and transmission system for helicopters with a single rotor, the basic characteristics of which include: Additional features should become clearer and more apparent with reference to the accompanying drawing, which illustrates one of several possible ways of organizing systems: Figure 1 illustrates an implementation option of the tail rotor and transmission system applicable to the helicopter with a single rotor.
This figure illustrates the tail rotor r with at least three blades with a fixed step.
Screw r is placed in the groove of the shaft-standard motor constant performance with axial cylinders pistons that is installed at the end of the tail beam t and connected by rigid or flexible input and output pipes with standard hydraulic variable pump with axial cylinders pistons pwhich shaft is driven by means of shaft m rotor using the normal mechanisms of transmission.
The control lever hwhich regulates the volumetric capacity and the countercurrent flow of the pump pis connected via a rod d and levers I with pedals f located in the cockpit. If the lever control is the exercise h means in position, the corresponding maximum volumetric efficiency of the pump, through the action of the pedal in the same direction as the rotation of the rotor, the speed of fluid flow in the motor tail rotor reaches its maximum, and hence the screw r will rotate at maximum speed, developing maximum traction to resist the reaction torque of the main rotor.
With the pedals in the intermediate position, the pump rate drops to zero, and the screw r remains without motion; this condition may be initiated by the pilot, when power is lost during flight in autorotation. If pedal f moving beyond the intermediate position, the rotation of the screw changes the direction on the opposite, thereby reversive cravings, allowing more than adequate and full control of the aircraft around the vertical axis of the rotor. Pedal f are placed in the usual way, with two pedals connected with the lever, which varies the volumetric capacity of the pump pusing the same design criteria that are typically used to connect the pedal controls the overall steps that change the step of the hinged blades in a traditional tail rotor.
At the design stage by regulating the ratio between the volume about what socialnoto of the motor n and the maximum volumetric capacity of the pump pit is possible to vary the gear ratio between the rotor and tail screw, allowing the use of the invention in a broader range of applications. The path of the hydraulic fluid is of the hydrostatic type and includes a drainage pipe ioil tank koil filter o may heatsink e and boot pump gwhich are usually equipped with a pump p.
Many modifications and variants can be applied to such crafted designs, all of which are part of the invention. Moreover, all details can be replaced by other technically equivalent.
- Vibration Identification & Minimization
- Tail rotor
- Tail Rotor Drive Shaft (TRDS)
In practice, the materials used and the size and number of components can vary as needed. Tail rotor for helicopters with a single rotor and a corresponding drive system, comprising: Tail rotor for helicopters with a single rotor and a corresponding drive system according to claim 1, characterized in that the system is equipped with a drain pipe ioil tank koil filter onradiator s and boot pump g.Schweizer 333 tail rotor drive shaft...
Tail rotor for helicopters with a single rotor and a corresponding drive system according to claim 1 or 2, characterized in that the screw r contains at least three blades b with a fixed step. Tail rotor for helicopters with a single rotor and a corresponding drive system according to claim 1 or 2, characterized in that the thrust can be changed by varying the flow rate of fluid through the hydraulic motor nthereby varying the rotational speed of screw r.
Tail rotor for helicopters with a single rotor and a corresponding drive system according to claim 1 or 2, characterized in that the tail rotor is made so that the rotation speed decreases with decreasing engine torque applied to the bearing screw, falling to zero in case of power loss, AutoRotate is.