Tail rotor faults usually include two types: one is the transmission system failure, mainly caused by fatigue and wear of internal parts or external fierce impact of the tail rotor drive shaft damage, so that the tail rotor tension loss;
One is the control system failure, which is mainly caused by the internal friction or external impact of the tail rotor control line damage, tail rotor pitch free change or stuck in a certain pitch position can not change, so that the pilot lost the control of the tail rotor pull.
Both of these faults are transient emergency faults, and the pilot needs to quickly identify and judge what type of tail rotor fault has occurred, and make the correct disposal in a short time to avoid the helicopter into a complex state.
The treatment of tail rotor failure is generally divided into three stages: transient transition stage, in which the pilot needs to restore the helicopter to a safe and controllable flight state through timely disposal, that is, the pitch, roll and deflection speed are all zero;
The maneuver flight phase, in which the pilot needs to adjust the helicopter’s course to maneuver the helicopter to the desired landing area;
The landing phase, in which the pilot performs a powered run or spin landing, etc.
Whether the helicopter is safe and controllable in these three stages after tail rotor failure depends on many factors, including the configuration of the helicopter, the flight state before the failure, the pilot’s attention, training and driving skills, and the type of tail rotor failure.
The failure of the tail rotor transmission system can cause the helicopter nose to deflect due to the back torque of the rotor.
When the air speed is high, the vertical tail’s directional stabilization effect can replace part of the tail rotor function, reduce or even eliminate the deflection, which is conducive to maintaining the direction.
The fault of tail rotor transmission system in high power and small airspeed condition will cause serious deflection, and the fault in low power and large airspeed condition will cause small deflection.
A special case of tail rotor transmission failure is when the tail rotor structure falls off due to damage. In this case, in addition to nose deflection, the helicopter nose will be lowered due to changes in the center of gravity of the helicopter.
The handling of tail rotor transmission system failure depends on the flight status of the helicopter at the time of failure.
In both hover state and flying condition occurs before the tail rotor driving system fault, in theory can pass down the total distance and shut down the engine rotation land, but waiting for the speed increased to a certain degree, end of deflection, the pilot with the helicopter flying back to a safe and controllable state needs a certain amount of time, will lose a certain height, so the height is very important.
When the altitude allows for “splurges,” a spin landing can be entered, while when the altitude is not high enough, the engine should probably not be shut down until the deflection stops, as it can at least be buffered with engine power while grounded.
If the tail rotor transmission system fault occurs, the helicopter has enough forward speed (close to cruising speed), equipped with vertical stability and the helicopter, due to the vertical fin can provide sufficient lateral force to balance the rotor torque, so even if the use of engine power, just keep a certain velocity, the helicopter will not appear deflection,
At this time, the helicopter can be controlled to choose the landing site in a wider range, establish the ideal landing route, and use a high speed glide landing.
But it is important to note the tail rotor driving system fault, although can through to the direction of the deflection in the opposite direction to compensate for part of the compression strut deflection, but this will increase the resistance, may make the helicopter reduced speed, the direction of the vertical tail stability will reduce airspeed decreases, so using a stick to overcome the deflection, must pay special attention to maintain the speed of the helicopter.
The main fault of tail rotor control system is tail rotor stuck.
The so-called tail rotor stuck is that the tail rotor blade installation Angle is fixed at a certain Angle due to some reason, such as the tail rotor control line is stuck and the pitch lever falls off, etc., and the pilot can not operate the rudder, or the rudder helicopter has no reaction.
Tail rotor stagnation can be divided into neutral position stagnation, high pitch position and low pitch position according to the position.
The neutral position refers to the tail blade is located near the middle installation Angle position, slightly higher or slightly lower, at this time the tail rotor can also provide a part of the pulling force;
The high distance position refers to the tail rotor blade deviates from the middle position more, stuck in the larger installation Angle, the tail rotor blade Angle of attack is larger;
The low distance position refers to the tail rotor blade deviates from the middle position more, stuck in the small installation Angle, the tail rotor blade Angle of attack is small, even negative Angle of attack.
The tail rotor stuck in different position, the fault phenomenon and the disposal method are different.
The pilot should accurately judge the position of the stagnation, and take corresponding methods to deal with it in time.
The main methods of determining the tail rotor stagnation position in the air are: rudder position judgment method, the tail rotor control system failure moment, if the rudder is stuck, then this position may be the tail rotor stagnation position, can be judged by the position relationship between left and right rudder before and after the tail rotor stagnation position;
Tail rotor binding, sideslip, air can be by the feeling of the sideslip tester in cockpit and the pilot to determine the sideslip direction, the helicopter forward line direction of blade with lateral spreads, from the tail rotor binding in high position, to the direction of the blade with lateral spreads after, from the tail rotor binding in low position, the greater the sideslip, binding the position deviation from the center of the more;
Total distance judgment method, the pilot can be put through the total distance method to determine the approximate location of a tail rotor binding, binding in the low position, mention the total line is apart from the helicopter forward direction of the blade deflection faster, and more sensitive, and put the total distance to the blade deflection after a delay, from binding in a high position, put the total from the helicopter blades after direction deflection faster, and more sensitive,
However, the deflection of the forward blade is relatively slow.
When the judgment is high from the binding, first adjust the speed to the economy, maintain level flight, and then establish a lower down line, overlooking the rotor helicopter clockwise on the left side of the slide right cross, overlooking the counterclockwise rotor helicopter cross slide left on the right side, fall stilling timing can be appropriately in advance, just put the total distance speed, control the rate of decline, close to the ground, start on the total distance,
Gradually eliminate the crossing Angle, when the vertical axis direction of the helicopter is consistent with the landing direction, and the state is stable, the helicopter is grounded.
When the judge is low from binding, because the tail rotor can provide at this time of high tension from binding much smaller, so the first thing to adjust to the greater speed, as far as possible using the vertical tail wind vane effect, maintain level flight, from the rest of the manipulation with high binding is similar, the difference between the two is that the size of the ground speed, high pitch binding ground speed is small, low from binding required ground speed is bigger.
In the process of tail rotor stuck at low pitch, it is easy to slow down too fast during the slide, which reduces the efficiency of the vertical tail wind vane, and causes the deviation of the helicopter direction and attitude. When the deviation is small, the helicopter can adjust the speed and the total distance of lifting and lowering to control the direction and attitude for landing, and when the deviation is large, it is necessary to go around decisively.
The latest market dynamics at any time to see, please pay attention to.
