Engine failure has been the cause of many aircraft crashes over the recent past. If the engine fails during hovering, the pilot must be very careful as not to be quick to lower the collective because this will lead to a crash. It is imperative to note that this normally occurs whenever the engine is not able to supply power to the main rotor for aircraft such as helicopters.
Problem
Autorotation (for landing) and Engine Failure
Failure of the driveline or engine is known to be the main reason as to why one would reform an autorotation even though during a complete failure of the tail rotor, the same can also be applied. One of the main reasons why some helicopters often have these problems is because very little attention is paid to their maintenance. In other cases, they may be caused by fuel contaminations or exhaustion which cause the engine to be disengaged from the main rotor, thus allowing it to rotate freely. An autorotation descent a power off maneuver can be very tricky, especially if a pilot has not received appropriate training to deal with such an emergency. In addition to this, experience is also vital because once the engine is disengaged from the main rotor system, the rotor blades will be solely driven by the upward flow of air through the rotor ( Padfield, 2014 ).
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Significance of the Problem
Engine failures are very critical because if they occur at low levels, then they may lead to a disastrous crash causing the death of those who are onboard the aircraft. For instance, if it fails when flying at a higher hover or below 500 feet, during takeoff, it may very difficult to control the helicopter ( United States, 2013 ). The most one can do is to put it in the normal auto-rotation but the time to allow for this will be very limited. In such cases, the helicopter normally crashes to the ground because the time frame for taking action is usually limited at such a low level. This is the main reason as to why pilots are always advised to hover at low levels and fly above altitudes of 500 feet.
Development of Alternative Actions
90
Autorotation
Padfield (2014) notes that at the 90
point, the progress of the turn is checked as the pilot glances at the landing area. The second turn of the same angle is made so that the aircraft can be rolled out on the center line. If it appears to be too close to this point, the bank angle is decreased and if it is too far then the bank angle is increased, changing the G loading thereby altering the airflow as it changes the rotor rpm. This motion helps to keep antitorque pedals in trim with the helicopter thus completing the turn as it touches down in the designated area.
180
Autorotation
According to United States (2013) , the aircraft must be aligned in the downwind side at a recommended speed that falls between 500 and 700 feet AGL, which would make the aircraft parallel to the touchdown area. If the aircraft is in a headwind or no wind position, then the ground track must be approximately established at a distance of 20feet away from the area where it would touch down. The existence of strong winds would require the pilot to shift the downwind leg farther out. The collective pitch control needs to be lowered smoothly once the aircraft is near the intended touchdown area as the rotor rpm is maintained in the green arc with the collective.
Recommendation
A straight in rotation may be the best alternative in the event that an engine fails during hovering. Here, the pilot lowers the pitch thus reducing the lift and drag at which point the helicopter will start to descend. One of the main disadvantages of this is that if it is not done too quickly, then the RPM of the main rotor will drop too far and the pilot will lose control of the aircraft ( United States, 2013 ). Thorough training is therefore very essential because it equips pilots with the skills and knowledge of how to deal with an engine failure in case it occurs while they are in the air. The advantage of the technique is that it has a higher probability of landing safely as compared to other methods.
References
Padfield, R. R. (2014). Learning to fly helicopters . New York: McGraw Hill Education
United States. (2013). Helicopter flying handbook . New York: Skyhorse Publishing
