Helicopters, with their unique design and capabilities, rely heavily on their engines for safe flight. When an engine fails, pilots must act swiftly and skillfully to ensure a controlled descent and a safe landing. In this article, we’ll explore what happens during helicopter engine failure, common causes, and the critical maneuvers pilots employ to land safely.
What Happens During a Helicopter Engine Failure?
- Autorotation: The Controlled Descent
- Contrary to Hollywood depictions, a helicopter does not plummet uncontrollably when its engine fails. Instead, pilots execute a manoeuvre called autorotation.
- During autorotation, the helicopter glides downward under the influence of gravity. The main rotor continues to turn due to the upflowing air, storing potential energy.
- The challenge lies in finding a suitable area for touchdown during this controlled descent.
- The Role of Potential Energy
- As the helicopter descends, the stored potential energy in the rotating rotor blades becomes crucial.
- To convert this potential energy into lift, the pilot adjusts the collective pitch control. This action allows the helicopter to cushion its landing and touch down smoothly.
Common Causes of Helicopter Engine Failure
- Fuel Starvation
- By far, the most common cause of engine failure is fuel starvation. Pilots misjudging their fuel requirements or attempting to “squeak it home” can lead to running out of fuel mid-flight.
- Sticking fuel quantity gauges can also contribute to this issue.
- Mechanical Failures
- Mechanical failures, including engine failure, transmission failure, and rotor system failure, can occur due to design defects, manufacturing defects, or improper maintenance practices.
- For example, malfunctioning tail rotors can cause a helicopter to spin out of control12.
Pilot Responses for Safe Landing
- Immediate Collective Lowering
- When an engine fails, the pilot’s first priority is to quickly lower the collective.
- The helicopter enters an immediate, steep descent, resulting in an upward flow of air through the rotor system.
- The descent rate stabilizes as the helicopter transitions into autorotation.
- Rotor RPM Management
- Maintaining rotor RPM (rotations per minute) is critical. If RPM drops too low, recovery becomes impossible, leading to a crash.
- Pilots must manage RPM carefully during autorotation.
- Selecting a Landing Area
- While in autorotation, pilots search for a clear area to touch down.
- Twin-engine helicopters (Category A) have more options, as they can often fly on a single engine.
- Older, less powerful helicopters (Category B) may descend more slowly, allowing for better landing site choices3.
In summary, helicopter engine failure demands swift action, precise control, and a thorough understanding of autorotation. By following established procedures, pilots can safely navigate this challenging situation and bring their aircraft to a controlled landing.
