How Do Helicopters Regulate Their Speed In The Air?

Helicopter pilots accelerate and decelerate by maintaining a fine balance between what are known as cyclic and collective control inputs.

Though fixed-wing aircraft and helicopters both fly through the skies, the ways they achieve and control flight are worlds apart. Horizontal acceleration and deceleration in a helicopter involve several systems working together in unison.

A helicopter’s main rotor is a collection of large blades attached to a control system towards the top of the vehicle. Its rotor is what is ultimately responsible for generating lateral thrust, and it is influenced by two primary controls: the cyclic and collective.

Simply put, the cyclic is the “stick” in the cockpit that controls the helicopter’s direction of flight. If a helicopter is hovering, the stick can make it go forwards, backward, or side-to-side.

The collective, meanwhile, is usually a lever in the cockpit that controls the pitch angle of all of the main rotary blades simultaneously, either increasing or decreasing the total lift generated by the rotor blades. Thus, in level flight, changes in the collective position will cause the helicopter to climb or descend.

To increase speed and accelerate, a pilot pushes the cyclic forward, causing the main rotor disk to tilt downward at the front. This forward tilt redirects some of the power from lift to thrust, propelling the helicopter faster through the air. However, this maneuver comes with a trade-off – a simultaneous loss of altitude. As the helicopter gains forward speed, it descends due to the redistribution of lift and thrust power.

Thus, some change in the collective lever position will be required to maintain a steady altitude during an acceleration. This means that helicopter pilots must continually find the right balance between acceleration and altitude control to avoid dramatic changes in the flight path. By gradually adjusting both the cyclic and collective, they can achieve smooth acceleration while maintaining a stable altitude.

Conversely, the pilot applies gentle rearward pressure on the cyclic to decelerate and reduce speed. This tilts the rotor disk downward at the rear, generating rearward thrust that counters the helicopter’s forward momentum. In a similar fashion, this maneuver has a secondary effect – the helicopter gains altitude, commonly referred to as ballooning.

To counteract the altitude change during deceleration, the pilot must lower the collective to prevent the helicopter from climbing. Additionally, the pilot must adjust the pedals to maintain the helicopter’s heading, as the change in thrust can affect the helicopter’s orientation.

Want answers to more key questions in aviation? Check out the rest of our guides here!

Achieving smooth acceleration and deceleration requires precise coordination of all control inputs. To ensure a balanced and controlled flight, the pilot must seamlessly combine cyclic, collective, and pedal adjustments. Mastery of these controls is essential, as any abrupt or uncoordinated movements can lead to unstable flight conditions.

During flight training, aspiring helicopter pilots dedicate significant time and effort to mastering these complex maneuvers. They learn to manage all flight controls in unison, developing the muscle memory and reflexes necessary for smooth and controlled speed adjustments.

In real-world scenarios, pilots face various flight conditions requiring them to adjust control inputs to achieve otherwise identical accelerations or decelerations. When flying against headwinds, for example, helicopters experience increased air resistance, which can reduce their ground speed. To compensate, pilots may need to increase engine power and adjust cyclic and collective inputs compared to power and input settings they might use in still air.

Mastery of cyclic and collective control techniques empowers pilots to confidently and smoothly adjust airspeeds as they navigate a wide variety of flight scenarios.

Sources: PilotTeacher

Matt's eyes have been turned to the sky for as long as he can remember. A former newspaper editor, Matt is a lifelong avgeek whose earliest memories include talking aviation with his grandfather, a retired US Air Force pilot. Matt has lived in Greece, Czechia, and Germany for studies and for work, and is currently based in the US, near Dallas. Matt recently took the plunge to become a pilot himself and is transitioning into an aviation career.