Lesson Notes By Weeks and Term v4 - SHS 2

Lesson Video

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Performance objectives

• Describe the basic flight controls of a rotary-wing aircraft.
• Identify the function of each control mechanism.
• Understand how control inputs affect the aircraft's movement.
• Analyze the relationship between controls and flight safety.

Lesson summary

Welcome, future engineers and pilots! Today, we are exploring one of the most fascinating machines in the sky: the helicopter, a type of rotary-wing aircraft. Unlike aeroplanes that need a long runway, helicopters can take off and land vertically, hover in one spot, and fly in any direction. This unique ability makes them essential in Ghana for everything from military operations and offshore oil rig support in Takoradi to potential emergency medical services in busy cities like Accra and Kumasi. To understand how a helicopter performs these amazing manoeuvres, we must learn about its flight controls.

Lesson notes

Introduction: How a Helicopter Flies

A helicopter generates lift using a set of rotating wings called rotor blades. Think of these blades as aerofoils, just like the wings of an aeroplane. As they spin through the air, they create a low-pressure area above the blade and a high-pressure area below it, generating an upward force called lift. The pilot's job is to precisely manage this lift to control the helicopter's movement. They do this using four main controls.

*(Teacher's Note: At this point, it is highly recommended to show a short video clip of a helicopter taking off, hovering, and manoeuvring. If a video is not available, use diagrams and pictures of a helicopter cockpit and a rotor system).* The Four Main Flight Controls The Collective Pitch Control (The Collective) What it is: A lever located to the left of the pilot's seat, which moves up and down. What it does: The collective changes the pitch angle of *all* the main rotor blades *simultaneously and equally*. The pitch angle is the angle at which the blade cuts through the air. How it works: When the pilot pulls the collective lever up, the pitch angle of all blades increases. This makes the blades "bite" into the air more aggressively, generating more lift. The helicopter climbs. When the pilot pushes the collective lever down, the pitch angle of all blades decreases. This generates less lift. The helicopter descends. Analogy: Think of the collective as the "elevator" or "lift control" of the helicopter. It controls the "up" and "down" movement without changing the helicopter's forward or sideways speed. It's like a dimmer switch for a light bulb: turning it up gives more power (lift), and turning it down gives less. The Cyclic Pitch Control (The Cyclic) What it is: A stick located in front of the pilot, between their knees. It can be moved forward, backward, left, and right. What it does: The cyclic changes the pitch angle of the rotor blades *individually* as they rotate through their 360-degree cycle. This action tilts the entire rotor disc (the imaginary circle the blades trace as they spin). How it works: The total lift from the rotor disc always acts perpendicular (at a 90° angle) to the disc itself. If the pilot pushes the cyclic forward, the rotor disc tilts forward. The lift vector now has a forward component, pulling the helicopter forward. If the pilot pulls the cyclic backward, the rotor disc tilts backward, and the helicopter moves backward. If the pilot moves the cyclic left or right, the rotor disc tilts left or right, and the helicopter flies sideways (strafes). Analogy: Imagine you are holding a large, flat plate with a small ball in the centre. To make the ball roll forward, you tilt the plate forward. To make it roll left, you tilt the plate left. The cyclic is the control that "tilts the plate" (the rotor disc), and the helicopter (the ball) follows. The Anti-Torque Pedals What it is: A pair of foot pedals, similar to those in a car, that the pilot operates with their feet. The Problem (Torque Effect): According to Newton's Third Law of Motion (for every action, there is an equal and opposite reaction), as the engine and transmission spin the main rotor in one direction (e.g., counter-clockwise), the body of the helicopter (the fuselage) wants to spin in the opposite direction (e.g., clockwise). This uncontrolled spinning is called the torque effect. The Solution (Tail Rotor): To counteract this, most helicopters have a smaller set of blades at the tail, called the tail rotor. This tail rotor acts like a small propeller, pushing air sideways to stop the fuselage from spinning. How the Pedals Work: The anti-torque pedals control the pitch of the tail rotor blades. Pushing the left pedal increases the tail rotor's thrust, pushing the tail to the right and causing the helicopter's nose to turn (yaw) to the left. Pushing the right pedal decreases the tail rotor's thrust, allowing the main rotor's torque to turn the fuselage. This pushes the tail to the left and causes the nose to turn (yaw) to the right. Primary Function: The pedals are used to control which direction the nose of the helicopter is pointing (yaw). The Throttle What it is: Usually a motorcycle-style twist grip located on the collective lever. What it does: The throttle controls the power output of the engine, which in turn controls the speed (RPM - Revolutions Per Minute) of the main rotor. How it works: For a helicopter to fly efficiently, the rotor RPM must be kept within a very narrow, constant range. When a pilot pulls up on the collective to climb, the increased blade pitch creates more drag, which would slow the rotor down. The pilot (or an automatic system called a governor) must simultaneously increase the throttle to provide more engine power and maintain the correct RPM. Conversely, lowering the collective requires a decrease in throttle. Modern Helicopters: Most modern helicopters have an automatic governor that manages the throttle, so the pilot can focus on the other controls. However, the pilot can override it if necessary.

Guided Practice (With Solutions) Question 1

Evaluation guide

• Describe the flight controls of a rotary -wing aircraft .
• Talk for Learning: With the aid of audio -visuals, learners watch and describe the control
• conceptual
• understanding