The Aviation Science

Helicopter Flight Control System 🛩️helicopter pilot manipulates the helicopter flight controls to achieve and maintain controlled aerodynamic flight. 🛩️Changes to the helicopter flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a deliberate way. 🛩️To tilt forward and back (pitch) or sideways (roll), requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift(forces) at different points in the cycle. 🛩️To increase or decrease overall lift requires that the controls alter the AoA for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration. 🛩️A typical helicopter has three flight control inputs—the cyclic stick, the collective lever, and the anti-torque pedals. 🛩️Depending on the complexity of the helicop...

Transonic Area Rule 🛩️The Transonic area rule, also called the Whitcomb area rule, is a design technique used to reduce an aircraft's drag at transonic and supersonic speeds, particularly between Mach 0.75 and 1.2. 🛩️This is one of the most important operating speed ranges for commercial and military fixed-wing aircraft today, with transonic acceleration being considered an important performance metric for combat aircraft and necessarily dependent upon transonic drag. 🛩️At high-subsonic flight speeds, the local speed of the airflow can reach the speed of sound where the flow accelerates around the aircraft body and wings. The speed at which this development occurs varies from aircraft to aircraft and is known as the critical Mach number. 🛩️The resulting shock waves formed at these points of sonic flow can result in a sudden increase in drag, called wave drag. To reduce the number and power of these shock waves, an a...

Hydraulic System 🛩️There are multiple applications for hydraulic use in aircraft depending on the complexity of the aircraft. For example, a hydraulic system is often used on small airplanes to operate wheel brakes, retractable landing gear, and some constant speed propellers. 🛩️On large airplanes, a hydraulic system is used for flight control surfaces, wing flaps, spoilers, and other systems. 🛩️A basic hydraulic system consists of a reservoir, pump (either hand, electric or engine-driven), a filter to keep the fluid clean, a selector valve to control the direction of flow, a relief valve to relieve excess pressure, and an actuator. 🛩️The hydraulic fluid is pumped through the system to an actuator or servo. A servo is a cylinder with a piston inside that turns fluid power into work and creates the power needed to move an aircraft system or flight control. Servos can be either single-acting or double-acting, based on the needs of the system. This means that the fluid can be...

Wet Sump Oil System ✳️The engine oil system performs several important functions: 🛩️Lubrication of the engine’s moving parts . 🛩️Cooling of the engine by reducing friction . 🛩️Removing heat from the cylinders . 🛩️Carrying away contaminants . 🛩️Providing a seal between the cylinder walls and pistons. ➡️Subscribe us for more aircraft knowledge and aircraft fact⬅️ ➡️Do Share with your Friends⬅️

Vortex Devices 🛩️Vortex devices maintain airflow at low speeds and delay the stall, by creating a vortex which re-energises the boundary layer close to the wing . 🛩️Vortex generator: small triangular protrusion on the upper leading wing surface; usually, several are spaced along the span of the wing. Vortex generators create additional drag at all speeds . 🛩️Vortilon: a flat plate attached to the underside of the wing near its outer leading edge, roughly parallel to normal airflow. At low speeds, tip effects cause a local spanwise flow which is deflected by the vortilon to form a vortex passing up and over the wing . 🛩️Leading-edge root extension (LERX): generates a strong vortex over the wing at high angles of attack, but unlike vortex generators it can also increase lift at such high angles, while creating minimal drag in level flight. ➡️Subscribe us for more aircraft knowledge and aircraft fact⬅️ ➡️Do Share with your Friends⬅️

Drag Reduction Devices 🛩️Anti-shock body: a streamlined pod shape added to the leading or trailing edge of an aerodynamic surface, to delay the onset of shock stall and reduce transonic wave drag. Sometimes called a Küchemann carrot . 🛩️Fillet: a small curved infill at the junction of two surfaces, such as a wing and fuselage, blending them smoothly together to reduce drag . 🛩️Fairings of various kinds, such as blisters, pylons and wingtip pods, containing equipment which cannot fit inside the wing, and whose only aerodynamic purpose is to reduce the drag created by the equipment ➡️Subscribe us for more aircraft knowledge and aircraft fact⬅️ ➡️Do Share with your Friends⬅️

Bleed Air from Engine 🛩️When air enters a turbine engine, it goes through a series of compressors, which significantly increase the air temperature and pressure before mixing that air with fuel and igniting it. A small portion of that compressed air, however, does not enter the combustion chamber and instead is redirected from the engine via valves, ducting and manifolds to various other areas of the aircraft. 🛩️Bleed air is extracted from the compressor of the engine or APU. 🛩️The specific stage of the compressor from which the air is bled varies by engine type. 🛩️In some engines, air may be taken from more than one location for different uses as the temperature and pressure of the air is variable dependant upon the compressor stage at which it is extracted. 🛩️Bleed air from that system can be utilized for internal cooling of the engine, cross-starting another engine, engine and airframe anti-icing, cabin pressurization, pneumatic actuators, air-driv...