The Aviation Science

APU Fire Detection & Extinguishing System 🛩️The APU fire protection system is similar in design to engine fire protection systems, but there are some differences. The APU is often operated with no personnel in the flight deck and; the APU fire protection system can operate in an unattended mode on the ground with the engines not running. 🛩️If there is an APU fire in the unattended mode, the fire extinguisher discharges automatically. The APU operates in the attended mode when at least one engine is running. If there is an APU fire in this mode, the crew discharges the bottle manually. Fire switches are located on the cargo fire/ engine control panel and the service and APU shutdown panel located outside the airplane on the nose landing gear. 🛩️If there is an APU fire, the APU fire detection system gives fire warnings and automatically stops the APU. The APU fire warning light comes on to identify the correct fire switch to use to extinguish the fire. The fire switch sole...

Helicopter Structure 🛩️The major components of a helicopter are the airframe, fuselage, landing gear, powerplant/ transmission, main rotor system, and antitorque system. 🛩️The airframe, or fundamental structure, of a helicopter can be made of either metal or wood composite materials, or some combination of the two. Typically, a composite component consists of many layers of fiber- impregnated resins, bonded to form a smooth panel. Tubular and sheet metal substructures are. 🛩️The major components of a helicopter are the airframe, fuselage, landing gear, powerplant/ transmission, main rotor system, and antitorque system. 🛩️The airframe, or fundamental structure, of a helicopter can be made of either metal or wood composite materials, or some combination of the two. Typically, a composite component consists of many layers of fiber- impregnated resins, bonded to form a smooth panel. Tubular and sheet metal substructures are usually made of aluminum, though stainless steel or...

Glide Slope 🛩️glide slope of ILS is defined as a system of vertical guidance embodied in the Instrument Landing System which indicates the vertical deviation of the aircraft from its optimum path of descent. 🛩️A glide slope station uses an antenna array sited to one side of the runway touchdown zone. The GS signal is transmitted on a carrier signal. 🛩️The centre of the glide slope signal is arranged to define a glide path of approximately 3° above horizontal (ground level). The beam is 1.4° deep (0.7° below the glide-path centre and 0.7° above). 🛩️The pilot controls the aircraft so that the glide slope indicator remains centered on the display to ensure the aircraft is following the glide path to remain above obstructions and reach the runway at the proper touchdown point (it provides vertical guidance). 🛩️Two signals are transmitted on one of 40 ILS channels. One is modulated at 90 Hz, the other at 150 Hz. These are transmitted from co-located ant...

Empennage 🛩️The empennage of an aircraft is also known as the tail section. Most empennage designs consist of a tail cone, fixed aerodynamic surfaces or stabilizers, and movable aerodynamic surfaces. 🛩️The tail cone serves to close and streamline the aft end of most fuselages. The cone is made up of structural members like those of the fuselage; however, cones are usually of lighter construction since they receive less stress than the fuselage. 🛩️The other components of the typical empennage are of heavier construction than the tail cone. These members include fixed surfaces that help stabilize the aircraft and movable surfaces that help to direct an aircraft during flight. The fixed surfaces are the horizontal stabilizer and vertical stabilizer. The movable surfaces are usually a rudder located at the aft edge of the vertical stabilizer and an elevator located at the aft edge the horizontal stabilizer. 🛩️The structure of the stabilizers is very similar to that which ...

Types of Radio Waves 🛩️Radio waves of different frequencies have unique characteristics as they propagate through the atmosphere. VLF, LF, & MF waves have relatively long wavelengths and utilize correspondingly long antennas. 🛩️Radio waves produced at these frequencies ranging from 3kHz to 3mHz are known as ground waves or surface waves. They follow the curvature of the earth as they travel from the broadcast antenna to the receiving antenna. Ground waves are particularly useful for long distance transmissions. Automatic direction finders (ADF) & LORAN navigational aids use these frequencies. ✈️High frequency (HF) radio waves travel in a straight line & do not curve to follow the earth’s surface. This would limit transmissions from the broadcast antenna to receiving antennas only in the line-of-sight of the broadcast antenna except for a unique characteristic. HF radio waves bounce off of the ionosphere layer of the atmosphere. This refraction extends the range of...

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...

Five Major Stresses 🛩️Aircraft structural members are designed to carry a load or to resist stress. Aircraft parts must be planned to carry the load to be imposed upon it. 🛩️The term stress is often used interchangeably with the word “strain.” They are not the same thing. External loads or forces cause stress. Stress is a material’s internal resistance, or counterforce, that opposes deformation. The degree of deformation of a material is strain. When a material is subjected to a load or force, that material is deformed, regardless of how strong the material is or how light the load is. 🛩️Here 5 major stresses to which aircraft is subjected ✳️Tension ✳️Compression ✳️Torsion ✳️Shear ✳️Bending ✈️Tension is the stress that resists a force that tends to pull something apart. The engine pulls the aircraft forward, but air resistance tries to hold it back. The result is tension, which stretches the aircraft. The tensile strength of a material is measured in pounds per square inc...

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...

Basic Clouds 🛩️Cloud type is determined by its height, shape, & characteristics. They are classified according to the height of their bases as low, middle, or high clouds, as well as clouds with vertical development. 🛩️Low clouds are those that form near the Earth’s surface and extend up to about 6,500 feet AGL. They are made of water droplets but can include supercooled water droplets that induce hazardous aircraft icing. Typical low clouds are stratus, stratocumulus, nimbostratus. Fog is also low cloud formation. This Clouds create low ceilings, hamper visibility, & can change rapidly. They influence flight planning & can make visual flight rules (VFR) flight impossible. 🛩️Middle clouds form around 6,500 feet AGL & extend up to 20,000 feet AGL. They are composed of water, ice crystals, & supercooled water droplets. Typical middle-level clouds include altostratus & altocumulus. These types of clouds are encountered on cross-country flights at highe...

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⬅️

Lateral and Longitudinal Balance 🛩️Balance refers to the location of the CG of an aircraft, and is important to stability and safety in flight. The CG is a point at which the aircraft would balance if it were suspended at that point. 🛩️The primary concern in balancing an aircraft is the fore and aft location of the CG along the longitudinal axis. The CG is not necessarily a fixed point; its location depends on the distribution of weight in the aircraft. 🛩️As variable load items are shifted or expended, there is a resultant shift in CG location. The distance between the forward and back limits for the position of the center for gravity or CG range is certified for an aircraft by the manufacturer. 🛩️The pilot should realize that if the CG is displaced too far forward on the longitudinal axis, a nose-heavy condition will result. Conversely, if the CG is displaced too far aft on the longitudinal axis, a tail heavy condition results. It is possible that the pilot could not c...

Airport Markings ➡️Subscribe us for more aircraft knowledge and aircraft fact⬅️ ➡️Do Share with your Friends⬅️

Runway Markings and Signs ➡️Subscribe us for more aircraft knowledge and aircraft fact⬅️ ➡️Do Share with your Friends⬅️

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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⬅️

High Lifting Devices 🛩️The most common types of High-lift devices are fixed slots, movable slats, leading edge flaps, and cuffs. 🛩️Fixed slots direct airflow to the upper wing surface and delay airflow separation at higher angles of attack. 🛩️The slot does not increase the wing camber, but allows a higher maximum CL because the stall is delayed until the wing reaches a greater AoA. 🛩️Movable slats consist of leading edge segments that move on tracks, At low AoA, each slat is held flush against the wing’s leading edge by the high pressure that forms at the wing’s leading edge. 🛩️As the AoA increases, the high pressure area moves aft below the lower surface of the wing, allowing the slats to move forward. 🛩️Some slats, however, are pilot operated and can be deployed at any AoA. Opening a slat allows the air below the wing to flow over the wing’s upper surface, delaying airflow separation. 🛩️Leading edge flaps and Leading edge cuffs , like trailing edge flaps, are ...

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...

Types Shock Waves 🛩️In physics, a shock wave is a type of propagating disturbance that moves faster than the local speed of sound in the medium. A shock wave carries energy and can propagate through a medium but is characterized by an abrupt, nearly discontinuous, change in pressure, temperature, and density of the medium. ✈️Normal Shocks 🛫In elementary fluid mechanics utilizing ideal gases, a shock wave is treated as a discontinuity where entropy increases over a nearly infinitesimal region. Since no fluid flow is discontinuous, a control volume is established around the shock wave, with the control surfaces that bound this volume parallel to the shock wave (with one surface on the pre-shock side of the fluid medium and one on the post-shock side). The two surfaces are separated by a very small depth such that the shock itself is entirely contained between them. Taking into account the established assumptions, in a system where the downstrea...

Inertial Navigation System 🛩️INSs contain Inertial Measurement Units (IMUs) which have angular and linear accelerometers (for changes in position). 🛩️some IMUs include a gyroscopic element (for maintaining an absolute angular reference). 🛩️Angular accelerometers measure how the vehicle is rotating in space. 🛩️Generally, there is at least one sensor for each of the three axes: pitch (nose up and down), yaw (nose left and right) and roll (clockwise or counter-clockwise from the cockpit). 🛩️Linear accelerometers measure non-gravitational accelerations of the vehicle. 🛩️Since it can move in three axes (up & down, left & right, forward & back), there is a linear accelerometer for each axis. 🛩️A computer continually calculates the vehicle's current position. 🛩️First, for each of the six degrees of freedom, it integrates over time the sensed acceleration, together with an estimate of gravity, to calculate the current velocity. Then it integrates the vel...