The first half of the equation of flight has to do with three factors: lift, force and gravity. To dive into these factors, we need to look into the physics of airplane flight and Newton’s Third Law of Motion: for every action, there is an equal and opposite reaction. The main key here is balance. To achieve flight we must first create forward thrust and lift to generate air pressure beneath the wings that will, in turn, lift the plane. This lift must create an imbalance where there is more lift or force upward than there is gravity pushing downward. Airplane wings are shaped with an angle of attack that maximises the amount of air hitting the bottom of the wing. Too much tilt and the airflow around the wings becomes too choppy and irregular and a plane fails to sustain lift and fly correctly. A 15 degree tilt tends to be the maximum sustainable angle for aerodynamic flight.

Once a plane is airborne, staying in the air is achieved by maintaining a balance between this lift and gravity, which establishes a state of having no net force applied to the aircraft. Where lift and gravity deal with the up and the down, thrust and drag work on the horizontal plane. Forward thrust must counteract the drag on a plane. Drag is the force of wind pushing the airplane back and is caused by all parts of the plane that block wind flow. A plane is propelled forward by propellers or jet engines and this forward motion is essential to sustained flight. When the force of thrust is higher than the drag, forward motion occurs.

The same way that a top/bottom air pressure imbalance causes lift, a left/right imbalance in the amount of air pressure exerted on the wings, enables the plane to steer. Much like a bird, a plane steers left or right by dropping one wing lower than the other. This wing drop increases the force of air on the one wing compared to the other and steering is possible. You now know how a plane goes up and down, forward and back, and left and right.

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From directional control to changes in altitude, an aircraft autopilot system can control many aspects of the flight, aiding the pilot when necessary, as well as making the trek smooth and efficient. Some may be surprised to know that aircraft can even control and execute a landing, though it is very uncommon. Less than 1 in 100 commercial airliner flights are ever landed through autopilot, and it is often reserved for times where visibility is extremely poor. Nevertheless, it is something that many planes are capable of doing, and it can be a very smooth and safe operation due to the expertise of pilots. In this article, we will discuss how autopilot is able to conduct landings by itself.

When the pilot approaches the airport for a standard landing, autopilot is often used as far as when the plane is a few miles from the landing strip and it becomes visible. From then, pilots disable autopilot and execute the landing themselves, ensuring that they are able to accommodate for any change or traffic that an autopilot system cannot adapt to. Sometimes, however, when there is a storm or heavy fog, visibility may be so short as to make manual landing extremely unsafe, or even impossible.

When an aircraft readies for autopilot landing, multiple controls and equipment have to be set. As the aircraft approaches the landing strip, pilots are attentive for any possible red flag or problem so that they may take immediate control. To ensure safe landings through autopilot, pilots have to undergo training every six months. Some of this training involves pilots going through simulations that put them through any possible problem to train them how to successfully navigate through them. Because of this, pilots are always at the ready to respond to anything during their landing.

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As aircraft burn large quantities of fuel during flight, the engines generate an intense amount of heat that spreads to the surrounding components. While half of this heat is flushed out as exhaust, the other half remains absorbed by the engine, posing a problem that could lead to damage of parts or even failure of the system as a whole. To mitigate this issue, aircraft utilize lubricant cooling systems to reduce the heat of the engine and its surrounding parts.

For standard gas turbine engines, both wet and dry sump lubrication systems can be utilized. While the wet sump has lubricant stored within the engine, the dry sump utilizes an external tank. Alongside the heat created through combustion, the friction between metal components also generates heat. Lubricating oil is thus used to provide a protective film layer on parts, replacing metal to metal friction with fluid friction. By reducing the friction between engine parts, efficiency of the system is also improved.

The lubricating oil acts somewhat like a sponge, absorbing the heat from the component it is coated on. After cooling the component, the oil transfers the heat to the oil cooling system in which it is cooled by a radiator. While cooling and lubricating the engine, the oil also acts as a cleaner and protector of the engine system. As the oil passes through components, it picks up and collects various particles that may damage parts, bringing them to a filter where they are then removed from the system. By coating the various parts in lubricant, the oil also serves as a temporary shield from corrosion.

While oil accounts for nearly half of the cooling in a system, some aircraft also utilize air cooling alongside the lubricant. By using captured bleed air, the turbine disks, blades, and vanes reduce their radiating heat and cool down. With the use of air alongside an oil cooling system, the amount of oil needed for cooling the engine and surrounding components is reduced.

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Aircraft come in many different shapes, sizes, functions, and applications. Because of this, varying materials are used depending on the plane’s performance needs. Early aircraft such as the Wright Flyer were built with wood and fabric. The aircraft frame was constructed with spruce and ash and much of the surface was covered with muslin, a plain cotton fabric. Modern aircraft are made from metal or composites like carbon-fiber and fiberglass, or a combination of these. Here is a rundown of some of the materials used in aircraft today.

The average commercial airliner is made from aluminum. Aluminium is strong but relatively lightweight, making it a highly popular material for use in aircraft. The widely-used Boeing 747 is an aluminum airplane for example. Years ago, aluminum made up seventy percent of the average aircraft, but that percentage has now dipped to around twenty. The majority of the non-structural material such as paneling and interiors are made from lightweight carbon fiber reinforced polymers.

Steel and titanium are two more metals used to construct aircraft. Steel, while incredibly strong, is also very heavy, making it a less desirable material. Titanium has similar strength to steel, but only about half the weight. Additionally, titanium is highly resistant to heat and corrosion. The world's fastest jet-propelled aircraft, the Lockheed Martin SR-71 Blackbird, is made from titanium.

Composite materials, a relatively new phenomenon in aviation, are quickly becoming more widely-used. A composite called graphite-epoxy is very strong and can weigh just half as much aluminum. More than half of the Boeing 787 Dreamliner is made from composites and as the industry continues to grow and evolve, composites will one become more popular.

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Integrated circuits are one of the most important technological innovations of the 20th century. Consisting of interconnected transistors, resistors, capacitors, diodes, and more all contained on a thin slice of material (typically silicon), integrated circuits are the basis for modern electronics.

Integrated circuits come in several different kinds of classifications. One of these is by chip size:

  • SSI: Small Scale Integration, with 3-30 gates per chip.
  • MSI: Medium Scale Integration, 30-300 gates per chip.
  • LSI: Large Scale Integration, 300-3,000 gates per chip.
  • VLSI: Very Large Scale Integration, has more than 3,000 gates per chip.

Integrated circuits can also come as:

  • Thin and thick film ICs
  • Monolithic ICs
  • Hybrid or multichip ICs

In thin and thick film ICs, passive components like resistors and capacitors are integrated but the diodes and transistors are connected as separate components to form a single and complete circuit. Thin and thick ICs produced commercially are the combination of integrated and discrete components. Thin film ICs are made by depositing films of a conducting material on a glass surface or ceramic base. Varying the thickness of the films deposited on the materials creates different resistivity, allowing resistors and capacitors to be manufactured. In thick film ICs, silk printing techniques are used to create the desired pattern of the circuit on a ceramic substrate. Thick film ICs are also called printed thin-film ICs.

Monolithic ICs, with both their active and passive discrete components and the connections between them, are formed on silicon chips. They are referred to as “monolithic” because the entire circuit is built onto a single crystal. They are the most common type of IC used today because of how cheap and reliable they are, and are used as amplifiers and voltage regulators in AM receivers and computer circuits. However, they have poor insulation between components and a low power rating.

Hybrid or multichip ICs are made up of multiple interconnected chips. The active components contained in this type of integrated circuit are diffused transistors or diodes.

Lastly are analog and digital ICs. Analog ICs process continuous signals, i.e. analog signals. They are used primarily in sound amplification, filtering, modulation, demodulation, and other similar purposes. Digital integrated circuits use a basic digital system with two defined levels of 0 and 1 (or ON and OFF). Microprocessors and microcontrollers use digital ICs as the basis for binary computer programming, and are utilized in all modern computers.

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Memory is the computer hardware integrated circuits that store information for immediate use in a computer. Memory is distinct from the hard drive because it allows the CPU to immediately access the data it needs. Most forms of memory are temporary, they do not save data permanently.

Memory can be divided into two basic categories, volatile and non-volatile. Volatile memory’s distinguishing trait is it does not save data permanently; if power is interrupted, the data is soon lost. Volatile memory is used as primary storage, where data is stored temporarily rather than saved permanently to secondary storage. The greatest advantage of volatile memory is that it is faster than mass storage like a hard disk drive.

The most common type of volatile memory is RAM, or random-access memory. First used in the 1970s, RAM stores data and machine code being used and allows it to be read or written at the same time regardless of the physical location of data inside the memory. RAM does not suffer from mechanical limitations like media rotation speeds the way hard disks or CDs do.

RAM is further divided into two types, dynamic random-access memory and static random-access memory. DRAM is commonly used in PCs, workstations, and servers. DRAM stores each bit of data in a storage cell consisting of a capacitor and a transistor and requires a new electronic charge every few milliseconds to compensate for leaking charge from the capacitor. The benefits of DRAM are that it is simple to design, fast, and cheaper compared to other types of memory. However, it is volatile and consumes a lot of power. Static random-access memory uses a cell of six transistors in cross-coupled flip-flop configuration. Unlike DRAM, SRAM does not require a periodic refreshment. SRAM is faster but more expensive than DRAM, and often used for cache memory.

Another type of memory is non-volatile memory. Non-volatile memory can retrieve stored information even after power has cycled. Non-volatile memory typically takes the form of read-only memory, or ROM. ROM is used in computers and electronics, and is distinguished from RAM in that it cannot be electronically modified after manufacture, only read. ROM is typically used to store software that rarely changes over a system’s life, known as firmware. Firmware is usually low-level control of a device’s hardware, like a TV remote’s controls. ROM has further variations, such as programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), and electrically erasable programmable read-only memory (EEPROM).

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Operating an aircraft’s engine at excessively high temperatures is dangerous. Outside of the correct temperature range, an engine can lose power and suffer damage such as scoring on the cylinder walls and burning or warping in the valves. Therefore, maintaining optimal temperatures is a central part of ensuring healthy engine operations in an aircraft.

In an engine, internal cooling is handled by the engine’s oil system. Oil that is circulated through an engine for lubrication purposes will also act as a heat-dissipating agent, drawing heat from the cylinder heads in the engine as it passes over them. The hot oil is cooled as it pumps through the radiator, before repeating the process as it passes over the cylinder heads once more. 

However, the external surface of an aircraft’s engine must be cooled as well.  In civilian prop-driven aircraft, this is handled via air-cooling that flows into the engine compartment through openings in the front of the aircraft engine cowling. Baffles rout this air over fins attached to the engine’s cylinders, where the air absorbs the engine’s heat. The hot air is then expelled through openings in the lower aft portion of the engine cowling. 

Air cooling does have its disadvantages, however. While air-cooling is effective in flight, where there is a reliable source of fast-moving air, the system is less effective while the aircraft is on the ground, while taxing, during take-offs, and other periods of high-power, low-speed operation. On the other hand, a high-speed descent can cause too much air to flow into the compartment, causing the engine to cool too quickly and causing cylinder heads to crack. In these situations, the oil-cooling system actually serves to warm and regulate cylinder temperature.     

Engine exhaust systems vent combustion gases overboard, provide heat for the cabin, and defrost the windshield. The exhaust system consists of piping attached to the cylinder, and a muffler and muffler shroud. The gases are pushed out of the cylinder through the exhaust valve, and from the exhaust valve out into the atmosphere. Engine exhaust contains carbon monoxide, an odorless, colorless gas that is toxic for humans. To prevent exposure, an exhaust system has to be kept in good condition and free of cracks. 

Some exhaust systems will also come with an exhaust gas temperature (EGT) probe. Situated at the exhaust manifold, the EGT gauge can determine the ratio of fuel and air entering the engine’s cylinders, based on how hot the exhaust is. This can in turn be used to regulate the fuel/air mixture and ensure a healthy fuel economy.

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As a plane descends and prepares for landing, it conjures an incredible amount of force around it. Planes are typically traveling at about 200 miles per hour when touching down on the runway; thus, they require a superb braking system. Even when idle, thrust is produced and travels forward as it acts against the deceleration systems. The braking system on aircraft are sufficient enough to stop most aircraft, yet in case of emergency, another deceleration method is needed for safety purposes and to prolong the longevity of the brakes.

An efficient modus operandi to achieve this need is thrust reversal. Thrust reversal is the process in which the engine of the aircraft temporarily redirects the thrust forward instead of backward. The reversal of the thrust counteracts the forward travel of the aircraft and assists in deceleration. Thrust reversal has also been used to reduce the airspeed mid-flight. Reverse thrust can be generated by a reversible pitch propeller, or on a jet engine by a target reverser.

Reverse thrust is usually enacted immediately after the plane touches down when aerodynamic lift limits the effectiveness of the brakes. It is always operated manually by the pilot, utilizing thrust levers to maintain full control. Although thrust reversal is a supplemental tool in bringing the aircraft to a stop, regulations dictate that an aircraft must be able to land regardless of the use of thrust reversal.

There are several different methods of obtaining reverse thrust on aircraft. The first one involves clamshell type deflector doors to implement a reversal of the gas exhaust stream. Another method involves utilizing external doors to reverse the exhaust flow. The last process involves fan engines using blocker doors that reverse the airflow.

Once the speed of the aircraft has slowed, it is crucial to shut down the reverse thrust to prevent the reversed air from lifting debris in front of engine intakes. If debris is ingested, it can cause severe damage. A powerback is when reverse thrust is used to move an aircraft away from the gate. Reverse thrust performs optimally when the aircraft is at higher speeds.

Smaller aircraft don’t require thrust reversal systems except in specialized situations.

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The average passenger aircraft has upwards of 1,000 various aircraft cable bundles installed within its structure. The wiring and cable assemblies serve integral tasks including flight control, data bus, fireproof redundancy, and more. Two of those cable systems that are imperative to avionics are flight control cables and data bus cables.  

Flight control systems manage a variety of monitoring and actuating tasks. These cables stretch from the cockpit to control surfaces within the airframe. They are typically stainless-steel wiring bundles that are coated in a black vinyl casing. Stainless steel is able to withstand greater temperature variations than the mostly aluminum frame of an aircraft but are still affected by the thermal contractions of the airframe.

In order to maintain efficient communication with control surface actuators and remain reliable under the many stressors encountered during a flight cycle, flight control cables are assembled using a pulley system. When a pilot actuates a control, a cable is rotated around the pulleys like a large steel belt. Each system is spring loaded, which helps account for slack that occurs when the aircraft encounters drastic temperature changes.

While flight control cables interact with actuators, data bus cables transmit digital signals between sensors and their corresponding display devices. A standard commercial airplane has 150 to 300 ft. (around 200 km) of this type of cable alone. Data bus cable structure often consist of a shielded “twisted pair” cable that is grounded at each end, and at every junction in the assembly. The most commonly used data bus system in civil aviation is the ARINC 429. Created by Aeronautical Radio Inc., it is the technical avionics standard for data bus cables used in commercial aircraft. This system operates using a double helix wiring, which enables bi-directional transmission to request data and transmit data across a single cable. 

Both flight control cables and data bus cables are essential to a pilot for proper monitoring of an aircraft during its flight cycle. As technology advances, it is possible we will see steel wiring replaced with fiber optics technology. The lighter, more reliable, cables have a lower electromagnetic field (EMF) and are notably more affordable. Newer airplanes such as the Airbus A380 and Boeing 787, have already incorporated fiber optic cables into some part of their avionics systems. As older aircraft phase out, it is likely we will see fiber optics technology become the new standard for aircraft cables.

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Aircraft engines create an immense amount of heat throughout their flight hours. High temperatures necessitate the presence of cooling instruments. An important member of these components is the cowl flap. Dare I reference the Star Wars prequels, an activated cowl flap resembles a mini version of the walkway extended from Padme’s J-type Star Skiff ship in the last scene of Revenge of the Sith. Though a cowl flap doesn’t sound as flashy, the lowering mechanism works almost identically, and is a valuable cooling component.

A cowl flap acts an open-air duct located at the bottom of the engine cowling, as opposed to an extendable walkway. It is one of the key mechanisms that aids in keeping an aircraft engine from overheating. Their specified design enables a cooling and depressurizing effect using the flow of air. Cowl flaps and inlets are most valuable during high power events, like takeoff and sudden increases in thrust. During these occasions, the engine is at its highest temperatures, as the heightened airspeed does not allow the same airflow that is achieved at low power cruising speed.          

There are two main types of cowl flap configurations, but they essentially follow the same series of cooling process functions. Incoming air travels through the engine cowl, and mixes with hot air from the combustion unit. The cooled air then circulates around the engine and exits the compartment through the underside of the engine cowling. With this design, the cowl flap allows the deflection of slipstream airflow. Following this step, a low-pressure environment is invariably formed around the engine, which then draws the air to coincidently cool cylinder components.

On most aircraft models equipped with a cowl flap, the design will include position control, or engagement of the flap, that can be activated by the pilot directly using mechanical or electrical controls. This construction is commonly seen on radial engine aircraft. Their small size and lower speed requirements allow the cowl flap to be a practical cooling addition.

Modern airliners, however, have phased out this version of the cowl flap, in favor of a permanent cowl component. Larger engines generate more heat and cannot afford the drag created by a lowered mechanism protruding from the airframe. Instead, aircraft of this nature are equipped with a more aerodynamic inlet, that functions as a permanently exposed flap on the underside of the engine cowling.

From radial aircraft to commercial airliners, the cowl flap mechanism is one of the many invaluable aircraft components designed to keep you flying cool.  

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Aviation is all about safety. And, the number one approach the aviation industry has taken to ensure safety is redundancy. The more warning systems and safety nets, the better. One of these systems are the annunciators. Annunciators relay, or “announce”, vital information to the operator or systems monitor.  Annunciators are a system of alarms, both visual and audible. They display the immediate condition of equipment. Annunciators devices are used in various industries including the aviation, maritime, and industrial industries. But, they’re the most common in aviation  

Typically, annunciators have an array of various colored lights and sound an alarm to indicate any abnormalities or emergencies. If an annunciator is activated, the annunciator must be acknowledged by the operator and corrective actions must be taken to clear the alarm. These annunciators can warn in case of emergencies that require immediate action. Annunciators play an essential role in the protection of the equipment and the lives of the cabin and crew.

In aviation annunciators have a vital role in the safety of the aircraft. Prior to flight tests must be completed to ensure the annunciators are working properly— the lights must illuminate properly, and the alarm sounds must be audible. The annunciators will be grouped together as they connect to a subsystem.  For example, the annunciators that connect to the engine would be grouped together; grouping makes them easier to notice.

Not only do the annunciators provide an alert when there is an emergency, they provide status updates on the equipment. The annunciators let the pilot know that all systems are operating properly or not.  Annunciators also allow the pilot to understand how the aircraft is operating and allows the pilot to take any corrective action as needed. The safety of the pilot, the crew, and the passengers is greatly increased thanks to the annunciator panel.

NSN Stocks, owned and operated by ASAP Semiconductor, should always be your first and only stop for all your rotable parts and consumable needs.  NSN Stocks is a premier supplier of annunciator panels and aircraft engine parts, whether new or obsolete. NSN Stocks has a wide selection of parts to choose from and is fully equipped with a friendly and knowledgeable staff that is always available and ready to help 24/7x365.  If you’re interested in a quote, email us at

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