If you have been on an aircraft flight before, you may know that passenger cabins can get very chilly or even very stuffy and hot depending on the flight. With one simple twist of the overhead fan, air conditioning (A/C) can make your ride much more of a pleasant experience. But how does this seemingly simple solution to our flight comfort actually work?

Aircraft air conditioning is supplied by air that is processed through two packs that work to regulate airflow and temperature as required. Despite there being many types of aircraft, the air conditioning system principles and operations remain the same. A/C packs are often located near the main landing gear of the plane on the left and right wings and remove excessive heat using bleed air that enters the packs from the aircraft bleed air system, supplying air to cabins at the desired temperature. The A/C system is based on an ACM (Air Cycle Machine) cooling device and is often called the “Pack”, or air conditioning package.

The aircraft pneumatic system is supplied by bleed air tap-offs on each engine compressor section and supplies the air cycle conditioning system. The bleed air is then directed from the pneumatic manifold into the primary heat exchanger of the packs. This bleed air is cycled through the primary exchanger where ram air removes some of the heat before it is compressed and enters the secondary heat exchanger to continue the cooling process. Cross flow of ram air continues to remove heat before the air moves into the ACM turbine inlet.

After leaving the secondary heat exchanger, bleed air moves through the hot side of the reheater for a first time before being cooled down using colder air from the condenser. The bleed air temperature is increased as it passes through the reheater a second time before moving into the turbine section. By increasing the temperature in the pack, the efficiency of the turbine is also increased. The ACM works to decrease the air temperature by expanding it through a turbine.

As the air leaves the turbine, it passes through the colder side of the condenser, decreasing the temperature of the air to a point below the dew point which turns the vapor into a liquid. Moving from the turbine into the water extractor, moisture is removed and goes to the water spray nozzles which sprays the water into the ram air duct. This works to cool the ram air stream, increasing the cooling efficiency by evaporation.

The passenger cabins are supplied with conditioned air from the mix manifold as the air moves through rise ducts and the side walls before exiting through the overhead distribution duct. The flight cabin is given conditioned air from the left pack and mix manifold, or the right pack if the left is not functioning. 50 percent of the cabin air is recycled for ventilation purposes by recirculation systems that use two fans to move air from the passenger compartment into the mix manifold.

At ASAP NSN Hub, owned and operated by ASAP Semiconductor, we can help you find the aircraft air conditioning system parts you need and more, new or obsolete. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at +1-920-785-6790.


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A phototransistor is an electronic switching and current amplification component that relies on exposure to light to operate, much like how normal transistors rely on electricity to operate. When light falls on the junction of a phototransistor, reverse current flows in proportion to the luminance of the light. This makes phototransistors excellent at detecting light pulses and converting them into digital electrical signals. Unlike normal transistors, they are operated by light rather than electric current, and provides a large amount of utility for a low cost.

Phototransistors work in a similar manner to photoresistors, but can produce both current and voltage, whereas photoresistors only produce current due to the change in resistance. Phototransistors have their base terminal exposed, and instead of sending current to the base, the photons of striking light activate the transistor. This is because a phototransistor is a bipolar semiconductor with its base region exposed to illumination, which focuses the energy that passes through it. Since they are used in almost every electronic device that depends on light. Phototransistors are frequently used in security systems and punch card readers, encoders, IR photodetectors, computer logic circuitry, lighting control, and relays.

Phototransistors come in several different configurations, including common emitter, common collector, and common base, with common emitter being the most frequently used. Compared to conventional transistors, it has more base and collector areas, and is made from gallium and arsenide for high efficiency. The base is the lead responsible for activating the transistor, and is the gate controller device for the electrical supply. The collector serves as the positive lead, and the emitter is the negative lead and the outlet for the larger electrical supply.

The advantages of phototransistors is that they produce a higher current than photo diodes, are relatively inexpensive to manufacture, simple to use, and small enough to fit several of them onto a single integrated computer chip. They are also very fast and can produce nearly instantaneous output (they operate literally at the speed of light, after all), and they produce a voltage, something that photoresistors cannot do. However, because phototransistors are made from silicon, they cannot handle voltages of over 1,000 volts, are more vulnerable to surges and spikes of electricity, and do not allow electrons to move as freely as other devices do, such as electron tubes.

At ASAP NSN Hub owned and operated by ASAP Semiconductor, we can help you find all the phototransistor systems and parts for the aerospace, civil aviation, and defense industries. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at 1-920-785-6790.


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Field effect transistors (FETs) are used to amplify weak signals, mostly wireless signals. This is useful for aircraft, that often operate dozens if not hundreds of miles away from the signal’s source. A field effect transistor is a type of transistor that alters the electrical behavior of a device using an electric field effect to control the electrical conductivity of a channel. FETs are classified into JFET (Junction Field Effect Transistor) and MOSFET( Metal Oxide Semiconductor Field Effect Transistor). Both are mainly used in integrated circuits, and are similar in operating principles, but different in composition.

JFET is the simplest type of field effect transistor in which the current can pass either from source to drain or drain to source. Unlike bipolar junction transistors, JFET uses the voltage applied to the gate terminal to control the current flowing through the channel between the drain and source terminals which results in output current being proportional to the input voltage. Featuring a reverse-biased gate terminal, JFETs are three-terminal unipolar semiconductor devices used in electronic switches, resistors, and amplifiers. JFETs are more stable than bipolar junction transistors and control the amount of current by the voltage signal. JFETs are broken down into two basic configurations

  • N-Channel JFET: the current flowing through the channel between the drain and source is negative in the form of electrons. It has lower resistance than P-Channel types.
  • P-Channel JFET- the current flowing through the channel is positive and has higher resistance than N-Channel JFETs.

MOSFET is a four-terminal semiconductor field effect transistor fabricated by the controlled oxidation of silicon and where the applied voltage determines the electrical conductivity of a device. In a MOSFET, the gate located between the source and drain channels is electrically insulated from the channel by a thin layer of metal oxide to control the voltage and current flow between the source and drain channels. MOSFETs are used in integrated circuits because of their high input impedance. They are mostly used in power amplifiers and switches, and in embedded system designs.

MOSFETs come in two configurations:

  • Depletion Mode MOSFET: the device is normally ON when the gate-to-source voltage is zero. The application voltage is lower than the drain-to-source voltage.
  • Enhancement Mode MOSFET- the device is normally OFF when the gate-to-source voltage is zero.

Comparing the two, JFETs are easier to manufacture and are less expensive. They are also less susceptible to damage because of their high input capacitance. MOSFETs are able to operate in high noise applications, and can operate in both depletion and enhancement mode, and have a higher input impedance.               

At ASAP NSN Hub, owned and operated by ASAP Semiconductor, we can help you find all the electrical transistors for the aerospace, civil aviation, and defense industries. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at 1-920-785-6790.


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Multiple instruments inside an aircraft’s cockpit are dependent on AC transducers. Transducers include synchros, resolvers, and linear/rotary variable differential transformers (LVDTs/RVDTs) and are used in numerous applications including navigation reference units, automatic direction finders, distance measurement equipment, and landing gear position and control. Synchros have been used in both commercial and military purposes; they are the transducer of choice when reliability is important and environment conditions are unforgiving.

Synchros and resolvers are essentially transformers in that they have primary winding and secondary winding. Just like a transformer, their primary winding is driven by an AC signal. Synchros, however, have a primary winding and three secondary windings, with each secondary winding mechanically oriented 120 degrees apart. A resolver has two primary windings and two secondary windings, spaced 90 degrees from each other. While electrically similar to transformers, they are mechanically more like motors, where the primary winding in a synchro or resolver can be rotated with respect to the secondary windings. For this reason, primary windings are also called rotors, while secondary windings are referred to as stators, due to their fixed position. In an automatic direction finder (ADF), the resolver or synchro is used to drive an indicator. As the aircraft turns the amount of coupling in the transducer changes proportionally, thus indicating for the pilot just how far their aircraft has actually turned.

Synchros are used to track the rotary output angle of a closed-loop system, which uses  feedback to achieve accuracy and repeatability. A synchro can be turned continuously, and since its secondary winding outputs are analog signals, provide infinite resolution output. As the shaft of a synchro turns, the angular position of its rotor winding changes in comparison to the secondary (stator) windings. The relative amplitude of the resulting AC output signals from the secondary windings indicates the rotary position of the synchro’s shaft.

The analog output signals that synchros generate must then be converted into digital form by a synchro-to-digital converter. Conventional analog-to-digital converters do not work well in this task, as synchros have inductive characteristics that affect such readings, synchro output signals can be distorted due to nonlinearities in the synchro and phase-shift the transducer, and synchro output signals typically contain lots of electric noise due to their working environment. Therefore, a synchro-to-digital converter must use transformer-isolated inputs and outputs.

At ASAP NSN Hub, owned and operated by ASAP Semiconductor, we can help you find all the synchros, resolvers, and transducers systems and parts for the aerospace, civil aviation, and defense industries. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at 1-920-785-6790.


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Preheating your engine can increase longevity — especially if you’re operating in temperatures below 32?. Metals expand and contract as temperature fluctuates, and each metal does this with varying rates of expansion and contraction. Steel and aluminum have drastically different expansion properties which can affect the clearances in critical parts of the engine. In colder environments, aluminum will contract approximately twice as much as steel. In hotter climates, aluminum will expand twice as much as steel. This is the most critical reason for engine preheating - engine component clearances.

Engine parts are designed to have certain clearance between each other when operating in standard temperatures and operating ranges. Yet, when it’s too cold, these components can get tight enough to cause damage to the engine — crankshaft bearings are one of those items. They are supported by an aluminum case, while the individual crankshaft is constructed of steel. In areas of low temperature, the aluminum case contracts to the point where the bearings are too tight and have a high chance of causing damage to the engine.

You may notice quite a few benefits if you’re able to keep your engine above 60?: reduced engine stress, cylinder wear, and more efficient run-up times. In an ideal world, you’d be able to heat the entire aircraft to minimize wear/tear in everything. Often times this isn’t plausible. That’s why many pilots use installed preheaters or portable preheaters.

Aircraft usually have electronic preheating systems built in. Basic preheaters are constructed using a small electric pad that is attached to the oil slump of the engine. Other preheaters use a variety of options to heat the different areas of an engine: this includes heated intake tube bolts, heated bands, case heaters, and heated valve cover bolts. The main element to take precautions against is condensation.

Condensation is the result of warm, moist air flowing over a cold surface. Since water is a key contributor to corrosion, preheating an aircraft with just an oil slump heater for extended periods of time can result in premature camshaft and cylinder wear. This can be avoided by investing in a complete engine heating system.

Portable engine heaters are a necessity if you don’t have a preinstalled version. These systems require electricity and propane to create a strong flow of hot air into the engine compartment. The air can be blown into the bottom cowl of the exhaust opening or through the front cowl at the air inlets. At a minimum, try and get the entire engine to be above 40? to prolong your engine’s long term-health.

At ASAP NSN Hub, owned and operated by ASAP Semiconductor, we can help you find all your preheating parts for the aerospace, civil aviation, and defense industries. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at +1-920-785-6790.



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An aircraft heating system is integral for safe operation of an aircraft. In the duration of its flight cycle, an aircraft will encounter volatile temperature changes and a heating system can help ensure all aircraft components maintain their necessary temperature for efficient and reliable operation. Two heating systems that are frequently utilized in aviation are exhaust heaters and combustion heaters. The systems share one similarity— both utilize the heating of ambient air, or ram air. Let’s take a look at how these heater systems work.

Exhaust heaters are most commonly seen on smaller, single-engine aircraft. The unit is installed around part of the engine’s exhaust system and is sometimes referred to as an exhaust shroud heater. An exhaust manifold delivers warm exhaust into the metal shroud. Ram air is also brought into the shroud from outside of the aircraft. The air is warmed by the exhaust, then routed through a heater valve to the cabin. In some models, the air is routed to the carburetor as well. Exhaust is then transferred to an outlet.

This type of heater doesn’t need an independent electrical system or engine power to operate, making it efficient in a small aircraft. However, this system is hazardous in the event of failures or defects within its hardware— a small crack in the shroud or exhaust manifold has the potential to leak lethal levels of carbon monoxide into the cabin. This system requires rigorous maintenance efforts to keep it operating safely.

Combustion heaters are seen on various aircraft sizes. A combustion system operates independently from the engine, and only relies on engine fuel from the main fuel system. The system incorporates a ventilating air system, fuel system, and ignition system to heat various components of an aircraft. In order to heat incoming air from the ventilating system, the combustion unit integrates an independent combustion system within a shroud in a heater unit, where fuel and air are mixed and ignited within an inner chamber.

Air intended for combustion is provided by a blower, which pulls air from outside the aircraft and ensures the air is pressurized to the correct specifications. Ram air is collected when the aircraft is grounded, through a ventilating air fan. The ram air is circulated around the combustion chamber and outer shroud, allowing it to heat through convection. Following this process, the heated air is then directed to the cabin. Exhaust from the same process is expelled from the aircraft.

A combustion unit is extremely versatile, which is why it is used on a variety of aircraft. Most are controlled and monitored by a pilot through a cabin heat switch and thermostat and incorporate various redundant safety features. These might include an overheat switch or duct limit.

As is recommended for any other aircraft system, it is important to follow aircraft manufacturer instructions and protocols in the maintenance of exhaust or combustion heaters.  Maintenance guidelines should specify intervals between maintenance and operational checks and should be stringently adhered to in order to ensure safe operation of an aircraft heating system.

At ASAP NSN Hub, owned and operated by ASAP Semiconductor, we can help you find the exhaust heating system parts, spark plug parts, and aircraft heating systems parts you’re looking for, new or obsolete. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at +1-920-785-6790.


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Exhaust systems are undoubtedly the bowels of any vehicle, automobile, or aircraft. The main function of the exhaust system is to allow for the smooth propulsion of gas emission from an engine out to its surrounding environment. This allows for proper gas exchange to take place in order to optimize fuel usage and energy output. In theory, this function could be performed by any metal tubing that leads from the engine to the tailpipe, however, there are many other requirements that must be considered in order for an exhaust system to function effectively. According to Federal Aviation Association (FAA) regulations, the exhaust system of an aircraft must be able to withstand high temperatures, corrosion, vibration and inertia loads, and must have means for flexibility in addition to performing its typical roles.

A structural aspect that must be put into consideration in designing an exhaust system is the maintenance of back pressure. The engine propels outward, creating a pressure that flows out. However, if there are too many bends, or if the piping of the exhaust system is too small, then the air pressure could build up in the opposite direction of the exhaust system, creating what is known as “back pressure”. The higher the back pressure, the more energy is needed for the exhaust to expel the gases outward. If the back pressure is higher that of the exhaust system, then the back pressure completely cancels out the exhaust and nothing gets expelled. To prevent this, exhaust pipes need to be wide enough and allow for optimal air flow. If pipes are too wide, not enough pressure will be built up, and the air will move too slowly.

Another consideration for a properly functioning exhaust system would be the routing of the exhaust pipes. Commercial aircraft exhaust can reach temperatures of 2000?, which can melt the cowling and other parts of the engines. The exhaust pipes must be designed in a way that is clear from areas that are unable to withstand such temperatures. The cowling around the engine may need adjustment in order to allow for adequate room for proper routing. However, it should also be noted that there will be a large difference between top temperatures of commercial planes and experimental builds.

Although not as important, you should be mindful of how much noise your aircraft creates. The sudden expulsion of air from any source can result in an audible sound, whether that be flatulence or exhaust. The engine is the lifeline of an aircraft, but the process of carrying away gas from the engine system can result in very loud sounds. This is why zero emission cars, such as any of the Tesla automobiles, create little to no sound when in use. Loud noise can be a distraction for pilots and pose as an overall safety concern. Unfortunately, the sound created from an aircraft is largely influenced by the structure of the exhaust system.

At ASAP NSN Hub, owned and operated by ASAP Semiconductor, we can help you fulfill all your engine cowling, aircraft exhaust system, or exhaust piping needs, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we’re always available and ready to help you find everything you need, 24/7x365. For a quick and competitive quote, email us at sales@asapnsnhub.com or call us at +1-920-785-6790.



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