The aerospace and defense industries are hectic industries that require a lot of information to be shared in a small amount of time. Part sourcing needs to be quick and efficient in order to accommodate for costly situations such as Aircraft on Ground (AOG). The NSN system was developed by the U.S. Department of Defense and is a key reason why the federal supply chain runs so efficiently today.

The premise behind the National Stock Number (NSN) system is uniformity and a set standard of communication. During WWII, the military found it difficult to quickly and efficiently source parts from manufacturers as there was no formal naming system. A part could have multiple names depending on the manufacturer that made it. This lack of a formal naming system led to inconsistencies in stock levels as there would be a surplus of components in one area and a deficit in another. In response to these issues, the DoD set out to form a uniform system that could be understood across countries with language barriers.

The key part of the NSN system is the 13-digit identification number that is assigned to all components that are sourced, stocked, and procured within the federal supply chain. NSNs are made up various subcategories that each provide more information about the individual component. The first four digits of the NSN are known as the federal supply group classification code (FSCG), which is further broken down to the federal supply group (FSG) and the federal supply class (FSC). The FSG is the first two numbers of the NSN and details which of the broad groups the component belongs to. In the aerospace industry federal supply group 15: aircraft and airframe structural components is important. The following 2-digits are the federal supply classification, which is the exact sub-category that the component belongs to. FSCG 1510 is under FSG 15 and includes fixed wing aircraft components.

The remaining nine digits of the NSN include the 2-digit country code and the 7-digit National Item Identification Number (NIIN). The NIIN is a random number assigned to the component, unlike the FSC or FSG the NIIN doesn’t further classify an item. A NIIN more or less tells you what the item is. The DLA uses a sequential system to generate the NIINs. It is possible to source parts using their NIIN, however it is more common to source parts using the full NSN.

NSNs and NIINs are not necessarily something to compare, but rather understand how they work together to identify an individual component. Without NSNs or NIINs it would be very difficult to tell one fastener from the next for example. Even larger aircraft components such as landing gear assemblies benefit from a clear naming system. Buy NSN stocks many different NSNs and NIINs that are all helpfully categorized on our website,

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A piston is part of a reciprocating engine with the purpose of transferring the force from the expanding gases in the cylinder to the crankshaft. In steam  reciprocating engines, valves are necessary to control the entry and exit of gases at the proper time in the piston’s cycle to ensure the engine is functioning properly. Piston engines mounted on aircraft have utilized several different types of valves over the years.

Sleeve valves were first patented by Charles Yale Knight, and were initially used in luxury automobiles such as Mercedes-Benz and Peugeot. Early sleeve valves used alternating twin sliding sleeves, but those used in aircraft, notably by Bristol, used a single sleeve that rotated around a timing axle set at 90 degrees to the cylinder axis. Named the Burt-McCollum valve after the two inventors that developed it separately, the greatest advantage of the sleeve valve was its mechanical simplicity and ruggedness, as well as consuming less oil than other sleeve valve designs. Sleeve valves were frequently used in both aircraft and automobiles up until the 1940s, when their replacement was introduced.

Poppet valves, also known as mushroom valves, control the timing and fuel quantity flowing into an engine like any other valve. Poppet valves operate the marionette as they move in response to remote motion transmitted by the engine, and instead of sliding or rocking over a seat to uncover a port the way that sleeve valves do, they lift in a movement perpendicular to the port. Because there is no movement in the seat, there is no need for lubrication. The issue with piston poppet valves lies in metallurgy and heat management.

In the early days of poppet valves, the metal used to make poppet valves was not resilient enough, and the rapid opening and closing of valves would cause the cylinder heads to rapidly wear out. This meant that the poppet valves would need to be re-ground every two years or so, causing high maintenance costs. Modern poppet valves are made from high-quality stainless steel, which averts this issue. Overheating was also a serious concern, causing excessive piston valve wear and defective sealing. This was solved by adding valve cooling systems, as well as sodium-filled valve stems that acted as a heat pipe to divert heat away from the valve head.

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Like other forms of aviation technology, aircraft propellers are not fixed and unchanging, but instead evolved, changed, and improved over the years, developing into different types depending on the needs of their users. In this blog, we will break down and examine some of the most common types of propellers.

The first type of propellers developed were fixed pitch propellers. As their name implies, fixed pitch propellers cannot change their pitch (the angle the propeller blades face) and are typically made from a single piece of material. Fixed-pitch propellers were first made from wood, in the years before World War 2. Wooden propellers are not carved from a single piece of wood, but instead five or more separate plies of wood that are laminated together to prevent warping.

Modern innovations have created other types of propellers. The first are controllable pitch propellers, which have a hydraulic system built into the propeller. This allows the pilot to adjust the pitch of the propeller while in flight, which gives them more control over the handling and flight characteristics of the aircraft. Propeller adapters also have a big advantage over some traditional propellers. 

Constant speed propellers use hydraulic or electrical means to adjust the blade pitch, which lets them compensate for increased or decreased power. This occurs automatically, so that if engine power increases the blade angle increases as well, and if the engine power decreases the blade angle decreases to match it. This is done to keep engine RPM constant, which improves the engine’s health.

Two-position propellers have two preset pitch angles that the pilot can switch between freely while in flight. Reversing propellers are constant speed propellers that are able to add negative pitch to the blades, which produces negative thrust, and effectively turns the propeller into a brake of sorts. This is used to shorten the amount of runway needed when landing larger aircraft.

Full feathering propellers are constant speed propellers that have the ability to turn in the wind in the event of engine failure. This helps eliminate drag and windmilling.

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When it comes to connecting components together within an aircraft, sturdiness is key. The two components should be solid and continuous, without any wiggle room. Under no circumstances should the coupling experience any sort of vibration. In general, vibrations jeopardize the strength and tension of a fitting or joint. While it may seem like a comfort issue, vibration can actually cause significant damage to the hardware of an aircraft. If a loose fitting is not adjusted the vibration can even lead to failure of the component.

One cause for vibration between hardware pieces is an incorrect balancing of the shaft coupling. Like all other aspects of aircraft systems and components, balance is a heavily regulated. A component is either balanced by a manufacturer, or it is balanced by the addition or subtraction of material during construction or maintenance. International Standards Order 1940-1:2003 outlines the balance quality requirements for rotors in a rigid state. The balance quality grade is used to define the limits of residual unbalance.

There are multiple options when it comes to correctly balancing a shaft coupling. An additional weight can be added to one side or plane only. This is known as static balancing and is typically used when the length/diameter ratio is less than one. If you were to imagine a cylinder, static balancing is the equivalent of drilling a hole in just one side. Dynamic balance is used if the length/diameter ratio is greater than one. For this balancing technique, adjustments are made to more than one area on our cylinder example.

The actual balancing of a shaft coupling can be split up in light of the placement of the shaft coupling on the aircraft. A manufacturer will cover the specified balance quality for a component. To ease assembly, components can be balanced in part, fitted, and then further balanced up to the industry standard. An alternative way of balancing a shaft coupling is to fit and balance one half of the shaft first. The other half of coupling can be assembled individually, with each of the components singularly balanced. The benefit of this way of balancing is the ability to interchange the various components of a system.

For example, individual brake discs can be removed and replaced, without having to rebalance the entire brake system. Ultimately this increases the rate of efficiency of any repair and maintenance, which in turn, mitigates the cost of aircraft maintenance. Due to their location within an aircraft or their load bearing properties, certain mechanisms dictate balancing procedures. For example, gear couplings must be balanced using a combination or sub-assembly. The relationship between the hub and the sleeve are not lined up until they are under a load, therefore any prior balancing would be incorrect.

Balance is a key characteristic of a sturdy, well-functioning system. If balance is not given the correct amount of care and attention, vibration will occur which leads to further issues down the line. 

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One of the most common, yet crucial, components in the construction of a vessel are its valves. They serve a wide array of functions ranging from regulating the flow of liquids to assisting in the operation of hydraulic lifts. However, one type of valve seems to appear more frequently than others, and that is the gate valve.

A gate valve has two variations: a rising stem and a non-rising stem. Rising stem gate valves are typically made from cast or forged steel. Its modus operandi is simplistic in that the round handle rotates a threaded shaft which is attached to its centerfold. The stem will rise as it opens the valve followed by a descent as it closes the valve. One can spot if the valve is opened or closed by observing the amount of stem that appears. A flush stem correlates to a closed valve while an exposed stem means it’s open.

The non-rising gate valve is intended to function in tight spaces, abandoning the rising stem mechanism of its counterpart. This module utilizes a rotating wheel, or handle, that turns either left or right corresponding to its opened and closed positions. When the handle is turned towards the left the valve is opened. When it’s turned towards the right it reflects a closed position. In both cases the handle is flush with the pipe as the operating processes inside are able to open and close the valve without the need to raise the stem.

Wear and tear comes naturally to these valves as they are designed to function against the current.  Proper maintenance and monitoring of these valves is critical in preserving their longevity and avoiding unnecessary leaks or malfunctions. In essence, a proactive approach proves beneficial in the long run.

A key concept to remember is that these valves are designed to be either fully closed or fully opened. An issue can arise if the measurements on the valves aren’t adequate, which will result in a change in the consistent flow of fluid.

Although these two valves are common components, they contribute a major part in the successful completion of a vessel.

At Buy NSN, owned and operated by ASAP Semiconductor, we can help you find all the valves and ship and marine parts you need; we’re always available and ready to help, 24/7x365. For a quick and competitive quote, email us at or call us at +1-919-348-4040.

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A bit of knowledge, know-how, and maintenance can keep a boat’s engine more efficient and working longer. Most aircraft operators know the importance of inspecting an aircraft before taking off. Although this is imperative in aviation— because you can’t just pull over to the side of the road when something goes wrong— it’s also important to keep a checklist when operating any other mode of transportation. Although a boat or car can stop and fix the issue, it still causes issues, such as diverting traffic or being stranded. Not to mention the cost of fixing an issue that could have easily been prevented.

It's very important to change an engine’s oil at the proper intervals, which can be found in the engine manufacturer’s manual. Because of advanced technology, it’s rare to need an oil change sooner than recommended. The reasons why someone might need to change the oil sooner is if the engine is subject to unusually heavy loads, high temperatures, or dirty air. The most common reason to change the oil sooner would be because a diesel-powered engine that has traveled outside of North America may end up using fuel that contains high levels of sulfur. Because the sulfuric acid accumulates in the oil and cannot be filtered out, it will cause damage to the engine; so, it’s important to monitor the levels and respond accordingly. Another important note to point out is that the oil filter should be changed every time the oil is changed— the filter contains dirty oil which will contaminate the fresh oil otherwise.

An easy way to prevent issues is to maintain good situational awareness— listen to the boat. A squealing noise may indicate that a belt is loose; a metallic tapping may indicate that the valves, lifters, or rocker arms are causing issues. Grinding, or grating, metal may indicate that a pump bearing needs to be replaced. If the exhaust is loud and emits a high pitch noise, it may indicate that there is less cooling water running through it.

Most operators know that an engine has a distinctive smell when it’s running well. However, there are also smells that indicate something is going wrong. Paying attention to these can prevent more issues and can save the operator money— the initial cost to fix a small issue is worth it compared to the cost of allowing further damage to occur. Burning rubber smells may indicate that the water flow is not reaching the water pump’s impeller. If this smell is coming from the engine, it’s important to check for a clogged water tank immediately. It may also indicate that an insufficient supply of cooling water is not reaching the exhaust manifold, the V-belt has slipped, or a coupler in the stern drive has failed. The smell of oil may indicate that the oil is leaking and dripping on the hot engine. A sweet smell may indicate an antifreeze leak. And last, but not least, a burnt hair smell may indicate an electrical shortage.

There are many ways to prevent corrosion and failures in marine engines. It’s not only important to follow the engine manufacturer’s recommendations, but also to maintain good situational awareness and not neglect something that seems off.

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In a recent episode of Car Masters: Rust to Riches, the Gotham Garage crew reconstructs a marine engine to function in a Mad-Max style Volkswagen bus. This overhaul required the complete rebuild of the bus frame, and automotive system to make it fully operational. The vehicle is coined, the Frank N’ Bus, and for good reason. Automotive parts and marine parts are suited specifically to their environment and can only be used interchangeably with substantial changes to systems and structure design. Let’s take a look at why.

The main differences between marine engine parts and automotive parts are in the placement of the engine itself. Marine engines, unlike automotive engines, are entirely enclosed. This leaves them more vulnerable to combustion and corrosion. Air cannot rush around the engine in a marine environment, unlike cars, whose engines are always partially exposed. This seemingly simple factor leads to integral differences in parts and regulation.

Take, for example, one of the most well recognized automotive devices, the carburetor. Both marine vessels and automotive vehicles require a carburetor in their engine. However, as you may know, a carburetor discharges overflow (unmixed fuel), that sometimes drips out of the device. In an automotive vehicle, this excess material can be expelled onto the ground.

The aforementioned is not the case in a marine engine. The contained nature of a marine engine makes overflow or vapor from a carburetor extremely hazardous. To safeguard against this, marine engines are equipped with vents to allow the excess material to be filtered back to the engine. A marine carburetor must be protected by an air filter as well, but one made of metal mesh. In a car, the carburetor is usually protected by an air filter made of plastic.

Another excellent example of the differences between the two environments, are the starter and alternator. In a marine version of these components, they are required to be ignition protected. This involves the installment of vents with flame arrestors and complete containment of the units to prevent corrosion. In an automotive engine, there is less risk with high voltage sparks. Automotive starters and alternators have exposed contacts that allow for air cooling and ventilation.

The distributor also varies considerably in both engines. The function of a distributor in both engines, speaking rudimentarily, is the same— its main purpose is to channel voltage to spark plugs in a spark-ignition combustion engine. This mechanism can emit high voltage sparks as well and requires protection similar to that of the starter and alternator. In a marine engine, yet again differentiating from an automotive environment, the distributor is completely sealed to limit corrosion, and is equipped with a vent and flame arrestors.

Both engines differ in mechanics and design. Due to the fragile environment of marine engines, they are also more highly regulated on an industry wide basis. Marine engines and fuel tanks must meet standards set by the U.S. Coast Guard and the American Boat & Yacht Council. So, while it is tempting to test out the compatibility of both engine parts, we recommend you’re prepared to do a complete rebuild vis-a-vis Gotham Garage before you make that venture. 

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A resistor is an electrical component that implements an electrical resistance inside a circuit element by using a passive two-terminal design. There are several different kinds of resistors on the market and most are made for use within an electronic circuit. Depending on the application, resistors from a certain manufacturer, in a certain size or material may be required. Because certain resistors can only handle the pre-determined values of ohms in specific scenarios, it’s important to choose the right resistor. And there are two categories of resistors, fixed and variable.

Fixed resistors are the most commonly used resistors to set the right conditions in electronic components. The values in these resistors are pre-set during the manufacturing stage and should never have to be adjusted to change the circuit. There are several different types of fixed resistors, ranging from carbon compositions or metal oxide films to thin films, etc. Carbon compositions are rarely used today because they are large and are likely to suffer irreversible changes in resistance over time. Today, the most commonly used fixed resistor is a thin film resistor, these are easily mass produced in the billions and are sufficient for most technology.

Variable resistors, also known as potentiometers, are used for their many different properties and range from carbon compositions to plastics. Because they have a slider and function as an adjustable voltage or potential divider, variable resistors are commonly used as volume or gain controls for stereos, sensors, and machines.

Resistors are important in the world of electronics because they control the flow of current, without them electronics would not perform at all. The selection of the right resistor for a specific application is also important; with the incorrect resistor, you could blow a circuit, resulting in a costly repair.

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Contrary to what some may think, it is preferable that planes take off against the direction of the wind rather than with it. You would think that taking off against the wind provides resistance and, in turn, causes the plane to use more fuel to pass through. And, you would think that taking off with the wind seems easier, because the wind would give the plane a little push to reach a higher altitude faster. But you’d be wrong.

Taking off against the wind is better because it’s easier to gain altitude in a shorter time frame and with less speed. The wind provides a force against the plane’s wings which helps lift the plane into the air instead of impeding it. Actually, in order to fly, planes use airflow going over and under the wings to lift them.

According to Snorri Gudmundsson, an Embry-Riddle Aeronautical University assistant professor, a plane must accelerate 30 mph more if there is little-to-no windspeed present during takeoff. Of course, it’s not realistic that the weather and wind will be ideal for every takeoff; but, when given the opportunity, pilots will take advantage of taking off into the wind.

The same principles apply to landing. It is much more efficient to land against the wind because it reduces the distance the plane must travel after landing on the runway. The wind puts force against the plane’s wings—as it does during takeoff—in order to come to a quicker halt. Going with the wind would just push the plane faster.

To sum it up, it is more efficient for planes to take off as well as land against the wind. This allows for the plane to use less ground speed to take off into the air and land on the runway.

Buy NSN, owned and operated by ASAP Semiconductor, should always be your first and only stop for all your hard to find or urgent aviation parts. Buy NSN is a premier supplier of aerospace parts. New or obsolete, we can help you find everything you need. We’ve got a vast and comprehensive inventory and a dedicated sales team ready to help you 24/7x365. If you’re interested in a quote or would like to learn more, contact the sales department at

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Jet engines are complex machines. By definition, they’re “any of a class of internal-combustion engines that propel aircraft by means of the rearward discharge of a jet of fluid, usually hot exhaust gases generated by burning fuel with air drawn in from the atmosphere.” Originally adapted from the piston engine, the first jet engine to incorporate a turbine design dates back as far as 1921. English inventor Frank Whittle patented his design in 1930, began testing in 1937, and achieved first flight in 1941. While development for Whittle was slow due to lack of interest, independent work in Germany was significantly faster with a patent issued in 1935 and the very first flight a turbojet-powered aircraft, the Heinkel HE-178, by 1939.

Generally, the jet engine involves two main components, the prime mover, which is usually a gas turbine, and the propulsor. The energy released from the combustion of a liquid hydrocarbon fuel is converted into mechanical energy in the form of high-pressure, high-temperature airstream by the gas turbine. Then, the mechanical energy is harnessed by the propulsor to generate a thrust to propel the aircraft.

For a jet engine to have high propulsive efficiency, the exiting jet velocity cannot greatly exceed the flight speed, and yet the thrust generated is proportional to the velocity excess that must be minimized. Because the requirements are so restrictive, jet engines have become very specialized, with each tailored to achieve a balance of good fuel efficiency, low weight, and compact size for use in their specific flight speed-altitude-mission application. However, they all share the same two major characteristics. One, in order to achieve high efficiency, the jet velocity is matched to the flight speed of the aircraft. Slow aircraft have low jet velocities and fast aircraft have high jet velocities. Two, to match the jet velocity to the flight speed, the size of the propulsor varies inversely with the flight speed of the aircraft. Slow aircraft have large propulsors and vice versa.

At Buy NSN, owned and operated by ASAP Semiconductor, we know how important it is that your jet engines are working at full capacity. So, as a premier supplier of aviation parts such as jet engine parts, turbines, and propellers, we make sure that our inventory is stocked with the highest quality parts and ready to ship immediately. If you’re interested in more information or a quote, email us at or call us at +1-919-348-4040.

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