Purchasing Efficiency Blog

Within aircraft, there are a multitude of systems that utilize hoses. Hoses can be installed for fuel lines, hydraulic systems, brakes, oil coolers, and more. Flexible aircraft hoses in particular are important in situations where parts may be subjected to vibration or the hose system needs a lot of flexibility. In this blog, we will discuss some of the important considerations and steps that should be taken into account when purchasing and installing a flexible aircraft hose.
 
When considering purchasing flexible hoses for your aircraft, it is important to decide whether you should purchase new, used, or surplus. When getting either used or surplus, buyers may find that they are much cheaper than new hoses. While this may make a great difference in their decision, some may be more wary of the shelf life of the hose. Shelf life, however, is often decided by the manufacturer based on their best guess, and commonly does not account for the actual life of the hose once it is installed and utilized in the aircraft. Nevertheless, ensuring that the hose is still flexible is important.
 
Before purchasing your hose, it is paramount that it is engineered to be capable for the application that you intend to use it for. Aircraft fuel and oil hoses need to be able to withstand the temperatures that they may be subjected to during use, and hoses for a hydraulic system need to meet needed operating pressures.
 
Ensuring the correct size of the hose is also always crucial for any system. Hoses are measured by their internal diameter, while a tube on the other hand may be measured from its external diameter. Sizes are also measured in 16ths of an inch, which is important to remember when finding the right fit. If you are cutting your own hose for installation, be sure that the cuts are clean so that they can be fitted properly. Also keeping extra length than what may be needed can allow for the tube to bend and flex.

At Purchasing Efficiency, owned and operated by ASAP Semiconductor, we can help you find the aircraft parts and flexible hose assemblies you need, 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 all the parts and equipment you need, 24/7x365. For a quick and competitive quote, email us at sales@purchasingefficiency.com or call us at +1-469-319-8300.

Hydraulic systems are a widely used, reliable, and cost effective method of creating motion and actuation for various components. They can be utilized for car braking systems, aircraft flight control systems, industrial machinery, and much more. Simply put, hydraulic systems work by pressurizing liquid in an enclosed space, which in turn transfers that pressure equally through the system which can be used to perform various tasks. With hydraulics, it is important that that pressure remains equal and there is a backup in case of leakage or failure. To prevent and solve this problem, many hydraulic systems utilize hydraulic bypass valves.
 
Hydraulic bypass valves work to maintain equal amounts of pressure within the hydraulic system. This is achieved through the use of a piston and spring that work together to divert or bypass fluid when needed. Normally, the piston remains closed and the fluid flows normally while there is equal pressure in the inlet and outlet of the spring. When one side begins to build up a great amount of unequal pressure, the spring begins to compress, pushing the piston which creates an opening. Fluid is then diverted into this new opening and typically is moved pack to a reservoir or another area of the system.

For example, in the case of a car braking system, the hydraulic bypass valve works to ensure the braking system does not fail in case of leaking or damage. Cars often rely on their front brakes for stopping power, and leakage can cause them to fail through a loss of fluid pressure. Hydraulic pressure in this case becomes uneven and the bypass valve redirects brake fluid to the back brakes to allow for safe stopping. Hydraulic bypass valves are seen in many other systems in which water and oil is utilized for actuation and creating motion, as well as they are always useful for maintaining safe and equal pressurization.

When you’re dealing with complex, highly-engineered, and expensive aircraft, it is important that every single piece does its job. From the engine down to the smallest fastener, each part has an important role to play. Bolts, a small but critical fastener in the construction of any aircraft, are no different. The stress of flight means that non-aviation grade hardware simply doesn’t do the trick. It has neither the strength nor the corrosion resistance to work effectively in flight. This has required aviation authorities to develop strenuous standards for aircraft bolts, as well as an exhaustive description and coding system.
 
Bolts used for aviation purposes are manufactured to AN (Army/Navy) standards. AN bolts are used for either tensile or load-bearing applications. They are made from a variety of different materials including cadmium-plated nickel alloy steel, corrosion resistant steel, or aluminum alloy. Their comprehensive coding system seems daunting but, once you break it down, is easy to follow. For example, a typical bolt coding will look something like this:
 
AN4-(H)10A
 
“AN” is a common prefix simply standing for Army Navy, the two authorities from which this coding system came. The number 4 denotes that the bolt has a diameter of 4/16th of an inch. If the bolt was 3/16th of an inch it would be AN3. The dash following AN4 seems like nothing, but actually signifies that the bolt is constructed of cadmium-plated steel. (H) designates that the bolt has a drilled head bolt and is left off the code in the event that no drilling in the head is necessary. The fourth section, the number 10, indicates that the bolt is ten inches in length. Much like the diameter, this number changes with the length of the part. The final character, the letter A, is used to show that a cotter pin hole is not required.
 
As you would expect, the bolt codes can differ drastically based on a number of factors and specifications. This standardized coding system is a convenient identification tool and can save operators a lot of headaches during their search for proper bolts.

The O-ring is a manufacturing component that has been around for over a century. Thanks to their design simplicity and practical nature, O-rings remain in widespread use to this day. Their function is as simple as their design, which serves to create a tight, leak-proof seal between two components. They are very similar to gaskets, although O-rings are normally used in higher-pressure environments where other seals parts would fail. O-rings work by sitting between two other pieces that will be connected. The O-ring lies in the connective joint between the two parts where, once under pressure, will shift around causing it to more tightly hold onto the inner and outer walls of the pieces it’s connecting.
 
Despite being a very simple part, O-rings come in a variety of types and materials. Some of the materials they’re made from include rubber, nitrile, silicone, fluorocarbon elastomer, metal, stainless steel, and NBR, a type of elastomer part. O-ring uses are as varied as the materials they come from. Here are just a few of them:

Although O-rings are an incredibly basic piece of technology, they are a vital component of many manufactured goods.

Bearings are used in many of the machines we use on a daily basis. If bearings didn’t exist, we would be constantly replacing parts, which would inevitably slow down productivity. The bearing parts were designed with a simple concept in mind— objects can roll better than they can slide. Bearing design is based on the magnitude and direction of the load that they are intended to support.
 
The beauty in the simplistic design of bearings is something to be admired. Ball bearings are essentially made up of a ball and a dual sided surface for dissipating stress that is applied to it. The ball carries the load of the weight while the force associated is what enables rotation. The method in which the force is absorbed depends on two factors: thrust load and radial load. Radial loads apply tension to the bearing which causes it to rotate. Thrust loads put stress directly on the bearing from an angled position. A deep groove ball bearing and tapered roller bearing can facilitate both loads. The load type and capacity to support weight are factors to consider when choosing the proper bearing for a job.
 
The ball bearing is the most common type on the market and can handle both thrust and radial loads. There are also roller bearings, ball thrust bearings, roller thrust bearings, tapered roller bearings, and magnetic bearings. Each one supports a different function. Roller bearings are used in objects such as conveyor belt rollers and are capable of holding heavy radial loads. The roller is constructed as a cylinder meaning the contact between the inner and outer race is a line. Ball thrust bearings are used in instances where low speed is key, and a radial load can’t fully be handled.
 
Roller thrust bearings are constructed to support large thrust loads. These bearings are commonly found in vehicle transmissions and are used to separate the gears. Tapered roller bearings have the ability to support both large thrust loads and large radial loads. Magnetic bearings contribute to the functionality of high-speed devices. This includes advanced flywheel energy storage systems. Bearings with rollers or balls can’t withstand the high-speed temperatures and would ultimately melt.

Bevel gears are gears where the axes of two shafts intersect, and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are typically mounted on shafts that are 90 degrees apart but can be designed to function at other angles as well. One of the most common use of bevel gears is in the differential of a vehicle, where it transmits power generated by the power engine to the vehicle’s wheels.
 
The two most important concepts in gearing are pitch surface and pitch angle. The pitch surface of a gear is the imaginary toothless surface that one would have by averaging out the peaks and valleys of the individual teeth. The pitch surface of an ordinary gear is in the shape of a cylinder. The pitch angle of a gear is the angle between the face of the pitch surface and the axis. Most kinds of bevel gears have pitch angles of less than 90 degrees and are therefore cone shaped. These are called external bevel gears, because their gear teeth point outwards. Internal bevel gears, meanwhile, have pitch angles of greater than ninety degrees, and have teeth that point inward. Bevel gears with pitch angles of exactly 90 degrees are known as crown gears.
 
Bevel gears can be classified into several different types, based on their geometry. Straight bevel gears have a conical pitch surface and teeth that are straight and tapering towards the apex. Straight bevel gears have a conical pitch surface and teeth that are straight and taper towards the apex. Spiral bevel gears have teeth that curve at an angle, which allows contact to be gradual and smooth. Zerol bevel gears are technically spiral bevel gears but have a spiral angle of zero at the middle of the face width, effectively combining the strengths of both straight and spiral bevel gears. Lastly, hypoid bevel gears are similar to spiral level, but the pitch surfaces are hyperbolic and not conical. A hypoid pinion is also larger in diameter than an equivalent bevel pinion. Lastly, mitre gears are a type of bevel gear with equal numbers of teeth and are primarily used to transmit rotational motion at a 1:1 ratio.

To understand how an airplane’s wings keep it in the sky, we first have to understand the forces influencing all aircraft - thrust, drag, lift, and weight. Thrust is the force that propels the aircraft forward provided by its engines, both piston and jet turbine. Drag is the force trying to pull the aircraft back, generated as the aircraft displaces the air in front and around it. Lift is the force generated by the airplane’s wings and the flow of air over and below them, while finally weight is the force of the Earth’s gravity trying to pull the plane back to the ground. 
               
 An airplane’s wings generate lift as they move through the air, but how exactly? They do so for two reasons: Bernoulli’s principle, and the shape of the wing itself, also known as the airfoil.  Bernoulli’s principle, named after the Swiss mathematician that discovered and described the phenomenon in 1738, states that as air speeds up, its pressure drops. An aircraft airfoil is shaped deliberately so that air going over the wing will be going faster than the air going under it. This means that the faster air going over the airfoil exerts less pressure than the high-pressure, slower-moving air going underneath it.  This results in lift that pushes the airfoil, and the rest of the airplane, up. 
               
Typically, a plane’s airfoil will be designed to provide enough lift to keep the plane level while flying at its cruising speed. But what about when a plane is taking off and landing? In those situations, the plane’s flaps and slats come into play to alter its airfoil and generate more lift.  
               
During takeoff and landing, the flaps located on the back of the wing extend downward from the trailing edge, altering the shape of the wing’s airfoil and generating more lift. This altered shape also generates more drag; this is useful for slowing down during landing, but it also means takeoff requires more thrust than normal. Slats also work on the same principle of altering the wing’s shape but are located on the leading edge of the aircraft. They are also used during takeoff and landing.

Vehicles go, but how do they stop? What components are involved in bringing a moving object to a halt? The answer lies within the aircraft braking system, specifically, brake calipers. Brake calipers play a crucial role in allowing your vehicle to stop and contribute to the overall safety of its operation. Understanding how they function can be essential in comprehending how the differing systems of your car.
 
Brake calipers are designed to fit over the brake rotor, with the brake pads being attached to the inside of the caliper. When the brake pedal is activated, brake fluid from the master cylinder creates hydraulic pressure that pushes the pistons in the brake caliper. The brake pads clamp down on the brake rotor to slow the car down or bring it to a complete stop. Because the rotor is attached to the wheels, they all slow down together.
 
There are two different types of calipers: fixed and floating. Fixed calipers are solidly mounted to a bracket, or spindle, with no sliding pins or bushings in its mount. The bracket is fastened to the rotor and typically consist of 2, 4, 6, or 8 pistons. There are an equal number of pistons on both the inboard and outboard halves of the caliper. When you apply pressure to the brakes, the pistons on both sides function in tandem and squeeze the pads against the side of the rotor. Fixed calipers provide a smoother braking feeling for the driver, which is why this type of caliper is found in performance and luxury vehicles. 
 
Floating calipers have the ability to move. However, this movement is in and out, and is relative to the rotor. It consists of pistons on one side and slides back and forth on bushing, or pins, acting as a clamp. When the brakes are applied, the piston pushes the brake pad on the inward side against the rotor. The caliper then slides on the bushings and squeezes the outward pad against the rotor. This forces the caliper to clamp the rotor between the brake pads. Since the pistons are located on the inward side of the caliper, it provides better clearance to the wheel, as opposed to a fixed mount caliper. Floating calipers are generally cheaper in cost as they only use a single piston.
 
Brake calipers deteriorate over time, limiting their functionality as they age. Heat generated from the braking system inevitably wears them down which is why routine maintenance is vital. You should have your brakes checked if you experience one of the following:

Helicopters typically have a 14- or 28-volt direct current electrical system. A volt is a unit of measurement that expresses the capability of the force that pushes electrical energy. Amperes are the unit of measurement for a current and describe the measure of an electrical quantity that is available in the system. Small piston-powered helicopters use an engine driven alternator because they are light, low maintenance, and produce a uniform electric output— even at low RPMs. In a turbine powered helicopter, starter/ generator systems are used. Once the engine is started, the battery powers the starter, which turns the engine. After this initial jump, the generator is powered by the engine.
 
A voltage regulator is used to distribute the electrical supply; it prevents excessive voltage, which can cause damage to various electrical components. After the electricity is passed through the voltage regulator, it goes to a bus bar, which then distributes the current to different electrical components. The battery is mostly used to start the engine, but also powers a few things when the engine isn’t running— such as radios and lights— and is a good emergency electrical power source. An ammeter is used to monitor the electrical current flowing to and from the battery. An ammeter that is charging represents the fact that the battery is charging while a discharging ammeter indicates that the electrical load is exceeding the output of the alternator or the starter generator of a helicopter.
 
Electrical components can be selected through electrical switches. If the capacity of the switch is exceeded, a solid state relay may be used. When an electrical component is overloaded, a circuit breaker will pop out. A fuse will burn out when it’s overloaded and can be easily replaced. Caution lights may also be utilized to display when there is an electrical component malfunctioning.

Helicopters fly using the same aerodynamic concepts that airplanes use; they use an airfoil to generate lift. The difference is that helicopters generate vertical thrust while aircraft generate horizontal thrust. When an airplane moves forward, the air flows across the wing and produces downwash which creates lift; the airplane has to gain enough speed for this force to overcome weight. When helicopter blades, or airfoils, begin spinning, it produces downwash which then creates lift. Speed is an important factor in generating enough force to overcome the weight in a helicopter as well. Vertical thrust allows a helicopter to take off vertically and hover.

Most helicopters use gas turbine engines over piston engines (reciprocating engines), but most modern helicopters use turboshaft engines. Turboshaft engines differ from turbojet engines in that they do not utilize exhaust to create thrust. Their main function is to generate shaft power which is used to run the rotor. Shaft power is transferred from the turbine blades. High pressure gas created in the combustion chamber is the force that rotates the turbine blades.

 The upper swashplate and the rotor blade system is attached to the rotor shaft, or mast, and they all begin rotating at the same time. A helicopter is controlled by the pilot with a collective, cyclic, two pedals, and the throttle. The collective is used to control the swashplate, which adjusts the blade pitch equally. A swashplate has two plates: one rotates with the rotor and one is fixed. A bearing is between the two plates. The upper plate is connected to the blades with a pitch change arm. The lower plate is connected to hydraulic servos which can raise, lower, or tilt the plate. Once this occurs, the pitch of the blades shift.

The collective control in the cockpit raises and lowers the swashplate and the cyclic control tilts the swashplate. These changes allow the pilot to steer the helicopter. Another rotor is added to a helicopter to counteract torque. This may be a coaxial rotor, which is attached to the same mast as the first rotor, or a tail rotor. The pedals allow the pilot to control the tail rotor. The pedals change the pitch of the tail rotor blades which control the sideways thrust. This allows the pilot to change the direction of the nose of the helicopter. The throttle increases or decreases the engines speed and therefore allows the pilot to control the amount of lift generated. All of these components are used simultaneously to takeoff, hover, change directions, and land.