AMNT 240 – Quiz 9.5 – Exam – Modules 7-9

The testing medium used to indicate the presence of a fault in magnetic particle inspection is a finely ground iron oxide that has a high permeability and low retentivity, and is nontoxic. It is usually suspended in a light oil such as kerosine.

A part magnetized circularly by the magnetizing current flowing lengthwise through it, will show up defects parallel to the long axis of the part.

An AN-818-5 nut will fit a 5/16-inch tube. (The last dash number is the tube diameter in 1/16-inch increments.) An AN-818-16 nut will fit a 1-inch tube. An AN-818-8 nut will fit a 1/2-inch tube.

Tubing made of 5052-O and 6061-T aluminum alloy in sizes from 1/8- to 3/8-inch OD should be flared with a double flare. Double flares are smoother than single flares and are more concentric. Also, the extra metal makes the flare more resistant to the shearing effect when the fittings are torqued.

The zero on the vernier scale is beyond the 1. This shows the measurement is more than 1 inch. It is beyond the 4. This shows it is more than 1.4 inch. It is beyond the first 0.025 mark on the bar. This shows that it is more than 1.425 inch. The 11 line on the vernier scale lines up with one of the marks on the bar. This 0.011 is added to the reading we have. The total reading is 1.425 + 0.011 = 1.436 inches.

Scratches or nicks not deeper than 10 percent of the wall thickness in aluminum alloy tubing, that are not in the heel of a bend, may be repaired by burnishing (forcing the displaced metal back into the nick or scratch) with a polished steel burnishing hand tool.

The dwell time (the time the penetrant is allowed to remain on the surface) is determined by the size and shape of the discontinuity being looked for.

Weld B is a double butt weld. Both sides of the material have been ground in a V and a bead is formed on both sides of the sheet.

A hand operated wheel-type tubing cutter is the best tool to use when cutting aluminum tubing, or any tubing of moderately soft metal.

The distance from the axis is found by dividing the moment by the weight. 1,400 ÷ 40 = 35 Since the moment is positive, the arm will also be positive. The generator is located +35 inches from the axis.

The center of a shaft or other circle can be found with the center head of a combination set. A combination set consists of a steel scale that has three heads that can be moved to any position on the scale and locked in place. The three heads are a stock head that measures 90° and 45° angles, a protractor head that can measure any angle between the head and the blade, and the center head that uses one side of the blade as the bisector of a 90-degree angle. The center head is placed against the circumference of the circle and a diameter is drawn along the edge of the blade. The head is moved about a quarter of the way around the circle and another diameter is drawn. The two diameters cross in the center of the circle.

Aliphatic naptha is a petroleum product between gasoline and kerosine in its characteristics. It is well suited for use as a cleaning agent for removing fingerprints, dust, and oily deposits that have settled on a surface to prepare the surface for painting. Dry-cleaning solvent, such as Stoddard solvent, leaves a slight residue on the surface that can interfere with the adhesion of the paint. Aromatic naptha is a coal tar derivative that is toxic and attacks acrylics and rubber products. It is not suitable for wiping down a surface before painting.

The cross on the head of a bolt identifies it as a standard AN bolt made of nickel alloy steel. The cross inside a triangle identifies the bolt as an NAS close-tolerance bolt. The single dash on the head of a bolt identifies it as a standard bolt made of corrosion-resistant steel.

The correct sequence for making a single flare on a piece of tubing is: (3) Slip the fitting nut and sleeve on the tube. (1) Place the tube in the proper size hole in the flaring block. (6) Center the plunger or flaring pin over the tube. (2) Project the end of the tube slightly from the tip of the flaring tool, about the thickness of a dime. (5) Tighten the clamp bar securely to prevent slippage. (4) Strike the plunger several light blows with a lightweight hammer or mallet. Turn the plunger one-half turn after each blow.

The material most generally used for firewalls on aircraft is stainless steel at least 0.015 inch thick. Mild steel, at least 0.018 inch thick and protected from corrosion, terneplate at least 0.018 inch thick, and Monel at least 0.018 inch thick may also be used.

When making an installation of rigid metal tubing, each run of the tubing must have at least one bend in it to allow for the shifting of the line as it is pressurized. This prevents excessive stress on the tubing.

There are two types of flare fittings that can be used in aircraft hydraulic systems. One type is the single-piece AN817 nut, and the other is the two-piece MS20819 sleeve and an AN818 nut. The AN818 nut and sleeve are preferred over the single-piece fitting because it eliminates the possibility of reducing the thickness of the flare by the wiping or ironing action when the nut is tightened. With the two-piece fitting, there is no relative motion between the fitting and the flare when the nut is being tightened.

There are four conditions that must exist before corrosion can occur: 1. The presence of a metal that will corrode, the anode. 2. Presence of a dissimilar conductive material, the cathode, which has less tendency to corrode. 3. Presence of a conductive liquid, the electrolyte. 4. Electrical contact between the anode and cathode. A passive oxide film is used as a corrosion preventive.

Some nonapproved commercial cleaning compounds can cause a chemical reaction with some of the metals used in aircraft structure. This reaction releases hydrogen gas that can be absorbed into the metal and cause hydrogen embrittlement which weakens the metal and can cause cracking and failure.

A moment is a force that causes rotation about a point, and in order to specify the direction of the rotation, signs (+) and (-) are assigned to the moment. In aircraft weight and balance, a positive moment is one that causes the aircraft nose to go up, and a negative moment is one that causes the nose to go down. Since a moment is the product of weight and the distance from the datum, and both of these are signed values, we have four choices for the sign of the moment: 1. A positive weight (weight added) and a positive arm (arm behind the datum) give a positive moment. 2. A positive weight and a negative arm (arm ahead of the datum) give a negative moment. 3. A negative weight (weight removed) and a positive arm give a negative moment. 4. A negative weight and a negative arm gives a positive moment.

Flexible hose may be used in any part of an aircraft fluid system where it has been proven by the aircraft manufacturer to be suitable. The hose must be able to carry the pressure, withstand the vibration, and pass the required fluid flow. The size of a flexible hose is approximately its inside diameter in 1/16-inch increments. This refers to the outside diameter of a rigid tube that has the equivalent flow characteristics.

The reference datum used for weight and balance purposes can be located anywhere the aircraft manufacturer chooses. Current practice is to locate it on or near the nose or out ahead of the aircraft. The reason for this is that all of the arms will be positive (they will all be behind the datum). If all of the arms are positive, the moment of all added weight will be positive, and the moment of all removed weight will be negative. This will simplify weight and balance computations and will give less chance for error.

Type Certificate Data Sheets or Aircraft Specifications include the maximum certificated gross weight of an aircraft.

Anodized surfaces should never be cleaned with anything that could scratch through the anodizing and expose the untreated alloy, or that could contaminate the surface. For this reason only aluminum wool or fiber bristle brushes are suitable for cleaning these surfaces.

ITEM WEIGHT ARM MOMENT Aircraft 1,500 28.4 42,600 Seats (remove) 24(-) 68.5 1,644(-) Modification 28 73 2,044 Seat 30 70.5 2,115 Radio 25 85 2,125 TOTAL 1,559 30.30 47,240 The empty weight of this aircraft is 1,559 pounds, and its empty-weight CG is located at fuselage station 30.30.

Mercury spilled in an aircraft requires immediate action for its isolation and recovery to prevent it from causing corrosion damage and embrittlement of the aluminum structural components. Mercury is highly toxic and spreads very easily from one surface to another.

Bernoulli’s principle is one of the most useful principles we have to explain the behavior of fluid (either liquid or gas) in motion. Bernoulli’s principle tells us that if we neither add energy nor take any energy from fluid in motion, an increase in the velocity of the fluid (its kinetic energy) will result in a corresponding decrease in its pressure (its potential energy).

Rigid tubing made of corrosion-resistant steel, either annealed or 1/4 hard, is used in high-pressure hydraulic or pneumatic systems where high strength and abrasion resistance are important.

An aluminum alloy part is heat-treated by being heated in an oven and then removed and immediately quenched in cold water. If there is a delay between the time the part is removed from the oven and the time it is quenched, the grains in the metal will grow. Because of this, there is a good probability that intergranular corrosion will develop along the boundaries of the grains within the metal.

Liquid penetrant inspection methods may be used to detect faults that extend to the surface on both ferrous and nonferrous metals and nonporous plastics.

A class-1 fit is a loose fit. This is used for coarse-thread stove bolts and square nuts. A class-2 fit is a free fit. It is used on some machine screws. A class-3 fit is a medium fit. It is used on almost all standard aircraft bolts.

Some of the common metals in the order of their electrochemical activity are: (Most anodic) Magnesium Zinc Cadmium 7075 Aluminum alloy 2024 Aluminum alloy Mild steel Copper Stainless Steel Chromium Gold (Most cathodic)

When making a good weld, the heat should be concentrated in the area being welded. The oxides that form on the base metal give an indication of the amount of heat put into the metal. Oxides formed for a distance of much more than 1/2 inch from the weld show that too much heat was put into the metal. The metal may have been weakened.

Self-locking nuts are used on aircraft to provide tight connections which will not shake loose under severe vibration. Do not use self-locking nuts at joints that subject either the nut or bolt to rotation.

Aluminum identified by the code number 1100 is 99 percent commercially pure aluminum.

All of the required equipment must be properly installed, and there should be no equipment installed that is not included in the equipment list.

Weld A is a single butt weld. Weld B is a double butt weld. Welds C are both butt welds. Weld D is a rosette weld. Weld E is a fillet weld. Weld F is an edge weld. Welds G are lap welds.

After the penetrant has been on the surface of a part for the correct dwell time, the surface must be thoroughly washed to remove all traces of the penetrant. When the surface is clean and dry, the developer is sprayed or dusted on. Any penetrant left on the surface or in the pores of the material will stain the developer and faults will not show up as sharp and clear marks.

Changes of fixed equipment may have a major effect upon the weight of an aircraft. Many aircraft are overloaded by the installation of extra radios or instruments.

The amount of torque used to screw a nut onto a bolt is critical in determining the integrity of a bolted joint. For torque to be uniform and to allow the torque specified by the manufacturer to be duplicated in the field, the following rule applies: Unless it is specified otherwise, the values given in a torque chart relate to clean, dry threads.

The stem of a poppet valve is checked for stretch by using a vernier micrometer caliper to measure the stem diameter in the center of the stem and at the spring end. If the center diameter is less than the diameter at the spring end, the valve stem has been stretched.

The vernier scale (the series of parallel lines on the sleeve) on a vernier micrometer caliper is used to give an indication of one ten thousandth of an inch (0.0001 inch) of spindle movement.

Scratches or nicks are allowed in a piece of aluminum alloy tubing provided it is no deeper than 10 percent of the wall thickness of the tube, and it is not in the heel of a bend. Scratches and nicks should be burnished out of the tube, to prevent stress concentrations.

When a piece of metal tubing is installed in a bonded clamp, any paint or anodizing oxide film must be removed from the portion of the tube where the clamp is to fit. Both paint and the oxide film are electrical insulators.

It is important when performing a dye penetrant inspection that the surface of the part be as clean as possible. Volatile petroleum-based solvents such as Stoddard solvent and naphtha are widely used for cleaning parts to be inspected.

Statement (1) is true. Bonded clamps (clamps in which the tube is contacted with a piece of bare metal) are used when installing metal tubing in an aircraft. Bonded clamps keep the tube at the same electrical potential as the aircraft structure. Statement (2) is also true. Unbonded (cushion) clamps are used when securing wire bundles to the aircraft structure. The soft cushion in the clamp prevents abrasion wearing away the insulation on the wire.

Stress-corrosion cracking is an intergranular cracking of the metal which is caused by a combination of stress and corrosion. Shot peening a metal surface increases its resistance to stress corrosion cracking by creating compressive stresses on the surface. Any applied tensile stress must first overcome the surface compression before the tensile stress is felt.

Inclusions are impurities trapped inside a piece of metal when it was cast. When the part is inspected by magnetic particle inspection, the inclusion does not show up as a clearly defined fault but the indication is fuzzy. Rather than sharply defined poles, there are several sets of poles that cause the oxide to form in a series of parallel lines.

Piston pin out-of-round can be measured with a vernier micrometer caliper. Measure each end of the pin in two directions at right angles to each other. The difference in the two readings is the amount the pin is out-of-round.