2A753 Volume 4 Structural Maintenance Journeyman

The symbol that is entered on the Air Force Technical Order (AFTO) Form 781A when an aircraft is considered unsafe or unfit for flight is the Red X. This symbol is used to indicate that the aircraft is not in a condition to be flown and requires maintenance or repairs before it can be considered airworthy. The Red X symbol serves as a clear visual indicator to anyone inspecting the aircraft that it should not be operated until the necessary corrective actions have been taken.

To clean dirt and grease from a surface to be sealed, it is recommended to use an approved solvent/cleaner. This is because an approved solvent/cleaner is specifically formulated to effectively remove dirt and grease without damaging the surface. Soapy water may not be strong enough to remove stubborn dirt and grease, while an alkaline cleaner or a high pressure water blaster may be too harsh and cause damage. Therefore, using an approved solvent/cleaner is the most suitable option for this task.

Before fine finishing the edges of an aircraft panel, it is important to fit test the panel. This involves checking if the panel fits properly in its designated position and aligns correctly with other components. By conducting a fit test, any issues or adjustments needed can be identified and addressed before proceeding with the fine finishing process. This ensures that the panel will be properly positioned and aligned, resulting in a high-quality finished product.

To apply uniform pressure to laminated fiberglass repairs, vacuum pressure is used. This method involves creating a vacuum seal around the repair area using a vacuum bag or similar device. The vacuum removes air from the area, causing the bag to press tightly against the repair, applying even pressure. This ensures that the fiberglass layers are properly bonded and eliminates any air bubbles or inconsistencies. Vacuum pressure is an effective and efficient method for achieving a uniform pressure during laminated fiberglass repairs.

When a new Air Force Technical Order (AFTO) Form 781A is initiated, discrepancies with a Red X must not be transferred to the AFTO Form 781K. The Red X symbol indicates that the aircraft or equipment is unsafe or unserviceable and requires immediate attention. These discrepancies need to be addressed and resolved before transferring them to the AFTO Form 781K, which is used for historical documentation.

Before applying an aerodynamic smoothing compound to repair seams, it is necessary to clean the area with an approved solvent. This is important because the solvent helps to remove any dirt, grease, or other contaminants that may be present on the surface. By cleaning the area thoroughly, the smoothing compound can adhere properly and provide a smooth and seamless repair.

When removing damage from a composite structure, it is important to remove a minimum of sound material. This means that only the damaged or compromised areas should be removed, while preserving as much of the intact structure as possible. This helps to maintain the structural integrity of the composite and minimize the loss of strength or stability. Removing a minimum of sound material also reduces the amount of repair work needed and ensures that the repaired structure remains as close to its original design as possible.

To determine if water has been removed or has migrated to another location when removing moisture from a honeycomb composite panel, it is necessary to re-inspect the area using nondestructive inspection (NDI). This method allows for a thorough examination of the panel without causing any damage. NDI techniques such as ultrasound or thermal imaging can be used to detect any remaining moisture or water migration within the panel. These techniques provide a reliable and accurate assessment of the moisture content in the honeycomb composite panel.

The correct answer is "an approved solvent". This is because using an approved solvent is the most effective way to clean the frame before installing a plastic assembly. Solvents are specifically designed to dissolve and remove dirt, grease, and other contaminants from surfaces. They can effectively clean the frame without causing any damage or leaving residue behind. Mild soap and water solution, high detergent soap, and alcohol may not be as effective in removing all types of contaminants from the frame.

The fuselage is the main aircraft structural assembly to which other assemblies, such as wings, nacelles, and empennage, are directly or indirectly attached. The fuselage is the central body of the aircraft, housing the cockpit, cabin, and cargo compartments, and providing structural support for the wings, tail, and engines. It is responsible for carrying the payload and passengers, and it plays a crucial role in maintaining the overall integrity and stability of the aircraft during flight.

When making a repair, the main concern is to restore the original strength of the object or structure. This means ensuring that the repaired area is as strong as it was before the damage occurred. By focusing on strength, the repair will be able to withstand the same forces and stresses as the original, maintaining the overall integrity and functionality of the object.

An angle drill is used to remove damage when the damage is in a limited space. This is because an angle drill is designed with a compact and angled shape that allows it to access tight and confined areas where a regular drill cannot reach. Therefore, it is the ideal tool to use when the damage is located in a limited space that requires a specialized drilling tool for repair or removal.

The given correct answer is "rivet spacing and row spacing are identical". This means that the distance between each rivet and the distance between each row of rivets in the layout pattern are the same. This is important for ensuring the structural integrity of the flush patch. If the rivet spacing and row spacing were different, it could lead to uneven distribution of forces and potentially weaken the patch. Therefore, it is crucial for the rivet spacing and row spacing to be identical in order to maintain the desired strength and stability of the patch.

If the one-part sealant does not go on smoothly, easily, and evenly when applying it to an area, the best course of action is to discard the sealant. This is because an uneven application can lead to improper sealing and potential issues in the future. It is better to start with a fresh sealant that can be applied properly rather than trying to salvage an ineffective one.

Bulkheads provide shape, strength, and rigidity to the aircraft fuselage. They are vertical partitions that separate the fuselage into different compartments, such as the cockpit, passenger cabin, and cargo hold. Bulkheads are usually made of strong materials like aluminum or composite materials, and they help to distribute the structural loads evenly throughout the fuselage. They also provide support to the skin of the aircraft and help maintain the shape and integrity of the fuselage during flight.

The sanded area of a scratch is washed down after each sandpaper grit is used to wash away the previously used sandpaper grit. This is important because as the sandpaper grit becomes filled with debris and particles from the sanding process, it becomes less effective in smoothing the surface. By washing away the used grit, the next grit can have a clean surface to work on, ensuring a more efficient and effective sanding process.

To use premixed frozen sealant, the correct approach is to simply thaw the sealant and use it. There is no need to use a heat gun or heat lamp to thaw the sealant, and it is not necessary to allow the sealant to thaw overnight. Thawing the sealant and using it directly is the most efficient and effective method.

The correct answer is when there is no discoloration on a clean drying cloth. This means that the surface is free from any dirt, stains, or residue that could affect the adhesion of the sealant. A clean drying cloth should not pick up any discoloration or residue when wiped across the surface, indicating that it is thoroughly clean and ready for the sealant to be applied.

The correct answer is manufacturer's instructions. When preparing to mix a two-part sealant, it is important to follow the manufacturer's instructions. These instructions provide specific guidance on the correct ratios and mixing procedures to ensure the sealant is properly mixed and will perform as intended. The manufacturer's instructions take into account the specific properties of the sealant and are designed to ensure optimal performance and durability. Following these instructions is crucial to achieve the desired results and to maintain the quality and effectiveness of the sealant.

To inspect for distortions, a grid made up of horizontal and vertical lines is used. This grid helps to identify any irregularities or deformities in the object being inspected. By comparing the lines of the grid to the lines of the object, any distortions or deviations from the expected shape can be easily detected. The grid provides a reference point for assessing the accuracy and integrity of the object's structure.

When fabricating a doubler for a flush skin repair in an open area, it is important to select material that is one-gage thicker than the skin. This is because the doubler is used to reinforce the damaged area and provide additional strength. By using material that is one-gage thicker, it ensures that the doubler will be able to effectively support the skin and distribute any loads or stresses. This helps to prevent further damage and ensures a strong and durable repair.

Drawing a diagram on cardboard showing the location of the fasteners ensures that they are placed correctly when the transparent plastic assembly is disassembled. This helps in reassembling the assembly accurately without any mistakes or misplaced fasteners. It prevents any loss of fasteners and ensures that they are installed in the correct positions, maintaining the structural integrity of the assembly. This also saves time and effort that would otherwise be spent on searching for the correct placement of fasteners.

When using an original door as a template, it is important to ensure that the original door has the proper fit. This means that the dimensions and proportions of the original door should be suitable for the intended purpose and location of the new door. By using a door with the proper fit as a template, it ensures that the new door will also have the correct dimensions and proportions, resulting in a well-fitting and functional door.

The vertical stabilizer is responsible for reducing sway or yaw about the vertical axis of an aircraft. It is a vertical fin located at the rear of the aircraft, usually attached to the tail section. The vertical stabilizer, along with the rudder, helps to stabilize the aircraft and maintain its directional stability. By providing a surface area perpendicular to the airflow, it counteracts any yawing motion caused by factors such as wind or uneven distribution of forces. This helps to keep the aircraft flying straight and level.

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Before fastening the doubler and filler together for a flush repair, the repair parts must be curved to the precise contour of the repair area. This is because the repair area needs to be properly aligned and shaped in order to ensure a flush and seamless repair. Curving the repair parts to the precise contour of the repair area helps to achieve this alignment and ensures that the repaired section blends in smoothly with the surrounding structure.

Composite materials are made up of multiple components, such as fibers and resins, that are combined to create a strong and lightweight material. These materials are often sensitive to temperature changes and can degrade if exposed to high temperatures. Storing composite materials in cold storage helps to maintain their integrity and prevent any damage. The maximum temperature permitted for storing advanced composite materials in cold storage is 0ºF. This extremely low temperature ensures that the materials remain stable and do not experience any degradation or loss of properties.

When making a step-joint repair to an aramid honeycomb composite panel, the replacement plies should be made to match each ply in the original panel. This means that the orientation and alignment of the replacement plies should be the same as the plies in the original panel. By matching each ply, the repair will be seamless and the structural integrity of the composite panel will be maintained.

A flap is an auxiliary flight control that is located on the trailing edge of an aircraft's wing. It is used to increase lift and decrease the aircraft's speed during takeoff and landing. By extending the flaps, the surface area of the wing is increased, which creates more lift. This allows the aircraft to fly at slower speeds while maintaining lift, making it safer for takeoff and landing. The rudder, elevator, and stabilizer are all primary flight controls that are responsible for controlling the aircraft's direction, pitch, and stability, respectively.

Buttock lines are reference lines on an aircraft that indicate vertical planes parallel to the plane of symmetry. These lines are used to aid in the design and construction of the aircraft, particularly in shaping the fuselage and other components. By using buttock lines, engineers can ensure that the various sections of the aircraft are symmetrical and aligned correctly, resulting in better aerodynamics and overall performance.

When fabricating a filler plate for a flush skin repair in an open area, using the cutout area as a template is the correct method. This means that the dimensions of the filler plate should match the dimensions of the cutout area that was removed from the damaged skin. By using the cutout area as a template, the filler plate will fit perfectly into the open area, ensuring a flush repair. This method is commonly used to ensure accuracy and to avoid any discrepancies in the dimensions of the filler plate.

A primer is a type of corrosion preventative that is applied before the installation of repair parts. Its purpose is to provide a protective coating to prevent corrosion from occurring on the repaired area. By applying the primer before installing the repair parts, it helps to ensure that the repaired area is adequately protected against corrosion, extending the lifespan of the repair and preventing further damage.

A film adhesive is used to provide a more uniform bondline thickness when making a metal-bonded honeycomb repair. This is because film adhesives are typically thin and can be easily applied in a consistent manner, resulting in a uniform thickness across the bondline. Foam adhesives, paste adhesives, and liquid adhesives may be more difficult to apply evenly, leading to variations in bondline thickness. Therefore, a film adhesive is the most suitable option for achieving a uniform bondline thickness in this scenario.

When the original panel is missing or badly damaged, it becomes necessary to make a template out of plastic. This is because the template will serve as a guide for trimming the replacement panel or door to ensure that it fits properly. Without the original panel, the template becomes essential in replicating the shape and dimensions of the missing or damaged part.

The first step when repairing a defective fillet seal is to select the proper sealant cutting tools. This is because using the correct tools will ensure that the sealant is cut cleanly and accurately, allowing for a proper repair. Cutting the faulty section from the fillet, cutting around the seal and at the base of the fastener, or grasping the seal with pliers and pulling it away from the structure may be necessary steps in the repair process, but selecting the proper sealant cutting tools is the initial step that needs to be taken.

When performing a visual inspection on nicked plastic assemblies, you are looking for white powdered glass in a chipped area. This suggests that the plastic has been damaged and there may be a risk of further spreading or deterioration. The presence of white powdered glass indicates that the plastic has been chipped or cracked, potentially compromising its structural integrity. This visual cue helps identify areas that may require repair or replacement to ensure the overall quality and safety of the plastic assemblies.

The correct answer is Two; 2" from the edge of the heat blanket. This means that when removing moisture from a wet laminate, two thermocouples are used and they are positioned 2" away from the edge of the heat blanket. The positioning of the thermocouples ensures that the heat is evenly distributed and the moisture is effectively removed from the damaged area.

The correct answer is "equipment manufacturer’s instructions." This is because when welding thermocouples, it is important to follow the instructions provided by the equipment manufacturer. These instructions are specific to the welding equipment being used and ensure that the thermocouples are welded correctly and safely. Following the manufacturer's instructions also helps to maintain the integrity and functionality of the thermocouples.

After entering a Red X discrepancy in the AFTO Form 781A, you would check the "STATUS TODAY" block on the Air Force Technical Order (AFTO) Form 781H. This block provides the current status of the aircraft or equipment, indicating whether it is operational or non-operational. By checking this block, you can determine the current status of the item in question and track any changes or updates.

When preparing a cutout for an "open area," the correct step is to relieve stress concentrations. This involves removing any damage and stop-drilling all cracks to prevent them from spreading further. By relieving stress concentrations, the structural integrity of the cutout area is improved, reducing the risk of further damage or failure. This step is crucial to ensure the safety and longevity of the structure.

When repairing damage to an aircraft, the first step in removing the damaged area is to determine how much undamaged area should be removed. This is important because it ensures that all the damaged parts are completely removed and replaced with new, undamaged material. Removing the appropriate amount of undamaged area also helps to maintain the structural integrity of the aircraft and prevent any further damage or issues in the future.

Before developing a rivet layout for a circular flush repair, it is important to first establish the center point of the cutout area. This is because the center point will determine the positioning of the rivets and ensure that they are evenly distributed around the repair area. Without determining the center point accurately, the rivet layout may be incorrect, leading to potential issues with the repair and compromising the structural integrity of the part. Therefore, establishing the center point is a crucial step in developing an effective rivet layout for a circular flush repair.

When doing a partial-through repair that is not done on a full core replacement repair, it is necessary to install a 0.010" aluminum sheet shim. This shim helps to provide additional support and stability to the repair, ensuring that it is properly aligned and secure. The shim fills any gaps or uneven areas between the repaired section and the surrounding structure, helping to distribute the load evenly and prevent any potential issues or damage. By installing the aluminum sheet shim, the integrity and strength of the repair are enhanced, making it a crucial step in the partial-through repair process.

Passing a listening device along the seams while the area is pressurized allows for the detection of aircraft sealant defects. By using a listening device, any abnormal sounds or leaks can be identified, indicating the presence of defects in the sealant. This method is effective as it directly targets the area of concern and provides real-time feedback on the condition of the sealant.

When selecting a resin to repair laminated fiberglass assemblies, it is important to know the resin used by the manufacturer. This is because using a different resin may not provide the same level of adhesion and compatibility with the existing fiberglass. Using the same resin ensures that the repair will be strong and durable, and that the repaired area will blend in seamlessly with the rest of the assembly.

Paste adhesives are generally lower in strength compared to other types of adhesives. This means that they may not provide as strong of a bond as other types of adhesives. However, it is important to note that this statement is true only when the paste adhesive is not a two-part mixture. If the paste adhesive is a two-part mixture, it can have higher strength compared to other types of adhesives.

To minimize fiber fuzz when drilling aramid composite materials, it is recommended to use a dagger spade or brad point bit. These types of drill bits have a sharp point that helps to penetrate the material cleanly without causing excessive damage to the fibers. They also have a flat cutting edge that helps to create clean holes without fraying or fuzzing the fibers. Using these types of drill bits reduces the likelihood of fiber damage and ensures a neater and more precise drilling result.

A puncture of a fiberglass panel that extends through one facing is classified as Class II damage. Class II damage refers to damage that can be repaired without compromising the structural integrity of the composite structure. This means that the puncture can be fixed and the panel can still function properly without any significant loss of strength or performance.

When performing a routing operation on a tapered surface, the minimum length of the required wedge blocks is 6". This is because the tapered surface requires a longer block to ensure stability and proper support for the routing operation. A shorter block may not provide enough contact area with the surface, leading to instability and potential errors in the routing process. Therefore, a 6" block is necessary to ensure the routing operation is performed accurately and safely.

When drilling holes in a delaminated area of a metal-bonded honeycomb panel for injecting adhesive, it is important to drill holes first at the top and bottom of the delaminated area. This ensures that the adhesive can flow effectively throughout the entire delaminated area, allowing for proper bonding and repair. By starting at the top and bottom, the adhesive can evenly distribute and fill any gaps or voids within the delaminated area, resulting in a stronger and more secure bond.