A&P General Subject Matter Areas: The Core Foundation for Aviation Mechanics

Mastering the A&P General subject matter areas is the essential first step for any aspiring aviation maintenance technician. This foundational block of knowledge serves as the gateway to both the Airframe and Powerplant ratings, ensuring that every mechanic possesses a standardized understanding of the scientific, mathematical, and regulatory principles that govern aircraft airworthiness. The Federal Aviation Administration (FAA) structures this curriculum to bridge the gap between theoretical engineering and practical line maintenance. Because the General exam covers such a broad spectrum—ranging from complex electrical theory to the legal nuances of maintenance logging—candidates must approach these topics with a focus on how they integrate into daily operations. Success in these areas demonstrates a candidate's readiness to handle the immense responsibility of returning aircraft to service safely and legally.

A&P General Subject Matter Areas and Their Importance

Role as a Prerequisite for Specialization

The General section functions as the structural bedrock for the more specialized Airframe and Powerplant ratings. Before a technician can troubleshoot a high-bypass turbofan engine or repair a composite wing structure, they must demonstrate proficiency in the core concepts that apply to all aircraft. The FAA mandates this sequence because the physics of fluid flow used in a hydraulic landing gear system (Airframe) are identical to those used in an engine oil lubrication system (Powerplant). By establishing a common vocabulary and set of mathematical tools, the General curriculum ensures that specialized training is not bogged down by remedial explanations of basic mechanics. Scoring well on the General written exam indicates a mastery of the Aviation Mechanic Airman Certification Standards (ACS), which specify exactly what a technician must know, consider, and do to meet the requirements for certification.

Regulatory Framework Overview

Aviation is one of the most heavily regulated industries in the world, and for good reason. The regulatory framework covered in the General section provides the legal authority under which a mechanic operates. This isn't merely about memorizing rule numbers; it is about understanding the Type Certificate Data Sheet (TCDS) and how it defines the configuration of an aircraft. You will be tested on the hierarchy of FAA mandates, distinguishing between mandatory compliance items and recommended practices. This section ensures that every technician understands the weight of their signature when they sign a maintenance release. A failure to grasp the regulatory context can lead to more than just a failed exam; it can result in legal liability or the compromise of flight safety due to unauthorized modifications or improperly documented repairs.

Link to Practical Skill Standards

The General subject matter areas are directly tied to the Practical Test Standards (PTS) and the newer ACS, which examiners use during the Oral and Practical (O&P) phases of certification. While the written exam tests your ability to calculate a center of gravity or identify a resistor color code, the practical application requires you to translate that knowledge into physical tasks. For instance, understanding the properties of materials—a key General topic—is vital when you are tasked with identifying different types of aviation hardware or selecting the correct cleaning solvent for a specific alloy. The FAA's goal is to ensure that a mechanic's theoretical knowledge supports their manual dexterity. Every formula learned in the A&P General written exam topics has a corresponding physical reality, such as determining the torque value for a critical bolt or measuring the voltage drop across a landing light circuit.

FAA Regulations and Mechanic Privileges

14 CFR Part 43: Maintenance Rules

Title 14 of the Code of Federal Regulations (CFR) Part 43 is arguably the most important document for a maintenance technician. It defines what constitutes maintenance, preventive maintenance, rebuilding, and alteration. As a candidate, you must understand the distinction between a Major Repair and a Minor Repair, as this dictates the required documentation—specifically the use of FAA Form 337. You will be expected to know who is authorized to perform maintenance and, more importantly, who is authorized to approve that work for return to service. The regulations also specify the performance rules: all work must be done using methods, techniques, and practices acceptable to the Administrator. Understanding Appendix A of Part 43, which lists major alterations and repairs, is a frequent focus of exam questions, as it determines whether a repair requires the oversight of an Inspection Authorization (IA) holder.

14 CFR Part 65: Mechanic Certification

While Part 43 governs the work, 14 CFR Part 65 governs the person. This regulation details the requirements for the issuance of mechanic certificates and ratings, including the eligibility requirements, knowledge, and skill tests. For the exam, you must be intimately familiar with the privileges and limitations of a mechanic. For example, a certificated mechanic may perform or supervise maintenance, but they cannot perform a Major Repair on propellers or any repair on instruments. Furthermore, Part 65 outlines the recent experience requirements, stating that a mechanic may not exercise the privileges of their certificate unless they have been actively working for at least six months within the preceding 24 months. Understanding these boundaries is critical for passing the exam and for maintaining a legal career in the hangar.

Required Records and Documentation

In the eyes of the FAA, if a task was not documented, it was not performed. The General exam places heavy emphasis on the permanent and temporary records required by 14 CFR Part 91.417. You must distinguish between records that must be kept for only one year (or until the work is repeated) and those that must be transferred with the aircraft when it is sold, such as the total time in service and the status of Airworthiness Directives (ADs). A key exam concept is the required content of a maintenance entry: a description of the work, the date of completion, the name of the person performing the work, and the signature, certificate number, and kind of certificate held by the person approving the work. Mastery of these documentation rules ensures that the aircraft's logbooks provide a clear, legal audit trail of its maintenance history.

Aviation Mathematics and Physics Fundamentals

Algebra, Geometry, and Trigonometry Applications

Aviation math and physics are not abstract exercises; they are daily tools for the technician. You will need to use algebra to solve for unknowns in formulas such as the calculation of piston displacement or compression ratios. Geometry is essential for determining the area of irregular wing surfaces or the volume of fuel tanks. Trigonometry becomes vital when dealing with vectors in weight and balance or calculating the tension in a control cable based on the angle of deflection. On the exam, expect to convert between fractions and decimals rapidly and to work with powers of ten for electrical calculations. A common scenario involves calculating the area of a circle ($A = \pi r^2$) to determine the force exerted by a hydraulic cylinder ($Force = Pressure \times Area$). Precision is non-negotiable, as rounding errors in aviation can lead to structural failure or fuel exhaustion.

Aerodynamics: Lift, Drag, and Stability

Understanding the physics of flight is central to troubleshooting flight control issues and structural rigging. Mechanics must grasp Bernoulli's Principle, which explains how the pressure of a moving fluid (like air) decreases as its velocity increases, creating lift. You will also be tested on the relationship between the four forces of flight: lift, weight, thrust, and drag. The exam frequently asks about the different types of drag—parasite and induced—and how they change with airspeed. Beyond lift, you must understand aircraft stability and the three axes of flight: longitudinal, lateral, and vertical. Knowledge of how a stable aircraft returns to equilibrium after a disturbance is necessary when performing a "symmetry check" on an airframe that has experienced a hard landing or extreme turbulence.

Fluid Dynamics and Material Science Basics

Fluid dynamics in the General exam focuses on Pascal's Law, which states that pressure applied to a confined fluid is transmitted equally in all directions. This principle is the foundation of every hydraulic system, from simple brakes to complex flight control actuators. Simultaneously, you must understand material science to identify how different metals and composites react to stress. You will encounter terms like tension, compression, torsion, shear, and bending. Exam questions often probe your knowledge of the Stress-Strain Curve and the point at which a material reaches its elastic limit. Understanding these properties is crucial when inspecting for fatigue cracks or selecting the correct heat-treatment process for a structural repair. Knowing why certain aluminum alloys are susceptible to intergranular corrosion while others are not is a hallmark of an expert technician.

Aircraft Drawings, Manuals, and Documentation

Interpreting Blueprints and Schematics

The ability to read aircraft drawings and documentation is a core competency. You must be able to interpret various types of drawings, including detail drawings, assembly drawings, and installation drawings. A significant portion of the exam focuses on identifying symbols used in electrical schematics and hydraulic diagrams. You need to understand "orthographic projection," which shows an object from different views (top, front, and side) to provide a complete picture of its dimensions. Mechanics must also be proficient in reading "logic flow charts" used for troubleshooting complex systems. On the exam, you might be given a schematic and asked to identify the state of a solenoid or the path of current flow when a specific switch is closed. Accuracy here is the difference between a quick fix and hours of wasted diagnostic time.

Using Maintenance Manuals and IPCs

Modern aircraft maintenance relies on the Manufacturer’s Maintenance Manual (MMM) and the Illustrated Parts Catalog (IPC). The General exam tests your ability to navigate these documents efficiently. You must understand the ATA iSpec 2200 (formerly ATA 100) numbering system, which standardizes the organization of maintenance data across the industry. For example, knowing that Chapter 24 always refers to Electrical Power and Chapter 32 to Landing Gear allows a technician to find information quickly in a high-pressure environment. You will also be tested on the use of "minimum equipment lists" (MEL) and how they interact with the master minimum equipment list (MMEL) to determine if an aircraft can fly with certain systems inoperative. This section confirms you can find the specific torque values, fluid types, and clearance tolerances required for airworthiness.

Understanding Service Bulletins and ADs

Not all maintenance information is found in the static manuals; much of it arrives via dynamic updates. Airworthiness Directives (ADs) are legally binding instructions issued by the FAA to correct an unsafe condition. You must know how to check for AD compliance and how to document it in the aircraft records. In contrast, Service Bulletins (SBs) are issued by the manufacturer. While SBs are generally not mandatory for Part 91 operators unless incorporated into an AD, they represent critical safety improvements. The exam will challenge you to distinguish between these two and understand the "effective date" and "compliance time" (often expressed in flight hours, cycles, or calendar time). A mechanic must be able to verify that all "applicable" ADs have been addressed before signing off an annual or 100-hour inspection.

Basic Electricity and Electrical Systems

DC Circuit Theory and Ohm's Law

Basic electricity for A&P begins with a thorough understanding of Direct Current (DC) circuits. At the heart of this is Ohm’s Law, expressed by the formula $E = I \times R$ (Voltage = Current $\times$ Resistance). You must be able to calculate total resistance in both series and parallel circuits. In a series circuit, total resistance is the sum of all individual resistances ($R_t = R_1 + R_2 + ...$), whereas in a parallel circuit, the reciprocal of the total resistance is the sum of the reciprocals of the individual resistances. The exam will require you to solve for power ($P = I \times E$) and understand how wire size and length affect resistance and voltage drop. These calculations are vital when adding new equipment to an aircraft to ensure the electrical system is not overloaded and the wire can handle the current without overheating.

Electrical Measuring Instruments

To troubleshoot electrical systems, a mechanic must be proficient with a Digital Multimeter (DMM). The General exam covers the correct way to measure voltage, current, and resistance. You must know that an ammeter is always placed in series with the circuit, while a voltmeter is placed in parallel. Measuring resistance requires the circuit to be de-energized to avoid damaging the meter. Beyond the DMM, you may be tested on the use of a "megohmmeter" (Megger) for testing insulation breakdown in high-voltage circuits or wiring buried deep in the airframe. Understanding "continuity" and how to use a test light or multimeter to find an open circuit, a short to ground, or a short to another circuit is a fundamental skill that is heavily weighted in the General subject matter areas.

Wiring, Grounding, and Circuit Protection

Aircraft electrical systems rely on redundant safety features. You must understand the function of circuit breakers, fuses, and current limiters. Unlike automotive fuses, aircraft circuit breakers are designed to be "trip-free," meaning they cannot be held closed manually if a fault exists. The exam also covers wire marking, routing, and the importance of shielded wiring to prevent Electromagnetic Interference (EMI) with sensitive avionics. Grounding and bonding are equally critical; "bonding" ensures that all parts of the aircraft are at the same electrical potential, which is vital for lightning protection and reducing radio static. You will be tested on the proper use of terminal lugs, the requirements for "service loops" in wiring, and the techniques for securing wire bundles using MS-standard clamps to prevent chafing against the airframe structure.

Weight and Balance Principles and Calculations

Terms: Arm, Moment, Center of Gravity

Weight and balance is a critical safety discipline within the A&P General subject matter areas. You must master the terminology: the Datum is the imaginary vertical plane from which all horizontal distances are measured; the Arm is the horizontal distance from the datum to an item; and the Moment is the product of the weight and the arm ($Weight \times Arm = Moment$). The most critical value is the Center of Gravity (CG), which is the point at which the aircraft would balance if suspended. On the exam, you will be required to calculate the CG by dividing the "Total Moment" by the "Total Weight." Understanding where the CG limits are—and why exceeding them is dangerous—is a recurring theme. An aircraft loaded too far aft may become unstable and impossible to recover from a stall, while one loaded too far forward may lack sufficient elevator authority for landing flare.

Performing Basic Weight and Balance Computations

Exam candidates must be able to perform "Weight and Balance" computations for various scenarios, such as adding or removing equipment or shifting cargo. A common question involves calculating the new CG after a piece of radio equipment is moved from the cockpit to the tail. You will use the formula: $Weight\ shifted \div Total\ weight = Change\ in\ CG \div Distance\ weight\ shifted$. You must also understand how to "weigh" an aircraft, including the use of scales, leveling the aircraft according to the TCDS, and accounting for Tare Weight (the weight of chocks, jacks, and grounding equipment that is on the scales but not part of the aircraft). Precision is required, as these calculations are used to update the aircraft's permanent weight and balance records, which must be accurate for every flight.

Effects of Loading and Modifications

Every modification to an aircraft, whether it is the installation of a new GPS or the removal of an old interior, affects the weight and balance. Mechanics are responsible for calculating these changes to ensure the aircraft remains within its "CG Envelope." The exam will test your knowledge of how "Useful Load" (pilots, passengers, fuel, oil, and baggage) relates to "Empty Weight." You must also understand the concept of Mean Aerodynamic Chord (MAC) and how to express the CG as a percentage of MAC, a common requirement for larger transport-category aircraft. Understanding these concepts allows a mechanic to advise an owner on whether a proposed modification is feasible or if it will require the installation of "ballast" to keep the aircraft within safe operating limits.

Ground Operations, Safety, and Human Factors

Aircraft Servicing and Safety Procedures

Ground operations are where many accidents occur, making safety a high-priority exam topic. You must be familiar with the procedures for "towing" an aircraft, including the use of a tow bar and the necessity of having a person in the cockpit to operate the brakes. Fueling safety is another major area; you must know the requirements for grounding the fuel truck to the aircraft and the aircraft to the earth to prevent static discharge. The exam covers the identification of different fuel types (e.g., Avgas 100LL is blue, Jet-A is clear/straw) and the consequences of "misfueling." Additionally, you must understand the procedures for starting and taxiing aircraft, including the use of standard hand signals and the precautions for avoiding "foreign object damage" (FOD) to engines and tires.

Hazardous Materials Handling

Mechanics work with various chemicals, including hydraulic fluids (like Skydrol), solvents, and composite resins. The General exam tests your knowledge of Safety Data Sheets (SDS) and the proper handling and disposal of hazardous materials. You must understand the specific risks associated with different fluids; for example, phosphate-ester based hydraulic fluids are fire-resistant but can cause severe skin and eye irritation. Knowledge of "Oxygen System" safety is also vital, particularly the prohibition of using oil or grease near oxygen components, which can cause spontaneous combustion. This section ensures that technicians can protect themselves, their colleagues, and the environment from the chemical hazards inherent in aviation maintenance.

Human Factors in Maintenance (Dirty Dozen)

The FAA recognizes that human error is a factor in the vast majority of aviation accidents. The General curriculum includes a study of Human Factors, specifically the "Dirty Dozen"—twelve common causes of maintenance errors, such as lack of communication, complacency, and stress. You will be tested on how to mitigate these risks through the use of checklists, proper lighting, and "assertiveness" when safety is at stake. Understanding the "PEAR" model (People, Environment, Actions, Resources) helps technicians analyze the workplace for potential failure points. By integrating human factors into the General exam, the FAA aims to foster a culture of safety where mechanics are as aware of their own psychological and physiological limitations as they are of the mechanical limits of the aircraft they maintain.