FAA Airframe and Powerplant (A&P) Mechanic Certificate — Advanced Study Guide

FAA Airframe and Powerplant (A&P) Mechanic Certificate — Advanced Study Guide

Credential: FAA Airframe and Powerplant (A&P) Mechanic Certificate (ratings: Airframe, Powerplant) Issuing body: Federal Aviation Administration (FAA), United States Jurisdiction: United States (federal) Level: Technician license-to-practice Prerequisites: Age 18+; read, write, speak, and understand English; qualify under one of three eligibility paths — (1) 18 months of practical experience for a single rating, or 30 months of concurrent experience for both ratings, documented under 14 CFR 65.77; (2) graduation from an FAA-approved Part 147 Aviation Maintenance Technician School; or (3) qualifying military training (JSAMTCC). Then pass the General + Airframe and/or Powerplant knowledge tests, plus oral and practical tests. Renewal: The certificate never expires, but 14 CFR 65.83 imposes a currency requirement to exercise privileges: within the preceding 24 months the mechanic must have served at least 6 months as a mechanic, as a technical supervisor of other mechanics, or in executive control of a repair station — or demonstrate ability to the Administrator.

1. Why an engineering study-guide series covers a technician certificate

The A&P is not an engineering license, but it is the gatekeeper of the continued airworthiness system that every aerospace engineer touches. Engineers write the maintenance manuals, service bulletins, and structural repair data; A&Ps decide what is "approved data" and who signs the return-to-service (RTS) statement under 14 CFR 43.13 and 43.15. If you work certification, fleet engineering, reliability, or MRO engineering, you will live in the boundary between the design data you produce and the maintenance actions an A&P is legally allowed to perform. Understanding the A&P exam content is understanding the language your maintenance-side counterparts speak.

2. Pathway: how the certificate is earned

Step 1 — Establish eligibility (Form 8610-2)

Present one of the three paths to the FAA (usually via a Flight Standards District Office or a Part 147 school's authority):

• Experience route (65.77): documented practical experience — 18 months for one rating, 30 months concurrent for both. The experience must be in the functions for which the rating is sought; "documented" means signed employer statements, not a résumé.
• Part 147 school route: graduate of an FAA-approved Aviation Maintenance Technician School (AMTS) with the prescribed curriculum (~1,900 hours total across General/Airframe/Powerplant subject areas).
• Military route: JSAMTCC-evaluated military training in the applicable specialty.

The FAA endorses FAA Form 8610-2 (Airman Certificate and/or Rating Application), which becomes the authorization to test.

Step 2 — Knowledge tests (written), at a PSI testing center

Governed by the FAA's Airman Certification Standards (ACS) and 14 CFR 65.75. Official structure per FAA publications (FAA ACS Companion Guide; Airman Knowledge Testing Matrix):

Multiple choice, single correct response. The knowledge-test report is valid 24 months: the oral and practical must be completed within that window or the written must be retaken. Fee is set by PSI (verify current pricing at psiexams.com before budgeting; knowledge tests have historically run ~$175 each).

Step 3 — Oral and practical tests (14 CFR 65.79), by a Designated Mechanic Examiner (DME)

The DME samples the same ACS subject areas in an oral interview and assigns hands-on practical tasks (projects): e.g., torque a bolted joint to spec, safety-wire a turnbuckle, perform a compression check, troubleshoot an electrical circuit, remove/install a component, complete a weight-and-balance revision entry. Oral and practical are typically a 6–10 hour event; each of the two must be passed (a failure on one does not invalidate a pass on the other, but any failed subject area must be retested). DME fees vary widely (~$600–$1,500 reported); confirm locally.

Step 4 — Stay current

Hold the certificate (no expiration), satisfy 65.83 currency, and log what you touch: an IA (Inspection Authorization, 14 CFR 65.91) is the natural upgrade after three years of A&P experience — it authorizes annual inspections and major repair/alteration approvals.

3. Knowledge domains

3a. General (AMG) — the foundation both ratings share

• Mathematics and science: basic algebra, ratios, proportions, areas/volumes, metric/English conversion, physics of levers, moments, pressure/force, temperature scales.
• Aircraft drawings: orthographic projections, section views, dimensions and tolerances, title blocks, revision control.
• Weight and balance: the safety-critical computation. The theory: an aircraft is in equilibrium when moments about the datum balance; center of gravity must lie within the certified envelope or the aircraft is not airworthy — an A&P may not sign RTS on a misloaded configuration. See §4 for the equations.
• Physics and basic aerodynamics: Bernoulli vs. Newtonian lift explanations (the exam expects the standard treatment: pressure differential plus downwash momentum), the four forces, angle of attack and stall, parasite vs. induced drag.
• Maintenance publications, forms, and records (14 CFR Part 43): what counts as "approved data" (type certificate data sheets, ADs, manufacturer's manuals, FAA-approved repair data) vs. "acceptable data" (AC 43.13-1B/2B, industry practice). The pivotal distinction: major vs. minor repairs and alterations — major items require approved data and Form 337; minor items require only acceptable data.
• Basic electricity: Ohm's law, series/parallel, AC/DC, batteries, magnetism, measuring instruments.
• Materials and processes: hardware identification (AN/MS/NAS bolt markings, thread classes), safety wiring, torque, corrosion identification and treatment, nondestructive inspection basics.
• Ground operation and servicing: starting, taxi, fueling, tiedowns, jacking.

3b. Airframe (AMA) — structures, systems, and the airframe half of the airplane

• Sheet-metal and nonmetallic structures: rivet selection (protruding vs. countersunk), rivet spacing rules (edge distance ≥ 2D, spacing 3D–4D pitch for single rows — these are the AC 43.13-1B canonical minimums), bend radius/allowance, composite layup and repair curing, wood and fabric covering.
• Flight controls: primary/secondary, cable tensioning, turnbuckle safetying, rigging checks, trim systems, fly-by-wire interfaces.
• Hydraulic and pneumatic systems: open vs. closed center systems, actuators, accumulators, reservoirs pressurization, fluid types (phosphate-ester Skydrol vs. mineral MIL-H-5606/83282 — never mix them; exam trap).
• Landing gear: oleo struts (air-oil), shock absorption, brakes (multiple-disc), anti-skid, retraction mechanisms and emergency extension.
• Environmental, pressurization, oxygen: pressurization schedules, outflow valves, oxygen system types and servicing precautions.
• Fuel, fire protection, de-icing: fuel system types, fire detection/extinguishing (halon replacements), thermal and pneumatic de-icing.
• Electrical and instruments: generators/alternators, bus architecture, instrument types (pitot-static, gyroscopic), communication/navigation basics.

3c. Powerplant (AMP) — reciprocating and turbine engines

• Reciprocating engine theory: the Otto (constant-volume) cycle — intake, compression, power, exhaust. Why the exam cares: detonation vs. preignition (detonation = uncontrolled explosion after normal ignition, preignition = ignition before the spark) are the two classic engine-destruction modes, and every power-setting, mixture, and cooling question hangs on them.
• Engine performance parameters: compression ratio, manifold absolute pressure (MAP), brake mean effective pressure (BMEP), specific fuel consumption. See §4 for the BMEP derivation — it is the single most useful unifying number in reciprocating engines: the theoretical constant pressure that would produce the measured brake power.
• Induction, fuel metering, ignition: carburetors vs. fuel injection; magneto theory (E-gap, the point of maximum flux change where the breaker should open — a perennial oral-exam favorite); spark plug heat ranges.
• Propellers: fixed-pitch, constant-speed (governor + pitch-change mechanism), feathering, beta/reverse range; blade angle vs. angle of attack; critical engine considerations.
• Turbine engine theory: the Brayton (constant-pressure) cycle — compression, combustion, expansion. Sections: compressor (axial/centrifugal), combustor (can/annular), turbine, exhaust. Starting, bleed air, FOD/erosion, EGT/TIT limits, compressor stall vs. surge (stall = local blade separation, surge = full-annulus flow reversal — know the difference).
• Engine systems: lubrication (wet vs. dry sump), cooling (air/oil), exhaust and turbocharging/supercharging, engine instruments, starting systems.

4. Key equations (with units and assumptions)

Weight and balance. Moment = weight × arm (in·lb or ft·lb, consistent units). CG location: CG = (Σ Wᵢ · armᵢ) / (Σ Wᵢ) , in inches (or mm) from datum. Assumptions: weights act at their CGs; arms measured from a fixed datum; ballast is a last resort, not a loading strategy. Empty-weight CG, useful load, and useful-load CG shift all derive from the same formula.

Ohm's law and power. V = I·R (volts), P = V·I = I²·R (watts). Series: R_total = ΣR; parallel: 1/R_total = Σ(1/Rᵢ). Assumption: resistive DC or resistive AC component; for AC circuits with reactance, use impedance Z.

Lift. L = ½·ρ·v²·S·CL, L in N (ρ in kg/m³, v in m/s, S in m²). Stall speed follows: v_stall = √(2W / (ρ·S·CL_max)).

Hydraulics. F = P·A (lbf = psi × in²). Pressure is transmitted undiminished (Pascal); flow rate determines actuator speed: v = Q/A (Q in in³/s, A in in²). Assumption: incompressible fluid, no leakage.

Compression ratio. r = (V_d + V_c) / V_c, where V_d = displacement volume, V_c = clearance volume. Dimensionless.

Otto-cycle ideal thermal efficiency. η = 1 − 1/r^(k−1), k = c_p/c_v ≈ 1.4 for air. Assumption: air-standard cycle, isentropic compression/expansion, constant-volume heat addition. Real engines run ~25–30% brake thermal efficiency; the gap is friction, pumping, incomplete combustion, heat loss.

Brayton-cycle ideal thermal efficiency. η = 1 − (1/r_p)^((k−1)/k), r_p = pressure ratio. Assumption: air-standard, isentropic compression/expansion, constant-pressure heat addition.

Brake mean effective pressure (reciprocating, 4-stroke). Derivation: brake power BHP = (work per power stroke × power strokes per minute) / 33,000 ft·lbf/min per hp. Work per power stroke = BMEP × V_d (BMEP in psi × in³ = in·lbf). For a 4-stroke, one power stroke per cylinder per 2 revolutions, so power strokes/min = N/2 per cylinder. Summing all cylinders: BHP = BMEP(psi) × V_d_total(in³) × N(rpm) / (2 × 12 × 33,000) — the 12 converts in·lbf to ft·lbf. So: BMEP (psi) = (2 × 12 × 33,000 × BHP) / (V_d × N). Assumption: steady rated power, standard units (hp, in³, rpm).

Torque. T = F·r (lbf·ft or N·m). Bolt torque values are always specified dry unless the data says lubricated — lubricating a dry-spec joint over-tensions it (exam/oral trap).

Refrigeration/cooling sanity check. Heat rejected ≈ fuel energy − brake power. For a 200-hp engine at 30% efficiency burning ~20 gal/hr, roughly 470 hp of heat must be rejected by cooling air and oil — this is why cooling baffles and cowl flaps are not cosmetic.

5. Worked examples

Example 1 — Weight and balance (aircraft-level, exam staple). An aircraft has an empty weight of 1,800 lb at arm 82.0 in. Load: pilot 180 lb at arm 75.0 in, fuel 240 lb (40 gal × 6 lb/gal) at arm 84.0 in, baggage 60 lb at arm 110.0 in.

• Empty moment: 1,800 × 82.0 = 147,600 in·lb
• Pilot moment: 180 × 75.0 = 13,500 in·lb
• Fuel moment: 240 × 84.0 = 20,160 in·lb
• Baggage moment: 60 × 110.0 = 6,600 in·lb
• Totals: weight = 2,280 lb; moment = 187,860 in·lb
• CG = 187,860 / 2,280 = 82.39 in. Then check 82.39 in. against the type certificate data sheet CG envelope at 2,280 lb gross weight. The mechanic's job: if it falls outside, the aircraft is not airworthy and no RTS signature is legal. Fuel burn during flight moves CG (usually forward as wing fuel burns aft of the datum or vice versa) — always check the landing CG too.

Example 2 — Hydraulic actuator force. A landing-gear actuator has a piston diameter of 3.0 in. and system pressure of 3,000 psi.

• Piston area: A = π·d²/4 = π × 9/4 = 7.069 in²
• Force: F = P·A = 3,000 × 7.069 = 21,207 lbf ≈ 21,200 lbf. Extension force exceeds retraction force for the same cylinder because the rod reduces effective area on the retract side — a favorite oral question ("why does the gear retract slower/weaker?").

Example 3 — Rivet shear capacity. A single-row lap joint carries 4,800 lbf in shear using AD4 (1/8-in.) rivets, each rated 389 lbf in single shear (MS20470 values are data-book numbers; the method is what matters).

• Rivets needed: 4,800 / 389 = 12.34 → 13 rivets minimum.
• Edge distance ≥ 2D = 0.25 in.; transverse pitch 3D–4D. Real joint design adds bearing and tear-out checks per AC 43.13-1B; the exam tests the shear division and the 2D/3D rules.

Example 4 — BMEP from rated power. A 4-stroke engine displaces 360 in³ and produces 180 BHP at 2,700 rpm.

• BMEP = (2 × 12 × 33,000 × 180) / (360 × 2,700) = 142,560,000 / 972,000 = 146.7 psi. Typical normally-aspirated aircraft engines run 120–160 psi BMEP at rated power — the number immediately tells you this engine is in the normal band, and an engine showing 100 psi at rated rpm is sick.

Example 5 — Electrical: parallel circuit current draw. Two landing-light bulbs (each 10 A at 28 V) wired in parallel plus a 5 A pitot-heat element, all on one bus.

• Total current: 10 + 10 + 5 = 25 A (parallel branches add).
• Power: P = 28 × 25 = 700 W. Circuit protection must be sized above continuous draw (typically 125–150% of continuous load for the wire/breaker combination) — never upsize a breaker without verifying wire gauge per the manufacturer's data.

6. Standards and regulations cross-reference

• 14 CFR Part 43 (Maintenance, Preventive Maintenance, Rebuilding, and Alteration): the mechanic's home regulation. Know 43.13 (performance rules — work must follow methods prescribed by the manufacturer or acceptable to the Administrator), 43.15 (additional performance rules), 43.11/43.16 (airworthiness directive compliance), Appendix A (major vs. minor definitions), Appendix D (annual/100-hour inspection scope). The exam and orals live here.
• 14 CFR Part 65 Subpart D (Mechanics): privileges and limitations — 65.81 (general privileges/limitations), 65.85 (airframe rating), 65.87 (powerplant rating), 65.83 (currency). An A&P may not supervise maintenance he/she is not qualified to perform, and may not approve major repairs without approved data.
• 14 CFR Part 65 Subpart E (Repairmen) and 65.91 (Inspection Authorization): know what an IA can do that an A&P cannot (annual inspections, major repair/alteration approvals) — orals probe this boundary.
• AC 43.13-1B / -2B (Acceptable Methods, Techniques, and Practices): "acceptable data" for minor repairs; the default answer when no manufacturer data exists.
• 14 CFR Part 21: type certificate, STC, PMA, TSO — the source of approved data. A mechanic installing an STC kit must verify the STC applies to the serial number and that the airplane's configuration matches the STC's approved model list.
• 14 CFR Part 25 (and Part 23/27/29): airworthiness standards — engineers design to these; mechanics encounter them as the basis for Instructions for Continued Airworthiness and Airworthiness Limitations (e.g., 25.1529, 25.571 damage-tolerance inspections).
• Human factors (MRM): Dirty Dozen; the oral exam increasingly probes human-factors awareness (fatigue, complacency, distraction).
• AS9100 context: repair stations and OEM MROs run AS9100/9110 quality systems; nonconformances, FOD control, and calibration traceability are the quality engineer's side of the same work.

7. Pitfalls, trap patterns, and exam strategy

Conceptual traps the oral examiner loves:

1. Approved vs. acceptable data. "The manual is silent — can you use AC 43.13?" Only for minor repairs/alterations. Major = approved data + Form 337, no exceptions.
2. Return-to-service authority. Only the person who performed or supervised the work (or an authorized repair-station/inspection person) signs RTS. You cannot sign off another shop's undocumented work.
3. Torque: dry vs. wet. Standard torque tables are dry; oil or anti-seize on the threads reduces friction and the same wrench reading produces higher bolt tension. Lubricating without a wet spec is over-torquing.
4. Magneto E-gap and timing. The oral probes why timing matters (internal vs. engine timing), not just the numbers.
5. Skydrol vs. 5606. Mixing phosphate-ester and mineral hydraulic fluids destroys seals. Identify fluid by the reservoir placard, not by color memory.
6. Compression checks. Differential compression: listen where the air escapes (intake, exhaust, crankcase breather, adjacent cylinder) to diagnose valves vs. rings — the oral wants the diagnosis logic, not the 60/80 number.
7. Weight and balance after repairs. Any repair or alteration that changes empty weight or CG requires a revised weight-and-balance record; weighing is required when the change is significant (AC 43.13 guidance).

Knowledge-test strategy: 60/100/100 questions at 70% pass means you can miss 18/30/30 and still pass — but the written score feeds the oral: the DME re-tests any coded subject area you missed. Study to understand, not to scrape 70%. Budget ~1 minute per question; flag calculation questions and return to them. No reference materials are provided or allowed on the written (it is closed-book), so memorize the canonical tables: standard atmosphere values, bolt identification markings, wire-gauge ampacity, common torque specs.

Oral/practical strategy: answer the question asked, then stop — volunteering extra systems invites extra questions. For practical projects: read the entire task card first, stage tools and data, announce what you are checking (examiners score methodical behavior), and never force a fastener or guess a torque value.

8. Practice problems (with answers)

1. Aircraft empty weight 2,050 lb at arm 78.4 in. Add: front seats 340 lb at 70.0 in., fuel 300 lb at 80.0 in., baggage 100 lb at 115.0 in. Compute total weight, total moment, and CG. Answer: weight 2,790 lb; moment 220,740 in·lb; CG = 79.1 in.
2. A brake actuator with a 2.5-in. bore sees 1,500 psi. What clamping force? If the master cylinder bore is 0.75 in., what force at the master cylinder produces the same pressure (ignore friction)? Answer: actuator area 4.909 in² → 7,363 lbf; master-cylinder force = 1,500 × 0.4418 = 663 lbf.
3. A 4-stroke engine displaces 520 in³, rated 300 BHP at 2,700 rpm. Compute BMEP. Is this plausible for a normally aspirated engine? Answer: BMEP = (2×12×33,000×300)/(520×2,700) = 169.2 psi — high for normally aspirated; suggests turbocharging/supercharging or check the numbers.
4. A 28-V bus feeds three parallel loads drawing 8 A, 12 A, and 6 A. Total power? If the circuit breaker is 30 A, is it correctly sized assuming the continuous-load rule (breaker ≥ 125% of continuous current)? Answer: 26 A total → 728 W; 125% × 26 = 32.5 A > 30 A breaker — undersized; needs the next standard size with wire-gauge verification.
5. List, from memory, the five elements of a major repair requiring Form 337 documentation vs. a minor repair entry, and state which regulation defines major/minor. Answer: major = per 14 CFR Part 43 Appendix A; requires approved data and FAA Form 337 filed; minor = acceptable data, logbook entry only.
6. During a differential compression check, air is heard escaping from the exhaust pipe with the piston at TDC on the compression stroke. Diagnose, and state the corrective maintenance category. Answer: leaking exhaust valve (valve/seat/guides); valve work is typically a major repair of the engine — requires approved data (manufacturer overhaul manual) and is signed off accordingly.

Exam facts (question counts, durations, pass scores) verified against FAA publications via web search 2026-09-30; fees and DME pricing vary — confirm locally. Knowledge-test validity and eligibility per 14 CFR Part 65. Original examples and problems are the author's.

Original ETS reference writing, verified against public sources on 2026-09-30. Thin sourcing is flagged inline. Not legal advice — confirm current editions with the issuing body.