Part-66 Module 1 cheat sheet

Order of operations: evaluate brackets, then indices/powers, then multiplication and division left to right, then addition and subtraction left to right.

Pythagoras: in a right triangle, hypotenuse squared equals the sum of the squares of the other two sides (a² + b² = c²).

Sine rule: a/sin A = b/sin B = c/sin C, used when one side and its opposite angle are known.

Cosine rule: c² = a² + b² − 2ab·cos C, used when two sides and the included angle are known.

Area of a circle = πr²; circumference = 2πr; volume of a cylinder = πr²h.

Common logarithm: log(ab) = log a + log b; log(a/b) = log a − log b; log(aⁿ) = n·log a.

Convert degrees to radians by multiplying by π/180; one full revolution = 2π radians = 360°.

Percentage change = (new value − old value) / old value × 100, expressed with sign to show increase or decrease.

Newton's second law: force = mass × acceleration (F = ma); weight = mass × gravitational acceleration (W = mg).

Kinetic energy = ½mv²; potential energy near Earth's surface = mgh; both measured in joules.

Work = force × distance moved in the direction of the force; power = work done per unit time (P = W/t).

Pressure = force / area, measured in pascals (1 Pa = 1 N/m²); in a fluid, pressure increases with depth.

Density = mass / volume; an object floats in a fluid if its average density is less than the fluid's density.

Moment of a force = force × perpendicular distance from the pivot; for equilibrium, clockwise moments equal anticlockwise moments.

Speed of sound in air near sea level is approximately 340 m/s and increases with temperature.

Heat transfer occurs by conduction (solids), convection (fluids) and radiation (no medium required).

Ohm's law: V = IR; power P = VI = I²R = V²/R.

Series circuit: resistances add (R = R₁ + R₂ + …); current is the same throughout; voltages sum to the supply.

Parallel circuit: 1/R = 1/R₁ + 1/R₂ + …; voltage is the same across each branch; branch currents sum to total current.

Kirchhoff's current law: sum of currents entering a node equals sum leaving; voltage law: sum of emfs equals sum of potential drops around a loop.

Capacitance in farads: C = Q/V; capacitors in parallel add; in series the reciprocals add.

Inductive reactance X_L = 2πfL; capacitive reactance X_C = 1/(2πfC); both in ohms.

Impedance in a series RLC circuit: Z = √(R² + (X_L − X_C)²); at resonance X_L = X_C and Z = R.

Three-phase star connection: line voltage = √3 × phase voltage; line current equals phase current.

A diode conducts when forward biased above its forward voltage drop (about 0.7 V for silicon, 0.3 V for germanium).

A Zener diode is operated in reverse breakdown to provide a stable reference or clamp voltage.

NPN transistor: current-controlled device; collector current ≈ β × base current; base-emitter junction must be forward biased to conduct.

Operational amplifier ideal properties: infinite open-loop gain, infinite input impedance, zero output impedance.

Inverting amplifier gain = −R_f/R_in; non-inverting amplifier gain = 1 + R_f/R_in.

A rectifier converts AC to DC; a full-wave bridge uses four diodes and conducts on both half-cycles.

A filter capacitor across a rectifier output smooths ripple; larger capacitance or higher load resistance reduces ripple.

Light-emitting diode forward voltage depends on colour/material; a series resistor limits the forward current.

Binary to decimal: sum each bit multiplied by its positional power of 2; hexadecimal uses digits 0–9 and A–F for values 10–15.

Two's complement represents negative numbers; the most significant bit is the sign bit; negate by inverting all bits and adding one.

Logic gates: AND outputs 1 only if all inputs are 1; OR outputs 1 if any input is 1; XOR outputs 1 if inputs differ.

De Morgan's theorems: NOT(A AND B) = (NOT A) OR (NOT B); NOT(A OR B) = (NOT A) AND (NOT B).

A flip-flop stores one bit; a latch is level-sensitive while a flip-flop is edge-triggered.

A multiplexer selects one of several inputs onto a single output; a demultiplexer reverses this.

ARINC 429 is a point-to-point serial bus using 32-bit words; ARINC 629 and AFDX support multi-transmitter architectures.

A data bus carries digital information between line-replaceable units; the display system converts bus data into symbology for the flight deck.

Aluminium alloys are classified by temper designation: O annealed, H strain-hardened, T solution heat-treated, W quenched and aged.

2024 aluminium alloy has high strength but lower corrosion resistance than 6061; 7075 has high strength with zinc as the main alloying element.

A rivet's grip length must match the combined thickness of the parts being joined; rivet diameter is typically about three times the sheet thickness.

Thread pitch is the distance between corresponding points on adjacent threads; a finer pitch gives greater resistance to loosening.

AN bolts are identified by dash numbers giving diameter and length in sixteenths of an inch; a letter suffix indicates the drilling of the shank for safety wire.

Aircraft control cables are made of preformed stainless or carbon steel; turnbuckles adjust tension and are secured with safety wire or clips.

Corrosion types include galvanic (dissimilar metals), stress (combined stress and corrosive environment) and intergranular (along grain boundaries).

A bearing's identification number indicates its type, bore size and sealing arrangement; sealed bearings retain factory lubricant.

Torque values are applied with a calibrated wrench; the torque is measured at the fastener unless a specified procedure states otherwise.

Safetying methods include lockwire (twist direction must pull the fastener tight), cotter pins, self-locking nuts and tab washers.

A torque wrench must be calibrated at intervals specified by the approved maintenance organisation; calibration records are retained.

Foreign object damage (FOD) prevention requires tool control, inspection of intakes and engines, and accountability of all tools.

Aircraft jacking requires the aircraft to be on level ground, with jacks rated for the load and the centre of gravity within limits.

A functional check verifies that a system operates within specified limits; an operational check verifies it functions as intended without measurement.

Corrosion inspection includes visual examination, eddy current, ultrasonic and dye penetrant methods depending on material and access.

Maintenance records must include the work performed, date, identity of the certifying person and reference to approved data.

Bernoulli's principle: in steady flow, an increase in fluid velocity produces a decrease in static pressure along a streamline.

Lift = ½ρV²SC_L; drag = ½ρV²SC_D; both increase with the square of airspeed.

Angle of attack is the angle between the wing chord line and the relative airflow; the critical angle is where lift is maximum before stall.

Induced drag decreases with increasing airspeed and increases with increasing lift coefficient (and therefore with load factor).

Parasite drag increases with the square of airspeed; total drag is the sum of induced and parasite drag and is minimum at the speed where they are equal.

The centre of pressure moves forward as angle of attack increases up to the stall.

Aspect ratio = span² / wing area; higher aspect ratio reduces induced drag.

Mach number = true airspeed / local speed of sound; compressibility effects become significant above the critical Mach number.

The SHELL model describes interaction between software, hardware, environment and liveware (the human); mismatches at interfaces produce error.

The 'dirty dozen' includes fatigue, complacency, distraction, pressure, stress, lack of communication, lack of resources, lack of teamwork, lack of knowledge, lack of assertiveness, norms and lack of awareness.

Hypoxia symptoms include euphoria, impaired judgement, cyanosis and headache; time of useful consciousness decreases with altitude.

Circadian rhythm disruption from shift work and time-zone crossing reduces alertness; rest periods and controlled napping mitigate it.

The 'Swiss cheese' model describes how latent conditions and active failures align to breach defences.

Vision at night relies on rods (low acuity, poor colour discrimination); scanning should use off-centre viewing to exploit the fovea's blind spot.

Noise above about 85 dB can cause hearing damage; hearing protection and exposure limits are specified in the maintenance environment.

A just culture distinguishes between human error and reckless behaviour when determining the response to an occurrence.

Part-66 defines the aircraft maintenance licence categories A, B1, B2, B3 and C, and the basic knowledge requirements for each.

Part-145 approved maintenance organisations must have a quality system, nominated personnel and procedures acceptable to the competent authority.

A Certificate of Release to Service (CRS) is issued after maintenance and certifies that the work has been carried out in accordance with approved data.

Part-M and Part-ML cover continuing airworthiness management; Part-145 covers maintenance organisations; Part-66 covers licensing.

Maintenance records must be retained for the period specified by the regulation; the operator or owner is responsible for retaining them.

An Airworthiness Directive is mandatory and must be complied with within the stated timeframe; it is issued by the state of design and adopted by the state of registry.

A Supplemental Type Certificate is required for a major modification not covered by the type certificate.

EASA Part-66 basic knowledge examinations require a pass mark of 75% for each module.

Primary flight controls are ailerons (roll), elevators (pitch) and rudder (yaw); secondary controls include flaps, slats, spoilers and trim.

A hydraulic system typically uses a reservoir, pump, pressure relief valve, accumulator, filter and selector valves; accumulator smooths pressure fluctuations.

A pressurisation system maintains cabin altitude and differential pressure; the outflow valve modulates cabin pressure.

Bleed air is taken from the engine compressor stages and used for air conditioning, pressurisation and anti-icing.

Fuel tanks may be integral (wet wing), bladder or rigid; venting prevents overpressure and allows fuel to expand.

A landing gear's oleo strut uses compressed nitrogen and hydraulic fluid to absorb landing loads; servicing requires correct gas pressure and fluid level.

Anti-icing uses hot bleed air on the leading edges; de-icing uses pneumatic boots or electrical heating.

A fire detection system in the engine uses continuous loop or spot detectors; the fire extinguisher system discharges into the protected zone.

A helicopter rotor produces lift and thrust; the rotor disc is the area swept by the blades.

Induced velocity through the rotor disc is highest in hover and decreases in forward flight as translational lift develops.

Dissymmetry of lift arises from advancing and retreating blades; flapping and blade pitch changes equalise lift across the disc.

Translational lift occurs above approximately 10–20 knots as the rotor moves out of its own downwash.

Tail rotor thrust counteracts main rotor torque; loss of tail rotor effectiveness can cause uncontrolled yaw.

Autorotation is a descent with the rotor driven by upward airflow; the pilot controls rotor RPM with collective pitch.

Ground resonance is a self-excited oscillation of the rotor and fuselage on the ground; correct oleo damping and rotor balance prevent it.

A helicopter's mast bumping can occur with low rotor thrust in low-g conditions; main rotor flapping limits must be respected.

Aircraft jacking requires the aircraft to be on level ground, with jacks rated for the load and the centre of gravity within limits.

A functional check verifies that a system operates within specified limits; an operational check verifies it functions as intended without measurement.

Corrosion inspection includes visual examination, eddy current, ultrasonic and dye penetrant methods depending on material and access.

Maintenance records must include the work performed, date, identity of the certifying person and reference to approved data.

Tool control and FOD prevention require accountability of all tools before and after maintenance.

Safety wire must be installed so that the twist pulls the fastener in the tightening direction.

A torque wrench must be calibrated at intervals specified by the approved maintenance organisation.

Aircraft weighing determines the empty weight and centre of gravity; results are recorded and used to calculate loading limits.

Part-66 defines the aircraft maintenance licence categories A, B1, B2, B3 and C and the knowledge requirements for each.

Part-145 approved maintenance organisations must have a quality system, nominated personnel and procedures acceptable to the competent authority.

A Certificate of Release to Service (CRS) certifies that maintenance has been carried out in accordance with approved data.

An Airworthiness Directive is mandatory and must be complied with within the stated timeframe.

A Supplemental Type Certificate is required for a major modification not covered by the type certificate.

Maintenance records must be retained for the period specified by the regulation; the operator or owner is responsible for retention.

EASA Part-66 basic knowledge examinations require a pass mark of 75% for each module.

Part-M and Part-ML cover continuing airworthiness management; Part-145 covers maintenance organisations.