Part-66 Module 5 cheat sheet

An EFIS installation comprises display units, symbol generators, a control panel and the attitude/air-data sources feeding them.

EICAS (Boeing) and ECAM (Airbus) replace discrete engine and system gauges with colour-coded display pages and alert messages.

Common display colour convention: red = warning, amber = caution, green = normal/active, cyan = advisory, white = labels and scales.

Electronic instruments are fed by air data computers (altitude, airspeed, Mach) and by IRS/ADIRS or AHRS (attitude, heading, track).

Redundancy is achieved with duplicated symbol generators and display units; a failed display can be switched to the remaining source.

A CRT display uses an electron gun, deflection coils and a phosphor screen; an LCD uses a backlight, polarisers and liquid crystal cells.

The PFD (EADI) presents attitude, flight director, ILS and speed/altitude; the ND (EHSI) presents heading, track, map and weather radar.

Older electronic instrument systems use ARINC 429 point-to-point links; newer architectures use ARINC 664/AFDX switched networks.

Binary place values are 1, 2, 4, 8, 16, 32...; convert to decimal by summing the weights of the bits that are set to 1.

One hexadecimal digit represents 4 bits; one octal digit represents 3 bits.

Two's complement of an n-bit number: invert every bit and add 1; the range is −2^(n−1) to +2^(n−1)−1.

BCD (8421) encodes each decimal digit separately in 4 bits, so 0010 0101 represents 25, not 37.

Gray code changes only one bit between successive values, preventing ambiguous readings from position encoders.

Decimal to binary conversion uses repeated division by 2, reading the remainders from the last to the first.

DAC/ADC resolution = Vref / 2^n, where n is the number of bits; quantisation error is ±½ LSB.

Serial-to-parallel conversion uses a shift register clocked once per incoming bit; parallel-to-serial uses a loadable shift register.

ARINC 429 word: 32 bits comprising an 8-bit label, SDI, data field, sign/status matrix and odd parity; rate 12.5 or 100 kbit/s, simplex over a twisted pair.

ARINC 629 is bi-directional, time-division multiplexed and operates at 2 Mbit/s (Boeing 777).

MIL-STD-1553B is a 1 Mbit/s command/response bus with one bus controller and up to 31 remote terminals.

ARINC 664 (AFDX) is switched full-duplex Ethernet at 100 Mbit/s using virtual links with guaranteed bandwidth (A380, B787).

CAN bus is a differential, multi-master bus with priority-based arbitration and rates up to 1 Mbit/s.

Parity detects an odd number of bit errors only; CRC detects burst errors and is used for data integrity checking.

Bus couplers isolate terminal stubs from the main bus, and bus terminators absorb energy to prevent signal reflections.

Simplex = one direction only, half duplex = both directions but not simultaneously, full duplex = both directions at once.

AND gives 1 only when all inputs are 1; OR gives 1 when any input is 1; NOT inverts a single input.

NAND and NOR are universal gates - any logic function can be built from either alone.

XOR gives 1 when the inputs differ; it is used for parity generation and for the sum output of a half adder.

De Morgan: NOT(A·B) = NOT A + NOT B, and NOT(A+B) = NOT A · NOT B.

Half adder: sum = A XOR B, carry = A AND B; a full adder additionally accepts a carry-in.

Combinational logic output depends only on present inputs; sequential logic output depends on past inputs (it has memory).

D flip-flop copies its input on the clock edge; JK toggles when J = K = 1; an SR latch has an invalid state when both inputs are 1.

Boolean expressions are simplified with Karnaugh maps by grouping adjacent 1s in groups of 1, 2, 4, 8...

The CPU contains the arithmetic logic unit, the control unit and registers; the ALU performs arithmetic and logic operations.

The address bus is unidirectional and n lines address 2^n locations; the data bus is bi-directional; the control bus carries read/write and interrupt signals.

The instruction cycle repeats fetch, decode and execute under control of the system clock.

RAM is volatile read/write; ROM is non-volatile; PROM is one-time programmable; EPROM is UV-erasable; EEPROM and flash are electrically erasable.

Flash memory is non-volatile, erased in blocks and used for loaded software and non-volatile configuration data.

Direct memory access lets a peripheral transfer data to or from memory without continuous CPU intervention.

Cache is small, fast memory between the CPU and main memory that reduces average access time.

Word length (8, 16, 32, 64 bits) defines the width of the data path and the size of values the CPU handles natively.

Integration scale: SSI under about 100 gates, MSI, LSI, and VLSI above roughly 10,000 gates per chip.

TTL is bipolar, normally 5 V, draws more current and is fast; CMOS uses MOSFETs, has very low static power, wide supply range and high noise immunity.

74-series devices are TTL-compatible logic; 40-series are CMOS; 74HC is high-speed CMOS with TTL-compatible levels.

Pin 1 of a DIP is marked by a notch or dot; pins are counted anticlockwise when the package is viewed from the top.

DIP and PGA devices may be socketed; SMD and BGA packages are surface-soldered and require reflow techniques.

A 100 nF decoupling capacitor is fitted close to each IC supply pin to shunt transient current and suppress noise.

Fan-out is the number of gate inputs one output can drive while keeping voltages within specification.

Linear ICs (op-amps, voltage regulators) process continuous signals; digital ICs process defined logic levels.

Multiplexing sends several independent signals over one transmission medium; demultiplexing recovers them at the far end.

A multiplexer with n select lines has 2^n inputs; the select code connects one chosen input to the single output.

FDM separates channels by carrier frequency; TDM separates them by recurrent time slots on the same channel.

Statistical (asynchronous) TDM allocates time slots on demand rather than permanently to each channel.

WDM multiplexes several optical wavelengths through one fibre (CWDM or DWDM).

Nyquist criterion: sampling rate must be at least twice the highest signal frequency to avoid aliasing.

PCM conversion has three steps: sampling, quantisation and encoding to a binary word.

ARINC 629 and many avionics data buses use time-division multiplexing to share the bus between terminals.

A fibre consists of core, cladding, buffer and jacket; light is guided by total internal reflection because the core index exceeds the cladding index.

Single-mode fibre has a core of about 9 µm, uses a laser source and suits long distances; multimode (50/62.5 µm) uses an LED for shorter links.

Graded-index multimode fibre reduces modal dispersion by progressively refracting rays towards the axis.

Operating windows are 850 nm, 1300 nm and 1550 nm; attenuation and loss are expressed in decibels, loss = 10 log(Pin/Pout).

Advantages: immunity to EMI and crosstalk, very high bandwidth, low weight and no spark or short-circuit hazard.

Sources are LEDs or laser diodes; detectors are PIN photodiodes or avalanche photodiodes.

Common connectors are ST, SC and LC; the link power budget equals source output minus receiver sensitivity minus connector/splice margins.

Never look into a fibre end or an unmated connector: laser light is invisible and can permanently damage the retina.

A CRT uses an electron gun, deflection yoke/coils and a phosphor-coated screen, and requires an EHT supply.

An LCD is non-emissive: a CCFL or LED backlight passes through polarisers, liquid crystal cells and colour filters.

TFT active-matrix LCDs have one thin-film transistor per pixel, giving better contrast and response than passive matrix.

OLED displays are emissive and therefore need no backlight, giving high contrast and wide viewing angle.

Resolution is quoted as pixel columns × rows; dot pitch is the physical spacing between adjacent pixels.

Brightness is measured in cd/m² (nits); contrast ratio compares full-white with full-black luminance.

Resistive touch screens respond to pressure; capacitive screens respond to a conductive finger.

ARINC 661 defines standard cockpit display symbology and the interface between display system and user applications.

ESD wrist straps contain a resistor of about 1 MΩ to bleed charge to ground safely while limiting current.

ESD damage may be latent, producing early-life failure long after the board was handled.

Sensitive devices are stored and transported in conductive or screening bags; ionisers and 40–60% relative humidity reduce charge build-up.

Handle boards by their edges and never touch connector pins or MOS gate inputs.

DO-178C is the certification standard for airborne software, with assurance levels A (catastrophic) to E (no safety effect).

Level A software requires the most rigorous verification, including MC/DC structural coverage of the code.

Software changes are controlled by part number, version and checksum/CRC verification after loading.

Only approved loading media and data may be used, and the loading is recorded in the aircraft maintenance records.

EMC means a system neither causes unacceptable interference nor is adversely affected by it; it covers emission and susceptibility.

Conducted interference travels along wires and is suppressed by filtering and decoupling; radiated interference travels as fields and is suppressed by shielding.

HIRF (high-intensity radiated fields) from radar and broadcast transmitters is addressed by DO-160 test levels and system protection design.

Bonding, grounding, shielding, filtering and twisted-pair wiring all reduce interference coupling.

Route signal and data cables away from power feeders and ignition leads to reduce crosstalk.

Ferrite beads and filters suppress high-frequency conducted noise on supply and signal lines.

Lightning induces large transients that are controlled by a low-impedance bonding network and transient suppressors.

Portable electronic devices radiate and may interfere with aircraft receivers, so their use is restricted by operating rules.

BITE monitors system health, stores fault codes and is interrogated through the MCDU or central maintenance computer.

ADIRS combines air data and inertial reference, using ring laser gyros or MEMS devices with accelerometers for attitude and heading.

Fly-by-wire replaces mechanical control runs with computers, electrical signalling and hydraulically or electrically powered actuators.

The FMS provides flight planning, performance computation, guidance and a periodically updated navigation database.

TCAS II displays intruder traffic and issues coordinated resolution advisories using transponder replies.

EGPWS combines a terrain database, radio altimeter and position data to give terrain warnings.

ACARS exchanges operational and maintenance data over VHF, HF or satellite datalink.

Modern types such as the A380 and B787 use ARINC 664/AFDX switched Ethernet as the core avionics network.