Part-66 Module 5 case studies

Part-66 Module 5 · Put your knowledge to work in context.

EASA Part-66 Module 5 - Digital Techniques / Electronic Instrument Systems - is one of the required knowledge modules in the aircraft maintenance licence (AML) syllabus for categories B1 and B2, and it is also widely used as a stand-alone digital-avionics fundamentals course. It is aimed at trainee and practising aircraft maintenance engineers, avionics technicians and students on Part-147 programmes who need to understand how modern aircraft generate, process, transport and display data. The Part-66 Module 5 case studies are 5 cases and about 3,555 words.

The 12.5 kbit/s Loop That Is Already Too Slow

A regional turboprop fleet still uses ARINC 429 low-speed links at 12.5 kbit/s. On the air-data bus the ADC transmits 38 words in one fixed repeating loop; each word is 32 bits and the transmitter uses the minimum 4-bit inter-word gap.

702 words, about 4 min 2

Three Hex Snapshots and a Confident Technician

A 12-bit two's-complement temperature channel uses an LSB of 0.0625 C and is specified for minus 55.0 C to plus 125.0 C. The raw 12-bit field can be read only as hexadecimal on the maintenance laptop.

597 words, about 3 min 3

Re-Routing a Fibre Link: Whose Margin Is It Anyway

An 850 nm multimode fibre link runs from a forward galley access point to the avionics bay. Measured data: launch power into the fibre minus 10.0 dBm; receiver minimum sensitivity minus 28.0 dBm; fibre attenuation 3.5 dB/km at 850 nm.

728 words, about 4 min 4

Cabin Lighting That Talks to the VHF Radio

After fitment of a new cabin LED lighting controller, the crew report occasional brief clicks and a wavering ident on VHF COM 1 (118-137 MHz) during taxi, and one unexplained autopilot disengagement during climb. The controller's power return is a 0.6 m wire bonded to a nearby composite panel with a single 6 mm bolt through paint; the harness to the lights runs parallel to the VHF antenna feeder for 3 m at 0.15 m spacing.

769 words, about 4 min 5

An Open Bag, a Fleece, and a Dash Number

A line engineer replaces a display unit's power supply card on the ramp. The card came in a pink anti-static bag that has been open in a tool tray for two days.

759 words, about 4 min