100+ Free Module 5 Digital Techniques Practice Questions

Explanation: The Symbol Generator (SG) or Display Electronic Unit (DEU) receives raw data from aircraft sensors and avionics computers via data buses (such as ARINC 429) or analog inputs, processes the data, and generates the graphic display symbology (deflection, raster, or digital video drive signals) rendered on the PFD and ND screens.

Explanation: Active Matrix LCDs (AMLCDs) utilize a matrix of Thin Film Transistors (TFTs) integrated into the glass substrate. Each subpixel has its own transistor acting as a switch to maintain the liquid crystal orientation and voltage charge until the next refresh frame, providing superior brightness, high contrast, wide viewing angle, and zero flicker required for modern cockpit displays.

Explanation: The Airbus ECAM Engine/Warning Display (EWD, upper/left display) continuously shows critical primary engine indications (N1 or EPR, EGT, N2/N3), slat and flap position indicators, gross weight, and the Memo/Warning/Caution text area for crew alerting.

Explanation: In accordance with standard avionics color coding (AMC 25.1322 / CS-25), RED is strictly reserved for Warning messages indicating an emergency condition requiring immediate crew awareness and immediate corrective action. Amber represents Caution (immediate awareness, subsequent action), Cyan/White represents Status/Memo, and Green represents normal/safe operation.

Explanation: The Combiner glass (or combiner optic) is a semi-reflective, highly transparent optical element mounted in the pilot's forward field of view. It reflects the projected, collimated symbology from the HUD Overhead Unit into the pilot's eyes while transmitting ambient light from the outside visual scene, allowing simultaneous viewing of flight symbology and external environment.

Explanation: Collimating optics (lens array or curved combiner glass) refract or reflect light rays emitted from the display source so that they emerge as parallel rays. This focuses the flight symbology optical image at infinity, enabling the pilot to view display symbols and real-world distant targets simultaneously without re-accommodating their eyes.

Explanation: EFIS architectures include standby or auxiliary Symbol Generators (e.g., SG 3 / AUX SG). If SG 1 fails, selecting the EFIS Display Switching / Reconfiguration switch on the switching panel routes the output of the operative standby Symbol Generator to the pilot's PFD/ND screens.

Explanation: Modern hybrid CRT instrument displays combine stroke (calligraphic) and raster writing. Stroke writing directly traces out line vectors to create crisp, high-brightness flight symbology (pitch ladder, horizon line, airspeed tape), while raster scanning sweeps the beam horizontally in lines to build up shaded background images (such as weather radar or terrain maps).

Explanation: CRTs act as large high-voltage capacitors (formed by the inner and outer conductive Aquadag coatings separated by glass). The extra-high tension (EHT) anode voltage (typically 12 kV to 25 kV) can retain a lethal capacitive charge long after power is disconnected. Technicians must discharge the CRT anode to chassis ground using an insulated grounding probe before handling.

Explanation: The Primary Flight Display (PFD) replaces traditional T-arrangement mechanical flight instruments (ADI, HSI, altimeter, ASI, VSI) by consolidating primary flight parameter indications—attitude, IAS, barometric altitude, vertical speed, heading, and Flight Mode Annunciator (FMA) statuses—into a comprehensive central display.