EADI-84 Electronic Attitude Director Indicator

The EADI-84 provides the primary electronic attitude and flight-director display. It shows aircraft pitch and bank attitude against an artificial horizon, together with the flight director, navigation deviation information, radio altitude, decision height, and autopilot status.

The EADI-84 also provides mode annunciations for the active lateral and vertical flight-control modes. In the projectmax implementation, these include HDG, VOR1, LOC1, FMS1, GS, ALTS, and VS, together with AP and YD status indications.

Attitude Display

The center of the EADI contains the aircraft attitude display.

The blue and brown background represents the sky and ground and moves with the aircraft’s pitch and bank attitude. A white horizon line separates the two areas.

The pitch ladder provides pitch references from −90° to +90°, with markings every 5 degrees and larger markings every 10 degrees. The aircraft symbol remains fixed at the center of the display while the attitude background and pitch ladder move around it.

The EADI also includes a fixed roll reference consisting of:

• 10°, 20°, 30°, 45°, and 60° bank marks
• A fixed center reference

The aircraft’s current bank is shown against this fixed scale.

Flight Director

The EADI displays the aircraft’s Flight Director (FD) commands when the Flight Director is active.

The projectmax EFD-84 supports two Flight Director presentation styles:

• V-bar
• Crosspointer

The selected presentation is determined by the EADI configuration.

The Flight Director provides separate pitch and roll commands. The commands are shown relative to the aircraft’s current attitude, allowing the pilot to maneuver the aircraft until the Flight Director indication is centered with the aircraft symbol. Flight Director commands are limited to ±15° on the display.

When the Flight Director is not active, the FD indication is removed from the display.

Lateral Navigation Deviation

The lower portion of the EADI contains the lateral deviation display.

Depending on the selected navigation source, the display can represent:

• LOC — Localizer
• VOR
• FMS
• RNV
• TCN — TACAN

The navigation source is automatically determined from the selected navigation system and approach information.

Different symbols are used for different navigation sources. VOR/RNV uses an octagonal symbol, FMS uses a cross-shaped symbol, and TACAN uses a circular cross symbol.

The deviation indicator moves left or right according to the selected navigation signal.

Glideslope Deviation

The right side of the EADI contains the vertical deviation indicator.

When a valid glideslope is available, the display provides a four-dot scale with a center reference and a moving glideslope pointer. The pointer moves according to the aircraft’s glideslope deviation — above, on, or below the glideslope.

A G/S warning indication is shown when a glideslope is expected but the signal is not valid.

Radio Altitude and Decision Height

The lower-right portion of the EADI displays radio altitude (RA) and decision height (DH).

Radio altitude is displayed when the aircraft is within 2,500 ft AGL. The value is displayed in feet, and its resolution changes with altitude:

• Below 1,000 ft — displayed in 10 ft increments
• Above 1,000 ft — displayed in 50 ft increments

The DH value is set using the DH knob on the DSP-84 control panel. The selected DH can be displayed for a short period after the setting is changed, even when the aircraft is above the radio-altimeter operating range.

When the selected decision height is reached, the EADI provides a DH annunciation.

If the radio altimeter system fails, an RA warning is displayed instead of the normal radio-altitude information.

Flight Control System Annunciations

The EADI provides basic status information for the automatic flight-control system.

Lateral modes: HDG, VOR1, LOC1, FMS1

Vertical modes: GS, ALTS, VS

A newly selected mode is temporarily displayed in white before changing to the normal green indication.

EADI Failure and Startup

When electrical power is initially applied, the EADI performs a simulated startup sequence.

The startup sequence lasts approximately 15–25 seconds and displays the aircraft symbol, pitch-reference boxes, and startup flags while the rest of the display remains hidden.

The startup sequence can display the following system flags:

• ATT
• DPU FAIL
• FD
• LOC
• GS
• RA
• DSP
• XDATA
• AOA

If the attitude source becomes invalid during operation, the attitude background and pitch information are removed and an ATT warning is displayed.

Symbology

Annunciators

Failure Flags