EFIS Control Panel and Barometric Reference

The reconfiguration article covered how the EIS is put back together when it breaks. This article covers how each pilot commands their own two screens in normal operation — through the EFIS control panel (EFIS CP), part of the left and right wings of the FCU, identical for captain and first officer. Its single most critical knob is the barometric reference: set it wrong and the altimeter shifts bodily — at best an ATC call, at worst a CFIT. So although the panel is a handful of buttons, the real weight is that one knob, which earns its own section.

1. Two panels, don't confuse them

Two easily-confused panels first:

• EFIS control panel (EFIS CP) — on the FCU wings; governs what content is on the screen (baro reference, FD/LS, ND mode/range/ADF-VOR). It is part of the Automatic Flight System, so it is integral with the FCU (ATA-22).
• EFIS switching panel — on the glareshield ends; governs brightness and reconfiguration (PFD/ND brightness, PFD/ND XFR, EFIS DMC selector — covered in the previous article).

In a line: the EFIS CP commands content (on the FCU), the switching panel controls brightness and transfer (on the glareshield). This article is the former. The two EFIS CPs are identical, giving the captain and first officer the same possibilities on their own PFD and ND.

2. The barometric reference — the most critical knob in the chapter

The baro reference control has an outer ring (unit) and an inner knob (turn to select value, pull/push to select reference). First the selectable range. Per FCOM DSC-31-50:

"The barometric reference is set to QNH and the QNH value is 1 013 hPa. The minimum QNH value that can be selected is 745 hPa (22.00 inHg) and the maximum is 1 100 hPa (32.48 inHg)."

Then the core actions — pull = STD, push toggles QNH/QFE. Per FCOM DSC-31-50:

"The flight crew turns the barometric reference knob to select the QNH or QFE value. The flight crew pulls or pushes the barometric reference knob to select the barometric reference (QNH, QFE, or STD). When the flight crew pulls the barometric reference knob, the barometric reference is set to STD. When the barometric reference is set to STD, and the flight crew pushes the barometric reference knob, the barometric reference changes to QNH or QFE (depending on the last barometric reference in use before switching to STD). When the barometric reference is set to QNH (QFE), and the flight crew pushes again the barometric reference knob, the barometric reference changes to QFE (QNH)."

As a feel in the hand:

• Pull = standard (STD): pull it climbing through the transition altitude; the PFD shows STD below the altitude tape, and turning the knob then does nothing (STD has no adjustable value).
• Push: from STD, push returns to whichever QNH or QFE was last in use; from QNH, push again jumps to QFE (and vice-versa). So the QNH↔QFE cycle is by push; entering/leaving STD is by pull/push.
• Turn: only useful in QNH/QFE, to set the hectopascals or inches.

One power-up default worth examining. Per FCOM DSC-31-50:

"At the EFIS CP power-up, the barometric reference is QFE and the QFE value is set to 1 013 hPa or 29.92 inHg, depending on the selected barometric unit."

Power-up default is QFE 1013 — so on every cold-cockpit power-up, one of the first actions is to push the reference to QNH and set the local value; do not leave it on QFE. And an easy-to-miss note. Per FCOM DSC-31-50:

"Note: The PFDs do not display the selected barometric unit."

The PFD shows only the number (1013, or 29.92) — not hPa or inHg — since Airbus takes the two magnitudes to be unambiguous. For a pilot used to the other unit this needs care: read the unit from the number. Why single out the baro knob: it is the only control in ATA-31 whose mis-setting directly threatens altitude. Where the QFE option is fitted, an inadvertent QNH↔QFE push is a real risk, especially into airfields that operate on QFE — cross-check it.

3. FD and LS pushbuttons — two switches, one symbology family each

Per AMM 31-60-00:

"(3) FD pushbutton switch This pushbutton switch, when pressed, enables the pilot to remove the FD bars from his PFD (or the Flight Path Director guidance symbols if the FPA/TRK mode is selected). NOTE: With the TRK/FPA mode selected, pressing the FD OFF P/BSW removes the FPD symbol, but not the FPV symbol. (4) LS pushbutton switch This pushbutton switch, when pressed, enables the pilot to have the LOC and GLIDE scales and deviation symbols on his PFD."

The key discrimination:

• The FD pushbutton removes the guidance bars (FD cross-bars / FPD) — not the FPV bird. With TRK/FPA selected, the bird stays after FD is off — the classic "I turned FD off, why is there still a bird?" — because the FPV is the flight-path vector, not guidance, and is not governed by the FD button.
• The LS pushbutton brings up the landing-system deviations (LOC + G/S scales), and also controls the QFU (ILS course) symbol on the PFD and ND heading scale. Press LS to fly an ILS.

4. ND mode, range and ADF-VOR

Three controls for the ND presentation. Per AMM 31-60-00:

"(1) Mode selector switch... ROSE mode... Three sub-modes: ROSE-NAV, ROSE-VOR, ROSE-LS... ARC mode... PLAN mode... ENG mode... (6) Scale selector switch... among those values: 10, 20, 40, 80, 160, 320 nautical miles. (7) ADF-VOR selector switches These 3-position selector switches enable each pilot to have ADF or VOR bearing pointers displayed on his ND... in any mode except the PLAN mode."

These govern how the ND is drawn and how far it looks: mode decides the ND's look (rose / arc / plan / engine standby), range decides the reach, ADF-VOR decides whether two bearing pointers hang on it. Symbol meanings are developed in the ND article; here it is enough to keep the control-versus-display split. One default: if mode or range data fails, the default is ROSE NAV + 80 NM.

5. Five optional-data pushbuttons — one at a time

Beyond the permanently-displayed data, the ND has five optional overlays. Per AMM 31-60-00:

"(8) Selection of data stored in the FMGEC data base... through five pushbutton switches marked CSTR, WPT, VOR-D, NDB, ARPT respectively. Each of these pushbutton switches has an exclusive function, which prevents cluttered display of information on the image."

Exclusivity is the point: WPT/VOR-D/NDB/ARPT show one at a time (CSTR is independent) — you cannot overlay all waypoints and all VORs at once, so the ND does not turn to soup. A lit button shows green bars; CSTR displays constraint values (altitude/speed) below waypoints.

6. OANS — optional airport map, seen at a glance

Per FCOM DSC-31-50:

"The On-board Airport Navigation System (OANS) is an optional function that provides the flight crew with a moving airport map on the ND... The OANS requires a dedicated EFIS control panel with a ZOOM notch on the range knob-selector. If OANS is not installed or is deactivated, a DEACT placard is present below the ZOOM notch on the EFIS control panel."

To tell whether OANS is fitted, look at the ZOOM notch on the range knob — a DEACT placard beneath it means not installed / deactivated. Even where the hardware is present but deactivated, turning the knob to ZOOM merely pins the ND to 10 NM and lights an LED; turn back to select the range wanted. The OANS itself belongs to airport navigation; here only its ZOOM notch on the EFIS CP concerns us.

7. Chronometer button and EFIS SWTG memo

The EFIS CP also carries a CHRONO button: press to show the onside ND chronometer, press again to freeze, a third to reset and remove (the chronometer itself lives in the electrical clock). Finally, whenever either EFIS DMC selector leaves NORM, a green EFIS SWTG memo appears on ECAM — a quiet "you are in a non-standard EFIS configuration" (echoing reconfiguration).

Self-test

[!note]- Q1. Barometric reference: what does pull do, what does push do from STD, and what does push do again from QNH? Pull = STD (turning then has no effect). From STD, push returns to the last QNH or QFE. From QNH, push jumps to QFE (and vice-versa). Turn sets the value in QNH/QFE.

[!note]- Q2. What is the power-up default reference and value, and does the PFD show the baro unit? Default QFE 1013 hPa (29.92 inHg). The PFD does not show the unit — read it from the number.

[!note]- Q3. After the FD pushbutton is pressed with TRK/FPA selected, is the FPV bird still there? Why? Yes. The FD button removes the guidance bars (FPD), not the FPV — the bird is the flight-path vector, not guidance.

[!note]- Q4. Which optional-data pushbuttons are mutually exclusive, and why? WPT / VOR-D / NDB / ARPT — one at a time (CSTR independent) — to prevent a cluttered ND.

[!note]- Q5. How do you tell at a glance whether OANS is fitted? Look at the ZOOM notch on the range knob — a DEACT placard beneath it means OANS is not installed or is deactivated.

Key takeaways

References

• FCOM DSC-31-50 — OANS/ZOOM, baro reference window and selector, pull/push logic, power-up default, PFD not displaying the unit.
• AMM 31-60-00 — EFIS CP controls: baro, FD/LS, ND mode/range/ADF-VOR, five optional buttons, EFIS switching panel.

Independent study material, not an Airbus publication and not endorsed by the manufacturer. Always defer to the current operator FCOM, FCTM, and QRH for operational use.