Indications on the PFD

The PFD is the screen you fly on — attitude, speed, altitude, heading, guidance, all on one display. But draw the boundary: what VLS means, how alpha protection is computed, belongs to the flight-control and auto-flight chapters (ATA-27/22); which ADR the altitude comes from belongs to ATA-34. ATA-31 owns how those numbers are drawn on the screen — how the display is laid out, how far the attitude can grow before the screen declutters, how baro and radio altitude are each constructed, and what flag is raised when a datum fails. This article walks the PFD from that display-system angle.

1. What the PFD provides, and specific ground indications

The PFD gathers the short-term information needed to fly: attitude and guidance, airspeed, baro/radio altitude and vertical speed, heading and track, the FMA, vertical/lateral deviations, radio navigation. The Flight Warning Computer monitors its main parameters (attitude, heading, altitude) — a disagreement raises CHECK (see reconfiguration). Some indications appear only on the ground. Per FCOM DSC-31-40:

"(4) PFD 1 (2 or 3) message (magenta) The display indicates which DMC drives the PFD. It appears only during tests on ground."

That magenta "PFD 3" is not a fault — it tells you, during a ground test, which DMC draws the screen; it does not appear in flight. The ground also shows the sidestick order display, the maximum-sidestick-deflection white dots, and, with a valid localiser below 30 ft RA, a green ground-roll guidance bar.

2. Attitude and the declutter logic — the screen sheds load as attitude grows

The attitude sphere is the heart of the PFD, and what most repays memorising is the declutter thresholds — when attitude grows dangerous, the PFD strips secondary symbols, leaving only the life-savers. First bank. Per FCOM DSC-31-40:

"This pointer indicates the bank angle. When the bank angle exceeds 45 °, all the PFD symbols except those for attitude, speed, heading, altitude, and vertical speed disappear. The display returns to normal when the bank angle decreases below 40 °."

Then pitch. Per FCOM DSC-31-40:

"When pitch angle exceeds 25 ° nose up or 13 ° nose down, all the PFD displays except attitude, speed, speed trend, heading, altitude, and vertical speed disappear. Beyond 30 °, large red arrowheads indicate that the attitude has become excessive and show the direction to move the nose in order to reduce it."

Three sets of figures: bank 45° declutters / 40° recovers; pitch 25° up, 13° down declutters; beyond 30° red arrowheads point the way out. The never-removed core: attitude, speed, heading, altitude, vertical speed (plus speed trend when pitch declutters). The meaning is "the more abnormal the attitude, the cleaner the screen" — during an upset recovery the pilot needs attitude and speed, not the FMA or navaids, and the PFD clears the clutter. The sphere also carries flight-control protection symbols (green "=" for bank-angle protection and pitch limits), replaced by an amber × if the protection is lost (mechanism in ATA-27).

3. The airspeed tape — the strip rules live in ATA-31

The tape carries a string of markers (VLS, alpha-protection speed, alpha-max speed, VMAX, VSW, V1, VR, F, S, Green Dot, VFE NEXT) — what they are and how they are computed belongs to ATA-27/22, but ATA-31 owns how they are drawn on the tape, and the core of that is the strip top/bottom rule. Per FCOM DSC-31-40:

"MINIMUM SELECTABLE SPEED (VLS): The top of the amber strip along the speed scale indicates this speed... ALPHA PROTECTION SPEED: The top of a black and amber strip... ALPHA MAX SPEED: The top of a red strip... MAXIMUM ALLOWABLE SPEED (VMAX): The lower end of a red and black strip... STALL WARNING SPEED (VSW): The top of a red and black strip along the speed scale defines this speed."

Weave the strip language bottom-up: the top of the bottom red-and-black strip is VMAX (the fast-end danger); toward the slow end, the top of the amber strip is VLS, the top of the black-and-amber strip below it is alpha-protection, and the top of the red strip is alpha-max (shown in pitch normal law); in alternate/direct law (no alpha protection) these are replaced by the top of the red-and-black strip, VSW (stall warning). One trap: VMAX and VSW are both "red-and-black strips", but VMAX is the lower end and VSW is the top — one guards overspeed, one guards stall, and the identical colouring is told apart by "which end of the strip". Speed meanings and law-dependence are in ATA-27. V1 (a "1", disappears after liftoff), VR (cyan circle), F/S (retract-flap/slat), Green Dot (clean), VFE NEXT (below 20 000 ft) follow MCDU entry or envelope computation. One pure display-system rule — how the whole string vanishes if the source fails. Per FCOM DSC-31-40:

"SPD LIM Appears when both FMGECs (flight envelope part) are inoperative, or in case of dual flap/slat channel failure. In this case, the following PFD information are lost: VLS, S, F, Green Dot, Vtrend, VMAX, VFE next, VSW."

SPD LIM means the tape has been crippled — the envelope source (FMGEC) is gone, so every envelope-computed marker vanishes, leaving only the basic speed scale. Seeing SPD LIM, expect no protection lines on the tape. The speed-trend arrow (speed reached in 10 s) shows above 2 kt and disappears below 1 kt, and also with an FMGEC failure.

4. The altitude tape — baro and radio altitude are two constructions

The altitude tape is the densest strip on the PFD. Setting the baro reference is covered in the EFIS CP article; here is how it is drawn: the altitude window is normally green digits on a white scale; it turns from yellow to amber when the aircraft deviates from the FCU-selected altitude; with an approach minimum entered, the digits turn green→amber below minimum. The target-altitude symbol is green/white/magenta by guidance state. Most distinctive is the field-elevation red ribbon at the bottom. Per FCOM DSC-31-40:

"A red ribbon on the right of the altitude scale represents the field elevation. This ribbon, which is driven by the radio altimeter signal, is displayed below 570 ft. It moves up... with the altitude scale as the aircraft descends. When the aircraft has touched down, the top of this ribbon is at the middle of the altitude window."

The 570 ft red ribbon is the landing ground-rush: it rises like the ground coming up, its top reaching the altitude-window centre at touchdown. Radio altitude itself has a stepped resolution. Per FCOM DSC-31-40:

"The radio height indication changes every 10 ft down to 50 ft, then every 5 ft down to 10 ft, then every foot."

The lower, the finer (10→5→1 ft) — foot-by-foot through the flare. The RA colour rules (green above DH+100 ft, amber below, once DH is entered) and the callout mechanism belong to ATA-34. Metric altitude is added by the FCU METRIC ALT button; landing elevation is a brown-strip top (shown in flight phases 7/8 with QNH selected).

5. Vertical speed — inertial first, amber if inertial is lost

Per FCOM DSC-31-40:

"The displayed vertical speed information is normally based on both inertial and barometric data. If inertial data is not available, it is automatically replaced by barometric information. In this case, the window around the numerical value becomes amber."

An amber VS window means inertial has been lost and baro VS is in use — baro VS is slow and lagging, so the colour change warns "this rate is less crisp than usual". Above 6000 ft/min the needle parks at the scale end; in descent with 1000 < RA < 2500 ft and VS > 2000 ft/min, or RA < 1000 ft and VS > 1200 ft/min, needle and digits also turn amber (a too-steep-descent caution).

6. Heading and true reference — auto-switch to TRUE in polar regions

The heading tape normally shows magnetic heading but auto-switches to true at high latitude. Per FCOM DSC-31-40:

"...the ADIRUs replace magnetic heading by true heading on the EFIS and DDRMI... the ADIRU causes the "SELECT TRUE REF" message to appear on the ND... In true heading configuration at slats extension, «TRUE» will flash for 9 s then remain steady."

TRUE showing = you are in a polar region and heading has switched to true (magnetic is unreliable there). Polar navigation is fully in ATA-34; here it is enough to recognise TRUE on the PFD/ND as "true-reference mode active".

7. FPV bird and guidance — two flight references

With TRK/FPA selected the PFD shows the FPV (flight-path vector, the "bird") — the aircraft's horizontal/vertical path over the ground after wind, to be used on a stabilised leg (a non-precision approach without FLS, a visual circuit), but not in dynamic manoeuvring where it lags. Two guidance sets: HDG/VS shows green FD cross-bars, TRK/FPA shows the flight-path director (FPD); with a valid localiser below 30 ft RA a green yaw bar appears (takeoff RWY mode, landing FLARE/ROLL OUT). The FD button removes the bars, not the bird — covered in the EFIS CP article. On deviations: after pressing LS the PFD shows LOC + G/S deviation scales (1 dot = LOC ±0.8° / G/S ±0.4°, flashing beyond ¼ dot); a non-precision approach (FINAL APP, non-LS) shows lateral (0.1 NM/dot, ±0.2) and vertical (100 ft/division, ±200) deviation scales — the deviation sources and conditions are in ATA-34. The FMA is in ATA-22.

8. Tail-strike pitch limit — the nose-up ceiling on takeoff and landing

An easily-overlooked but, on a long fuselage, very real symbol. Per FCOM DSC-31-40:

"The pitch limit indicates the maximum pitch attitude to avoid the tail strike risk at takeoff and landing. During takeoff, the indication progresses from the pitch limit value with main landing gear compressed, to the pitch limit value with main landing gear extended... During landing, the indication is a fixed value corresponding to the main landing gear compressed. The indication appears at 400 ft radio height."

It is a "do not pitch above this line" limit on the sphere — during rotation it moves up dynamically as the gear extends (a longer strut brings the tail nearer the ground, tightening the limit); on landing it shows a fixed value from 400 ft RA. Pitch approaching the line means "any more nose-up and the tail will scrape". Where the rising-runway option is fitted, with a valid localiser, RA available and no yaw bar, a runway symbol rises from the bottom of the pitch scale at 200 ft RA (vertical driven by RA, lateral by LOC) — fit per the configuration table.

9. Altitude alert (C chord) — approaching or deviating from the selected altitude

The altitude alert is FWC-generated but displayed on the PFD, a typical cross-system item. Per FCOM DSC-31-40:

"The FWC generates an altitude warning (C chord sound, and PFD's altitude window pulses in yellow or flashes in amber), when the aircraft approaches a preselected altitude or flight level or when it deviates from its selected altitude or flight level. This warning results from a comparison between the altitude (ADIRS) and the preselected altitude displayed on the FCU."

Cancellation and inhibition. Per FCOM DSC-31-40:

"The continuous C chord is cancelled by selecting a new altitude, by pushing the ECAM control panels' EMER CANC pb, or by pressing either MASTER WARN pb... The altitude alert is inhibited: - When the slats are out with the landing gear selected down, or - In approach after the aircraft captures the glideslope, or - When the landing gear is locked down. - In the case of a TCAS RA."

The C chord is the altitude alert's signature sound (see the aural article). The inhibition logic has a common thread — "you are deliberately leaving the cruise altitude": slats out with gear down, glideslope captured, a TCAS RA manoeuvre, all mean "I know I am leaving the selected altitude", so it need not sound.

10. Flags — no data, raise a flag

Every class of PFD datum that fails raises a flag (a full page in DSC-31-40). One general rule. Per FCOM DSC-31-40:

"Note: All the flags flash for 9 s then remain steady, except V1 INOP which is displayed steady."

"Flash 9 s then steady" is the rhythm across the PFD/ND — flash to catch the eye, steady so as not to nag. The value of the flag system is that when data is lost the screen does not fool you with a stale value, but plainly raises a flag saying "this one is gone" — another way glass beats electromechanical: a stuck needle may go unnoticed, a lost PFD datum always flags.

PFD flags / messages — quick reference (from FCOM DSC-31-40; all flash 9 s then steady except V1 INOP, which is steady):

(TCAS-related flags are in the surveillance chapter, ATA-34.)

Self-test

[!note]- Q1. At what bank and pitch does the PFD declutter, and what remains? What appears beyond 30°? Bank > 45° (recovers < 40°); pitch > 25° up or 13° down. There remain attitude, speed, heading, altitude, vertical speed (plus speed trend). Beyond 30°, red arrowheads point the recovery direction.

[!note]- Q2. What drives the 570 ft red ribbon, and where is it at touchdown? The radio altimeter signal; displayed below 570 ft. At touchdown its top is at the middle of the altitude window.

[!note]- Q3. VMAX and VSW are both red-and-black strips — how are they told apart? By which end: VMAX is the lower end of the strip (overspeed), VSW is the top (stall). One guards fast, one guards slow.

[!note]- Q4. How is the altitude alert (C chord) cancelled, and by what common thread is it inhibited? Cancelled by selecting a new altitude, EMER CANC, or either MASTER WARN. Inhibited when you are deliberately leaving the cruise altitude — slats out with gear down, glideslope captured, gear locked down, or a TCAS RA.

[!note]- Q5. What is the general flag rhythm, and the one exception? Flash for 9 s then remain steady — except V1 INOP, which is displayed steady from the start.

Key takeaways

References

• FCOM DSC-31-40 — full PFD symbology: ground indications, attitude declutter, airspeed strips and SPD LIM, altitude tape / 570 ft ribbon / RA steps, vertical speed, true reference, FPV/guidance, tail-strike limit, altitude alert, flag inventory.
• AMM 31-64-00 — PFD detailed logic and controls.

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.