The signs

PHASE’s grammar is deliberately sparse. Each visual variable carries one piece of information only: the shape gives the object’s place in time, the fill gives its effect, the outline says whether the crew knew, the label style says what the analysis can claim.

Shapes: when, and for how long

The diamond: what happens

The diamond marks something that happens at an instant and has no duration: a clearance, a warning, a selection, a callout, a stated decision, the onset of a failure. A diamond never stretches.

What happens and what it sets up are two objects. The onset of the failure is a diamond; the resulting loss of a system is a bar.

Read aloud: “at the moment when”.

The bar: what lasts

The bar marks something that unfolds or remains true over time: an ongoing activity, a condition that holds, a process the analysis treats as active.

Its length is the duration the analysis retained, and nothing else. It says nothing about intensity, severity or level of competency.

A bar is either work (troubleshooting a failure, hand-flying) or a state (fatigue, a speed deviation, storms along the route). The test: “is someone doing this?”. The answer decides how the bar ends.

Read aloud: “while”.

The delta: not what was expected

The delta marks the finding that an action, or a lack of action, did not match what was expected: an error, a deviation, an omission, a delay. It is the only shape in the Error stratum, and it appears nowhere else. It is always instantaneous and never filled.

The activity concerned stays in its competency stratum; the resulting state goes in the aircraft corridor. The fact, the finding and the state are three objects. An omission is coded only if the source material states it, and the label describes the observable inaction: “no callout”.

Read aloud: “this is not what was expected”.

Fill: what effect

The fill gives the object’s contribution within the sequence, and nothing else. It applies to diamonds and bars, never to the delta.

Fill	Meaning	Read aloud
White	Protects or recovers: prevents degradation, holds margins or restores control.	“thanks to this”
Grey	Weakens: reduces margins or delays recovery.	“because of this”
Hatched	Neither for nor against: information with no effect on the outcome, kept because it gives meaning to the sequence.	“neither thanks to this nor because of it, but worth knowing”

Protecting and recovering share the same white. The difference shows in the position relative to the aircraft state: an object that comes first and prevents protects; an object during which an undesired state ends recovers.

There is only one shade of grey. Several grey bars in one stratum read as an accumulation, never as an intensity.

Hatching is also used when the source material does not allow the effect to be qualified. The object is drawn neutral, and the record states that the effect cannot be determined.

The fill is not a grade. The same communication can protect at one moment and weaken at another.

Marks: what is added on top

Dashed outline: they didn’t know yet

The outline is dashed as long as a threat or an aircraft state is outside the crew’s awareness: the information has not reached them, or there is no trace of detection. The outline turns solid at the first trace of awareness (a callout, a corrective action, a finding in the report), and the bar is split at that moment.

The dashed outline applies only to threats and aircraft states, never to competencies or the delta. It says only that the crew knew the fact existed, not that they had grasped what it meant.

Label in italics: suggested, not stated

The label says what happened in operational language, without judgement: “original plan maintained”, not “inappropriate strategy”.

In roman type, the object is established. In italics, the analysis has not established it: it is strongly supported, probable, a hypothesis to examine, or not determinable. The rule applies to every stratum. An object the analysis has set aside does not appear on the chart.

Chevrons: where the object stops

Mark	Meaning	Read aloud
Three chevrons	The object continues beyond what the source material can establish. At the start: it was already there before the window. At the end: no end point is set.	“it continues beyond the chart”
One chevron, at the end only	A piece of work that necessarily ended, but with no trace of when. The end is set by rule, with a conventional length that is the same for all.	“it ended, but I don’t know when”

Closing an object that is still open would amount to claiming it had stopped: that would be inventing information. The conventional length does the opposite: nobody decides anything with it, and it is not to be measured.

Split and arrow

A bar is split when its effect or extent changes, when the crew becomes aware of the threat, or when an activity eases off. Each segment carries its own fill. If the source material establishes a direction, the next segment carries ↑ or ↓ in its label: the arrow shows a rise or a fall, never a level.

No colour, no severity scale

PHASE’s grammar encodes a contribution and a status, never a severity. There is no red, amber or green on the chart. No thickness, transparency or blur is used to show uncertainty or intensity.

All of a chart’s information survives a black-and-white printout, which also makes it readable for people with colour vision deficiency.

To see these signs in context, open the diversion in degraded configuration demo or the FDM/ASR case. For the overall reading, see Reading a chart.