The Control Index

The Control Index answers a question every instructor asks: how far ahead of the aircraft is the crew, and when do they fall behind it?

It is PHASE’s own reading. It is experimental. Its levels, markers and assignment rule are being developed from cases and have not been formally validated. It is presented as such.

What it reads

“Index” here means a reading aid. It is neither a calibrated measurement nor a score.

The Control Index reads the depth of the crew’s time horizon, set against what the rest of the flight requires. Being ahead of the aircraft means acting now on what is coming. Being behind it means spending most of your resources on what has already happened.

Position alone is not enough: depth matters. Thirty seconds of horizon is plenty at 200 ft on final. The same thirty seconds at 10 NM, with a descent still to plan, means deviations are coming.

Two bubbles

The horizon is made of two bubbles:

• the aircraft bubble: state, near-term path, energy, configuration, modes;
• the environment bubble: navigation, ATC, weather, terrain, traffic, plan and options.

Each gets its own reading. The level given to a segment is that of the shorter bubble, not an average. Both readings stay in the record, because the asymmetry is instructive: it shows where attention was fixed.

Four levels

Level	Name	In short
I	Anticipatory control	The horizon extends well beyond what is required. Options kept open, tasks done ahead.
II	Reactive control	The horizon just covers what is required. Everything gets done, with no time to spare.
III	Loss of temporal control	Behind the aircraft, but the catch-up has a plan and the crew is holding to it.
IV	Disorganised control	Behind the aircraft, and the activity is coming apart. The situation sets the pace.

Level II is not a degraded level. It is the normal level in a busy phase, such as an approach: experts settle into it to keep control at an acceptable cost. Each phase thus has an expected level, I in cruise, II on approach. What matters is the gap from that level, and when the transition happens.

The levels are not a progression. They jump, return and fall silent. A segment can be not determinable: that is a result in its own right, never an interpolation.

Placed by hand

The analyst places the Control Index segment by segment. A segment is an interval containing at least two processing loops. A level is proposed only when an established aircraft fact and an established crew fact agree, with no contrary fact.

A placement is never “established”. At best it is probable, or with reservations, or not determinable. It never carries information that is not already in the coding.

Loop breaks and markers

Two markers date the loss of the lead:

• the tipping point, the event that costs the crew its lead and sets up a state;
• the entry into level III, at the first available signal not picked up, when the source material states it.

A loop break is a function with no observable output between two coded moments: the signal was available, the expected response did not come in time. This term replaces any vocabulary of internal state. It describes what can be seen, not what was going on in someone’s head.

For each segment, the record also states what became of the four core tasks, in priority order: aviate, navigate, communicate, manage. Each one is held, dropped, carried out with the wrong content, or carried out without effect. That shows what the activity was still holding on to.

On the chart

The Control Index occupies a single band below the strata, aligned with time. It carries only three marks:

• a Roman numeral per segment, constant over the interval;
• a blank when the segment is not determinable;
• a break sign when an available signal was not picked up: a loop break.

A vertical dashed line marks a change of level. The band takes no diamonds, bars or fills. The justification for each segment is in its record: the facts, their status, what is missing, and the analyst’s decision.

Read aloud: “where is the crew relative to the aircraft?”

What it is not

• It is not a measure of workload, stress or expertise.
• It is not a measure of situation awareness, which the SAW competency already covers.
• It is not a severity scale.
• It describes a sequence, never a person.

Its use is formative. No summative use is envisaged. Agreement between instructors on segment placement has yet to be established: it is one of the validations open to research partners (see Status and limits).