Reading the instrument panel

The live screen is built to be read in one glance from arm's length. Everything on it answers one of two questions: am I on time? and what do I do about it?

Leg 1 of a flight running slightly fast: 85 knots against an 83-knot target, projected to reach CP1 about half a minute early.

┌──────────────────────────────────────────────┐
│ LEG 2 OF 4        [AIRBORNE] [AUTO]          │  header
│ ▰▰▰▰▰▰ ▰▰▰▰▰▰ ▱▱▱▱▱▱ ▱▱▱▱▱▱                  │  leg progress
│ ↗ KJXN                                       │  next waypoint
├──────────────────────────────────────────────┤
│              ⬆  TOO SLOW                     │
│                +0:24                         │  delta card
├──────────────────────┬───────────────────────┤
│ DISTANCE             │ DESIRED TRACK         │
│ 7.4 NM               │      (compass)        │
│ to KJXN              │        073°T          │
├──────────────────────┼───────────────────────┤
│ GROUND SPEED         │ LEG TIME              │
│ 112 kts   TARGET 128 │ 6:12                  │
│ ▰▰▰▰▰▰▰▰▱▱▱|▱▱       │ ▰▰▰▰▰▰▰▰▰▱▱▱▱         │
│                      │ planned 8:00          │
└──────────────────────┴───────────────────────┘
│              Leg Control                     │
└──────────────────────────────────────────────┘

On an iPad, or an iPhone in landscape, the four tiles lay out as a single wide row instead of a 2×2 grid. The content is identical.

The header

LEG n OF m with a segmented bar underneath — one segment per leg, green for legs already flown, highlighted for the one you are on, grey for the ones ahead. Below it, the identifier of the waypoint you are currently flying toward.

The status pills tell you what state Navigator is in:

Pill	Meaning
PRE-FLIGHT (orange)	Not airborne yet. Nothing is being timed.
AIRBORNE (green)	Timing is running.
AUTO (blue)	Automatic leg switching is armed. Its absence means you are switching legs by hand.
GDL90 (green)	A GDL90 source is selected and position reports are arriving.
GDL90: NO DATA (orange)	A GDL90 source is selected but nothing has been received yet.

The delta card

The big number. It is the projected finish time of the current leg against its planned time — not the error so far, but where you will end up if you keep flying exactly as you are:

elapsed on this leg + (distance remaining ÷ current ground speed) − planned leg time

Reading	Colour	Means
ON TIME	Green	Projected within ±3 seconds of plan. Change nothing.
TOO SLOW +M:SS	Red	You will arrive that much late. Speed up.
TOO FAST −M:SS	Orange	You will arrive that much early. Slow down.

The sign follows clock convention: plus is late.

Because the projection uses your current ground speed, it moves around early in a leg — a few knots of variation over ten miles is a lot of projected seconds — and settles as you close on the waypoint. Fly the trend, not the twitch.

Distance

Great-circle distance in nautical miles from where you are to the next waypoint, with that waypoint's identifier underneath. It is direct distance, not distance along your intended course, so it decreases even when you are well off course.

Desired track

The initial great-circle bearing from your present position to the next waypoint, in degrees true, with a needle on a fixed dial.

Two things to keep straight:

• The dial is north-up and does not rotate. The needle points at the bearing to the waypoint in true degrees. It is not a heading indicator and not an HSI — it does not know which way the airplane is pointing.
• It is true, not magnetic. Apply your local variation before comparing it to anything in the panel.

Because it is recomputed from your present position, it is a direct-to bearing. Flying the needle takes you to the waypoint; it does not put you back on the original course line between the two waypoints.

Ground speed

Your current ground speed in knots, and next to it TARGET — the ground speed that would put you over the next waypoint exactly on planned time:

distance remaining ÷ (planned leg time − elapsed leg time)

The number is coloured against the target, and the bar underneath shows the same thing graphically, with a tick mark at the target:

Colour	Means
Green	Within 5 knots of target, or no target available
Orange	Below target — you need to speed up
Blue	Above target — you can ease off

When the target goes absurd

The time remaining in that formula is floored at half a second. Once you are past the planned time for a leg, the divisor is essentially zero and the target becomes a number no airplane can fly. That is arithmetic, not advice — at that point the leg is already late, and the delta card is the number to be reading. The same happens when a leg has no planned time: the target reads zero and the tile shows plain grey.

Leg time

Elapsed time on the current leg as M:SS, with a progress bar against the planned time and the planned time spelled out underneath. The clock and the bar turn red the moment you pass planned — a second signal, independent of the delta card, that this leg has run long.

A leg with no planned time — an unscored leg — shows the elapsed clock and "no planned time", with no bar.

Flying the panel

A workable scan for a scored leg:

1. Delta card. Green? Nothing to do. Look at it again in thirty seconds.
2. Not green? Look at ground speed and the target next to it. That is the correction, in knots, already computed for you.
3. Make the change small and early. A five-knot correction with eight miles to run buys back more time than a twenty-knot correction in the last mile — and it is far easier to be settled and stable at the checkpoint.
4. Glance at distance to know how much runway you have left for the correction to work.
5. At the checkpoint, expect the haptic and watch the header roll over to the next leg. If it doesn't, take control by hand.