One layout, borrowed from airliners.
Every primary flight display in the world, from a jet to a 57 mm instrument in an ultralight, uses the same arrangement, and it is not arbitrary. The attitude fills the centre, because attitude is what you fly. Airspeed runs up the left side and altitude up the right, exactly where the airspeed indicator and altimeter sat in the classic six-pack — so a pilot's eyes go to the correct side of the panel without retraining. Heading lies along the bottom. Vertical speed hangs off the altitude tape, because it is a rate of change of that number and nothing else.
What changed is the shape of the presentation. A round dial gives you position at a glance — the needle is at two o'clock, therefore 120 — but it must be read. A tape gives you rate and direction for free: numbers streaming downward means you are accelerating, and how fast they stream is how hard. The classic criticism of tapes is that they lose the instant absolute value the needle gave. Glass answers with the trend vector, and once you have flown behind one, the argument is over.
Fly the tapes.
Leave the airspeed alone at a comfortable 72 kt and roll the bank to 60°. Nothing about the aeroplane changed, but the red bar climbs up the tape toward you: a 60° turn doubles the load factor and multiplies the stall speed by 1.41. This is the single most valuable thing a glass panel does that a needle never did — it moves the danger mark to where the danger actually is, continuously, instead of printing one number on a placard for a condition you are not in.
The colours are a contract.
The bands beside the airspeed tape are the same markings as on the old dial, and each is a promise from the designer. The white band runs from the stall in landing configuration to the maximum flap speed: the flaps may be out anywhere in it. The green band goes from the clean stall to the maximum structural cruising speed — normal operation, rough air included. The yellow band above it is permitted only in smooth air, because a gust there can exceed the design load. The red line is never exceed, and it is a structural and flutter limit, not a suggestion.
One speed is deliberately not painted on the tape: the manoeuvring speed. It is not a fixed number — it falls as the aircraft gets lighter, which makes it the wrong sort of thing to print on a coloured band. Modern displays that show it compute it from the weight you entered, and that is worth knowing about your own panel: a speed that is calculated is only as good as what you told the instrument.
What the middle of the screen is really doing.
The attitude display is an AHRS solution drawn as a picture. The pitch ladder is calibrated in degrees, the bank pointer reads against a fixed scale at the top, and the little trapezoid under it — the one that used to be a ball in a curved glass tube — still says exactly what it always said: step on the side it has slid toward. Everything else on the screen is subordinate to that horizon, because in poor visibility attitude plus power is the whole of aircraft control.
Which puts a hard requirement on the box. It must align on the ground while genuinely stationary, it must survive a full day of thermals and turns without walking away from the truth, and it must know when it does not know. The AHRS article explains the sensor fusion; the operational summary is short: let it finish its alignment before you move, and believe the red X when it appears.
Four failures worth recognising instantly.
The attitude solution has been declared invalid — usually a sensor fault or a failed alignment. It is a promise kept: the display refuses to draw a horizon it cannot vouch for.
The most dangerous failure, because it is silent. A blocked pitot freezes the airspeed; a blocked static freezes the altitude. Cross-check against GPS ground speed and the other altimeter.
A drifting AHRS, most often after an alignment taken while the aircraft was moving. Land, restart on a stationary aircraft, and let it finish before taxiing.
A supply problem, not an instrument problem — which is exactly what a built-in backup battery is for.
And one structural point about the class of equipment. Instruments for ultralight and Experimental aircraft are typically non-TSO: outstandingly capable, extensively calibrated, and not certified for installation in a type-certificated aeroplane. Fly them for what they are — which is why a backup battery inside the instrument is not a luxury feature but the answer to the most common failure of all, the one where the aircraft loses its supply and the panel goes dark.
Attitude, airspeed, altitude and heading in a 57 or 80 mm cutout — every sensor inside, backup battery as standard, navigation and 3D terrain on the pro.
The fully round display with no covered area and WiFi inside — the configurator now lives in the instrument.
Airspeed, vertical speed and altimeter in one device with a backup battery — the iris approved for certified aircraft.