It might come as a surprise that the modern aviation tape altimeter does not show the ground until the aircraft is below approximately 500 ft. Or that the altitude predictors and preselected altitude values "park" at the edge of the display, saturated, during normal climbs and descents, only flash by in seconds when the aircraft passes the preselected value. Furthermore, the tape altimeter becomes a useless blur during high-rate maneuvers. For these reasons, tape altitude and airspeed scales have been largely eliminated from fighter aircraft Head Up Displays (HUD).

Nevertheless, linear tape displays have largely replaced round dials in modern aircraft instrument panels, but at a cost: traditional linear tapes entail a compromise between scale range, legibility, and resolution. Nowhere is this more evident than for the humble altimeter whose required resolution is twenty feet, over a range that often exceeds 40,000 ft. Clearly, both requirements cannot be reasonably accommodated while remaining legible, particularly under highly dynamic circumstances – until the introduction of the Dynamic Non Linear Display (DNLD) concept.

The following example centres on a DNLD altimeter, although the concept applies equally to any form of tape display that suffers from the range/resolution/legibility trade-off. DNLD comprises a tape divided into three regions: the central linear region has the highest resolution and is used for fine tracking tasks, such as maintaining an accurate altitude. The central region is flanked on either side by non-linear regions of a gradually decreasing scale to defined end-points. For the altimeter, the lower end-point is mean sea level, so the ground is always visible, regardless of the aircraft's altitude. The upper end point is typically tech aircraft's ceiling. The non-linear scaling is arranged so there is no discontinuity or jump between the inner and non linear regions. The effect is like condensing a very large tape measure with a magnifying glass at its centre, with a smooth transition across the entire scale.

The DNLD altimeter, unlike conventional displays, always shows the ground, always shows predicted values on scale, and always retains the preselected values in view. The resulting display retains all of the fine-tracking capability of a linear display, while expanding the display range to cover all foreseeable values. This improves pilot situational awareness far beyond what is attainable by round dials or traditional linear tapes. The patented DNLD technology has been extensively evaluated in flight simulations and during dedicated flight trials, to overwhelming acclaim.