Laws for the Design of the Universal Cockpit Displays

Laws for the Design of the Universal Cockpit Displays


Major technological advances have occurred in the form of AMLCDs and electronics facilitating the design of the ultimate set of primary cockpit displays. Increased display design flexibility has led to a divergence, as evidenced in several new primary flight display designs. A set of twelve laws are proposed. The application of these laws will result in more cost-effective, reliable, and universal cockpit displays.

Keywords: aircraft, displays, primary, design laws, universal displays


The new color flat-panel active-matrix liquid-crystal display (AMLCD) has created an opportunity for designing the most integrated, functional, and universal set of cockpit instruments in the history of aviation. With the coupling of this development and the evolution in electronics, the industry has truly reached a new paradigm. Examples of the new cockpit in the new paradigm are evolving and are exhibited in the Boeing 777, Lockheed 141B upgrade, Lear 45, Raytheon T-6A, and others—but we are not there yet. These four examples are all new cockpits or upgrades that use AMLCDs and depart significantly in their portrayal of the primary set of instruments.

The thesis is that the industry could and should converge to a single, uniform set of cockpit instruments based on the historical evolution of instrument formats that are infused with flat-panel displays and optimized for situation awareness. The set of cockpit instruments would include a subset for primary flight, navigation, and engine instruments. The discussion herein will concentrate on the primary flight instruments as an example.

Primary flight instruments in the various new AMLCD cockpits do not look the same to the pilot. Levels of integration vary from almost none to nearly complete integration. The functionality is different, with mixtures of tight and loose scan patterns, fly-to and fly-from command needles and round dials and tapes. There is less universality in the present mix of the AMLCD panels than there was before the glass cockpit, as exhibited in a sampling of new AMLCD panels.

The flat-panel version of the glass cockpit offers a significant improvement in design opportunity over the CRT because of the CRT display volume issue. The CRT served the cockpit well and forged the way to integration of the primary set of instruments. The size of the flat-panel AMLCD allows the designer to integrate packaging, thus eliminating other boxes and extra cabling and allowing sensors to be included in the same box. The size of the AMLCD allows the concept of a single instrument box, again with electronics, symbol generators, and sensors all self-contained. The single box concept is very important for universality in aircraft size, maintenance, and situation awareness.

The integrated, functional, universal primary flight instrument in the new paradigm is transparent to the electronic display technology. Obviously, the display must have all the performance and features required for aviation. So far, the only display technology that meets all the requirements of the new paradigm is the color AMLCD for the integrated primary displays. At some time in the future a new technology may arrive, and, when it does, it could be substituted for the AMLCD. Pilots need not know the difference, and new training should not be required.

The latest AMLCDs have performance parameter capabilities that exceed those of CRTs. The main advantages are in weight, power, volume (size), and reliability. However, the AMLCD performance exceeds that of CRTs in other areas such as:

Luminance uniformity
Resolution uniformity
Immunity to ambient illumination washout and color de-saturation
Fault tolerance
Night vision goggle compatibility
Brightness and dimmability
Increased usable display area to panel area
Environmental and mechanical qualifications

The CRT has an inherent wider viewing angle and wider operating temperature range than does the AMLCD, but the AMLCD meets the needs of aviation.

Cockpit Display Objective

The first thesis is that the art and science of flying is now transparent to and independent of vehicle type and display technology. This is the fundamental guiding principle behind the laws for cockpit design that follow. The mission may be different, the size may vary, the power plant may change, and the configuration may be variable, but the fundamental pilotage tasks are the same. The pilot must be able to cause the aircraft to fly straight and level; maintain a heading, altitude, and air speed; climb, descend, and turn; control power in the presence of turbulence and phugoid and aerodynamic oscillations; navigate; and determine failures, all in meteorological instrument conditions (MIC) without visual reference to the ground.

The second thesis is that all flying can be done with a single universal set of instruments. The main set is for primary flight, navigation, and power. The three would give sufficient situation awareness so that the pilot could complete or alter the mission within the full design envelope of MIC.

This quest for the single universal cockpit display set is the objective. It is postulated that the state of the art in aerodynamics, power plants, electronics, sensors, and electronic displays has matured enough to achieve this objective during the transition to flat-panel displays.

However, the new flat-panel display cockpits are not converging into a single universal cockpit but are diverging. We can design into the electronic display any visual image desired. In the first step, as in the Boeing 757 and 767, the electronic image duplicates the classical electromechanical flight director. In the second step, as in the Airbus 320 and the McDonnell Douglas MD11, true fusion of the classical “T” instrument set, or primary flight set, was integrated and portrayed on a single electronic display.

As this integrated display of the primary flight instruments is implemented with flat-panel AMLCDs in different aircraft such as the Boeing 777, Lockheed C-141B upgrade, Lear 45, and Raytheon T-61, significant liberties are being taken, and the opportunity for a single universal primary flight instrument is being significantly diluted. For example, the speed tapes on the Boeing 777 have the highest speed indicated at the top, while on the Lockheed C-141B (upgrade) the highest speed is indicated at the bottom. The new trainer (JPATS) Raytheon T-6A has no integration and has round dials for velocity and altitude. Similarly, there are numerous other symbol and color-coding differences.
Laws for Cockpit Instrument Display Design

The single universal cockpit instrument design has not yet evolved. For this to occur, it is necessary and appropriate to promote a set of laws for its design. These laws are believed to be invariant and transparent to the display technology.

There are two overall guiding principles that form the basis of and cause the need for the laws for aircraft instrument design:

First Principle: The pilot is immersed inside the aircraft and is literally wearing the aircraft.

Second Principle: Cockpit display designers are no longer constrained by the nuances of dials, meters, and gauges. Display designers can now literally make any display image conceivable.

Of the twelve laws indicated below, the first five are paramount and relate to socioeconomic issues. The remaining seven laws relate to display images and how they are designed.

Laws for aircraft instruments

First Law—Economic Reality: Avionic display technology cannot move ahead of commercial display technology. Due to the small production volume and long product life of aircraft, the industry cannot support the infrastructure as a display technology innovator. It is far more economical for avionic displays to be derivatives of commercial displays than to be developed and manufactured solely for aviation.

Second Law—Pilot Culture: Avionic display and control symbology and procedures must evolve from the present pilot community culture. The transition of pilots between new and old aircraft panels within a fleet, or from employer to employer, must be as easy as possible to minimize the necessity of retraining and to enhance safety. Detraining and retraining pilots is to be avoided due to cost and subtle safety issues.

Third Law—Cost-effectiveness: Any changes to the cockpit must be cost-effective. Changed hardware or software must be better and less expensive. New concepts in aviation displays technology must improve reliability and safety and be less expensive. All cost and savings elements include the expense of pilot retraining.

Fourth Law—International Occupation: Piloting is an international occupation, and all changes must converge to common pilot-interchangeable display images and procedures. Every effort that is feasible should be made to make all cockpits as identical as possible. This is done to enhance safety as pilots transition from one type of aircraft to another, from student to pilot, from old aircraft to new aircraft, from carrier to carrier, from military to civilian, from country to country, etc.

Fifth Law—Military Exception to the First Laws: Everything technically and financially possible must be done to achieve and maintain air superiority. Doing too much may cause financial disaster.

Sixth Law—All and Only Data Display: For primary flight instruments, all and only data used for piloting and situation awareness must be updated and be readable at all times.

Seventh Law—Color as Aid Only: Availability and readability of alphanumeric and symbolic images are independent of their color. Color is orthogonal information to alphanumerics and symbols.

Eight Law—Failure Recognition and Recovery: Pilot is to analyze and deduce system and/or display failures, and reconfigure and complete the mission objective with single-point failure and generic failure.

Ninth Law—Fly-To: All command symbols and error symbology are to be of the fly-to polarity.

Tenth Law—Inside-Out and Heading Up: All graphic images are to portray polarity as if the pilot were inside the aircraft looking out. Rotating images of maps, weather, etc., are to be oriented with aircraft heading up at the top of the display.

Eleventh Law—Round Scales and Linear Scales: A tape or linear scale is to be used for bounded values and a round scale for unbounded values. Air speed and altitude are examples of bounded values. Heading and roll angle are examples of unbounded values.

Twelfth Law—Presentation of Image: A digital image is to be used if the value is used for reading, and an analog presentation is to be used if the value is used for flying. For example, digital readout should be used for reporting altitude, and analog scale should be used to fly the aircraft. Both digital and analog altitude readings are needed to fly an aircraft.


Complete freedom of display image design, integration of the primary instruments, new AMLCD technology, and new autonomous GPS navigation thrust the aircraft displays discipline into a new paradigm. The design guidelines we had in the past, from MIL-STD-1472, MIL-STD-884, MIL-HDBK-759, FAA Advisory Circulars, SAE ARPs, etc., must now be viewed from a new perspective. Most were written before this new paradigm. We need to start with a fresh sheet of paper if we are to capitalize on the new opportunities before us.

The single universal cockpit will never occur without use of common design rules or laws for the new generation of cockpits. The objective cannot be legislated into existence; it can only evolve. Once it has been attained for new cockpits, it may then be cost-effective to go back and change all the old cockpits as they are upgraded.

Now that we can make any desired display image in glass electronic displays, a concentrated effort is needed to cause them to converge into ultimate single universal display images. However, ultimate display images have not yet been designed, nor have they been agreed upon.

In most new AMLCD glass cockpits desired air speed is displayed as a vertical tape, as is appropriate, and the present air speed is displayed digitally. This is consistent with the eleventh and twelfth laws. However, to follow the fly-to polarity of the ninth law, with the pilot controlling the pitch of the aircraft, the highest air speed should appear at the bottom of the tape.

The rules or laws used to design the ultimate display images are postulated herein. These may change, and new ones may be added before the ultimate single universal display images are agreed upon. Once the ultimate cockpit images are determined, they will hopefully evolve further to improve continuously the art and science of pilotage and the safety of flight. Without agreement on fundamental design rules that are taken as laws, the cockpit display images of the new paradigm will diverge, as they appear to be doing now.


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