There are some interesting developments happening in the field of aviation. Flying cars of different configurations, currently in limited production, are expected to save billions of litres of fossil fuels now wasted in traffic jams in metros all over the world. Like highways, now skyways are also being planned. There are many new entrants in the business jets manufacturing sector. Production of medium- and long-range jets has been doubled to cater to the increasing air traffic all over the world.
Integrated avionics software and large displays are creating cockpits that offer pilots dramatic new perspectives. They include QWERTY key-boards and trackballs, interfacing with a graphical ‘point-and-click’ display navigation system.
A conventional cockpit relies on numerous round dial mechanical gauges to display information. Today, glass cockpits look and behave like computers with Windows data that can be manipulated with mouse and other click devices—familiarly known as WIMP (Windows, Icons, Menus, Pointers) technology. Touchscreens in the cockpits are enhancing the entry and observation of flight data more efficiently.
With the increasing processing power of on-board computers, additional features like electronic flight bags (an electronic information management device) and electronic fl bags (device storing engineering and commercial data) are being incorporated in cockpits, which drastically reduce the enormous documentation.
Let’s take a detailed look at these and other advancements in cockpit design.
Digital data buses
Today, like the majority of desktop computers, most operational and flying cockpits have human-machine interfaces, that are based on WIMP interfaces. Some of them standardise upon the ARINC 661 international standard digital data bus for interactivity management.
Digital data buses greatly improve the intercommunication between aircraft systems and cockpits. Previously, large amounts of aircraft wiring were required to interconnect each signal with the other equipment. As systems became more complex and more integrated, this problem aggravated. Digital data transmission techniques use links that send streams of digital data between equipment. These data links comprise only two or four twisted wires and therefore the interconnecting wiring is greatly reduced.
Common types of digital data transmission are single-source single-sink, single-source multiple-sink, multiple-source multiple-sink and fibre-optic data buses.
Single-source, multiple-sink. In this technique, one transmitting equipment can send data to a number of recipient equipment (sinks). ARINC 429 is an example of this data bus which is widely used by civil transports and business jets.
Multiple-source, multiple-sink. In this system, multiple transmitting sources may transmit data to multiple receivers. This is known as a full-duplex system and is widely employed by military users (MIL-STD-1553B) and the Boeing 777 (ARINC 629).
Major digital data buses in use today are:
1. ARINC 429 (A429)
2. MIL-STD-1553B, also covered by Def Stan 00-18 Part 2 and STANAG 3839
3. ARINC 629 (A629)
4. Fibre-optic bus
Of these, A429 and A629 are commonly in use on civilian aircrafts. MIL-STD-1553 is a military standard.
Integrated flight management system
Today, the glass cockpit uses several displays driven by integrated flight management systems that can be adjusted to display flightinformation as needed.
Auto-pilots integrate both fly-by-wire of flight controls and power-by-wire engine controls. These generally divide a flight into taxi, take-off, ascent, level, descent, approach, landing and taxi phases. Landing on runway and controlling the aircraft on rollout, i.e., keeping it at the centre of the runway, is CAT-3B landing, used on the majority of major runways today. Landing, rollout and taxi control to stand is CAT-3C.
Basically, integrated flight control systems should control the primary and secondary flight control surfaces. Primary control surfaces are pitch, yaw and roll motions of the aircraft. Secondary flight control surfaces help the aircraft to take off and land like leading-edge slats and spoilers. The horizontal stabiliser at the rear controls the pitch motion, the rudder yaw or direction, while the Ailerons control the roll motion of the aircraft.
On-board computers with associated software control the flight of the aircraft. Both primary and secondary flight control surfaces are automatically controlled, reducing the workload of the pilot.
The autopilot controls the engine power and is familiarly called power-by-wire concept. Full authority digital engine control (FADEC) enables matching of air-fuel ratio at various speeds, loads and altitudes to produce optimal power and reduce emissions. FADEC is integrated to the autopilot.
GPS devices in cockpits
GPS provides geographical location in term of latitude and longitude of the destination.
Pilots can use the touchscreen panel to check information about nearest airports, weather reports, runway patterns and distance. When a plane lands, a button push gives the pilot the more familiar car GPS screens. GPS systems used in aircrafts now have an accuracy of 1 cm. This is accomplished by using GPS in conjunction with accurate altimeters and differential GPS. The differential GPS interacts with airports (base stations) in addition to satellites.
Some manufacturers provide landing facility with GPS alone or with an option for ILS (Instrument Landing System) facility. Most business jets use GPS for landing.
Basic flight instruments
Various manufacturers implement different features and philosophies in the cockpit flight management system All of them aim at reducing the pilot’s workload and situational awareness from take-off to landing.
The primary component of glass cockpits is the electronic flight instrument system, which displays all the information about the aircraft’s situation, position and progress. Comprising left- and right-side primary flight displays and multi-function display screens, it primarily covers horizontal and vertical position, but also indicates time and speed. The second part of the glass cockpit, comprising over- and under-centre display screens, shows the aircraft’s system conditions and engine performance.
Majority of the system-related controls (such as electrical, fuel, hydraulics and pressurisation), for example, are usually located in the ceiling on an overhead panel. Radios are controls such as the autopilot, usually placed just below the windscreen and above the main instrument panel on the glareshield.
As aircraft displays have advanced, so have the sensors that feed them.
Traditional gyroscopic flight intruments have been replaced with altitude and heading reference systems and air data computers, improving reliability and reducing cost and maintenance. GPS receivers are integrated into glass cockpits.
EICAS/ECAM warning systems
While on-board computers manage all the systems and take full control of the aircraft flight and propulsion systems, central advisory warning system draws the attention of the crew by flashing lamp in the direct vision of the pilot.
Multi-function display units are used for presentation of the aircraft data. Areas on the screen can be reserved for display of warning messages.
The engine indication and crew alerting system (for Boeing) or electronic centralised aircraft monitor (for Airbus) allow the pilot to monitor the following information: values for N1, N2 and N3, fuel temperature, fuel flow, the electrical system, cockpit or cabin temperature and pressure, control surfaces and so on. The pilot may select display of information by means of button press.
Electronic flight bag
Electronic flight bag is an electronic information management device that helps pilots perform flight management tasks more easily and efficiently with less paper. It is a general-purpose computing platform intended to reduce, or replace, paper-based reference material often found in the pilot’s carry-on flight bag, including the aircraft operating manual, flight crew operating manual and navigational charts (including moving map for air and ground operations).
Electronic fly bag
Airline operators induct aircraft at various stages spread over many years. Configurations of the aircraft also vary as the engine selection for a particular aircraft depends on the customer. Airline operators have a major challenge of managing the maintenance, repair and overhaul (MRO) data for different aircrafts and different subsystems covering all disciplines of engineering.
Now each aircraft is equipped with an electronic fly bag that has all the engneering data for maintenance schedules as well as commercial data like the fuel consumed and passenger occupancy.
e-flight offers a comprehensive approach to data management that will tie the aircraft into an organisation’s ground-based computer networks. The airlines use e-flight to set up information technology infrastructure in order to keep the aircraft in the loop on the ground or in the air.
Other advanced features being included are the weather radar system and free-flight. The weather radar system provides the pilot with a complete view of hazardous weather using artificial intelligence and image processin technologies to automatically detect, characterise and avoid severe weather.
Free-flight is a concept of air-traff management based on satellite navigation and data link communication.
B.S Sastry is retd. project director LCA ex-consultant to IT firms for automative and aerospace divisions & B. Ramana is an aerospace engineer