Flight Deck Avionics

Avionics

When Orville and Wilbur Wright demonstrated the first manned flight they could have never imagined the dramatic changes their actions would catalyze. In less than a century we went from dreaming of flight to transporting millions of passengers daily. With the advent of modern aviation and Fly by wire systems came aircraft electronic systems, or “Avionics”. Early flight instrumentation systems consisted of simple dials indicating aircraft airspeed, attitude, altitude, rate of turn, heading, and vertical speed to allow the pilot to focus on the essentials of Aviate and Navigate. Avionics systems today are composed of a complex system of components, interfaces, and wireless technology. With the advent of aircraft to ground communication devices, pilots essential tasks in priority order are now Aviate, Navigate and Communicate 2 (ANC). In addition to primary systems that support the ANC functions, there are avionics systems that have been added to enhance both passenger and crew member comfort such as pressurized cabins, food service systems and in-flight entertainment systems.

In response to ever increasing air traffic, the FAA has a plan to implement a number of improvements to existing ATC (Air Traffic Control) systems, weather, and aircraft Navigation and Communication systems. These improvements are under the umbrella name “NextGen“. These improvements will be discussed in their respective Aviate, Navigate and Communicate section below.

Aviate

Flight Control (FC) systems are responsible for auto pilot and control of the aircraft control systems. From the flight deck the pilots can typically set a desired airspeed and flight plan that the FC can use to control the aircraft control surfaces. Aircraft control surfaces include a rudder for yaw, ailerons for roll and elevators for pitch.

In transport category aircraft the Engine Indication System (EIS) typically has a dedicated display for the pilots that shows all relevant engine parameters such as fuel, oil quantity, temperature and pressure and other engine parameters. Additional pages may include diagrams of aircraft systems such as the fuel system, brakes, and circuit breakers. The EIS system monitors parameters and notifies the pilots with status, caution and warning messages as necessary.

All air data information such as airspeed, altitude, air pressure, and vertical speed are measured and recorded electronically in a monitoring and recording system on the aircraft. This information is sent to the appropriate other systems and is displayed on Primary Flight Displays (PFDs) and Multifunction Displays (MFDs). If present conditions need the pilot’s attention, he is warned visually on the screen, aurally through his headset or flight deck speakers or physically through the control stick shaking. The other systems also use this data to calculate necessary information. The PFDs usually have an HSI (Horizontal Situation Indicator), ADI (Attitude Direction Indicator), Altitude and other pertinent information. These displays also sometimes include weather indications, traffic and collision avoidance systems (TCAS) and Ground Proximity Warning Systems (GPWS) to warn the pilot if the aircraft is too close to the ground and display terrain and obstacles that are below the aircraft.

Navigate

Navigation Systems (NAV) are one of the most important components of an avionics package. Knowing where the aircraft is located and following the correct flight path is necessary to arrive at your desired destination. Many NAV systems not only keep track of where the aircraft is located but they also allow you to load your specified flight plan and monitor whether the aircraft is staying on track. Some NAV systems also alert when there is deviation to the specified flight plan. A complex handoff system occurs between the NAV system and the Flight Control (FC) system to allow for the aircraft to automatically maneuver the aircraft. The pilot first programs the desired flight plan into the FMS, including all waypoints, altitudes, airports and runways. Once this is programmed in the pilot then “couples” the autopilot making it follow the desired flight plan. The pilot will also direct the FC to maintain a set speed and/or vertical speed while following the prescribed flight plan.

As part of the Next GEN program, Performance Based Navigation (PBN) adds RNAV (Area Navigation) and RNP (Required Navigation Performance) functions.  RNAV allows aircraft to use navigation aids to follow any flight plan within reach of navigation aids such as GPS. Prior to the introduction of RNAV and for aircraft without RNAV or RNP capability, flight paths would follow existing airways that followed ground-based navigation aids (NAVAIDs). RNAV increased flight efficiency by allowing aircrafts to fly more direct routes. RNP increases this efficiency even further by allowing pilots to fly even shorter flight paths. As specified in AC 90-101A, “RNP is a statement of the 95 percent navigation accuracy performance that meets a specified value for a particular phase of flight or flight segment and incorporates associated onboard performance-monitoring and alerting features to notify the pilot when the RNP for a particular phase or segment of a flight is not being met. ” Essentially, each flight procedure or airspace requires a specific accuracy for the position of the aircraft. An RNP of 10 would mean that the navigation system would need to calculate it’s position to within 10NM accuracy. Approach charts show the specific RNP value required for each segment of the RNP approach. RNP Authorization Request (AR) approaches require special approval, hence “Authorization Request”,  from the FAA and are described in AC 90-101A.

As aviation navigation continues to progress, a push has been made to eliminate the need for physical paper charts and checklists and make cockpits “paperless”. EFBs (Electronic Flight Bags) are devices that can be loaded with aeronautical charts, approach charts and checklists. These devices can be as simple as a handheld tablet computer or can be designed and manufactured specifically as an EFB.

Communicate

Flight Communication (COM) systems are responsible for communication between the aircraft and the ground, other aircraft and satellites. VHF and HF radios are present on the aircraft for COM and NAV functions. With the advent of modern radios came aircraft to land communication systems. In the existing system, pilots communicate to ground ATC systems via analog audio systems. NextGen introduces a new system called DataComm. DataComm will allow pilots to use digital, text based communications to ATC using controller-to-pilot datalink communication (CPDLC) that is directly sent to the FMS to re-route and to the pilot to be acknowledged. For re-routes, this will save time by eliminating the need for the pilot to repeat back the re-route information to ATC and manually enter the re-route data into the FMS.

ADS-B (Automatic Dependent Surveillance – Broadcast) is another NextGen Improvement that replaces existing radar technology. An aircraft equipped with ADS-B Out transmits its GPS location, ground speed and other information to satellites. This information is then sent to ground stations and can be accessed by ATC or other aircraft. ADS-B In-equipped aircraft receive this traffic information and also receive weather updates directly to the flight deck. Weather information received is in the form of graphical weather and text-based NOTEMS (Notices to Airmen) and relevant weather.

Passenger Flight Information/Entertainment

Although not directly involved with the pilot’s objectives to Aviate, Navigate or Communicate, pleasing the passengers is a high priority for airlines. Many passenger aircraft include electronic systems to provide the passengers with information and entertainment ranging from music radio stations to wi-fi and flight information.

 

1 “Chapter 10, Aircraft Instrument Systems”, https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/amt_airframe_handbook/media/ama_Ch10.pdf

2 “General Aviation Joint Steering Committee Safety Enhancement Topic January 2015 Fly the Aircraft First”,  http://www.faa.gov/news/safety_briefing/2015/media/SE_Topic_15_01.pdf

3 “NextGen”, http://www.faa.gov/nextgen/

4 “FAA Set To Expand Data Comm System”, http://www.ainonline.com/aviation-news/air-transport/2015-05-27/faa-set-expand-data-comm-system

5 “AC 90-101A:Approval Guidance for RNP Procedures with AR”, http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2090-101A.pdf

6 “Equip ADS-B”, http://www.faa.gov/nextgen/equipadsb/ins_and_outs/

7 “ELECTRONIC FLIGHT BAGS (EFBS)”, http://www.nbaa.org/ops/cns/efb/