Cockpit communication

A new digital audio cockpit system will bring significant improvements to pilots and aircraft operations compared to current analogue audio. The Digital Radio and Audio Integrating Management System (DRAIMS) received EASA certification* in March 2020 for the A320 Family.

Airbus is working towards similar certification for the A330 Family and studying potential installation on the A350 Family. The digital audio system will become the baseline for A320 and A330 Family aircraft over the next few years.

Here we look at the changes to the aircraft systems architecture linked to the installation of digital audio, what benefits it brings and the different operating modes from a flight crew perspective.

Customer Experience

Testimonies from Captain Dan Wood, Flight Operations Technical Manager and Martin Delahaye, Assistant Technical Pilot who are are coordinating the digital audio implementation at EasyJet.

It’s a definite improvement from the previous RMP. Pilots have fed back that the audio quality is significantly better. They are also happy with the brightness control during night flights.

Captain Dan Wood, Flight Operations Technical Manager

Most comments [from crews] relate to the appreciation of the in-ear RAD ALT [auto call-outs] and ECAM [warnings and cautions] plus clear audio quality.

Martin Delahaye, Assistant Technical Pilot

Understanding the digital audio system

Although the audio system peripherals (radios, boomsets, headsets, interfaced computers such as FWS, TCAS & GPWS, ….) have evolved and improved significantly over the years, the core elements of the audio system on A320 and A330 Family aircraft have remained essentially unchanged since the initial type certification of those aircraft types.

In the legacy architecture, the heart of the system, the Audio Management Unit (AMU), is connected to all peripheral equipment using multiple analogue links. Additional standalone computers such as the Cockpit Amplified Loudspeaker, the Audio Mixing box and the SELCAL box, perform functions not included in the AMU. The Human Machine Interface (HMI) is principally based on two separate control panels, the Radio Management Panel (RMP) and the Audio Control Panel (ACP). There is some limited synchronisation between RMPs, and in case of system failure requiring reconfiguration, the flight crew need to intervene manually (AUDIO SWITCHING control).

The digital audio system is designed to:

• improve and streamline the architecture, simplifying installation and increasing robustness
• update the HMI to bring it into line with solutions available on the A350 and A380
• increase synchronisation and simplify operating procedures to reduce crew workload
• integrate additional functions and provide provisions for future upgrades
• improve aircraft dispatch capability and remove some airline maintenance tasks

Improving and streamlining the architecture

The AMU has a completely new design. It now includes some of the previously external computers (such as the SELCAL box) and has a dual channel configuration with internal reconfiguration capability to improve robustness. Wherever it is technically feasible, links are now digital between the AMU and the peripheral equipment. Now, the RMPs (and not the AMU) manage the boomsets, headsets, hand microphones, oxygen mask microphones and loudspeakers. The power supply has been updated with dual power supply for RMP and AMU to ensure higher levels of equipment and function availability in the case of degraded electrical configurations.

The digital audio system is compatible with all peripheral equipment in the Airbus catalogue. This covers VHF, HF, SATCOM, boomsets (including those with a noise reduction function), headsets, TCAS and transponders.

Modernising the interface for the crew

Previously there were 3 separate panels: the Radio Management Panel, Audio Control Panel and XPDR/TCAS Control Panel

Now the RMP, ACP and XPDR/TCAS CP are combined into a new single control panel known as the RMP (Radio and Audio Management Panel)

The RMP builds on the service-proven design from the A380 and A350, but takes into account the desire to implement new functions, as well as the physical installation constraints of the A320 and A330 cockpits. Different cockpit layouts are available according to operators’ needs: 2 RMP + 1 ACP, 3 RMP or 3 RMP + ACP. The RMP has a single part number and can be programmed such that the HMI is coherent with the installed equipment. For example, if the aircraft is not equipped with an HF radio, then the associated menu key and transmissions keys will not be illuminated and pressing on those keys will have no effect. Some functions are controlled via a Line Select Key (LSK) and the RMP software can be programmed to give access, or not, as required (for example, CPDLC LOAD function), or to accurately reflect the aircraft configuration (for example, STBY NAV function and NAVAIDS listening).

A320 and A330 cockpits. Different cockpit layouts are available according to operators’ needs: 2 RMP + 1 ACP, 3 RMP or 3 RMP + ACP. The RMP has a single part number and can be programmed such that the HMI is coherent with the installed equipment. For example, if the aircraft is not equipped with an HF radio, then the associated menu key and transmissions keys will not be illuminated and pressing on those keys will have no effect. Some functions are controlled via a Line Select Key (LSK) and the RMP software can be programmed to give access, or not, as required (for example, CPDLC LOAD function), or to accurately reflect the aircraft configuration (for example, STBY NAV function and NAVAIDS listening).

Increasing synchronisation and simplifying operating procedures

Some of the main changes are explained below, with further details provided in the section “digital audio operating modes from a flight crew perspective”:

• The RMP allows the pilot to see at a glance the active and standby frequencies selected for all the installed radios of each type (up to 3 VHF radios, 2 HF radios and single or dual channel SATCOM installations). The SEL indicator has been deleted.
• All information is now fully synchronized between all RMPs in the cockpit. This includes active and standby frequencies of all installed radios, and STBY NAV tuning.
• Shortcut keys have been implemented for the squawk codes and the principal operating modes of the TCAS.
• Alerts from the FWS, TCAS and GPWS are broadcast through the boomsets and headsets, in addition to the loudspeakers.
• Failure case management has been simplified and the appropriate procedures are available in the FWS; for example, in case of RMP failure, the single action of switching off the associated RMP automatically activates the reconfiguration onto the remaining available HMI (RMP or ACP).

Integrating additional functions

• The RMP now incorporates the controls for the TCAS and transponder, which allows for the dedicated control panel for those systems to be removed.
• For compatible SATCOM solutions (currently under development), the RMP now allows control of the dialing, directory functions and system settings, as opposed to them being hosted in the MCDU for legacy SATCOM solutions.
• The RMP has spare keys and adequate processing power to be able to add new functions as and when they become available.

Improving aircraft dispatch capability and alleviating airline maintenance

The digital audio system has advantages in terms of installation, maintenance and operations:

• Nearly 4kg of weight reduction per aircraft due to wiring simplification and harness diameter reduction.
• Nearly 4kg of weight reduction per aircraft due to the reduced number and size of LRU, thus contributing to fuel savings.
• Power consumption reduction of up to 26% (according to installation configuration).
• Data-loading capability for future evolutions, avoiding equipment removals for retrofit.
• Removal of scheduled maintenance tasks, due to increased reliability.
• Single AMU and RMP hardware part numbers for reduced inventory, instead of different part numbers depending on equipment installed on aircraft.
• Improved audio quality and reduced interference and background noise due to the use of digital communications protocol.
• High level of commonality between A320, A330, A350 and A380 audio system HMIs.
• Reduced crew workload thanks to intuitive HMI, fully synchronised information and simplified failure case management.

Digital audio operating modes from a flight crew perspective

Once an aircraft is out of service the likelihood of issues caused by the wear and tear of routine flying is reduced. Nevertheless, without proper protection a host of new threats to the condition of the aircraft can emerge depending on the climate and conditions the aircraft is stored in. Weather can cause problems. If rain, snow, salty air, dust or sand enter air ducts, they can degrade or contaminate the mechanical parts they come into contact with. Extremely high winds can also cause damage to an aircraft that might be considered safe and stable in normal circumstances. High humidity, lightning strikes and volcanic ash also require special consideration.

Protection against unwelcome ‘passengers’ is also vital. It only takes weeks for rodents, birds and insects to cause serious damage to a previously pristine cabin with seats, carpets and wiring all vulnerable particularly if a nest is established. Returning to service without an expensive and time-consuming deep-clean and repair operation is unthinkable. In extreme cases, infestation can also lead to blocked ducts, some of which could have safety repercussions – again thorough checks and remedial actions take time so avoiding the problem is the best solution.

RMP general presentation

The RMP contains the following elements:

A full colour display, with a brightness controller, which can also be used to switch off the RMP if required by procedure or for maintenance purposes. The brightness and colour of the keys and knobs on the RMP is harmonised with the other control panels in the cockpit and is controlled with the cockpit integrated lighting commands.

• Menu keys, used to access the different pages for display. According to the aircraft configuration, only the relevant keys will be illuminated.
• Line Select Keys (LSK) which have different functions according to the page being used: switching between active and standby frequencies/codes (VHF, HF, squawk code), cycling through operating modes (TCAS, transponder), accessing sub-menus (STBY NAV, SATCOM SETTINGS, …), clearing messages (CALL RESET, information messages, …).
• Shortcut keys for control of the most common operating modes of TCAS. Each press of the shortcut key cycles through the available modes according to the flight phase.
• A numeric keypad for entering or correcting frequencies, telephone numbers, squawk codes, ….
• Up/down keys for scrolling in applicable fields on different pages.
• A Push-to-talk switch (“PTT”) for performing interphone or external communications.
• Transmission keys for all available audio channels. According to the aircraft configuration, only the relevant keys will be illuminated.
• Reception knobs for all available audio channels, including NAVAIDS.

VHF and HF pages

The VHF and HF pages show the active and standby frequencies, or DATA if selected, on all available radios. The squawk code and TCAS shortcuts remain displayed.

Standby frequencies are entered by selecting the relevant LSK on the right hand side (cyan box appears) and using the numeric keypad. A push on the relevant LSK on the left hand side swaps the active and standby frequencies.

Partially entered frequencies are completed (if valid) and invalid frequencies are highlighted in amber and accompanied with information in the message area.

If a radio has its transmission key selected, the name is shown in green reverse video, e.g. VHF1

If a radio has its reception knob selected, a loudspeaker symbol is shown. The loudspeaker symbol is shown crossed out if a radio is selected for transmission, but not reception.

For HF radios, the modulation mode can be selected. The selected mode is shown in cyan reverse video, e.g. ON

If a SELCAL is received, the RESET message is shown in the message area, a buzzer sounds, and the associated transmission key flashes amber.

In CPDLC operations, the message area shows a LOAD message if the appropriate uplink is received from the active ATC centre.

TEL page

The TEL page shows the call status, the call priority level and telephone number (or directory name) on all available SATCOM channels. The squawk code and TCAS shortcuts remain displayed.

New telephone numbers are entered by selecting the relevant LSK on the right hand side (cyan box appears) and using the numeric keypad, the up/down keys or the DIRECTORY sub-menu.

If a call is received, the RESET message is shown in the message area, a buzzer sounds, and the associated transmission key flashes amber. The details of the incoming call are shown on the TEL page.

ATC page

The ATC page shows the status and all operating modes of the transponder and TCAS. The active system or operating modes are shown in cyan reverse video eg: XPDR1. 

Standby operating modes (for example, TCAS DISPLAY MODEs with TCAS on STBY) are shown in a cyan box.

Each press of the relevant LSK cycles between all the available systems or operating modes.

The IDENT command allows crews to respond to the ATC request.

The squawk code can be modified via the ATC page, or directly from any VHF, HF or TEL pages, by using the left hand LSK to select the code (cyan box appears) and then using the numeric keypad. After a few seconds the squawk code is shown in green to confirm its selection.

NAV page

The upper part of the NAV page is used to activate the STBY NAV function in case of FMS failure. After selecting STBY NAV, the access to all available RAD NAV means according to aircraft configuration is given via the LSK on the left hand side of the screen (for example, LS or VOR). Selecting those LSK gives access to sub-menus which can be used to enter frequency/channel and course information. If the STBY NAV function is activated, an indication STBY NAV is shown in reverse video on VHF, HF and TEL pages.

The lower part of the NAV page is used for listening to the different NAVAIDS (AUDIO NAV). Only the installed NAVAIDS are shown on the screen. The right hand LSK cycles through all the available means. Once selected, the NAVAID signal can be heard using the NAV reception knob. For installed NAVAIDS which make use of the BFO signal, the VOICE ON/OFF command is displayed and can be selected using the relevant LSK.

MENU page

The MENU page can show different prompts for the LSK according to the aircraft configuration. One example of information shown on this page includes the SELCAL code and access to the SATCOM SETTINGS sub-menu.

Certifying authority feedback

During the certification flight test campaign, the authorities declared:

“The new digital audio system performed as per design. All the communications were always clear from all the installed equipment, no interference was experienced during the flight, all the information provided in the RMP was well visible and the pilot did not notice any objectionable reflections. The new logic of operation is easy and intuitive. Even during high workload situations an airline pilot would easily operate with the new RMP and find all the communications clear and intelligible.”

* extract from EASA certification flight test report

Watch the video: A320neo digital audio

Conclusion

The digital audio system, which will become the baseline on A320 and A330 Family aircraft over the next years, has been designed with installation, maintenance and operation improvements in mind. Experience in flight testing, both for development and certification, with Airbus, authority and airline flight crew members, showed that the digital audio system provides excellent audio quality, and the new RMP was considered very easy and intuitive to use, even by crew members with very limited exposure to the digital audio system.

GLOSSARY

FWS Flight Warning System

GPWS Ground Proximity Warning System

RMP Radio and audio Management Panel

SELCAL function (SELective CALling) System allowing the air traffic controller to alert the flight crew without the crew having to permanently monitor the radio frequency. SELCAL is still standard operational practice on any oceanic crossing.

TCAS Traffic Collision and Avoidance System