Recording digital cockpit-ground communication on an accident-protected speech recorder

The invention relates to an apparatus for and a method of recording digital messages which are exchanged between a pilot of an aircraft and staff on the ground, comprising an accident-protected speech recorder and a data link device on board the aircraft.

At the present time it is not yet usual for the communication between the pilot of an aircraft and an air traffic controller to be effected completely digitally, instead analog speech radio is used. In accordance with certain approval regulations it is necessary for that conventional speech communication to be recorded on an accident-protected flight recorder (speech recorder). In new and modern aircraft however there are devices which permit an additional digital communication between a pilot and for example an air traffic controller by means of a keyboard and a display screen. That digital form of communication is also referred to as controller-pilot-data link-communication (CPDLC), in which respect data link stands for the data connection which is initiated for example by a data link device on board the aircraft. With widespread application CPDLC is replacing conventional speech communication in a certain fashion, at least from the point of view of the approval authorities. It will therefore be understood that in the very near future that digital form of communication must also be recorded on board the aircraft on an accident-protected storage unit, like speech-supported communication. That permits evaluation of the communication in the event of a possible flight incident investigation.

In the case of aircraft which are operated at the present time or which are in the course of manufacture however such recording is not yet provided and is technically not viable. On the one hand the existing speech recorder does not have an

input channel which can record such digital signals in their present form. On the other hand the devices which implement the digital communication do not have a suitable output by which the messages could be transmitted directly to the speech recorder. Furthermore, recording of the digital messages on an accident- protected flight data recorder which is also present, is not possible at the present time, on board the aircraft. The data recorded by the flight data recorder usually originate from numerous condition sensors of aircraft systems and are stored cyclically. The available storage space in the flight data recorder permits the storage of all continuously existing data at given intervals over a desired period of time, for example 24 or 25 hours. To provide sufficient storage space for an additional communication channel which is not only restricted to the irregular exchange of messages between air traffic controllers and aircraft pilots but which also includes messages between aircraft in flight (air traffic data, for example ADS-B), relatively expensive upgrading of the flight data recorder would be required.

For cost saving reasons there is hitherto no readiness on the part of the operators and aircraft manufacturers to install a completely new system which permits both conventional speech recording and also the recording of digital messages. The necessity for a recording should not force the operators of the aircraft to introduce new speech recorders, new flight data recorders and/or new units for digital communication with additional functions.

Therefore the object of the invention is to reduce or entirely eliminate at least one of the above-indicated disadvantages. In particular the object of the invention is to provide a method and an apparatus which, while further using the devices for digital communication and the conventional speech recorder, permit recording of the digital communication.

That object is attained by a method in that a speech synthesis unit arranged between the data link device and at least one input of the speech recorder on board the aircraft converts the digital messages into analog speech signals which are recordable by the speech recorder. That is of advantage as the conventional

speech recorder can still be used, and likewise the data link device. The addition of a speech synthesis unit does not involve high costs as speech synthesis software and such signal processors have long been available in a large number of different variations. Furthermore it is possible for the conventional methods and procedures of a flight incident investigation to be carried out on the basis of speech recordings on the speech recorder without conversion or upgrading to novel data detection devices.

It is particularly advantageous if the speech synthesis unit produces separate speech signals for incoming and outgoing messages. In that way it would be more easily possible for the respective message source to be clearly identified.

The involvement of different sounds, in particular different voice registers or characteristics in respect of the separate speech signals is also preferred for the reason that this greatly simplifies distinguishing the respective message source when listening to the speech signals in the event of a flight incident investigation.

It is further desirable if the speech synthesis unit produces speech signals with a male voice from the incoming messages and speech signals with a female voice from the outgoing messages. It is possible in that way to clearly distinguish the directions in which the messages are flowing. For the same reason it is advantageous conversely for speech signals to be produced with a female voice from the incoming messages by means of the speech synthesis unit and for speech signals in a male voice to be produced from the outgoing messages.

Combining the separate speech signals to afford a speech signal to be recorded is further preferred. That means that just one signal input is sufficient for recording the combined speech signals and the incoming and outgoing messages are in dialogue form at the signal input.

It is further advantageous if the speech signal is fed into a signal input of the accident-protected speech recorder. Then, in a flight incident investigation, the

combined speech signals can be listened to like a conventional dialogue which is conducted by way of speech radio.

Finally it is preferred that the signal input is used for a microphone of a third crew member of the aircraft for feeding in the digital messages. The use of that signal input which is used only in exceptional situations eliminates the need for replacement of the speech recorder.

In addition the above-specified object is attained by an apparatus in that arranged between the data link device and at least one input of the speech recorder on board the aircraft is a speech synthesis unit which converts the digital messages into analog speech signals which are recordable by the speech recorder. An apparatus which is particularly preferred is one which carries out the method described hereinbefore, by virtue of the stated advantages.

The above-specified object is finally attained by an aircraft, in particular a passenger aircraft, in that arranged between the data link device and at least one input of the speech recorder on board the aircraft is a speech synthesis unit which converts the digital messages into analog speech signals which are recordable by the speech recorder. Advantageously and by virtue of the specified advantages that aircraft carries out a method in accordance with the above- described method.

A preferred embodiment of a method according to the invention and apparatus is described in greater detail with reference to the Figures in which:

Figure 1 shows a diagrammatic view of the recording of digital messages with specially adapted devices for freshly developed aircraft (state of the art);

Figure 2 shows a diagrammatic view of the recording of digital messages using the original devices by the method and apparatus according to the invention; and

Figure 3 shows a passenger aircraft.

Figure 1 shows a usual arrangement of communication and storage devices which can record both speech and also data, but which is used only in freshly developed or future aircraft. The interface between the digital communication devices and the aircraft pilot is implemented by a display and control unit 2. The aircraft pilot here receives the digital messages in readable form or can himself initiate messages and send them for example to an air traffic controller. The display and control unit 2 is connected to a data link device 6 by way of a data connection 4. At the data link device a connection is made with transmitting and receiving units (transceivers) 8 so that digital messages can be transmitted and received by way of various radio systems (HF, VHF, mode S, SatCom).

The data link device 6 is also connected by way of a connection 10 to an especially developed cockpit speech and data link recorder 12. There, the entire digital message stream is stored and is available to be called up for a certain time. Usually the cockpit speech and data link recorder 12 is accident-protected in such a way that it remains unscathed in the event of the aircraft crashing. In a flight incident investigation the stored messages or the recorded speech can be listened to and evaluated.

The cockpit speech and data link recorder 12 is also connected to an audio management unit 14 which by way of separate inputs passes the signals from the microphones 16 of the crew and the cockpit microphone 18 in suitably processed form to the cockpit speech and data link recorder 12. There finally, besides the digital messages, any audio signal from the cockpit and from the crew is also recorded.

For that purpose, it is necessary for the cockpit speech and data link recorder 12 to be designed to store digital messages, and likewise the data link device 6 must have one or more corresponding suitable outputs for the digital data. Subsequent upgrading or conversion of existing components would be excessively costly due to removal and reinstallation and the replacement of some essential components. The apparatus described in Figure 1 cannot be implemented in aircraft which already exist or which with the design established are already in production.

Figure 2 shows an arrangement according to the invention of communication and storage devices. The display and control unit 2 for digital communication is connected to a data link device 20 by way of two connecting lines 22 and 24 which can also be of a unidirectional nature. There, a connection is made to transceivers 8, by way of which a data connection can be made to the ground. The data link device 20 also has two further lines 26 and 28 as branches from the lines 22 and 24, which are connected to a speech synthesis unit 30. The digital messages are converted into audio signals which a human being can understand in the speech synthesis unit 30 which is also referred to as the 'digital/audio translator'. The transmitted data are preferably in a standardised form, in which respect the messages themselves are usually encoded as digital text data.

The speech synthesis unit 30 itself produces two analog speech signals which can be recorded on a conventional cockpit speech recorder 34. Those two speech signals include the messages and communications which are displayed on the display and control unit 2 (speech signal 1 ) and the messages and communications which the aircraft pilot inputs and sends to the ground (speech signal 2), in each case in spoken form. Those two speech signals are then mixed together and consolidated like a spoken dialogue on to a common signal. The two speech signals should involve acoustic differences, for example one speech signal can be executed by a male voice and one speech signal can be executed by a female voice. In that way the direction of the message flow can be very easily determined in the evaluation procedure. Further voice differences which are necessary by adding further sources (for example of the co-pilot) are certainly possible.

The consolidated signal is passed by way of a line 32 into the input of an audio management unit 14. In addition the signals from the microphone of the crew 16 and from the cockpit microphone 18 also pass into the audio management unit 14. The collected signals are finally passed to the cockpit speech recorder 34 where they are recorded.

It is to be noted that usually the cockpit speech recorders have only four inputs for audio signals, whereby no input is available for the signal from the speech synthesis unit 30. By virtue of the change to two-man cockpits however it is necessary only very rarely and in particular situations (for example in pilot training and so forth) that a corresponding microphone input is made available for a third crew member so that this input can be used for the signal from the speech synthesis unit 30. Older aircraft admittedly sometimes still have 3-man cockpits, but they are not affected by this invention as because of relatively old technology on board they also do not afford any digital communication which has to be recorded.

Figure 3 further shows a passenger aircraft 36 in which the digital messages exchanged between the aircraft and for example an air traffic controller are recorded by the method according to the invention by a speech synthesis unit 30 on a conventional accident-protected speech recorder 34.

This recording according to the invention of digital communication on a conventional cockpit speech recorder provides a relatively inexpensive solution for recording digital messages on an accident-protected speech recorder without having to replace the existing equipment by fresh developments.