Communication methods between a tanker aircraft and a receiver aircraft in an in-flight refueling operation

Transmission of data and audio messages between tanker and receiver aircrafts to facilitate air refueling operations using a boom device, wherein the method includes transmitting a data message from one aircraft to the other aircraft as an analog signal via the electro-magnetic connection which is also used for transmission of audio messages between the aircrafts which may be operating in a radio silence environment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to EP 13382253.6 filed Jun. 28, 2013, the entire content of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to in-flight refueling operations with a boom device and more particularly to communication methods between a tanker aircraft and a receiver aircraft which facilitate the in-flight refueling operation.

BACKGROUND

A usual method of in-flight refueling operations, illustrated inFIG. 1, is based on the use of a boom device15to interconnect the tanker aircraft11with the receiver aircraft13. The boom15is basically an extensible or telescoping tube attached to the bottom of the tanker aircraft11by means of a mechanical articulation which provides the passage of fuel from the tanker aircraft11to the receiver aircraft13.

In the tanker aircraft11, the operator monitors visually all steps and procedures to carry out a safe refueling operation. In particular, the operator controls the movement of the boom15until it is physically connected to the receptacle19of the approaching receiver aircraft13. After completion of the refueling operation in a given session the boom15is retracted to its safety position in the tanker aircraft11.

Refueling operations are very sensitive and must be performed in a very precise and accurate way due to security reasons.

Currently, communications between the tanker aircraft and the receiver aircraft are performed by means of visual signals transmitted from the tanker aircraft and voice communications between the boom operator in the tanker aircraft and the pilot of the receiver aircraft.

For transmitting visual signals to the receiver pilot to facilitate the approaching operation the tanker aircraft includes several Pilot Director Lights (PDL) at its bottom with conventional symbols.

For voice communication radio system are used and, in radio silence environments, an audio transmission system in an intercom mode between the tanker aircraft11and the receiver aircraft13through an electro-magnetic connection between the tanker aircraft and the receiver aircraft available when both aircraft are coupled is used. InFIG. 2, which represents a known nozzle16of a boom device15, a coil17that allows establishing said electro-magnetic connection together with another coil in the receptacle19of the receiver aircraft13can be seen.

These communication means do not meet all the communication needs between the tanker and the receiver aircraft and the present invention is directed to solving that problem.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide communication methods of data messages between the tanker aircraft and the receiver aircraft to improve the in-flight refueling operations in, particularly, radio silence environments.

This and other objects are met by a method of transmitting data messages through the electro-magnetic connection which is used for contact and disconnection detection and audio communications in radio silence environment between the tanker aircraft and the receiver aircraft comprising the following steps:

a) providing in the aircraft that emits the message a digital data frame containing a data message and a control signal for its sending;

b) converting in the aircraft that emits the message said digital data frame into a digital data signal and transforming this signal into an analog data signal conditioned to a suitable voltage level for its transmission to the target aircraft of the message;

c) transmitting the signal obtained in the previous step to the target aircraft via said electro-magnetic connection;

d) transforming in the target aircraft the received analog data signal into a digital data signal and converting this signal into a digital data frame.

The method comprises the simultaneous transmission of a data message from the tanker aircraft to the receiver aircraft and of a data message from the receiver aircraft to the tanker aircraft.

The method may comprise the transmission of messages that include data messages and voice messages. In such case, the method also comprisesin step a), providing in the aircraft that emits the message an analog audio signal containing the voice message and a control signal for its sending;in step b), converting in the aircraft that emits the message the analog audio signal into a second analog audio signal conditioned to a suitable voltage level for its transmission to the target aircraft and filtered to remove frequencies above a predetermined frequency f1 and mixing the second analog audio signal with the analog data signal for obtaining an analog audio and data signal;in step d), separating the analog data signal and the analog audio signal contained in the analog audio and data signal received in the target aircraft.

In one embodiment of the method comprising the transmission of data messages and voice messages is contemplated that:in step b), the transformation of the digital data signal into an analog data signal is performed by means of a Frequency-Shift Keying modulation process obtaining a modulated signal in two frequencies f2, f3 for the logic levels 0 and 1, being f2 lesser than f3 and being f2 greater than f1;in step d) the separation of the analog data signal and the audio data signal is made filtering in parallel the analog audio and data signal to eliminate, respectively, the frequencies below f2 and the frequencies above f1.

Other desirable features and advantages of the invention will become apparent from the subsequent detailed description of the invention and the appended claims, in relation with the enclosed drawings.

DETAILED DESCRIPTION OF THE INVENTION

The method of the present invention comprises any kind of transmission of messages via the electro-magnetic connection between the coils17,18of, respectively, the nozzle16of the boom device15of the tanker aircraft11and the receptacle19of the receiver aircraft13, comprising the simultaneous transmission of a voice message and a data message or the transmission of a data message from the tanker aircraft11to the receiver aircraft13and/or from the receiver aircraft13to the tanker aircraft11.

A detailed description of the method of the invention for different transmissions of messages between the tanker aircraft11and the receiver aircraft13follows.

Transmission of Data Messages Between the Tanker Aircraft and Receiver Aircraft (SeeFIG. 3)

A digital data frame24generated by a device of the tanker aircraft11(indicating, for example, the remaining time to complete the ongoing refueling operation) is converted into a digital data signal25at step35. That signal is conditioned to a suitable voltage level for its transmission to the receiver aircraft13in step37and is subjected to a modulation process in step39to obtain an analog data signal26.

Preferably, the modulation process of step39is a Frequency-Shift Keying (FSK) modulation process that generates two fixed frequencies f2, f3 corresponding respectively to the logic levels 0 and 1.

Other modulation processes, particularly the Amplitude-Shift Keying (ASK) or the Phase-Shift Keying (PSK) modulation processes can also be used in step39.

The transmission of the analog data signal26to the next step is controlled by a switch41according to the content of the Request to Send (RTS) signal29of the data message.

The analog data signal26is injected into the coil17of the nozzle16of the boom device15and transmitted to the receiver aircraft13through the electro-magnetic connection with the coil18of the receptacle19of the receiver aircraft13.

In the receiver aircraft13the switch75controls the reception of the analog data signal26. In step79said signal is de-modulated to obtain the digital data signal25and in step81is converted in the digital data frame24to be sent to its destination.

Similarly a digital data frame94generated by a device of the receiver aircraft13(indicating, for example, the pressure of the received fuel) is converted in step65into a digital data signal95, is conditioned to an appropriate voltage level for its transmission to the tanker aircraft11in step67and is subjected to a modulation process in step69to obtain an analog data signal96.

The transmission of the analog data signal96to the next step is controlled by a switch71according to the content of the RTS control signal99of the data message.

The analog data signal96is injected into the coil18of the receptacle19of the receiver aircraft13and transmitted to the tanker aircraft11through the electro-magnetic connection with the coil17of the nozzle16of the boom device15.

In the tanker aircraft11the switch45controls the reception of the analog data signal96. In step49said signal is de-modulated to obtain the digital data signal and in step51is converted in the digital data frame94for being sent to its destination.

Simultaneous Transmission of Data Messages and Voice Messages Between the Tanker Aircraft and the Receiver Aircraft (SeeFIG. 4)

An analog audio signal21, generated by the equipment of the boom device operator or of another crewman of the tanker aircraft11when a voice message directed the pilot of the receiver aircraft13is issued (informing him, for example, about the start of the refueling operation), is conditioned to a suitable voltage level for its transmission to the receiver aircraft13and filtered to remove frequencies above a predetermined frequency f1 to eliminate treble tones (preferably f1=5 KHz) in step31obtaining a second analog audio signal22. The transmission of the analog audio signal21to the next step is controlled by a switch33according to the activation/deactivation of the Push to Talk (PTT) signal23of the voice message.

A digital data frame24generated by a device of the tanker aircraft11(indicating, for example, the remaining time to complete the ongoing refueling operation) is converted into a digital data signal25at step35. That signal is conditioned to a suitable voltage level for its transmission to the receiver aircraft13in step37and is subjected to a modulation process in step39to obtain an analog data signal26.

In case of using a Frequency-Shift Keying modulation, the two frequencies f2 and f3 of the analog data signal26should be greater than the above-mentioned frequency f1. Suitable values for these frequencies f2 and f3 are, for example, 15 KHz and 20 KHz respectively, which are greater than the frequency of the voice message to allow simultaneous transmission of a voice message and a data message.

The transmission of the analog data signal26to the next step is controlled by a switch41according to the content of the Request to Send (RTS) signal29of the data message.

In step43the second analog audio signal22and the analog data signal26are mixed for its simultaneous transmission and the mixed signal is amplified. The resultant signal27that thus contains a voice message and a data message is injected into the coil17of the nozzle16of the boom device15and transmitted to the receiver aircraft13, through the electro-magnetic connection with the coil18of the receptacle19of the receiver aircraft13, resulting the signal28.

In the receiver aircraft13switches75and83allow receiving the signal28.

In step77the signal28is filtered to pass only the analog data signal26that is de-modulated in step79to obtain the digital data signal25that is converted in step81in the digital data frame24to be sent to its destination.

The signal28is also filtered in step85to pass only the analog audio signal22to be sent to its destination.

Likewise an analog audio signal91, generated by the equipment of the pilot of the receiver aircraft when emits a voice message directed to the operator of the tanker aircraft11(informing him, for example, about the fuel volume needed) is conditioned to a suitable voltage level for its transmission to the tanker aircraft11and filtered to remove frequencies above a predetermined frequency f1 to eliminate treble tones in step61obtaining a second analog audio signal92. The transmission of the second analog audio signal92to the next step is controlled by a switch63according to the activation/deactivation of the PTT signal93of the voice message.

A digital data frame94generated by a device of the receiver aircraft13(indicating, for example, the pressure of the received fuel) is converted into a digital data signal95at step65. That signal is conditioned to a suitable voltage level for its transmission to the tanker aircraft11in step67and is subjected to a modulation process in step69to obtain an analog data signal96.

The transmission of the analog data signal96to the next step is controlled by a switch71according to the content of the Request to Send (RTS) signal99of the data message.

In step73the second analog audio signal92and the analog data signal96are mixed for simultaneous transmission and the mixed signal is amplified. The resultant signal97that thus contains a voice message and a data message is injected into the coil18of the receptacle19of the receiver aircraft13and transmitted to the receiver aircraft13through the electro-magnetic connection with the coil17of the nozzle16of the boom device15resulting the signal98.

In the tanker aircraft11switches45and53allow receiving the signal98.

In step47the signal98is filtered to pass only the analog data signal96that is de-modulated in step49to obtain the digital data signal95that is converted in step51in the digital data frame94to be sent to its destination.

The signal98is also filtered in step55to pass only the analog audio signal92to be sent to its destination.

Simultaneous Transmission of Data Messages and Voice Messages from the Tanker Aircraft to the Receiver Aircraft (SeeFIG. 5)

This is a particular case of the above in which communication occurs in one direction only.

Transmission of Voice Messages from the Tanker Aircraft to the Receiver Aircraft and of Data Messages from the Receiver Aircraft to the Tanker Aircraft (SeeFIG. 6)

It is a particular case of that illustrated inFIG. 4in which communication occurs in two directions for different types of messages.

Transmission of Voice Messages from the Receiver Aircraft to the Tanker Aircraft and of Data Messages from the Tanker Aircraft to the Receiver Aircraft (SeeFIG. 7)

As in the above is a particular case of that illustrated inFIG. 4in which communication occurs in two directions for different types of messages.

An advantage of the method of the present invention is that it enables the establishment of a digital communication channel between a tanker aircraft11and a receiver aircraft13through the electro-magnetic connection between the coil17of the nozzle16of the boom device15and the coil18of the receptacle19of the receiver aircraft13.

Another advantage of the method of the present invention is its utility for refueling systems of unmanned receiver aircraft requiring the exchange of data messages with the tanker aircraft.

Another advantage of the method of the present invention is that it enables the establishment of a redundant system for detecting contact between the tanker aircraft and the receiver aircraft.

Although the present invention has been described in connection with various embodiments, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made, and are within the scope of the invention.