Method and system of transmitting and receiving data originating
from an aircraft black box
The invention relates to a method of transmitting and receiving data
originating from a black box on board an aircraft.
A black box, also known as a recorder, is a device installed on board
aircraft that stores various flight data, sound data and optionally visual data,
during the flight. The flight data originates from various sensors present on
board the aircraft that collect various flight data, as well as from computers that
supply flight parameters.
The data stored in a black box also comprises audio recordings and
optionally video recordings of the activity inside the cockpit (discussions
between crew members, etc.).
Such black boxes are generally orange in colour and fitted with a
radio transmitter so that they can be located more easily, for example, following
an air disaster.
However, the recovery of these black boxes following an air disaster
is very complex, particularly because the great majority of the earth's surface
has an uneven topology.
The recovery of black boxes from the bottom of the ocean or in
crevasses within mountain chains is in fact very difficult.
However, the data contained in these devices is very important, even
vital, for finding out the causes of an air disaster and working to better deal with
the cause with a view to preventing the recurrence of the same type of disaster.
The present invention aims to overcome this drawback by means of
communicating data stored in one or more black boxes of an aircraft in flight,
said communication taking place from the aircraft to the outside thereof and,
more specifically, to at least one other aircraft.
According to a first aspect, the subject matter of the invention is more
specifically a method of transmitting data in flight, characterized in that it
comprises a step of transmitting data between a first aircraft and at least a
second aircraft, the data transmitted being data stored in at least one black box
on board the first aircraft.
Thus, the data from a black box or recorder is transmitted during the
flight outside the aircraft in question, thus making it possible to ensure that said
data will be accessible (as it is backed up on another aircraft) in the event that
an air disaster occurs on said aircraft and the black box cannot be found or is
unreadable.
It will be noted that the second aircraft receiving the data can, when it
lands, be used to make a copy of the data on the ground.
Generally, the transmission of such data between two aircraft can
take place continuously depending on the communication links possible or
intermittently, regularly or otherwise, automatically or following manual
triggering initiated in an emergency by a crew member.
It will be noted that the first aircraft can, depending on the
circumstances, transmit black box(es) data to several other aircraft and not to
just one, in order to increase the chances of transmitting reliably and therefore
backing up the data.
It must be noted that the second aircraft to which the data is
transmitted is not known in advance. It is selected after a decision to transmit
the data has been made (for example, decision made on board the first aircraft).
The fact of transmitting the data to a second aircraft that is not a
predetermined aircraft provides flexibility and reliability for the data transmission
and makes it possible to ensure that the data can be transmitted at any time (by
selecting a second aircraft when this is necessary) and whatever the
geographical region being overflown.
The invention makes it possible to back up black box data even if the
region being overflown has no satellite coverage.
Furthermore, other data can be transmitted with the black box data,
for example, depending on the circumstances and applications envisaged.
According to one possible feature, the data originating from said at
least one black box requires for its transmission a bandwidth of at least 100
kbits/s. Such a bandwidth is necessary for transmitting the flight data and audio
data recorded in the cockpit.
In the event of transmission of video data, a bandwidth of at least 2
Mbits/s would be preferable.
According to a possible feature, the method comprises a prior step of
storing the data to be transmitted in an intermediate storage space separate
from said at least one black box.
It is advisable to place the data to be transmitted in a storage space
separate from said at least one black box so that the data can be processed
without having to modify the design of said at least one black box.
According to a possible feature, the method comprises a prior step of
processing the data to be transmitted with a view to reducing the bandwidth
necessary for transmitting the data.
This makes it possible to free up bandwidth on the network to enable
other communications to be established or a larger volume of data to be
transmitted.
According to a possible feature, the method comprises a prior step of
encrypting the data to be transmitted.
This step aims to ensure the confidentiality of the data that will be
transmitted between the two aircraft.
Thus, only authorized entities with appropriate decryption equipment
are capable of examining the data transmitted.
An aircraft receiving black box(es) data originating from another
aircraft is not generally considered to be an entity authorized to read said data
and, in this regard, does not therefore have means of decryption. The data
received is therefore unreadable for the receiving aircraft.
According to a possible feature, the method comprises a step of
selecting a means of communication from a plurality of communication means.
It will be noted that a means of communication can be chosen
preferentially for use first (for example, the radio link) and other means are
envisaged if the preferred means is not for example available, or, for example, if
it does not meet a predetermined criterion in relation to the new flight conditions
of the first and second aircraft.
The data is transmitted for example by radio means or by any other
wireless communication means (for example, mobile telephone network,
yviMAX, etc.) or by satellite means.
According to another aspect, the data is transmitted on a
communication network comprising mobile communication nodes that are
aircraft in flight.
The transmission of such data to another aircraft constitutes a safety
mechanism for said data as it thus allows a copy (backup) thereof to be made
outside the aircraft in question.
According to a possible feature, the method comprises a prior step of
searching on the network for at least one mobile communication node in flight
with which the first aircraft (the transmitting mobile node) is capable of
communicating.
According to a possible feature, the method comprises, prior to the
transmission step, a step of selecting in flight at least one non-predetermined
mobile communication node, said at least one node being selected from a set of
mobile communication nodes in the network as a function of at least one
predetermined selection criterion.
Generally, said selection aims to determine for example the "besf'
node, that is, the node that is most appropriate in relation to the selection
criterion/criteria applied at a given moment.
This makes it possible to ensure that there will always be a (nonpredetermined)
receiving node within communication range of the transmitting
node (the first aircraft) so that the black box(es) data can be transmitted, at any
time and whatever the geographical region being overflown.
According to a feature, said at least one predetermined selection
criterion is at least one of the following criteria: (an) aircraft producing a signalto-
noise ratio (signal quality) above a predetermined threshold, (an) aircraft
having (a) similar or identical flight plan(s) (to maximize the availability period of
the receiving aircraft), (an) aircraft belonging to the same airline or the same
alliance of several airlines, (an) aircraft made by the same manufacturer, (an)
aircraft within communication range, the aircraft furthest away from the first
aircraft (to reduce the relative movement between the transmitting aircraft and
the receiving aircraft), (an) aircraft in descent phase.
These criteria fall into different categories. Some criteria relate to
communication between the aircraft (signal-to-noise ratio, aircraft flying in the
same direction, aircraft within communication range, etc.), while others are less
technical ((an) aircraft belonging to the same airline, made by the same
manufacturer, etc.).
The most appropriate node(s) of the nodes in the network are for
example identified on the basis of the signal-to-noise ratio coming from the
nodes, with preference given for example to the maximum signal-to-noise
ratio(s).
Alternatively, depending on the direction of the aircraft in question,
preference can be given to the aircraft that will remain within the field
(communication range) of the aircraft in question for longest (aircraft going in
the same direction).
Thus, several aircraft in flight each constitute mobile communication
nodes of a communication network and black box data is transmitted between a
first and a second mobile nodes of said network, permanently or quasipermanently,
for example at a given frequency.
Further selection criteria can be applied alone or in combination with
one or other of the above criteria.
According to a possible feature, the method comprises a step of
requesting the establishment of a connection with the selected node, prior to the
transmission of the data.
It will be noted that the node search, most appropriate node selection
and connection establishment request steps are generally performed by the
transmitting node.
According to another aspect, the invention relates to a method of
receiving data that comprises a step of receiving in flight, from a first aircraft,
data stored in at least one black box on board the first aircraft, the receiving
step taking place on board a second aircraft.
According to a feature, the method of receiving data comprises a
prior step of checking the availability of a storage space with a view to storing
the data to be received.
It is preferable that a space be available to re.ceive said data in order .
to avoid needless transmission.
Said checking is performed on the second aircraft, at the request of
the first, after receipt of the connection establishment request.
According to a feature, the method comprises a step of storing the
data received either in a storage space available on board the second aircraft
receiving the data or, if said space is unavailable, in a storage space reserved
to this end.
A further subject of the invention is a data transmission system,
characterized in that it comprises means of transmitting data in flight between a
first aircraft and at least a second aircraft, the data transmitted being data
stored in at least one black box on board the first aircraft.
The transmission system comprises, in the form of corresponding
means, one or more features of the method set out above, or even all of said
features, and thus enjoys the same advantages.
A further subject of the invention is a data receiving system on board
an aircraft, characterized in that it comprises means of receiving in flight, from a
first aircraft, data stored in at least one black box on board the first aircraft, said
system being on board a second aircraft.
According to another aspect, the invention relates to an aircraft
comprising a transmission system and/or a receiving system as briefly disclosed
above.
Further features and advantages will become apparent during the
following description, given as a non-limitative example only, with reference to
the attached drawings, in which:
- Figure 1 is a general diagrammatical view of a transmission system
according to an embodiment of the invention;
- Figure 2 is a diagrammatical view showing several aircraft
constituting mobile nodes of a communication network;
- Figure 3 is a general algorithm for establishing a connection
between two aircraft;
- Figure 4 is a general diagram of a receiving system according to an
embodiment of the invention;
- Figure 5 is an algorithm for a data transmission method according
to the invention;
- Figures 6a and 6b are two algorithms for a connection method and
a data receiving method according to the invention respectively.
As generally shown in Figure 1 and denoted by the reference marked
10, a system according to the invention on board an aircraft comprises two
black boxes or recorders 12 and 14, one of which stores a set of data from
various computers on board the aircraft, for example flight data (data reflecting
the behaviour of the aircraft in flight) and the other of which stores audio data
recorded in the cockpit. It will be noted that according to the invention, the
aforementioned data can be distributed differently between the two black boxes,
and that other types of data can be stored in one and/or the other of the boxes,
such as video data recorded in the cockpit and in the aircraft environment.
Furthermore, according to another variant, one or more other black boxes can
be added to store the flight data and the audio data and/or other types of data,
such as the aforementioned video data, differently. Hereafter, when reference is
made to one and/or the other of the black boxes 12 and 14, it is understood that
this can apply to a different number of black boxes and any type of data.
The system 10 also comprises a data transmission system 16.
The system 16 comprises means 18 of encrypting the data intended
to be transmitted outside the aircraft originating from one or both of the black
boxes 12, 14.
It will be noted that the data contained in one and/or the other of the
black boxes can be identical from one black box to another, or different.
Furthermore, according to a variant, the data originating from one
and/or the other of the black boxes can correspond to all of the data stored in
each one of them or a selection of said data.
It will be noted that the aim of the data encryption is to ensure the
confidentiality of the data that will be transmitted. In particular, said data will be
transmitted to another aircraft and it must only be readable by a duly authorized
entity or by a collection of authorized entities. To this end, the encryption has
the effect of rendering the data unintelligible.
The encryption takes place for example by means of a public key and
private key system, the use of the public key held by each of the entities in
question (transmitter and receiver authorized to examine the data) being
necessary for decryption.
It will be noted that threshold schemes can also be implemented to
ensure greater confidentiality of the data. The principle of a threshold scheme is
that several entities authorized to decrypt the data share the decryption key; the
entities must all therefore agree to proceed with decryption.
The system 16 optionally comprises means of prior processing of the
data originating from one and/or the other of the black boxes 12 and 14.
Data selection means can for example form part of the means 18.
It will be noted that the optional processing means ensure, for
example, the optimization of the volume of data in order to reduce the
bandwidth used for the transmission thereof.
As an example, the effective one-way bandwidth (non-satellite)
between two aircraft is 5 Mb/s.
The system 16 also comprises a physical storage medium 20 (for
example, a magnetic medium) that can be a buffer memory area or a storage
space on a hard disk.
The data originating from one and/or the other of the black boxes,
previously encrypted, is stored in the separate intermediate storage space 20.
The system 16 also comprises means 22 of processing the data (for
example, a microprocessor, a dedicated electronic circuit, an FPGA type
programmable component, etc.) from the storage space 20.
This processing can perform several functions.
Firstly, the processing makes it possible to format the data into a
data frame.
This formatting consists, for example, of structuring the data in the
form of a signal comprising one or more headers and a signal body containing
the payload.
The processing can also comprise a second encryption, which here
makes it possible to guarantee the integrity of the data to be transmitted,
previously encrypted by the means 18.
This second encryption consists for example of calculating a
signature from ,the data that has been previously encrypted. Such a signature
can be obtained by calculation using a mathematical formula applied to the
encrypted data. The encrypted data will then be transmitted with the signature
calculated in this way.
The system 16 also comprises data transmission means 24. These
means use a procedure for communication between a transmitting aircraft and a
receiving aircraft that is linked to the communication protocol chosen for the
communication means used. This procedure established between the two
aircraft makes allows the transmitted signal to be made more robust insofar as it
makes it possible to detect errors such as a packet not reaching its destination,
the loss of integrity of the packet, etc. The packet can thus be retransmitted if
an error is detected.
The system 16 also comprises means 26 making it possible to
establish one or more connections between the aircraft comprising the system
10 and one or more aircraft.
The aircraft in flight constitute mobile nodes of a communication
network.
Figure 2 is a diagrammatical representation of several mobile modes
30, 32, 34, 36 of such a communication network 40.
In this figure, the aircraft represented by the mobile node 30
corresponds to the aircraft comprising the system 10 in Figure 1.
9
The communication protocol used to transmit the data supports a
connected connection mode.
It will be noted that the communication management means 26 first
perform a phase of discovering the topology of the communication network of
which the aircraft in question forms part.
During this discovery phase, the means 26 examine, by sending a
signal and possibly receiving a reply signal, whether there is a mobile
communication node within radio range.
The transmission takes place for example over a two-way radio
communication link.
The advantage of radio-type communication lies in the width of the
bandwidth and the fact that the use thereof is free of charge, or that the cost is
included in a package, without any additional charges depending on
consumption.
If no reply is received, optionally the means 16 can send the signal
over a satellite link either in order to identify, by the return signal, one or more
mobile communication nodes capable of forming a communication pair in
connected mode on this communication link or in order to send it to an
installation on the ground.
The advantage of satellite communication lies in the geographical
coverage thereof, and in the fact that it does not depend on atmospheric
conditions.
The means 26 comprise more particularly several sub-means:
- sub-means of searching for at least one mobile communication
node in the network (for example, with reference to Figure 2, the search is
performed by the nodes 32, 34 and 36 of the network 40);
- sub-means of selecting a mobile communication node from the
nodes found, said node meeting one or more predetermined criteria (the
selection of a particular node from the nodes 32, 34 and 36 in Figure 2 is
carried out for example in relation to a predetermined criterion such as the best
signal-to-noise ratio provided by said nodes; another node selection criterion
can be the node in the network that remains within communication range for the
longest (for example, the node 30).
- sub-means of establishing a connection with the selected node.
When a connection is established with the selected node, the
transmission system 16 then proceeds to transmit the data (which has been
processed as set out above) to the selected node.
It will be noted that the selected node was not determined in
advance. The node 30 was only informed of the existence of the node selected
to receive its data after the selection process described above.
Figure 3 shows a mechanism for establishing a connection between
the aircraft 30 and one of the aircraft 32, 34, 36 in Figure 2.
As shown in Figure 3, the algorithm comprises a first step 81 of
searching for one of more mobile communication modes in the network 40.
As indicated above, during this search step, the type of
communication network that will be used for transmission is selected, namely a
radio communication network, an optical communication network, or another
type of wireless communication network, or even a satellite communication
network.
The search for the best node is performed for each physical layer
implemented (radio, satellite, optical, etc.). The best physical layer is selected,
for example, in the software the algorithm for which is shown in Figure 3. An
order of preference of the physical layer is for example defined. For example, as
long as radio communication is available (i.e. the nodes are within range and
available for communication), this medium is chosen; otherwise the 4G network
is chosen, and failing this, the satellite network.
In each of the three steps in the example, the search for the best
node takes place.
As in the example in Figure 2, a radio communication type network
has for example been chosen and the most appropriate node(s) must then be
chosen in order to ensure the reliability and to optimize the data interchanges
between the node 30 and this/these node(s).
\'
The following selection step S2 provides for the selection of one or
more nodes that meet one or more predetermined criteria.
One of the predetermined criteria is for example the maximization of
the signal-to-noise ratio of the signal from a node.
Another criterion can for example lie in the aircraft that has/have
similar flight plans to that of the aircraft 30 in order to maximize the availability
time of the node(s).
Searching for aircraft that belong to the same airline as the aircraft 3
can also be used as a criterion.
One or several of these criteria in combination can be used.
It will be noted that the search and selection steps are performed
either periodically or on demand, for example following a loss of connection with
an aircraft.
The algorithm in Figure 3 comprises a step S3 of requesting
connection with the previously selected node(s).
The aim of this connection establishment request is to inform the
future· receiving node that the transmitting node 30 wishes to transmit sensitive
information.
When the node receiving the connection request accepts it on the
basis of conditions specific thereto (the node is not, for example, already
actively connected to this aircraft or another aircraft, one or more storage
spaces are available in the receiving node, etc.), the connection is established.
The step of transmitting the data from the aircraft 30, for example, to the aircraft
32 accepting the connection then takes place (step S4).
The algorithm ends with step 5, which ends the connection.
It must be noted that, on selection of a new best receiving node, two
options can be envisaged:
- the first option consists of replacing one of the poorer connections
still active with the aircraft 30 by a connection with the new node that has just
been identified;
- the second option consists of keeping this new best node as the
backup node and the connection thereto will only be made after the existing
communication with a so-called current node has been lost.
Figure 4 is a diagrammatical representation of a data receiving
system 50 on board an aircraft. The aircraft in question is for example the
above-mentioned aircraft 32, which is the best candidate for retrieving recorder
or black box data from the aircraft 30 in light of the selection criterion put in
place (for example, geographical proximity).
The system 50 comprises means 52 of receiving the data transmitted
by the aircraft 30 that are, for example, radio, optical, satellite, etc. receiving
means depending on the physical communication link used.
The system 50 also comprises a backup storage space 54 and a
reserved storage space 56 in the event that the space 54 is unavailable. The
data received is then stored in the appropriate space.
It will be noted that the aircraft 32 comprises the same means as
those shown in Figure 1, which makes it possible, if the type of communication
permits (two-way communication), for the aircraft 32 to transmit its data to the
aircraft 30.
When the aircraft 32 lands, the data from the aircraft 30 is then
retrieved, stored for a limited period, and optionally centralized by the airline or
a region or an airport with a view to possible use after decryption.
Figure 5 shows an algorithm for a data transmission method
according to the invention.
This algorithm is implemented on board the aircraft that will transmit
data present in its black boxes or recorders.
The algorithm is for example implemented by the system 16 in Figure
1 after retrieval of the data originating from the black boxes or recorders 12 and
14.
This algorithm comprises several steps including a first algorithm
initialization step, marked 810.
The next step 812 of the algorithm is a test to check whether or not
the aircraft is in alert mode.
13
Alert mode characterizes the fact that the aircraft is faced with one or
more critical problems. It is a mode that defines that outgoing communications
from this aircraft take priority over other transmissions that are not in this mode.
This mode can be activated manually or automatically and the aim
thereof is to transmit the data (or certain selected data) contained in the black
boxes to an aircraft or a set of aircraft located nearby (for example, the aircraft
32, 34 and 36 in Figure 2) and force recording by one or more of these aircraft
in this region.
It will be noted that the data is transmitted, for backup purposes, via
a means of communication chosen in relation to a predetermined criterion such
as its availability or because it constitutes a preferred means (e.g.: radio).
However, if this means cannot be used for any reason (e.g.:
unavailability of the means and for example momentary loss of the
communication network), then the use of other means of communication is
envisaged for the data transmission.
For example, another means of communication can be selected
automatically as a second preferred means (for example, satellite).
As will be seen below with reference to the procedure for receiving
data by a receiving aircraft (node), some of the aircraft detecting information in
alert mode are obliged to back up this data, as well as the geographical position
of the aircraft in difficulty, to a backup storage space.
Provision is made for the communication protocol to collect
information from the aircraft in difficulty.
It must therefore be noted that in alert mode, the data transmission
system of the aircraft in question (for example the aircraft 30 in Figure 2) can be
capable of transmitting black box data via a satellite link to a station on the
ground, in order to warn the emergency services and the investigation team as
soon as possible.
When alert mode is detected, several options can be envisaged.
Firstly, it is possible to provide for a change in the flight plan of an
aircraft located in the geographical region in which the aircraft in difficulty is
situated, so that the former can follow the latter for as long as possible and
P1
collect flight information from this aircraft, together with its position. As provided
for in step 814 in Figure 5, in alert mode the suspension or abandonment of
existing connections with aircraft can be envisaged, with the exception of
connections already established from one or more aircraft in alert mode, in
order to free up bandwidth. This makes it possible to provide the aircraft in
difficulty with as much bandwidth as possible and thus optimize the collection of
data coming from that aircraft.
It will also be noted that in order to optimize the collection time of the
data from the aircraft in difficulty, the broadcasting of this data to several aircraft
instead of just one can be envisaged, or the broadcasting of this data using
several different physical layers (radio, optical, satellite, etc.).
When the decision is made to transmit black box data outside the
aircraft, the data is retrieved by the means 22 from the storage space 20.
The next step 816 provides for the fragmentation of the data to be
transmitted into data packets, each made up of a header and a payload
containing the useful data.
This fragmentation is performed depending on the physical layer and
communication protocol used.
All of the packets are thus transmitted to the same recipient.
It will be noted that, in the event that the data is broadcast to several
aircraft, the same packets will for example be transmitted in parallel to all of
those aircraft.
The next step 818 is a test used to determine whether there are any
data fragments left to be transmitted. If there are no more fragments awaiting
transmission, the algorithm is then ended in step 820.
If there are fragments left to be transmitted, then step 818 is followed
by a step 822 consisting of creating and adding a header to the data signal to
be transmitted (packet).
The header(s) created in this way are useful for managing the data.
As an example, it comprises flags or markers indicating the presence
of specific information such as information used to identify the aircraft (code),
etc.
The algorithm comprises a next step 824 for adding information to
the signal to be transmitted in order to guarantee the integrity of the data to be
transmitted.
The processing performed to ensure the integrity of the data is the
processing already described with reference to Figure 1 and is performed by the
means 22.
The next step 826 makes provision for notifying, in the signal to be
transmitted, the indication that the information that the data to be transmitted
comes from an aircraft, configured in alert mode. This indication is for example
added to the header created in step 822.
The next step 830 makes provision for the data to be transmitted in
packets on the physical link (either by radio link, satellite link, optical link or 4G
link, etc.), as already described above, after execution of the algorithm in Figure
3.
The topology discovery mechanism described with reference to
Figure 3 is suitable for a radio network with mobile nodes as well as a satellite
network and must take into account the performance aspects in order to avoid
excessive consumption of bandwidth and local resources.
It will be noted in this regard that it can be envisaged, for an aircraft
wishing to establish a connection, that it broadcasts a connection request in
accordance with a timer operating periodically or pseudo-periodically.
It will be noted, furthermore, that a connection is established for
example at least in one of the protocol layers.
In the embodiment, the connection is preferably established in a
single layer as several connections on different protocol levels make the
transmission system more complex and less efficient.
A very dense radio network such as the network of the global aircraft
fleet in flight at a given time (t) must be capable of withstanding a very heavy
load without affecting its operation.
To this end, and to avoid potential blockages (for example, saturation
of the frequency band) the number of connections per aircraft is limited.
"
•
Thus, if N denotes the number of outgoing connections, N' the
number of incoming connections, M the total number of connections and K the
number of backup locations, the applicant has established the following
relationships:
N'=N
M =2xN
K = M + 1, the digit "1" denotes a storage location that is always
reserved for the storage of data from an aircraft in alert mode.
In the embodiment, two outgoing connections and two incoming
connections are used.
One of the means of communication used to transmit the data uses a
two-way radio communication network to transmit and receive data between
mobile nodes.
Such a network is not necessarily dedicated to the use planned for
the implementation of the invention, and can also be used to perform one or
more other functions of the aircraft.
The system used is for example a Wi-Fi or WiMAX system that
provides the bandwidth, the range (maximum distance within which
communication is physically possible) and the properties necessary for the
implementation of the invention (for example, the technology must make it
possible to provide the required level of security, manage service quality, etc.).
It will be noted that the transmission step S30 is followed by the step
S18 already described above in order to check whether there are any data
fragments left to be transmitted.
Returning to the test step S12 already described above, when alert
mode is not identified, the next step S31 makes provision for the fragmentation
of the data to be transmitted if necessary.
This step is identical to step S16 already described above.
Step S31 is followed by a test step S32 used to determine whether
there are any data fragments left to be transmitted.
If not, this step is followed by step S20, which ends the transmission
algorithm.
11'
If there are, step 832 is followed by a step 834 that makes provision
for creating and adding one or more headers to the data signal to be
transmitted.
This step is identical to step 822 already described above.
The next step of adding information to guarantee the integrity of the
data (836) is identical to step 824 already described above.
The next step 840 makes provision for transmitting the data
configured in the previous steps on a physical link as already described above
in step 830.
The data is thus transmitted to the aircraft previously selected as the
receiving node in the network that is most suitable for the transmission.
If several valid aircraft have been detected, that is, several aircraft
have been selected as meeting one or more predetermined criteria, a first
connection is made with the most suitable of these aircraft.
As a priority, the black box data transmitted to this aircraft is that
which is most important in the event of an investigation, that is, the most recent.
It must be noted that, as far as possible, the data is transmitted in
real or quasi-real time, that is, as and when the data is acquired by the black
box(es).
A second connection is for example made with another aircraft
selected for transmitting older data, for example data several minutes old (for
example, t - 15 min.).
The second connection is for example established with the second
"best" pair found during the search for mobile nodes in the network.
It will be noted that transmission priority is granted to the data
obtained in real time.
Thus, as soon as the physical link is lost or a better link is detected,
the transmission algorithm is executed in order to re-establish real-time data
transmission.
This takes place even if another active transmission has to be ended
as a result.
• 8tep 840 is then followed by the test step 832 already described
above. It will be noted that the hardware platform used in the transmission
system 16 in Figure 1 is for example a PC-type open platform, the trust level of
which is improved by the use of a hardware encryption component such as for
example a TPM (Trusted Platform Module) defined by the TCG (Trusted
Computing Group).
Figure 6a shows an algorithm for part of a method for receiving data
according to the invention.
This algorithm is implemented in an aircraft of the mobile network as
shown in Figure 2 and for example in the aircraft 32 selected by the aircraft 30
as being the best communication partner.
This algorithm starts with an algorithm initialization step 850.
The algorithm comprises a step 852 of receiving a connection
request from the aircraft 30 and is followed by a test step 854.
During this step, it is checked whether a connection is already active
with the aircraft 30 from which the connection request originates.
If so, this step is followed by a step 856 of rejection of the connection
and the algorithm is then ended by a step 858.
If, on the other hand, there is no active connection with the aircraft
30, step 854 is followed by a step 860.
During this step, a test is performed to determine whether or not the
aircraft 30 is in alert mode.
If so, this step is followed by a step 862 for accepting the connection
request, then a step 864 for ending other current communications (abandoning
or blocking the other connections existing between the selected aircraft 32 and
other aircraft).
It will be noted that alert mode is defined in the aircraft from which
the connection request originates, for example, on the basis of the detection of
certain predetermined events that can be linked to the detection of critical faults
and/or are linked to worrying flight parameter measurements (for example,
exceeding predetermined thresholds).
Alert mode is thus chosen in order to prioritize the receipt of the black
box data transmitted by any mobile node located in a geographical region
allowing the data to be received.
Step S64 is followed by a step S58 ending the algorithm.
Returning to step S60, when the result of the test performed shows
that the aircraft is not configured in alert mode, a next test step S66 is
performed.
During this step, it is determined whether there is storage space
available on board the aircraft (backup location).
If not, the connection is rejected (step S56).
Otherwise, when storage space is available, the connection is
accepted (step S68).
It will be noted that when the aircraft from which the connection
request originates is not configured in alert mode, the receipt and storage of
data coming from that aircraft are not prioritized if no storage space is available.
As will be seen below with reference to Figure 6b, this is not the case
when alert mode is detected.
The algorithm in Figure 6b gives more specific details of the backup
process for the black box data collected on board the selected receiving aircraft.
This algorithm starts with an initialization step S80, followed by a test
step S82 that checks for the presence of data fragments (packets) to receive.
If there are none, this step is followed by step S84 ending the
algorithm.
Otherwise, if there are data fragments left to receive, then this step is
followed by a step S86 of checking the integrity of the data received.
The means put in place to check the integrity of the data are known
to a person skilled in the art (for example, use of a signature for example in the
MD5 or RSA algorithms). If the data received is not identical to the data
transmitted, provision is made for processing so that the transmitting aircraft is
alerted and the data can therefore be retransmitted.
Step S86 is followed by a step S88 for checking the information in
the header(s) of the data signal received.
During this step, the identification of any markers or flags indicating
to the receiving node that the transmitting node is an aircraft in difficulty takes
place.
The checking step is used for example to identify other information
such as the transmitter's identifier, receiver's identifier, packet serial number,
etc. This information is useful for organizing and subsequently finding the data if
necessary.
Step S88 is followed by a test step S90.
During this step, depending on the results of step S88, it is
determined whether or not the aircraft from which the black box data originates
is in alert mode.
If not, this step is followed by a step S92 for storing the data received
in an available storage space (backup location).
Otherwise, when the result of the test performed in step S90 shows
that the data originates from an aircraft in alert mode, then this step is followed
by a test step S94.
During this step, it is checked whether there is storage space
available on board the aircraft. In particular, it is checked whether the standard
storage space is available as a priority to avoid "filling up" the reserved area.
If standard storage space is available, then step S94 is followed by a
step S96 for storing the black box data received in this space (backup location).
If, conversely, no standard storage space is available, then step S94
is followed by a step S98 for backing up the black box data to a reserved
storage space (dedicated location).
The existence of specific available storage space is thus guaranteed
so that data can always be received from an aircraft in alert mode.

CLAIMS
1. Data transmission method, characterized in that it comprises a
step of transmitting data in flight between a first aircraft (30) and at least a
second aircraft (32), the data transmitted being data stored in at least one black
box (12, 14) on board the first aircraft (30).
2. Method according to claim 1, characterized in that the data
originating from said at least one black box requires for its transmission a
bandwidth of at least 100 kbits/s.
3. Method according to claim 1 or 2, characterized in that it
comprises a prior step of selecting a means of communication from several
communication means.
4. Method according to claim 3, characterized in that the means of
communication comprise radio means, satellite means or any other wireless
communication means.
5. Method according to one of claims 1 to 4, characterized in that
the data is transmitted on a communication network (40) comprising mobile
communication nodes (30, 32, 34, 36) that are aircraft in flight.
6. Method according to claim 5, characterized in that it comprises,
prior to the transmission step, a step of selecting in flight (S2) at least one nonpredetermined
mobile communication node, said at least one node being
selected from a set of mobile communication nodes in the network as a function
of at least one predetermined selection criterion.
7. Method according to claim 6, characterized in that said at least
one predetermined selection criterion is at least one of the following criteria:
(an) aircraft producing a signal-to-noise ratio above a predetermined threshold,
(an) aircraft having (a) similar or identical flight plan(s), (an) aircraft belonging to
the same airline or the same alliance of several airlines, (an) aircraft made by
the same manufacturer, (an) aircraft within communication range, the aircraft
furthest away from the first aircraft, (an) aircraft in descent phase.
8. Method according to claim 6 or 7, characterized in that it
comprises a step (83) of requesting the establishment of a connection with said
at least one selected node, prior to the transmission of the data.
9. Data receiving method, characterized in that it comprises a step
(852) of receiving in flight, from a first aircraft (3D), data stored in at least one
black box (12, 14) on board the first aircraft, the receiving step taking place on
board at least a second aircraft (32).
10. Method according to claim 9, characterized in that it comprises a
prior step (856) of checking the availability of a storage space with a view to
storing the data to be received.
11. Method according to claims 9 and 10, characterized in that it
comprises a step (892, 898, 896) of storing the data received either in an
available storage space or, if this is unavailable, in a reserved storage space.
12. Data transmission system (16), characterized in that it comprises
means of transmitting data in flight between a first aircraft (30) and at least a
second aircraft (32), the data transmitted being data stored in at least one black
box (12, 14) on board the first aircraft.
13. Data receiving system (50) on board an aircraft, characterized in
that it comprises means (52) of receiving in flight, from a first aircraft (30), data
stored in at least one black box (12, 14) on board the first aircraft, said system
being on board a second aircraft.
14. Aircraft (30; 32) characterized in that it comprises a transmission
system (16) according to claim 12 and/or a receiving system (50) according to
claim 13.