Title of Invention

METHOD AND DEVICE FOR DETECTING DEGRADATION OF PERFORMANCE OF AN AIRCRAFT

Abstract The device (1) comprises a set (2) of information sources, a central unit (3) connected to said set (2) of information sources and able to detect a degradation of performance of an aircraft, and warning means (5) connected to the central unit (3), said central unit (3) comprising means (7, 8) for computing at least one current weight and a current drag of the aircraft and, on the basis of said current weight, a theoretical drag of said aircraft, means (10) for implementing at least one first set of comparisons, which relates to the drag and which comprises at least one comparison between said current drag and said theoretical drag, and means (12) for determining whether a degradation of performance of the aircraft exists, at least on the basis of said first set of comparisons.
Full Text The present invention relates to a method and a device for detecting degradation of performance of an aircraft.
It is known that, despite certification complying with the regulations, aircraft, in particular transport planes, may encounter situations which significantly degrade the aerodynamics, without the crew being aware thereof. Such a situation may give rise to a surprise effect which may be the cause of an unsuitable reaction from the crew, all the more so since, when the degradation of the aerodynamic performance becomes significant, the flight qualities are modified and the control of the aircraft becomes much more difficult.
The causes of degradation of performance that are best known are in particular icing, the absence of deicing on the ground of an iced-up airframe, snow, freezing rain, the application of deicing or anti-icing fluid, the picking up of insects on leading edges, the loss of a part of a leading edge or of a panel of the flying surface.
When an aircraft is confronted with one of the aforesaid situations causing a degradation of its performance, its resistance to progress through the air increases and the drag grows. In such a case, if the power is not modified, the aircraft loses speed while it is holding altitude, or the rate of climb drops when it is holding speed, which may of course become very dangerous and is not acceptable.
The present invention is aimed at aiding the crew in such situations that are liable to be dangerous. It relates to a method for detecting, simply, rapidly and accurately, a degradation of performance of an aircraft, in particular a degradation of performance which is due to conditions of severe icing of the

aircraft.
For this purpose, said method is noteworthy according to the invention in that the following sequence of steps is carried out automatically and repetitively:
a) we compute at least:
a current weight of the aircraft;
on the basis of said current weight, a
theoretical drag of said aircraft; and
a current drag of said aircraft;
b) we implement at least a first set of comparisons,
c) which relates to the drag and which comprises at
d) least one comparison between said current drag and
e) said theoretical drag; and
f) we determine whether a degradation of performance
g) of the aircraft exists, at least on the basis of
h) said first set of comparisons.
Advantageously, if a degradation of performance of the aircraft is detected in this step c), then at least one corresponding alert message is emitted in a next step d)•
Thus, by virtue of the invention, it is possible to simply and rapidly detect a degradation of performance of an aircraft, by taking account of the values of drag, including a theoretical drag which is computed on the basis of the estimated weight of the aircraft, and to warn the crew upon such a detection. The crew can then in full knowledge of the facts take all the necessary measures to remedy such a situation which is liable to be dangerous-
In a preferred embodiment, in step a):
said current weight of the aircraft is computed on the basis of the initial weight before the flight and of a consumption of fuel during the flight

which depends at least on the altitude of the
aircraft during the flight and on the type of said
aircraft; and/or
said theoretical drag CXth is computed on the
basis of the following expression:
CXth = fl(CZ2) + f2(RE) + ∆CXf
in which:
• CZ is a value of draG dependent on the current
• weight of the aircraft;
• f1 (CZ2) is a function dependent on CZ2;
• f2(RE) is a function dependent on the Reynolds
• number RE; and
• ACXf is a value dependent on CZ2 and CZ; and/or
said current drag CXa/c is computed on the basis of the following expression:

in which:
• R is a constant value;
• S represents the area of the flying surface of the
• aircraft;
• TAS is a computed air speed;
• G is a value dependent on TAS; and
• T is a value of traction.
The present invention may be implemented regardless of the phase of flight of the aircraft. However, in a preferred embodiment, a check is performed to verify whether the aircraft is or is not in cruising flight, in particular by checking whether a standard mode of capture of altitude is engaged on said aircraft.
Advantageously, when, by virtue of the above check, it turns out that the aircraft is not in cruising flight, in step c) , we determine whether a degradation of the

performance of the aircraft exists, solely on the basis of said first set of comparisons relating to the drag.
In this case, advantageously, a degradation of performance of the aircraft is detected if one of the following two conditions A and B, relating to said first set of comparisons, is fulfilled:

for which:
CXa/c is the computed current drag of the
aircraft;
CXth is the computed theoretical drag of the
aircraft;
∆CX1, ∆CX2 and ∆CX3 are predetermined values of
drag;
∆CX2 is for example equal to ∆CX1;
∆CXa/c is a deviation of current drag between two
different predetermined instants; and
∆CXth is a deviation of theoretical drag between
two different predetermined instants.
Additionally, when, by virtue of the above check, it turns out that the aircraft is in cruising flight:
in step a), a theoretical cruising speed is
computed on the basis of said current weight of
the aircraft, and a current speed of the aircraft
is measured;
in step b), a second set of comparisons is
implemented, which relates to the speed and which
comprises at least one comparison between said
current speed and said theoretical cruising speed;
and
in step c) , we determine whether a degradation of
performance of the airc.raft exists, likewise on

the basis of said second set of comparisons relating to the speed, therefore on the basis of both said first and second sets of comparisons relating respectively to the drag and to the speed.
In this case, advantageously, in step a) , said theoretical cruising speed is computed on the basis of the current weight of the aircraft, of a measured altitude of the aircraft and of a deviation of temperature between a standard temperature and a measured temperature.
Moreover, advantageously, in step c) , a degradation of performance of the aircraft in cruising flight is detected if one of the following two conditions C and D, relating to said first and second sets of comparisons, is fulfilled:

for which, in addition to the aforementioned parameters:
∆CX4 and ∆CX5 are predetermined values of drag;
IAS is the measured speed of the aircraft;
IASth is the computed theoretical cruising speed;
and
AlASl is a predetermined deviation in speed.
When neither of the aforesaid conditions C and D is fulfilled in cruising flight, advantageously, in step c) , a degradation of performance of the aircraft is detected if one of the following two conditions E and F, relating to said first and second sets of comparisons, is fulfilled:


for which, in addition to the aforementioned parameters:
∆CX6 and ∆CX7 are predetermined values of drag;
∆CX6 is less than ∆CX4;
∆CX7 is for example equal to ∆CX5;
∆IAS2 is a predetermined deviation of speed; and
∆IAS2 is greater than ∆IAS1.
Furthermore, advantageously, if none of the aforementioned conditions C, D, E and F is fulfilled in cruising flight, a check is performed to verify whether one of the two following conditions G and H, relating to said first and second sets of comparisons, is fulfilled:

for which:
• ∆CX8 and ∆CX9 are predetermined drag values, ∆CX8
being less than ∆CX6; and
• ∆IAS3 is a predetermined deviation of speed, which
is less than ∆lASl and than ∆IAS2; and
if one of said conditions G and H is fulfilled, a message indicating that the cruising speed is low is emitted in step d).
Additionally, in a particular embodiment, when a degradation of performance is detected, regardless of

the flight phase:
a measured speed IAS (in particular the speed
indicated by an anemometer) is compared with a
computed minimum operational speed MSIS, relating
to severe icing conditions; and
if said speed IAS is less than said speed MSIS, a
message requesting an increase in speed is
emitted.
Furthermore/ advantageously:
steps a) to c) mentioned above are carried out only if flaps and the landing gear of the aircraft are retracted; and/or
steps b) and c) mentioned above are carried out only if at least one icing condition specified below is fulfilled and additionally if a measured static air temperature is greater than a predetermined value.
The present invention also relates to a device for detecting and warning of degradation of performance of an aircraft.
According to the invention, said device of the type
comprising:
a set of information sources;
a central unit connected to said set of
information sources and able to detect a
degradation of performance of an aircraft; and
warning means connected to said central unit,
is noteworthy in that said central unit comprises:
means for computing at least one current weight of
the aircraft, a current drag of said aircraft and,
on the basis of said current weight, a theoretical
drag of said aircraft;
means for implementing at least one first set of
comparisons, which relates to the drag and which
comprises at least one comparison between said
current drag and said theoretical drag; and

means for determining whether a degradation or performance of the aircraft exists, at least on the basis of said first set of comparisons.
Moreover, advantageously, said central unit furthermore comprises:
means for computing a theoretical cruising speed, on the basis of said current weight of the aircraft;
means for measuring a current speed of the aircraft;
means for carrying out a second set of comparisons, which relates to the speed and which comprises at least one comparison between said current speed and said theoretical cruising speed; and
means for determining whether a degradation of performance of the aircraft exists, likewise on the basis of said second set of comparisons relating to the speed-Additionally, in a preferred embodiment:
said set of information sources comprises a flight data acquisition unit, of FDAU type, which, in standard fashion, carries out the acquisition of data for a flight data logger, of FDR type ("Flight Data Recorder"); and/or
said warning means, which are intended to warn the crew of a degradation of performance or of a low speed, comprise a aircraft performance interface unit of APIU type which, in standard fashion, carries out the management of the signaling, as well as the recording of messages in a flight data recorder of the aforesaid FDR type.
Said warning means may be of visual type and/or of audible type.
The figures of the appended drawing will elucidate the

means for determining whether a degradation of performance of the aircraft exists, at least on the basis of said first set of comparisons.
Moreover, advantageously, said central unit furthermore comprises:
means for computing a theoretical cruising speed, on the basis of said current weight of the aircraft;
means for measuring a current speed of the aircraft;
means for carrying out a second set of comparisons, which relates to the speed and which comprises at least one comparison between said current speed and said theoretical cruising speed; and
means for determining whether a degradation of performance of the aircraft exists, likewise on the basis of said second set of comparisons relating to the speed-Additionally, in a preferred embodiment:
said set of information sources comprises a flight data acquisition unit, of FDAU type, which, in standard fashion, carries out the acquisition of data for a flight data logger, of FDR type ("Flight Data Recorder"); and/or
said warning means, which are intended to warn the crew of a degradation of performance or of a low speed, comprise a aircraft performance interface unit of APIU type which, in standard fashion, carries out the management of the signaling, as well as the recording of messages in a flight data recorder of the aforesaid FDR type.
Said warning means may be of visual type and/or of audible type.
The figures of the appended drawing will elucidate the

manner in which the invention may be embodied, in these figures, identical references designate similar elements.
figure 1 is the schematic diagram of a device in accordance with the invention.
figure 2 is a chart showing the successive steps of a method implemented by the device in accordance with the invention.
The device 1 in accordance with the invention and represented diagrammatically in figure 1 is a device for detecting and warning of degradation of performance of an aircraft (not represented), in particular of a transport plane. Although not exclusively, said device 1 is intended more especially for detecting a degradation of performance due to a problem of severe or excessive icing on the aircraft.
To do this, said device 1 which is carried on board the aircraft, is of the type comprising:
a set 2 of the information sources;
a central unit 3 connected by way of a link 4 to
said set 2 of information sources and able to
detect a degradation of performance of said
aircraft; and
warning means 5 which are connected by way of a
link 6 to said central unit 3.
According to the invention, said central unit 3
comprises:
means 7 for computing at least one current weight
W of the aircraft;
means 8 which are connected by way of a link 9 to
said means 7, for computing a current drag CXa/c
of said aircraft and, on the basis of said current
weight W, a theoretical drag CXth of said
aircraft;

means 10 which are connected by way of a link 11 to said means 8, for implementing at least a first set of comparisons, which relates to the drag and which comprises at least one comparison between said current drag CXa/c and said theoretical drag CXth; and
means 12 which are connected by way of a link 13 to said means 10, for determining whether a degradation of performance of the aircraft exists, at least on the basis of said first set of comparisons.
Thus, by virtue of the invention, said device 1 is able, on the one hand, to detect simply and rapidly a degradation of performance of an aircraft, by taking account of the values of drag CXa/c and CXth, of which the theoretical drag CXth is computed on the basis of the estimated weight W of the aircraft, and, on the other hand, to warn the crew upon such a detection, by way of said warning means 5.
In a particular embodiment, said means 7 computes said current weight W of the aircraft, on the basis of the initial weight WO before the flight and of a consumption of fuel during the flight which depends at least on the altitude of the aircraft during said flight and on the type of said aircraft. This computation is carried out, for example each second, starting from the takeoff of the aircraft until its final landing. To do this, said initial weight WO may be input by a crew member into the device 1, with the aid for example of an actuable rotator forming part of said set 2. As regards the consumption of fuel, it may be presented on an array, as a function of the altitude and possibly of the speed of the aircraft (unless taking account of a predetermined maximum speed for each of the various phases of flight), said array possibly being recorded directly in said means 7 or in a database (not represented) of said device 1.

Furthermore, said means 8 compute said theoretical drag CXth, on the basis of the following expression: CXth = fl(CZ2) + f2(RE) + ∆CXf
in which:
CZ is a value of drag specified below, dependent
on the current weight W computed;
f1 (CZ2) is a function dependent on CZ2;
f2(RE) is a function dependent on the Reynolds
number RE; and
∆CXf is a value dependent on CZ2 and CZ.
The functions fl(CZ2) and f2(RE) may be presented in the form of arrays which may be defined empirically. Moreover:
said value CZ may be computed with the aid of the
following expression:

in which:
• g is the acceleration due to gravity;
• p is the density of the air;
• S is the area of the flying surface of the
• aircraft; and
• TAS is an air speed computed in a standard
fashion; and
said value ∆CXf may be computed with the aid of
the following expression:
∆CXf = Al.CZ2 + A2.CZ + A3
with Al, A2 and A3 predetermined coefficients,
defined for example empirically.
Additionally, said means 8 compute said current drag CXa/c on the basis of the following expression:


in which:
R is a constant value (ideal gas constant);
S represents the area of the flying surface of the
aircraft;
TAS is a computed air speed;
G is a value dependent on TAS and on a geometric
altitude Zg; and
T is a value of traction.
The present invention may be implemented regardless of the phase of flight (climbing, cruising, descending) of the aircraft. However, this implementation depends on the phase of flight. As will be seen in greater detail hereinbelow, in the cruising phase, values of drag of the aircraft and speed values specified hereinbelow will be taken into account, whereas in the other phases of flight, only said values of drag will be taken into account.
Also, said central unit 3 moreover comprises:
means 14, which are connected by way of a link to said means 7, for computing a theoretical cruising speed IASth, on the basis of said current weight W of the aircraft;
means which are for example integrated into the set 2, for measuring a current speed IAS of the aircraft; and
means 16 which are connected by a link 17 to said means 14, for carrying out a second set of comparisons, which relates to the speed and which comprises at least one comparison between said current speed IAS and said theoretical cruising speed IASth.
Moreover, said means 12 which are aimed at determining whether a degradation of performance of the aircraft exists, may also take account (depending on the phase of flight) of said second set of comparisons relating

to the speed, received by way of a link 18 from said means 16.
Said means 14 compute said theoretical cruising speed IASth on the basis of the current weight W of the aircraft, of a measured altitude Zp of the aircraft, and of a deviation of temperature AISA between a standard temperature Tstd and a measured static air temperature SAT.
In a preferred embodiment, said means 14 use to do this the following expression:
ISth = aO + al.W + a2.W2 + a3.∆lSA + a4.W.∆lSA + a5.∆lSA2 + a6.Zp + a7.Zp.W + a8.Zp.∆lSA + a9.Zp2
The parameters aO to a9 are predetermined values dependant on the type of aircraft considered and defined for example empirically.
Additionally, the device 1 in accordance with the invention also comprises means forming for example part of the set 2, for checking whether the aircraft is or is not in cruising flight. For this purpose, these means check for example whether a standard mode of altitude capture is engaged on said aircraft, and this is done for a predetermined duration, for example from 2 minutes.
When, by virtue of the above check, it turns out that the aircraft is not in cruising flight (altitude capture mode not engaged or not engaged for the aforesaid predetermined duration), said means 12 determine whether a degradation of performance of the aircraft exists, solely on the basis of said first set of comparisons relating to the drag, received from said means 10.
In this case, said means 12 detect a degradation of performance of the aircraft if one of the following two

conditions A and B relating to said first set of comparisons is fulfilled:
condition A: • CXa/c > CXth + ∆CX1, for a
predetermined duration, for
example 30 seconds;

for which:
CXa/c is the computed current drag of the
aircraft;
CXth is thus the computed theoretical drag of the
aircraft;
∆CX1, ∆CX2 and ∆CX3 are predetermined values of
drag;
∆CX2 is equal to ∆CX1;
∆CXa/c is a deviation of current drag CXa/c
between two different predetermined instants tl
and t2, for example the current instant tl and a
previous instant t2 corresponding to a
predetermined duration (for example 30 seconds)
before the current instant tl. Thus, ∆CXa/c =
CXa/c(tl) - CXa/c(t2); and
∆CXth is a deviation of theoretical drag CXth
between two different aforementioned instants tl
and t2: ∆CXth = CXth(tl) - CXth(t2).
On the other hand, when, by virtue of the above check, it turns out that the aircraft is in cruising flight (altitude capture mode engaged), the means 12 determine whether a degradation of performance of the aircraft exists, likewise on the basis of said second set of comparisons relating to the speed, received from said means 16 (in addition to said first set of comparisons relating to the drag, received from said means 10).
In this case, said means 12 detect a degradation of performance of the aircraft if one of the following two

conditions C and D, relating to said first and second sets of comparisons, is fulfilled:
condition C: • CXa/c > CXth + ∆CX4; and
• IAS for a predetermined duration, for example 30 seconds; condition D: • CXa/c > CXth + ∆CX4; and
• IAS • ∆CXa/c > ∆CXth + ∆CX5
for which, in addition to the aforesaid parameters: ∆CX4 and ∆CX5 are predetermined values of drag; IAS is thus the measured current speed of the aircraft;
IASth is thus the computed theoretical cruising speed; and AIAS1 is a predetermined deviation in speed.
When neither of the aforesaid conditions C and D is fulfilled in cruising flight, said means 12 check conditions E and F and detect a degradation of performance of the aircraft if one of said following two conditions E and F relating to said first and second sets of comparisons is fulfilled:
condition E: • CXa/c > CXth + ∆CX6; and
• IAS for a predetermined duration, for example 30 seconds; condition F: • CXa/c > CXth + ∆CX6;
• IAS • ∆CXa/c > ∆CXth + ∆CX7
for which, in addition to the aforesaid parameters: ∆CX6 and ∆CX7 are predetermined values of drag; ∆CX6 is less than ∆CX4; ∆CX7 is for example equal to ∆CX5; ∆IAS2 is a predetermined deviation of speed; ∆IAS2 is greater than ∆lASl;
If, during one of the aforesaid checks, a .degradation

of performance of the aircraft is detected, said warning means 5 emit at least one appropriate corresponding alert message. To do this, said warning means 5 may comprise:
at least one viewing screen 19 for displaying
alert messages; and/or
standard audible means 20, which are provided in the flight deck of the aircraft.
Additionally, if none of the conditions C, D E and F above is fulfilled in the cruising phase, said means 12 check whether one of the following conditions G and H is fulfilled:
condition G:
• CXa/c > CXth + ∆CX8; and
• IAS • for a predetermined time,
condition H:
• CXa/c > CXth + ∆CX8;
• IAS • ∆CXa/c > ∆CXth + ∆CX9,
• in which:

• ∆CX8 and ∆CX9 are predetermined drag values,
• ∆CX8 being less than ∆CX6; and
• ∆IAS3 is a predetermined deviation of speed,
• which is less than ∆lASl and than ∆IAS2; and
if one of said conditions G and H is fulfilled, said warning means 5 emit a message indicating that the cruising speed is low.
Additionally, in a particular embodiment, when the central unit 3 detects a degradation of performance:
it compares a measured speed IAS with a computed minimum operational speed MSIS, relating to severe icing conditions; and
if said speed IAS is less than said speed MSIS, said warning means 5 emit a message requesting an increase in speed.

Said speed MS IS is computed on the basis of the following expressions:

in which, in addition to the aforesaid parameters: VO is a predetermined speed value; K is a predetermined coefficient; R is the ideal gas constant;
TO is the standard temperature at sea level; y is a predetermined value;
P is the static pressure at the level of the aircraft;
PO is the static pressure at sea level; and CZmax is a predetermined value.
In a particular embodiment:
said means 8 and 14 carry out the aforesaid computations, generally every second, only if flaps and the landing gear of the aircraft are retracted. Such a retraction is checked with the aid of standard means forming for example part of the set 2 of information sources; and said means 10, 12 and 16 carry out the comparisons and the aforesaid processing operations, only if the static air temperature SAT measured is greater than a predetermined value, for example 5°C, and if one of the following icing conditions is fulfilled:
• an accretion of ice has already been detected
during the flight in progress;
• a luminous icing indicator is lit;
• a system for deicing the fuselage of the
• aircraft is operational.
Additionally, in a preferred embodiment:

said set 2 of information sources comprises a flight data acquisition unit, of FDAU type which, in standard fashion, carries out the acquisition of data for a flight data logger (not represented) , of FDR type ("Flight Data Recorder"); and/or
said warning means 5 comprise an aircraft performance interface unit of APIU type which, in standard fashion, carries out the management of the signaling, as well as the recording of messages in a flight data recorder of the aforesaid FDR type.
The method implemented by the device 1 in accordance with the invention is presented hereinafter with reference to the chart of figure 2.
This method comprises:
a preliminary step El of inputting the initial
weight WO into the device 1;
a computation step E2 for computing the current
weight W (means 7);
a verification step E3 for checking whether the
flaps and the landing gear of the aircraft are
retracted. If the response is negative ("N"
standing for "no"), we return to step E2,
otherwise ("Y" for "yes"), we go to a computation
step E4, then to a verification step E5;
said computation step E4 for computing:
• the current drag CXa/c;
• the theoretical drag CXth;
• the deviation of current drag ∆CXa/c;
• the deviation of theoretical drag ∆CXth;
• the theoretical cruising speed IASth; and
• the minimum operational speed MSIS;
said verification step E5 for checking whether at least one of the aforesaid icing conditions is fulfilled and whether a static air temperature SAT

measured is greater than a predetermined value. If the response is negative, we return to step E2, otherwise we go to a verification step E6; said verification step E6 for checking whether the aircraft is or is not in cruising flight:
• if it is not, we go to a verification step E7;
• and
• if it is, we go to a verification step E8;
said verification step E7 for checking whether the aforesaid conditions A and B are fulfilled:
• if they are, we go to a step E9, then to a step
• E10; and
• if they are not, we return to step E2;
said step E9 of emitting a message alerting the
crew of a degradation of performance (warning
means 5);
said step E10 of comparing the speed IAS with the
speed MSIS. If the speed IAS is greater than or
equal to the speed MSIS, we return to step E2,
otherwise we go to a step Ell;
said step Ell of emitting a message requesting an
increase in speed (warning means 5);
said verification step E8 for checking in cruising
flight whether the aforesaid conditions C and D
are fulfilled:
• if they are, we go to said step E9; and
• if they are not, we go to a step E12;
said verification step E12 for checking in cruising flight whether the aforesaid conditions E and F are fulfilled:
• if they are, we go to said step E9; and
• if they are not, we go to a verification step
• E13;
said verification step E13 for checking in cruising flight whether the aforesaid condition G is fulfilled:
• if it is not, we return to said step E2; and
• if it is, we go to a step E14;
said step El 4 of emitting a message indicating




1. A method for detecting a degradation of
performance of an aircraft,
wherein the following sequence of steps is carried out automatically and repetitively:
a) we compute at least:
a current weight of the aircraft;
on the basis of said current weight, a
theoretical drag of said aircraft; and
a current drag of said aircraft;
b) we implement at least a first set of comparisons,
c) which relates to the drag and which comprises at
d) least one comparison between said current drag and
e) said theoretical drag; and
f) we determine whether a degradation of performance
g) of the aircraft exists, at least on the basis of
h) said first set of comparisons,
2, The method as claimed in claim 1,
wherein, if a degradation of performance of the aircraft is detected in step c) , then at least one corresponding alert message is emitted in a next step d).
3. The method as claimed in claim 1,
wherein in step a), said current weight of the aircraft is computed on the basis of the initial weight before the flight and of a consumption of fuel during the flight which depends at least on the altitude of the aircraft during the flight and on the type of said aircraft.
4, The method as claimed in claim 1,
wherein in step a), said theoretical drag CXth is computed on the basis of the following expression:

CXth = fl(CZ2) + f2(RE) + ∆CXf in which:
CZ is a value of drag dependent on the current
weight;
fl (CZ2) is a function dependent on CZ2;
f2(RE) is a function dependent on the Reynolds
number RE; and
ACXf is a value dependent on CZ2 and CZ.
5. The method as claimed in claim 1,
wherein in step a), said current drag CXa/c is computed on the basis of the following expression:

in which:
R is a constant value;
S represents the area of the flying surface of the
aircraft;
TAS is a computed air speed;
G is a value dependent on TAS; and
T is a value of traction.
6. The method as claimed in claim 1,
wherein a check is performed moreover to verify whether the aircraft is or is not in cruising flight.
7. The method as claimed in claim 6,
wherein, when the aircraft is not in cruising flight, in step c) , we determine whether a degradation of performance of the aircraft exists, solely on the basis of said first set of comparisons relating to the drag.
8. The method as claimed in claim 7,
wherein in step c), a degradation of performance of the aircraft is detected if one of the following two conditions A and B, relating to said first set of

comparisons, is fulfilled:

for which:
CXa/c is the computed current drag of the
aircraft;
CXth is the computed theoretical drag of the
aircraft;
ACX1, ACX2 and ACX3 are predetermined values of
drag;
∆CXa/c is a deviation of current drag between two
different predetermined instants; and
∆CXth is a deviation of theoretical drag between
two different predetermined instants.
9. The method as claimed in claim 6,
wherein, when the aircraft is in cruising flight:
in step a), a theoretical cruising speed is computed on the basis of said current weight of the aircraft, and a current speed of the aircraft is measured;
in step b), a second set of comparisons is implemented, which relates to the speed and which comprises at least one comparison between said current speed and said theoretical cruising speed; and
in step c) , we determine whether a degradation of performance of the aircraft exists, likewise on the basis of said second set of comparisons relating to the speed,
10, The method as claimed in claim 9,
wherein in step a) , said theoretical cruising speed is computed on the basis of the current weight of the aircraft, of a measured altitude of the aircraft and of

a deviation of temperature between a standard temperature and a measured temperature.
11. The method as claimed in claim 9,
wherein in step c), a degradation of performance of the aircraft is detected if one of the following two conditions C and D, relating to said first and second sets of comparisons, is fulfilled:

for which:
CXa/c is the computed current drag of the
aircraft;
CXth is the computed theoretical drag of the
aircraft;
∆CX4 and ACX5 are predetermined values of drag;
IAS is the measured speed of the aircraft;
IASth is the computed theoretical cruising speed;
∆IAS1 is a predetermined deviation in speed;
∆CXa/c is a deviation in current drag between two
different predetermined instants; and
∆cxth is a deviation in theoretical drag between
two different predetermined instants.
12. The method as claimed in claim 11,
wherein in step c) , a degradation of performance of the aircraft is detected if one of the following two conditions E and F, relating to said first and second sets of comparisons, is fulfilled:


for which:



CXa/c is the computed current drag of the
aircraft;
CXth is the computed theoretical drag of the
aircraft;
∆CX6 and ACX7 are predetermined values of drag;
∆CX6 is less than ACX4;
IAS is the measured speed of the aircraft;
IASth is the computed theoretical cruising speed;
∆IAS2 is a predetermined deviation of speed;
∆IAS2 is greater than ∆lASl;
∆CXa/c is a deviation of current drag between two
different predetermined instants; and
∆CXth is a deviation of theoretical drag between
two different predetermined instants.
13. The method as claimed in claim 12,
wherein, if none of the conditions C, D, E and F is
fulfilled, a check is performed to verify whether one
of the following two conditions G and H, relating to
said first and second sets of comparisons, is
fulfilled:

for which:
• ∆CX8 and ∆CX9 are predetermined drag values,
ACX8 being less than ∆CX6; and
• ∆IAS3 is a predetermined deviation of speed,
which is less than ∆lASl and than ∆IAS2; and
if one of said conditions G and H is fulfilled, a message indicating that the cruising speed is low is emitted in step d).

14. The method as claimed in claim 1,
wherein, when a degradation of performance is detected: a measured speed IAS is compared with a computed minimum operational speed MSIS, relating to severe icing conditions;
if said speed IAS is less than said speed MSIS, a message requesting an increase in speed is emitted.
15. The method as claimed in claim 1,
wherein steps a) to c) are carried out only if flaps and the landing gear of the aircraft are retracted.
16. The method as claimed in claim 1,
wherein steps b) and c) are carried out only if at least one icing condition is fulfilled and if a measured static air temperature is greater than a predetermined value.
17. A device for detecting and warning of degradation
of performance of an aircraft, said device (1)
comprising:
a set (2) of information sources;
a central unit (3) connected to said set (2) of information sources and able to detect a degradation of performance of an aircraft; and warning means (5) connected to said central unit (3), wherein said central unit (3) comprises:
means (7, 8) for computing at least one current weight of the aircraft, a current drag of said aircraft and, on the basis of said current weight, a theoretical drag of said aircraft; means (10) for implementing at least one first set of comparisons, which relates to the drag and which comprises at least one comparison between said current drag and said theoretical drag; and means (12) for determining whether a degradation

of performance of the aircraft exists, at least on the basis of said first set of comparisons,
18. The device as claimed in claim 17,
wherein said central unit (3) furthermore comprises:
means (14) for computing a theoretical cruising
speed, on the basis of said current weight of the
aircraft;
means (2) for measuring a current speed of the
aircraft;
means (16) for carrying out a second set of
comparisons, which relates to the speed and which
comprises at least one comparison between said
current speed and said theoretical cruising speed;
and
means (12) for determining whether a degradation
of performance of the aircraft exists, likewise on
the basis of said second set of comparisons
relating to the speed,
19. The device as claimed in claim 17,
wherein said set (2) of information sources comprises a flight data acquisition unit.
20. The device as claimed in claim 17,
wherein said warning means (5) comprise an aircraft performance interface unit.


Documents:

0797-che-2005-abstract.pdf

0797-che-2005-claims.pdf

0797-che-2005-correspondnece-others.pdf

0797-che-2005-description(complete).pdf

0797-che-2005-drawings.pdf

0797-che-2005-form 1.pdf

0797-che-2005-form 3.pdf

0797-che-2005-form 5.pdf

0797-che-2005-others.pdf

797-CHE-2005 AMENDED CLAIMS 31-12-2010.pdf

797-CHE-2005 EXAMINATION REPORT REPLY RECIEVED 31-12-2010.pdf

797-che-2005 form-3 31-12-2010.pdf

797-che-2005 other patent document 31-12-2010.pdf

797-CHE-2005 OTHER PATENT DOCUMENT. 31-12-2010.pdf

797-CHE-2005 POWER OF ATTORNEY 31-12-2010.pdf

797-che-2005-abstract image.jpg


Patent Number 246850
Indian Patent Application Number 797/CHE/2005
PG Journal Number 12/2011
Publication Date 25-Mar-2011
Grant Date 17-Mar-2011
Date of Filing 24-Jun-2005
Name of Patentee AVIONS DE TRANSPORT REGIONAL
Applicant Address 1, ALLEE PIERRE NADOR, 31700 BLAGNAC, FRANCE
Inventors:
# Inventor's Name Inventor's Address
1 PETIT, GERARD 45, AVENUE D'ITALIE, 31400 TOULOUSE, FRANCE
PCT International Classification Number B64D 15/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 04 07034 2004-08-28 France