SYSTEM FOR GENERATING AN ANOMALY SIGNAL DURING TAKEOFF ON BOARD AN AIRCRAFT

Abstract

A method for monitoring an aircraft during takeoff is triggered when a first speed threshold is reached. During successive computational cycles, the following steps are implemented: obtaining a current ground speed; calculating the time taken by a numerical aircraft model to increase its speed to the current ground speed; multiplying this time by the current ground speed, and deducing (205), by integration, the theoretical distance traveled by the aircraft. And when a second speed threshold is reached, the following steps are implemented: estimating (208) an acceleration degradation based on the difference between the actual distance traveled by the aircraft and the theoretical distance traveled by the aircraft; and generating an alert when the acceleration degradation estimate exceeds a degradation threshold.Thus, reliable information to aid in a decision to abort takeoff is provided with a low computational cost. Figure to be published with the abbreviation: Fig. 2.

Description

Title of the invention: SYSTEM FOR GENERATING AN ANOMALY SIGNAL DURING TAKEOFF ON BOARD AN AIRCRAFT Technical field

[0001] The present invention relates to the generation, on board an aircraft during takeoff, of an information, alert or alarm signal in the event of an anomaly detected during takeoff. STATE OF PRIOR ART

[0002] The takeoff procedure of an aircraft, from the release of the brakes to the aircraft becoming airborne, constitutes a critical phase of aircraft operation. Incidents may occur due to performance losses, changes in wind direction and intensity, or other reasons.

[0003] To improve safety during takeoff, solutions have been developed to provide an aircraft pilot with safe and accurate information enabling him to decide whether the takeoff procedure should be aborted or corrected before the aircraft taxiing on the runway reaches a critical speed VL. The critical speed VI is defined as the speed up to which the takeoff can be aborted and beyond which the takeoff must be continued.

[0004] A system for generating an information, alert, or alarm signal on board an aircraft in the event of an anomaly during takeoff is already known from French patent FR 2 650 101 Bl in the event of an anomaly, before the aircraft reaches a critical roll speed below which the takeoff process may be modified or aborted, and above which the takeoff must be continued. This information, alert, or alarm signal is issued only when the aircraft's speed and the distance traveled by the aircraft on the runway are, respectively, less than the critical speed VI and the associated theoretical distance traveled, to allow, if necessary, a safe aborted takeoff.However, with such a system, the transition between the point at which an aborted takeoff is still possible and the point at which an aborted takeoff is no longer possible is abrupt, and the pilot does not know exactly when this transition will occur. Furthermore, in the event of a problem, the pilot has no way of knowing what braking margin is available.

[0005] An improvement to the system proposed by patent FR 2 650 101 Bl is also known from patent EP 0 704 783 Bl, in which new information is provided to the pilot to allow the pilot to refine their judgment regarding whether or not to continue the takeoff procedure in the event of an anomaly. The improver proposes, by calculating during the aircraft's takeoff acceleration phase the By calculating the distance required for the aircraft to stop (including the distance already traveled) and comparing it to the available runway length, the pilot has continuous information on the braking margin and, consequently, the decision time available. For example, in the event of a problem during takeoff with thrust below maximum, if there is still a significant decision margin, the pilot can attempt to increase thrust, even if it means aborting the takeoff later if the thrust increase is insufficient to restore a safe situation. One drawback of the improvement proposed by patent EP 0 704 783 B1 is that it requires significant computing resources, particularly for continuously calculating the aircraft's stopping distance during its takeoff acceleration phase.

[0006] It is therefore desirable to overcome these drawbacks of the prior art. In particular, it is desirable to provide a solution that assists an aircraft pilot in deciding whether to abort or not to take off, while limiting the computational resources required. Description of the invention

[0007] A method for monitoring an aircraft during takeoff is thus proposed here, the method being implemented by a system in the form of electronic circuitry, the method being triggered when the aircraft reaches a speed greater than a first predefined speed threshold SI, the method comprising the following steps during successive computation cycles:

[0008] - obtain a current ground speed GSC of the aircraft;

[0009] - calculate a time A tt taken by a numerical aircraft model to increase its ground speed up to the current GSC ground speed from the current GSC ground speed that the aircraft had in the previous calculation cycle;

[0010] - multiply the time A tt by the current ground speed GSC of the aircraft observed at considering the calculation cycle, and deduce, by integration over all calculation cycles since crossing the first predefined speed threshold SI, the distance Dt theoretically traveled by the aircraft to reach the current ground speed GSC.

[0011] The method further comprises the following steps, when the aircraft reaches a speed greater than a second predefined speed threshold S2 which is greater than the first predefined speed threshold SI:

[0012] - calculate an estimate of acceleration degradation degree from the fran choice of the first predefined SI speed threshold, by a calculation corresponding to a ratio between, on the one hand, the difference between the distance actually traveled by the aircraft to reach its current ground speed GSC and the theoretical distance the distance traveled by the aircraft to reach this current ground speed (GSC), and on the other hand, the theoretical distance traveled by the aircraft to reach this current ground speed (GSC); and

[0013] - generate an alert, informing that a takeoff aborted is recommended, when the acceleration degradation estimate Degr is greater than a predefined degradation threshold S.

[0014] Thus, reliable information to aid in a decision to interrupt or not take off is provided with a low cost in computing resources.

[0015] According to a particular embodiment, the system adjusts the acceleration degradation estimate Degr by an approximation reduction constant C.

[0016] According to a particular embodiment, the distance Dt is calculated as follows: [OO17] &tj*GSc) = J(( AGSC*GW I^F^^GS^

[0018] where:

[0019] - A GSC represents the variation in the current ground speed GSC since the previous computational cycle;

[0020] - GW represents the gross weight of the aircraft; and

[0021] - ^Fn represents an estimate of the sum of forces exerted on the aircraft at each calculation cycle considered.

[0022] According to a particular embodiment, the sum ^Fn of the forces exerted on the aircraft 10 is estimated by a calculation corresponding to:

[0023] £ f„ = TH - DF*GW.g) - CR * (GW *g - LF)

[0024] where:

[0025] - TH represents a thrust of the aircraft at the calculation cycle considered;

[0026] - DF represents a drag force of the aircraft at the calculation cycle considered;

[0027] - CR represents a coefficient of friction on the ground;

[0028] - LF represents a lift force of the aircraft at the calculation cycle considered;

[0029] - 8 represents the unit of acceleration, i.e., approximately 9.81 m / s²; and

[0030] - SL represents a runway slope at takeoff, expressed as a percentage.

[0031] According to a particular embodiment:

[0032] - a first calibrated air velocity information, voted between two computers re The system responsible for rudder management is used to check if the first predefined speed threshold SI is exceeded and is also used to check if the second speed threshold S2 is exceeded, and

[0033] - a second calibrated air velocity information, coming from a system of type ADIRS (“Air Data Inertial Reference System” in English) is used for calculating the distance Dt.

[0034] According to a particular embodiment, the first predefined speed threshold SI is equal to 35 knots and the second predefined speed threshold S2 is between 75 and 85 knots, preferably equal to 80 knots.

[0035] According to a particular embodiment, the system is activated when the speed of the aircraft is greater than a predefined initial speed threshold S0 lower than the first speed threshold SI.

[0036] According to a particular embodiment, the predefined initial speed threshold S0 is equal to 30 knots.

[0037] According to a particular embodiment, the predefined degradation threshold S is equal to 15%.

[0038] Also proposed herein is a computer program that can be stored on a medium and / or downloaded from a communication network for reading by a processor. This computer program includes instructions for implementing the above-mentioned process in any of its embodiments when said program is executed by the processor. Also proposed herein is a non-transient information storage medium for storing such a computer program.

[0039] Also proposed here is a system for monitoring an aircraft during takeoff in the form of electronic circuitry configured to implement the following steps, when the aircraft reaches a speed greater than a first predefined SI speed threshold, during successive calculation cycles:

[0040] - obtain a current ground speed GSC of the aircraft;

[0041] - calculate a time A tt put by a numerical aircraft model, to increase its ground speed up to the current GSC ground speed from the current GSC ground speed that the aircraft had in the previous calculation cycle;

[0042] - multiply the time A tt by the current ground speed GSC of the aircraft observed at calculation cycle considered, and deduce, by integration over all calculation cycles since crossing the first predefined speed threshold SI, a distance Dt theoretically traveled by the aircraft to reach the current ground speed GSC.

[0043] The electronic circuitry is further configured to implement the following steps when the aircraft reaches a speed greater than a second predefined speed threshold S2 which is greater than the first predefined speed threshold SI:

[0044] - calculate an estimate of acceleration degradation degree from the fran choice of the first predefined speed threshold SI, by a calculation corresponding to a ratio between, on the one hand, the difference between the distance actually traveled by the aircraft to reach its current ground speed GSC and the distance theoretically traveled by the aircraft to reach this current ground speed GS^ and on the other hand, the theoretical distance traveled by the aircraft to reach this current ground speed GSe; and

[0045] - generate an alert, informing that a takeoff aborted is recommended, when the acceleration degradation estimate Degr is greater than a predefined degradation threshold S. Brief description of the drawings

[0046] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of at least one exemplary embodiment, said description being made in relation to the accompanying drawings, among which:

[0047] [Fig-1] schematically illustrates, in top view, an aircraft equipped with a system of monitoring during takeoff;

[0048] [Fig.2] schematically illustrates a method for generating, on board the aircraft, a warning signal in case of insufficient acceleration during takeoff;

[0049] [Fig.3A] schematically illustrates a first example of integration of the takeoff monitoring system with aircraft avionics;

[0050] [Fig. 3B] schematically illustrates a second example of integrating the takeoff monitoring system with aircraft avionics; and

[0051] [Fig.4] schematically illustrates an example of a hardware platform allowing to implement, in the form of electronic circuitry, the takeoff monitoring system.

[0052] DETAILED DESCRIPTION OF EMBODIMENT METHODS

[0053] Fig. 1 thus schematically illustrates, in top view, an aircraft 10.

[0054] The aircraft 10 includes a take-off monitoring system 101 (“Take-Off Mo- "nitoring" in English). The 101 takeoff monitoring system is in the form of electronic circuitry, and is typically integrated into an avionics 100.

[0055] Avionics 100 also typically includes an ADIRS (Air Data Inertial Reference System), an FMS (Flight Management System), a FADEC (Full Authority Digital Engine Control) system, an FWS (Flight Warning System), an EIS (Electronic Information System) including, in particular, an ECAM (Electronic Centralized Aircraft Monitoring) system, a CFDIU (Centralized Fault Display Interface Unit), and an SFCC (Slat Flap Control Computer). Avionics 100 also typically includes other electronic systems.

[0056] The 101 takeoff monitoring system is, for example, integrated into a system of type FMGC (“Flight Management Guidance Control” in English).

[0057] The takeoff monitoring system 101 implements a method for generating, on board the aircraft 10, a warning signal in the event of insufficient acceleration during takeoff. This method is schematically illustrated in [Fig.2].

[0058] In step 201, the takeoff monitoring system 101 is activated. For example, the takeoff monitoring system 101 is activated when a takeoff monitoring system 101 inhibit signal is set to FALSE. Also, the takeoff monitoring system 101 is activated, for example, when the speed of the aircraft 10 exceeds a predefined initial speed threshold S0. As an example, the initial speed threshold S0 is set at 30 knots (approximately 55 km / h) in Calibrated Airspeed (CAS). Below this value, the ADIRS-type system does not transmit CAS calibrated airspeed information, thus avoiding unnecessary processing.

[0059] In a step 202, the takeoff monitoring system 101 checks whether the aircraft 10 has a calibrated airspeed (CAS) greater than a first speed threshold SI. The first speed threshold SI is non-zero and is preferably strictly greater than the initial speed threshold S0. However, the first speed threshold SI may be equal to the initial speed threshold S0. The first speed threshold SI is chosen so as to avoid resource-intensive calculations in an aircraft speed range where the numerical aircraft model would show large dispersions (particularly due to the variability of the aircraft's thrust in the first few meters of takeoff). In particular, the first speed threshold SI makes it possible to abstract the calculation of any constraint of immobilizing the aircraft 10 on the runway before initiating the takeoff procedure. For example, the first speed threshold SI is equal to 35 knots (approximately 65 km / h).This avoids the need for resource-intensive calculations during the initial takeoff phase. If the first SI speed threshold is reached, step 203 is performed accordingly; otherwise, step 202 is repeated.

[0060] In step 203, the takeoff monitoring system 101 activates calculations, more specifically of the theoretical distance Δt traveled by the aircraft 10, in order to obtain an estimate of the acceleration degradation Δr, as detailed later. The calculations are performed in computational cycles.

[0061] In a step 204, the monitoring system 101 triggers a new calculation cycle.

[0062] In a step 205, the monitoring system 101 calculates the theoretical distance traveled by the aircraft 10 since the triggering of the previous calculation cycle, and in a step 206, the monitoring system 101 performs, by integration, a calculation of the theoretical distance Δt traveled by the aircraft 10 since crossing the first speed threshold SL

[0063] The distance Dt is obtained by a calculation corresponding to:

[0064] D{ = J( A t*GSc) = J( ( A GS^GW^Fn) *GSC)

[0065] where:

[0066] - GSC represents the current ground speed of aircraft 10 at each calculation cycle considered;

[0067] - AL represents the time theoretically spent by the aircraft 10 to increase its ground speed up to the current GSC ground speed since the previous calculation cycle;

[0068] - A GSC represents the variation in the current ground speed GSC since the previous computational cycle;

[0069] - GW represents the gross weight of the aircraft 10; and

[0070] - ^Fn represents an estimate of the sum of the forces exerted on the aircraft 10 to each calculation cycle considered.

[0071] Thus, at each calculation cycle, the takeoff monitoring system 101 calculates the time A tt taken by a numerical aircraft model to increase its ground speed to the current ground speed GSC of aircraft 10, starting from the current ground speed of aircraft 10 at the previous calculation cycle. The takeoff monitoring system 101 multiplies this time A tt by the current ground speed GS of aircraft 10 observed at the calculation cycle in question. Consequently, no theoretical ground speed calculation is performed, which significantly limits the computational resource requirements. And by integrating over all calculation cycles since crossing the first speed threshold SI, the takeoff monitoring system 101 deduces the theoretical distance Δt traveled by aircraft 10 to reach the current ground speed GSC since crossing the first speed threshold SL.

[0072] During the very first calculation cycle, the takeoff monitoring system 101 simply stores the GSC, GW, and yp information, and / or any information enabling their determination, in order to calculate the distance Dt during the next calculation cycle. Alternatively, this GSC, GW, and yp information, and / or any information enabling their determination, is obtained by the takeoff monitoring system 101 upon crossing the initial speed threshold S0. Calculations can thus begin from the very first calculation cycle.

[0073] In a particular embodiment, the sum yp of the forces (expressed here in Newtons or KiloNewtons) exerted on the aircraft 10 is estimated, at each calculation cycle, by a calculation corresponding to:

[0074] £ pn = th-DF-(^ ^GW.g) - CR* (GW *g - LF)

[0075] where:

[0076] - TH represents the thrust of aircraft 10 during the cal- cycle culatory considered;

[0077] - DF represents the drag force of the aircraft 10 at the calculation cycle considered;

[0078] - CR represents a coefficient of friction on the ground, for example equal to 0.006;

[0079] - LF represents the lift force of the aircraft 10 at the calculation cycle considered; And

[0080] - 8 represents the unit of acceleration, approximately 9.81 m / s². ; and

[0081] - SL represents the (signed) slope of the runway at takeoff, expressed here in percentage.

[0082] When the slope of the runway at takeoff is not precisely known to the takeoff monitoring system 101 (for example because this information is not provided by the avionics 100), the slope SL can be set to a default value, for example 1%, or even to a zero value.

[0083] In a step 207, the takeoff monitoring system 101 checks whether the aircraft 10 has a calibrated airspeed (CAS) greater than a second speed threshold S2. The second speed threshold S2 is strictly greater than the first speed threshold SL. The second speed threshold S2 is preferably set so as to avoid a high-energy rejected takeoff (RTO). For example, the second speed threshold S2 is between 75 knots (approximately 139 km / h) and 85 knots (approximately 157 km / h), preferably equal to 80 knots (approximately 148 km / h) or 90 knots (approximately 167 km / h).

[0084] If the second speed threshold S2 is reached, a step 208 is carried out accordingly; otherwise, step 204 is repeated with a triggering of a new calculation cycle.

[0085] In step 208, the takeoff monitoring system 101 calculates the acceleration degradation estimate Degr since crossing the first speed threshold SL. The takeoff monitoring system 101 calculates this acceleration degradation estimate Degr of the aircraft 10 by the calculation corresponding to a ratio between, on the one hand, the difference between the distance actually traveled by the aircraft 10 to reach its current ground speed and the distance theoretically traveled by the aircraft 10 to reach this current ground speed, and on the other hand, the distance theoretically traveled by the aircraft 10 to reach this current ground speed.

[0086] In a particular embodiment, the acceleration degradation of aircraft 10 is estimated as follows:

[0087] Degrees - 100°C

[0088] where:

[0089] - Dr represents the actual distance travelled by aircraft 10 since crossing of the first speed threshold SI; and

[0090] - C is an approximation reduction constant, which can be adjusted in a way empirical depending on the aircraft model 10 considered and which, in a particular embodiment, may be zero.

[0091] For example, the actual distance Dr is calculated as follows, at each calculation cycle (preferably during step 205, in addition to the calculation of the distance A):

[0092] Dr = ^At^GSc)

[0093] where A tr represents the duration of a computational cycle.

[0094] In step 209, the takeoff monitoring system 101 checks whether the acceleration degradation estimate Degr exceeds a predefined degradation threshold S. For example, the degradation threshold S is equal to 15%. Beyond this degradation threshold S, the acceleration degradation Degr is considered to be too great to allow takeoff, and a takeoff abort is recommended. Step 210 is then performed; otherwise, step 211 is performed.

[0095] In step 210, the takeoff monitoring system 101 generates an alert, indicating that a takeoff abort is recommended, for example via an FWS-type system, an ECAM-type system, or a CFDIU-type system. This alert can also be recorded in a DFDR-type system (Digital Flight Data Recorder) via an FDIMU-type system (Flight Data Interface & Management Unit). Step 211 is then performed.

[0096] In step 211, the takeoff monitoring system 101 is deactivated, and the algorithm in [Fig.2] is terminated.

[0097] In a particular embodiment, the CAS calibrated airspeed information used comes from different sources: a synchronized CAS calibrated airspeed information, voted between two redundant FAC (Flight Augmentation Computer) type computers in charge of control surface management, and a standard CAS calibrated airspeed information, from the AD 1RS type system. The synchronized CAS calibrated airspeed information is then used to verify the crossing of the first speed threshold SI and the crossing of the second speed threshold S2, and the standard CAS calibrated airspeed information is used to verify the crossing of the initial speed threshold S0 and for the calculations of the distance Dt.

[0098] In order to feed the digital aircraft model to determine the theoretical distance Dt based on the actual conditions of the aircraft 10, the takeoff monitoring system 101 obtains information from the avionics 100 relating to measurements taken by sensors located at various points on the aircraft 10 and / or information derived therefrom. In particular, the takeoff monitoring system 101 obtains the following information from the avionics 100 in real time:

[0099] - information relating to the thrust of the aircraft 10 (such as, for example, an in NI type formation (rotation speed of a low-pressure assembly of each propulsion engine) or EPR engine pressure ratio ("Engine Pressure Ratio" in English) allowing, with Mach number information and a conversion table, to deduce the thrust of the aircraft 10);

[0100] - information relating to speed, ambient conditions, altitude and aircraft inertial reference frames 10;

[0101] - information relating to a current configuration (orientation) of devices leading edge high-lift devices (“slats” in English) and trailing edge high-lift devices (“flaps” in English) of the aircraft 10;

[0102] - aircraft gross weight information GW 10.

[0103] This information allows the takeoff monitoring system 101 to determine the sum yp of the forces exerted on the aircraft 10 using the aircraft digital model.

[0104] Furthermore, in a particular embodiment, the takeoff monitoring system 101 obtains runway slope information for takeoff from the avionics 100.

[0105] Examples of integration of the takeoff monitoring system 101 with avionics 100, which notably allows the takeoff monitoring system 101 to obtain this information, are schematically illustrated in [Fig.3A] and 3B.

[0106] As illustrated in Figs. 3A and 3B, the monitoring system 101 is configured to receive information from the FADEC 301 type system, information from the ADIRS 302 type system, information from the SFCC 303 type system, information from the FMS 304 type system.

[0107] Thus, for example, the 101 monitoring system is configured to:

[0108] - receive, from the FADEC 301 type system, information relating to the thrust of aircraft 10, such as NI type information (rotation speed of a low pressure assembly of each propulsion engine), TRA ("Throttle Resolver Angle" information and possibly information indicating whether a particular propulsion engine is inoperative;

[0109] - receive, from the ADIRS 302 type system: information from aircraft current speed 10, such as calibrated airspeed (CAS), ground speed (GS) and Mach number information; ambient conditions information, such as total air temperature (TAT) and static pressure (PSTAT) information; current altitude information (often denoted Zp); and inertial reference information, such as current load factor information (often denoted Nz);

[0110] - receive, from the SFCC 303 type system, information relating to the current configuration (orientation) of the leading-edge and trailing-edge high-lift devices of aircraft 10; and

[0111] - receive, from the FMS 304 type system, the gross weight information GW of aircraft 10.

[0112] The takeoff monitoring system 101 is configured to transmit a warning signal to the FWS 306 type system, indicating that a takeoff abort is recommended, when the monitoring system 101 has determined that the acceleration degradation estimate Degr is greater than the predefined degradation threshold S. The FWS 306 type system is configured to transmit the warning signal, or information derived from it, to the CFDIU 307 type system. The pilot of aircraft 10 is thus informed.

[0113] In the example shown in Figs. 3A and 3B, the FMS 304 system is configured to provide the EIS 305 system with the takeoff monitoring system 101 inhibit signal. When this signal is FALSE, the takeoff monitoring system 101 is activated, and when this signal is TRUE, the takeoff monitoring system 101 is inhibited. The EIS 305 system is configured to forward the takeoff monitoring system 101 inhibit signal to the FWS 306 system. The FWS 306 system is configured not to retransmit to the CFDIU 307 system any warning signal emanating from the takeoff monitoring system 101 when the takeoff monitoring system 101 inhibit signal is TRUE.

[0114] Compared to the example in [Fig.3A], the example in [Fig.3B] takes into account the slope of the runway at takeoff. Thus, the monitoring system 101 is configured to receive runway slope information at takeoff from a 308 type TAWS (Terrain Avoidance and Warning System) and / or EGPWS (Enhanced Ground Proximity Warning System).

[0115] Fig. 4 schematically illustrates an example of a hardware platform for implementing, in the form of electronic circuitry, the 101 takeoff monitoring system.

[0116] The hardware platform then comprises, connected by a communication bus 410: a processor or CPU (Central Processing Unit) 401; a RAM (Read-Only Memory) 402; a read-only memory 403, for example of the ROM (Read Only Memory) or EEPROM type (Electrically-Erasable Programmable ROM); a storage unit, such as a hard disk drive (HDD) 404, or a storage media reader, such as an SD card reader (Secure Digital); and an I / F interface manager 405.

[0117] The I / F interface manager 405 enables the takeoff monitoring system 101 to interact with one or more pieces of equipment of the aircraft 10, more particularly avionics equipment 100 of the aircraft 10, as previously described in particular in relation to Figs. 3A and 3B.

[0118] The processor 401 is capable of executing instructions loaded into RAM 402 from ROM 403, external memory, a storage medium (such as an SD card), or a communication network. When the hardware platform is powered on, the processor 401 is capable of reading instructions from RAM 402 and executing them. These instructions form a computer program causing the processor 401 to implement all or part of the steps and operations described herein.

[0119] All or part of the steps and operations described herein can thus be implemented in software form by the execution of a set of instructions by a programmable machine, for example a DSP (Digital Signal Processor) or a microcontroller, or be implemented in hardware form by a dedicated machine or electronic component (chip) or a dedicated set of electronic components (chipset), for example an FPGA (Field Programmable Gate Array) or ASIC (Application-Specific Integrated Circuit). Generally speaking, the 101 takeoff monitoring system includes electronic circuitry adapted and configured to implement the operations and steps described herein.

Claims

1.

2.

3. Demands Method for monitoring an aircraft during takeoff, the method being implemented by a system (101) in the form of electronic circuitry, the method being triggered when the aircraft (10) reaches a speed greater than a first predefined speed threshold SI, the method comprising the following steps during successive calculation cycles: - obtain a current ground speed GSC of the aircraft (10); - calculate a time A tt taken by a numerical aircraft model to increase its ground speed to the current ground speed GSe from the current ground speed GSC that the aircraft (10) had in the previous computation cycle; - multiply the time A tt by the current ground speed GSC of the aircraft (10) observed in the calculation cycle considered, and deduce (205), by integration over all calculation cycles since crossing the first predefined speed threshold SI, the distance Dt theoretically traveled by the aircraft (10) to reach the current ground speed GSC; the process further comprising the following steps, when the aircraft (10) reaches a speed greater than a second predefined speed threshold S2 which is greater than the first predefined speed threshold SI: - calculate (208) an estimate of the acceleration degradation Degr since crossing the first predefined speed threshold SI, by a calculation corresponding to a ratio between, on the one hand, the difference between the distance actually traveled by the aircraft (10) to reach its current ground speed GSC and the distance theoretically traveled by the aircraft (10) to reach this current ground speed GSC, and on the other hand, the distance theoretically traveled by the aircraft (10) to reach this current ground speed GSC; and - generate (210) an alert, informing that a takeoff aborted is recommended, when the acceleration degradation estimate Degr is greater than a predefined degradation threshold S. Method according to claim 1, wherein the system (101) adjusts the acceleration degradation estimate Degr by an approximation reduction constant C. A method according to any one of claims 1 and 2, wherein the distance Dt is calculated as follows: D, = J( A t,*GSc) = / ( ( A GS*GW*GSC) where: - A GSC represents the variation of the current ground speed GSC since the previous calculation cycle; - GW represents a gross weight of the aircraft (10); and - re represents an estimate of the sum of forces exerted on the aircraft (10) at each calculation cycle considered.

4. A method according to claim 6, wherein the sum yp of the forces exerted on the aircraft 10 is estimated by a calculation corresponding to: EF„ = TH - DF - ( *GW.g ) - CR* ( GW *g - LF ) where: - TH represents a thrust of the aircraft (10) at the calculation cycle considered; - DF represents a drag force of the aircraft (10) at the calculation cycle considered; - CR represents a coefficient of ground friction; - LF represents a lift force of the aircraft (10) at the calculation cycle considered; - S represents the unit of acceleration, i.e. approximately 9.81 m / s2; and - SL represents a runway slope at takeoff, expressed as a percentage.

5. A method according to any one of claims 1 to 4, wherein: - a first calibrated airspeed information, voted between two redundant computers in charge of the control surface management, is used to check whether the first predefined speed threshold SI is crossed and is also used to check whether the second speed threshold S2 is crossed, and - a second calibrated airspeed information, from an ADIRS type system, is used for the calculations of the distance Dt.

6. A method according to any one of claims 1 to 5, wherein the first predefined speed threshold SI is equal to 35 knots and the second predefined speed threshold S2 is between 75 and 85 knots, preferably equal to 80 knots.

7. A method according to any one of claims 1 to 5, wherein the system (101) is activated when the speed of the aircraft (10) is greater than a predefined initial speed threshold S0 lower than the first speed threshold SI.

8. A method according to claim 6, wherein the initial speed threshold

9.

10. The predefined S0 is equal to 30 nodes. A method according to any one of claims 1 to 5, wherein the predefined degradation threshold S is equal to 15%. System (101) for monitoring an aircraft (10) during takeoff in the form of electronic circuitry configured to implement the following steps, when the aircraft (10) reaches a speed greater than a first predefined SI speed threshold, during successive calculation cycles: - obtain a current ground speed GSC of the aircraft (10); - calculate a time A tt put by a numerical aircraft model, to increase its ground speed up to the current ground speed GSC from the current ground speed GSC that the aircraft (10) had in the previous calculation cycle; - multiply the time A tt by the current ground speed GSC of the aircraft (10) observed at the calculation cycle considered, and deduce (205), by integration over all the calculation cycles since crossing the first predefined speed threshold SI, a distance Dt theoretically traveled by the aircraft (10) to reach the current ground speed GSC; the electronic circuitry being further configured to implement the following steps, when the aircraft (10) reaches a speed greater than a second predefined speed threshold S2 greater than the first predefined speed threshold SI: - calculate (208) an estimate of the acceleration degradation Degr since crossing the first predefined speed threshold SI, by a calculation corresponding to a ratio between, on the one hand, the difference between the distance actually traveled by the aircraft (10) to reach its current ground speed GSC and the distance theoretically traveled by the aircraft (10) to reach this current ground speed GSC, and on the other hand, the distance theoretically traveled by the aircraft (10) to reach this current ground speed GSC; and - generate (210) an alert, informing that a takeoff aborted is recommended, when the acceleration degradation estimate Degr is greater than a predefined degradation threshold S.

Images