GB2285688A

GB2285688A - Flight data recorder

Info

Publication number: GB2285688A
Application number: GB9500678A
Authority: GB
Inventors: Osamu Naruse
Original assignee: Kokusai Electric Co Ltd
Current assignee: Kokusai Denki Electric Inc
Priority date: 1994-01-13
Filing date: 1995-01-13
Publication date: 1995-07-19
Anticipated expiration: 2015-01-13
Also published as: GB9500678D0; GB2285688B; JPH07205898A; JP3331036B2

Abstract

In a flight data recorder receiving inputs from airframe sensors and possibly also from a voice circuit and recording data at a prescribed (relatively low) sampling rate in a memory 9 which is protected in event of an accident by a secure enclosure 8, data at a higher sampling rate and useful in assessing maintenance requirements are additionally recorded, without increasing the size of the device, by use of an external memory 5. An airframe sensor interface 3 samples the data input from the airframe sensors at a high sampling rate by clock timings of a frequency 5 to 100 times higher than the prescribed sampling frequency and outputs the sampled data. A control circuit 4 records data sampled at the prescribed intervals in the secure memory 9, while at the same time monitoring the data sampled at the high sampling rate and, upon detection of an abrupt data change, records the corresponding abnormally changing data in the external memory 5. <IMAGE>

Description

FLIGHT DATA RECORDER The present invention relates to a flight data recorder, which is loaded on an aircraft to automatically record various kinds of data on the conditions of the airframe and engines during a flight in order to investigate the causes of crash or unexpected accidents.

An aircraft is usually loaded with an automatic recorder called a flight data recorder for recording instrument information and airframe conditions during a flight, together with a voice recorder for recording voices of pilots, and in the event of an accident, the recorded airframe information is analyzed to discover the cause of the accident.

The flight recorder is designed to record on a storage medium (a memory) pieces of information which are fed from various sensors disposed at required positions on the airframe. The storage medium is housed in a special protection enclosure capable of holding the stored contents undamaged under hostile environmental conditions including vibrations, shocks and high temperatures in case of an accident.

In recent years, studies have been made to perform maintenance on an aircraft and on-board equipment through utilization of airframe information recorded in the flight data recorder during takeoff and landing and during a flight; some techniques therefor have already reached the stage of practical use. It is highly effective in service and maintenance of the airframe and engines to store and statistically manipulate various kinds of information that are fed from airframe sensors over the long term, such as fatigue of the airframe, and to store data about aircraft accidents in the past.

To utilize data recorded in the flight data recorder for the maintenance of the airframe and engines, it is customary to build a data base by reading out and storing the data recorded in the flight data recorder every 2 to 8 hours of a flight in case of a small aircraft and every 3 to 25 hours of a flight in case of a large aircraft and to analyze the airframe information thus acquired over a longer period of time. On the basis of the data thus stored in the data base, the conditions of the airframe and engines are evaluated and their preventive diagnosis and servicing are made, as required, to provide increased flight safety of the aircraft.

Such a flight data recorder is required to be lightweight because it is loaded on aircrafts; its miniaturization is particularly important for a small aircraft such as helicopter. Hence, the recording capacity of the recording medium is inevitably subject to physical restrictions, and the recorded data sampling intervals at which to sample the airframe sensor output and the number of kinds of data allowed to store are also limited accordingly.

Fig. 3 of the accampanying drawings illustrates in block form an example of the construct-ion of a conventional flight data recorder.

In Fig. 3, reference numeral 1 denotes a recorder controller, under the control of which data inputs fed from a number of airframe sensors disposed at required places on the airframe as sensors exclusive for the detection of data about the conditions of engines and maneuvering of the aircraft, its navigation information, etc. and voice inputs from an area microphone and a talking-voice receiving microphone are formatted as predetermined and then recorded on a magnetic tape or written into a semiconductor memory provided as a recording medium in a storage 2.

Reference numeral 2 denotes the storage. A memory 9, such as a recording tape or semiconductor memory, is enclosed in a special enclosure 8 designed to protect the recording medium enclosed therein even if the enclosure should be exposed to great impacts, high pressures and intense fire when the airframe explodes and bursts into flames in the event of an accident. To this end, the enclosure 8 is formed by a special metal case.

Reference numeral 13 in the recorder controller 1 denotes an airframe sensor interface circuit into which pieces of information from various sensors are input and from which data sampled at prescribed sampling frequency is output for each item. Reference numeral 14 denotes a control circuit, which converts the format of the data inputted from the sensor interface circuit 13 and provides the data to be stored to a recorder driving circuit 7.

Reference numeral 6 denotes a voice signal input circuit, which receives a voice signal input and outputs it to the recorder driving circuit 7. The recorder driving circuit 7 is a driving circuit for applying a recording signal and a recording control signal to the storage to write the input data from the control circuit 14 into the memory 9 in the storage 2.

While the prior art example of Fig. 3 is a combined voice-flight data recorder having a flight data recorder and a voice recorder combined, as proposed by the inventor of this application with a view to downsizing and miniaturization (see Japanese Pat. Appln.

No. 307048/93), the present invention is also applicable to a flight data recorder with no voice recorder.

In the conventional flight data recorder mentioned above, according to the Minimum Operating Performance Specification (ED-56) for flight data recorders, the voice recording time is prescribed to be 30 or 60 minutes at the minimum, whereas the flight data recording time is mostly determined by the one-flight time of the aircraft concerned; in case of a small helicopter or the like, the data recording time is prescribed to be substantially in the range of 2 to 4 hours.

As referred to previously, however, the recording capacity of the recording medium has the physical restriction and the data inputs from the airframe sensors are all sampled by the airframe sensor interface circuit.

The sampling period in this instance is prescribed to a range from once to four times per sec according to the item of each airframe data. In the utilization of the flight data recorder for the maintenance of the airframe, the conventional sampling period does not allow the detection of short-time, sudden change in data, and hence is not suited to the enhancement of the efficiency of maintenance and the preventive diagnosis based on the results of the subsequent data analysis.

Fig. 4 of the accompanying drawings is explanatory of conventional sampling operations of data. For example, when the output level of the airframe sensor fluctuates during a flight as indicated by the broken line in Fig. 4A, the levels marked by numerals with parentheses are sampled and data detected at the sampling period prescribed for each standard item as shown in Fig. 4B is stored in the memory 9. When the contents of the memory 9 are read out after a flight, the levels at the sample points (3) and (4) exhibit abnormally high values indicating the detection of a substantial change in level (an event information) that happened in the sampling cycle periods (b), but the changes (a) and (c) between the sample points (1) and (2) and between (3) and (4) are not detected.

As in this example, it is impossible, with the conventional sampling periods of once to four times per sec, to accurately record the event information of the airframe and hence to acquire sufficient data for maintenance use; in particular, sensor information about the item which is likely to undergo an abrupt change, such as airframe vibration, cannot accurately be detected.

One possible method that has been proposed to solve such a problem of the prior art is to reduce the length of each sampling period by increasing the sampling frequency by 5 to 10 times higher than in the past, but this method calls for increased capacity of the memory for storing high-speed sampling data, presenting a new problem that the physical restriction of miniaturization cannot be satisfied.

Another method is to detect and record only event information about a large change in the sensor output level, but the accident analysis for which the flight data recorder is primarily intended requires data continuously detected for a long time during a long-distance flight; hence, this method has a shortcoming that irregular, intermittent or discontinuous event information data alone is insufficient to clear out the cause of an unforeseen accident.

An object of the present invention is to provide a flight data recorder which solves the above-mentioned problems of the prior art and permits recording of not only long-time, continuous data but also the event condition indicating a sudden data change.

The flight data recorder according to the present invention, comprising an airframe sensor interface circuit for receiving the data input from each airframe sensor and outputting sampled data, and a control circuit for converting the output from each airframe sensor interface circuit to a predetermined format and storing it in a memory of a protected storage, is characterized in: that an external memory is provided; that each airframe sensor interface circuit outputs data obtained by sampling the data input from each airframe sensor at a high sampling rate of a sampling frequency 5 to 100 times higher than that prescribed for accident analysis use; and that the control circuit converts, to a predetermined format, those pieces of data sampled at intervals of the above-said prescribed sampling frequency obtained from the data sampled at the high sampling rate and stores them in the memory of the protected storage, while at the same time, monitors the data sampled at the high sampling rate and stores, in the external memory, in the data sampled at the high sampling rate.

The data inputs from a number of airframe sensors are sampled at high sampling rate at a clock frequency 5 to 100 times higher than that in the past according to individual items, and data of the conventional low sampling rate is stored in the memory 9 in the enclosure 8. At the same time, the data sampled at the high sampling rate is monitored for each item; when a sudden change exceeding a predetermined value is detected, it is decided as the occurrence of event information and the data concerned is stored in a newly provided external memory. The combined analysis of the pieces of data thus stored in the both memories provides accurate information about the airframe conditions during a flight, which is highly useful for maintenance of the airframe.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a block diagram illustrating an embodiment of the present invention; Figs. 2A and 2B are diagrams explanatory of the operation of the present invention; Fig. 3 is a block diagram showing a prior art example; and Figs. 4A and 4B are diagrams explanatory of the operation of the prior art example.

With reference to Fig. 1 illustrating in block form an embodiment of the present invention, the same constituents as those in the prior art example of Fig. 3 are identified by the same reference numerals and no description will be given of them.

Reference numeral 3 denotes an airframe sensor interface circuit, which is shown to be single, but in practice, such interface circuits are provided in correspondence to a number of sensors, respectively, and according to the item corresponding thereto, each airframe sensor interface circuit provides clock pulses of a frequency 5 to 100 times higher than that in the past to an analog-to-digital (A/D) converter, samples the data input at a high sampling rate and outputs the sampled data.

Reference numeral 5 denotes a newly provided external memory, which is provided separately of a memory in a control circuit 4 and the memory 9 in the storage 2. The external memory 5 stores therein only high-speed sampled data (event information) which is obtained when the output from the respective airframe sensor exhibits a specific phenomenon. To allow ease in reading out the stored contents after a flight, a detachable memory card, for example, is used as the external memory.

Reference numeral 4 denotes a control circuit. The control circuit 4 receives the high-rate sampled data from the airframe sensor interface circuit 3 and, as in the past, provides data sampled at the conventional low sampling rate, that is, data sampled with the prescribed sampling period, to the recorder driving circuit 7 in the memory 9 of the storage 2 to be protected from an accident.

At the same time, the control circuit 4 monitors the highrate sampled data and, upon detection of a value or rate of change that goes beyond the range prescribed for each item, writes the high-rate sampled data (event information) of the specific phenomenon into the external memory 5.

After the completion of a flight, a playback or readout equipment provided on a terrestrial station is used to read out the prescribed low-rate sampled data recorded in the memory 9 in the storage 2 during a normal flight and the high-rate sampled data recorded in the external memory 5 and these read-out pieces of data are analyzed in combination for use as data for maintenance.

Figs. 2A and 2B are diagrams explanatory of sampling of data according to the present invention. Fig. 2A shows variations in the airframe sensor output level (indicated by broken line) and high-rate sampling points (indicated by white circles) as is the case with Fig. 4A. Fig. 2B is a diagram explanatory of recorded data, in which FRD recorded data is the prescribed low-rate sampled data continuously recorded in the memory 9 in the storage 2 over a long period of time. The pieces of data at the high-rate sampling points (indicated by hatching) on the output levels (a), (b) and (c) indicating short-time, abrupt changes are data recorded as event information in the external memory 5.

Such items as the sampling periods and the recording and storage information of the data to be recorded in the memory 9 housed in the strong enclosure 8 of the storage 2 are defined by MIL-STD-2124 FLIGHT DATA RECORDER FUNCTIONAL STANDARDS FOR. The airframe sensor information of each item is continuously sampled and successively recorded.

The reason for this is that it is necessary in the analysis of an accident to continuously observe and analyze the operating condition of each equipment at the time of occurrence of any accident.

On the other hand, the data for maintenance need not be continuously recorded. Taking the number of revolutions of an engine as an example, data important for maintenance is the cumulative total of the operating time of the engine, the number of times when exceeded an upper limit value and the cumulative total of the operating time at each rated number of revolutions (such as the cumulative total of the operating time at 100% of the rpm rating, the cumulative total of the operating time at 90% of the rpm rating, ...).

The sample values need not be recorded in the form of continuous data, but instead event-like changes in the output level of the airframe sensor is important.

Thus, it is for accident analysis use to record the input information from the airframe sensors with the prescribed sampling periods; for maintenance use, it is important to record only the event information and the cumulative totals of the above-mentioned data. The present invention permits storage of such maintenance data without involving the use of many storage media.

As described above in detail, the present invention allows simultaneous recording of the accident analysis data and the maintenance data by sampling the airframe sensor signals at a high sampling rate, By storing the maintenance data in the external memory other than the internal memory, the present invention minimizes the device geometry and enables highly accurate maintenance data to be stored and read out; hence, the invention is great utility in practical use.

Claims

1. A flight data recorder, comprising an airframe sensor interface circuit for receiving the data input from each airframe sensor and outputting sampled data, and a control circuit for converting the output from said each airframe sensor interface circuit to a predetermined format and storing it in a memory in protected storage, characterized in: that an external memory is provided; that said each airframe sensor interface circuit outputs data obtained by sampling the data input from said each airframe sensor at a high sampling rate of a sampling frequency 5 to 100 times higher than that prescribed for accident analysis use; and that said control circuit converts, to a predetermined format, those pieces of data sampled at the intervals of said prescribed sampling frequency obtained from said data sampled at the high sampling rate and stores them in said memory in said protected storage, while at the same time, monitors said data sampled at the high sampling rate and stores, in said external memory, abruptly changing data in said data sampled at the high sampling rate.

2. A flight data recorder according to claim 1, in which a threshold value for said abruptly changing data is determined for said each airframe sensor.

3. A flight data recorder substantially as herein described with reference to Fig. 1 with or without reference to Figs. 2A and 2B of the accompanying drawings.