Patent GB-1305941-A (GB)
IPC: G06F17/40
Filed: 1970-02-27
Abstract: 1305941 Monitoring aircraft data UNITED AIRCRAFT CORP 27 Feb 1970 [28 Feb 1969] 9683/70 Heading G4H Apparatus for monitoring data derived from measured parameters such as pressures, temperatures, engine speed, fuel flow rate, &e. in an aircraft comprises a circuit for comparing the measured values of the parameters with predetermined values such as upper and lower limits of the parameters during a sequential scan of the parameters and for recording the measured values when they exceed these limits, the measured data of an entire scan also being recorded if one or more of the measured values exceeds the limits and a parameter numeral being printed to identify each parameter which exceeds the limits. Analogue parameters are fed via switches (70-74), Fig. 2 (not shown), to a muliplexer (76) in a circuit 10 where they are converted into digital signals accompanied by a sign bit as each parameter is scanned. This digital data as well as digital data derived from measured digital parameters is fed to a multiplexer (86), Fig. 3 (not shown), in a circuit 12. A memory 32 stores data relating to each parameter such as the addresses of upper and lower fixed limits in a main storage 20, floating limit data, addresses of previous and current parameter values in the storage 20 and data 54 relating to the number of times the parameters may be allowed to exceed the limits before their values are recorded. The memory 32 also provides analogue address signals 60, 61 to the circuit 10 on receipt of successive parameter identification signals "PARAM O-N" to scan the measured analogue parameters and provides digital address signals 62 to the circuit 12 to cause scanning of the digital parameters. Digital data is therefore fed from the multiplexers to a register 14 connected to the storage 20 and the "true" and "complement" inputs of an adder 18. The storage 20 is connected to a recorder 22 and a register 24 which feeds a printer 26 as well as the inputs of the adder 18. The least significant bits of the register 24 are fed to a parameter history register 28 which includes a counter 58 for counting the number of times a parameter exceeds the limits. A comparator 56 compares this number with the value 54 stored in the memory 32. When these values are equal recording of the subsequent parameter values is able to take place. The main storage 20 is controlled by a storage address register 30 connected to the outputs of the memory 32. Each of the parameters is scanned sequentially during a ten millisecond period defined by a clock 130 and each parameter scanned steps a counter 124 which provides the parameter identifcation signal "PARAM O-N". The data analysis occurring during each ten millisecond period is controlled by a programme counter 118 incremented by a two microsecond clock 128. The two most significant bits of the counter 118 are fed to a decoder 132 which provides four distinct periods during each ten millisecond period namely a "start" period, a "floating limit" period, a "fixed limit" period and an "end of parameter" period. The three least significant bits of the counter 118 generate timing signals PGM 0-7 which control the circuits during each of the four distinct periods. During the "start" period the address of the parameter value from a previous scan is fed to the register 30 via gates controlled by the timing signals PGM 0-7 and the selected parameter value is fed to the register 14. The previous scan of parameters is recorded by reading the storage 20 if any one of the previously scanned parameters has exceeded a limit. During a "floating limit" period the current parameter value is fed from the register 14 to the "true" input of the adder 18 and the previous value is fed from the register 24 to the "complement" input. The two values are subtracted and the adder provides an overflow signal if the current value is less than the previous value. The difference between the two values is subtracted from a pre-set floating limit deviation to see if the current parameter value is within the floating limit. If it is not within the limit the entire scan of parameter values is recorded during the next scan. During a "fixed limit" period the lower limit address 38 is gated into the register 30 which reads out the lower limit from the storage 20 and transfers it to the register 24. The lower limit is then fed to the "complement" input of the adder 18 and the current parameter value in the register 14 is fed to the "true" input of the adder. If the current value is lower than the lower limit an overflow from the adder 18 causes printing of the parameter identity number and the time on the printer 26. Similar operation occurs for the upper limit. The comparison of the number of transients of the parameter with the pre-set number also takes place during this period. During an "end of parameter" period the current parameter address is gated into the register 30 to cause storage of the current parameter value and the contents of the register 28 are transferred to the register 14 for storage and use in subsequent scans. The apparatus is provided with amode decode circuit 16 to enable the parameters to be recorded during each scan (fast mode) or once every hundred scans (slow mode), the former mode being used during starting and take-off whilst the latter mode is used during taxiing. Also, during climb and descent one set of floating limits (mode FL1) may be used whilst during cruising another set of floating limits (mode FL2) may be used.