US3713090A

US3713090A - System for use in conducting aircraft check lists

Info

Publication number: US3713090A
Application number: US00069254A
Authority: US
Inventors: C Dickinson
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-09-03
Filing date: 1970-09-03
Publication date: 1973-01-23
Anticipated expiration: 1990-01-23

Abstract

The system is for use in an aircraft, and it includes a number of pre-recorded messages or check lists, either emergency (in which case selection is automatic) or normal operational. Each message includes a number of separate items arranged in sequence. A desired list is selected either manually by the pilot or automatically by an emergency sensor, and a pre-recorded audio signal announces the first item over a speaker. The tape is then shut off, giving the pilot time to check the item. The pilot, when he is satisfied the item is operational, presses a reply bar to proceed with subsequent items. The tap re-winds automatically when the end of a message is reached and shuts down at the start of message position. In the case of an emergency, the system will interrupt a previously selected message if it is also not an emergency check list, return to the start of the proper emergency check list, and transmit an emergency radio signal. Circuitry permits repetition of an item if desired; and the pilot may selectively reset the message in high speed before completing it.

Description

United States Patent Dickinson 1541 SYSTEM FOR USE IN CONDUCTING AIRCRAFT CHECK LISTS [76] Inventor: Clarance B. Dickinson, Tower 6,

Bath & Tennis Club, North Green Bay Rd., Lake Bluff, Ill.

[52] US. Cl...340/27 R, 179/100.2 S, 179/1002 MD [51] Int. Cl. ..G08g 5/02 [58] Field of Search...340/27 R, 221; 179/1002 MD,

[56] References Cited UNITED STATES PATENTS 3,059,062 10/1962 Ojala ..l79/l00.1 3,294,924 12/1966 Fein ....l79/100.2 MF 3,298,010 1/1967 Dubosq et al.... ....l79/l00.2 MF 3,015,702 l/l962 Vogel et al. ..340/221 2,718,628 9/1955 Bartlett et a1 ..340/27 R @ITEH mm RESET KAUDIO'CHECIK' P PRE START per.

[ 1 Jan. 23, 1973 Primary ExaminerKathleen l-l. Claffy Assistant Examiner Thomas L. Kundert Attorney-Dawson, Tilton, Fallon & Lungmus [57] ABSTRACT The system is for use in an aircraft, and it includes a number of pre-recorded messages or check lists, either emergency (in which case selection is automatic) or normal operational. Each message includes a number of separate items arranged in sequence. A desired list is selected either manually by the pilot or automatically by an emergency sensor, and a pre-recorded audio signal announces the first item over a speaker. The tape is then shut off, giving the pilot time to check the item. The pilot, when he is satisfied the item is operational, presses a reply bar to proceed with subsequent items. The tap re-winds automatically when the end of a message is reached and shuts down at the start of message position. In the case of an emergency, the system will interrupt a previously selected message if it is also not an emergency check list, return to the start of the proper emergency check list, and transmit an emergency radio signal. Circuitry permits repetition of an item if desired; and the pilot may selectively reset the message in high speed before completing it.

5 Claims, 6 Drawing Figures ire-"gaz 3 PAIENTEDmza 1915 SHEET 3 BF 3 6E 5 hi SPEU LLQUNIU SYSTEM FOR USE IN CONDUCTING AIRCRAFT CHECK LISTS RELATED APPLICATION This is a continuation-in-part application of my copending application, Ser. No. 841,675, filed June 26, 1969 and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system which is installed in an airplane and is used in assisting a pilot to check various items that are required, for example prior to take-off, prior to landing, etc.

Normally, there are a number of check lists that a pilot must routinely go through in order to operate the airplane. For example, there may be a Pre-Start check list which must be gone through even before starting the engines, a Pre-Flight check list or Pre-Take Off check list, a Landing check list, and so on. Normally, the check lists are prepared in sequential order on a paper, and a co-pilot reads the item to the pilot who then makes the cheek and reports back to the co-pilot. During this time, the entire attention of the co-pilot as well as the pilot must be given to conducting the check lists.

2. Prior Systems It has been suggested to pre-record certain check lists, for example on magnetic tape, so that the pilot may play the tape and conduct the check list. Such systems do not permit flexibility in permitting the pilot to proceed at his own speed. That is, the actions required of a pilot in a Landing check list may be performed more rapidly than the actions required in a Pre- Start check list when the engines are not even started. Further, such systems make no provision for incorporation of emergency check lists.

SUMMARY The present invention provides for a number of check lists (sometimes referred to as messages) both normal operational check lists such as Pre-Start, Pre- Take off, Landing, etc. and emergency check lists. If desired, there may be a priority in the emergency check lists.

The pilot is permitted to select one of the desired pre-recorded check lists by means of the dial, and visual indicia indicate to the pilot which check list he is running through. On each of the check lists, individual items are recorded so as to be played back over a headset or speaker to be heard by the pilot, and after each item is played back, the tape is stopped, but the system remains operational. After the pilot has performed the required function, he presses a reply bar which causes the next recorded item to be plated back. Thus, the pilot may proceed at his own speed; yet, the co-pilot or other assistant is completely freed from the menial task of reading and checking a list. That is, the invention allows one crew member to handle all the check list procedures, and frees the remaining crew to stay fully oriented toward the approach of any aircraft in the flight area. As most lists are performed in high density areas, it is felt that this advantage will greatly enhance aircraft safety.

At night, the inventive system permits the selection and performance of lists in areas of critical density without lights for illumination that might disturb a pilots night vision. Further, in emergency situations, the system completely frees remaining crew to handle the aircraft or assist in carrying out procedures other than calling off items to be checked. The system enables the crew to carry out Pre-FIiglit check procedures faster, thereby expediting departure of aircraft.

The system contains provisions for deferring any standard check list item with the visual indication that one item has been deferred and must be completed before the check list is complete. Further, an emergency automatically triggers an announcement to the pilot over a speaker system as to what the emergency is and applicable check procedures immediately follow for assisting the pilot in isolating the fault. The automatic emergency detection system further energizes a broadcast over the standard emergency channel which is 121.5 KI-Iz.

Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment wherein identical reference numerals will refer to like parts in the various views.

THE DRAWING FIG. I is a front elevational view of a pilot's control panel of the type employed by the present invention;

FIG. 2 is a schematic representation, partially broken away, of the magnetic tape on which messages are recorded;

FIG. 3 is a functional block diagram of the selection gates for the recorded messages and the audio portion of the system;

FIG. 4 is a schematic diagram, partially in functional block form, illustrating circuitry for controlling the tape transport;

FIG. 5 is a functional block diagram of the electronic circuitry for a preferred embodiment of the invention; and

FIG. 6 is a circuit diagram, partially in functional block form, of the deferred item function.

DETAILED DESCRIPTION Referring first to FIG. 1, reference numeral 10 generally designates the faceplate panel of a plug-in module adapted to be fitted into the instrument panel of an aircraft and easily accessible to a pilot or operator. The controls utilized by the pilot include an on/off switch 11 which also includes a deferred item position, a start-reply bar 12 which controls a switch which is spring-biased in a forward (open) position, an item repeat push button switch 13 which is also spring-biased in a forward (open) position, a manual reset push button switch 14, also spring-biased in a forward (open) position, a volume control knob 15 for adjusting the volume of the audio signal that is: pre-recorded on the tape, a selector switch 16 which is peripherally ar ranged relative to the volume control knob 15 and which selects one of the pre-reco'rded messages, and a display window generally designated 17 for indicating by means of alpha-numeric indicia which of the prerecorded messages has been selected by the knob 16. Each of the titles of the pre-recorded messages, such as the Pre-Start" check list (as illustrated), Pre-Take Off" etc., are printed on a band of plastic and gears move the spools on which the film is mounted in response to the pilot's turning the knob 16 so that the correct title for the selected checklist is displayed. However, any number of well known mechanisms may be used for performing this function.

Turning now to FIG. 2, a magnetic tape designated by T, is shown in the form of an elongated strip. At the center and ends of the tape there are portions designated 18 and 18a respectively from which the oxide coating of the tape is removed to provide a window (i.e. translucent or transparent portion). The ends of the tape are wound on the two reels of a magnetic tape transport which may be of the type sold as model DP by the Kinelogic Corporation, Pasadena, California and corresponding to military designation RO-254A/A SQ. In this type of tape deck, the tape is provided in an enclosed cartridge, and there are separate heads for erasing, for recording, and for playback. There is also provided a source of light on one side of the tape and two photocell sensors on the other for detecting respectively the center of tape position (window 18) or the end of tape position (window 18a). The center of tape position is sometimes referred to herein as the Start of Tape or S.O.T., signal, for short. As will be made more clear in subsequent discussion, when the S.O.T. signal is sensed, the drive motor for the tape deck is shut off, and the tape may be moved in either direction.

The tape T in the illustrated embodiment is arranged in eight separate tracks, and these are designated respectively Tl-T8. Tracks Tl-T4 start at the center of the tape (that is, adjacent the start of tape window 18) and extend to the left end of the tape. Tracks T5-T8 start the center of tape and extend to the right end of the tape. Each of the tracks Tl-T8 has a separate recorded message, usually comprising a number of consecutively located individual instructions (sometimes referred to as items). For example, the track T8 is shown diagrammatically as including two separate items designated Item 1" and Item 2, to be followed by a number of additional items. Each of the items is separated by a tone, referred to the end of item tone, whereas the very end of the track includes an end of item tone followed by an end of tape tone. The tones involved may be 3.5 KHZ signals, the end of item tones occurring for less than 2-5 seconds and the end of tape tone occurring for 0.5 seconds in addition to the last end of item tone.

Persons skilled in the art will appreciate that the invention is not limited to any particular number of tracks, nor to any particular combination of emergency or non-emergency checklist, nor to any particular tape deck. For convenience, therefore, the subsequent description will relate to eight separate tracks, three of which have pre-recorded emergency messages and the remaining of which are non-emergency messages such as check-lists. It will also be appreciated that any number of playback heads may be used, and for convenience it will be assumed that there are four, one for each of the double sets of tracks (each set comprising one track to the left of the center position and one to the right ofit).

The selector switch 16 is a rotary switch having nine different terminals including a center one which is connected to a source of power and is provided with a moveable contact for engaging any one of the remaining light terminals. The switch is settable to the eight different positions for the purpose of connecting the source of power to one of five different output lines, two of which are shown in FIG. 3 and designated respectively S1 and S5, the other lines being similar in structure and performing a function similar to the one to be described in connection with lines S1 and 5-5. Line 5-] is coupled to one input of an AND gate 25 and line 8-5 is connected to a similar input of an AND gate 26, the other inputs of the AND

gates

25 and 26 is a signal designated W. The signal W is the inversion of the emergency signal that is, when an emergency arises a signal is generated, and the negative of that signal (as by feeding it through a signal inverter) is coupled to the other inputs of the AND

gates

25 and 26. The AND

gates

25 and 26 are digital logic gates ofa conventional type which generate an output signal only when both of the input signals have a logic 1 present. For purposes of explanation it will be assumed that a logic 1 is some positive voltage and a logic 0 is ground, but the invention is not so limited. Thus, in an emergency situation the AND gates associated with the outputs from the channel selector switch 16 are disabled. The output of the AND gate 25 is connected to the enable lead of a gate 27, and the output of the AND gate 26 is connected to a similar enable lead of a gate 28. The gates 27 and 28 are of a conventional type having a signal input lead and an enable lead. The signal input lead is adapted to receive a continuous signal such as an audio frequency signal, but that input signal will not be transmitted to the output of the gate unless there is also a digital 1 present at the enable lead of the gate. The input signals to the gates 27 and 28 are the output signals from the playback heads of tracks T1 and T5 respectively. It will be appreciated that each of the playback heads associated with the non-emergency tracks will have a gate similar to the AND gate 25 and the gate 27 so that the recorded signal will be passed through its associated gate 27 only when the channel selector switch has selected that particular track and there is not an emergency condition existing. The output of the gates 27 and 28 as well as any similar gates are connected to a node designated 30.

The three emergency tracks T6-T8 are coupled to gates similar to gate 27, two of which are shown and designated 31 and 32. The gate 31 receives at its input the output of track T6, and the gate 32 receives the output of the playback head associated with track T8. The respective enable leads of the gates 31 and 32 (as well as any other emergency message gates) are coupled from specific emergency sensors. For example, if the pre-recorded message on track 6 is a checklist to be used during the case of an engine fire, a temperature or smoke sensor will be mounted within the engine so as to generate a signal when an engine fire occurs. This signal will enable the gate 31 to couple the recorded message from track T6 to the node 30 while, at the same time, disabling the gates (27, 28) and associated with the non-emergency messages.

The node 30 therefore carries the audio signal from either: (1) a manually selected pre-recorded checklist, or (2) an automatically sensed pre-recorded emergency message or checklist. The node 30 is connected to the input of a pre-amplifier circuit 34, the output of which is connected to an amplifier circuit 35. The volume control knob controls the value of a variable resistor generally designated by reference numeral 36 which is connected between the input and output terminals of the amplifier 35. Thus, the control knob 15 determines the output volume of the audio signal which is fed through a gate 37 and into the audio system, schematically shown by the speaker 39. The gate 37 is similar to the previously described gates 27 and it includes an enable lead E which receives a signal designated Mute which, as will be described later is a signal generated, for example, during rewind of the tape so that the audio noise does not appear on the speaker system. The output of the pre-amplifier 34 is also connected to the input of a high pass filter circuit 40 (i.e. higher than audio frequency to block the signals of the pre-recorded messages) designed to sense the tone signal for the end of item tone and the end of tape tone. This signal is passed through an amplifier 41 and into two different detector circuits generally designated by

reference numerals

42 and 43. The detector circuit 42 includes a resistance-capacitance network including a resistor 44 and a capacitor 45 connected in circuit so that the signal on the capacitor 45 builds up according to a predetermined time constant. When the signal reaches a certain level, a level detector circuit 47 generates an output signal, denoted the end of item signal. The detecting circuit 43 includes a similar resistor and

capacitor

49, 50 and diode 51. The signal building up on capacitor 50 when a tone is detected will generate an end of tape signal when it exceeds a threshold set by a level detector circuit 52. The time constant of the detecting circuit 42 is designed to be shorter than the time constant of the level detector 43 that is, the end of tape signal is generated not by an end of item tone (which is not of long enough duration), but only when an end of tape signal is present, lasting about 0.5 seconds longer than an end of item tone.

it will be appreciated in the previous description that in reality the signals picked up from tracks T1 and T5 are picked up from the same head. Similarly, the track pairs T2, T6 and T3, T7, and T4, T8 are picked up from individual heads.

Turning now to FIG. 4, the control (speed and reversing) of the tape transport motor will now be explained in greater detail. The channel selector switch is again generally designated by reference numeral 16, and it is shown as having eight separate terminals or contacts and a wiper arm. The wiper arm is connected to a source of power so as to energize whichever of the contacts 51-88 are selected. The contacts Sl-S4 (corresponding to tracks Tl-T4) are connected to separate inputs of an OR gate 60. Similarly, the contacts S5-S8 (corresponding to tracks TS-T8) are connected to inputs of an OR gate 61. The output of the OR gate 60 is connected to the set input of a flip flop 62; and the output of the OR gates 61 is connected to the reset input of the flip flop 62. The flip flop 62 is of the type that its 1 output carries a signal whenever a ground signal (or logic 0) appears at its set input, and the same output carries a 0 when the reset input is similarly set. Whatever the output state of the flip flop 62, it will be reversed when its trigger input is pulsed. The trigger input of the flip flop 62 is received from an OR gate 64, the function of which will be described in greater detail subsequently. The 1 output of the flip flop 62 is connected to the coil of a relay generally designated by reference numeral 65 which is the forward/reverse relay, controlling the reversing of the tape transport motor which is schematically shown within the dashed line 66. The motor has a set of high speed windings generally designated 67 and a set of low speed windings generally designated 68. The tape reels are schematically shown and generally designated 69 with the playback heads schematically shown at 70. The coil of relay 65 controls the switching of four separate switches, 65a-65d which are in effect two double-pole, double-throw switches for reversing the current to the

windings

67 or 68, whichever is energized. As is conventional, the motor windings are capacitor-coupled to the power lines that feed them. One of the power lines is designated 73 and the other is designated 74. The line 74 is connected to the wiper arm of a two-position contact generally designated by reference numeral 75 which is controlled by a relay, the coil of which is designated 77. The circuitry which energizes the coil of relay 77 will be described in greater detail below.

The lines 73 and 74 are coupled to a power supply 80 (which may be the aircraft power supply) by means ofa set of normally open contacts 81 which are actuated by the coil of a relay 82. The coil of relay 82 is connected in series with a set of contacts 83 and a transistor 84, the coil being connected to the collector of the transistor 84. The transistor 84, as shown, is normally biased in an on or conducting condition, and the base of the relay is coupled by means of an inverter circuit 86 to the output of an OR circuit 87. Two inputs of the OR circuit are from the center of tape photocell (schematically shown at 88 and generating a signal when light is sensed through window 18 of the tape) and the other input being received from the previously described level detector circuit 52 for end of tape signals.

The normally open contacts 83 are controlled by the coil of relay 90 which is connected in series with the normally open contacts 91 of a relay 92. Also connected in series with the contacts 91 in coil 90 is a J-K flip flop 93. A master memory circuit 94 is connected in circuit to energize the coil of relay 92. The master memory circuit 94 may be a conventional memory circuit which is capable of being set and reset; whereas, the J-K flip flop is a type commonly known in the trade having a set input, a reset input and a clock input. The signals present at the set or reset inputs are transmitted to the output terminals of the flip flop when a signal is received at the clock input of the flip flop.

Turning now to FIG. 5, the master memory 94 and the flip flop circuit 93 are shown at the upper right hand corner as feeding a block functionally labeled Control Circuitry of FIG. 4 including the circuitry previously disclosed in connection with FIG. 4 which need not be repeated here.

The Set input of the master memory 94 has two separate set input terminals; one is connected to the output of a NAND gate 98. The memory 94 is set on a 0 signal. A NAND gate is one in which the output signal is a 0 only when all the inputs are ls, otherwise the output signal is a 1. It is thus an inverting AND gate, and is commonly known. One input of NAND gate 98 is received from the output of another NAND gate 99; and the other input is received from a lead designated 100 and energized by a signal labeled SOT denoting the inverse of the Start of Tape signal. That is, a 1 signal will be present on the lead 100 to energize one input at the NAND gate 98 only when the tape is not in its center position (that is, when the tape is playing). The S OT signal is generated by a photocell, the output of which is passed through an inverter.

The function of NAND gate 99 is to rewind the tape to the start position in high speed either upon pressing the reset switch 14 or upon the occurence of an emergency and the tape is in the middle of a message. One input of the NAND gate 99 is coupled to the output of an Inverter 112; the input of which is fed by a 1 signal I unless the Reset switch 14 is depressed. The other input of the NAND gate 99 is received from the set output of a flip flop circuit 101. The flip flop circuit 101 is a conventional flip flop circuit having a set input (S), a reset input (R) and a trigger input (T). The set input is energized by the W signal and the trigger input is ener-' gized by the output of a NAND gate 102. The output of the NAND gate 102 is also connected to one input of an AND gate 103, to one input ofa NAND gate 104, to an Emergency Broadcast Transmitter 102A, and to an inverter which generates a signal to disable the gates which transmit the check lists non-emergency (see 27, 28 in FIG.-3). The reset input R of the flip flop 101 is received from the end of tape (EOT) signal (generated by the level detector circuit 52 of FIG. 3). The EOT signal also is fed through an inverter circuit 106 to the other input of the AND gate 103. The output signal of the AND gate 103 feeds the set (S) input of a memory flip flop circuit 107 which locks out other emergency check lists once one is being played. The reset input of the flip flop circuit 107 is energized by an automatic reset circuit designated 108 so that once the flip flop 107 is set, it may be reset only by turning off the power and turning it on again. The reset circuit 108 generates an output signal only when power is turned on, and it may be of a conventional RC circuit of the type used to set flip flops and registers to an initial state when power is turned on.

The NAND gate 102 has three separate inputs, each energized by a separate one of the automatic emergency sensor, schematically designated by the block 109. The signal on each input line is normally a I, so that the output of NAND gate 102 is a I only when there is an emergency condition. The output of the memory cireuit 107 is fed into an inhibit circuit in the automatic emergency sensors 109 to inhibit the transmission of a subsequent signal to the playback head selection circuitry when the memory circuit 107 is in a set condition. Thus, if an emergency arises, one of the outputs of the automatic emergency sensors 109 will energize the NAND gate 102 which will, in turn, set flip flop 107 through AND gate 103. At the same time, the state of flip flop 101 is reversed so that if a non-emergency check list is being performed, the system is triggered into a reset condition, whereas if no list is being played, the selected emergency list will be started immediately.

The other input of the NAND gate 104 is received through an inverter circuit 110 from the lead 100, representing the SOT signal. The NAND gate 104 feeds one input of a NAND gate 111. The other input of the NAND gate 111 is received from the start-reply switch 112 on which there is present a 1 signal until the startreply bar 112 is depressed by the pilot. The output of the NAND gate 111 is a I only when all the inputs are ()s; and it is coupled through an inverter 111a to one input of a NAND gate 113, the other input of which is received from the output of the inverter 110. Both inputs to the NAND gate 113 will be 0's (to reset flip flops 93 and 94) therefore, when the tape returns to the center position, the operator is not pressing the startreply bar 112 and there is no automatic emergency signal being generated.

The output of inverter 111a is coupled directly to the input set terminal (S) of the flip flop 93. The reset input of flip flop 93 is connected to the output of previously described reset circuit 108 which is also connected to the reset input of flip flop 94.

Turning now to the central portion of FIG. 5, there are two J-K flip flops designated respectively 116 and 117, each having a J input, a K input, a clock input (C), a first output labeled Q, a second output labeled 6 and a reset R. As is known in the art, a signal will appear at the Q output if a 1 signal is present at the set input and a transient signal is is transmitted to the clock input. These two flip flops and their associated circuitry and connections are sometimes referred to collectively as the Item Repeat Counter (or Register) that is, the function of the logic associated with these two flip flops is to reverse the operation of the tape in response to a signal from the pilot so that an item just completed will be repeated without going back to the start of the tape.

The item repeat switch is shown in electrical schematic in the lower portion of FIG. 5 and designated by reference numeral 13a. When the switch 13a is actuated it transmits a 1 signal to an OR gate 118 as well as to an inverter circuit 119. The other input of the OR gate 118 is received from an AND gate 120; and the output of the OR gate 118 is connected to the clock input of the

J-K flip flops

116 and 117. The Q output of the flip flop 116 is directly connected to the J input of the flip flop 117, and the Goutput of the flip flop 116 is directly connected to the K input of the flip flop 117.

The 0 output of the flip flop 116 is also connected to one input of the previously described AND gate 64 (also seen in FIG. 4), the output of which is connected to the trigger lead of flip flop 62 for reversing the tape drive motor when the Item Repeat switch is actuated. The output ofa NOR gate 115 (fed by inverter 1110) is connected to the reset inputs of the

flip flops

116, 117 in the Deferred Item Counter.

The 6 output of the flip flop 116 is directly connected to the K input of the flip flop 117 and to one input of an AND gate 123 and to one input of an AND gate 124. The other input of the AND gate 124 is received in the 6 output of the flip flop 117; and its output is fed to an inverter circuit 125. The output of inverter 125 is connected to an input of the AND gate 120, to an input of an OR gate 130, and to the input of an inverter a which has its output connected to an input of an AND gate 135. The other input of the AND gate 120, as already mentioned, is the End of Item signal. The Q output of the flip flop 117 is directly con nected to the K input of the flip flop 116, and the Q output of the flip flop 117 in addition to being connected to one input of the AND gate 124 is connected to the J input of the flip flop I16 and to an input of a NOR gate 122.

A high speed (sometimes called reset) memory 127 which is a conventional flip flop circuit having a set (S) and a reset (R) input its reset input receives and is triggered by the change of the OT signal. When the tape is re-wound to the center position so that the QT signal goes from a l to a 0, the negative leading edge will reset the memory 127. The set input of the reset memory 127 is received from the output of the NAND gate 98. The output of the high speed memory is fed directly to the speed control (relay coil 77 of FIG. 4) and the motor control portion of the system to cause the tape transport motor to operate in high speed durmg reset.

The output of the memory 127 is fed to an input of an OR gate 130, the other input of which is received from the inverter circuit 125 and the output of which is fed to mute the speaker in the system, and this may simply be done by reverse-biasing a transistor coupling the output of the read head to the amplifier 35 of FIG. 3, and is well within the skill of the art. The output of the OR gate 130, therefore, mutes the speaker. This occurs during high speed rewind and during the time at which the tone recorded on the tape are being read back. The output of the reset memory 127 also feeds an input of a NOR gate 133, the output of which is connected to the trigger input of the flip flop 93. The output input of the NOR gate 133 is ac coupled through a capacitor 134a from the output of an inverter 134, the two inputs of which are received respectively from the AND gate 135 and a monostable circuit 136. The input of the monostable circuit is received from the AND gate 123.

As mentioned, one input of the AND gate 135 is connected to the output of inverter circuit 135a; the other input of the AND gate 135 is connected to the E01 signal.

OPERATION To operate the system, the pilot or operator turns the switch 11 (FIG. 1) to the ON condition to connect power to the logic circuitry and to the tape drive. At this time the tape will normally be in its center position. The operator then adjusts volume by means of the knob 15 and selects which of the pre-recorded check lists he desires to comply with using knob 16. The selection circuitry has already been explained in connection with the description accompanying FIG. 3 and the manually selected inputs T1-T5. Thus, the selected playback head will be directly connected to the pre-amplifier 34 of FIG. 3 and to the speaker 39 through the amplifier 35 and gate 37. Preferably the title of the check list is recorded on film and mechanical means are provided for moving the correct title into the window 17 on the control panel 10 so that the pilot knows that the check list he has selected is the correct one.

When the power is turned on, the reset circuit 108 generates a signal to reset flip flop 107 and to reset master memory 94 as well as flip flop 93. The reset circuit 108 may be a resistor and capacitor circuit with an output transistor for amplification of the type which are conventionally employed in digital systems to insure that all flip flops, registers, etc. are set in the proper state when power is turned on. If the playback head is not at a center of tape position (i.e. start of message), memory 94 and flip flop 93 will be set through inverter 110, NAND gate 104, NOR gate 111 and inverter 111A; and the tape will begin to play until an End of Item tone is sensed. If the pilot desires to reset the tape, he presses the reset switch 14, the operation of which will be explained presently.

To start a check list, the pilot presses the start-reply bar 12 to close the switch at this time. Both inputs to NAND gate 111 are normally ls so its output will be a 0; when the switch 12 closes, the output of inverter 111a will energize the set input to the master memory 94 (which sets on a ground input). This will energize coil 92 (FIG. 4) to close contacts 91. The same signal from inverter Illa will set flip flop 93, the output of which will energize coil (FIG. 4) to close contacts 83 thus energizing coil 82 since transistor 84 is normally conducting. This, in turn, will close contacts 81 to supply power to the tape drive motor (either forward or reverse depending upon which of the tracks of the tape have been selected).

At the same time, depression of the start-reply bar transmits a 0 to the input of NOR gate 115; and since the other input of NOR gate 115 is also 0 (the Q output of flip flop 116 being a 0 at this time), the output of NOR gate 115 will go to a I until the start-reply bar is released, and the transition from a 0 to a I will reset both

flip flops

116 and 117 if they have not already been reset. The start-reply bar is also illuminated from the rear by means of two lamps and a holding relay (not shown) to indicate that the selected check list has been started.

The tape will then be driven forward and the first item of the prerecorded message will be played over the speaker 39 of FIG. 3. At the end of each item the level detector 37 will generate an End of Item signal which will be transmitted through the AND gate (the other input also being a l), thl inverter 134 and ac coupled to transmit a momentary 0 to one input of the NOR gate 133. Since the output of the reset (or high speed) memory 127 is also a 0,.the momentary 0 from inverter 134 will cause the NOR gate 133 to trigger the flip flop 93 to reverse its state. It will be appreciated that flip flop 94 is not reversed, and can only be reversed by a signal indicating that the tape is at a center position. In order to then play the next item, the pilot must depress the start-reply bar 12 again. This will then generate a signal to set the flip flop 93 again and thereby energize the coil 90 as already described. When the end of a message is reached, the EOT signal from detector 52 will trigger flip flop 101 to send the system into an automatic reset mode in high speed.

If the pilot or operator desires to reset the message back to its starting position, he depresses the pushbutton 14 which will transmit a 0 to NAND gate 99 which, in turn, will cause its associated input to NAND gate 98 to become a I. If the tape is not at the center position, both inputs to NAND gate 98 will. be a 1 and its output a 0. The change from a l to a 0 sets master memory 94 and sets high speed memory 127 so that the reversing will be in high speed. The output of the high speed memory 127 will trigger flip flop 93 through NOR gate 133 to reverse its output states and start the tape drive motor after the reversing contacts 65a-65d have been actuated. The high speed memory 127 will also energive the mute lead through OR gate 130 and it will lock out the effects of B01 signals by transmitting a l to the NOR gate 133. The other input to AND gate 98 will be fed by a signal indicating that the tape is not at the center of tape position so that flip flop 93 will energize the tape drive motor to rewind the tape in high speed. When the tape reaches its center position the SOT signal will be and the inverter 110 will generate an output signal which will be fed to the NAND gate 113 to reset

flip flops

93 and 94 and de-energize the drive motor.

In order to understand the operation of the item repeat function, reference is made to Table I set forth below wherein the logic states of the O outputs of

flip flops

116 and 117 are indicated by 0s and ls. The left column represents the state of the 0 output of flip flop 116 and the center column represents the state of the 0 output of flip flop 117.

TABLE I FF 116 FF 117 Operation 0 Normal 1 0 Reverse l l 0 1 Forward 0 0 Normal It will be recalled that every time the pilot presses the startreply bar, the flip flops in the Item Repeat Counter (namely, 116 and 117) are reset through NOR gate 115. Starting with the item repeat counter in its normal state, that is, when the Q outputs of each of the

flip flops

116 and 117 are in the 0 state, the system operates normally. When the pilot pushes the item repeat button, he eloses the switch 13 to send a 1 signal through the OR gate 118 to the clock inputs of the

flip flops

116 and 117. The flip flops, however, trigger on the negative edge of the clock signal so that nothing happens until the operator removes his finger from the switch 13a. Then, because the 6 output of flip flop 117 has a 1 signal, that signal will be transferred to the J input of flip flop 116 so that its output will also become a 1; and the Item Repeat Counter is in the state represented by the second line of Table 1, namely when the Q output of flip flop 116 has a 1 and the 0 output of flip flop 117 has a 0.

When the 1 on the 6 output of the flip flop 116 goes to 0, the output of AND gate 124 goes to a 0 and the output of inverter 125 goes to a l thus transmitting a mute signal to amplifier 37 through OR gate 130 and sending a 1 signal to AND gate 120 and inverter 135a. The AND gate 124 is a decoder which generates a 1 signal at the output of inverter 125 whenever the Item Repeat Register is in any state but that corresponding with line 1 ofTable I, that is, during an Item Repeat Cycle. Thus, the l signal at AND gate 120 permits subsequent EOI signals to pass through OR gate 118 to trigger the clock inputs to flip

flops

116 and 117; and the 1 signal to Inverter circuit 135a will disable AND gate 135 to prevent subsequent EOI signals from triggering flip flop 93.

When the pilot releases the Item Repeat switch, the state of flip flop 116 switch, so that the AND gate 64 will be enabled to reverse the direction of travel of the tape drive motor. Next, the pilot pushes the start-reply bar to set flip flop 93, and the tape will be driven in a reverse direction. The first thing that happens is that the read head will pass over an End of Item tone which will pass through AND gate 120 and OR gate 118 to pulse the clock inputs of the

flip flops

116 and 117 and thus cause them to assume the inputs state of line 3 of Table I. The tape will continue to be re-wound until the read head passes over the next previous End of Item tone which will generate a signal that will trigger the flip flops in the Item Repeat Counter to assume the state of line 4 of Table I. When this state is sensed by AND gate 123, it will trigger monostable circuit 136 which will, in turn, transmit a signal to reverse the state of flip flop 93 and shut off the drive motor and also to reverse the state of flip flop 62 to again reverse the direction of the drive motor i.e. to cause it to be set up for forward (or original) direction of motion. However, the tape will not be moved in the forward direction at this time because the flip flop 93 has been reset. At this time, the playback head will be in a position which is two End of Item signals closer to the center of tape than it had been before the pilot closed the Item Repeat switch.

Now, the pilot may re-play the previously played item by pressing the start-replay switch 12 a second time and holding it down until he hears the first tone subside. Operation thereafter is normal because his pressing the start-reply switch resets the Item Repeat Counter.

If an automatic emergency should arise, a first signal is generated by an appropriate sensing mechanism to select the proper one of the tracks T6-T8 by enabling its associated

gate

31, 32. That the proper track will then be coupled through the amplifiers to the speaker 39. Normally, all of the outputs of the generator are 1 s, so an emergency signal will energize the NAND gate 102 which feeds an emergency broadcast radio transmitter 102A to transmit an emergency on the universal emergency frequency. The gate 102 also triggers the flip flop 101 to reverse its state. Thus, if the tape were in the middle of a message, the drive motor will be shut off, but if the tape were in the center, it will be turned on with the proper playback head selected. If the tape had been running, the system goes through a complete reset cycle and then comes back to the center of tape. When the tape reaches the center position, master memory 94 cannot be reset because NAND gate 113 blocks reset in the emergency condition. The combination of SOT signal and emergency condition will give a restart through NAND gate 104 and NOR gate 111. If, on the other hand, the system had been off, the output of gate 104 will change immediately without the reset because there is an SOT signal out of inverter 110. If the tape is in the middle of a message then the flip flop 101 is generating a 1 output signal to set the master memory 94 and the reset memory 127 so that it will be reversed in state and transmit a signal through NAND gate 99 and reset the tape to the start of tape position through circuitry which has already been described. When the tape reaches the Start of Tape position, the inverter will energize the NAND gate 104, and a signal will pass through the NOR gate 111 to set both

flip flops

93 and 94 and the emergency message will be played.

At the end of each check list as well as at the end of each emergency message there will be generated an end-ofrtape (EOT) signal which will be transmitted to trigger the flip flop 62 and to energize a second lead of the AND gate 103. The output of the flip flop 101 is transmitted through the NAND gate 99 to reset the tape to its start position. The AND gate 103 generates an output signal when the OR gate 102 is energized indicating that an emergency message is being played and when an end of tape signal present. The output of the AND gate 103 sets a flip flop 107 to generate a signal which shuts off the system after the emergency message has been played. Thus, in the case of one emergency signal being generated others cannot interrupt it although it will be apparent that an automatic emergency message will interrupt a pre-recorded check list in progress. The flip flop 107 will be reset by the circuit 108 only after the pilot turns power off and then back When the pilot desires to skip an item on the check list, he turns the switch 11 to the deferred item position. Referring to FIG. 6, it will be seen that this position shorts two contacts which connect a free-running vmultivibrator circuit 170 to energize a lamp driver 171 which then feeds a square wave signal to the filament of a lamp (or lamps) 172 located behind the translucent cover for the start-reply bar, designated 173. This will remind the pilot that he has deferred one item, but it does not otherwise affect operation.

Having thus described in detail a preferred embodiment of the inventive system it will be apparent to per sons skilled in the art that elements may be substituted for those which have been disclosed to perform similar functions and that other modifications to the disclosed embodiment may be made while continuing to practice the inventive principles; it is, therefore, intended all such modifications and substitutions be covered as they are embraced within the spirit and scope of the claims.

I claim:

1. A system for use in performing check lists in an aircraft comprising: a magnetic tape recorder with a reversible drive motor having high and low speeds and a magnetic tape having a plurality of prerecorded check lists including normal check lists and emergency check lists, each check list having a plurality of recorded items and an end of item signal after each item, a start of message signal, and an end of tape signal, each emergency check list associated with a predetermined emergency condition in said aircraft; an

emergency sensor associated with each emergency check list for generating an emergency signal in response to the occurrence thereof; a selection gate circuit associated with each recorded normal check list and actuatable by an operator to select non-emergency check lists; first circuit means responsive to the absence of a signal from said emergency sensors for permitting said selection gates to transmit a recorded normal check list only when there is no emergency; audio circuit means receiving the output signals of said selection gates for playing recorded normal check lists and for generating an end of item signal when detected and an end of tape signal when detected; second circuit means including a start-reply switch actuatable by the pilot and bistable circuit means for energizing said drive motor when in a first state and for stoppin said drive motor when in a second state, actuation 0 said start-reply switch setting said bistable circuit to said first state in the absence of an emergency signal; third circuit means responsive to an end of item signal for setting said bistable circuit to said second state to stop said drive motor after each announced item; fourth circuit means for reversing said drive motor in high speed in response to an end of tape signal while locking out said end of item signals; and fifth circuit means responsive to an emergency signal for 'rewinding the tape in high speed if it is not at a start of message position and for selecting and playing an associated emergency check list.

2. The system of claim 1 further comprising item re peat circuit means including a switch actuatable by the pilot to selectively reverse said tape one item and to reverse said motor back to a forward drive position in response to a second-detected end of item signal while locking out said item repeat signal from said bistable circuit.

3. The system of claim 2 further comprising a deferred item switch actuatable by a pilot and blinker light means visible to said pilot for indicating that an item on a check list has been deferred.

4. The system of claim 1 further comprising emergency transmitter means for broadcasting an emergency radio message in response to an emergency signal from any of said emergency sensors.

5. The system of claim 1 wherein said fourth circuit means further comprises means responsive to said start of message signal for stopping said recorder after returning said tape to said start position.

Claims

1. A system for use in performing check lists in an aircraft comprising: a magnetic tape recorder with a reversible drive motor having high and low speeds and a magnetic tape having a plurality of pre-recorded check lists including normal check lists and emergency check lists, each check list having a plurality of recorded items and an end of item signal after each item, a start of message signal, and an end of tape signal, each emergency check list associated with a pre-determined emergency condition in said aircraft; an emergency sensor associated with each emergency check list for generating an emergency signal in response to the occurrence thereof; a selection gate circuit associated with each recorded normal check list and actuatable by an operator to select non-emergency check lists; first circuit means responsive to the absence of a signal from said emergency sensors for permitting said selection gates to transmit a recorded normal check list only when there is no emergency; audio circuit means receiving the output signals of said selection gates for playing recorded normal check lists and for generating an end of item signal when detected and an end of tape signal when detected; second circuit means including a start-reply switch actuatable by the pilot and bistable circuit means for energizing said drive motor when in a first state and for stopping said drive motor when in a second state, actuation of said start-reply switch setting said bistable circuit to said first state in the absence of an emergency signal; third circuit means responsive to an end of item signal for setting said bistable circuit to said second state to stop said drive motor after each announced item; fourth circuit means for reversing said drive motor in high speed in response to an end of tape signal while locking out said end of item signals; and fifth circuit means responsive to an emergency signal for rewinding the tape in high speed if it is not at a start of message position and for selecting and playing an associated emergency check list.

2. The system of claim 1 further comprising item repeat circuit means including a switch actuatable by the pilot to selectively reverse said tape one item and to reverse said motor back to a forward drive position in response to a second-detected end of item signal while locking out said item repeat signal from said bistable circuit.