Abstract of
GB886304
886,304. Warming devices on aircraft. BENDIX CORPORATION. Oct. 2, 1959 [Oct. 16, 1958], No. 33540/59. Class 4. [Also in Group XXXVII] Aeronautical apparatus for producing a prescribed action e.g. an audible or visible signal, when either a predetermined value of Mach. number or of airspeed had been reached, comprises a first device controlled in response to dynamic pressure alone so as to be moved to an active position when said airspeed value has been reached, a second device controlled jointly in response to dynamic and static pressures so as to be moved to an active position when said Mach number value is reached, and an actuator device operated by movement of either said first or said second device to its active position to effect said prescribed action. The device has a hermetically sealed housing 12 having two inlet ports, one 14 which enables the static pressure inside the housing to equal that of the ambient air outside and another 16 which connects the interior of a capsule or airspeed diaphragm 18 to a pitot pressure line which transmits dynamic air pressure. One side of capsule 18 is rigidly mounted relative to housing 12 by a support 20 through which, and a line 22, the capsule connects to port 16. An evacuated and sealed capsule 24 is mounted on housing 12 through a diaphragm support 26, an overload spring 28 and a stem 30. The capsules 18 and 24 are respectively connected to adjustable linkages 32 and 34 in turn respectively connected to an arm 36 and a movable contact 42. Arm 36 carries at its ends contacts 38 and 40 interconnected by a lead 52, contact 40 co-operating with contact 42 and contact 38 with a contact 44 secured to housing 12 by a stem 46 and an overload spring 48. Contact 40 is connected by lead 50 and contacts 42 and 44 by leads 58 and 54 to a relay 56 associated with a device 60 connected to a suitable warning device (not shown). In operation the device is preset by adjustment of linkages 32 and 34 to limits within which it is intended to operate. Providing the device is operating below the preset limits of airspeed and Mach number all contacts remain open, but should the preset airspeed be exceeded contacts 38 and -44 will close to energise relay 56 and should the preset Mach number be exceeded contacts 40 and 42 will close also to energise relay 56. With both preset airspeed and Mach number exceeded all contacts will be closed.
1. Aeronauticalapparatus for producing a prescribed action when either a predetermined value of airspeed, or a predetermined value of Mach number, has been reached whichever of said values is reached first, comprising a first device controlled in response to dynamic pressure alone so as to be moved to an active position when said airspeed value is reached, a second device controlled jointly in response to dynamic and static pressures so as to be moved to an active position when said
Mach number value is reached, and an actuator device operated by movement of either said first or said second device to its active position to effect said prescribed action.
2. Aeronautical apparatus for producing a prescribed action when either a predetermined value of airspeed, or a predetermined value of
Mach number, has been reached whichever of said values is reached first, comprising a first electric contact device controlled in response to dynamic pressure alone so as to be moved to an active, e.g. circuit-closing, position when said airspeed value is reached, a second electric contact device controlled jointly in response to dynamic and static pressures so as to be moved to an active, e.g. circuit-closing position, when said Mach number value is reached, and an electrical actuator device, e.g.relay, connected in circuit with both said contact devices and operated by movement of either contact device to its active, e.g. circuitclosing, position to effect said prescribed action.
3. Apparatus according to claim 2, wherein each of said contact devices comprises a pair of contacts, both said pairs have their one contacts displaced simultaneously by an element, e.g. manometric capsule, responsive to dynamic pressure, the other contact of said one pair is stationary, and the other contact of the otherFair is displaced by an element, e.g.
manometric capsule, responsive to static pressure.
4. Apparatus according to any preceding claim, having means for separately adjusting the initial position of each of said first and second devices with respect to its active position.
5. Apparatus according to claim 2 or 3, having means for separately adjusting the initial spacing of the contacts in each contact device.
6. Apparatus according to claim 2, 3 or 5, having means for resiliently absorbing excess pressure between the contacts of each contact device.
7.Aeronautical- apparatus substantially as described in the specification with reference to, and as illustrated in Figure 1 of the accompanying drawings.
Description
COMPLETE SPECIFICATION
Sensitive Speed Instrument for Aircraft
We,THB BENDIX CORPORATION, formerly known as Bendix Aviation Corporation, a corporation of the State of Delaware, United
States of America, of Fisher Buildings, Detroit, Michigan, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the followingstatement:
The present invention relates to a sensitive speedinstrumentfor aircraft for producing a prescribed action, such as an audible or visual signal, when a predetermined maximum safe airspeed and/or mach number has been reached by the aircraft.
Various types of instruments are used to warn the pilot of an aircraft when the maximum safe speed of the craft has been reached.
These instruments have primarily been dial indicating instruments in which combinations of pointers and indexes are used to indicate the maximum safe speed and when such speed has been reached. In using these instruments the pilot would gather the facts and draw his conclusion. With the advent of high performance aircraft it has become more necessary to relieve the pilot of as many tasks in flying the aircraft as possible and to minimize the human error factor. An instrument in which a conclusion is given the pilot will aid the pilot in the safe flight of his aircraft. An object of the present invention is to provide an instrument which does not require the pilot's visual attention but one in which the conclusion desired is obtained on an audible signal or a visual signal. The invention is designed to provide a signal which will inform the pilot when the maximum safe speed or maximum preset speed of the craft has been reached and to thus overcome the deficiencies of the present indicating instruments. The maximum safe speed of an aircraft is a speed under which structural fatigue of an aircraft will not occur and maximum preset speed is any speed of the aircraft at which a visual or audible signal is desired.
There are several speed designations which are used to represent the speed of an aircraft, such as: indicated airspeed, true airspeed, equivalent airspeed and mach number. Each of these designations of speed can also be used for indicating the maximum safe speed of an aircraft Present methods generally call for using only one such speed designation in indicating maximum safe speed. With the advance in the performance of aircraft an instrument indicating maximum safe speed in at leastNvo speed designations may be necessary for the safe flight of the aircraft.
The speed at which an aircraft may safely operate without causing a structural failure of the craft is dependent upon the structural design of the aircraft. The airframe manufacturer will determine the maximum safe speed and present the speed limitations in terms of an airspeed and/or mach number. Because of the wide range of altitudes which aircraft now operate, an indicator which will only give a safe airspeed or mach number will not safely define the operational limits of the aircraft.
While changing altitude and holding airspeed constant, mach number will vary substantially and conversely, while changing altitude and holding mach number constant, airspeed will vary substantially.
An object of the present invention is to provide a sensitive warning instrument for aircraft which will provide an electrical signal when the aircraft reaches a predetermined speed.
Another object of the present invention is to provide a sensitive mach-airspeed warning device for aircraft which will transmit an electrical signal when the aircraft reaches either a predetermined mach number and/or airspeed, whichever is reached first.
A further object of the present invention is to provide a sensitive mach-airspeed warning device in which means are provided to allow variations in the preset of the maximum mach number and airspeed, which will permit the same instrument to be used in various types of aircraft.
A further object of the present invention is to provide a sensitive mach-airspeed warning device for aircraft which will transmit an electrical signal when the maximum safe airspeed or mach number for the particular aircraft has been reached.
The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawing wherein an embodiment of the invention is illustrated. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description and is not to be construed as defining the limits of the invention.
In the drawings:
Figure I is a schematic diagram of one embodiment of the invention.
Fig. II is a graph showing the safe speed limits for a representative aircraft in terms of the criteria indicated airspeed and altitude.
The following two tables show the need for anindicating device which can be used to indicate maximum safe indicated airspeed and mach number. Table I indicates that with a constant mach number the indicated airspeed varies substantially when there is an altitude variation. Thus, an indicator which would be used to indicate only maximum mach number is not satisfactory where the aircraft's structural limits are also defined by a particular maximum safe indicated airspeed. Table II presents a reverse situation; where the indicated airspeed is held constant, the mach number varies substantially with variations in altitude. Thus, an indicator which would be used to indicate only maximum indicated airspeed is not satisfactory where the aircraft's structural limits are also defined by a particular maximum safe mach number.
TABLE I
At constant mach number
Indicated
Altitude, feet Mach No. Airspeed, Knots
0 0.80 528
20,000 0.80 372
40,000 0.80 242
60,000 0.80 151
80,000 0.80 94
TABLE II
At constant indicated airspeed
Indicated
Altitude, feet Airspeed, Knots Mach No.
0 400 .605
20,000 400 .854
40,000 400 1.237
60,000 400 1.863
80,000 400 2.909
The values for Tablesland II were taken from Volume I of "Tables and Data for Computing Airspeeds, Altitudes and Mach Numbers Based on the WADC 1952 Model Atmosphere."
The tables demonstrate the inadequacy of a speed indicator which would indicate only maximum mach number or indicated airspeed where the structural limits of the aircraft are limited by both. For example, in Table I, if the maximum safe mach number for a craft is 0.80 mach and the maximum safe indicated airspeed is 372 knots, then an aircraft which flies at the permitted0.80 mach, but has altitude below 20,000 feet is flying at a speed which is beyond the safe speed for the aircraft.
A similar example may also be shown by
Table II; if the maximum safe indicated airspeed for a craft is 400 knots and the maxmum safe mach number is 0.854, then an aircraft which flies the permitted 400 knots, but has altitude above 20,0000 feet, is flying at a speed which is beyond the safe speed for the craft.
Referring now to the drawing, and in particular to Figure I, there is shown a machairspeed device 10 designed for use as a warning device when an aircraft has reached a predetermined airspeed and/or mach number.
The mach-airspeed warning device 10 has a hermetically sealed housing 12 having two inlet ports 14 and 16. Static pressure inlet port 14 permits the pressure inside the hermetically sealed housing 12 to be equal that of the ambient air outside the aircraft. Total or pitot pressure inlet port 16 permits the connecting of a pressure responsive device inside the hermetically sealed housing to a pitot pressure line which transmits the aircraft's impact pressure.
A first fluid pressure responsive element such as capsule 18 (airspeed diaphragm) has one side rigidly mounted relative to the hermetically sealed housing 12 by means of diaphragm support 20. The airspeed diaphragm18 is joined to pitot pressure inlet port 16 through fluid line 22 and diaphragm support 20. The second side of airspeed diaphragm 18 is free for movement responsive to changes in pitot pressure.
A second fluid pressure responsive element such as capsule 24 (aneroid diaphragm) is an evacuated sealed capsule. One side of the aneroid diaphragm 24 is securely mounted to the housing 12 through a supporting structure which comprises a diaphragm support 26, an overload spring 28 and a stem 30. The second side of the aneroid diaphragm 24 is free to move responsive to changes in the static pressure.
The fluid pressure responsive capsule 18 and 24 may take a variety of forms, such as a diaphragm or bellows.
Advantageously, the movable or free side of airspeed diaphragm 18 and aneroid diaphragm 24 are connected to adjustable means of any well known form, but preferably comprising adjustable linkages such as linkages 32 and 34.-Adjustable linkage92 is connected toarm 36 two which-movable-ontacts-- 3s-and 49- - areaffixed Movable contact 42 isconnected to the free side of aneroid diaphragm 24 through adjustable linkage 34 and is positioned to move in the same path of movement as contact 40. Fixed contact 44 is mounted to the housing 12 through a supporting structure which comprises a stem 46 and an overload spring 48. Fixed contact 44 is positioned in theparh of movement of movable contact 38.
The device may be considered in two sections, the maximum airspeed section and the maximum mach section. The maximum airspeed section will indicate when a predetermined maximum airspeed is reached and the maximum mach section which will indicate when a-maximum predetermined machnum- ber is reached by the aircraft.
In the maximum airspeed section, upon the engagement of movable contact 38 and fixed contact 44 an electrical circuit is completed, which results in the energization of relay 56.
This electrical circuit comprises wire 50, contact 40, wire 52, contacts 38 and 44 and wire 54. In the maximum mach section, upon the engagement of movable contact 40 with movable contact 42 an electrical circuit is completed which results in the energization of relay 56. This electrical circuit comprises wire 50, contacts 40 and 42 and wire 58.
Relay 56 is associated with a suitable electrical receptical 60 which may be connected to a suitable warning device (not shown).
Figure II graphically presents the operational value of the inventive device. The maximum safe values of mach number and indicated airspeed were selected for the purpose of illustration as limiting criteria for a representative aircraft, it being expressly understood that the invention is not limited thereto. The device does just as readily operate in the supersonic speed range as well as in thesub- sonic speed range as illustrated in the graph.
In the graph, indicated airspeed(totaI pressure) is plotted along the abscissa and altitude (static pressure) is plotted along the ordinate.
Both the total and static pressures are expressed in inches of mercury. For the purpose of illustrating the invention, 0.80 mach number and 400 knots were plotted on the graph, these two values represent the maximum mach number and indicated airspeed for which the mechanism illustrated in Figure I has been preset
The mach and airspeed lines have defined four areas on the graph, areas A, B, C, and
D. The area to the right of 0.80 mach line, areas B plus D, represents the condition in which the aircraft has exceeded0.80 mach number. The area to the right of the 400 knot line, areas C plus D, represents the condition in which the aircraft has exceeded 400knots
In operation, the device as illustrated in
Figure- I and preset for anaircraft--with thelimited presented in- Figure-:- I-' will. 6peeate as follows. Electrical- contacts 38 and 44 are maximum airspeed contacts and electrical contacts 40 and 42 are the maximum mach contacts and are not engaged prior to the flight of the aircraft. When the aircraft flies at an altitude and indicated airspeed within area A then neither contacts 38 and 44 or contacts 40 and 42 will be engaged. When the aircraft is flying at an altitude and airspeed within area B then contacts 40 and 42 will be engaged and contacts 38 and 44 will be separated. When the aircraft is flying at an altitude and airspeed within area C then contacts 38 and 44 will be engaged and contacts 40 and 42 will be separated. When the aircraft is flying in area D then contacts 38 and 44 and contacts 40 and 42 will be engaged. When any of the contacts are engaged an electrical circuit is completed and relay 56 is energized resulting in the warning of the pilot that he has exceeded the preset maximum indicated airspeed and/or maximum mach number.
The inadequacy of a warning device which would indicate either mach number or indicated airspeed is readily apparent from Figure
II. An aircraft which would not structurally withstand speeds in the excess of 0.80 mach or 400 knots could not safely use an indicating device which would serve to indicate either maximum airspeed or mach number.
An aircraft which has an instrument which would indicate only maximum safe airspeed would exceed the structural limitations of the aircraft when flying at a speed less than the maximum safe airspeed and within area B of the graph, the pilot would have no indication that he has exceeded the structural limitations of the craft by flying at such speed and would be in serious difficulty. Similarly an aircraft which has an instrument which would indicate only maximum safe mach number would exceed the structural limitations of the aircraft even when flying within such safe mach number, if the speed at which it is safe to fly is exceeded when flying within area C. As before the pilot would have no indication of this condition.
While the indicating device as shown in
Figure I is of the construction shown and described, it is understood that the instant invention is not limited to any particular form or division. Moreover, other changes and modifications of the indicating device contemplated herein may be made by those skilled in the art without departing from the scope of the invention as defined by the appended
