Technical Field

This invention relates to variable displays in helicopters, or other dynamic systems, in which a parameter is displayed against a background which varies in dependence upon an operational mode of the dynamic system.

Background Art A helicopter is an example of a dynamic system having a large number of characteristics that are contemporaneously important and should be made known to the pilot or other operator in a clear and meaningful way. In order to provide the greatest amount of information with the least amount of confusion, it is known to use graphic displays (sometimes referred to as "analog displays") in manners, and against backdrops, which assist in portraying the information in a clear fashion. However, there are times when the meaning of a given value of a parameter is relatively benign or normal under one set of circumstances and the same numerical value of the same parameter may represent caution or danger in another set of circumstances. The problem with graphic displays is that if the ranges of certain meanings for one set of circumstances is superposed over the range of meanings for other circumstances, and separated, for instance, by color, clutter and therefore lack of clarity nonetheless result. Stated in another way, there is a limit to the amount of information which can be clearly displayed in a single graphic format.

Disclosure of Invention

Objects of the invention include provision of a variety of information on a display, without clutter. According to the present invention, the scale of a graphical display, upon which the magnitude of a parameter is indicated, provides a different indication of the meaning of various ranges of parameter magnitude, in different formats, in dependence upon respectively different modes of operation of the dynamic system. According to the invention, a dynamic, graphic representation of a scale representing a range of normal parameter values appears at different points along the scale in dependence upon the mode in which the dynamic system is operating. According further to the invention, ranges of values on the scale which represent values of the indicated parameter indicative of a particular characteristic of the dynamic system appear at different points along the scale in dependence upon the mode of operation of the dynamic system. According to the invention still further, the characteristics may include operation of the dynamic system which requires caution and dangerous operation of the dynamic system. The ranges for different characteristics may be presented in different colors or have other graphic distinctions. A display according to the invention may optionally have digital representations of numbers indicative of the boundaries of the various ranges. The display also may optionally have a dynamic, digital representation of the parameter along with the analog representation.

The invention may be practiced in an aircraft, and the disclosed embodiment is a display of rotor speed in a helicopter, in which the normal range about

a set reference rotor speed appears at different points along a rotor speed scale in dependence upon whether the aircraft is operating in a normal mode (100% ±3% of rated speed) , a load factor (or speed) enhancement mode (107% ±3% rated speed) , or a quiet mode (95% ±3% of rated speed) . In addition, different ranges outside of the normal range are indicated as being either caution zones or danger zones in dependence upon the operational mode. Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.

Brief Description of the Drawings

Fig. 1 illustrates an electronic display in accordance with a first exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a normal mode. Fig. 2 illustrates an electronic display in accordance with a first exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a load factor enhancement mode.

Fig. 3 illustrates an electronic display in accordance with a first exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a quiet mode.

Fig. 4 illustrates an electronic display in accordance with a second exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a normal mode.

Fig. 5 illustrates an electronic display in accordance with a second exemplary embodiment of the

invention utilized in an aircraft, when the aircraft is operating in a load factor enhancement mode.

Fig. 6 illustrates an electronic display in accordance with a second exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a quiet mode.

Fig. 7 illustrates an electronic display in accordance with a third exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a normal mode.

Fig. 8 illustrates an electronic display in accordance with a third exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a load factor enhancement mode. Fig. 9 illustrates an electronic display in accordance with a third exemplary embodiment of the invention utilized in an aircraft, when the aircraft is operating in a quiet mode.

Fig. 10 is a simplified, partial block diagram of an aircraft incorporating the present invention.

Fig. 11 is a logic flow diagram of a rotor speed mode routine for use with the invention in the aircraft of Fig. 10.

Best Mode for Carrying Out the Invention Referring to Figs. 1-3, a display 9 of a first embodiment of the present invention is created on a cathode ray tube screen either in an analog, stroke- write fashion, or (as is preferred) , digitally, employing a pixel raster. The type of technology utilized to create the display is irrelevant to the invention.

Figs. 1-3 illustrate a first embodiment of the invention, which comprises a display 10 resembling a semi-circular tape divided into segments by tick marks

11-13 representative of various magnitudes of rotor speed (Nr) . The display 9 represents rotor speeds between 85% of rated rotor speed and 120% of rated rotor speed. Fig. 1 is how the display 9 appears when the aircraft is operating in a normal engine/rotor speed mode, herein referred to simply as the normal mode. The normal display (Fig. 1) is in effect when the engine set speed (and therefore the rotor speed which is geared thereto in a fixed manner) is set at 100% of rated speed and allowed to vary between 97% of rated speed and 103% of rated speed. Therefore, to represent the proper operating range in a normal mode, the tick marks 11 appear at 97%, 100% and 103%. Additionally, a tick mark at 110% indicates maximum permissible speed of the rotor. The doubly-hatched portion of the tape 10, between speeds of 110% and 120%, represents a speed danger zone. The singly- hatched portion of the tape, between 103% and 110% as well as between 85% and 97%, represent caution zones. The speeds which the tick marks represent are displayed digitally adjacent to the tick marks as seen in Figs. 1-3. In one embodiment of the invention, the caution zones and the danger zone are illuminated on the tape with amber light, the danger zone being further demarcated by means of blank stripes therein, giving it a choppy, intermittent look. In other embodiments, the caution zones may be illuminated in amber light and the danger zone may be illuminated in red or blue light, or otherwise, as desired. In this embodiment, the normal zone (between 97% and 103%) is not illuminated, other than at the tick marks. The display 9 includes a pointer 14 having a base 15 which may comprise an oval, or a circle, within which the current magnitude of rotor speed is displayed digitally, whereby the arrow operating with the tape

provides an analog indication and the base of the arrow provides a digital indication of current rotor speed.

When load factor (speed) enhancement mode (LFE mode) is not inhibited in the aircraft, and the combination of vertical acceleration and rate of vertical descent are such as to cause the engine control to shift into the LFE mode, the display of Fig. 2 is used instead of that of Fig. 1. The display of Fig. 2 is the same as that of Fig. 1 with several exceptions. The tick marks 12 are indicative of, and the adjacent digital speed values indicate speeds of 92%, 103%, 107% and 110% of rated rotor speed. Furthermore, the region between 85% and 92% is also considered a danger zone, and is appropriately identified, either by color or by blank lines within color, as described with respect to Fig. 1 hereinbefore. Only one area, that between 92% and 103% is deemed to be a caution area. The display 9, when operating in the LFE mode shown in Fig. 2, also has an upward indicating arrow 16 attached to the base 15 of the arrow 14. This is an indicator of the engine control having shifted into the LFE mode.

In the embodiments herein, the pilot may, by operating a switch on the engine control panel, cause the engine control to go into a quiet mode which lowers the engine speed (and therefore the rotor speed) somewhat. When this occurs, the quiet mode display of Fig. 3 is generated in place of the display of either Fig. 1 or Fig. 2. This display differs from the display of Fig. 1 in these respects: the tick marks 13 and digital representations are for 92%, 95%, 98% and 110%, so that the normal operating range is shifted downwardly by 5%, and there is a downwardly

pointing arrow 17 indicating that the engine control is operating at reduced speed in the quiet mode.

The display of the present invention differs from those heretofore available in providing two completely distinct variations in a single display, where the display nonetheless displays the same value within the same ranges. The first difference in the display of the present invention is where the tick marks appear, and their digital speed identification. The second difference is that the characteristics

(meaning) of the various speeds that may be indicated on the device is altered, a particular example being the fact that when in the LFE mode (Fig. 2) , the lowest range (85% - 92%) is a danger area, in contrast with the same speeds representing only a caution area when in the normal mode (Fig. 1) or in the quiet mode (Fig. 3) . In addition, the up arrow 16 is added in Fig. 2 and the down arrow 17 is added in Fig. 3 in order to flag and identify modes that are other than normal.

The display of Figs. 1-3 is very easy for the pilot to use since the digital and the analog indication of the instantaneous speed are adjacent, the mode flags (arrows 16, 17) are also adjacent to the analog and digital representation of the speed, and the normal range is clear with the usual ±3% tick marks about the set reference speed tick mark (100%, 107% or 95%, respectively).

A display 20 of a second embodiment of the invention is illustrated in the normal, LFE and quiet modes in Figs. 4-6, respectively. The display 20 is designed to be much less occlusive than the display 9 so that it may be used within a helmet display (or other heads up display) wherein the real world may be viewed through visual queues such as the display 20.

The various regions, normal, caution, and danger are delineated by single, double, or triple arcs, respectively. There is no digital indication of the edges of the zones, at tick marks 11a, 12a, 13a in the display. The base 15a of the display 20 is a circle, and the arrows 14a, 16a and 17a are shaped differently in the display 20 than in the display 9. The low ranges of Fig. 4 differ from Fig. 1, illustrating that the nature of the ranges are irrelevant to the invention. While the display 9 is the preferred embodiment for use on a heads down, panel flight display, and the display 20 is the preferred display for use in a helmet or other heads up display, a display 23 shown in Figs. 7-9 illustrates how the principles of the invention may be used in a non-circular display, in which the various zones are expressed by width: a normal range is a plain line, a caution range is a narrow rectangle, and a danger range is a wide rectangle. Similarly, the digital indication of current rotor speed is created at the base of the display 23, rather than adjacent to the analog indication provided by arrow 14b. The point is, the principles of the invention may be employed in a wide variety of displays provided that the ranges, and the significance or characteristics of the ranges are altered depending upon the mode which is related to the parameter being displayed.

Referring now to Fig. 10, a display of the invention illustrated in Figs. 1-6 may find utilization in a helicopter flight control system in which the display 9 is created on a panel flight display 26 (along with other display graphics, not shown) and the display 20 is created on a helmet display 27 (along with other display graphics, not shown) , both of which are created and controlled by a

mission and graphics computer 28, utilizing graphics creation programs of any known type. The mission and graphics computer 28 exchanges information with a flight control computer 29 which also receives information from an engine control panel 30. The engine control panel in this embodiment has a mode switch 31 which allows the pilot to select either the normal mode or the quiet mode, and a load factor enhancement disable switch 32 which, in the position shown, disables the capability of the system to automatically transfer into the higher speed, load factor enhancement mode. The flight control computer 29 exchanges signals with the controls 32 of the engines 33 which are connected to the rotor 34 by a shaft 35 through gears 36, all in the well-known way. The engine speed, and therefore the rotor speed, may be controlled by whether the aircraft is in the normal mode, the quiet mode, or the LFE mode, and the appropriate display 9, 20, 23 selected either to be one of those in Figs. 1, 4, 7; Figs. 2, 5, 8; or Figs. 3, 6, 9; respectively. The choice may be made in the mission and graphics computer 28, or in any other suitable part of an overall flight control system, in response to a wide variety of programming. One example of the manner in which the mission and graphics computer 28 may control the present invention is illustrated in Fig. 11. Therein, a rotor speed (Nr) mode routine is reached through an entry point 40 and a first test 41 determines if the mode switch 31 is set to quiet, or not. If it is not, then the system may be in the normal mode or the LFE mode. A negative result of test 41 reaches a test 42 to determine if the load factor disable switch 32 (Fig. 10) is set to disable the load factor enhancement mode. If it is, then an affirmative result of test 42

will reach a step 43 where the engine (and therefore rotor) reference speed is set equal to 100% of rated speed, ±3% of rated speed. Then a test 44 determines if a rotor speed display switch 45 (Fig. 10) is turned on or not. If it is, an affirmative result of test 44 reaches a step 46 to turn on the normal mode display (Figs. 1, 4 or 7) . But during the normal mode of operation, if the display is not positively turned on by means of the switch 45, a negative result of test 44 reaches a step 47 to turn off the rotor speed display so that nothing will appear in the area where the rotor speed display 9, 20, 23 would normally appear. After performing either step 46 or 47, the computer reverts to other programming through a return point 48.

If the mode switch is not set to quiet and the load factor disable switch is not set, negative results of test 41 and test 42 will reach a test 51 to determine if load factor enhancement conditions exist or not. These are the conditions referred to hereinbefore which may be those set forth in U.S. Patent 5,314,147, incorporated herein by reference, or such other mode shifting characteristics as may be desired. The particular cause of shifting modes is not relevant to the invention, which reacts to the shifting of the mode. An affirmative result of test 51 will reach a step 52 where the reference speed for the engine and therefore the rotor is set to 107% of rated speed ±3% of rated speed, and a step 53 turns on the LFE mode display of either Fig. 2, Fig. 5 or Fig. 8, herein. Then other programming is reverted to through the return point 48.

On the other hand, if the mode switch 31 is set to the quiet mode, an affirmative result of test 41 reaches a test 55 to see if the battle switch is on,

indicating that extreme maneuvers may be required. If so, quiet mode is prohibited, so a negative result of test 55 reaches step 43, as before. If the battle switch is not on, a test 56 determines if the aircraft is on the ground or not, by sensing weight on the wheels. If the aircraft is on the ground, then the quiet mode is not permitted since it could interfere with ground maneuvering and/or takeoff. In that case, an affirmative result of test 54 reaches the step 43 to ensure that the reference speed of the engine (and therefore the rotor) is set at normal (100% ±3%) . And then the normal display will either be on or off, depending upon the results of test 44, as before. Other programming is then reached through the return point 48.

If the quiet mode switch is set to quiet, and the aircraft is not on the ground, an affirmative result of test 41 together with negative results of tests 55 and 56 will reach a test 57 to ensure that the helicopter is flying at a threshold airspeed to be sure that the quiet mode does not engage just after takeoff, should the switch have been set to quiet while on the ground. If the speed is adequate, an affirmative result of test 57 reaches a step 58 in which the engine reference speed and therefore the rotor speed is set to 95% of rated speed ±3% of rated speed, and a step 59 in which the quiet mode display (Fig. 3, 6 or 9) is turned on, and then other programming is reached through the return point 48. The embodiments described herein provide a different display, in the same display area, for each of four different modes, quiet, LFE, normal with the display on, and normal with the display off. These modes are defined by mode signals: thus, the normal mode (with or without the display) can be provided as

a combination of the quiet switch being on with weight on the wheels, or the quiet switch being off with the load factor enhancement disable switch being on, or with LFE conditions not present. The load factor mode can be reached only with the mode switch set to normal, the load factor enhancement disable switch set to off, and operating conditions indicating that load factor enhancement should engage. The quiet mode is actually reached by a combination of the mode switch being set to quiet and the absence of a weight on wheels indication. When in the normal mode, the display will either be on or off in dependence upon how the Nr display switch is set. The routine of Fig. 11 is reached many times in each second, and therefore any of the foregoing modes is set, by presenting unique signals, many times each second. For instance, modes are established by passing through particular steps: 43 and 46; 43 and 47; 52 and 53; and 55 and 56. Thus, as used herein, the term "mode" not only includes the reference speed set point, but also whether the display is on or off. In the invention, the section of the scale which is presented in a fashion to indicate dangerous operation, as described hereinbefore, varies depending upon the mode; in the particular embodiments, the danger section for the LFE mode includes a low speed danger section, which differs from the normal and quiet modes. However, a danger section could easily be used at the low end of the normal mode display, if desired. Thus, although the invention has been shown and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and

thereto, without departing from the spirit and scope of the invention. I claim: