3 Slide Rule. 3.1 Introduction. The slide rule section of the main menu gives access to a number of autonomous calculations which are completely separate from any flight plans generated by Acmenav; it can be considered as an electronic equivalent of the E6B type manual navigation computer. The calculations are divided into the following groups: performance related calculations, general calculations, metric conversions, fuel conversions and time addition. Each of these groups is given its own option in the slide rule section of the main menu and is discussed in turn below. 3.2 Performance related calculations (Psion p). 3.2.1 Introduction. On selecting the performance option from the slide rule section of the main menu (or using the hot key combination Psion p), you will be presented with another menu (called the performance slide rule menu) which allows you to select which performance calculation you wish to carry out. Selecting the exit option from the special section of this menu (or using the hot key combination Psion x) returns you to Acmenav's main menu. The calculations available are divided into two groups, category #1 and category #2. Category #1 calculations are calculations that are most likely to be used frequently, whilst category #2 calculations are the ones that are less likely to be frequently used. It was stated earlier on in this manual that certain dialogue boxes cannot be backed up to the previous one by pressing ; this is the case in all of the following calculations. Pressing whilst any of the following input dialogue boxes is on display just advances the calculation to the next input dialogue box. Once an answer is on display, pressing returns you to the performance slide rule menu. On initial entry to the performance slide rule menu, a message would have appeared in the bottom left of the screen, telling you that kinetic heating compensation was turned on. Currently, the only calculation that makes use of kinetic heating compensation is RAS-TAS. Kinetic heating is therefore discussed in more detail in section 3.2.5. 3.2.2 Converting pressure alt' into density alt' (Psion d). On selecting Pres alt'-Dens' alt' from the category #1 section of performance slide rule menu (or using the hot key combination Psion d) , you will be presented with a dialogue box that requires you to enter the ambient air temperature in either degrees Celsius or degrees Fahrenheit. Once this dialogue box has been completed by pressing , another will appear requiring you to enter the pressure altitude in either feet or metres. Once this second dialogue box has been completed by pressing , the entered pressure altitude will be converted into density altitude that is initially displayed in feet. The density altitude can be displayed in metres by pressing or the left or right arrow key. 3.2.3 Converting ISA Temperature to ISA altitude (Psion i). On selecting the ISA Temp'-alt' option from the category #1 section of performance slide rule menu (or using the hot key combination Psion i) , you will be presented with a dialogue box that requires you to enter an ISA temperature in either degrees Celcius or degrees Fahrenheit. Once this dialogue box has been completed by pressing , the inputted temperature will be converted to an ISA equivalent pressure altitude that is initially displayed in feet. The equivalent pressure altitude can be displayed in metres by pressing or the left or right arrow key. See appendix A for a list of the assumed ISA conditions. 3.2.4 Converting ISA Altitude to ISA temperature (Psion s). On selecting the ISA Alt'-temp' option from the category #1 section of performance slide rule menu (or using the hot key combination Psion s) , you will be presented with a dialogue box that requires you to enter a pressure altitude in either feet or metres. Once this dialogue box has been completed by pressing , the inputted pressure altitude will be converted to its equivalent ISA temperature which is initially displayed in degrees Celcius. The equivalent temperature can be displayed in degrees Fahrenheit by pressing or the left or right arrow key. See appendix A for a list of the assumed ISA conditions. 3.2.5 Converting RAS to TAS (Psion r). It should be understood that there is presently a limit on this calculation. Pressure altitudes in excess of twenty thousand feet (FL 200) cannot be entered. It was also stated in section 3.2.1 that kinetic heating compensation can be used in this calculation. When an aircraft flies through the air, air molecules heat the surface of aircraft very slightly. In exactly the same way, the temperature of the pitot tube is also artificially slightly raised, consequently, the OAT reading that you get in the cabin is slightly higher than it should be. Kinetic heating compensation allows for this phenomena by reducing the OAT reading by an amount according to a simple model. If the OAT reading is obtained from a source that is not subject to kinetic heating, just select the kinetic heating off option in the special section of the performance menu so that compensation will not be applied. Similarly, selecting kinetic heating on means that all subsequent calculations will be made with kinetic heating compensation applied. This setting reverts to its default (compensation on) when you exit the performance slide rule menu. Selecting the RAS-TAS option from the category #1 section of the performance slide rule menu (or using the hot key combination Psion r), causes a dialogue box to be displayed that requires you to input the pressure altitude in either feet or metres. Once this dialogue box is completed by pressing , a second dialogue box will appear that requires you to enter the RAS (CAS) in one of a variety of different units. Once this second dialogue box has been completed by pressing , a third will appear that requires you to enter the ambient air temperature in either degrees Celsius or degrees Fahrenheit. On completing this third and final input dialogue box by pressing , the true airspeed will be displayed initially in knots. Additional units can be displayed by pressing or the left or right arrow key. 3.2.6 Calculating the mach number index (Psion m). Selecting the Mach no' index option from the category #2 section of the performance slide rule menu (or using the hot key combination Psion m), causes a dialogue to be displayed that requires you to enter the local speed of sound in any one of a variety of speed units. Once this dialogue box has been completed by pressing , a second dialogue box will appear that requires you to enter your true airspeed, again in any one of a variety of units. Once this second dialogue box has been completed by pressing , the mach number index will be displayed calculated to two decimal places. 3.2.7 Converting JSA Temperature to JSA altitude (Psion t). On selecting the JSA Temp'-alt' option from the category #2 section of performance slide rule menu (or using the hot key combination Psion t), you will be presented with a dialogue box that requires you to enter a JSA temperature in either degrees Celsius or degrees Fahrenheit. Once this dialogue box has been completed by pressing , the inputted temperature will be converted to a JSA equivalent pressure altitude that is initially displayed in feet. The equivalent pressure altitude can be converted into metres by pressing or the right or left arrow key. See appendix A for a list of the assumed JSA conditions. 3.2.8 Converting JSA Altitude to JSA temperature (Psion a). On selecting the JSA Alt'-temp' option from the category #2 section of performance slide rule menu (or using the hot key combination Psion a), you will be presented with a dialogue box that requires you to enter a JSA pressure altitude in either feet or metres. Once this dialogue box has been completed by pressing , the inputted pressure altitude will be converted to its equivalent JSA temperature and displayed initially in degrees Celsius. The equivalent JSA temperature can be displayed in degrees Fahrenheit by pressing or the right or left arrow key. See appendix A for a list of the assumed JSA conditions. 3.2.9 Calculating the local speed of sound (Psion l). On selecting the Loc' spd' snd' option from the category #2 section of the slide rule menu (or using the hot key combination Psion l), you will be presented with a dialogue box that requires you to enter the ambient air temperature in either degrees Celsius or degrees Fahrenheit. Once this dialogue box is completed by pressing , the local speed of sound will be displayed, initially in knots. Additional units can be displayed by pressing or the right or left arrow key. 3.3 General calculations (Psion g). 3.3.1 Introduction. On selecting the general option from the slide rule section of the main menu (or using the hot key combination Psion g), you will be presented with a second menu (called the general slide rule menu) that allows you to select which general calculation you wish to perform. Selecting the exit option from the special section of this menu (or using the hot key combination Psion x) returns you to Acmenav's main menu. The calculations available are divided into two groups, category #1 and category #2. Category #1 calculations are calculations that are most likely to be used frequently, whilst category #2 calculations are the ones that are less likely to be frequently used. It was stated earlier on in this manual that certain dialogue boxes cannot be backed up to the previous one by pressing ; this is the case in all of the following calculations. Pressing whilst any of the following input dialogue boxes is on display just advances the calculation to the next input dialogue box. Once an answer is on display, pressing returns you to the general slide rule menu. The distance and track options in this menu should work worldwide; they should not be phased by the international date line, the equator, or the prime meridian. A series of over 2500 test routes was run through the routine with a 100% success rate. However, if you intend to fly over a combination of these, I suggest you split the leg into at least two parts. Polar overflights cannot be calculated accurately (a 180ø heading change is inevitable which the system cannot account for mathematically), however, it is unlikely that the you would be interested in such trivial details as bearings when flying over the poles! 3.3.2 Calculating a ground speed (Psion g). On selecting the ground speed option from the general slide rule menu (or using the hot key combination Psion g), you will be presented with a dialogue box that requires you to enter your TAS in any one of a variety of units. Once this dialogue box has been completed by pressing you will be presented with a second one that requires you to enter the track (true) you wish to fly. Once this second dialogue box has been completed by pressing , two more dialogue boxes will appear in turn that require you to enter the wind direction and speed respectively. For absolute accuracy, the wind direction should be expressed in degrees from true north (this is usually how it is reported). The wind speed can again be entered in any one of several units. After the fourth dialogue box has been completed by pressing , the ground speed will be displayed, initially in knots. Additional units can be displayed by pressing or the left or right arrow keys. 3.3.3 Calculating the distance between 2 points (Psion d). On selecting the distance option from the general slide rule menu (or using the hot key combination Psion d), you will be presented with a series of four dialogue boxes that require you to enter the departure latitude, the departure longitude, the arrival latitude and the arrival longitude in turn (see section 2.8 of this manual for an explanation of how latitude and longitude may be expressed). Once the arrival longitude dialogue box has been completed by pressing , the distance between the two points will be displayed, initially in nautical miles. The distance can be displayed in additional units by pressing or the left or right arrow keys. 3.3.4 Calculating a heading (Psion h). On selecting the heading option from the general slide rule menu (or using the hot key combination Psion h), you will be presented with a dialogue box that requires you to enter your TAS in any one of a variety of speed units. Once this dialogue box has been completed by pressing , you will be presented with a second one that requires you to enter the track (true) that you wish to fly. Once this second dialogue box has been completed by pressing , two more dialogue boxes will appear in turn, that require you to enter the wind direction and speed respectively. For absolute accuracy, the wind direction should be expressed in degrees from true north (this is usually how it is reported). The wind speed can again be entered in any one of several units. After the fourth dialogue box has been completed by pressing , the heading (true) will be displayed. 3.3.5 Calculating the bearing between 2 points (Psion t) On selecting the track option from the general slide rule menu (or using the hot key combination Psion t), you will be presented with a series of four dialogue boxes that require you to enter the departure latitude, the departure longitude, the arrival latitude and the arrival longitude in turn (see section 2.8 of this manual for an explanation of how latitude and longitude may be expressed. Once the arrival longitude dialogue box has been completed by pressing , the initial great circle track between the two points will be displayed. It is important to remember that by definition, a great circle track continually changes, so for very long routes, the final great circle track will be considerably different to the initial great circle track. For legs of up to around 300 nautical miles, the initial great circle track can be taken to be the track (true) between the two points, however, if you plan to hand fly longer legs than this, it would be sensible to split up the long leg into a series of smaller ones. In any event, if you are flying over areas where no navaids are available, it is very important to assess your latitude and longitude regularly and remain flexible! 3.3.6 Calculating a crosswind component (Psion c) This option can be used to calculate the crosswind component experienced either during the en-route phase of a flight or during the approach to a runway. On selecting the crosswind option from the general slide rule menu (or using the hot key combination Psion c), you will be presented with a dialogue box that requires you to enter the track. This figure will either be your track made good (for an in-flight wind component assessment) or the track (true) of a runway you are making an approach to. Once this dialogue box has been completed by pressing , two more dialogue boxes will be presented in turn that require you to enter the wind direction (true) and speed (in any one of a variety of units). Once the wind speed entry dialogue box has been completed by pressing , the crosswind component will be displayed, initially in knots. The wind component can be expressed in other units by pressing or the left or right arrow key. 3.3.7 Calculating a headwind component (Psion w). This option can be used to calculate the headwind component experienced either during the en-route phase of a flight or during the approach to a runway. On selecting the headwind option from the general slide rule menu (or using the hot key combination Psion c), you will be presented with a dialogue box that requires you to enter the track. This figure will either be your track made good (for an in-flight wind component assessment) or the track (true) of a runway you are making an approach to. Once this dialogue box has been completed by pressing , two more dialogue boxes will be presented in turn that require you to enter the wind direction (true) and speed (in any one of a variety of units). Once the wind speed entry dialogue box has been completed by pressing , the headwind component will be displayed, initially in knots. The wind component can be expressed in additional units by pressing or the left or right arrow key. 3.4 Performing metric conversions. (Psion m). 3.4.1 Introduction. Acmenav is equipped with a comprehensive metric conversion facility that allows many common units (and a few not so common ones) to be converted into other units. The available conversions are divided into two broad categories, category #1 conversions and category #2 conversions. As in the performance and general slide rule options, category #1 conversions are the ones that are more likely to be used frequently whilst category #2 conversions are the ones that are less likely to be used frequently. The available conversions are then further divided into the following types: altitude, length, volume, weight, speed, temperature and pressure calculations. The operation of each of the different calculation types is the same so familiarity with one of the types is sufficient to understand the others. Selecting the metric option from the slide rule section of the main menu (or using the hot key combination Psion m), causes a second menu (called the metric conversion menu) to be displayed which allows you to select the conversion type. Selecting exit from the special section of this menu (or using the hot key combination Psion x) returns you to the main Acmenav menu. Once an answer is on display, pressing returns you to the metric conversion menu. 3.4.2 General operation. On selecting a calculation type from the metric conversion menu, you will be presented with a dialogue box that requires you to input the start value, select the start units and select the target units. Pressing whilst this dialogue box is on display returns you to the metric conversion menu. Once this input dialogue box has been completed by pressing , an answer dialogue box appears that gives the start value and units, and the target value and units (in that order). Additional conversions can be made directly from this answer dialogue box simply by editing the start value and changing the start and target units as required. Once you have finished making your metric conversions for the selected calculation type, simply press and you will be returned to the metric conversion menu. 3.4.3 Altitude conversions (Psion a). Conversions available between feet and metres. 3.4.4 Length conversions (Psion l). Conversions available between nautical miles, statute miles, and kilometres. 3.4.5 Volume conversions (Psion v). Conversions available between UK gallons, US gallons and litres. 3.4.6 Weight conversions (Psion w). Conversions between pounds and kilogrammes. 3.4.7 Speed conversions (Psion s). Conversions available between knots, kilometre per hour, statute miles per hour, feet per second, and metre per second. 3.4.8 Temperature conversions (Psion t). Conversions available between degrees Celsius, degrees Fahrenheit and kelvin. 3.4.9 Pressure conversions (Psion p) Conversions available between millibars (or hpa) and inches of mercury. 3.6 Converting fuel volumes to weights. (Psion f) 3.6.1 Introduction. Acmenav is preprogrammed with the specific gravities of avgas, avgas low lead and avtur fuels, allows the input of fuel volumes in a variety of units, and can display the resultant fuel weights in pounds or kilogrammes. 3.6.2 Fuel type. Upon selecting the fuel option from the slide rule section of the main menu (or using the hot key combination Psion f), a dialogue box will be displayed that requires you to select the fuel type. The only consequence of this dialogue box is that the default specific gravity will be set by this operation (this value can still be changed later on). Pressing while this dialogue box is on display returns you to the main menu. 3.6.3 Entering a volume. Once the fuel type dialogue box has been completed by pressing , another dialogue box will appear that requires you to enter a fuel volume in either UK gallons, US gallons or litres. At this stage you can also edit the default specific gravity. Pressing whilst this dialogue box is on display, returns you to the fuel type dialogue box. 3.6.4 Fuel weight. Once the fuel volume dialogue box is completed by pressing , the fuel weight will be displayed, initially in pounds. To display the weight in kilogrammes, just press either the left or right arrow key or the tab key. Pressing whilst this dialogue box is on display returns you to the fuel volume input dialogue box. If you called the fuel option from the centre of gravity option and then continued to press from the answer screen, you would eventually be returned to that option with whichever fuel weight value was highlighted (either kilogrammes or pounds). 3.7 Time addition (Psion t). 3.7.1 Introduction. This option is used to add up elapsed flying times and is ideal for totalling up flying times on the completion of normal logbook pages or for the calculation of ETA's. 3.7.2 Operation. Upon selecting the time option from the slide rule section of the main menu (or using the hot key combination Psion t), you will be presented with a one line dialogue box that requires you to enter the start time in hours and minutes. Once this dialogue box has been completed by pressing , the dialogue box will change its appearance. The top line will show the total cumulative time, whilst the bottom line allows the entry of further times. To continue totalling times, just continue entering the hours and minutes and then press . Pressing whilst this answer screen is on display returns you to the main Acmenav menu.