Configuring your Aircraft

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The Aircraft Library

SkyDemon maintains a library of different aircraft profiles on your computer, phone or tablet, so that if you have access to more than one aircraft (or you are just curious) you can plan flights using different aircraft to compare their performance. To access the Aircraft Library on your PC, you can either use the Aircraft button on the toolbar or in the Setup menu, or click on the aircraft that's currently in use in the Flight Details window. This will display a list of all aircraft profiles stored on your system with a green tick shown next to the aircraft currently in use. To switch to a different aircraft for the current route, just click on it then press Use Aircraft. The window disappears, and your flight details are recalculated using the new aircraft. You can also use the Aircraft Library to edit individual aircraft profiles, and you will also see buttons for 'Save to Cloud' and 'Load from Cloud' which allow you to share files between PC, iPad, iPhone and Android just as you did with your routes.

On your iPad, iPhone and Android device the Aircraft Library can be found by tapping the Setup button on the toolbar (this may be found under the button marked '...' or 'More') and selecting Aircraft. You will be shown a list of all your saved aircraft profiles, with a tick next to the one that's in use. To create a new aircraft click Create (+). If you would like to edit an aircraft profile just tap on it and choose Edit Aircraft. You can also save the aircraft profile to Cloud Storage, or simply select it for use from this menu.

The 'Find Online' button in the Aircraft Tools menu gives you access to aircraft profiles submitted to us by other SkyDemon users. These can be saved and edited to include your own aircraft's specific details. The Tools menu also gives you the option to open one of your own previously saved aircraft profiles from the Cloud.

As well as accessing the Aircraft Library from the Setup menu, you can also select an aircraft in the Flight Details tab, by tapping on the aircraft that is currently in use.

Aircraft profiles are just files stored on your computer. To explore them, navigate to the SkyDemon folder within your personal Documents folder, then find the Aircraft folder within that. You can share these files with friends, or go to our online forum to look for aircraft profiles posted by other SkyDemon customers. If you find one, simply save it to the Aircraft folder in the SkyDemon folder on your PC, restart SkyDemon, and you should see the new aircraft in your list. You can read more about sharing Aircraft profiles and other data here.

There are many variables that make up a full aircraft profile, and these are discussed in the remainder of this section.

Simple Aircraft

When you first launch SkyDemon you are provided with a simple aircraft model that allows you to start using all of SkyDemon's main flight-planning features without first needing to define a more comprehensive aircraft profile.

The Simple Aircraft is set by default when you first get started. In the Flight Details window you will see the option to set a speed for your planned route as well as an altitude, allowing SkyDemon to make the relevant calculations for your route time. When using the Simple Aircraft model, the Weight and Balance feature is disabled, and no fuel calculations are performed, as they require a little further configuration on the part of the user. All of these elements are covered in more detail below.

If you would like to return to the Simple Aircraft model at any time you can select it in the Flight Details window by tapping on the aircraft that is currently in use.

Basic Properties and Fuel

The first box is the name of the aircraft, which is usually just the manufacturer and model. Below this you can enter the registration of the aircraft. At the bottom of the page there are controls for setting the aircraft type, equipment and colour/markings, which map directly to the ICAO flightplan output if you should choose to use it.

In this section of the Aircraft Editor you will also see the option to set a default level for your aircraft, which automatically sets the altitude for any route you plot when using this aircraft. The default is set to 3000ft, but if you normally fly at much lower altitudes you can set your own default level, to avoid having to make the change each time you start a new route. When you switch the aircraft associated with a route, the route level is updated to match the default level of the new aircraft.

This page also contains basic fuel information for the aircraft, such as which types of fuel it uses and whether fuel is referred to by volume or by weight. If fuel is specified by volume then the units are litres, US gallons or UK gallons. If fuel is specified by weight then the units are kilograms or pounds.

Taxi/Takeoff specifies how much fuel is required for the taxi and takeoff phase of the flight. Landing specifies how much fuel is likely to be required from arriving overhead at your destination to shutting down the engine. Enter the maximum conceivable values in these fields to be safe; your aircraft POH or balance sheet may suggest appropriate values.

Holding Time specifies the time in minutes that should be allowed for holding at the destination airfield. This sometimes varies between aircraft but 45 minutes is a common value. When calculating the minimum required fuel, SkyDemon uses this value combined with the most fuel-efficient power setting (see later). Contingency is a percentage added to the enroute fuel calculations to add a safety margin and 5% is a common value.

Climb and Descent

SkyDemon models every stage of your flight including all climbs and descents needed to achieve your requested levels. This requires some knowledge by the software of the performance characteristics of your aircraft, and though the list of fields can be daunting it is reasonably easy to configure a very accurate model. Set the service ceiling according to the value given in your POH.

For the climb, you will need the rate of climb of your aircraft at sea level and at its service ceiling. The service ceiling of an aircraft is usually defined as the altitude at which climb performance decreases to 100 ft/min so this value is normally used. Indicated airspeed is the speed indicated during a climb. You will also need to enter the fuel burn at sea level and at the service ceiling. If you don't know the fuel burn in a climb at the service ceiling, just enter the same value as at sea level.

For the descent, you need to enter the descent rate in ft/min, the airspeed indicated and the fuel burn while descending.

Cruising Speed and Gliding

When specifying the speed for your journey or for a leg, you do not explicitly choose a speed but rather a known power setting for the aircraft, which will produce a given indicated airspeed for which the fuel burn rate is known. These configurations are known as cruise profiles and you can set up as many for an aircraft as you like.

The power settings for your aircraft are displayed in a list. To edit one, select it then change the values displayed in the boxes below the list. To create a new one, PC users will select an existing one and click Copy, or on iPad, iPhone and Android tap the '+' button. To delete one, select it and press Del. To show the delete button on your iPad and iPhone just decide which power setting you would like to remove and swipe your finger from left to right over the relevant box. For Android press and hold your finger to reveal the Delete button. You cannot delete the last profile in the list. The profile name is used later to select the setting from the Flight Details window, and is likely to be something like "2400 RPM". The indicated airspeed is the airspeed indicated by your aircraft while flying with this power configuration, and is converted to true airspeed automatically by the flight modelling engine, however you also have the option to enter True Airspeed directly, if known. Fuel burn is the amount of fuel burned per hour while flying with this power configuration.

You should be able to refer to your POH for all the information required on this page.

To select a power setting for your current aircraft simply click on the Power/Speed link in the Flight Details window and choose from the dropdown menu. You can also add a new setting from this drop-down menu by selecting Different Power/Speed. The one that's currently in use will have a grey tick next to it.

It is also possible to input your best Glide Indicated Airspeed and Glide Ratio when editing your Aircraft Profile. These values are taken into account along with altitude and wind speed/direction when using our GlideSafe feature to calculate your safe gliding radius.

Weight and Balance

It is possible to enter both the lateral and longitudinal centre of gravity and empty weight of your aircraft in the Aircraft Properties window. The centre of gravity is usually either measured in inches or centimetres, but the units do not matter as long as you are consistent with the other inputs on the page.

Loading Points

SkyDemon performs weight and balance calculations for your aircraft as you plan a route, and to do this it needs to know about each of the loading points applicable. A loading point is just a place in the aircraft where weight is applied, whether fuel, passengers, baggage or anything else. These are usually provided in the POH or a balance sheet accompanying the aircraft. When you create a new aircraft profile we populate it with a list of typical loading points that you can start with. You can edit the name or lever arm of any of them by clicking the Edit button when using SkyDemon Plan on the PC. iPad, iPhone and Android users can just tap the box they'd like to edit. The lever arm is the latitudinal or longitudinal distance from the datum used for all weight and balance calculations (the same datum as used in the empty centre of gravity) and is unitless, but ensure you use the same units as you used above.

There will normally be a loading point called Fuel. As long as there is such a loading point, SkyDemon will automatically enter the fuel weight as you specify how much you're going to take. If your aircraft has multiple tanks and they cannot share a loading point you can add a new fuel tank by clicking the 'Add' button and selecting 'Fuel Tank' from the drop-down menu, or just by tapping the 'Add Fuel' button on your iPad, iPhone or Android device. It is possible to specify the maximum capacity of each of your fuel tanks, as well as setting a default fuel amount.

The actual weights for the loading points are entered later using the Weight & Balance window on the main map screen (in the Flight Details tab on iPhone, iPad and Android), however you can add default weights to each of the loading points, such as default fuel, or your own weight, so that you do not need to enter these values each time. Your specified default weights can be edited in the Weight & Balance section of the Aircraft Editor window by highlighting the loading point and clicking Edit, and will be applied the next time you create a new route.

Acceptable Loading Envelope

In the POH there is usually a graph with a polygon representing the acceptable loading envelope of the aircraft. The graph is usually set up in such a way that distances from the datum (lever arm) go horizontally along the x axis, and aircraft weights go vertically up the y axis. When your actual centre of gravity and total weight of the aircraft is calculated, the value is plotted on the graph. If it falls within the polygon, the aircraft is safely configured.

Describing the envelope to SkyDemon requires typing out the x and y coordinates that make up the polygon one by one, starting at the bottom left corner and working around clockwise finishing with the bottom right corner in the format x ₁,y ₁, x ₂,y ₂, x ₃,y ₃, etc. So, to produce the diagram on the right enter 83,550 to represent the first point, then another comma, then 83,890, and so on. You can use spaces to further separate values:

83,550, 83,890, 87,1060, 93,1060, 93,550

In some cases, the weight and balance graph in your POH may have inch-pounds or some other moment unit (eg. kilogram-metres). In this case, to determine the value for the x axis that will make sense within SkyDemon you must convert moment to distance using the formula: Distance = Moment / Weight. Therefore, look at the x and y values of each point, and calculate x divided by y to determine what the new x value will be for each point in turn.

Next: Route Analysis and Briefing