How do I create the envelope?

AvPlan EFB uses two pieces of data for each corner, a weight and arm length, to build the envelope.  The Moment Limits are not used, as this is a combined figure of both of the above.

From your POH, use this type of graph (from a C172):

CofG_Limits.png      

Not this type (i.e. the Moment Envelope from the same aircraft):

Moment_Envelope.png

  • Tap Settings > Aircraft Type Database > [your type] > Weight and Balance.
  • Tap the Edit button in the top-right corner of the screen.  You should see green plus signs appear down the left side of the window.
  • Tap a green plus to add a corner. This will form Corner 1.  It doesn't matter what corner you start in, AvPlan always moves clockwise around the envelope.  However, it's always a good idea to start in the bottom-left of the envelope.
  • You'll need the weight and the arm.  In the above example (figure 6-8), Corner 1 would be 35 inches at 1500 lbs.  Note that you can set the weight and arm units on the Basic Details page of your aircraft profile.  
  • Tap the back button to return to the list.  There should now be one entry.
  • Tap the green plus, and add Corner 2's details.  In the above case, it'll be 35 inches at 1950 lbs.
  • Corner 3 will be 41 inches at 2550 lbs.
  • Continue around the envelope until the complete shape is created. The amount of corners will depend on the structure of the shape. In the above C172 example, there are five corners required.  (note, there is no need to create Corner 1 twice)

C172_Envelope.jpeg

  • It may look slightly different as the scale of the graph may differ to the one in the POH.  This doesn't mean the graph is incorrect, as long as the relative shape is correct.
  • If you wish to also add the Utility Category envelope to the display, continue around the envelope for a second time, but with the corners associated with the reduced limits.  You'll end up with around 10 corners.

 

Sometimes, a graph is not provided by the manufacturer in the POH, so the envelope needs to be created from a word picture.  These are usually found somewhere in the Limitations section.

 Consider this scenario:

Screenshot_2018-08-21_21.32.44.png

You'll also need to know the MTOW, which will give you half the corner details.

Screenshot_2018-08-21_21.37.14.png

So, the only other figure you'll need to obtain is the empty weight of the aircraft.  For the purposes of the example, we'll use 306 kg.

  • Corner 1 will be 1860 mm at 300 kg.  (a weight just below the empty weight)
  • Corner 2 will be 1860 mm at 599 kg. (MTOW)
  • Corner 3 will be 2040 mm at 599 kg
  • Corner 4 will be 2040 mm at 300 kg.

This will create a rectangular envelope, which most two-seat wet-wing GA aircraft have.

Tecnam_Envelope.jpeg

 

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