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ATP Digital course - rate of descent formula

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  • ATP Digital course - rate of descent formula

    Hi everybody,

    this is a comment about the rate of descent formula in the attachment. It shall not exactly be meant as wrong but I think that, to be more precise, the signs before "power required" and "power available" should be swapped. This is because the sentence following the formula states that the result has a negative value, as it is a descent. And, as said in the following paragraph, if there is no power available (and during glide there actually is no power available), the result of the formula must be negative, meaning we are in a descent.

    Do you agree with me or did I understand the text wrong somehow?
    Thanks a lot.

  • #2
    Hi Eric,

    I agree that the maths have become tangled here. I would change the top line to read: "power available - power required".
    With no power available, we will then get a negative figure. (We'll get a positive rate of climb when we have excess power)
    In fact, this calculation now goes beyond the requirements of EASA Learning Objectives, and will be removed from the next edition of ATPdigital.



    • #3
      Hi Ben,

      if I may suggest, I think this formula helps understanding the concept of rate of descent and to demonstrate what actually happens during the glide. This is my way of thinking on things having a physical implication and/or reference, so I like studying this way formulae rather than memorising concept. For this reason, I would suggest you to change the signs of "power available" and "power required" but to keep the formula in the theory course.

      I don't know if I clearly explained my thought.