Results 1 to 3 of 3
Like Tree1Thanks
  • 1 Post By earboth

Math Help - How to calculate the Point of equal time between departure and destination?

  1. #1
    Newbie
    Joined
    Mar 2012
    From
    Sweden
    Posts
    2

    How to calculate the Point of equal time between departure and destination?

    Hi this is propably really simple but i can't understand it.

    PET or point of equal time is a term used in aviation. It defines a point along a route where the time to continue is the same as the time to return to the aerodrome of departure. I have a hard time understanding how it is calculated in my book that i use in school.
    This is how they explain it:

    dpet= the distance to the pont of equal time
    GSr=The groundspeed to return from PET to departure
    GSo=the groundspeed to continue from the PET to destination
    D=the total distance between departure and destination

    time home from PET=time on from PET

    dpet/GSr=(D-dpet)/GSo
    So far I understand but what i don't understand is how they have transposed the formula to dpet=D*GSr/(GSo+GSr)

    Please help it would be easier to understand than to just learn a formula by heart.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,830
    Thanks
    123

    Re: How to calculate the Point of equal time between departure and destination?

    Quote Originally Posted by alban View Post
    Hi this is propably really simple but i can't understand it.

    PET or point of equal time is a term used in aviation. It defines a point along a route where the time to continue is the same as the time to return to the aerodrome of departure. I have a hard time understanding how it is calculated in my book that i use in school.
    This is how they explain it:

    dpet= the distance to the pont of equal time
    GSr=The groundspeed to return from PET to departure
    GSo=the groundspeed to continue from the PET to destination
    D=the total distance between departure and destination

    time home from PET=time on from PET

    dpet/GSr=(D-dpet)/GSo
    So far I understand but what i don't understand is how they have transposed the formula to dpet=D*GSr/(GSo+GSr)

    Please help it would be easier to understand than to just learn a formula by heart.
    \frac{dpet}{GSr}=\frac{D-dpet}{GSo}

    \frac{dpet \cdot GSo}{GSr}=D-dpet

    dpet \cdot GSo=(D-dpet) \cdot GSr

    dpet \cdot GSo=D \cdot GSr - dpet \cdot GSr

    dpet \cdot GSo +  dpet \cdot GSr=D \cdot GSr

    Now factor out dpet on LHS and afterwards divide through by the bracket.
    Thanks from alban
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2012
    From
    Sweden
    Posts
    2

    Re: How to calculate the Point of equal time between departure and destination?

    Thanks earboth!
    Exactly what i was looking for. It's scary how fast it's forgotten when you don't use it.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Calculate point
    Posted in the Trigonometry Forum
    Replies: 0
    Last Post: November 13th 2011, 03:32 PM
  2. Replies: 1
    Last Post: October 19th 2010, 03:57 AM
  3. Replies: 4
    Last Post: July 17th 2010, 09:48 AM
  4. Calculate acceleration with time and distance?
    Posted in the Math Topics Forum
    Replies: 3
    Last Post: February 23rd 2010, 10:51 AM
  5. Replies: 2
    Last Post: May 19th 2009, 02:26 PM

Search Tags


/mathhelpforum @mathhelpforum