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3 Answers

What temperature to use when calculating TFD to climb

Asked by: 405 views Private Pilot, Student Pilot

Riddle says to: Find the difference between standard temperature and actual temperature for both cruise and departure pressure altitudes. Then, find the average of the differences and increase TFD numbers according to the note in the POH. 

Will my examiner be ok with me using the average temperature (standardized) or should the standardized surface temperature be used since that is more conservative? 

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3 Answers

  1. KDS on Sep 29, 2017

    Let me give you a generic answer to your question.

    “Will my examiner be OK with ……….”. Maybe. It depends. I once sat in a check ride administered by an examiner at a 142 school for an advanced rating. He asked the applicant a question, which the applicant answered correctly. The examiner told him that was wrong. That lead to a very interesting discussion after the test. My point in telling that story is that your examiner may not be okay with the right answer and he may be okay with the wrong answer (I’ve seen that one too). All you can do is give the most accurate answer that you can and if you can back it up with something (an FAA publication or reference is always the best), then so much the better.

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  2. murryn5 on Oct 04, 2017

    Thanks KDS! Follow up question: My instructor says I should use the TFD to climb chart in the C172 POH to get my time, fuel, and distance to climb. Should I use the values from this chart in my nav log until my TOC, and then calculate my cruise performance with my E6B?

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  3. KDS on Oct 09, 2017

    That would seem to be the most accurate way to do it. Or, stated differently, to check that your initial calculations are holding true.

    However, let me throw in the practical versus the theoretical. It’s always right to plan the flight and then check the plan against the actual flight. But, if it gets down to the point where the details make a difference, I don’t feel good about what is happening. I like big margins.

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