Recently got my PPL - now studying for instrument rating

Discussion in 'Pilot Training' started by Slackyhacky, Jan 8, 2017.

  1. Slackyhacky

    Slackyhacky Pre-Flight

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    Jeremy
    Got my PPL in October - haven't flown since (money issues).

    But I am studying for instrument rating.

    A question occurred to me that I have never thought about.

    It is regarding barometric pressures.

    The book says that for every 1000ft, the barometric pressure (with regards to mmHg) changes 1 inch.

    I get that temperature changes barometric pressure - but wouldn't temperature change that standard rate of change also (1 inch to 1000ft)? Does that ratio hold constant in every column of air? That seems strange to me.
     
  2. MAKG1

    MAKG1 Touchdown! Greaser!

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    Yes, but the temperature effect on the lapse rate is weaker than the altitude effect. And it's already included in the standard atmosphere.

    You can have a few hundred feet error at altitude with extreme temperatures, with the altimeter set correctly. This is covered in all the instrument textbooks.
     
  3. coloradobluesky

    coloradobluesky En-Route

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    There is a standard temperature for every elevation. Most charts have it for every 1000'. The actual temperature varies.
    That 1" per 1000' is an approximation. What it actually is depends on the atmosphere at that place and time. It varies.
     
  4. luvflyin

    luvflyin Pattern Altitude

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    It does. Cold shrinks the column of air. There are procedures to compensate for that. There are airports that are designated as cold weather airports and special mimimums apply. Go to the AIM and read 7-2-3 c., d, and e.
     
  5. BalooAirService

    BalooAirService Pre-Flight

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    how far are you into your studies?.
    there is a moment when everything clicks.. and your brain goes "ok.. this makes sense".
    that moment in IFR training (studying) is when the approach plates (truly understanding the plate) becomes as easy to read as a VFR sectional.. the enroute charts are pretty simple.
    good luck.