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4 Answers

Theorizing about temperatures…The effect of Farenheit vs. Celsius

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General Aviation

If I have two thermometers (one is scaled to Farenheit and the other is scaled to Celsius) and I stick them both in the oven and increase the heat.  (Notice, I'm not saying HOW many degrees I incresase the heat b/c that is relative to the thermometer)

So, I increase the heat.  The Farenheit thermometer shows a 10 degree increase and the Celsius therometer shows a 5.5 degree increase.  The same AMOUNT of heat is acting on both thermometer, but they're each showing a different degree of increase.

This brings me to my point...

If I'm looking at a takeoff distance chart and it says increase your distance by 10% for every 10 degree above standard Farenheit.  
I'm at sea level.  Therefore, if the temperature is currently 69 degrees F...I would increase the distance by 10%. 
However, 69 F is basically equal to 20.5 degrees C.  And 20.5 is only 5.5 degrees above the Celsius standard of 15 degrees.  However, I suppose it's safe to say the plane would behave the same way at 20.5C as it would at 69F.  If the takeoff chart was based on Celsius...I guess it would be "adjusted differently."  It may state something to the effect of increase 10% for every 5.5 degree above standard.
If I'm in Canada (metric system) and it is 20C today...and 30C tomorrow...that is an increase of 10 degrees.  However on the Farenheit scale, 20C = 68 degrees...and 30C = 86 degrees...That's a whole heck of a lot hotter than a "10 degree" increase.
I guess an increase of 10 degrees in Canada doesn't feel nearly as hot as it does in the U.S.  Wait, I guess that's not accurate to say either...I guess the point is that you have to know your units and scale!

Am I way off base?

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4 Answers

  1. Brian on Nov 12, 2010

    “Am I way off base?
    Will let you know soon as I figure out what base you’re looking to be on. 🙂
    In all seriousness, just pay attention to the units of measure. As long as your units are uniform you will be alright, be them Celsius or Fahrenheit.

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  2. Gary Moore on Nov 12, 2010

    I think you just might be over analyizing it a bit.  A lot of things could affect your ‘test’ ovens don’t always heat evenly across their volume, the thermometers proabably are super accurate etc…Brian’s correct – keep track of yoru units and don’t worry about it….

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  3. Aviatrix on Nov 12, 2010

    Lol!  I didn’t actually have a “test oven.”  I was just saying that I think if you had two thermometers in the oven and applied the same amount of heat evenly…one thermometer would display a higher reading that the other…due to scale.

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  4. Jason Schappert on Nov 12, 2010

    This might be overthinking something that is really basic.
    As long as your units of measurement are the same across the board it shouldn’t be a problem.
    I like your test oven though hhehe! teasing

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