C172 Airspeed Temperature Adjustment.

[Woodrow]

Hi Guys. Hope all is well. Could I trouble someone to explain to me how I adjust the temperature at altitude gauge within the airspeed indicator. The way I've been doing it is to move the temperature numbers to match the outside air temperature but whenever I check my ground speed it never matches up with what the gauge is saying. To get the speed don't I look at the speed numbers on the inner white dial. Hope someone can help or refer me to a manual that will explain it to me.
Thanks Folks

Mark. ....

[AKar]

The numbers within the window represent altitudes. To get TAS, you'll move the altitude number that matches your current altitude to align with current outside temperature. For instance, if you fly at 8000 ft and OAT is -5°C, you'll move the number 8 in the window to appropriate position in between 0°C and -10°C lines.

-Esa

[Woodrow]

The numbers within the window represent altitudes. To get TAS, you'll move the altitude number that matches your current altitude to align with current outside temperature. For instance, if you fly at 8000 ft and OAT is -5°C, you'll move the number 8 in the window to appropriate position in between 0°C and -10°C lines.

-Esa

Thanks for the reply. I'll give it a go right now. 1st class. Much appreciated. Mark.

[Oracle427]

You need to match to the current pressure altitude with the altimeter set to 29.92 in hg, or you can do the mental math to approximate. It can add up to a measurable difference.

The result aa Esa noted is TAS and not ground speed. To determine the ground speed you will need to account for the winds aloft.