Hi all.

I'm studying for IFR and I found a question relating to Cold Weather Correction chart.
Here's the question:

Imagine that you are flying an approach to the Prince George Airport in B.C. The airport elevation is 2,267' and the temperature at the airport is -27C. The highest point in the vicinity of the intermediate approach segment which you are flying is 4,320' ASL while the mininum IFR altitude on the segment is 5,400'. Assume that youre altimeter indicates 5,400' which is set to the correct altimeter setting of 30.03"Hg. However you forget to apply the appropriate cold weather correction. Use the altitude correction charts as published in the Cap Gen to estimate your clearance above the high point.

A) 4,850'
B) 450'
C) 891'
D) 189'

I'm struggling with this question.
The chart can be easily found on the internet, so I'm not going to post it here.

Thank You

Well, I didn't do the nitty gritty of finding the exact ratio for interpolating between the fields, but....

You need to find the correction for the altitude you're at, then, if you "forget" to apply it, you'd just subtract it from your indicated altitude of 5400, and that will give you the altitude which you would actually be flying at given the conditions. Then, just see what your ground clearance is over that point.

Look at the chart to get the correction for your height ABOVE the aerodrome. 5400-2267= 3133.
*Roughly* looking at the chart for the correction for -30 and 3000 is 570. It will be a bit different given it's 3* lower and 133 feet higher. Find the ratio between values to get the exact amount, but I get about 550. In actual flying, this is the value you would add to your 5400' ASL, (indicating 5970) to ensure you are actually at 5400 ASL. But that isn't what the question is asking.

Since you were told to "forget", you would be physically flying 550 feet lower than your indicated 5400', at 4850'.

At that altitude, what's the clearance over your high point? 4850'-4320'=530'

Since I didn't get the exact correction # it'll be a few feet off from any of the choices, but it's certainly closest to 450'. I'm assuming that's the correct answer... not sure why what I get is 80' off- but I drink heavily on Saturday mornings.

What part of the question is giving you difficulty?
DC

The key thing to remember about cold weather corrections is that it's all in height above station elevation. I'd be willing to bet the three wrong answers given are what you get when you correct from sea level, obstacle top height, and possibly by mixing up addition and subtraction.

LnS.