The “A” in HAT
The next letter in the HAT check acronym, A for altimeter, is not as critical as the H, if operating in daytime VMC conditions, but could lead to an early demise, if it is dark out, or there are clouds obscuring your vision outside of the airplane. Again, I know I am not the only pilot who has mistakenly set my altimeter, having an error of 1000 feet. Now if you have set your altimeter 1000 feet too low, the possibility of coming to a screeching halt on the downwind is nowhere near as great as when you do the opposite, and set it 1000 feet too high.
Just a few weeks ago I was working with a client in my PA-12. As we approached the airport and were descending to pattern altitude, I noticed that the houses appeared to be getting much bigger than they usually do. Questioning my client as to proper pattern altitude I got the correct answer, but when I asked how much further we might be descending, I was a bit dismayed to hear “another 800 feet”. (Indeed, the altimeter showed another 800 feet to descend to pattern altitude.) I suggested that we ignore the altimeter for the time being, and fly “out the window”, and that we would check the altimeter once we were ground bound. When we did that, the altimeter indicated that we were 1000 feet above the ground. Obviously if this incident had occurred at night, or in low IMC conditions, I would most likely not be writing this article.