Page 234 - PPL-engelsk 2025

Meteorology

One must be able to require that an altimeter ensures safe clearance over

obstacles along the route.

Can it do that?

It worked fine with the small plane throughout the summer and fall.

But then winter came, and one day the peak was covered with clouds.

The experienced pilot, who had flown this route many times, decided to climb

to 4010 feet, hold the course for 10 minutes, and then descend again.

That was the day the pilot's number of departures exceeded his landings.

What was the reason?

Well, the altimeter only shows correctly in the standard atmosphere and at the

reference points at airports, as previously discussed.

Deviation from the standard atmosphere temperature is corrected by:

o
4% per 10 C temperature deviates from the standard
atmosphere temperature

If the temperature is low, the distance between the isobaric surfaces is smaller

than on warm days. So, on cold days, the altimeter will read higher than it

should.

REMEMBER:

When the temperature is low, you are lower.!!!

When flying over longer distances, the pressure at MSL can vary significantly.

Therefore, you would actually need to constantly adjust the altimeter.

The problem is solved by the rule that all aircraft flying above a certain altitude

must fly with the altimeter set to the standard pressure of 1013.25 hPa.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 234