This is what airline pilots USED to know.

[bvar22]

140. YES!!!... Brilliant!!! ...You are really "showing your stuff" in THIS thread!!!

[font size=3]We doan need no stinkin Altimeters[/font]

The Wright Brothers flew 120' at an altitude of 10' in 1903 without an altimeter,
so, obviously, the altimeter is just a useless ornament used to decorate the cockpits of every airplane made since 1914.

I defer my experience as a pilot, lifelong love of sport aircraft, and the commercial license I have held since 1967 to your much greater intelligence, knowledge of aircraft, aerodynamics, history of aviation, the principles of powered flight, and the basic skills necessary to fly them.

The Barometric Altimeter is one of the two most important single instruments fitted to aircraft. Despite many attempts during the last 50 years to displace it by altitude measuring equipment using other principles, there is no sign that any of these methods will eclipse it in the foreseeable future."

<snip>

A practical altimeter existed long before the Wright Brother's first flight in 1903, but it is curious that no well documented record of altimeters being carried in aeroplanes before about 1913. This is probably due to concentration on the immense problem of practical flight, and it was not until flights involving crossing relatively high ground started to become other than a major adventure that the need for altitude measurement arose.

http://www.flightglobal.com/pdfarchive/view/1968/1968-1%20-%200235.html