WikiProject Aviation / Aircraft (Rated Start-class)
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## what if the plane banks?

I have a question: what happens if an aircraft makes a turn, and in the process, banks? Logically, the altimeters will point sideways, and the height that they measure will increase, even to infinite when a plane banks 90° . What if the plane pulss up or dives? Are these altimeters stabilized? From what i read, most passenger jets have an altimeter to the left and one to the right. Are their different measurements used to calculate the angle of banking? And what if the terrain isn't flat? How do altimeters know wether the reading that comes from the roof of a skyscraper is the right one, or the one from the adjacent street? Are radar altimeters controlled by barometric altimeters to check for sudden and unlogical changes in altitude? This article leaves me with a lot of questions. Can sombody who knows the matter well enough provide answers to these questions please? thanks. -karelke- —Preceding unsigned comment added by 193.190.253.150 (talk) 19:28, 4 March 2009 (UTC)

You would only have a problem during bank if you had a very sharp (directional) beam. If the beam is wider, some part that goes, wlog, to the left as seen from the airplane, will strike the ground first, directly under the plane as seen from the ground, bounce back first, and, in the end, give a correct reading even during bank. And "sudden and unlogical changes in altitude (values shown)" do indeed happen if the terrain is not flat. As I understand it, a famous example is Funchal Airport, where the altimeter reading suddenly drops quite a bit when the airplane comes over the runway from the sea, which is quite a bit lower. (And if you bank 90° during approach, an incorrect altimeter reading will be the least of your problems.) ospalh (talk) 21:14, 7 March 2009 (UTC)

## Frequency change?

I don't see how this

Alternatively, the change in frequency of the wave can be measured, the greater the shift the further the distance travelled. This method can achieve much better accuracy than the aforementioned for the same outlay and radar altimeters that use frequency modulation are industry standard.

is supposed to work. Frequency changes with distance traveled? That's news to me. Could someone pleas clarify? ospalh (talk) 20:40, 7 March 2009 (UTC)

The German page mentions FMCW, sounds reasonable, but a link would still be nice. ospalh (talk) 09:05, 8 March 2009 (UTC)
Done. Since all commercial radio altimeters in the US -- and so, I suspect, nearly all radio altimeters in general -- use FMCW, I started a section in this article about FMCW. Still needs work. I hope in the meantime the link in that section -- as ospalh suggested -- to our FMCW article gives an adequate explanation. --DavidCary (talk) 01:43, 25 January 2014 (UTC)

## primary term

Please discuss the term priority of the term Radar altimeter versus the term common to aviation applications radio altimeter. 75.210.125.201 (talk) 03:15, 28 April 2013 (UTC)