Question about radio altimeter

Apr 24, 2006 2 Replies
V

Normally flush mounted radio altimeters on aircraft have an arrow pointing forward. It is also given in the manuals that while installing the antenna the arrow must be pointing forward.



As I understand the principles of operation, the RA transmits signals directly downwards and another similar antenna recieves the echo to compute the distance from ground. Then why the arrow. Is the RA antenna also directional in some way.



I don't know where else to put this question. If this is not the right group to discuss this topic then please suggest which other group should I go to.



Thanx.



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K

To my understanding both Rad Alt ant are omni direction. Their P/n: most of the time are the same. In some installation one ant is located fwd from the other ant. The arrow marking helps to differentiate the two.

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P

** Very likely the RA's antennas are both highly directional and the 4.3 GHz (70mm) microwave energy is focussed into a beam which points directly down.

Possibly, the beam is made deliberately wider in one direction which is then aligned with the wings of the aircraft to allow the RA to function better ( or at all) during steep banking manoeuvres.

....... Phil

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