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markjj

Radio Altimeter Issue

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Hello everyone, I have a slight issue with the 777 and its radio altimeter.  I was on approach to runway 16R at YSSY, and at about 200 feet AGL, the aircraft suddenly idled as if I was commencing my flare.  The 777 AT system automatically idles thrust at 25 feet AGL (or maybe it's 20), and it looks as if the idle command was prompted by a false radio altimeter reading of 20 feet when I was really still about 200 feet above the ground.  Perhaps it was a building or a tree that caused the false reading.  I have my settings maxed out, so it seems reasonable to believe that a ground object is causing this premature idle, which in turn ruins the rest of the approach.  Anyone else having similar issues?  Thanks 

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It's been months since I landed YSSY 16R... they were operating 34L my last two arrivals; however, I did not have a problem at any time that you describe.  Have you repeated the approach to see if that reoccurs?  Were winds calm or gusty?

It's not reasonable to believe any such ground object in reality would be a factor for a CAT II capable approach.

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I don't think trees and buildings can generate a radio altimeter return in FSX. 

If the problem is repeatable it might be worthwhile deleting ARPT_RWY.dat (which is in the FSX/PMDG/NAVDATA folder). The file will rebuild automatically using the current navdata.

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Hey guys, thanks for the replies.  I have repeatedly tried the approach and still get the same issue, regardless of weather.  It only occurs on the 16R approach, as the 34's are all over water.  I will try deleting the ARPT_RWY.dat file and see if that makes any difference.  As silly as it seems for a tree or a building to generate a RA return, I cannot think of another explanation given that the RA literally appears as 20 feet AGL for not more than a second before returning to normal.  It is but a momentary "spike", if you will, thus prompting me to believe that it is some sort of obstruction that is causing the return.  Again, I'll try deleting the file and see if that helps.  Thanks again!

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