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This will be a non issue





This will be a non issue  

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Author: Sparky   Date: 12/11/2021 3:08:17 PM  +1/-0   Show Orig. Msg (this window) Or  In New Window

"This AD was prompted by a determination that radio altimeters cannot be relied
upon to perform their intended function if they experience interference from wireless
broadband operations in the 3.7-3.98 GHz frequency band (5G C-Band). The FAA is
issuing this AD because radio altimeter anomalies that are undetected by the automation
or pilot, particularly close to the ground, could lead to loss of continued safe flight and
landing."


 


IN my Professional opinion of having worked avionics in the mil and civilian marketplace for a total of 28 years.  This is the FAA jumping through their AZZes for a lot of what ifs and could bes.  They are gonna issue a NOTAM if they get reports of an area they feel has been negatively causing interference to some rad alts.  This will most likely be IF it occurs near OUTER Markers on ILS approaches.  The lower an aircraft gets the stronger the return will be from the terrain bounce of the signal that the rad alt rt is looking for.  I personally don't think it will be an issue at all as quality rt's from honeywell and such higher end brands used in professional aviation will have much higher discrimination when it comes to freq.  The rad alts are running at 4.2-4.4GHz.  That's miles away from 3.7-3.9GHz as far as a good reciever is concerned.  The threat of a harmonic interference would also be minimized the lower the aircraft is to the ground.  I.E. You could have more harmonic issues if the interference in question occurs at say 2500ft due to time span for signal return from the ground bounce. But at lower alts that signal return is gonna be tighter and closer to what the reciever is expecting to see in a return.  Also we shall now consider amplitude.  Which in my opinion is the biggest factor in this that will make this a non issue.  The RF return from a rad alt is gonna be much greater in amplitude than any stray 5g phone call that might cross your path unless they decide to build a cell tower right on the ILS approach of a major runway and you happen to fly right over SAID tower.  I live on the ILS approach of 04R LFT and I'm on antenna tv, have been since 2002.  When I get a Jumbo fly directly over my home on that precision approach path my tv gets blasted and scrambled by the rad alt beaming down from that SOB, blanks out and then comes back after a second or two after direct fly over.  THis was back when we were analog and still does it now that we've gone digital.  SO yeah,  the rad alt is pumping out some power.  If they think some lil weak AZZ cell phone signal is gonna cause interference with that I'd be very surprised.  The majority of Rad Alt fluctuation issues i've solved have been antenna bonding related.  None have ever been interference or EMI related.  We even had issues on our first 76's where the fluctuations was an issue that the manufacturer had installed the antennas on the belly.  Directly on the belly.  Yes, I'm talking about Sikorsky, they fk'd up.  Well a belly on a 76 is not exactly flat.  It's round...so if you send a signal out from a curved belly in a 5 degree arc and expect it to bounce back and return and be detected by another antenna facing an angle of 5 degree in the opposite direction...yeah....don't work so well.  This problem was solved by yours truly with 5 degree wedges manufactured for the fleet and then in turn sold back to sikorsky so they could fix their own $#!+.  Apparently they claimed they had no problems with returns over land, but they don't fly over water like we do that has diminished return due to wave action on the surface.   SO when I tell you this will be a non issue....  you can take that to the bank.


 


 


Also I'm non vaxed.


Balls on ya chin

 
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AD 20121-23-13.. +2/-0 5G interference... 12/11/2021 8:27:56 AM