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  #31  
Old 04-30-2019, 12:41 AM
jliltd jliltd is offline
 
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Quote:
Originally Posted by RFSchaller View Post
This thread prompted me to look at FAR 91.227 out of curiosity. It looks like when you donít file a flight plan or request ATC services you can Omit your call sign and ICAO code but if you file or request ATC services you have to broadcast your ICAO code. See 91.227(d) (8) and (11).
Yes. Exactly right. That is specifically why the anonymous switch only works when squawking VFR code (1200 in USA). That's when the ICAO code is scrambled and randomized. Any other discrete code entered into the transponder disables anonymous mode and transmits the true ICAO code regardless of the switch position. And there are certain circumstances where ATC requires non-anonymous mode even whilst squawking VFR which is why the FAA doesn't allow automatic anonymous mode (i.e. permanently grounding pin 5 on the GDL 82 to airframe ground point) but rather requires a pilot selectable switch (grounds pin 5 through the switch for enabling anonymous mode). For example, I believe flying on a VFR flight plan and squawking 1200 then anonymous mode must be disabled.

Jim
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  #32  
Old 04-30-2019, 06:56 AM
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Quote:
Originally Posted by jliltd View Post
For example, I believe flying on a VFR flight plan and squawking 1200 then anonymous mode must be disabled.
Darn. I hate to say it, but....reference please.
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  #33  
Old 04-30-2019, 07:16 AM
moosepileit moosepileit is offline
 
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It's for SAR as much as anything else.

https://www.faa.gov/air_traffic/publ...section_5.html

Aircraft that is equipped with ADS-B avionics on the UAT datalink have a feature that allows it to broadcast an anonymous 24-bit ICAO address. In this mode, the UAT system creates a randomized address that does not match the actual ICAO address assigned to the aircraft. After January 1, 2020, and in the airspace identified in ß 91.225, the UAT anonymous 24-bit address feature may only be used when the operator has not filed a flight plan and is not requesting ATC services. In the anonymity mode, the aircraft's beacon code must set to 1200, and depending on the manufacturer's implementation, the aircraft's call sign might not be transmitted. Operators should be aware that in UAT anonymous mode they will not be eligible to receive ATC separation and flight following services, and will likely not benefit from enhanced ADS-B search and rescue capabilities.
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  #34  
Old 04-30-2019, 08:05 AM
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Interesting. The AIM says VFR or IFR. 91.227 (d)8 and 11 simply says "flight plan". I have to agree with Jim's interpretation...if you file any flight plan, you can't go anonymous, even when squawking 1200.

Thank you gentlemen.
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  #35  
Old 04-30-2019, 01:04 PM
jliltd jliltd is offline
 
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Correct. Hence the requirement for a mode selector switch. AOPA is trying to get an exemption to allow anonymous mode when on a VFR flight plan, squawking 1200 and not requesting ATC services. That is not currently allowed.

https://www.aopa.org/news-and-media/...ds-b-incognito

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