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What can you use as viable weather information landing at an airport with ATIS inoperative due to the tower being closed after hours? Let's assume the approach secondary weather source is also unavailable but the ADS-B weather information is current.

My real question is: can you use ADS-B weather legally in this situation to shoot an approach if needed?

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    $\begingroup$ If flying under Part 91 you don't need any reported weather minimums to attempt an approach, and if you can see the runway environment at the DA / MAP then you can land. However, the gotcha may be the altimeter setting, which you do need in order to know where the DA / MDA is. I don't know whether it's permissible to use the FIS-B weather for the field as the source of the altimeter setting. I would be surprised that the weather data could make it to the FIS-B stream without also being available to ATC. Sometimes using a nearby airport's altimeter setting is allowed, with increased mins. $\endgroup$ – pericynthion Feb 21 at 8:24
  • $\begingroup$ Are you asking about US regulations, or some other country's? $\endgroup$ – Pondlife Feb 21 at 15:21
  • $\begingroup$ I edited your question to - hopefully! - make it clearer. If I got something wrong don't hesitate to edit again or roll back. Having said that, if there's no working weather source at the airport then where is the ADS-B data coming from? And although you asked about ATIS, this scenario is probably more likely to occur at a non-towered airport with ASOS/AWOS. $\endgroup$ – Pondlife Feb 21 at 18:05
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How is the ADS-b weather derived? If the ATIS is inop, it will usually be because the sensor equipment is inop. If that is the case, how would ADS-b get the data for that airfield? If the sensors are working and the transmitter is inop, you would get the weather directly from ATC. If you were in IMC and/or IFR, your Approach plate would list an alternate source of weather info, and/or minimums adjustments when the weather is not available.

Saying that, having the weather is not a requirement to land at a Class G or E airport in VMC. Most airports will revert to one of these when the tower closes. A pressure sensitive altimeter is not necessary in VMC. Title 14 CFR, Part 91.205(b) just says “Altimeter”.

In all other cases, follow the regs below:

91.121 Altimeter settings
(a) Each person operating an aircraft shall maintain the cruising altitude or flight level of that aircraft, as the case may be, by reference to an altimeter that is set, when operating—
(1) Below 18,000 feet MSL, to—
(i) The current reported altimeter setting of a station along the route and within 100 nautical miles of the aircraft;
(ii) If there is no station within the area prescribed in paragraph (a)(1)(i) of this section, the current reported altimeter setting of an appropriate available station; or
(iii) In the case of an aircraft not equipped with a radio, the elevation of the departure airport or an appropriate altimeter setting available before departure; or.
(2) At or above 18,000 feet MSL, to 29.92” Hg.

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  • $\begingroup$ 205(b) applies to VFR, not VMC. 205(d) is for IFR so it would apply to an aircraft shooting an approach, whether in VMC or IMC. $\endgroup$ – Pondlife Feb 21 at 17:59
  • $\begingroup$ @Pondlife - If the OP were flying VFR, shooting a visual approach or canceled their flight plan prior to shooting the approach, 205(b) would apply. Clearance would not even be possible in Class G. You are right if the OP remains IFR, though. $\endgroup$ – Dean F. Feb 21 at 18:46
  • $\begingroup$ Yes, the word "approach" can be a bit fuzzy for sure. Having said that, a "visual approach" is still an IFR procedure. $\endgroup$ – Pondlife Feb 22 at 0:53
  • $\begingroup$ Thank you for the response, I had ATC have them read the weather at the destination to have it on tape and it they read the exact same thing that I read on the ADS-B. So is ADS-B going to be a substitute for ATIS / radio broadcast AWOS/ASOS? $\endgroup$ – Melvin Toro Mar 8 at 1:40

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