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8 Answers

Is Readback of Altimeter Settings Required?

Asked by: 2883 views , , ,
FAA Regulations, Student Pilot

I've been taught to read it back, and I think it's important for separation purposes. I've heard some pilots who don't read it back when I'm cruising along with approach or center. Thanks.

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8 Answers

  1. Kris Kortokrax on Dec 31, 2014

    91.121 is the regulation that requires you to obtain the altimeter setting during cruise. There is no regulation that requires you to read it back. Have you ever heard center or approach chew out a pilot for not reading it back? You can also obtain the altimeter setting from AWOS, ASOS or ATIS. Who do you read it back to in those cases?

    The important thing is that you have it.

    As you cruise along in your 172, there is not likely to be a great change in the altimeter setting. Different story if you are cruising across the country at FL350 for hours.

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  2. Mark Kolber on Dec 31, 2014

    There are very, very few “required” readbacks identified anywhere in FAA materials. None in the regs. The AIM recommends reading back “those parts of ATC clearances and instructions containing altitude assignments, vectors, or runway assignments as a means of mutual verification.” And controllers are required to obtain readbacks of runway hold short and LASHO instructions although most will also insist on readbacks of other items such as runway assignments and taxi instructions.

    Pilots will read back more than the small AIM group, also as a way of mutual verification.

    Keeping in mind that one will sometimes hear “Attention all aircraft BigCity altimeter now 29.98,” it’s pretty clear what that’s not one of the required readbacks. Some pilots read it back; some pilots don’t; some pilots do it sometimes. Neither is incorrect.

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  3. Matthew Waugh on Jan 01, 2015

    Altimeter readings is one of those things that pilots and controllers use as punctuation – we say it while we’re letting our brain absorb something else and deciding if we have anything else intelligent to say. Mostly we don’t, but rarely does that stop us.

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  4. Heather McNevin on Jan 02, 2015

    It isn’t a requirement to read it back, but if you do read it back to me I am going to ensure you said the same number I did. Many times I have caught a pilot who misheard me and read back an incorrect altimeter (or at least not the one I gave them). While not required, a readback is another chance for either party to catch a mistake.

    I won’t get after anyone if they don’t readback an altimeter though, not at all like I would for an altitude not read back. Usually the readback of the altimeter is more of an acknowledgement that the pilot heard me. If they didn’t respond somehow, I would wonder if they missed the transmission. If the transmission was just the altimeter, reading back your callsign is acceptable to. Just something to make sure I know you heard me, or else I’m gonna say it again. So, to shut me up, just acknowledge me somehow!

    On occasion, I see an aircraft that is indicating several hundred feet off of their assigned altitude and in cases like that I will read them a nearby altimeter setting. The altitude deviation might be from a change in barometric pressure or an inattentive pilot. If the pilot returns to their assigned altitude after issuance of the altimeter, either way the problem is solved. If not, then I have to investigate if something is wrong with the pilots ability, the aircrafts equipment, or my radar equipment.

    Also, be aware that my altimeters (at the Center) don’t update very frequently and are often over an hour old. So keep an eye on altimeters yourself too and don’t just trust the controller!

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  5. Andre Berthet on Jan 03, 2015

    Chris wrote: different story if you are cruising across the country at FL350 for hours.

    At FL350 which is in the class A Airspace (FL180 to FL600) your altimeter(s) must be set at the standard pressure of 29.92 inHg or 1,013.2 hPa.

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  6. Kris Kortokrax on Jan 03, 2015

    It’s Kris, not Chris. You forgot the spelling of my name from the top of the web page to the bottom?

    I’m well aware of 91.121(a)(2). I was referring to the possibility for a big difference between the altimeter settings that one might experience between transitioning into Class A on the east coast and transitioning out of Class A airspace on the west coast.

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  7. Andre Berthet on Jan 04, 2015

    Sorry for having misspelled your name in my original message.
    However, I don’t understand your point. Why would a pilot flying, let’s say from JFK to LAX, care about differences in the altimeter settings between these two airports? Most of his flight will be in the Flight Levels with the altimeter set at 29.92. The only times this pilot will have to adjust his altimeter, assuming he is cleared to his cruising altitude of FL350, will be before take-off, upon passing FL180, and upon descending through FL180. What’s so difficult with that? Who really cares if the atmospheric pressure between two points 3000 Miles apart is different? I will not elaborate on this point any further, because it is not relevant to the original question.

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  8. Kris Kortokrax on Jan 04, 2015

    The original question dealt with times when it might be desirable to read back an altimeter setting.

    After flying across the country and descending through IMC and shooting an approach in IMC, it would seem to me that this would be a situation where the potential difference in altimeter settings would be important enough to read it back for verification, even though there is no requirement to do so.

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