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Looking at the ATC transcript from MH370, I noticed that nowhere is the QNH communicated to the aircraft. That seemed odd to me... it seems that every time I talk to a tower or airways they tell me what the QNH is in their location.

So, is it normal for airliners to not be told what the QNH is before takeoff? Or in communications with DEPARTURE or RADAR?

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    $\begingroup$ It's normal that they don't communicate an altimeter setting if you let them know you have the current ATIS information. Once you climb into the flight levels you don't need it anymore. $\endgroup$
    – falstro
    Jun 5, 2014 at 19:07

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Airline pilots generally get the QNH from the airport ATIS or similar. If they don't get it from there, ground control will give it before taxi.

Above the transition level (11,000 feet (3,350 m) in Malaysia, 18,000 feet in the US), the altimeter is set to the standard pressure (29.92 inHg, 1013 hPa), also referred to as QNE. It doesn't take that long to climb through this point, so they would keep the departure QNH set until reaching the transition altitude. They won't need to set it again until they begin their descent near their destination.

So after setting it before taxi, the next time they would need it is on approach before they descend below the transition level. Again, they can get the ATIS from their arrival airport for QNH. If not, the approach controller will give them the QNH.

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  • $\begingroup$ You can also figure out the QNH by simply setting the altimeter to the airfield level. $\endgroup$
    – GdD
    Jun 6, 2014 at 7:33
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    $\begingroup$ @GdD; while true, ATC are required to tell you what the local QNH is unless you tell them you already know it (by stating you have received a particular ATIS information) $\endgroup$
    – falstro
    Jun 6, 2014 at 9:04
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QNH and other airport information is communicated to incoming flights through ATIS.

The only acknowledgement of this you will hear through ATC is aircraft first contacting the controller saying "with information Oscar" or similar, which means they have already heard the ATIS bulletin.

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