This is the forum where our students can discuss things relating to their studies or experiences they have had while studying Bob's courses. Please keep it clean, professional and of course entertaining!
S70BlackHawk created the topic: QNH altimeter settings
So I was flying IFR into Mackay from Rockhamton at 6000 FT to conduct the RNAV RWY 32 Via Bavam (4700FT). Tower was open and therefore the Class D started at 4500 Feet below the Class C I was in. Upon reaching the terminal area and just before handoff to tower at 25Nm Mackay I received ATIS and set the local QNH instead of Area QNH that Centre had passed to me earlier. I hadn't reached my true top of descent point yet.
The other pilot said, I would of failed an IPC for that (because I set Local QNH before the top of descent point). I said, but I'm setting the local QNH within 100Nm as per AIP and prior to the IAF for the approach I was about to fly. And because I've received ATIS and reported I've have received it, then when I contact tower they should expect that I would of set local QNH. After all, QNH is a required readback, and required to be set prior to the IAF for the approach.
He said no, because I was still in Class C Brisbane centre's airspace and therefore should be still cruising or descending in their airspace on Area QNH.
I don't think this is correct, and MATS states that ATC will take into account aircraft using Local QNH or Area QNH. Also the Area QNH is not to differ more than 5 HPa, so the maximum error could only be 150 Feet.
I also said, that once in the terminal area and received AWIS from a Class G non-towered aerodrome I would also set local QNH even before reaching overhead an aid such as a VOR reversal approach. Which was wrong too. I am supposed to wait until top of descent strictly???
Have been flying for almost 20 Years and seen the change from previous AIP altimeter setting to the current one. Maybe he is still thinking the old rule applies? He used the justification that "why does Brisbane Centre give you Area QNH?" so that whilst in their airspace as an IFR aircraft I need to be on Area QNH.
Would appreciate some input for this one as I have my IPC due again and don't want to fail!
Thanks for you interesting post. This has always been a thorn in my saddle. If you read the AIP ENR 1.7 para 2.1.2 (a) & (b) along with the diagram on AIP ENR 1.7 Page 4, it clearly states that you should use Area QNH for cruise ONLY if the Local QNH of an aerodrome within 100nm is NOT available. That is to say, the Area QNH is intended to be a back up, and is used only if the Local QNH within 100nm is not available.
For a great many flights, the Local QNH within 100nm will be available either through AWIS, ATIS or even a TAF. I've always found it a bit weird that, if the Local QNH within 100nm is available, the Area QNH MUST NOT be used.