Busting Altitude Problem

[Ray Proudfoot 8,930]

Hi John,<>You're setting QNH too soon. Wait until you hear 'altimeter check' during the decent and set it then to QNH.You can request Altimeter Check during most phases of the flight. Press zero a couple of times and you should get the option but the key is setting the altimeter only when you hear 'Altimeter Check'.Cheers,

[Guest John Morgan]

Thanks Ray,I will use the procedure you suggest,Best wishes, John MorganAberystwyth, Wales

[Guest John Morgan]

Dear Ray,I have now carried out my test Manchester-Edinburgh flight four times or so and I still have the same problem. My cruise altitude is 20000 feet. On the last occasion I was cleared to 13000 feet and on the way down I was cleared to 12000 feet. I was again accused of busting my altitude for no apparent reason. The controller does say "I need you down withing 30 miles" but this restriction was certainly met.You say >>You're setting QNH too soon. Wait until you hear 'altimeter check' during the decent and set it then to QNH.<

[PeteP 2]

Ray - I hope you don't mind me butting in here.John,I cannot fathom why putting in the apparently correct QNH in hectopascals does not satisfy the controller's requirements.The problem is being caused the fact that you are using the QNH when you should be using the standard setting of 1013.2 hPa. Flying in the UK, Radar Contact would not allocate you a cruising altitude of 20000ft, neither would you be cleared to altitude 13,000ft or altitude 12,000ft - it would be FL200, FL130 and FL120 respectively. The difference being that altitudes are based on QNH but flight levels (FL) are based on the standard pressure setting of 1013.2 hPa.Before we go any further, please read my reply (posted this morning)to Iain Smith in the thread "Crazy Controller" http://forums.avsim.net/dcboard.php?az=sho..._id=18818&page=and follow this link to an earlier post I made on the same subject: http://forums.avsim.net/dcboard.php?az=sho...id=16233&page=3 You'll also find some relevant information in the RC manual sections on Transition Level and Transition Altitude which you'll find on pp 107-108. I hope all the above info will help you understand the altimeter setting procedures in use outside the US. To sum up, you use QNH until you pass the Transition Altitude when you're going up and then use the standard setting of 1013.2 until you pass the Transition Level when you're coming down. If you listen carefully, RC gives you plenty of help in deciding what setting you should be using. If you're cleared to a flight level then you should have 1013.2 on your altimeter sub-scale; if you're cleared to an altitude (and RC always uses this word!) you should have the local QNH set. To help you know when you're passing the TA going up or the TL coming down, your co-pilot will say "altimeter check.Easy innit!;)

[Ray Proudfoot 8,930]

Hi John,Sorry to hear you're having problems with TA, TL and QNH. Let's see if we can sort you out.You will never file a flightplan to be at 20,000ft. The Transition Altitude at Manchester is 5,000ft and at Edinburgh it's 6,000ft. So your filed cruise level would be FL200.You don't report any problems getting up to the cruise level so you're obviously setting standard pressure during the climb when you hear 'Altimeter Check'. Good. You're half-way there :-)When you're ordered to descend you've probably been given an instruction such as "Speedbird 123, Descend and maintain Flight Level one eight zero". You're still on standard pressure so you dial up 18000 on the autopilot and you start to descend.Shortly after that you probably received a further clearance down to FL130 and the controller will have said "Descend and maintain flight level one three zero". He won't have said "thirteen thousand feet". Very soon after that you were cleared down to the crossing restriction Flight Level. In your case it was FL120. You should still be on standard pressure. Providing you level out at FL120 by 40 miles from EGPH you won't get told off. I suggest you create a waypoint in your flight plan to assist with reaching that point and being at the correct flight level.You appear to have been turned away from your filed route at a heading of 90 degrees. This is because you didn't get down to FL120 in time. Probably because you were on QNH already and flying higher than you were assigned. Hence the telling off.At FL120 you will then be cleared down to FL80 or thereabouts. Note that you're still being cleared down to a Flight Level so you must still be on standard pressure. It's likely at this time you will be given the QNH for Edinburgh. Make a mental note of it but do not adjust the altimeter - yet.You will then be given a further clearance down. Probably to 5,000ft. Note the difference. No more Flight Levels. Somewhere between FL70 and 5,000ft you will hear "Altimeter Check". When you hear "Altimeter Check" adjust the altimeter to the QNH given to you earlier. When you level off at 5,000ft you will now be on local (QNH) pressure and further descents will be given down to 3,000ft or thereabouts and heading changes will also be given for an ILS intercept to EGPH.I hope that clears everything up for you so you can enjoy a weekend of flying :-)Cheers,

[Ray Proudfoot 8,930]

Hi Pete,Both typing simultaneously!! :-eekI think between us John has all the info he could possibly need. I never mind you butting in - even at the bar when it's my round! :-beerchugCheers,

[Guest John Morgan]

Thank you Ray and Peter P, I really do appreciate your help.I've got it now. I had not realised the subtleties involved in the controller clearing me to FL120 as compared with 12000 feet. Though I knew there were differences, flying within FS made me think that the transition altitude of 18000 feet was much more general than it appears to be. I am very suprised to see such low and different levels in EGCC and EGPH. One would have thought that it would have been standard at some constant level within Europe as well.I have just completed a late night flight to Edinburgh and all went satisfactorily. I only wish the controllers I previously dealt with had as much patience with me as you!Best wishes, John Morgan

[PeteP 2]

Well done, John. I think you'll enjoy your flights a little more now you're getting the hang of altimetry. It is, indeed, frustrating that there's no common standard for these things, even within Europe, but we are slowly moving in that direction. The UK, for example, has just changed the classification of its airspace above FL195 to come into line with other parts of Europe and a common Transition Altitude has been on the agenda for some years - I've heard 10,000ft from several sources - so we are getting there slowly. Maybe one day...:-) Pete

[Ray Proudfoot 8,930]

Hi John,Nice to hear you've now got the hang of things :-) There is a big learning curve for those brought up on the default FS ATC especially when flying outside of the US.Welcome to the real world!:-beerchug

[Ray Proudfoot 8,930]

Hi Pete,<<...and a common Transition Altitude has been on the agenda for some years - I've heard 10,000ft from several sources ...>>Won't that take all the fun out of simulator flying? :-( We need variety to keep it interesting.Cheers,

[Guest holla]

I seem to be having a similar problem with descents. Am also flying PMDG 737 and the FMC calculates TOD but I am always told by RC to start my descent well before this which I do using descend now in FMC. All seems to go well using MCP to control descent but after landing I always get told off for missing transition altitudes. RC seems to want me much lower than than the FMC would indicate, any reason for this, I don't want to sit and keep asking for higher or lower altitudes, just want to know how to stop being asked for my papers when taxiing to the gate!! Regards, Mark Holland (Long time user of Flight Sim and RC, first time poster)

[Ray Proudfoot 8,930]

Hi Mark,The short answer to this is ... Controllers control, FMC's don't ;-)The controller doesn't know about our fancy FMCs/CDUs. He just wants us to start descending when ordered to. I'm sure our resident real world controllers will have something to say about this :-)You do have an option with the descent. Providing you manually ack instructions you can select a PD if you want to stay higher for a little longer. Just choose that option when it presents itself.I hope that helps. Welcome to the forum :-)Cheers,

[Guest holla]

Hi Ray,Thanks for the quick reply, think I have found the answer. It was me being a bit thick with regard to altimeter settings. Just read loads of posts on this and hope I have understood. Just about to go East Midlands to Faro, let you know if it works. Problem is, with a flight plan, charts, coffee, ashtray and notes on altimeter settings on the desk I think I have lost Saitek X45!!. Thanks again.Regards, Mark

[Ray Proudfoot 8,930]

Hi Mark,A bigger desk beckons ;-) BTW, did you mean you get busted for missing your crossing restriction? You need to be down at either FL110 or FL120 at 40 miles from the arrival airport. TL depends on near-side or far-side approach. Creating a waypoint to meet that rule is very handy.Enjoy your next flight!

[Guest holla]

Sorry, yes I did mean crossing restriction. Seems low for 40 miles out, never seems that way in real life but it must be. Taken off and climbing out so I will try the waypoint thing.Thanks, Mark