Some people say: During climb, leave the STBY altimeter setting to departure field setting, it could be useful in case you have to come back in a serious emergency.
Other people say: At transition (European transition, quite low) change ALL altimeters to 1013, to have one more crosscheck available for the other two altimeters during cruise, and above all not to have a false, misleading setting during descent ("Have we updated the setting to destination or not?"). If you have to come back in emergency, you will have to update anyway the whole cockpit, and if unable to talk to ATC you have the setting written down on the flight log.
In small aircraft, particularly if unpressurised, thus making it far more likely that you will be operating below TA, I'd leave it on QNH of airport of departure, thereafter on regional QNH (or for any other unusual situation).
Everything else, yes, put all altis on the same setting.
I strongly agree with you not to follow the academic rule of changing altimeters AT transition, but to always have them set in accordance with the altitude you have in the altitude select window. Unfortunately, there are still many guys out here who strictly observe the transition level/altitude, and it's GUARANTEED soon or late they will forget to change, and with low pressure in the approach area the result will be !
I generally agree with MAX whereby you set 1013 as soon as you are cleared to a flight level in the climb and QNH as soon as you are cleared to an altitude in descent. However companies I have worked for required the Standby to be left on QNH for the duration of the flight, as both MSA and driftdown are altitudes not FL's. The exception to this is if you are operating above FL290 where RVSM checks require all 3 to be set to 1013.
Yes you should do what your company SOPs say but I thought that, on climb, you should set 1013 (on all but the standby altimeter) as soon as you are cleared to a Flight Level. Not to do so risks a level bust.
As a pilot in the American Air Farce, I've never understood why the rest of the world does not agree to the American standard of FL180. No, we certainly are not right all the time in the Land of the Free, but changing altimeters to FL at 3000 feet seems to invite terrain clearance problems. It's so late in the approach that it can be missed and causes the problem on departure of "stop climb at 4000" instead of climbing to FLs. FL 180 is high enough that you are well away from any terrain.
As an ATCO and in order to keep vertical separation I expect pilots to fly altitudes (local QNH) below TL and TA, an flight levels (1013) above. In the event one departure has to stop climb at a certain altitude due to inbound traffic, if both altimeters are not set to local QNH, the 1000 ft separation is not granted.
Here is another one for you, and I am sure we are not unique. In cruise we set the Standby to line up with the other altimeters. 1013 does not give a very accurate reading and useless in RVSM. At least if the others go down you have something realistic to follow and in RVSM ayou are less likely to bump into someone comming the other way !
As an ATC I cannot make any comment on the use of multiple altimeters in aircraft, so, from a controller's perspective, I'm separating my aircraft on the assumption that everyone at or below the Transition Altitude has an altimeter set to QNH, and everyone at or above the Transtion Level have altimeters set to 1013.
I don't care which altimeter you use, as long as when I ask you to report the level you're passing, its based on the correct setting above or below the Transition Layer. That way, when you tell me you're 1000FT apart, YOU ARE 1000FT APART!!!
This is even more critical when 500FT separation is in use. I often correct 300FT variations in Mode C altitude information on radar due to incorrect pressure settings on altimeters.
300FT variation (Aircraft A) + 300FT variation (Aircraft B) = 600FT
500FT Separation Standard minus 600FT total variation =
Remember, my radar cannot measure what altitude or level you're at, only you and your transponder can give me that information...
Last edited by Spank me baby!!!; 15th May 2003 at 15:53.
Different states may have different requirements but here is a quote from the UK AIP ENR 1-7-2 (24 Jan 02) under Altimeter Setting Procedures:-
5.1.4. ....When cleared for climb to a Flight Level, vertical position will be expressed in terms of Flight Level, unless intermediate altitude reports have been specifically requested by ATC.
I would be interested to know what the ICAO Pan-Ops says these days - it's a while since I looked but I suspect it's the same as the UK AIP.
By the way, Galaxy Flyer, point well taken about having a higher TA but it's only 3,000 ft in the UK outside controlled airspace. Go to places like LHR etc. and it's 6,000 ft although the lack of commonality would make good for another thread!
As a controller, I would expect the pilot of any high-performance aircraft to be able to follow my instructions/requests. If the cleared level is an altitude, I would expect level reports etc to be QNH-based, if it's a FL, I would expect level to be referenced to 1013. If it's vital to be certain what setting is used I'll double check by asking the pilot (and use Mode C if it's available).
I'll do my best not to swap between the two settings (e.g. having cleared the pilot to a FL to then give a stop your climb at an altitude) but these things can and do happen for various reasons. If I have to do it I'll always give the QNH again if it's a stop at an altitude. Whilst it may be an inconvenience, pilots seem able to comply with instructions in these cases whatever altimeter setting procedures are used.
I've always got half a mind on vertical searation when I'm working around the Transition Layer and will build in a buffer to a clearance that will at least ensure a degree of vertical space if the wrong pressure is set.
No, it's not fail-safe and, no, it's not the perfect situation. And certainly building in a bit of extra vertical can't be done all the time (and probably never at some places). As a side issie, I kinda like the 10000ft or 18000ft Transition Alt idea but I'm wary of saying 'let's do it' without giving it a lot of thought to see what other problems might emerge because the rest of the UK's airspace and procedures are based on the lower levers.
My attitude may seem insular but reading this thread clearly shows the range of altimeter setting procedures that are used. Sitting on the ground, I'm not going to try and second guess what altimers are set at what pressure setting on any particular aircraft! If you're a pilot and feel happy that you could comply with the (sometimes messy) level instructions that a controller gives because you've always got altimeters set up to let you, this is good. If not, is it something to raise with your Ops?
It appears to come as a surprise to controllers and pilots who are used to the situation in other countries (Oz and the USA in particular) that the UK does not have a standard TA/TL, and that it tends to be a lot lower than in those other countries.
What you need to bear in mind is the size of the UK, which, together with the density of population, the density of airports and therefore density of controlled airspace and density of air traffic, requires active Air Traffic Control down to a much lower level.
Furthermore, we do not have fantastically high lumps of cumulo-granite so above 4,406' there isn't so much of a problem with inadvertently bumping into the terrain. It does happen, of course, but you need to try a bit harder than you do in some parts of the world.
In my previous airline when the SID ended at a FL, we took off on QNH and setting 1013 was one of the post-take-off actions (which triggered the request for the after take-off checks). For reasons that, I am sure, most people here can understand, I am not entirely happy with the concept of SIDs ending at a FL rather than an altitude.
I believe (I may be wrong) that PANS OPS says you can set 1013 when less than 2,000' from TL and cleared to a flight level. You may be making difficulties for yourself if you set 1013 immediately you are cleared to a FL since you may be asked for your passing altitude on the way. In some machines I've flown, climb performance was not brilliant, so getting to within 2,000' of TL could take a while!
Oh yes SMB, 3/4/5/6 and Naples Italy 8 for starters! Need more?
Spitoon - FYI - BA's procedure (737) is to set 1013 when above acceleration altitude (normally 1500' QFE) and cleared to a FL (no mention of within 2000'), but the standby remains on QNH until above MSA and TA, so is normally available for an altitude check.
Re the US system of flight levels above a comon very high transition altitude, I have the following questions;
An aircraft flies from the east coast to the west coast IFR at 14000ft. What are the laid down procedures that ensure;
a) The pilot has access in flight to the most appropriate QNH?
b) The flight does not hit a VFR flight coming the other way that hasn't reset the QNH for the past 1000nm?
Do Area Control Sectors have a QNH that they use for all flights within their sector?
When is this QNH updated and how much R/T time does it take to tell everyone on frequency and get an acknowledgement of the new QNH including some "say again"'s.
Since the QNH could be different in every sector how often do pilots change QNH on average per flight?
Finally, if the QNH in two sectors is measured at the centre of the sector, and the distance from the QNH source to the sector boundaries is 200nm, what is the worst case separatin minima of opposite direction aircraft on vastly different QNH and planned 500ft vertical separation plus some mode C error?
Of course, it looks like a great idea. However it seems to me to be an extra burden because - leaving FL350, passing FL190, set the sector (area) QNH which ensures separation from other enroute traffic then, before making the approach, set aerodrome QNH.
Seems like extra altimeter setting requirement to me.......like going back to using QFE again!