Altimeter Set Up

[A-3TWENTY]

Hi all ,

Whem do you all set your altimeters from QNE to QNH ? When cleared to an altitude or passing the TL?

On the QRH 3.06 states "When cleared to altitude: Baro ref - Set/x check" while on FCOM 3.03.17 states "Baro ref: Set QNH (or QFE) on the EFIS control panel and on the standby altimeter, when approaching the transition level and when cleared for an altitude"

I`ve always set my altimeter when cleared to an altitude , but now I am flying to an airlene which states we should do it only when passing the TL.
I fly in Europe.

A-3TWETY

[Denti]

On the way up we switch passing the transition altitude, on the way down when cleared to an altitude which can be much higher than the transition level. Since switching nowadays is only a single button action instead of twiddling around it is easy enough to switch back to standard when we get recleared to a flightlevel.

[A-3TWENTY]

Hi,

I totally agree with you and it is what I have done for years,, actually all my life.

But look down what airbus replied whem questioned about that:

ANSWER:

On the QRH 3.06, the procedure aims to inform that the flight crew must change the barometric reference when crossing the transition altitudes. This procedure is generic and has to be applied during climb at transition altitude and during descent when the ATC authorises to keep on the descent.
In the FCOM 3.03.17, we detail this procedure when the flight phase is descent. When the ATC gives clearance to an altitude and when the aircraft reaches the transition level (also given by the ATC), set the barometric reference corresponding to the approach/terrain (QFE or QNH). In addition, the flight crew should crosscheck the altitude on the PFD and the baro reference displayed on FCU.

As a conclusion, we recommend to refer to the FCOM 3.03.xx procedures to have more complete information.

We hope this satisfactorily responds to your request. We encourage you to provide us with your feedback using the questionnaire below, and we remain available for any additional information and assistance.

Best Regards,

David MARCONNET
Flight Operations Engineer
A320/A330/A340 FMGS Operational Standards - STLS AIRBUS Customer Services

[Rainboe]

I think it right to say most airlines now do as follows:
In the climb, when cleared to a flight level, set standard immediately, whatever the transition altitude. Standby altimeter remains on QNH until passing Climb MSA.
In descent, whenever cleared to an altitude, set QNH immediately, whatever transition level. Standby altimeter set to QNH before descent commences.

The problem with lower transition altitudes and a low cleared flight level is if you have a low pressure area and wait for transition to change to standard, you may instantly exceed your cleared flight level. Rates of climb are so high now that great care has to be taken.

[D O Guerrero]

We have a slightly different procedure - in the climb, set standard once above 3000' AGL AND cleared to climb to a FL. Standby Alt stays on QNH til above the MSA. On the way down, once cleared to an altitude.

[9.G]

A320 the answer to your question is given in the SOP:

– BARO REF......................................................... ....................................SET
• Passing transition attitude and cleared for flight level (baro setting flashing on PFD) set STD on EFIS control panels and on standby altimeter.
• Cross check baro settings and altitude readings.

The reason for this modification is given TR No 046 - 1
SUBJECT: ATC WITH ENHANCED SURVEILLANCE
REASON FOR ISSUE:
The temporary revision is issued to advise operators that the transition level, when the flight crew selects ‘“STD” on the FCU, the last QNH or QFE barometric pressure settings is transmitted to the ground, instead of the standard pressure value(1013 hpa). Only the FCU selected altitude, if used
by the ATC on ground, may be misinterpreted. The real aircraft altitude transmitted to the ground is not affected, because the standard barometric altitude is transmitted, regardless of the barometric setting selected on the FCU. In addition, the “STD” value is correctly transmitted to the other aircraft systems.
VALIDITY:All A320 equipped with an ATC certified with the enhanced surveillance (Mod 35240)
FILING INSTRUCTION:Updated the record of temporary revision and insert the following pages:
Page 1 of 2 following 00-01 Page 1
Page 2 of 2 facing 3.03.14 Page 2

Always worthwhile to read your books gents.
Cheers,:ok:

[bfisk]

In our bookwork it says TA and TL on the way up and down respectively, but it also says that when cleared to an altitude and the use of FL is no longer expected, QNH may be set. We also use setting of QNE and QNH as triggers for climb and approach checklists respectively.

Common practice is TA on the way up and when cleared to an altitude on the way down.

[10W]

Is there anywhere in Europe that would require a QNE to be used ?

[Tinstaafl]

Procedure depends on what part of the world you're in. Oz & USA set when passing TA/TL. UK sets when cleared.

[bfisk]

10W: unsure of what you are asking?

It may not be 100% accurate by definition, but in this thread atleast, I understand the term "QNE" to be the same as the standard pressure setting.

Edit: Google finds 2 definitions of QNE:
1) In radio communication, the baseline pressure setting is referred to by the Q code QNE.
2) QNE: reading in feet on an altimeter set to 1013.2 millibars (standard pressure) when the aircraft is at aerodrome elevation.

[Rainboe]

Picture this. QNH is 980Mhz or millipascals or whatever we are meant to call them now. TA is 3000' (yes- there are such places! But you can use higher numbers to illustrate). You are cleared to TO and checking in to radar at 1500', you are cleared to maintain FL50. Dutifully, passing 3000'TA with a ROC 2500fpm, you reset 1013. By the time you look up passing 3000', your altimeter change trigger, you see your altimeter has immediately jumped 33mb x 30'=1000'. After registering the trap you fell in, you realise you are climbing at 2500fpm with 700' to go! What if you had only been cleared to FL40? You would have busted your perfect record by 1000'.

Not a good scenario. There is no reason when cleared above TA to delay setting 1013 as soon as possible to prevent the possibility of an altitude bust. Indeed, if we are cleared to take off with an initial FL restriction, as the last flap is selected up, we go to 1013 without delay, before even the After Take-off check. Delaying it means forgetting it. Taking it as early as possible means you have fewer cues to miss doing it. If your standard procedures have not already changed to this, they will do! Altitude busts are not 'cool'. I was nearly taken out in a 747 by a berserk Learjet over Dayne, probably doing just such a thing- I never found out what his excuse was, but it was close.

[Looker]

EGJJ Jersey fits the above scenario perfectly and consequently the altimeter setting SOP becomes part of the departure brief to avoid level busts on low pressure days.

[10W]

10W: unsure of what you are asking?

It may not be 100% accurate by definition, but in this thread atleast, I understand the term "QNE" to be the same as the standard pressure setting.

Edit: Google finds 2 definitions of QNE:
1) In radio communication, the baseline pressure setting is referred to by the Q code QNE.
2) QNE: reading in feet on an altimeter set to 1013.2 millibars (standard pressure) when the aircraft is at aerodrome elevation.

Google is not a formal aeronautical baseline recognised by the world of aviation ;)

ICAO PANS Doc8400 has more formal weight with the authorities and agencies around the world. Hence QNE (although commonly referred to as such) is not the same as Standard Pressure Setting.

ICAO defines it in this document as a question to a ground station meaning ''What indication will my altimeter give on landing at ... (place) at ... hours, my sub-scale being set to 1013.2 millibars (29.92 inches)?'' or a message from a ground station meaning ''On landing at ... (place) at ... hours, with your sub-scale being set to 1013.2 millibars (29.92 inches), your altimeter will indicate ... (figures and units).''

My questions stands, is there anywhere in Europe with the geography to require the use of this to overcome the limits of altimeter setting scales ? I would think not.

[Microburst2002]

ICAO PANS OPS Altimeter setting procedures , Part III, section 1, state that you change the baro reference setting to STD in the climb at TA. In descent, if cleared to an altitude you can set QNH, but you may wait until the TL, at the latest.
Any other procedures are simply not ICAO compliant.
However, as you say there are reasons for setting STD before TA because of that level bust problem when cleared to a FL very close to the TA when RoCs are high (at low altitudes). Maybe they should increase the transition layer. If I recall correctly, in the UK it can be pretty narrow (500 ft?).
In other countries the TA is very high, maybe 13,000 ft and/or the TL is fixed (at say FL150) rather than given by ATC. In these, there would no problem with ICAO procedure.

There have been numerous level busts due to stopping a descent at a FL after having been cleared to an altitude. It is in the human nature to forget things when unexpected things happen. In my opinion, there is no use in setting QNH at FL410 if cleared to 5,000. You can always wait a little bit, say until FL100 when TA is 5,4 or 6 thousand, or FL200 if TA is very high.

But my point is: can an airline lay down a procedure in its SOPs that is not compliant with ICAO PANS OPS?

[Rainboe]

In other countries the TA is very high Most European countries have somewhere in the region of 6000' TA. The UK is not unusual. Does Pans Ops still apply?

[MU3001A]

When do you all set your altimeters from QNE to QNH ? When cleared to an altitude or passing the TL?

Easy, set QNE on the way up passing 17,000' when cleared to a FL as part of the standard climb checklist and set QNH on the way down passing FL190 when cleared to an altitude as part of the standard descent checklist.

Related questions, why do the Europeans persist in needlessly complicating the issue by sticking with a variety of TA/TL's and why would anyone follow their lead?

[Kiltie]

"But my point is: can an airline lay down a procedure in its SOPs that is not compliant with ICAO PANS OPS?"

Yes it can, but only if the governing authority of its country of origin is too lazy to spot it in the Operations Manuals which it is supposed to proof-read before approving! Many of these odd-sentenced statements have slipped through the net before.

[bfisk]

10W: Thank you, I learned something new then.

However I think that for the purpose of this discussion, one should read QNE as SPS, otherwise the whole thread would be nonsensical. And the thread itself, is highly relevant, in my opinion, definitions aside.

:)

[Microburst2002]

There are many ways to do things, of which many are sensible and good, but... ICAO states the way it must be done quite clearly, so...

Can we just ignore the rule?

If, god forbid it, one day there was a mid air colision due to non ICAO standard altimeter setting procedures on the part of one (or two) airplanes, what would happen?
I don't think that setting 1013 just after take off is a good operating practice, even if you keep stand by altimeter in QNH till MSA. If one airfield has a very low TA and you are cleared to a FL very close to it because of a too narrow transition layer it is OK, but it is not OK doing it with a 18,000 ft TA, is it?

[9.G]

Most European countries have somewhere in the region of 6000' TA. The UK is not unusual. Does Pans Ops still apply? Madrid in the heart of Spain TA 13000 ft how bout that my friend? Wanna know why? Well, coz the MSA is 10000 ft on the NW side. Rings the bell? TA is there for a purpose and most of the time above MSA/RVA simply coz MSA is based on local QNH when practical. That doesn't preclude usage of STS for MSA in mountainous airdromes. This is at least relevant for departures. If you level off for any reason below TA with STD set on your FCU and don't revert the setting to the local QHN not only are you gonna have to deal with RA but avoid planting your new shiny BUS into the mountains coz ATC still thinks you're on QNH as we saw in the TR and will radar vector you around using MRV altitudes. As for high rate of climb simply reduce your take off thrust at 1000 ft AAL and you'll have instead of 2500 ft/mn only 1800 ft/mn somewhere around that. It's gonna buy some time enough to pull the BARO button. Apart from that whenever such low QNH is in place rest assured the transition layer will be adjusted to 2000 ft as it's a common practice. ICAO has thought about that as well my friend they ain't born yesterday.
Cheers:ok:

[Microburst2002]

haha

Yes, of course it can happen. It does happen, as you say.
But it shoul not. That is my point. We should do it as is prescribed, and that's it.
Because, if not...
Which other rules can we ignore? and ...
Who determines which rules can be ignored and which have to be followed?
:8

[Rainboe]

Let's have a little pause for thought about TAs and why they are what they are. The idea is that you can fly on standard setting without bumping into cumulogranite, whatever the temperature and MSL pressure. The US with its Rockies at 15,000' needs a TA of 18,000'. We have the Alps in Europe, but not as big. But other countries don't need such TAs. Even Spain at Menorca has a 'normal' TA. France, UK, Germany, Italy..... all 'normal' too. But having a high TA like 18,000 or 24,000' is a plain PITA- needing QNHs reset constantly as you move altimeter setting regions when below TA. Maybe they need it like that in the Mountain area, but the coastal regions and Central? An 18,000' TA is a nonsense.

Indeed, it is the US/Canada that are the oddities, and frankly, I didn't like it. Coming late like that, it is too easy to forget to change over well into the climb when things have gone quieter. Changing early, it is usually wrapped up in the After Take Off check as well.

[MU3001A]

it is too easy to forget to change over well into the climb when things have gone quieter That's why we have a climb checklist and a descent checklist, both triggered by TA/TL which is constant and standard instead of changing from location to location, just like the 10,000' speed reduction. KISS principle folks, why make things more complicated than they need to be? The US doesn't have altimeter setting regions either, you will always get the local altimeter setting of the airport or weather station nearest to you from ATC.

[Zeffy]

MU3001A

That's why we have a climb checklist and a descent checklist, both triggered by TA/TL which is constant and standard

Are you saying that the TL is constant in the U.S?

Please refer to 14 CFR 91.121 (b) (http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=409c219b719da69c208e0cc6bf1e8db7&rgn=div8&view=text&node=14:2.0.1.3.10.2.4.11&idno=14)

If the SOP/checklist is anchored to FL180, a crew could be setting up for an altitude bust when QNH is significantly lower than standard -- e.g.:

QNH is 29.11"

Aircraft is cleared to descend to 17,000.

Crew is descending at 2000 fpm and waits until "FL180" to set QNH.

What will the altimeters read when re-set from STD to 29.20?

How much room will remain to capture the assigned altitude?

[MU3001A]

Constant in the sense that it is never FL60 or FL50 or FL120, but always FL180 unless FL180 is unusable because of low pressure. When ATC issues a clearance to an altitude from a flight level they are required to state the local altimeter setting and if I don't get one I will ask and I change the altimeter setting passing 17,000' on the way up and passing FL190 on the way down and I never descend or climb the last 1,000' at 2,000' per minute.

[Rainboe]

You display a certain arrogance that the 'US way is the only way'. In fact, I always had to adjust to special strange US rules- 250 below 10 (not needed or desired most other countries), TA 18,000' (totally unnecessary outside Mountain area). The east and west coasts and central should have TAs of 6000' or slightly higher. It's quite easy. Maybe we should all come around to TAs of 10,000' worldwide to wrap it up in that check, but TAs of 18,000'? A nonsense for anywhere that doesn't have mountains up to 15,000'

[9.G]

Rainboe, just to throw my 2 cents here. Have a look at the approach plates for Milano highest point 15203 to be exact Radar minimum altitudes FL 195. I'm utterly surprised how many pilots out there are simply not aware about TL principals of determination. Clearly low pressure adjustment is applied where necessary.
Cheers:ok:

[Rainboe]

I was a regular at Milan. I am a regular at Bergamo. I have been a regular at Mexico City, Denver, Nairobi, Johannesburg, Teheran, Bogota (the highest). I know about TAs, TLs and VERY high MSAs, pressure altitudes and density altitudes (and I still get accused of being just a flightsimmer by idiots here!). IMO, the US/Canada does not have it right. I think TAs should be 6-10,000' unless there is a very good local reason not to have that figure. 18,000' is ridiculous when there are no repectable mountains within 1000 miles, so the assumption that the whole world should have 18,000' is absurd. And 250kts below10 doesn't cut it for me. If Mr. Boeing wanted speed restricted to 250, he'd have restricted the aeroplane. We have 313 below 8 on the 757 and red line on the 737. People pay for jet speeds, they give them turboprop movement. If the option is there, go for it- and if the copilot won't, I ask why he is applying his own set of limitations- let's just stick to Mr. Boeing's please.

[A-3TWENTY]

Probably they set this standard in US after a few missed the altimeter setting during descend.

:8:8:8


250 Kt below FL100 is good just in case you meet a feather plane in your way.

:ok:

[Rainboe]

That's the usual excuse, however bird strikes are rare, and Mr. Boeing is perfectly happy with anything up to 320kts to low altitude, so I think it is a bit constipated to artificially decide 250kts will 'do'. If people want to fly their own particular limitation of 250kts, then that's fine, but not with me on board please- I'm always in too much of a hurry, with a schedule to keep thank you very much! Terribly sorry for the birdie, but we can't keep sharing the same bit of sky- you lose! I like birds- I was feeding swans and ducks just yesterday, and they live outside my house. They can rule up to 1000'. Above that, it belongs to Boeings and Airbuses

[FullWings]

Looking at it from a safety perspective, what advantage is there in delaying a change of pressure reference when your cleared level/altitude/height requires this new reference to be correct? Anything which is not acted on immediately is liable to omission. Not having the right barometric datum can cause conflict with other aircraft and the ground!

I see postings like: 'We'll pick it up in the checklist passing TA/TL'. What triggers this checklist, especially in a non-EFIS cockpit? If it relies on someone noticing passing TA/TL on their altimeter (no bugs, lights, sounds, etc.) then it is liable to omission, especially if the workload is high or there are distractions. Also, as pointed out by others, effecting a change at TL/TA may be too late when in low QNH conditions.

In the moderately rare case of 'stop climb/descent at FLXX/XXXXft', you can change back to whatever reference you need, there and then.

As far as procedures and ICAO goes, airlines' ops. manuals are generally signed off by their respective NAAs as being compliant with regulation...

[Denti]

Based on a boeing recommendation we changed our speed policy below FL100 to max 300kts and max 250 below 5000', originally for a mix of 737 classics and NGs, nowadays NG only. Company policy is 250 below 10, the limit up to 300 may only be used on request by ATC. And i guess everyone has a schedule to keep, its just a question of how it is planned and that is more of a management decision (net management) than a pilot decision. If net management plans block and turn around times that are impossible to keep they will have a problem with airport slots sooner rather than later.

[MU3001A]

You display a certain arrogance that the 'US way is the only way'.

Clearly it's not the only way. Just the simplest and the most effective way to combine transition altitude with the delineation of Class A airspace, while freeing up as much airspace as possible for non IFR traffic. KISS principle folks.