Altimeter Set Up

[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?

[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)

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

[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.




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

[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.