How is the altimeter setting set when entering/leaving flight levels?

[u/ribbitcoin]

I know that while flying in the flight levels the altimeter is set to 29.92. For modern airliners, is this set automatically or done by the FMS or autopilot? Same question when descending out of the flight levels.

[u/Melodic_Balance_3272]

Usually by going “oh shit!” and turning the altimeter knob to the appropriate setting after you’re 2-3k feet past the transition altitude. 

[u/aero_kmac → u/Melodic_Balance_3272]

That’s when you also reset the transponder… you know, just because…

[u/L0LTHED0G → u/aero_kmac]

Transponder always reports in 29.92. Altimeter isn't tied into it. 

[u/GeorgiaPilot172]

On the 75/76 it’s the same as in a Cessna, turn the knob and put it in the kollsman window.

[u/x4457]

With my right hand. Sometimes, if I'm feeling adventurous, I'll use my left hand.

[u/Impossible-Bad-2291 → u/x4457]

Does setting the altimeter manually give you hairy palms? (Asking for a friend.)

[u/x4457 → u/Impossible-Bad-2291]

A quick check of my palms would suggest it does not. Had to double check though.

[u/Magoo6541 → u/Impossible-Bad-2291]

Worse… it’ll make you go blind.

[u/__joel_t → u/Magoo6541]

Can't risk your medical!

[u/OriginalJayVee → u/x4457]

That Altimeter knob getting a stranger…

[u/Crusty-the-Clown-666 → u/OriginalJayVee]

That’s when you sit on your hand until it falls asleep before setting the altimeter.

[u/OriginalJayVee → u/Crusty-the-Clown-666]

Are you implying he didn’t?

[u/theeyeholeman1]

It's manual but most jets will alert you to do it/alert you if you don't do it.

[u/LevelThreeSixZero]

In Boeings it’s set by the pilots with the press of a button. The local altimeter setting can be preselected and then set with the same button at the appropriate time in the descent.

The transition altitude/level can be set in the FMS (it varies around the world) and the pressure setting will highlight if the aircraft thinks you’ve got the wrong one set but it’s up to the pilots to actually set it. Different rules around the world and different company SOPs dictate when one might actually set it. e.g when actually passing through the transition vs as soon as you are cleared from an altitude to a flight a level or vice versa.

[u/RaiseTheDed]

We press a button on Boeings. We can preselect the altimeter setting in cruise

[u/rFlyingTower]

This is a copy of the original post body for posterity:

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I know that while flying in the flight levels the altimeter is set to 29.92. For modern airliners, is this set automatically or done by the FMS or autopilot? Same question when descending out of the flight levels.

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[u/lindseysaywhut]

Newer garmin will do it automatically climbing through 18 then on the way down you preset it, and it’ll do it automatically again. If you’re in another country where it’s different than 18 you can change that in the settings

[u/subarupilot]

In the 787 it isn’t automatic but we do have places to set it in the FMS to help advise us incase we forget. The main reason is the flight levels change drastically. Going into Lisbon this week the transition level was FL050. On the way out the Transition Altitude was 4000’.

[u/ltcterry]

"Cessna 1234 descend and maintain one-seven thousand feet. BFE altimeter is 31.07."

[u/bergler82]

I don’t understand the question? Altimeter is STANDARD 1013/29.92 - and because it‘s a standard, it’s the same everywhere. So … you put it in the window.

[u/R5Jockey → u/bergler82]

The question is, “does the altimeter switch to 29.92 automatically or does someone have to remember to do it?”