A320 tropopause, auto callout 50,40,30,20,10....

[JAT469]

Hello, can you explane me why is important to set tropopause value in mcdu during preparation for flight and what is basic thing aboug that and aerodynamic and safety and performance?

My second question: why we have auto call out 50 40 30 20...what is main reason for that? 20 ok 10 ok but why 50,40,30... is that some reminder for something...some trigger ?


Thank you

[capt. solipsist]

Default tropopause is 36,090 ft. If you're flying FL360 or lower, it's a non-issue. But if you're flying higher on considerably long sectors, predictions are gonna be affected, based on the assumption that the temperature remains constant.

[Centaurus]

My second question: why we have auto call out 50 40 30 20...what is main reason for that? 20 ok 10 ok but why 50,40,30... is that some reminder for something...some trigger ?

Only guessing here. These auto call-outs are handy if landing in heavy rain where rain refraction on the windshield can give an optical illusion and this may lead to potentially hazardous flare height. Also if landing in fog whether autoland or semi-visual the call-outs are useful as an aid to expected flare height. But for a purely normal landing they can be a distraction especially in cases where the auto-callout is inoperative and the PM calls out these heights from his radio altimeter and is usually far too late and the aircraft bashes into the runway as he is singing out 50, 30 Oooops crash.
One final advantage of the auto-call-outs is that if the pilot is wearing his bifocals instead of his trifocals and thus depth perception is compromised, the call-outs are an aid to depth perception.

[AerocatS2A]

50, 40, 30 is code for "here comes 20 and 10." Seriously, they provide a trend with the rate they are called. "504030", when compared to the usual "50...40...30...", lets you know, when your eyes are outside, that you have a high rate of descent. Yes of course you shouldn't need it, but it's another little piece of the situational awareness puzzle.

I agree it can be a distraction, particularly when the callouts in different aircraft don't quite match each other and you have to remember, "is this the one that calls 10 too high?" It's easier to land without them than it is to ignore them.

[Dan Winterland]

Auto call outs are customer defined and set using pins. Our 320s only have 50,30,10 which I like better.

[vilas]

Having flown more without call outs I can say that when your flare height changes due to change over to another type it helps initially to start flare at correct height. With some experience you really don't need them but it is a help in the background. I did not find them distracting.

[Amadis of Gaul]

We never set tropopause value. I guess, our sectors aren't long enough.

[JAT469]

Thank you very much for your time . About call outs i understand my point of view wax same, but for tropopause i am not sure what is different,long short flights

[OK4Wire]

Some of our long haul flights start out where the tropo may be 50,000', and by the time you are thinking about doing your first step climb, the tropo is now 29,000'.

I always make sure the tropo in the MCDU is roughly what I expect for the approximate position of my next step climb. I think that gets me a better prediction.

[Aircav]

The tropopause setting tells the FMS when to stop assuming the temperature decrement for height. Above the setting it assumes a constant temperature so with a low trop and a high setting the box will still take into account a reduction of temp with alt. This in turn will mean incorrect OPT and REC MAX values. On short flights not so much of a problem but on the bigger bus's doing long haul there can be significant variations.

[phiggsbroadband]

50....40....30.2010

From a mathematical point of view, two numbers will just give the Speed of descent... 3 numbers will give Speed and any rate of change of speed (acceleration)... 4 numbers will give Speed, Acceleration, and change of acceleration...


The Fifth number is most likely just to get your initial attention....?

[Metro man]

I enter the actual SAT in the WIND page when I'm in the cruise and I enter the actual wind just before I cross a waypoint.

[giggitygiggity]

I was always told the 50... 40... 30.... 20.... (and hopefully not ... 10...) calls are really designed to allow you to listen for the cadence and alert you to and sink/float you may not be picking up with the Mk 1 Eyeball. I found these enormously helpful when I was new on the bus. Still uselful on poorly lit runways without centre-line lights and in miserable conditions.

They also allow you to brace for a hard landing even if you have your eyes closed

[Meikleour]

Metro Man: Are you aware that the FMGS only looks at pilot inserted winds more than 200nm. ahead of the aircraft - other times it uses the sensed FM wind values.

So, what does your technique achieve?

[Metro man]

Some of our waypoints can be more than 200nm apart on overwater legs, whether the flight plan forcast wind is going to be more accurate than my actual inserted wind 200nm away is a good question.

I believe the FMS only considers changes more than a certain number of degrees or knots so small changes aren't worth inserting.

[underfire]

50 for TCH...

[Meikleour]

Metro Man: The only point I was trying to make was - if future waypoints are far enough away it makes sense to insert a W/V but why do it just as you pass over the waypoint?
I presume this is your company SOP - but what is the logic?

[Amadis of Gaul]

Gives him something to do after the crossword and sudoku are done. Which is important.

[Bill Smith]

If you set ToC temp from your Flight Plan you don't have to worry about the Tropo

[sonicbum]

According to the FCOM it says that "In order to receive the best predictions...(omissis)...the system uses the temperature value at a given altitude, associated with the tropopause entered on the INIT A page, to optimise the temperature profile.