flight007
Topic Author
Posts: 4
Joined: Tue Jan 01, 2019 11:07 am

QFE-kollsman window

Tue Jan 01, 2019 1:36 pm

If we have aircraft stay on airport at 4000 meters and set pointers to 0 feets,how much hPa will kollsman window show?
On 4000m is only approx 600hPa but barometric scale in kollsman window is only 950-1050hPa.

Or same question ask on diffrent way,If we fly above this airport(at 4000m) and ask airport for QFE,how can we set 600hPa in window if this number do not exist on scale?
 
GalaxyFlyer
Posts: 1960
Joined: Fri Jan 01, 2016 4:44 am

Re: QFE-kollsman window

Tue Jan 01, 2019 2:33 pm

Mechanical altimeters bottom out at 28” Hg, which is 950Hpa, so you can’t set QFE at that elevation. 28” is about 2,000’. You’ll either have to add the field elevation in millibars to the current QFE to obtain the local QNH or request the local QNH. In your example, the height of 4000m is be about 616 Hpam add 616to the QFE equals QNH.

GF
 
GalaxyFlyer
Posts: 1960
Joined: Fri Jan 01, 2016 4:44 am

Re: QFE-kollsman window

Tue Jan 01, 2019 4:17 pm

The modern “glass” cockpit altimeters I’ve seen go down to 16” which is what you’d need to use QFE at 4000m. Now, are they certified that low, I can’t say.


Gf
 
flight007
Topic Author
Posts: 4
Joined: Tue Jan 01, 2019 11:07 am

Re: QFE-kollsman window

Tue Jan 01, 2019 4:22 pm

GalaxyFlyer wrote:
The modern “glass” cockpit altimeters I’ve seen go down to 16” which is what you’d need to use QFE at 4000m. Now, are they certified that low, I can’t say.


Gf

Is that mechanical altimeters or electric/electronic alt?
I am talking about classic mechanic altimeters,that almost every goes "only" 950-1050hpa...
 
GalaxyFlyer
Posts: 1960
Joined: Fri Jan 01, 2016 4:44 am

Re: QFE-kollsman window

Tue Jan 01, 2019 4:29 pm

I’m not sure of the difference, I’m just aware that old mechanical ones stop at 28” and the glass cockpit ones go down to 16”. Does China really use QFE at the Tibetan airports?

GF
 
flight007
Topic Author
Posts: 4
Joined: Tue Jan 01, 2019 11:07 am

Re: QFE-kollsman window

Wed Jan 02, 2019 12:48 pm

GalaxyFlyer wrote:
I’m not sure of the difference, I’m just aware that old mechanical ones stop at 28” and the glass cockpit ones go down to 16”. Does China really use QFE at the Tibetan airports?

GF


I dont know ,but they can give you QFE if you ask them.If I want that altimeter indicate height above Tibetan airport I must know airport current pressure QFE..But aiport is on 600hPa so I can not set this number in kollsman window if its not exist on scale! :mad: :mad:

So in classic altimeters I can use QFE settings only for airport/terrain which is below 600m altitutude . Above 600m is pressure lower then 950hPa so this pressures do not exist on scale.
 
GalaxyFlyer
Posts: 1960
Joined: Fri Jan 01, 2016 4:44 am

Re: QFE-kollsman window

Wed Jan 02, 2019 2:06 pm

That is correct

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