Barometric Setting?

[Hog_No32]

Finally you begin to really really read the charts, great!

 

So, then I am asking again since you didn’t answer that: When it is true what you say and the altitudes/heights in brackets really correspond to heights above ground that you read off of your radio altimeter, how comes the difference between these heights and the barometric QNH altitudes (thise without brackets) is consistenly 4 meters all the way through the approach despite the fact that the terrain below the approach path is anything but flat?

[Gaspipe]

Finally you begin to really really read the charts, great!

 

So, then I am asking again since you didn’t answer that: When it is true what you say and the altitudes/heights in brackets really correspond to heights above ground that you read off of your radio altimeter, how comes the difference between these heights and the barometric QNH altitudes (thise without brackets) is consistenly 4 meters all the way through the approach despite the fact that the terrain below the approach path is anything but flat?

 

Nothing to do with QFE. Per the Jepps chart legends:

 

14—

Decision height

shown in feet Above Ground Level based on the straight-in approach reference datum

 

And you don't have to be rude. Do you even have a instrument rating?

[Hog_No32]

And how does the Jeppesen chart legend apply to the Chinese AIP charts? Apples and oranges. And DH is not shown in the profile view anyway, neither on Jepp nor in Chinese AIP charts.

 

You don‘t even need the Chinese chart legend since the meaning of the heights is explained in the headline. Which you again prefer to ignore.

Edited August 29, 2018 by Hog_No32

[Gaspipe]

And how does the Jeppesen chart legend apply to the Chinese AIP charts? Apples and oranges. And DH is not shown in the profile view anyway, neither on Jepp nor in Chinese AIP charts.

 

You don‘t even need the Chinese chart legend since the meaning of the heights is explained in the headline. Which you again prefer to ignore.

 

Seriously? Conversation over as you just don't get it

[Hog_No32]

True, I still don‘t get why you compare apples with oranges. I don‘t get why you can‘t answer my simple questions with 30+ years of experience...and an instrument rating!

 

But I agree with you that it appears pointless to continue this discussion. Good night.

[Gaspipe]

True, I still don‘t get why you compare apples with oranges. I don‘t get why you can‘t answer my simple questions with 30+ years of experience...and an instrument rating!

 

But I agree with you that it appears pointless to continue this discussion. Good night.

 

Does it occur to you that the Jepps chart and the AIP chart are the same? Where's your apples and oranges coming from? They are the same thing.

 

One more time. On a QNH defined approach, which is the chart you listed and my Jepps chart is the same, you must use the QNH altimeter setting as all minimums are based on your QNH altimeter setting. The decision height numbers in parentheses are simply reference numbers for height above ground and you would not use those numbers. They are for reference only and only come into play for CAT 2 or CAT 3 approaches which would use the radar altimeter for decision height. You would not use the altimeter at all, QNH or QFE, it doesn't matter. If you used your method of simply flying the parentheses numbers as a QFE setting on the altimeter, which are only 4 meters difference, it would work but it's not legal. What happens in the event of a missed approach? The missed approach altitude is 1200m and does not have any parentheses numbers associated with it. What would you do, dial in the 1196? You can't do that.

 

 

On a QFE defined chart, for example Almaty (UAAA), you need to set the QNH setting and then convert that to QFE on the altimeter and fly the approach from there.

Edited August 30, 2018 by Gaspipe

[Flamin_Squirrel]

Yeah ok. 30+ years experience doing this, you?

 

And 0 years experience flying outside of your own narrow frame of reference it would seem. I wouldn't talk with such authority when the limits if your own knowledge have already been exposed.

[escaner]

You may want to read my post again: I said they publish procedural altitudes as QFE (height related to threshold elevation) for approach procedures. I did not say the use those in ATC clearances (which you may be exposed to) and obviously you don't see these heights in your commercial chart sets. But if you would use the AIP plates (which would be legal) you would work on QFE for approaches. See attached sample chart.

 

That chart says that heights are related to runway 13 threshold elevation. Heights are always in reference to an stated elevation as opposed to altitudes that are in reference to MSL.

 

That is a standard chart with altitudes as main reference and heights in parentheses for radio-altimeter reference in the approach and for minimums (DH, MDH: always in parentheses). The previous statement only warns you that all those heights (not altitudes!) are not e.g. AAL (reference to airport elevation) or to the actual ground elevation at that point, but to the runway threshold elevation.

[TwanV]

Hah I had this discussion before. It's a fact that the brits always want to do things differently, but the reason why people fly QNH is simple, suppose you have two airfields fairly close to each other (not a problem in Russia ok) at different altitudes and terrain is a factor on approach. With QNE one would have to have two charts of the surroundings. With QNH, one will suffice, i.e. altitude is equal to height.

One can also argue QNH is safer due to the fact that when accidentally interchanged and you assume QNH at all times where you actually have a QFE reading you will survive. the other way around means you hit the deck.

Edited August 30, 2018 by TwanV

[David OC]

This has all been discussed before and is a good topic to get confused with...:D

 

There is a great old post here by Slothface.

 

Snippet below

 

 

This is all good and well knowing that QNH is the best pressure setting to use in a region for vertical situational awareness. But it is not always possible to get the regional pressure setting QNH from accurate means and a reliable network of meteo stations. Remote airfields and isolated combat zones are just 2 examples where it'd be difficult to get an accurate QNH when you dont have access to good forecasts and numerous pressure sensing stations.

 

If pressure info isn't available then you can get QFE easily by selecting an altimeter setting that reads zero on the airfield. The number in the altimeter pressure window is your QFE.

 

To get QNH, you just need to know your elevation AMSL and set that in your altimeter. Airfield elevation = 250ft. Set altimeter to read 250ft. Pressure in the altimeter pressure window shows your QNH. (You have to remember that this wont be the lowest forecast QNH pressure for the day and just be cautious at low level. But thats why a radio altimeter is handy!)

 

 

I'm guessing here major airlines out of major airports would never use QFE and USA GA pilots have never used QFE.

 

Also Russia is changing to QNH

 

Article snippet "Big change: Russia finally moving to QNH"

 

Quick example for ULLI ILS 10L, so you get the idea:

 

The ALT/HEIGHT conversion box is gone

The “Alt Set” or Altimeter Setting box shows hPA (Hectopascals) instead of MM (millimeters), which means a QNH-based approach

Previously charts showed QFE in bold which meant that was the preferred altimeter setting, now it’s QNH.

 

 

 

 

Much more info by a pilot for pilots http://code7700.com/altimeter_metric.htm

 

 

.

Edited August 30, 2018 by David OC

[David OC]

Google Translate http://www.favt.ru

 

In the area of the Pulkovo airfield (St. Petersburg), a pilot project has been launched to carry out the flights to the average sea level (QNH)

 

Work on the transition to a new QNH system The Federal Air Transport Agency, in conjunction with the FSUE "State Corporation for ATM" (a branch of "Aeronavigation of the North-West"), began to run since August 2016. From 2 February 2017, the crews of Russian and foreign aircraft arriving and departing from St. Petersburg Pulkovo Airport have switched to the new standards for the implementation of flights for the QNH system for Russia - flights at atmospheric pressure, the values ​​of which are given to the average sea level .

 

Flights of civil aviation aircraft are carried out practically the same way throughout the world.

 

Take-off aircraft performs with the barometric airborne altimeter pressure take-off aerodrome, then after a set of a given transition altitude, the crew resets the pressure of the airborne barometric altimeter from the airport to the standard atmosphere pressure QNE (1013.25 h Pa), common for all aircraft. This ensures the possibility of safe and reliable separation of aircraft in the vertical plane.

 

When approaching the landing aerodrome, the crew at the transition echelon rearranges the pressure of the onboard barometric altimeter from the standard one to the airfield landing pressure and performs the landing stage.

 

The implementation of this simple scheme for performing an aircraft flight from take-off to landing is presented in the form of two options. The absolute majority of the world's states, which account for almost 100% of the world's takeoff / landing operations, use aerodrome pressure, reduced to sea level according to the standard atmosphere (QNH), as the airfield pressure.

 

These two variants of one scheme for performing flights from take-off to landing have a significant difference. Take-off / landing operations using QNH aerodrome pressure are safer compared to take-off / landing operations with aerodrome pressure QFE. This statement is a consequence of the fact that, in general for aerodromes in the world, the pressure difference between QNH and QNE is significantly less than the pressure difference between QFE and QNE for the same aerodromes. Therefore, errors in setting the airdrome pressure or standard atmosphere on the altimeter, when flying with QNH, have less serious impact on the risk of aviation events than the errors in setting the pressure for flights using QFE.

[Ventus_Clu]

The “Alt Set” or Altimeter Setting box shows hPA (Hectopascals) instead of MM (millimeters), which means a QNH-based approach

 

This just means you get mm of mercury as your pressure settings (QNH or QFE) and nothing to do with what pressure setting the approaches are based from. We give hPA as standard but can give In.HG whenever requested (usually by the USAF) or, because were clever and think on our toes, we know thats what they will want and we give it to them in the first place.

 

Same as if we get a civil aircraft (excluding GA) we will give them QNH instead of QFE (which we give as standard). This is just how we operate and civil airports in the UK operate very differently. But I guarantee controllers all over the world will have a good idea of what different aircraft they're controlling will require and adapt accordingly where procedures permit.