Altimeter confusion...

Here's a nice little video about basic altimeter principles I found.

[...]

In case any of you were interested. :thumbup:

Awesome! :thumbup:

Let me recap. According to that video, Flight Levels use the ICAO standard atmosphere of 1013.25 hPa as reference. That would mean that the altitude above MSL (and AGL for that matter) for any given Flight Level would change with barometric pressure. Did I understand this correctly? And if so, is this still correct today (the video looks 1950ish)?

Awesome! :thumbup:

 

Let me recap. According to that video, Flight Levels use the ICAO standard atmosphere of 1013.25 hPa as reference. That would mean that the altitude above MSL (and AGL for that matter) for any given Flight Level would change with barometric pressure. Did I understand this correctly? And if so, is this still correct today (the video looks 1950ish)?

Yes, and yes it's still the same.

Does anyone know which altitude is displayed (e.g. MSL) when viewing your aircraft from the F2 external view?

I think that's your true altitude, ie. your actual height over the DCS sea level irrespective of atmospheric conditions.

Yes, and yes it's still the same.

Thanks. :thumbup:

In the mean time, I also looked it up in the Wikipedia, which is also very clear about it:

A flight level (FL) is specific barometric pressure, expressed as a nominal altitude in hundreds of feet. The pressure is computed assuming an International standard sea-level pressure datum of 1013.25 hPa (29.92 inHg), and therefore is not necessarily the same as the aircraft's true altitude either above mean sea level or above ground level.

 

QNH is dialed in at start (as set by the mission editor or generated through current dynamic weather).

 

QNH is not dialed in at start :( no matter what the ME is set at.

Jesus DCS needs to provide QNH somewhere.

QNH is not dialed in at start :( no matter what the ME is set at.

 

Jesus DCS needs to provide QNH somewhere.

Absolutely, that would be great!

As a workaround, I started using the airport charts from the DCS docs folder to set the altimeter to the correct altitude MSL at my departure airport, thus giving me the QNH setting. With static weather, that should give me correct MSL values all over the map.

With dynamic weather and possibly changing air pressure across the map, it isn't worth much, and that's where QNH provided by ATC would come in really handy.

In any case, it would be great if ATC or someone else was able to provide this data - the sugar coating would be if we could request both QFE and QNH (like "Kutaisi, Tusk 1-1, request QNH" and "Kutaisi, Tusk 1-1, request QFE"). :thumbup:

BTW, how is this handled in RL? Do pilots "Request QFE" and "Request QNH", or is this data usually supplied by ATC as part of take-off and arrival communications, so that the pilot shouldn't usually need to request it individually?

As a workaround, I started using the airport charts from the DCS docs folder to set the altimeter to the correct altitude MSL at my departure airport, thus giving me the QNH setting.

I do the same and it's definitely a valid means of obtaining a valid altimeter setting. Real world this is done at non-towered aerodromes when a weather report is not available.

BTW, how is this handled in RL? Do pilots "Request QFE" and "Request QNH", or is this data usually supplied by ATC as part of take-off and arrival communications, so that the pilot shouldn't usually need to request it individually?

In the real world (and talking generic A-10 flying here) the QNH setting would be obtained prior to departure from the Automated Terminal Information System or ATIS which is a recorded message that can tuned on a VHF radio and is specific to each airport. It's updated by the tower controller whenever the weather changes.

En-route, if cruising above the transition altitude (read more here: http://www.skybrary.aero/index.php/Transition_Altitude/Level) you would set a standard altimeter setting of 1013hPa.

If cruising below transition the 'area' QNH would be provided by ATC or if ATC isn't available the forecast QNH would be used - this is obtained from your pre-flight weather briefing.

On approach to a towered airport, ATC would give you the 'local' QNH of the airfield when they clear you to descend below the transition layer. For example: "Tusk11, descend to 4000, QNH 1022".

That's a brief overview of how it's done IRL, hope that helps.

In the real world (and talking generic A-10 flying here) the QNH setting would be obtained prior to departed from the Automated Terminal Information System or ATIS [...]

 

That's a brief overview of how it's done IRL, hope that helps.

Wow, yeah, that helps indeed, thanks! :thumbup:

This really affects the A10 since the ALT SCE is locked at the BARO setting and switching the knob does nothing :(

So now ED implemented QNH but only in inches of mercury and milimiters of mercury! :doh:

No Hpa/Mb???.... ok

Does Russia use Hpa/Mb?

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So that means 0 altitude is the runway?

It's probably the official airfield elevation. At my airport we have a runway that is 153 feet elevation on one end, and 6,500 feet down to the other end it drops to 80 feet elevation. The official field elevation is 153 feet.

+1

 

DCS ATC needs sooo much more love...

Unfortunately, or fortunately, DCS is a COMBAT simulation. There's a very big difference in how air traffic is handled in peaceful airspace verses in a war zone. In a war zone things can be very dynamic. Airspaces can pop up and close down in quick order, complete with command & control authorities that have to be contacted to enter and leave. These airspaces are in conjunction with missions, of course, and are designed to keep friendly fire to a minimum. It's way more complex than nice stable ATC. But, Civilian ATC would be totally unrealistic in a combat environment.This would mostly affect Center Operations. There would still be radar approach control and tower operations that would probably be controlled by military controllers (host nation, Air Force, Navy/Marines, or God help us...dare I say, Army "controllers.")

I do agree with you, however, the approach and tower ops can and should be greatly improved performance wise. But I think it's clear that ED doesn't see it very important. I mean look at the airports. We still don't have functional VASI or PAPI systems. It's more important to ED for players to blow stuff up than anything else in the sim. I don't even bother with ATC anymore. It is so full of bugs.

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