DAMN IT. I JUST DONT GET QFE 2 QNH SETTINGS in F-5E

Again: QNH is always in the briefing. (Static weather)

Just a little release for the guys that get frustrated: DCS calculates the height for the altimeter slightly incorrect. This bug has been reported. The impact on flying in VMC is little but calculating things for an IFR flight is almost pointless at the moment.

For OPs question:

Do not listen to ATC, set QNH, check recovery airfield charts for elevation and go with that! Fly safe!

I don’t really understand all this ignore ATC/QFE thing here. Surely it is easier setting to QFE of landing runway rather than having to mentally calculate altitude from QNH and runway height. No?

Imakan, lots of people (me being one of them) have no use for QFE having spent whole lives/careers/ etc using QNH, as outside of Russia the entire rest of the world uses QNH. Additionally, as has been mentioned, all of the published instrument approaches for the Caucus and Nevada are written to use QNH. Finally, as has already been covered in this thread multiple times, most western aircraft aren’t made for QFE. For example, the F5 altimeter only rolls down to 28.10. This means, given ISA conditions, the F5 CAN NOT use QFE at fields above ~1800 MSL.

Also for the OP,

Dave, I think you are making things much harder on yourself than you need to by keeping your F10 map in metric. The only device on your aircraft to show your altitude indicates feet above mean sea level. The only device on your aircraft to measure distance for the purpose of radio navigate indicates nautical miles. The idea that metric units are somehow related to a JTAC/CAS call (outside of adjustments like drop 50, left 100, etc) is incorrect. The Army and the Marines use the same 9 line format to call for CAS. Line 3 of a fixed wing CAS request is the distance from the IP to the target in nautical miles. Line 4 is the target elevation, given in feet above mean sea level. No where in a 9 line fixed wing CAS call is a metric unit used.

If you are just flying the F5 I can’t see any reason to use metric units on your F10 map at all, maybe that could help reduce some of these headaches.

No where in a 9 line fixed wing CAS call is a metric unit used.

Line 8? :smartass:

I agree with most of what you said. But following many, many discussions on the topic, I've read numerous times that some airlines as well as some places in the western world do indeed prefer QFE to this day (well, as of two or three years ago, when I last followed such a discussion).

I'd say in DCS it's really pilot's choice, as long as the pilot understands the systems (QNH, QFE, standard pressure setting), their limitations and when not to use them.

Having said that, personally I also prefer QNH over QFE at all times, including VFR. Knowing height above the airfield doesn't help me shoot a 3° approach unless I also know the proper distance, which requires either a chart based on height above aerodrome, or proper visual references, in which case I don't really need the altimeter anyway. :P

My exceptions to "at all times" would be local flights and, most of all, aerobatics, where the barometric altimeter would be more reliable than the radar altimeter (if the aircraft even has one) when the fuselage doesn't point to the ground.

Yurgon, you do indeed have me on line 8, I was incorrect there. Never let it be said I am not gracious even in defeat haha. Safe flights!

:thumbup:

Imakan, lots of people (me being one of them) have no use for QFE having spent whole lives/careers/ etc using QNH, as outside of Russia the entire rest of the world uses QNH. Additionally, as has been mentioned, all of the published instrument approaches for the Caucus and Nevada are written to use QNH. Finally, as has already been covered in this thread multiple times, most western aircraft aren’t made for QFE. For example, the F5 altimeter only rolls down to 28.10. This means, given ISA conditions, the F5 CAN NOT use QFE at fields above ~1800 MSL.

I appreciate and understand your comments. However, that doesn't mean that using QFE, where appropriate, is not a legitimate tool to use. Surely just a matter of preference.

Imacken, I feel like this thread is slipping into a QNH v QFE discussion; while that is no doubt valuable and I am guilty of helping it go in that direction, it is missing the point that in the scenario posed by the OP QFE is not a valid solution, it is physically impossible to use.

Regardless, I certainly didn't intend to talk you out of a technique that clearly works for you and many others and if that is how I came over, rather than just stating why I prefer QNH, my bad.

I used to have to train on this in the real world as there are many aircraft that don't have the capability to set QFE at high elevation airports (Like the F5E in DCS)

It sucks.

Jeppesen charts provide runway elevation in the pressure units for the field you are using as in the example below.

Tbilisi reports pressure in Hectopascals (hPa) and the runway elevation is 58 hPa above QFE pressure (or you can set 58 hPa below QNH to get QFE)

Of course you need an hPa to Inches of Mercury (Hg) to Millimeters of Hg chart handy for all this unless your altimeter has a hPa/MMhg window

DCS needs a complete set of Jeppesen approach charts I guess. they also have a ton of other workarounds for Western aircraft on them as seen below.

PMCELI OK, I am lost again.

"Tbilisi reports pressure in Hectopascals (hPa) and the runway elevation is 58 hPa above QFE pressure (or you can set 58 hPa below QNH to get QFE)

Of course you need an hPa to Inches of Mercury (Hg) to Millimeters of Hg chart handy for all this unless your altimeter has a hPa/MMhg window"

What , what, and the what?? Now, I beg you, explain in plain English what one has to do to set the Altimeter correctly in DCS: F-5E. While airborne and some distance, say 50 nm, from Tbilisi airport in DCS.

Convert hPa 58 into what number and add to what number? The QFE from ATC?

I do not , at all, understand, how runway elevation is given in hPa. hPa is air pressure. Runway elevation , above MSL, is a constant. Air pressure is variable depending on time of day, and weather. None of this makes any sense to me. If I was sitting in a classroom at Emery Riddle Aeronautical university,

I have this chart with Runway elevation of 58 hPa, and I receive some QFE number . Is there a math formula I have to do. Or a look up table

Here is conversion, but it makes ZERO sence to me , as what I have to do to get correct Altimeter setting.

https://www.sensorsone.com/inhg-to-mmhg-barometer-conversion-table/

Certainly, you add 58 hPa of pressure to whatever is reported QFE to get estimated QNH. But real life Tbilisi is 1,624' while DCS Tbilisi is 1,532'. So DCS would have a 54.85 (call it 55) hPa number instead of 58 on the paper.

If QFE is given X'' Hg then X+55 hPa is X+0.162''Hg. (1 hectopascal = 0.029529... inch of mercury). Did this at Tbilisi with QNH 29.92'' Elev. 1532'. QFE is 28.30". Reported altitude at 1532' with estimated 29.92'' (28.30+01.62) setting is 1539'.

So one could make a table of "Hg (or mmHg, mb, atm, psi) to add to every airfield in the game. For most situations it would be pretty accurate. If you doing this in your head maybe multiply by 3 for hundredths of inHg (55x3= 165 hundredths inHg or +1.65"). For this approximation in Tbilisi case the error is about 14'.

I'm really amazed how no one in this whole topic was able to provide a clear and concise answer that a 6 year old would understand. The OP asked several times to use an exemple from a situation in game, instead we have lot of folks trying to show off their superior theory knowledge on the matter. I'm not (really) throwing at you any rock guys, but it would be greatly appreciated if you abstained from replying if you're not able to provide an effective answer. While theory is required to fully understand how the system works, we - humble human beings - need some real situation context to understand those principles as a whole.

I'm sorry Dave to not helping you but I'm sharing your boat here. Nonetheless, your question is a very good exemple of how mediocre is the F-5E manual (and from what I read on the others subforums, this is a general consensus among modules). I really enjoy mastering a module and I've been myself hold back because of topics non discussed or lightly explained in the flight manual. Comprehensive flight manuals should be mandatory in a sim like DCS.

I'm really amazed how no one in this whole topic was able to provide a clear and concise answer that a 6 year old would understand.

DaveRinder, QFE is just a method of turning a barometric altimeter into a poor man's radar altimeter so it reads 0 when touching down at the airfield the QFE value is associated with. Instead of measuring your altitude above sea level, a QFE setting is essentially adjusting the altimeter pressure knob so that the barometric altimeter needle reads 0 while on the ground. It may not be possible to adjust the altimeter to such a value if the airfield you are taking off from is higher in elevation, or the altimeter pressure setting itself wasn't designed to perform this way and has a narrower selection band.

 

Further, if you are flying an aircraft with a dedicated radar altimeter readout, than a QFE setting on your barometric altimeter is pointless and redundant.

 

However, if you want the correct pressure altimeter setting in your barometric altimeter, and don't want to do all the fancy math, all you have to do is, prior to takeoff, adjust the pressure setting until the barometric altimeter matches your current field elevation. You can do this by referencing the airport info in F10, or by checking your elevation in the info bar while in external view. Setting the barometric altimeter to match field elevation is a common practice in real-world aviation when weather reporting or ATC is unavailable, like a small un-towered airstrip in the countryside.

 

If you are doing a mission starting in the air, you can check the QNH readout in the brief, or put the aircraft in level flight, check your aircraft elevation in external view or the F10 map, and adjust the barometric altimeter to match.(...)

That pretty much sums it up... and there is a reason, why 6 years old are not allowed to fly airplanes. :D

Comprehensive flight manuals should be mandatory in a sim like DCS.

Flight manuals are covering the individual aircrafts systems, performance and DCS specific interactions. They are by no means a "Learn how to fly" guide, and honestly, they are not required to, as there are so many publicly available guides and manuals out there to teach you basic airmanship.

So in the manual you will find where the knob for the altimeters pressure adjustment is, but the intricacies of QFE vs. QNH are covered in more basic publications.

The original poster somehow answered his question in post #5

(...)"Minumum QNH? altmeter setting on DCS:F-5E is 2810."(...)

So if the barometric pressure in the F-5E cannot be set lower than 28.10 it is not possible to set a QNH or QFE below 28.10... :smilewink:

 

On this mission at arrival field, elevation 1360 meters/4460 feet. That means that if set on ground the altimeter setting is 2968.

So how in the bloody hell do I take ATC QFE of 25.23 and turn it into correct QNH altimeter setting of 2968 or 29.68 .

For the theory part: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/14_phak_ch12.pdf

From the above: "Since weather stations are located around the globe, all local barometric pressure readings are converted to a sea level pressure to provide a standard for records and reports. To achieve this, each station converts its barometric pressure by adding approximately 1 "Hg for every 1,000 feet of elevation. For example, a station at 5,000 feet above sea level, with a reading of 24.92 "Hg, reports a sea level pressure reading of 29.92 "Hg. [Figure 12-8] Using common sea level pressure readings helps ensure aircraft altimeters are set correctly, based on the current pressure readings."

Now for the example, field elevation is 4460 feet and QFE is 25.23. If you do want your altimeter to read zero when on the runway you must set the QFE. This is out of range for the F-5 altimeter as you have observed. Now if we want to see field elevation on the altimeter we must set the QNH. Your question is how to obtain QNH from QFE. Since we do know the elevation is 4460ft and the Pilot’s Handbook of Aeronautical Knowledge told us 1000ft elevation is approx 1inHg we can make a rough calculation and ad 4.46inHg to the QFE 25.23 and find 29.69 for the QNH. Not too far from the 29.68 you found by experimenting.

The FAA's Pilot’s Handbook of Aeronautical Knowledge is free to download and is an excellent read for DCS players with limited or no RW aeronautical experience.

 

(...)"Minumum QNH? altmeter setting on DCS:F-5E is 2810."(...)

 

So if the barometric pressure in the F-5E cannot be set lower than 28.10 it is not possible to set a QNH or QFE below 28.10... :smilewink:

Thanks Shagrat :thumbup:

AHH... Thank you. But I do not understand what you are describing.

I get a QFE of say 25.53. 58 + 25.53 = 93.53 which already sounds wrong.

"QFE is given X'' Hg then X+55 hPa is X+0.162''Hg. (1 hectopascal = 0.029529... inch of mercury)." ????? What does this mean?

58 * 0.029529 = 1.712682

So bligh me! I am not understanding what in the bloody heck you are describing. Where is .162 coming from?

I am just amazed that this is that complicated.

... = 93.53 which already sounds wrong.

 

...

I am just amazed that this is that complicated.

Yes that is wrong. Forget the 58. That is hPa. Your altimeter is in inHg. Do not waste time converting hPa to inHg.

Answers were given here https://forums.eagle.ru/showpost.php?p=3391542&postcount=8

and here https://forums.eagle.ru/showpost.php?p=3395207&postcount=40

It is really simple.

Have you tried googling "qfe to qnh conversion"? The first hit (stackexchange) explains it pretty well. As long as you are able to find the airfield elevation and have a calculator (for dividing by 30 or 900), the conversion is pretty straight forward.

Thanks for linking to my post Dolfo, I was starting to think no one actually read it haha. Rep inbound for the PHAK reference. And +1 to not worrying about hPa in this case.

The original problem was DCS ATC gives pressure in QFE. The F-5 altimeter cannot set QFE for high elevation .airports.

There is no solution to this problem that results in the F5 altimeter reading zero at touchdown at a high elevation airfield.

All other remedies require that you know the field elevation and math.

QNH is QFE plus field elevation. The field elevation becomes your new zero when QNH is set.

It is that simple.

What is required are accurate charts and the ability to correctly apply them, same as the real world.

DCS has no cartography department. Trying to fly IFR in a simulation that has no accurate charts is why this thread seems so confounding.

If you cannot set QFE then you MUST know field elevation and derive and set QNH and convert everything accordingly. There is no “easy” solution.

The OP never asked how to make the altimeter show zero when the aircraft is on the ground. He asked how to convert QFE to QNH, just look at the very title of the thread. "DAMN IT. I JUST DONT GET QFE 2 QNH SETTINGS in F-5E"

Also from the first post...

DAMN IT. I JUST DONT GET QFE 2 QNH SETTINGS in F-5E

 

So how in the bloody hell do I take ATC QFE of 25.23 and turn it into correct QNH altimeter setting of 2968 or 29.68 . I am not seeing any relationship where 27 or 30 goes into.

 

No cartography department so that means we have no plates? The 476th would disagree with you.

476 vFG Flight Info Pubs Their TACAN approaches and SIDs out of Vaziani are a riot.

Plus you don't need charts, even on a server with no own ship on the F10 map you can always see field elevation of the field you will be landing at.

To convert QFE to QNH there is an easy solution. Dolfo and I have both covered it. Field elevation in MSL of landing airport divided by 1000. Round this number to two decimal places, add it to QFE. Put this in the Kollsman window, you have QNH. Not simple? Move a decimal point three places left and add. I can do that in my head and I am terrible at mental math.

Two people have answered the OP's question and shown the math using the scenario posed by his original post. Our work is visible, if it is wrong please explain how. I'm not trying to be contentious but much like 33-DFTC I am floored that this thread can possibly still be going on.

"QNH is QFE plus field elevation. The field elevation becomes your new zero when QNH is set."

OMG! OK I starting to beleive that, in fact, I am an idiot. But the above make no sense to me.

Pmiceli QFE is Quiery Field Elevation. Field elevevation is in feet or meters. QFE , as given by ATC is a pressure deviation. Lets say QFE, from ATC , as 25.53. Field Elevation is 1000'.

So per your formula its 25.53 + 1000 = 1025.23 which makes no damned sense whatsoever. That is my stumbling block, as reading on this on net and here, is that apple units of measurement + orange units of measurement = sour grapes. I am looking for a simple straightforward formula, to properly set Altimeter, and no explanations I have gotten so far makes any frigging sense to me.

Prior to the posting of Tbilisi approach chart, I understood procedure for setting Altimeter, prior to landing as;

((Elevation of field in feet) / 1000 ) + QFE as given from ATC.

So for field at elevation of 1000' above MSL with QFE from tower as 25.23.

(1000/1000) + 25.23 = 26.23. Then I find F-5E altimeter cannot go below 2810. So as I see it my understanding is deeply flawed.

Now back to the chart. Tbilisi airport is at elevation of 58 hPa. As soon I saw that , I had a WTF!! moment. Everything I thought I got, I did not. Becouse does it mean for elevation to in pressure units , hPa is heptapascals. What do I with number where does it go, what is it converted into. As per your explanation of QNH as QFE + field elevation . So for QFE of 25.25 + 58 = 93.25. An impossible setting.

So what do you mean when QNH=QFE + Field Elevation? This is a basic question and I am getting nowhere. Explanations and definitions do not make any sense to me.

" The field elevation becomes your new zero when QNH is set." As described it is incomprehensible. What new zero, what was old zero. Zero AGL?

Please take a look at this conversion table.

https://www.sensorsone.com/inhg-to-mmhg-barometer-conversion-table/

I don't see anything usefull as it relates to setting altimeter.

Then there is this.

https://www.pprune.org/tech-log/244661-qfe-qnh-conversion.html

Likewise, the explanation yields impossible to set numbers.

(Field elevation in feet /30) + QFE = QNH altimeter setting. Does not work, or I am misunderstanding something basic.

 

Prior to the posting of Tbilisi approach chart, I understood procedure for setting Altimeter, prior to landing as;

((Elevation of field in feet) / 1000 ) + QFE as given from ATC.

So for field at elevation of 1000' above MSL with QFE from tower as 25.23.

(1000/1000) + 25.23 = 26.23. Then I find F-5E altimeter cannot go below 2810. So as I see it my understanding is deeply flawed.

 

Hi Dave, please stop trying to do anything with hPa or anything that involves dividing anything by 27 or 30. You have the math correct in your above example. The problem with the scenario you pose is that if a field with an elevation of 1000 feet had a pressure setting that low it would be in one of the worst hurricanes ever recorded- that is the only way to get that low of a QNH setting. If you try your math again with a more reasonable QNH like 29.50 (QFE 28.50 in this example) you will see that you are doing it correct, you just chose an unrealistic QFE as a base point for that airport.

AHH... Thank you. But I do not understand what you are describing.

I get a QFE of say 25.53. 58 + 25.53 = 93.53 which already sounds wrong.

 

"QFE is given X'' Hg then X+55 hPa is X+0.162''Hg. (1 hectopascal = 0.029529... inch of mercury)." ????? What does this mean?

58 * 0.029529 = 1.712682

So bligh me! I am not understanding what in the bloody heck you are describing. Where is .162 coming from?

I am just amazed that this is that complicated.

It isnt complicated.

QNH is QFE plus field elevation. If you arent on the ground the only way to accurately set the difference is to know how to convert field elevation to its pressure equivilent.

You must know the field elevation and how to make the conversion accurately.

In the real world we relied on a chart such as the example and either an altimeter with dual windows (hPa and “ Hg) or a conversion chart. This was mostly a training exercise in the classroom because every weather station has QNH instantly available.

Your 58 hPa to “ Hg was wrong. If you do the math wrong, you will never understand what is going on.

58 hPa is 1.71 inches of Mercury not .162.

For enroute operations 100 feet per tenth of an inch of mercury is a close enough approximation. So if QFE is reported as 28.10 “Hg at an airport elevation of 2000 feet, QNH is approximately 30.10 “ Hg

For instrument approaches, that is not precise enough. In the real world, if you cant get the local altimeter setting you either can’t fly the approach or you use the altimeter setting from a nearby source and add a correction to the approach altitudes.

Places that use QFE ( no one anymore IIRC, even Russia is QNH) would provide QNH on request.

In DCS, you are going to need to have QNH or the ability to convert QFE accurately using known field elevation or the runway elevation for the instrument approach you plan to use.