ATC communication

Can someone please explain how the communication with ATC works?

When i get takeoff clearance, i get "Takeoff runway 9, climb 300 QFE 28.43".

How should i interpret that?

Runway designations is no problems, they are named after the general heading of the runway.

QFE 28.43 is what altitude the airfield is located at. But i don't know how to set the altimeter when i get eg. 28.43.

"Climb 300" is the big mystery in my life atm. So please help me :) :joystick:

AFAIK its a WIP leftover from BS ATC comms. QFE is the russian pressure setting. Not sure how its related to the A-10 which has a 4 digit "pressure set knob".

(manual P121 "Rotate this knob clockwise or counter clockwise to manually set a barometric altitude."). That imples that you just put the actual runway alt in there instead of farting about with pressures. Not sure where to find those apart from charts available in the forum. Not ingame)

The "300" is most likely the same BS leftover. Thats high for the shark!

Hmm, changing QNH/QFE on the altitude gauge does not move the needle as it should.

QFE is an altimeter setting given in inches of mercury, mm of murcury or Hecto Pascals/milibars which will equate to your altimeter reading zero on landing at any airport where the QFE conversion is stated.

Simply put -

QFE is the altimeter setting for altitude above the field or runway to be more exact

QNH is the altimeter setting for altitude above mean sea level

Russia is still the only country that I know of that uses QFE as a standard below 18,0000 ft.

For a quick altimeter pressure conversion calculator go here -

http://www.srh.noaa.gov/epz/?n=wxcalc_altimetersetting

My point is still valid however, barometric setting has no effect, non functional.

TBH thats one less thing to worry about for me. That was the least exiting knob in black shark ;)

Looks to me that current ATC communication is not just WIP, but also too simplified and thus non-functional.

First, the runway heading IRL is ALWAYS two digits, like "Runway Zero Niner".

Second, the tower should give you a departure vector, traffic information etc. Hopefully in time we get really decent ATC and comms in general. In my opinion, it should be something between Jane's F/A-18 and Microsoft FSX.

In fact, to my knowledge, Sweden uses QFE as well, but slowly transfers to QNH.

Oh, and "Climb to 300" means you should climb to 300 meters, which is a standard circuit altitude.

My point is still valid however, barometric setting has no effect, non functional.

Actually it does have effect, I hadn't noticed it either but in a mission I created I was using the ATC coms coming back to the airport when I got the altimeter setting from the tower which was much higher than what I had set. I then noticed on starting the mission again that the altimeter wasn't climbing right after liftoff, resetting the altimeter to the setting ATC had used earlier fixed the problem.

I've also discovered that if you create any altitude triggers that they are based on the altimeter setting in the mission in meters.

Lastly, the altitudes in the Mission Editor and stated in ATC instructions are in meters and do not correspond to the altimeter in the aircraft.

Concerning altimeter settings this might clear the story up a bit...:

In general all ICAO associated countries(that's nearly the whole world, not sure about russia tough) use the standard icao regulations concerning altimeter settings. Basically it works this way:

As Ronth pointed out there are several altimeter settings:

QNH = pressure above mean sea level

QFE = pressure at altitude of current airfield

QNE = standard pressure setting according to ISA which is 1013,21 hectopascal

The pressures can be given either in hectopascal or inches of mercury they are different units but represent the same pressure. In europe hectopascal(hpa) is used, not sure about the rest of the world.

1 hectopascal is +- 8 meters which is +- 26 feet.

The altimeter setting defines at which pressure your altimeter indicates 0. So when the pressure on the ground at an airfield(this would be the QFE) is 1018 hpa and you are standing at that airfield and set the altimeter at 1018 hpa the altimeter should indicate your altitude as 0 feet.

The regional ATC defines a transition altitude(TA) and transition level(TL). When departing the altimeter is set to the local QNH(pressure above mean sea level) which is given with the startup clearence and is also pronounced in the local ATIS. The TA/TL are given in the ATIS aswell but are not given directly by the ATC(nor with ifr flights).

When climbing after departure and passing the TA you should enter the QNE(1013,21 hpa), this is not instructed by the ATC but a standard procedure any pilot(civil/mil) should perform.

When descending through the TL you should enter the local QNH which is given to you by the ATC, e.g. "PH-WNM descend to 3000 feet, local qnh 1013"

Now when above the TA/TL everybody has the same altimeter setting: 1013,21hpa and this is obviously for a reason. When above the TA/TL the ATC does not give altitude instructions in feet but in flightlevels(FL), 100 feet is 1 flightlevel so FL100 = 10.000feet and FL55 is 5.500feet.

When an ATC seperates 2 aircraft flying in the opposite direction by giving them a 500feet altitude difference(minimum alt seperation for ifr flights) and they both have 1013hpa the ATC can be sure that the aircraft will pass each other with no harm.

If this wouldn't be done imagine what could go wrong.

The N123A is flying at FL120 with the local qnh from his airport which is 1010hpa.

The PH-WNM is flying at FL125 with the local qnh from his airport which is 991hpa.

They should have 500 feet altitude seperation: FL125-FL120 = FL5 = 5 x 100 feet = 500 feet.

But they have different altimeter settings: 1010hpa - 991hpa = 19hpa = 19 * 26 = 494 feet.

Due to their different altimeter settings the PH-WNM actual altitude above mean sea level is only 6 feet higher than the actual altitude above mean sea level of the N123A.

So basically the ATC has seperated them with 500 feet altitude difference but due to invalid altimeter settings they actually only have a 6 feet altitude difference which would obviously be very very dangerous and would nearly certainly result in a collision...

The standard TA/TL is 18.000 feet / FL180 but in some countries their are different standards. For instance in the the Netherlands the TA/TL is somewhere between 4000 and 7000 feet / FL40 - FL70.

Good effort.

But minimum vertical separation is 1000ft. It used to be 2000ft above FL290 prior to RVSM.

Allright, here’s the longwinded explanation with a bit of trivia thrown in. Some (most) of it duplicates the previous post, with a few minor corrections which are, by and large, without practical importance.

An altimeter does not measure altitude. It measures the pressure difference from a set reference level and displays this pressure difference. However, as the pressure drop as you climb through the atmosphere is rather well known, you can put a scale on the instrument which is in feet of altitude rather than units of pressure. Et voila - an instrument which shows your altitude above a reference level.

To get correct indications, you need to tell the instrument what the pressure is at this reference level. That's the altimeter setting.

In civilian aviation, you are mainly concerned with staying clear of terrain and being separated from other traffic. Thus it makes sense to use an altimeter setting which displays your altitude above mean sea level. The QNH altimeter setting is the reference pressure which will give you the threshold elevation when parked at the threshold. It is the pressure at mean sea level*. Very handy, as it means you will be 1000 feet above that peak reaching up to 3430 feet if your altimeter reads 4340 feet. This altimeter setting is given by ATC when they first clear you to an altitude, and also whenever it changes.

Now, military aviation have different priorities. They are concerned with getting back to the aerodrome safely, but they want to be self-reliant and do not want to depend on knowing the exact altitude of the aerodrome or someone else calculating reference pressures for them. They also tend to land at the same aerodrome from which they departed. Thus it makes sense to just use whatever altimeter setting gives a readout of zero feet when they are parked at the runway threshold. That altimeter setting is the barometric pressure at the threshold, and is known as the QFE. While they could switch to QNH when operating in civvie world, many don't.

Flying in the bush, QFE also makes good sense. You can't get QNH when not in touch with ATC and when the elevation of the field is not known. That's probably the reason for gliders sticking with QFE, at least in my neck of the woods, and I'd assume the reason for Russia using QFE as well.

The merits of having a correct altitude from a reference altitude hold until you are well clear of all terrain. Once clear of terrain, it's a terrible chore having to keep your altimeter setting updated as you traverse different control zones with different reference airports. It also creates a risk of separation loss between aircraft, as excellently described above. If cumulugranitus is not a factor, it is much more convenient to simply use a standard setting - and to use this for all traffic, to ensure separation without having to bother with updating the altimeter setting all the time. This standard setting is the normal standard atmosphere pressure at mean sea level – 29.92 inHg (inches of mercury) or 1013.25 mbar – and is known as QNE.

When climbing, you set your altimeter to QNE (1013.25) as you’re given (or, if uncontrolled, aim for) your first flight level. There’s a transition altitude (TA), which is the highest altitude. Above this altitude, it’s all in hundreds of feet, or flight levels. For Bitumi, the TA is 7000 feet. In other words, if you want to fly at 7000 feet or lower, you keep the QNH or QFE setting. If you want to fly at 9000 feet, you switch to QNE and refer to 9000 feet as FL 90.

Coming back down, there’s a transition level. This changes as the barometric pressure changes, to maintain 1000 feet of separation between the lowest flight level and the transition altitude, and is thus given by ATC. This can be by radio but is typically in an automated transmission of weather and other important information known as an ATIS (Automated Terminal Information Service, “XXX information Delta Weather at XXX … ILS runway 13 in use Transition Level 80”). You will know when to switch though, as you’ll be cleared down to FL110 (“descend FL110”) and then to “descend 4000 feet, QNH 992”.

The Q codes are known as – surprisingly – Q codes. They stem from the days of using Morse code to communicate, and there are gazillions of Q codes for various things. Other well known Q codes in aviation are QDR (QD Romeo) and QDM (QD Mike) which mean bearing from and to a station, respectively.

Another important point to understand about altimeters is that they will misread if the atmosphere is not equal to the standard atmosphere the altimeter is calibrated to. Remember, it is measuring the pressure change and displaying it as feet of altitude. If the pressure change with altitude in the atmosphere is not as per the atmosphere standard, your poor altimeter's assumption on how to translate pressure differences into altitudes are not completely valid anymore. In theory, you need to apply a temperature correction to all altitudes used to remain clear of terrain when the temperature drops between the sea level standard of plus 15 degrees centigrade. In practice, I don’t think many people bother while it is above freezing on the ground. It is a bit of a mess, as both the altitude and the altitude above the reference aerodrome play a part. In A-10, you can ignore this altogether.

*) Assuming a standard atmosphere between the aerodrome and mean sea level - if you do not understand this distinction, don't worry about it. It is of little practical importance.

BTW, RVSM is AFAIK not in place worldwide as of yet.

Good expaination Exangelus and BlueRidgeDx is correct regarding the seperation, it's basicly 1000ft unless you're in a non- RVSM environment then it's still 2000ft.

Russia is the only country that I'm aware of currently using QFE as a standard below transition level.

Russia and China still use altitudes and flight levels based on meters instead of feet and transition levels/altitudes vary from country to country and at times airport to airport within the same country depending on the altimeter setting.

Even better effort!

I might mention that at least in the US, the military uses QNH just like everyone else.

There's a caveat of course, in that the A-10 will set the altimeter to whatever is required in order for the altimeter to read TDZE during takeoff (QFE).

They do this so the IFFCC can take a Delta update during the takeoff roll - it happens automatically at about 70kt. After takeoff, they're supposed to return to QNH in order to ensure appropriate seperation.

Thanks for the correction on minim seperation altitude which is indeed 1000ft ;)

This might be a bit far off the hook but effte mentions gliders primarily use QNE but this depends. With local flights sticking to the airfield of departure(typically maximum 5 km out) they indeed use QFE but during cross-country flights they do use QNH but typically take the QNH from the departure field and than they won't change it until just before landing or when crossing controlzones or tma's...

Regular VFR traffic is 90% of the time in contact with a FIS and get constant QNH updates but due to the growing numbers of cross-country flying gliders the FIS get rather tired of handling all the unpredictable gliders that in general gliders are requested not too contact FIS for flight monitoring but only if they directly need information.

And one minor correction. When any aircraft(@effte, you mentioned this in particular to mil aircraft) set their altimeter subscale to QFE when departing they will have to set it either to a new QFE or local QNH provided by the ATC because after a flight of several hours the pressure at the same airfield might have dropped or raised quit alot(up to 10hpa in a single day!!) due to temperature differences and moving pressure systems which makes their original QFE from the beginning of the day bogus..

Yeah, I semi-knew about the USAF using QNH (and probably many other air forces) but I guess I self-censored myself and left it out. ;)

Whoa... interesting about the delta reading! I'm a sucker for systems trivia. Is this simulated?

BTW, the plates for Batumi show the LOC frequency as 110.3, while DCS has it at 110.15. Any suggestions on the right forum part for posting that particular discrepancy?

Haha well self-cornering is a healthy action; we all do now and it thus increases our IQ with another millipercent! :P

With delta reading you mean deltagliders? I'm talking about gliders as in soaring planes ;) I'm a fanatic glider pilot, the pic is one takes last august during a competition I participated in :D

Some of this sound right but some of it wrong. I was a controller in the USAF about 17 yrs ago so my knowlege is a bit dated.

Seems to me we never used flight level (FL) until altitude was over 18,000 feet. Flight level was thousands of feet.

Altimeter was always given in inches mercury without saying the decimal point IE:" Runway two one in use, altimeter two niner niner two, wind two seven zero at one zero"

Simulating ATC in and of itself would be a whole nother simulation. There are mountains of information you have to know as a pilot or controller, stick to the basics. I'd rather see game development time spent on battle simulation than ATC.

What happens when I blow your radar up or it gets shut down? Non radar traffic procedures.....eeeeewwwww.....booring and it makes your brain hurt lol

Seems to me we never used flight level (FL) until altitude was over 18,000 feet. Flight level was thousands of feet.

TA is 18.000 in the U.S. Due to the Rockies, I think, and the peculiar inability to cope with different sectors with different TAs. ;) Most of the rest of the world it varies depending on the local terrain, and is generally far lower. As I said, 7000 feet at Batumi.

Flight levels are hundreds of feet. FL90 = 9000 feet. 19.000 feet = FL190. Should come back right about... now... and that's where the facepalm comes in handy. ;)

Altimeter was always given in inches mercury without saying the decimal point IE:" Runway two one in use, altimeter two niner niner two, wind two seven zero at one zero"

Again a US thing. Rest of the world, I think you'll find mbars the standard in most places.

"ABC123, descend 4000 feet, QNH 992"

"Uuuuuuh... could you give us that in inches, ABC123"

"Sure. ABC123, descend 48.000 inches, QNH 992"

:P

I agree with effte, I'm not a professional(as a job that is) pilot nor controller but do have logged quit some hours in gliders and are 100% confident the info from effte and me is accurate. And seventeen years is alot of time, especially in aviation, things change.

And indeed the TA/TL is depended on the terrain, here in the Netherlands the highest point is I believe +- 200m amsl and the lowest +- -70m amsl :P and therefore the TA/TL is between 4000 and 7000 feet..

Hey guys,

I fly for a living and have experience flying in several countries around the world. Much of what has been stated here is accurate while some of it is a little off.

The transition level in the US has more to do with controlled airspace (above 18,000ft) and uncontrolled airspace (below 18,000 ft outside of any airport control zones or terminal control areas)

In other countries this is not the case as the transition level can change from region to region or airport to airport and in many cases the transition level can vary based on the altimeter setting even though the airspace below transition level is also controlled airspace.

Russia is the only country that I know of currently using QFE settings below transition level. It's also important to understand that QFE settings can be different for different runways on the airport. As an example, Moscow's Domodedovo airport with parallel runways provides different QFE altimeter settings for each runway because the touchdown zone elevation differs between runways.

Foreign carriers who don't operate on QFE use QNH altimeter settings and a conversion chart to descend to the appropriate altitudes.

Most countries outside the US issue altimeter settings in hecto pascals and QNH inches or will provide QNH in inches on request. The US operates strictly on QNH inches but can provide hecto pascals on request.

Most countries assign altitudes in Feet while China, Mongolia, Korea and Russia and a few others use meters, although their flight levels may be aligned differently ie. you can fly 10400 meters in China but would have to transition to 10600 meters when transitioning into Russian airspace.

I know we're getting a bit off track here for what's used in the simulator, but I just wanted to mention a few of those things from my experience.

FL90 is 90,000 feet, not 9,000. Above 18k is when you get to using flight levels. I know this because I just logged 2 sorties this week.

Whoa... interesting about the delta reading! I'm a sucker for systems trivia. Is this simulated?

The Delta mode is certainly simulated, though I don't know about the automatic update during takeoff. I would assume it's there, because you have the ability to go into the Delta Cal submenus with the IFFCC switch in TEST. So evidently, they've fleshed the system out pretty well.

BTW, the plates for Batumi show the LOC frequency as 110.3, while DCS has it at 110.15. Any suggestions on the right forum part for posting that particular discrepancy?

I actually mentioned this error in another thread that ended up getting pretty badly derailed. It had to do with ILS frequencies and the associated DME channels. I'm not sure that anyone from ED ever actually acknowledged the issue, but they probably know about it...I think.

Not sure which forum would be best...General, Avionics, and Model Errors seem like good candidates to me. I reserve the right to be wrong, though.

FL90 is 90,000 feet, not 9,000. Above 18k is when you get to using flight levels. I know this because I just logged 2 sorties this week.

Hmmm. Do you do much international flying?

FL90 is a perfectly valid altitude depending on where you're flying in the world. In much of the rest of the world, as has been stated several times in this thread, the Transition Altitude is much lower than the standard 18,000ft here in the US.

FL's below 180 look weird to us Americans, but they exist. It would be a little less ambiguous if they put in the leading zero, but they don't. As such, FL90 is translated as 9,000ft. FL900 would be 90,000ft.

Hmmm. Do you do much international flying?

 

FL90 is a perfectly valid altitude depending on where you're flying in the world. In much of the rest of the world, as has been stated several times in this thread, the Transition Altitude is much lower than the standard 18,000ft here in the US.

 

FL's below 180 look weird to us Americans, but they exist. It would be a little less ambiguous if they put in the leading zero, but they don't. As such, FL90 is translated as 9,000ft. FL900 would be 90,000ft.

I've flown international with the USAF plenty of times. Most of my hours logged were accomplished overseas. I was speaking for US standards.

Ok, well, no harm no foul.

But to be fair, I thought his post pretty explicitly addressed US vs. International procedure and usage.

No biggie. I'm just sayin'. :)

PS - Can you say what you're flying? I'm not sure FRED can generate 2 sorties in a week, lol. So that leaves Tankers, Herks, and a few things that start with "E".