Hi all,
Does anyone find the short distance you can pick up the VHF ATIS current airfield weather conditions unrealistic. From past experience in the real world at cruise altitude of, say FL350, ATIS information can generally be copied at distance over 100NM from the airfield. In MFS sometimes at a busy airfield you cant copy the ATIS until you are only 20NM away. It is a bit of a rush to replan the approach when the Runway has changed from that briefed and expected.
This may be a bug that hasn’t been addressed as yet.
An Airport VHF Atis originates from a Transmitter at the airport, and has a limited range (on purpose), so that other further away airport can be on the same Atis Frequency.
While the Atis range will increae with Altitude, it is certainly not 100nm !
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Automatic Terminal Information Service (ATIS)
Arrival ATIS transmissions on a discrete VHF radio frequency are engineered according to the individual facility requirements, which would normally be a protected service volume of 20 NM to 60 NM from the ATIS site and a maximum altitude of 25,000 feet AGL.
Sorry N6722C but I was a Flight Engineering officer on B747 200-300 for many years and I can assure you that an ATIS was generally picked up well before top of Descent so that the landing data and approach briefing could be completed. If you were cruising at FL350 by simple maths using a 3 degree descent profile you would start your descent at 105NM. The ATIS would be copied well before that. It was my job. My point is, during an approach in MFS to Heathrow, the ATIS was not picked up until almost approach was commenced, unrealistic in my view.
I agree with the OP. Back when I got ATIS over the radio (it’s via ACARS these days) we would receive it well over 100NM out. Otherwise you can’t prepare the arrival and approach. It’s supposed to give you advanced warning of what’s going on at the airport, not be a surprise sprung on you at the last minute.
Personal Comments and Observations
Whether or not you agree with the physics, the sim limit for ATIS VHF LoS is about 60NM at the outside, even at FL310. That’s just a “sim-ism” to steal someone’s very apt term.
D-ATIS doesn’t exist, and neither do dispatchers who could call the info up out -of-band.
You can however pull METAR for the Dest, and derive likely active. You may end up picking the wrong STAR but given ATC doesn’t even care about your Arrival choice, that’s not really a game breaker.
True. But can it be fixed to be available at a more realistic range. For a little bit more sim-ism realism.
There is a Wishlist for it.
Yes correct. The runway in use which comes on the ATIS is most important so you can plan your approach. Using the wind direction from the Metar to select your runway is a hit and miss affair. Many times after picking up the ATIS at 20 miles or so there has been a change in the runway which results in a bit of a panic. Not unlike the real thing! If you are talking to ATC you can always ask for the runway in use, but unless you are on Vatsim this option is not available.
Maybe the more precise issue with MSFS ATIS is that the range is Fixed to 60nm, irrespective of relative altitude between the airport and the aircraft ( and of course MSFS does not take into account any “line if sight” rules, wrt terrain)
(Excluding the terrain line of sight), Not a difficult thing to program – been done before in FSX Mods.
That’s not to say the Terrain line of sight should not be modeled, - its just takes another level of calculation.
It would also be more realistic, if Noise was introduced with increasing range, on both the ATIS, as well as the Nav radio audio .
Again, not a difficult task, once again, it was done with FSX Mods.
I do not believe that the actually programming of these features is difficult (OK, I know, because I have done them in the past as a Mod in FSX), but rather the difficulty is for a traditional fantasy games programming company, to adapt to real work simulation, and acquire the required aeronautical expertise, or even appreciate the importance and existence of such physical phenomena.
VHF communication systems are the most widely used for maintaining contact between ground and aircraft. This employs “Line Of Sight” transmission, which translates to a range of about thirty miles for an aircraft operating at 1,000 feet above the ground, or about 135 miles with an aircraft operating at 10,000 feet.
Good “Bedtime reading” (Yawn)
https://www.faa.gov/documentlibrary/media/order/6050_32b_with_chg_1_and_2_incorporated.pdf
One thing that I found surprising, the Low power of ATIS transmitters.
Power output of an AWOS/ASOS operating on a discrete VHF channel should not exceed 2.5 W.
I’m very sure that has been in.
There is a VHF Degredation setting that’s been present for a while in the Sound Options.
It is simply impossible that you got the discreet VHF ATIS broadcast at a distance “well” greater (or even close to) 105 nm. Sorry. I’m not doubting you got the weather somehow, and perhaps even the same information as the ATIS broadcast (e.g. relayed in some form). You did not, however, get a VHF frequency at that distance. It’s just not possible. There’s a lot of reasons for this, not least of which the power of ATIS transmitters is limited to 10 watts. A 10,000-watt VHF will broadcast 60 nm. So do the math. Secondly the distance an ATIS is allowed to be broadcast is restricted to the radar environment of the controlling agency of the primary airport. In other words, they cannot broadcast ATIS a further distance than approach control radar.
You may have gotten the weather, but you didn’t pick up ATIS on 118.7 from 100+ NM.
No, he’s right, I also used to get ATIS over 100 miles out. Everything was done before top of descent and that was at around 100 miles. We didn’t have any means other than radio to get an ATIS.
Ok sim pilot, from a real pilot yes you can absolutely get ATIS from far out. When I used to fly corporate jets hanging out in the mid 40’s it was possible to pick it up at almost 200nm out. Now that I fly for an airline in the mid 30’s the range we can pick it up is reduced but still well over 100nm. That being said it doesn’t matter since like someone above posted, we simply use ACARS.
Sorry to get snooty with you but you were absolutely wrong.
I do not believe it is implemented for the audio of the Nav Idents
Com Radios yes (maybe). (Including Atis & AWOS)
While there is a VHF Degradation, and that does act on any ATC you hear, I don’t believe it acts correctly on any AI aircraft “you” may hear (or not hear), talking to ATC, which should be a factor of THEIR distance from you and your relative altitudes.
ie I do not recall ever just hearing ONE side of another AI’s Plane’s communication with ATC
" You did not, however, get a VHF frequency at that distance. It’s just not possible. There’s a lot of reasons for this, not least of which the power of ATIS transmitters is limited to 10 watts. A 10,000-watt VHF will broadcast 60 nm."
FM is a modulation type, and has no effect on range. I have personally use four watt FM for a link of well over a thousand miles, though this was exceptional.
Frankly, you are incorrect in almost every one of your assertions.
But we did many, many times like for twenty odd years. VHF is line of sight as has been pointed out. If you tune an airfields VOR/DME frequency you will receive the DME range at about the same time as the ATIS comes in. They are both VHF transmissions and you will get them out over 100NM. Even low wattage VHF will travel a long distance in line of sight. Anyway, if they get they ACARS up and running in some of the jet transportS like the FBW A320, that’s where you will get the ATIS from as is done currently. The VHF ATIS is still broadcasted at major airfields but it will eventually be phased out
NOTE:
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Atis/Awos is VHF, and typically limited to 2.5W
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DME is UHF
A typical DME ground transponder for en-route or terminal navigation will have a 1 kW peak pulse output on the assigned UHF channel.
Yes, you are correct, DME is UHF, which has a shorter range than VHF. The reason is, is that UHF is less likely to bend around terrain and even more line of sight. EHF is even more very point to point ( used in space travel ) Conversely, as you go down in Frequency transmission tend to bounce and bend? Until you get to HF or even LF where it can skip off the ground and reflect of the ionosphere therefore transmission can occur over many miles. Anyway, that is getting way off topic. The request is, can MFS make the reception of ATIS at a more timely distance in some manner to reflect a bit more realism in the Sim. Thank you
I consistently get ATIS broadcasts over 100 NM out while in the flight levels with 200 NM being about the longest distance ATIS has been picked up from the transmitter. The book says one thing but in the real-world things can vary greatly. 8,000 hour corporate pilot here.