Airspace Class

[mgh 89]

The airports.dat file has the following comment:# AirspaceClass = airport's ICAO airspace class: B, C, D, or GWhat use does FS make of this and why is Class A omitted?The Heathrow (EGLL) CTR is Class A but is shown as Class B in airports.dat.

[RFields5421 1]

I have yet to find a reason for it to be included, however it is useful for sorting airports by similar type.You also have to remember there must be ONE rule for the entire world for FS to work. The US uses a modification of the ICAO rule.In the US FAA definition:"Class A - Generally, that airspace from 18,000 feet MSL up to and including FL600, including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska. Unless otherwise authorized, all persons must operate their aircraft under IFR." "Class B - Generally, that airspace from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of IFR operations or passenger enplanements. The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more layers"The UK has no Class B airspace - it's definition of class A airspace is:"All airways up to FL 245 with the exception of those airways lying within the Belfast CTR/TMA and the Scottish TMA. The Terminal Control Areas (TMAs) around London and Manchester. The London Control Zone around Heathrow and the Channel Islands Control Zone; these areas are thus off-limits to VFR flights (however Special VFR is used as a get-around this). The CTAs of Daventry, Cotswold and Worthing."However the actual designation used in FS is not important because FS treats the EGLL airspace as it treats the KJFK, KORD or KLAX airspace.Remember it is a computer programming control code of some type. Using a recognized definition is easier, but they could just has well called Classes B, C, D, G - classes L, M, S, N for Large Airports, Medium Airports, Small Airport, Non-controlled Airports.This is a handy explaination - however being Wikipedia - I will not vouch for it's accuracy:http://en.wikipedia.org/wiki/Airspace_classes

[mgh 89]

ICAO only defines the classes of airspace in terms of separation and services - not its location so I can't see why Microsoft couldn't use the correct designations.I have looked into this further and found that while the SDK allows CLASS_A as one of the Boundary types FS doesn't seem to use it. The Heathrow CTR which is Class A (dark blue broken line) appears simply as "Controlled Airspace" as does the Gatwick CTR which is Class D.The airspace boundaries are correctly named but the London TMA boundaries which are Class A appear in FS9 as "Class B Airspace" as does the Worthing CTA. The Solent CTA which is Class D also appears as "Class B Airspace". In fact I can't find anything other than "Class B Airspace" after quite a few random attempts around southern England.I find this very surprising given the care Microsoft took to get the airspace boundaries in the correct position, and to include military danger areas and even very small restricted areas around the individual prisons, especially as the SDK seems to allow Class A airspace.

[RFields5421 1]

You have to remember all the boundaries and such are created in a batch process from data which their aviation sources, probably Jeppsen, provides.There may be some hand tweaking, but I'd be surprised if it was much.When you are dealing with a dataset as large as the entire world, you have to assume the data is valid, and leave room for addon developers to make modifications later.

[mgh 89]

I think you miss my point.I can't imagine any data source that gave accurate airspace boundaries would give incorrect airspace designations. So if Microsoft used accurate boundaries (as it did) why did it introduce incorrect airspace designations? An automated batch process would surely have picked the correct airspace designation as well as the boundaries? This suggests to me that Microsoft deliberately changed the designations. In the UK Microsoft seems to have adopted the rule that CTRs are "Controlled Airspace" and that any other controlled airspace is Class B. Anyone know what the case is elsewhere in the world?The impression I have is that Microsoft made provision in the structure of FS9 for a much more detailed ATC system than it provided. This is not a criticism. It was prudent to make this provsion even if, in the event, Microsoft decided not to use it. I wonder, however, if this provision be used in the future as FS moves towards on-line ATC?

[RFields5421 1]

Okay, I understand that point.In the UK Microsoft seems to have adopted the rule that CTRs are "Controlled Airspace" and that any other controlled airspace is Class B. I'm certain their batch process had a "If UK and airspace equals Class A - list as Class B" type routine.Also understand the FS2004 data is old - fall 2002 or earlier. Only by looking at old charts can we see if they got something wrong.Now please understand this one - Does it make a difference in aircraft / ATC behavior?The airspace designation is used as a control code for certain of flight and ATC behaviors. The correct label is NICE, but as long as MS uses the label as a behavior control code - there has to be one standard.I'm beginning to really wish MS would use the ICAO definitions of airspace and many other items which different countries do differently.Of course then large sections of the US airspace would operate incorrectly, as would the UK Class A airspace.US Class B airspace and UK Class A airspace have very similar operational rules. Is the ATC and aircraft behavior in the UK Class A airspace wrong - other than the label?To set the program for one set of rules for the US, another set of rules for the UK, another set of rules for Germany, another set of rules for Australia, another set of rules for the rest of the world.That would be possible - but then you would have the problem of finding a way to reload the program / rules when someone flies across the channel.I read a lot of posts about regionalizing FS. I'm not a very good programmer, but if for the airspace rule we want MS to add five additional check cycles. For the transition altitude - we want MS to add almost 30 additional check cycles, for each ATC statement, we want MS to add almost 100 additional check cycles.It doesn't take much to realize that FS would spend more processing power on checking regionalizations than on flying the aircraft.

[mgh 89]

I admire your valiant defence of Microsoft but...."In the UK Microsoft seems to have adopted the rule that CTRs are "Controlled Airspace" and that any other controlled airspace is Class B. I'm certain their batch process had a "If UK and airspace equals Class A - list as Class B" type routine."Why? The airspace definition is the same regardless of where it it in the world. If FS needs to treat Class A and Class B airspace the same then why not include a simple test in FS "If airspace == Class A then airspace = Class B"."Also understand the FS2004 data is old - fall 2002 or earlier. Only by looking at old charts can we see if they got something wrong.""US Class B airspace and UK Class A airspace have very similar operational rules. Is the ATC and aircraft behavior in the UK Class A airspace wrong - other than the label?"There never has been any Class B airspace in the UK on principle. Class B allows both IFR and VFR flights and requires ATC to provide separation between all aircraft. The UK, and several other counties, don't do this so don't have Class B airspace."To set the program for one set of rules for the US, another set of rules for the UK, another set of rules for Germany, another set of rules for Australia, another set of rules for the rest of the world.That would be possible - but then you would have the problem of finding a way to reload the program / rules when someone flies across the channel.I read a lot of posts about regionalizing FS. I'm not a very good programmer, but if for the airspace rule we want MS to add five additional check cycles. For the transition altitude - we want MS to add almost 30 additional check cycles, for each ATC statement, we want MS to add almost 100 additional check cycles.It doesn't take much to realize that FS would spend more processing power on checking regionalizations than on flying the aircraft."There would be no need for any additional check cycles if FS dealt with the standard ICAO airspace classifications which are perfectly adequate. A Case statement would be all that would be needed to select the appropriate airspace classification.I'll admit that this discussion, thought interesting, is academic. I haven't found that FS does anything with the airspace and airport classifications, apart from the warning messagage in the GPS. Certainly flying around southern England they might as well not be there. Of course, someone could prove me wrong.To reiterate a point in an earlier post, I believe Microsoft made provision for a comprehensive ATC system then decided not to implement it - probably for very good reasons, including the fact it realised it would fiendishly difficult.