What controls AI Approaches?

[BlinkNFG 0]

Hi,What controls the way AI planes approach runways (i.e angle and rate of descent)?. The reason I ask is I am having a few problems with Heathrow. I have noticed that not all planes approach the runways correctly. Some come in at an angle and land across the runway ending up on the grass or apron and then have to taxi back to the runway before taxing to the stand. Others come in too high and are not able to land (instead they report 'going missed').It is Aerosoft's Mega Airport Heathrow but I have edited the afcad to change some of the parking (to reflect recent changes). Is it possible in doing so I have damaged the approach data? Is that stored in the Afcad? I also use AI separation but that shouldn't effect angle of approach should it?Any advice would be appreciated. Many thanks.Jon

[RFields5421 1]

The approach system in FS2004 and FSX has a lot of capability and complexity. Usually more than most simmers want to learn.However for AI aircraft, the approaches fall down to a few basic types.If there is an ILS approach in the code for the runway, the AI aircraft will fly a straight-in approach. It will be called an ILS approach by the ATC, but the AI aircraft does not use the ILS - but does fly by the numbers programmed into the ILS approach.If there is no ILS and the weather is not IMC - i.e. the visibiity is more than 3 miles - the AI aircraft will fly a visual approach - a long straight in approach which looks a lot like most ILS approaches.If the weather is IMC with visibility less than three miles, and there is no ILS, the AI aircraft will fly another approach if available.I forget the exact order of preference, but I think it is VOR, NDB, GPS/RNAV in that order.AI aircraft can fly some complex approaches very well - PADU is a great example as the B737 comes in and does a descending circle to land. It's kind of sad because in bad weather the AI aircraft land on either end of the PADU Rwy 12/30 with a nice tight circle to land after crossing over the NDB - avoiding the surrounding terrain.But in good weather, the AI aircraft fly through the mountains on approach when landing on either end of the runway.At PHNL, the AI aircraft will fly a perfect Offset LDA approach to land on Rwy 26L. Watching the B747 make that final turn at 500-700 ft AGL, less than a mile from the runway is neat.Jim Vile has worked out some of the trickier airports in the world - like Innsbruck - so that AI aircraft fly complex approaches to land without hitting the terrain.The one 'problem' with this method is the approach must be called an ILS approach in the code, and by ATC, even though no ILS will exist in the FS world. This sometimes causes confusion with some user aircraft, not knowing the limitations.Now, none of this should apply to Heathrow - which is a pretty basic, simple airport approach wise.I'm not sure what is causing your problem, but two possibilities I see are:(1) someone has moved some of the key elements - like the runways - and not changed all the code to move the approaches. We see this all the time when people move a runway with AFCAD too far for the AI aircraft to adjust from the approach code to the runway link line. This adjustment only occurs in the last few hundred feet of flight. So if the AI aircraft flies the approach code correctly, and finds the runway is moved - they usually land in the grass alongside the runway and taxi over.There is one heck of a lot of XML code work necessary to move a runway more than a few dozen feet in FS and make everything line up again.While the default airport approach code is kept in the same section under the airport header as the parking, taxiways and runways - Lee Swordy specifically setup AFCAD to not touch this data. You cannot change the approaches, or break the approaches with AFCAD.And the moving runway issue usually results in consistent errors for almost all AI aircraft.(2) this might be an intended impact of AI Smooth and the way it slews AI aircraft around to keep them apart. Heathrow in FS is simply incapable of handling a real world volume of traffic. The longer you are at the airport, the longer the pile of moved aircraft becomes and the more issues pile up. True, many of the moved aircraft just disappear in the air and pop up at the gate before their next scheduled takeoff.Does your issue occur primarly with some particular models, while some models seem to make the landing just fine?That could be related to the model flight dynamics trying to cope with a runway movement and the slew effect.While I mentioned AI aircraft can fly beautiful circle to land patterns, the sad fact is that most of the great AI models - especially the heavies - have flight dynamics based on underweight B737. These provide a great fast approach, fast stop and clear the runway behavior for straight in approaches, but can make the AI aircraft fall out of the sky if it attempts to fly a complex approach.