How to simulate low flying exercises (?)

[kungfuman]

I have a very simple method for creating low level flightplans. But it is based on an assumption that may be flawed. I have not found anything amiss myself, but then again my testing of the results is pretty minimal.

All I do is set the flightlevel for all the low level legs to 002 (chosen specifically according to my preference, but could be any arbitrary low altitude), and the type of flight to VFR.

My assumptions are:

1. VFR flights create less interaction between the aircraft and ATC services, due to no lengthy vectored approach procedures. The occasional military callsign heard over the fs9 civilian r/t channels is a welcome addition, but I think hearing these aircraft receive vector instructions for non-existant approaches to waypoints and weapon ranges from civilian ATC is better kept to a minimum.

2. VFR approaches will be very similar to IFR approaches in the case where there is no runway to land on. Both will go missed, which is the effect we want at weapon range waypoints, plus it won't detract from the enroute waypoints (especially if they are in LFAs).

3. FS9 will always ensure adequate ground clearance throughout the leg, so setting a flightlevel below (or within a couple of hundred feet above) ground level will result in ai aircraft exhibiting the low level behaviour sought after.

I have used it extensively for many of the MAIW legs (those for which it might be appropriate) in the UK, as well as my own UK flightplans for the NBAI Chinooks I have at RAF Odiham, and the NBAI Apaches at Wattisham. Another place this works well is for the above helicopters used in my heli flightplans for Afghanistan. Other aircraft on my system also benefit from this method, such as an occasional C-130 training flight, or some of the other training/test aircraft - from Tucanos in Yorkshire to aircraft of the ETPS.

I notice that no one else uses this method, including flightplanners that I consider to be way more experienced than myself. So naturally, I think there must be some good reason for this. Are my simple assumptions indeed flawed?

One or two of you may have downloaded the Indian fighter flightplans I shared on Avsim, which also make some use of this method. Has anyone got any feedback about this aspect of them?

Looking forward to your thoughts on this, as I don't wan't to be sharing flightplans that don't work!

[Garysb]

Hi
Onething you will have to be careful of is hills
Ai does not change direction for hills

Also Nicks Helos are not designed for VFR


Gary

[kungfuman]

What I have found is that while ai doesn't change heading for hills, it does change height - simply climbing above any terrain that it approaches on its extended track. Once passed the obstacle, it descends towards its "flightplan" height until FS9 steps in again to make it level out before it collides with the ground. How good FS9 is at this task I don't know, but it has worked on the flights I have observed. However, I'm conscious that following my ai might affect things too.

What difference does it make if one uses an IFR model for VFR flights? (A genuine question, not rhetoric! )

[Firebird]

Hmmm when I was trying a similar thing a copy of years ago I thought that IFR traffic would amend its path due to height or obstacles, but that VFR didn't and crashed in to hills.
Admittedly I think I was testing with Sea Kings in Wales, Mirages in France and Typhoons in Austria. I might have not tested right to create these impressions, but that's why I dropped it. I wanted VFR low flying not IFR.

If you further tests that prove that VFR behaves in the same manner as IFR at low level then I will revisit the Austrian ones especially.

[MIKE JG]

VFR planned AI will fly directly into hills and mountains, sometimes they come out the other side, sometimes they don't. They will not change their height to miss the terrain.

[kungfuman]

By that, do you mean that FS9 is "not particularly good" at avoiding hills?
I have actually watched as VFR ai change altitude according to the terrain. I accept that I might just be lucky, but it certainly does do this in the conditions that I have observed.

I have also seen VFR traffic fly through hills on approaches and departures from airfields (ie. Luckla in Nepal), but I am more interested in the enroute behaviour. For example, if it turns out that FS9 is "not very good" at terrain clearance, the minimal capability that it does have could still be taken advantage of, if we only knew better exactly what the limitiations are.

ps. Thanks for the input so far Keep it coming!

[kungfuman]

Another thought on your reply MikeJG:

Could that be the case only when the VFR ai traffic is already at its correct flightplanned altitude, at which point it may be reluctant to deviate in response to the terrain?

In the method I am using, the ai traffic never get the chance to descend to the flightplanned altitude in the first instance, so perhaps they are more open to influence from terrain factors. Could that explain my results?

[Firebird]

I am trying to remember my tests here, so I may be not 100% accurate.

What I found for the Austrian Typhoon tests was that the airfield, LOXZ, is surrounded by mountains. If I tested VFR circuits and approaches the aircraft flew into mountains. It tried to bank out of the way, sometimes it was successful, sometimes it wasn't. The IFR approaches went way out and had a hard time descending safely to get in.

What I have decided is that when I eventually get around to finishing this package there will be no circuits at Zeltweg.

My guess is that there is a very strict approach regimen in real life there.

[Victory103]

I was trying to something like this for the US, as we have tons of IFR/VFR Military Training Routes (MTRs) throughout. I have all the current pubs to add the waypoints, but really didn't know how to start or how to get the AI aircraft to follow them without shooting an approach to each waypoint. My plan was to just complete the flightplans around generally flat areas as to avoid the hills.

This was somewhat brought on by a RW flight last year where I had 2x USAF T-1's cross my path flying a low level MTR.

[swp53]

Hi Guys,
My experience with this is that if VFR it depends how quickly the terrain height changes. If gradual then normally the aircraft will clear terrain particularly if the aircraft speed is not too fast.
With IFR the aircraft will allways produce a clearence between terrain of 2000ft including over the sea.
IFR flights from RAF Valley to St Athan whether Tornados, Typhoons or Hawks allways followed the contours of the land with a 2000ft clearence.

On a seperate note regarding Circuits (patterns) I found that if the circuit is VFR its 1000ft above airport level and IFR is 2000ft so if you want circuits at that height you have to set the pattern altitude at 0ft in afcad any figure entered in pattern altitude is added to the inbuilt heights i.e. if you set pattern at 1000ft the AI aircraft will fly a VFR pattern at 2000ft and IFR at 3000ft. Thats what I found anyway.

This is in FS9/FS2004 not checked what happens in FSX yet.
Regards,
Steve.

[kungfuman]

Thanks Steve,

Didn't know about the effect of changing circuit height.

So it sounds like the low level technique will only work over terrain that's not too abrupt. Well, that's a start. If true, I can see a lot of potential for using it, provided I choose my routes carefully.