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Autorouter issues and questions (merged)

Yesterday I was in MonchenGladbach EDLN and decided to fly ifr back to Rotterdam. Normally the routing would be to the north with a big detour. Eurofpl found a route 168nm. (Straight distance being 87).

Autorouter found a track with only marginal xtra at 4000ft!

Really great!

I would enjoy the enhancement that I can export or copy the correct route straight into Eurofpl.

Great work guys!

You were able to fly on a Eurocontrol flight plan at just 4000ft?

One could not do that in the UK.

Shoreham EGKA, United Kingdom

Autorouter found this route and I just copied it to eurofpl and validated it. It was accepted ..

You flew at 4000ft? I know that’s no problem under IFR in Northern Germany where the only terrain features are windmills, I’ve done it myself several times. Don’t know about low level IFR in Holland.

I think the 4000ft comes from the default minimum level, which is FL040.

I am amazed one could actually fly that and get an IFR service, but evidently one can. In the UK this would absolutely not work.

Shoreham EGKA, United Kingdom

The Dutch will accept you as well however you are not in class A.

I played around some more. From Rotterdam the northwesterly direction (towards Schotland is normally FL180+. Ditto for the southeasterly direction (towards Friedrichshafen).

Autorouter found routes at FL060 in both directions.. (To the southeast via an exitpoint I had never heard of and which is not on a SID).

It is proving to be a very interesting routingprogram.

I am now playing with Geneva – Pula .. however that seems to run over Zurich???

The router uses a mathematical optimization strategy, walking a path and assigning penalties to each turn. These penalties determine what the router considers to be “good” or “better”. There are three general optimization targets you can choose: time, fuel and preferred level. Time is the default. A climb would be a penalty because it makes you fly slower. However, the climb might also reduce the distance because it opens up some routes and depending on your aircraft, it might increase the airspeed. This means a lot depends on your aircraft model and how closely it matches reality. My aircraft gets faster the higher you climb and it is fastest + most efficient at its service ceiling. The autorouter will therefore see a strong incentive to send me high up.

If the autorouter chooses 4000ft it could mean two things: going higher would incur a significant overhead or your aircraft is configured to fly fast at low levels. For most normally aspirated airplanes, the “sweet spot” is between FL080 and FL100.

These optimization criteria can be infinitely complex and internally we support a lot more than what the user can choose. In the future we will have to refine this further. One example is that with the standard “time” target we do not look at fuel consumption which is fine for a piston but a turboprop might be able to fly let’s say only 15% slower at a lower level but the fuel burn makes it so bad that it rather wants a higher overhead and be able to fly high up. You can set a minimum level but that can have some negative consequences because it tells the router than the enroute segment cannot be below that level. When departing from some class G aerodromes in the UK (e.g. Biggin Hill), the enroute segment starts at FL040.

When departing from some class G aerodromes in the UK (e.g. Biggin Hill), the enroute segment starts at FL040.

I would not call it the “enroute segment”, but we have done that one to death. It needs a more specialised solution, and even if you have one, it may still be preferable to do departures to the west using a Z flight plan.

One cannot fly Eurocontrol IFR enroute in the UK below about FL090-100, often much higher to remain in CAS, with some exceptions which are either routes rigged up for a purpose (e.g. FTO training) or routes where ATC don’t care anyway because you are soon getting out of the UK (e.g. Shoreham-Caen).

Last Edited by Peter at 21 Apr 09:07
Shoreham EGKA, United Kingdom

As Achim was talking about the rules used for the optimization engine, may I suggest one other setting that may be helpful to some:

  • no oxygen required

Think about the case of a family with young children.

Last Edited by Stephan_Schwab at 21 Apr 10:13
Frequent travels around Europe

I believe the 4000ft was probably chosen because of the big overhead on the normal route.

For EHRD to EDSB all routes normally start with woody nik bub which means heading south over Brussels (FL100 required) before heading east.

Autoroutre comes up with


Which ia a lot shorter, almost direct line!

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