Currently, SkyDemon computes the minimum safe altitude by checking for obstacles within a corridor on each side of each leg. This means that whenever the route makes a turn at a waypoint, there is a sector on the outside of the turn which is not checked for obstacles/terrain.

I don't know if this is the intended behaviour or not, but it would arguably be more useful if SkyDemon also checked this sector.

With the new SERA minimum altitude for night VFR being 1000 ft above the highest obstacle within 8 km of the (estimated) aircraft position, you would want to use SkyDemon to compute the minimum altitude. Currently, this is a problem not only at turning points but also at the beginning and end of the route as obstacles/terrain behind the first waypoint and after the final waypoint are also not considered.

The best solution would be if SkyDemon checked not only the "corridor", but also a (semi)circle around the beginning and end of each leg. That would solve both the turning point and the beginning/end problem.

I have checked this using SkyDemon 3.2.0 on a PC.

SkyDemon does actually check for obstacles in those sectors and applies them to the calculated MSAs. I haven't checked to make sure, but I think you're right that terrain isn't checked. Looking up the terrain in those sectors is non-trivial and that's why we haven't made this change so far.

I haven't actually checked for terrain, but for obstacles it doesn't work reliably.

An "outside turn" obstacle will affect the MSA for only one of the two legs, when it should properly apply to both. And if the turn is more than 90°, the obstacle isn't considered at all.

Do you have any official guidance to support your assertion that such obstacles/terrain should affect both legs?

Obviously, that depends what you want to use the MSA for!

But, yes, in case you want the MSA to be the minimum altitude for night VFR, that I mentioned. SERA.5005(c)(5) reads:

except when necessary for take-off or landing, or except when specifically authorised by the competent authority, a VFR flight at night shall be flown at a level which is not below the minimum flight altitude established by the State whose territory is overflown, or, where no such minimum flight altitude has been established:

(i) over high terrain or in mountainous areas, at a level which is at least 600 m (2 000 ft) above the highest obstacle located within 8 km of the estimated position of the aircraft;

(ii) elsewhere than as specified in i), at a level which is at least 300 m (1 000 ft) above the highest obstacle located within 8 km of the estimated position of the aircraft.

"within" implies to the side of, ahead of, as well as in rear of the aircraft. So in this case, for an obstacle located within 8 km of a turning point, it should affect both legs.

Ok, I don't agree that those rules are necessarily applicable to general VFR flights conducted by day. Nevertheless, we will start thinking about an efficient way we might be able to improve upon our existing MSA calculation.

If one is flying from A to B and there are some mountains just the other side of B, one may well object to the MSA calculation including those mountains.

Great!An option, perhaps...?

MSA should take into account obstacles and terrain a certain distance around the course. This is to allow navigational inaccuracies and small deviations from the planned course. Since I could very well overshoot a waypoint, I would feel safer if msa also took care if the area beyond it for, e.g. a mile or so.

-- Chris.

MSA should take into account obstacles and terrain a certain distance around the course. This is to allow navigational inaccuracies and small deviations from the planned course. Since I could very well overshoot a waypoint, I would feel safer if msa also took care if the area beyond it for, e.g. a mile or so.

-- Chris.

The SERA-rule mentioned by lhe is very relevant if you want to use the new EIR, where you take of and land VFR. The transition point to and from IFR has to be at least 1000 ft above the highest point (terrain or obstacle) within a radius of 8 km.

I start training for the EIR next month and would like to continue using SD. But apart from this MSA issue, SD also has to unlock the flight rules part of the flight plan filing. For now, it only allows V(FR), where I will need to file a X-plan (VFR-IFR-VFR).