Altitude Set Problem for GPS Flightplan

[frankc99 0]

I thank everyone who reads this post and apologize if it's been answered elsewhere. I've been searching everywhere and simply have not found this issue addressed.

 

I recently purchased Aerosim's add on for the Boeing 787. Nice! I have FSX all tweaked and everything looks and performs great...except for this.

 

I am not an advanced FSX user; mainly to state I do not yet create and fly IFR positive control flight plans. I create direct, VFR, GPS routes. I prefer to create a very long direct final into the landing runway. I will typically enter a waypoint over 100 miles from the runway, allow the airplane to turn, then start a slow descent to "approach" altitude. I like to acquire the LOC/GS  approx. 20 miles out that necessitates the "approach" altitude at 5000' AGL. 

 

Here is the problem. When I first create the VFR/GPS flight plan, flight planner always picks a "default" altitude. This seems to be random, but perhaps based on other factors, however I enter a 0 altitude. I always manually select altitudes when I fly through the autopilot.

 

Now, when I am in flight, and cross the waypoint for the approach, the airplane/autopilot/flight plan starts a descent, based on some random altitude. It over rides the altitude hold and goes to VS descent.

 

Every time I load a flight plan I check the altitude, set to 0, but same problem. This only happens if my current hold altitude is above whatever "random" altitude flight planner selects. It has not "yet" tried to climb to altitude.

 

I have deleted plans and created new, but I believe it may be in this random altitude setting by FSX.

 

Any ideas?

 

Thanks, fc

 

 

 

[frankc99 0]

I believe I may have found a solution to this problem.

 

Logic dictates one cannot fly an airplane at 0 altitude, so flight planner then picks an altitude; by default, randomly or however. This explains why saving a 0 altitude flight plan always results on an altitude entry being made.

 

So I decided to approach the problem from the other side and saved a very high altitude; for now at 50,000 ft. My first flight using a plan that always fails due to the original problem went off flawlessly. Just as I hoped.

 

I have a couple of other plans that I will adjust and test, but it seems this will work.

 

I still want to know why the original problem occurs in the first place.

[fs4fun 366]

I don't think the airplane should ignore your altitude hold and start descending on its own. Does that also happen using a default airplane like the 737?

 

I read somewhere the Aerosim 787 has some VNAV capability. Maybe that is why it descends? Normally though, an aircraft in VNAV mode will still not override your selected altitude, but it sounds like that is what's happening here. I looked to see if Aerosim had any manuals that could be downloaded but could not find any. Personally I would hesitate to buy any addon that does not have a freely downloadable manual.

 

I think the cruise altitudes chosen by the default flight planner are based on the minimum altitudes needed for terrain clearance, and also it will pick top-of-climb (TOC) and top-of-descent (TOD) points and calculate intermediate altitudes for waypoints that are before TOC or after TOD. I wonder if your addon is automatically trying to follow those altitudes.

[frankc99 0]

The Aerosim B787 is the only airplane that has this problem. The FSX B737 and 747 both fly fine.

 

You are correct about the VNAV in the autopilot and the TOC and TOD requirements.I haven't yet delved into this aspect. But I agree the problem may be there.

 

Anyway, my workaround works fine.

 

Thanks for your reply.

 

fc