Twin Otter autopilot altitude issue?

[pusser 1]

Once I have loaded FSX and then the aircraft, set altitude, take off and set autopilot, the aircraft climbs normally to the set altitude for cruise. After landing, if I then plan a second flight, set the altitude and start the flight, the aircraft is, as likely as not, to climb ONLY as high as the last set level during the previous descent, even though I have set a higher cruise level. My video here shows what happens. In this instance, my previous flight level had been 2000ft. I descended to 1000ft for approach. Then for the next flight, set altitude to 2000ft but the aircraft climbed and levelled off at 1000ft. This actually makes it difficult to fly because no amount of manual climbing to the set altitude helps. The aircraft will always want to go back to the level last set in the previous flight.

 

[MarkHurst 173]

6 hours ago, pusser said:

My video here shows what happens

 

I can't see this happening in your video - it starts and ends straight and level. I also can't tell if the ALT mode is set, as the video is too fuzzy. However, I am confident it is. You do understand that setting the ALT ALERT function will not trigger the climb? From your video and description, I think you have done this:

 

- Been flying on ALT mode at 1000 feet, then switched off the A/P.

- Landed.

- Set a new target altitude on the ALT alerter.

- Taken off.

- Switched on A/P. ALT mode is still set and will try to re-acquire the altitude it was previously holding (1000ft).- Pressed the ALT ALERT button.

- The aircraft continues to hold the previously set altitude because ALT mode is still set. The ALT ALERT chimes intermittently because - coincidentally - you are holding an altitude that is 1000ft different to the target set on the ALT ALERT dial. You keep passing through this as the A/P makes small adjustments to hold 1000ft.

 

What you need to do differently is switch off ALT mode and initiate a climb. Then your new target will be acquired and ALT will switch back on. One way to do this is by nudging the pitch wheel on the yoke pedestal.

[pusser 1]

Yes, maybe my video did not show exactly what was happening but I do understand why the alt alert was chiming.

8 hours ago, MarkHurst said:

What you need to do differently is switch off ALT mode and initiate a climb. Then your new target will be acquired and ALT will switch back on. One way to do this is by nudging the pitch wheel on the yoke pedestal.

 

I'll give it a try. Thanks for your help.

[pusser 1]

I had this same issue arise today. I had completed a flight during which I had set the altitude on descent to be 2000ft. After landing, I set the altitude for the next flight to 3000ft. Upon takeoff, I began the climb and the aircraft levelled off at 2000ft. I recorded this using FRAPS and hope that it can be seen on my video.  I followed on with your suggestion and turned off "Alt Alert" and pitched up using the trim wheel, turned Alt Alert back on and the aircraft climbed and leveled off at the set level. I tried to replicate the issue yesterday but was unable to. The only difference today was that I was also running a version of kAcars by http://www.fs-products.net/

 

https://youtu.be/2d_etPeUayg

 

 

[MarkHurst 173]

37 minutes ago, pusser said:

I followed on with your suggestion and turned off "Alt Alert" and pitched up using the trim wheel

 

No, that wasn't my suggestion. You need to turn off the autopilot's ALT mode, by pressing the ALT button. This is not the same as the ALT ALERT button. Basically, if the Autopilot panel has the little orange lights around the ALT button (I still can't tell in your video) then ALT mode is still active and the A/P will hold whatever altitude it was holding before.

 

P.S. the trim wheel will have no effect if the autopilot is engaged. You need to pitch up using the thumbwheel on the Pitch and Turn panel (on the yoke pedestal).