Stall in Auto Pilot C208B

Please tag your post with #pc and/or #xbox.pc

Are you on Steam or Microsoft Store version?steam

Do you have any add-ons in your Community folder? If yes, please remove and retest before posting.

Are you using Developer Mode or made changes in it?no

Brief description of the issue:stall in autopilot speed 150

Provide Screenshot(s)/video(s) of the issue encountered:

Detail steps to reproduce the issue encountered: About 3/4 of the flight plane goes into a stall even thought speed is very high approximately 150

PC specs for those who want to assist (if not entered in your profile)

Build Version # when you first started experiencing this issue: last update

Did you submit this to Zendesk? If so, what is your ticket #?Not submitted to zendesk

This has occurred at least 4 times. 3/4 of way through a flight in autopilot at 150 knots the aircraft stalls and goes into a dive.
Flights have been in Germany and the US. Any one else experiencign this??
BW

Severe icing? Confirm the stall warning is active?
If not, how do you determine if it’s an actual stall?

The cockpit voice comes on and says: 'STALL, STALL" Speed is about 150 and aircraft takes a nose dive. This occurs in autopilot 3/4 of way through the flight. Happens consistently.

There are lots of factors that can cause a stall, you don’t give enough information about the conditions you are flying in, altitude etc…

Are you using any mods? Have you tried with an empty or renamed community folder?

The only item which can increase the stall speed is icing and the single item which causes a stall is a too high AoA.

At MTOW the clean stall speed is ~80kts. I have actually no idea what could cause a stall at 150kts.

I’m not sure how much of this MSFS simulates but there are other factors to be considered.

factors affecting the stall speed, in summary; aircraft weight, air density, maximum lift coefficient, and the load factor. Stall speed is proportional with the aircraft weight. Stall speed increases, as the weight increases; and decreases as the weight decreases.

Since I have replicated the problem at least 4x with different flights, I cannot see how it is related to aerodynamics or icing. It occurs when I have the autopilot engaged. I will try the last flight with no autopilot engaged to see what happens. I am thinking that it must be a bug in the programming. Nevertheless, I will try the flight again with no auto engaged. Thanks for the interest and feedback.
BW

All the factors you have mentioned are simulated. These are the basics in every flight sim, but none of them explains the extremely high stall speed or needs to be considered.

@Blackwolf07777 again, do you have any mod installed? Is the community folder empty?
Even liveries are known ro cause strange problems.

What is your Angle of Attack when you go into a stall?
Sounds like the AP has increased nose up trim (perhaps in order to maintain or climb to a specific altitude) and it just keeps increasing it.

I see this sometimes in the vanilla Beechcraft Baron but only when entering cloud or other weather have momentarily reduced airspeed. Trim increases to keep nose up. Stall. (And trim remains at extreme value when you assume manual control)

I now check my throttle, prop pitch and mix when there is “weather” and adjust for a high enough airspeed that the aircraft remains stable.

If assuming control after a stall the first thing I’m doing is adjusting pitch trim back to neutral.

That’s what it sounds like to me. The AP struggles to either maintain climb, or altitude hold as ice builds, the nose continues to rise until it stalls.

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Here is a screen shot . Level flight speed 95K. Aircraft turns and goes into a spin. Acts as though the aircraft is just below stall speed…
I tried the same flight with no autopilot…no problem.
Must be a autopilot glitch…I think…but I am just a simmer not a programmer.
BW

This is not a C208. This is the six pack C172 is it not?

My apologies. I forgot to mention that I changed aircraft because I thought that the problem might be with the 208. Nevertheless, I got the same result…a stall at 90K. Thanks for your observation. I should have noted that in my post.
BW

You’re at 9000 with pitot heat off?

That’s a well known AP problem and has nothing to do with a stall.
AFAIK this is a joystick problem and the lack of a sufficient dead zone.
What are the deadzones on your axis?
For testing I would either increase the deadzones to 25% or even disconnect the joystick.

For the aircraft to stall in level flight, the nose must be at least 10-15dg above the horzion.

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Why not? You aren’t allowed to fly in icing conditions with the 172 anyway.

This sounds like the cause to me as well FWIW. I think the suggestion to do a test with joystick unplugged is a good one

I will repeat the flight with the 208 and ensure that pilot heat is on.
After I engage autopilot, I will disengage my yoke.
By the way I have not seen this problem in xplane. Thanks. again to all.
BW