I’m just thinking there is an issue with the stock one…if it’s engaging LVL and FLC…those modes oppose each other. LVL is like “hey servos, pitch down to horizon.” FLC says “hey servos, pitch up to meet speed xyz”
I use it all the time. Seems to work fine.
I was under the impression that LVL was just a roll mode, not tied to the vertical system at all. Either way, I just did a very nice flight in the Bonanza from KDAN to KGSO using VOR radials and the Loc/GS for 23L, and had zero issues - except for the fact that I forgot this thing stalls WAY before the 172 would… 
At least on the real GFC500 - LVL button, surrounded by a blue box, will do exactly that…level the wings first, then pitch up or down to the horizon line. On the Cirrus Perspective G1000 it does about the same thing.
TBM has that too - even saw a video demonstrating it. But I think that’s a different thing altogether, because even if the AP is off, that will engage it and get you out of trouble. On the regular G1000, you’ll notice that the green “LVL” indicator is under the roll mode section.
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Watched the video, you’re engaging VS/FLC while on the runway, you see the FD shoot up as it keeps directing more and more nose up to obtain the requested climb. Once you engaged the AP the servos go chasing the FD and you stall out faster than it can stabilize. Either wait until already established in climb out to set VS/FLC, or wait for the FD to stabilize before engaging the AP. As per the POH the AP should also not be engaged until you exceed both 80KIAS and 400ft AGL. Following this you shouldn’t see this issue arise any further.
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You should be able to arm FLC on the ground though.
I guess i didn’t pay close enough attention to when he enabled AP. I watched it again just now on mobile - I can’t even see the FD bar. Where’d it go?
When I engaged mine right off the ground I was trimmed for climb - that may be the difference
I was easily above 80kts and with the flaps up, the gear up I don’t see how an extra 100ft of altitude would prevent me pitching vertically. I was a good 30 seconds into the flight. I did see the FD shoot downwards towards the runway, I didn’t request a rate of climb either, I requested an altitude and a velocity at which to climb and when I enabled the AP that velocity was something like 5-10 kts below the velocity of the plane which should have gently pitched the plane to lose 5kts, that’s a very gentle rate of climb.
I would mention this happens to me even when I’m cruising around, I just wanted to demonstrate the issue as quickly as possible.
I now see the FD sky it while taking off. Ok so I set a velocity of 96kts to climb at yeah? Why would the FD go UPWARDS at 70-80kts when it wants to go faster than that? You aren’t suggesting that the normal behaviour of FLC is to pitch up when the plane needs to go faster to match the selected velocity?
This also happens to me - climbing out on runway heading at 1,000’ AGL in G1000 Bonanza at 95 knots. I have altitude set for 6,000’ FLC set for 93 knots and HDG as the lateral control. I am in a stabilized climb and press AP - the nose INSTANTLY climbs to 30° above the horizon and the elevator trim INSTANTLY goes to 100% UP. This happens EVERY time I depart KSBA on Rwy 7.
I turn OFF AP and regain control. I get the plane into a stabilized climb at 95 knots (~750 fpm VS) and on the heading set in the AP and again turn on the AP - INSTANT 100% UP elevator trim and imminent stall.
EVERYTIME!
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This only happens when FLC is selected - if I have a VS of 750 (for example) set and engage the AP - the plane continues a nice climb at the selected VS, no matter what VS I am flying just prior to engaging the AP.
When I engage the AP with FLC speed set to more than the current speed the AP does not command a huge nose up response. So - it appears that logic of the AP is to command a violent climb to drive the airspeed down to the requested FLC speed IF the AP is engaged when the current IAS is more that the FLC speed.
That may be the case, I have no idea why it only happens with the G1000 though.
I did some small amount of testing and found that my experience with VS mode being broken may be tied to attempting to use FLC mode during that flight. I haven’t scientifically tested the VS mode in the past like I have the FLC because it is an intermittent problem with VS and I don’t remember if during those flights I had toggled FLC or stalled during a climb or something. It appears that using FLC mode permanently ■■■■■ the AP for that flight for me, meaning even with ALT, FLC and VS mode disabled, having recovered from the 100% pitch issue enabling AP at any point will trim me 100% for the rest of the flight.
I have had flights where I have recovered it, through sheer mashing buttons, enabling different AP modes, enabling and disabling the flight director, turning AP on and off repeatedly, manually removing the trim each time it sometimes eventually stops trying to take me on a 1 way trip to meet God.
Same thing here, very frustrating.
I’ve had the same thing happen, and have discovered that if I hand-fly to my proper course direction and stabilize the climb, then engage the autopilot, it seems to work every time. If I take off, raise the gear and hit the autopilot, it will often crash.
AFAIK, that is how most GA autopilot systems work IRL. The aircraft has to be hand-flown to the proper attitude, pitch, etc prior to engaging the AP. Please correct me if I am wrong.
This I can’t confirm on my side. I always use FLC to climb and VS to descend, never had any issues.
I (like some others suggested) always hand-fly the departure until I’m stable in the climb and on-course of GPS when enabling AP.
To avoid the sudden climb, use FLC not with a pre-set speed but simply engage it with the current speed during climb and then, if required, dial it back in increments which will gradually increase pitch to match the speed.
That works well for me, while I don’t want to say that the way you use it is wrong. It’s just a hint how you could have a more comfortable flight.
Also I have the G36 mod installed, it changes some performance values and might also have impact on the behavior.
Just Check the “Known Issues” Site:
Autopilot
- We are looking into the bug reports and will provide additional information.
the autopilot doesn’t work for me in any propeller plane. i think we just have to wait for the next patch. i’m currently flying without an autopilot. (i know that this is not a real help) 
Having worked on and installed autopilots in the past, you are generally correct about GA AP systems. They’re not like airliners or jets designed to be engaged very shortly after takeoff. In the GA world the systems are not typically sophisticated enough to null out large control surface deflections and you’ll sometimes have systems attempting to max out elevator trim and disconnecting the whole AP.
I have yet to try this out in the G36 to see if it works the way I would expect it to, but then again I’ve never worked or flown on anything with avionics like the G1000.
It is also good pilotage to only engage the AP once the aircraft is in its stabilized climb (trim included). I tend to only ask autopilot to hold what I’ve done, rather than genuinely fly the airplane for me; I’ll do the majority of my pitch changes by hand, then reengage the system so I can focus on other tasks. In the real world, autopilots are often finicky and break kinda frequently, so you learn to use it as a pilot aid, rather than depending on it to fly for you. Like cruise control in your car, it’s nice to have, but you shouldn’t need it to drive on the highway.
I’ll also add how I use the FD/AP in the 172:
On the ramp, I’ll set my altitude, runway heading bug, enable the FD, and set the FLC for the enroute climb airspeed. The command bars activate and frig off to somewhere. I’ll line up, takeoff (using Vx or Vy as appropriate) and get to at least 500’AGL before I start looking for the command bars again. Once I’m at about pattern altitude, I’ll nose down to get my enroute climb airspeed (matched up with command bars by this point) and engage the AP. Then I’ll move the heading bug to fly me to the route, only engaging the NAV once it’s almost perfectly lined up.
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It has been said by many that FLC is iffy at best. Try using VS and pick a moderate climb rate to start. If you have power to spare, then increase. If you notice your speed dropping, bring the nose down.