How the Autopilot works - IAS and VS
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Hello!
I know that the 146 simulates quite old systems. But currently the AP begins to wildly pitch up and down after some time when in IAS hold mode (activated at around 250 kts IAS for descend). The speed goes anywhere and the autopilot is suddenly pitching up and down resulting in vertical speeds of 2500fpm up and down, fluctuating very fast. Also VS is mostly not able to hold the target.I am very gently with thrust and attitude when it comes to the old AP simulated.
Anyone else having this problems? I opened a ticket to have them take a look.
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Lateral navigation worked so far for me, I have only problems with speed and climb/descend. Yes, the AP clearly needs some work at this state!
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IAS-mode works okay if you treat it with care. Only suuuper slow throttle moves and avoid activating it while accelerating/slowing very rapidly. I use it for every flight during the climb and often during the descent.
For the climb, I will be in pitch mode for accelerating to climb speed. Once approaching the desired speed i will gradually increase pitch (using the trim keybinds) so it approaches the desired speed slowly and the AP doesn't have to make a huge change once it is engaged.
Cruise to descend is the more challenging part. Again pitch mode or sync is probably a good idea to use! You can even go directly from ALT to IAS mode and still keep passengers (in my case from AirHauler) happy though.
Requires you to slow down the throttle adjustment to a crawl. Never timed it but I might take something like 20 seconds to fully reduce the throttle. Also note that from high flight levels you might not want to reduce the throttles all the way to flight idle, as the plane drops like a rock up in the thin air. Once you get down lower you can then gradually reduce to flight idle.VS mode I use less and haven't had too many issues with (other than the new option to adjust rate with the trim keybinds not working, as anther thread deals with).
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@Rhinozherous Just descend mode, which keeps power at least at a level where N2 is high enough for pressurisation (and anti-ice) if you try to reduce it too much.
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To clarify how the IAS mode works in the 146, this is a basic IAS HOLD mode, meaning that the IAS at the time of engagement will be held by the autopilot. Making rapid throttle changes will cause changes to the aircraft's pitch as the aircraft wants to maintain that constant IAS. This is true of the real aircraft too and it's why the autopilot SYNC mode exists so pilots can smoothly transition between autopilot modes. It should be remembered that the 146 is an older aircraft type, it doesn't have a fancy autopilot with VNAV or an autothrottle like modern airliners, so it's up to the pilots to control passenger comfort.
We aren't aware of any issues with the 146s autopilot since the V2 update where we improved the altitude capture logic, so if you are experiencing any autopilot issues we would recommend opening a support ticket via the following link and we can investigate that further: https://www.justflight.com/support
Mark - Just Flight
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@Mark Do you know if real 146 pilots used VS mode more then IAS? So far I did not find a video of the real cockpit on YouTube showing the AP in descent.
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@Rhinozherous Videos are very few and far between for the 146, there are some good videos out there though. I'll like a couple below:
https://www.youtube.com/watch?v=3vnAESy8R8Q&t=1576s
https://www.youtube.com/watch?v=M_oOrtkNAMc&t=3019s
With regards to autopilot modes in the climb/descent, the following is stated in the FCOM:
"For the climb, when flaps are up and the initial clean climb speed is achieved, IAS is the best mode to select, followed by MACH at the higher altitudes. To transition from one climb speed to another, use SYNC, VS or PITCH. Do not make prolonged use of the PITCH or VS mode in the climb as dangerously low speeds can be achieved; over-speed conditions can also be achieved."
"For the descent, MACH/IAS modes are appropriate if the conditions are smooth; thrust lever movements should be made slowly and smoothly especially when reducing thrust to enter the descent. If the conditions are not smooth, the AP control is often poor; in these cases use VS mode or PITCH mode.
To transition from one descent speed to another, use SYNC, VS or PITCH. To change vertical speed, use SYNC or PITCH."
Hope that helps.
Mark - Just Flight
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I've also noticed it is very easy for the AP to (correctly) disconnect if you fly too slowly.
Engine management and use of flaps takes practice and experimentation on approach.
Depending on weight etc., I'm having to drop a notch of flaps close to 200 kias,and further flap extensions causes massive drag... as does the airbrake. As such it is very easy to drop below the yellow bug -- which of course I keep forgetting to set by clicking on the placard.
It's challenging- but good fun - to fly.
