Elevator trimming

I just looked at it… the trim wheel in the DC-6. And there’s indeed a delay. I think it’s the logic I described. It ‘assumes’ one click, so there’s a timer to see if you let go of the button or not (else you might trim too much). Then if you don’t let go, it starts rolling. It holds off perhaps 300 - 500 milliseconds or somewhere in that range. At least in my setup.

Then I thought: could this be a windows setting? Cause it’s almost like the delay you get when you press a key. But no joy. Changing the keyboard repeat delay doesn’t change the joystick-button repeat delay. Must be some internal sim value.

The only workaround I can think of then: bind the trim to two keyboard keys and set the repeat-delay of the keys really short.

Thank you for your feedback. The problem using the keyboard for me is that most of the times I’m flying in VR. If I find another solution I tell you.

The only solution for me is setting the small wheel axis on the throttle to elevator trim, the problem is that I like to keep it as propeller axis.

In another thread someone is trying it with the mouse wheel. But seems to be too slow (as in: you have to scroll till your finger drops off). Seems unpractical to me anyway. I do agree with @PZL104 that it’s most handy close by on the joystick. It’s too important (unless flying an Airbus I suppose).

I don’t have any extra options on my joystick. It would be nice if they make this button delay optional (or settable in length).

I have it on the joystick as well, my only complaint is the delay. It seems a standard value for all button commands, which makes sense for flaps up or down for exemple, as you want one position at a time, but for the trim it doesn’t work properly.

Yes, I just looked at some raw data, when you press a joystick button. And it is as I thought. There’s only a DOWN event and an UP event. There’s no automatic repeat.

So the sim is reading the DOWN, then has to ‘predict’ if there’s gonna be an UP following or if it’s being kept down. So they delay a bit… if the UP isn’t arriving within that time frame, they assume the button is still down and they start to repeat. Really similar to the keyboard.

What I’m wondering if there’s some variable that could be set in some cfg file somewhere, to change that delay value.

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Interesting, perhaps we can find it somewhere. The ideal would be to change only the trim values, if possible.

Trim up or down assigned to a single button is indeed a one-time press, meaning you need to keep hitting that button if your desired trim configuration (which isn’t necessarily level) is a few presses away. That was my old joystick configuration. It became somewhat easier when I got a dedicated Trim Wheel.

In either configuration (two buttons or a hardware wheel), you must WAIT to see the input’s effect. That’s true in real life too - the few times I could trim for straight and level. The trim is not instantaneous. In fact, the Wheel can be more treacherous than two buttons - if I rotate it, not even a full rotation, but just a few notches up or down can drastically change my trim stability depending upon speed, orientation and control surface configuration (i.e., flaps, spoilers etc). So I have to wait to see the effect.

A little OT, but not really - this is why Force Feedback matters. Elevator Trim isn’t primarily intended to neutralize the controls (i.e., take your hands off, you continue holding your attitude) but you can certainly do that for things like straight and level. It’s designed to help you take the load off of pulling or pushing the control yoke in the case of descents or climbs. That’s why an FF yoke or stick could pull or push back as needed to show Trim effectiveness.

Barring that, all you have is to watch what your pitch ladder is doing in relation to how much pitch input you’re applying. If climbing at full power say on take-off, you’re aiming for a certain pitch in order to get optimum rate of climb at the power setting you have. The tendency for the aircraft with flaps down will be to pitch further up than your desired setting, hence you’ll dial in some nose-down to ease the burden of having to push on the yoke.

That will change again when your speed starts to exceed safe flap deployment and you’re starting to configure for an eventual change to cruise. Take the flaps out, and you’ll see the aircraft nose down. Now you have to take out the trim you dialed in with flaps deployed and bring it back to maintain a still nose-up attitude until you’ve reached the desired cruise alt.

But that does take time, and you need to see what happens in between each trim input. Not an eternity, but certainly a few beats of the clock in between presses, or in my case, dialing in a notch or two of up/down.

Yes, personally I’m not sure if getting rid of that time delay will actually improve matters. Because the plane needs time to respond anyway. One might still perceive a somewhat natural delay. But nevertheless, this repeat delay does seem to sit in the way a bit. There’s no such delay if you would manually scroll a wheel. In that sense, using the mouse wheel (an idea I read in another thread), was kind of a good idea I thought. It’s just too disconnected from a joystick for me (and apparently comes with its own problems).

It does make me wonder why it took an Airbus for this stuff to become automated… as in… why wasn’t ‘autotrim’ implemented earlier in more airplanes? Is it that hard?

Well, autopilots are “auto-trimming” when in certain modes. I don’t think autotrim is such a good idea for when the plane is flying manually. You could end up in a vicious circle where the pilot is imposing a pitch change that the plane doesn’t understand is deliberate.

Well, I don’t have in-depth knowledge. But I think it might be also be a philosophy difference? I think the Airbus does it too when you’re flying it manually. So the designers didn’t seem bothered by it?

But when I think about it… it actually seems that using the stick in an Airbus is not much different than turning the trim wheel in a non-automated plane? Cause you can pull the stick back to ‘the middle’ and the input stays.

But well… I can speculate about it, but I better read up on it before my ignorance shows too much and @PZL104 has to jump in again :slight_smile:

I disagree. That’s exactly what trim is for.

Taking the load off = neutralizing the input.
If you trim the aircraft for a climb/descent, the neutral point of the elevator/stabilizer changes you can (and should!) take the hands off the controls.

Autotrim isn’t an Airbus invention and not even a FBW thing.
It’s often simply used to reduce the required amount of trimming in certain cases.
E.g. (at least) on the CRJ100/200 the pitch moment during flap retraction/extension would have been extremely large, distracting and hence considerable increasing the workload.
So Canadair used autotrim during flap retraction/extension to reduce the workload.

If an aircraft has an autopilot, it isn’t difficult to implement at all.

On many AP equipped aircraft there’s a function called CWS (ControlWheelSteering) or similar, depending on the company.
If you push and hold a yoke button, the autopilot servos disengage and you can e.g. pull the aircraft up from level flight into a climb attitude.
As soon as the you have achieved the new pitch attitude you release the button, the AP takes over again and immediately retrims the aircraft.

And that’s exactly how Airbus describes its FBW systems; If you fly an Airbus manually, it’s like flying a conventional aircraft with the AP engaged and continuously operating CWS.

It’s the philosophy of how to control and aircraft and the feedback you get from it.

Personally I dislike the Airbus flight path stability and autotrim function because you get zero feedback from the aircraft.
If you slow down or speed up, if the ROD increased or decreases you always have to watch the relevant instruments, because there’s no feedback from the aircraft.
‘Flying’ an A320 IRL is like playing Ace combat. You are pointing the aircraft where you want it to go.

That’s why it’s so frustrating for me that Asobo turned the 787 into an Airbus a few updates ago.

I always felt sorry for the new copilots who start their airline career on an A320, since they will most likely never ‘feel’ the aircraft they are flying.

I guess that’s an interesting point of contention for CFIs. Mine (I only had a few lessons) let me try once to trim straight-and-level and then remove my hands from the controls. Now mind you I had a slightly nose up with the VSI at about 50-100 fpm so it was nowhere near perfect but neither was it dangerous. He let things stew for about ten seconds (it was an eternity for me) and then looked me and said “I never want to see your hands off the controls ever again as long as I’m in the cockpit with you and you’re flying.” :grin:

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That’s a nice story and it perfectly describes what trimming is about.
Even in the perfectly trimmed case, regardless if in level flight or e.g. on the ILS, you only temporarily remove the hand from the stick/yoke, just to check if you are not subconsciously applying slight pressure.

That’s what I like in MSFS. Even if you are trimmed for level flight in e.g. the 152, there are always slight variations in v/s and you have to apply tiny corrections.
A v/s of 50ft/min means that you have 1min to correct this error and to stay within in the very narrow ±50ft IFR checkflight limit.

That’s not what I consider neutralized controls. It’s about not having to continuously apply considerable pressure on the stick/yoke to counteract an out of trim situation.

We’ll I broke that rule the other day (mental raspberry to him lol), and I trimmed the Aerobat for a 17nm island hop, couldn’t get it to 1500 steady, but I did get it stabilized around 2100’ and just over 2000 rpm. I just needed to correct the heading drift from the wind, but gradually made my way over the water.

There was a low cloud base that I had just started to skip under at that altitude. I was so focused on the instruments to trim s&l that when I finally looked up using the mouse view, I got a small brief case of vertigo even though I wasn’t moving per se. There was no horizon reference, just wispy clouds all around. I immediately started my instrument scan again and put the nose down. That was cool.

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Thank you for your feedback, apparentely there is no solution for this. I don’t see the point of the trim input having this annoying delay. The fact that you need some time to see if the airplane is trimmed has nothing to do with the actual input delay. And you can perfectly trim with a non-FFB stick as you can try to bring it to the spring neutral position, it is just a matter of getting used to it.

There is no input delay. I see the Trim Wheel in cockpit moving in unison with my manipulation of my hardware Trim Wheel. Before that, when assigned to two buttons on my joystick, the in cockpit wheel behaved similarly. Taking into account the delay to watch the effect of dialing in a few notches of trim, there isn’t anything wrong in terms of functionality.

Well, if this forum allowed me to post a video I would be able to show the delay. There is an input delay when you use buttons. A delay that doesn’t make any sense.