Why can't elevator trim be quickly centered?

[oneleg]

I'm trying to understand the logic of why there are no facilities or short-cut keys for automatically center the elevator trim.  Am I just missing something?

[jgf]

In the real world there's no need to do this.  Trim is something slowly and steadily changed as flight conditions change, fuel is burned off, etc.  If you need to adjust it more quickly in the sim it's probably a control sensitivity or repeat rate adjustment that needs tweaking.

[oneleg]

18 hours ago, jgf said:

In the real world there's no need to do this.  Trim is something slowly and steadily changed as flight conditions change, fuel is burned off, etc.  If you need to adjust it more quickly in the sim it's probably a control sensitivity or repeat rate adjustment that needs tweaking.

Thank you for the tip. To test, I changed the elevator_trim_effectiveness value in Just Flight's Turbo Arrow aircraft.cfg file from the default 1 to 5 but that didn't seem to make a difference (I'm probably overlooking something.)

[jgf]

That's a major change, I don't know if there's a limit there but it rarely takes more than a 0.5 edit.  I usually have the opposite issue - leveling off for cruise i have a 200-300ft/sec climb, give one click of down trim and it goes to a 200-300ft/sec descent, can't seem to hit that sweet spot in the center;  change the trim effectiveness to around 0.7-0.8 and it's fine.  I think this works as a percentage, 1.0 being 100% of design, 1.1 being 10% more effective, 0.9 being 10% less effective.

 

There's also a "repetition rate" adjustment in the controls config which sets how much the adjustment changes as you hold down the key/button, raising this value will give faster response.

[PhrogPhlyer]

On 9/20/2023 at 3:47 AM, jgf said:

In the real world there's no need to do this.  Trim is something slowly and steadily changed as flight conditions change, fuel is burned off, etc.

This a valid statement for fixed-wing aircraft, which is appropriate for oneleg's Arrow. 

For rotary-wing, many have no trim mechanism, or there may be some form of trim centering system. On the CH-46 there is a pitch trim system, mostly used for fwd or aft CG (controlled with the hat button on top of the cyclic grip). Also there is CDRB or Collective Differential Release Button (collective in this case means the cyclic is reset collectively in pitch and roll axis's). For example, if you were in a turn, holding pressure on the cyclic, you would press the CDRB (thumb button on the cyclic grip) and the "neutral" position of the cyclic is reset to where you are holding the control. So a little bit of small trim adjustments and instantaneous centering  adjustment.

[oneleg]

On 9/21/2023 at 1:25 AM, jgf said:

There's also a "repetition rate" adjustment in the controls config which sets how much the adjustment changes as you hold down the key/button, raising this value will give faster response.

I searched for the "repetition" and "repeat" in the Arrow's aircraft.cfg file but could not locate those two in the file. Where can I find the controls config? 

(The in-game control setting for the repetition rate under Options/Controls is already at the max setting but I find the repetition rate as still slow to respond to trim adjustments in Just Flight's Arrow.)

[oneleg]

22 hours ago, PhrogPhlyer said:

many have no trim mechanism, or there may be some form of trim centering system.

This made me think. Isn't altitude hold effectively the same as elevator trim? If the result is the same, why then does 'elevator trim' exist?

[PhrogPhlyer]

2 hours ago, oneleg said:

This made me think. Isn't altitude hold effectively the same as elevator trim? If the result is the same, why then does 'elevator trim' exist?

Best answer I can give is it depends on what is installed on the aircraft. Not everything has an altitude hold, but a trim wheel is on most fixed wing aircraft.

Also, my statement was referring to rotary wing aircraft, which do not have trim wheels.

[jgf]

The AP controls altitude via the pitch trim, a fact i use to advantage with some aircraft that are problematic with pitch.  Rather than fighting the trim wheel (two buttons on the joystick in my case) I activate altitude hold briefly then turn it off;  this is particularly helpful with those aircraft with major pitch changes when flaps are raised/lowered.

 

There are some basic APs you can add to any aircraft for this, the simplest is one button which toggles alt and heading hold.

[oneleg]

On 9/22/2023 at 5:28 PM, jgf said:

There are some basic APs you can add to any aircraft for this, the simplest is one button which toggles alt and heading hold.

Presumably using something like FSUIPC.

[snave]

Use Num Pad 5 with the keypad lock OFF. This centres all controls AND trim. If it is not applied by default, you can add it manually.