newbie question

[impulse200]

Hi everyone. 
Re-learning to fligh after 7 years hiatus. Now fighting to take spit in the sky. 

In pre-flight procedures section of DCS Spit there's point on setting elevator trim neutral. In in-game tutorial - 1 notch nose-heavy.

But what position is "neutral" on trimmer indicator? There's no word on it in DCS manual. Are the trimmers set to "neutral" by default?

[impulse200]

OMG, guess I've found the description. But not in the cockpit instruments section but in the AIRCRAFT SYSTEMS / Trimmers:

Quote

The elevator trimmer is controlled by a large handwheel (30) on the left side of the cabin. On the left side of the dashboard is an indicator (24) showing the position of the trimmer relative to the elevator. The neutral position of elevator trim on the indicator is marked by 2 bars from the middle position towards "NOSE UP". Two full revolutions of the wheel are required to move the trimmer from the arrow's middle position to the extreme end.

So this should be neutral, right?

 

[DD_Fenrir]

Manual is wrong. 
 

[Sarge55]

I always used the screw head as neutral. 

[Art-J]

11 hours ago, DD_Fenrir said:

Manual is wrong. 
 

If it is, so is the flight model then, because 1 notch above screw head works best for both takeoff and level flight in cruise. In the end, OP needs to know more how it works in the game rather than in real airplane.

[impulse200]

So the consensus is the middle tick of the gauge (screw head) is the neutral elevator trim position. Right?

[grafspee]

According to spit mk II manual, this gauge shows trim tab relative position to elevator

Edited February 15, 2022 by grafspee

[Art-J]

2 hours ago, impulse200 said:

So the consensus is the middle tick of the gauge (screw head) is the neutral elevator trim position. Right?

Consensus is - we don't know. Both current combat sims featuring Spit (DCS and Il-2GB) have two ticks up implemented as "neutral", whatever they mean by that. Whether it's historically correct or not is debatable, 'cause I haven't seen any real life drawing / diagram supporting / disproving that approach. 

You see what DCS manual claims. At the same time takeoff tutorial mission contradicts the manual by forcing you to crank the pointer one tick below screw (as if the screw was neutral after all), but that only makes the plane way too nose-heavy for both takeoff and cruise, and that doesn't make sense either.

I stick with what manual says and flight model does, not giving a damn about the question of "correctness". There are far more serious problems with this module to deal with (cooling system being the primary offender).

[Skewgear]

13 hours ago, impulse200 said:

So the consensus is the middle tick of the gauge (screw head) is the neutral elevator trim position. Right?

Probably. The original pilots' notes say 1 division nose down for takeoff but IMHO that needs a specific technique to prevent nosing over. (stick fully back when you select takeoff power, then ease it forward as speed builds to bring the nose down slowly)

For normal takeoff at full load with no bombs I set trim neutral (as in centre of the gauge/pointing at the screw), full right rudder trim and around +8lbs boost at full rpm. The DCS Spitfire will happily take off at +2lbs boost (on a long runway!) if you want a slower and easier experience.

You need to be quick to tap the rudder and prevent any swing developing on takeoff.

11 hours ago, Art-J said:

There are far more serious problems with this module to deal with (cooling system being the primary offender).

What's wrong with the cooling system?

[Reflected]

As for the elevator trim, according to the manual it had to be set to 1 division nose down at lighter loads (training) and to neutral at full loads (ammo, full tanks and drop tank". However, depending on what HOTAS you use (spring centered, etc..) this may or may not work for you in game. Experiment. When you get airborne you don't want the aircraft to want to climb, but you don't want to have to keep pulling on the stick either.

[Nealius]

On 2/15/2022 at 3:09 PM, Art-J said:

because 1 notch above screw head works best for both takeoff and level flight in cruise.

1 notch above screw causes excessive pitch up and near-wing stall as soon as the main gear leaves the ground when flying with combat loads. 1 notch below screw achieves the smoothest, trouble-free takeoff for me. I haven't bothered checking cruise trim, so can't comment on that one.

[Art-J]

On 2/16/2022 at 10:02 AM, Skewgear said:

What's wrong with the cooling system?

Mostly lack of thermostatic valve simulation in the system, which means if you intend to make a high altitude flight with historical econo power settings for maximum range, you're guaranteed to have your engine overcool and seize after a while. On the other side of the spectrum is a tendency to overheat at low speeds, a hot topic in Mustang section of the forum as well.

We've been told revision of cooling simulation of all V-12s in the game is in the works, so some of these issues might disappear then, but just like everything in DCS, whether the new implementation drops in couple of months or two years is anyone's guess.

[reece146]

Can you not adjust trim and use an external view to see where the trim tab is set? I'll have to check that out later...

Not that it matters - set the trim to what gives the desired feedback from the aircraft until you get an intuitive feel for what the setting does to the aircraft versus the gauge.

FWIW, one notch below is what I set for takeoff otherwise I ignore the gauge.

$0.02

Edited February 19, 2022 by reece146

[Art-J]

Last time I checked, years ago I admit, pointer being level on the indicator meant tab being flush with the elevator on external model. Keep in mind, however, that 3D model animations are not tied to flight model, so that doesn't mean much.

[reece146]

Went for a quick flight - needle pointing at the screw head is trim tab flush with the elevator. Moving the trim tab through out it's range matches the visuals to the gauge.

 

[DD_Fenrir]

There’s a multitude of factors at play.

1. Unequal elevator travel. 27 degrees up and 23 degrees down.

2. Unequal elevator trim tab travel.

3. elevator position at cruise speed and power settings is considerably displaced down.

4.  ‘trim neutral’ is an ambiguous term; can mean the point the tab chord is aligned with the elevator; can mean pre-defined speed and power setting. In an aeroplane as heavily modified from its first variant as the Spitfire IX it’s unsurprising that these figures may not match. 

[impulse200]

Thanks everyone for input. I found that "needle to the screw head" (and rudder "O" letter up   )works best for me. But trim using buttons is so-o-o-o slo-o-o-o-w-w-w. Could it be improved without using analog axis?

[razo+r]

If you click on it and drag your mouse it's much quicker.