Take Off Trim

[Caldera]

Hey All,

 

OK...  

 

I had assumed that SAS Take Off Trim been already activated for a runway/warm mission start.  True or False?

 

If TO TRIM has been activated and then I manually trim does this actually have any effect on aircraft trim?

 

For runway/warm mission starts I have learned to keep the Gun Control in SAFE as PAC seems to cause some pitch down trim.  But, none the less as soon as I lift off the nose feels really heavy.  Climbing out, I would typically turn on PATH HOLD at around 200 knots letting the flaps automatically retract.  The nose just falls out of the sky if I do not apply quite a bit of nose up trim before I do that and PATH HOLD will not stay engaged.  

 

Maybe I have a misconception (again) as I had thought that activating TO TRIM was supposed to make the nose lighter for take off.  True or False?

 

Would SAS TO TRIM be a designed to compensate for a specific take off weight or density altitude?

 

Thanks again,

Caldera

[Rakamora]

If you press takeoff trim and green light lights up immediately and stick not moving t/o trim was already set. If pressing t/o trim and it takes a while for the light to light up and stick moving t/o trim was not set. Make it a habit before lining up on runway to press t/o trim check half flaps and arm seat.

 

And i forgot, dont worry about gun-pac until fencing in. Master arm on when approaching target area, happy flying!

Edited March 11, 2021 by Rakamora

[jaylw314]

The Takeoff Trim button just neutralizes all the trims.  It's just a fixed setting, it doesn't compensate for anything.  It's simply the trim setting that makes the trim tabs flush with their control surface, so expect to have to trim the plane once you're established in the climb.

[Caldera]

Thanks guys I appreciate your time.

 

If I got this right, the TO TRIM button basically does the same thing as the key bind Trim: Reset?

 

Caldera

[Yurgon]

On 3/11/2021 at 4:28 AM, Caldera said:

I had assumed that SAS Take Off Trim been already activated for a runway/warm mission start.  True or False?

 

Like Rakamora said, just hit the TO TRIM button and you'll get instant feedback (either the takeoff trim light comes on, or it doesn't).

 

And yes, when the player aircraft is set to start hot on ramp or ready for takeoff on the runway, the takeoff trim should be preset.

 

On a side note, while the takeoff trim is close to the SAS switches, it's not "SAS Take Off Trim", it's just "Takeoff Trim" and is independent of SAS, as far as I know.

 

On 3/11/2021 at 4:28 AM, Caldera said:

If TO TRIM has been activated and then I manually trim does this actually have any effect on aircraft trim?

 

Absolutely, yes!

 

On 3/11/2021 at 4:28 AM, Caldera said:

For runway/warm mission starts I have learned to keep the Gun Control in SAFE as PAC seems to cause some pitch down trim.

 

Unless you intend to kill a target a mile or two beyond the runway, you should definitely keep all weapons safe during takeoff.

 

On 3/11/2021 at 4:28 AM, Caldera said:

Climbing out, I would typically turn on PATH HOLD at around 200 knots

 

Nothing wrong with that, as long as you've properly trimmed the aircraft before engaging the autopilot.

 

When changing the aircraft's attitude in any way, including accelerating and decelerating, you should also disengage the autopilot every now and then, re-trim, and re-engage the autopilot. Otherwise the autopilot might try to hold the parameters as best it can, and as soon as you disconnect the AP, the aircraft bounces like crazy.

 

On 3/11/2021 at 4:28 AM, Caldera said:

letting the flaps automatically retract.

 

Hell, don't do that! If you happen to decelerate below circa 200 knots for whatever reason, the flaps will come out again and your lift (and drag) will change. If you don't happen to pay close attention to the tiny flaps indicator, you might miss it and fly a draggy Hog around, barely able to accelerate above 200 knots again (could be a problem at high altitude, or in a steep climb). Plus, the flaps will inhibit the launch of certain weapons like the Maverick.

 

Long story short, my understanding is that the automatic flaps retraction is there to prevent damage to the flaps. It's not there to accommodate lazy pilots.

 

So, after takeoff, ensure positive rate of climb, gear up, wait till roughly 140ish, 150ish knots, re-confirm positive rate of climb, and then retract the flaps.

 

On 3/11/2021 at 4:28 AM, Caldera said:

The nose just falls out of the sky if I do not apply quite a bit of nose up trim before I do that and PATH HOLD will not stay engaged. 

 

That is exactly correct.

 

On 3/11/2021 at 4:28 AM, Caldera said:

Maybe I have a misconception (again) as I had thought that activating TO TRIM was supposed to make the nose lighter for take off.  True or False?

 

It just makes sure that the jet is not trimmed nose down or up or right or left wing down, which could send the jet into a possibly inescapable death trap during the takeoff roll. The controls will be as neutral as they get.

 

On 3/11/2021 at 4:28 AM, Caldera said:

Would SAS TO TRIM be a designed to compensate for a specific take off weight or density altitude?

 

I don't think so. AFAIK, it always sets the control surfaces to the exact same setting, regardless of aircraft weight or density altitude.

 

2 hours ago, Caldera said:

If I got this right, the TO TRIM button basically does the same thing as the key bind Trim: Reset?

 

I've never used the trim reset. You can test it by pressing trim reset and then checking if the takeoff trim lights up as soon as you press the TO TRIM buttons.

 

Let us know how the test goes!

[Nealius]

I'm curious what takeoff weight the OP is at. I've never experienced issues with the nose dropping on takeoff, but I also don't load my jet up higher than 86% MTOW, sometimes 92% but rarely. There also could be a axis binding issue going on.

[Foka]

You can take off with Hog at 101-102% of weight, maybe more. It just take a bit longer, but of course it's not recommended.

[jaylw314]

7 hours ago, Foka said:

You can take off with Hog at 101-102% of weight, maybe more. It just take a bit longer, but of course it's not recommended.

FWIW, max gross weight is a structural limit, not a power limit.  If you pull max rated G at max gross weight, you have some percent safety margin before any structural damage.  I can't recall any of these numbers off hand, but the upshot is you could probably take off at 120% of max gross weight fine, but if you hit some turbulence you might be in for a very bad day.

[Caldera]

Yurgon, 

 

Thank you!

 

Others,

 

Because mostly these are practice sorties, I have been taking off anywhere from 70% to 110%.  Lately closer to 110% (or more).  I am sure I have allot of extra drag also.  The bird feels really heavy at 110% and the extra nose heavy trim confused me.

 

From the start, I was convinced that in a simulation the trim being set to any thing other than neutral was entirely normal for the initial spawn into the game.  I had some misconceptions about what TO TRIM actually did.  With SAS, I was thinking that it was some what like a mechanical take off trim configuration that is set according to a few variables including take off weight being one of them. 

 

My thinking, if the initial trim is already set at neutral then TO TRIM must do something else...

 

Approximately 91% of my time in DCS has been in the A-10C and with 8.954678954389007% in the P-51D.  Are there aircraft in DCS where the trim starts out as any thing other than neutral for the initial plop into the game?

 

I guess the thing for me to do is check that trim is neutralized and then set it to my preferences based on experience prior to take off.  Either way not a big deal really as it is just as easy to trim out in the air.

 

Thanks again,

Caldera

[Foka]

Neutral trim and T/O trimm are two completly different things. Neutral trim is set to 0. And T/O trim deepnds on plane, weight, wind, etc.

For example for Hornet T/O trim from airfield is 12 degrees, for carrier ops it's 16-19 degrees, depending on weight.

[=52d= Skip]

When the T/0 TRIM button is depressed, the pitch and roll trim motors and the two elevator tab trim motors are driven to neutral. With the T/0 TRIM button depressed, the yaw trim knob in neutral setting, and the five trim motors at neutral setting, the TAKEOFF TRIM light comes on.
 

[jaylw314]

7 hours ago, Foka said:

Neutral trim and T/O trimm are two completly different things. Neutral trim is set to 0. And T/O trim deepnds on plane, weight, wind, etc.

For example for Hornet T/O trim from airfield is 12 degrees, for carrier ops it's 16-19 degrees, depending on weight.

Takeoff trim and neutral trim mean the same thing in the A-10.  There no system for adjusting for weight/balance.  From the A-10C flight manual:

 

"When the T/O TRIM button (Figure 1-18) is depressed, the pitch and roll trim motors and the two elevator tab trim motors are driven to neutral"

 

Edit: oops, Skip beat me to it!

Edited March 14, 2021 by jaylw314

[Sierra99]

If you are exceeding ANY flight manual limitations during Takeoff....all bets are off. Flight manual limitations exist for a reason. They didn't pull numbers out of a hat or make them up to sound good. In real life screwing up your takeoff data can be fatal.

 

that being said, sure you can take off at whatever weight you wish in a simulator...but don't question the flight model when you are already operating off of the page.

[Caldera]

Thanks all,

 

From the sound of it I did not read the manual well enough, put that on my list of flubs.  I have gotten into a bad habit of not reading the manual well because I keep stumbling on discrepancies.

 

Sierra,

 

I never at any time questioned the flight model.  If it sounded to you like I did that,  it was not intentional on my part and my apologies.  I simply was a little bent on what TO TRIM was supposed to be doing in the DCS A-10C.   I often put myself in the seat as my very own test pilot just to see what happens.

 

For the rest, maybe you should look into the 8 Israeli F-16's who managed to drop a few bombs on an Iraqi nuclear reactor flying 99% of the way at less than 100 feet so overloaded with fuel and ordinance that they could barely get off the runway.  And about how they refueled hot once more after taxiing out to the runway.  And how they also dropped their multiple external fuel tanks from 100 feet somewhere in Saudi Arabia while still being laden with bombs (I believe at least a couple did not go off).  Pretty much none of that is found in the F-16 manual any where is what I am guessing. 

 

What a hoot that flight was!

 

Caldera

[Caldera]

My bad,

 

On 3/11/2021 at 8:05 PM, Yurgon said:

I've never used the trim reset. You can test it by pressing trim reset and then checking if the takeoff trim lights up as soon as you press the TO TRIM buttons.

 

Let us know how the test goes!

 

From my quick testing, there is not allot of difference.   Using TO TRIM the stick seems to center faster than using Trim: Reset but the result is the same.  The stick ends up being centered.  I guess I should  test TO TRIM while I am in flight.  That, I have not done.

 

I used trim reset fairly often when I was flying in either of the P-51's, usually right after take off.  I didn't think it was very realistic.  I could be wrong. 

 

Even IL-2 has trim reset...

 

Caldera

[silverdevil]

propeller planes also have rudder trim to help counteract the torque of the engine. The real plane needs 5° right trim. in A-10 i have never really required any trim for right or left unless there is wind. nor needed any other control surface trim. just go easy on the stick.

[jaylw314]

12 hours ago, silverdevil said:

propeller planes also have rudder trim to help counteract the torque of the engine. The real plane needs 5° right trim. in A-10 i have never really required any trim for right or left unless there is wind. nor needed any other control surface trim. just go easy on the stick.

 

Trim is more helpful IRL since stick and rudder forces are higher can be pretty darn tiring after a while, so it's considered good airmanship.  With our sim stuff, significantly less crucial, but still good airmanship.

 

Rudder trim might be useful to neutralize asymmetric loadout or a damaged engine, but I've never needed it with CH rudder pedals.  I suspect IRL I would kill for rudder trim

 

20 hours ago, Sierra99 said:

If you are exceeding ANY flight manual limitations during Takeoff....all bets are off. Flight manual limitations exist for a reason. They didn't pull numbers out of a hat or make them up to sound good. In real life screwing up your takeoff data can be fatal.

 

that being said, sure you can take off at whatever weight you wish in a simulator...but don't question the flight model when you are already operating off of the page.

 

Operations above MGTOW are restricted by regulation, not by physics, and it's common--or at least not unheard of--to get waivers for those regulations.  If you need to ferry a plane across the ocean, you can apply for flight above MGTOW to accommodate the necessary fuel and survival equipment.  Whether the FAA approves it is probably related to what else you propose to mitigate risk.  IIRC some commercial ops in Alaska can fly above MGTOW to carry survival gear under some circumstances.  The important part to learn in those ops is that while your performance may only be marginally reduced, your margin for structural failure may be significantly reduced.

[silverdevil]

i definitely use trim while in air and if needed on ground depending on load. i do not unless needed on ground with jets. i do in prop planes in this and another sim.

[Sierra99]

On 3/15/2021 at 12:59 AM, Caldera said:

Thanks all,

 

From the sound of it I did not read the manual well enough, put that on my list of flubs.  I have gotten into a bad habit of not reading the manual well because I keep stumbling on discrepancies.

 

Sierra,

 

I never at any time questioned the flight model.  If it sounded to you like I did that,  it was not intentional on my part and my apologies.  I simply was a little bent on what TO TRIM was supposed to be doing in the DCS A-10C.   I often put myself in the seat as my very own test pilot just to see what happens.

 

For the rest, maybe you should look into the 8 Israeli F-16's who managed to drop a few bombs on an Iraqi nuclear reactor flying 99% of the way at less than 100 feet so overloaded with fuel and ordinance that they could barely get off the runway.  And about how they refueled hot once more after taxiing out to the runway.  And how they also dropped their multiple external fuel tanks from 100 feet somewhere in Saudi Arabia while still being laden with bombs (I believe at least a couple did not go off).  Pretty much none of that is found in the F-16 manual any where is what I am guessing. 

 

What a hoot that flight was!

 

Caldera

American were accused of supplying them with Laser guided weapons because of the accuracy of their drops in CCIP.

 

No worries about the rest. I hope I didn't come across mad or irritated . Wasn't my intention.

[Frederf]

On 3/11/2021 at 8:16 PM, Caldera said:

Thanks guys I appreciate your time.

 

If I got this right, the TO TRIM button basically does the same thing as the key bind Trim: Reset?

 

Caldera

The DCS reset function is not a real control in the airplane. It should neutralize all trims: roll, pitch, and rudder. The cockpit button only drives the pitch and roll tabs to their T/O position. If yaw trim knob is out of center then the verify light won't come on. The pilot has to center the yaw knob manually.

 

The reset trim function should never be used by a simulation user attempting to simulate flying the airplane as as close as possible to a real pilot. It is a sort of debugging tool.

 

Takeoff trim is not necessarily designed to automatically liftoff but mostly to provide the most stable and controllable takeoff.

[Chump]

T/O trim on ground, trim in air, reset trim (DCS style) once RTB to have neutral controls on the ground. I know that the reset functionality isn't realistic, but I don't want to try to get the level equal using the GUI window. All I would need to do is hit T/O trim again to get airborne.