trisho0

Trim question for PMDG 737NGX

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1 minute ago, downscc said:

There are many good sources of aviation basics available.  If you find the AIM too technical then I'm not sure where you are in terms of education and background.  The AIM is a very basic document orientated towards the student pilot studying for a private pilots license.  Give it a look.

I visited AIM and saved a copy to read on it. When I started reading from I found so technical for me. I am not a Pilot. I have technical studies not related with flying but for work. I am still learning with PMDG planes. I will take another look at the AIM saved info. 

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Posted (edited)
1 hour ago, skelsey said:

No. I think you're getting very confused :).

Did you try the exercise I suggested in my earlier post?

I did what Ephedrin said and I was be able to trim the 737NGX plane right after takeoff. Instead of holding the stick from Joystick I was trimming and yes, noticed the nose was controllable up and down following the PFD line. So, when the plane was in about 1K lower than the programmed altitude is when I armed autopilot. From then the flight was fine until landed.

Also, learned trim is for attitude and stick is for altitude. You say trim for pitch attitude.

Edited by trisho0
correcftions done

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2 hours ago, Stearmandriver said:

Sick and Rudder, meh.  Let's all get "Conquest of Lines and Symmetry" and debate the relative merits of leading pulls, bottom rudder on roll entries etc ;-). 

Any day that I'm upside down is a bad one in my book. lol

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1 hour ago, trisho0 said:

I did what Ephedrin said and I was be able to trim the 737NGX plane right after takeoff. Instead of holding the stick from Joystick I was trimming and yes, noticed the nose was controllable up and down following the PFD line. So, when the plane was in about 1K lower than the programmed altitude is when I armed autopilot. From then the flight was fine until landed.

Also, learned trim is for attitude and stick is for altitude. You say trim for pitch attitude.

Well... That's not quite it. Stick is for attitude, and attitude controls altitude (in conjunction with power). Trim is to hold the desired attitude without needing to hold constant stick pressure. 

All of what I just said is a concise explanation, but probably not real useful since you have no frame of reference.  You're at the point where you need a full lesson combining all these bits and pieces we're discussing into a cohesive whole. 

There are plenty of good books available... The official FAA handbook is available online, free. For this discussion, you probably want chapter 3, Basic Flight Maneuvers. 

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/airplane_handbook/

Also, it will be a lot easier to understand these concepts in a smaller airplane than a 737.  In FSX, the stock Cessna 172 will work just fine. 

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Trim is ONLY used to take forces off the controls. NOTHING else. That's the sense of it. Early airplanes in WW1 didn't have any trim tabs and the pilots had to hold the stick back or forth to hold the nose where it should be. this is possible of course but incredibly exhausting. So they invented the elevator trim. as soon as you have to hold the stick back or forth to keep the nose up or down, use the elevator trim, stabilizer trim, what ever it is called on the airplane you fly, and you can release the pressure. I really don't understand what's so difficult about it... When you have constant pressure on the controls, use the trim to release it. that's so logical, easy, even at the simulator... Don't think too much.. just do it.

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18 hours ago, trisho0 said:

I did what Ephedrin said and I was be able to trim the 737NGX plane right after takeoff. Instead of holding the stick from Joystick I was trimming and yes, noticed the nose was controllable up and down following the PFD line. So, when the plane was in about 1K lower than the programmed altitude is when I armed autopilot. From then the flight was fine until landed.

Also, learned trim is for attitude and stick is for altitude. You say trim for pitch attitude.

I owe you an apology.  When I learned to fly in 1974, the AIM was the basic guide to piloting.  Now it seems it is more about the aviation environment, navaids, airspace and the such.  I misdirected you.  The correct basic guild to piloting and all things airplane is their Pilot Handbook (here: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/ ).  This very comprehensive handbook covers everything a student pilot should learn about piloting basics, including Ch 6 Flight Controls and specifically in this case pg 6-8 Secondary Controls and pg 6-10 Trim Systems.  The adjustable stabililzer used by larger aircraft such as the NG is on page 6-12 but I think  it would benefit you to read the entire section on flight controls.

Again, sorry for the misdirect.  I couldn't swallow that the AIM was too technical for you so on checking I found that it simply failed to cover the pertinent material on this topic.

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4 hours ago, Ephedrin said:

Trim is ONLY used to take forces off the controls. NOTHING else. That's the sense of it. Early airplanes in WW1 didn't have any trim tabs and the pilots had to hold the stick back or forth to hold the nose where it should be. this is possible of course but incredibly exhausting. So they invented the elevator trim. as soon as you have to hold the stick back or forth to keep the nose up or down, use the elevator trim, stabilizer trim, what ever it is called on the airplane you fly, and you can release the pressure. I really don't understand what's so difficult about it... When you have constant pressure on the controls, use the trim to release it. that's so logical, easy, even at the simulator... Don't think too much.. just do it.

Many thanks Marc. So, not much to use Trim but just to control attitude (not altitude). What about controlling the tail? via trimming right? I mean, the plane takeoff and if the nose is going too high then trimming nose down a bit until the plane is on airborne. Once on airborne continue flying with stick, no need more trimming. I assume if no trimming before the plane leaves the ground runway then is the reason why I have sometimes a message "tail on strike". Hmmm ..... learning....

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47 minutes ago, downscc said:

I owe you an apology

Please Dan, no need apologize. This thread is really one of the best classroom including those handbooks from the https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/

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5 minutes ago, trisho0 said:

Many thanks Marc. So, not much to use Trim but just to control attitude (not altitude). What about controlling the tail? via trimming right? I mean, the plane takeoff and if the nose is going too high then trimming nose down a bit until the plane is on airborne. Once on airborne continue flying with stick, no need more trimming. I assume if no trimming before the plane leaves the ground runway then is the reason why I have sometimes a message "tail on strike". Hmmm ..... learning....

You are better off controlling pitch during takeoff during the initial climb below 400 AGL and forget trim until after acceleration height.  Sure, a tap on trim during this time for me might be done without thinking but primary pitch control is always with the yoke/stick.  Pitch trim changes are continuous as flaps retract and airspeed increases and your first opportunity to trim for pitch is once established in a steady attitude climbing at 250 KIAS.

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16 minutes ago, downscc said:

You are better off controlling pitch during takeoff during the initial climb below 400 AGL and forget trim until after acceleration height.  Sure, a tap on trim during this time for me might be done without thinking but primary pitch control is always with the yoke/stick.  Pitch trim changes are continuous as flaps retract and airspeed increases and your first opportunity to trim for pitch is once established in a steady attitude climbing at 250 KIAS.

This is exactly I was doing ever until this thread started. All flight I did with only joystick, no trimming. But now, as I trim the plane doesn't get "Tail On Strike" as I had sometimes before.

You say, trimming for pitch is once established  in a steady climbing. I don't see the needs to do that if the plane is already on airborne and the AP will be armed. I will check handbooks later.

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35 minutes ago, trisho0 said:

I don't see the needs to do that if the plane is already on airborne and the AP will be armed.

You should trim out any control forces prior to engaging the autopilot, technically. If you're too far out of trim, the AP won't take it, or you'll have an abrupt pitch change when you let go of the stick in order to get the AP on (as pressure on the yoke will cause the AP to kick off).

As I've mentioned to you a few times already, I'd really suggest paying attention to what people are telling you instead of pushing back with "well I'm doing this and it works." You can put your car in park without using the parking brake (if you drive an automatic car), but that actually puts a lot of strain on your transmission. Just because you can, and it "works" doesn't mean that you should.

Everyone in this thread has jumped in to help you get a better handle on things because they have experience, and knowledge where you don't (and that's not a bad thing - everyone has to learn over time). Do them the favor of listening to them after they've volunteered their time to help you out.

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2 hours ago, scandinavian13 said:

You should trim out any control forces prior to engaging the autopilot, technically. If you're too far out of trim, the AP won't take it, or you'll have an abrupt pitch change when you let go of the stick in order to get the AP on (as pressure on the yoke will cause the AP to kick off).

How far out of trim will be if before takeoff I set trim accordingly (FMC info). I use the Stick carefully on the initial climb by looking at the horizon PFD and flaps up following the Primary Flight Display. PFD is telling me when is time for flaps. I don't have AP issues yet.

2 hours ago, scandinavian13 said:

Everyone in this thread has jumped in to help you get a better handle on things because they have experience, and knowledge where you don't (and that's not a bad thing - everyone has to learn over time). Do them the favor of listening to them after they've volunteered their time to help you out.

I follow them and your help as well. It's just trimming procedures wasn't clear to me. I want to do trimming but all I see is the plane nose goes up or down as I want. Helpers ask me to take a look at handbooks and that is what I am doing to understand trimming.

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4 hours ago, trisho0 said:

How far out of trim will be if before takeoff I set trim accordingly (FMC info).

Doesn't matter. TO trim is set to allow you to rotate the aircraft effectively. Trim as appropriate after takeoff to follow the flight director without pressure on your hardware. You're approaching this too over-analytically. Trim until you don't need to hold pressure on the yoke. Done. It's really that simple.

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15 hours ago, trisho0 said:

How far out of trim will be if before takeoff I set trim accordingly (FMC info). I use the Stick carefully on the initial climb by looking at the horizon PFD and flaps up following the Primary Flight Display. PFD is telling me when is time for flaps. I don't have AP issues yet.

I follow them and your help as well. It's just trimming procedures wasn't clear to me. I want to do trimming but all I see is the plane nose goes up or down as I want. Helpers ask me to take a look at handbooks and that is what I am doing to understand trimming.

You'll set the trim from the FMC on the ground.

You'll rotate and pitch up to ~15deg and set the trim again to remove the pressure on the yoke.

At acceleration, you'll pitch to ~9deg and you'll have to trim until you're done accelerating to 250kts (or whatever your target).

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On ‎6‎/‎12‎/‎2018 at 9:25 PM, scandinavian13 said:

Doesn't matter. TO trim is set to allow you to rotate the aircraft effectively. Trim as appropriate after takeoff to follow the flight director without pressure on your hardware. You're approaching this too over-analytically. Trim until you don't need to hold pressure on the yoke. Done. It's really that simple.

I did several times this procedure and yes it worked perfectly in the Cessna C172 and found the trimming changes the attitude rapidly. Trim helps me with Cessna more than 737NGX. Rarely tried with small planes before because I like PMDG and Level-D, all more realistic. I don't need trimming the PMDG maybe because I use Logitech Extreme 3D Pro Joystick which I don't sense the pressure. I think if I get a better joystick design probably I would feel the pressure. Trimming is clear for me now. 

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