Trim question for PMDG 737NGX

[trisho0 23]

On ‎6‎/‎13‎/‎2018 at 8:34 AM, Spin737 said:

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).

I understand that and Cessna did a good attitude changes but I don't realize pressure from joystick. I think your joystick is similar to Pilot Training classroom and I guess you can feel pressure from Yoke. I don't because my joystick is not that sophisticated but I can fly my birds.

[MarkJHarris 128]

The 737 Yoke is held by a spring, nothing really that much different to a sim yoke. It moves the elevators. If the trimmer moves the stabiliser, the elevators, being hung off the back will be in line for minimum drag with the yoke centred.

In a Cessna, you trim by moving a tab at the back of the elevator. This provides an aerodynamic force that holds the elevator displaced and literally takes the force out of you holding it there. 

Different mechanical systems. Please also remember the horizontal stabiliser is by far the most powerful surface on a 737.

Now, where your issue comes is in using a toy joystick.....

If you get down to basics, you are pulling against a spring to lift the nose up. Try to move gently, to avoid tail scrapes. 2-3' per second is correct. You lift the nose, and by 8-9' you should hear a click, as the weight on wheels logic triggers the release of a relay in the overhead panel.

Now move the nose up to 15'. Hold it there. 

Do you need to push your joystick forwards or back to keep it in place?  If it's back, then you need to trim up just slightly. If down then trim forward. Just a quick tap of the button, that's all. Now relax your joystick. Is it staying put? If so, great. If not, then use the joystick to move the nose to the right pitch and hold it as required and repeat process. V2+20kts target speed. (V2 +15 for the 737-700).

[Spin737 102]

4 hours ago, MarkJHarris said:

The 737 Yoke is held by a spring, nothing really that much different to a sim yoke. It moves the elevators. If the trimmer moves the stabiliser, the elevators, being hung off the back will be in line for minimum drag with the yoke centred.

In a Cessna, you trim by moving a tab at the back of the elevator. This provides an aerodynamic force that holds the elevator displaced and literally takes the force out of you holding it there. 

Different mechanical systems. Please also remember the horizontal stabiliser is by far the most powerful surface on a 737.

Now, where your issue comes is in using a toy joystick.....

If you get down to basics, you are pulling against a spring to lift the nose up. Try to move gently, to avoid tail scrapes. 2-3' per second is correct. You lift the nose, and by 8-9' you should hear a click, as the weight on wheels logic triggers the release of a relay in the overhead panel.

Now move the nose up to 15'. Hold it there. 

Do you need to push your joystick forwards or back to keep it in place?  If it's back, then you need to trim up just slightly. If down then trim forward. Just a quick tap of the button, that's all. Now relax your joystick. Is it staying put? If so, great. If not, then use the joystick to move the nose to the right pitch and hold it as required and repeat process. V2+20kts target speed. (V2 +15 for the 737-700).

Exactly. $35M yoke or $15 joystick - you trim it for hands-off. 

[kevinh 409]

On 6/18/2018 at 1:32 PM, MarkJHarris said:

 

The 737 Yoke is held by a spring, nothing really that much different to a sim yoke.

 

It’s not a spring and much more complex than a sim yoke. The column force, provided by a computer controlled hydraulic feel unit, varies with dynamic pressure and stabiliser position. At a given flight condition it behaves like a spring but the forces are much higher than a hobbyist sim yoke or joystick. Trimming by feel is a much harder with hobby equipment because the forces are much lighter.

[Ephedrin 418]

47 minutes ago, kevinh said:

Trimming by feel is a much harder with hobby equipment because the forces are much lighter.

Still, a flight sim yoke comes closer to a 737 yoke than to a GA airplane‘s yoke. The 737 (as all boeings) has a center position even in flight while a GA airplane has a „zero force point“ that varies with the trim setting.

[kevinh 409]

7 hours ago, Ephedrin said:

Still, a flight sim yoke comes closer to a 737 yoke than to a GA airplane‘s yoke. The 737 (as all boeings) has a center position even in flight while a GA airplane has a „zero force point“ that varies with the trim setting.

True, but that doesn't really help with trimming a PC sim. It just means the trimming process for a GA plane (or any aircraft using elevator trim tabs) is less realistic.

As in all things, practice makes perfect and the more you fly without autopilot the easier it gets.

[Bobsk8 12,584]

9 hours ago, kevinh said:

It’s not a spring and much more complex than a sim yoke. The column force, provided by a computer controlled hydraulic feel unit, varies with dynamic pressure and stabiliser position. At a given flight condition it behaves like a spring but the forces are much higher than a hobbyist sim yoke or joystick. Trimming by feel is a much harder with hobby equipment because the forces are much lighter.

I flew a 767 -400 Level D sim at the Delta Training center years ago. I was surprised when hand flying it at the force needed to fly level, if the trim was off a little bit. Constant tweaking of the trim was needed, 

[Ephedrin 418]

1 hour ago, kevinh said:

True, but that doesn't really help with trimming a PC sim.

Actually I think it does: as soon as yoi have to push or pull your yoke or stick to maintain nose attitude: trim.

[skelsey 765]

1 hour ago, kevinh said:

practice makes perfect

Correct practice makes perfect 😉. Practicing the incorrect technique, however, leads to frustration.

Although the stick forces on typical consumer sim hardware are light, they are more than sufficient to provide trim cues except for the completely ham-fisted (and I admit that for all the very gifted simmers I have flown with I have certainly come across some who fall in to that category!). More of an issue, I would say, is having the base of the stick/yoke firmly secured to the desk so that the forces can be felt consistently and the stick does not go sliding all over the desk when inputs are made! However, I have successfully taught many students to trim correctly and accurately in FS over the years so it certainly is possible, and in very little time if the correct technique is utilised. A light, relaxed, fingertip grip is essential.

Worth noting that some aircraft have very light stick forces in real life as well -- I was very pleasantly surprised when I went up with a friend in a Eurostar three-axis microlight recently to find that fingertip pressure was almost too much: certainly in the cruise one barely had to breathe on the stick to produce a very effective response, far lighter than any aircraft (or hardware) I've flown in FS (rudder forces, on the other hand, were quite firm and far beyond any consumer hardware). A very good example of less very much being more when it comes to control inputs!

On a related note -- oddly enough I can remember that many, many years ago (in the days of FSW95) I had a QuickShot joystick which had 'trim' thumbwheels on both axes which, as I recall, actually mechanically moved the centre point of the joystick. And they say things have moved on in the last 20 years!

[Ephedrin 418]

8 hours ago, skelsey said:

Correct practice makes perfect 😉. Practicing the incorrect technique, however, leads to frustration.

Although the stick forces on typical consumer sim hardware are light, they are more than sufficient to provide trim cues except for the completely ham-fisted (and I admit that for all the very gifted simmers I have flown with I have certainly come across some who fall in to that category!). More of an issue, I would say, is having the base of the stick/yoke firmly secured to the desk so that the forces can be felt consistently and the stick does not go sliding all over the desk when inputs are made! However, I have successfully taught many students to trim correctly and accurately in FS over the years so it certainly is possible, and in very little time if the correct technique is utilised. A light, relaxed, fingertip grip is essential.

Worth noting that some aircraft have very light stick forces in real life as well -- I was very pleasantly surprised when I went up with a friend in a Eurostar three-axis microlight recently to find that fingertip pressure was almost too much: certainly in the cruise one barely had to breathe on the stick to produce a very effective response, far lighter than any aircraft (or hardware) I've flown in FS (rudder forces, on the other hand, were quite firm and far beyond any consumer hardware). A very good example of less very much being more when it comes to control inputs!

On a related note -- oddly enough I can remember that many, many years ago (in the days of FSW95) I had a QuickShot joystick which had 'trim' thumbwheels on both axes which, as I recall, actually mechanically moved the centre point of the joystick. And they say things have moved on in the last 20 years!

 

I've initially learnt to fly on an ASK13. Old, wooden/steel glider airplane, double seater, heavier than it looks. I was 14/15 and alsmost couldn't move the stick fully to the right with one hand in flight. normal "cross country" speed is 100-130km/h and the forces on the elevator were very (!) strong for an untrained 15 years old. Flying straight forward I used to put the trim lever a good cm forward. When I found a thermal and circled at ~80km/h I almost certainly pushed that trim lever back again, the forces were just too strong. though you normally fly a bit nose heavy in a thermal, at least in a K13. But flying out of trim is reaaaally exhausting. after several hours you really are happy that you actually have this little green lever. 

On the other side the DR400 I flew was extremely light on controls. I also can't say that I needed a lot of force on the HK36. Significantly less than on a C172. In the Remorqueur I sometimes simply didn't touch the trim when I knew there would be a lot of movement, for example when flying "low" (while LOW isn't possible in Germany at all, lol) 

Now at home I prefer really low forces on my yoke and I even have dismounted one of the springs inside (actually it broke off, but shhh) and lubricated the yoke's shaft. But still, as long as I have to hold it forward or back, I use the trim almost automatically. Though I still prefer flying approaches a little bit nose heavy. It (subjectivly) gives me a better feel of the airplane.And you seldomly become too slow when your attention is on your girlfriend for a second xD

[Ephedrin 418]

5 minutes ago, Ephedrin said:

Practicing the incorrect technique, however, leads to frustration.

I always found it completely wrong adjusting the level flight or rate of climb/decent with the elev trim. Some people who have trim tabs on their (real world) yokes even start a decent using trim. I really have problems to understand why.. a little bit too much and your nose dives down too fast and you have to counter steer and have to pull against the trim.. Doing this you have NO feel of your airplane. it's a more expensive mouse click... But very very common.

 

Edit: Okay, no idea what I did here, but actually I wanted to quote Simon and edit my previous post.. xD Cell phone issues 😃

Edited June 20, 2018 by Ephedrin

[kevinh 409]

18 hours ago, Ephedrin said:

Actually I think it does: as soon as yoi have to push or pull your yoke or stick to maintain nose attitude: trim.

Marc, I was talking about the point you had made previously, that the trimmed column position in a sim yoke doesn’t move, as in the 737. How does your reply relate to that? What you said applies to any aircraft, whether the trimmed yoke position moves or not. 

[Ephedrin 418]

1 hour ago, kevinh said:

Marc, I was talking about the point you had made previously, that the trimmed column position in a sim yoke doesn’t move, as in the 737. How does your reply relate to that? What you said applies to any aircraft, whether the trimmed yoke position moves or not. 

Yes I think I read your post differently from what you meant 🙈

[kevinh 409]

17 hours ago, skelsey said:

Correct practice makes perfect 😉. Practicing the incorrect technique, however, leads to frustration.

 Although the stick forces on typical consumer sim hardware are light, they are more than sufficient to provide trim cues

The only incorrect technique I know of is to fly using the trim. As long as you learn to use the trim to zero elevator control force it’s all good.

Of course. If the stick force is insufficient people wouldn’t be able to trim at all. But higher, more realistic, forces would make trimming much easier.

[trisho0 23]

On ‎6‎/‎18‎/‎2018 at 12:36 PM, Spin737 said:

Exactly. $35M yoke or $15 joystick - you trim it for hands-off.

I think Yoke is not a joystick. Yoke is for real aircraft and joystick is for sim platform. We can trim via Yoke but not via joystick because no pressure is feeling …..so, no need trimming for my birds (lol). I can't afford such sum for a Yoke but at least I learned on it works.