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Trim Tutorial (Read 2949 times)
Dec 4th, 2009 at 7:36pm

Staiduk   Offline
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Hello - just to let everyone know and not step on anyone's toes (just in case someone else is as well): I'm making up a trim tutorial right now - it seems it might be valuable for sim-pilots who have a less than perfect understanding of trim. I spent some time looking at the trim info in the Learning Center and what M$ laughably calls a 'flight lesson' and quite frankly; I'm not at all surprised sim pilots are so often confused about proper aircraft handling. Grin I'm trying to do it with video; if that fails I'll write it out as a forum topic. Should be up Sunday. (It better be - The Roar of the Rings starts this weekend and I never miss Curling finals!  Cheesy

Hope it helps!
 

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Reply #1 - Dec 5th, 2009 at 1:03am

Mobius   Offline
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Sounds like a great idea.  Trim seems to be one of those things that people never really realize how important it is.
 

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Reply #2 - Dec 5th, 2009 at 10:08pm

olderndirt   Offline
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If you or anyone can come up with a fix or better method, I'll worship at your shrine  Smiley.
 

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Reply #3 - Dec 12th, 2009 at 7:05pm

machineman9   Offline
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Trim is something I never quite understood until I did it for real and I could feel what it was supposed to do and how it affects the aircraft. Now, when flying on FS, I can have a good idea of how much trim needs to be applied and it makes flying so much easier. London to Cosford in my DC-3 at 7000ft with only minor changes to trim along the way... Imagine the wrist ache if you had to do that flight or longer ones whilst holding the plane at that height yourself!  Shocked



I wish you the best on your project, it really is an important skill to learn. It is fairly basic, but helps so much.
 

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Reply #4 - Dec 13th, 2009 at 9:43pm

Staiduk   Offline
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OK; the trim tutorial is up at SimTeevee - and it only took three bloody hours for it to upload.  Roll Eyes

Grin

It's still 'pending approval' but I haven't got any more time to hang around; night's falling, the temperature's dropping towards -40c fast and I've got a long walk ahead of me. I'll be back tomorrow - I'd appreciate a serious critique of the tute. Go to Sim TV, enter my name in the search feature and you'll find it.

Cheers!
 

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Reply #5 - Dec 14th, 2009 at 10:55am

olderndirt   Offline
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Excellent.  Perhaps 'vertical speed' rather than 'vertical airspeed' and why no use of the attitude indicator?  The VSI, especially in flightsim, wouldn't be my first reference.  Now, wouldn't it be great if there was a way to define the number of keystrokes or joystick clicks required for each trim exercise?  Smiley.
 

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Reply #6 - Dec 14th, 2009 at 3:22pm

Staiduk   Offline
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Glad you like it, Dirt.

I agree - 'vertical speed' is correct and I wish I could change it - for some reason I always get the "bluh-bluh-bluh's" trying to dictate into that stupid little camera and after about a hundred attempts; I wound up saying "ahhhh - good enough!" It wasn't - of course - until I'd compiled the video and deleted all the material (20 bloody gigs of it! Holy snakes!) that I started going "Ummm.... I don't like that..." Roll Eyes There were a couple of spots in there like that.

As for why I didn't use the attitude indicator; it's just how I was trained - establish SLF via outside cues; using the VSI as reference. To be honest, using the attitude indicator wouldn't be my first choice; possibly since the aircraft I first got my license on didn't have one at all; or even an artificial horizon. Smiley

As for number of clicks on the trim; it flat-out wouldn't work. I adjust all my aircraft so 'Elevator_Trim_Effectiveness' in the .cfg reads 0.25 which gives a much smoother response than stock. Also; the value would change with different conditions - temp., loading, etc. and some - like me when I'm flying the Citabria - have the trim mapped to a lever axis anyway. So overall, I thought it better to trim according to the aircraft's behaviour rather than trying to determine fixed numbers.

Cheers! And thanks again! Smiley Smiley
 

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Reply #7 - Dec 14th, 2009 at 10:11pm

olderndirt   Offline
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Staiduk wrote on Dec 14th, 2009 at 3:22pm:
. To be honest, using the attitude indicator wouldn't be my first choice; possibly since the aircraft I first got my license on didn't have one at all
Sounds reasonable to me - never had one either.  Strictly needle, ball, airspeed and a low freq receiver.  Thanks for the .cfg trim tip - I cuss that stupid thing every flight  Smiley.
 

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Reply #8 - Dec 15th, 2009 at 7:25am

Brett_Henderson   Offline
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Wow..  superb tutorial.  Thanks for taking the time to put it together..

If a sim-pilot takes the time; to take to heart, the theories and techniques you describe so well.. and practices them until their application becomes second nature.. he'll be well on his way to ANSWERING sim flight training questions..

Smiley
 
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Reply #9 - Dec 15th, 2009 at 12:23pm

RickG   Offline
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I have to agree with the others---great tutorial, Staiduk! As you mentioned, a bit long, but I don't think you could have shortened it by much. I took a lot of notes, so now I can refine my technique and  trim properly now.  Many thanks for your effort.  Rick
 

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Reply #10 - Dec 15th, 2009 at 4:40pm

aeroart   Offline
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How do you get into Sim TV? I Googled it, and got an opening page, but no place to enter a search. Can someone provide a URL? Thanks.

Art
 
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Reply #11 - Dec 15th, 2009 at 6:59pm

aeroart   Offline
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Never mind. I found it.

Art
 
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Reply #12 - Dec 15th, 2009 at 8:25pm

olderndirt   Offline
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Staiduk wrote on Dec 14th, 2009 at 3:22pm:
I adjust all my aircraft so 'Elevator_Trim_Effectiveness' in the .cfg reads 0.25 which gives a much smoother response than stock.
Pure excitement!  After resetting my trim .cfg to your setting, I fired up the sim, setup for takeoff (same number of trim clicks) and opened the throttle.  That sucker came off like a homesick angel and flew right on up into a full power stall.  Had to put my beverage down to recover - makes me wonder how I ever survived  Smiley.
« Last Edit: Dec 15th, 2009 at 10:17pm by olderndirt »  

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Reply #13 - Dec 16th, 2009 at 5:29pm

Staiduk   Offline
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ROFL - alcoholic beverage, by any chance? Wink

Thanks for the kind responses folks; I appreciate it. Smiley

Dirt:
Quote:
Sounds reasonable to me - never had one either.  Strictly needle, ball, airspeed and a low freq receiver.


You learned on a Cub, right? I envy you - flying's too complicated nowadays. It used to be needle, ball and the rushing wind as your speed gauge; at some point it turned into regulations, air law, log books and certifications. I came in kind of at the end of that old era and miss it dearly.

Rick:
Quote:
I took a lot of notes, so now I can refine my technique and  trim properly now.

Glad I could help. Smiley A little bit of knowledge and a lot of practice is all it takes. Smiley


I just REALLY wish I could redo that climb-speeds bit - it's astonishing how bad you can describe something at three in the morning. Cheesy
 

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Reply #14 - Dec 16th, 2009 at 6:40pm

olderndirt   Offline
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Staiduk wrote on Dec 16th, 2009 at 5:29pm:
I just REALLY wish I could redo that climb-speeds bit - it's astonishing how bad you can describe something at three in the morning. Cheesy
It's great - hindsight is often more of a hindrance. 
 

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Reply #15 - Dec 20th, 2009 at 10:29am

Scott B.   Offline
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Great tutorial.  I wish this was around when I was first starting flight simulation.  I finally stumbled around on how it's done, but this would have made it much easier for me!
 
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Reply #16 - Mar 31st, 2010 at 3:44pm

The Google Cat   Offline
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Just joined this forum to say thanks for your trim tutorial. Rod Machado's introduction to trim in FSX is completely useless and it left me with more questions than answers. Your tutorial has made things so much clearer.

Cheers,

PaulC.
 
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Reply #17 - Mar 31st, 2010 at 6:28pm

beaky   Offline
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Forgot I hadn't commented on this...   Grin

It's a great approach to teaching trim to sim-only pilots; I like the general tone and the way the jargon is handled. And as a pilot, without knowing your pilot credentials, I'd be able to tell that you are a pilot, based on your apparent understanding of the mechanics of throttle, trim,and wing.

But FWIW, there's a few things in the tute that bother me, so here's some constructive and supportive criticism. I'd even suggest re-doing it so that some of the voice-over stuff is different...you can re-do this; why not?

But again, it stands well as it is, and the average clueless noob will benefit enormously from it.


Here goes:

- In explaining how the throttle is not "really" the speed control and the elevator not "really" the up/down control, there's two things that must be cleared up, because I have found that many sim-fliers, student pilots, and non-pilots have some firm but incorrect ideas stuck in their brains, and the right tools must be used to dig this junk out of there.


First: the throttle produces lift, but not by increasing airflow over the wings via the propwash!! I know you don't mean to say that, and I know that prop wash does figure into the lift equation, somewhat, with many aircraft, but this is such a common misconception that it must be squelched aggressively.

Rather than simply say "More power=more lift", it may be better (and not be too advanced) to say:

"The faster a wing goes the more lift it produces, so while an increase in thrust will make the airplane speed up, unless there is a change in pitch, the airplane will tend to climb, and actually slow down." 

And the converse:

"Reduce thrust, and the airplane will descend,and without a change in pitch, it will actually speed up." This is more information, but it explains effectively how power produces lift.

I think it's important to point it out.

Despite their knowledge of jets and pusher props, many people still think that with prop aircraft, MCA, for example, where you "hang on the prop" has something to do with propwash making the wings more effective.  Roll Eyes

Before they can understand how trim is used, they have to get rid of that fallacy.


Another problem most noobs have is that they don't realize that the role of throttle and elevator is the same in all modes of flight, even though you do different things with them at different times in different modes of flight. But they are hung up on how throttle and elevator inputs affect level flight, so they don't see it.


So many noobs and sim-fliers will say "But wait a minute! How can the throttle be the altitude control?! I know if I'm flying level, and I  move the elevator up or down, I'll go up or down!! I've done it!!"

This is why any tute on trim must include:

"You can climb or descend using only the throttle, so the throttle can be used to control altitude."


And because of that:

"To climb or descend continuously, without changing airspeed, you must change the throttle setting. So the throttle can be used to control altitude."




After this, I like the way you explain about elevator and airspeed...you present this info as the counterpart to the throttle thing, which is great...

But the term "vertical airspeed" is... well, I know you understand the difference between airspeed and vertical speed, but most noobs are confused about it, and tacking "airspeed" on there will only make it worse, IMHO.  Undecided
Maybe this is a Canadian thing, like the English/American "angle of attack/angle of incidence" thing, but I think my logic is sound, regardless (as with the AOA/AOI thing, *cough*).  Grin

And again, to shake the arguments of "How can the elevator be the speed control?! If I'm flying level, I need more power to go faster!! I've done it!!" it's vital to say:

"You can go faster or slower without touching the throttle, by using the elevator. So the elevator can control your airspeed. "

And:

"To fly continuously at a given speed, without changing altitude, you must change the elevator position, so the elevator can be used to control airspeed."



I'd then point out that all four of these axioms are true for any mode of flight: climbs, descents, level flight, turns, etc.

Suggest, at this point, maybe, that they can test all four of these rules in the sim,any way they want, and they will see that they are always true.


The first part of the actual tutorial:

I'd first point out not so much that trim lets you maintain altitude hands-off, but that it lets you maintain the necessary elevator position you want without continuous pressure on the yoke or stick.

They need to know that the trim mechanism simply holds the elevator in a given position, but you don't need to get into an explanation of trim tabs, flying tails, etc... just invite them to move the trim and look at the controls. I say this because they have to be thinking about the elevator and how it affects pitch, and thus airspeed as well as altitude, because let's face it, that's the crux of the problem- they don't get it even as regards flying without using trim.

That is why you explained all that stuff in the introduction, right?  Grin

  I just think it all needs to "come back home" to the principles explained in the intro,and right about here would be perfect.




Leveling off from climb/descent:

"PAT/APT": I hate most mnemonics, myself, but these are strong, simple ones. Only problem I see there is a common one with mnemonics (and one of the reasons I don't like them):

"P-A-T" stands for "power-attitude-trim", yet throughout the tute, you sometimes say "throttle" instead of "power", etc. Some students may get confused with the "P" and "T" thing... "is 'P' really 'pitch' here? Is 'T' 'trim' or 'throttle?' "
Undecided

  It would be much more idiot-proof if you always used the same word, when discussing the use of PAT/ATP, that the letters in the mnemonics stand for.

Use of the VSI while leveling off:

I agree with the criticisms about using the VSI as a primary reference for leveling off: "chasing the needle" is bad stuff. I was taught to use the VSI mostly to confirm I had the desired climb or descent rate, not for leveling off from climbs or descents.

I'd include a warning about "chasing the VSI needle", that's a common student habit, and it's a bad one.

The altimeter is used for this purpose in IFR flight, so it stands to reason that it's the best primary in VFR flight as well. After all, the target, when levelling off, is some altitude, not "zero vertical speed", right? Even when levelling off without a particular alitude in mind, I have found it's easier to level off smoothly by referencing the altimeter first... even at a very low vertical speed, it's movement is easy to detect, especially with a tape-type readout on a PFD or HUD. And even when just out chucking an airplane around, one should be thinking about one's altitude.

Students should note the VSI reading when completing their level-off, for sure... but in that maneuver, as in maintaining altitude in level flight, it's more of a "trend monitor" than a primary instrument.




Changing airspeed in level flight:

No problems there, that's a great explanation, especially the "it's easy" part. It was also wise to talk about this after explaining how to level off, rather than before. At first I was going to tell you otherwise, but then I remembered that this is how I was taught, and yes, it really is a little harder than leveling off!  Cheesy

The step drills:

Very well explained... and good progression in difficulty.

The "two rules":

Definitely worth mentioning, but I feel slightly that these should have been mentioned in the part before the drills, rather than right after mentioning about climbing or descending while changing airspeed. A minor point, but it might help clarify the APT/PAT thing more. To me, they're just sort of out of place here.

I do like, however, how you bring those rules back later.  Cool

The discussion of V-speeds: I really think this belongs in another tute, although you explain them well. I know that you can't fully implement all this knowledge about trim without knowing your airplanes' V-speeds, but... whatever; that's just my gut feeling. It'd more than is needed to get the basic idea of using trim.

The Lazy Eight: reminds me that I haven't done one of those in a long time!  Cheesy   Another good explanation.

But you know, between that and the V-speeds, you have another great tute right there. Add ground-ref maneuvers and short/soft ops to that, and you'd really have something... "Aircraft Performance", or whatever.
Like the V-speed discussion, I think it goes a bit beyond "here's how trim should be used".



That's it... hope you understand that I am very impressed with the work you put into this and the quality of the presentation, as well as your knowledge... just trying to be constructive.

And if you're thinking "Well, I'd like to see how Mr. Smarty Pants would do with one of these video tutes!", you should know that watching this, I realized that my planned "Compass, Clock, Chart" tute should really be a video instead of a pdf. So you may find out...  Grin

Still waiting for word on the legality of free distribution of complete NOAA charts, but I may do a VFR nav tute anyway, showing glimpses of real charts, even if I have to forget the "chart package" project.











 

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Reply #18 - Mar 31st, 2010 at 8:28pm

olderndirt   Offline
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Good one - you condensed a five line paragraph into a page and a half Cheesy
 

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Reply #19 - Apr 1st, 2010 at 2:26am

beaky   Offline
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olderndirt wrote on Mar 31st, 2010 at 8:28pm:
Good one - you condensed a five line paragraph into a page and a half Cheesy


Cheesy  Cheesy Cheesy
I'm feeling verbose today... um, yesterday... goodnight...  Grin
 

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