TRIM YOUR SIM: Theory & Practice

welcome back to my channel in this video i'd like to discuss something that during my many years in the cockpit flying civilian light aircraft military and finally airline flying a subject that often doesn't get a lot of attention but especially for beginners is really important and that's the use of elevator trim no matter what kind of flying you're doing the key to a smooth and precise flight is the proper use of trim and especially elevator trim now i'm going to do a little flight here and let's head out to the practice area i'm going to fly this in virtual reality but when we get to the maneuvers i'll switch over to a 2d panel to give you a better look now in this relatively short video i'm going to show you a little bit of the theory of elevator trim and why it is so critical to smooth operation of the aircraft then i'm going to discuss some of the differences between trimming a real airplane and trimming the sim especially with a non-force feedback yoke then i'm going to do a short demo of uh trimming show you uh the visual references and how that works and finally i'm going to talk about how your selection of a yoke or joystick might be affected by what you learn in this video just a little side note here as we're climbing out i strongly encourage you to try vr flying if you haven't already like so many things in life until you try it you won't miss it but once you try it you'll have trouble living without it at this point both x-plane and microsoft flight simulator have done a good job implementing vr and don't be misled by youtube videos like this portraying vr because it just it can't capture one tenth of what vr flying is really like [Music] i know trimming an aircraft and pitch sounds like a fairly basic topic but i have noticed that whether in a new student in the airplane or someone that i sit down for the first time in the simulator the concept of trim is quite foreign to them so i thought by making this video it might be a reference that others could also use to introduce people the idea of trimming a sim so as we continue heading out to the practice area let's talk about the system that controls pitching the aircraft namely the elevators and the important role that pitch trim plays if you want to control your airplane precisely and smoothly so to understand aircraft pitch control we're going to have a little physics for pilots and for that we'll return to the playground for simplified understanding you can think of the aircraft in pitch much like a teeter-totter when the riders position themselves correctly the teeter-totter stays level and won't rotate but any adult who's ridden a teeter-totter with a child knows that you have to position yourselves closer if you're heavier to keep things balanced in equilibrium this tendency to rotate called moment or torque is a function of the force and the distance from the balance point if the sum of all the moments applied to the teeter-totter equals zero then there is no rotation now an aircraft has a center of gravity which is the point about which it will rotate much like the fulcrum on the teeter-totter if moments are applied to the aircraft but this creates a slightly different situation since the fulcrum is on one side and both forces are applied on one side of the teeter-totter they need to oppose one another to stop rotation since the aircraft's lift shown in blue here is aft of the center of gravity point for all statically stable aircraft the tail force must provide a down force to counterbalance that but less force due to the long moment arm this is generally accomplished by extending a fin on the aft of the tail up and down to create a moment to cause the aircraft to pitch up and down so let's look at our aircraft in level flight because the aircraft is flying level the lift force must equal the weight and the tail must provide adequate downforce to keep the aircraft from pitching up or down so that the lift moment and the tail moment are equal there's no tendency for the aircraft or nose to rotate up or down now let's look at what happens if the aircraft starts to slow down to maintain the same amount of lift to keep the aircraft level the aircraft needs a higher angle of attack because there's less air flowing over the wing also the tail is less effective because there's less air flow there too so it needs a greater deflection of the elevator obviously the control stick is connected directly to the elevator so when forces on the elevator increase the force on the stick would increase also creating quite a hardship for the pilot applying constant force and trying to hold that force that is the reason we need trim for example if you're flying final with a 20 pound pole on the stick it's very hard to feel a few ounces of change that you need to make the precise changes in the flare that you'd like to make on the other hand if you can trim the forces out so that the stick has zero force you can feel even the smallest changes as you make precise inputs the small inputs that are necessary to fly the aircraft smoothly and precisely a well-trimmed aircraft can be flown by the fingertips with feather light control so now we know we need it let's look at what trim actually is and how it works most light aircraft have a trim tab which is a smaller tab located on the elevator that can affect as we'll see shortly the position of the elevator in the cockpit there is normally a wheel where rotating the wheel top of the wheel in the direction you want the nose to go will cause the trim to be applied and many aircraft also have a thumb switch on the yoke or control stick to allow trim to be applied in addition to the wheel which usually is a manual backup in that case when the cockpit trim control is actuated it causes the trim tab to rotate causing a force which pushes the elevator in the direction necessary to reach the equilibrium position so that the nose is in trim this eliminates the requirement for the pilot to hold force on the control yoke to hold the elevator in the correct position because the elevator is directly linked to the control stick or yoke the oak should remain in a constant position as the forces are trimmed out of the elevator most standard simulator joystick and control yokes don't operate this way they have centering springs which pull the yoke back to the neutral center position where there's zero force we'll discuss how that changes things later the good news is i can tell you as a pilot with tens of thousands of flight hours that i really didn't notice a difference in the way the trim felt even though the yoke did move back slightly when i released the pressure as i was trimming out the forces so let's convert some of this theory into practical application you can see i've got the throttle quadrant on the left where you'll be able to see the trimming the aircraft profile on the upper right and the trim off to the left and then the view out the front window we're going to do is get level at about 2 000 feet here heading towards the southwest and then what we'll do is uh i'm going to change speeds you can see we're about 90 knots now what i'm going to do is change the speed and we're going to watch the the changes that are required in the trim initially i'm going to demo this without making any trim changes i'm just going to hold the pressure on the stick okay here i'm pulling the power back and just allowing the air speed to bleed off and you can see that the pitch attitude with the reference to the glare shield just trying to hold that zero vvi by just increasing the back pressure pulling a little harder and a little harder as we get back to about 70 after 20 knots quite a bit of force on the stick what i'm going to do here is just release the stick and just see how fast the nose starts to drop okay there we go okay i'm going to recover quickly pull it back up i'm going to add try that one more time just to show you notice the movement of the of the earth with respect to the nose okay there we go now i'm going to make just a little bit of trim change here now and then try this again let me get it leveled off here and uh now put a couple turns of trim in and i'm going to try it you notice it doesn't drop nearly as fast pull it back up put a couple more turns of trim in and then i'm going to let go and you see it's dropping a lot slower so you can see that trim really is helping now i'm going to put a little more trim in here and watch what happens when i drop the nose now just barely drops so that's what we're looking for we're looking for trying to find that point where where we can let go and the vvi will stay level that main thing is that the nose doesn't go up or down it's very consistent just very slow and that can't make big changes okay let's speed up and go the other way now it takes quite a bit more force to hold that nose down uh when you're when you get going fast we'll get it up from that 90 where we started we'll take it up to 100 or so maybe 100 knots and i'm going to hold this nose down and try to get the speed right here again level at 3000 about 210 heading and see how quick that nose comes up comes up very very briskly let me get it back to level here try this one more time just let it let it go and on it's i'm just letting go of the stick and watching how fast the nose that's how much just 10 knots can make a trim change actually we went from from 70 to 100 so 30 knots but anyway a big change in trim now okay so we've got this thing leveled off i'm going to start putting trim in now nose down trim and each time i let go of this here see it comes up a lot slower so you can see the trim really is and that's going to be our main cue that we have the airplane level unfortunately unlike in a real airplane you don't get that seat of the pants feel and that's a big big help much harder to do it in the sim now there we go we got it trimmed up take our hands off you can see it's almost perfect there so what i'm going to do now is uh pull the power back again and this time i'm just going to trim as i go watch me i'm just trimming back and each time i trim i'm kind of easing a little pressure off and seeing if the nose drops trying to hold it where it is i start letting the pressure off and if the nose starts to go up or down i keep i just hold that nose in the level attitude and just make the change and that's that's how it's done you got to watch that horizon in the nose or the top of the glare shield and look for the movement and watch it like a hawk and make just make an effort to hold it there as you relieve the pressure with the trim and ease off on the stick until you can release it and there's no relative movement just remember every time you change speed or power you're going to probably have to make a trim change it's a constant process it never stops and it becomes second nature after not too long in time fight the tendency to try to fly the aircraft with trim fly the airplane with the elevator and then trim out the forces now i've been flying this in my vr goggles and only in looking at the video here i see that i pulled the prop lever back instead of the throttle and it did seem to respond but i don't know maybe it's set up to be hooked to the throttle also uh maybe from another setup but anyway much easier to just to see these pitch changes in vr than it is looking at a 2d screen i don't know why but it may be the three-dimensional effect or what but it's very easy to see when the nose starts to climb and drop much easier to fly level much easier to do everything with vr goggles and i i certainly uh encourage you to give that a try again that's my favorite way to fly although there's still some limitations with a really hard training for vfr flying around you can't beat it now at the beginning of the video i teased about how the choice of a yoke might be affected by what we've talked about today and i want to talk a little bit about that to conclude this video when i first started uh simming it came from a long history of military actually civilian military and also airline flying 23 000 hours so a lot of flying time and i bought a saitek yolk you know one that looks like this i gotta tell you guys this uh this yoke just about drove me crazy i couldn't fly worth a darn and the main problem was trimming there's a hard detent a spring centered detent that kind of catches every time you go through the center location now we just talked about that we're trying to fly all the time trimmed which means zero force so i'm constantly going in and out of that detent and it would restrict the movement enough to to mess it up you know in the flare i would be kind of zeroed out on the trim and i try to pull back and nothing would happen and then i'd suddenly break through that detent and i get a an over correction and i hated it it was terrible trimming while you're just cruising along i was always fighting it i went to oshkosh uh talked to the guys at a2a and uh this was quite a while back but scott the owner's son was was working the booth he couldn't have been more than about 12 maybe 10 or 12 at the time and he uh he said i told him about my problem and he said i got a ch yoke here why don't you try that so i sat down with this relatively cheap plastic yolk no way it was made as well as the satech it had a plastic shaft but i was in heaven this thing was totally smooth it had no restriction it was flimsy but it flew like an airplane and i decided maybe i will stick with this hobby i was frustrated by that seitek yoke now i know lots of people fly with the saetech yoke and i know lots of people have modified the yoke by removing the springs and putting some rubber bands and stuff in there to get rid of that detent i tried it i didn't have good luck with that but that is definitely the problem that center d-10 is right where you should be flying almost all the time with a trimmed airplane and you're constantly having to fight that thing and for me it just wasn't worth it i even tried a few uh more expensive yolks that didn't have that problem but had sticky shafts and that's the other thing i'd avoid a shaft that's that hangs up or sticks you need a nice smooth movement i have a yoko that has a ball bearings in the shaft is very smooth very well made but it's expensive but there's lots of less expensive systems out there including the honeycomb that work just great they're very smooth they fly great and they don't cost an arm and a leg so that's something i would watch for if you're going to go out and buy a new yolk and the same thing with uh with joysticks too well in summary trimming is an important part of flying and good flying requires good trimming using pitch trim on an airplane becomes second nature pretty quick so not a lot of people talk about it and that's why i wanted to do this video just remember fly the airplane with the elevator always put the nose where you want it to be then use the trim to trim out the forces in the stick in the case of the simulator you're going to be easing off the pressure trimming easing off if the nose moves continue trimming and finally eventually be able to release the stick and not have the nose move up or down that's the goal the good news is although it's slightly different in an airplane because the stick actually moves and stays where you trim it the skills are transferable perfectly to a real airplane i learned that going the other way transferring the skills from the airplane to the sim but i can assure you that you'll have no trouble and the skills that you learn will be very portable finally if you're having trouble trimming the aircraft or if you're getting ready to buy a new yoke you might consider uh the what i've said about the stickiness in center detents i find those to be pretty much deal breakers for me and i just thought i'd share that with you if i had not been a pilot and i was just starting out with a seitech yoke i would probably still be using it and i'm sure eventually you can probably get used to it but it's definitely negative learning if you ever intend to fly a real airplane and it in my opinion is a lot harder because you're learning to compensate compensate for something that that shouldn't really be there well thanks for watching i know this is a fairly basic video if it didn't apply to you you might share it with some of your friends who are just starting out or maybe guests in your sim and they might have an idea a little bit about what trim is before they jump into into the simulator if you like my videos please subscribe like share with your friends i love your comments especially interested uh if what you think of this kind of uh format where it's more of a basic sim instruction instead of some of the more technical things i do hope to see you for the next one you

Channel: Russ Barlow

Views: 2,293

Keywords:

Id: pmIFctYMEm4

Length: 20min 18sec (1218 seconds)

Published: Tue Dec 14 2021