Trim question...

ferrari-tech said:
I was taught for every attitude there is a pitch/power setting.
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Pitch=attitude (or, 1/3 of attitude, along with roll and yaw angles). I think what you learned was the for any given performance point (airspeed, turn rate, and climb/descent rate) there is an attitude and power setting to give it.

So pretty much anytime one of these changes the required trim changes.
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Not necessarily. As long as you're trying to maintain the same speed, changes in pitch (and the concomitant change in climb/descent rate) are obtained by power changes, and should not require much if any trim change. But any time you want to change speed, a trim change will be necessary for the plane to maintain the new speed without holding fore/aft pressure on the yoke, whether you change attitude or not -- and you'll need to change power setting at the same time in order to maintain the same climb/descent rate at the new speed.
 
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Clark1961 said:
Please read what I originally typed: pitch for airspeed. Do I really need to type anything more? If you want to substitute one term for another that is your business. I would ask that you not try to obfuscate to seek the appearance of authority but that is your call entirely.
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You trim for speed, not for attitude. You may be at any of a wide range of attitudes while maintaining a given speed, depending on the climb/descent rate you command with power. OTOH, if you are trimmed up at say 90 knots at a given power setting, and reduce power, the pitch attitude will drop, descent rate will increase (or climb rate will decrease), and pitch attitude will decrease without you touching the trim control. That's a demonstration we do on Flight #1 of the PIC instrument training syllabus.
 
Ron Levy said:
Pitch=attitude (or, 1/3 of attitude, along with roll and yaw angles). I think what you learned was the for any given performance point (airspeed, turn rate, and climb/descent rate) there is an attitude and power setting to give it.
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Thank you!!!!

And power is thrust. Let's get this down to the basics.
 
kgruber said:
Thank you!!!!
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You're welcome.
And power is thrust. Let's get this down to the basics.
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OK, yes, the power of the engine produces thrust from the prop. But for practical purposes, the term "power" will do when talking about the throttle movements in light piston-powered airplanes. And even LSO's call for "power", not "thrust", when you're decelerating and sinking behind the boat.

BTW, if all CFI's taught this stuff from the first ride in primary training (or even before in pre-flight ground training), the general level of skill in aircraft control among light plane pilots would improve dramatically. We'd see a lot fewer landing accidents, and transition to higher performance aircraft and the attainment of the extra precision required for the instrument rating and commercial pilot certificate would all be a lot easier to achieve.
 
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Clark1961 said:
And what attitude gives that speed?
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Depends on what power you have set. At sea level, I can fly my Tiger at 90 KIAS at any pitch attitude from around -5 degrees with no power to +10 degrees with full power. Of course, climb/descent rate will vary from like -800 ft/min to +800 ft/min (or more, if light), but the speed (and trim setting) will be the same throughout that range.
You can't have it both ways Ron.
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I'm only saying it one way -- trim controls hands-off speed, not attitude, i.e., there is no trim setting which gives you a particular attitude regardless of power setting, but speed will stay fairly constant regardless of power if trim is set and left alone and you don't introduce a fore/aft force on the stick. However, as a separate issue, attitude and power combine to produce a given performance point (even if you're holding 50 lb of stick force to overcome the trim being wrong for the speed). Likewise, I can change attitude with power, without changing trim or touching the yoke, and speed will stay about the same, but that will also change performance (specifically, climb/descent rate).
 
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Ron Levy said:
Depends on what power you have set. At sea level, I can fly my Tiger at 90 KIAS at any pitch attitude from around -5 degrees with no power to +10 degrees with full power. Of course, climb/descent rate will vary from like -800 ft/min to +800 ft/min (or more, if light), but the speed (and trim setting) will be the same throughout that range.
I'm only saying it one way -- trim controls hands-off speed, not attitude, i.e., there is no trim setting which gives you a particular attitude regardless of power setting, but speed will stay fairly constant regardless of power if trim is set and left alone and you don't introduce a fore/aft force on the stick. However, as a separate issue, attitude and power combine to produce a given performance point (even if you're holding 50 lb of stick force to overcome the trim being wrong for the speed). Likewise, I can change attitude with power, without changing trim or touching the yoke, and speed will stay about the same, but that will also change performance (specifically, climb/descent rate).
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No you didn't say it one way. Now you are putting conditions on it, e.g. Hands off. Attitude and power equal performance and that is the bottom line.
 
RotorAndWing said:
Son did you ever take an elementary aerodynamics course? :rolleyes:
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Son, did you ever take an elementary communications course? Folks are using terms inaccurately and now you want to attack me for pointing that out. Get real boy.
 
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Clark1961 said:
Son, did you ever take an elementary communications course? Folks are using terms inaccurately and now you want to attack me for pointing that out. Get real boy.
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You should get real "boy". :rofl:

Please go back and reread about basic aerodynamics. If you have trouble with the terminology come back and we'll help ya out. :rolleyes:
 
Clark1961 said:
No you didn't say it one way. Now you are putting conditions on it, e.g. Hands off. Attitude and power equal performance and that is the bottom line.
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You need to carefully re-read everything I wrote, because you are seriously misquoting me and distorting what I said. You also need to read some basic aero books as R&W suggested, because there is no contradiction between the two concepts I stated, but there is a definite inaccuracy in saying "attitude controls speed" as you suggested six posts up. There is an interplay between attitude and power which makes the two inseparable. OTOH, trim has its own purpose, which is to set the speed which the aircraft will seek without pressure being applied to the stick -- not to "control" either attitude or altitude by itself.
 
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Two comments struck me:
if you're a tad high above the glideslope, I want to see a forward input on the yoke, followed by trim to correct the pressure
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That seems like a great way to speed up, which will require more pressure/trim, which will lead to more speed, and more pressure/trim, etc.

Surely a better reaction would've been to reduce power and leave the yoke/trim alone?

Every power change requires a change in trim.
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It depends on what your goal is. When I was practicing constant speed climbs and descents during IFR training, you'd trim for a given speed and then simply reduce or increase power to initiate a climb or descent.

I agree there are many times where you'll be altering power and trim at the same time, but the two are not inextricably linked.

Regarding the 1.3 vs 1.1Vso, I use 1.3 VSo until I'm seconds away from the threshold, and then start a speed reduction, touching down at about 1.05Vso (indicated, not calibrated, so I'm actually going faster than that).

And here's what that looks like: http://www.youtube.com/watch?v=87zlNmZG2sk

For my airplane, there isn't much in the way of float as the speed reduction from 1.3 to 1.1 happens relatively quickly.
 
As somebody who hasn't even started training yet, I'm concluding from this thread going 4 pages and almost 100 responses in just a couple days means the subject of "trim" is one of those aviation religious wars, like debating the safety of singles vs twins.

It's got me wondering when I do start training, how much stuff the instructor tells me is fact, versus biased personal opinion?
 
There's no religious war to trim. Some struggle not using it, some have an easy time using it. Muscling planes is just not necessary.
 
LoneAspen said:
It's got me wondering when I do start training, how much stuff the instructor tells me is fact, versus biased personal opinion?
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There are some things which are facts, like physics, but there are many other things which are technique. These are the things most people argue about. Not only will different pilots have different opinions but in many instances it will depend on the airplane you are flying.
 
LoneAspen said:
As somebody who hasn't even started training yet, I'm concluding from this thread going 4 pages and almost 100 responses in just a couple days means the subject of "trim" is one of those aviation religious wars, like debating the safety of singles vs twins.

It's got me wondering when I do start training, how much stuff the instructor tells me is fact, versus biased personal opinion?
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I didn't see a single post that said trim was unnecessary. There is wide agreement that it is needed for competent flying, and a little disagreement about details.
 
Everskyward said:
There are some things which are facts, like physics, but there are many other things which are technique. These are the things most people argue about. Not only will different pilots have different opinions but in many instances it will depend on the airplane you are flying.
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Best post of the thread. :)

Fly the speed required. Nobody cares how you do it, unless your instructor sees your arms shaking because the muscles are working so hard you're fatigued.

Trim will fix that unenjoyable experience. :)
 
asechrest said:
It took me a good chunk of my training to figure this out. My landing attempts were a dive toward the ground with a last minute arresting rather than a smooth round out. I actually don't much care for the term flare, because I think it gives the student and an inaccurate picture of what should I actually be happening.
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Yeah. Diving at the runway is another mistaken attempt to fix a high approach. Doesn't work, since you arrive in ground effect with way too much speed and end up floating all the way down the runway. I used to teach the students to slow down by pulling the nose up and letting the sink rate fix it; in other words, get below best glide speed for whatever flap setting is being used, if any. Once you're just above the proper glideslope, drop the nose to get back to the proper speed.

I once passed an instructor checkride using a dive. It was a demonstration of a forced approach to the runway, and the examiner had the throttle closed. I could see, by the time I was down to 500 feet, that I was going to fall a little short of the runway. I retracted the flaps and dove down into ground effect and once the runway was easily assured I extended the flaps and landed. The examiner had never seen that before.

Dan
 
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LoneAspen said:
As somebody who hasn't even started training yet, I'm concluding from this thread going 4 pages and almost 100 responses in just a couple days means the subject of "trim" is one of those aviation religious wars, like debating the safety of singles vs twins.

It's got me wondering when I do start training, how much stuff the instructor tells me is fact, versus biased personal opinion?
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yeah, I would say try not to get involved in this advanced trimonometry "discussion" and just listen to your instructor for now. or, when you have an instructor.
 
If this thread has taught me anything, it's the fact that I really know next to nothing LOL.
 
Dan Thomas said:
Yeah. Diving at the runway is another mistaken attempt to fix a high approach. Doesn't work, since you arrive in ground effect with way too much speed and end up floating all the way down the runway.
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If you're already on speed, just a bit high, you need to increase your descent rate without changing airspeed. You do that by reducing power and allowing the trim system to cause the plane to stay on trimmed speed by dropping the nose slightly. So, you are making both a power and pitch change, but the pitch change is not commanded directly -- it is, rather, a consequence of the reduction in power and the airplane's fundamental tendency to seek trimmed speed. Note that if you do this, you do not have to change trim setting since you'll still be at the same airspeed, albeit with a greater descent rate and slightly lower pitch attitude.
 
Ron Levy said:
If you're already on speed, just a bit high, you need to increase your descent rate without changing airspeed. You do that by reducing power and allowing the trim system to cause the plane to stay on trimmed speed by dropping the nose slightly. So, you are making both a power and pitch change, but the pitch change is not commanded directly -- it is, rather, a consequence of the reduction in power and the airplane's fundamental tendency to seek trimmed speed. Note that if you do this, you do not have to change trim setting since you'll still be at the same airspeed, albeit with a greater descent rate and slightly lower pitch attitude.
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That works fine if you're a little high. The guys diving at the runway are way too high and should be going around if they can't get it down without diving.

Dan
 
Dan Thomas said:
That works fine if you're a little high. The guys diving at the runway are way too high and should be going around if they can't get it down without diving.

Dan
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If you're way high you can also pull the throttle and pull the nose up to the bottom of the white arc and sink like a rock. If you're solo you can also throw in a slip, I don't like doing them with passengers as it makes them uneasy, they don't even notice a hard sink. S-turns also work. There's a ton of ways to lose altitude and not increase kinetic energy.
 
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Henning said:
If you're way high you can also pull the throttle and pull the nose up to the bottom of the white arc and sink like a rock. If you're solo you can also throw in a slip, I don't like doing them with passengers as it makes them uneasy, they don't even notice a hard sink. S-turns also work. There's a ton of ways to lose altitude and not increase kinetic energy.
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The heavier the aircraft is the less these techniques will work, thus why when not stabilized by 500' (vfr) prompts a go around.
 
I never considered that mastery of energy was a negative. The problem with teaching "big jet" technique to GA pilots is that they lack the tricks in their bag that can save their ass when the **** hits the fan. Stabilized approaches are nice, but when the fan stops turning and the only place you have to stick it is a small field, having 'go around' as the only thing you know or are comfortable with to correct your approach at the bottom, the results are likely to be suboptimal.
 
Henning said:
I never considered that mastery of energy was a negative. The problem with teaching "big jet" technique to GA pilots is that they lack the tricks in their bag that can save their ass when the **** hits the fan. Stabilized approaches are nice, but when the fan stops turning and the only place you have to stick it is a small field, having 'go around' as the only thing you know or are comfortable with to correct your approach at the bottom, the results are likely to be suboptimal.
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OK, now you are shifting to an emergency landing technique. Stay on topic.

No one is teaching "big jet technique" but stabilized approach and why it's important to develop good habits and technique. On a normal approach trying to salvage the approach and landing is bad form.
 
RotorAndWing said:
OK, now you are shifting to an emergency landing technique. Stay on topic.

No one is teaching "big jet technique" but stabilized approach and why it's important to develop good habits and technique. On a normal approach trying to salvage the approach and landing is bad form.
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Well, it's a practice issue. If you never practice technique in marginal situations, then you aren't likely to select these options and/or perform them well when the need arises. Every flight for most GA pilots should be treated as a training flight since most don't fly enough to begin with. Therefor when the opportunity presents itself to practice something, it's a good idea to do so. GA planes don't have a spool up issues so 500' for stable isn't really a critical, a go around can be executed considerably lower than that in most circumstances.
 
Henning said:
. GA planes don't have a spool up issues so 500' for stable isn't really a critical, a go around can be executed considerably lower than that in most circumstances.
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Has nothing to do with "spool up issues". :nonod: The 500' "gate" is a point of "am I stabilized or not". Trying to go lower and "salvage" the approach is bad technique, period.

As far as go arounds are concerned, yes in any aircraft (small or big) go around's can be done all the way to touchdown.

The main point is developing techniques that prevent the average pilot from trying to attempt a salvaged approach and landing. There are lots of accidents that are attributed to just that.
 
Dan Thomas said:
That works fine if you're a little high. The guys diving at the runway are way too high and should be going around if they can't get it down without diving.
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That is, of course, true, but we're talking about how to make corrections here, not how to tell when you're too far out of parameters to continue the approach.
 
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