Trim Use During Approach Phase in Visual Patterns
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Trim Use During Approach Phase in Visual Patterns
Hello everybody, I'd like to share with you an article I had recently posted on the IAFTP website. My thoughts are meant to be associated with light single prop training A/C. Please comments ... but don't be too cruel 
Abstract:
Thanks to the fact that small SEPs are light, there’s no a real need for trimming all the time for every speed or flap setting. In this way the student has the chance to gain a “control/muscle memory” throughout the pattern, starting from the last time he trimmed the aircraft. He understand that now, the force he’s applying is due to the fact he is controlling the speed during the descent, managing the energy, instead of letting simply the nose down; in the same way he understand more easily how to control his rate of descent with power.
Details:
Once in downwind, memory items/flow are performed, entering slow flight condition at the required speed with the 1st notch of flaps, then a/c is trimmed to obtain a neutral feeling on the control column for that airspeed.
We are in a situation that require the a/c to cooperate with us and fly almost by itself, so we can spend a couple of seconds giving a glance to the checklist, deal with communications and stay focused on traffic avoidance, so trimming here is important.
When it’s time to turn on base, power is reduced to initiate a positive nose down tendency and base turn is started at max 20° of bank; during this maneuver the nose dipping movement is seconded applying a minimum back pressure on the elevator, this in order to obtain an initial deceleration to, lets say, 70 kts while descending.At this stage no trim is required, it’s an energy management phase therefore feeling how the airflow act on the elevator is very important, as well as maintain sensitivity over load changes.
Once on base the rate of descent is adjusted and flaps are set as required; even if 2nd notch of flaps is added no trim is really needed, as pitch changes are neglectable and flaps induced movements are absorbed with the joke while speed is kept constant, the attention is focused on final turn planning and height and energy management.
Final turn is achieved in the same way using the 20° bank and 70kt limitation, and then as soon as the a/c is stable and wings leveled, speed and flaps are set as required. Once on final trim is finally used to lighten up a little bit the loads on the elevator, but not to a neutral feeling.
Summary of Effectiveness:
In my opinion this practice help the trainees that tends to over control, and those who use too much trim in the wrong way, as it were a flight control.
Thanks to the fact that small SEPs are light, there’s no a real need for trimming all the time for every speed or flap setting. In this way the student has the chance to gain a “control/muscle memory” throughout the pattern, starting from the last time he trimmed the aircraft. He understand that now, the force he’s applying is due to the fact he is controlling the speed during the descent, managing the energy, instead of letting simply the nose down; in the same way he understand more easily how to control his rate of descent with power.
At the same time this help in dealing with go-arounds especially unexpected ones, where an excess of nose-up trim associated with flaps at slow speeds, can produce unhealthy climbing attitudes if power is suddenly applied; this is maybe not a problem for a seasoned pilot, but can be scary and hard to manage for a beginner.In addition, to give precise and simple parameters to comply with ( max bank, min airspeed) and avoid messing with the trim, will help in achieving a better initial stick&throttle feeling, while keeping him in a safe speed/attitude envelope.
Abstract:
Thanks to the fact that small SEPs are light, there’s no a real need for trimming all the time for every speed or flap setting. In this way the student has the chance to gain a “control/muscle memory” throughout the pattern, starting from the last time he trimmed the aircraft. He understand that now, the force he’s applying is due to the fact he is controlling the speed during the descent, managing the energy, instead of letting simply the nose down; in the same way he understand more easily how to control his rate of descent with power.
Details:
Once in downwind, memory items/flow are performed, entering slow flight condition at the required speed with the 1st notch of flaps, then a/c is trimmed to obtain a neutral feeling on the control column for that airspeed.
We are in a situation that require the a/c to cooperate with us and fly almost by itself, so we can spend a couple of seconds giving a glance to the checklist, deal with communications and stay focused on traffic avoidance, so trimming here is important.
When it’s time to turn on base, power is reduced to initiate a positive nose down tendency and base turn is started at max 20° of bank; during this maneuver the nose dipping movement is seconded applying a minimum back pressure on the elevator, this in order to obtain an initial deceleration to, lets say, 70 kts while descending.At this stage no trim is required, it’s an energy management phase therefore feeling how the airflow act on the elevator is very important, as well as maintain sensitivity over load changes.
Once on base the rate of descent is adjusted and flaps are set as required; even if 2nd notch of flaps is added no trim is really needed, as pitch changes are neglectable and flaps induced movements are absorbed with the joke while speed is kept constant, the attention is focused on final turn planning and height and energy management.
Final turn is achieved in the same way using the 20° bank and 70kt limitation, and then as soon as the a/c is stable and wings leveled, speed and flaps are set as required. Once on final trim is finally used to lighten up a little bit the loads on the elevator, but not to a neutral feeling.
Summary of Effectiveness:
In my opinion this practice help the trainees that tends to over control, and those who use too much trim in the wrong way, as it were a flight control.
Thanks to the fact that small SEPs are light, there’s no a real need for trimming all the time for every speed or flap setting. In this way the student has the chance to gain a “control/muscle memory” throughout the pattern, starting from the last time he trimmed the aircraft. He understand that now, the force he’s applying is due to the fact he is controlling the speed during the descent, managing the energy, instead of letting simply the nose down; in the same way he understand more easily how to control his rate of descent with power.
At the same time this help in dealing with go-arounds especially unexpected ones, where an excess of nose-up trim associated with flaps at slow speeds, can produce unhealthy climbing attitudes if power is suddenly applied; this is maybe not a problem for a seasoned pilot, but can be scary and hard to manage for a beginner.In addition, to give precise and simple parameters to comply with ( max bank, min airspeed) and avoid messing with the trim, will help in achieving a better initial stick&throttle feeling, while keeping him in a safe speed/attitude envelope.
Thank you for sharing your thoughts on this. I think I see what you are trying to say, but I am somewhat confused by
Do you mean to say negligeable rather than neglectable? If so it makes more sense even if I think you are mistaken. The amount of pitch change is rather type specific, what are you using as an example? And I suppose joke is a typo for yoke?
I suspect most early students will be forgetting about the trim anyway, rather than conciously not trimming, maybe we should just let it happen?
Once on base the rate of descent is adjusted and flaps are set as required; even if 2nd notch of flaps is added no trim is really needed, as pitch changes are neglectable and flaps induced movements are absorbed with the joke while speed is kept constant, the attention is focused on final turn planning and height and energy management.
I suspect most early students will be forgetting about the trim anyway, rather than conciously not trimming, maybe we should just let it happen?
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IMHO this will not work well, if the aircraft is out of trim students are far more likely to allow the aircraft to trend towards its out of trim attitude and ends up with more problems.
Actually, what you are suggesting seems to be how many students ( and even some PPLs) fly the aircraft until they learn to trim properly and they struggle for exactly the reason that they ARE out of trim.
Actually, what you are suggesting seems to be how many students ( and even some PPLs) fly the aircraft until they learn to trim properly and they struggle for exactly the reason that they ARE out of trim.
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My two pence...
I found that the practice of course trimming initially to remove the pressure on the elevator to maintain the attitude, followed by a fine trim to correct for small changes in attitude, worked well. By doing it this way, the student will have at least got the aircraft more or less trimmed to an acceptable level prior to the fine trim taking place. I found that some students got predicated on the need to trim (overly) accurately in the approach attitude and especially at the early stages meant that airmanship, circuit planning , speed/attitude control went out the window as the work load increased. I'd personally prefer someone to be slightly out of trim but fly a safe and accurate circuit than get fixated on trimming and let the fore mentioned go out the DV panel!
I found that the practice of course trimming initially to remove the pressure on the elevator to maintain the attitude, followed by a fine trim to correct for small changes in attitude, worked well. By doing it this way, the student will have at least got the aircraft more or less trimmed to an acceptable level prior to the fine trim taking place. I found that some students got predicated on the need to trim (overly) accurately in the approach attitude and especially at the early stages meant that airmanship, circuit planning , speed/attitude control went out the window as the work load increased. I'd personally prefer someone to be slightly out of trim but fly a safe and accurate circuit than get fixated on trimming and let the fore mentioned go out the DV panel!
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For Piper Classique, thank you.
Those thoughts are referred to a light SEP training a/c, like a C150/C152, I'm sorry about my "Itanglish" but difference between neglectable and negligeable is not very clear for me at the moment (I'll do some research now :-) ).
What I meant was that, passing from flap1 to flap2, pich changes are small and considered
that we are slow and descending with a nose down attitude, this changes are hardly
visualized and sensed by the pilot. So, once the pilot knows about the effects that flap
produce on that particular a/c (nose up or down moment), he will compensate for it
using the yoke (thanks again) but without acting on the trim. The pilot will rather
concentrate on mantaining the required speed and descent slope.
For Foxmoth
Well, the a/c is not really out of trim, the a/c is trimmed for a speed, lets say 75 kts on
downwind. On downwind the a/c is trimmed at that particular airspeed in order to
mantain level flight, so you can do all your stuff etc... yes, in downwind I need a nicely
trimmed airplane. When turning on base power is reduced, a/c will naturally put the nose
down looking for that 75 kts he wants, here the pilot stop the nose drop just by means
of the elevator in order to obtain a lower airspeed, lets say 70 kts.
The difference is just 5 kts, not very much out of trim. In this way, using a little muscle, the pilot will have immediately a better understanding on what is going on about lift and gravity, about energy balance while trading altitude for speed and, most important, load factor.
Thank you again for your comments
Those thoughts are referred to a light SEP training a/c, like a C150/C152, I'm sorry about my "Itanglish" but difference between neglectable and negligeable is not very clear for me at the moment (I'll do some research now :-) ).
What I meant was that, passing from flap1 to flap2, pich changes are small and considered
that we are slow and descending with a nose down attitude, this changes are hardly
visualized and sensed by the pilot. So, once the pilot knows about the effects that flap
produce on that particular a/c (nose up or down moment), he will compensate for it
using the yoke (thanks again) but without acting on the trim. The pilot will rather
concentrate on mantaining the required speed and descent slope.
For Foxmoth
Well, the a/c is not really out of trim, the a/c is trimmed for a speed, lets say 75 kts on
downwind. On downwind the a/c is trimmed at that particular airspeed in order to
mantain level flight, so you can do all your stuff etc... yes, in downwind I need a nicely
trimmed airplane. When turning on base power is reduced, a/c will naturally put the nose
down looking for that 75 kts he wants, here the pilot stop the nose drop just by means
of the elevator in order to obtain a lower airspeed, lets say 70 kts.
The difference is just 5 kts, not very much out of trim. In this way, using a little muscle, the pilot will have immediately a better understanding on what is going on about lift and gravity, about energy balance while trading altitude for speed and, most important, load factor.
Thank you again for your comments
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I disagree with letting the sods ever fly out of trim.
They should be taught what attitude they should be holding for every configuration change and power setting.
Then trim after the aircraft has settled.
Once its in trim they can then have the over controlling habit beaten out of them.
Use what you like one hand on the power and one hand on the stick if they still have to firm a grip stick a pencil across there fingers so they can only grip with there middle finger.
The trick is not to let them wander with the attitudes even in transition periods they should be holding a attitude and not just letting the nose pick its own.
TO/climb thats your attitude.
Down wind thats your attitude
Base thats you attitude
Approach thats your attitude
Go-around thats your attitude
All done and practised away from the circuit. The only thing you should be teaching in the circuit is the last 10 ft.
If you teach them right they should be able to do it with no instruments at all and the speeds etc will be bang on the numbers.
They should be taught what attitude they should be holding for every configuration change and power setting.
Then trim after the aircraft has settled.
Once its in trim they can then have the over controlling habit beaten out of them.
Use what you like one hand on the power and one hand on the stick if they still have to firm a grip stick a pencil across there fingers so they can only grip with there middle finger.
The trick is not to let them wander with the attitudes even in transition periods they should be holding a attitude and not just letting the nose pick its own.
TO/climb thats your attitude.
Down wind thats your attitude
Base thats you attitude
Approach thats your attitude
Go-around thats your attitude
All done and practised away from the circuit. The only thing you should be teaching in the circuit is the last 10 ft.
If you teach them right they should be able to do it with no instruments at all and the speeds etc will be bang on the numbers.
Last edited by mad_jock; 25th Oct 2012 at 15:40.
Another factor which should be considered when trimming on final approach is the possible need for a go around. Having an out of trim a/c is not very helpful when you are close to the ground and trying to reconfigure for best climb, reducing flap and trying to stay on the centre line in a Xwind. On the other hand, if a student is used to having an out of trim a/c it may be less of a problem.
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On the other hand, if a student is used to having an out of trim a/c it may be less of a problem.
Instead of teaching them set that power, nail that attitude reconfigure while maintain that attitude and trim as required.
Its no wonder trimming an aircraft seems to be a forgotten art these days.
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Trim...
...all the time, for every config change, wherever you are. So much easier in the end.
If they can't trim the aeroplane by this stage, take them back out of the circuit and do some more exercise 4!
My 2p.
DD
If they can't trim the aeroplane by this stage, take them back out of the circuit and do some more exercise 4!
My 2p.
DD
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Personally I detest flying out-of-trim & think this is a bad idea for the reasons expounded by MJ & others. I'd have thought at the circuit bashing stage it would just make it that much harder for the student to nail attitude/airspeed & flying with neutral stick/yoke force down to the flare just seems to me to be the right way of doing things.
On the occasions I've flown gliders I've found most BGC instructors teach flying the last part of the approach 'out-of-trim'; this feels unnatural to me (as does speeding up for the approach!) & if I don't retrim I really have to concentrate to prevent the airspeed bleeding off on short final.
In addition, learning to feed in some forward pressure (and hopefully a bit of rudder correction too) when advancing the throttle for the go-around will engender good habits in students that will help prevent nasty incidents if they ever transition to more powerful types.
And on a tapered wing PA-28, the trim change that accompanies the first stage of flap extension/retraction would make this decidedly uncomfortable.
On the occasions I've flown gliders I've found most BGC instructors teach flying the last part of the approach 'out-of-trim'; this feels unnatural to me (as does speeding up for the approach!) & if I don't retrim I really have to concentrate to prevent the airspeed bleeding off on short final.
In addition, learning to feed in some forward pressure (and hopefully a bit of rudder correction too) when advancing the throttle for the go-around will engender good habits in students that will help prevent nasty incidents if they ever transition to more powerful types.
And on a tapered wing PA-28, the trim change that accompanies the first stage of flap extension/retraction would make this decidedly uncomfortable.
Last edited by Sillert,V.I.; 25th Oct 2012 at 19:37.
The trick is not to let them wander with the attitudes even in transition periods they should be holding a attitude and not just letting the nose pick its own.
On the occasions I've flown gliders I've found most BGC instructors teach flying the last part of the approach 'out-of-trim'; this feels unnatural to me (as does speeding up for the approach!) & if I don't retrim I really have to concentrate to prevent the airspeed bleeding off on short final
All done and practised away from the circuit. The only thing you should be teaching in the circuit is the last 10 ft.
Absolutely!
For the OP neglectable means you can forget about it, it isn't important. Negligeable means it is small, which is not the same as not important.
On a go around the out of trim forces can be large.....so you do need to be able to hold an attitude despite the best or worst efforts of the aircraft.
Type specific comes in here. Rallye, super cub, spring to mind.
Interesting thread which links to the question of things we could teach better
I am totally with MJ on this issue. The most important skill required to fly a proper circuit and landing is to by looking out the window be able to set thr correct attitude for what ever you want the aircraft to do. If the student goes immediately to the right attitude and holds it, an out of trim condition will be obvious and they can apply a bit of grim in the appropriate direction.
I see a continuing widespread problem in flight training with students going to the circuit before they have truly mastered ex 5 to 9. That IMO is invariably the root cause of students who are not progressing in the circuit.
Finally the last thing I do before starting in the circuit is to at altitude, have the student practice the 4 legs of the circuit in the practice area. This gets them used to the rhythm of the circuit, reinforces attitude and speed control but without the pressure of landing and since each final will, of course, end with an overshoot in this exercise it reinforces this often neglected part of circuit training.
I see a continuing widespread problem in flight training with students going to the circuit before they have truly mastered ex 5 to 9. That IMO is invariably the root cause of students who are not progressing in the circuit.
Finally the last thing I do before starting in the circuit is to at altitude, have the student practice the 4 legs of the circuit in the practice area. This gets them used to the rhythm of the circuit, reinforces attitude and speed control but without the pressure of landing and since each final will, of course, end with an overshoot in this exercise it reinforces this often neglected part of circuit training.
Last edited by Big Pistons Forever; 25th Oct 2012 at 20:02.
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Be in trim all the time...except
Throughout the pattern the student or any pilot should have the aircraft in proper trim (elevator/stab). One should be able to release the controls having the plane maintain speed and attitude.
I allow a bank up to 30 degrees from downwind to base and 15 degrees from base to final.
Once the plane is in trim on final, no application of trim to make the flare should be done...here is where the muscles can actually feedback speed info to the pilot...the heavier the yoke the slower you are going towards touchdown speed (vref minus 5 or so...down to a full stall landing).
Trimming into the flare might give you a grease job once in awhile but you are not ''feeling'' the speed as outlined above. This is for all planes, not just small GA stuff.
and Gosh I hate the C150/52. Much prefer piper cherokees and even the tomahawk. Better visiblity!
I allow a bank up to 30 degrees from downwind to base and 15 degrees from base to final.
Once the plane is in trim on final, no application of trim to make the flare should be done...here is where the muscles can actually feedback speed info to the pilot...the heavier the yoke the slower you are going towards touchdown speed (vref minus 5 or so...down to a full stall landing).
Trimming into the flare might give you a grease job once in awhile but you are not ''feeling'' the speed as outlined above. This is for all planes, not just small GA stuff.
and Gosh I hate the C150/52. Much prefer piper cherokees and even the tomahawk. Better visiblity!
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The sooner a pilot learns to:
1) select and maintain a visual attitude
2) accurately trim to maintain that attitude (and retrim for every power, configuration and speed change)
3) maintain a good lookout while doing the above,
the sooner you can start teaching them to fly.
Essential building blocks, not to be modified according to whether you are in the circuit or not. Topper, you are describing how to thoroughly confuse a student, not teach them!
1) select and maintain a visual attitude
2) accurately trim to maintain that attitude (and retrim for every power, configuration and speed change)
3) maintain a good lookout while doing the above,
the sooner you can start teaching them to fly.
Essential building blocks, not to be modified according to whether you are in the circuit or not. Topper, you are describing how to thoroughly confuse a student, not teach them!
- I was trying to be too polite!
Come on, people. The OP, who is not a native english speaker, has at least done some thinking about what he is trying to achieve, which is a pilot who has some feel for the aeroplane.
He doesn't suggest not teaching correct trim, or at least I don't think this is what he is advocating. As far as I can interpret his post, and I agree it is not entirely clear, he is saying that he does not advocate trimming out a transient load, and is emphasizing the need to be able to hold a required attitude.
Sevenstrokeroll says it better...
I certainly take issue with
If he means that is the last time he expects the trim to be used, which would imply nose heavy on base leg and final approach. Or is he trying to say trim after the turn from downwind to base? As the base leg and the final approach are not transient phases, yes of course the aircraft should be trimmed correctly. As indeed it should for all steady states. But once the attitude and power are set on final or anywhere else would you expect a retrim for every gust?
I don't think we need to be rude to each other here, there is enough of that elsewhere on the forums.
Seriously, Whopity? Four days? Please name and shame!
He doesn't suggest not teaching correct trim, or at least I don't think this is what he is advocating. As far as I can interpret his post, and I agree it is not entirely clear, he is saying that he does not advocate trimming out a transient load, and is emphasizing the need to be able to hold a required attitude.
Sevenstrokeroll says it better...
Once the plane is in trim on final, no application of trim to make the flare should be done...here is where the muscles can actually feedback speed info to the pilot...the heavier the yoke the slower you are going towards
touchdown speed (vref minus 5 or so...down to a full stall landing).
touchdown speed (vref minus 5 or so...down to a full stall landing).
When turning on base power is reduced, a/c will naturally put the nose
down looking for that 75 kts he wants, here the pilot stop the nose drop just by means
of the elevator in order to obtain a lower airspeed, lets say 70 kts.
down looking for that 75 kts he wants, here the pilot stop the nose drop just by means
of the elevator in order to obtain a lower airspeed, lets say 70 kts.
I don't think we need to be rude to each other here, there is enough of that elsewhere on the forums.
I wondered how some schools were managing a 4 day FI Course, now we know!
Avoid imitations
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I was always taught (and in turn taught others) to trim any aircraft properly, at all times.
If a pilot is taught to routinely fly the aircraft out of trim, at any stage of flight, it seems obvious to me what might go wrong. Especially on final approach to an unfamiliar airfield in poor visibility, where some of the pilot's attention might get diverted away from the proper priority of poling the aircraft. If you're not flying the aircraft, it will fly you. You know where I'm going with this....
If a pilot is taught to routinely fly the aircraft out of trim, at any stage of flight, it seems obvious to me what might go wrong. Especially on final approach to an unfamiliar airfield in poor visibility, where some of the pilot's attention might get diverted away from the proper priority of poling the aircraft. If you're not flying the aircraft, it will fly you. You know where I'm going with this....