Trim on final & bad habbits
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Joined: Apr 2002
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From: UK
Trim on final & bad habbits
The other day, I decided to trim on final, thinking it would make landing a little easier, and less exhaustive (C172). It worked too!!
However, my instructor did not teach me this... is this good practice, or one of these bad habbits I've heard him talk about.
Talking of bad habbits, what are common ones people get after gaining their PPL?
However, my instructor did not teach me this... is this good practice, or one of these bad habbits I've heard him talk about.
Talking of bad habbits, what are common ones people get after gaining their PPL?
Avoid imitations
Joined: Nov 2000
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From: Wandering the FIR and cyberspace often at highly unsociable times
Depends on aircraft type. If you're using full flap, you may need to retrim on finals after it's selection.
If the aircraft isn't in trim, then the landing is hardly going to be easy. It needs to be done promptly and positively however; on final you need HOTAS as much as possible and should be looking outside.
If the aircraft isn't in trim, then the landing is hardly going to be easy. It needs to be done promptly and positively however; on final you need HOTAS as much as possible and should be looking outside.
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From: 75N 16E
Some aircraft POH's recommend trimming on final. For example the Seneca II POH recommends that 'three turns of nose up trim on final will help achieve the proper flare' or words to that affect. Works too. Not so important for a simple single, but on a complex like the Seneca, when you retard the throttles, the props act like big air brakes and the nose tends to get quite heavy....
Cheers
EA
Cheers
EA
Joined: Apr 2000
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From: 30 West
If you relax your already light hold on the stick/yoke and there is any residual force or the aircraft changes pitch - trim. You can't hold anything steady if you are out of trim. This is as important on a Cub as well as a 757. Airbus however, select pitch, pause, relax - Aaaaaaargh 
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From: New South Wales
However, my instructor did not teach me this... is this good practice, or one of these bad habbits I've heard him talk about.
It's tricky in training because you have to follow a single set of guidance fairly rigidly, otherwise you get in a pickle. Once you get your licence though it's worth flying with a number of different people and generally figuring out what works best for you. Eventually, you'll find a style which suits you and which you'll then develop. As long as you're safe, don't sweat minor issues like this one. I can't for the life of me see what's wrong with trimming on final.
QDM
Joined: May 1999
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From: UK
Hi all,
Yes I teach my students to trim on final approach - I do to - probably down to 200' I will trim...
Why need to trim on final approach? Because
1. You may change the aircraft configuration - u/c or flaps
2. if you alter the throttle one iota you need a trim change
3. approach speed and threshold speed are unlikely to be the same.....if you fly threshold speed on base you are endangering yourself...so a change in airspeed results in a change in trim.
4. if you change the attitude on the final approach its best to trim - if you hold the pitch change in then you are making a lot more work for yourself and the approach will not be as accurate.
Hope this helps.
Yes I teach my students to trim on final approach - I do to - probably down to 200' I will trim...
Why need to trim on final approach? Because
1. You may change the aircraft configuration - u/c or flaps
2. if you alter the throttle one iota you need a trim change
3. approach speed and threshold speed are unlikely to be the same.....if you fly threshold speed on base you are endangering yourself...so a change in airspeed results in a change in trim.
4. if you change the attitude on the final approach its best to trim - if you hold the pitch change in then you are making a lot more work for yourself and the approach will not be as accurate.
Hope this helps.
Joined: Jun 2002
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From: New South Wales
This kind of teaching -- don't trim on final -- is what's wrong with much of flying training as it stands today, isn't it? Students taught to fly airliner-type, enormous circuits, often onto strips of tarmac onto which you could land the space shuttle. I learnt to fly like this the first time round at Hurn as it then was and you simply don't get the runway 'picture' fixed in your mind, because you don't have to. You have a mile and a half to land! Let's see much shorter, tighter, lower level circuits into small grass strips being taught to a much more frequent degree.
My advice to aspirant pilots is don't train at massive huge airports if you want to go on and fly little planes. Fine for airliners, but not anything else.
QDM
My advice to aspirant pilots is don't train at massive huge airports if you want to go on and fly little planes. Fine for airliners, but not anything else.
QDM
I say there boy
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From: Somewhere
Was taught in an FI course to trim on finals if required - in fact a part of the demonstration that I was taught was to briefly remove your hands from the controls to show how the aircraft is still in trim, descending at the required rate to the aiming point at the approach speed.
cheers!
foggy.
cheers!
foggy.
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From: uk
Off the thread slightly, but in agreement with QDMx3. I was doing a bit of circuit bashing at the weekend, and instead of honing my circuit flying skills, half of the time I was worrying about the Cessna 152 whose pilot appeared to think that when he lost sight of the airfield on the horizon over his shoulder was the appropriate time to turn downwind.
I always thought that circuits were supposed to be tight enough that if your engine failed at any time, that there was a reasonable chance of getting back to the runway.
Circuit bashing for the student (I remember) was about consolidating the critical takeoff and landing skills. Wide circuits mean fewer landings per hour. Are students being taken advantage of in a cynical exercise to generate more revenue for flying clubs?
Or am I just too cynical?
I always thought that circuits were supposed to be tight enough that if your engine failed at any time, that there was a reasonable chance of getting back to the runway.
Circuit bashing for the student (I remember) was about consolidating the critical takeoff and landing skills. Wide circuits mean fewer landings per hour. Are students being taken advantage of in a cynical exercise to generate more revenue for flying clubs?
Or am I just too cynical?
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From: Just South of the last ice sheet
I used to wind in full nose up trim on my L4 Cub and she would flutter down the approach at idle in a 3 point attitude. Made landings dead easy.
When I tried it in the Auster it felt as if I was trying to loop. Ooops, much more effective trim......Had to think about it then and just trim as appropriate. Ooooh these complex aeryplanes
Bad habits, I had plenty after flying the Cub from a grass strip. Took a bit of willpower to go out and pick out as many faults as I could before my bi-ennial flight test with the man from the CAA (which I passed I hasten to add) instead of just fannying around like I usually do
When I tried it in the Auster it felt as if I was trying to loop. Ooops, much more effective trim......Had to think about it then and just trim as appropriate. Ooooh these complex aeryplanes
Bad habits, I had plenty after flying the Cub from a grass strip. Took a bit of willpower to go out and pick out as many faults as I could before my bi-ennial flight test with the man from the CAA (which I passed I hasten to add) instead of just fannying around like I usually do
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From: Dorset
Undertheweather - I'm with you on this one. I did half my PPL training in Canada and after about 4 hrs trg, my instructor would chop the throttle on me if he thought I was flying wide circuits and make me prove whether I could hit tarmac! Soon got me out of the habit of flying wide circuits! Got back to UK and was instantly slapped around the head for flying tight circuits (at Bournemouth!0 - these are nothing like as wide as Perth fly them!!
I always feel more comfortable if I feel I can land inside the airfield boundary after an in-circuit power failure - I currently fly a Fuji which glides like a brick - maybe I should never fly outside the airfield boundary
I always feel more comfortable if I feel I can land inside the airfield boundary after an in-circuit power failure - I currently fly a Fuji which glides like a brick - maybe I should never fly outside the airfield boundary
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From: New South Wales
my instructor would chop the throttle on me if he thought I was flying wide circuits and make me prove whether I could hit tarmac
QDM
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From: England
As far as I can see, if an aircraft is out of trim, then you trim it. It should be an automatic response. You will never manage to fly an ILS down to MDA unless the aircraft is in trim. The only time I don't trim is in turns (because the aircraft will then still be trimmed correctly when I roll out) and when I want a very short climb or descent followed by level flight (eg when changing from, say, 3000' on regional QNH to 3000' on aerodrome QNH).
Agree fully with QDM re learning at short fields for two reasons:
1. Its easier to make the change short-to-long than vice-versa.
2. You get practice at making go-arounds so you learn as second-nature to make a decision on every approach... are you going to land or are you going around? I think some people go through the far hedge because it never occurs to them to go-around.
I also agree with undertheweather that most circuits flown at airfields today are far too large. Sometimes this is necessary to avoid noise-sensitive villages, but often it there appears to be no reason other than a CFI once drew a particular circuit on the map. Perhaps its to give students "thinking time" during the circuit. I don't know.
I learnt at a small airfield and we weren't allowed to do touch-and-goes, plus the circuit was extremely large (for valid noise reasons). However, it took me a lot of time and money to learn to land because I only got four landing in each hour's lesson. At another airfield with a smaller circuit and touch-and-goes (plus a longer 418 metre runway) I could do twelve landings in an hour. What I am probably saying is that the optimum is probably to have a runway that is short, but not too short and a safe tight circuit. Pity we have to live and fly in the real world !
Agree fully with QDM re learning at short fields for two reasons:
1. Its easier to make the change short-to-long than vice-versa.
2. You get practice at making go-arounds so you learn as second-nature to make a decision on every approach... are you going to land or are you going around? I think some people go through the far hedge because it never occurs to them to go-around.
I also agree with undertheweather that most circuits flown at airfields today are far too large. Sometimes this is necessary to avoid noise-sensitive villages, but often it there appears to be no reason other than a CFI once drew a particular circuit on the map. Perhaps its to give students "thinking time" during the circuit. I don't know.
I learnt at a small airfield and we weren't allowed to do touch-and-goes, plus the circuit was extremely large (for valid noise reasons). However, it took me a lot of time and money to learn to land because I only got four landing in each hour's lesson. At another airfield with a smaller circuit and touch-and-goes (plus a longer 418 metre runway) I could do twelve landings in an hour. What I am probably saying is that the optimum is probably to have a runway that is short, but not too short and a safe tight circuit. Pity we have to live and fly in the real world !
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From: UK
I was always taught to trim whenever I'm not flying a "transient manouvre" (e.g. turning, spiral dive ).
I normally set carb-heat, power & flaps mid-way down base leg, then trim . Once turned onto final, make whatever adjustments are needed to make the picture out the front look right, re-trimming if necessary. Then - with about a mile to run, the carb-heat comes off and I don't worry about the trim any more. There shouldn't be any serious amount of back or forward pressure necessary on the CC at that time... If there is - then go around!!
).I normally set carb-heat, power & flaps mid-way down base leg, then trim . Once turned onto final, make whatever adjustments are needed to make the picture out the front look right, re-trimming if necessary. Then - with about a mile to run, the carb-heat comes off and I don't worry about the trim any more. There shouldn't be any serious amount of back or forward pressure necessary on the CC at that time... If there is - then go around!!
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Tomahawk
Let's analyse what trim is for.
It's for removing the weight from the controls when the aircraft is at the appropriate attitude.
I don't know why your instructor did not teach you to trim on final and I won't try to second guess him.
Three points to bear in mind:
1 - when you remove power in the flare, the aircraft will start to decelerate and any sensible aircraft will pitch down to try and regain its trimmed airspeed.
2 - on most light singles, this pitch down is countered unconciously by the pilot and the control forces are light enough for this to be practical - however some heavier singles (e.g. PA32R) require trim to be added in the flare ro reduce the back pressure to manageable proportions; this is not an old wives tale, its in the POH
3 - if you sit on the flight deck of a jet or a jet sim and watch an autoland, the a/p in the models I've observed tends to slightly over trim nose up before the flare
Having said all of this, trying to fly the a/c using the trim instead of the yoke as a low hours pilot is not good and I could understand why an instructor may feel it better to encourage a pilot to develop a feel of the plane by using the yoke properly.
On training type aircraft this forces allow this, but as you have discovered the trim, used sensibly, is a wonderful aid!
Enjoy your flying.
Let's analyse what trim is for.
It's for removing the weight from the controls when the aircraft is at the appropriate attitude.
I don't know why your instructor did not teach you to trim on final and I won't try to second guess him.
Three points to bear in mind:
1 - when you remove power in the flare, the aircraft will start to decelerate and any sensible aircraft will pitch down to try and regain its trimmed airspeed.
2 - on most light singles, this pitch down is countered unconciously by the pilot and the control forces are light enough for this to be practical - however some heavier singles (e.g. PA32R) require trim to be added in the flare ro reduce the back pressure to manageable proportions; this is not an old wives tale, its in the POH
3 - if you sit on the flight deck of a jet or a jet sim and watch an autoland, the a/p in the models I've observed tends to slightly over trim nose up before the flare
Having said all of this, trying to fly the a/c using the trim instead of the yoke as a low hours pilot is not good and I could understand why an instructor may feel it better to encourage a pilot to develop a feel of the plane by using the yoke properly.
On training type aircraft this forces allow this, but as you have discovered the trim, used sensibly, is a wonderful aid!
Enjoy your flying.
Last edited by Final 3 Greens; 29th July 2002 at 21:57.
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From: Location: Location:
We need to remember....
Trim is a function of Airspeed and not attitude.
Therefore if you fly an approach in a cessna 172 at say 70 knts and do not change the trim from say the trimmed state speed which is of course 70knts then ssais 172 will gladly stick 2 fingers up at you as it floats 1/2 way down the runway.
A good landing comes from a good approach, in any airplane you have a Vapp and Vref approach at one speed, touch down at another.
I teach accurate speed control down finals and at the height of a double decker bus - Pitch Up - Retrim to the revised speed of eith er 60 or 65 knots and the airplane will then dissipate energy and give a cushioned touchdown on the runway.
Energy is a function of Airspeed squared.
Try and land at 70 knots = 4900 units of energy
Try and land at 60 knots = 3600 units of energy
a 25% decrease in energy for a 10 knot speed reduction.....
Hey presto ace QFI landing every time.
The trim wheel helps maintain the correct selected speed
Trim is a function of Airspeed and not attitude.
Therefore if you fly an approach in a cessna 172 at say 70 knts and do not change the trim from say the trimmed state speed which is of course 70knts then ssais 172 will gladly stick 2 fingers up at you as it floats 1/2 way down the runway.
A good landing comes from a good approach, in any airplane you have a Vapp and Vref approach at one speed, touch down at another.
I teach accurate speed control down finals and at the height of a double decker bus - Pitch Up - Retrim to the revised speed of eith er 60 or 65 knots and the airplane will then dissipate energy and give a cushioned touchdown on the runway.
Energy is a function of Airspeed squared.
Try and land at 70 knots = 4900 units of energy
Try and land at 60 knots = 3600 units of energy
a 25% decrease in energy for a 10 knot speed reduction.....
Hey presto ace QFI landing every time.
The trim wheel helps maintain the correct selected speed