The Use Of the Trim Wheel
I assume that you mean the pitch trim wheel?, since that's the most universal.
Depending upon aircraft, it either moves an elevator trim tab, changes tension on a spring/bungee in the elevator circuit, or moves the natural angle of an all-flying tailplane.
It allows the pilot to set the hands-off trim speed of the aeroplane (for a given flap/power/gear/airbrake setting anyhow), allowing the aircraft to be flown hands-off, or reducing pilot effort to fly at a given speed. This substantially reduces pilot workload, allowing him or her to then concentrate on other tasks - such as navigation, management, communications, and so-on.
When you start learning to fly, you'll cover this in your first few lessons.
I have flown aeroplanes without trimmers, but they're rare and generally very low performance and low-capability.
G
Depending upon aircraft, it either moves an elevator trim tab, changes tension on a spring/bungee in the elevator circuit, or moves the natural angle of an all-flying tailplane.
It allows the pilot to set the hands-off trim speed of the aeroplane (for a given flap/power/gear/airbrake setting anyhow), allowing the aircraft to be flown hands-off, or reducing pilot effort to fly at a given speed. This substantially reduces pilot workload, allowing him or her to then concentrate on other tasks - such as navigation, management, communications, and so-on.
When you start learning to fly, you'll cover this in your first few lessons.
I have flown aeroplanes without trimmers, but they're rare and generally very low performance and low-capability.
G
In the very light craft I fly, one sees more and more electrically actuated trim tabs, doing away with the "wheel" notion". Changing nothing about the function, as already well described and explained.
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I have flown aeroplanes without trimmers, but they're rare and generally very low performance and low-capability.
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I hate those electronic trim hats, we had one on the club tecnam and you could never feel the trim change quite like the good ole fashion wheel.
not that i can talk about trim managment..... rpm up, rpm down....
not that i can talk about trim managment..... rpm up, rpm down....
Only half a speed-brake
Happily yours,
FD.
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Please dont forget the larger the trim wheel the more dangerous.
The damn things go whirling round like a large circular chain saw blade on their own accord.
Who designed the things on larger aircraft? Have there been serious injuries or amputations by a runaway trim wheel?
Even the old Citation is bad enough
Pace
The damn things go whirling round like a large circular chain saw blade on their own accord.
Who designed the things on larger aircraft? Have there been serious injuries or amputations by a runaway trim wheel?
Even the old Citation is bad enough
Pace
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you could never feel the trim change quite like the good ole fashion wheel
Runaway trim wheels whats that?
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The trim wheel sets the speed at which the plane will fly.
Engine power doesn't change the speed; it merely affects the rate of climb or descent.
The fact that the trim wheel can be used to null-out the yoke pitch force is a side effect, but erroneously most PPL training usually plugs this as the sole reason for the trim wheel
The trim mechanism (with the trim tab) is a negative feedback control system which controls the AOA to maintain the set airspeed. It does it by continually adjusting the elevator position.
Engine power doesn't change the speed; it merely affects the rate of climb or descent.
The fact that the trim wheel can be used to null-out the yoke pitch force is a side effect, but erroneously most PPL training usually plugs this as the sole reason for the trim wheel
The trim mechanism (with the trim tab) is a negative feedback control system which controls the AOA to maintain the set airspeed. It does it by continually adjusting the elevator position.
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And, it costs nothing to use. So don't be scared of it. It's your friend. Which is contrary to lots of people I have known, who seemed to fly in the belief that they get charged an extra £10 for every time they touched it...
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The key point is that the trim wheel controls the difference between the wing AoA and the tailplane AoA, with hands off the controls.
(obviously the whole aeroplane can still pitch up or down). As Genghis described, there are various ways to achieve this.
For any given AoA difference, the 'whole-aircraft AoA' is stable at a particular angle to the airflow. If you pitch down and then take your hands off, the tail rises and gets pushed down again. After a few ups and downs, you return to your original AoA. Conversely if you pitch up.
In straight-and-level flight, trimming for an AoA is effectively trimming for speed, as IO540 said.
But if you trim for 100Kts S&L, then start a hands-off banked turn, the aircraft will try to maintain the previous AoA, not the previous speed.
This means the nose will drop, and you will descend, so now the aircraft is supporting the higher G weight at a faster speed but at the original AoA.
A gust can start the turn, in which case this whole procedure can occur hands-off.
If your aircraft has a separate tendency to steepen bank angles, you will get a spiral dive.
In IMC, you won't see it happening. The "seat of the pants" won't feel any turn, though you might feel heavy as though you were pitching up...
(obviously the whole aeroplane can still pitch up or down). As Genghis described, there are various ways to achieve this.
For any given AoA difference, the 'whole-aircraft AoA' is stable at a particular angle to the airflow. If you pitch down and then take your hands off, the tail rises and gets pushed down again. After a few ups and downs, you return to your original AoA. Conversely if you pitch up.
In straight-and-level flight, trimming for an AoA is effectively trimming for speed, as IO540 said.
But if you trim for 100Kts S&L, then start a hands-off banked turn, the aircraft will try to maintain the previous AoA, not the previous speed.
This means the nose will drop, and you will descend, so now the aircraft is supporting the higher G weight at a faster speed but at the original AoA.
A gust can start the turn, in which case this whole procedure can occur hands-off.
If your aircraft has a separate tendency to steepen bank angles, you will get a spiral dive.
In IMC, you won't see it happening. The "seat of the pants" won't feel any turn, though you might feel heavy as though you were pitching up...
IO540, some would say the attitude determined by use of the elevator sets the speed, and the trim is used to hold it there.
Splitting hairs I know, but some grumpy old instructors insisted on bursting my eardrums if I ever dared trickle the trim without setting the attitude first.
Splitting hairs I know, but some grumpy old instructors insisted on bursting my eardrums if I ever dared trickle the trim without setting the attitude first.
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You can also get lovely steep turns by flying with one hand on the trim wheel but dont tell the instructor that either 
Trim can freeze. I was waiting for a clearance to climb into CAS to FL 120.
I was down at around 4000 feet just in plus temperatures and in very heavy rain. I was cleared to climb in the Seneca and headed up trimming the aircraft into the climb.
All was fine untilthe level off where shock of horrors the trim had frozen solid in the climb attitude.
I had no choice with the forces but to explain the situation and head down in an ungainly fashion and some quite considerable out of trim forces to melt the lot off.
Having done that it was the climb all over again to FL120.
But that is something to consider as you could be sitting there with heavy forces wondering whats going on.
Pace
Trim can freeze. I was waiting for a clearance to climb into CAS to FL 120.
I was down at around 4000 feet just in plus temperatures and in very heavy rain. I was cleared to climb in the Seneca and headed up trimming the aircraft into the climb.
All was fine untilthe level off where shock of horrors the trim had frozen solid in the climb attitude.
I had no choice with the forces but to explain the situation and head down in an ungainly fashion and some quite considerable out of trim forces to melt the lot off.
Having done that it was the climb all over again to FL120.
But that is something to consider as you could be sitting there with heavy forces wondering whats going on.
Pace
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The trim wheel sets the speed at which the plane will fly.
Engine power doesn't change the speed; it merely affects the rate of climb or descent.
Engine power doesn't change the speed; it merely affects the rate of climb or descent.
We don't fly the airplane off the trim wheel. The stick or control column establishes speed by setting angle of attack, and the trim wheel is used to trim off control forces.
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Splitting hairs I know, but some grumpy old instructors insisted on bursting my eardrums if I ever dared trickle the trim without setting the attitude first
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Trim in steep turns
"You can also get lovely steep turns by flying with one hand on the trim wheel but dont tell the instructor that either."
My instructor leaned toward trim to assist steep turns. Bank over, dial in two deep pulls on the trim wheel and concentrate on bank without strain on pitch.
In general, it was Pitch, Power, Trim...love the comment that trim is already paid for so use it freely.
My instructor leaned toward trim to assist steep turns. Bank over, dial in two deep pulls on the trim wheel and concentrate on bank without strain on pitch.
In general, it was Pitch, Power, Trim...love the comment that trim is already paid for so use it freely.
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While riding around in the back of a friend's Piper Aztec, I would entertain myself by quietly unzipping the headliner aft ot the back seat, and finding the elevator trim cable up there. With a distraction of "hey what's that down there?" I could put the elevator a good bit out of trim, and amuse myself watching him re trim it, and figuring out why it was necessary.
Now on the other hand, the first time I ever flew a Cessna 340, my five fellow occupants, all of whom were pilots, left me flying left seat (to my profound delight) and went in the back for lemonade. Some time later, the plane pitched violently nose down, and I struggled to maintain control, as one of them entered the cockpit backward through the curtain. I had failed to be alert for the fact that they had been all moving farther and farther back in the cabin, and I had been retrimming, without wondering why I needed to. We all learned a startling lesson about the affect of changing the arm of the load in flight!
Now on the other hand, the first time I ever flew a Cessna 340, my five fellow occupants, all of whom were pilots, left me flying left seat (to my profound delight) and went in the back for lemonade. Some time later, the plane pitched violently nose down, and I struggled to maintain control, as one of them entered the cockpit backward through the curtain. I had failed to be alert for the fact that they had been all moving farther and farther back in the cabin, and I had been retrimming, without wondering why I needed to. We all learned a startling lesson about the affect of changing the arm of the load in flight!