I think I am using Pitch trim incorrectly

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Styggron
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I think I am using Pitch trim incorrectly

Post by Styggron »

Hello everyone,

I would greatly welcome pointers from both real pilots and sim pilots on this one.
I suspect I am using pitch trim incorrectly.

What I understand about Pitch Trim
First, if I understand pitch trim correctly, is so as I could for example have level flight and have the plane "straight" ie not pitched up but still flying level. It helps the pilot fly so as not to make constant adjustments on the column such as pulling back (ha! or is it rotating?) ) and pushing forward.


How I use pitch trim
This is flying a C172 (FSX default in this case)
1. When descending, I tend to use the throttle / flaps to help the controlled descent.
2. I use the pitch trim to pitch the plane downwards a little to help this
3. if I need to make adjustments such as descending too quickly etc I also use pitch trim to pitch the plane upwards a little as well as using a combination of throttle and flaps.

QUESTION 1
Is the above correct ? I suspect I am doing this all wrong though.


QUESTION 2
Should I be trimed in a particular way for a descent and landing ? ie should I be trimed to be pitched up a little to help the back wheels touch the ground first ? I suspect no because then I can't see the runway, so I should be flaring manually without pitch trim.

On the trim wheel I don't see any markings bar TO (Take off) so I don't know if it should be set somewhere for landings and/or decent.


Thanks everyone. I bet I am doing this completely incorrectly. :D
Accufeel V2, C172 , B377+L049+COTS, B17G, Piper Cub,Commanche,Cherrokee,Spitfire,Bonanza, P47,P40,both Mustangs
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speedy70
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Re: I think I am using Pitch trim incorrectly

Post by speedy70 »

Hi Styggron.

The purpose of trimming is to free the pilot from having to exert a constant pressure on the controls. This is often used to maintain straight and level flight, however trimming can also be used at any phase of flight - for example to maintain a constant rate of climb or descent.As you mention.

The most basic form, as found on most light aircraft is elevator trim. Usually operated by a wheel, it moves the elevator up or down by a small amount in the same sense as the yoke (back to go up, forward to go down). This can be used to settle the aircraft into level flight.

You can use the commands Z to turn on the AP, ctrl-z to maintain level flight and ctrl-h to maintain heading this will give you straight and level flight in the basic FSX autopilot.

Most of us have two buttons on our yokes/joysticks to trim up or down.
The cheat to trim for level and straight flight is to use the autopilot.

Go to Honolulu which has huge runways make your approach and when just above the runway cut your throttle gently try not to land by gently pulling back on the stick but do not let the nose get above the end view of the runway,hopefully you will touch down just as the stall horn starts.KEEP PRACTISING.

See here
http://www.flyaoamedia.com/aviation/trim-land-like-pro/

Cheers Chris

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Oliver Branaschky
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Re: I think I am using Pitch trim incorrectly

Post by Oliver Branaschky »

Just to clarify: You should never control the pitch of your aircraft by using trim. It's the elevator that controls pitch. Only when the aircraft has reached the desired pitch attitude would you manipulate the trim wheel to eliminate any undesirable control pressure.


Viele Grüße/Best regards
Oliver

Oliver Branaschky

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AKar
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Re: I think I am using Pitch trim incorrectly

Post by AKar »

To add to the earlier replies,
Styggron wrote:First, if I understand pitch trim correctly, is so as I could for example have level flight and have the plane "straight" ie not pitched up but still flying level.
...this is incorrect. The trim does it alter the airplane's steady-state pitch attitude which is achieved during a given flight condition: the pitch attitude during level flight (of course, to similar extend during any kind of flight as long as the pitch and and roll angles are relatively small!) depends mainly on your airspeed and weight. This is because at a given airspeed and weight, some angle of attack is required to provide the lift force necessary, and trimming can't do much at all about the required angle of attack. If your airplane, at a given weight and airspeed, flies straight & level flight at three degrees nose-up pitch attitude, it does so regardless of your trim setting - the varying thing would be the control effort by you, the pilot, to keep the nose at that attitude.

In that sense,
Styggron wrote:ie should I be trimed to be pitched up a little to help the back wheels touch the ground first ? I suspect no because then I can't see the runway, so I should be flaring manually without pitch trim.
...this is also incorrect approach into the issue, for the flare attitude would be the same regardless of it being done with the trim or by the use of elevator. In fact, the pitch trim affects via the elevator in these planes. Still, in general the flare should be flown with elevator, not with the trim - instead the trim is used to neutralize the pitch control forces during the approach.

-Esa

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Styggron
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Re: I think I am using Pitch trim incorrectly

Post by Styggron »

Oliver Branaschky wrote:Just to clarify: You should never control the pitch of your aircraft by using trim. It's the elevator that controls pitch. Only when the aircraft has reached the desired pitch attitude would you manipulate the trim wheel to eliminate any undesirable control pressure.


Viele Grüße/Best regards
Oliver

Oliver Branaschky
Ok so I should not use the pitch trim to help pitch down during landings ? But Speedy says I can ("for example to maintain a constant rate of climb or descent.As you mention") .

I would use pitch so I don't have to keep the control pressure up to stay pitched down a little.

A little confused as the posts here seem to be contradictory ? Who is correct ? Me I don't know I'm only asking the question.
No one has answered question 2 yet though. :)
Accufeel V2, C172 , B377+L049+COTS, B17G, Piper Cub,Commanche,Cherrokee,Spitfire,Bonanza, P47,P40,both Mustangs
Aircraft Factory Avro Anson, Albatros DIII,Heinkel He-219, F4U Corsair, P51H Mustang, Avro 504, BF109
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Oliver Branaschky
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Re: I think I am using Pitch trim incorrectly

Post by Oliver Branaschky »

You would pitch down (if you have to at all, that is, reducing power should be sufficient in most cases) by using the elevator. Only when you have stabilized the aircraft's pitch attitude you would use the trim to neutralize the control pressure. So it's elevator first, then trim.


Viele Grüße/Best regards
Oliver

Oliver Branaschky

speedy70
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Re: I think I am using Pitch trim incorrectly

Post by speedy70 »

You can use trim to maintain a rate of climb or descent but it is very dangerous to use down pitch for landing.

Landing pitch is mostly controlled by use of the throttle with small trim adjustments.

Have you read the attachment I added for you?

Try the landing procedure I told you.

Cheers Chris
Last edited by speedy70 on 27 Jun 2016, 11:27, edited 1 time in total.

Tomas Linnet
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Re: I think I am using Pitch trim incorrectly

Post by Tomas Linnet »

Q2:

You'll need to change the trim several times on your approach as your speed will change several times.
Have a look at this chart made by fellow A2A and Student Pilot: https://www.dropbox.com/s/j9frf1obqqp0o ... 2.pdf?dl=0

Or come visit us at the CIX VFR club. We offer excellent FS Flight Simulator Lessons( yeah I know, you don't do multiplayer, but think about it :D )

there is no specific setting for the trim as it depends on weight and weight distribution. therefor it's not possible to say: 3.2° for take off and 3,9° for landings.
Kind Regards
Tomas

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Styggron
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Re: I think I am using Pitch trim incorrectly

Post by Styggron »

speedy70 wrote:You can use trim to maintain a rate of climb or descent but it is very dangerous to use down pitch for landing.

Landing pitch is mostly controlled by use of the throttle with small trim adjustments.

Have you read the attachment I added for you?

Try the landing procedure I told you.

Cheers Chris
I did indeed that is an excellent article. Going to see how I go. Thank you :) and yes it is very dangerous to use pitch down for landings :shock:
Oliver Branaschky wrote:You would pitch down (if you have to at all, that is, reducing power should be sufficient in most cases) by using the elevator. Only when you have stabilized the aircraft's pitch attitude you would use the trim to neutralize the control pressure. So it's elevator first, then trim.


Viele Grüße/Best regards
Oliver

Oliver Branaschky
Why doesn't this forum have multiquote :(

Thanks for that. Yes I do indeed try to use throttle,flaps and elevators to land. I have been using pitch to point my plane downwards which I think is wrong.

Tomas Linnet wrote:Q2:

You'll need to change the trim several times on your approach as your speed will change several times.
Have a look at this chart made by fellow A2A and Student Pilot: https://www.dropbox.com/s/j9frf1obqqp0o ... 2.pdf?dl=0

Or come visit us at the CIX VFR club. We offer excellent FS Flight Simulator Lessons( yeah I know, you don't do multiplayer, but think about it :D )

there is no specific setting for the trim as it depends on weight and weight distribution. therefor it's not possible to say: 3.2° for take off and 3,9° for landings.
Thankyou Tomas. I had a look at that doc, umm what is AGL when it says 400' AGL ? Thank you for the kind offer on flying lessons.
Accufeel V2, C172 , B377+L049+COTS, B17G, Piper Cub,Commanche,Cherrokee,Spitfire,Bonanza, P47,P40,both Mustangs
Aircraft Factory Avro Anson, Albatros DIII,Heinkel He-219, F4U Corsair, P51H Mustang, Avro 504, BF109
Watch my incompetent flying Twitch

speedy70
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Re: I think I am using Pitch trim incorrectly

Post by speedy70 »

Above Ground Level.

Cheers Chris

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Oliver Branaschky
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Re: I think I am using Pitch trim incorrectly

Post by Oliver Branaschky »

AGL is height Above Ground Level, as opposed to MSL: altitude above Mean Sea Level. Mind the different wording of height vs. altitude.


Viele Grüße/Best regards
Oliver

Oliver Branaschky

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Styggron
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Re: I think I am using Pitch trim incorrectly

Post by Styggron »

When I take off and have a steady climb, and retract the flaps, can I stabilise my climb with pitch trim ? I have been doing this and from the posts I gather this is ok ?

Of course when you put the flaps back up you drop a little so I "catch" the drop manually and then pitch trim to pitch up for a steady climb.

This is ok ?
Accufeel V2, C172 , B377+L049+COTS, B17G, Piper Cub,Commanche,Cherrokee,Spitfire,Bonanza, P47,P40,both Mustangs
Aircraft Factory Avro Anson, Albatros DIII,Heinkel He-219, F4U Corsair, P51H Mustang, Avro 504, BF109
Watch my incompetent flying Twitch

speedy70
Senior Master Sergeant
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Joined: 28 Aug 2008, 18:01
Location: Devon,UK

Re: I think I am using Pitch trim incorrectly

Post by speedy70 »

Yes.
Cheers Chris

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Styggron
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Re: I think I am using Pitch trim incorrectly

Post by Styggron »

speedy70 wrote:Yes.
Cheers Chris
Excellent. Looks like I am finally doing something right. :D
Accufeel V2, C172 , B377+L049+COTS, B17G, Piper Cub,Commanche,Cherrokee,Spitfire,Bonanza, P47,P40,both Mustangs
Aircraft Factory Avro Anson, Albatros DIII,Heinkel He-219, F4U Corsair, P51H Mustang, Avro 504, BF109
Watch my incompetent flying Twitch

FishermanIvan
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Re: I think I am using Pitch trim incorrectly

Post by FishermanIvan »

It's an easier concept to understand in the real airplane as well, since you actually exert pressure on the yoke. For example, on a downwind leg in a 172, I'm usually at 2100 rpm, and as I cross parallel to the threshold, throttle comes back to 1700 rpm. Naturally, this will cause the nose to drop, so right away it's two spins on the trim wheel to maintain level flight. You just kinda figure out what sort of trim movements you're gonna need to keep the airplane flying how you want it.

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