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TBM 930 Rudder Trim

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On the G3000(mod) rudder trim scale displayed on the MFD, there is a green tab to the right of the center position. Is this supposed to be the rudder trim setting for takeoff/climb to counter the engine/prop torque effect, and then you are expected to reset the rudder trim to approximately the center position for level flight?

Al

Edited by ark

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i thinks its just a visual indication of your trim,,, u know the actual buttons to change trim are located at the rear of the throttle stack ,,on the very end,, u gotta look forward and zoom back and down its above the fuel tank selector,

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44 minutes ago, AmeliaCat said:

i thinks its just a visual indication of your trim,,, u know the actual buttons to change trim are located at the rear of the throttle stack ,,on the very end,, u gotta look forward and zoom back and down its above the fuel tank selector,

Thanks for the reply. What you are referring to are the aileron trim buttons, not the rudder trim. The rudder trim is controlled from the yoke, as is the pitch trim.

In any case, I do understand what I described is a visual indication of the rudder trim setting, and I currently set the rudder trim through a button on my yoke using FSUIPC7. What I'm asking about is the correct interpretation of the rudder trim display on the G3000.

Al

Edited by ark

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2 hours ago, ark said:

On the G3000(mod) rudder trim scale displayed on the MFD, there is a green tab to the right of the center position. Is this supposed to be the rudder trim setting for takeoff/climb to counter the engine/prop torque effect, and then you are expected to reset the rudder trim to approximately the center position for level flight?

Al

Yes but your right feet are the counter to the p-factor you're referencing on takeoff. It is generally used to counter crosswind in cruise and give a crab angle.


SAR Pilot. Flight Sim'ing since the beginning.

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21 minutes ago, Flyfaster_MTN002 said:

Yes but your right feet are the counter to the p-factor you're referencing on takeoff. It is generally used to counter crosswind in cruise and give a crab angle.

I am use to the need for right rudder on takoff in a single engine prop a/c. As for a cruise crab angle, I usually simply adjust the heading and remain in fully coordinated flight. Are you suggesting use of a slip in cruise?

Thx,

Al

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44 minutes ago, ark said:

I am use to the need for right rudder on takoff in a single engine prop a/c. As for a cruise crab angle, I usually simply adjust the heading and remain in fully coordinated flight. Are you suggesting use of a slip in cruise?

Thx,

Al

Single engine hp= 200-300hp. TBM engine hp = 850shp 🙂 

Don't confuse crab angle with a slip


SAR Pilot. Flight Sim'ing since the beginning.

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1 hour ago, Flyfaster_MTN002 said:

Single engine hp= 200-300hp. TBM engine hp = 850shp 🙂 

Don't confuse crab angle with a slip

3 hours ago, Flyfaster_MTN002 said:

It is generally used to counter crosswind in cruise and give a crab angle.

Sorry -- don't get your point.

I can understand you might need some right leg 'rudder help' on takeoff in an a/c like the TMB 930, which is why I asked the the question in the first place. I don't have any experience in turbo a/c.

However, your statement about setting up a crab angle at cruise by using rudder trim is not correct in my opinion. Adjusting the rudder trim from its 'non-crosswind' cruise setting results in uncoordinated flight which is a slip or skid. Rather, to set up a cruise crab angle you simply turn the a/c to the heading needed to maintain the course track.

Al 

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Here's what the POH has to say:

After Start section

Adjust the indicator in green range TO (TAKEOFF)

Before Takeoff section:

Yaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adjusted
Adjust abeam ”TO” index.

Climb section

Only when flaps are confirmed UP :

- Trims (Pitch, Roll and Yaw) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adjusted

And you're right about the crab, therefore the POH doesn't mention any Trim related topics for Descent/Before Landing/Landing. Trimming for coordinated flight goes without saying though.

Edited by Tom_L

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4 hours ago, Tom_L said:

Here's what the POH has to say:

After Start section

Adjust the indicator in green range TO (TAKEOFF)

Before Takeoff section:

Yaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adjusted
Adjust abeam ”TO” index.

Climb section

Only when flaps are confirmed UP :

- Trims (Pitch, Roll and Yaw) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adjusted

And you're right about the crab, therefore the POH doesn't mention any Trim related topics for Descent/Before Landing/Landing. Trimming for coordinated flight goes without saying though.

Thanks, good info!

Al

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13 hours ago, ark said:

However, your statement about setting up a crab angle at cruise by using rudder trim is not correct in my opinion. Adjusting the rudder trim from its 'non-crosswind' cruise setting results in uncoordinated flight which is a slip or skid. Rather, to set up a cruise crab angle you simply turn the a/c to the heading needed to maintain the course track.

Even in a very fast moving air mass, once an aircraft is in flight, it becomes part of the moving air mass, and the relative wind speed in relation to the airframe is zero. The aircraft itself does not “feel” a crosswind (or headwind or tailwind for that matter) in flight. The crab angle is only required to make good a specific ground track, and the specific heading is established using roll, as in any other turn.

I can certainly see where rudder trim would be useful to compensate for torque/p-factor in a powerful single-engine turboprop like the TBM, but where rudder trim really comes into its own is on a multi-engine aircraft in case of engine failure.

  • Upvote 1

Jim Barrett

Licensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.

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28 minutes ago, JRBarrett said:

The aircraft itself does not “feel” a crosswind

Not to criticise, but out of interest: Wouldn't that be true only for a sailplane? A powereed airplane is moving by itself through the moving airmass. And some FMC's will show head- and crosswind components in flight. It's been a while since I have drawn my last wind-triangle though....😁

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1 hour ago, Tom_L said:

Not to criticise, but out of interest: Wouldn't that be true only for a sailplane? A powereed airplane is moving by itself through the moving airmass. And some FMC's will show head- and crosswind components in flight. It's been a while since I have drawn my last wind-triangle though....😁

It moves through the airmass, but because the airmass itself is moving there is no “wind” in relation to the airframe no matter how fast the airmass is moving. The aerodynamic effect in a powered aircraft is just the same as if the air was not moving at all. Wind speed is measured in relation to the ground. Once the aircraft has no physical connection to the ground, the ground is no longer part of the equation of motion.

If you take a ride in a hot air balloon that is moving a 20 knot wind. It will move over the ground at 20 knots, but in the balloon basket, the air is absolutely dead calm. You could even drop a feather over the side, and the feather will descend straight down, because it too is moving with the wind. I actually saw this demonstrated on a hot air balloon ride I took a few years ago.

This is true for an aircraft flying in an airmass moving at constant velocity and direction, which is normally the case at higher altitudes where the wind flow is laminar. Closer to the ground, terrain can cause both horizontal and vertical gusts which are felt as turbulence.

Certainly there can be situations where the speed or direction of the moving airmass changes rapidly (wind shear) which can have a negative impact on aircraft performance. As you probably know there were some major airliner accidents in the US many years ago caused by sudden loss of airspeed caused by low level wind shear associated with thunderstorm microbursts.

An aircraft that has the ability to display wind speed and direction in flight can only do so if it is equipped with a system capable of independently measuring the aircraft’s motion in relation to the ground, such as GPS or IRS. It calculates the wind speed by comparing the aircraft’s true airspeed to its ground speed, and determines wind direction by comparing actual heading to ground track.

Some sim airplanes incorrectly show wind speed and direction while on the ground, which is incorrect. In real aircraft, the wind display does not appear on the PFD until the aircraft becomes airborne.

A pilot could do the wind speed calculation manually with an E6B. Indicated Airspeed is read from the airspeed indicator, and corrected for temperature and pressure altitude to derive TAS. Ground speed is calculated by the time required to fly between two waypoints which are a known distance apart. Headwind or tailwind component is calculated by comparing TAS to ground speed. The direction can be calculated on the wind triangle side of an E6B by comparing heading to ground track. 

Edited by JRBarrett
  • Like 1

Jim Barrett

Licensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.

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43 minutes ago, JRBarrett said:

but in the balloon basket, the air is absolutely dead calm

Yeah, I remembered that part, alright. But the rest - guess i'm back to my PPL-books. Thx a lot!

Edited by Tom_L

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Just to clear this up, rudder trim is not used to counter 'crosswind'. A TBM like all aircraft is designed to fly at a speed range, usually at cruise power no rudder trim is required. If you depart from that speed range, for example; when climbing or descending or in slow straight and level flight, then you will require a rudder input. Rudder trim then comes into play. It is as simple as that, establishing a crab angle has nothing to do with rudder trim.

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