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Voj

Stab Trim

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When I set my stab trim for takeoff I feel as if I am estimating the value on the wheel dial.I cant seem to see the actual value as in the tutorial (p44&45) when setting the Stabilizer value.Can any one point out how else I can determine if it is correct or is it safe anywhere in the green band and roughly to what is says in the CDU ?Would this be why every time I take off I have an audible alert, and sometimes not or is it that have a missed a step in the takeoff config ?


Vojislav Kostic

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When I set my stab trim for takeoff I feel as if I am estimating the value on the wheel dial.I cant seem to see the actual value as in the tutorial (p44&45) when setting the Stabilizer value.Can any one point out how else I can determine if it is correct or is it safe anywhere in the green band and roughly to what is says in the CDU ?Would this be why every time I take off I have an audible alert, and sometimes not or is it that have a missed a step in the takeoff config ?
When finalized your preflight in CDU you will see the value there.Then just Hover your mouse over the wheel, when you dial in your value./ Leffe

Leif A Mikkelsen

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When finalized your preflight in CDU you will see the value there.Then just Hover your mouse over the wheel, when you dial in your value./ Leffe
I can see the value in the CDU say 5.03 or what ever decimal place, but I dont see any value when I hover over the trim wheel. Is there a particular spot to hover over ? I am guessing the last 2 decimal places and is the estimate then correct ? or are there tolerances in the 2 decimal places not being exact ?

Vojislav Kostic

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I can see the value in the CDU say 5.03 or what ever decimal place, but I dont see any value when I hover over the trim wheel. Is there a particular spot to hover over ? I am guessing the last 2 decimal places and is the estimate then correct ? or are there tolerances in the 2 decimal places not being exact ?
You must have Tooltips assigned in FSX.Also you should see the decimals, but say if it says 5.75 in CDU and you set it to 5,72.....that´s more than good enough./ Leffe

Leif A Mikkelsen

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I can see the value in the CDU say 5.03 or what ever decimal place, but I dont see any value when I hover over the trim wheel. Is there a particular spot to hover over ? I am guessing the last 2 decimal places and is the estimate then correct ? or are there tolerances in the 2 decimal places not being exact ?
Leffe beat me to it by just a few seconds.

Kenny Lee
"Keep climbing"
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Is there anywhere a button with witch I can return the trim to the exact center position (after landing)? Does such a button generally exist in real live?regards Tobias

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No Tobias,Why should the airplane have such a button? On the ground nobody (maybe the maintaince guys, but for a turn around not really nessesary, or?) cares if the stab is 4,7 or 5,7. ;)


John Rubens
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I used to use 'Tool Tips' to get the trim as close to what the CDU says as possible, but after contemplation, realized that real world crews don't have such details in there settings. I turned off 'Tool Tips' and just set the trim as close as I could visually with the analog indicator on the stab wheel and I have never had a problem attributable to stab trim being off the mark.After takeoff, when I've established a steady asscent, I will adjust the trim to remove pressure from my control column and engage the Autopilot.


Jeff Johnson (RWS)

 

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Voj, I think this subject has come up before but estimating is just fine. Just like you see in your VC there's no way to really get the exact trim setting from your CDU. Besides, like Jeff said, your more than likely going to have to trim off the excess pressure after you're airborne.


Arrey Ati
KATL Supertug

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In the real aircraft they only have access to that scale, and with a flaps 5 takeoff, 5 units of trim is about standard. On the ground after landing you'll just have to return the trim to around 5 units manually, there's no button.


Andrew McCluskey

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I used to use 'Tool Tips' to get the trim as close to what the CDU says as possible, but after contemplation, realized that real world crews don't have such details in there settings. I turned off 'Tool Tips' and just set the trim as close as I could visually with the analog indicator on the stab wheel and I have never had a problem attributable to stab trim being off the mark.After takeoff, when I've established a steady asscent, I will adjust the trim to remove pressure from my control column and engage the Autopilot.
That is correct answer Jeff... I feel it the same way.

Best regards

Petr

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I used to use 'Tool Tips' to get the trim as close to what the CDU says as possible, but after contemplation, realized that real world crews don't have such details in there settings. I turned off 'Tool Tips' and just set the trim as close as I could visually with the analog indicator on the stab wheel and I have never had a problem attributable to stab trim being off the mark.After takeoff, when I've established a steady asscent, I will adjust the trim to remove pressure from my control column and engage the Autopilot.
That is correct answer Jeff... I feel it the same way.
Yeah, I've posted similar about the trim issue a few times. I think it's just the personality type of those who tend to be aviation enthusiasts to want to have everything set exactly right. Aviation is an inexact science. It's very precise, but it's still not perfect.-You will never plan a flight and hit the numbers you expected from the planning versus actual.-Wind aloft will always differ from the reports-Your wind correction angle on your plan will always differ from actual-Fuel burn will always differ from the POH...and so on.So why plan? Why run the numbers? Because they'll be close.Here's a big shocker for most:When pilots are handed the load sheet by the rampies, they know the exact weight of the plane, right? Nope!Each checked bag weighs exactly 40 pounds, carry on bags are 20, and each adult is 165 (slightly more in the winter - yes, some airlines do compensate). These numbers vary by airline, and most airlines use their own metrics, but my point is that the actual weight could be vastly different from what's assumed.Moral of the story:The FMC says trim to 5.03. Look at the scale and roll the trim wheel until it looks like it's right at 5. That's close enough to 5.03, right?Where does that number come from? That weight and CG you just entered into the FMC. Where did that weight come from? A guesstimate by your dispatcher and rampie at how much weight is in there. Oh, the bag and passenger counts may be spot on, but again, the weights are averaged. So, what good does that 0.03 do for you? It doesn't, really.Nothing is ever perfect, especially with people and weather.

Kyle Rodgers

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That is a very well written summary of what is often refered to as "measuring with a micrometer but cutting with an axe". I say ffrom my point of view as a person who worked in this area of aviation, if you get within 500 pounds weight of a 737 real/loadsheet, that is not a bad number. Especially if you dont use actual bag weight.


--Peter Fabian 
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