# Calculating Trim Pre-Takeoff

Hello, and I’m sorry if this is in the wrong category. I try to make my flights as realistic as possible, from the angle of attack to v speeds. As you may know, angle of attack is the best angle an aircraft can have to reach v speeds as fast, and as efficiently as possible. The only way to angle an aircraft properly for takeoff without using the elevators is with trim. So my question is what is the best way to calculate trim, not based on normalities, before takeoff?

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Should I change the title to ‘How Do I Calculate Trim Before Takeoff?’?

yes you should

Hey there!

Take a look at this link below for more information. There is not really one set in stone way to calculate trim, as it varies from flight to flight.

I am in a 737-700 weighing 112000 lbs taking off with Flaps 5. Helpful?

You won’t really know what trim you need before you get airborne. Unless you do some kind of IF loadsheet (which I suspect doesn’t exist).

Best bet is to take off and then trim.

I think this is a good question, and I agree with @Stu that in IF we don’t have the necessary info to determine this.

An interesting read on this can be found here

As mentioned, the best way in IF is to set your trim shortly after takeoff.

That is not what angle of attack is. Angle of attack is the direct relation between the relative wind direction and the chord line of the wing.

As for your question of how to calculate trim there isn’t any in this sim. Trim in real life isn’t based on a percentage of trim but rather the degree of deflection. Best way to do it in the sim is to find what fits best for that aircraft and weight combination.

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@baseball_inferno I would recommend starting in solo mode with zero trim and a full plane-run it down the runway, pull back as much as you need to get your initial pitch angle and see how much trim you need to use to get comfortable. Run a few test runs to come up with a good setting. I know this is for a 737 but in the A320 for takeoff I usually use 18-25% depending on the weight-heavier I’ll use a touch more/lighter I’ll use a bit less. The same applies for Approach-I settle in-usually 23-30% in an A320, the A321 and A330 can get between 50-60% trim on approach. I JUST posted this exact answer the other day I’ll see if I can dig it up.
In real world ops, the trim is calculated based off the % of MÁC or Mean Aerodynamic Chord for a given weight and Center of Gravity. I hope this helps a bit.

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