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I've been trained to know the calculated gross weight and center of gravity for takeoff and landing for every flight for which I have acted as pilot in command.

I've had other instructors dispute that this is not a requirement and simply being familiar enough with the aircraft to reasonably be able to estimate that you're within C.G. tolerances considering the fuel and passengers is satisfactory.

Are there any regulations that explicitly define the requirements of pre-flight weight and balance familiarization for civil airplanes requiring an AFM containing takeoff and landing distance data?

If not, surely there is some catch-all so lawyers can sue us easier; what would that most likely be based on case law? 14 CFR 91.13, the "all available information concerning that flight" clause from 14 CFR 91.103, or something else?

Note that 14 CFR 91.103(b) requires familiarization with runway lengths of intended use and takeoff and landing distance data for any flight; myself and others would argue that being able to meet that condition would require, at a minimum, familiarization with certain weather metrics and knowing the airplane's loaded gross weight.

However, I am still not seeing an explicit requirement to know a specific C.G. figure.

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    $\begingroup$ I don't have enough detailed knowledge of the legal requirements, but wouldn't knowing the CG be a necessary step to ensure the aircraft is loaded within its safe envelope? Mostly because "being familiar enough with the aircraft to reasonably be able to estimate that you're within C.G." is the equivalent of "it felt right to me, no idea why it stalled on takeoff, Your Honor" and won't stand up to scrutiny. We stopped flying like that in the 60-70s, thankfully $\endgroup$
    – AEhere supports Monica
    Commented Apr 30, 2019 at 9:02
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    $\begingroup$ For every flight? That means that every time I want to take the Cherokee up for a spin, I should do a new weight & balance computation? I don't think so :-) $\endgroup$
    – jamesqf
    Commented Apr 30, 2019 at 16:14
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    $\begingroup$ @jamesqf Yes, every flight. Of course, if the load will be (roughly) the same as a previous flight and you didn't date your work... $\endgroup$
    – StephenS
    Commented Apr 30, 2019 at 18:20
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    $\begingroup$ In my training Tomahawk, we couldn’t fill her up with dual crew due MTOM limit, so we took something like 3/4 tanks. I am rather tall, so my seat was far back, and my instructor was shorter, so a bit more forward. CG and mass was calculated once, aircraft basic index wasn’t modified ever, and all flights used same setup. I can assure you that CG calculation was meticulously done and cross checked once prior first dual flight and then once prior first solo (full tanks now). Any time after that, we’d brief that we were in known standard configuration. $\endgroup$
    – Cpt Reynolds
    Commented Apr 30, 2019 at 19:19
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    $\begingroup$ @user71659: It's not whether it would take 30 seconds or 30 minutes, it's that it's pointless. My weight does not change by a significant amount between flights (indeed, it hasn't changed much in my adult life); I know the Cherokee can carry 4 people and fuel, so with just me I'm well within limits. I'd expect the same to be true if I borrowed a 172 or similar plane. I would do a calculation only if I was going to carry a load that concievably might exceed weight & CG limits. $\endgroup$
    – jamesqf
    Commented May 3, 2019 at 1:04

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True. It is the pilot-in-command's responsibility to determine if the aircraft is safe for flight. 14 CFR § 91.3(a) makes the PIC directly responsible for that.

The 2016 FAA Weight and Balance Handbook also states:

4. The pilot in command (PIC) has the responsibility prior to every flight to know the maximum allowable weight of the aircraft and its CG limits. This allows the pilot to determine during the preflight inspection that the aircraft is loaded so that the CG is within the allowable limits

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