36 Month Reweigh Rule: Weight and Balance Records for Pilots

Weight and balance records are the documented proof of an aircraft’s basic empty weight, empty-weight center of gravity, equipment list, and every revision made to those numbers since the aircraft left the factory. They matter because every preflight CG calculation depends on them being accurate, and the pilot in command is legally responsible for confirming that weight and CG fall within limits before every flight.

TL;DR:

• Reweighing should occur when cumulative weight or CG shifts reach a small percentage of the aircraft’s maximum permissible values; otherwise, calculation updates suffice.
• Maintaining up-to-date equipment lists and change logs is critical, especially after modifications, to prevent drifting out of alignment with actual aircraft conditions.
• Digital recordkeeping systems centralize current weights, change history, and supporting documents, reducing errors and simplifying audits or inspections.
• Reweighing every three years is recommended for most general aviation aircraft, with adjustments based on modification activity and record accuracy.
• Properly formatted worksheets and preflight checks that compare calculated weights and CG against published limits are essential for flight safety and legal compliance.

Table of Contents

• What Belongs in Your Weight and Balance Records
• What FAA Rules Say About Recording Changes and Reweighing
• How to Calculate CG: Moments, Arms, and a Worked Example
• Templates and Worksheets That Actually Work on a Kneeboard
• A Preflight and Maintenance Checklist for Reliable Records
• How Digital Recordkeeping Improves Weight and Balance Accuracy
• Why Meticulous Weight and Balance Habits Pay Off for the Life of an Aircraft
• A Simpler Way to Keep Weight and Balance Records Current
• Primary Sources Worth Bookmarking
• Sources

What Belongs in Your Weight and Balance Records

Your weight and balance file isn’t one document. It’s a small stack of interconnected records, and each piece answers a different question about the airplane’s current condition.

The basic empty weight (BEW) is the airplane’s weight with all standard equipment, unusable fuel, and full operating fluids, but no pilots, passengers, cargo, or usable fuel. The empty-weight center of gravity (EWCG) tells you where that weight balances relative to the aircraft’s datum, usually expressed in inches from a reference point or as a percentage of mean aerodynamic chord. Together, BEW and EWCG form the baseline every future loading calculation builds on.

The equipment list itemizes every piece of installed equipment that factors into the empty weight, along with its individual weight and arm. This list matters more than most owners realize. When a shop swaps an old vacuum-driven attitude indicator for an electric one, or adds a new avionics stack, the equipment list has to change with it. An outdated equipment list is one of the most common ways weight and balance records drift out of sync with the actual airplane.

A weighing report documents the most recent actual weighing: the date, the facility or technician who performed it, the scale readings at each point, and the resulting BEW and EWCG. The FAA-H-8083-1B Aircraft Weight and Balance Handbook walks through this procedure in detail, including how to reference EWCG against the datum and mean aerodynamic chord, and it stresses that a mechanic’s job isn’t just weighing the airplane correctly. It’s recording that data correctly too.

Then there’s the change log, sometimes called a weight and balance revision record. Every time equipment is added, removed, or relocated, an entry should capture:

• The date of the change
• Who performed it (mechanic name and certificate number, or repair station)
• A description of what was added, removed, or modified
• The weight change and its arm, plus the resulting shift in moment

Finally, keep the aircraft’s placards and limitations paperwork with the rest of the file. If a modification changed a loading limit or added a new operating restriction, the placard reflects it, and your records should explain why.

Where these documents live

Most owners keep weight and balance records in three places, and honestly, that’s the source of a lot of confusion.

The aircraft records binder (sometimes just called the maintenance records) is where the weighing report, equipment list, and change log typically live alongside airworthiness directive compliance records and major repair or alteration forms.

The POH or AFM contains the manufacturer’s loading charts, moment envelopes, and CG limit graphs. It’s not usually where you record your specific airplane’s current BEW, but it’s the reference tool you use alongside your actual numbers.

The maintenance logbook entries note when a weight and balance revision happened, cross-referencing the more detailed change log or weighing report kept in the records binder.

As for how long to keep weighing certificates: the current one stays with the aircraft indefinitely, since it defines the active BEW and EWCG. Superseded weighing reports and older equipment lists are worth retaining too. If a dispute ever comes up over when a particular piece of equipment was added, or a buyer’s mechanic wants to trace the weight history during a prebuy inspection, that paper trail is what settles it. A well-organized aircraft recordkeeping system makes this kind of historical lookup fast instead of a filing-cabinet excavation.

What FAA Rules Say About Recording Changes and Reweighing

The FAA doesn’t require you to reweigh your airplane every time you install a new radio. Instead, AC 120-27F sets incremental thresholds that determine when a weight or CG change is significant enough to demand a fresh calculation, and when the cumulative effect of small changes is significant enough to demand an actual reweighing.

The logic is straightforward once you see it laid out. Small changes get tracked by calculation and added to the running record. Larger changes, or an accumulation of smaller ones that crosses a defined threshold, require the aircraft to go back on the scales.

AC 120-27F sets a nominal reweighing interval of about three years for individually maintained aircraft, with allowances for extending that interval under documented weight-control programs, and provisions for fleet or sample weighing under certain operational structures. For most general aviation owners flying a single airplane outside a fleet program, planning to reweigh every few years is appropriate.

The distinction between “record it” and “reweigh it” comes down to whether you can trust the math. If you know exactly what was removed and installed, and you have accurate weight and arm data for both items, a calculation is legitimate and expected. The FAA Weight and Balance Handbook treats this as standard practice for mechanics performing minor alterations.

But calculations compound uncertainty. Every swapped seat, reupholstered interior, added antenna, and relocated battery introduces a small margin of error. Do that ten times over three years without ever putting the airplane back on the scale, and you may be flying on an EWCG that no longer reflects reality. That’s exactly why AC 120-27F builds in the cumulative thresholds in the table above. It’s a way of forcing a reality check before the drift becomes dangerous, not just theoretically wrong.

There’s also a subtler trigger worth knowing: if you’re ever uncertain whether prior calculations were done correctly, or if a previous owner’s records look incomplete or inconsistent, reweighing resets the baseline and removes that uncertainty entirely. Given how affordable a weighing typically is relative to the risk of flying on bad numbers, many owners choose to reweigh proactively rather than lean on the minimum interval.

How to Calculate CG: Moments, Arms, and a Worked Example

Every weight and balance calculation, no matter how sophisticated the airplane or the software behind it, comes down to two formulas.

1. Moment = Weight × Arm. The arm is the horizontal distance from a reference point called the datum to the item being weighed. The datum’s location is defined in the aircraft’s TCDS or POH, and it can be anywhere the manufacturer chose, sometimes even ahead of the nose.
2. CG = Total Moment ÷ Total Weight. Add up every item’s moment, add up every item’s weight, then divide. The result is your center of gravity’s distance from the datum, which you then compare against the CG envelope published for your aircraft.

The NASA explainer on aircraft center of gravity breaks this down clearly, and it’s worth reading once even if you’ve done these calculations for years, because it makes the underlying physics obvious instead of mechanical.

A few terms worth knowing cold:

• Datum: the zero reference point from which all arms are measured
• Arm: distance from the datum to an item’s individual CG
• Moment: the turning effect of a weight at a given arm (weight times arm)
• MAC / %MAC: mean aerodynamic chord, often used on larger or more complex aircraft instead of inches from datum, expressed as a percentage

Here’s why you can’t calculate CG once and call it done for the flight. As fuel burns, both total weight and total moment change, and they don’t always change in the same direction relative to the envelope. A trainer with forward-mounted fuel tanks might get more aft as fuel burns off toward landing, since a nose-heavy tank load shifts the weighted average rearward. That’s why you compute CG separately for the zero-fuel condition, the ramp weight before taxi, the takeoff weight after engine start and taxi burn, and the landing weight after cruise fuel burn.

A simplified Cessna-style example illustrates the calculation: with a certain empty weight and arms, adding pilot, passenger, and fuel weights at specific arms, you multiply weights by arms to get moments, sum totals, then divide total moment by total weight to find CG; compare the CG against published limits in the POH to confirm legality. This mirrors the step-by-step method Studentpilot uses to teach the same math.

One pitfall trips up more pilots than it should: published moment tables in many POHs list moment divided by 100 or by 1,000 to keep the numbers manageable on the page. If you copy a moment value straight off the chart without checking which scaling factor the page header specifies, your final CG can be off by an order of magnitude. Always read the column heading before you touch the calculator.

Templates and Worksheets That Actually Work on a Kneeboard

A usable weight and balance worksheet doesn’t need to be complicated. It needs four columns, done consistently, every time.

Divide the total moment by total weight and you get your CG location, which you then plot against your aircraft’s published envelope. That’s the entire mechanism behind every fancier tool, spreadsheet, or app you’ll ever use.

Most factory POHs give you one of two formats for doing this in the airplane: a straightforward loading table like the one above, or a loading graph where you plot weight against a moment index scale and read the CG position visually. Loading graphs are faster once you’re used to them, but they hide the arithmetic, which means an error in your inputs (wrong fuel weight, wrong passenger arm) is harder to catch than it is on a table where every number is visible.

A few practices separate a worksheet that actually protects you from one that’s just paperwork:

• Build separate rows or a separate mini-table for zero-fuel, ramp, and landing weight cases rather than trying to cram all three onto one form.
• Write the BEW and EWCG at the top of every worksheet from the current weighing report, not from memory or an old logbook entry.
• Staple or clip the current weighing certificate and equipment list to the back of your kneeboard worksheet packet if you fly the same airplane often. It’s a fast cross-check when something doesn’t add up.
• Note the date of your BEW figure on the worksheet itself. If it’s approaching 36 months old, that’s your cue to check the reweigh schedule.

Keep a blank version of this worksheet in your flight bag alongside your POH. Fill it in fresh for any load configuration you haven’t flown before, rather than assuming “close enough” based on a similar flight from last month.

A Preflight and Maintenance Checklist for Reliable Records

Good weight and balance recordkeeping isn’t a once-a-year task. It’s a habit that touches both the flight line and the maintenance hangar, and it works best when both sides know their part.

Before every flight, run through this sequence:

1. Pull the current BEW and EWCG from the aircraft records, not from a number you remember.
2. Load your actual weights (crew, passengers, baggage, fuel) into the POH loading chart or your worksheet.
3. Calculate CG for the zero-fuel case if your aircraft’s envelope requires it, then ramp weight, then anticipated landing weight.
4. Compare each case against the published envelope, checking both weight limits and CG limits independently. A load can be under gross weight and still outside the CG envelope, or within CG and still overweight.
5. Confirm the fuel burn plan doesn’t carry the airplane outside limits by the time you land, especially on aircraft where CG moves aft as fuel depletes.

After any maintenance, modification, or equipment change, the mechanic’s responsibilities kick in:

1. Update the equipment list with the item’s description, weight, and arm.
2. Log the revision in the change log with date, technician, and the resulting shift in moment.
3. Compare the cumulative change against the AC 120-27F thresholds covered earlier and flag whether a reweigh is now due.
4. Note the revision in the maintenance logbook with a cross-reference to the detailed weight and balance change entry.

When scheduling an actual weighing, insist on calibrated platform scales rather than improvised equipment. The EAA’s guidance on weight and balance is blunt about this: informal methods like bathroom scales introduce inaccuracies that defeat the entire purpose of weighing the airplane. Ask for written proof of scale calibration and file it with the weighing report, along with signatures identifying who performed the weighing and who verified the results.

Pro Tip: Keep a running note of your aircraft’s BEW age on the first page of your weight and balance file. A simple “last weighed: [date], next due: [date]” line takes ten seconds to write and saves you from discovering a lapsed interval mid-preflight.

How Digital Recordkeeping Improves Weight and Balance Accuracy

Paper systems work, right up until a weighing report goes missing, a change log entry gets skipped during a rushed annual, or nobody notices the 36-month clock has quietly run out. Digital recordkeeping doesn’t change the underlying regulations. It changes how reliably you catch the gaps before they become a problem.

A well-built digital system centralizes the pieces that paper files scatter across a binder:

• A single, current BEW and EWCG figure that updates the moment a revision is logged, instead of living on a sticky note until someone transcribes it
• Timestamped change-log entries that record who made a change and when, automatically, rather than relying on someone remembering to write it down
• Attached weighing certificates and calibration proof stored alongside the record they support, so the documentation trail survives even if the paper copy gets lost in a hangar move
• Loading calculators that handle the zero-fuel, ramp, takeoff, and landing cases without manual arithmetic, cutting down the moment-scaling errors that trip up paper worksheets

This is where digital aircraft records earn their keep for owners juggling more than one airplane, or flight schools tracking a fleet where different aircraft have different equipment lists and different reweigh dates.

If you’re evaluating any digital solution for this purpose, whether it’s Squawkfree or something else, judge it against a short list of practical criteria rather than marketing language: Does it maintain a clear audit trail showing who changed what and when? Can it attach source documents like weighing certificates directly to the record they support? Does it import flight data automatically, reducing manual entry errors that creep into hand-logged records? And can you actually search past revisions quickly during a prebuy inspection or an FAA ramp check, rather than flipping through a binder?

Aviation regulators have leaned toward accepting electronic records for years, provided the system meets the same integrity standards paper always had. If you want the fuller legal picture on that acceptance, the discussion in electronic logbook compliance under FAA §43.9 lays out what “meets the requirement” actually means for GA owners and flight schools moving away from paper.

Why Meticulous Weight and Balance Habits Pay Off for the Life of an Aircraft

The pilots I trust most with weight and balance aren’t the ones who can do the math fastest. They’re the ones who treat the paperwork with the same seriousness as the flight itself, because they understand that a wrong number on the page is just as dangerous as a wrong number in the cockpit.

Here’s what the conventional advice tends to miss: the value of accurate records isn’t really about passing an FAA inspection, though it does that too. It’s about every future decision that depends on trusting a number you didn’t personally verify. A prebuy mechanic trusts your BEW when evaluating a used airplane. A new owner trusts your equipment list when deciding whether that avionics upgrade was properly accounted for. You trust your own logbook entry from eighteen months ago when you’re loading four adults and full bags for a trip you haven’t flown before.

That chain of trust breaks the moment someone gets casual about a revision entry, or skips a reweigh because the calculations “probably” still hold. I’d rather see an owner reweigh a year early after a significant interior refresh than lean on math that’s technically defensible but practically stale. The cost difference between a proactive reweigh and a deferred one is minor. The safety difference, and frankly the resale difference, is not.

Transparent change logs also protect you in ways that only show up years later. An aircraft with a clean, complete weight and balance history sells faster and with fewer questions than one where the buyer’s mechanic has to reconstruct what happened during three different ownership changes. Treat every revision entry as something a stranger will eventually read and rely on, because eventually, one will.

— Trent

A Simpler Way to Keep Weight and Balance Records Current

Digital recordkeeping solutions exist for the gap this article just walked through: the space between knowing what your weight and balance records should contain and actually keeping them that way, revision after revision, year after year.

Instead of a binder where the current BEW lives on one page and the weighing certificate lives somewhere else entirely, some digital platforms centralize your BEW, EWCG, equipment list, and revision history in one place, with weighing certificates and calibration documents attached directly to the entries they support. Every change carries a timestamp and an audit trail, so you’re never guessing who updated what or when the last reweigh happened. Automated flight-data import also means fewer manual entries feeding into your broader maintenance picture, which cuts down the transcription errors that quietly corrupt paper systems over time.

If you’re tired of chasing down which binder has the current weighing report, take a look at the Squawkfree platform and see how it handles your aircraft’s records.

Primary Sources Worth Bookmarking

The regulatory guidance behind this article comes from a small set of documents worth keeping on hand rather than relying on secondhand summaries.

• FAA-H-8083-1B, Aircraft Weight and Balance Handbook: the full procedural reference for weighing aircraft, determining EWCG, and understanding loading computations.
• AC 120-27F, Aircraft Weight and Balance Control: the source for recording thresholds, the 36-month reweigh baseline, and cumulative-change triggers.
• NASA’s center of gravity explainer: a clean walkthrough of the moment and CG formulas behind every calculation in this guide.
• EAA’s weight and balance guidance: practical advice on scale selection and calibration for anyone scheduling an actual weighing.

Pilots managing certification paperwork more broadly may also find useful parallels in FAA certification and risk management guidance written for a different corner of aviation compliance, since the underlying discipline of documented, auditable change tracking applies well beyond weight and balance alone.

Sources

• FAA-H-8083-1B — Aircraft Weight and Balance Handbook
• AC 120-27F — Aircraft Weight and Balance Control
• NASA — center of gravity calculation explanation
• EAA — weight and balance advice

Recommended

• Aircraft Recordkeeping Requirements: An Owner’s Compliance Guide
• Aircraft Maintenance Logs: FAA Compliance Guide for 2026
• 100-Hour Inspection Rules for Owners & Flight Schools
• Part 91 Maintenance: What Owners and Operators Must Know