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Weight & Balance
Every airplane has a weight limit and a balance limit, and you have to be inside both — at takeoff and after the fuel burns off. Load a sample trainer below: each item adds weight at its arm (its distance from the datum), the moments sum, and the center of gravity is just total moment ÷ total weight. Watch the dot land inside the envelope — or not.
The envelopes, weight limits and station caps are the real certificated figures for each type, from its FAA or EASA type certificate. The basic empty weight and CG are representative rather than certificated — those come off an individual airframe's weighing record. To run your own numbers, use the Weight & Balance calculator.
● takeoff (current fuel) · ○ zero fuel · ┄ Utility limits (where they differ)
Cessna 172S Skyhawk SP. Takeoff weight 2280 pounds, CG 40.5 inches — Within limits. With the tanks dry, CG 39.6 inches — Within limits. Normal category only — in Utility it is over maximum takeoff weight by 80 lb (limit 2,200 lb).
| Item | Weight (lb) | Arm (in) | Moment (lb·in) |
|---|---|---|---|
| Empty aircraft | 1680.0 | 39.5 | 66,360 |
| Front seats | 340.0 | 37.0 | 12,580 |
| Rear seats | 0.0 | 73.0 | 0 |
| Baggage area 1 | 20.0 | 95.0 | 1,900 |
| Baggage area 2 | 0.0 | 123.0 | 0 |
| Fuel | 240.0 | 48.0 | 11,520 |
| Total | 2280.0 | 92,360 |
CG = ΣM ÷ ΣW = 92,360 ÷ 2280.0 = 40.51 in
Limits from the type certificate. Rev. 88 p.30 §XII. Datum: lower portion of the front face of the firewall.
Basic empty weight and CG are sample data (1,680 lb at 39.5 in) — they come off an individual airframe's weighing record and no certificate states them. Use your own aircraft's W&B form.
Some arms are not certificated figures: Front seats (37 in), Baggage area 1 (95 in), Baggage area 2 (123 in). The TCDS gives the front seats as a 12-inch adjustable range (34.0-46.0 in), not a point. 37.0 in is a representative forward-ish seat position. There is no universally conservative choice: computing at 46.0 can mask a FORWARD-limit violation and at 34.0 an AFT-limit one. Move the seat position for your own loading.
- Utility category is approved for 2 persons, so the rear seats must be empty. 3A12 states no baggage restriction for Utility; your POH may impose one, and it wins.
- 3A12 NOTE 1 requires the certificated empty weight to include unusable fuel (18 lb at 46.0 in) and full oil (15.0 lb at 13.1 in FORWARD of datum). Check your weighing record already accounts for both.
Two failure modes, two different fixes. Too heavy is a weight problem — no amount of CG shuffling fixes it; you offload. Out of CG is a balance problem — you shift or remove load until the dot is back in the box. And because the fuel sits at its own arm, burning it moves the CG: the hollow dot is where you'll be with the tanks dry. Which way it moves depends on where the tanks sit relative to the loaded CG — on all three of these trainers the fuel is aft of the CG range, so burning it walks the dot forward, and on these sample numbers it stays inside the box at both ends. On a type whose tanks sit forward of the CG, the travel runs the other way and can leave the envelope by the time you land. That is why the examiner checks both ends of the burn rather than trusting the takeoff number. These are sample numbers; your airplane's real empty weight and CG come off its own weighing record, and the POH always wins.
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Next step
- Weight & balance tool
- Weight & balance worksheet (printable)
- How much weight to move to fix the CG (E6B)
- Find your weak areas — the free 24-question Readiness Test, scored by knowledge area.
- Create a free account for the full bank: 2,074 verified questions with the FAA source on every answer, a timed practice exam, and a missed-questions drill.
The Private Pilot Quick-Review Study Guide covers this in chapter 4 (performance and weight & balance). It is in CFI review and not on sale yet; the guide page has the list for launch notes.