EN DE
Lesson 7 · Flight Performance & Planning

Loading the Aeroplane & Reading the POH

The standard mass terms, unit conversions, the weighing report and the load & trim sheet — EASA PPL theory

~20 min SEP · VFR EASA Part-FCL

The previous lesson taught the physics of balance — mass, arm, moment and the CG envelope. This one is the paperwork half the exam loves: the standard names for each mass, the unit conversions, and how to pull real numbers out of a weighing report and a POH to fill a load & trim sheet.

1 — The Standard Mass Terms

Every mass on a flight has a precise name, and the exam uses them exactly. They stack up from the empty aeroplane to the moment you take off, and back down to landing:

From empty to take-off — the mass ladder
Basic empty mass (BEM) airframe + unusable fuel + full operating fluids + fixed equipment 770 kg
+ Traffic load crew, passengers and baggage (the "useful load") + 260 kg
= Zero-fuel mass (ZFM) everything except usable fuel 1 030 kg ≤ MZFM 1 080 kg
+ Usable fuel all the fuel that can be burned + 101 kg
= Ramp / taxi mass mass at engine start, before taxi 1 131 kg ≤ max ramp 1 155 kg
− Taxi fuel fuel burned start-up to line-up − 2 kg
= Take-off mass mass as the wheels leave the ground 1 129 kg ≤ MTOM 1 150 kg
− Trip fuel fuel burned to destination − 60 kg
= Landing mass mass at touchdown 1 069 kg ≤ MLM 1 120 kg

Each step has its own structural ceiling. A load can pass MTOM yet bust MZFM (too much in the cabin, too little in the tanks), so check every limit — not just take-off mass.

  • Basic empty mass (BEM) — the aeroplane itself: airframe, unusable fuel, full operating fluids (oil, coolant) and fixed equipment. It does not include usable fuel, crew, passengers or baggage.
  • Traffic load (or useful load) — what you add: crew, passengers, baggage.
  • Zero-fuel mass (ZFM) — BEM + traffic load, i.e. everything except usable fuel.
  • Ramp / taxi mass — ZFM + all usable fuel, at engine start.
  • Take-off mass — ramp mass minus the fuel burned taxiing.
  • Landing mass — take-off mass minus the trip fuel.

Load the cabin to fix the CG, not just the mass
Where you put the traffic load is as important as how much it is. Moving a bag from the rear hold to a front seat, or seating a heavier passenger forward, shifts the CG — sometimes that is the only way to bring an out-of-limits load back inside the envelope.

2 — The Maximum Masses

Each step in that ladder has its own structural ceiling, certified for the airframe and published in the POH:

  • Maximum ramp mass — the most the aircraft may weigh at start-up (a hair above MTOM, to allow for taxi fuel).
  • Maximum take-off mass (MTOM) — the most it may weigh as it leaves the ground.
  • Maximum landing mass (MLM) — the most it may weigh at touchdown.
  • Maximum zero-fuel mass (MZFM) — the most it may weigh with no usable fuel; it limits how much you may load into the cabin.

Why MLM is usually less than MTOM
Landing puts a far bigger vertical load through the structure than a steady cruise. To keep that landing impact within limits, the certified landing mass is set below the take-off mass — the aircraft is expected to burn off fuel before landing. MZFM exists for a related reason: fuel in the wings relieves wing-root bending, so the mass carried in the fuselage is capped separately.

Two more limits you read off the POH rather than calculate:

  • Performance-limited mass — on a short, hot, high or wet runway the performance charts may cap the mass below MTOM. You take the lower of the structural and performance limits.
  • Baggage-compartment limit — both a total mass and a floor-loading placard (e.g. 75 kg·m⁻²). A dense, small item can bust the per-area limit while well under the total.

3 — Units & Conversions

POHs — especially American ones — mix litres, gallons, kilograms and pounds, and moments come in kg·m or lb·ft. Convert before you calculate. Try it:

Convert it — fuel, mass and moment units

AVGAS density ≈ 0.72 kg/L. 1 US gal = 3.785 L, 1 Imp gal = 4.546 L, 1 kg = 2.205 lb, 1 lb = 0.454 kg. The exam expects you to convert before you read a US-units POH.

The conversions worth memorising
AVGAS ≈ 0.72 kg/L; 1 US gal = 3.785 L, 1 Imp gal = 4.546 L; 1 kg = 2.205 lb. To convert a moment, convert its mass and arm to the target units first — kg·m and lb·ft are not interchangeable by a single factor you should guess.

4 — Reading the Weighing Report & POH

Your numbers come from two documents. The weighing report is produced when the aircraft is weighed — done periodically and after any major repair, modification or equipment change. It gives the current basic empty mass, its moment and the empty CG. The POH gives the datum, the arms for each station, and the CG limits:

Weighing report — OE-ABC
Date weighed 14 MAR 2024 Re-weigh after major repairs, equipment changes, or on the periodic schedule — then this report is the new authority.
Basic empty mass 770.0 kg Includes airframe, unusable fuel, full operating fluids and fixed equipment — but no usable fuel, crew or payload.
Empty-mass moment 693.0 kg·m The moment to start your load sheet with (BEM × empty arm).
Empty CG 0.900 m aft of datum Moment ÷ mass = 693.0 ÷ 770.0 = 0.900 m. This is the CG at basic empty mass.
POH §6 loading data
Datum 0.00 m at firewall The reference all arms are measured from — quoted in the POH, not chosen by you.
Station arms front 0.94 · rear 1.85 · bag 2.40 · fuel 1.20 m Each seat row, the baggage hold and the tanks have a fixed arm — read them, never guess.
CG limits 0.89 m (fwd) → 1.20 m (aft) The allowed CG range. Stated as distance from the datum here; some POHs give it as % MAC.
Max baggage 40 kg / 75 kg·m⁻² Both a total and a floor-loading (per-area) placard limit — the floor limit can bite before the mass limit.

The weighing report gives you the starting point (BEM + moment); the POH gives the arms and limits. Extract both before you touch the load sheet.

Distance from datum, or % MAC
CG position is quoted two ways. Small aircraft usually give it as a distance aft of the datum (e.g. 0.90 m). Larger types give it as a percentage of the mean aerodynamic chord (% MAC) — the same point, expressed as how far back along the wing’s representative chord it sits. Read which convention your POH uses before comparing to the limits.

When the aircraft isn’t standard
If your aircraft differs from the standard configuration — optional avionics fitted, a seat or door removed, long-range tanks — its empty mass and arm are not the book figures. Extract the corrected basic empty mass and moment for that exact aircraft from its current weighing record / equipment list (or the POH supplement), not the generic table.

5 — The Load & Trim Sheet

Now put it together. A load sheet lists every mass against its arm, totals the mass and moment columns, and divides to get the CG — the same bookkeeping as Lesson 6, but on the operator’s form and checked against every limit:

Load & trim sheet — OE-ABC
ItemMass (kg)Arm (m)Moment (kg·m)
Basic empty mass 770 0.90 693.0
Front seats 160 0.94 150.4
Rear seats 80 1.85 148.0
Baggage 20 2.40 48.0
Zero-fuel mass 1 030 1.009 1 039.4
Usable fuel (100 L) 72 1.20 86.4
Take-off mass 1 102 1.022 1 125.8
✓ 1 102 kg ≤ MTOM 1 150 · CG 1.022 m inside 0.89–1.20 · ZFM 1 030 ≤ 1 080 — legal at both ends

Add the mass and moment columns, divide the totals for the CG, then check it against every limit. A loading graph (or index method) does the same arithmetic graphically — you read each item’s moment off a line instead of multiplying. If the CG still falls outside the envelope, fixed trim ballast can move it back in.

Three ways to the same CG
You can reach the loaded CG by (1) arithmetic — mass × arm, total, divide; (2) a loading graph — read each item’s moment off a printed line and sum; or (3) an index — a scaled moment that keeps the numbers small. All three give the same answer; the exam may show you any of them.

6 — Practice: Fill the Sheet, Read the Verdict

Work this end to end. BEM 770 kg @ 0.90 m; pilot + front passenger 170 kg @ 0.94 m; one rear passenger 85 kg @ 1.85 m; baggage 15 kg @ 2.40 m; fuel 90 L @ 1.20 m. Limits: MTOM 1 150 kg, MZFM 1 080 kg, CG 0.89–1.20 m.

  1. Fuel mass: 90 L × 0.72 = 64.8 kg.
  2. Masses: 770 + 170 + 85 + 15 + 64.8 = 1 104.8 kg (≤ 1 150 ✓). ZFM = 1 040 kg (≤ 1 080 ✓).
  3. Moments: 693.0 + 159.8 + 157.25 + 36.0 + 77.76 = 1 123.8 kg·m.
  4. CG: 1 123.8 ÷ 1 104.8 = 1.017 m (inside 0.89–1.20 ✓).
  5. Verdict: every limit met — legal. Now re-check at zero fuel: 1 040 kg, moment 1 046.05 kg·m, CG 1.006 m — still inside.

Knowledge Check

Question 1
The basic empty mass (BEM) of an aeroplane includes:
Question 2
An aircraft's zero-fuel mass is:
Question 3
On most aeroplanes the maximum landing mass (MLM) is less than the MTOM because:
Question 4
You have 110 litres of AVGAS. Its mass is approximately:
Question 5
From which document do you read the current basic empty mass and empty-mass moment?
Question 6
A POH gives the CG limits as 0.89 m to 1.20 m. Your completed load sheet shows a take-off CG of 1.017 m and mass 1 104.8 kg (MTOM 1 150). The load is:
Question 7
A loading graph (or index method) is used to:
Question 8
A baggage compartment is placarded '40 kg max, 75 kg·m⁻²'. This means:

Help keep me flying

Support new lessons

This platform is independent, free, and ad-free. If it helps your training, your support helps fund new lesson production, visuals, and hosting.

Your support keeps me flying and new lessons coming.

Help keep me flying