Mass and Balance, Performance Planning and Loading Limitations
This domain combines loading and performance: mass definitions, structural and CG limits, load sheets and standard masses, then take-off and landing performance against declared distances and obstacles. Items are usually numeric and hinge on applying a factor in the correct direction.
Masses and limits (CAT.POL.MAB.100)
- Dry operating mass plus traffic load gives zero-fuel mass, which must not exceed MZFM; plus fuel gives take-off mass, limited by MTOM; landing mass is limited by MLM.
- CG must stay within limits for take-off, in flight and landing; the load sheet shows mass, CG or index, and the trim setting.
- Standard masses may be used, commonly 85 kg per passenger for aeroplanes with 20 or more seats and 75 kg for smaller aircraft, with defined figures for crew and hand baggage; unusual loads need actual masses.
- Last-minute changes are limited and must be reflected in the final figures given to the crew.
Declared distances
- TORA, TODA (may include a clearway, at most half the TORA), ASDA (may include a stopway), and LDA, which may be shorter than the TORA.
Performance rules (CAT.POL.A)
- Take-off mass must allow the aircraft to stop or continue after an engine failure at V1 within the declared distances, and the net take-off flight path must clear obstacles by the required margin.
- Landing: the landing distance available must be at least the required landing distance. For turbojet aeroplanes the required distance is the actual landing distance multiplied by 1.67 on a dry runway; on a wet runway a further 1.15 applies when no demonstrated wet data is used.
Worked example
LDA 2400 m, dry runway, turbojet. The factored requirement must not exceed the LDA, so the maximum permissible actual landing distance is 2400 divided by 1.67, about 1437 m. If the AFM gives 1500 m for the expected landing mass and conditions, the flight cannot land there and must reduce mass or change aerodrome. On a wet runway the same aircraft would need even more distance because of the additional 1.15 factor.
Traps
- Multiplying the AFM distance by 1.67 instead of dividing by it.
- Forgetting the wet factor when no demonstrated wet-runway data exists.
- Using TODA where TORA or ASDA is intended.
- Placing a clearway longer than half the TORA or counting it in the accelerate-stop distance.