The precision with which an elevator car stops with its floor level aligned with the landing floor level, expressed in millimetres above or below the landing; poor levelling creates a trip hazard and is a key quality and accessibility measure.
Full Definition
Levelling accuracy (also called landing accuracy or floor-levelling tolerance) is one of the most critical performance parameters of an elevator installation. Standards and requirements: (1) EN 81-20 — requires that the car stops within ±10 mm of the landing floor level under normal load conditions (empty to full load), and that re-levelling or automatic levelling correction restores the car to within ±20 mm if settling occurs due to load change or rope stretch; (2) EN 81-70 — requires ±10 mm levelling accuracy for accessibility because wheelchair users require a flush transition between car floor and landing; a step exceeding 10 mm is a mobility barrier; (3) Hydraulic elevators — prone to settling as oil temperature changes or small leaks develop; hydraulic systems must have automatic re-levelling to correct within ±10 mm; (4) VVVF drives — modern variable-speed drives with closed-loop position feedback (encoder on motor or governor rope) can achieve ±1–3 mm levelling accuracy in normal conditions. Causes of poor levelling: worn guide shoes (car sway), encoder drift, deceleration ramp miscalibration, rope stretch on high-rise installations. Levelling accuracy is checked during commissioning and annual maintenance; a plumb line or laser levelling gauge is used to measure the step between car sill and landing sill.
