Gravity, controlled, active: a guide to levelling systems
When it comes to crane man baskets, the technical feature that most affects safety, stability and operator comfort is the levelling system. In this article we look at why levelling is a critical requirement, how the different families of systems actually work, and which practical criteria guide the choice.
Why levelling matters
During crane manoeuvres, the boom never moves in a perfectly linear way: it lifts, slews, extends and retracts, and every movement tends to tilt the platform away from the horizontal plane. The levelling system is the mechanism that keeps the working floor as horizontal as possible, regardless of the boom’s position, and it addresses four concrete needs :
- operator safety : a tilted floor increases the risk of loss of balance, slipping or falling during manoeuvres, especially when the operator has to move inside the basket or handle tools with both hands. It also increases the risk of objects or materials sliding off and falling, a danger for anyone standing below in the work area;
- operational comfort, working on a stable floor reduces physical and mental fatigue during prolonged work at height. A crane basket that keeps swaying or tilting forces the operator into a constant effort to compensate for balance, a factor that adds to the fatigue of the work itself and, over the course of a day, can affect the quality and safety of the intervention;
- regulatory compliance : the type of levelling system and the associated electronic devices, such as the angle sensor, are often linked to the classification requirements set out in the BS EN 280 standard. It is therefore not just a matter of comfort : the presence or absence of certain devices can determine whether a man basket qualifies as a MEWP;
- precision of the work carried out : for tasks requiring fine manual work, such as facade work, welding or precision installations, a stable floor is not only a safety matter but also a quality one. A floor that keeps swaying makes it harder to carry out precise work consistently.
The main families of levelling systems
Gravity levelling
The simplest system is gravity levelling. The gravity levelling basket is connected to the boom through a pivot point that allows it to swing freely, much like a pendulum : when the boom tilts, the platform naturally tends to keep its horizontal position under the sole effect of gravity, with no electronic or active mechanical intervention.
With no electronic components to power, this system requires no electrical supply at all : by design it is the simplest and most robust, with fewer parts subject to failure and lower running costs. The trade-off is that correction happens through natural oscillation, with a certain margin of settling during more abrupt or rapid boom movements, and with greater sensitivity to sudden gusts of wind compared with an actively-corrected system.
This simplicity of design, however, is also its strength : it is the most “no-frills” system in the range, but for that very reason the most versatile. Not relying on any power supply, it is ready to use in any circumstance, with no need to check battery charge or crane compatibility beforehand.
Controlled levelling
The controlled levelling system introduces an intermediate level of automation. Unlike the gravity system, here an electronic device, powered at 12V or 24V depending on the configuration, monitors the platform’s attitude and steps in to keep it in the correct position, rather than relying on passive oscillation alone.
This results in a more stable and predictable attitude during manoeuvres, a real advantage for anyone working at height continuously or with booms that have a wide angular range, where the margin of oscillation of a purely mechanical system can become a fatigue factor over time. Since it requires an electrical supply, this system assumes the crane has a compatible electrical output, something to check when choosing but which involves no structural changes to the vehicle.
Active levelling
Active levelling represents a further step forward. A dedicated electronic board, built into the system and mounted inside the basket, manages the platform’s horizontality continuously, not just correctively, constantly sending inputs to the electro-hydraulic control unit so that the basket maintains the correct attitude throughout the manoeuvre. The CPU that manages this control typically operates across a voltage range of around 18V to 30V, against a nominal supply of 24V, to absorb the normal voltage dips or spikes that installations with long outreach are subject to.
A technical point worth knowing : in the event of a power interruption, the system stops actively correcting the attitude. The basket physically remains in the position it was in, but without continuous automatic control, making a manual check of the attitude necessary before resuming work.
Hydraulic and electro-hydraulic levelling
Hydraulic self-levelling platforms and electro-hydraulic ones follow a different logic, designed for configurations with several operators and higher capacities. In the hydraulic version, the platform draws directly on the crane’s hydraulic system, from which it receives the oil needed for levelling and rotation manoeuvres : a direct hydraulic connection is therefore essential. In the electro-hydraulic version of these aerial work platforms, the platform is fitted with its own electro-hydraulic control unit and a battery pack that powers the motor, avoiding a direct hydraulic connection to the crane, at the cost of a potentially higher overall weight due to the onboard control unit and batteries.
In both versions, rotation (±90°) is managed hydraulically via a dedicated lever on the control box, a sensible choice given the number of operators on board and the loads involved : manually orienting a platform of this size under load would be physically demanding and less precise.
Manual rotation
Manual rotation is a separate feature, not a levelling system, available on both gravity and controlled-levelling baskets : it allows the operator to orient the basket by up to ±90° relative to the attachment point, acting directly on it, without needing the crane to move the entire boom. It is useful whenever the job requires reaching surfaces at different angles during the same intervention, and it does not interfere in any way with the levelling system, which continues to manage horizontality entirely independently of the basket’s orientation.
Comparison table
| System | Operating principle | Power supply | Automation |
|---|---|---|---|
| Gravity | Passive oscillation under gravity | None | None |
| Controlled | Electronic correction of attitude | 12/24V | Intermediate |
| Active | Continuous control via dedicated electronic board | 24V (CPU operating range 18-30V) | High, continuous |
| Hydraulic | Levelling and rotation via the crane’s hydraulic circuit | Crane’s hydraulic system | High, managed by the crane |
| Electro-hydraulic | Independent electro-hydraulic control unit + battery pack | Onboard batteries | High, self-contained |
How to choose the right system
The type of crane and its fittings is the first filter to consider : the availability of a compatible electrical output (12/24V) or an auxiliary hydraulic system determines the choice before any other factor comes into play. A controlled, active or hydraulic system requires the crane to be fitted accordingly : checking this before settling on a model avoids discovering an incompatibility only at installation time.
The type of work matters just as much. Brief, occasional jobs sit well with the simplicity and immediacy of the gravity system, which needs no check of battery charge or electrical connections before use. Prolonged, repetitive or precision work instead benefits from a controlled or active system, where continuous stability pays off over time against the higher initial investment.
The boom’s angular range matters too : booms with a wide angular range or long outreach put more strain on the levelling system, and gain the most from an actively-corrected system, less prone to settling than a freely-oscillating one.
The number of operators on board naturally steers the choice toward different product families : single or two-person configurations are covered by standard baskets, with any type of levelling; from 3 operators upward, hydraulic or electro-hydraulic platforms become the natural choice, designed to handle higher capacities alongside levelling.
The working environment also affects the decision : sites exposed to wind, or industrial settings requiring continuous precision, favour actively-controlled systems over free oscillation, which is more sensitive to sudden external forces.
Finally, how often the equipment is used is a practical criterion that is often underrated : equipment used daily justifies investing in a more sophisticated system, while occasional use often makes the simplicity, and lower maintenance cost, of a gravity system preferable.
Maintenance and inspection
The maintenance required changes with the complexity of the system. Gravity systems, having the fewest components subject to wear (no electronics, no dedicated wiring), need checks focused mainly on the mechanical and structural side. Controlled and active systems add periodic checks of the electrical and electronic parts, while hydraulic and electro-hydraulic platforms also require checks of the hydraulic circuit, or of the control unit and batteries.
In all cases, the levelling system is one of the components covered by the thorough examination requirements under the Lifting Operations and Lifting Equipment Regulations 1998 (LOLER). Lifting equipment used to lift people, which includes crane man baskets, must be thoroughly examined at least every 6 months, compared with 12 months for most other lifting equipment, on top of the routine maintenance to be carried out according to the manufacturer’s instructions.
Platforms man baskets
Platforms, a division of Ormet with over 50 years of experience in the lifting sector, manufactures the entire range of solutions described in this article : from gravity levelling baskets, in single, two-person and manual-rotation versions, to Easy controlled levelling baskets, and SL active levelling baskets with the latest electro-hydraulic technology. For requirements involving several operators at once, the range is completed by hydraulic self-levelling platforms and electro-hydraulic self-levelling platforms.
Every system is designed to meet a specific operational need : the right choice depends on the type of work, how often it is used, and the level of precision required. The Platforms team is available to help you choose the configuration best suited to your operating context.
FAQ – Frequently asked questions
Is a levelling system a legal requirement?
There is no general requirement imposing a specific type of levelling system. Gravity, controlled and active levelling are all legitimate approaches : what regulations require, for classification as a MEWP under BS EN 280, is the presence of specific electronic devices such as the angle sensor, regardless of the underlying principle by which the basket stays level.
How often should the levelling system be checked or maintained?
The levelling system is one of the components covered by the thorough examination requirements under LOLER 1998. Lifting equipment used to lift people must be examined at least every 6 months, alongside routine maintenance carried out according to the manufacturer’s instructions.
Do levelling systems work on all cranes?
It depends on the system. Gravity systems need no power supply and are compatible with any crane fitted with a suitable hook. Controlled and active systems require the crane to have a compatible electrical output (12/24V); hydraulic platforms require the crane to be fitted with an auxiliary hydraulic system for the purpose.
Does the angle sensor only matter for MEWP classification, or does it also play a role in levelling itself?
The angle sensor detects the tilt of the boom/basket and supplies the data that the controlled and active electronic systems use to correct the attitude : it is therefore not just a paperwork requirement for MEWP classification, but an active functional component in the non-gravity systems.
Can a gravity basket later be upgraded to a more advanced system?
Some gravity models, if not fitted with an angle sensor, can be made compliant with BS EN 280 and classified as a MEWP by installing an electronic kit available as an accessory, without needing to replace the whole basket.
Does wind affect how the levelling system performs?
Yes, differently depending on the system : gravity systems, relying on freedom of movement, are more sensitive to sudden gusts than actively-corrected systems. In all cases, every system remains subject to the wind limits set by the manufacturer, beyond which work must stop.