Unwanted Hydraulic Lock Out

Problems in the Pile?

The Annoying Problem of Unwanted Hydraulic Lockout

Ever driven into a pile of muck, or similarly dense material, only to have your telehandler hydraulics lockout? Having to override them is a real pain, isn’t it? I’ll bet you’ve lost count of the times it’s happened.

Safety systems like these protect us from overloading the machine and causing damage – to ourselves and others - by ensuring the telehandler is safe in operation.

But we all know that the reason for buying and using a telescopic handler is its sheer versatility. It becomes the "go-to" machine, everyone’s favourite, often taking precedence over traditional loaders. The trouble is when you’re simply loading and travelling across uneven ground, these safety systems kick in and restrict the machine, when locking the hydraulics doesn’t appear to be necessary. It can be incredibly frustrating.

If you’re looking to place the blame, then lay it firmly at the door of the "longitudinal stability indicator." More commonly known by its initials LSI, this system comprises the all-too-familiar flashing warning light that results in that frustrating lockout.

It works by monitoring the forward and backward stability of the machine, via sensors on the rear axle. Designed to flex under the weight of the machine, the pressure on the rear axle is released as the machine tips forward. As the axle straightens, the sensors detect a change in pressure and send a signal to the LSI.

Telehandler stability is measured within a "stability triangle," which aims to keep the machine’s centre of gravity (CG) within it. If systems detect that the CG is close to leaving the triangle, the LSI system kicks in – in this case, triggering the hydraulic lock – to prevent the operator from tipping the machine, perhaps causing harm to themselves or others.

Of course, these systems are there for the operator’s own safety. They’re a vital component of most telehandlers and, for the most part, they work well.

So back to that situation where you’ve driven into the muck pile, or when you’re driving down a bumpy track and the safety system constantly locks out, bleeping away merrily.

On some machines, you can override the sensor, but on others you have to restart the machine each time the LSI engages. It’s hardly the most convenient way to break material from a pile on a busy day! Hydraulic lockout is something we hear from telehandler operators all the time, so we know how it’s regarded as a huge nuisance on most farms.

It’s why Caterpillar sought to provide an in-built solution to this problem. All Cat® Telehandlers feature an intelligent LSI system, featuring "passive" and "active" modes. These help operators avoid unwanted lockout, keeping their machines moving.

When the machine is in-gear with the park brake disengaged, Cat Telehandlers enter passive mode. This means the LSI sensor will alert the operator to potential instability, but won’t lock out the hydraulics. Operators can drive into piles with a grain bucket or muck fork and easily tear out material, or drive over rough terrain, without the inconvenience of a hydraulic and boom lockout.

"Active" mode comes into play when the machine is in neutral, or the handbrake is engaged, for duties such as bale stacking. The basic principle of our system is that the safety system works when you truly need it, without impacting your productivity.

At Caterpillar, we want to ensure you, as the operator, get the most out of your machine. We don’t want you to spend precious time overriding a stability system when everything’s working safely. Our unique system saves you time – and stops you pulling your hair out over having to press the same switch all day.

It’s just another part of the solution offered by our telehandlers: productive, efficient machines designed with the operator in mind.

If you want to see our passive LSI mode in action, check out one of our videos on YouTube and see for yourself how much simpler things are when you run a Cat Telehandler. Time is priceless on the farm – don’t waste yours!


Matt Kelly – I’m the Telehandler Global Product Marketing Specialist. It’s my responsibility to work with customers to understand how their machines are so critical to their work: where they’re performing well, as well as things we can improve still further.

This day-to-day customer feedback is crucial for the continuing development of Cat Telehandlers. I love being involved in it.

Cat Telehandlers

Cat Telehandlers

Cat Telehandlers

Cat Telehandlers