Magic Glasses: Removing the Fly Jib When It Is Not Needed
- 5 days ago
- 3 min read
At first glance, leaving the hydraulic fly jib on the crane feels efficient. It is already fitted. It might be needed later. No one wants to remove and refit equipment unnecessarily.
Put on the Magic Glasses, and you see something different. You see permanent deadweight, reduced capacity, higher ground pressures, and added structural stress - all before the lift even begins.
Quick Scene-Setter
A Hiab is on site, completing general lifts. The hydraulic fly jib is attached to the end of the boom but retracted.
Today’s work is straightforward:
Main boom only
No need for extra reach
Loads well within the chart
At first glance, everything looks fine.
What Most People See
The jib is on but retracted.
It is not being used.
The Hiab still shows capacity on the display.
The load is well under the rated capacity.
The assumption is simple:
“If we are not using it, it does not matter.”
What the Magic Glasses Show You
1. The Jib Is Permanent Deadweight
Even while not in use, the fly jib is still a weight at the end of the boom.
That weight:
Sits at the outer extension
Acts as a constant lever
Reduces net lifting capacity
It does not disappear because it is folded.
At every radius, the Hiab is already carrying that weight before you pick up the load.
2. Stability Margin Reduces
Crane stability is governed by moment and geometry.
When weight is added at the end of the boom:
The centre of gravity shifts
The overturning moment increases
The safety margin reduces
Even with a light load, the Hiab is working harder than it would without the jib fitted.
That difference may not matter on easy lifts.
It matters when you are near chart limits or working at a longer radius.
3. Ground Bearing Pressure Increases
More overturning moment means:
Higher reaction on the stabilisers
Increased ground bearing pressure
Less tolerance for marginal ground
If the ground is soft, variable, or poorly compacted, that extra deadweight reduces your buffer.
You are using up stability margin without gaining anything in return.
4. Increased Wear on the Crane
High-cycle lifting with a fitted jib:
Loads the extension cylinders continuously
Increases wear on sliding pads
Adds leveraged stress to outer boom sections
Over time, unnecessary weight means unnecessary wear.
Removing the jib when it is not needed reduces fatigue exposure.
5. Configuration Errors Become More Likely
If the jib is fitted:
The Hiab must be set to the correct configuration
The rated capacity system must match the physical setup
Hook position must be correct for heavy main boom lifts
If the configuration is wrong, the Hiab may allow a lift that exceeds true capacity.
That risk disappears when the attachment is removed.
The Controls That Matter
If the fly jib is not required for the job:
Remove it for prolonged periods of main boom work
Confirm the Hiab configuration matches the physical setup
Use the correct load chart for the configuration in place
Review stabiliser loads and ground capacity
Secure all pins and connections properly if it remains fitted
Include Hiab configuration in the lift plan discussion
Do not assume “not in use” means “neutral.”
Magic Glasses Checklist - Hydraulic Fly Jib
Is the jib required for today’s lift?
Has the correct configuration been selected?
Has the jib weight been considered in the capacity?
Are stabiliser loads acceptable for the ground conditions?
Is the Hiab working near the chart limits?
Would removing the jib increase the safety margin?
Leaving a fly jib fitted when it is not required feels convenient. In reality, it reduces lifting margin, increases stabiliser load, and adds structural stress.
Removing it when not needed:
Increases available capacity
Reduces ground pressure
Reduces wear
Simplifies configuration
Magic Glasses are about seeing the hidden load before the visible load.
Before the next lift, ask:
Do we actually need it today?
Magic Glasses: The magic glasses come from the reality of - when I look at my books, I don't see a problem. But when my accountant looks at the books, it's a whole different story. He must have a special set of glasses.
As PCBU's, Officers and Workers, we have an obligation to learn what we are up to and the risks. Our actions and the standards we accept also affect those around us. This magic glasses post is made to help others see what we see.
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